Heat Treatment Practice for 1.2379 (DIN 1.2379)

Heat treatment decides whether 1.2379 reaches its intended properties. The grade can be correct, the analysis can be correct and the part can still fail if the cycle is copied from a similar job with a different section size.

Delivery condition

Material is normally supplied as hardened and tempered to 58 to 62 HRC. Record the incoming condition before any processing begins, because a hardness check on arrival is the cheapest way to catch a mix-up before value is added to the part.

Austenitising and quenching

Preheat slowly to 800 C before raising to the 1000 to 1050 C austenitising temperature. Quench in oil, warm oil or gas. Temper at least twice, keeping away from the 300 to 500 C range.

Distortion and dimensional control

Sections in this family move during quenching. Allowance for distortion, careful support in the furnace, controlled quench agitation and, on large parts, rough machining before heat treatment followed by finish machining afterwards are the practical controls.

Inspection after heat treatment

Require hardness readings at defined positions, a hardness survey through the section where hardenability matters, and non destructive testing where the part carries load. A certificate that reports a single surface hardness value proves very little about blanking and piercing dies.

Hubei Keyspark Special Steel Co., Ltd. runs two 20-ton EAF furnaces, two 20-ton LF ladle furnaces, a 20-ton VD unit and a 5-ton ESR furnace, with open-die forging, 12 precision heat treatment furnaces, four vacuum annealing furnaces and over twenty machining centres. Annual capacity is about 15,000 tonnes.

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