Carbon (carbon) steel: types, production and application. Low carbon steel: composition and properties

Steel is a product of ferrous metallurgy, the main product of which is building fittings, rolled metal products of various profiles, pipes, parts, mechanisms and tools.

Steel production

Ferrous metallurgy is also engaged in steel. Cast iron is a hard but not durable material. Steel - durable, reliable, ductile, prone to being used in foundry, rolling, forging and stamping.

There are several ways to smelt steel:

1. Converter. Equipment: Charge (raw materials): scrap steel, limestone. Only carbon steels are produced.
2. Martenovsky. Equipment: open-hearth furnace. Charge: liquid pig iron, steel scrap, iron ore. Universal for both carbon and alloy steels.
3. Electric arc. Equipment: electric arc furnace. Charge: steel scrap, cast iron, coke, limestone. Universal method.
4. Induction. Equipment: induction furnace. Charge: steel and cast iron scrap metal, ferroalloys.

The essence of the steel production process is to reduce the amount of negative chemical inclusions in order to obtain a metal that is popularly called "iron", or rather, an iron-carbon alloy with a carbon content of not more than 2.14%.

Deoxidation processes

For steel at the final stage of smelting, a boiling process is characteristic, which is influenced by the nitrogen, hydrogen, and carbon oxides inherent in it. Such an alloy in the solidified state has a porous structure, which is removed by rolling. It is soft and plastic, but not strong enough.

The deoxidation process consists in the deactivation of boiling impurities by introducing ferromanganese, ferrosilicon, and aluminum into the alloy. Depending on the amount of residual gases and deoxidizing elements, steel can be semi-calm or calm.

The finished steel of the required degree of deoxidation is poured into molds for crystallization and use at subsequent technological stages in the manufacture of finished steel products.

Classification of carbon steel

All steel that exists on the world market can be divided into carbon and alloy. All grades of carbon steel are divided into different classifier groups and designation features.

Based on the main classification features, there are:

1. Carbon structural steels. They contain less than 0.8% carbon. They are used for the manufacture of fittings, rolling products and castings.
2. Carbon tool steels containing 0.7% to 1.3% carbon. They are used for tools, instrumentation equipment.

According to the methods of deoxidation:

• boiling - deoxidizing elements (RE) in the composition of less than 0.05%;
• semi-calm - 0.05%≤RE≤0.15%;
• calm - 0.15%≤RE≤0.3%.

By chemical composition:

• low-carbon (0.3% ≤ C);
• medium carbon (0.3≤С≤0.65%);
• high-carbon (0.65≤С≤1.3%).

Depending on the microstructure:

• hypoeutectoid - in such steel, carbon in the composition is less than 0.8%;
• eutectoid - these are steels with a carbon content of 0.8%;
• hypereutectoid - steels with a carbon content of more than 0.8%.

By quality:

1. Regular quality. Sulfur here contains less than 0.06%, phosphorus - no more than 0.07%.
2. Quality steels. They do not contain sulfur and phosphorus more than 0.04%.
3. High quality. The amount of sulfur here does not exceed 0.025%, and phosphorus - no more than 0.018%.

According to the main standard, carbon steel grades are distributed into:

• structural of ordinary quality;
• structural quality;
• instrumental quality;
• instrumental high quality.

Features of marking structural steel of ordinary quality

Steels of ordinary quality contain: C - up to 0.6%, S - up to 0.06%, P - up to 0.07%. Let's look at how this carbon steel is marked. GOST 380 defines the following nuances of designation:

• A, B, C - group; A - not indicated in stamps;
• 0-6 after the letters "St" - a serial number in which the chemical composition and (or) mechanical properties are encrypted;
• G - the presence of Mangan Mn (manganese);
• kp, ps, cn - degree of deoxidation (boiling, semi-calm, calm).

The numbers from 1 to 6 after the degree of deoxidation through a dash are categories. In this case, the first category is not indicated in any way.

The letters M, K at the beginning of the brand can mean a metallurgical method of production: open-hearth or oxygen-converter. By the way, carbon steels of ordinary quality are represented by the quantitative composition of grades, approximately 47 pieces.

Classification of structural steels of ordinary quality

Carbon steels of ordinary quality are divided into groups.

