improve the hardness of ST13 steel plate

What measures can be taken to improve the hardness of ST13 steel plate if it's too hard?
When ST13 steel plate's hardness is too high, improvements need to be made by adjusting material properties and adapting the processing technology to restore its good stamping formability. Specific measures are as follows:
1. Production (Manufacturers adjust material properties)
Optimizing the annealing process
Annealing is the key method for reducing the hardness of ST13 steel. If the hardness is too high, adjustments can be made through the following methods:
Increasing the annealing temperature: Within the standard range, appropriately increase the annealing temperature (for example, from the conventional 700-720°C to 720-740°C, but avoid overheating). This promotes the complete decomposition of pearlite into ferrite, reduces internal stress, and lowers hardness.
Extending the holding time: Increasing the annealing holding time (for example, from 2-3 hours to 3-4 hours) promotes uniform grain growth, stabilizes the microstructure, and further softens the material.
Slowing the cooling rate: Using slow cooling with the furnace instead of air cooling reduces residual stress during the cooling process and prevents a rebound in hardness caused by rapid cooling. Adjust the Rolling Process
If the high hardness is caused by excessive cold work hardening during cold rolling, reduce the number of rolling passes or the rolling pressure, control the deformation (e.g., reduce the total deformation from 60%-70% to 50%-60%), minimize the work hardening effect, and reduce the hardness at the source.
Control the Raw Material Composition
If the hardness is increased due to excessive levels of strengthening elements such as manganese and silicon in the raw materials, fine-tune the composition within the standard range (e.g., reduce the manganese content to 0.2%-0.3%) to reduce the solid solution strengthening effect and avoid exceeding the hardness standard.
II. Processing (User-Adapted Stamping Process)
If the steel plate has already been shipped and the hardness is too high, optimize the stamping process to reduce processing risks:
Add a softening pretreatment
Perform a low-temperature annealing (e.g., hold at 600-650°C for 1-2 hours followed by slow cooling) on the steel plate. This "stress relief annealing" reduces some of the hardness and improves plasticity (suitable for small batches, but care must be taken to avoid compromising dimensional accuracy). Optimize Stamping Parameters
Increase the stamping temperature: Use a warm stamping process (heating to 150-250°C). This increased temperature reduces the material's yield strength and hardness, improving fluidity and reducing the risk of cracking (especially suitable for complex-shaped parts).
Adjust mold parameters: Increase the die corner radius (to reduce local stress concentration), increase the blank holder force (to inhibit cracking caused by excessive material flow), or use a stamping oil with better lubricity (to reduce frictional resistance).
Step Forming
For deep-draw or complex-shaped parts, switch from single-pass forming to multi-pass forming. Minimize the deformation in each pass to avoid material fracture due to high hardness and insufficient plasticity. Annealing steps can be added between passes to eliminate work hardening.
Notes: Adjustments must be based on the core properties of ST13 (high elongation and good stampability). Avoid excessively reducing the hardness, which could lead to insufficient strength (e.g., deformation during use).
Before mass production, verify the results through small-sample testing to ensure that the adjusted hardness still meets the product's molding accuracy and performance requirements.