Study On Process Of Ultra Heavy H Section Steel With Low Temperature Impact Resistance

With the development of economic construction,steel structure industry has also been rapid development,the application of steel structure include high-rise buildings,offshore platforms and other industries.With the development of steel structural application and the breakthrough of manufacturing technology,steel structure has development to large-sized,heavy-duty,high-rised Low temperature impact resistance H section steel with the flange thickness of 28mm to 36mm has been developed combing with the existing smelting and rolling process conditions of Heavy H Section Steel Line,using complex micro-alloyed method and controlled rolling process,all properties of the product have already reached the technical requirements.The main conclusions are as follow.(1)The V-Ti-N-Ni complex micro-alloyed method process had been used according to the characteristics of low rolling ratio and high finish rolling temperature in the roling process of ultra thick H section steel.(2)By studying the high temperature plastic behavior of the beam blank,the brittle region of the beam blank were 1250?1350? and 700?825?.(3)By studying the austenite continuous cooling behavior,the microstructure were mainly ferrite and pearlite when the cooling rate less than 5?/s,the bainite structure began to appeared when the cooling rate greater than 5?/s,the martensite structure began to appeared when the cooling rate greater than 30?/s,the transition temperature range of ???were from 744? to 797?.(4)By studying the austenite growing behavior during the reheating process,the grain coarsening temperature was from 1150? to 1200?.By studying the recrystallization behavior,the recrystallization temperature range was from 850? to 900?.(5)By studying the testing rolling process,the rolling temperature was the main factor that affected the microstructure and the mechanical properties of the products,especially the low temperature impact properties,the effect of rolling deformation and rolling ratio were small.(6)The microstructure of small batch trial product were homogeneous and fine Ferrite and Pearlite structure,the second phase precipitates were fine,the ratio of the particles size below 18nm was 53.2%.The strength and the low temperature impact toughness met the technical requirements,the FATT was below-50?.