• Group A: steels that must exactly match the specified mechanical properties. They are supplied to the consumer most often in the form of sheet and diversified products (sheets, tees, I-beams, fittings, rivets and cases). Grades: St0, St1 - St6 (kp, ps, sp), categories 1-3, including St3Gps, St5Gps.
• Group B: steels that must be regulated by the necessary chemical composition and properties. Castings and rolled products are produced, which will be subjected to additional machining by pressure in a hot state (forging, stamping). Marks: Bst0, Bst1 (kp-sp), Bst2 (kp, ps), Bst3 (kp-sp, including Bst3Gps), Bst4 (kp, ps), Bst 6 (ps, sp), categories 1 and 2.
• Group B: steels that must meet the required chemical, physical, mechanical and technological properties. This group is characterized by a variety of grades from which plastic sheet metal is made, durable fittings for working in areas of significant temperature differences, critical parts (bolts, nuts, axles, piston pins). All products of different composition, properties and grades of this group are united by good technological weldability. Grades: VSt1-VSt6 (kp, ps, sp), VSt5 (ps, sp), including VSt3Gps, categories 1-6.

Structural steels of ordinary quality are alloys that have a wide variety of uses in industry.

Marking of carbon quality steel

Carbon quality steels have in the composition of S and P no more than 0.04%, respectively.

Marking (GOST 1050-88):

• numbers 05-60 - encrypted presence of carbon (minimum - 0.05%, maximum - 0.6%);
• kp, ps, cn - the degree of deoxidation ("cp" is not indicated);
• G, Yu, F - contain manganese, aluminum, vanadium.

Exceptions to labeling

Carbon quality steels in their marking have exceptions:

• 15K, 20K, 22K - high-quality steels, applicable in boiler building;
• 20-PV - carbon - 0.2%, steel is applicable in the manufacture of pipes by hot rolling, in boiler building and installation of heating systems, contains copper and chromium;
• OSV - steel for the manufacture of wagon axles, contains nickel, chromium, copper.

For all grades of quality steels, the possible need to use thermal (for example, normalization) and chemical-thermal treatment (for example, carburizing) is typical.

Classification of carbon quality steels

This type of carbon steels can be divided into 4 groups:

1. Highly plastic material applicable for cold machining (rolling), sheet and pipe rolling. Grades - steel 08ps, steel 08, steel 08kp.
2. A metal used in hot rolling and stamping that will perform under thermally aggressive conditions. Grades - from steel 10 to steel 25.
3. Steel that has found application in the manufacture of critical parts, including springs, springs, couplings, bolts, shafts. Grades - from steel 60 to steel 85.
4. Steels that require reliable operation in aggressive conditions (for example, the chain of a caterpillar tractor). Grades steel 30, steel 50, steel 30G, steel 50G.

It is also possible to divide into 2 groups all known grades of carbon steel from the quality class: conventional structural and manganese-containing structural.

Application of carbon structural steel

Carbon tool steels are characterized by high strength and toughness. They are necessarily subject to multi-stage heat treatment.

Brand designation (GOST 1435-74):

• U - carbon instrumental;
• 7 -13 - the carbon content in it is 0.7-1.3%, respectively;
• G - the presence of manganese in the composition;
• A is high quality.

An exception to the basic principles of marking carbon tool steels is the material for parts of watch movements A75, ASU10E, AU10E.

Requirements for carbon tool steels

In accordance with GOST, tool steels must comply with a number of characteristics.

Required physical, chemical and mechanical properties: quality indicators of hardness, impact strength, strength, resistance to temperature changes during operation (during cutting, drilling, shock loads), corrosion resistance.

Given technological properties:

• resistance to negative processes of cutting technology (chip sticking, hardening);
• good machinability by turning and grinding;
• susceptibility to heat treatment;
• overheat resistance.

To improve the quality of mechanical and technological indicators, tool steels are subjected to multi-stage heat treatment:

• annealing of the starting material before making tools;
• hardening (cooling in salt solutions) and subsequent tempering of finished products (mainly low tempering).

The obtained properties are determined by the chemical composition and the resulting microstructure: martensite with cementite and austenite inclusions.

Use of carbon tool steels

The described steels are used for the manufacture of all kinds of tools: cutting, percussion, auxiliary.

