Warmwalzen

Warmwalzen, or warm rolling, is a metal forming process in which metal stock is deformed at temperatures between ambient temperature and the recrystallization temperature of the material. The exact temperature range depends on the alloy and product, but the aim is to allow substantial plastic deformation without full recrystallization.

During warm rolling, the workpiece is heated and kept within the target range throughout deformation, using furnaces, induction heating, or in-line heating along the mill. Rolling is carried out in several passes with controlled reductions, and temperature, lubrication, and speed are closely monitored.

Material behavior under warm rolling differs from cold and hot rolling. The reduced flow stress compared with cold work lowers energy consumption and tool wear, while avoiding some of the pronounced work hardening seen at room temperature. The process can yield a good surface finish and tighter tolerances than hot rolling, with a microstructure that may undergo partial recovery and controlled recrystallization, influencing grain size and mechanical properties.

Applications and advantages: Warm rolling is used for steel, aluminum, copper, and other metals to produce sheets, strips, bars, and rails where a balance of strength, ductility, and surface quality is required with lower processing costs than hot rolling. It can reduce scale formation, distortion, and residual stresses relative to hot rolling, while avoiding the extreme work hardening of cold rolling.

Limitations: The process requires precise temperature control; properties are sensitive to holding time and uniformity of heating. Warm rolling is not a substitute for cold rolling when maximum strength and uniformity are needed, nor for hot rolling when very large reductions or high-temperature formability are required.