What is the effect of tempering on the properties of H13 steel?

Tempering lowers internal stress, stabilizes dimensions, greatly increases toughness, and modifies hardness to the practical range of 48–52 HRC. It is a crucial procedure to guaranty that H13 steel has outstanding general qualities.

 

1. Improvement of Core Performance

Performance in the Quenched State Prior to Tempering and the Tempered State Following Tempering

Low toughness and high brittleness Martensite precipitates carbides as a result of significantly increased tempering, which lessens brittleness and increases impact resistance.

High levels of internal stress that are effectively released During tempering, the thermal and structural strains produced during quenching are progressively removed.

Dimensional Stability: Poor and easily distorted The workpiece is much better after stress release and is less likely to undergo micro-deformation when used again.

Hardness Potentially >55 HRC (High) 48~52 HRC (Ideal Range) Tempering temperature management keeps hardness within the ideal service range.

Practical Value: Tempering H13 workpieces can increase their service life by more than three times. Untempered workpieces are vulnerable to cracking under high injection molding pressure.

 

2. Modifications to the Microstructure

Microstructure of the quenched state: Unstable quenched martensite + retained austenite with many internal stresses and dislocations.

Evolution of the tempering process:

Martensite starts to break down beyond 200°C, resulting in the precipitation of ε-carbides;

400–500°C: Carbides disperse and retained austenite changes;

550–600°C: The microstructure is stable, and fine, homogeneous carbides and tempered martensite develop.

Metallographic features: A dark tempered martensite matrix with uniformly dispersed fine carbide particles makes up the microstructure following appropriate tempering.

 

3. Crucial Elements of Process Management

550–600°C is the tempering temperature. A temperature that is too high will reduce hardness, whereas a temperature that is too low will result in insufficient stress release.

Tempering cycles should be performed at least twice in order to avoid residual stress rebound following the initial tempering.

Cooling Technique: Air cooling to prevent sudden cooling that could cause tension again.

Supporting Testing: To guaranty process control, hardness reports and furnace temperature profiles must be supplied for every batch.

Safety Principle: "One quenching, two temperings" is the unbreakable H13 tempering treatment regulation that cannot be disregarded.