• Steel U7, U7A - hammers, chisels, axes, chisels, sledgehammers, chisels, fish hooks.
• Steel U8, U8A, U8G - saws, screwdrivers, center punches, countersinks, cutters, pliers.
• Steel U9, U9A - metalwork tools, tools for cutting wood.
• U11, U11A - rasps, taps, auxiliary tools for stamping and calibration.
• U 12, U12A - reamers, taps, measuring tools.
• U13, U13A - files, shaving and surgical instruments, stamping punches.

A rational choice of carbon steel grade, its heat treatment technology, understanding of its properties and features is the key to a long service life of manufactured, processed or used structures or tools.

Such products are distinguished by a high content of the chemical element C. Its share in the iron + carbon alloy is at least 0.55%. What properties it gives to steel, its grades - all this will be the topic of conversation.

There is no separate standard for high carbon steels. This metal is just one of the varieties of alloys of iron and carbon. It got its name because of the increased content of the element C (6th position in the periodic system). The classification of all steels, as well as marking, is quite complicated.

Detailed information on all carbon metals can be found in various GOSTs. As a rule, first of all, specialists turn to such standards as No. 1050 of 1988 and No. 380 of 2005, in which footnotes to other regulatory documents are indicated for certain positions.

Features of high carbon steels

• Percentage of chemical elements: C - (0.55 - 1.7); Mn - (0.3 - 0.9).
• Insufficient viscosity. For this reason, structural products (parts) are not produced from high-carbon steels.
• Increased strength and wear resistance. But this is only if the carbon content does not exceed 0.8 - 0.9%. A further increase in the share of C sharply reduces the numerical values ​​of these characteristics.
• Poor weldability, since high temperatures initiate the formation of cracks in the metal, pores, the appearance of hardened segments due to intense carbon burnout. Therefore, the working area must be preheated (up to 225 ± 25 ºС).
• High production cost. It is this, as well as individual properties, that limit the scope of such steels.

What is made

• Steel shot used for abrasive processing of materials - DSR (chopped), DSC (chopped) and DSL (cast).
• Rope wire.
• Springs.
• various kinds.

Basically, all parts made of high-carbon steels are made by stamping, since pressure methods, due to the low plasticity of the material, are ineffective.

The tables below will certainly help the reader understand which grade of high carbon steel he needs for specific purposes.

All brands often have additional symbols in the designation, which are affixed at the end. There are quite a few of them, so only the most common.

High carbon steel

High carbon steel - steel with a carbon content over 0.6%(up to 2%).

Purpose and production

Their main purpose is the receipt of a rope wire. Used in the manufacture patenting, quickly cooled to obtain a fine-grained F + P structure (ferrite + perlite) and immediately subjected to cold deformation - drawing. The combination of ultrafine structure and work hardening makes it possible to obtain a mechanical stress in the wire = 3000 - 5000 MPa. Due to the low viscosity, structural parts made of this steel do not do. For the manufacture of bearings, chromium-alloyed (from 0.35 to 1.70% (wt.) Cr) ​​steel grades ShKh4, ShKh15, ShKh15SG, ShKh20SG containing 0.95-1.05% (wt.) carbon (GOST 801- 78. Bearing steel. Specifications). High-carbon steel is used to make steel shot DSL (cast), DSK (chopped) and DSR (chopped) for shot blasting of surfaces - abrasive cleaning or hardening (GOST 11964-81. Cast iron and steel technical shot. General specifications). For the manufacture of springs, wire from steels KT-2 (0.86-0.91% (wt.) C) and 3K-7 (0.68-0.76% (wt.) C) is used.

Welding

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See what "High carbon steel" is in other dictionaries:

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Stainless steel

Heat resistant steel- Phases of iron-carbon alloys Ferrite (solid solution of interstitial C in α iron with a body-centered cubic lattice) Austenite (solid solution of interstitial C in γ iron with a face-centered cubic lattice) Cementite (iron carbide; Fe3C ... Wikipedia

heat resistant steel- Phases of iron-carbon alloys Ferrite (solid solution of interstitial C in α iron with a body-centered cubic lattice) Austenite (solid solution of interstitial C in γ iron with a face-centered cubic lattice) Cementite (iron carbide; Fe3C ... Wikipedia

Low carbon steel is ubiquitous. Its popularity is based on physical, chemical properties and low cost. This alloy is widely used in industry and construction. Let's take a closer look at this

Compound

Steel is iron enriched with carbon during the smelting process. Carbon smelting is characterized by the presence of carbon, which determines the basic properties of the metal, and impurities: phosphorus (up to 0.07%), silicon (up to 0.35%), sulfur (up to 0.06%), manganese (up to 0.8% ). So, mild steel contains no more than 0.25% carbon.

