Development Of Continuous Heat Treatment Device For Pipes

As a kind of economic and efficient steel, steel pipe has been widely used in the national economy. With ultra fast cooling as the key technology, the new generation TMCP has been more maturely used in sheet, strip, wire, H-shaped steel and other fields. Due to the pipe geometry and specifications, rolling process, equipment units and other factors, the application of controlled cooling technology in steel pipe production is relatively less. It’s still at the exploratory stage of development.In order to promote the application of new generation TMCP technology in the field of steel pipe production, Baoji Steel Pipe Plant and Northeastern University signed a "research and development of continuous heat treatment device for National Oil and Gas Pipe Engineering Technology Research Center" project. Through the unique design of the nozzle structure of the cooler, they developed oblique slit nozzle system for steel pipe ultrafast cooling, and successfully applied to the pipe continuous heat treatment device. The oblique slit nozzle system solved the cooling rate small, uneven cooling problems in steel pipe controlled cooling process. Pipe continuous heat treatment device combines induction heating, resistance furnace insulation, ultra fast cooling controlled cooling, spray and drenching quenching and other features, and can treat required specification steel pipe in a variety of heat treatment process. It provides device protection for people to optimize the production process, improve the micro structure and properties of steel pipe, and develop new varieties of high-quality steel pipe.The content and conclusions of this thesis are as follows:(1) According to the needs of steel pipe heat treatment process, continuous heat treatment device successively set a medium frequency induction furnace, high temperature resistance furnace, ultrafast cooling device, spray and drenching quenching device, low temperature resistance furnace and other equipments. The entire process line designed compactly, high automation and easy to operate. According to process requirements, people can select the desired device combination to meet the needs of multi-function heat treatment of steel pipe. (2) With the mechanical structure drawings and pictures of equipment and parts unit, an elaboration was given to heat treatment process, equipment layout, structure principle and function characteristics of each monomer. In addition, the structure and function of water supply system, hydraulic system, temperature tracking system was briefly described, and some key designed parameters and equipment of water supply systems were calculated and selected.(3) In order to solve the problem that resistance heating rate is small, prone to iron oxide and medium frequency induction heating speed is fast, but holding time is short, frequency induction rapid heating+resistance furnace hot insulation way has been used in continuous heat treatment device, and improved the quality of steel pipe heat treatment. To enable different pipe heating temperature uniformly. the height of the inductor can be adjusted. Resistance furnace using the side door open design to ensure rapidly loading and unloading pipe, and effectively reduce the temperature difference between the front and rear of baked pipe.(4) In order to solve the problem that controlled cooling technology is relative lack in pipe research and application, ultrafast cooling technology has been applied to continuous heat treatment device. Northeastern University independently developed the ultra fast cooling annular oblique slit nozzle unit. Due to the special design, the nozzle can form high-pressure cooling water in a larger annular hole. If pipe diameter is larger than hole diameter, the pipe will full contact cooling water and occur nucleate boiling cooling when pass the nozzle unit. This cooling way has a large cooling rate and evenly cooling result. Furthermore, the height of annular nozzle units can be adjusted up or down to enable different pipe cooling uniformly.(5) On the basis of equipment layout and control tasks, the principles and structures, hardware configuration and functional task allocation of automatic control system have been rationally designed. Relying on control system hardware structure, Siemens automation and graphical programming software STEP7and monitoring software WinCC have been selected to build software platform for device real-time monitoring and control. For the convenience of those who view the data during the heat treatment, WinCC SQL2005database platform has been used to build a custom database which can store critical process set parameters. In addition, control functions that combine with WinCC have been applied to program a data archiving and report printing system for people to record test results.(6) By the specific heat treatment test, a detailed description of pipe heat treatment process steps was given; Parts of ultra fast cooling test results were analyzed. Test results show that the spray cooling rate of ultra fast cooling device meets the requirements of pipe controlled cooling process.