Basic classification of carbon steel

1. Carbon steel

Carbon steel, also known as carbon steel, is an iron-carbon alloy with carbon content of ωc less than 2%. Carbon steel seems to contain small amounts of silicon, manganese, sulfur, and phosphorus in addition to carbon.

According to the purpose, the carbon steel can be divided into carbon structural steel, carbon tool steel and easy cutting structural steel three types. Carbon structural steel can be divided into building structural steel and machine manufacturing structural steel two kinds. According to the carbon content can also be carbon steel two types of low carbon steel (ωc≤0.25%), carbon steel (ωc=0.25%-0.6%) and high carbon steel (ωC > 0.6%)

According to the amount of phosphorus, sulfur this can be carbon steel can be divided into ordinary carbon steel (iron, sulfur is higher), good quality carbon steel (phosphorus, sulfur is lower) and primary quality steel (phosphorus, sulfur is lower) like carbon steel the higher the carbon content, the higher the hardness, strength is high, but the plasticity will be reduced.

2. Carbon structural steel

This kind of steel is more absolute guarantee of mechanical properties. So its brand can reflect the mechanical properties of its material, with Q+ number can be expressed, "Q" is the compromise point "Qu" Chinese pinyin prefix.

The number means the yield point value, for example, Q275 means that the yield point of the bow is 275Mpa, if the letter A, B, C, D is marked behind the brand, it means that the steel quality grade is different, including the amount of S, P reduced in turn, the steel quality in order to improve.

If the letter "F" is marked after the grade, it is surging steel, superscript "b" is semi-sedated steel, and those not marked "F" or "b" are sedated steel. For example, Q235 -- AF is used to represent grade a boiling steel with a compromise point of 235MPa, and Q235 -- C is used to represent grade C calm steel with a yield point of 235MPa.

Carbon structural steel is generally not heat treated, but can be used in supply. Normal Q195, Q215, Q235 steel carbon quality fraction is low, good brazing performance, plasticity, toughness, there will be a certain strength, often rolled into sheet, steel bar, welded steel pipe, etc.

Act on Bridges, buildings and other structures and manufacture other rivets, screws, nuts and other parts. Q255 and Q275 steel carbon quality fraction slightly higher, higher strength, plasticity, toughness better, can be welded, usually slab condensation steel, strip steel and steel plate as structural parts to manufacture simple ah mechanical connecting rod, gear, coupling, pin and other parts.

3. good quality structural steel

The premise of this type of steel is to ensure the same chemical composition and mechanical properties. The grade is a two-digit number that represents the 10,000 fraction of the mass fraction of the carbon you calculate in the steel (ω) *10000). For example, 45 steel means that the mass fraction of carbon in steel you calculate is 0.45%; 08 steel can indicate that the average carbon mass fraction in steel is 0.08%.

High quality carbon structural steel is mainly used to make machine parts. The image is heat-treated to increase its mechanical properties. Reference carbon mass scores vary and have different uses.

08, 08F, 10, 10F steel, high plasticity, toughness, with high excellent varieties of cold forming properties and welding properties, often cold rolled into sheet, used to make instrument shell, automobile and tractor cold stamping parts, such as car body, tractor cab;

15, 20, 25 steel is used to make small size, light load, surface does not require wear resistance, heart strength requirements are not high carburizing parts, such as piston pin, template, etc.;

30, 35, 40, 45, 50 steel after heat treatment (carburizing + low temperature tempering) has a good training of comprehensive mechanical properties, that is, its own high strength and high plasticity, toughness, mainly used for the production of shaft parts, Or 40, 45 steel can be used in the manufacture of automobile, tractor crankshaft, connecting rod, general machine tool spindle, machine tool gear and other high stress shaft parts;

55, 60, 65 steel heat treatment process (forging + medium temperature tempering) with high elastic limit, often used to make the load is not large, relatively large size (beam section is greater than 112~15mm) of the spring, such as pressure regulation and speed spring, plunger spring, cold coil spring.

