Resistance to hot cracking
Generally, the rough roll is mainly required for strength and thermal crack resistance; the work roll of the small 20-roll mill has a weight of only about 100 grams, and the weight of the support roll of the wide plate mill has exceeded 200 tons. When selecting the rolls, the main material of the safety bearing (all grades of cast iron, cast steel or forged steel, etc.) is selected according to the basic strength requirements of the rolling mill.
The finishing roll speed is higher, and the final product to be rolled must have a certain surface quality, and it is mainly required for hardness and wear resistance. Then consider the wear resistance that should be used when the rolls are used. Due to the complex wear mechanism of the rolls, including mechanical stress, thermal action during rolling, cooling, chemical action of the lubricating medium, and other effects, there is no uniform indicator for comprehensive evaluation of roll wear resistance. Since the hardness is easy to measure and can reflect the wear resistance under certain conditions, the radial hardness curve is generally used to approximate the wear resistance index of the roll.
In addition, there are some special requirements for the rolls. For example, when the amount of pressing is large, the rolls are required to have a strong biting ability and are more resistant to impact;
When rolling thin gauge products, the requirements for the rigidity, uniformity of the structure, processing accuracy and surface finish of the rolls are stricter;
When rolling a profiled section of a section, it is also necessary to consider the cutting performance of the working layer of the roll body.
When using rolls, some performance requirements of the rolls are often opposite to each other. The roll purchase cost and maintenance cost are very expensive. Therefore, the technical and economic advantages and disadvantages should be fully weighed, and whether the cast or forged, alloy or non-alloy is decided. , single material or composite.