Diesel Exhaust Valve Automatic Surfacing Technology And Quality Control

Currently domestic Marine low-speed diesel exhaust valves were widely adopted cobalt-based alloy surfacing. By using this method, welding products were easier to appear rupture, crack, surfacing layer falls off, etc. These problems can be solved by using Ni-based alloy surfacing technology, but the technology had been monopolized by many developed countries, thus developing Ni-based alloy surfacing exhaust valve technology becomed very urgent. Based on this, a process research of welded exhaust valve was put forward.Base on the material and structure of the workpiece, the welding ability was analysis. The welding area fusion mechanism.was analyzed according to the macroscopic metallographic testing, hardness testing and microstructure metallographic scanning testing. In order to guidance welding process through the weldability and fusion mechanism research.Each of arc welding robot system composition was selected,the coordination movement of welding positional and precisional experiment was designed. Through the orthogonal experiment design, the exhaust valve surfacing welding process parameters was optimized and welding technology parameter was determined. The multilayer surfacing which weld bead spacing for weld width of 30% was optimized. Weld smoothness and fusion was good.According to the characteristics of the workpiece structure, the simulator and experiments were designed, the translation amount of simulated sample surfacing appearance influence was studied. And then a reasonable sermons way was determined. Comparing the simulator and exhaust valve differences, process scheme and welding sequence was formulated and optimized. The domestic first high quality exhaust valve was completed.Several of the possible affecting factors of girth weld appearance which contains weld appearance, metal transition, arc starting and off, amount of overlap and interpass temperature was Controlled.The weld appearance was optimized. A small amount of 2% active gas CO2 can reduce molten pool surface tension, improved weld appearance, affected the metal transition on fusion.According currently used short-circuit transition way, control method and parameters were proposed. The arc starting and off and its forming and lap quantity problem were controlled. The diluted rate of the hardfacing layer was controlled. For welding appeared defects in the process, such as incomplete fusion, the model and control method was put forward and finally improved the welding quality. The exhaust valve quality was evaluated with visual inspection, penetration inspection and ultrasonic inspection after welding,. Welding surface appeared golden and flat with visual detection, without undercut phenomenon. No defects existed with penetration inspection test. There was no exceed requirements of defects in the whole layer with ultrasonic test, Product quality accorded with exhaust valve quality standard and it belonged to qualified product.