SEARCH RESULT

A number of studies have been conducted to reduce the use of fossil fuels and gas emissions in power generation industry. In recent years new material technology has emerged depending on this quest. CrMo steels are widely used at power plant constructions as piping and tubing. They are known as heat resistant materials due to high creep strength, as well as their low thermal expansion and high conductivity. During the few decades, high chromium steels have been developed by alloying with elements such as W, Ni, Nb, V, Ti as a result of extensive studies carried out in some countries with the participation of various project partners. In Europe E911 steel was developed which includes 9% Cr, 1% Mo and 1-2% W. E911 steel has martensitic microstructure under air cooling after normalizing. Therefore it is used as tempered condition following normalizing. This paper presents microstructural and mechanical characterization of E911 weld metal. The types and transformations of phase and microstructures of all-weld metal have been investigated through scanning electron microscopy, optical microscope, x-ray diffraction analysis. The elemental analysis of weld metal was determined by x-ray fluorescence and mechanical tests of the weld metal were carried out. In this study it was observed that the microstructure of E-911 steel consisted of tempered martensite, and in some regions δ-ferrite phases were present. According to examined of thermal analysis, in the heating A1, A3, Tcurie temperatures are 850, 890, 750 oC respectively and in the cooling Mf temperature is 650 oC, Ms temperature is 690 oC. When X-ray analysis was examined, carbides (Cr7C3, Cr23C6) in the microstructure were detected. In SEM examinations, in addition to these carbides, Mo2C, W2C and VC were observed inside grain and grain boundary. The Brinell hardness test was carried out at room temperature and under a load of 187,5 kgf. The average Brinell hardness is 230 HB. The micro hardness tests were applied for 20 seconds under 50 gram load. The average micro hardness of δ-ferrite zone in microstructure was determined as 165 HV (~ 164 HB). Yield strength, tensile strength and elongation were determined as 550 MPa, 712 MPa, % 18 respectively according to tensile test results at room temperature.

International Iron & Steel Symposium
UDCS

Emin Salur Mustafa ACARER Fikret KABAKCI Selcuk KESKINKILIC Filiz KUMDALI ACAR

High CrMo (W) steel is widely used in ultra-super critical (USC) power plant applications operation temperature up to 620 oC. The steels and their weld metal are used for tempered condition. Tempering temperature must be below Ac1 temperature of the weld metal. Welding of the steel is generally applied by shielded metal arc welding (SMAW) with multi-pass process. In this study, stick electrodes were fabricated for high chromium tungsten steel in Gedik Welding Company. Microstructure and mechanical properties of the all weld metal produced by the stick electrodes were investigated following tempering at 760 oC for 4h. Microstructure was characterized by optical microscope (OM) and scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS). Differential scanning calorimetry (DSC) analyze was used to determine transformation temperature of the weld metal. Hardness measurement, tensile test and charpy impact test were carried out. Fracture surfaces of the samples were also investigated via SEM.

International Iron & Steel Symposium
UDCS

Fikret KABAKCI Mustafa ACARER Selcuk KESKINKILIC Filiz KUMDALI ACAR İsmail Hakkı Kara