激光焊接速度对高锰塑性诱发孪晶钢组织性能影响

WELDING SPEED EFFECT ON MICROSTRUCTURE AND MECHANICAL PROPERTIESOF LASER WELDED HIGH MANGANESE TWINNING INDUCED STEELS

用CO2连续激光焊接器,以不同焊速焊接Fe-Mn-C系TWIP钢试样。使用OM,SEM观察焊接试样的形貌组织在焊缝区,热影响区,以及基体的变化,并结合XRD检测观察:发现原伴有少许退火孪晶的室温单相奥氏体经单相拉伸变形后有少量γ→ε和γ→ε→α协同大量变形孪晶共存于焊后拉伸试样中,即焊后高锰TWIP钢变形时同时发生TRIP效应和TWIP效应。此外,通过背散射电子衍射技术(EBSD)探讨激光焊接后,不同焊速下焊缝区,热影响区和母材的晶粒取向差与晶界特征变化。结果表明本试验中,激光焊接参数为2.5 kW,2.5 m/min下的试样组织性能最优,对焊钢板可达到32%的延伸率,534 MPa的屈服强度和1 100 MPa的抗拉强度。

The research of wehting speed effect on mierostructure and mechanical properties of TWIP steels of Fe-Mn-C system was investigated through using CO2 continuously laser wehting equipment. The microstructure of welding joint was observed by means of OM and SEM in three different areas, that is, fusion zone （FZ）, heat affected zone （HAZ） and base metal （BM）. In order to study the performance of laser welded TWIP steels further, x-ray diffraction （XRD） was used to detect the change in welded tensile test samples, especially in comparison with phase change pre- and post- tensile test. The XRD data showed both the TRIP effect and TWIP effect happened on deformed high manganese welded TWIP steels, that is, a large amount of deformed twin with certain α- and α-martensite were appeared after tensile test. Additionally, electron back scatter diffraction （EBSD） was taken into account to evaluate the grain boundary character distributions and the misorientation after laser welding in FZ, HAZ and BM, separately. The conclusion of the research indicated that the laser welding speed of 2.5 m/min had better mechanical properties than that of 2.0 m/min. The welding of 2.5 m/min, specifically, had more than 32% in elongation rate as well as 543 MPa and 1 100 MPa in the yield strength and the tensile strength respectively.