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U ovom radu je analizirana problematika TIG zavarivanja visokolegiranih Cr-Ni čelika s posebnim naglaskom na korijensku zaštitu. Svrha rada je utvrditi utjecaj kisika pri korijenskoj zaštiti na svojstva zavarenog spoja ovisno o različitim parametrima zavarivanja. U teorijskom dijelu, opisan je TIG postupak zavarivanja pri čemu je posebna pozornost usmjerena na zavarivanje austenitnih visokolegiranih Cr-Ni čelika i probleme koji se mogu pojaviti tijekom toga. Detaljno je opisan utjecaj kisika u korijenskoj zaštiti na svojstva zavarenog spoja i utjecaj pravilnog izbor zaštitnog plina s obzirom na vrstu osnovnog materijala. Izvršen je pregled postojećih sustava za korijensku zaštitu i metoda obrade površine nakon zavarivanja. U eksperimentalnom dijelu provedeno je navarivanje uzoraka izrezanih iz cijevi od visokolegiranog Cr-Ni čelika oznake X5 CrNi 18-10 (HRN EN 10088-3:2015). Navarivanje uzoraka je provedeno automatiziranim TIG postupkom s različitim unosima topline, različitim plinovima za korijensku zaštitu i različitim koncentracijama kisika u plinu za korijensku zaštitu. Nakon navarivanja, provedena je vizualna analiza uzoraka te ispitivanje na rupičastu koroziju sukladno normi ASTM G48-99a i izrada makroizbrusaka. Uzorci ispitivani na rupičastu koroziju su analizirani sukladno normi ASTM G46-94, a na makroizbruscima je provedena kvalitativna vizualna analiza. Na kraju eksperimentalnog dijela, dane su preporuke za pravilno zavarivanje ovisno o koncentraciji kisika i unosu topline. This paper analyses the problematics of TIG welding of high-alloyed Cr-Ni steels with special emphasis on root protection. Purpose of this analysis is to determine the influence of oxygen on the properties of the welded joint, depending on the different parameters of welding. In the theoretical part, the TIG welding process is described, with special attention focused on the welding of austenitic high-alloyed Cr-Ni steels and the potential problems which may occur during the process. The influence of oxygen in root protection on the properties of the welded joint and the influence of the correct choice of shielding gas, considering the type of basic material, are described in details. An overview of the existing systems for root protection and surface treatment methods after welding was carried out. In the experimental part, welding of samples cut from pipes made of high-alloyed Cr-Ni steel marked X5CrNi-18-10 (HRN EN 10088-3:2015) was conducted. The welding of the samples was carried out by an automated TIG process with different heat inputs, different root protection gases and different concentrations of oxygen in the root protection gas. After welding, visual analysis of samples, along with testing for pitting corrosion, according to ASTM G48-99a standard and production of macrographs were carried out. Samples tested for pitting corrosion were analyzed according to ASTM G46-94 standard while a qualitative visual analysis was performed on the macrographs. At the end of my research, recommendations were given for proper welding, depending on the oxygen concentration and heat input. |
