# A Smart Handheld Welding Torch Device for Manual Spot Laser Welding
## 1 Introduction
investigated the CO\({}_{2}\) laser lap joints between 0.4 to 1.6 mm Inconel 718 sheets. They reported that the lap welds' fatigue behavior suits aircraft engines' requirements despite microcracks [35]. High-irradiance lasers hitting metal surfaces create a complex, dynamic process in which metal can change rapidly from being highly reflective to a strong absorber. This effect was found by [PERSON] et al. It was discussed in an experimental study by [36]. Duplex stainless steels (DSSs) are a category of stainless steels used in any application where both high strength and excellent corrosion resistance are required. This favorable combination of properties is provided by their biphasic microstructure, consisting of ferrite and austenite in approximately equal volume fractions. DSSs, just like thin materials, are sensitive to heat treatments, welding processes, or thermal cycles. Therefore, micro-laser welding applications are also widely used in DSSs [37]. Although welding technology has matured, defects may occur due to improper manual operation, unstable environments, and welding equipment problems [38]. In manual micro-spot laser welding, the gap between the mating surfaces of sheet materials and the torch-surface angle (the angle between the laser beam and the weld surface) are critical variables to achieving sufficient weld strength without creating heat marks on the visible surface. While the effects on weld bead geometry in laser welding are already well understood, the detailed characteristics of visual micro-laser welding have not been adequately clarified. In examinations, it has been seen that the variable most prone to error in manual micro-laser applications is the torch-surface angle. Therefore, this study investigated the effect of angular positioning errors between the laser beam and the weld surface on the weld quality. The torch-surface angle is considered the most error-prone variable in manual micro-laser applications. Experimental results show that the laser welding angle is one of the most critical parameters affecting the formation of the desired weld cross section on thin stainless sheet surfaces. It would not be appropriate to perform visual micro-welding without providing angular positioning precision. The processes applied to the surface to eliminate these visual defects in production increase the costs by reducing the production speed. The high temperature and methods used to remove traces on the surface reduce the corrosion resistance of the stainless surface. Welding test samples were prepared by combining stainless steel sheets, frequently used in the production of inox kitchen equipment, with different laser welding angles (laser beam-surface angle). Test sample production was carried out on a welding stand equipped with a digital protractor (UNI-T LM320B), keeping all other parameters constant only by changing the angular position of the welding torch. The weld strength of the test specimens obtained was determined by tensile tests; thus, the best weld angle range that would not create a heat trace on the visible surface was determined. The device, which guides the welding operator with visual signals and ensures welding occurs in the correct angular position, was programmed according to these angle values. With the smart and standard welding torch, the operator was asked to prepare test samples manually by welding sheets in random angular directions. In this paper, the effect of the smart welding torch on the manual welding quality is discussed by comparing the tensile test results of the prepared samples and the microscope images. With the discovery of micro-laser application, it has been possible to weld thin inox sheet surfaces without creating defects on the surfaces where the main structures can be seen. In this way, thin inox sheets began to be used as an aesthetic element on the visible surfaces of machines and devices.