According to the microstructure, heat-resistant steel in die steel can be roughly divided into the following four categories:

1)珠光体或铁素体一珠光体耐热钢。这类钢一般在正火高温回火后使用，其组织属于铁素体l碳化物的亚共析钢，其合金元素总含量一般不超过5％。由于这类钢的抗氧化合金元素含量不高，故工作温度范围为350—620℃，常用作锅炉、气轮机中工作的耐热零件。

1) Pearlite or ferrite - pearlite heat resistant steel. This kind of steel is generally used after normalizing and high temperature tempering. Its structure belongs to hypoeutectoid steel with ferrite l carbide, and the total content of alloying elements is generally no more than 5%. Due to the low content of antioxidant alloy elements in this kind of steel, the working temperature range is 350-620 ℃, which is often used as heat-resistant parts in boilers and gas turbines.

2)马氏体耐热钢。这类钢一般经过淬火一高温回火后使用，这类钢中一部分是在lcr13马氏体不锈钢基础上发展起来的，使用状态是回火马氏体，主要用作气轮机叶片；另一部分以马氏体耐热钢为阀门钢，使用状态是回火索氏体o

2) Martensitic heat resistant steel. This kind of steel is generally used after quenching and high temperature tempering. Part of this kind of steel is developed on the basis of lcr13 martensitic stainless steel. The service state is tempered martensite, which is mainly used as gas turbine blades; The other part takes martensitic heat-resistant steel as valve steel, and the service state is tempered sorbite o

3)铁素体耐热钢。属于抗氧化钢，系高铬钢加入硅、铝等元素形成的钢。

3) Ferritic heat resistant steel. It belongs to oxidation resistant steel, which is a high chromium steel formed by adding silicon, aluminum and other elements.

4)奥氏体耐热钢。它是在奥氏体不锈钢的基础上发展起来的，可以在600~810℃范围使用，作为抗氧化用钢可工作到1200℃左右。根据其强化方法的不同又分成固溶强化的简单奥氏体耐热钢、用碳化物沉淀硬化的奥氏体钢、用金属问化合物沉淀硬化的奥氏体钢等。奥氏体耐热钢可用作燃气涡轮、发动机、工业炉耐热构件等高温材料。

4) Austenitic heat resistant steel. It is developed on the basis of austenitic stainless steel and can be used in the range of 600 ~ 810 ℃. As an anti-oxidation steel, it can work to about 1200 ℃. According to different strengthening methods, it can be divided into simple austenitic heat-resistant steel strengthened by solid solution, austenitic steel hardened by carbide precipitation, austenitic steel hardened by metal compound precipitation, etc. Austenitic heat-resistant steel can be used as heat-resistant components of gas turbine, engine and industrial furnace.

按性能和用途，模具钢中耐热钢可分成三大类：

According to performance and application, heat-resistant steel in die steel can be divided into three categories:

1)抗氧化钢。应具有高温抗气体腐蚀(主要是抗氧化)能力。

1) Oxidation resistant steel. It shall have high temperature gas corrosion resistance (mainly oxidation resistance).

2)热强钢。应具有良好的热稳定性和一定的高温强度。

2) Hot strength steel. It shall have good thermal stability and certain high temperature strength.

3)气阀钢。是动力设备大量使用的钢，它应具有上述西方面的高温性能。

3) Air valve steel. It is a steel widely used in power equipment. It should have the high temperature performance of the above western surface.

耐热合金按基体元素，一般分为铁基、镍基、销基等耐热合金；按生产工艺，可分为变形耐热合金和铸造耐热合金两大类。变形耐热合金按其高温性能、成型特点，又可分为热稳定变形耐热合金和热强变形耐热合金两种类型。

According to the matrix elements, heat-resistant alloys are generally divided into iron-based, nickel based, pin based and other heat-resistant alloys; According to the production process, it can be divided into deformation heat-resistant alloy and casting heat-resistant alloy. According to its high-temperature properties and forming characteristics, wrought heat-resistant alloys can be divided into two types: thermally stable wrought heat-resistant alloys and thermally strong wrought heat-resistant alloys.