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Representation of cast iron grades: (according to GB5612-85)

2011-3-1 Keboer Group 1206

The various cast iron codes are composed of the first uppercase letters of the Chinese pinyin letters representing the characteristics of the cast iron. When the code letters of the two cast iron names are the same, the uppercase normal letters can be distinguished by adding the lowercase normal letters. The same name cast iron, when subdivision is required, the first capitalized Chinese alphabet of Chinese Pinyin with its subdivision characteristics is arranged behind.

Cast iron name, code and brand representation

Cast iron name..................code number..................

Gray cast iron........................HT.........................HT100

Vermicular graphite iron..................RuT........................RuT400

Ductile iron..................QT.........................QT400-17

Black heart malleable cast iron..............KHT........................KHT300-06

White heart malleable cast iron..............KBT........................KBT350-04

Pearlite malleable cast iron............KZT........................KZT450-06

Wear-resistant cast iron..................MT.........................MT Cu1PTi- 150

Anti-wear white cast iron..............KmBT....................KmBTMn5Mo2Cu

Anti-wear ductile iron..............KmQT.........................KmQTMn6

Chilled cast iron..................LT.........................LTCrMoR

Corrosion-resistant cast iron..................ST.........................STSi15R

Corrosion-resistant ductile iron..............SQT........................SQTAl15Si5

Heat-resistant cast iron..................RT.........................RTCr2

Heat-resistant ductile iron..............RQT........................RQTA16

Austenitic cast iron................AT.........................----

A set of numbers following the code number in the grade indicates the tensile strength value; when there are two sets of numbers, the first set represents the tensile strength value and the second set represents the elongation value. The two sets of numbers are separated by "one".

White cast iron: The carbon in white cast iron is all in the form of infiltrated carbon (Fe3c), which is bright white due to the fracture. Therefore, it is called white cast iron. Because of the large amount of hard and brittle Fe3c, white cast iron has high hardness and brittleness and is difficult to process. Therefore, it is rarely used directly in industrial applications, and is only used for a few parts that require wear resistance and are not subject to impact, such as wire drawing molds, ball mill iron balls, and the like. Mostly used as blanks for steel making and malleable cast iron.

Gray cast iron; most or all of the carbon in cast iron exists in free form flake graphite. The fracture is gray. It has good casting performance, good machinability, wear resistance, good wear resistance, simple melting and low cost, and is widely used in the manufacture of complex castings and wear parts.

Gray cast iron is divided into ferritic-based gray cast iron, pearlite-ferrite-based gray cast iron and pearlite-based gray cast iron according to different matrix structures. Because of the presence of flake graphite in grey cast iron, graphite is a component with low density, low strength, low hardness, and plasticity and toughness tending to zero. It exists as if there are a large number of small gaps on the steel matrix, that is, the bearing area is reduced and the crack source is increased. Therefore, the gray cast iron has low strength and poor toughness and cannot be subjected to pressure processing. In order to improve its performance, a small amount of ferrosilicon, silicon calcium and other inoculants are added to the molten iron to refine the pearlite matrix before casting. The malleable cast iron: malleable cast iron is cast into white mouth with iron and carbon alloy with low silicon content. The cast iron blank is then subjected to high-temperature annealing for a long time to decompose the cementite into a group of flocculent graphite. The wrought iron is a graphitized white cast iron.

The 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 black heart malleable cast iron structure is mainly ferrite (F) basic + group flocculent graphite; the pearlite malleable cast iron structure is mainly pearlite (P) matrix + clustered flocculent graphite. The other type is white heart malleable cast iron. The structure of white heart malleable cast iron is determined by the section size. The small section is made of ferrite. The surface area of ​​large section is ferrite, the core is pearlite and annealed carbon.

The graphite is fine and evenly distributed, and the cast iron is treated by this incubation. It is called brooding cast iron.

Ductile iron: A certain amount of spheroidizing agent (usually ferrosilicon, magnesium, etc.) is added before the casting of molten iron (spheroidal iron) to spheroidize the graphite in the cast iron. Since carbon (graphite) exists in a cast iron matrix in a spherical shape to improve the splitting action on the matrix, the tensile strength, yield strength, plasticity, and impact toughness of the ductile cast iron are greatly improved. It has the advantages of wear resistance, shock absorption, good process performance and low cost. It has been widely used to replace malleable cast iron and some cast steel and forged steel parts, such as crankshafts, connecting rods, rolls, and automobile rear axles.

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