灰铸铁同质焊缝电弧冷焊接头冷裂纹研究进展

Advance of Researches on the Cold Cracking of the Gray Cast Iron Cold-welding with Homogenous Welding Consumables

关键词:  灰铸铁  冷裂纹  同质焊缝  电弧冷焊  研究进展

Key words:  gray cast iron  cold crack  homogenous weld  arc cold-welding  research and development

摘要:

从焊缝石墨形态及焊缝组织对冷裂纹的影响、铸铁型焊缝冷裂纹产生机理及裂纹萌生与扩展的微观过程、热影响区冷裂纹研究、铸铁焊接接头冷裂纹试验方法等四个方面综述了国内外灰铸铁同质焊缝电弧冷焊焊接接头冷裂纹的研究进展。研究发现,石墨呈球状时可以大为改善焊缝的抗裂性;利用贝氏体马氏体二次相变应力松弛效应可以降低灰铸铁焊缝裂纹敏感性;裂纹容易在相邻石墨间的窄铁素体基体桥处萌生与扩展;扩散氢对灰铸铁接头热影响区冷裂纹影响小而马氏体相变影响大。在灰铸铁焊接冷裂纹试验方法方面,重点讨论了能定量评定焊缝抗裂性的铸铁焊缝拘束裂纹试验及平板刚性拘束裂纹(PRRC)试验。

Abstract:

In this paper, the advance of researches on the cold cracking of the gray cast iron cold-welding with homgenous consumables both at home and abroad is summarized in four aspects including:(1) the effect of the graphite morphology and microsturcture of the weld on the cold cracking; (2) the mechanism of the cold cracking, and its initiation and propagation in the cast iron welds; (3)the research on the HAZ cold crack; (4)the development of the cold crack testing methods for the cast iron welded joints. These researches revealed: the crack resistance is much improved when the graphite is turned spheroidal from flake in the weld; the crack suscept ibility of the gray cast iron weld can also be de-creased by the twice stress-relaxation effecl of both bainitic and martensitic transformations; the crack is easily initiating and propagating at the narrow ferrite matrix bridge between neighbouring graphites; the effect of the diffusive hydrogen on the HAZ cold crack is less strong than that of the martensite transformation. The cold crack testing methods both the re-straint cracking test and the plate rigid restraint cracking (PRRC) test for cast iron welds are emphasized because they can quantitatively evaluate the cracking resistance of the cast iron welds.