# A Smart Handheld Welding Torch Device for Manual Spot Laser Welding
## 1 Introduction
Few studies have been conducted on laser micro-spot welding of stainless-steel alloys [12; 13]. [PERSON] et al. presented a finite element model (FEM) comparing simulation with experimental tests for laser micro-spot welding of 2.5 mm thick austenitic AISI 304 stainless steel sheets in a bead-on-plate configuration [12]. [PERSON] et al. investigated the effect of laser power and focal distances in laser micro-spot welds on 0.254 mm thick austenitic AISI 302 stainless steel sheets in an overlapping joint configuration [13]. [PERSON] et al. investigated various aspects of replacing existing micro-resistance spot welding (micro-RSW) with micro-laser spot welding to join Inconel 718 thin foils to a thick 410 steel stack. They evaluated the results based on weld quality, mechanical strength, microstructural properties, and high-temperature weld strength [14]. Especially for micro-laser spot welding of ultra-thin foils, pulsed laser welding is the preferred method over continuous wave laser welding because the former method offers precise temperature control, reducing the heat-affected zone, residual stresses, and heat input [15]. Pulsed laser welding is used in various micro-welding applications, including medical device manufacturing, sensors with thin membranes, welding of markers to stents, and fabrication of microturbines using ultra-thin foils [16; 17; 18; 19]. In general, pulsed laser welding involves an intermittent supply of a high-intensity energy beam that periodically focuses on melting and solidifying the material in succession. Process parameters in pulsed laser welding include pulse energy/laser power, pulse width, pulse frequency, laser spot size, and welding speed used to achieve satisfactory weld quality [20; 21]. After the first study that successfully welded Inconel 600 tubular components (1.0 to 1.2 mm Inconel stack) for nuclear power plants using a pulsed laser, joining materials with high-temperatureresistance, such as Inconel to stainless steel, by the micro-laser welding method has been a popular research topic of recent years [22; 23; 24; 25]. As a result of the laser-based additive manufacturing technology, the ability to manufacture the metal has dramatically increased. In this way, products that cannot be obtained with conventional methods can be produced, and more economical and simple solutions can be produced by combining different materials with desired properties, as in the production of composite materials [26]. Recycled nickel alloy powder was applied to the 3D printing obtained by selective laser melting by [PERSON] et al. They investigated the effects of the chemical composition of the alloy's main elements on the products' mechanical properties. They proved they could be used in other selective laser melting methods without side effects [27]. Although the product obtained by additive manufacturing in the laser sintering method is the same, [PERSON] et al. examined the effects of the production method (with differences in the laser scanning direction) on the material structure [28]. [PERSON] et al. investigated the causes of various structural part defects frequently encountered in additive manufacturing products created by selective laser melting at different laser powers and scanning speeds [29]. [PERSON] et al. investigated the effect of the absorption rate of IN718, one of the most widely used nickel alloys, at different laser powers and scanning speeds, on the melt pool properties [30]. These studies show that additive manufacturing technology can offer a wide range of solutions for very different materials due to the laser welding method. Similarly, there are studies on combining Inconel alloys with different steels [31; 32; 33; 14; 34]. [PERSON] et al. investigated the effect of laser energy in micro-laser welding of 100 m thick AISI 316L stainless steel foil. They concluded that microstructural and mechanical reliability could be achieved by precise control of laser pulse energy [15]. In contrast, [PERSON] et al.