How steels are classified by quality - Metals and their processing

Classification of steels by purpose. Classification and marking of steel:

Steel is a malleable, deformable alloy of iron, a certain amount of carbon (no more than 2.14%), as well as a small amount of other elements. This material is widely used for the manufacture of a wide variety of devices, tools and building structures.

The classification and use of steels depend on many factors that need to be examined in more detail.

By changing the chemical composition of this material due to the concentration of carbon and the introduction of alloying elements, it is possible to obtain a wide range of steels with completely different properties, which allows the use of this material in all sectors of the economy.

Steel: classification, application, marking

First of all, it is worth saying that steel can be carbon and alloy. This depends on whether special alloying elements were added to the alloy - aluminum, nickel, chromium, molybdenum, titanium, boron, vanadium, manganese and others. All these additives are used to increase the specific properties of steel, and the best result is achieved by complex alloying.

In general, steels are classified:

by appointment;
by quality;
by production method;
by microstructure;
by chemical composition.

Chemical composition

As already mentioned, the classification of steels depending on the chemical composition divides this material into two large groups:

alloyed;
carbonaceous.

In turn, each of these groups can be further divided into several parts. The classification of alloy steels implies the presence of the following types:

low-alloyed ones contain a small amount (up to 2.5%) of alloying additives;
medium alloyed - the number of additional elements does not exceed 10%;
highly alloyed are characterized by the presence of alloying elements in an amount of more than 10%.

You can also divide the second group. The classification of carbon steels looks like this:

high-carbon are characterized by a carbon content of more than 0.6%;
medium-carbon contain from 0.25 to 0.6% carbon;
low-carbon - up to 0.25%.

Microstructure

In a normalized state, steels are:

pearlitic - characterized by a low content of alloying elements and, after normalization, have the structure: pearlite, pearlite + ferrite, pearlite + hypereutectoid carbide;
martensitic - have a reduced critical hardening rate and a fairly high content of alloying elements;
austenitic - increased content of alloying elements, under the influence of which the structure is achieved: austenite, austenite + carbide.

Classification of carbon steels in the annealed state:

hypoeutectoid is used, for example, for hot deformation dies;
hypereutectoid has a structure consisting of pearlite and cementite, usually used for making tools;
carbide (ledeburite) - for example, high-speed steel;
ferritic - stainless, heat-resistant, heat-resistant, high-chromium steel.

Quality and production method

Of course, the quality of steel depends on the presence of harmful impurities in it in the form of sulfur and phosphorus. Depending on this indicator, the classification of steels looks like this:

ordinary - sulfur (S) up to 0.06%, phosphorus (P) up to 0.07%;
qualitative - sulfur up to 0.04%, and phosphorus up to 0.035%;
high-quality - the same indicators are reduced to 0.025%;
especially high-quality - less than 0.015% sulfur and up to 0.025% phosphorus.

The method of steel production determines its structure, composition and properties. Thus, ordinary steel (ordinary) is most often smelted in open hearths or Thomas and Bessemer converters, after which it is formed into fairly large ingots.

This steel has an increased amount of non-metallic additives. High-quality steels are produced using more advanced methods, for example in an electric furnace, and especially high-quality steels are additionally purified from oxides and sulfides using ESR - electroslag remelting.

Such steels are made exclusively alloyed.

Deoxidation

There is also a classification of steels depending on the degree of deoxidation, that is, on how much oxygen was removed during the manufacturing process. Based on this parameter, steels are:

boiling - slightly deoxidized, saturated with oxygen;
calm - completely deoxidized;
semi-quiet - steels in which oxygen has been partially removed.

Aluminum, manganese and silicon are used for deoxidation of low-carbon steels. Boiling steel is usually deoxidized with ferromanganese into semi-quiet steel; in addition, a small amount of ferrosilicon is added, and the calm steel, in addition to the previous components, is treated with aluminum and silicomanganese.

What does steel marking mean?

Oddly enough, the classification of brands has become quite diverse, and there is no single world system. In a number of countries, including Russia, alphanumeric markings have been adopted.

High-quality carbon steels are designated by a two-digit number, which indicates the quantitative carbon content (in hundredths of %). Carbon steels are marked with the letter “U” and a number expressing the amount of carbon (in tenths%) - U9, U12, etc.

Letters are also used to designate the main alloying element, for example: “P” - phosphorus, “A” - nitrogen, “T” - titanium, “B” - niobium, “G” - manganese, “Y” - aluminum, “D” " - copper, "M" - molybdenum, "P" - boron, "K" - cobalt, "B" - tungsten, "E" - selenium, "H" - nickel, "C" - silicon, "X" - chromium, “C” - zirconium. The number behind the letter characterizes the amount of the corresponding element, and the one at the very beginning indicates the carbon content (in hundredths of %). If the amount of the latter is greater than or equal to 1%, then the original figure may not be indicated at all.

The letter “A” at the end of the brand indicates that it is high-quality. The same letter in the middle indicates that the steel is alloyed with nitrogen. If it is at the beginning, then this indicates that this is free-cut steel with increased machinability. Particularly high-quality steel is marked with the letter “Ш” added at the end and written with a hyphen. Brands that do not contain the letters “A” or “W” are of high quality.

There are also certain groups of steels, additionally marked with letters:

"E" - magnetic;
"E" - electrical;
“R” - high-speed;
"Ш" - ball bearing.

Of course, there are still quite a few subtleties, but we can say that Russian markings are quite simple and understandable, while the designations adopted in other countries are much more complex.

No less interesting is the classification of steels by purpose, let's talk about it in more detail.

Structural steels

Construction - low-alloy, as well as ordinary quality, with good weldability.
For cold stamping - rolled sheets of low-carbon grades of normal quality.
Case-hardened - low-carbon and some alloy steels used for the manufacture of parts that experience dynamic loads and work with surface wear.
Improved ones are subjected to heat treatment (hardening and high tempering). These are medium-carbon, chromium, chromium-nickel, chromium-nickel-molybdenum, chromium-silicon-manganese, chromium steels with boron.
High-strength - steels that, through heat treatment and a special composition, have achieved double the tensile strength compared to conventional structural analogues.
Spring-type systems can maintain elasticity for a long time and have sufficient resistance to fatigue and destruction; These include steels alloyed with chromium, boron, silicon, vanadium and manganese.
Ball bearings are characterized by high wear resistance, strength and endurance, which is achieved through high (up to 1%) carbon content and the inclusion of chromium.
Automatic ones are used for the production of mass-produced parts processed using automatic machines (bolts, screws, washers, nuts, etc.); To facilitate processing, sulfur, lead, tellurium and selenium are additionally introduced into such steels, which leads to brittle short chips and reduces friction.
Corrosion-resistant - high-chromium steels containing nickel; the more chromium they contain, the more pronounced the corrosion resistance, while the carbon content should be minimal.
Wear-resistant ones are used in places of abrasive friction, shock and high pressure, such as an excavator bucket or tractor tracks.

