The Classification Analysis Of 24 Kinds Commonly Used Steel Material

1. Carbon steel

Carbon steel, also called carbon steel, is an iron-carbon alloy with a carbon content of ωc less than 2%. Carbon steel generally contains a small amount of silicon, manganese, sulfur, and phosphorus in addition to carbon.

Carbon steel can be divided into three types: carbon structural steel, carbon tool steel and free-cutting structural steel according to its purpose. Carbon structural steel can be divided into two types: building structural steel and machine-made structural steel. According to the carbon content, carbon steel can be divided into low carbon steel (ωc≤0.25%), medium carbon steel (ωc=0.25%-0.6%) and high carbon steel (ωc>0.6%)

According to the amount of phosphorus and sulfur, carbon steel can be divided into ordinary carbon steel (higher phosphorus and sulfur), high-quality carbon steel (lower phosphorus and sulfur) and high-quality high-quality steel (lower phosphorus and sulfur) Generally, the higher the carbon content of carbon steel, the higher the hardness and the higher the strength, but the lower the plasticity.

2. Carbon structural steel

This type of steel mainly guarantees mechanical properties. Therefore, its grade reflects its mechanical properties. The Q+ number is used to indicate the initial Chinese pinyin of the word "qu" where "Q" is the yield point. The number indicates the value of the yield point. For example, Q275 indicates that the yield point is 275Mpa. If the letters A, B, C, and D are marked after the grade, it means that the quality of the steel is different. The amount of S and P decreases in turn, and the quality of steel increases in turn. If the letter "F" is marked at the end of the grade, it is rimmed steel, marked with "b" is semi-killed steel, and those without "F" or "b" are killed. For example, Q235-AF means Class A boiling steel with a yield point of 235MPa, and Q235-C means Class C killed steel with a yield point of 235MPa.

Carbon structural steel is generally not subjected to heat treatment, but is directly used in the supply state. Usually Q195, Q215, Q235 steel has low carbon mass fraction, good welding performance, good plasticity, toughness, and certain strength. It is often rolled into thin plates, steel bars, welded steel pipes, etc. Used in bridges, buildings and other structures and manufacturing common rivets, screws, nuts and other parts. Q255 and Q275 steels have slightly higher carbon mass fraction, higher strength, better plasticity and toughness, and can be welded. They are usually rolled into section steel, bar steel and steel plate as structural parts and manufacture simple mechanical connecting rods, gears, and couplings. Parts such as knots and pins.

3. High-quality structural steel

This type of steel must ensure both chemical composition and mechanical properties. The grade is the ten thousand fraction (ωс*10000) that uses two digits to indicate the mass fraction of the average carbon in the steel. For example, 45 steel means that the average carbon mass fraction in steel is 0.45%; 08 steel means that the average carbon mass fraction in steel is 0.08%.

High-quality carbon structural steel is mainly used to manufacture machine parts. Generally, heat treatment is required to improve mechanical properties. According to the different carbon mass fraction, there are different uses. 08, 08F, 10, 10F steel, high plasticity, toughness, excellent cold forming performance and welding performance, often cold rolled into thin plates, used to make cold stamping parts on instrument housings, cars and tractors, such as car bodies, tractors Cab, etc.; 15, 20, 25 steel is used to make carburized parts with small size, lighter load, wear-resistant surface, and low core strength requirements, such as piston pins, prototypes, etc.; 30, 35, 40, 45, 50 steel has good comprehensive mechanical properties after heat treatment (quenching + high temperature tempering), that is, it has higher strength and higher plasticity and toughness. It is used to make shaft parts. For example, 40 and 45 steel are often used in manufacturing. Crankshafts, connecting rods of automobiles and tractors, general machine tool spindles, machine tool gears and other shaft parts that are not stressed; 55, 60, and 65 steel have high elastic limits after heat treatment (quenching + medium temperature tempering), and are often used in production Springs with low load and small size (section size less than 12~15mm), such as pressure and speed regulating springs, plunger springs, cold coil springs, etc.

