Influence of Carbide Types and Amounts on the Wear of Graphite‐Containing Alloys for Work Rolls

• Published in: Steel research international Vol. 94; no. 4
• Main Authors: Paar, Armin, Aigner, Michael, Reiter, Maximilian, Fischbacher, Martina, Laubbichler, Ingrun
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-04-2023
• Subjects: carbide types; Cemented carbides; Cementite; Chill rolls; Graphite; Hot rolling; Hot rolling mills; indefinite-chill; Microstructure; surface degradation; three-disc wear test rigs; wear profiles; Wear resistance; Wear tests; work roll materials; Work rolls
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.202200485

In the surface‐critical stands in hot rolling mills, the so‐called indefinite‐chill alloys are used as shell materials for the work rolls. The microstructure of these materials consists of cementite and graphite, as well as different other carbides, which are embedded in a martensitic/bainitic matrix. In the past 10 years, indefinite‐chill materials are intensively developed to meet the higher requirements in today's rolling mills. To measure the increase of the wear resistance, a wear test rig is designed and developed, which allows testing work roll materials under conditions that are very close to those in a rolling mill but still on a laboratory scale. This study shows the investigation results of four different indefinite‐chill and graphitic HSS alloys with different carbide amounts and types. The strong influence of MC and M2C/M6C‐carbides can be clearly seen but besides the carbides, also other microstructural phases have an influence on the wear of the alloys. It can be confirmed that with higher fractions of hard carbides the wear on the tested materials decreases. The results also clearly show that there has to be a correct balance between the different carbide types as well as the balance between the carbide, graphite, and matrix fractions.
To develop materials with maximum wear resistance and highest surface quality for rolling mill rolls, it is necessary to achieve a microstructure that consists of different carbides. However, there is no clear rule yet about the fraction of these carbide types to meet all requirements. Scanning electron microscope, phase analysis, and wear tests reveal interesting insights.