The working conditions of hot working die require that the hot working die not only has good process performance, but also has high strength, toughness, hardness and thermal stability at different temperatures. These properties are mainly determined by the chemical composition, smelting process and heat treatment of the steel.

热作模具钢按合金元素及热处理后性能分为低耐热高韧性热作模具钢、中耐热韧性钢、高耐热性钢以及特殊用途热作模具钢。

According to alloy elements and properties after heat treatment, hot work die steels can be divided into low heat resistance and high toughness hot work die steels, medium heat resistance and toughness hot work die steels, high heat resistance hot work die steels and special purpose hot work die steels.

1、高韧性热作模具钢的应用

1. Application of high toughness hot work die steel

此类钢中碳的含量一般在0.5﹪左右，合金元素总质量分数3﹪左右，主要用于热锻模具。传统的热锻模具钢有5CrMnMo、5CrNiMo等，这类钢有较好的淬透性、冲击性能较好、导热性能好、有较高的热疲劳抗力，在400℃左右工作条件下能承受急冷急热的状况，一般模具不超过250mm淬透，否则中心部位会出现中温转变产物。

The content of carbon in this kind of steel is about 0.5% and the total content of alloying elements is about 3%. It is mainly used for hot forging dies. The traditional hot forging die steels include 5CrMnMo, 5CrNiMo, etc. these steels have good hardenability, impact property, thermal conductivity and high thermal fatigue resistance. They can withstand the condition of rapid cooling and heating at about 400 ℃. Generally, the die is not hardened more than 250mm. Otherwise, the middle temperature transformation products will appear in the central part.

由于淬透性的限制，随着模块截面的增大，要求进一步提高模具材料的淬透性，以使模具的心部能够得到较高的均匀的性能。为此问题，国内外研发了一系列提高合金含量的高淬透性模具钢，这些新研制的高韧性热作模具钢淬火温度范围宽、淬透性好、高温强度高，并且具有良好的韧性、热稳定性、抗冷热疲劳和抗热磨损等性能，在中小热锻模上使用。

Due to the limitation of hardenability, with the increase of module cross section, it is required to further improve the hardenability of die material, so that the core of the die can get a higher uniform performance. In order to solve this problem, a series of high hardenability die steels with high alloy content have been developed at home and abroad. These newly developed high toughness hot work die steels have wide quenching temperature range, good hardenability, high temperature strength, good toughness, thermal stability, cold and hot fatigue resistance and hot wear resistance, and are used in medium and small hot forging dies.

2、中耐热韧性钢的应用

2. Application of medium heat resistant toughness steel

中耐热韧性钢的特点是碳质量分数较低（一般为0.3﹪~0.5﹪），合金元素含量中等，含有较多的Cr、W、Mo、V等碳化物形成元素，Cr含量较高一般为wcr=3﹪~5﹪。wMo=1﹪~3﹪，Cr和Mo使钢的淬透性大大提高；含有V使钢具有较好的抗过热敏感性，对提高模具的热硬性和热强性非常有效，在500~600℃具有较高的硬度热强性和耐磨性，可达650℃。该类钢淬透性很好，对100mm厚工件空冷即能淬透，其综合性能好。

The characteristics of medium heat resistant toughness steel are low carbon content (generally 0.3 ‰ ~ 0.5 ‰), medium alloy element content, more carbide forming elements such as Cr, W, Mo and V, and high Cr content (generally WCR = 3 ‰ ~ 5 ‰). WMO = 1 ‰ ~ 3 ‰, Cr and Mo greatly improve the hardenability of the steel; V makes the steel have better resistance to overheating, which is very effective to improve the thermal hardness and strength of the die, and has higher hardness, thermal strength and wear resistance at 500 ~ 600 ℃, up to 650 ℃. This kind of steel has good hardenability. It can harden 100 mm thick workpiece by air cooling, and its comprehensive properties are good.