1. Carbon content of steel

含碳量是影响冷作模具钢性能的决定性因素。一般，随着含碳量的增加，钢的硬度、强度和耐磨性提高，塑性、韧性变差。对于高耐磨的冷作模具钢，碳的质量分数一般控制在0.7%~2.3%，以获得高碳马氏体，并形成一定量的碳化物；对于需要抗冲击的高强韧性冷作模具，其钢材的碳的质量分数一般控制在0.5%~0.7%，以保证模具获得足够的韧性。

Carbon content is the decisive factor affecting the properties of cold working die steel. Generally, with the increase of carbon content, the hardness, strength and wear resistance of the steel are improved, and the plasticity and toughness become worse. For the high wear-resistant cold work die steel, the carbon content is generally controlled at 0.7% ~ 2.3% to obtain high-carbon martensite and form a certain amount of carbide; for the high-strength and toughness cold work die which needs impact resistance, the carbon content of the steel is generally controlled at 0.5% ~ 0.7%, so as to ensure that the die can obtain sufficient toughness.

2.合金化特点

2. Alloying characteristics

冷作模具钢的合金化主要特点是：加入强碳化物形成元素，获得足够数量的合金碳化物，并增加钢的淬透性和回火稳定性，以达到耐磨性和强韧性的要求。所加入的主要元素及其作用简述如下：

The main characteristics of alloying of cold working die steel are as follows: adding strong carbide forming elements to obtain enough alloy carbides, increasing hardenability and tempering stability of steel, so as to meet the requirements of wear resistance and strength and toughness. The main elements and their functions are described as follows:

（1）锰锰会强烈地增加钢的淬透性，大幅度降低钢的Ms点，增加淬火后残留奥氏体量，这对防止工件变形、淬裂，稳定外形尺寸是有利的。但降低钢的导热性，有较大的过热敏感性，并加剧第二类回火脆性。所以，锰宜与钼、钒、铬、钨复合添加。在抗冲击及高强韧性冷作模具钢中的用量受到限制。

(1) Manganese and manganese can strongly increase the hardenability of the steel, greatly reduce the MS point of the steel and increase the retained austenite volume after quenching, which is beneficial to prevent the deformation and crack of the workpiece and stabilize the overall dimension. However, reducing the thermal conductivity of the steel has a greater overheat sensitivity and aggravates the second temper brittleness. Therefore, manganese should be combined with molybdenum, vanadium, chromium and tungsten. The amount of cold working die steel with impact resistance, high strength and toughness is limited.

（2）硅硅会增加钢的淬透性和回火稳定性，显著提高变形抗力及冲击疲劳抗力；也可提高抗氧化性和耐蚀性。但硅促使钢中的碳以石墨形式析出，造成脱碳倾向比较严重，并增加钢的过热敏感性和第二类回火脆性。

(2) Silicon silicon can increase the hardenability and tempering stability of steel, significantly improve the deformation resistance and impact fatigue resistance, and also improve the oxidation resistance and corrosion resistance. However, silicon promotes the precipitation of carbon in the form of graphite, which results in serious decarburization tendency and increases the superheat sensitivity and the second temper brittleness of steel.

（3）铬铬会显著地增加钢的淬透性，有效提高钢的回火稳定性。钢中随着含铬量的增加，依次生成（Fe·Cr），C、（Fe·Cr），C、（Fe·Cr）aC等碳化物，这些碳化物稳定性较好，从而减小钢的过热敏感性，提高钢的耐磨性。铬对钢表面具有钝化作用，使钢具有抗氧化能力。但铬含量较高会增加碳化物不均匀性和残留奥氏体量。一般在低合金冷作模具钢中铬的质量分数为0.5%~1.5%；在高强韧性冷作模具钢中，铬的质量分数为4%~5%；在高耐磨微变形模具钢中，铬的质量分数为6%~12%。

(3) Chromium and chromium can significantly increase the hardenability of steel and effectively improve the tempering stability of steel. With the increase of chromium content in steel, carbides such as (Fe · CR), C, (Fe · CR), C, (Fe · CR) AC are formed in turn. These carbides have good stability, which can reduce the overheat sensitivity of steel and improve the wear resistance of steel. Chromium has passivation effect on the surface of steel, which makes the steel have oxidation resistance. However, the higher chromium content will increase the carbide inhomogeneity and retained austenite content. Generally, the mass fraction of chromium is 0.5% ~ 1.5% in low alloy cold working die steel, 4% ~ 5% in high strength and Toughness Cold Work Die steel, and 6% ~ 12% in high wear resistance and micro deformation die steel.

（4）铝钼可提高淬透性和高温蠕变强度；回火稳定性和二次硬化效果也强于铬；并能抑制铬、锰、硅引起的第二类回火脆性，但钼会增加脱碳倾向。常用冷作模具钢中的钼质量分数一般为0.5%~5%。

(4) The results show that Al Mo can improve hardenability and creep strength at high temperature, temper stability and secondary hardening effect are better than Cr, and can inhibit the second temper brittleness caused by Cr, Mn and Si, but Mo can increase decarburization tendency. The mass fraction of molybdenum in common cold working die steel is generally 0.5% ~ 5%.

（5）钨钨的一大优点是会造成二次硬化，显著提高钢的热硬性；其提高耐磨性和降低钢的过热敏感性的作用优于钼。但钨会强烈地降低钢的导热性，过量的钨还会使得钨的碳化物不均，钢的强度和韧性降低。在高承载能力冷作模具钢中，钨的质量分数小于18%，并且有以钼或钒代替钨以减少钨含量的趋势。

(5) One of the advantages of W-W is that it can cause secondary hardening and significantly improve the thermal hardness of steel, and its effect on improving wear resistance and reducing overheat sensitivity of steel is better than that of molybdenum. But tungsten will strongly reduce the thermal conductivity of steel, excessive tungsten will also make tungsten carbide uneven, the strength and toughness of steel will be reduced. In the cold working die steel with high bearing capacity, the mass fraction of tungsten is less than 18%, and there is a tendency to replace tungsten with molybdenum or vanadium to reduce the content of tungsten.

（6）钒钒主要以V.C，形式存在于钢中。由于V.C，稳定难溶，硬度极高，所以钒能显著提高钢的耐磨性和热硬性；同时钒还可细化晶粒，降低钢的过热敏感性。但祝含量过高，会降低钢的可锻性和磨削性。故钒的质量分数一般控制在0.2%~1.5%。

(6) Vanadium and vanadium mainly exist in steel in the form of V.C. Because V.C is stable, insoluble and has high hardness, vanadium can significantly improve the wear resistance and thermal hardness of steel; at the same time, vanadium can refine the grain size and reduce the overheat sensitivity of steel. However, if the content is too high, the malleability and grindability of the steel will be reduced. Therefore, the mass fraction of vanadium is generally controlled at 0.2% ~ 1.5%.

（7）钻、镍钻的主要作用是提高高速钢冷作模具的热硬性，增强二次硬化效果。在硬质合金冷作模具材料中，钻是重要的粘结剂。

(7) The main function of drill and nickel drill is to improve the thermal hardness of high speed steel cold working die and enhance the secondary hardening effect. Drill is an important binder in cemented carbide cold working die materials.

镍既能提高钢的强度又能提高钢的韧性，同时还可提高钢的淬透性；含量较高时，可显著提高钢的耐蚀性。但镍有增加第二类回火脆性的倾向。

Nickel can not only improve the strength and toughness of steel, but also improve the hardenability of steel; when the content of nickel is higher, the corrosion resistance of steel can be significantly improved. However, nickel tends to increase the second temper embrittlement.