Effects Of Rolling And Annealing Process On Forming Properties Of GF08Al Steel

At present,the economic development of China has entered a new normal.The problems such as overcapacity and environmental pollution are increasingly serious.Transforming and upgrading,changing the mode of development,adjusting industrial structure and optimizing strategy are the development direction of our steel industry.Guofeng Iron is also facing many challenges by using the Ultra Fast Cooling technology on the production line of 620mm narrow strip steel.Taking the products of different UFC process as the esearch objects,the effects of hot rolling and cold rolling on the microstructure and properties of GF08Al steel are studied and the comprehensive forming properties under specific process are also analyzed in the project background of Research on Hot Rolled Ultra Fast Cooling Process and Forming Properties of GF08Al steel and platform of The State Key Laboratory of Rolling and Automation.The main work and research results of this paper are as follows:(1)The yield strength,tensile strength and uniformity of cooling increases obviously,the microstructure and properties difference between hot and cold spots drops significantly by using UFC technology.When the coiling temperature is about 478?,the precipitation proportion of AlN reduces and the content of the interstitial solid solution nitrogen increases with the final cooling temperature drops.(2)In terms of GF08Al steel cooling at 700?,the recrystallization temperature is 620? and 580? respectively when the rolling reduction is 60%and 80%,and the best heating speed should be controlled in 40?50?/h during recrystallization annealing process.When annealing temperature is between 600? and 630?,forming properties of two kinds tested steel are poor,and it can not satisfy DC03 properties requirements.When the annealing temperature is between 660? and 690?,the tested steel cooling at 700? can meet DC03 properties requirements if heat preservation time is more than 12h,while the tested steel cooling at 650? can also satisfy DC03 properties requirements if heat preservation time is more than 15h.(3)Compared with the tested steel that is cooled at 700?,the density of {111} and content of {111} component in the tested steel cooling at 650? are stronger and the content of {001} component is lower under single stage annealing process.What is more,under the condition of two stages annealing process,the content of {111} component is the highest and the content of {001} component is the lowest in the tested steel cooling at 650?,and the tested steel cooling at 700? is just the opposite.(4)It is found that stamping cracking is caused by irregular series chain cementite with large size distributed in ferrite grain boundary and the orange peel phenomenon is caused by the mixed grain structure.Measures must be taken form hot rolling process and batch annealing process to avoid such defects.The microstructure of GF08Al annealed sheet is homogeneous polygon ferrite with fine cementite,grain size level of which is between 6 and 8.The comprehensive mechanical properties of different location in same furnace are different,only partial tested steel can also satisfy DC03 properties requirements.