| The building of strategic oil reserves is very important to the national economic security. The construction of large floating roof oil storage tanks with volume more than 100,000 m3 requires steels with high strength, good toughness and favorable welding properties. However, more than 90% high-strength oil storage tank steels depend on imports; it's expensive and can not ensure date of delivery. For profit of business and our country, the National Development and Reform Commission urges to manufacture domestic oil storage tank steels in China, on one hand to meet the needs of the domestic market, build strategic oil reserve for the country's security; On the other hand, to improve domestic production technologies and theories of the heavy plate and elevate the technical level of enterprises. Considering the welding process of large-scale tank's, when the plate thickness is 21mm was used V-groove and Gas-electric welding, and the input energy is 90～100kJ/cm. Therefore many technologies of large-scale input energy storage tank steels needed to research and developed. In this paper, combine Northeastern University with 4300mm heavy plate R&D center of ShouQin Metal Materials Co.,Ltd, to research oil storage tank steel plate, and systematic study on thermal deformation of tested steel. The main thesis is as follows:(1) Using thermal simulation experiment to determine the critical temperatures of tested steel; drawing static and dynamic CCT curves and researching the cooling rate, holding temperature and deformation on the impact of continuous cooling transformation. The results showed that the beginning transformation temperatures decrease with the increasing of cooling rates; deformation increases the beginning transformation temperatures.(2) Studying on the relationship between total reduction in non-recrystallization zone and mechanical properties and microstructure of tested steels. The results showed that the tested steel with total reduction about 60% in non-crystallization zone has the best mechanical properties.(3) Studying on the influence of reheat quenching or direct quenching on mechanical properties and microstructure of tested steel; It showed that the steels with tow processes:the offline quenching and tempering(950℃+40min,650℃+50min) and online quenching, offline tempering(835℃,650℃+50min), have similar mechanical properties.(4) The different online quenching temperatures on the influence of microstructure and mechanical properties of tested steel have been studied. The results show that with the quenching temperatures at 910℃,880℃and 850℃, the mechanical properties of steel remains basically unchanged, the most appropriate quenching temperatures of tested steel is between 850℃and910℃.(5) Carrying out industrial trial of SG610D steel, studying on the microstructure and mechanical properties of the steels with rolled state and quenched and tempered state. Comparing with rolled state, the mechanical properties of tested steel with quenched and tempered has greatly improved; Comparative experiment showed that the mechanical properties of SG610D steel with quenched and tempered achieve the requirement of similar products of Japan. SG610D steel can be used for domestic construction of large oil storage tank. |
PDF Full Text Request