Cast iron (2)

               
Update: 20-12-2019
               
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3) malleable cast iron Malleable cast iron is made of i […]

3) malleable cast iron

Malleable cast iron is made of iron and carbon alloys with low carbon and silicon content into white cast iron blanks, and then subjected to long-term high temperature annealing treatment to decompose the cementite into flocculent graphite. White cast iron.

Malleable cast iron is divided into two types according to the microstructure after heat treatment; one type is black-heart malleable cast iron and pearlescent malleable cast iron. The structure of black heart malleable cast iron is mainly ferrite (F) basic flocculent graphite; the structure of pearlite malleable cast iron is mainly pearlite (P) matrix flocculent graphite. The other type is white-heart malleable cast iron. The structure of the white-heart malleable cast iron is determined by the section size. The small section is made of ferrite, the surface area of ​​the large section is ferrite, the core is pearlite, and annealed carbon.

4) Ductile iron

Add a certain amount of nodulizing agent (commonly ferrosilicon, magnesium, etc.) to cast graphite in cast iron before pouring the molten iron (nodular pig iron). Because carbon (graphite) exists in a cast iron matrix in a spheroidal shape, improving its cleavage effect on the matrix, the tensile strength, yield strength, plasticity, and impact toughness of ductile cast iron are greatly improved. And has the advantages of wear resistance, shock absorption, good process performance, low cost, etc., has now widely replaced malleable cast iron and some cast steel, forged steel parts, such as crankshafts, connecting rods, rolls, automobile rear axles, etc. According to GB1348-88, nodular cast iron grades are divided into two types: single cast and auxiliary cast test blocks; in addition to the several commonly used cast irons described above, there are also wear-resistant white cast iron, chilled cast iron, and heat-resistant cast iron. Foundry pig iron can change its internal structure, improve and improve its mechanical properties through forging, metamorphism, spheroidization, etc. Therefore, cast pig iron can be divided into white cast iron, gray cast iron, malleable cast iron, ductile cast iron and special cast iron.

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