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本文采用了含碳偏上限(0.18％C)及偏下限(0.15％C)的四种15MnVN钢板的轧向及横向试件,经热模拟后测定并对比了粗晶区组织在室渴及-40℃下的冲击及断裂韧性;并辅以弯曲载荷下对启裂部位的动态观察及断口腐蚀对照等方法研究了不同t8/5下粗晶区组织参量的变化与韧性变化的关系,以及脆化的机理.结果表明:(1)15MnVN钢中含碳量对熔合线韧性有很大影响,含碳量从下限增至上限,韧性显著恶化.(2)含碳偏高时,熔合线韧性恶化的原因:一是上贝氏体中富碳的M-A相引发解理的脆化作用;二是伴随网状先共析铁素体的析出,晶界上析出富碳的M-A相所造成的晶界脆化.(3)含较低磷(0.15％C)时,粗晶区韧性有显著改善,因而适当降碳是改善15MnVN钢熔合线韧性的有效措施之一.(4)在含碳较高的15MnVN钢粗晶区中,由于碳所引起的脆化是主要矛盾方面,硫的有害作用相对居次要地位,因而仅降硫对改善韧性的作用不太显著,只有降碳的同时降硫才能有效地改善熔合线韧性。
In this paper, rolling and transverse specimens of four 15MnVN steel plates with the upper limit of carbon (0.18% C) and the lower limit of 0.15% (C) were used. After thermal simulation, 40 ℃ under the impact and fracture toughness; supplemented by the bending load of the crack site dynamic observation and fracture corrosion control methods such as t8 / 5 under the coarse grain region changes in the relationship between the organizational parameters and toughness, as well as crisp (1) The carbon content in 15MnVN steel has a great influence on the toughness of the fusion line, the carbon content increases from the lower limit to the upper limit, and the toughness deteriorates significantly. (2) When the carbon content is high, the toughness Causes of deterioration: First, the carbon phase of the bainite MA induced cleavage brittle effect; the second is accompanied by reticular proeutectoid ferrite precipitation, grain boundary precipitation of carbon-rich MA phase of the crystal (3) With the lower phosphorus (0.15% C), the toughness of the coarse-grained zone is significantly improved, so proper carbon reduction is one of the effective measures to improve the toughness of the fusion line of 15MnVN steel. (4) High 15MnVN steel coarse grain area, due to the embrittlement caused by carbon is the main contradiction, the relative adverse role of sulfur in secondary status, so only Effect of improving the toughness of the less significant, while only reducing the sulfur reduction of carbon in order to effectively improve the toughness of the weld line.