4. Carbon tool steel

Carbon tool steel is a high-carbon steel that basically does not contain alloying elements. The carbon content is in the range of 0.65%-1.35%. Its production cost is low, the source of raw materials is easy to obtain, and the machinability is good. After heat treatment, high hardness and It has high wear resistance, so it is a widely used steel to make various cutting tools, molds, and measuring tools. However, 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 the steel will drop sharply and lose the working ability. In addition, carbon tool steel, if made into larger parts, is not easy to harden, and is prone to deformation and cracks.

5. Free-cutting structural steel

Free-cutting structural steel is the addition of some elements that make the steel brittle, making the steel brittle and broken into chips during cutting, which is beneficial to increase the cutting speed and extend the life of the tool. The element that makes steel brittle is mainly sulfur. Lead, tellurium, bismuth and other elements are used in ordinary low-alloy free-cutting structural steel.

The sulfur content of this steel is in the range of 0.08%-0.30%, and the manganese content is in the range of 0.60%-1.55%. Sulfur and manganese in steel exist in the form of manganese sulfide. Manganese sulfide is very brittle and has a lubricating effect, which makes the chips easy to break and helps improve the quality of the processed surface.

6. Alloy steel

In addition to iron, carbon and a small amount of inevitable silicon, manganese, phosphorus, and sulfur elements, steel also contains a certain amount of alloying elements. The alloying elements in steel include silicon, manganese, molybdenum, nickel, chromium, vanadium, and titanium. , Niobium, boron, lead, rare earth, etc. and one or more of them, this kind of steel is called alloy steel. The alloy steel systems of various countries vary with their respective resource conditions, production and use conditions. Foreign countries have developed nickel and chromium steel systems in the past, while my country has developed alloys based on silicon, manganese, vanadium, titanium, niobium, boron, and rare earths. Steel system.

Alloy steel accounts for more than ten percent of the total output of steel. Generally, alloy steels smelted in electric furnaces can be divided into 8 categories according to their use. They are: alloy structural steel, spring steel, bearing steel, alloy tools Steel, high-speed tool steel, stainless steel, heat-resistant non-skinned steel, silicon steel for electrical engineering.

7. Ordinary low alloy steel

Ordinary low alloy steel is an ordinary alloy steel that contains a small amount of alloying elements (in most cases, the total amount does not exceed 3%). This kind of steel has relatively high strength, relatively good comprehensive performance, and has corrosion resistance, wear resistance, low temperature resistance, good cutting performance, welding performance, etc. Under the condition of saving a lot of rare alloy elements (such as nickel, chromium), usually 1t ordinary low-alloy steel can be used on top of 1.2-1.3t carbon steel, and its service life and scope of use are far beyond that of carbon steel. Ordinary low-alloy steel can be smelted in open hearth and converter using general smelting methods, and the cost is similar to that of carbon steel.

8. Alloy steel for engineering structure

This refers to alloy steel used in engineering and building structures, including weldable high-strength alloy structural steel, alloy steel, alloy steel for railways, alloy steel for geological and petroleum drilling, alloy steel for pressure vessels, high-manganese wear-resistant steel, etc. . This type of steel is used for engineering and building structural parts. Among the alloy steels, the total content of this type of steel alloy is relatively low, but it is produced and used in a large amount.

9. Alloy steel for mechanical structure

This type of steel refers to alloy steel suitable for manufacturing machines and mechanical parts. It is based on high-quality carbon steel, appropriately adding one or several alloying elements to improve the strength, toughness and hardenability of the steel. This type of steel is usually used after heat treatment (such as quenching and tempering treatment, surface hardening treatment). It mainly includes two categories of commonly used alloy structural steel and alloy spring steel, including quenched and tempered alloy steel, surface hardened alloy steel (carburized steel, nitride steel, surface induction hardened steel, etc.), and cold plastic forming Use alloy steel (steel for cold head forging, steel for cold extrusion, etc.). According to the basic composition series of chemical composition, it can be divided into Mn series steel, SiMn series steel, Cr series steel, CrMo series steel, CrNiMo series steel, Ni series steel, B series steel, etc.

10. Alloy structural steel

The carbon content of alloy structural steel is 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, nickel, chromium, and molybdenum. Alloy structural steel is easy to harden and is not easy to deform or crack, which is convenient for heat treatment to improve the performance of steel.

