H13 Heat Treatment Basics: Hardening and Tempering for Die Casting Dies

A practical overview of the H13 (1.2344 / SKD61) hardening cycle — austenitizing, quenching and the double temper that die shops actually run.

Target

For aluminum die casting, dies are typically used at 44–48 HRC (NADCA practice), balancing heat-check resistance against cracking.

The cycle

Preheat in steps (e.g. 650 °C, then 850 °C) to reduce thermal shock.
Austenitize at 1020–1050 °C, hold long enough for section uniformity.
Quench — high-pressure gas (vacuum furnace) or oil; cool fast enough to avoid grain-boundary carbides, uniformly to avoid distortion.
Double temper at 550–600 °C, each temper followed by cooling to room temperature. The first temper transforms retained austenite; the second tempers the fresh martensite.

Common mistakes

Single tempering — leaves untempered martensite and early cracks.
Slow quench in thick sections — carbide networks and poor toughness.
Tempering in the 475–525 °C trough without care — watch toughness requirements.

After treatment

Nitriding or nitrocarburizing the finished die extends soldering resistance and life; re-nitride during scheduled maintenance. Always verify hardness on the die itself, not only on a test coupon.