Ultra-pure ferritic stainless steel and its manufacturing method and use

Abstract

An ultra-pure ferritic stainless steel, a manufacturing method, and use thereof. The ultra-pure ferritic stainless steel comprises in percentage by weight, C≤0.025%, N≤0.025%, Si≤1.00%, Mn≤1.20%, Cr: 18.00%-24.00%, Nb: 0.40%-0.75%, Mo: 1.75%-2.50%, W: 0.80%-1.20%, Cu: 0.30%-0.60%, Al≤0.015%, Ti≤0.01%, P≤0.03%, S≤0.01%, and satisfies 3.4%≤2Nb+Mo+W≤5.2% and 32%≤Cr+4.7Mo+2.4W+11.5Cu≤45%, with the balance being Fe and inevitable impurities. With the composite strengthening of Nb, W and Mo, and the reasonable matching of Cu, Al and Ti, the obtained ultra-pure ferritic stainless steel can meet the requirements of working and serving at higher temperatures, has good high-temperature strength, high-temperature fatigue life and high-temperature oxidation resistance, has good cold working performance and good brazing performance.

1 . An ultra-pure ferritic stainless steel comprising in percentage by weight: C≤0.025%, N≤0.025%, Si≤1.00%, Mn≤1.20%, Cr: 18.00%-24.00%, Nb: 0.40%-0.75%, Mo: 1.75%-2.50%, W: 0.80%-1.20%, Cu: 0.30%-0.60%, Al≤0.015%, Ti≤0.01%, P≤0.03%, S≤0.01%, and satisfying 3.4%≤2Nb+Mo+W≤5.2% and 32%≤Cr+4.7Mo+2.4W+11.5Cu≤45%, with the balance being Fe and inevitable impurities. 
     
     
         2 . The ultra-pure ferritic stainless steel according to  claim 1  comprising in percentage by weight: C≤0.015%, N≤0.015%, Si≤0.80%, Mn≤1.00%, Cr: 18.00%-21.00%, Nb: 0.40%-0.65%, Mo: 1.90%-2.40%, W: 0.90%-1.20%, Cu: 0.3%-0.5%, Al≤0.013%, Ti≤0.01%, P≤0.03%, S≤0.005%, and satisfying 3.6%≤2Nb+Mo+W≤4.9% and 33%≤Cr+4.7Mo+2.4W+11.5Cu≤41%, with the balance being Fe and inevitable impurities. 
     
     
         3 . The ultra-pure ferritic stainless steel according to  claim 1  comprising in percentage by weight: C≤0.01%, N≤0.01%, Si: 0.30%-0.80%, Mn: 0.40%-1.00%, Cr: 18.00%-20.00%, Nb: 0.50%-0.60%, Mo: 2.00%-2.30%, W: 1.00%-1.20%, Cu: 0.35%-0.45%, Al≤0.01%, Ti≤0.008%, P≤0.02%, S≤0.003%, and satisfying 4.0%≤2Nb+Mo+W≤4.8% and 34%≤Cr+4.7Mo+2.4W+11.5Cu≤39%, with the balance being Fe and inevitable impurities. 
     
     
         4 . A manufacturing method of an ultra-pure ferritic stainless steel, comprising a smelting process, a casting process, a hot rolling process, a continuous annealing process after hot rolling, a cold rolling process, a continuous annealing process after cold rolling, wherein the composition of molten steel prepared in the smelting process is the same as that of the ultra-pure ferritic stainless steel according to  claim 1 . 
     
     
         5 . The manufacturing method of an ultra-pure ferritic stainless steel according to  claim 4 , wherein in the hot rolling process, a heating temperature of a cast billet before hot rolling is 1200-1260° C., and a coiling temperature after hot rolling is 620-700° C. 
     
     
         6 . The manufacturing method of an ultra-pure ferritic stainless steel according to  claim 4 , wherein in the continuous annealing process after hot rolling, an annealing temperature is 1000-1060° C. and a holding time is controlled at 1.5-2.0 min/mm. 
     
     
         7 . The manufacturing method of an ultra-pure ferritic stainless steel according to  claim 4 , wherein a total deformation rate in the cold rolling process is ≥55%. 
     
     
         8 . The manufacturing method of an ultra-pure ferritic stainless steel according to  claim 4 , wherein in the continuous annealing process after cold rolling, an annealing temperature is 1000-1060° C. and a holding time is controlled at 0.9-1.2 min/mm. 
     
     
         9 . Use of the ultra-pure ferritic stainless steel according to  claim 1  in the preparation of an automobile exhaust system. 
     
     
         10 . An automobile exhaust system, wherein at least a portion of the automobile exhaust system comprises the ultra-pure ferritic stainless steel according to  claim 1 .