Stainless steels
It is impossible to imagine modern life without anti-corrosion steel. The development of such an alloy has made it possible to make a qualitative breakthrough not only in metallurgy, but also in many other areas. Stainless steels differ from classical ones in that in addition to iron and carbon, they also contain chromium. It is the addition of chromium that gives the alloy anti-corrosion properties.
Stainless steel products are very diverse. You can find a wide selection of products from any manufacturer. For example, high-quality products, as confirmed by numerous reviews, can be ordered in the BSM - Metal online store.
Stainless steels
Physical properties
Stainless steel has gained high popularity not only due to its anti-corrosion properties, but also due to its variety of physical properties. Modern corrosion-resistant steels are produced by adding various impurities to the steel.
The physical properties of the finished steel depend on the amount and type of impurity. It should be noted that some grades of stainless steel are susceptible to corrosion after a long period of use. This is due to the composition, that is, the addition of this or that metal. Such an alloy has other advantages that eliminate susceptibility to oxidation.
It is necessary to highlight the main physical properties of stainless steel, which qualitatively distinguish it from a number of other metals. These properties include:
- High strength. Products made from stainless steel are characterized by increased strength in comparison with analogues. Due to its resistance to physical stress, the products are not damaged and do not lose their original shape. High-quality steel remains reliable for more than ten years.
- Resistance to aggressive external environment. Such steel is practically not subject to changes due to environmental conditions. This allows you to maintain the performance properties of the product for a long time.
- Heat resistance. Stainless steel products are resistant to high temperatures, even when exposed to open fire. Also without changing shape, size and properties under significant temperature changes.
- Environmental friendliness. Anti-corrosion properties prevent the oxidation process. In addition, the material does not contain harmful components, therefore it is widely used in the food industry.
- Anti-corrosion properties. The main property that such steel has is that it prevents rust. Moreover, the alloy does not corrode even after exposure to acids or alkalis.
- Appearance. The appearance of stainless steel products is qualitatively different from items made of other materials. Steel has a clean, shiny appearance that does not change after a long period of use.
- Compliance. Such an alloy is easy to process, and making an object of the desired shape from it is not difficult.
The choice of stainless steel with certain physical properties depends on the purpose of its use. Today, a variety of components for the production of stainless steel allows you to create a material with the necessary characteristics.
Chemical composition
The chemical composition of stainless steel depends on the type and grade of the alloy. The main features that characterize stainless steel are the presence of at least 10.5% chromium and low carbon content. Carbon is very important in steel making as it gives the required strength. The percentage component of which in the anti-corrosion alloy should not exceed 1.2%.
Stainless steel may also contain Titanium, Phosphorus, Molybdenum, Sulfur, Nickel and Niobium. Depending on the chemical composition, stainless steel is divided into several types.
The most widely used is stainless steel of group A2. Group A2 contains 10% nickel, 18% chromium and 0.05% carbon. Most of it is occupied by the base, namely iron with accompanying components.
The composition of steels in this group includes 0.05% carbon, 2% molybdenum, 12% nickel and 17% chromium. Due to the presence of molybdenum in the composition, the alloy is resistant to acid, so the name “acid-resistant” is often applied to it.
Anti-corrosion steels of group A, due to their chemical composition, are easy to weld. That is why this type is widely used in industry. From such steel it is possible to produce parts of almost any shape, with a strong connection of the component parts.
Particular attention in production is paid to steel for the food industry. In this case, corrosion-resistant steel should not contain foreign components that can negatively affect the taste of products, as well as impurities hazardous to human health.
The resistance of steel to corrosion depends on the amount of chromium. The larger its component, the more stable the alloy. Classic stainless steel used under normal conditions contains no more than 13% chromium. To withstand an aggressive environment, the proportion of chromium must exceed 17%. This corrosion-resistant alloy is suitable for use in acidic environments.
Highly resistant alloys retain their properties even in nitric acid of 50% saturation. For resistance against stronger acids, the percentage of nickel in the composition is increased and other components are added in small quantities.
Classification of stainless steels
The classification of stainless steels varies among countries, but has common principles. Stainless steel marking is carried out depending on the chemical composition, properties and internal structure of the finished material. Based on this, steel is divided into the following types:
- Ferritic. This group of steels is characterized by a high chromium content, usually more than 20%. Therefore, this type is sometimes called chromium. This chemical composition contributes to high resistance to aggressive external environments. Alloys of this group have magnetic properties. Ferritic steels are relatively cheap and are widely used in industry, second only to austenitic steels.
- Austenitic. A group of anti-corrosion alloys that are characterized by a high content of chromium and nickel. Due to this, they are distinguished by increased strength and flexibility in comparison with analogues. Also easy to weld and resistant to corrosion. Most widely used in industry. They belong to non-magnetic metals.
- Martensitic. A special type of stainless alloy. It is characterized by increased strength and wear resistance. They are not exposed to high temperatures, and at the same time contain a minimal part of harmful components that do not emit vapors during intense heating. This group includes heat-resistant, corrosion-resistant steel.
- Combined. A special type of steel that combines the properties of the above groups. Such innovative steels are developed individually depending on the properties required by the customer. Today, austenitic-ferritic and austenitic-martensitic steels are distinguished.
Stainless steel parts
In turn, grades of stainless steel of the austenitic group are divided into 4 types:
- A1 is steel that contains a significant amount of sulfur, which is why it is more susceptible to corrosion than others.
- A2 is the most widely used grade. Easily weldable without loss of physical properties. Frost-resistant, but susceptible to corrosion in an aggressive acidic environment.
- A3 is a derivative of A2, but with the addition of stabilizing components. It is characterized by increased resistance to high temperatures and acidic environments.
- A4 – alloy with the addition of molybdenum (up to 3%). Characterized by resistance to acidic environments. Widely used in shipbuilding.
- A5 – similar to the A4 brand. It differs only in the ratio of stabilizing components. Manufactured for increased resistance to high temperatures.
Types of stainless steel are not limited to the above types. Since even the slightest changes in the percentage of components can significantly affect the properties of steel.
Scope of application of stainless steels
Since their development, corrosion-resistant steels have been used only in high-tech production in such areas as aircraft manufacturing, nuclear energy, petrochemical production and mechanical engineering. Today, stainless steels are widely used in various areas of our lives.
Stainless steel car detail
Let us highlight the main areas of use of stainless alloys:
- Mechanical engineering. Stainless steel is widely used for the production of cars, industrial machines and various units. Ferritic and austenitic types are commonly used.
- Chemical industry. The chemical industry is accompanied by the use of aggressive substances, the maintenance of which requires special equipment. Austenitic alloys are used for its production. Production tanks, pipes and vessels are not exposed to chemicals and do not lose their performance properties.
- Energy. In the electrical power industry, only high-strength materials are used, since the strength and reliability of working units are of particular importance.
- Pulp and paper industry. Almost all equipment in this area is made of high-quality stainless steel.