Tool steels

The classification of tool steels can also be represented by several points:

Carbon, alloy and high-speed steels are used for cutting tools;
for measuring instruments, the material must, first of all, have constant dimensions, be polished, have sufficient hardness and wear resistance; To obtain such characteristics, tool steel is often hardened and case-hardened;
die steels must have sufficient wear resistance, hardness, heat resistance and hardenability; this group can also be further divided into cold forming steels, hot forming steels and roller steels.

Steels with special chemical and physical properties

In addition to all of the above, there are also steel grades with special properties:

electrical steel - an alloy of iron and silicon, sometimes alloyed with aluminum; used in the production of magnetic circuits for various electrical equipment;
superinvar is an alloy of iron, nickel and cobalt used in the manufacture of high-precision equipment;
heat-resistant - has increased resistance to destruction at temperatures above 900 °C, alloyed with aluminum, silicon, nickel;
heat-resistant - used for the manufacture of parts for gas turbine units; such steels are designed to work under load at high temperatures for some time.

Source: https://www.syl.ru/article/187482/new_klassifikatsiya-staley-po-naznacheniyu-klassifikatsiya-i-markirovka-stali

Comex

Steel is a metal alloy of iron and carbon, necessary for the production of semi-finished products and products by plastic deformation in cold and hot states. To change the properties of a material, various elements can be added to its composition. Thus, with an increase in the amount of carbon, the strength of steel increases. If it is more than 2.14% in the alloy, we get cast iron.

The main qualities of steel are strength, ductility, toughness, hardness, elasticity, and heat resistance. However, it inherited its susceptibility to corrosion from iron.

Classification of steels by chemical composition:

carbon steel, without improving (alloying) components;
alloy steel, to which alloying elements (manganese, chromium, nickel, tungsten, silicon, molybdenum, vanadium) are added to improve technological properties.

Through research, stainless steel and galvanized steel were also obtained.

Carbon steel

Carbon steels (CS) are low-alloy compositions consisting of 99.5% iron. Strictly dosed various additives determine the operational, mechanical and technological properties of alloys. Carbon compositions account for up to 80% of the total amount of steel produced. There are over two thousand grades of these alloys. According to the area of use, they are divided into structural, tool, and also ordinary quality steel (for example, wire rod).

In terms of quality, the classification of carbon steel provides:

ordinary steel, which can be cold-rolled or hot-rolled;
high-quality structural steel in the form of forged and hot-rolled billets, silver bars (round bars), calibrated steel.

High-quality structural steel is used for the production of critical components of machines and mechanisms, stamping. The main advantages of the US include:

optimal ratio of consumer properties and price;
high modulus of elasticity, which allows its use in power structures, where the performance of the structure depends on the rigidity of the material;
heat treatment of steel increases its strength, but practically does not change the elastic modulus (an important process in the heat treatment of metal is hardening of carbon steel, on which the quality of the product depends, the hardening speed is in the range of 200-600 C per second);
Amenable to finishing by pressure and cutting, welding is excellent.

Thanks to these advantages, the control system has found wide application in the production of mass products.

Marking of carbon steels

Carbon and alloy steels are classified according to:

structural composition;
chemical composition;
quality;
purpose;
degree of deoxidation.

The main feature that determines the name and grade of steel is its chemical composition. This marking of steels also takes into account production conditions, quality, and area of application.

If the grade of steel is known, then its properties are quite easy to understand. For example, ordinary quality carbon dioxide is marked with two letters and a number, which indicates the presence of carbon in tenths of a percent (Article 1 - Article 7).

Alloy steels, in addition to markings and numbers, have letters indicating additives in the steel. For better orientation, there are marking tables.

Chemical composition of steel

Depending on the chemical composition, carbon steels are divided into three types:

low-carbon – carbon is present in small quantities (up to 0.25%). These compositions are well deformed in both cold and hot states.
Medium carbon - carbon present 0.3-0.6%. Such alloys are characterized by good ductility, fluidity and at the same time strength.
High-carbon (0.6 - 1.4%) - have increased density and unique characteristics, which are determined by the peculiarities of the structure.

To reduce the number of non-metallic inclusions and refine grains, steel is deoxidized. The smaller the number of non-metallic inclusions and the more uniformly they are distributed, the lower the threshold of brittleness of the material and the higher the impact strength and strength.

Classification according to the degree of deoxidation implies: calm, semi-calm, boiling steels.

Boiling steel

Boiling steel production technology ensures minimal waste and the yield of the largest amount of usable metal. Due to the absence of silicon, steel is very ductile and is used for the manufacture of products by deep drawing.

Boiling steels are deoxidized with manganese until the presence of oxygen is 0.02-0.04% and then poured into ingots. Emitted CO bubbles create a picture of steel boiling, which explains its name. When marking, it is additionally indicated by KP.

As a result of the fact that boiling steel requires a small amount of deoxidizer, and the top part of the ingot is not scrapped, it is cheaper than semi-calm and calm steel.

Ingots from such steel are used for the production of sheets, plates, pipes, wire, and long products.

Calm steel

This type of metal belongs to structural carbon steels. It is obtained by deoxidation with aluminum, manganese and silicon. The level of oxygen in it is so reduced that no reaction occurs between carbon and oxygen during metal processing.

Calm steel is distinguished by a dense structure and has good mechanical properties. It is less prone to negative reactions to welding heat and to aging. The features of a uniform (homogeneous) microstructure give the alloy maximum corrosion resistance and ductility.

In terms of cost, this is the most expensive steel. It is used for the construction of rigid metal structures, non-load-bearing and load-bearing elements. It is made from:

procurement of parts for pipelines;
basic elements for railway tracks;
sheets, shapes, etc.

Semi-quiet steel

Semi-quiet steels have a middle position between boiling and calm types of raw materials. They contain oxygen, which gives the raw material less pronounced properties of plasticity and hardness. They harden without boiling, however, with the release of gases. The chemical composition is heterogeneous.

