What to do if the hardness of H13 material fluctuates greatly after tempering?

Precise control of the tempering process, furnace loading parameters, raw material pre-inspection, and process monitoring are the four features of a systematic optimization that should be used when the hardness of H13 material varies significantly after tempering. With a single piece fluctuation of ≤2 HRC, this will guaranty that the hardness is steady between 48 and 52 HRC.

 

1. Fundamental Causes and Solutions

Causes and Remedies

Inconsistent Temperature

To make sure the temperature differential inside the furnace is ≤±5°C, use a PID temperature-controlled furnace that is set to 580℃±5°C and take numerous temperature readings.

Unreliable Cooling Rate

To increase the consistency of thermal circulation, keep workpieces at least 5 cm apart, refrain from stacking, and make use of tooling racks.

Inadequate Tempering Cycles

It takes two cycles of tempering. Cool to room temperature following the first tempering before carrying out the second.

Deviation in Raw Material Composition

Before tempering, use XRF to determine whether Cr (5.0%~5.5%), Mo (1.1%~1.75%), and V (0.8%~1.2%) fulfill the requirements.

Practical Case: By improving the furnace loading density and temperature control system, Jingmo Technology decreased the hardness difference of H13 manifold plates from 3.1 HRC to 1.4 HRC.

 

2. Data Closed Loop and Process Control

Piece-by-Piece Multi-Point Inspection: Determine the range, measure three to five spots on each piece (center, edge, thickness boundary), and make sure the HRC is less than two;

Verification of Metallographic Sampling: ≥5% of each batch is sampled to ensure that the microstructure consists of scattered carbides and homogenous tempered martensite;

Maintain Furnace Temperature Curves: To establish process traceability, keep thorough heating and cooling data for every furnace;

Create Quality Archives: To make problem reviews easier, keep track of hardness data, operator details, and equipment numbers.

Advice: To quickly spot trend deviations (like a steady decline in average hardness), control charts can be created using data from several successive batches.

 

3. Suggestions for On-Site Optimization

Give local compliance service providers priority, such as Wuhan Heat Treatment Plant and Jingmo Technology, who facilitate prompt delivery and comprehensive reporting;

Steer clear of high-temperature measurements: To avoid thermal softening influencing the readings, cool the workpiece to room temperature (<50°C) before measuring;

Before using the device, calibrate it. Make sure the inaccuracy is ≤±1 HRC on a standard block to prevent systematic deviations.

"Accurate temperature, sufficient number of tests, and data archiving" are the safety principles that enable complete process control and reproducibility.