- Food industry. There are increased requirements for the production, storage and transportation of food products. Therefore, in the manufacture of equipment, you can only use glass, several types of plastic and stainless steel. This ensures an increased level of hygiene.
In the food industry, an alloy containing a small number of components is usually used, since the equipment is not exposed to ultra-high temperatures and aggressive substances. Frost-resistant materials are used for refrigeration units.
- Aerospace sector. Special types of stainless steel began to be used to build airplanes, rockets and spaceships.
- Construction. Stainless steel is widely used in construction and design. Such sheets are scratch-resistant and do not leave hand marks.
Corrosion-resistant steels are also used in many fields, due to the variety of types and properties.
Source: https://stankiexpert.ru/spravochnik/materialovedenie/nerzhaveyushhie-stali.html
Selecting Stainless Steel | Guide to choosing corrosion-resistant steel
The high demand for stainless steels is explained by their special properties, which standard carbon alloys lack. A huge variety of types of corrosion-resistant steel allows you to select the metal to successfully perform a wide variety of technological tasks.
Corrosion-resistant steels include metal alloys that are highly resistant to corrosion processes in different atmospheric and climatic conditions, water, aggressive gas and chemical environments. Anti-corrosion properties are ensured by enriching carbon steel with special elements, the most important of which is chromium. Its minimum content in the structure of alloys is 10.5%.
Currently there are about 250 brands of stainless steel. The most used alloying elements are nickel, cobalt, titanium, molybdenum, niobium. Carbon, which is necessarily included in the composition, gives the finished products the necessary strength and hardness. Changing the proportions of chemical elements produces a metal with different properties, intended for specific areas of use.
Characteristics of stainless steels and their areas of application
All types of stainless steel compounds can be divided into several groups. Each combines materials with specific chemical properties and internal structure.
- Austenitic (highly alloyed chromium-nickel metals, marking A)
- Ferritic (chromium, marking F)
- Martensitic (carbon, marking C)
- Combined
One of the most common and sought after types. The high content of nickel and chromium (up to 33%) provides exceptional corrosion resistance and unsurpassed strength to the products. An important advantage is manufacturability. The material welds well, is more viscous and plastic than ferrite, and is not magnetic. Austenitic grades include: 04Х18Н10, 12Х18Н10Т, 12Х18Н9Т, 12Х18Н9, 08Х18Н10, AISI 304, AISI 316, etc.
The scope of their use is wide.
Austenitic types of alloys are used as a structural material from which products are made by cold stamping and welding. These can be various containers, casing, pipelines, equipment for food processing and storage, pharmaceutical, medical, laboratory equipment, parts for the mechanical engineering, automotive, aircraft industries, technological units for the chemical industry.
Brands: 15Х28, 08Х18Т, etc. This group of metals has a high chromium content (up to 20%). It ensures product resistance to extremely aggressive chemical environments and high magnetic properties.
Anti-corrosion resistance is lower than that of metals of the austenitic group, therefore ferritic types are used in those areas where the requirements for this parameter are not so significant.
The main consumers of chromium ferritic steels are manufacturing enterprises in the chemical industry, heavy engineering, and the energy sector.
They are used for the production of equipment and parts operating in acidic and alkaline solutions, household instrument making, and the food industry.
Grades: 20Х13, 40Х13, 30Х13, etc.
Due to the high carbon content, these are the most durable alloys among stainless steel. Metal products of this group are extremely wear-resistant, work well at high temperatures, but are more susceptible to corrosion processes.
This type of metal can be subject to thermal hardening; this type includes corrosion-resistant, heat-resistant steel, which successfully resists oxidation and is suitable for use at high temperatures.
Metal products retain their original properties even under constant thermal influence; the material is characterized by a minimal content of harmful impurities.
Examples of grades: 08Х22Н6Т, 12Х21Н5Т, etc.
Combined grades can have an austenitic-martensitic or austenitic-ferritic structure and organically combine the positive properties of alloys of these types.
Main grades of stainless steels
To better understand the composition and basic properties of stainless alloys, it is important to know the principle of their marking. The principle of decoding the brand is as follows:
- the first numerical indicator indicates the amount of carbon in hundredths of a percent;
- the designations X - chromium, M - molybdenum, H - nickel show the content of these elements, calculated as a percentage.
Most popular brands:
GOST 20Х13 (AISI 420, DIN 1.4021) – stainless steel with a martensitic structure, cannot be welded, is not prone to temper brittleness, and does not form internal defects during the production process. Used for the manufacture of measuring and cutting tools, springs, leaf springs.
GOST 12Х17 (AISI 430, DIN 1.4016) – ferritic stainless steel heat-resistant grade, does not contain nickel. Characterized by good anti-corrosion resistance in moderately aggressive chemical environments and high temperatures.
GOST 12Х18Н9 (AISI 304, DIN 1.4301) is a heat-resistant, corrosion-resistant alloy used in welded structures in contact with aggressive media. It is used for sheet parts, welded equipment, heat exchangers, pressure devices.
GOST 08Х18H10 (AISI 304H, DIN 1.4948) is an austenitic type of heat-resistant, corrosion-resistant alloy, used for the production of rolled pipes, components and assemblies for the chemical and engineering industries, heat exchangers, and industrial tanks.
GOST 03Х18H11 (AISI 304L, DIN 1.4306) - chromium-nickel grade is used for the production of equipment, tanks and pipelines for the chemical industry, in the production of nitric acid and other aggressive substances.
GOST 08Х18H10Т (AISI 321, DIN 1.4541) is a stainless, heat-resistant and heat-resistant alloy, non-magnetic, resistant to oxidation and has good weldability without preheating. It is used as food and technical stainless steel for the production of rolled sheets and pipes, welded equipment, the manufacture of containers, tanks, tanks and equipment in the chemical and oil and gas industries.
GOST 03Х17H14М2, 03Х17H14М3, (AISI 316, 316S, 316L) - non-hardening austenitic grade, areas of application - welded parts, equipment for the pulp and paper and chemical industries, boiler bodies, tanks and installations for the coal industry.
GOST 08Х17H13М2Т (AISI 316Ti, DIN 1.4571) – structural heat-resistant heat-resistant stainless alloy is used for fasteners and welded structures in various industries.
GOST 20Х23H18 (AISI 310S, DIN 1.4845) – heat-resistant and heat-resistant austenitic stainless steel used for the manufacture of forgings, clamps, combustion chambers, fasteners and elements of boilers, used pipes, couplings.
When choosing stainless steel, you should take into account the operating conditions of the metal, the expected load, and the necessary additional properties of the product. If you are in doubt about how to choose the right stainless steel, it is better to contact a specialist. Leave a request on the website, and our managers will give recommendations on selecting the optimal grades of stainless alloys for the given operating conditions.
Source: https://indust.by/info/articles/metalloprokat/oblasti-primeneniya-nerzhaveyushchey-stali/
Stainless steel for knives: pros and cons, types and properties
The choice of brand and metal alloy is key in the production of knives. The quality of the product, its resistance to wear and mechanical damage, maintaining the sharpness of the blade, etc. depend on it.
