# A Smart Handheld Welding Torch Device for Manual Spot Laser Welding
## 1 Introduction  
High-energy laser welding is frequently used for joining thin-walled stainless surfaces due to the heat exposure of a narrow region, low residual stresses, uniform grain structure, high efficiency, and low operating costs compared to conventional welding processes. It is a complex process to determine the welding parameters for joining thin stainless materials in a way that does not create visual defects. This is because, although it is desired that the welding process is delicate enough not to have visible defects, the connection is also expected to be strong enough to last for the life of the device. Laser welding has advantages such as minimum thermal degradation, good mechanical properties, and excellent reproducibility due to precise temperature control [1, 2]. Although it can be used successfully for thin sheet metal welding, it also has deep penetration capability [3]. As a result of these advantages, laser welding offers higher welding speed and efficiency than conventional arc welding. In addition to these criteria in the production of inox kitchen and hotel equipment, where visuality is at the forefront, the welding processmust be done so delicately that it does not leave a heat trace on the visible surface of the thin plate. However, unique welding methods are required to laser thin bond sheets of stainless metal with no heat marks on their visible surfaces. Otherwise, small thicknesses of thin metal sheets with the effect of excessive heat can cause visible heat traces, even in micro-welding. Therefore, the minimum heat input to the light sheet is technically and economically practical. Technically, micro-laser welding is applied so that a melting volume in the form of a pyramid is formed from the invisible surface to the visible surface. In this way, the visible thin stainless sheet is less affected by heat. This application economically requires lower laser power associated with less heat input, less equipment investment, and lower operating costs. In industries, welding of modern engineering materials, including stainless steel and titanium alloys, finds various applications due to the need to tailor the location of materials where a transition in mechanical properties, temperature, pressure, and/or performance in service is required. Due to the numerous advantages and wide range of uses of laser welding, it is important to update, understand, and model industrial application processes [4]. Studies in the literature focusing on laser micro-welding of austenitic stainless steels have analyzed the effect of laser welding parameters on weld width and weld penetration depth. Porosity, which deteriorates the strength of the welded part, is often observed in deep-penetration laser welds [5; 6; 7; 8]. In order to optimize the laser welding process and ensure high weld quality and strength, it is necessary to understand how porosity occurs in the welding process and to find methods to reduce or eliminate pore defects. [PERSON] and [PERSON] used mathematical models to investigate transport events leading to pore formation and explored possible solutions to reduce or eliminate pore formation in laser welding [9]. The results show that pore formation in pulsed laser welding is due to two competing factors: the solidification rate of molten metal and the molten metal's backfilling during precipitation. [PERSON] et al. investigated the effect of different shielding gases on forming pores in laser seam welds of 20 mm thick AISI 304 plates [10]. The results showed that shielding gas had a significant effect on the pore formation, and few pores were present in the seam welds when Ar was used, but almost no pores were present in the seam welds when N2 or gas was not used. [PERSON] et al. compared laser seam welding of AISI 304 and AISI 316 stainless steel alloys [11]. The results showed that higher linear heat input is required for the AISI 304 alloy compared to the AISI 316 alloy to achieve the maximum ultimate strength of the seam weld.