Alloy Steels
ALLOY STEELS I. A. ALLOYING ELEMENTS
Any metallic element added during the making of steel for the purpose of increasing corrosion resistance, hardness, or strength. The metals used most commonly as alloying elements in stainless steel include chromium, nickel, and molybdenum.
Characteristic of alloying elements Very important elements for alloy steels are manganese, nickel, chromium, molybdenum, vanadium, tungsten, silicon, copper, cobalt and boron. All commercial steels contain 0,3-0,8% manganese, to reduce oxides and to counteract the harmful influence of iron sulphide. There is a tendency nowadays to increase the manganese content and reduce the carbon content in order to get a steel with an equal tensile strength but improved ductility. Nickel and manganese are very similar in behaviour and both lower the eutectoid temperature. Nickel steels are noted for their strength, ductility and toughness, while chromium steels are characterized by their hardness and resistance to wear. Chromium can dissolve in either alpha- or gama-iron, but, in the presence of carbon, the carbides formed are cementite (FeCr)3C in which chromium may rise to more than 15%; chromium carbides (CrFe)3C2 (CrFe)7C3 (CrFe)4C, in which chromium may be replaced by a few per cent, by a maximum of 55% and by 25% respectively. The chrome steels are used wherever extreme hardness is required, such as in dies, ball bearings, plates for safes, rolls, files and tools. The combination of nickel and chromium produces steels having all these properties, some intensified, without the disadvantages associated with the simple alloys. Molybdenum dissolves in both alpha- or gama-iron and in the presence of carbon forms complex carbides (FeMo)6C, Fe21Mo2C6, Mo2C. Molybdenum is also a constituent in some high-speed steels, magnet alloys, heat-resisting and corrosion-resisting steels. | | | |
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B. Alloy steel
Any metallic element added during the making of steel for the purpose of increasing corrosion resistance, hardness, or strength. The metals used most commonly as alloying elements in stainless steel include chromium, nickel, and molybdenum.
Characteristic of alloying elements Very important elements for alloy steels are manganese, nickel, chromium, molybdenum, vanadium, tungsten, silicon, copper, cobalt and boron. All commercial steels contain 0,3-0,8% manganese, to reduce oxides and to counteract the harmful influence of iron sulphide. There is a tendency nowadays to increase the manganese content and reduce the carbon content in order to get a steel with an equal tensile strength but improved ductility. Nickel and manganese are very similar in behaviour and both lower the eutectoid temperature. Nickel steels are noted for their strength, ductility and toughness, while chromium steels are characterized by their hardness and resistance to wear. Chromium can dissolve in either alpha- or gama-iron, but, in the presence of carbon, the carbides formed are cementite (FeCr)3C in which chromium may rise to more than 15%; chromium carbides (CrFe)3C2 (CrFe)7C3 (CrFe)4C, in which chromium may be replaced by a few per cent, by a maximum of 55% and by 25% respectively. The chrome steels are used wherever extreme hardness is required, such as in dies, ball bearings, plates for safes, rolls, files and tools. The combination of nickel and chromium produces steels having all these properties, some intensified, without the disadvantages associated with the simple alloys. Molybdenum dissolves in both alpha- or gama-iron and in the presence of carbon forms complex carbides (FeMo)6C, Fe21Mo2C6, Mo2C. Molybdenum is also a constituent in some high-speed steels, magnet alloys, heat-resisting and corrosion-resisting steels. | | | |
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B. Alloy steel