Stainless steel for knives is increasingly being chosen as the main material and the reason for this is its special operational and technical characteristics.
To understand the relevance of such a choice, it is necessary to analyze all the pros and cons of choosing a material, first find out their varieties and key properties.
History of the creation of stainless steel
The first mention of stainless steel dates back to 1915. A British company from Sheffield announced the creation of a unique alloy that is resistant to corrosion, has an excellent appearance and is resistant to abrasion. According to the creators, it was an excellent material for cutlery, including cutting ones.
Naturally, the controversy regarding the stainless steel patent attracted a lot of attention because, in fact, the ancestor of the alloy was the classic high-carbon steel used throughout the world.
Despite this, the metal, in fact, has improved technical characteristics and has nothing in common with the production of a high-carbon alloy.
More than a hundred years have passed since the creation of the material and it is no longer considered an invention for cutlery, and stainless steel for knives is used to create piercing and cutting objects not only in the kitchen.
Advantages, disadvantages and main competitors of stainless steel
Stainless steel has been used in the production of cutting tools for over a hundred years. During this time, no direct analogues of the product were invented that would differ in similar technical parameters or price, so knives still have three main competitors:
- Knives made of ferrous metal alloys. They are susceptible to corrosion, even taking into account external coating, the durability of such products is questionable, while a stainless steel knife oxidizes tens of times slower.
- Ceramic. They have a couple of critical disadvantages: difficulty in maintenance and the inability to chop and cut dense or hard materials. Stainless steel does not have such disadvantages.
- Cutting tools made of high carbon materials. The key to the production of such metals remains the addition of certain components. It is worth noting that there is now a wide range of stainless steel materials on the market, with the addition of high-carbon components, so comparison with analogues is not required here.
Classic 3 mm stainless steel used in production (cutting, forging or peening) has a number of physical properties that are significantly superior to analogues. The advantages of stainless steel products include:
- ease of maintenance;
- low cost of production;
- possibility of using various alloys and steel grades;
- elasticity of the material;
- lifetime;
- resistance to natural and chemical oxidizing agents.
It is these parameters that remain key in choosing a knife based on stainless steel. Despite the very impressive technical indicators, various alloys of stainless metals also have disadvantages:
- lack of usual shine,
- insufficient elasticity
- immunity to sudden temperature changes.
In fact, a lot depends on the type of stainless steel chosen in the product.
Types of stainless steel
Depending on the production method and the proportion of material used, stainless steel differs in a number of characteristics. Almost all known and popular stainless steel alloys are used to create knives, but the key here remains the method of operation, size and load level. It is foolish to say that a kitchen knife and a hunting cleaver have an identical load. That is why alloys of different characteristics and grain sizes are used in their production.
In most cases, it is the grain size that indicates the type of metal. Steelworkers, blacksmiths and cutting tool professionals can identify the type of stainless steel by its appearance, but for the average user, the production method and type of stainless steel remain a mystery.
https://www.youtube.com/watch?v=GvK6G-Pc1Go
In total, we can distinguish several main types of steel, which differ in the method of creation and processing, performance characteristics and appearance:
Ferritic
One of the cheapest types of alloy, which includes chromium (up to 30% content) and low-carbon (no more than 0.1% content) compositions. Ease of processing and good performance properties make it an excellent choice for the production of static elements.
Among the advantages: average metal strength, ductility and average density. For such a material, the destructive indicator is a temperature difference, which eliminates the possibility of hardening.
Ferritic alloy is rarely used to make knives, but can be found in inexpensive kitchen sets.
Austenitic or chromium-nickel
The complexity of the composition determines a special approach to production. Excellent resistance to corrosion and minor damage due to the content of nickel (from 6 to 12% of the composition), carbon, chromium (from 16 to 26% of the composition) and molybdenum.
Heat treatment significantly reduces the strength of the alloy, but cold hardening allows it to be increased. The complexity of metal processing makes it a rare basis for creating cutting tools.
In most cases, it is used in the production of high-quality and expensive knives that are designed for a long service life.
Ferritic-austenitic or two-phase
Like any two-phase alloys, ferritic-austenitic stainless steel has average indicators of the metals displayed in its name, so there is no point in analyzing them in detail. Cutting tools cannot be made on its basis, so you should beware of knives with such an alloy.
Martensitic
One of the very popular alloys in the world, containing chromium steel (no more than 17% in the composition) and carbon (no more than 1% in the composition).
Martensitic stainless steel is highly susceptible to forging, hardening and tempering, making it the best possible choice for knife production, particularly due to its price-quality ratio.
Thanks to hardening, the metal is quite dense and hard, which is considered a critical technical indicator, but the low chromium content in it negatively affects its resistance to corrosion.
In general, this is general information that may be important when choosing an alloy, but the question of what is the best stainless steel for a knife remains open. If you delve deeper, you should not touch on the alloy as such, but specifically on the grade of stainless steel, so that the answer to the question is not so vague. There are hundreds of grades of stainless steel, each of which has certain technical characteristics, which makes it almost impossible for the average user to study the issue in detail.
Choosing a stainless steel brand
As already mentioned, a large number of steel grades does not make it possible to fully consider the advantages and disadvantages of each. As an example, let's look at several options for stainless steel, which is common in use.
Stainless steel AISI 304
The “premium” segment includes AISI 304 stainless steel, which is widely used in chemical and food production. This grade of steel has improved corrosion resistance, which allows it to be used in the production of cutting, pocket and kitchen knives without fear of oxidation.
Austenitic alloy with a high content of chromium and nickel and unique resistance to short-term temperature changes, the ability to withstand temperatures up to 900 C0.
AISI stainless steel holds hardening well, but in terms of resistance to mechanical damage (cutting bones, wood, frozen foods) it is significantly inferior to the next contender for the title of best brand.
Stainless steel 12x18n10t
Austenitic stainless steel alloy 12x18n10t, which is used mainly in areas of increased environmental exposure.
More often, this steel is used in the production of building materials placed outdoors, but the presence of carbide-forming titanium in the composition has also found application in the chemical, food and oil industries.
Vague GOST indicators play a cruel joke on the consumer, which makes it possible to create second-rate metal by slightly varying the volume of components. Stainless steel of this brand is very expensive, so products based on it will not cost the buyer cheap, although its service life is, without exaggeration, long.
Stainless steel 1.4034 (X46 Cr13)
A knife made of stainless steel grade 1.4034 (X46 Cr13) is an excellent indicator of the high quality and strength represented by a martensitic alloy. An excellent indicator of strength, wear resistance and anti-corrosion effect, but the elasticity of the metal is relatively low, which makes this brand of stainless steel a good option only for kitchen or cutlery cutting utensils.
Summarize
When choosing a knife (regardless of its size, shape or purpose), the key indicator of quality remains the material of the spine and blade.
In fact, when choosing stainless steel as a base, the consumer receives an excellent and durable tool that is easy to use and has a number of unique technical parameters.
