热浸镀铝钢的扩散工艺研究

Effects of Processing Parameters of Diffusion on Microstructure and Properties of Hot Dip Aluminizing Steel

通过对热浸镀铝的20号碳钢进行不同扩散工艺试验，研究了渗铝层在800℃氧化过程中的组织形貌变化和抗氧化性能。结果表明，当扩散温度为750℃时，在2～6h扩散时间内，随时间延长，氧化速率增加；当扩散温度为850。C时，在2～4h扩散时间内，随时间延长，氧化速度减慢，4h时达到极小值，而后随时间延长，氧化速度又逐渐增大；当扩散工艺为900℃×2h时，抗氧化性能最好。研究表明，在高温氧化期间，经扩散处理后渗铝层／基体界面空洞逐步连接成平行于表面的线状裂纹，其内产生了内氧化，对扩散型热浸镀铝钢的抗氧化性能有直接影响。

Microstructural evolution and oxidation resistance of hot dip aluminized layer on 20 steel were investigated during oxidization at 800 ℃ with different diffusion treatment. The results indicate that the oxidized rate at 800 ℃ is increased with extending time in the range of 2 to 6 hours when diffusion temperature is 750 ℃, while the oxidized rate is decreased with extending diffusion time in the range of 2 to 4 hours, and the minimum oxidized rate can be observed at 4 hours, then it is gradually increased with the diffusion time more than 4 hours when the diffusion temperature is 850 ℃. The desirable oxidation resistance of the hot dip aluminized layer can be obtained with the diffusion temperature of 900 ℃ for two hours. In addition, SEM observation reveals that the void in diffusion treated aluminized layer/substrate aggregates gradually into the linear crack parallel to surface, in which the internal oxidation occurs, during high temperature oxidation, which will evidently affects the oxidation resistance of hot dip aluminizing steel.