Alloy structural steel is widely used in the manufacture of various transmission parts and fasteners for automobiles, tractors, ships, steam turbines, and heavy-duty machine tools. Low-carbon alloy steel is generally carburized, and medium-carbon alloy steel is generally quenched and tempered.

11. Alloy tool steel

Alloy tool steel is a medium and high carbon steel containing a variety of alloying elements, such as silicon, chromium, tungsten, molybdenum, and vanadium. Alloy tool steel is easy to harden, and is not easy to deform and crack. It is suitable for manufacturing large-sized and complex-shaped cutting tools, molds and measuring tools. For different purposes, the carbon content of alloy tool steel is also different. The carbon content ωc of most alloy tool steels is 0.5%-1.5%, and the carbon content of hot-deformed die steels is low, ωc is in the range of 0.3%-0.6%; the steel for cutting tools generally contains carbon ωc1%; cold working Die steel has a higher carbon content, such as graphite die steel with a carbon content of ωc up to 1.5%, and high-carbon and high-chromium type cold-working die steel with a carbon content of more than 2%.

12. High-speed tool steel

High-speed tool steel is a high-carbon and high-alloy tool steel. The carbon content of the steel is 0.7%-1.4%. The steel contains alloying elements that can form high-hardness carbides, such as tungsten, molybdenum, chromium, and vanadium.

High-speed tool steel has high red hardness. Under high-speed cutting conditions, the temperature is as high as 500-600℃ and the hardness does not decrease, thus ensuring good cutting performance.

13.Spring Steel

The spring is used under impact, vibration or long-term alternating stress, so spring steel is required to have high tensile strength, elastic limit, and high fatigue strength. The process requires spring steel to have a certain degree of hardenability, not easy to decarburize, and good surface quality, etc.

Carbon spring steel refers to high-quality carbon structural steel with carbon content ωc in the range of 0.6%-0.9% (including normal and higher manganese content). Alloy spring steel is mainly silico-manganese steel, their carbon content is slightly lower, mainly by increasing the silicon content ωsi (1.3%-2.8%) to improve performance; in addition, there are alloy spring steels of chromium, tungsten, and vanadium. In recent years, combining the resources of our country, and in accordance with the requirements of new technologies in the design of automobiles and tractors, new steel types with elements such as boron, niobium, molybdenum, etc. have been developed on the basis of silico-manganese steel, which prolongs the service life of the spring and improves the spring Steel quality.

14. Bearing steel

Bearing steel is the steel used to make balls, rollers and bearing rings. Bearings are subjected to great pressure and friction during work, so the bearing steel is required to have high and uniform hardness and wear resistance, as well as a high elastic limit. The uniformity of the chemical composition of the bearing steel and non-metallic inclusions The content and distribution, carbide distribution and other requirements are very strict.

Bearing steel is also called high-carbon chromium steel, with a carbon content of ωc of about 1% and a lead content of ωcr of 0.5%-1.65%. Bearing steel is divided into six categories: high carbon chromium bearing steel, chromium-free bearing steel, carburizing bearing steel, stainless bearing steel, medium and high temperature bearing steel and antimagnetic bearing steel.

15. Electrical silicon steel

Silicon steel used in the electrical industry is mainly used to manufacture silicon steel sheets for the electrical industry. Silicon steel sheet is a large amount of steel used in the manufacture of motors and transformers.

According to chemical composition, silicon steel can be divided into low silicon steel and high silicon steel. Low silicon steel contains silicon content ωsi=1.0%-2.5%, which is mainly used to manufacture motors; high silicon steel contains silicon content ωsi=3.0%-4.5%, which is generally used to manufacture transformers. Their carbon content ωc=0.06%-0.08%.

16. Rail steel

The rails are mainly subjected to the pressure and impact load of rolling stock, therefore. Sufficient strength and hardness and certain toughness are required. The commonly used steel rail is carbon killed steel smelted in open hearth and converter. This steel contains carbon ωc=0.6%-0.8%, which belongs to medium carbon steel and high carbon steel, but the manganese content in steel is relatively high, at 0.6%. -1.1% range. In recent years, ordinary low-alloy steel rails have been widely used, such as high-silicon rails, medium-manganese rails, copper-containing rails, and titanium-containing rails. Ordinary low-alloy steel rails are more wear-resistant and corrosion-resistant than carbon steel rails, and their service life is greatly improved.

