Development of Technology for Microstructure Control during On-line Heat Treatment Process for Hot-rolled Seamless Steel Pipe

In the conventional manufacturing process for the hot-rolled seamless steel pipe,the pipe as rolled was air-cooled down to the ambient temperature. And due to absence of proper on-line microstructure control of the pipe,properties had to be controlled depending on addition of much more alloy elements,and the subsequent heat treatment process. Described here in the paper were the progresses of development and application of the controlledcooling technique for the hot-rolled seamless steel pipe, and the applications of improvement and control of histomorphology,microstructure refining and cooling route control. As for the currently-used microstructure control during the manufacturing process of hot-rolled seamless steel pipe,emphases of further research were proposed, focusing on the improvement of cast billet quality and fine grain homogenization. The new technological system of microstructure control for the whole manufacturing process was expected to be set up by means of taking the controlledcooling technique as the key,optimizing chemical composition,and comprehensively using the strengthening mechanism. Then the potential of the materials can be further tapped, and finally the overall improvement of product quality and reduction manufacture for the hot-rolled seamless steel pipe can be achieved.