How to Adjust the Hardness of H13 Material
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Controlling the tempering temperature and holding time is the fundamental technique for modifying the hardness of H13 material. The hardness may be carefully controlled within the optimal range of 48–52 HRC by adjusting within the range of 550–600°C.
1. Hardness and Tempering Process Parameters
Temperature Hardness Range (HRC) Tempering: Relevant Situations
550°C 50~52 HRC High wear resistance specifications, but brittleness must be avoided
The ideal ratio of strength, toughness, and wear resistance is 49–51 HRC at 580°C (recommended).
600°C 48–50 HRC High hardness requirements, with a small amount of softening acceptable
Practical Advice: A hardness shift of 1~2 HRC can occur for every ±10°C temperature change. For fine-tuning, a baseline of 580℃±5℃ is advised.
2. Crucial Controls
Conduct two cycles of tempering: To avoid stress rebound and unstable hardness, the parts must be air-cooled to room temperature following the initial tempering.
Adequate holding time: at least two hours per time; for thicker sections, add thirty minutes for every twenty-five millimeters of thickness.
Precise temperature control: To guaranty a furnace temperature differential of ≤±5°C, use a PID temperature-controlled furnace in conjunction with multi-point temperature measurement.
Standardized furnace loading: To prevent stacking and enhance regular heat circulation, workpiece spacing should be at least 5 cm.
Case Study: The tempering temperature was raised from 560°C to 580°C in a plant. The H13 nozzle's toughness rose by 20%, its hardness dropped from 51.5 HRC to 50.2 HRC, and there were no more brittle fractures.
3. Verification Techniques for Adjusting Hardness
On-site Testing: Measure each piece at three to five crucial points using a portable hardness tester to make sure:
48–52 HRC is the average hardness.
Range of a single piece ≤2 HRC
Metallographic Sampling: Verify that the microstructure consists of scattered carbides and homogenous tempered martensite;
Maintain Furnace Temperature Curves: Obtain complete process traceability to facilitate process evaluation.
"Precise temperature, sufficient number of tests, and data archiving" are the safety principles that guaranty dependable performance following adjustment.
