| Hydrogenation reactor is typically used in high temperature, high pressure and high corrosive environment, the presence of hydrogen and other environmental. In order to meet the requirements of using, domestic chrome-molybdenum steel is generally used as a material of the barrel and the cylinder wall cladding layer of corrosion resistant metal. With the high deposition rates of the high-speed electroslag welding, we can greatly improve production efficiency, and there are obvious economic benefits because of the less consumption of welding strip and the flux at the same time. Therefore, high-speed electroslag welding technology has been more and more studied in the protection measure of the inner wall of pressure vessel. This paper refers to the service environment, the structural characteristics and cost and other factors of hydrogenation reactor, using the high-speed electroslag welding, and E309 LNb surfacing material, surfacing single-layer 347 austenitic stainless steeling the Hydrogenation reactor cylinder with 12Cr2Mo1 R test plate, and annealing treatment after the welding; then we evaluated the high-speed electroslag welding by chemical analysis, lateral bending test to measure ferrite content and corrosion resistance etc; Finally, we used X-ray diffraction analysis, optical microscopy analysis, spectrum analysis, studied on the microstructure and corrosion resistance of the welding test plate in 690 oC long annealing process by measuring the ferrite content to provide basic data for the hydrogenation reactor design, manufacture, use, maintenance.High-speed electroslag welding procedure qualification results showed that the ferrite content, chemical composition can meet the relevant technical requirements, through the organization structure of the test resulting weld overlay cladding layer meet organizational requirements. Experimental scoliosis and corrosion tests are qualified, welding method described in this paper can be used in the surfacing layer performance standards, meet the relevant technical requirements.The results annealing welding test plate structure are showed by XRD, SEM and other testing methods, it turned out that during the annealing process, the microstructure of austenite microstructure is barely changed. And the EDS analysis showed that the grain boundary layer surfacing Nb carbide is formed, which ensures the process of using carbide weld overlay capability against even more sulfuric acid. The microstructure of the substrate can be obviously seen that after annealing for 72 hours, the microstructure of the tempered bainite is lost during the annealing time and precipitated particles at the same time. And the precipitated particles by EDS analysis, showed that the carbide is Mo. With the annealing, element diffusion happened on both sides of the fusion line because of the concentration gradient of Fe?C?Cr?Ni?Mo?Nb elements on both sides of the fusion zone and formed a C segregation layer in the vicinity of the fusion line, and had a enriched region of Nb, Cr, Mo, Ni near the fusion line.Annealing corrosion resistance findings surfacing test panels showed that with the increase of annealing time, there is a slight increase in the corrosion rate after surfacing from 8 h ~ 32 h to stress annealing, and remained stable, and corrosion resistant decreased a little, but remained stable too. Stress relief annealing process corrosion rate decreased rapidly from welded to 8 h ~ 32 h, the corrosion resistance is improved rapidly, from surfacing EDS analysis can be seen that with the start of annealing, Nb has been segregated at the grain boundary, also will increase the corrosion resistance, which is consistent with the results obtained EDS.Microhardness results during annealing of the sample showed that with the increase of annealing time, the ferrite content showed a downward trend in the cladding layer. It can be seen from the distribution of the hardness that the microhardness overall downward trend during the annealing time. Near the surfacing layer side, there will be a very small range of great hardness peak from the fusion line within about 0.1 mm ~ 0.3 mm range, mainly because of the diffusion of C. C diffused into Surfacing layer E347 during the annealing process and formed a carbon layer, this layer leads to an increase in the carbon content and the carbon content in this layer is much higher than the surrounding carbon content, also means that the hardness in this layer increases. This is consistent with the EDS analysis. |
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