国内外不同厂家制造的蒸汽发生器换热管在进行350 ℃高温拉伸试验时,试样断裂后均呈双螺旋断口。采用宏观观察、力学性能测试、金相检验及扫描电镜分析等方法,对双螺旋断口的形成原因进行了分析。结果表明:高温拉伸过程中温度的升高和扭矩所引起的层状撕裂行为是双螺旋断口形成的主要原因。

When the heat exchange tubes of steam generators manufactured by different manufacturers at home and abroad were subjected to 350 ℃ hot tensile test, the double helix fracture appeared after the sample was broken. The formation reason of double helix fracture was analyzed by macro observation, mechanical property test, metallographic examination and scanning electron microscope analysis. The results show that the lamellar tearing behavior caused by temperature rise and torque during hot tensile test process were the main reason for the formation of double helix fracture.