Study On Microstructure And Property Of 444 Ferritic Stainless Steel By Thin Strip Casting And Conventional Process

In this paper,studies was carried out on microstructure and mechanical properties,evolution of texture and formability,corrosion property and weldability of 444 ferritic stainless steel in conventional and twin-roll strip casting process,and emphases were put on the evolution of texture and formability of two processes.Experiment was done by cast strip in different rolling temperature with the purpose of studying the microstructure and mechanical properties of cold rolled and annealed sheets after annealing at different temperatures.Researches showed that the rolling temperature for cast strip did not much affect the mechanical properties of cold rolled and annealed sheets after annealing at different temperatures,eventually selecting 1000?.With the cold rolling annealed temperature increasing,the grain size of the finished sheets kept growing.The conventional cold rolled annealing temperature is 1000?.Considering mechanical properties,formability and corrosion resistance,the selection of cold rolled annealing temperature in the strip continuous casting process is 1050?.The tensile strength of conventional finished sheets after annealing at 1000? was higher than cast strip after annealing at 1050? with the 9MPa,yield strength was lower than cast strip with 19MPa,elongation was lower than cast strip with 4%and hardness of both was about 178HV.This paper studied the texture evolution of two modes of production,and showed that the initial tissue of the cast strip was the weak texture.In the subsequent hot rolling and hot rolled annealing,advantage in {001}<110>? texture was forming and advantage in{112}<110>? texture and a faint y texture was forming in the process of cold rolling.In the subsequent annealing process,the major y texture was forming.The y texture was increasing with the increase of annealing temperature,meanwhile the intensity of<111>//ND orientation was increasing on the basis of the microscopic texture.The texture intensity in conventional process is greater than the one in strip continuous casting process,and both of the evolution of the texture are almost the same,and eventually y texture intensity of conventional finished sheets was greater than the one in strip continuous casting process,causing that r value of conventional finished sheets is greater than the one in strip continuous casting process at the same annealing temperature.The r value of finished sheets in strip continuous casting process was 1.36 in annealing temperature at 1050?,and the conventional one in annealing temperature at 1000? was 1.41.Owing to the chemical composition,finished sheets in strip continuous casting process with<111>//ND and<001>//ND grain clusters with zonal distribution along the rolling caused the surface of the finished sheets with ridging phenomenon and therefore finished sheets in strip continuous casting process in ridging was more serious than conventional one.It was researched about corrosion resistance of two process.The composition of chromium of the conventional process was 1%more than continuous casting process,leading that the conventional pitting resistance equivalent was greater than thin continuous casting process.The pitting potential was on the rise with the increase of annealing temperature.Pitting potential of finished sheets in strip continuous casting process at 1050? was 0.477V,and the conventional finished sheets at 1000? was 0.5 V,was 4.6%higher than the pitting potential of finished sheets in strip continuous casting process at 1050?.FeCl3 immersion corrosion was carried out,and weight loss rate of the conventional finished sheets was 6.491 g/(m2·h),and the one in strip continuous casting process was 7.077 g/(m2·h),was 4.4%lower than finished sheets in strip continuous casting process.Weldability for both finished sheets has been studied,studies have shown that weld microstructure are typical of the columnar crystal of the solidified structure and the grain size in heat affected zone is bigger than parent metal.For different distances from the center of weld,hardness changed as a wave on the whole.Weld center had high hardness and it can be seen hardness value was fluctuant along the fusion line and the hardness of strip continuous casting process was greater than conventional finished sheets in weld as a whole.The heat affected zone for two process had different degree of poor chromium,which resulted in increasing weight loss rate of immersion corrosion.Due to the component factors,the weight loss rate of the conventional finished sheets was 6.886 g/(m2·h).and the one in strip continuous casting process was 7.301 g/(m2·h).