The role of alloying elements (Aluminum(Al), Boron(B), Copper(Cu), Sulfur(S))
Although the alloying elements are very small, they can determine the type and characteristics of the steel that people produce. It can make a difference between steel and steel. Then let's explore the following elements.
(1)Aluminum(Al)
Aluminum is mainly used to deoxidize and refine grains. In the nitriding steel, a hard and corrosion resistant nitriding a layer is formed. Aluminum can suppress the aging of low carbon steel and improve the toughness of steel at a low temperatures. When the aluminum content is high, the oxidation resistance of the steel and the corrosion resistance in the oxidizing acid and the H2S gas can be improved. And it can improve the electrical and magnetic properties of the steel. Aluminum has a large solid solution strengthening effect in steel, which improve the wear resistance, fatigue strength and core mechanical properties of carburized steel.
In the difficult alloy, aluminum and nickel form a compound. Thereby improving the smelting strength. The aluminum-containing iron-chromium aluminum alloy has near-resistance characteristics and excellent oxidation resistance at high temperatures, and is suitable for electroslag alloy materials and chrome-aluminum resistance wires.
When some steels are deoxidized, if the aluminum is used too much, it will cause the steel produce an abnormal structure and promote the steel to form a graphitization tendency. In ferritic and pearlitic steel, when the aluminum content is high, the high temperature strength and toughness are lowered, and take some difficult for smelting and casting.
(2)Boron(B)
The mail role of boron in steel is to increase the hardenability of the steel. Thereby save the other more rare metals. For this purpose, the content is generally specified in the range of 0.001% to 0.005%. It can replace 1.6% nickel, 0.3% chromium or 0.2% molybdenum. And should pay attention to replace the molybdenum. Because of the molybdenum can avoid or reduce temper brittleness. But boron has a slight tendency to promote temper brittleness, so it is impossible to completely replace molybdenum with boron.
Boron is added to medium carbon steel, which improves the hardenability and improves the performance of steels with a thickness of 20mm or more. Therefore, 40B and 40MnB steel can be replaced 40Cr and 20Mn2TiB steel can be replaced 20CrMnTi carburized steel. But the effect of boron gradually decrease due to the carbon content of steel gradually increase, it even disappears. When selecting boron-containing carburized steel, it must be considered that after the carburization of the part, the hardenability of the carburized layer will be lower than the hardenability of the core. Spring steel is generally required to be completely hardened, and usually the spring area is not large, and it is advantageous to use boron-containing steel. The effect of boron on high-silicon spring steel fluctuates greatly, which is inconvenient to adopt. Boron has a strong affinity with nitrogen and oxygen. When add 0.007% boron into the boiling steel which can eliminate the aging of steel.
(3)Copper(Cu)
The prominent effect of copper in steel is to improve resistance to atmospheric corrosion of ordinary low alloy steel. Especially when used in combination with phosphorus. Adding copper also increases the strength and yield ratio of the steel. And there is no adverse effect on the welding performance. The rail steel(U-Cu) containing 0.20% to 0.50% of copper has a corrosion-resistant life of 2-5 times that of a general carbon steel rail in addition to wearing resistance.
When the copper containing over 0.75%, after solution treatment and aging. It can produce aging strengthening effect. When the copper containing is low. Its role is similar to nickel. But relatively weak. When the copper containing is high, it is bad for thermal deformation processing and cause copper brittleness during hot deformation processing. Adding 2% to 3% of copper to austenitic stainless steel can improve its corrosion resistance in an acidic medium.
(4)Sulfur(S)
Sulfur is also a harmful element under normal conditions. It producing hot brittleness of steel and reducing ductility and toughness of steel. Cracks are caused during forging and rolling. Sulfur is also detrimental to weldability and reduces corrosion resistance. Therefore, the sulfur content is usually required to be less than 0.055%, and the high-quality steel is required to be less than 0.040%. The addition of 0.08-0.20% sulfur to the steel improves the machinability and is commonly referred to as free-cutting steel.
(1)Aluminum(Al)
Aluminum is mainly used to deoxidize and refine grains. In the nitriding steel, a hard and corrosion resistant nitriding a layer is formed. Aluminum can suppress the aging of low carbon steel and improve the toughness of steel at a low temperatures. When the aluminum content is high, the oxidation resistance of the steel and the corrosion resistance in the oxidizing acid and the H2S gas can be improved. And it can improve the electrical and magnetic properties of the steel. Aluminum has a large solid solution strengthening effect in steel, which improve the wear resistance, fatigue strength and core mechanical properties of carburized steel.
In the difficult alloy, aluminum and nickel form a compound. Thereby improving the smelting strength. The aluminum-containing iron-chromium aluminum alloy has near-resistance characteristics and excellent oxidation resistance at high temperatures, and is suitable for electroslag alloy materials and chrome-aluminum resistance wires.
When some steels are deoxidized, if the aluminum is used too much, it will cause the steel produce an abnormal structure and promote the steel to form a graphitization tendency. In ferritic and pearlitic steel, when the aluminum content is high, the high temperature strength and toughness are lowered, and take some difficult for smelting and casting.
(2)Boron(B)
The mail role of boron in steel is to increase the hardenability of the steel. Thereby save the other more rare metals. For this purpose, the content is generally specified in the range of 0.001% to 0.005%. It can replace 1.6% nickel, 0.3% chromium or 0.2% molybdenum. And should pay attention to replace the molybdenum. Because of the molybdenum can avoid or reduce temper brittleness. But boron has a slight tendency to promote temper brittleness, so it is impossible to completely replace molybdenum with boron.
Boron is added to medium carbon steel, which improves the hardenability and improves the performance of steels with a thickness of 20mm or more. Therefore, 40B and 40MnB steel can be replaced 40Cr and 20Mn2TiB steel can be replaced 20CrMnTi carburized steel. But the effect of boron gradually decrease due to the carbon content of steel gradually increase, it even disappears. When selecting boron-containing carburized steel, it must be considered that after the carburization of the part, the hardenability of the carburized layer will be lower than the hardenability of the core. Spring steel is generally required to be completely hardened, and usually the spring area is not large, and it is advantageous to use boron-containing steel. The effect of boron on high-silicon spring steel fluctuates greatly, which is inconvenient to adopt. Boron has a strong affinity with nitrogen and oxygen. When add 0.007% boron into the boiling steel which can eliminate the aging of steel.
The prominent effect of copper in steel is to improve resistance to atmospheric corrosion of ordinary low alloy steel. Especially when used in combination with phosphorus. Adding copper also increases the strength and yield ratio of the steel. And there is no adverse effect on the welding performance. The rail steel(U-Cu) containing 0.20% to 0.50% of copper has a corrosion-resistant life of 2-5 times that of a general carbon steel rail in addition to wearing resistance.
When the copper containing over 0.75%, after solution treatment and aging. It can produce aging strengthening effect. When the copper containing is low. Its role is similar to nickel. But relatively weak. When the copper containing is high, it is bad for thermal deformation processing and cause copper brittleness during hot deformation processing. Adding 2% to 3% of copper to austenitic stainless steel can improve its corrosion resistance in an acidic medium.
(4)Sulfur(S)
Sulfur is also a harmful element under normal conditions. It producing hot brittleness of steel and reducing ductility and toughness of steel. Cracks are caused during forging and rolling. Sulfur is also detrimental to weldability and reduces corrosion resistance. Therefore, the sulfur content is usually required to be less than 0.055%, and the high-quality steel is required to be less than 0.040%. The addition of 0.08-0.20% sulfur to the steel improves the machinability and is commonly referred to as free-cutting steel.
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