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Establishment of Grain Refining Technique of Magnesium Alloy Castings

镁合金铸件晶粒细化技术的建立

基本信息

批准号：
11225211
负责人：
MOTEGI Tetsuich
金额：
$ 17.66万
依托单位：
Chiba Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2002
项目状态：
已结题

项目摘要

Grain refining of magnesium alloy AZ91 by semi-solid casting was investigated, and semi-solid continuous casting to produce fine-and globular-grained billet was performed. In addition, iron removal by applying of magnetic field was also examined because it could be attributed to improve the reliability of grain refining.The feature of this semi-solid process is that inclined cooling plate equipped with casting unit gives the semi-solid slurry. When the melt pass through the cooling plate, it makes a numerous number of fine primary particle crystallize out by the cooling effect of the plate and successively dropped as semi-solid slurry into the pre-heated tundish set at the plate end. Such slurry was kept for a given time in the tundish and then quenched into water. Microscopic examination of the as-solidified structure shows that the most desirable structure (60μm in average grain diameter) arises from the following conditions ; casting temperature of 878K, plate length of 200mm and plate angle of 60deg. Further, when continuous casting was applied to the slurry, the billet which is the length of 600mm and the diameter of 40mm, could be successfully obtained.Generally, iron has precipitated as fine particles in molten magnesium due to its small solubility, e.g., about 0.01% in magnesium at 973K. Therefore, iron removal by electromagnet was examined. A pure iron bar magnetized by electromagnet was inserted into molten Mg-0.05Fe alloy at 973K, and then the melt was as-solidified in the furnace. Metallographic examination suggests that fine iron particle tend to magnetically gather with each other and made some cluster in magnesium.

采用半固态铸造法对AZ 91镁合金进行了晶粒细化研究，并采用半固态连续铸造法制备了细晶和球晶坯料。此外，还研究了施加磁场的除铁方法，因为它可以提高晶粒细化的可靠性。这种半固态工艺的特点是配备有铸造装置的倾斜冷却板提供半固态浆料。当熔体通过冷却板时，在板的冷却作用下，使大量细小的初生颗粒结晶出来，并以半固态浆料的形式依次滴入板端部预热好的坩埚中。将这种浆料在搅拌器中保持给定时间，然后在水中骤冷。对凝固组织的显微观察表明，在浇注温度为878 K，板长为200 mm，板角为60 °时，获得了最理想的组织（平均晶粒直径为60μm）。此外，当将连续铸造应用于浆料时，可以成功地获得长度为600 mm、直径为40 mm的坯料。通常，铁由于其溶解度小而在熔融镁中以细小颗粒析出，例如，在973 K时，镁的含量约为0.01%。因此，检查了通过电磁铁的铁去除。将电磁铁磁化的纯铁棒插入973 K的Mg-0.05Fe合金熔体中，然后在炉内进行凝固。金相分析表明，细小的铁颗粒在镁合金中倾向于磁性聚集，形成团簇。