How to optimize the tempering process of H13 material?

Two tempering procedures, uniform furnace loading, and exact temperature control are the cornerstones of optimizing the tempering process of H13 material. The hardness is guarantyd to be steady at 48~52 HRC with fluctuations ≤2 HRC when process monitoring and data traceability are combined. A methodical optimization strategy is as follows:

 

1. Key Process Parameter Optimization

The item

Optimization Recommendation

Justification

Controlling the Temperature

Control the temperature precisely between 550 and 600°C; 580°C is advised.

Insufficient stress release occurs when the temperature is too low, and decreased hardness occurs when the temperature is too high; every ±10°C can result in a hardness shift of 1~2 HRC.

The quantity of rounds of tempering

Two temperings are required; the first tempering must be cooled to room temperature before the second.

enhances microstructure stability and stops residual stress rebound.

Keeping Time

For thick and large portions, prolong by 30 minutes for every 25 mm of thickness every two hours.

guaranties adequate tempering of the core, preventing surface and interior irregularities.

Cooling Technique

It is not permitted to use water cooling, oil cooling, or air cooling to room temperature.

stops the introduction of new stress or secondary quenching.

Practical Advice: Choose a tempering furnace with multi-point temperature measurement and PID temperature control, and keep the furnace's temperature differential within ±5°C.

 

2. Optimizing Thermal Circulation and Furnace Loading

Optimal Loading Spacing: To prevent stacking and guaranty consistent hot air circulation, keep a minimum of 5 cm between workpieces.

Optimal Placement Direction: To avoid uneven cooling brought on by localized restriction, alternate between thick and thin parts.

Use of Fixtures: To secure workpieces and enhance the consistency of heat transfer, use supports that can withstand high temperatures.

Enhanced Gas Circulation: To increase temperature consistency, turn on forced convection or furnace fans.

Case Study: By maximizing the furnace loading density, Jingmo Technology decreased the hardness difference of H13 manifold plates after tempering from 3.1 HRC to 1.4 HRC.

 

3. Closed-loop Process Monitoring and Quality

Furnace Temperature Curve Recording: To guaranty regulated and traceable temperatures, full heating and cooling curves are recorded for every furnace.

100% Hardness Testing: Following tempering, a portable hardness tester with a range of ≤2 HRC is used to assess hardness at three or more locations per piece.

Verification of Metallographic Sampling: To ensure that the microstructure is uniform tempered martensite + scattered carbides, ≥5% of the batch is sampled.

Raw Material Pre-inspection: XRF is utilized to verify that the Cr (5.0%~5.5%), Mo (1.1%~1.75%), and V (0.8%~1.2%) components satisfy the requirements prior to tempering.

"Precise temperature, sufficient number of tests, and data archiving" are the safety principles that guaranty complete process traceability and reproducibility.