The preliminary heat treatment of cold working die mainly includes annealing, normalizing and quenching and tempering. The main purpose is to remove the residual structure defects of the blank, which is conducive to the subsequent cold and hot processing, and improve the service performance and life.

1.正火工艺及质量控制

1. Normalizing process and quality control

正火的目的是碳素工具钢、合金工具钢的网状碳化物，细化不均匀的片状珠光体。对于存在带状组织的钢，考虑易产生切削裂纹，故采用正火比退火更有效果。对于高碳高合金模具钢，由于一次碳化物不易在奥氏体中固溶，正火效果小，故一般不采用。正火温度是根据钢种来确定。

The purpose of normalizing is to eliminate the network carbide of carbon tool steel and alloy tool steel and refine the uneven flake pearlite. For the steel with banded structure, considering that it is easy to produce cutting cracks, normalizing is more effective than annealing. For high carbon and high alloy die steel, the primary carbide is not easy to dissolve in austenite and normalizing effect is small. The normalizing temperature is determined according to the steel grade.

正火时，加热温度不宜过低，否则网状碳化物不能充分溶于奥氏体中，正火后可能存在残留网状碳化物，对以后的球化退火不利。冷却时，为抑制碳化物沿晶析出，应采用快的冷却速度，于哪种冷却速度合适，应根据钢种、模具大小及变形开裂倾向而定。例如，模具尺寸大时，应采用雾冷；尺寸小者则可空冷或风冷。对于存在带状组织的钢，更应快冷。

When normalizing, the heating temperature should not be too low, otherwise the network carbides can not be fully dissolved in austenite, and there may be residual network carbides after normalizing, which is unfavorable to the subsequent spheroidizing annealing. During cooling, in order to restrain the precipitation of carbides along the grain, a fast cooling rate should be adopted. As for which cooling rate is appropriate, it should be determined according to the steel grade, die size and deformation cracking tendency. For example, when the mold size is large, fog cooling should be used; when the mold size is small, air cooling or air cooling can be used. For the steel with banded structure, it should be cooled more quickly.

2.球化退火工艺及质量控制

2. Spheroidizing annealing process and quality control

球化退火的目的是获得满意的机械加工性能，并为淬火做好组织准备。球化退火组织对热处理后的强韧性、畸变、开裂倾向、耐磨性、断裂韧度有显著的影响。

The purpose of spheroidizing annealing is to obtain satisfactory machinability and prepare microstructure for quenching. The spheroidized annealed microstructure has a significant effect on the strength and toughness, distortion, cracking tendency, wear resistance and fracture toughness after heat treatment.

球化退火的温度，以保证能加速球化过程和形成均匀的球化组织，要避免退火温度过低而出现残留的厚片状碳化物，温度过高而出现新的片状及棱角状碳化物。球化退火的等温温度和保持时间要选择在以不出现片状或片状与球状混合组织、并有合适的球化速度范围为宜。

The temperature of spheroidizing annealing should be set to ensure that the spheroidizing process can be accelerated and uniform spheroidizing structure can be formed. It is necessary to avoid the residual thick flake carbides when the annealing temperature is too low and the new flake and angular carbides when the annealing temperature is too high. The isothermal temperature and holding time of spheroidizing annealing should be selected in the proper range of spheroidizing speed with no lamellar or mixed lamellar and spherical structure.

3.冷作模具调质处理工艺

3. Quenching and tempering process of cold working die

调质处理的目的是获得细珠光体和超细碳化物，碳化物网、带，加工后的残留应力，改善组织，便于机械加工，防止淬火开裂和减小淬火畸变。

The purpose of quenching and tempering is to obtain fine pearlite and ultra-fine carbide, eliminate carbide mesh and band, eliminate residual stress after processing, improve microstructure, facilitate machining, prevent quenching cracking and reduce quenching distortion.

冷作模具钢的调质处理，可采用在常规加热温度淬火后进行640-680℃高温回火的工艺。调质后的硬度一般《229HBW。

The quenching and tempering of cold work die steel can be carried out at 640-680 ℃ after quenching at conventional heating temperature. The hardness after quenching and tempering is generally 229hbw.

冷作模具在热处理前还应进行去应力退火，其目的是机械加工或已破损模具经焊补加工后的残留应力，减少淬火开裂和变形倾向，或避免高速钢返修淬火时出现的萘状断口。通常碳素工具钢去应力退火的加热温度为630-650℃，保温1-2h；高合金工具钢的加热温度为680-700℃，保温1-3h。

Stress relief annealing should be carried out before heat treatment of cold working die, so as to eliminate the residual stress of machined or damaged die after welding, reduce the tendency of quenching cracking and deformation, or avoid naphthalene fracture of high speed steel during repair and quenching. Generally, the stress relief annealing temperature of carbon tool steel is 630-650 ℃ and the heat preservation time is 1-2h, while that of high alloy tool steel is 680-700 ℃ and the heat preservation time is 1-3H.