Microstructure and Toughness of Friction Stir Weld of Thick Structural Steel

Abstract

Friction stir welding (FSW) was performed with single-sided one-pass butt welding using 12 mm thick structural steel plates with 400 N mm -2 grade of tensile strength. The microstructures and mechanical properties such as the Vickers hardness, tensile strength, and Charpy V-notch toughness of the weld joint were investigated, which verified the inhomogeneous features of the microstructure and toughness within the stir zone (SZ). Thermal cycle examinations with or without deformation at the peak temperature were undertaken using a thermomechanical testing apparatus in order to study the predominant factors on the microstructural evolution and resulting toughness within the SZ. It is indicated that the variation in the thermal cycle, especially the peak temperature, within the SZ plays a predominant role in defining the inhomogeneous features within the SZ.

Controlling hard zone formation in friction stir processed HSLA steel

“…There are strong linear correlations between weld cooling rate and both post-weld lath width and 95th percentile hardness. These results are consistent with Allred (2013) and Matsushita's (2011) findings using physical weld simulations: both reported that cooling rate dominated the simulated microstructure.…”

“…Some studies have used physical weld simulations, such as hot compression and hot torsion tests, to investigate the effects that strain, strain rate, peak temperature, and cooling rate have on the weld microstructure. Matsushita et al (2011) varied the peak temperature, strain, and strain rate while holding the cooling rate constant in hot compression samples. They found that the strain and strain rate had a negligible effect on the microstructure and suggested that the thermal effects had a much larger influence on the microstructure.…”

Effects of Al‐Ni powder addition on dissimilar friction stir welding between AA7075‐T6 and 304 L

“…The friction stir welding process is a potential state‐of the‐art technology to join dissimilar materials and has shown to reduce the generation of intermetallic phases significantly to form high quality joints. This advanced solid‐state joining technique, although relatively new, has showed improved welding capability when used in the joining of aluminum, magnesium alloys and mild steel . Friction stir welding is expected to be applied in dissimilar materials joining, based on several successful results in recent studies .…”

Effect of Linear Friction Welding Conditions on Charpy Absorbed Energy for Medium-high Carbon Steel Plates

“…誉田 登 1) ＊ ・北村 智孝 2) ・森 正和 1) ・青木 祥宏 3) ・森貞 好昭 3) ・藤井 英俊 3) Effect of Linear 17,18) や Friction Stir Weld 継 手 [19][20][21] では強度設計が可能となっている。一方，LFW に関 しては，接合部の金属組織や残留応力は解明 22) され始めて おり，強度設計に必要となるシャルピー衝撃特性や疲労特 性などの破壊特性に関しては，Ti 合金については解明 23,24)…”