Affecting Steel Properties, the role of steel properties, in double steel is a sharp edge. As the amount of carbon increases, the use of the material, but at the same time improves the use of carbon, but at the same time also need to improve the tensile strength and impact resistance, improve the tensile strength and impact resistance of the material to adjust the impact decreases.
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3C carbon steels, and of which the hardness grade can be increased.
The strength and grade of the carbon content of the steel, the lower the anti-carbon content of the steel and; ringing the character of the steel and the more carbon content, the strength and its degree, but on similar.
The carbon content of, usually the carbon content of the manufacturing method: usually manufacturing with carbon steel (0.25) type low carbon (carbon content of 6%) of mechanical materials high carbon steel (carbon content > 0.7%), commonly used as tools, tools and moulds.
Silicate additives and deoxidisers are added during the steelmaking process, so that the silicon content of the sedimented steel is 0.15-0.30%. When the silicon content of the steel exceeds 0.50-0.60%, silicon is refined into an alloying element.
The element can significantly improve the elasticity, elastic limit, contact point and tensile strength, so the steel content is extensive, containing 0.15-0.37% silicon in spring steels such as 65Mn and 82B. 1.0-1.2% silicon in tempered structural steel, continuous steel strength by 15-20%.
Combined with molybdenum, tungsten, chromium, etc., has the effect of improving corrosion resistance and oxidation resistance, can be used in the manufacture of carbon steel; containing silicon 1.0-4.0% low carbon steel, has a very high magnetic conductivity, used in the industrial manufacture of silicon steel sheet.
Of course, silicon is not harmless, it reduces the weldability of the steel.
In the steelmaking process, manganese is a good agent for being oxygenated and sulphur. The amount of manganese removed from steel is generally 0.30-0.0%. When the amount of carbon steel exceeds 0.70%, it is considered to be “manganese steel”.
Compared to steel, for example, it has a milder commonality. It also has a higher strength and hardness, can improve the hardenability of steel, improve the hot workability of steel, 40% higher than A3 steel containing 11-14% manganese steel shovel has a very high wear resistance, mill machine bucket, ball use plate, etc..
High manganese content also has a complementary. It should be noted that high manganese content, steel has the tempering brittleness phenomenon; manganese has the obvious role of promoting growth, the heating process; when the manganese mass ratio of more than 1%, the performance of steel will be reduced.
Sulphur comes from steelmaking ore and fuel coke. It is a harmful element in steel.
Sulphur is present in steel in the form of iron sulphide (FES), which forms a compound with Fe with a low melting point (985°C) and a typical hot working temperature of 1150-1200°C for steel. Therefore, during the hot working of steel, the FES compound melts prematurely and cracks the workpiece, a phenomenon known as ‘thermal embrittlement’. The higher the sulphur content, the more severe the thermal embrittlement. Therefore, it is necessary to control the sulphur content of the steel.
High quality steel s < 0.02-0.03%, high quality steel s < 0.03-0.045%, normal steel s < 0.055% – 0.07%. In individual cases, it is necessary to add sulphur. For example, the addition of 0.08-0.20% sulphur to steel improves machinability and is often referred to as free-cutting steel.
Sulphur is also harmful to weldability and reduces corrosion
Phosphorus is carried into the steel by the ore. Generally speaking, phosphorus is also a harmful element. Although phosphorus increases the strength and hardness of steel, it causes a significant reduction in plasticity and impact toughness. Especially at low temperatures, steel becomes significantly more brittle, known as “cold brittleness”.
Cold brittleness reduces the cold workability and weldability of the steel. The higher the phosphorus content, the greater the cold brittleness, so the stricter the control of phosphorus content in steel. High-grade quality steel: P<0.025%; high quality steel: P<0.04%; ordinary steel: P<0.085%.
Oxygen is a harmful element in steel. It enters the steel naturally during the steelmaking process. Although manganese, silicon, iron and aluminium are deoxygenated at the end of the steelmaking process, they are not completely removed. The presence of oxygen in steel in the form of inclusions such as FeO, MnO, SiO2 and Al2O3 reduces the strength and plasticity of the steel. In particular, it has a serious impact on fatigue strength and impact toughness.
