What is included in stainless steel

Stainless steel material (stainless steel wire): types and applications – Machine

Stainless steel wire is a type of rolled metal made of heat-resistant, anti-corrosion and high-alloy steel, made in the form of a long universal structure resembling a thread or cord.

As a rule, it has a round cross-section.

Due to its properties, stainless steel wire is widely used in many areas: mechanical engineering, oil production, chemical industry, construction, food industry, medicine and much more.

Classification

Four types of stainless wire are available:

• knitting;
• hardened;
• welding wire;
• spring stainless wire.

According to the production method, cold-rolled and hot-rolled wire are divided. Depending on the type of processing of the finished product (metal surface), stainless steel wire is divided into the following types:

• oxidized;
• copper-plated;
• light wire (no oxides).

According to the accuracy of execution, stainless steel wire is divided into normal and high accuracy. Depending on the physical properties of stainless steel wire, the first and second plasticity classes of the product are distinguished.

Labeling, packaging and storage

Stainless steel wire is produced in accordance with GOST 18143-72 from anti-corrosion, heat-resistant alloy steel with a cross-section from 0.2 to 7.5 mm. The marking of the wire determines its chemical composition, production technology and type of metal surface treatment. The numbers indicate the percentage of elements that determine the basic properties of the product. As an example, stainless steel wire 12Х18Н10Т:

• 12 – carbon content not more than 0.12%;
• X18 – chromium 18%;
• H10 – nickel 10%;
• T – titanium about 1%.

The presence of other elements, the content of which does not exceed 1%, is not indicated in the labeling. In the designation of cold-rolled stainless steel wire, the last one is indicated by the letter “X”. Oxidized stainless steel wire has a tarnished color and is marked with the letter “T”.

Basically, this type of marking is applied to wire produced by heat treatment (hot rolled). Light-colored stainless steel wire without tarnish or oxides is designated “TS”. The letter “P” is added to the marking of a high-strength product.

The plasticity class is indicated by the corresponding numbers: 1 – first, 2 – second.

Stainless steel wire requires careful handling during transportation and storage. Depending on the diameter, it is packaged in skeins or wound on reels and protected from mechanical damage with film or paper. Transportation is carried out mainly in covered vehicles. Stainless steel wire is stored in closed heated warehouses.

Production

Stainless steel wire is a long metal structure made in the form of a cord.

All over the world it is produced in two ways: by cold drawing or by drawing heat-treated metal blanks (hot drawing).

As a rule, the cross-section of the stainless steel wire is round; in exceptional cases it can be oval, square, trapezoidal or hexagonal.

Wire is supplied to the consumer in coils, coils, and spools. The quality of the resulting product depends on the production method. The resulting wire is subjected to subsequent surface treatment, depending on which oxidized or light-colored products are obtained. Oxidized stainless steel wire is widely used in the electrical industry.

Quality requirements

Highly alloyed stainless wire contains from 0.01 to 0.24% carbon and more than 30% alloying elements. The basis is iron.

The surface must be smooth without holes, nicks, delamination, cracks and clean - without film, scale and other contaminants. The surface of the wire may contain scratches, individual dents, local rippling, and scratches, including drawn ones.

The presence of defects is allowed, the depth of which does not exceed the maximum deviation in accordance with the diameter of the section.

Quality control of stainless wire is carried out in several comprehensive ways, which include:

• Accurate control in accordance with GOST of the diameter of the rod and curl.
• Testing of finished products for deformation and rupture.
• Measuring the level of electrical resistance.
• Determination of the composition of the chemical elements of the steel used in the section.

Application area

Stainless steel wire is used in many areas of economic activity. Products made of copper and brass are characterized by high resistance to corrosion, but at the same time they are much softer and less resistant to tearing.

• Electric power industry is one of the areas where stainless steel wire is most in demand. Due to their resistance to chemical influences and high temperatures, stainless steel products are used in the manufacture of electrical equipment and important components.
• In the oil industry it is used in the production of drilling equipment and oil pipelines.
• Stainless steel wire is used in furniture production.
• Food industry. In the production of equipment for processing, storing and transporting food products. Stainless steel has good hygienic properties.
• Use in the chemical industry due to its resistance to oxidation and other chemical influences.
• In the production of medical equipment, including high-precision surgical instruments.

• In construction for the production of reinforcing elements.
• In mechanical engineering in the manufacture of springs, cables, braids. Elements made of stainless wire are resistant to mechanical stress and have proven themselves both as part of a structure and as independent elements.
• For the manufacture of household items: household appliances, appliances, dishes, etc.
• For welding work. This is one of the main areas of application of stainless wire. It is actively used in aircraft and shipbuilding, automotive industry, for the construction of structures in aggressive environments, etc.

Stainless steel welding wire

Stainless steel wire can be used for any type of welding work. Electrodes and welded meshes are made from it. It is used in construction for the construction of complex structures.

Welding (surfacing) stainless steel wire for semi-automatic machines is a consumable material for welding work in an environment of protective gases or without them.

The resulting seam does not require additional heat treatment.

Source: https://regionvtormet.ru/prochee/material-nerzhavejka-provoloka-iz-nerzhaveyushhej-stali-vidy-i-oblasti-primeneniya.html

Types of stainless steel

Stainless steel is a generalized name for the alloy. In fact, there are a great many varieties of it. Each type has its own qualities and characteristics, and, accordingly, its purpose. To select the right material, you must first familiarize yourself with the existing groups.

Group distribution

Stainless steel is divided into groups according to the qualities they possess.

• corrosion-resistant – resistant to corrosion, which can form as a result of electrochemical and chemical influences;
• heat-resistant - are not subject to chemical destruction in gas environments where temperatures can reach 550°C (such alloys are also called scale-resistant and their operation is allowed in an unloaded or lightly loaded state);
• heat-resistant - stainless steel that can be operated under load at high temperatures (sometimes the time frame under which work in such conditions is allowed is precisely established).

Distribution by chemical composition

Changing the chemical composition allows you to adjust the technical qualities of stainless steel. Today there are three main types, which are classified according to the amount of chromium they contain.

1. Chrome:
   • 0.45% carbon, 12-14% chromium – resistant to chemical corrosion, not susceptible to acetic and nitrogenous environments, can be used in environments with a high content of water vapor;
   • 0.1% carbon, 16-18% chromium - anti-corrosion properties are maintained even when exposed to high temperatures (up to 900 ° C), they have high resistance to sulfur, organic acids, and soap solutions;
   • 18-28% chromium, no carbon - anti-corrosion qualities are maintained at temperatures up to 1150 °C.
2. Chrome-nickel:
   • 18% chromium, 8% nickel – resistant to nitric, phosphoric and sulfuric acids;
   • 1.5-2.5% molybdenum – resistant to sulfuric and acetic acids;
   • 3% copper – intended for use in low-corrosive environments under tensile loads;
   • 2-3% silicon – is resistant to sulfuric and hydrochloric acids.
3. Chromium-manganese-nickel - has additives of appropriate substances to give stainless steel qualities regarding resistance to lactic and acetic acids (this type is designed specifically for the food industry).