Stainless steel for knives is an excellent choice and you can understand this if you evaluate all the advantages and disadvantages of the material, as well as analyze in detail the key types and properties of alloys.
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Source: https://kavkazsuvenir.ru/blog/nerzhaveyuschaya-stal-dlya-nozhej
Nickel-free corrosion-resistant steel grades
Inexpensive corrosion-resistant nickel-free chromium steel grades AISI 409 and 430 (400 series) are among the most in demand on the rolled metal market today.
According to the ASTM A240 standard, nickel-free chromium steel grades AISI 409 and 430 (AISI 400 series) are classified as general use and can be adapted to various operating conditions in any industry. In addition, this is the optimal choice of material for solving a whole range of technical problems.
The mechanical properties of rolled sheets of various stainless steels in accordance with ASTM A240 and A 176-99 standards are given in Table. 1.
It should be noted that the actual values of the tensile strength, yield strength and relative elongation of rolled sheets made of steels 409, 430 and 439 significantly exceed the values regulated by the A240 standard (B = 500-550 MPa; 0.2 = 250-350 MPa; 5 = 25- thirty%).
Mechanical properties of rolled sheets according to ASTM A240 standard
table1
Steel grade, its approximate Russian analogue and class Strength, MPa (min., except grade 420) Yield strength (0.2%), MPa (min.) Elongation, % (min) Hardness HB (max) 304 (08Х18Н10) , austenitic 316, (03Х17Н14М2), austenitic 321 (08Х18Н10Т), austenitic 409 (~08Х13), ferritic 420 (20-40Х13), martensitic* 430 (08Х17), ferritic 439 (08Х17Т), ferritic| 515 | 205 | 40 | 201 |
| 515 | 205 | 40 | 217 |
| 515 | 205 | 40 | 217 |
| 380 | 205 | 22 | 179 |
| max.690 | 217 | ||
| 450 | 205 | 22 | 183 |
| 415 | 205 | 22 | 183 |
*) Martensitic stainless steel (analogous to domestic steels 20-40Х13), which is strengthened by heat treatment and has high wear resistance.
This steel has good ductility (as supplied), high impact strength, good corrosion resistance and heat resistance. In the annealed (softened) delivery state, the steel structure is a mixture of ferrite and carbide phases. When heated to a temperature of 1000-1060 ° C and subsequent quenching (in air or in oil), martensite is formed, the hardness of which is directly proportional to the carbon content.
The resulting chromium carbides further dispersely strengthen the steel structure, increasing its hardness (up to 55 HRC) and wear resistance after quenching and tempering.
400 series steels retain fairly high mechanical properties at elevated operating temperatures, ensuring the structural strength of the equipment.
If stainless steel structures are operated for a long time at high temperatures, then temperature-time factors that can negatively affect the strength characteristics should be taken into account.
For example, domestic nickel-containing stainless steels and steels of the 300 series (with the exception of grades 321 and 347), in contrast to steels of the AISI 400 series, when operated for just a few hours in the temperature range of 450-750 ° C, can be susceptible to a very dangerous type of corrosion destruction - intergranular corrosion (ICC). And chromium ferritic steels of the 400 series are not prone to high-temperature MCC at temperatures up to 1000 °C.
One of the main reasons for the destruction of stainless steel structures is often corrosion caused by the electrochemical heterogeneity of the heat-affected zones of welds and the base metal. Therefore, reducing the carbon content in steels is an important factor in preventing crevice and knife corrosion in welded joints.
The low carbon content in ferritic steels of the AISI 400 series (actually up to 0.03%) and the low value of strain hardening compared to nickel-containing steels determine not only high resistance to MCC, but also the ability to weld well and be relatively easy to machine mechanically without the hardening inherent in austenitic steels. steels.
Sometimes, during high-temperature heating, the time factor can affect the strength properties of chromium stainless steels.
430 steel, containing 16-18% chromium, can lose strength properties when cooled, but only after very long continuous operation (more than 100 hours) in the temperature range of 425-530 ° C due to the so-called 475-degree embrittlement.
Chromium-sparing 409 steel is not susceptible to this type of failure and is therefore preferred for use in structures subject to such very long periods of heat (for example, continuous cycle convection ovens operating in the temperature range up to 500°C).
Technological properties of various groups of steels are given in table. 2.
Technological properties of steels of the 300th and 400th series
Mechanical processing (milling, turning) Satisfactory GoodHardening by heat treatment Not hardened Not hardenedDrawing Excellent ExcellentPerforation Satisfactory GoodGuillotine cutting Satisfactory GoodSheet separation stamping Satisfactory GoodStamping Good GoodGrinding Satisfactory Satisfactory
Weldability Excellent Excellent*
*) When using austenitic filler materials that provide high strength properties and increased ductility of the weld.
Chromium stainless steel, compared to nickel-containing austenitic stainless steel, has a low coefficient of thermal expansion (CTE) and increased thermal conductivity. This predetermines its predominant use (including rolled pipe) in various heat exchange structures.
Welded structures and pipelines made of chromium steels change dimensions significantly less during temperature fluctuations, which reduces destructive fatigue loads due to temperature changes and prevents possible leaks from hydraulic connections.
In addition, having a relatively low thermal inertia (specific heat capacity), structural elements made of ferritic chromium steels warm up faster (and, accordingly, cool down) with lower energy consumption. This allows you to avoid possible inertial overheating, which is very important for a wide range of food industries.
These steels can withstand high peak temperature loads (up to 950°C) and can be continuously operated at temperatures up to at least 700°C.
The physical properties of various groups of steels are given in table. 3.
Physical properties of stainless steels
table3
Steel grade Density, kg/m3 Modulus of elasticity, Gpa Coefficient of thermal expansion, x10/6/°C Thermal conductivity at 100°C, W/m Specific heat capacity (0 - 100°C), J/kg K304 316 321 409 430| 7900 | 193 | 17,2 | 17,8 | 18,4 | 16,2 | 500 |
| 7950 | 193 | 15,9 | 16,2 | 17,5 | 16,2 | 500 |
| 7900 | 193 | 16,6 | 17,2 | 18,6 | 16,1 | 500 |
| 7680 | 200 | 11,7 | 12 | 12,4 | 24,9 | 460 |
| 7750 | 200 | 10,4 | 11 | 11,4 | 26,1 | 460 |
Food and processing industries
Chromium stainless steels, which have high corrosion resistance in many food environments, can be used for the manufacture of technological equipment used at various stages of food production (washing or hygienic processing of raw materials, products and equipment, grinding, separating and sorting products, mixing, heat treatment, packaging and packing, transportation, etc.). According to the conclusion of the All-Russian Scientific Research Institute of Steel Corrosion, the AISI 400 series, in accordance with GOST 13819, are “very resistant” or “resistant” in boiling drinking water, superheated water steam, cheese grains, boiling vegetable and animal fat, meat products, wine, ethyl alcohol, beer, beer wort, etc. These steels can be used, for example, for the manufacture of malthouse equipment (malt preparation, malting, tanks for washing and soaking barley for malting, dryers for green malt, malt cleaning equipment, sprouting machines, devices for removing sprouts and dust, etc.). P.).
