Study On The Techniques And Performances Of Stainless Steel Scraps Recycling

Metal recycling industry in China has achieved a rapid development since the new century, promoting the development of relevant industries, which is significant in speeding up the transformation and upgrading of relevant industries and developing the circular economy. In this paper, a market research of metal recycling industry has been done and the recycling of stainless steel scrap has been studiedIn this paper, the 18Cr-8Ni-2Mo recycling stainless steel was prepared with the stainless steel scraps by the process of "intermediate frequency furnace remeltingâ†'AOD refiningâ†' horizontal continuous casting".The microstructure and properties and the effects of solution treatment on the microstructure and mechanical properties of the 18Cr-8Ni-2Mo recycling stainless steel were studied. Moreover, the CF3M stainless steel castings with strong corrosion-resistance were prepared by the process of investment casting, using recycling stainless steel bar, baled stainless steel scrap, scrap returns as melting charge.The effects of different furnace charge on microstructure, mechanical properties, pitting corrosion resistance and intergranular corrosion resistance of the CF3M stainless steel casing were studied.The manufacture process of CF3M stainless steel casting has been optimized and the ultra-low carbon stainless steel casting has been prepared by the intermediate frequency furnace.The results reveal that the microstructure of the 18Cr-8Ni-2Mo recycling stainless steel is austenite and a little ferrite.With the increase of holding temperature and hold time of solution treatment, the content of ferrite, the tensile strength and brinell hardness of the recycling stainless steel decrease, but the elongation rate increases and the ductility improves. The tensile strength, elongation rate and brinell hardness of the recycling stainless steel without solution treatment are 713.65MPa,57.3% and 157.The tensile strength, elongation rate and brinell hardness of the recycling stainless steel with solution treatment(holding temperature 1080℃, holding time120minutes, water quenching) are 549.07MPa,61.33% and 152.The various performances of the CF3M stainless steel casting used recycling stainless steel bar as melting charge are better than the casting used baled stainless steel scrap, scrap returns as melting charge.With the ratio of recycling stainless steel bar in the furnace charge increases, the mechanical properties, pitting corrosion resistance and intergranular corrosion resistance of the casting gets better. The various performances of the CF3M stainless steel casting used recycling stainless steel bar only as furnace charge are the best and its tensile strength, yield strength, elongation rate and brinell hardness are 605MPa,334.2MPa,60.46% and 175. Its pitting potential and pitting corrosion rate (ferric chloride solution test) are 428.5mV and 14.30 g/(m2·h)and its Ir/Ip ratio of intergranular corrosion resistance is 0.078.