Distribution by structure

Stainless steel in this category is divided into three types:

• pearlitic – contains a small amount of alloying substances;
• martensitic - the composition includes two or three alloying substances;
• austenitic - the highest quality material, may contain different amounts of components that are allowed in the alloy.

09 June 2016

Source: https://tdspecstal.ru/articles/klassifikatsiya-nerzhaveyuschey-stali.html

Corrosion-resistant steel - what is it?

The high popularity of such a material as stainless steel is explained by its unique characteristics that ordinary carbon steel alloys do not possess. Thanks to the wide variety of stainless steel grades available on the modern market, they can be selected to successfully solve various technological problems.

The appearance of stainless steel structures does not change throughout their entire service life

What is unique about stainless steels?

Stainless steel was patented in England in 1913. The author of this invention, which, without exaggeration, became the most important stage in the development of not only steel, but also other industries, is metallurgist Harry Brearley.

The addition of an element such as chromium to their chemical composition made it possible to endow ordinary steel alloys with unique characteristics and obtain corrosion-resistant steels from them.

It is chromium, which must be at least 10.5% in stainless steel alloys, that provides these materials with such characteristics as:

• exceptionally high corrosion resistance;
• very high strength;
• good weldability;
• ease of processing using cold deformation methods;
• long service life without loss of original characteristics;
• aesthetically attractive appearance of products made from alloys of this category.

Influence of alloying elements on the properties of steels

Stainless steels necessarily contain chromium and iron in their chemical composition. These elements complement each other, which is what gives these materials such unique characteristics. In particular, chromium, combining with oxygen, creates an oxide film on the surface of the stainless alloy, which becomes a reliable obstacle to corrosion processes.

In order to provide stainless steel with additional characteristics and significantly improve existing properties, alloying additives are introduced into its chemical composition - nickel, titanium, molybdenum, niobium, cobalt, etc. This alloying makes it possible to create various types of stainless steel alloys that differ from each other their characteristics and, accordingly, purpose.

We are already so accustomed to corrosion-resistant steel that we don’t even notice how much more comfortable our lives have become due to the presence of stainless steel in it.

Stainless steel contains carbon in its chemical composition, which gives it high hardness and strength. It should be noted that this chemical element is an essential component of any steel alloy and has a serious impact on its properties.

The unique characteristics of stainless steel make it possible to successfully use this metal in a variety of areas related to the operation of products and equipment in conditions of high humidity and constant exposure to aggressive environments.

Stainless steels are actively used for the production of products for both industrial and household purposes.

In particular, it is from this metal that cutlery and knives are most often made, elements of communications and enclosing structures, equipment parts, etc.

Classification methods

The characteristics of stainless steels are determined both by the chemical composition of the alloys and by the characteristics of their internal structure. Depending on these parameters, all steels classified as stainless steel are divided into four groups.

Ferritic (chromium)

The chemical composition of steels of this group contains chromium in a volume of 20% (which is why they are called chromium). Due to the significant chromium content, products made from such steels are able to successfully withstand even very aggressive environments. Steel alloys of this group have good magnetic characteristics.

Chemical composition and mechanical properties of ferritic steels

Large consumers of ferritic steels are enterprises of the heavy and chemical industries; elements of heating equipment are produced from stainless alloys of this type, as well as much more.

Alloys of the ferritic group occupy a fairly large share of the stainless steel market and, in terms of their level of demand, are only slightly inferior to materials with an austenitic internal structure, but are much cheaper than the latter.

Austenitic

These are stainless steels, a significant proportion of the chemical composition of which (up to 33%) is chromium and nickel. Consumers prefer these alloys due to the fact that such materials are characterized by high strength and exceptional corrosion resistance.

Chemical composition and applications of heat-resistant austenitic stainless steels (click to enlarge)

Martensitic and ferritic-martensitic

Due to the peculiarities of the internal structure, such alloys have the highest strength among steels. In addition, they are characterized by good wear resistance and a minimal amount of harmful impurities in their composition.

It is this category that includes heat-resistant, corrosion-resistant steel, which can not only successfully withstand oxidative processes, but also be operated under conditions of constant exposure to high temperatures, without losing its original properties.

chemical elements in martensitic and ferritic-martensitic steels (click to enlarge)

Combined

This includes steels with a combined internal structure: austenitic-ferritic and austenitic-martensitic. Such innovative materials optimally combine the best properties of all the above types of stainless steels.

Chemical compositions of corrosion-resistant steels of the austenitic-martensitic class

Possession of information about which group a particular grade of stainless steel belongs to allows you to optimally select alloys for solving certain technological problems.

The most popular brands and areas of their application

To choose the right stainless steel for the manufacture of products for a specific purpose, you can use special reference books that list both all grades of such material and their main characteristics. Meanwhile, in each of these groups there are the most popular brands, which are most often chosen by the consumer. Let's list them.

• 10Х17Н13М2Т and 10Х17Н13М3Т are steels that are characterized by good weldability and excellent corrosion resistance. Thanks to these properties, stainless steel alloys of these grades are successfully used for the production of products that, during their operation, are constantly exposed to high temperatures and aggressive environments. The properties of steels of these grades are formed due to the presence in their chemical composition of the following elements: chromium (16–18%), molybdenum (2–3%), nickel (12–14%), carbon (0.1%), silicon (0 .8%), copper (0.3%), sulfur (0.02%), phosphorus (0.035%), manganese (2%), titanium (0.7%). If there is a need to select stainless steels of these grades, then you should keep in mind that their foreign analogues can also be purchased on the domestic market, namely: SUS316Ti (Japan), 316Ti (USA), OCr18Ni12Mo2Ti (China), Z6CNDN17-12 (France) ).
• 08Х18Н9 and 08Х18Н10 are stainless steel alloys from which pipes of both round and any other cross-section are made. These materials are used for the production of various structures used in the mechanical engineering and chemical industries, as well as for the production of pipeline elements and furnace devices. The chemical composition of these grades of steel contains the following elements: chromium (17–19%), carbon (0.8%), titanium (0.5%), nickel (8–10%).
• 10Х23Н18 - steel of this grade is characterized by a high content of nickel (17–20%) and chromium (22–25%), as well as manganese (2%) and silicon (1%) in its composition. This combination of elements gives the alloy the required characteristics and creates an increased tendency to temper brittleness. It should be noted that the alloy of this grade belongs to stainless steels of the heat-resistant category.
• 08Х18Н10Т - a stainless alloy of this brand is characterized by high resistance to oxidation processes, as well as good weldability, and to obtain a high-quality connection using this technology, the products do not need to be preheated, and they also do not require heat treatment after welding. To improve the strength characteristics of products made from such steel, they must be hardened, as specified in the relevant regulatory document.
• 06ХН28МДТ - an alloy of this grade is optimally suited for creating welded structures that will subsequently be used in aggressive environments. The chemical composition of this steel contains the following elements: chromium (22–25%), nickel (26–29%), copper (2.5–3.5%).
• 12Х18Н10Т – products made from steel of this grade are mainly used to equip enterprises in the chemical, pulp and paper, construction, food and fuel industries. This metal is characterized by thermal resistance, good impact strength and practicality of use.
• 12Х13, 20Х13, 30Х13 and 40Х13 – stainless steel alloys of these grades are practically impossible to weld, but they also have positive properties. The latter lies in the fact that these steels do not have a tendency to temper brittleness, and their internal structure is not affected by defects, which in professional language are called flakes. Cutting and measuring tools, as well as springs and springs for various purposes are made from these grades of stainless steel.
• 08Х13, 08Х17, 08Х18Т1 are stainless steel alloys of the ferritic group, from which products are produced that do not experience shock loads during operation, as well as exposure to low temperatures.

