What is the optimal hardness of H13 material after tempering?
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After tempering, the ideal hardness range for H13 material is 48–52 HRC. This series ensures reliable mold service under high temperature and high pressure situations by striking the ideal balance of strength, toughness, and wear resistance.
1. The connection between performance and hardness
Range of Hardness
Performance
Risk Alert
48–52 HRC (Suggested)
Combining wear resistance and impact resistance for optimal overall performance
Ideal for the majority of hot-working molds
<48 HRC
matrix softening, increased wear, and susceptibility to collapse
In high-load situations, it is not advised.52 HRC
Considerably more brittleness and a greater chance of cracking
Strict crack control is required, and it is only appropriate for specific needs.
Practical Application: In Wuhan, tempering at 580°C for two hours for two cycles is the standard procedure. The hot runner nozzle life can exceed 500,000 cycles, and the actual measured hardness is steady at 49–51 HRC.
2. How Can Hardness Be Verified to Meet Requirements? Precise Temperature Control: A PID temperature control system is used to set the tempering temperature at 580℃±5°C.
Two Tempering Cycles: Prior to the second tempering, the parts must air cool to room temperature following the first tempering.
Adequate Holding Time: Each tempering cycle lasts at least two hours; for thicker parts, increase the holding time by thirty minutes for every twenty-five millimeters of thickness.
Multi-Point Temperature Measurement Verification: To prevent localized overheating or cold zones, the furnace's temperature differential is ≤±5°C.
Case Study: After just three days of operation, a company's tempering temperature was too low (530°C), resulting in a hardness of 53.5 HRC and brittle fracture.
3. Standards for Hardness Testing
Measurement Point Layout: Each part is measured at three to five locations (center, edge, and thickness boundary).
Acceptance Criteria:
48–52 HRC is the average value.
Range for a Single Part: ≤2 HRC
Data Archiving: Test data and furnace temperature curves are stored for traceability.
