地锚拉杆镶嵌锻造后再结晶的研究

Study on recrystallization of earth anchor rods after mosaic forging

从耐腐蚀性能的角度讨论了地锚拉杆镶嵌锻造的必要性。拉伸试验表明,地锚拉杆镶嵌锻造后,实用强度达不到设计要求的28.8 k N,断裂部位发生在拉杆镶嵌锻造部分,且靠近锁紧扣孔口。对拉杆镶嵌锻造部分的前后组织进行了金相观察,结果显示,拉杆冷变形后的细长晶粒经镶嵌锻造后重新转变成了等轴晶粒,产生了再结晶,冷变形强化效果消失是导致其实用强度下降的根源。进一步研究表明,拉杆产生再结晶是由高温锁紧扣锻坯热传导致其温度升高造成的。故镶嵌锻造前,在拉杆镶嵌锻造部分浸涂一定比例的混合液,使拉杆镶嵌锻造后的温度低至再结晶温度以下。采用此方法后的拉伸实验结果表明,地锚拉杆镶嵌锻造后实用强度未明显下降,金相分析也表明未产生再结晶。

For corrosion resistance of earth anchor rods, the necessity of mosaic forging was investigated. Tensile tests show that the utility strength of earth anchor rods is below 28.8 kN after mosaic forging, and failed to satisfy the design standard. Furthermore, the fracture occurs in the mosaic forging part of anchor rods near to the shackle porthole. The microstructure of anchor rods was examined by optical microscope （OM）. The results show that the elongated grains induced by cold deformation transform into equiaxed grains after mosaic forging, where recrystallization occurs. Thus, work hardening after cold deformation disappears which resulting in the degradation of utility strength. Then, it is believed that the temperature rise caused by heat conduction from the shackle is the main reason for recrystallization. Therefore, with earth anchor rods dip coating into mixed liquid with fixed proportion before mosaic forging, the temperature after mosaic forging decreases below the recrystallization temperature. The following tensile tests show that no obvious degradation in utility strength is observed after mosaic forging. At the same time, recrystallization is also not found by OM.