THIS IS INTERESTING: What is called steel improvement

Semi-quiet steel is melted using boiling steel technology, but with subsequent deoxidation of the metal in a mold or ladle. As a rule, aluminum or silicon is used for deoxidation.

The following grades of steel are used to produce:

stripes, circles, squares, hexagons, corners, embedded parts;
pipe and sheet metal.

Steel is one of the most important metal materials

Steel is one of the main metal materials that is used in the production of tools, instruments, and machines. Its widespread use is justified by the presence of a whole complex of high mechanical, technological, physicochemical properties.

In addition, steel has a relatively low cost and can be produced in large quantities. The production process of this material is constantly being improved, as a result of which the quality and properties of steel can ensure trouble-free operation of modern devices and machines under high workloads.

Source: https://komeks.com.ua/article/klassifikaciya-staley-po-stepeni-raskisleniya

Marking of steels: principles of classification, metal content depending on the type of alloy

Steel is a malleable and wrought alloy of iron and carbon (as a permanent impurity). Also contains other alloying elements and other harmful impurities. carbon should not exceed 2.14%.

By changing the chemical composition of this alloy using carbon concentration and adding alloying elements, it is possible to obtain a wide range of different grades of this metal that will have different properties.

This is what allows this material to be used in most industries.

Classification and marking of steel occurs according to the following parameters:

chemical composition;
structure;
appointment;
quality and method of production;
degree of deoxidation.

By chemical composition

Depending on the chemical composition, this metal is divided into two types: carbon and alloy. In turn, carbonaceous materials are divided into:

low-carbon (carbon content below 0.2%);
medium-carbon (carbon content in the range of 0.2% - 0.45%);
high-carbon (carbon content above 0.5%).

Alloy steels are classified according to the total total amount of alloying elements (the carbon content is not summed up; manganese begins to be considered an alloying element when its content in the alloy is more than 1%, silicon - more than 0.8%). The following are distinguished:

low alloy (below 2.5%);
medium alloyed (within 2.5% - 10%);
highly alloyed (more than 10%).

By structure

Such a classification feature as the structure of the material is considered less stable, since it depends on the cooling rate, alloying, heat treatment method and some other variable factors. However, the structure of the finished material still allows for an objective assessment of its quality. Classification of steel by structure in the annealing and normalization states. In the annealing state, the following are distinguished:

hypoeutectoid - contains excess ferrite in its structure (for example, used for hot deformation dies);
eutectoid - the structure consists of perite;
hypereutectoid - contains secondary carbides in the structure (mostly used in the manufacture of tools);
carbide (or ledeburite) - the structure contains primary carbides (for example, high-speed cutting);
ferritic (stainless, heat-resistant and others);
austenitic.

After the normalization process, steel is divided into the following classes:

pearlitic - contain a low amount of alloying elements, structure after normalization: pearlite, pearlite + ferrite, pearlite + hypereutectoid carbide;
martensitic - contain a high amount of alloying elements, as well as a relatively low critical hardening rate;
austenitic - characterized by a high content of alloying elements, structure: austenite, austenite + carbide.

By purpose

Based on their purpose, steels are divided into structural, instrumental and special purpose (having special properties).

Structural ones are used for the manufacture of all kinds of parts in devices, machines, and elements of building structures. They are divided into:

ordinary quality;
improved;
cemented;
automatic;
high strength;
spring-spring.

Tools are used for the manufacture of cutting, measuring and other tools. They are divided into the following groups:

for the manufacture of cutting tools;
for the manufacture of measuring instruments;
for the manufacture of stamping and pressing equipment.

Special purpose are alloys with special physical and/or mechanical properties. There are:

stainless (corrosion-resistant);
heat resistant;
heat resistant;
wear-resistant;
magnetic;
non-magnetic, etc.

By quality and production method

In this case, quality is understood as the entire set of properties of the metal, which are determined by the metallurgical process of its manufacture. The quality of steel is determined by the presence of harmful impurities in it. First of all, these are the chemical elements sulfur and phosphorus. Depending on their content they are divided into:

ordinary quality - containing up to 0.06% sulfur and 0.07% phosphorus;
high-quality - up to 0.035% sulfur and 0.035% phosphorus;
high-quality - no more than 0.025% sulfur and 0.025% phosphorus.
especially high quality - no more than 0.015% sulfur and 0.025% phosphorus.

According to the degree of deoxidation

Deoxidation is the process of removing oxygen from a liquid alloy. Undeoxidized steel has relatively low ductility and is more susceptible to brittle fracture during heat treatment under pressure. According to the degree of deoxidation they are divided into:

calm;
semi-calm;
boiling.

The process of deoxidizing still steels in a smelting furnace/or ladle using manganese, aluminum and silicon. Solidification in the mold occurs quietly, without gas evolution. A shrinkage cavity is formed in the upper part of the ingots.

This type has anisotropy, that is, the mechanical properties are different and depend on the direction - the plastic properties in the transverse direction (along the rolling direction) are significantly lower than in the longitudinal direction.

In addition, in the upper part of the ingot the content of sulfur, phosphorus and carbon is increased, and in the lower part it is reduced. This significantly worsens the properties of the product, sometimes even to the point of rejection.

Deoxidation in boiling water occurs only due to manganese. Excess oxygen during solidification partially reacts with carbon, releasing gas bubbles (carbon monoxide). This is where the impression of “boiling” is created.

In this type there are practically no non-metallic inclusions arising from deoxidation products. It is a low-carbon alloy, with a minimum silicon content and a high content of gaseous impurities. Used in the manufacture of car body parts, etc.

Has good cold formability.

Semi-quiet steels occupy a middle position between calm and boiling steels. Deoxidation is carried out in two stages: partly in the melting furnace and ladle, and finally in the mold. In the mold, deoxidation occurs due to the carbon contained in the metal.

Decoding steels in materials science

Belongs to the class: structural carbon quality. Chemical composition: carbon - 0.17−0.24%; silicon - 0.17−0.37%; manganese - 0.35−0.65%; sulfur - up to 0.04%; phosphorus - up to 0.04%. Widely used in boiler making, for pipes and heating pipelines for various purposes; in addition, the industry produces rods and sheets.

HVG transcript

Belongs to the class: alloyed instrumental. Used for the manufacture of measuring and cutting tools, taps, broaches.

