One of the problems in producing the welded joints of complexly-alloyed heat-resistant steels is the providing of the required level of weld metal impact toughness. The improvement of its ductility and toughness is attained by a postweld high-temperature tempering using the modes regulated by the developer of welding electrodes. In case of welding of an experimental high-chromium martensite steel by electrodes Thermanit MTS616 (10Kh9V2MFB type) with account for conditions of its fulfillment, the heat treatment was required by 30-40 o C lower than that usually applied for welds of the mentioned type. The effect of modes of the manual arc welding and duration of tempering at 730-720 o C on hardness and impact toughness of weld metals was determined. Intervals of holdings were found in tempering, during which the secondary hardening was observed. The modes were selected, providing the required level of impact toughness of welds (impact energy KV ≥ 41 J). It is shown that alongside with the selected duration of temperature the important factor, providing the increase in toughness of the deposited metal, is the application of multi-pass welding at the reduced energy input. 11 Ref., 4 Figures. K e y w o r d s : heat-resistant martensite steel, manual arc welding with covered electrodes, weld metal, high-temperature heat treatment, tempering mode, hardness, impact toughness Received 29.02.2016Figure 4. Temperature versus holding at high tempering to provide the required impact toughness of metal of welds in manual arc welding: 1 -recommendations of electrode manufacturer; 2 -results of experiments
Manufacture of exhaust-heat boiler of steam-gas plant of 150 MW capacity for Alchevsk Iron & Steel Works allowed using the secondary metallurgical gases as alternative to the nature gas. Its modular design, high closeness of arrangement in heat-exchange blocks of thin-walled small-diameter pipes of heating surfaces decreased the dimensions of the plant and increased its efficiency factor up to 44.6 %. Due to a narrow gap between the pipes the butts of these pipes occurred to be hard-to-reach for welding and control. This caused the increase in the amount of inadmissible defects in welds, and also made the welded joints of pipes almost not suitable for the repair. The making of welded joints on different stands by applying methods of argon-arc and combined welding allowed improving the quality, gave an opportunity to perform repair and to realize their X-ray, ultrasonic and visual-optic control. The manufactured heat-exchange blocks withstood the hydraulic test without appearance of leakage in welded joints, were installed and put into service. Significant saving of fuel for industrial enterprises of the metallurgical industry is the application of secondary fuel gases, such as blast furnace, converter, coke gases, forming during the metallurgical processes. Their application as a fuel, alternative to natural gases, was feasible by using steam-gas plants (SGP) of a combination cycle. In these plants the gases are mixed to form the safe concentration and required heat-generating ability and are burnt out, and the generated heat is converted into mechanical and electric energy. At Alchevsk Iron & Steel Works (AMK) a complex of SGP of total power of 300 MW (two blocks of 150 MW) was manufactured. The designing of SGP was made by the Mitsubishi Heavy Industries Company (Japan) with participation of Industrial Union of Donbass [1]. Construction of steam-gas electric plant for utilization of blast furnace, converter and coke gases (similar to AMK) was planning at F.E. Dzerzhinsky Dneprovsky Iron & Steel Works. The Iron & Steel Works «Azovstal» also announced about implementation of two SGP [2]. At AMK the operation of two steam-gas blocks allows providing the almost full need in electric power, keeping the standards for harmful gas blow-outs, accepted in EU.One of the SGP main components is an exhaust-heat boiler, which was designed from heatexchange modules of the evaporator, steam superheater and economizer.The heat-exchange modules were assembled of header panels, each of them has inlet and outlet headers (Figure 1, a, b) with three rows of A, B and C holes on the lateral surface, in total 40 pcs in each one (Figure 2, a). Concentrically to these holes the connecting pipes are welded-on by fillet weld, which in turn are joined by butt weld to pipes of heating surfaces (Figure 2, b). The fillet joints of connecting pipes and butt joints of pipes of heating surfaces were made with a full penetration. Connecting pipes in the middle and edge row were bent at 25 and 50° angle, respectively. Diameter of pipes and connecti...
Carried are the investigations on development of low-carbon chromium electrodes of 05Kh6MF type. Effect of coating composition on carbon content in deposited metal of Kh6M type was investigated. It is determined that joint introduction of chromium and zirconium oxides in 5-10 wt.% amount at simultaneous removal of marble from the coating is the most efficient for carbon reduction. Slag system of fluoride-magnesium oxide type coating was developed, providing reduction of carbon content in the deposited metal to 0.04-0.06 wt.% at sufficiently low content of diffusible hydrogen. Electrodes of ANL-10 grade for welding of dissimilar joints of chromium martensitic steels of 10Kh9NMFB type and chromium-nickel austenitic steels of 10Kh18N10T type were developed on its basis. The electrodes provide for stable arcing, insignificant spattering, good weld formation in all spatial positions and easy separation of slag crust. 12 Ref. , 3 Tables, 2 Figures. Figure 2. Effect of chromium oxide on content of residual (1) and diffusible (2) hydrogen in deposited metal 05Kh6MF K e y w o r d s :
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