4. Carbon tool steel

Carbon tool steel is basically no alloying elements of high carbon steel, carbon content in the range of 0.65%-1.35%, its production cost is low, raw material sources are easy to obtain, good machinability training, heat treatment can also be obtained high hardness and high wear resistance, so it is more and more widely distinguished steel, separate manufacturing of a variety of cutting tools, molds, measuring tools.

But the red hardness of this kind of steel is poor, that is, when the working temperature is greater than 250℃, the hardness and wear resistance of steel will be sharply reduced and lost the ability to work. At the same time, carbon tool steel, if made into larger parts, is not easy to harden, but prone to wear and cracks.

5. Easy cutting structural steel

Easy cutting structural steel is to form some elements in the steel to make the steel brittle, so that the steel can be easily broken into debris when cutting, which can improve the cutting speed and shorten the tool life to the maximum extent. Sulfur is the main element that makes steel brittle. Lead, tellurium, bismuth and other elements are used in common low-alloy and easy cutting structural steel.

The sulfur content of this steel ranges from 0.08% to 0.30%, and manganese content ranges from 0.60% to 1.55%. Sulfur and manganese in steel are unknown in the form of manganese in the vulcanization process. Manganese in the vulcanization process is brittle and has lubricating effect, which makes the chips easy to break and helps to enhance and improve the quality of the thin layer processed.

6. Alloy steel

In addition to containing iron, carbon and a small amount of unavoidable silicon, manganese, phosphorus, sulfur elements, but also contains what will be a certain amount of alloy elements, alloy elements in steel silicon, manganese, molybdenum, nickel, chromium, vanadium, titanium, niobium, boron, lead, rare earth and one or several, this steel is called alloy steel.

Alloy-steel systems of various countries are different with their respective resources, production and using conditions. Nickel and chromate system was previously developed abroad, while our country is developed to give main consideration to silicon, manganese, vanadium, titanium, niobium, boron and rare earth.

Alloy steel accounts for about ten percent of the total output of steel, just like smelting in electric furnace according to the use of alloy steel can be divided into two categories of 8 categories, they are: alloy structural steel, spring steel, bearing steel, alloy tool steel, highway tool steel, stainless steel, refractory dry skin steel, electrical silicon steel.

7. Other low alloy steels

Common low alloy steel is a common alloy steel containing some small amount of alloying elements (in most cases less than 3% of the total amount). The strength of this steel is relatively high, see professional performance is better, and has corrosion resistance, wear resistance, low temperature resistance these better cutting performance, welding performance and other water saving scarce alloy elements (such as nickel, chromium) under the conditions, usually 1t ordinary low alloy steel can top 1.2-1.3t carbon steel can be used, its service life and use range is far more carbon steel. Ordinary low alloy steel can not be smelted as smelting method in open furnace, converter smelting, the cost is close to carbon steel.

8. Alloy steel for engineering structure

This refers to the alloy steel of engineering and building structural belts, except weldable high-strength alloy structural steel, alloy reinforcement steel, alloy steel for railway, alloy steel for geological oil drilling, alloy steel for pressure vessels, high-manganese wear-resisting steel, etc. This kind of steel is widely used in electronic engineering and building structural parts. In alloy steel, the total alloy content of this kind of steel is low, but the processing production, less use.

9. Alloy steel for mechanical structure

This type of steel refers to alloyed steels that are distinguished from those used to make machinery and mechanical parts. It is on the basis of good quality carbon steel, properly formed one or several alloy elements, the use of which can improve the strength, toughness and hardenability of steel. Most of these steels are used after heat treatment (such as tempering treatment, complete surface treatment).

The main attention and specific usage of alloy structural steel and alloy spring steel two categories, Kozelisk quenching treatment of alloy steel, shot peening treatment of alloy steel (carburizing steel, carburizing steel, surface high frequency hardening steel, etc.), cold plastic forming of alloy steel (cold top forging steel, cold drawing steel, etc.).