Source: https://tokar.guru/metally/stal/klassifikaciya-i-markirovka-stali.html

How are steels classified by chemical composition?

by chemical composition;
by structure;
by appointment;
by quality;
according to the degree of deoxidation.

According to the chemical composition, steels are divided into:

– carbon	(classification by carbon content) – low-carbon (up to 0.2%) – medium-carbon (0.2–0.45%) – high-carbon (containing more than 0.5%)
– alloyed	(classification according to the sum of alloying elements) – low alloyed (up to 2.5%) – medium alloyed (2.5–10.0%) – highly alloyed (more than 10.0%)

When determining the degree of alloying, the carbon content is not taken into account; manganese and silicon are considered alloying elements when their content is more than 1 and 0.8%, respectively.

Classification of steels by structure

The structure of steel is a less stable classification feature, since it depends on the cooling rate (wall thickness of the castings), the degree of alloying, heat treatment mode and other changing factors, but the structure of the finished product allows you to objectively assess its quality.

Steels are classified according to their structure in the states after annealing and normalization.

In the annealed state, steels are divided into:

hypoeutectoid - having excess ferrite in the structure
eutectoid – the structure of which consists of pearlite
hypereutectoid - in the structure of which there are secondary carbides released from austenite
ledeburite – the structure of which contains primary (eutectic) carbides
austenitic
ferritic

After normalization, steel is divided into the following structural classes:

Classification of steels by purpose

Structural – steels intended for the manufacture of machine parts and elements of building structures.

Structural steels are divided into:

ordinary quality;
improved;
cemented;
automatic;
high strength;
spring-spring.

Tool steels – steels used in the manufacture of cutting and measuring instruments.

Tool steels are divided into subgroups according to production:

for cutting tools;
for measuring instrument;
for stamping and pressing equipment.

Special purpose – steels with special physical and mechanical properties.

Special purpose steels are divided into:

stainless (corrosion-resistant);
heat resistant;
heat resistant;
wear-resistant;
magnetic;
non-magnetic, etc.

Classification of steels by quality

According to the quality of steel, they are classified into:

ordinary quality - containing up to 0.06% sulfur and 0.07% phosphorus;
quality - containing up to 0.035% sulfur and 0.035% phosphorus;
high-quality - containing no more than 0.025% sulfur and 0.025% phosphorus;
especially high quality - containing no more than 0.015% sulfur and 0.025% phosphorus.

Quality refers to the totality of steel properties determined by the metallurgical process of its production (smelting method). The homogeneity of the chemical composition, structure and properties of steel depend on the content of harmful impurities and gases.

Classification of steels by degree of deoxidation

According to the degree of deoxidation, steel is classified into:

Deoxidation is the process of removing oxygen from liquid steel.

Mild steels are deoxidized with manganese, aluminum and silicon in a smelting furnace and ladle. They solidify in the mold quietly, without gas evolution, with the formation of a shrinkage cavity in the upper part of the ingots.

Dendritic segregation causes anisotropy in mechanical properties. The plastic properties of steel in the transverse section (relative to the direction of rolling or forging) are significantly lower than in the longitudinal section.

Zonal segregation leads to the fact that in the upper part of the ingot the content of sulfur, phosphorus and carbon increases, and in the lower part it decreases. This leads to a significant deterioration in the properties of the product made from such an ingot, up to rejection.

Boiling steels are deoxidized only by manganese, which is not enough. Before casting, they contain an increased amount of oxygen, which, when the ingot solidifies, partially reacts with carbon and is released in the form of gas bubbles of carbon monoxide, giving the impression of “boiling” of the steel.

Boiling steel contains practically no non-metallic inclusions of deoxidation products. These steels are smelted low-carbon and with a very low silicon content (less than 0.07%), but with an increased amount of gaseous impurities. When rolling ingots, gas bubbles filled with carbon monoxide are welded. Rolled sheets made from this steel are intended for the production of car body parts by drawing; they have good cold formability.

Semi-quiet steels, in terms of the degree of their deoxidation, occupy an intermediate position between calm and boiling steels. They are partially deoxidized in a melting furnace and in a ladle, and finally in a mold due to the carbon contained in the metal. The segregation in ingots of semi-quiet steel is less than in boiling steel, and approaches the segregation in ingots of calm steel.

The classification and use of steels depend on many factors that need to be examined in more detail.

Classification of steels: by purpose, composition, application - Website about

The combination of characteristic static cyclic strength and stiffness is achieved by varying the carbon content and alloying components. Different qualities of steel are obtained as a result of the use of certain chemical and thermal technologies in production.

Classification of carbon steels

Carbon alloys are divided according to the following characteristics:

amount of carbon contained;
purpose;
structure in a state of equilibrium;
degree of deoxidation.

Depending on the amount of carbon, the material is divided into categories:

high-carbon - more than 0.7%;
medium carbon - 0.3−0.7%;
low carbon - up to 0.3%.

As a result of the resulting quality, steel alloys are divided into:

high quality;
ordinary;
quality.

Oxygen is removed from the metal in its liquid state to reduce brittleness during hot forming, a process called deoxidation. Based on the nature of hardening and the degree of deoxidation, the material is classified as boiling, semi-calm and calm.

Depending on the resulting structure in the equilibrium state, the material is divided into:

eutectoid, characterized by a pearlite structure;
hypoeutectoid, containing pearlite and ferrite;
hypereutectoid - with secondary cementite and pearlite.

According to the intended use, metal is divided into groups:

structural (improvable, high-strength, cemented, spring-spring), used in construction, instrument making, mechanical engineering and aircraft manufacturing;
instrumental for hot (200˚C) and cold pressing dies, measuring and cutting tools).

Structural metals

The deoxidation group is designated SP, PS, KP - calm, semi-quiet and boiling, respectively. Category A is used for the production of parts obtained by cold working, Category B is used for elements manufactured by welding, forging, and heat treatment. Steel B is more expensive than the previous categories and is used for the production of critical structures and welding elements.

All three categories of ordinary carbon steels are used to make metal structures and parts in instrument making and mechanical engineering with light loads, in cases where performance is determined by the required rigidity. Metals in the form of reinforcement are placed in reinforced concrete structures. From categories B and B, welded trusses, frames and metal components are made, which are then covered with cement mortar.

Medium-carbon groups with a large margin of safety are used for rails, wheels of railway cars, pulleys, shafts and gears of mechanical devices and machines. Some materials in this group are allowed for heat treatment.