Source: http://razvitie-pu.ru/?page_id=4387
Categories and technical specifications
The constant increase in the use of stainless steel in many industries is due to its unique characteristics:
- high corrosion resistance,
- high strength,
- good weldability,
- excellent processability by cold stamping.
There are five main categories of stainless steel based on their microstructure: Austenitic, Ferritic, Duplex, Martensitic, Heat Resistant.
Austenitic is non-magnetic and contains nickel in addition to chromium, which increases corrosion resistance. Austenitic stainless steels are the most widely used group of stainless steels. With increased chromium content up to 20% - 25% and nickel up to 10% - 20%, austenitic stainless steels better resist oxidation at high temperatures and can be used for the manufacture of furnace elements exposed to high temperature heating.
- Ferritic - magnetic, have a low carbon content and chromium as the main element, usually at the level of 13% - 17%.
- Duplex stainless steels have a mixed, ferritic-austenitic structure. chromium varies from 18% to 28%, and nickel from 4.5% to 8%. Duplex varieties find their use in aggressive chlorine-containing environments,
- Martensitic grades are magnetic and typically contain 12% chromium and medium carbon content. They are hardened by quenching and tempering like simple carbon steels, and are therefore used mainly in the manufacture of cutlery, cutting tools and general mechanical engineering.
- Heat-resistant steels have a chromium content of typically 17% with the addition of nickel, copper and niobium. Because these steels can be hardened and resist aging well, they are ideal for mine pumps, valve spindles and aerospace applications.
- Austenitic and ferritic grades account for approximately 95% of stainless steels used. Of the ferrite grades, the most widely used is grade 430, the so-called. “nickel-free” stainless steel. They have good strength and mechanical characteristics, which is ensured by a high chromium content and low carbon content, and low cost compared to chromium-nickel stainless steels.
Among austenitic grades, grade 304 is widely used, which is the most versatile and widely used of all grades of stainless steels. It is also designated 18-10 (food grade).
In recent years, steels of the 300 series are gradually losing ground to the more cost-effective austenitic steels of the 200 series, in which expensive nickel is partially replaced by manganese and nitrogen.
These grades of stainless steels are actively produced and offered in the market by Indian enterprises. After all, they are given primacy in the development of these brands.
The mechanical properties of stainless steels make it possible to reduce the thickness of the materials used, thus reducing material consumption without reducing strength characteristics. Austenitic and Duplex grades do not lose strength even at low temperatures, and allow the use of smaller thicknesses compared to carbon steels, achieving significant savings.
Sheets offered on the market can have the following types of surfaces:
- matte;
- frosted mirror;
- mirror;
- polished;
- fine grinding;
- covering with a protective film.
The use of stainless steels in household appliances
The uniqueness of the stainless steel surface is its density; it has no pores or microcracks for the penetration of dirt or bacteria. Ease of care and cleaning, its environmental neutrality and resistance to aggressive substances compared to other materials make it indispensable for the manufacture of household stoves and other kitchen appliances. An important factor is a good and smooth (without kinks, irregularities or scratches) metal surface.
Strict restrictions on the solubility of heavy metals present in food contact equipment are already in place and will certainly be tightened in the future.
According to European standards, the amount of chromium and nickel dissolved from steel during the standard test according to ISO 6486/1 is allowed no more than 2 mg/dm2. For austenitic steels, the amount of dissolved nickel and chromium is less than 0.02 mg/dm2, i.e.
about 1% of the permissible value.
The following grades are classified as food grade corrosion-resistant steels:
| Steel grade according to GOST 5632-72 | Analogous to ASTM A240/A 240M-05a |
| 08Х18H10 | 304 |
| 08Х18Н10Т | 321 |
| 12Х18Н10Э (T) | 303 |
Steel tarnish colors
Iron alloys, including corrosion-resistant ones, when heated, become covered with a thin film of iron oxides of a wide variety of color shades and tarnish colors appear, which correlate with certain heating temperatures. There are so-called “heat-resistant” alloys, in which the temperature at which oxides begin to form is higher than that of other alloys, but such grades are not food grade and are very expensive due to their high nickel content.
For carbon steel
| Heating temperature | Tarnish color |
| 220 | light yellow |
| 240 | dark yellow |
| 255 | brown-yellow |
| 265 | brown-red |
| 275 | purple-red |
| 285 | violet |
| 295 | cornflower blue |
| 315 | light blue |
| 330 | grey |
For stainless steels
| Temperature | 12Х18Н9Т | ХН75МБТУ |
| 300 | light straw | — |
| 400 | straw | light yellow |
| 500 | reddish brown | yellow |
| 600 | violet blue | brown |
| 650 | blue | blue |
| 750 | — | blue |
Most importantly, the duration of heating has a significant impact on the color of the surface. Indeed, more or less prolonged processing can cause steel to turn blue at a temperature lower than that required for the appearance of even a straw-yellow color.
Stainless steel manufacturing plants
At the moment, there are actually three sources of supply for consumers and sellers of stainless steel products: Russian-made corrosion-resistant steel, high-quality metal from European and South American manufacturers, and rolled products from India and Southeast Asia.
Due to the instability of nickel prices, manufacturers are currently refocusing on steel grades other than the 300 series. For China, these are primarily ferritic steels that do not contain nickel at all; for India and commercial enterprises in China - the 200th series with a reduced nickel content and additional additives that reduce the hardness of the alloy and increase its corrosion-resistant properties.
Currently, the market is unevenly divided between steel series. The most expensive 300 series is traditionally used most widely (brands such as AISI 304, AISI 316, AISI 321, AISI 310 S, AISI 309 S and others), the use of the 200 series, which is unfamiliar to domestic manufacturers, is most limited.
In recent years, as a result of research and experimentation, steel grades of this series have undergone significant changes in the chemistry and technological rolling process and currently deserve closer attention. Steel 200 groups are cheaper than AISI 304 by approximately 16-17%. AISI 430 (nickel-free) steel is even cheaper - about 50% compared to AISI 304. With rising nickel prices, this difference may increase even more.
However, the use of this grade of steel is still controversial in relation to food products and medical technology.
Manufacturing plants in Russia
- Chelyabinsk Metallurgical Plant",
- Volgograd Metallurgical Plant "Red October"
- Izhora factories
Manufacturing plants in Europe
- Acerinox, SA Spain,
- Marcegaglia SpA, Italy,
- Arcelor Stainless Int. France,
- Outokumpu Stainless, Finland,
- ThyssenKrupp, Germany.
