Very broad market prospects of nuclear power valve, but valve manufacturing technology behind nuclear valves and high parameters valve depends mainly on imports, with the construction of nuclear power in China gradually into the fast lane, the nuclear localization of complex "has become more and more intense. Therefore, to master the key technology of nuclear valves and high parameters Valve Manufacturing, to retain the domestic market, to explore the international market, has been a priority. According to statistics, the world's nuclear power plant accident caused a failure due to the valve means sealing surface accounted for 1/4 of the nuclear accident. Therefore, very strict requirements for nuclear valve materials and manufacturing processes, in particular the nuclear valve sealing surface. This is because the sealing surface is not only because the valve is periodically opened and closed by abrasion, extrusion and impact action, but also because of which the working environment and the medium and subjected to high temperatures, corrosion, oxidation, and other effects, so should have good comprehensive service performance.
Nuclear power valve sealing surface strengthening process overview
Commonly used welding technology welding nuclear valve sealing surface, and to ensure the the valve sealing surface welding quality and improve the efficiency of surfacing production depends not only on the surfacing material, and also depends largely advanced welding technology and high The efficiency of automated welding equipment. Valve surfacing methods of valve sealing surface welding technology research began in the early 1960s, after 40 years of development, from the to SMAW and oxygen - acetylene flame surfacing and other non-automated, low efficiency surfacing mainly developed to the widespread adoption of efficient, automated surfacing methods, such as flame surfacing, plasma arc surfacing as well as laser cladding, etc.. Advanced surfacing technology countries competing research, which was undoubtedly the most promising laser cladding technology. The technology rise in the 80s of the 20th century, and it is the use of a laser beam having a high energy density so that certain special properties of the material fast melt condensate at the surface of a substrate and with the substrate forming metallurgical combination, constituting with the base body composition and properties completely different from the high-performance alloy cladding layer. Table 1 lists several powder thermal spraying, arc, plasma spraying, laser cladding, the technical characteristics. Visible laser cladding layer and the substrate is completely metallurgical bonding, low dilution, high yield.
Laser cladding technology and its applications in nuclear power valve
The laser melting 筱 technology features
Laser cladding process has accurate control of heat input, high welding speed, fast cooling, heat distortion, thickness, composition and dilution rate, good controllability, get organized dense, high-performance (such as wear resistance, resistance to corrosive energy, oxidation resistance, thermal barrier performance, heat pitting and erosion wear, etc.) of the alloy surfacing layer with traditional surfacing methods do not have the advantage of laser cladding technique is applied to the sealing surface enhanced by widespread attention at home and abroad, and has been applied in many fields.
Shi-Hong Shi compare laser cladding, plasma welding, dilution rate and morphology of the cobalt-based alloy surfacing layer flame surfacing ways. Laser cladding dilution rate is lower than plasma spray layer and flame surfacing layer. Laser cladding layer solid melting bonding layer thinnest, narrowest width of the heat affected zone, is 1/8 to 1/12 of the plasma spray layer heat-affected zone, is the width of the heat affected zone of the flame surfacing layer 1/15 to 1 / 20, and the grain of the laser cladding tinier. Sun Yihua comparison and analysis of high chromium iron-based alloy laser cladding layer and the surfacing layer quality and performance, the same tiny laser cladding, high hardness, good wear resistance. Laser cladding layer a smaller dilution and fine organization, the melt layer design elements give full play its due role. Was determined that the laser melting layer microhardness, corrosion-resistant, anti-friction and wear performance are better than or much higher than the plasma and flame surfacing layer.
The application of laser cladding technology in nuclear power valve
Due to the rapid development of nuclear power in support of national policy and the needs of the market economy, to grasp the development of the high parameter nuclear power valve technology is imminent, highlighting the advantages of laser cladding surface hardening technology and good results in practical applications, many scholars are working to in its application to the study of nuclear power valve sealing surface enhanced.
Gordon Wong Cladding Co-based alloys using laser welding technology try in the nuclear valve disc sealing surface on the austenitic matrix, and compared with plasma spray layer and arc surfacing layer, the test results show that enhanced laser cladding layer smooth surface, a laser cladding layer can reach 3mm. Melting layer tissue compared with other conventional welding technology, the rejection rate of less than 5%, the grain refinement, dilution rate, high yield, the lowest rate of corrosion in acid, alkali medium. Shi-Hong Shi also tested the hardness and wear resistance of the coating, laser cladding layer average hardness HV740 ~ 860, while the plasma arc surfacing layer average hardness HV520 ~ 560. 2 strengthening process the surfacing layer after 3000 shocks wear were 1.2mg and 2.53mg.
EPRI In conclusion, a variety of valve sealing surface enhancement technology test that highlight the advantages of laser cladding can effectively reduce the thermal residual stress reducing cracks followed to reduce the dilution of the coating and substrate, which can reduce the accumulation layer Number without lowering the wear resistance of the coating. The literature using solid-state laser cladding Norem 02 and Setliet 21 wire, good wear resistance of the cladding layer.
Fully visible laser cladding technology is a promising advanced surface treatment technology, an effective way to improve the quality of the valve sealing surface, and has been successfully into the application stage. Using laser cladding technology to control the composition of the cladding layer and reasonable choice of the cladding process, the substrate can strengthen the performance of the technology is difficult to get other surface, and give full play to the potential of raw materials.
Article explains:
Paper series site or of self-publish, the site post aims to deliver more information to the visitor.
2, involving work content, copyright and other issues, please contact site within 30 days, we will be the first time to make appropriate treatment! About copyright issues, please contact: 13515194999
3, Zhuanzhai this article please indicate from: Jiangyin City Oulei Si valve valve repair factory www.olschina.com
4 other links:
Valve repair valve repair valve repair equipment valve grinding machine imported valve repair power station valve repair control valve maintenance |
