Cast iron can be divided into:
1 gray cast iron. The carbon content is relatively high (2.7% to 4.0%), the carbon is mainly in the form of flake graphite, and the fracture is gray, referred to as gray iron. Low melting point (1145 ~ 1250 ° C), small shrinkage during solidification, compressive strength and hardness close to carbon steel, good shock absorption. It is used to manufacture structural parts such as machine bed, cylinder and box.
2 white cast iron. Carbon and silicon content are low, carbon is mainly in the form of cementite, and the fracture is silvery white. When the solidification shrinks, it is easy to produce shrinkage cavities and cracks. High hardness, brittleness, and can not withstand impact loads. Used as a blank for malleable cast iron and as a wear-resistant part.
3 malleable cast iron. After being annealed from white cast iron, the graphite is distributed in a flocculent shape, referred to as tough iron. It has uniform texture, wear resistance and good plasticity and toughness. Used to make parts that are complex in shape and can withstand strong dynamic loads.
4 ductile iron. The gray cast iron hot metal is obtained by spheroidizing treatment, and the precipitated graphite is spherical, which is referred to as ductile iron. It has higher strength, better toughness and plasticity than ordinary gray cast iron. Used in the manufacture of internal combustion engines, auto parts and agricultural machinery.
5 vermicular graphite cast iron. The gray cast iron hot water is obtained by the creeping treatment, and the precipitated graphite is in the form of a worm. The mechanical properties are similar to those of ductile iron, and the casting properties are between gray cast iron and nodular cast iron. Used to make parts for automobiles.
6 alloy cast iron. Ordinary cast iron is obtained by adding an appropriate amount of alloying elements (such as silicon, manganese, phosphorus, nickel, chromium, molybdenum, copper, aluminum, boron, vanadium, tin, etc.). The alloying elements change the matrix structure of the cast iron, and thus have the corresponding properties of heat resistance, wear resistance, corrosion resistance, low temperature resistance or no magnetism. Used to manufacture parts for mines, chemical machinery, instruments, meters, etc. Cast steel
Steel used to cast castings. A type of casting alloy. Cast steel is divided into cast carbon steel, cast low alloy steel and cast special steel.
1 cast carbon steel. Cast steel with carbon as the main alloying element and containing a small amount of other elements. Less than 0.2% carbon is cast low carbon steel, carbon content 0.2% to 0.5% is cast medium carbon steel, and carbon content greater than 0.5% is cast high carbon steel. As the carbon content increases, the strength of the cast carbon steel increases and the hardness increases. Cast carbon steel has high strength, plasticity and toughness, low cost, and is used in heavy machinery to manufacture parts with heavy loads, such as rolling mill stands, hydraulic press bases, etc.; Parts that are subject to impact, such as bolors, side frames, wheels and couplers.
2 cast low alloy steel. Cast steel containing alloying elements such as manganese, chromium and copper. The total amount of alloying elements is generally less than 5%, which has a large impact toughness and can obtain better mechanical properties by heat treatment. Cast low alloy steel has better performance than carbon steel, which can reduce the quality of parts and improve the service life.
3 casting special steel. Alloy cast steels, tailored to meet specific needs, come in a wide variety and usually contain one or more high-alloy elements to achieve a particular property. For example, high manganese steel containing 11% to 14% manganese can withstand impact and wear, and is mostly used for wear parts of mining machinery and engineering machinery; various stainless steels with chromium or chromium nickel as main alloying elements, used in corrosion or 650 Parts that work at temperatures above °C, such as chemical valve bodies, pumps, vessels, or turbine casings for large-capacity power plants.
Although both of them are iron-carbon alloys, they have different metallographic structures after crystallization due to the different percentages of chemical elements such as carbon, silicon, manganese, phosphorus and sulfur, but show many different mechanical properties and process properties. . For example, in the cast state, the elongation, section shrinkage, and impact toughness of cast iron are lower than that of cast steel; the compressive strength and vibration damping performance of cast iron are better than that of cast steel; the liquid fluidity of gray cast iron is better than that of cast steel. In the casting of complex thin-walled castings; in the bending test, cast iron is brittle fracture, cast steel is bending deformation. and many more. Therefore, they are suitable for casting different parts of the machine.