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  当前位置 -> 行业资讯- 分析冷拔钢管的冷处理裂纹与预防措施 发布时间:(2018/12/28)

分析冷拔钢管的冷处理裂纹与预防措施


冷拔钢管多为中,高碳合金钢,淬火后还有部分过冷奥氏体未转变成马氏体,保留在使用状态中成为残余奥氏体,影响使用性能。预防措施:(1)冷拔钢管淬火后冷处理之前将冷拔钢管置于沸水中煮30—60min,可消除15%-25%淬火内应力并使残余奥氏体稳定化,再进行-60摄氏度常规冷处理,或进行-120摄氏度深冷处理,温度愈低,残余奥氏体转变成马氏体愈多,但不可能全部转变完,实验表明,约有2%-5%残余奥氏体保留下来,按需要保留少量残余奥体可松弛应力,其缓冲作用,因残余奥氏体又软又韧,能部分吸收马氏体化急剧膨胀能量,缓和相变应力;若置于零度以下继续冷却,能促使残余奥氏体发生马氏体转变,因此,冷处理的实质是淬火继续。室温下淬火应力和零度下淬火应力叠加,当叠回应力超过该材料强度极限时便形成冷处理裂纹。

Cold-drawn steel pipes are mostly medium and high carbon alloy steels. After quenching, some undercooled austenite does not transform into martensite, and retains as retained austenite in service state, which affects service performance. Preventive measures: (1) Boiling cold-drawn steel tube in boiling water for 30-60 minutes before quenching can eliminate 15%-25% internal stress and stabilize retained austenite, then conventional cooling treatment at - 60 degrees Celsius or deep cooling treatment at - 120 degrees Celsius. The lower the temperature, the more retained austenite transforms into martensite, but it is impossible to complete the transion. The experiment shows that about 2% retained austenite transforms into martensite. The retained austenite retains between%-5% and retains a small amount of residual austenite to relax stress as needed. Its cushioning effect is that retained austenite is soft and tough, which can partly absorb the rapidly expanding energy of martensitization and alleviate the phase transion stress. If the retained austenite is cooled below zero, the martensitic transion of retained austenite can occur. Therefore, the essence of cooling treatment is to continue quenching. The superposition of quenching stress at room temperature and quenching stress at zero degree results in the ion of cold treatment cracks when the superposition response exceeds the strength limit of the material. 

(2)冷处理完毕后取出冷拔钢管投入热水中升温,可消除40%-60%冷处理应力,升温至室温后应及时回火,冷处理应力进一步消除,避免冷处理裂纹形成,获得稳定组织性能,确保冷拔钢管产品存放和使用中不发生畸变。

(2) After the cold treatment, the cold-drawn steel pipe is taken out and heated in hot water, which can eliminate 40%-60% of the cold treatment stress. When the temperature rises to room temperature, it should be tempered in time. The cold treatment stress should be further eliminated to avoid the ion of cold treatment cracks, obtain stable structure and properties, and ensure that no distortion occurs in the storage and use of cold-drawn steel pipe products.

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