The working parts of cold working die bear many kinds of mechanical forces, such as tension and compression, bending, impact, fatigue, friction and so on. Therefore, the cold working die steel should have the ability of deformation resistance, fracture resistance, wear resistance, fatigue resistance and bite resistance after corresponding heat treatment. In order to meet the working characteristics of cold working die, in addition to carbon tool steel, there are alloy tool steel with alloy elements, which contain more alloy elements such as Cr, Ni, Mn, Mo, etc.

合金元素降低钢的马氏体相变点Ms，淬火后有一定量的残留奥氏体，有利于减少淬火变形，也有利于韧性提高。淬火后的组织中除了含碳马氏体和残留奥氏体外，还有细小分布的碳化物，尤其是合金碳化物，碳化物相的高熔点、高硬度、高脆性对钢的硬度、强度、耐磨性、回火抗力、二次硬化能力、细化晶粒等都有很大的影响。因此要特别重视碳化物的作用，注意控制碳化物的种类、形态和分布状态。

Alloying elements reduce the martensitic transformation point ms of the steel, and there is a certain amount of retained austenite after quenching, which is conducive to reducing the quenching deformation and improving the toughness. In addition to carbon bearing martensite and retained austenite, there are also fine distributed carbides, especially alloy carbides. The high melting point, high hardness and high brittleness of carbide phase have great influence on hardness, strength, wear resistance, tempering resistance, secondary hardening ability and grain refinement of steel. Therefore, it is necessary to pay special attention to the role of carbides and to control the types, forms and distribution of carbides.

淬火回火是冷作模具零件强韧化的主要方法。零件的热处理工艺过程必须结合生产实际，模具的大小、形状、工作状态、损坏机理等不同，会导致模具零件淬火工艺参数如淬火的奥氏体化温度或淬火温度偏离常规的温度范围。

Quenching and tempering is the main method of strengthening and toughening cold working die parts. The heat treatment process of parts must be combined with the actual production. The size, shape, working state and damage mechanism of the die will lead to the deviation of quenching process parameters such as austenitizing temperature or quenching temperature from the conventional temperature range.

回火的工艺规范则取决于模具零件的热处理技术要求。通过不同的热处理方法，可使工件具备一定的强度的同时还具备足够的韧性，保证了模具的正常工作寿命。所以冷作模具钢的热处理应注意以下几点：

The process specification of tempering depends on the technical requirements of heat treatment of die parts. Through different heat treatment methods, the workpiece has certain strength and enough toughness, which ensures the normal working life of the die. Therefore, the heat treatment of cold working die steel should pay attention to the following points:

1）冷作模具钢含合金元素量多且品种多，合金化较复杂，冷作模具零件形状复杂、加工周期长，钢的导热性差，而奥氏体化温度又高，因此加热、冷却过程中要注意热应力和组织应力的产生，多采用预热或阶梯式升温及等温淬火、分级淬火、高压气淬、空冷淬火等方法。

1) The cold working die steel contains many alloying elements and varieties, and the alloying is more complex. The shape of the cold work die parts is complex, the processing cycle is long, the thermal conductivity of the steel is poor, and the austenitizing temperature is high. Therefore, attention should be paid to the generation of thermal stress and structural stress in the process of heating and cooling. Preheating or step heating, isothermal quenching, staged quenching, high pressure gas quenching and air cooling quenching are used method.

2）为保护钢的表面质量，加热介质应予重视，所以普遍采用控制气氛炉、真空炉等加热设备和方法，盐浴加热应充分脱氧、净化。

2) In order to protect the surface quality of steel, attention should be paid to the heating medium. Therefore, advanced heating equipment and methods such as controlled atmosphere furnace and vacuum furnace are widely used. Salt bath heating should be deoxidized and purified.

3）为了进一步强化，常采用冷处理、或渗氮等表面强化处理方法。

3) In order to further strengthen, surface strengthening methods such as cold treatment or nitriding are often used.