Types of stainless steel surfaces

How to decipher the markings

Marking of stainless steels, the rules for the formation of which are stipulated by the provisions of regulatory documents, carries the following information:

• the number in first place indicates the quantitative content of such a chemical element as carbon in the alloy composition (for example, in steel grade 08Х17 carbon is contained in an amount of 0.08%, and in 40Х13 - 0.4%);
• after the letters in the marking, each of which indicates the corresponding chemical element (X - chromium, H - nickel, M - manganese), numbers are placed indicating its content in whole percentages.

  Steel 40xma characteristics

An example of decoding the designation of stainless steel

In general, if we talk about the rules for marking steel alloys classified as stainless, they are practically no different from those adopted for marking steels of any other type.

Source: https://varimtutru.com/korrozionnostoykaya-stal-chto-eto-takoe/

Stainless steels: how composition affects properties

Alloy steels occupy a significant share of the metallurgical products market. These include the so-called “stainless steels” - a group of alloys characterized by increased resistance to corrosion. Since their appearance, the range of such steels has expanded to several hundred items. Therefore, a system for their classification and labeling was developed.

It is worth noting that the name “stainless steel” does not entirely correctly reflect its properties. Any iron-carbon alloy is exposed to oxygen and aggressive substances, but for this to affect its performance properties, it takes different times. Therefore, stainless steels are more correctly called corrosion-resistant.

By composition

Chromium, nickel, vanadium, molybdenum, titanium and some others are used as alloying additives that increase the resistance of the iron-carbon alloy to rust formation.

Corrosion resistance is also increased by manganese and silicon introduced to deoxidize and neutralize sulfur. Based on the main alloying elements, stainless steels are classified as chromium, manganese, etc.

Some additives are used to impart special structural or technological properties to steels, for example, to crush carbides and increase impact toughness.

The basic alloying elements of stainless steel are chromium and nickel. They both enter into solid solution with iron and increase corrosion resistance.

When oxidized, they form a thin oxygen-impermeable film on the surface of a steel product, resistant to chemical, electrochemical and atmospheric influences. Nickel expands the austenite region in iron-carbon alloys.

Chromium narrows it, but is a carbide-forming element and binds carbon. The ratio of nickel and chromium has a decisive influence on impact strength, weldability and ability to withstand cold deformation.

Carbon, as one of the essential components of steels, negatively affects corrosion resistance. However, the hardness and wear resistance of steel depends on its content. For example, 95Х18 has less pronounced corrosion-resistant properties compared to 40Х13, despite its higher chromium content.

By properties

A more clear idea of ​​alloys is given by dividing them into groups according to properties:

• Corrosion resistant. Steels are highly resistant to atmospheric corrosion and can be used under normal conditions in a loaded state. Examples include stainless steel used for the manufacture of utensils and equipment for the food industry: 08Х18Н10, 20Х13, 30Х13.
• Heat resistant. A distinctive feature of such alloys is their high resistance to scale formation at high temperatures. Heat-resistant stainless steels are used for the manufacture of heat exchangers for boiler and pyrolysis plants (15Х28), valves for automobile and aircraft engines (40Х10С2М), parts for heating metallurgical furnaces (10Х23Н18).
• Heat resistant . A number of alloys have been developed that can operate under load at high temperatures without significant deformation and destruction. They use complex alloying systems (05Х27У5, 15Х12ВН14Ф, 37Х12Н8Г8МФБ). Steel type 20Х13 also has moderate heat resistance.

By structure

Based on their microstructure, stainless steels are divided into the following classes:

• austenitic;
• ferritic;
• martensitic;

In addition to them, there are intermediate groups:

• austenitic-ferritic;
• martensitic-ferritic;
• martensitic-carbide.

Heat treatment has a great influence on corrosion resistance, since it affects the phase composition of most stainless steels. Stability decreases when carbide heterogeneity occurs. This phenomenon is caused by the so-called intercrystalline corrosion.

When steels are heated to temperatures in the range of 500 – 800 °C, chains of carbides and areas with a reduced chromium content are formed at the grain boundaries. In the body of the grain, the content of alloying elements remains high. This type of corrosion is often observed in weld areas.

To combat this phenomenon, the steel composition is stabilized by introducing a small amount of titanium.

Austenitic steels

During crystallization, austenitic steels form a single-phase system with a face-centered crystal lattice. One of the most prominent representatives of the class is alloy 08Х18Н10.

Due to the high nickel content in stainless steels of this class (up to 30%), the austenite phase remains stable down to – 200 °C, and the carbon content does not exceed 0.12%. Steels with this structure are characterized by the absence of magnetic properties.

Most of them have good machinability.

Austenitic steels are necessarily subjected to heat treatment - hardening, tempering or annealing. The cooling rate practically does not change the hardness, but it affects the resistance to liquid and gaseous aggressive media, stabilizes the grain size and resistance to deformation.

Additional elements are introduced into the alloying systems of austenitic chromium-nickel steels:

• molybdenum – to prevent pitting and operation in reducing atmospheres
• titanium and niobium – for protection against intercrystalline corrosion.
• silicon – to increase acid resistance;
• manganese - to improve casting qualities.

Ferritic steels

This class includes chromium steels with low carbon content. They have a body-centered cubic lattice, which determines their magnetic properties.

Ferritic steels have lower corrosion resistance compared to austenitic steels and cannot be strengthened by heat treatment, but have higher technological properties. They are easier to machine and weld better, and their cost is significantly lower.

At temperatures of 300 – 400 °C, steels acquire high ductility, and they can be used to produce volumetric stamped parts of complex shapes.

chromium in such steels reaches 27%. Molybdenum, titanium and aluminum are used as stabilizing additives.

Martensitic steels

Alloys of this class contain at least 0.15% carbon and 11% chromium. Martensite has a microscopic needle-like structure and, when magnified, looks the same as carbon steel after hardening.

The crystal lattice has a tetragonal shape and is characterized by high internal stresses. This determines high strength properties and hardness. For example, for 40X13 it is up to 52 - 55 HRC.

