锻造工艺对外头盖侧法兰开裂的影响

Effect of forging process on crack of shell flange-rear head end

对换热器在较低压力的试压中外头盖侧法兰开裂的原因进行了分析。通过对外观、表面硬度、化学成分、力学性能、材料金相、应力水平及锻造工艺的全面检测,发现法兰颈大端的转角处的材料硬度明显偏高,晶粒较粗且欠均匀,不似正火组织的正常形态。确定终锻温度偏低及正火工艺不规范是法兰开裂的主要原因,同时提出了确保换热器产品质量的措施。

The reasons why the shell flange-rear head end cracked during hydraulic test for a heat exchanger on a lower pressure were analyzed. After full checks and tests for the appearance of flange, surface hardness, chemical composition of material, mechanical properties, metallurgical phase, stress level and forging process, it was found that the hardness of turn angle on large end of flange neck was super high. And the metallurgical phase was not normalized structure because the crystal grains were coarse and asymmetricaly. So, incorrect fabricating process, such as the lower final forging temperature and normalized tempering temperature is the main cause. Measures were put forward to assure the heat exchanger quality.