锻制B3钢大直径磨球性能控制试验研究

Study on Performance Control of Large-diameter Forged Grinding Ball for B3 Steel

锻制B3钢大直径磨球经余热淬火热处理常出现裂纹和硬度梯度过大两类缺陷。通过试验分析,确定了淬火温度、冷却介质（PAG淬火剂）流速以及冷却介质浓度为影响磨球性能的主要因素;设计了L_9（3～4）正交试验,获得了优化试验参数。试验结果表明：冷却介质流速和淬火温度是造成裂纹、硬度梯度过大的主要参数。淬火温度高、冷却介质流速快,裂纹废品率较低,但硬度分布不均匀;反之,裂纹废品率高,但硬度分布较均匀。优化淬火工艺参数为：淬火温度780℃、冷却介质流速为快速、冷却介质浓度为0配比。经过小批量实际生产验证,获得了表面硬度≥58 HRC、心部硬度≥54 HRC的磨球,且裂纹率低于5%。

Aiming at the two defects of cracks and uneven hardness of B3 forging steel balls with large diameters after heat treatment with residual heat, it was found that the quenching temperature, the cooling medium velocity and the cooling medium concentration were the main factors influencing the performance of the steel balls through research in workshops, and an orthogonal test of L9 ＂four factors of three levels＂ was designed to optimize the procedure parameters. The results show that cooling medium velocity and quenching temperature are the main reasons for cracks and uneven hardness. The crack defect ratio is low with uneven hardness when the quenching temperature is high and cooling medium velocity is fast. On the contrary, the crack defect ratio is high, but hardness is evenly. The optimized procedure parameters are quenching temperature of 780 ℃, faster quenching media flowing speed, PGA concentration of zero through four times of orthogonal optimization experiments. In operation according to the group of parameters, a better result is achieved which is that milling balls surface hardness ≥58 HRC, core hardness ≥54 HRC, and that the crack defect ratio is less than 5%.