Contents lists available at ScienceDirect Infrared Physics & Technology journal homepage: www.elsevier.com/locate/infrared Regular article Investigating the effect of process parameters on the mechanical properties and temperature distribution in fiber laser welding of AISI304 and AISI 420 sheet using response surface methodology Amirhosein Mosavi a,b , Ahmad Soleimani c , Alireza Karimi c , Mohammad Akbari c , Arash Karimipour c , Aliakbar Karimipour d, ⁎ a Environmental Quality, Atmospheric Science and Climate Change Research Group, Ton Duc Thang University, Ho Chi Minh City, Vietnam b Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Vietnam c Department of Mechanical Engineering, Najaf Abad University, Esfahan, Iran d Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam ARTICLEINFO Keywords: Fiber laser Response surface methodology Tensile strength Molten pool Nozzle distance ABSTRACT Fiber laser welding of austenitic and ferritic stainless steel was performed based on response surface metho- dology to systemically analyze the effect of process parameters on the weld characterizations. The laser welding input parameters were selected (laser power, welding speed and nozzle stand of distance) while the tensile strength of the joint and temperature near the molten pool were considered as the main responses. Variation of nozzle distance about 5 mm had less effect on the temperature domain near the molten pool and weld tensile strength. Increasing the nozzle distance and moving the focal point position to the upper surface of the sheet surface led to the notable improvement of the tensile strength about 20 percent. In other words, transition of the focal point thorough the material thickness clearly reduced the joint strength due to creating more volume of martensitic micro-structure and finally cracking during the tensile test from HAZ region of ferritic steel. The interaction of the laser power and welding speed had noticeable impact on the molten pool temperature. Evidently, the rate of temperature reduction due to an increased welding speed is greater at higher laser power. Amongtheinvestigatedparameters,theweldingspeedhadthehighesteffectsonthetensilestrengthofthejoint. Increasing the laser power from 300 to 360 W raised the tensile strength about 20%. Interaction of the laser power and welding speed resulted in about 300 °C of the temperature reduction due to an increased welding speedathigherlaserpowerof395Wvariationofnozzledistanceatdifferentlasepowerlevelslesseffectabout5 percent in comparison to the welding speed versus nozzle distance although the similar trend was observed for both of them. 1. Introduction Joining of materials is of a particular importance in different in- dustries, including shipbuilding, automotive, and nuclear power plants [1–6]. Joining processes include different thermal methods of electric arc welding, electron beam or laser beam welding that could be taken into account [7–10]. Laser beam welding is one of the most effective and efficient welding methods of joining materials due to its high ac- curacy, high width/depth ratio, low heat input, and small volume of heat-affected zone in comparison to the fusion zone [11–13]. Laser beam welding is widely utilized to join components of the same or different materials. Kawahito et al. [14] evaluated the fiber laser welding of stainless steel AISI 304. The results indicated that augmentation of welding speed and more concentrated laser beam had desirable impacts on both fusion zone and HAZ region. Cui et al. [15] investigated the weld bead appearance, microstructure and micro- hardness of joints by applying fiber laser welding to 3 and 6 mm plate thicknesses of stainless steel AISI 304. The results demonstrated that acceptable weld joint could be achieved using a 2 kW laser power and weldingspeedof20mm/s.Inotherstudytheshapeofthepulseimpact on the weld defects and the weld microstructure were investigated for the ND:YAG single-spot welding of magnesium alloy [16]. Welding of the thick steel plate and forming the underfill on the surface of the laser-welded samples by using a fiber laser and maximum power of 10 kW was experimentally analyzed. The keyhole weld at full pene- trationwithunderfilloftopsurfaceandundercutofbottomsurfacewas https://doi.org/10.1016/j.infrared.2020.103478 Received 26 June 2020; Received in revised form 21 August 2020; Accepted 25 August 2020 ⁎ Corresponding author. E-mail addresses: amirhosein.mosavi@tdtu.edu.vn (A. Mosavi), aliakbarkarimipour@duytan.edu.vn (A. Karimipour). Infrared Physics and Technology 111 (2020) 103478 Available online 01 September 2020 1350-4495/ © 2020 Elsevier B.V. All rights reserved. T