This paper examines the mechanical and microstructural properties of thermomechanical rolling and direct quenched ultra high strength steel (UHSS) joints in the butt welded with different position applications. The influence of heat inputs according to the welding position on solidification appearance, microstructure, impact toughness, hardness, and tensile properties are investigated. Weld metal (WM) microstructure belonging to both PA (horizontal) and PF (vertical) positions consists of acicular ferrite mainly that morphology of them altered depending on heat input and cooling time. Besides acicular ferrite, martensite/austenite constituents (M/A) happened in PF-WM microstructure and it partially affects impact toughness. Heat affected zone (HAZ) size is less than PA except for root because of applied weaving amplitude on PF position affected heat flow and decreased exposed average peak temperature time. Martensite phase is dominant where HAZ of next to the last bead with high hardness values for top and bottom. Furthermore, necklace type M/A constituents were formed when the HAZ of the prior weld passes was reheated with subsequent weld passes.

本文研究了热机械轧制和直接淬火超高强度钢 (UHSS) 接头在不同位置应用的对接焊中的机械和显微组织性能。研究了根据焊接位置的热输入对凝固外观、微观结构、冲击韧性、硬度和拉伸性能的影响。属于 PA（水平）和 PF（垂直）位置的​​焊缝金属 (WM) 显微组织主要由针状铁素体组成，它们的形态会根据热输入和冷却时间而改变。除了针状铁素体，马氏体/奥氏体成分 (M/A) 出现在 PF-WM 显微组织中，它部分影响冲击韧性。除了根部，热影响区 (HAZ) 尺寸小于 PA，因为在 PF 位置上施加的编织幅度会影响热流并减少暴露的平均峰值温度时间。马氏体相占主导地位，其中 HAZ 靠近最后一个焊道，顶部和底部具有高硬度值。此外，当先前焊道的热影响区在随后的焊道中重新加热时，会形成项链型 M/A 成分。