Effect Of Processing Parameter Of Controlled Cooling On Microstructure And Phase Transformation Of Wire Rod ER70S-6

With development of welding industry of China , the automatic level of welding will be enhanced step by step. The use of high efficiency solder materials will increase quickly. As a trend, CO₂ gas shielded welding will be used more and more widely. As the current international prevalent products , the raw materials of CO₂ gas shielded welding are often adopted ER70S-6 of USA standard or YGW-11 of Japan standard. It was not too long that the domestic factory had been to produce high speed rolled wire rods ER70S-6,there was a little problem more or less. So it is very important to research the effect of processing parameters of controlled cooling on phase transformation and microstructure.In this thesis,the chief research target is about the continuous cooling transformation (CCT) curve of wire rods ER70S-6 of xiangtan Iron and Steel Company .The primary content include:(1) the dynamic CCT cure of cooling after hot rolling,and the effect of different cooling rate on the CCT curve.(2) Via the analysis on the microstructure of hot simulated specimen,and combined with the CCT curve,make certain that the relation between controlled cooling and microstructure performance and mechanical properties on room temperature.The continuous cooling transformation(CCT) curve was constructed chiefly by means of dilatometry,and combined with metallography to exact fix on the phase transition points of different cooling rate.By the use of THERMECMASTOR-Z ,let the specimen cooling in the inert gas on the different cooling rate,and the temperature-dilatation curve was measured. Base on the curves characteristic points,we can make certain the phase transformation points(Fs,Ps,Bs,Ms),and the dynamic continuous cooling transformation(CCT) curve of steel has been investigated.At last, the rules of processing parameters of controlled cooling on microstructure, quantity of ferrite,crystalline grain size of steel were studied also.All these results will give a valuable theoretical reference to practical manufacture.