The carbon content of hot working die steel with high heat resistance is not high, but the content of alloying elements is high. The mass fraction of alloying elements in most die steels is 8 ‰ ~ 10 ‰, and some are as high as 11%. This kind of steel has high heat resistance, that is, high high high temperature strength and high temperature hardness. It can work at 600 ~ 700 ℃, and has high heat resistance, good hardenability and strong secondary hardening effect, Good tempering resistance, high fatigue resistance and fracture toughness. The high heat resistance steel is suitable for the mould which requires high heat resistance, wear resistance, low toughness and less complicated shape.

主要用于制造压力机镦锻模，挤压机上加工高强钢、不锈钢、钛合金、耐热合金等尺寸小于150mm的模具、压铸模以及较高工作温度（600~690℃）、高磨损条件下工作的热作模具。

It is mainly used for manufacturing upsetting die of press, processing high strength steel, stainless steel, titanium alloy, heat-resistant alloy, die-casting die with size less than 150 mm and hot working die under high working temperature (600 ~ 690 ℃) and high wear condition.

传统的热作模具钢3Cr2W8V钢具有以上特性，能在600~650℃条件下长期服役，因此广泛应用于高耐热热作模具。但是该钢如果冶炼不当、铸锭较大、铸模温度过高及钢液过热时，3Cr2W8V钢锭中的元素偏析特别严重，共晶碳化物的数量会增多，因此造成模具脆裂报废的事故时有发生。而且高钨钢有脱碳倾向，这是模具磨损快、粘模严重、表面早期出现热疲劳裂纹的原因之一。

The traditional hot work die steel 3Cr2W8V has the above characteristics and can be used in 600 ~ 650 ℃ for a long time, so it is widely used in high heat resistance hot work die. However, if the steel is not properly smelted, the ingot is large, the mold temperature is too high and the liquid steel is overheated, the element segregation in 3Cr2W8V ingot is particularly serious, and the amount of eutectic carbide will increase, so the accidents of die brittle cracking and scrapping occur from time to time. The decarburization tendency of high tungsten steel is one of the reasons for the rapid wear of die, serious die sticking and early thermal fatigue cracks on the surface.

为此类问题，国内研发了一些新的钢种：如HD钢和Y系列钢。

In order to solve these problems, some new steel grades have been developed in China, such as HD steel and Y Series Steel.

HD(4Cr3Mo2NiVNb)钢是为了适应700℃左右工作温度而研制的新型高耐热性钢。HD钢是在4Cr3Mo3V钢的基础上，适当降低Mo、V的含量，加入质量分数为wNi=1﹪、wNb=0.15﹪，提高了钢的高温韧性及热稳定性，在700℃仍可以保持40HRC的硬度。在硬度相同的情况下，HD钢比3Cr2W8V钢的断裂韧度高50﹪，700℃高温时抗拉强度高70﹪，冷热疲劳抗力和热磨损性能分别高出1倍和5﹪，用其制作的热挤压模具使用寿命也高于3Cr2W8V钢。

Hd (4Cr3Mo2NiVNb) steel is a new type of high heat resistance steel developed to adapt to the working temperature of about 700 ℃. HD steel is based on 4cr3mo3v steel, the content of Mo and V is reduced appropriately, the content of WNI is 1% and wNb is 0.15%. The high temperature toughness and thermal stability of the steel are improved, and the hardness of 40HRC can be maintained at 700 ℃. Under the same hardness, the fracture toughness of HD steel is 50% higher than that of 3Cr2W8V steel, and the tensile strength at 700 ℃ is 70% higher than that of 3Cr2W8V steel. The cold and hot fatigue resistance and hot wear resistance of HD steel are 1 times and 5% higher than that of 3Cr2W8V steel, respectively. The service life of hot extrusion die made of HD steel is also higher than that of 3Cr2W8V steel.

Y系列模具钢是针对压铸模特点结合我国矿产资源而研制的新钢种。Y10（4Cr5Mo2MnVSi）钢淬透性好，主要用于铝合金压铸模。与Y10钢相比，Y4（4Cr3Mo2MnVNbB）钢中的Cr、Si含量下降了，碳化物不均匀性下降，同时以硼来提高淬透性和热强性，加入微量铌可提高M6C和MC型碳化物的稳定性，因此能细化晶粒，降低过热敏感性，提高热强性和热稳定性，可用于熔液温度为880~960℃的铜合金热压铸模。Y系列钢用于压铸模上，其使用寿命较3Cr2W8V钢有很大提高。

Y Series die steel is a new kind of steel developed for die casting point combined with China's mineral resources. Y10 (4cr5mo2mnvsi) steel has good hardenability and is mainly used in aluminum alloy die casting die. Compared with Y10 steel, the content of Cr and Si in Y4 (4cr3mo2mnvnbb) steel decreases, and the inhomogeneity of carbides decreases. At the same time, boron is used to improve the hardenability and thermal strength. The addition of Trace Niobium can improve the stability of M6C and MC carbides, so it can refine the grain, reduce the overheating sensitivity, and improve the thermal strength and thermal stability. It can be used for hot die casting of copper alloy with melt temperature of 880 ~ 960 ℃. The service life of Y Series steel used in die casting die is much longer than that of 3Cr2W8V steel.