Laser Beam Welding of 600 MPa Quenched and Tempered High-Strength Steel

Conventional fusion arc welding of high-strength quenched and tempered steel can be improved through the use of non-conventional laser beam welding. This article presents the investigations of autogenous bead on plate and butt CO2 Laser Welding (LW) of 7 mm thick high-strength quenched and tempered low alloy SM570 (JIS) steel plates. The influence of laser welding parameters, mainly welding speed, defocusing distance and shielding gas flow rate on the weld profile, i.e., weld zone penetration depth and width, microstructure and mechanical properties of welded joints was determined. All welded joints showed smooth and uniform weld beads free from superficial porosity and undercuts. The selected best welding conditions were a laser power of 5.0 kW, welding speed of 500 mm/min, argon gas shielding flow rate of 30 L/min and a defocusing distance of -0.5 mm. It was observed that these conditions gave complete penetration and minimized the width of the weld bead. The microstructure of the welded joints was evaluated by light optical microscopy. The weld metal (WM) and heat-affected zone (HAZ) near weld metal achieved maximum hardness (355 HV). The tensile fractured samples showed the ductile mode of failure and ultimate tensile strength of 580 MPa.

极薄高强钢板辊压式连续淬火装备技术与应用

极薄高强钢板高平直度淬火是行业技术难题。基于对高效换热和淬火变形机理的新认识,提出宽薄钢板受约束淬火变形机制和低残余应力淬火方法,发明多机架高刚度液压伺服控制棍系、高强均匀阵列射流水刀等核心部件,研制成功国际首套极薄高强钢板辐压式淬火装备和非对称淬火、差速拉伸淬火、逐级约束淬火等淬火新技术,自主集成了3~6mm极薄超高强钢板热处理工艺技术体系,3mm钢板淬火不平度W3~4mm/2m,钢板热处理后切割不变形、焊后180。折弯不开裂,实现批量稳定淬火生产。

1500 MPa级超高强钢复杂薄壁结构焊接变形预测

基于MSC.Marc通用有限元软件平台,开发了同时考虑材料非线性、几何非线性和边界非线性的热-弹-塑性有限元方法用于模拟1 500 MPa级超高强钢薄板接头的焊接变形;同时也开发了基于固有应变理论的弹性有限元方法来计算大型复杂结构的焊接变形。首先,以1500MPa级超高强钢薄板对接接头为研究对象,分别采用热-弹-塑性有限元方法和固有应变法模拟了焊接变形,并与试验结果进行比较,计算误差均小于15%。随后,以1 500 MPa级超高强钢大型复杂薄壁结构为研究对象,采用热-弹-塑性有限元法计算薄壁结构中典型焊接接头在自由和强制拘束条件下的固有变形,考察拘束条件对焊接接头变形的影响。最后,基于固有应变理论计算了超高强钢复杂薄壁结构的整体焊接变形,并研究了强制拘束对薄壁结构焊接变形的影响。数值模拟结果表明,采用外部强制拘束可以在一定程度上减小薄壁结构的总体变形。

极薄高强钢板辊压式连续淬火装备技术与应用

极薄高强钢板高平直度淬火是行业技术难题。基于对高效换热和淬火变形机理的新认识,提出宽薄钢板受约束淬火变形机制和低残余应力淬火方法,发明多机架高刚度液压伺服控制辊系、高强均匀阵列射流水刀等核心部件,研制成功国际首套极薄高强钢板辊压式淬火装备和非对称淬火、差速拉伸淬火、逐级约束淬火等淬火新技术,自主集成了3~6 mm极薄超高强钢板热处理工艺技术体系。应用该装备技术后,3 mm钢板淬火不平度不大于3~4 mm/2 m,钢板热处理后切割不变形、焊后180°折弯不开裂,实现批量稳定淬火生产。