According to the chemical composition basically mixed series can be collectively known as Mn series steel, SiMn series steel, Cr series steel, CrMo series steel, CrNiMo series steel, Ni series steel, B series steel.

10. Alloy structural steel

The carbon content of alloy structural steel is much lower than that of carbon structural steel, generally in the range of 0.15%-0.50%. In addition to carbon, it also contains one or several alloying elements, such as silicon, manganese, vanadium, titanium, boron and nickel, chromium, molybdenum and so on. Alloy structural steels are easily hardenable and easily deformed or hulled so that later annealing can improve the properties of the steel.

Alloy structural steel is becoming more and more widely used in the manufacture of automobiles, tractors, ships, steam turbines, heavy machine tools of various transmission parts and fasteners. Low - carbon alloy steel appears to be carburized and medium - carbon alloy steel appears to be involved in conditioning.

11. Alloy tool steel

Alloy tool steel is medium and high carbon steel with a variety of alloy elements, such as silicon, chromium, tungsten, molybdenum, vanadium, etc. Alloy tool steels are easy to harden, and when able to re-develop wear and cracks, they are suitable for producing large and complex cutting tools, dies and measuring tools for the same purpose, but the carbon content of alloy tool steels is quite different.

The carbon content of most alloy tool steels is 0.5%-1.5%, and the carbon content of steel for thermal shift die is lower, and ωc is in the range of 0.3%-0.6%. Cutting tool steel image containing carbon ωc1%;

The carbon content of cold working die steel is higher, such as the carbon content of graphite die steel ωc is up to 1.5%, and the carbon content of high carbon and high chromium cold working die steel is up to more than 2%.

12. high speed tool steel

Xixia high-speed tool steel is high carbon and high alloy tool steel, the carbon content of ωc in steel is 0.7%-1.4%, what alloy elements can naturally form high hardness carbide, such as tungsten, molybdenum, chromium, vanadium.

High speed tool steel with high red hard, under the conditions of high speed cutting, temperature soluble inflammation 500-600℃ hardness is not reduced, so long as good quality cutting performance

13. Spring

The spring is used under shock, vibration or constant alternating stress, because there is no requirement that the spring steel has high tensile strength, elastic limit and high fatigue strength. In the process, spring steel is required to have hardenability, easy to decarbonize and good surface quality

Carbon spring steel is the carbon content of ωc in the range of 0.6%-0.9% of high quality carbon structural steel (and normal and high manganese content). Alloy spring steel is usually silicon manganese series steel, their carbon content is slightly lower, mainly by increasing the silicon content of ωsi (1.3%-2.8%) can improve the performance;

There are chromium, tungsten, vanadium alloy spring steel. In the past few years, our resources have been controlled, and according to the requirements of new technology design for automobile and tractor, a new steel with boron, niobium, molybdenum and other elements has been successfully developed on the basis of silicon manganese steel, which has lasted the service life of spring and improved the quality of spring steel.

14. Bearing steel

Bearing steel is used to manufacture ball, roller and bearing ring steel. Bearing is subjected to so much pressure and friction when working, so it requires bearing steel to have high and uniform hardness and wear resistance, as well as high elastic limit. The uniformity of the chemical composition of the bearing steel, the content and wide distribution of non-metallic inclusions, the distribution of carbide and other requirements are extremely strict.

Bearing steel, also known as high carbon chromium steel, contains carbon ωc is about 1%, lead content ωcr is 0.5%-1.65%. Bearing steel is divided into three types of high-carbon chromium bearing steel, non-chromium bearing steel, carburized bearing steel, 304 stainless steel bearing steel, medium and high temperature bearing steel and anti-magnetic bearing steel.

