Forming Challenges and Solutions in Stamping High-Strength Steel

High-strength steel exhibits significantly different behavior compared to conventional low-strength steel during stamping. The associated forming difficulties have become key concerns in die development and production control.

1. Significant Increase in Forming Load

The higher yield strength of high-strength steel leads to a notable increase in the load required for plastic deformation. When processed on standard stamping equipment, issues such as press capacity reaching its limit, insufficient energy, and inadequate machine rigidity are commonly observed. Localized deformation of dies and rebound of pads may also occur, negatively impacting part quality and dimensional stability.

Countermeasures:

Reinforce die structures by adding supports and, when necessary, localized ribs or strengthening inserts;

Select stamping equipment with higher rigidity and energy reserves; servo-hydraulic presses may be considered for improved load control;

Account for variations in load curves during process evaluation to prevent localized overloading.

2. Dimensional Inaccuracy Due to Elastic Recovery

High-strength steel shows substantial elastic recovery after unloading, particularly in bending and flanging operations. This makes it difficult to precisely control final part geometry and often leads to cumulative deviations in welding or assembly alignment.

Countermeasures:

Use numerical simulations during die design to predict springback and apply geometric compensation accordingly;

Introduce stretch-bending techniques to increase plastic strain and reduce residual elastic recovery;

Include post-form calibration operations where necessary to improve dimensional consistency.

3. Edge Cracking Tendency

Due to the lower elongation of high-strength steel, strain concentration at trimmed edges becomes more severe. Conventional shearing processes often introduce microcracks at the edge, which propagate during subsequent flanging or deep drawing, resulting in fracture.

Countermeasures:

Set shearing clearance according to material strength and thickness; avoid overly narrow gaps that cause excessive strain hardening;

Use laser or plasma trimming for edge refinement in critical areas to improve cross-sectional integrity;

Implement hole expansion ratio (HER) testing as a material qualification standard to screen out coils with inadequate edge formability.

4. Die Wear and Surface Damage

The higher hardness of high-strength steel subjects dies to increased friction and wear, particularly in high-contact-stress zones such as draw beads and flanging radii. Over time, adhesive wear, galling, and surface damage may occur.

Countermeasures:

Select tool steels with high wear resistance (e.g., DC53, ASP series), and use modular die components for replaceability in critical areas;

Apply PVD-based hard coatings (e.g., TiCN, AlCrN) on forming surfaces and maintain polished finish to control friction;

Use stamping lubricants specifically formulated for high-strength steel with strong adhesion and high-pressure tolerance, and ensure uniform application.