The alloy chilled cast iron roll is formed by using the supercooling degree of molten iron itself and the method of cold surface chilling 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. Its high hardness and excellent wear resistance are used in a small bar and wire rod mills and narrow-strip steel finishing mills.
Alloy infinite 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 roll body of the infinite chilled cast iron roll. The content of graphite is from the surface of the roll body. As the depth increases, the hardness decreases, so there is no obvious boundary between the working layer of the roll body and the core. When the material of the infinite chilled cast iron roll contains high alloy elements of chromium, nickel and molybdenum, it is a high nickel-chromium infinite chilled cast iron roll, which is produced by full flushing (overflow method) or centrifugal composite casting process. There are many 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 crack resistance and is widely used. It is used for finishing rolls in wide, medium and heavy plate mills and strip mills.
The characteristic of this roll is that the graphite is evenly distributed from the roll body to the core, so it has high tensile strength, can withstand heavy loads, and has good wear resistance. The matrix structure is carbide, pearlite or acicular bainite. Alloy ductile iron rolls can be roughly divided into pearlitic ductile iron rolls and bainitic 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.
Chromium, nickel and molybdenum alloy elements are added to the ductile iron roll, and the pearlitic ductile iron roll is obtained after 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.
Nickel, manganese, chromium, molybdenum and other alloying elements are added to the ductile iron roll. It has a needle-like structure (bainite + a small amount of martensite) matrix, which is higher in strength, toughness and wear resistance than pearlitic ductile iron rolls. Sex has also improved significantly. It can be produced by static casting and centrifugal casting, but the acicular bainitic ductile iron roll has high alloy content and large casting stress, and the centrifugal composite casting process can obtain ideal comprehensive performance.
The high-alloy composite cast iron roll produced by the centrifugal composite casting process is made of wear-resistant high-chromium white cast iron containing 12% to 22% of chromium as the outer material of the roll body, and generally, ductile iron is used as the material of the roll core and roll neck. . Due to the existence of lath-shaped M7c3-type eutectic carbides, chrysanthemum-shaped M2c-type eutectic carbides and granular M23C6-type secondary carbides in the matrix, high-chromium composite cast iron rolls have excellent anti-wear properties and are widely used. It is used as the work roll for rough rolling and finishing of hot strip rolling mill, the rough rolling and finishing work roll of wide and medium plate rolling mill, and the finishing work roll of small section steel and plate rolling mill.