Low-carbon alloys have good ductility during cold working, but have a small margin of safety.

They are produced in the form of sheets, the material is soft, easily stamped, stretched, this includes tin and metal for enameled household items.

When cementing steels in production, the surface strength indicator increases, which makes it possible to produce light-loaded gear wheels, cams, etc.

Medium-carbon metals and similar compositions with an increased percentage of manganese are characterized by average strength, but their ductility and toughness are reduced.

THIS IS INTERESTING: How to connect two wires

Based on the operating conditions of the spare parts, the method of strengthening steels in the form of normalization, low-temperature and high-frequency hardening, etc. is determined.

They are used to make high-strength wire, springs, and springs with increased requirements for wear resistance.

Automatic types

phosphorus and sulfur reduce quality indicators, sulfur reduces anti-corrosion properties, sulfides lead to a violation of the homogeneity of the metal. This class of steel is used to make parts of complex shapes and surfaces, and fasteners designed for light loads.

Alloy types

These include metals containing alloying additives in amounts up to 2.5%. The letter designations of the brand include letters indicating certain impurities, and the number after them indicates the percentage of the element. If its content is less than 1.5%, then the additive is not included in the designation.

carbon in this group of steels is normalized by the amount of 0.1−0.3%; the main properties after thermal, chemical treatment and low tempering after hardening include:

high hardness of the material on the surface;
reduced strength of the middle layers and increased viscosity.

Steels are used for the production of machine parts and devices designed to work with shock and variable loads under conditions of increased wear.

Cementable materials

To increase hardness, contact endurance, wear resistance, and hardenability, chromium, magnesium, and nickel are used; the latter element increases viscosity and reduces the cold brittleness limit. Cementable compounds are divided into two groups:

average strength with a yield threshold less than 700 MPa;
increased strength with a similar indicator in the range of 700−1100 MPa.

Based on the content of additives, the following types are distinguished:

chromium compounds and chrome vanadium, cemented to a depth of less than 1.5 mm;
chromium-manganese compositions include titanium 0.06%, manganese and chromium 1% each, they tend to internally oxidize during gas carburization, which leads to a decrease in strength characteristics;
chromium-nickel-molybdenum alloys are representatives of the martensitic class and are characterized by reduced warping, which is due to air hardening and alloying with rare earth metals, which increase hardenability, static strength and impact resistance.

Spring-spring alloys

Parts operate under conditions of elastic deformation and are subject to cyclic loads, so steels are required to have high levels of fluidity, ductility and fracture resistance. Includes:

manganese - less than 1.2%;
silicon - less than 2.7%;
vanadium - up to 0.26%;
chromium - up to 1.25%;
nickel - less than 1.75%;
tungsten - less than 1.2%.

To ensure reliable operation of tools, steel must have special properties, which manifest themselves differently in each group of materials depending on production and technology for introducing additives.

Ball bearing molds

Hardening of parts (rollers, ball bearings and rings) is carried out in an oil bath at a temperature of 850−870˚С, they are cooled to ensure stability to 25˚С before tempering. Since bearing and similar elements experience strong dynamic loads during operation, they are made of metals with further heat treatment and carburization.

Wear-resistant types

Wear resistance increases with increasing surface hardness of the material. For long-term operation, the following qualities of the alloy are important:

resistance to destruction due to abrasive friction;
long-term operation under conditions of high pressure and shock loads.

Cast steel has an austenite structure, in which excess manganese carbide precipitates at the grain boundaries, leading to a decrease in strength and toughness. To obtain an austenitic single-phase structure, the workpieces are quenched in an aqueous environment at a temperature of about 1100˚C.

Corrosion resistant

Stainless metals are divided into chromium-nickel and chromium. Chromium compounds are used for plastic parts that are produced by stamping and welding. This type is divided into ferritic, martensitic-ferritic and martensitic alloys. To increase impact resistance, they are hardened in oil at a temperature of about 1000˚C under high tempering conditions with temperatures ranging from 600-800˚C.

Heat-resistant alloys

Low-alloy compositions containing up to 0.25% C and other alloying additives: chromium, tungsten, nickel are used for the manufacture of elements operating at temperatures above 500˚C.

Quenching and normalization is carried out in oil at a temperature of about 890−1050˚С.

Pearlitic steels are used to make parts that are subject to creep in operation under low loads, for example, steam heating pipes, fittings for steam boilers, and fasteners.

Source: https://nzmetallspb.ru/tehnologii/klassifikatsiya-stalej-po-naznacheniyu-sostavu-primeneniyu.html

Steel: main types, classification, purpose

The modern construction industry cannot do without the use of steel. The alloy, which has many markings and classes, is used in both small and large construction, and also takes part in decorative and finishing works. By its specificity, steel is a combination of iron and carbon. The peculiarity lies in the percentage of these components.

1 kg of alloy contains 98% iron and only the remaining 2% is carbon. With an increase in the amount of carbon, a new alloy can be obtained - cast iron. The component composition contains other metals: chromium, magnesium, etc.

This combination makes it possible to regulate the production process, create new, sought-after grades of steel, and also use this alloy in many areas of humanity.

Typology and types of steel

It was previously noted that the basic components of steel are iron and carbon. Based on this ratio, the alloy, according to typology, is characterized as alloyed, low-alloyed and carbon. Not only the properties, but also the technical characteristics of the material depend on the typology.

Quality is an indicator of the ratio of carbon to iron. With a lower percentage, the final product is soft, elastic and suitable for further processing and production of cold-rolled and hot-rolled metal products. Steel, with an increased amount of iron, is intended for the manufacture of elements that serve as components of simple mechanisms that are not responsible for weight distribution or complex functions.

An alloy containing C2 in a percentage of 0.5 to the bulk is hard (alloyed). The most popular product in the construction industry. The material plays a major role, namely: restraining the weight of the structure.

The service life of the material is high, from 50 to 75 years. The alloy does not corrode and does not deform in unfavorable temperature conditions. Simply put, any product made from hard alloy is extremely wear-resistant and can withstand volumetric loads.

In the structure of large automotive and loading equipment, alloy and carbon steel play an important role, since these materials are able to withstand significant mechanical loads without deformation or destructive processes. But, during the production process, certain difficulties arise with fastening the parts.

Alloy steel is not weldable. Several elements can be connected by heating to high temperatures and then applying two parts.