The ability of ferrite to dissolve nitrogen is very low. When supersaturated nitrogen dissolved in steel, after a long period of storage or heating to 200-300 ℃, will occur in the form of nitride nitrogen precipitation, improve the hardness and strength of steel, reduce plasticity and aging add Al, Ti or V injected into the steel for nitrogen fixation in AlN, tin or VN nitrogen fixation can eliminate the tendency to aging.
In structural and tool steel, chromium can significantly improve the strength, hardness and wear resistance, so that the steel has good oxidation resistance and corrosion resistance. It is an important alloying element for stainless and heat-resistant steels; it can also improve the hardenability of steel.
However, chromium also raises the brittle transition temperature of steel and increases the tempering brittleness of steel, causing unnecessary trouble during processing.
Nickel can increase the strength of steel while maintaining good plasticity and toughness. Nickel has high resistance to acid and alkali corrosion, rust and high temperature heat resistance. However, because nickel is a relatively scarce resource, other alloy elements should be used to replace nickel chromium steel.
Molybdenum can refine the grain of steel, improve hardenability and thermal strength, and maintain sufficient strength and creep resistance at high temperature (long-term stress and deformation at high temperature, called creep). Molybdenum is added to structural steel to improve mechanical properties. It can also inhibit the embrittlement of alloy steel due to fire. Adding molybdenum to tool steel can improve redness.
Titanium is a strong deoxidizer in steel. It can compact the internal structure of the steel and refine the grain force; Reduce aging sensitivity and cold brittleness. Improve welding performance. Intergranular corrosion can be avoided by adding appropriate titanium to Cr18Ni9 Austenitic stainless steel.
Vanadium is an excellent deoxidizer for steel. Adding 0.5% vanadium to steel can refine microstructure and grain, and improve strength and toughness. The carbides formed by vanadium and carbon can improve the hydrogen corrosion resistance under high temperature and high pressure.
Tungsten has a high melting point and a large ratio. It is its own alloy element. Tungsten and carbon form tungsten carbide with high hardness and wear resistance. Adding tungsten into tool steel can significantly improve red hardness and thermal strength, and can be used for cutting tools and forging dies.
Niobium can refine the grain, reduce the superheat sensitivity and temper brittleness of the steel, and improve the strength, but the plasticity and toughness decrease. Adding niobium to ordinary low alloy steel can improve the resistance to atmospheric corrosion and hydrogen, nitrogen and ammonia corrosion at high temperature. Niobium improves weldability. Adding niobium to austenitic stainless steel can prevent intergranular corrosion.
Cobalt is a rare and precious metal, which is mainly used in special steels and alloys, such as heat-resistant steels and magnetic materials.
Copper can improve strength and toughness, especially atmospheric corrosion. The disadvantage is that it is easy to produce thermal brittleness during hot working, and the plasticity decreases significantly when the copper content exceeds 0.5%. When the copper content is less than 0.50%, it has no effect on the weldability.
Aluminum is a commonly used deoxidizer in steel. Adding small amounts of aluminum to steels can refine grains and improve impact toughness, such as 08Al steels used for deep drawing sheets. Aluminum also has anti-oxidative and anti-corrosion properties.
The combination of aluminum, chromium and silicon can significantly improve the high temperature peeling performance and high temperature corrosion resistance of steel. The disadvantage of aluminum is that it affects the hot workability, weldability and machinability of steel.
Adding a small amount of boron to steel can improve the compactness and hot rolling properties of the steel and increase the strength.
Rare earth elements refer to the 15 lanthanides with atomic numbers 57-71 in the periodic table. These elements are all metals, but their oxides are similar to “earth”, so they are often referred to as rare earths.
Adding rare earths to steel can change the composition, shape, distribution and properties of inclusions in steel, thereby improving various properties of steel, such as toughness, weldability and cold workability. Rare earths are added to plowshare steel to improve wear resistance.
