What types of cast iron rolls are there?

1) alloy chilled cast iron roll

Alloy chilled cast iron rolls use the supercooling degree of molten iron itself and the method of chilling the cold surface to form a white layer. There is basically no free graphite in the matrix structure of the working layer of the roll body, and the metallographic structure is fine pearlite and carbide. It has high hardness and excellent wear resistance and is used in a small bar, wire rod mills and narrow strip finishing stands.

(2) alloy infinite chilled cast iron roll

The alloy infinitely chilled cast iron roll is a material between chilled cast iron and gray cast iron. There is evenly distributed graphite in the matrix structure of the working layer of the infinitely chilled cast iron roll body. The graphite content starts from the surface of the roll body. As the depth increases, the hardness decreases accordingly. Therefore, there is no obvious dividing line between the working layer and the core of the roll body. When the material of an infinite chilled cast iron roll contains high chromium, nickel, and molybdenum alloy elements, it is high nickel chromium infinite chilled cast iron roll, which is produced by full flushing (overflow method) or centrifugal composite casting process. There are more carbides in the matrix structure of the working layer of the high-nickel-chromium infinite chilled cast iron roll body, so it has high wear resistance. The existence of graphite in the matrix structure makes it have good thermal cracking resistance and is widely used It is used as finishing rolls for wide, medium, and thick plate mills and strip mills.

 

(3) Alloy ductile iron roll

The characteristic of this kind of roll is that the graphite from the roll body to the core is uniformly distributed in a spherical shape, so it has high tensile strength, can withstand heavy loads, and has good wear resistance. The matrix structure is carbide and pearlite or acicular bainite. Alloy ductile iron rolls can be roughly divided into pearlite ductile iron rolls and bainite ductile iron rolls according to the matrix structure of the roll body. Alloy ductile iron rolls have good thermal shock resistance and wear resistance, and are widely used as rolls for large blooming mills, section steel mills, continuous bar mills, and large seamless tube mills.

 

(4) Pearlitic ductile iron rolls

 

Chromium, nickel, and molybdenum alloy elements are added to the ductile iron roll, and the pearlite ductile iron roll is obtained through special heat treatment. The pearlitic ductile iron roll has good strength, high-temperature performance, and accident resistance, and the hardness drop of the working layer is small.

 

(5) Acicular bainite ductile iron roll

 

Nickel, manganese, chromium, molybdenum, and other alloy elements are added to the ductile iron roll, which has a needle-like structure (bainite + a small amount of martensite) matrix, which is stronger than the pearlitic ductile iron roll, with better toughness and wears resistance Sex is also significantly improved. It can be produced by static casting and centrifugal casting, but due to the high alloy content and high casting stress of the acicular bainite ductile iron roll, the ideal comprehensive performance can be obtained by adopting the centrifugal composite casting process.

 

(6) High chromium composite cast iron roll

A high-alloy composite cast iron roll is produced by using wear-resistant high-chromium white cast iron containing 12% to 22% chromium as the outer layer of the roll body, and generally using ductile iron as the roll core and roll neck material, and adopting centrifugal composite casting process. Due to the presence of lath-like M7c3-type eutectic carbides, chrysanthemum-like M2c-type eutectic carbides and granular M23C6-type secondary carbides in the matrix, high-chromium composite cast iron rolls have excellent wear resistance and are widely used It is used as the front-end work roll of rough rolling and finish rolling of hot-rolled strip continuous rolling mill, the rough rolling and finishing work roll of wide medium and heavy plate mill, and the finishing work roll of small section steel and plate mill.

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