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齿轮传动轴用钢ML45Mn2在冷镦成形过程中出现冷镦开裂问题,对开裂样品宏观形貌、化学成分、气体含量及显微组织进行了分析。结果表明,原工艺(670℃×2 h→730℃×6 h→680℃×7 h→缓冷到500℃出炉)退火后,截面上碳化物分布很不均匀,表层呈现沿晶分布的网状碳化物;碳化物的形状也不规则,是引起开裂的主要原因。改进球化退火工艺(670℃×2 h→740℃×6 h→(13℃/h)670℃×7 h缓冷→500℃出炉)后,碳化物的形态和分布得到明显改善,满足冷镦成形要求。其冷镦开裂率由100%下降到2%以内。
The cold heading and cracking of ML45Mn2 steel during gear upsetting were analyzed. The macroscopic morphology, chemical composition, gas content and microstructure of cracked samples were analyzed. The results show that the carbide distribution in the cross section is very uneven after annealing in the former process (670 ℃ × 2 h → 730 ℃ × 6 h → 680 ℃ × 7 h → slow cooling to 500 ℃) Carbides; Carbides also have irregular shapes and are the main cause of cracking. After the ball annealing (670 ℃ × 2 h → 740 ℃ × 6 h → (13 ℃ / h) 670 ℃ × 7 h slow cooling → 500 ℃ baked), the morphology and distribution of carbides are obviously improved, Upset forming requirements. Its cold heading cracking rate dropped from 100% to less than 2%.