The effect of SiC addition to structural steel weld metals

ABSTRACTM.Sc.ThesisTHE EFFECT OF SiC ADDITION TO STRUCTURAL STEEL WELD METALSAhmet TESL MOĞLUAfyonkarahisar Kocatepe UniversityGraduate School of Natural and Applied SciencesDepartment of Metal EducationSupervisor: Asst. Prof. Şükrü TALAŞToday, improving the properties of existing materials is a prime instead of developignew materials. Microstructural properties of materials and the effect of improvement onmicrostructure is very important for such materials. Microstructure of materials isaffected by methods and techniques during the manufacturing. The effect ofmicrostructure on the properties of materials are well known by Hall-petch equation.This equation shows that the strength is increased by the reduction in grain size. We canconclude that materials with finer grains can have higher strength values.In this study, the effect of SiC (Silicon Carbide) on microstructure of weld metal hasbeen investigated using standard metallographic techniques. SiC added weldingelectrode was used to weld on commercial steel at three different welding current, andmicrostructures at the beginning, middle and the end of the weld seam have beeninvestigated. Since heat treatment has a substantial effect on the grain growth the size ofSiC and grain size have been investigated following the heat treatment. Three different6heat treatment were applied to the specimen: 400 ˚C, 800 ˚C and 1200 ˚C. In the firsthalf of our study, grain size measurements have shown a decrease with respect toincrease in weld current. In the second part of our study, following the heat treatment at400 ˚C, there was no substantial change in grain size at all weld currents. When 800 ˚Cheat treatment was applied to the middle part of the weld the grain size became finer insize. The end of the weld seam has produced sam! e effect as 800 ˚C heat treatmentfollowing the heat treatment at 1200 ˚C.2007, 78 PagesKeywords: Structural Steel, SiC, Heat treatment.7