Usage of Ti-surface-modified filler material to increase the joint strength of High-Strength Low Alloyed (HSLA) steels u
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Usage of Ti‑surface‑modified filler material to increase the joint strength of High‑Strength Low Alloyed (HSLA) steels under different load types Kai Treutler1 · Volker Wesling1 Received: 30 March 2020 / Accepted: 12 November 2020 © The Author(s) 2020 OPEN
Abstract Welding-related loss of strength, especially in the case of fatigue, significantly reduces the range of applications for high-strength fine-grained structural steels. In order to counteract this situation, the aim of the work is to increase the strength of welded joints made of high-strength fine-grained structural steels by using coated welding consumables. This is described using the example of a titanium coating for quasi-static and abrupt dynamic load and fatigue. The thermomechanical rolled fine-grained structural steel S700MC is used as the base material, using a welding filler of the same type. MAG welding was used to produce the fillet welds on a T-joint. In addition to tensile tests at four different load speeds up to 2 m/s, the results of fatigue tests are presented. In addition, the microstructure of the weld seams is examined by metallographic methods and the scanning electron microscope. A comparison with two joints from an unmodified variant and another steel grade with comparable properties (S690QL) serves to classify the results. It is shown that the use of modified filler metals has a significant influence on the overall strength of the welded joint due to the rounding of the weld toe. Thus, the fatigue strength can be increased by around 50%. In addition, the strength under sudden dynamic load can be increased by 10%. Keywords GMA welding · Surface-coated filler material · HSLA steels · Fatigue · Sudden dynamic loads
1 Introduction In order to fully utilize the properties of high-strength steels, it is essential to achieve their strength properties under different types of loads (quasi-static, suddenly dynamic and cyclic fatigue), including integrally in the area surrounding welds. This is usually not given by the thermal effects of the welding processes. Notches caused by welding in particular have a negative influence on the properties here. The aim of the investigations carried out is to reduce this negative effect of welding-related notches. For this purpose, the composition, the welding process and the surface tension of the melt are positively
influenced in MAG welding by means of a surface coating on the filler metal. Currently, in arc welding, various possibilities are currently used to influence the weld seam characteristics. These are, among others, the modification of the viscosity of the melt and the arc characteristics through the use of different shielding gases [1, 2], and modern welding process controls [3, 4]. The use of nanoparticles on the welding filler surface is also currently being investigated for the modification of the weld metal properties and the arc [5]. Besides the application of nanoparticles on the filler surface, a complete surface coating on the filler surface can be applied by magnetron sputteri
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