Research And Application Of On-line Cooling Control System For Hot Rolled Seamless Tube

This paper is set in the development of PQF460 hot-rolling seamless pipe on-line controlled cooling technique in Yantai LuBao steel Pipe Co.,Ltd,and the research work is started aiming at the automatic control system which adds cooling controlled equipment after the diameter is decided.Based on the new on-line controlled cooling equipment of rolling line,the systematic research and analysis on the control methods of main technical functions of its basic automation,heat exchange coefficient in the process of steel pipe cooling,temperature field characteristics and cooling strategies,the related research results have applied to production practice and obtained good application effects.The main research contents and results of this paper are as follows:(1)Based on the Yanbao PQF460 hot-rolling seamless pipe on-line controlled cooling equipment,and according to the requirements of controlling cooling technique,hot-rolling seamless pipe position trailing control methods are developed.It achieves the accurate position trailing control under the requirements of the fastest 42s' production rhythm,and practical application indicated that the position trailing error is less than 0.2m;based on this,the transmission control system for on-line controlling cooling stability is established specific to the hot-rolling seamless pipe tilting and rolling transmission control timing.The field practice certified that the steadily operating on-line controlled cooling basic automatic control system satisfied the control requirement of fast-paced production on the production line.(2)According to the heat transfer theory,the heat transfer differential equation in the steel pipe on-line cooling process is set up.Combined with the measured data on the production line of PQF460 hot-rolling seamless pipe,and finite element numerical simulation analysis,the average heat exchange coefficient in the pipe cooling process is required.The calculation results showed that:in the process of pipe controlled cooling,the average heat exchange coefficient on its exterior wall can reach 8000 W/(m2*K);the average heat exchange coefficient on the inner wall is little,among 100-300 W/(m2*K).(3)Combined with the required heat transfer coefficient in the process of hot-rolling seamless pipe on-line cooling,using finite element model,the temperature distribution regularity on the direction of pipe thickness in the cooling process is analyzed.The results showed that:when the wall thickness of steel pipe is below 15mm,the temperature gradient on the direction of pipe thickness is not large;when the wall thickness is above 20mm,large temperature gradient shows on the direction of steel pipe thickness.Therefore,the cooling uniformity on the thickness direction in the pipe controlled cooling process is a significant factor to be considered in the hot-rolling seamless pipe on-line cooling path control.(4)It is the internal requirement for lining products' organization property modulation to establish reasonable control cooling strategies,and to accomplish the uniform control cooling on the hot-rolling seamless pipe in different thickness specifications.Combined with the temperature gradient analysis on the direction of pipe thickness in different cooling paths,three kinds of control strategies of hot-rolled seamless pipe are developed:continuous cooling method,sparse cooling and intermittent cooling methods,which satisfies the requirement of control cooling that thick less than 60mm.(5)Applying the research results to practical production,good application effects were obtained.The production practice showed that the on-line control system for hot-rolled seamless pipe which has been developed runs steadily and smoothly,the temperature control accuracy after on-line cooling is ±20?,satisfying the temperature control requirements for multi-specification products,and the after cooling products satisfy the related performance index requirements.Since the equipment and technology of hot-rolling seamless pipe control cooling came into use,significant effects have showed in terms of product organization control,product comprehensive mechanical property improvement and technical process reduction.