Steel with other alloying elements besides iron and carbon is called alloy steel. An iron-carbon alloy formed by adding an appropriate amount of one or more alloying elements to ordinary carbon steel. Depending on the added elements and the appropriate processing technology, special properties such as high strength, high toughness, wear resistance, corrosion resistance, low temperature resistance, high temperature resistance, and non-magnetic properties can be obtained.
The main alloying elements of alloy steel are silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, aluminum, copper, boron, rare earth, etc.
Among them, vanadium, titanium, niobium, zirconium, etc. are strong carbide-forming elements in steel. As long as there is enough carbon, they can form their own carbides under appropriate conditions. When there is a lack of carbon or under high temperature conditions, they enter the solid solution in an atomic state; manganese, chromium, tungsten, and molybdenum are carbide-forming elements, some of which enter the solid solution in an atomic state, and the other part forms substitutional alloy cementite; aluminum, copper, nickel, cobalt, silicon, etc. are elements that do not form carbides and generally exist in the solid solution in an atomic state.
Effect of alloying elements on heat treatment of steel
1. Effect on austenitization-Most alloying elements (except nickel and cobalt) slow down the austenitization process. Therefore, during heat treatment, a higher heating temperature and longer holding time are required than for carbon steel. - Carbides are not easy to decompose.
2. Effect on austenite grain size-Most alloying elements have the effect of hindering the growth of austenite grains. But manganese and boron are the opposite, which can promote the growth of austenite grains. Therefore, except for manganese steel, alloy steel is not easy to overheat when heated. This is conducive to obtaining fine martensite after quenching; it is also conducive to appropriately increasing the heating temperature so that more alloy elements are dissolved in austenite to increase hardenability and improve the mechanical properties of steel.
3. The influence of alloy elements on the transformation of austenite - except cobalt, all alloy elements shift the C curve to the right, reduce the critical cooling rate of steel, and improve the hardenability of steel. Some alloy elements also change the shape of th
alloy seamless pipe
