基于数值模拟的挤压参数对AZ91镁合金管转角焊合室分流挤压焊合压力的影响规律研究

Simulation Research on Effect of Extrusion Parameters on Welding Pressure During Porthole Extrusion Process of AZ91 Pipe Through Angle Welding Chamber Die

摘要:

提出了一种镁合金管材转角焊合室分流挤压新工艺，该工艺可在有效延长焊合室长度和焊合时间前提下保证舌针刚度，从而保证管材尺寸精度，并且可通过转角剪切变形机制增加预焊合金属变形量和动态再结晶程度，从而有利于提高管材性能和焊缝焊合性能。利用有限元法揭示了转角焊合室分流挤压成形过程中金属的流动特征，应变分布特征和焊合室内的静水压力分布特征。结果表明，整个挤压过程无金属折叠，从而保证管材的表面质量；流经转角后预焊合金属变形量明显增加，有利于提高管材质量和焊缝质量。最后，研究揭示了坯料初始温度，挤压速度和模具转角对焊合室内静水压力的影响规律。结果表明，随着挤压速度的增加和模具转角的增大，转角焊合室内静水压力增大；随着坯料预热温度的增加，转角焊合室内静水压力呈先增大后减小的趋势。

Abstract:

A novel porthole extrusion process combined with corner extrusion principle for AZ91 pipe was presented. This new extrusion process can not only extend the length of the welding chamber, but also increase the rigidity of the latch needle, thereby ensuring the dimensional accuracy of pipe. Meanwhile, this new extrusion method can increase the deform degree and improve the dynamic recrystallization of the pre-welded metal, which can improve the welding quality and pipe quality. Then, the metal flowing characteristic, distribution feature of effective strain and mean stress in the corner porthole chamber were revealed; the results show that the effective strain of the separated metal becomes larger after flowing through the corner of the welding chamber, which can promote the quality of the welding seam. And the mean stress in the welding chamber is larger than 240 MPa, which satisfies the welding pressure condition. The influence rules of extrusion speed, die angle and billet preheating temperature on the mean stress in the welding chamber were also discussed; the result shows that the higher extrusion speed and the higher preheating temperature of the billet can enhance the mean stress in the welding chamber, which can improve the welding quality. The larger die angle can lead to higher mean pressure.