Die steel is a hot working die steel with both strength and toughness widely used in the world. H13 die steel has high toughness hardenability and cold and hot fatigue resistance, and is not easy to produce thermal fatigue cracks. These characteristics are also determined by H13 heat treatment process.

退火工艺

Annealing process

模具钢属于共析钢，采用常规完全退火或等温球化退火。H13模具钢的完全退火工艺为:850~900℃×3~4h，保温结束后随炉冷到500℃以下出炉空冷;等温球化退火艺:845~900℃×2~4h/炉冷+700~740℃×3~4h炉冷，≤40℃/h，≤500℃出炉空冷。

Die steel belongs to eutectoid steel, which adopts conventional complete annealing or isothermal spheroidizing annealing. The complete annealing process of H13 die steel is 850 ~ 900 ℃ × 3 ~ 4h, after heat preservation, the furnace is cooled to below 500 ℃ and discharged for air cooling; Isothermal spheroidizing annealing process: 845 ~ 900 ℃ × 2 ~ 4H / furnace cooling + 700 ~ 740 ℃ × 3 ~ 4H furnace cooling, ≤ 40 ℃ / h, ≤ 500 ℃ outlet air cooling.

模具钢经退火处理后，适宜的组织由球状珠光体和少量粒状碳化物组成，要求热处理硬度达到HB192~229，可以获得较好的加工性能。对于质量要求较高的H13钢模具，还应进行防止白点退火。

After annealing treatment, the appropriate structure of die steel is composed of spherical pearlite and a small amount of granular carbide. It is required that the heat treatment hardness should reach hb192 ~ 229, and better machinability can be obtained. For H13 steel dies with high quality requirements, anti white spot annealing shall also be carried out.

淬火工艺

Quenching process

模具钢的淬火回火工艺可以采用盐浴炉真空炉和流动粒子炉加热，模具表面光洁，热处理变形小，零件寿命长。特别是外热式刚玉流动粒子炉保护加热，吸收了盐浴炉和真空炉加热的共同优点，很适合热作模具钢的热处理加热。

The quenching and tempering process of die steel can be heated by salt bath furnace, vacuum furnace and mobile particle furnace. The die surface is smooth, the heat treatment deformation is small and the service life of parts is long. In particular, the external heated corundum flow particle furnace absorbs the common advantages of salt bath furnace and vacuum furnace, and is very suitable for the heat treatment and heating of hot working die steel.

模具钢采用盐浴炉作为加热设备时的通用淬火工艺是:400~500℃预热，650~840℃预热，1020~1050℃奥氏体化，保温结束后可视使用性能要求采用空淬油淬气淬或分级淬火，分级温度可取500~540℃。

When salt bath furnace is used as heating equipment for die steel, the general quenching process is: 400 ~ 500 ℃ preheating, 650 ~ 840 ℃ preheating, 1020 ~ 1050 ℃ austenitizing. After heat preservation, air quenching, oil quenching, gas quenching or step quenching can be adopted according to the performance requirements, and the step temperature can be 500 ~ 540 ℃.

回火工艺

tempering process 

模具钢淬火后应进行2~3次回火，以期获得所要求的力学性能。淬火后的模具温度在低于70℃时就应尽快回火，这对尺寸较大形状复杂的热作模具尤为重要。同时，为避免热作模具回火时重新产生残余应力，回火加热和冷却应缓慢进行。

After quenching, the die steel shall be tempered for 2 ~ 3 times in order to obtain the required mechanical properties. When the temperature of quenched die is lower than 70 ℃, it should be tempered as soon as possible, which is particularly important for hot working dies with large size and complex shape. At the same time, in order to avoid the re generation of residual stress during tempering of hot working die, tempering heating and cooling shall be carried out slowly.

模具钢的回火工艺应根据热作模具的工作条件和具体的失效形态来确定回火温度和硬度。一般H13模具钢大都采用540~650℃×3h高温回火，以提高模具的韧性和减少残余奥氏体(Ar)在模具钢中发生转变而引起脆性。

The tempering process of die steel should determine the tempering temperature and hardness according to the working conditions and specific failure modes of hot working die. Generally, high-quality H13 die steel is mostly 540 ~ 650 ℃ × 3H high temperature tempering to improve the toughness of the die and reduce the brittleness caused by the transformation of residual austenite (AR) in the die steel.