Advances in research and application of underwater welding technology (2)
The water curtain type underwater welding method was first proposed by Japan. The welding structure of the conventional water curtain welding is divided into two layers. The welding joint strength of this method is not lower than that of the base material, and the welding joint surface bend and back bend can reach 180. degree. The torch is light and flexible, but the visibility problem is not solved. The protective gas and the soot turbid and turbid the water in the weld zone, and the welder is basically in a blind welded state. In addition, the distance and inclination of the nozzle from the surface of the weldment are strict, and the technical requirements of the welder are high. In addition, the reverse effect of the steel plate on the high-pressure water is not effective when welding the lap joint and the angle joint. Well, manual welding is very difficult and should be developed in the direction of automation. Recently, Japan has successfully developed a mechanized water curtain type underwater welding mechanism, which can well weld large moving parts under water [5]. For water curtain type local dry underwater welding, Hoffmeister et al. established a relationship between the minimum protective gas flow and heat input and pressure based on reducing the amount of hydrogen adsorption. Mattias et al. designed a new exhaust hood based on the understanding of the principle of the radial aspirator, which reduced the pressure in the welding zone of the hood and obtained a good weld. 1.3 Dry underwater welding 1.3.1 High pressure dry underwater welding Phase 1: With the development, optimization and trial operation of the welding auxiliary equipment, the welding capacity of the plasma arc welding and GMAW welding is demonstrated in the range of 0-250 Bar under the condition that the welding process is all linear welding. At the same time, some position welding was carried out, and an evaluation system for welding mechanical properties and weld microstructure was established. 1.3.2 Normal pressure dry underwater welding 2 Trends in underwater welding technology research (1) Since each welding method (wet method, local dry method, dry method) has its own advantages and adaptations, the situation in which multiple underwater welding methods coexist will exist for a long time. Previous page wire holder is made of high quality 304 stainless steel, It is easier to clean without rust, safe, healthy and durable, Prevent rust or chemicals from contaminating food and damaging health. Suitable for putting the wine glass holder. Goblet Rack,Stainless Steel Goblet Rack,Wine Glass Holder,Wine Glass Rack Shenzhen Lanejoy Technology Co.,LTD , https://www.copper-nut.com
Zhang Xudong et al. studied the underwater dry laser welding. The basic physical phenomena of underwater laser welding were studied by the method of wire-filled thermal welding. The gas nozzle was used to form a local dry space. The protection effect depends on the nozzle structure and Parameters such as gas flow rate and nozzle outer diameter have a significant effect on the protection effect. The mechanical properties of the underwater weld under good protection conditions are consistent with those in the atmosphere.
Compared with dry welding, the local dry method does not require a large and expensive drainage chamber, and the adaptability is significantly increased. It combines the advantages of both wet and dry methods. It is a more advanced underwater welding method and the focus and direction of current underwater welding research. Partial dry underwater welding can directly obtain the joint quality close to the next step. At the same time, due to the simple equipment, low cost and flexibility of wet welding, it is a promising underwater welding method.
Dry welding is a method in which the water around the welded part is removed by gas, and the submersed welder is welded under completely dry or semi-dry conditions. When performing dry underwater welding, it is necessary to design and manufacture a complicated pressure chamber or working chamber. . According to the pressure in the pressure chamber or the working chamber, dry underwater welding can be divided into high pressure dry underwater welding and normal pressure dry underwater welding.
The dry underwater welding test is generally carried out in a high pressure simulation chamber, and the welding process qualification test can also be carried out in the pressure chamber. The Harbin Welding Research Institute began to study dry-water underwater welding since the 1980s. It first carried out experimental research work in the simulated experimental cabin, and then went to the actual site for verification. Chen Jinhong and Xiao Zhiping used high-pressure dry welding to repair the water pipe in Guangzhou, which made the underwater welding technology in China gain new development [7]. The underwater high-pressure welding chamber of CENPES Center in Brazil consists of six parts: environmental control room, gas supply room, gas recovery room, high pressure room, electrical control room and automatic welding machine. High-pressure automatic TIG, MIG, FCAW, SMAW welding processes are available. The short-circuit transition behavior of the flux-cored arc welding of the 600-100 m water depth in Germany, the influence of the power output power and the gradient on the droplet transfer, the reaction mechanism of the molten pool, the influencing factors of oxygen adsorption and the selection of shielding gas were carried out by the GKSS center in Germany. In the study, the research results were applied to the design of high-pressure welding chambers and achieved satisfactory results. In the past seven years, the Cranfield University Welding Engineering Research Center has applied automatic welding technology to deep water welding at a water depth of 2500 m equivalent to 250 Bar [8,9]. This deep water high pressure welding study is carried out in three stages:
Phase 2: Using the orbital welding equipment, further plasma arc welding and GMAW welding experiments were carried out for C-Mn pipe steel and 13Cr steel, and arc monitoring technology was developed for deeper microstructure and mechanical evaluation.
Phase 3: At this stage, Cranfield University is focusing on hot-slag welding and high-pressure GMAW welding for specific pipeline maintenance work, and further optimizes the second phase of the process to make it more complex. Operating parameters. The position welding of different occasions - flat welding, vertical welding, overhead welding and various welds are studied to reduce the difficulty of deep water welding. The welding research team concluded that the high-pressure GMA welding provides a feasible connection method in the water depth range of 400m to 2500m, which can repair the strip welds in deep water pipelines and supports without any problems. It can guarantee the sealing performance of the hot water slag connection of deep water pipeline.