Steel has anti-corrosion properties and does not collapse in places with high humidity.

Stainless steel is a separate category of material

The main criterion that can reduce the service life of any alloy that contains iron is corrosion. Its destructive impact affects not only the appearance of the part. Rust deforms a metal product from the inside, rendering it unusable over time. About a quarter of a century ago, metallurgy experts found a solution to this problem: stainless steel.

Stainless steel is a universal material used in many industries. Mechanical engineering, construction of multi-story buildings, shipbuilding and even aircraft manufacturing cannot do without the use of stainless steel.

It is difficult to deform this alloy, because it is resistant to changes in pressure and temperature, and is also categorically not subject to corrosion.

Craftsmen and blacksmiths prefer to use stainless steel as a starting material for the production of souvenirs and consumer products.

What is special about this material? This popularity is due to its incredible corrosion-resistant properties, as well as the safety of the final product even at high temperatures.

Marking and designation of steels

Steel is not a single material, but a collection of numerous components. Marking allows you to indicate the ratio of specific elements in the component composition, as well as assign the alloy to a specific group.

As a rule, using the designation, the basic properties of steel are determined - resistance to mechanical loads, withstand pressure and changes in temperature conditions, as well as resistance to rust.

In some situations, the marking indicates the amount of iron and C2 included in the alloy.

The final decoding allows you to classify the alloy into a specific group. There are three classifications (groups):

Structural view.
Building.
Instrumental.

Each group has certain advantages and disadvantages over representatives of another classification. Let us consider in detail what the positive and negative sides of a certain group are.

Construction group

Participates in the manufacture of structural parts, supports, fittings and piles used for the construction of large-scale objects or high-rise buildings. Very often used in the metal rolling industry. The structural group includes two types of steel: alloy and carbon. In turn, alloy steel is divided into four subclasses:

Basic quality. There are no foreign impurities, with the exception of chromium. The final product is marked “St”.
Optimal quality. Approximately 0.05% is foreign elements. The rest of the alloy is made up of iron and C2. There are no markings on the parts.
High Quality. To increase technical characteristics and strength, nickel is added in an amount of 0.003 per total weight of the alloy. Marked with the letter “A” on the final product.
Top quality. Foreign impurities are not used so that the percentage of strength does not decrease. In the middle of the marking there is the letter “Ш”.

A separate subclass that does not belong to the usual subcategories is high-speed steel. It is used as a polishing material, since the malleability of the alloy exceeds 50%. Using heat treatment, the final product is hardened and the strength coefficient is significantly increased.

If high-speed steel is available, the product is marked “KB”.

Construction group

The main direction is the construction sector. The steels of the construction group are used to make fastening equipment that is used as a support for a residential or warehouse space. The final product can withstand weight up to several tons, while maintaining its original appearance. The characteristic marking is the letter “C” at the very beginning.

Labeling is a very important thing, therefore, in order to select quality products, you should master the terminological language in advance in order to select the required material. Low alloy steels are not suitable for construction work, but they can be used for the production of cold rolled metal products.

Classification

The last, but very important point is the classification of steel. It is possible to characterize the alloy taking into account the following criteria:

Component composition.
Percentage of iron, carbon and auxiliary additives.
Susceptibility to rust.
Application specifics.

Some aspects do not require careful study, but the component composition, the presence of foreign additives and susceptibility to rust are key points that allow you to choose not only high-quality, but also durable products.

Component composition

This indicator specifies the amount of C2 used to make the alloy. According to GOST, products with a deficiency or excess of carbon cannot be allowed for consumption due to non-compliance with the set of safety rules.

Structuring is a process characterized not only by the presence of C2 and iron, but also by the presence of additional materials that help improve the basic parameters - strength, corrosion resistance and durability. To achieve the required result, you need to heat the steel to 800 degrees and leave it to cool. If the material cools down within 3-4 hours - 100% compliance with GOST standards. The products can be used in construction and large mechanical engineering.

Percentage of auxiliary additives

It was previously noted that steel contains auxiliary additives that allow optimizing the quality of the final product and the alloy itself. For example, to increase resistance to temperature changes, the presence of sulfur in the material is necessary. This combination leads to compaction of the outer shell, which will allow the alloy to maintain its original structure without changes. In addition to sulfur, bromine, molybdenum and other additives are added to steel.

Susceptibility to corrosion

One of the basic points of classification. Corrosion occurs not only in conditions of high humidity, but also due to improper storage and use of the alloy and the final product.

Carbon is a natural catalyst for corrosion, but it is impossible to completely suppress this process. To get rid of such an unpleasant problem, stainless steel, which was mentioned earlier, was developed and used in wide production.

But, in addition to stainless steel, there is a separate component composition, with the participation of sulfur, which blocks the further development of rust not only inside, but also outside the product.

Unfortunately, only hard alloys can be protected from the harmful effects of natural destructive factors.

Source: https://ssopromat.ru/materialyi/stal-osnovnyie-vidyi-klassifikatsiya-prednaznachenie/

Steel classification

Steels are classified:

by chemical composition;
by structure;
by appointment;
by quality;
according to the degree of deoxidation.

Classification of steels by chemical composition

According to the chemical composition, steels are divided into:

– carbon	(classification by carbon content) – low-carbon (up to 0.2%) – medium-carbon (0.2–0.45%) – high-carbon (containing more than 0.5%)
– alloyed	(classification according to the sum of alloying elements) – low alloyed (up to 2.5%) – medium alloyed (2.5–10.0%) – highly alloyed (more than 10.0%)

When determining the degree of alloying, the carbon content is not taken into account; manganese and silicon are considered alloying elements when their content is more than 1 and 0.8%, respectively.

Classification of steels by structure

Steels are classified according to their structure in the states after annealing and normalization.

In the annealed state, steels are divided into:

hypoeutectoid - having excess ferrite in the structure
eutectoid – the structure of which consists of pearlite
hypereutectoid - in the structure of which there are secondary carbides released from austenite
ledeburite – the structure of which contains primary (eutectic) carbides
austenitic
ferritic

After normalization, steel is divided into the following structural classes:

pearlitic
austenitic
ferritic

Classification of steels by purpose

Structural – steels intended for the manufacture of machine parts and elements of building structures.

Structural steels are divided into:

ordinary quality;
improved;
cemented;
automatic;
high strength;
spring-spring.

Tool steels – steels used in the manufacture of cutting and measuring instruments.

