PSI - Issue 59

D. Nosov et al. / Procedia Structural Integrity 59 (2024) 656–663 D. Nosov et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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In general, welding is the most economical way of both manufacturing and extending the service life of a band saw blade. However, high quality welding requires skill and experience, and improper welding can result in a weak or brittle joint that can easily break during use. There are two main modes of contact welding used to join the ends of the band saw blade: Butt welding: In this method, the ends of the sheet are cut straight and then placed in a clamping device that holds them in place with the butt ends. Then an electric current is passed through the ends of the sheets, heating them until they melt and form a weld. The clamping device maintains pressure on the ends of the sheets until the weld cools and hardens. Bevel welding: in this mode, the ends of the sheets are cut at an angle to create a V-shaped butt. The two ends of the sheets are installed and held in place with a clamping device. An electric current passes through the ends of the sheets, heating them until they melt and fuse together. The resulting weld has a triangular cross-section with the apex of the triangle located in the center of the blade. The opening angle of the V-shaped end is selected depending on the thickness and width of the tape, as well as taking into account the brand of the material. Not widely used, but no less effective, is the method of contact welding of the tape into a finger, using a spot welding machine. In this case, the two ends of the sheet overlap and are held in place by a clamping device. Contact spot welding is performed. An electric current is passed through the upper and lower sheet, heating it until they melt and fuse together. Both butt welding of straight ends and oblique ends are effective methods of joining the ends of the band saw blade. However, it is generally considered that bevel welding is stronger and more reliable because it provides a larger surface area of the weld and allows for a more uniform distribution of the welding current. Butt welding is simpler and more productive, but welds may be more prone to failure or cracking under high loads (Martin et al., 2022). The choice of welding mode depends on the specific requirements of the application, as well as the skills and experience of the operator. Steel grade 65G is spring-loaded, has high elasticity and wear resistance. Demonstrating high resistance of the surface to abrasion, burrs and delamination and significant resistance to elastic deformations, under the influence of shock loads, steel 65G is prone to premature aging and the formation of cracks. It is characterized by low flocking sensitivity and a tendency to brittleness. In addition, due to its chemical composition and properties, this brand is not used for the manufacture of welded structures. Steel 65G steel is well forged and works under conditions of other deformation processing, however, with large compressions, an intermediate softening heat treatment may be required. It is recommended to use high-speed and hard alloys for cutting. Steel 65G requires additional heat treatment operations. Heat treatment of the seam after contact welding of the band saw is carried out to increase the strength and durability of the weld. This process involves heating the welding zone to a certain temperature and then slowly cooling it to room temperature. The heat treatment process usually includes the following stages:  Preheating: the welding place is heated to a temperature of about 400...500°C to remove residual stresses and ensure uniform heating of the material.  Soaking: The weld area is held at this temperature for a period of time to allow the material to completely "soak" and ensure even temperature distribution throughout the weld.  Cooling: After welding, the heat affected zone (HAZ) region and the welded joint are slowly cooled to room temperature. The cooling rate is carefully controlled to prevent any thermal shock that could cause cracking or weakening of the weld. The specific temperature and duration of each stage of the heat treatment process will depend on the materials being welded and the specific application requirements. It is important to carefully follow the manufacturer's instructions and use the appropriate equipment and methods to ensure high quality welding (Zhou et al., 2019). The critical cooling rate of a welded joint made of 65G steel depends on a number of factors, including the composition of the steel within standard values, environmental conditions, and the welding method used. However, as a general rule, the critical cooling rate for this type of steel is usually around 20…30°C per second. The critical cooling rate refers to the minimum cooling rate required to prevent the formation of undesirable microstructures in the weld and HAZ. If the cooling rate is too low, the weld may be prone to cracking or other