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25
2022
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07
Casting of the foundry
The molding of foundry cast iron parts includes gray cast iron parts and ductile iron parts, which are produced by professional smelting or simple equipment. Although they are both iron-carbon alloys, their metallographic structures after crystallization are different due to the different contents of carbon, silicon, manganese, phosphorus, and sulfur in the chemical composition. It shows many differences in mechanical and processing functions.
Casting in the foundry
The foundry's cast iron parts are formed with gray cast iron parts and ductile iron parts, produced by professional smelting or simple equipment. Although they are both iron-carbon alloys, their metallographic structure after crystallization is different due to the different content of carbon, silicon, manganese, phosphorus, and sulfur in the chemical composition. It shows many differences in mechanical and processing functions.
In the casting technical state of the foundry, the elongation, section reduction rate, impact, and resistance of ductile iron parts are higher than those of gray cast iron; the compressive strength and shock absorption function of gray cast iron are better than those of ductile iron; in the bending test, cast iron is brittle fracture, and ductile iron is bending deformation, etc.
Gray cast iron: more wear-resistant, but the strength is still relatively low, the toughness and plasticity are slightly worse, and the weldability is slightly larger. Cast iron technology has appeared in China in the Han Dynasty, and nodular graphite cast iron parts can also be developed. Cast iron can also be divided into gray cast iron and white cast iron according to the composition of graphite.
Ductile iron: Ductile iron is currently widely used by most companies, and China's annual export volume is also very high, accounting for a certain proportion. Generally used in railways, construction, metallurgical machinery industry, mining equipment, etc., ductile iron parts have similar functions to cast iron, but are superior to gray cast iron in elongation.
For general enterprises, if the carbon content of cast iron parts is too high, it will directly lead to the brittleness and reduced strength of cast iron parts, and the comprehensive working performance will continue to decline. The carbon and silicon content of cast iron parts should not be too much during use, otherwise it will affect the mechanical system performance of cast iron parts.
The effect of excessive carbon content in cast iron parts in the foundry. Iron with a carbon content of more than 1.70% is called cast iron, and steel with a carbon content of less than 1.70% is called steel. Generally, steel with a carbon content higher than 0.60% is called high carbon steel, steel with a carbon content between 0.25%-0.60% is called medium carbon steel, steel with a carbon content less than 0.25 is called low carbon steel, and steel with a carbon content less than 0.04% is called industrial pure iron. It plays an important role in the performance of carbon steel. As the carbon content increases, the hardness and strength of the steel increase, but the toughness and plasticity decrease. Conversely, if the carbon content decreases, the hardness and strength will decrease, while the toughness and plasticity will increase.
Iron-carbon alloy with a carbon content of more than 2.11%. Industrial cast iron materials generally contain 2.5% to 3.5% carbon. Carbon in cast iron exists mostly in the form of graphite structure, and sometimes in the form of cementite. In addition to carbon, cast iron also contains 1% to 3% silicon, as well as elements such as manganese, phosphorus, and sulfur. Corrosion-resistant cast iron also contains elements such as nickel, chromium, molybdenum, aluminum, copper, boron, and vanadium. Carbon and silicon are the main design elements that affect the microstructure and properties of cast iron. Cast iron can be divided into gray cast iron, white cast iron, and mottled cast iron according to the different forms of carbon.
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