Southeast Asia
- Jindal Stainless, India,
- Zhejiang Baocheng Stainless Steel Manufacture Co., Ltd. China,
- Jiangsu Xi'erfa Group Co., Ltd. China,
- YUSCO(Yieh United Steel Corp.) Taiwan,
- NISCO (Taiyuan Iron & Steel Group) Company Ltd, China
Source: https://engitime.ru/metallicheske-materiali/nerzhaveyushhie-stali.html
Stainless steel grades and their characteristics
Stainless steel is a type of alloy steel that is resistant to corrosion due to its chromium content of 12% or more. In the presence of oxygen, chromium oxide is formed, which creates an inert film on the surface of the steel, protecting the entire product from adverse influences. The modern market can offer various grades of stainless steel for use in a wide variety of industries.
Not every grade of stainless steel demonstrates the resistance of chromium oxide film to mechanical and chemical damage. Although the film recovers when exposed to oxygen, special grades of stainless steel have been developed for use in aggressive environments.
Popular steel grades
Russia has a developed steel industry and has its own designations for steel grades, but the most popular grades have foreign analogues.
These are steels of the so-called 300 and 400 series, which are distinguished by high characteristics of corrosion resistance, resistance to aggressive environments, ductility and strength.
They are practically universal and are used for the production of a wide variety of products - from medical instruments to large building structures. The 200 series is gradually catching up with them in popularity due to its favorable price-quality ratio.
Types of steel 300 series
Chromium-nickel stainless steel of this group in its chemical composition is austenitic, austenitic-ferritic and austenitic-martensitic, depending on the percentage of carbon, nickel, chromium and titanium. This is the most versatile stainless steel, the properties of which ensure its consistently high demand in the market.
AISI 304 (08Х18Н10)
In demand in all industries, this stainless steel, however, has gained fame as “food grade”. Its chemical composition and properties make it most suitable for use in the food industry. It is easy to weld and shows high corrosion resistance characteristics in aggressive environments. It is also often chosen for the chemical, pharmaceutical, petroleum and textile industries.
AISI 316 (10Х17Н13М2)
316 stainless steel is obtained by adding molybdenum to 304 stainless steel, which further increases corrosion resistance and the ability to maintain properties in aggressive acidic environments, as well as at high temperatures. This stainless steel is more expensive than 304 and is used in the chemical, oil and gas, and shipbuilding industries.
AISI 316T (10Х17Н13М2Т)
This grade of stainless steel contains a small amount of titanium, which increases the strength of the material, making it resistant to high temperatures, as well as chlorine ions. Used in welded structures, for the manufacture of gas turbine blades, in the food and chemical industries. Affordable price and high technical characteristics make this stainless steel very popular.
AISI 321 (12-08Х18Н10Т)
Stainless steel, the characteristics of which are determined by the increased titanium content. Easily weldable, resistant to temperatures up to 800 o C. Widely in demand for the manufacture of seamless pipes, as well as pipeline fittings - flanges, tees, bends and reducers.
Types of steel 400 series
This series has a narrower range than the 300th. This includes stainless steel with a high chromium content; it contains almost no other alloying elements, which has a positive effect on its cost. The low carbon content makes these stainless steels ductile and easy to weld.
AISI 430 (12Х17)
This is stainless steel with a high percentage of chromium and low carbon. This ratio contributes to high strength and at the same time ductility. AISI 430 bends, welds and stamps well. Retains its properties in corrosive and sulfur-containing environments, and is resistant to sudden temperature changes. It is used in the oil and gas industry, as well as as a decorative material for finishing buildings and premises.
Types of steel 200 series
So far we can only talk about one grade of steel in this series, but it is successfully catching up with its competitors in the 300 and 400 series.
AISI 201 (12X15G9ND)
AISI 201 stainless steel is much cheaper than stainless steel of other series with similar properties. In it, expensive nickel is partially replaced by manganese and nitrogen. The advantageously balanced chemical composition makes the characteristics of AISI 201 stainless steel not inferior to AISI 304 and AISI 321. It has found its application in the medical and food industries. It is also used in the manufacture of round and profile pipes, which are required to create railings, handrails and fences.
Source: https://www.kp.ru/guide/marki-nerzhavejushchei-stali.html
Corrosion resistant steel - what is it?
Popular brands of stainless steel of domestic and foreign production.
AISI 304 is the most common and popular steel grade. It is characterized by high strength, elasticity, resistance to oxidation, and is easy to weld.
AISI 316 and 316Ti steel is an improved version of AISI 304,
with increased anti-corrosion resistance and resistance to aggressive environments.
AISI 430 is an economical option for corrosion-resistant material, ideal for stamping, deformation and perforation.
Stainless steel is a type of alloy steel that is resistant to corrosion due to its chromium content of 12% or more. In the presence of oxygen, chromium oxide is formed, which creates an inert film on the surface of the steel, protecting the entire product from adverse influences. The modern market can offer various grades of stainless steel for use in a wide variety of industries.
Not every grade of stainless steel demonstrates the resistance of chromium oxide film to mechanical and chemical damage. Although the film recovers when exposed to oxygen, special grades of stainless steel have been developed for use in aggressive environments.
Sales of stainless steel throughout Russia and the CIS
The MetPromStar company sells stainless steel of all grades, equipped with quality certificates and meeting international standards.
Flexible pricing and a wide selection of rolled steel attract both large enterprises and small private companies as clients. MetPromStar consultants are ready to answer all questions regarding any brand of stainless steel.
Delivery is carried out throughout Russia and the CIS countries. It is possible to individually manufacture stainless steel products according to customer sketches.
As you can see, among the wide range of stainless steel types, an acceptable compromise can always be found (except in special cases). Certain grades of stainless steel are interchangeable within certain limits, but are slightly or much cheaper than their “analogues” from other series. To choose the best option, it is always better to contact technical consultants from a reputable company.
The concept of metal corrosion.
Corrosion is the process of destruction of metal under the influence of the external environment. According to the mechanism of occurrence, a distinction is made between chemical corrosion, which occurs under the influence of gases and non-electrolytes (oil), and electrochemical, which develops in the event of metal contact with electrolytes (acids, alkalis, salts, humid atmosphere, soil, sea water).
Electrochemical corrosion has its own varieties: uniform (over the entire surface) and local (in certain areas of the surface). In a heterogeneous, and often in a homogeneous, metal, the corrosion process is often realized due to the appearance of microgalvanic elements on the surface of the steel due to the presence of areas there that have different electrochemical potentials.
Electrochemical heterogeneity can be caused both by the presence of several phases in the alloy and by the difference in the electrochemical potential at the grain boundary and in the bulk of the grain. In this case, intercrystalline (intercrystalline) corrosion occurs along the grain boundaries. Steels that are resistant to electrochemical corrosion are called corrosion-resistant (stainless) steels.
The resistance of steel against corrosion is achieved by introducing into it elements that form dense protective films on the surface, firmly connected to the base, preventing direct contact with the external environment, and also increasing its electrochemical potential in this environment.
Figure 1 shows the distribution of the most popular grades of stainless steels of the AISI 400 group and the AISI 300 group in the coordinates: electrochemical potential of steel – PI index. The higher the steel grade is in this figure, the higher its electrochemical potential and, therefore, the higher the corrosion resistance of the steel.
