弯曲参数对304不锈钢管材大曲率无芯弯曲成形性的影响

Effect of bending parameters on formability of large curvatureno-mandrel bending of 304 stainless steel tube

针对管材无芯弯曲多缺陷耦合的成形问题,以管材壁厚变化率及截面短轴变化率作为成形指标,在不同弯曲参数下进行304不锈钢管材大曲率无芯弯曲试验,结合硬度测试及微观组织表征,研究了弯曲参数对弯曲成形及微观组织演变的影响规律。结果表明:随着弯曲速度、弯曲角度及相对管径的增大,壁厚变化率呈增加趋势,且壁厚增厚率始终大于壁厚减薄率,同时,弯管截面畸变程度加剧。在各弯曲参数下,管材弯曲内外侧均发生奥氏体向马氏体转变,马氏体组织含量及硬度与壁厚变化率呈正相关关系,中性层几乎不存在马氏体。通过选择合适的工艺,最终弯制出相对弯曲半径为1.4的合格弯管。

Aiming at the forming problem of multi-defect coupling in tube no-mandrel bending,the large curvature no-mandrel bending tests of 304 stainless steel tube were carried out under different bending parameters with the variation rate of tube wall thickness and the variation rate of cross-section short axis as the forming indexes.Combined with hardness test and microstructure characterization,the effect laws of bending parameters on bending forming and microstructure evolution were studied.The results show that with the increase of bending speed,bending angle and relative tube diameter,the wall thickness variation rate shows an increasing trend,and the wall thickness thickening rate is always greater than the wall thickness thinning rate.At the same time,the cross-section distortion degree of the bent tube is increased.Under each bending parameter,the austenite to martensite transformation occurs in the inner and outer sides during tube bending.The martensite content and hardness are positively correlated with the wall thickness variation rate,and there is almost no martensite in the neutral layer.By selecting the appropriate process,a qualified bent tube with relative bending radius of 1.4 is finally bent.