Manufactured by high frequency weldingeffects of heat treatment applications on steel pipes

ABSTRACT MANUFACTURED BY HIGH FREQUENCY WELDING EFFECTS OF HEAT TREATMENT APPLICATIONS ON STEEL PIPES Rahmi HIDIR Düzce University Graduate School of Natural and Applied Sciences, Department of Mechanical Engineer Master's Thesis Supervisor: Assoc. Prof. Dr. Ali GÜRSEL May 2022 In pipe manufacturing, high frequency welding is increasing day by day with continuous butt seam. Increasing production brings with it high quality standards to always deliver the best product to the end user.. In this study, it is aimed to remove the stresses caused by welding and to obtain a higher quality, durable and long-lasting product by taking samples from the products manufactured in different purposes of the high frequency induction welding (HFIW) used in the pipe industry, and examining the properties of them before and after the heat treatment under the same conditions. In this study, three different types of profile samples manufactured from thin pipes used as home appliances, towel warmers and furniture materials were subjected to mechanical tests before and after welding, and after heat treatment were observed. The material quality of the welded pipe was determined as Erdemir Standard 6112 for towel warmer, 7114 for home appliance and 1311 for furniture material, and their thickness was kept as 1 mm in all. Three-step tests were applied to the produced samples: before welding, after welding and after heat treatment. Applied tests and analyzes; the data obtained from mechanical (tensile) tests, hardness analysis, pipe crushing and taper opening test methods, seam strength tests, and also microstructure analyzes were employed. The effects of the heat treatment were determined in the samples examined, besides the stresses caused by the heat input in the high frequency welding, it was observed that there were also stresses arising from the heat treatment, and it was tried to determine what should be done to make the products that go beyond the quality standards in accordance with the standards by removing the stresses caused by both processes. At the end of the study, it was observed that the mechanical properties on the material were improved if appropriate heat treatment was applied to the hardened area under the influence of welding during production. In this way, the stresses and imperfections that occur during pipe forming and high frequency welding were able to eliminated. Keywords: Pipe Manufacturing, High Frequency Welding, Welding Stress, Heat Treatment.