Molybdenum, niobium, vanadium and tungsten are introduced as additional alloying elements. Martensitic steels, due to their high hardness, are difficult to cut and have low ductility.

One of the main technological properties of corrosion-resistant steels with this structure is the ability to self-harden. Martensitic transformation occurs upon cooling in air. To increase heat resistance, steel after hardening is tempered with sorbitol or troostite.

Source: https://acea-spb.ru/stati/nerzaveusie-stali-kak-sostav-vliaet-na-svoistva

Steel: composition, properties, types and applications. Stainless steel composition

Many people know that steel is a product obtained by melting other elements. But which ones? What does steel contain? Today, this substance is a deformable alloy of iron and carbon (its amount is 2.14%), as well as a small proportion of other elements.

General information

It is worth noting that steel is an alloy that contains up to 2.14% carbon in its composition. An alloy containing more than 2.14% carbon is already called cast iron.

It is known that the composition of carbon steel and ordinary steel is not the same. If a conventional substrate contains carbon and other alloying (improving) components, then the carbon product does not contain alloying elements. If we talk about alloy steel, then its composition is much richer.

In order to improve the performance characteristics of this material, elements such as Cr, Ni, Mo, Wo, V, Al, B, Ti, etc. are added to its composition.

It is important to note that the best properties of this substance are ensured precisely by adding doped complexes, and not just one or two substances.

Microstructure

The microstructure of steel differs depending on its condition. If the alloy is annealed, then its structure will be divided into carbide, ferritic, austenitic, and so on. With a normalized microstructure of the substance, the product can be pearlitic, martensitic or austenitic.

The composition and properties of steel determine whether a product belongs to one of these three classes. The least alloyed and carbon steels are the pearlitic class, the middle ones are martensitic, and the high content of alloying elements or carbon transfers them to the category of austenitic steels.

It is important to note that an alloy such as steel may also include some negative elements, a high content of which worsens the performance of the product. These substances include sulfur and phosphorus. Depending on the content of these two elements, the composition and types of steel are divided into the following four categories:

• The rank and file became. This is an alloy of ordinary quality, containing up to 0.06% sulfur and up to 0.07% phosphorus.
• High quality. of the above substances in these steels is reduced to 0.04% sulfur and 0.035% phosphorus.
• High quality. They contain only up to 0.025% of both sulfur and phosphorus.
• The highest quality alloy is assigned if the percentage of sulfur content is no more than 0.015, and phosphorus is no more than 0.025%.

If we talk about the process of producing an ordinary alloy, then most often it is produced in open-hearth furnaces or in Bessmer, Thomas converters. This product is bottled into large ingots. It is important to understand that the composition of steel, its structure, as well as quality characteristics and properties are determined precisely by the method of its manufacture.

Open hearth furnaces are also used to produce high-quality steel, but more stringent requirements are imposed on the smelting process in order to obtain a high-quality product.

Melting of high-quality steels is carried out only in electric furnaces. This is explained by the fact that the use of this type of industrial equipment guarantees an almost minimal content of non-metallic additives, that is, it reduces the percentage of sulfur and phosphorus.

In order to obtain an alloy of particularly high quality, they resort to the method of electroslag remelting. The production of this product is possible only in electric furnaces. After completing the manufacturing process, these steels are always only alloyed.

Types of alloys by application

Naturally, a change in the composition of steel greatly affects the performance characteristics of this material, which means that the scope of its use also changes. There are structural steels that can be used in construction, cold forming, and can also be case-hardened, tempered, high-strength, and so on.

If we talk about construction steels, they most often include medium-carbon and low-alloy alloys. Since they are mainly used for the construction of buildings, the most important characteristic for them is good weldability. Various parts are most often made from case-hardened steel, the main purpose of which is to work under conditions of surface wear and dynamic loading.

Other steels

Other types of steel include improveable steel. This type of alloy is used only after heat treatment. The alloy is exposed to high temperatures to harden it and then tempered in some environment.

The type of high-strength steels includes those in which, after selecting the chemical composition, as well as after undergoing heat treatment, the strength reaches almost a maximum, that is, approximately twice as much as that of the usual type of this product.

Spring steels can also be distinguished. This is an alloy that, as a result of its production, has received the best qualities in terms of elastic limit, load resistance, and fatigue.

Stainless steel composition

Stainless steel is an alloy type. Its main property is high corrosion resistance, which is achieved by adding an element such as chromium to the alloy composition. In some situations, nickel, vanadium or manganese may be used instead of chromium. It is worth noting that by melting the material and adding the necessary elements to it, it can obtain the properties of one of three grades of stainless steel.

The composition of these types of alloy is, of course, different. The simplest are considered to be ordinary alloys with increased resistance to corrosion 08 X 13 and 12 X 13. The next two types of this corrosion-resistant alloy must have high resistance not only at normal, but also at elevated temperatures.

Source: https://FB.ru/article/341012/stal-sostav-svoystva-vidyi-i-primenenie-sostav-nerjaveyuschey-stali

Stainless steel grades and their interpretation

In the modern capitalist world, with its crazy speed of life, gigantic volumes of transmitted and received information, in the world of large corporations that set the pace of life - in all this turmoil it is becoming increasingly difficult to find grains of that information that is not blurred by advertising, which, having been typed into the search bar of your Internet -browser you hope to discover. Today, with your permission, we will help you understand some of the features of the material that quietly serves you faithfully, but to which you are unlikely to attach any special importance.

Let's talk today about an indispensable assistant in cooking. About the material from which your guide to the time of day may be made, shimmering with cold light on your wrist. Let's talk about the material that densely surrounded you, but which you will once again not pay attention to, being in high spirits from discussing a recent football match with a colleague while you are going down the elevator to the dining room at lunchtime.

We will tell you about the basis of many critical designs and products used in almost all industries. Finally, we will discuss the essence of what stands apart in the issue of protection from the effects of aggressive environments and of which, for all these needs, more than 48 million tons are smelted in the world annually. Let's say a word about stainless steel. And moving from the general to the specific, we will study the most common grades of stainless steel. And let's try to decipher them.

Stainless steel surrounds us almost everywhere. Since it is closely connected with our lives, and there are many areas of its application, this is what leads to a great variety of brands. The ancestor of the existing corrosion-resistant steel grades is the “waterproof” alloy patented in England in 1872, which has grown as a result of numerous research and experiments of metallurgists into a whole family, classified according to the crystalline structure of the metal and consisting of the following classes:

• Austenitic
• Ferritic
• Martensitic
• Duplex

There are also classes in GOST 5632-72: martensitic-ferritic, austenitic-martensitic and austenitic-ferritic. The most common and has a wide range of different steel grades is austenitic. Here, for example, we present corrosion-resistant steel that comes into contact with food - AISI 304. Let's look at this particular representative of this class.

Stainless steel AISI 304

A little about the designation. The basis is the classification of the American Institute of Steel and Alloys (which, in fact, in English looks like the American Iron and Steel Institute, AISI), which appeared in the 30s of the last century, due to the need to streamline the technical terminology of the metallurgical industry.

