通过拉伸、冲击和断裂韧性等力学试验方法，光学显微镜、SEM、TEM和XRD等分析测试方法以及热力学平衡计算方法，对一种发动机壳体用低合金超高强度钢（30Cr3）的组织和性能进行了研究。结果表明：试验钢30Cr3的室温平衡转变组织为αFe和碳化物（包括MC、M23C6、M7C3）；30Cr3钢具有很好的淬透性，正火处理后，主要得到马氏体组织；在回火过程中，ε碳化物在马氏体板条内弥散析出。在试验条件下，30Cr3钢的抗拉强度和屈服强度随着回火温度的升高而逐渐提高，在250 ℃回火时，抗拉强度达到最大值1870 MPa；而随着回火温度的提高，冲击韧性和断裂韧性逐渐降低。
With ThermoCalc software the equilibrium phases of a low alloyed ultrahigh strength steel 30Cr3 for engine case were studied. By mechanical test, transmission electron microscopic(TEM), scanning electron microscopic (SEM) and XRD observation the performance of 30Cr3 steel was investigated. The results showed that at room temperature the structure components of 30Cr3 steel after equilibrium phase transformation are αFe and carbides (MC、M23C6、M7C3). 30Cr3 steel has good hardenability after normalization,of which microstructure is mainly martensite.During tempering εcarbide is precipitated in martensite laths.The tension strength and yield strength of 30Cr3 steel first rise up with a max.Tension strength of 1870 MPa at 250 ℃, then decline with tempering temperature; the impact energy and fracture toughness decline with increase of tempering temperature.
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