X70高钢级大壁厚管线钢管落锤撕裂试验的影响因素

Influence Factors of DWTT for High Grade and Thick Wall X70 Linepipe

落锤撕裂试验(DWTT)是评定管线钢管延性断裂和脆性断裂的重要方法。针对某规格为φ765.2 mm×31.8 mm的X70高钢级大壁厚管线钢管全壁厚和单面减薄(19 mm)试样DWTT结果存在较大差异的问题,从材料的不均匀性、韧脆转变温度、断口剪切面积评定方法、减薄试样加工方法和试验设备等方面分析了影响X70管线钢管DWTT结果的因素。通过分析得出对于高钢级大壁厚管线钢管,尽量采用大能量落锤撕裂试验机和全壁厚人字型缺口试样进行DWTT,同时建议开展落锤撕裂试验机支座圆弧半径的研究,将现落锤撕裂试验标准中的支座圆弧半径由(14.3±1.59)mm改为(20±5.0)mm。

Drop-weight tear test（DWTT） is an important way to predict the pipeline will crack in brittle fracture way or in ductile fracture way. For the matter of great difference of DWTT results between the specimen with thickness reduced to 19 mm by machining from one surface and the specimen with full wall thickness of 4765.2 min× 31.8 mm high grade and large thick wall X70 pipeline, the influence factors of DWTT results for thick wall X70 pipeline were analyzed from inhomogeneity of materials, ductile-brittle transition temperature, evaluation method for shear area rating of the fracture surface, machining method of the specimen with reduced thickness and the test equipments. Some solutions just as carrying the test on equipments with larger energy and using the full wall thickness specimens with Chevron notch were put forwards to avoid the test errors. The research for effects of rods size which supporting the specimens on DWTT results was proposed to carry out, and the rods size of the current criterion was recommended to change from （14.3±1.59） mm to （20±5.0） mm.