Research On The DQ-T Production Of New Technology For Strategic Petroleum Storage Tank Steel

With the development of economy, the consumption and import of petroleum are increased year by year. Strategic petroleum reserve to protect national economic security has become a major issue. We have to product large floating roof tanks with a single storage volume greater than100,000m3in order to construct for bascal national strategic reserve, in which requires steels with high strength, good toughness and combination with good welding property, and industrial production is difficult. Heretofore, China always used steel plates made in Japan to build petroleum storage tank, it’s expensive and could not guarantee the supplying time. In order to reverse this negative situation as soon as possible, the National Development and Reform Commission urges to manufacture domestic petroleum storage tank steels in China, to meet the strong needs of the domestic market. Considering the welding process of large-scale tank’s, when the plate thickness is21mm was used V-groove and Vibrative Electron Gas Arc welding, and due to this kind of plate requiring high heat input welding more than100KJ/cm, therefore, in industrial production in how to effectively improve mechanical properties of petroleum storage tank steel and the large heat input welding process performance of the many theoretical and technical problems need to be solved. In this context, combining with NEU-Hunan Valin Xiangtan Iron and Steel Group Co., Ltd cooperation issues, the present paper investigated the DQ-T production of new processes of the petroleum storage tank plate, researched and analyses the relationship between the trial of conventional mechanical properties of steel, large heat weldability and corrosion resistance with process parameters.The contents and conclusion in this paper are summarized as follows:(1) The Xiangtan Iron and Steel Smelting12MnNiVR steel petroleum storage tank for the study, studied the effect of different heat treatment parameters on structure and mechanical properties, the proper heat treatment temperature parameters were determined as:When using controlled rolling and re-heating quenching plus offline tempering process produces steel, the appropriate process was940℃×40min quenching plus640℃×50min tempering; When using without recry-stallization controlled rolling and directly quenching plus offline tempering produces steel, the appropriate process was810℃online quenching plus offline620℃×50min tempering; When using recrystallization controlled rolling and direct quenching plus offline tempering process produces steel, the appropriate process was950癈online quenching plus offline640℃×50min tempering.(2) Under three different heat treatment conditions, the main microstructure of the test steel was sorbite, the laws of the microstructure of the fine differences impact on the mechanical properties were:The strength and hardness of direct quenching steel was significantly higher than that of re-heating quenching steel, but its plasticity and toughness decreased. The order of the increasing intensity was:CR&Q<CR&DQ<RCR&DQ; The order of the descending elongation was:CR&Q>RCR&DQ>CR&DQ; The order of the descending impact energy was:CR&Q>CR&DQ>RCR&DQ.(3) High heat input welding thermal cycle simulation of the three different processes for manufacturing test steels has been tested by MMS-300thermal mechnical simulation tester. When the peak temperature was1400℃and the heat input energy was100KJ/cm, by HAZ of low-temperature impact test results and SEM and OM of fracture face and microstructure analysis showed that:CR&DQ+T steel had the best performance of large heat input welding; CR&Q+T steel followed it, and the Large heat input welding performance of RCR&DQ+T steel is poor.(4) Selected the same kind of steel plate produced in Baosteel and Japan, and tested the mechanical properties of steel for a series of comparative analysis. Experimental results showed that the basic mechanical properties of test steel reached to the level of similar products in Baosteel and Japan; Large heat input welding thermal simulation performance in addition to RCR&DQ+T is poor, the other two manufacturing process of the toughness of steel plate achieved to similar levels of physical, therefore, it can be used for the construction of large petroleum storage tanks.(5) Used without recrystallization controlled rolling and directly quenching plus offline tempering process manufacturing12MnNiVR steel and Baosteel steel production08MnNiVR petroleum tank corrosion resistance for a comparison test. It showed that08MnNiVR sample of full immersion corrosion rate was0.3427mm/a, and full immersion of test steel corrosion rate was0.3015mm/a, it can be seen that12MnNiVR hydrogen sulfide corrosion-resistant steel plate was better than that of08MnNiVR.