Specifically, analyzing the designation of brands according to the AISI classification can tell us little. For the AISI 304 alloy, the first digit “3” indicates that it belongs to the austenitic class, and the subsequent “0” and “4” simply inform about the serial number of the steel in the entire group of austenitic class stainless steel. In a word, melancholy.

If we consider the domestic analogue of the AISI 304 brand, which according to GOST 5632-72 is 08Х18Н10, then deciphering the stainless steel grade will become a much more exciting activity. At its core, the decoding of GOST stainless steel grades is much more informative for us than the AISI classification. Briefly about what this set of letters and numbers is - 08Х18Н10.

This is not “zero eight x eighteen ah ten” and not “zero eight x eighteen ah ten”, but I have heard such things from time to time. This is “zero eight ha eighteen en ten.” The marking designation according to the Russian standard uses only numbers and letters of the Russian alphabet, alternating one after another.

All stainless steels are called alloyed, and the markings indicate exactly the main alloying components, but we will tell you what this word means a little later. Now let’s see how the marking and decoding of corrosion-resistant steels looks in more detail.

certificate for stainless steel AISI 304 (08Х18Н10)

Decoding the stainless steel grade

Let's decipher the grade of stainless steel AISI 304, or rather the domestic analogue 08Х18Н10. This set of letters and numbers is nothing more than a symbol for the content of the main chemical elements present in stainless steel. Why conditional? - you ask.

Because when developing GOST, the drafters introduced permissible deviations up or down, expressed as a percentage, for each permissible limit of the mass fraction of a chemical element used in the smelting of a particular grade of steel.

The decoding of the grade numbered 6-29 in GOST 5632-72 looks like this: the first digits are “08” - and not only for this grade of stainless steel, but for all grades that have numbers in front - an indicator of the quantitative carbon content in steel, and more precisely, the mass fraction as a percentage. When smelting steel 08Х18Н10 carbon is allowed no more than 0.08%. Next comes “X”, aka “ha”, aka chrome. It is the main alloying component of stainless steel.

The number “18” that follows is a quantitative designation of the mass fraction of chromium. According to GOST, it allows from 17 to 19%. Then comes “N”, aka “en”, aka nickel. The second most important element. Well, “10,” as you probably already guessed, is a quantitative indicator of the mass fraction of nickel. And according to the standard, this stainless steel should have from 9 to 11%. Everything is simple and clear.

About doping

The word "alloying" comes from the German "legieren", meaning "to fuse" or translated from the Latin "ligare" - to bind. Alloying means the process of adding, in our case, to steel, various elements to obtain special characteristics of the stainless steel obtained as a result of this very alloying. Alloying improves the properties of the metal. This process itself is akin to cooking.

Look - both in metallurgy and in the kitchen they cook. In both cases, all actions take place when exposed to high temperatures. In both cases, many components are used to obtain the final result, be it the ingredients of some gourmet dish or the chemical elements of some grade of steel added to iron and carbon. Both in the kitchen and in the steel shop, the “cooking” process takes place in several stages.

In both cases, you can “over-salt” and end up with, for example, steel of the wrong quality, or prepare a dish after eating which you will immediately want to drink a glass of water. And even in both cases, the “dish” is prepared according to clearly defined rules: either according to a cookbook, or according to GOST or TU.

Yes, and in the end, each of the options has its own special properties: for food it is taste, color, smell, consistency, and for stainless steel it is resistance to corrosion under the influence of aggressive environments and precipitation while maintaining such qualities of steel as strength and hardness , plasticity.

What is included in stainless steel?

chemical composition of stainless steel

A few words about the “ingredients” used in the “cooking” of stainless steel. Or more precisely about alloying elements and their properties. By the way, steel is divided according to the degree of alloying. Austenitic corrosion-resistant steels are classified as high-alloy steels, since the total mass fraction of alloying elements is at least 10%, and the iron content is more than 45%.

Let's continue the story about austenitic high-alloy chromium-nickel stainless steel 08Х18Н10, also known as AISI 304, which has alloying elements totaling approximately 28% (18% chromium and 10% nickel). This stainless steel is an alloy in which chromium (Cr) with nickel (Ni) and several other elements are added to iron (Fe) and carbon (C) during smelting. Carbon is responsible for hardness and strength, reducing toughness and ductility.

A high carbon content will begin to reduce the cold brittleness threshold and can lead to difficulty welding the metal. Directly in imported stainless steel AISI 304, in contrast to its domestic counterpart, the percentage of carbon is much lower. Chromium in the alloy plays the role of the main “defender” in the fight against corrosion caused by exposure to aggressive environments and various temperatures.

Since, thanks to chromium interacting with oxygen, a thin passive film of chromium (III) oxide Cr2O3 is formed due to the adsorption of oxygen occurring on the surface without destroying the crystal lattice of the original metal. This passive film, uniform in composition and evenly distributed over the entire surface of the metal, contributes to the appearance of stainless properties.

Chromium, interacting with nickel, provides a stable austenitic structure, which contributes to high ductility, hardenability, good stampability and weldability of products. Nickel increases corrosion properties and prevents metal grain growth when heated.

Chromium also increases the heat resistance of nickel, which, in turn, lowers the threshold of cold brittleness, which allows the use of stainless steel 08Х18Н10 in the temperature range from cryogenic -196 °C to high 800 °C. At temperatures above this value, metal oxidation occurs, accompanied by scaling and decarburization of the steel with complete volatilization of the protective passive film.

Speaking about the contact of AISI 304 stainless steel with food, I would like to note the influence of chromium and nickel. The combination of these two components in the alloy increases the corrosion properties and allows the use of products in aggressive environments.

Although each product on store shelves has its own acidity levels, the acidic environment formed during the cooking process when interacting with stainless steel, even under the influence of temperatures during heat treatment of products, becomes insufficiently aggressive to affect or damage the integrity of the protective passive film layer , with which the steel is coated.

And this, in turn, prevents the release of any harmful impurities from the metal that can interact with products. Therefore, steel can come into contact with food without any consequences.

Stainless steel AISI 430 and the meaning of this steel grade

The second and most important grade of stainless steel will be deciphered: AISI 430. The number “4” indicates that the steel belongs to the ferritic class. The other two, as in the previous version, are the serial number in the group. The analogue according to GOST 5632-72 is steel 12Х17. She is “twelve ha seventeen”. The basis of this alloy, again, is iron.

Carbon is allowed no more than 0.12%. The number “12” tells us this. Since there is more carbon stated here than in stainless steel 08Х18Н10, this steel has slightly worse weldability, but at the same time it does not lose its strength properties.

But, again, “twelve” is “twelve”, and in the chemical composition of imported AISI 430 steel the mass fraction of carbon is still less than in the domestic version. Apparently they save on alloying components. Let's continue. Chromium, which is “X”, also known as “ha”, in high-alloy chromium stainless steel of the ferritic class 12X17 is allowed according to GOST from 16 to 18%.