15. electrical silicon steel

The silicon steel used in electric appliance industry is mainly used to manufacture silicon steel sheet for electric appliance industry. Silicon steel sheet is a small amount of steel used in the manufacture of motors and transformers. According to the chemical composition of silicon steel can be divided into low silicon steel and high silicon steel. Low silicon steel silicon content of ωsi=1.0%-2.5%, mainly pay attention to the use of motor manufacturing; High silicon steel silicon content of ωsi=3.0%-4.5%, generally used to manufacture transformers. Their carbon content is ωc=0.06%-0.08%.

16. Rail steel

The rail should pay attention to be able to withstand the pressure and impact load of rolling stock, and. Those require sufficient strength and hardness and some toughness. Usually distinguished rail is open furnace and converter smelting carbon killed steel, this steel contains carbon ωC=0.6%-0.8%, a class of medium and high carbon steel, but steel manganese content of ωMn is higher, in the range of 0.6%-1.1%. In recent years, the scope of application according to the structure of most low alloy steel rail, such as high silicon rail, manganese rail, copper rail, titanium rail and so on. Most low alloy rail than carbon rail wear resistance, corrosion resistance, service life is much improved.

17. Shipbuilding steel

Shipbuilding steel refers to the steel mainly used in the manufacture of sea ships and small inland river hull structures. The reason is that the hull structure is manufactured according to the structural spot welding method, which does not require the shipbuilding steel to have better spot welding properties. As for those who require a certain strength, toughness and, of course, low temperature resistance and corrosion performance. In the past, mild steel was mainly used as shipbuilding steel. Some time ago, a lot of ordinary low-alloy steel is needed, and we have steel types such as 12 manganese ships, 16 manganese ships, 15 manganese vanadium ships and other steel types. These kinds of steel have high strength, good toughness, easy to process and welding, seawater corrosion resistance and other professional characteristics, can be successfully used to manufacture ten thousand tons of ocean ships.

18. Bridge steel

Railway or road bridge to withstand the impact load of vehicles, bridge steel is not required to have a certain strength, toughness and good quality of fatigue resistance, but the black material quality of steel is particularly high. Strong alkaline open hearth steel is often used for bridge steel. Recently, special low alloy steels such as 16 manganese and 15 manganese vanadium nitrogen have been finally used.

19. Boiler steel

Boiler steel more refers to the use of superheater, main steam tube and boiler fire chamber hot surface is used. The performance requirements of boiler steel should pay attention to the good welding performance, a certain extreme high temperature strength and alkali parts corrosion resistance, oxidation resistance, etc. The correct boiler steel is low carbon killed steel from open furnace smelting or low carbon steel from electric furnace smelting, carbon content of ωc in the range of 0.16% to 0.26%. High pressure boilers are manufactured using pearlite or austenitic heat resistant steels. In the past ten years, most low-alloy steel boilers have been routinely built, such as 12 manganese, 15 manganese vanadium, 18 manganese molybdenum niobium and so on.

20. Steel for welding rod

This type of steel is used in the manufacture of arc and gas welding electrode wire. The composition of steel varies with the same material welded. According to the need to roughly divided into carbon steel, alloy structural steel and stainless steel three types. The sulfur and phosphorus content of these steel is not 00.03%, ωs, ωp, which is higher than that of steel. These steels are not required to have mechanical properties, but only to be tested for chemical composition.

21. Stainless Steel

Stainless steel acid resistant steel is made of stainless steel, it is composed of stainless steel and acid resistant steel two parts. Simply put, can resist atmospheric rapid corrosion of steel called stainless steel, and can positively resist chemical media (such as acid) acid corrosion of steel called acid resistant steel. For example, the chromium content of ωcr 012% steel has the characteristics of stainless steel; According to the microstructure of stainless steel after heat treatment and cocoa is divided into five categories: ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, austenitic - ferritic stainless steel and precipitation hardening stainless steel.

22. Heat resistant steel

Under high temperature conditions, natural antioxidants and sufficient high temperature strength including good ideological and moral heat resistance of steel is often called heat resistant steel.