Source: https://crast.ru/instrumenty/korrozionnostojkaja-stal-chto-jeto-takoe
Decoding stamps
The marking of alloy steels consists of letters and numbers. At the beginning there is a two-digit number that characterizes the amount of carbon in hundredths of a percent. The following are letters of the Russian alphabet, denoting a specific element:
- X – chromium;
- N – nickel,
- T – titanium;
- B – tungsten;
- G – manganese;
- M – molybdenum;
- D – copper.
After the letter designation of the alloying element in the decoding there is a number indicating its content in stainless steel, rounded to the nearest whole percent. If there is no such figure, then the additive in the alloy is in the range of 1-1.5%.
Grades of heat-resistant and heat-resistant stainless steels
Heat resistance, otherwise called “scale resistance,” is the property of a metal to resist gas corrosion at high temperatures in an unloaded or lightly loaded state.
Definition! To improve this characteristic, chromium, silicon and aluminum are introduced into the composition of stainless steels. These elements, combining with oxygen, form dense structures that increase the resistance of steel to temperatures above +550°C. Nickel by itself does not affect heat resistance, but in combination with Cr, Al and Si it increases their efficiency.
Heat-resistant steels are steels that function at high temperatures and loads without a tendency to short-term and long-term creep.
Table of areas of application of scale-resistant and heat-resistant steels
| Type | Brand | Temperature at which active reaction with air begins, °C | Areas of use |
| Chromium, scale resistant | X18 | +850+900 | Equipment, products and structures operated at T up to +900°C without load |
| High chromium, scale resistant | Х25 Х25ТХ28 | +1100+1150 | Metal products intended for operation without load up to T +1150°C, Х25Т – for the production of thermocouples |
| Silchrome, scale-resistant | Х25С3Н | +1100 | For heating units and heaters operating at temperatures up to +1100°C |
| Highly alloyed, scale resistant and heat resistant | Х23Н18 | Loaded products and structures intended for operation at T up to +1000°C | |
| Х20Н35 | Metal products operated at T +1000°C |
Stainless steel grades for the manufacture of chimneys
When purchasing modular chimney systems, you need to find out what kind of steel they are made of. On sale you can find chimneys that are about one and a half times cheaper than other products in this category. In their production, AISI 201 steel (12X15G9ND) is used.
According to international standards, it is necessary to use steel grade AISI 321 (08Х18Н12Т), the cost of which is approximately 2 times higher than the cost of AISI 201. It is impossible to visually distinguish AISI 201 from AISI 321, moreover, both alloys are non-magnetic.
They can only be distinguished by chemical analysis.
Differences in chemical composition
| Brand | WITH | Mn | P | S | Si | Cr | Ni | Cu | Ti |
| AISI 201 | Up to 0.15% | 7-9,5 | Up to 0.1% | Up to 0.03% | Up to 1.0% | 13-18 | 0,3-3,0 | 0,5-2,5 | — |
| AISI 321 | Up to 0.08% | Up to 2.0 | Up to 0.05% | Up to 0.03% | Up to 1.0% | 17-19 | 9,0-12,0 | — | Min 0.5% |
AISI 201 steel has low anti-corrosion characteristics, instability of the structure, and the risk of cracks during drawing. Its use will lead to rapid failure of the chimney due to rapidly developing corrosion. This steel is mainly distributed in China and India.
Well-known foreign and conscientious Russian manufacturers, in addition to AISI 321 steel, use high-alloy alloys stabilized by Ti. They are acid and heat resistant. The use of cheaper steels (AISI 409, AISI 430) for gas exhaust pipes that do not meet acid resistance requirements leads to their failure soon after the start of the heating season.
Stainless steels for the food industry
Corrosion-resistant steels are indispensable for industries producing equipment, tools and utensils intended for contact with food products. Their advantages:
- Resistance to various types of corrosion - chemical and electrochemical. In each specific case, it is necessary to select brands that are resistant to the environments with which they will come into contact during operation. These are normal atmospheric conditions, water, salt water, acidic, alkaline, chloride solutions.
- Good machinability. Modern tools make it possible to weld, cut, form and process corrosion-resistant alloys on lathes, milling and drilling machines in the same way as “ferrous” steels.
- Compliance with sanitary and hygienic standards. Thanks to various processing methods - grinding, polishing to a mirror finish - a surface is obtained that is practically free of pores and cracks into which dirt and pathogenic microorganisms can penetrate.
- Good mechanical characteristics. Thanks to them, it is possible to produce products and structures of smaller thickness and weight without compromising technical properties. Austenitic steels are more resistant to low temperatures compared to general purpose metals.
- Aesthetics. Electropolishing, satin finishing and other surface treatment methods provide a stylish look to stainless steel products.
Table of properties and areas of application of food grade stainless steels
| Steel grade according to GOST | AISI | Characteristics | Areas of use |
| 304 | 08Х18Н10 | It welds well, can be electropolished, retains high strength at normal and low temperatures, and is resistant to intercrystalline corrosion. | Equipment, tools, technological pipelines of food, petrochemical, pharmaceutical and medical industries, for utensils intended for high-temperature processing of products are not used |
| 316 | 03Х17Н14М2 | The presence of molybdenum increases the technical characteristics of the alloy at high temperatures | Installations, technological equipment, containers for the food and chemical industries |
| 321 | 12Х18Н10Т | Good weldability, maintaining performance characteristics at temperatures up to +800°C | Equipment for the chemical and oil refining industry |
| 409 | 08Х13 | Characteristics are satisfactory | Crockery and cutlery |
| 410 | 12Х13 | Heat resistance, resistance only to mildly aggressive environments | Winemaking equipment, alcohol containers |
| 420 | 20Х13-40Х13 | Versatility, ductility, wear resistance, increased corrosion resistance | Dishes, kitchen sinks |
| 430 | 08Х17 | Strength, thermal conductivity, good machinability, corrosion resistance | Utensils for heat treatment of products, including steam |
| 439 | 08Х13 | Possibility of use in various operating conditions | Alloy for mass use - production of refrigerators, sinks, washing machines |
Table of stainless steel grades used in the food industry
| Industry | Stamps |
| Dairy products – product sterilization and storage, cheese making, transportation tanks, ice cream and milk powder production | Austenitic steels – 304, 316, 321 |
| Fruit canning, juice production. In such industries, steel comes into contact with an environment containing sulfur dioxide | Grades containing molybdenum |
| Preparation of soups and sauces (these are aggressive mixtures with high acidity, containing chlorides) | Molybdenum-containing grades |
| Bakery, requirements - hygienic, smooth surfaces of tables and mixing equipment | Austenitic steels – 304, 316, 321 |
Source: https://www.navigator-beton.ru/articles/marki-nerzhaveyushhej-stali.html
Corrosion resistant steel. Steel grades: GOST. Stainless steel - price
Every year a lot of metal is lost due to corrosion. However, even greater damage is caused by the failure of metal products as a result of corrosion. The costs required to replace parts or routine repairs of instruments, cars, sea and river vessels, equipment used in chemical production, many times exceed the cost of the material used to manufacture them.