Since the depth limit of human saturated diving is 650m, it is difficult for skilled deepwater welders to train. In order to realize deep water welding and underwater welding automation, underwater automatic orbital welding systems and underwater welding robots have developed rapidly. TIG welding has the characteristics that the melting rate increases with the increase of pressure, the low hydrogen adsorption rate, the automatic welding can be realized, the magnetic field and the corresponding power source can effectively control the arc, and the earliest is used to develop the underwater high-pressure rail welding system. Orbital high pressure TIG welding is a mature and currently popular submarine pipeline welding technology. At present, the underwater high-pressure rail TIG welding system mainly includes the OTTO system of Aberdeen Subsea Offshore Ltd, the THOR-1 system of Comex, and the IMT system of Norsk Hydro and SNITEF.
The National “10th Five-Year Plan†863 Program “Underwater Dry Pipeline Maintenance System†undertaken by Beijing Institute of Petrochemical Technology is progressing smoothly. It is adapting the welding power supply and conducting welding simulation experiments. Cable length under normal pressure. It can still be welded normally above 200m. The high pressure welding test chamber is being manufactured and will be delivered in the near future. Research work on underwater high-pressure double-layer automatic welding machines is also underway.
The welding takes place in a sealed pressure chamber, the pressure in the pressure chamber being equal to the atmospheric pressure on the ground, independent of the ambient water pressure outside the pressure chamber. In fact, this type of welding is neither affected by water depth nor by water, and the welding process and welding quality are the same as those of land welding. The cost of dry-pressure dry welding equipment is more expensive than high-pressure dry-process underwater welding, and there are more welding assistants, so it is generally only used for deep water and welding important structures. The biggest advantage of this method is that it can effectively eliminate the influence of water on the welding process. The welding conditions are exactly the same as those in the land welding, so the welding quality is also the most guaranteed. At present, there are few applications of atmospheric dry dry underwater welding technology, and there is no difference between welding process and welding metallurgy and onshore welding. TDS Company of the United States is developing a device capable of performing atmospheric dry dry underwater welding at 600m deep water for welding pipes with a pipe diameter of 900mm and a wall thickness of 32mm. The dry gas chamber is cylindrical, with a diameter of 2.4m and a length of 3.66m. The ends are oval. At present, there is no normal pressure dry underwater welding equipment in China.
(2) The quality of wet-water underwater welding is mainly affected and restricted by factors such as underwater welding rod and underwater flux-cored welding wire. Britain, the United States and other countries have developed a variety of high-quality underwater welding rods, and we should accelerate development. High quality underwater electrode, underwater flux cored wire. Usually, the water depth of wet welding is less than 100m. The current efforts are to achieve a breakthrough in the wet welding technology of 200m water depth.
(3) Based on advanced technology, some progress has been made in the monitoring of the welding process, mainly in the automation and intelligence of underwater dry and local dry welding. For example, telemetry remote control technology has achieved preliminary application in underwater welding. Remote control telemetry technology can be used to achieve welding processing in underwater installation inspection. At present, progress has been made in installation and maintenance of underwater pipelines [10], recently South China University of Technology Liao Tianfa and others used VC++ programming to implement serial communication (SPC) for remote control of weld seam alignment before underwater welding and weld seam tracking during welding [11]. The automated orbital welding system and the underwater welding robot system automatically monitor the welding process, provide good welding quality, save man-hours, and reduce the diver's work intensity. However, there are still many problems in the current underwater welding robot system. The flexibility, volume, working environment, detection and monitoring technology and reliability have yet to be further developed and improved. This is our current direction.
(4) The emergence and development of analog technology for the production of welding
The development of the "theoretical-numerical simulation-production" model has created conditions for welding technology to undergo a leap from experience to science, from qualitative to quantitative. At present, the simulation of the temperature field, flow field, weld pool and weld stress of the on-shore welding process has made great progress. The simulation of welding arc has also been studied, but the simulation research on underwater welding is still lagging behind. Hans-Peter Schmidt et al. in Germany conducted a simulation study on the underwater high-voltage welding arc with a current in the range of 50-100A and a pressure of 0.1-10Mpa and tungsten argon protection. The mathematical method was used to solve the conservation equation and the temperature was obtained. Distribution of speed, pressure and current. The measurement of the arc temperature agrees well with the theoretical distribution. With the development of the offshore oil and gas industry and the advancement of China's ocean engineering to the deep sea, we should pay attention to and accelerate the numerical simulation research on underwater welding. At present, we are also working on the numerical simulation of welding arc in high pressure environment.
(5) Computer simulation is a very useful technology, which has been applied in the research of welding process development, welding equipment development and control system improvement [12]. Dag.Espedalen et al. carried out simulation research on high-pressure dry underwater welding. Firstly, SolidEdge was used to build a 3D model of the welding chamber and welding robot, and then converted into an I-grip motion model to prepare a suitable control program for the entire submarine pipeline. The maintenance operation process is demonstrated [13]. Through welding simulation, it is helpful to conceive new solutions and to find problems in advance, which is an area that we should study in the future. .
China leading manufacturers and suppliers of Wine glass holder,Goblet Holder, and we are specialize in Wine Rack,Hanging Wine Rack, etc.