Thermomechanical rolling

All rolling processes require a uniformly heated slab when leaving the furnace.

Thermomechanical rolling is used to achieve the optimum in grain refinement. For obtaining the fine-grain structure a number of measures are required. The slab reheating temperature must be kept at the lowest possible level in order to limit the grain growth. Roughing is rolled in the range of the recrystallization temperature.

The standard thermomechanical rolling process operates by keeping the final deformation at low temperatures around 650 to 750 degrees Celsius. This method provides high strength but is not the most favourable for the toughness of the material.

A more advantageous method of TM rolling is frequently applied at voestalpine Grobblech. The final rolling temperature is kept in the non recrystallizing area.
A subsequent accelerated cooling leads to an extremely fine bainitic transformation structure. This process combines high strength and highest toughness. The chemical composition, microalloying elements and a low carbon content result in a low carbon equivalent with excellent weldability.

The thermomechanical rolling process is unique because the combination of highest strength and good toughness with a low carbon content cannot be achieved with any heat treatment. The main fields of application for TM rolling are line pipe steels from X65 up to X100, high-strength cold forming grades, steels for offshore and sour service applications.