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《理化检验》物理编辑部: 编辑同志,你们好!今年贵刊第一期的“咨询与服务”专栏刊登的关于锻造与热处理加热过程中出现的裂纹如何鉴别的问题解答,我们阅读后很受启发。贵刊能否给我们就工件在锻造与热处理冷却过程中所形成的裂纹对其形貌特征、鉴别方法再作些介绍,谢谢。 宋彤彤 河南黄河水泵厂理化室 宋彤彤同志: 您好,编辑部请我就您提出的问题作些解答,现简复如下,供参考。锻件在高温热锻变形过程中,因操作不当,特别是在临界(即相变)温度以下继续施加锻锤使其强烈变形,此时将导致锻件表面产生裂纹,这种裂纹不是沿晶分布,而是穿晶形的,开口处夹有氧化皮,其尾部有尖端、无氧化皮。产生开裂之原因是,因低于临界温度,锻造已不在奥氏体单相区内进行,塑性已明显降低;如在更低的温度下锻造,则等于在冷态下对其施加不适当的应力则产生裂纹的可能性就更大。还有些裂纹是由于终锻温度过高,锻件又作不适当的冷却,如放入水中快冷或快速喷水冷却,导致局部相变、体积膨胀,在热应力和组织应力的双重作用下致使锻件表面开裂。这种裂纹亦是穿晶型的,比较细直,尾部尖端无明显的氧化皮。
Physical Editing: Editorial Comrades, Hello! This year’s issue of the first issue of the “Advisory Services” column published on the forging and heat treatment in the process of how to identify the problem of cracks in the answer, we read very much Inspired. Can you give us the workpieces in the forging and heat treatment of the formation of cracks in the process of its morphological characteristics of the identification method to make some introduction, thank you. Song Tong Tong Henan Yellow River Pump Plant Physics and Chemistry Room Song Tong Tong Comrades: Hello, the editorial department asked me to make some answers to your questions, are summarized below, for reference. Forging in the hot forging deformation process, due to improper operation, especially in the critical (ie, phase change) below the temperature to continue to apply forging deformation of the strong, this will lead to cracks on the surface of forgings, the crack is not distributed along the crystal, Instead, we wear a crystalline form with oxide scale on the opening, a sharp tip at the tail, and no scale. The reason for cracking is that the forging is out of the austenite single phase zone below the critical temperature and the ductility has been significantly reduced; forging at a lower temperature is equivalent to applying an improper Stress is more likely to crack. Some cracks are due to the final forging temperature is too high, forgings and improper cooling, such as into the water fast cooling or rapid water cooling, resulting in local phase change, volume expansion, thermal stress and stress caused by the dual role Forging surface cracking. This crack is also through-crystal type, relatively straight, tail tip no obvious oxide skin.