Influence of microstructure on degradation of cast graphitic high-speed steel

Work rolls used in hot rolling of steel suffer severe wear caused by combinations of adhesion, abrasion, rolling contact fatigue, thermal fatigue, and tribo-chemical corrosive attack. Depending on the specific wear mecha-nisms, damage of these rolls may include loss of material, surface, and subsurface cracking, as well as impairment of the surface finish. In this work, wear tests were performed using a custom-designed roll test rig which sim-ulates the contact conditions between the work roll, the back-up roll and the hot-rolled steel. To simulate typical conditions occurring in a hot rolling mill, different contact pressures and rolling temperatures were considered. Wear and damage mechanisms were analyzed by optical microscopy and scanning electron microscopy (SEM). A systematic approach was used for correlating wear and microstructure of the roll materials. Therefore, graphitic high-speed steels (G-HSS) with different fractions and types of carbides were investigated. MC and M2C/M6C were identified to influence mainly the wear behavior of G-HSS. Increasing the fraction of these carbides reduced the wear rate but increased the surface roughness. The optimum balance between carbide types, graphite content and metal matrix has been identified as mandatory for achieving high wear performance of work roll materials.

Automated summary

Work rolls used in hot rolling of steel are subject to severe wear due to multiple factors such as adhesion, abrasion, rolling contact fatigue, thermal fatigue, and tribo-chemical corrosive attack. Wear tests were conducted using a custom-designed roll test rig to simulate the contact conditions in a hot rolling mill. Optical microscopy and scanning electron microscopy (SEM) were used to analyze the wear and damage mechanisms. Graphitic high-speed steels (G-HSS) with different fractions and types of carbides were investigated, and it was found that MC and M2C/M6C mainly influenced the wear behavior of G-HSS. The optimal balance of carbide types, graphite content, and metal matrix was identified as crucial for achieving high wear performance of work roll materials.