It increases corrosion resistance, in particular, increases resistance to crevice corrosion in neutral and slightly acidic environments, and also increases heat resistance, hardenability and wear resistance.

certificate for stainless steel AISI 430 (12Х17)

Let’s complete the analysis by decoding the AISI 321 grade. Since we have already deciphered the AISI 304 stainless steel grade, we will only add the differences, because we have an analogue according to GOST 5632-72 – steel 08Х18Н10Т.

And it differs from its predecessor in chemical composition by the presence at the end of the designation of the letter “T”, also known as “te”, denoting titanium. And this is still the same austenitic stainless steel.

Titanium, forming hard TiC carbides with carbon, increases creep resistance at high temperatures. Titanium also increases resistance to intergranular corrosion.

certificate for stainless steel AISI 321 (08Х18Н10Т)

This concludes our short excursion. We hope this detailed instruction will help you understand the aspects of deciphering different brands of stainless steel. If you have any questions, please contact us - the StenlisPro company - by phone (812) 320-14-01.

 

• PRICES FOR STAINLESS SHEET
• PRICES FOR STAINLESS STEEL CIRCLES
• PRICES FOR STAINLESS STEEL PIPES

Source: https://generalsteel.ru/marki-nerzhaveyushhix-stalej-i-ix-rasshifrovka/

All about stainless steel

Corrosion-resistant (stainless) steel is a complex alloy steel that is resistant to corrosion in the atmosphere and aggressive environments.

Stainless steel classification

Stainless steels are steels with a chromium content of at least 12%. Chromium creates a protective film on the metal surface, which is very inert, due to which steels become corrosion-resistant and stainless. The great advantage of chrome film is its ability to recover with the participation of oxygen after physical and chemical influences.

Stainless steels are divided into the following main groups:

• austenitic;
• ferritic;
• martensitic;
• ferritic-austenitic.

Austenite is a face-centered and high-temperature variation of iron alloys, a collection of alloying elements that form a solid solution. Steels of this type, in addition to chromium, contain a certain amount of nickel (10-25%), which makes it possible to increase their resistance to corrosion. There are no magnetic properties. High strength, resistance to oxidation and high temperatures make this type of stainless steel the most used in industry. Nomenclature series - 300.

Ferrite is the main component of iron and its alloys; it is a solid solution formed by carbon and alloying elements. The structure of ferrite is a body-centered cubic crystal lattice. Exhibits magnetic properties. Reduced chromium inclusion (less than 17%). High resistance to oxidation in acidic environments. They are widely used in the chemical and food industries. Second in popularity after austenitic steels. Nomenclature series - 400.

Martensite is a microstructure that has an acicular type, which appears in hardened alloys and pure polymorphic metals. The physical mechanism for creating martensite is completely different from similar processes occurring in steel when temperature conditions change.

The martensitic process is diffusionless; atoms move along a shear mechanism at high speeds of thousands of meters per second. Martensitic steels exhibit magnetic properties. Low chromium and carbon content. They have good gas corrosion resistance in slightly aggressive environments.

The basis of application is cutting tools, structural elements in the food and chemical industries. When hardened with nickel and copper, they resist wear well and can be used for industrial equipment.

Areas of use of stainless steel

It should immediately be noted that the use of stainless steel directly depends on its type, or more precisely on its corrosion resistance. It is also important that the corrosion resistance of steels is applicable in certain aggressive environments.

That is, it is necessary to take into account which components of the environment will act on the stainless steel and what type of corrosion it will be predominantly exposed to.

Let's consider options for using stainless steel in various areas of the national economy and industry, taking into account the characteristics of their classes.

Stainless alloys with high resistance to scaling are used in electrical engineering. This stainless steel also has significant electrical resistance. In addition, their use is also beneficial from the economic side - the basis of scale-resistant ones is inexpensive iron. Scale resistance is achieved through additives made of passive metals - chromium, aluminum, silicon. Thus, these elements act as alloying elements.

Heat-resistant stainless steel is used in shipbuilding and for the manufacture of aircraft and missile components. For example, parts of turbines and jet engines are made from such stainless steels.

Ferritic steels are actively used in the food industry. The specific properties of these steels make it possible to satisfy the most stringent demands in this area. Stainless steel sheets with the desired properties are smelted from them. The main restrictions here are due to hygiene requirements. In particular, the use of alloying additives has been significantly reduced. Various instruments for medical purposes and parts for automobiles are also made from such steels.

Stainless steels with a high content of alloying elements are used for pipelines and power generation. Only such stainless steel has the necessary corrosion resistance.

Austenitic stainless steels are widely used. Various equipment for the chemical, food and pulp and paper industries are made from this stainless steel. Pipes and stainless steel circles are used in the machine tool industry and the automotive industry. All kinds of metal structures are produced from it, which are increasingly popular in building architecture.

Mechanical engineering and metallurgy cannot do without stainless steel. Reliability, ease of processing, aesthetics and compatibility with other non-metallic elements allow the use of stainless steel in interior design and other areas of art. People are increasingly aware of the presence of stainless steel in everyday life.

Many household items are partially made of stainless steel.

A large consumer of stainless steel is the transport engineering industry. Huge volumes of cargo transportation with varying environmental aggressiveness require the use of high-alloy steels of the best grades. Stainless steels of this class allow the creation of multi-purpose containers, with the help of which significant savings are achieved in this area.

Stainless steel: properties and applications

Stainless steel is a practical and durable material. This steel appeared about a hundred years ago. However, it began to be widely used in construction and architecture quite recently.

Advantages of stainless steel:

• durability;
• ease of maintenance (requires only periodic cleaning with a soft sponge and detergent);
• attractive appearance. It is ideal for wide application in architecture and design;
• Easy to manufacture: can be formed, cut, welded and processed in the same way as traditional steel;
• corrosion resistance, including in many acids, alkalis and chloride solutions;
• strength. Austenitic and duplex grades do not lose their mechanical properties even at low temperatures;
• hygiene. The unique surface of the alloy has no pores or cracks, which means it ensures cleanliness and prevents the growth of bacteria. Thanks to this, stainless steel is recognized as the most hygienic material for food preparation. It is used in conditions with strict sanitary standards: in hospitals, public kitchens, slaughterhouses, and agricultural processing enterprises. Recently, the use of stainless steel in the manufacture of vessels (containers, holding tanks) for the food industry has been constantly increasing.

The birth and development of stainless steel

The first stainless alloys were produced about a century ago, but stainless steel has only found widespread use in construction today. Stainless steel panels are one of the best materials for external and internal wall cladding. It can be found in the design of retail premises, modern business centers, restaurants, etc. Sculptures and advertising metal structures are made from stainless steel, roofing is laid and drainage communications of buildings are constructed.

Stainless steel has become an indispensable material due to its durability, ease of maintenance, aesthetic appearance and multifunctional use. It can be formed, cut, welded and processed in the same way as regular steel.

Resistance to acids, alkalis, salts and chlorine is used in the chemical industries. Most types of stainless steel have high strength, including at low temperatures. The smooth, non-porous surface of the products meets hygienic standards.

