The Effect of Improved Cooling on the Microstructure and Mechanical Properties of Friction Stir‐Welded Advanced High‐Strength Dual‐Phase Steel,Steel Research International

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The Effect of Improved Cooling on the Microstructure and Mechanical Properties of Friction Stir‐Welded Advanced High‐Strength Dual‐Phase Steel
Steel Research International ( IF 1.9 ) Pub Date : 2020-08-25 , DOI: 10.1002/srin.202000253
Mahdi Mahmoudiniya _{1,

2} , Amir Hossein Kokabi ₃ , Massoud Goodarzi ₁ , Leo A. I. Kestens _{2,

4}

Affiliation

The heat‐affected zone (HAZ) softening is considered one of the most significant challenges during welding of ferrite–martensite dual‐phase (DP) steels. In fact, the strain localization in the softened area results in a premature fracture that degrades the mechanical properties of the joint. Herein, the objective is to investigate the effectiveness of improved cooling using a high thermal diffusivity backing plate (BP) to reduce HAZ softening and enhance the mechanical properties of friction stir‐welded DP700 steel. Accordingly, friction stir butt welding of DP700 steel was conducted using copper and mild steel BPs. The findings show that the replacement of steel BP with copper significantly reduces the weld temperature. It is also observed that the thermal diffusivity of the BP has a substantial effect on the microstructure development and mechanical properties of the welded joint. Increasing the thermal diffusivity of the BP results in a reduction of HAZ softening from 20 to 7 HV and improving tensile strength and total elongation of the joint by 40 MPa and 6.2%, respectively. Work hardening behavior and absorbed energy before the fracture are significantly improved by the replacement of steel BP with a copper.

中文翻译：

改进冷却对搅拌摩擦焊接高级高强度双相钢组织和力学性能的影响

热影响区（HAZ）软化被认为是铁素体-马氏体双相（DP）钢焊接过程中的最重大挑战之一。实际上，应变局部化在软化区域中会导致过早断裂，从而降低接头的机械性能。本文的目的是研究使用高热扩散背板（BP）改善冷却以减少HAZ软化并增强摩擦搅拌焊接DP700钢的机械性能的有效性。因此，使用铜和低碳钢BP进行DP700钢的摩擦搅拌对接焊接。研究结果表明，用铜代替钢BP可以显着降低焊接温度。还可以观察到，BP的热扩散率对焊接接头的微结构发展和机械性能有很大影响。增加BP的热扩散系数会导致HAZ软化从20 HV降低到7 HV，并将接头的拉伸强度和总伸长率分别提高40 MPa和6.2％。通过用铜代替钢BP可以显着改善断裂之前的工作硬化行为和吸收的能量。

更新日期：2020-08-25

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