Forged semi-steel roll material and its heat treatment

In the roll products, in addition to the common forged steel, cast steel and cast iron three major types of rolls, there is also a class of forged semi-steel and forged white iron series rolls, this new material in the entire family of ferrous materials is also unique.
As we all know, some of the two-roll hot rolling stand of the deep hole type rolls, the requirements of both high toughness, wear resistance and resistance to thermal cracking and other performance, the traditional roll material is difficult to meet.

Conventional forged steel rolls generally below 1.3% carbon content, after forging process to make the matrix uniform and dense, mainly using heat treatment methods to adjust the organization and hardness, to obtain high toughness, forged steel rolls in the absence of a eutectic carbide, but you can adjust the carbon content with the alloying elements to strengthen the matrix, so that the matrix to obtain less than 10% dispersion of secondary and tertiary alloying carbides to improve the wear resistance of the cold state. When used as a hot roll, the matrix is softened by heat, wear resistance is significantly reduced, and poor resistance to thermal cracking.
Common cast iron rolls and other carbon content are more than 2.5%, is a sub-eutectic alloy cast iron. The commonality of such rolls is the existence of eutectic transformation in the solidification process, in a reasonable choice of carbon content, graphitization elements and carbide formation elements under the premise of the contrasting relationship between the number of cold-type control of a eutectic carbide number and morphology, in order to obtain a high degree of hardness and wear resistance. The organization contains 20%-40% large eutectic carbides, even in the hot state can maintain high hardness and wear resistance, and can impede the propagation of thermal cracks and get good resistance to warmth. At the same time, a large number of carbides can also cause a decrease in strength and an increase in brittleness.

Therefore, the demand for comprehensive performance required new materials to ensure that people firstly used cast semi-steel and ductile cast steel, but the strength and toughness is still too insufficient. Finally, this demand led to the emergence of forged semi-steel and forged white iron rolls.

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