Selection of Tool Steel for Roll Forming Dies

Roll forming is a continuous cold working process in which a strip or sheet is progressively bent through multiple roll stations. The tooling remains in constant contact with the material, and deformation is distributed rather than concentrated.

This operating condition determines how roll forming dies fail. The dominant mechanism is not impact or fracture, but surface degradation under sustained contact and sliding. Abrasive wear gradually alters the roll profile, leading to dimensional deviation in the formed section. At the same time, adhesive wear—typically observed as galling or surface scratching—damages both the tool surface and the product finish.

Material selection is therefore governed by how effectively the tool steel controls these two mechanisms over long production runs.

Selection Logic

The primary requirement is stable wear resistance under continuous sliding contact. In applications with high strip tension or strong forming resistance, the roll surface must maintain its geometry over time. This drives selection toward high-carbide tool steels when abrasive wear is the limiting factor.

However, increasing wear resistance reduces chipping resistance under load. Although roll forming is not impact-dominated, localized pressure, misalignment, or strip variation can still introduce stress concentrations. If the material lacks sufficient toughness, edge chipping or surface cracking can occur before wear becomes critical.

When forming stainless steels, high-strength materials, or coated strips, friction increases and adhesive wear becomes dominant. In these conditions, resistance to galling becomes more important than maximum hardness.

Under preheated forming conditions, resistance to thermal cracking must also be considered, although it is not the primary driver in most roll-forming applications.

Machinability and response to surface treatments directly affect regrinding frequency and tooling cost. Many roll-forming dies rely on nitriding or hard-chrome plating to control surface damage, and the base material must remain stable during these processes.

Recommended Tool Steels

Selection should be based on the mechanism that limits tool life in production.

• If failure occurs as a gradual loss of profile, wear resistance should be prioritized, and D2 is typically effective.
• If chipping or instability appears before significant wear, tougher grades such as O1 or L6 are more reliable.
• If galling or surface damage controls tool life, A6 or surface-treated low-alloy steels are more suitable.
• If high-strength materials cause rapid degradation, high-speed steels such as M42 become necessary.

The correct choice is defined by the dominant failure mechanism, not by maximum hardness.

Summary Table