As for other additives, manganese and silicon serve to deoxidize (remove oxygen from which reduces brittleness during hot deformation). But an increased percentage of sulfur can lead to cracking of the alloy during heat treatment, phosphorus - during cold treatment.

How to get

The production of a low-carbon alloy can be decomposed into several stages: loading iron and scrap (charge) into the furnace, thermal treatment to the state of melting, removal of impurities from the mass.

Three methods are used to execute such processes:

• Open-hearth furnaces. The most common equipment. The melting process takes place within a few hours, which allows laboratories to monitor the quality of the resulting composition.
• Convector ovens. Produced by purging with oxygen. It should be noted that the alloys obtained in this way are not of high quality, since they contain a greater amount of impurities.
• Induction and electric furnaces. The production process goes with the use of slag. In this way, high-quality and specialized alloys are obtained.

Consider the features of the classification of alloys.

Kinds

Low carbon steel can be of three types:

• Regular quality. In such alloys, the sulfur content does not exceed 0.06%, phosphorus 0.07%.
• quality. The composition contains: sulfur up to 0.04%, phosphorus up to 0.035%.
• High quality. Sulfur content up to 0.025%, phosphorus content up to 0.025%
• Special quality. Low content of impurities: sulfur up to 0.015%, phosphorus - up to 0.025%.

As mentioned earlier, the less impurities, the better the quality of the alloy.

Low-carbon steel GOST 380-94 of ordinary quality is divided into three more groups:

• A. determined by its mechanical properties. The form of delivery to the consumer is most often found in the form of multi-section and sheet metal.
• B. The main indicators are the chemical composition and properties. Optimal for mechanical action by pressure under a thermal factor (forging, stamping).
• IN. For these types of alloys, the following properties are important: technical, technological, physical, chemical and, accordingly, composition.

According to the process of deoxidation, steel is divided into:

• Calm. The curing process is going smoothly. No gases are released during this process. Shrinkage occurs in the middle of the ingot.
• Semi-calm. An intermediate view of steel between calm and boiling compositions.
• Boiling. Solidification occurs with the release of gas. Shrinkage shell of hidden type.

Basic properties

Low-carbon steel is highly ductile, easily deformed in a cold state and in a hot state. A distinctive feature of this alloy is good weldability. Depending on the additional elements, the properties of the steel may vary.

Most often, low-carbon alloys are used in construction and industry. This is due to the low price and good strength properties. Such an alloy is also called structural. The properties of low carbon steel are encrypted in the marking. Below we will consider its features.

Marking features

Ordinary mild steel has the letter designation CT and digital. The number should be divided by 100, then the percentage of carbon will be clear. For example, CT15 (carbon 0.15%).

Consider the marking and decipher the notation:

• The first letters or their absence indicates belonging to a particular quality group. It can be B or C. If there is no letter, then the alloy belongs to category A.
• St means the word "steel".
• The digital designation is the encrypted percentage of carbon.
• kp, ps - denotes a boiling or semi-calm alloy. The absence of a designation indicates that the steel is calm (cn).
• The letter designation and the number after it reveal which impurities are included in the composition, and their percentage. For example, G - manganese, Yu - aluminum, F - vanadium.

For high-quality low-carbon steels, the lettering “St” is not put in the marking.

Color coding is also used. For example, grade 10 mild steel is white. Special purpose steels may be designated by additional letters. For example, "K" - is used in boiler building; OSV - used for the manufacture of wagon axles, etc.

Manufactured products

There are several groups of steel products:

• Sheet steel. Subspecies: thick sheet (GOST 19903-74), thin sheet (GOST 19904-74), broadband (GOST 8200-70), strip (GOST 103-76), corrugated (GOST 8568-78)
• Corner profiles. Equal-shelf (GOST 8509-93), unequal-shelf (GOST 8510-86).
• Channels(GOST 8240-93).
• I-beams. ordinary (GOST 8239-89), I-beams wide-shelf (GOST 26020-83, STO ASCHM 20-93).
• Pipes.
• Profiled flooring.

Secondary profiles are added to this list, which are formed due to welding and machining.