Indirect losses can also be significant. These include, for example, gas or oil leaks from pipelines damaged by corrosion, food spoilage, destruction of building structures, and much more. Therefore, the fight against metal corrosion is of paramount importance.
Why does metallic materials deteriorate?
Before moving on to the question of what corrosion-resistant steel is, let's understand the concept of corrosion and the essence of this process.
Translated from the Latin corroder - corroding. The slow spontaneous destruction of metals and alloys based on them, which occurs under the chemical influence of the environment, is called corrosion. The reason for this destruction is the chemical interaction (redox reactions) of metal materials with the gaseous or liquid medium in which they are located.
What are corrosion-resistant steels and alloys?
Products made of stainless and heat-resistant steel or their alloys are designed to work in aggressive environments at high or normal temperatures. Therefore, the main requirement for materials in this group is heat resistance (resistance to a gas environment or high temperature steam) or corrosion resistance (the ability to effectively withstand the effects of aggressive factors at normal temperatures).
Corrosion resistance is characteristic of metal products, on the surface of which in an aggressive environment a strong passivating film is formed, which prevents the penetration of aggressive substances into deeper layers of the metal and interaction with them.
In other words, corrosion-resistant steel is steel that is resistant to intergranular, chemical, electrochemical and other corrosion.
Classification by microstructure type: austenitic grade stainless steel
The resistance of this class to corrosion is increased due to the alloying elements of nickel (from 5 to 15%) and chromium (from 15 to 20%).
Austenitic alloys are insensitive to intergranular corrosion, provided that the carbon content in them is less than its solubility limit in austenite (0.02-0.03% or less). Non-magnetic, well subject to welding, cold and hot deformation.
They have excellent technology. This is the best steel for the manufacture of fasteners, welded structures and use in various industries.
Stainless steels belonging to the martensitic class can be magnetic and have higher maximum hardness values than austenitic ones. Hardening is achieved by quenching and tempering. Well suited for the production of products intended for use in medium to low intensity environments (for example, a number of food industry products or the production of razor blades).
Ferritic class
With high corrosion resistance, the properties of these grades are similar to low-carbon steel. The average chromium content is 11-17%. They are used in the production of household appliances, elements of architectural interior decoration, and kitchen utensils.
Austenitic-ferritic class
Corrosion-resistant stainless steels of this class are characterized by a reduced nickel content and a high chromium content (from 21 to 28%). Additional alloying elements include niobium, titanium, and copper. After heat treatment, the ratio of ferrite and austenite is approximately one to one.
The strength of austenitic-ferritic steels is twice that of austenitic steels. At the same time, they are ductile, resist shock loads well, have a low level of stress-corrosion cracking and high resistance to intergranular corrosion. Recommended for use in construction, manufacturing industry, and for the manufacture of products that will come into contact with sea water.
Austenitic-martensitic class
chromium from 12 to 18%, nickel - from 3.7 to 7.5%. Additional elements are chrome and aluminum. They are strengthened by hardening (t > 975 °C) and subsequent tempering (t = 450-500 °C). Austenitic-martensitic stainless steels are highly weldable and have high mechanical properties.
Stainless steel: price (factors influencing formation)
Corrosion-resistant metals include expensive alloying elements such as chromium, nickel, titanium, and molybdenum. Their cost is decisive in pricing.
Since other grades (carbon, structural, ball bearing, tool, etc.) contain the listed elements in much smaller quantities, the cost of corrosion-resistant steels is always higher in comparison with them.
However, the price may vary depending on market conditions and the costs required to produce stainless steel.
Mechanical properties
Grades of corrosion-resistant steels must have mechanical properties that meet the requirements of established manufacturing standards. These include:
- maximum hardness on the Brinell scale (HB);
- relative extension (%);
- yield strength (N/mm2);
- tensile strength (N/mm2).
After production, each batch (melting) of commercial products is checked for compliance of the mechanical properties and microstructure of the steel grade with GOST. The results of laboratory testing of samples are indicated in the manufacturing certificate.
Steel grade designation system
A wide range of alloys and steels are produced in various countries around the world. However, there is not yet a unified international system for their labeling.
There are several naming systems in use in the United States of America. This situation, due to the presence of a large number of standardization organizations (AJS, ANSI, ACJ, SAE, AWS, ASTM, ASME), creates certain difficulties for partners, contractors and customers of metal products from American manufacturers from other countries.
In Japan, steels are marked with letters and numbers indicating their group (low-alloy, high-alloy, special-purpose alloys, medium-alloy, high-quality, high-quality, etc.), the serial number in it and the properties of the metal.
In the countries of the European Union, designations are regulated by the EN 100 27 standard, which determines the procedure according to which the name and serial number are assigned.
The Russian Federation uses an alphanumeric system developed during the Soviet Union, in accordance with which steel grades are designated. GOST requires that each alloying chemical element included in the metal be indicated in a capital Russian letter.
For manganese it is G, silicon - C, chromium - X, nickel - H, molybdenum - M, tungsten - V, vanadium - F, titanium - T, aluminum - Yu, niobium - B, cobalt - K, zirconium - C, boron - R.
The numbers following the letter indicate the content of alloying elements as a percentage. If the steel contains less than 1% of the alloying element, then the number is not entered; if the content is from 1 to 2%, a 1 is placed after the letter. The two-digit number indicated at the beginning of the grade is necessary to indicate the average carbon content in hundredths of a percent within the grade composition.
Range of products made from stainless steel
Corrosion-resistant steel is used to produce the following products:
- heat-treated etched and polished sheets;
- heat-treated unetched sheets;
- thermally untreated and unetched sheets;
- warm, cold and hot-deformed seamless pipes;
- hot-rolled steel strips for general purposes;
- calibrated hexagons;
- stainless steel circles;
- stainless steel wire (heat-treated and cold-drawn);
- castings with special properties;
- forgings;
- other types for which GOSTs and technical instructions (TU) have been developed.
Application area
Being one of the best examples of strength, aesthetics, resistance to the destructive forces of corrosion and high temperatures, recyclability and durability, having an excellent surface finish that meets all sanitary and hygienic requirements, corrosion-resistant steel is widely used in almost all areas of economic activity. activities.
Stainless steel is in high demand in the petrochemical, chemical, pulp and paper, food industries, construction industry, electric power industry, shipbuilding and transport engineering, in the fields of instrument making and environmental protection.
The efficiency and durability of products made from stainless steel is determined by the correct choice of its class and grade, understanding of the physical and chemical properties and microstructure. By using metals that are resistant to the destructive effects of corrosion, in strict accordance with their properties, we are able to take advantage of all the undeniable advantages of modern technologies.
Source: https://FB.ru/article/148579/korrozionnostoykaya-stal-marki-stali-gost-nerjaveyuschaya-stal---tsena
