Common alloying elements of steel (part two)
Copper -- It has a moderate segregation tendency which when reaching a comparable content is detrimental to the thermal deformation process of steel. Copper has a negative impact on forging, but it does not seriously affect arc welding and oxyacetylene welding. As a disadvantage to the surface quality, copper increases the original surface defects of steel with vulcanizing agent. However, when w(Cu) exceeds 0.20%, it will help to improve its corrosion resistance in the air, and steel with copper content over 0.20% is also called weathering steel.
Chromium -- The addition of chromium to steel is commonly used to enhance corrosion resistance and oxidation resistance, and to improve hardenability and high temperature strength, or to enhance wear resistance of high carbon steels. Chromium is the third hardest element. Complex chromium-iron carbides slowly dissolve into the austenite and must have sufficient heating time before the forging is quenched. Chromium can be used as a hardening element and is often used with toughness-enhancing elements such as nickel to produce good properties. Chromium can lift the strength at higher temperatures, and it can generally be used with molybdenum for the same purpose.
Nickel -- It is a ferrite fortifier when used as an alloying element in structural steel. Since nickel does not form any carbide-based compound in the steel, it remains dissolved in the ferrite, thereby increasing the strength and toughness of the ferrite phase. Nickel steel is easier to heat treat because it can reduce its critical cooling rate. The combination of nickel and chromium produces higher hardenability, impact strength and fatigue resistance than carbon steel can achieve. Nickel alloys also have super low temperature strength and toughness.
Molybdenum -- Molybdenum increases the hardenability of steel and is particularly useful when this hardenability is to be kept within specified limits. This element can reduce the temper brittleness of steel to a minimum, especially when its content (mass fraction) is 0.15%-0.30%. Hardened steel containing molybdenum must be fired at a higher temperature in order to obtain the same softening effect. Molybdenum is unique in that it can be improved by the high temperature tensile strength and creep resistance of steel. Its ability to retard ferrite transformation is far beyond its ability to delay the transformation of austenite to bainite, so that bainite can be formed during the continuous cooling of molybdenum-containing steel.
Vanadium -- It is one of the strong carbide forming elements. It can provide strength and toughness when its solubility in ferrite reaches a certain degree. Vanadium steel exhibits finer texture than steel with similar composition and no vanadium. The vanadium is dissolved into the austenite before quenching to improve its flatness, and to have a secondary quenching effect on tempering, and improve the thermosetting property.
Chromium -- The addition of chromium to steel is commonly used to enhance corrosion resistance and oxidation resistance, and to improve hardenability and high temperature strength, or to enhance wear resistance of high carbon steels. Chromium is the third hardest element. Complex chromium-iron carbides slowly dissolve into the austenite and must have sufficient heating time before the forging is quenched. Chromium can be used as a hardening element and is often used with toughness-enhancing elements such as nickel to produce good properties. Chromium can lift the strength at higher temperatures, and it can generally be used with molybdenum for the same purpose.
Nickel -- It is a ferrite fortifier when used as an alloying element in structural steel. Since nickel does not form any carbide-based compound in the steel, it remains dissolved in the ferrite, thereby increasing the strength and toughness of the ferrite phase. Nickel steel is easier to heat treat because it can reduce its critical cooling rate. The combination of nickel and chromium produces higher hardenability, impact strength and fatigue resistance than carbon steel can achieve. Nickel alloys also have super low temperature strength and toughness.
Molybdenum -- Molybdenum increases the hardenability of steel and is particularly useful when this hardenability is to be kept within specified limits. This element can reduce the temper brittleness of steel to a minimum, especially when its content (mass fraction) is 0.15%-0.30%. Hardened steel containing molybdenum must be fired at a higher temperature in order to obtain the same softening effect. Molybdenum is unique in that it can be improved by the high temperature tensile strength and creep resistance of steel. Its ability to retard ferrite transformation is far beyond its ability to delay the transformation of austenite to bainite, so that bainite can be formed during the continuous cooling of molybdenum-containing steel.
Vanadium -- It is one of the strong carbide forming elements. It can provide strength and toughness when its solubility in ferrite reaches a certain degree. Vanadium steel exhibits finer texture than steel with similar composition and no vanadium. The vanadium is dissolved into the austenite before quenching to improve its flatness, and to have a secondary quenching effect on tempering, and improve the thermosetting property.