Stainless steel is deservedly called the new generation steel (“Brand of stainless steels”).

In order for steel to serve successfully and for a long time, it is necessary to carefully select the grade of stainless steel. Thus, for the manufacture of prefabricated tanks, we recommend using austenitic corrosion-resistant steel AISI 304 (08Х18Н10), because It is precisely this that corresponds to the “price-quality” formula.

Types of steel surfaces:

We offer for consideration the grades of stainless steel from which Iceberg tanks are made.

AISI 304

Austenitic, low carbon. Easy to weld, resistant to intergranular corrosion. High strength at low temperatures. Can be electropolished. It is the most versatile and widely used of all stainless steel grades. Areas of application: used in installations for the food, chemical, textile, petroleum, pharmaceutical and paper industries.

AISI 316

An improved version of AISI 304 (with the addition of molybdenum), which makes it particularly resistant to corrosion. The technical properties of this steel at high temperatures are much better than those of similar steels that do not contain molybdenum.

Molybdenum (Mo) makes steel more protected from pitting corrosion in chloride environments, sea water and acetic acid vapors.

AISI 316 and 316L are used for chemical equipment, instruments that come into contact with sea water and the atmosphere, in the manufacture of equipment for developing photographic films, in food processing plants, waste oil containers.

AISI 316Ti

The presence of titanium (Ti), five times the carbon content, provides a stabilizing effect on the deposition of chromium carbides (Cr) on the crystal surface. Areas of application: parts with increased resistance to high temperatures and to environments with the presence of new chlorine ions, blades for gas turbines, cylinders, welded structures, manifolds. Also used in the food and chemical industries.

AISI 321

Chromium-nickel steel with titanium (Ti) additive, especially recommended for welded structures and for use at temperatures between 400°C and 800°C. Resistant to corrosion. Areas of application: equipment for the oil refining industry, chemical equipment and equipment resistant to high temperatures. It is also used for the manufacture of welded equipment in various industries (pipes, furnace fittings, heat exchangers).

AISI 430

These are the most widely used ferritic chromium steels. They have good strength and mechanical characteristics, which is ensured by a high chromium content and low carbon content; are well deformed and used in drawing and stamping processes.

Unlike austenitic nickel-containing steels, low-carbon chromium ferritic steels are resistant to corrosion processes in various sulfur-containing environments. Therefore, products made from AISI 430 steel can be used in systems for pumping gas, oil and pure petroleum products.

Structures made from AISI 430 change dimensions less during temperature fluctuations. This type of steel is also used in the food industry.

Source: https://complex1.ru/vsye-o-nerzhaveyushchey-stali/

The metal that makes steel stainless is

About metalsStainless steel

Wikipedia says this:

Steel not subject to corrosion - stainless steel

Corrosion is a process during which metal is destroyed under the negative influence of the environment.

The mechanism of such processes makes it possible to divide them into chemical, electrochemical corrosion, as well as those arising under the influence of electrolytes (acids, alkalis, salts, soil, high humidity, etc.), non-electrolytes (oil) and gases.

The main alloying element contained in stainless steel, which determines its corrosion resistance, is chromium. The more it is contained in a metal, the more resistant it is to harmful influences.

Stainless (corrosion resistant) steels

Corrosion-resistant, or in other words, stainless steels, are metals that are resistant to electrochemical corrosion with a chromium content above 17%. To make steel more resistant to corrosion, elements are introduced into it that form insoluble oxide films on the surface, very dense and closely associated with the base.

They prevent direct contact with the external environment and increase the electrochemical potential of steel in this environment. The condition of its surface plays a significant role in the corrosion resistance of steel.

Corrosion resistance will be much higher if the surface of the material is polished and free of point defects, which are often concentrators of destructive processes. For stainless steel, there is an abbreviation “ICC” - intergranular corrosion.

This concept describes the uneven (grain) structure of the metal, due to which chromium carbides (Cr23C6) can actively form at the grain boundaries during heating. This results in the underlying grain structure being unified by chromium below the 12% threshold.

Most often, this phenomenon is subject to hardenable stainless steels, which have too high a percentage of carbon with a low chromium content (13%). At the same time, the hardenability of steel makes it possible to achieve greater hardness of the material if the percentage of carbon is higher than chromium, however, in this case, ductility is lost.

But such characteristics as hardness and hardening ability may not be the main requirements for stainless steel. In this case, they try to reduce the carbon content to a minimum in order to reduce the tendency of the metal to MCC.

Reducing the likelihood of MCC occurrence is also achieved by introducing strong carbide-forming elements into the material, examples of which are niobium and titanium. In these cases, the formation of carbides such as NbC and TiC is observed, while chromium remains in solid solution, thereby imparting anti-corrosion properties to the steel.

Additional alloying with molybdenum is used to impart even higher anti-corrosion properties and resistance of steel to particularly aggressive environments.

Division of stainless steels into classes

All stainless steels can be divided into three main classes according to their structure: martensitic, ferritic and austenitic stainless steels. There are also related classes of stainless steels, for example, austenitic-ferritic and so on.

Martensitic and ferritic steels differ from austenitic steels in their ability to magnetize. Therefore, using a magnet, you can only determine which of the three classes stainless steel belongs to, but in no case assess its quality.

About alloying elements

Manganese and nickel are the two main alloying elements that determine the austenitic structure of steel. In addition, these elements also influence some of the mechanical properties of the material. Example: steel containing about 18% chromium and 9% nickel has good ductility and can be deep drawn during stamping.

True, the price of nickel has recently increased, and cheaper substitutes are being used instead. Thus, economically alloyed steels appeared with a nickel content of about 4-5% and, as a substitute for expensive nickel, 8-10% manganese. To stabilize the structure of this type of steel, about 2% copper is also added to its composition.

Unlike its more expensive counterpart, sparingly alloyed steel often cracks when deep drawn: this tendency to crack is the main disadvantage of this type of steel. It is worth noting that the appearance of cracks can be detected both during the drawing process and after some time.

But the likelihood of cracking depends primarily on the thickness of the steel - if the sheet is thin, then the likelihood of such problems occurring is much higher than when drawing a thick sheet.

Good weldability is an advantage of austenitic steels. When mechanically polished, such steels obtain an excellent mirror shine. They are well polished using electrochemical and electrolytic plasma polishing: in this case, a higher nickel content gives a better result.

Ferritic stainless steels are primarily a nickel-free material with a high chromium content (up to 23%). Such steels are distinguished by increased rigidity compared to austenitic steels, and at the same time they may not be inferior to them in terms of corrosion resistance. This occurs due to the presence of niobium or titanium in the structure with a reduced percentage of carbon.

Good weldability, deep drawing ability, lower price compared to chromium-nickel austenitic steels are the main advantages of this class. But there is also a noticeable disadvantage: ferritic steel is difficult to mechanically polish.