17. Shipbuilding steel

Shipbuilding steel refers to the steel used to manufacture sea-going ships and large inland river hull structures. Because the hull structure is generally manufactured by welding, the shipbuilding steel is required to have better welding performance. In addition, certain strength, toughness and certain low temperature and corrosion resistance are required. In the past, low-carbon steel was mainly used as shipbuilding steel. Recently, ordinary low-alloy steel has been widely used, and existing steel grades such as 12 manganese ship, 16 manganese ship, 15 manganese vanadium ship and other steel grades. These steel grades have comprehensive characteristics such as high strength, good toughness, easy processing and welding, and seawater corrosion resistance, and can be successfully used to manufacture 10,000-ton ocean-going ships.

18. Bridge steel

Railway or highway bridges bear the impact load of vehicles. Bridge steel requires certain strength, toughness and good fatigue resistance, and requires high surface quality of the steel. Alkaline open-hearth furnace killed steel is often used for bridge steel. Recently, ordinary low alloy steels such as 16 manganese and 15 manganese vanadium nitrogen have been successfully used.

19. Boiler steel

Boiler steel mainly refers to materials used to make superheaters, main steam tubes and heating surfaces of boiler fire chambers. The performance requirements for boiler steel are mainly good welding performance, certain high temperature strength, alkali resistance to corrosion, oxidation resistance, etc. Commonly used boiler steels include open-hearth smelted low-carbon killed steel or electric furnace smelted low-carbon steel, with a carbon content of ωc in the range of 0.16%-0.26%. When manufacturing high-pressure boilers, pearlitic heat-resistant steel or austenitic heat-resistant steel is used. In recent years, ordinary low-alloy steels have been used to build boilers, such as 12 manganese, 15 manganese vanadium, 18 manganese molybdenum niobium and so on.

20. Steel for welding rod

This type of steel is specially used for the manufacture of arc welding and gas welding electrode wires. The composition of steel varies with the material being welded. According to needs, it can be roughly divided into three categories: carbon steel, alloy structural steel and stainless steel. The sulfur and phosphorus content of these steels ωs and ωp are not more than 0.03%, which is higher than the requirements of general steel. These steels do not require mechanical properties, but only check the chemical composition.

21.Stainless steel

Stainless acid-resistant steel is referred to as stainless steel, which is composed of two parts: stainless steel and acid-resistant steel. In short, steel that can resist atmospheric corrosion is called stainless steel, and steel that can resist corrosion by chemical media (such as acids) is called acid-resistant steel. Generally speaking, steel with chromium content ωcr greater than 12% has the characteristics of stainless steel; according to the microstructure after heat treatment, stainless steel can be divided into five categories: ferritic stainless steel, martensitic stainless steel, and austenite Stainless steel, austenitic-ferritic stainless steel and precipitation hardening stainless steel.

22.Heat-resistant steel

Under high temperature conditions, steel with oxidation resistance, sufficient high temperature strength and good heat resistance is called heat resistant steel. Heat-resistant steel includes two types: oxidation-resistant steel and heat-strength steel. Anti-oxidation steel is also called unskinned steel. Hot-strength steel refers to steel that has good oxidation resistance at high temperatures and high high-temperature strength. Heat-resistant steel is mainly used for parts that are used for a long time at high temperatures.

23.High temperature alloy

Superalloy refers to a kind of heat-strength material with sufficient enduring strength, creep strength, thermal fatigue strength, high-temperature toughness and sufficient chemical stability at high temperatures, and is used for thermodynamic parts that work at high temperatures around 1000°C.

According to the difference of its basic chemical composition, it can be divided into nickel-based superalloy, iron-nickel-based superalloy and cobalt-based superalloy.

24.Precision alloy

Precision alloys refer to alloys with special physical properties. It is an indispensable material in the electrical industry, electronics industry, precision instrument industry and automatic control system.

Precision alloys are divided into 7 categories according to their different physical properties, namely: soft magnetic alloys, deformed permanent magnetic alloys, elastic alloys, expansion alloys, thermal bimetals, resistance alloys, and thermoelectric alloys. The vast majority of precision alloys are based on ferrous metals, and only a few are based on non-ferrous metals.

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