M2 high speed steel
M2 high speed tool steel was born in 1937. Due to its excellent performance and suitable price, it is still the most widely used high speed steel. It is often used in the processing of aerospace superalloy, ultra-high strength steel and stainless steel and other difficult to work materials.
A large number of scientific research and production workers to optimize the production process and improve the quality of performance is still in progress.
The high temperature mechanical properties of M2 high speed steel were studied by thermal simulation method in this work, which provided a meaningful reference for the production of related M2 steel.
Raw materials used in the test are taken from industrial M2 steel round bars (diameter: Φ12mm). The chemical composition of the test steel is shown in Table 1 (mass fraction).The raw materials were processed into Φ10mm×120mm high-temperature tensile samples. The Gleeble-3800 testing machine was used to heat the samples to the test temperature, and then the high-temperature tensile and mechanical properties were tested.The test temperature was 1000 ~ 1250℃ and the strain rate was 5×10-3/s.
- Tensile specimens were observed with German LEICAMEF4M optical microscope.
- Hitachis -4300 was used for SEM observation and EDS analysis of carbides.
The test results show that:
(1) The zero plasticity temperature of M2 high speed steel is 1220℃, and the zero strength temperature is 1250℃.
(2) The good plastic zone of M2 high speed steel is in the temperature range of 1150 ~ 950℃. In this range, it enters into the high temperature zone where the matrix structure is austenite single phase, and dynamic recrystallization provides good plastic properties.
(3) The brittle zone of M2 high speed steel ranges from 1175℃ to melting point TS temperature, and the melting of low melting point eutectic carbides occurs within this temperature range, which significantly reduces the ductility and strength of the steel.
(4) There exists a low temperature superplasticity zone near 800℃, which is the coexistence zone of α+γ two phases of M2 steel. The improvement of carbide breakage and homogeneity by hot working in this zone is worthy of further attention.
