High Strength And Toughness X60 Pipeline Steel The ASP Process Optimization And Strengthening Mechanism

X60 pipeline steel plate was high grade hot rolled product which must have high strengh, toughness, fatigue resistance, tearing resistance, corrosion resistance and welding capacity. The X60 pipeline steel plate was developed successfully in ASP product line of Jinan I&S Group and during the development rational chemical constitution and procuction control technique were adopted for example low carbon, low silicon, high manganese, low sulfur and TMCP technology, further more five different chemical compositions and corresponding producton process control methods were designed based on the respective requirement of customers.In order to guarantee that the thick specification of X60 pipeline steel plate obtains the good comprehensive mechanical properties, and solve the problem of insufficient thickness of the intermediate casting blank and the little deforming of under recrystallization temperature The ASP prodution line had 6 finish rolling stands but the F2 finish rolling stand was truncated to raise the single pass reduction and total reduction which occurred under recrystallization temperature, so there was little deforming occurred at part-recrystallization temperature and the duplex grain structure was avoided. Otherwise to gain excellent mecanical property of X60 pipeline steel some adjustments were carried out that included lowering the finishing temperature and final cooling temerature and introducing forepart laminar cooling.During the development there was one sticking point to be regarded which was the higher yield ratio of thin steel strip and a great deal of tentative plans were put in practice to settle it. Finally the answer was found that was a combination of producton process control means which consisted of setting reasonable finish rolling start temperature, finish rolling end temperature, Useing two section of cooling-down method, closuring first three groups of cooling water coarse adjustment section, to expand the time of the rolled piece in the high temperature, reduce the cooling rate of the coarse adjustment stage, causing the water volume of laminar cooling in the coarse adjustment section and the delicate adjustment realized the reasonable combination, optimized the laminar cooling craft; Moreover, "the hot tail" craft was adopted and the performance of the steel volume was consistent..In order to inquire into the X60 pipeline steel plate's organizational structure to the performance the influence mechanism which produced in ASP product line of Jinan I&S Group, The influence of casting blank quality, microstructure, non-metal inclusion and educt on the product performance was studied. Based on the study of strengthening mechanism it was indicated that grain refining, dislocation hardening, solid solution strenghthening and deposit intensification were all acting and grain refining and nanometer deposits intensification were dominating.