Tool steels are divided into subgroups according to production:

for cutting tools;
for measuring instrument;
for stamping and pressing equipment.

Special purpose – steels with special physical and mechanical properties.

THIS IS INTERESTING: How to knit reinforcement with a screwdriver

Special purpose steels are divided into:

stainless (corrosion-resistant);
heat resistant;
heat resistant;
wear-resistant;
magnetic;
non-magnetic, etc.

Classification of steels by quality

According to the quality of steel, they are classified into:

ordinary quality - containing up to 0.06% sulfur and 0.07% phosphorus;
quality - containing up to 0.035% sulfur and 0.035% phosphorus;
high-quality - containing no more than 0.025% sulfur and 0.025% phosphorus;
especially high quality - containing no more than 0.015% sulfur and 0.025% phosphorus.

Classification of steels by degree of deoxidation

According to the degree of deoxidation, steel is classified into:

calm (sp);
semi-calm (ps);
boiling (kp).

Deoxidation is the process of removing oxygen from liquid steel.

Boiling steels are deoxidized only by manganese, which is not enough. Before casting, they contain an increased amount of oxygen, which, when the ingot solidifies, partially reacts with carbon and is released in the form of gas bubbles of carbon monoxide, giving the impression of “boiling” of the steel.

Literature

Materials Science / Yu.T. Chumachenko, G.V. Chumachenko. – Rostov n/d: Phoenix, 2005. – 320 p.
Materials Science / O.V. Travin, N.T. Travina. M.: Metallurgy. 1989. 384 p.
Metallurgy / A.P. Gulyaev. M.: Metallurgy, 1986. 544 p.
Materials Science / A.M. Adaskin, V.M. Zuev. – M.: ProfObrIzdat, 2001. – 240 p.
Handbook of a young revolver turner / E.O. Peshkov. M., Higher School, 1966. 179 p.
Welder's reference book / A.M. Kitaev, Ya.A. Kitaev. M.: Mechanical Engineering, 1985. – 256 p.
Materials in instrument making and automation: Handbook / Ed. Yu.M. Pyatina. – M.: Mashinostroenie, 1982. – 528 p.
General technical reference book / Under general. ed. E.A. Skorokhodova. – M.
: Mechanical Engineering, 1989. – 512 p.

Source: http://weldworld.ru/theory/materialovedenie/stali/klassifikaciya-staley.html

Classification of steel according to chemical and mechanical properties

Steel - produced from a mixture of cast iron and metal in converters, open-hearth furnaces (open-hearth furnaces are now closed) and electric furnaces.

Carbon steel is a metal without alloying elements.

Alloy steel – steel with the addition of alloying elements such as Mn and Si.

The Metpromsnab company sells these steel grades from stock and on order.

Steels are divided into groups according to different properties and chemistry. composition

Steels are classified according to the following principles:

• by chemical composition;
• by structural composition;
• by quality (by production method and content of harmful impurities);
• according to the degree of deoxidation and the nature of solidification of the metal in the mold;
• as intended.

Carbon steels according to chemistry. composition can be divided into groups:

• low-carbon – less than 0.3% C;
• medium carbon – 0.30.7% C;
• high carbon – more than 0.7% C.

Depending on the content of alloying additives:

• low alloyed – less than 2.5%;
• medium alloyed – 2.510%;
• highly alloyed – more than 10%.

Alloy steels are also divided into classes according to composition:
• in the annealed state - hypoeutectoid, hypereutectoid, ledeburite (carbide), ferritic, austenitic;
• in a normalized state – pearlitic, martensitic and authenite.

The pearlitic class includes carbon and alloy steels with a low content of alloying additives.
To the martensitic class - with a higher level and to the austenitic class - with a high content of alloying additives.

Steels are also classified according to quality:

S, % P, %
Ordinary quality (ordinary) less than 0.06 less than 0.07
High quality less than 0.04 less than 0.035
High quality less than 0.025 less than 0.025
Extra high quality less than 0.015 less than 0.025
Steel is divided according to the degree of deoxidation:
• Calm (short designation sp).
• Semi-quiet (short designation ps).
• Boiling (short designation kp).

Steels are also classified according to their purpose:
• Structural.
• Instrumental.
• Steels with special physical and chemical properties.

Structural steels are divided into:

• Construction.
• For cold stamping.
• Improveable.
• Highly durable.
• Spring-type.
• Ball bearing.
• Corrosion resistant.
• Heat resistant.
• Heat resistant.
• Wear-resistant steels.

Let's summarize.

Steel is a structural material in the broad sense of the word: including steels for machine parts, building structures, tools and for special working conditions - heat-resistant, stainless steel, etc.
The main qualities of steel are hardness, strength, toughness, ductility, elasticity, and heat resistance.

The Metpromsnab company is engaged in the wholesale and small wholesale sales of such steel grades as structural, carbon, low-alloy, wear-resistant steel. With us you will always find: steel 3sp-5, steel 09G2S, steel 45, steel 40X, steel 10HSND, steel 15HSND, steel S355J, steel 30KhGSA, steel 65G, as well as wear-resistant steels (analogs WELDOX, HARDOX) S690QL, A514-B , 16ХГМФТР, 25ХГС.

Source: https://metpromsnab.com/klassifikacija-stali/

Wear-resistant steels, their characteristics and types

14 August 2018 12:01

// Rolled metal

Wear-resistant steels include alloys intended for use in extreme conditions. Thanks to their special chemical composition, they withstand severe abrasive wear, exceptional mechanical and compressive loads, sliding and friction.

There are many manufacturers and types of rolled products on the high-strength steel market, which can be difficult to understand even for professionals.

From this article you will learn how to choose the right wear-resistant steel, and why in different industries it is simply necessary to use high-quality wear-resistant alloys.

The main property of wear-resistant steels is increased hardness, which is ensured by the presence of manganese and other alloying elements in the composition.

Moreover, the stronger the load on the element, the more wear-resistant and hard the part becomes, and the destruction of the surface and internal structure does not occur.
With high strength values, the material remains plastic, does not crumble, and can be welded.

When choosing a high-strength alloy, it is important to consider the conditions and intensity of operation of the part or assembly. Hardened rolled products have increased resistance to all types of wear.

Characteristics of wear-resistant steels

The main property of wear-resistant steels is increased hardness, which is ensured by the presence of manganese and other alloying elements in the composition.

