以天然气分输减压阀阀体用1.6220铸钢为研究对象, 采用低温拉伸以及低温冲击试验方法研究了其热轧态和调质态的力学性能随试验温度的变化规律, 获得了其韧脆转变温度, 观察了不同温度下冲击试样的断口形貌。结果表明: 随着试验温度的降低, 该铸钢的屈服强度和抗拉强度显著提高, 断面收缩率和伸长率逐渐下降; 调质处理明显改善了铸钢的低温力学性能, 调质态铸钢的屈服强度、抗拉强度、塑性均比热轧态的高, 韧脆转变温度由热轧态的2.76 ℃降低到-14.46 ℃; 随着温度的降低, 铸钢的断裂形式由韧性断裂向解理断裂转变。

With 1.6220 cast steel for pressure regulating valve body of natural gas transportation as the research object, the change law of mechanical properties versus temperature of the hot rolled and quenched & tempered cast steels was studied by the low temperature tensile test and impact test, and then the ductile-brittle transition temperature was calculated. The fracture morphology at different temperatures was also observed. The results show that with the decrease of the temperature, the yield strength and tensile strength of the cast steel increased and the percentage reduction of area and elongation reduced. The quenching and tempering treatment significantly improved the low temperature mechanical properties of the cast steel. The yield strength, tensile strength and plasticity of the quenched & tempered cast steel were higher than those of hot rolled one, and the ductile-brittle transition temperature of the cast steel in quenching & tempering state decreased to -14.46 ℃ from 2.76 ℃ in hot rolled state. With the temperature decrease, the fracture pattern of the cast steel changed from cleavage fracture into dimple fracture.