热拔工艺对高氮无镍奥氏体不锈钢线材开裂的影响

在开发一种高氮无镍奥氏体不锈钢线材时,热拔线材表面出现了大量的裂纹。通过金相、扫描电子显微分析和能谱检测,对其开裂原因进行研究。发现线材的表面裂纹基本垂直于拉拔方向,裂纹在表面产生,之后向线材内部发展。线材表层存在着大量的富Cr和N的氮化物析出,沿晶析出的析出相,会导致孔洞形成,这些孔洞相连,形成微裂纹,最终导致沿晶开裂。通过加长加热区、提高拉拔速率保证了线材表面温度,避免了表面裂纹的产生,获得了质量满足要求的高氮无镍奥氏体不锈钢线材,并最终给出了建议的热拔工艺。

Influence of hot drawing process on cracking of high nitrogen nickel free austenitic stainless steel wire rod

During developing a high nitrogen and nickel free austenitic stainless steel wire rod, a large number of cracks appeared on the surface of the hot drawn wire rod. The cracking reasons were studied by means of optical microscopy, scanning electron microscopy and energy dispersive spectrometer. It was found that the surface cracks of the wire rod were basically perpendicular to the drawing direction. The cracking occurred on the surface and then developed into the inner. A lot of Cr-rich and N-rich nitrides separated on the surface of the wire rod. The precipitated phase along the grain boundaries would lead to the formation of voids, which could connect each other to form microcracks. After that, the intergranular cracking and fracture occurred. By lengthening the heating zone and increasing the drawing speed, the surface temperature of the wire rod was ensured, the surface cracking was avoided. The high nitrogen nickel free austenitic stainless steel wire rod with high quality was manufactured. Finally, the recommended hot drawing process was given.