Areas of application of wear-resistant alloys

The use of high-strength steels increases the service life of equipment, machines and mechanisms, significantly reduces the costs of their repair and maintenance, and eliminates production downtime. Rolled metal is used in a variety of industries.

Automotive
production Production of parts and assemblies subject to intense loads and operating under friction conditions - rollers and bearing balls, bushings, replaceable linings, piston rings, crankshafts and other shaped products, armored elements.
Road and construction equipment
Manufacturing of excavator buckets, cutting edges of equipment, visors of dredges, hydraulic hammers, leveling elements for asphalt paving machines. As a lining for equipment chutes, crushers, containers, drum blades, concrete mixers.
Heavy quarry and mining equipment
Manufacturing of cutting edges of equipment, bodies for dump trucks, transportation tanks and chutes, bunkers, lining of storage tanks and other elements of crushers, cutting tools.
Railway industry
Cladding of cars, as elements of railway tracks, links of caterpillar mechanisms, crosspieces, etc.
Agricultural machinery and equipment for logging
End mechanisms of a timber loader, reloader, elements of a squeezing press, plow equipment, equipment for transporting and storing silage.
Machine tool industry
As elements of production equipment subjected to severe loads and friction: shafts, assemblies, assemblies, parts.
Construction industry
Manufacturing of metal structures for various purposes, requiring special structural strength. For these purposes, structural grades are used.

Types and grades of wear-resistant steels

When studying the classification and selection of wear-resistant alloys, it is necessary to take into account that a number of brands of domestic manufacturers are designated by indices, and foreign markings do not contain information on the chemical composition.

Graphitized grades (U16 (EI336), 60G, 65G, 70G, 40Х, 40ХН, 45ХН, etc.) are characterized by a high carbon content; the composition also includes chromium, nickel, and graphite. Rolled products are strengthened under dynamic loads and are difficult to process.

Ball bearing alloys GOST 801-78 (ShKh20, ShKh15) are a type of tool steel and have high strength and wear resistance, hardness and the required level of toughness. High-manganese grades (G13L, 110G13L) - in addition to manganese, the composition also includes iron, carbon, and chromium. They have the highest wear resistance, which is combined with low hardness and high strength. According to domestic standardization, alloys comply with GOST 977-88.

As you can see, the high quality and reliability of high-strength steels make their use justified in many industries and mechanical engineering. These alloys have firmly gained a position in the rolled metal market and are very popular.

Source: https://indust.by/info/articles/metalloprokat/iznosostoykaya-stal/

Steel classification

A malleable alloy of iron, carbon and other impurities is called steel.

Steel production involves fusing cast iron and scrap metal in specialized furnaces.

Almost all types of steel are a structural material, everything that is used in construction, in mechanical engineering, in the creation of mechanical parts, etc.

Characteristic

The main characteristics of steel are:

strength,
plasticity,
viscosity,
elasticity,
hardness,
fatigue,
resistance to cracking,
resistance to low and high temperatures.

Why are they so important

Due to its strength, it is possible to withstand operating stresses.
Due to plasticity, it ensures resistance to significant deformations, avoiding destruction in areas of overload.
Due to viscosity, the work of external forces is absorbed and the development of cracks is prevented.

In the production of springs, springs or other elements operating under the influence of elastic deformation and the influence of cyclic loads, the most important criteria are high elastic limits, steel yield, endurance, ductility, and resistance to brittle fracture.

Steel with a significantly higher level of strength is called high-strength . Its key indicators are:

sufficient plasticity,
low susceptibility to tearing and brittleness at low temperatures,
significant resistance to brittle fractures,
good weldability,

And all this with the necessary strength.

High-strength steels include medium-carbon alloy steels.

Steels are classified according to the following criteria:

chemical composition;
structure;
quality (production technology, presence of bad components);
degree of deoxidation and nature of hardening;
specific purpose of steel.

Chemistry.

Considering the amount of carbon, steel can be:

low-carbon - carbon content up to 0.3%;
medium-carbon - the presence of carbon in the range of 0.3-0.7%;
high-carbon - carbon content more than 0.7%.

Alloying

In order to impart special properties to the alloy, alloying components or their combinations are added to it.

Chromium, nickel, molybdenum, aluminum, titanium, vanadium, sulfur and manganese (in increased concentration) are used as alloying impurities The best results are obtained when several components are introduced at once.

Alloy steels are classified according to the total content of alloying impurities. So alloy steel is:

low-alloyed - containing alloying impurities up to 2.5%;
medium alloyed - the content of alloying impurities is in the range of 2.5-10%;
highly alloyed - the presence of alloying components is over 10%.

Structure

Alloy steels and alloys are divided into structure types (state diagram of the iron-carbon system):

hypoeutectoid,
hypereutectoid,
ledeburite (carbide),
ferritic,
austenitic,
pearlite,
martensitic.

The pearlitic structure includes carbon, alloy steels with a small presence of alloying impurities, the martensitic structure - with an average amount, and the austenitic structure - with a large presence of alloying components.

Impurities

The quality of steel depends on the production technology and the number of components. Considering the quality, there are 4 classes of steel:

Group	S, %	R, %
Raw steel (ordinary quality)	up to 0.06	more than 0.07
High quality	up to 0.04	more than 0.035
High quality	up to 0.025	more than 0.025
Particularly high quality	up to 0.015	more than 0.025

Ordinary steel

Carbon steel of ordinary quality is the most popular (St0, St3ps/sp, St5kp) and a wide range of rolled metal products are produced from it.

Quality steel

This class includes carbon and alloy steels with a certain content of sulfur and phosphorus (08kp, 10ps, 20).
The production process of high-quality and ordinary grades of steel is similar, the difference is the quality of the charge and the technology of melting and casting.

Taking into account the degree of deoxidation and the nature of solidification, ordinary and high-quality steel is divided into:

calm (sp),
semi-calm (ps),
boiling (kp).

The difference between them lies in the content of elements such as oxygen, nitrogen, hydrogen. Boiling steel contains the maximum amount of them.

High quality steel

It is smelted in electric furnaces, which ensure the proper purity of non-metallic components (S, P up to 0.03%) and gas.

Especially high-quality steel is subjected to electroslag remelting, which ensures purification from sulfide or oxide (S up to 0.01%, P up to 0.025%).

The presented classification is not complete. We will look at the differences between steels by nature of purpose in the next publication.

Source: https://vikant.com.ua/news/Kl_Steel