Selection of friction stir welding tool rotational speed for joining dual phase DP600 steel sheets – an experimental approach

Abstract

In the present work, mechanical and microstructural properties of friction stir welded similar DP600 steel were investigated. The sheets were butt welded with a single pass and three different rotational speeds such as 700, 800, and 900 rpm. The other parameters such as the tool traverse speed, tool tilt angle, and plunge depth were kept constant (50 mm/min, 2°, and 0.2 mm, respectively). The highest tensile strength of 528 MPa (82.6% of joint efficiency) was obtained for a weld sample prepared with 800 rpm and the lowest tensile strength of 350 MPa (54.7% of joint efficiency) was obtained for 700 rpm produced joint. Microstructural characterization was carried out using an optical microscope and scanning electron microscope coupled with EDAX. The planimetric method was used to find the average grain size of different stir zones. Grain size number (G) for 700, 800, and 900 rpm was found to be 12.83, 11.35, and 10.5, respectively. Microhardness tests were conducted using a micro Vickers hardness tester. The highest hardness of 345.2 HV and lowest hardness of 145.9 HV was found in the stir zone of 800 and 700 rpm, respectively. A three-point bend test was conducted for all the weld samples and the mode of failure was also analyzed using fractographic analysis.

Keywords:

• Friction stir welding
• dual phase 600 steel
• microstructure
• mechanical properties

Acknowledgments

The authors are grateful to NIT Manipur, KITS Warangal, RGKUT Basara, and NIT Warangal for the support to carry out the investigations.

Disclosure statement

No potential conflict of interest was reported by the author(s).