Applications

The scope of use of low-carbon steel is quite wide and depends on the marking:

• St 0, 1, 3Gsp. Wide application in construction. For example, low carbon steel reinforcing wire,
• 05kp, 08, 08kp, 08y. Good for stamping and cold drawing (high plasticity). Used in the automotive industry: body parts, fuel tanks, coils, parts of welded structures.
• 10, 15. They are used for parts that are not subjected to high loads. Boiler pipes, stampings, couplings, bolts, screws.
• 18kp. A typical application is structures that are produced by welding.
• 20, 25. Widely used for the production of fasteners. valve tappets, frames and other parts of agricultural machines.
• 30, 35. Lightly loaded axles, sprockets, gears, etc.
• 40, 45, 50. Parts experiencing medium loads. For example, crankshafts, friction discs.
• 60-85. Parts subjected to high stress. These can be railway rails, crane wheels, springs, washers.

As you can see, the product range is extensive - it is not only low-carbon steel wire. It is also the details of complex mechanisms.

Low alloy and low carbon steel: differences

To improve any characteristics of the alloy, alloying elements are added.

Steels that contain a low amount of carbon (up to a quarter of a percent) and alloying additives (a total percentage of up to 4%) in the cheba are called low-alloyed. Such rolled products retain high weldability, but at the same time, different properties are enhanced. For example, strength, anti-corrosion performance and so on. As a rule, both types are used in welded structures, which must withstand a temperature range from minus 40 to plus 450 degrees Celsius.

Welding features

Welding of low-carbon steels has high rates. The type of welding, electrodes and their thickness are selected based on the following technical data:

• The connection must be firmly fastened.
• There should be no seam defects.
• The chemical composition of the seam must be carried out in accordance with the standards specified in GOST.
• Welded joints must comply with the operating conditions (resistance to vibrations, mechanical stress, temperature conditions).

Can be used various from gas welding to carbon dioxide consumable electrode welding. When selecting, take into account the high fusibility of low-carbon and low-alloy alloys.

As for the specific scope of application, low-carbon steel is used in construction and engineering.

It is selected on the basis of the required physical and chemical properties at the output. The presence can improve some properties (resistance to corrosion, temperature extremes), but also worsen others. Good weldability is another advantage of such alloys.

So, we found out what products from low-carbon and low-alloy steel are.

High carbon stainless steel is a metal alloy containing relatively large amounts of carbon. The amount of carbon can be 1.2% and as little as 0.2%. The reasons for this vary depending on the manufacturer and the type of blade used.

Stainless steel is an alloy that contains 10.5% or more chromium (Cr) and iron (Fe) more than 50%. Chromium is the element that makes stainless steel stain resistant. In fact, stainless steel should be referred to as stain-resistant steel, as it can stain, but is less likely than pure steel. Stainless steel is also very easy to care for and does not require regular maintenance to keep its beauty. Low carbon steel is softer and doesn't have a blade edge, which is a very good thing.

Carbon steel has a good edge when sharpened properly and regularly, and is a much harder material to use in knife construction. Carbon steel knives corrode more easily and require regular lubrication. Follow the manufacturer's instructions for sharpening and seasoning to extend the life of your carbon steel knife.

When you combine carbon steel and stainless steel for high quality carbon stainless steel, you get the best out of each alloy. This steel is resistant to rust or staining, is very hard and has a low maintenance edge. This is generally considered to be a higher quality stainless steel alloy.

As with all others, there are better and better products out there. Some of the challenges manufacturers face when making high carbon stainless steel are carbon content, tempering, and chromium content. The carbon content will harden the steel, so if too much is added, the alloy becomes brittle. If manufacturers use too little carbon, there is not enough carbon to solidify the steel. The chromium content can also have a huge impact on the final product. Chromium attracts carbon, which means that carbon can steal chrome from stainless steel. When this happens, the final product is less resistant to stains than it should be. Tempering can also produce a very brittle blade. High carbon stainless steel generally has a fairly low heat tolerance of around 500 F (260 C) before it becomes too brittle for knife use.

When buying a knife, it is better to follow the rule: "you get what you pay for." Make sure the blade goes all the way through the handle. You will want to see the rivets holding the handle together. It should also feel good in your hands. A quality knife means you won't cut through your food; instead, you will use less effort. A high quality high carbon stainless steel knife, or any high quality knife for that matter, is a safer product for your kitchen. The less effort you put into grinding your food, the less likely your clutch will slip and cause an accident.