The martensitic class of stainless steels is represented, for the most part, by nickel-free steels with a low chromium content (about 13%), but with a high carbon content (minimum 0.2%). The main advantage of such steels is excellent hardening ability, but due to Due to insufficient chromium content, such material is prone to MCC. But in the hardened state, the surface hardness of the steel is very high (HRC 45-65). To avoid chromium burnout, as well as carbide formation, martensitic steels are hardened in an inert gas environment. Additional alloying with titanium and molybdenum is often used for such steels in order to increase corrosion resistance and reduce the likelihood of MCC. For the processing of martensitic steels, the method of forging and stamping in a non-hardened state is used. After hardening, mechanical polishing is used. Martensitic steel is unsuitable for polishing using EPP due to the loss of shine and the acquisition of black color in electrolyte solution for chromium-nickel steel.

There are only a few standardization systems for stainless steels worldwide. In the CIS countries (as it was in the USSR) this is the GOST system, in America - AISI, in Europe - EN, separately in Germany - DIN, in Japan - JIS.

Source: https://steelfactoryrus.com/metall-kotoryy-delaet-stal-nerzhaveyuschey-eto/

Stainless steel: application of grades

Stainless steels are iron alloys that contain at least approximately 11% chromium. Chromium is a key alloying element in stainless steels. Chromium content of more than 11% forms a “tenacious” protective film on any fresh surface, which is a protective barrier against corrosion.

Criteria for choosing stainless steel

Selecting the grade of stainless steel to use in a product or structure is usually based on several criteria, including

• fulfillment of functional requirements
• machinability
• price.

Stainless steels have the following fundamental advantages:

• Corrosion resistance and overall high durability. Stainless steels have high corrosion resistance in contact with many types of media, gaseous, liquid and solid.
• High mechanical strength at high temperatures and good strength and ductility at low temperatures. Stainless steels have high strength, ductility and toughness over a wide temperature range, from cryogenic temperatures to 1000 ºС.
• Attractive appearance. Stainless steel is a modern material, one of the main properties of which is maintaining an attractive appearance for a long time.
• Ease of processing: Stainless steel easily lends itself to various types of forming (drawing, stamping, etc.) and connections (welding, gluing, etc.).
• Stainless steel does not change the taste of food. This property of stainless steels is very important in agricultural, food and beverage production.
• Stainless steels are very easy to clean, disinfect and sterilize. They also have high resistance to the reagents that are used for these purposes (for example, high pressure steam for sterilization).
• Low total cost (taking into account the entire life cycle). When considering the cost of supplying the equipment plus the cost of maintaining it over its entire service life, stainless steel is a cost-effective material.
• Scrap recycling. Stainless steel scrap can be recycled 100% to produce stainless steel at the same quality level as the original material [1].

Application of stainless steels

The combination of the above criteria ensures that stainless steels are widely used in the agricultural, food and processing industries, including the production of the following products:

• fruit juices,
• beer,
• chocolate,
• tomatoes,
• cheeses,
• guilt.

Stainless steels are widely used:

• in transport engineering (railway passenger cars and tanks, automobile tanks, refrigerated containers, bus bodies),
• in chemical and petrochemical engineering,
• in the oil industry,
• in the electronics industry (e.g. non-magnetic components),
• in the construction industry (curtain facades, elevator cabins, escalators, roofing, chimneys, street equipment).

This list is by no means exhaustive. Stainless steels are used in a wide variety of everyday items, of which “silver” coins are a good example.

Stainless steel grades

Based on the above criteria, below is a list of applications for the corresponding stainless steel grades. These grades belong to one of five “families” of stainless steels:

• austenitic
• ferritic
• duplex austenitic-ferritic
• martensitic
• heat-resistant austenitic

What are austenitic stainless steels?

These steels are the most popular grades of stainless steel due to their high formability and high corrosion resistance. Due to the presence of alloying elements that stabilize austenite, especially nickel, these stainless steels have a face-centered cubic austenitic structure. These steels are not strengthened by heat treatment, but can increase their strength through cold deformation treatment, that is, cold hardening.

Figure 1 – Austenitic face-centered lattice

Figure 2 – Austenitic stainless steel pump housing

Chemical composition

0.015-0.1% C; 17-20% Cr; 7-25% Ni; 0-4% Mo     

Application

• Milk storage containers
  – X5CrNiMo18-10 / 1.4301
• Containers for storing white wines
  – X2CrNiMo17-12-2 /1.4404
• Beer kegs
  – X5CrNi18-10
• Equipment for catering establishments, hospitals, food storage and preparation – X5CrNi18-10– X2CrNiMo17-12-02

  – X2CrNi18-9

• Kitchen sinks and associated drainage equipment
  – ​​X5CrNi18-10
• Dishwashers: tanks and inner walls
  – X5CrNi18-10
• Kitchen utensils
  – X5CrNi18-10
• Cutlery and plates
  – X5CrNi18-10
• Bus and wagon bodies
  – X5CrNi18-10
• Smoke channels – X5CrNi18-10– X2CrNiMo17-12-2– X1NiCrMoCu25-20-5

  depending on technology (rigid, flexible, single or double wall, condensing or non-condensing, fuel type, etc.)

• Hot water tanks – X2CrNiMo17-12-2

  – X6CrNiMoTi17-12-2

What are ferritic stainless steels?

Ferritic stainless steels have a low carbon content (≤ 0.08%). For this reason, they do not exhibit significant hardening after quenching. The ferrite structure has a body-centered cubic lattice (Figure 3). Ferritic stainless steels are magnetic.

Figure 3 – Ferritic cubic body-centered lattice

Ferritic steels are characterized by reduced toughness in the zone of influence of welding due to significant grain growth during welding.

What are duplex austenitic-ferritic steels?

The microstructure of duplex stainless steels consists of a mixture of austenite and ferrite. These steels exhibit the characteristics of both these phases in strength and ductility. Compared to austenitic steel grades, duplex steels show higher strength and noticeably higher corrosion resistance in chloride solutions.

Most popular brand

X 2 CrNiMo 22-5-3: 0.02% C – 22% Cr – 5.5% Ni – 3% Mo

What are martensitic stainless steels?

Martensitic stainless steels have the highest carbon content (up to 1.2%). Their mechanical properties can be improved by hardening. Martensitic stainless steels are magnetic.

Heat-resistant austenitic stainless steels

These grades of the iron-chrome-nickel system have high strength at elevated temperatures and resistance to carburizing atmospheres. The basic chromium content rises to 20-25%, and the nickel content ranges from 10 to 35%. All grades that are optimized for high temperature applications have a high carbon content.

• Furnace components, heat exchangers: – X12CrNi23-13

  – X8CrNi25-21

• Burners:
  – X12CrNi23-13
• Furnace casings:
  – X15CrNiSi20-12
• Automotive exhaust pipes:
  – X15CrNiSi20-12

Source: https://steel-guide.ru/klassifikaciya/nerzhaveyushhie-stali/marki-nerzhaveyushhej-stali-vybor-i-primenenie.html