Successful Development of Super Duplex Stainless Steel

In the last a few days, self-development of stainless steel plate used for coal moisture dryer body in coking project matched with TISCO New Stainless Steel Projects has made a great breakthrough, and super duplex stainless steel S32750 medium plate was developed successfully, which symbolizes that TISCO became the first enterprise to produce super duplex stainless steel in China.

S32750 is typical representative of the super duplex stainless steel. Compared with common 2205 duplex stainless steel, contents of Chrome , Molybdenum and Nitrogen in S32750 stainless steel increase to a certain degree, especially content of Nitrogen attaining about 2800ppm, point-corrosion resistant index (PREN) reaching 43, therefore it has performance of higher strength, of better chloridion-pitting resistance and of stress corrosion resistance. It is suitable for being applied in the industrial fields such as petrochemical industry, oil refining, vacuum salt making, flue gas desulphurization etc. where corrosion environment is more critical. Such steel can be produced only in a very few countries currently.

During the development, researchers made the practical plans after serious examination, and carried out smelt making of stainless steel with high Nitrogen contains by adopting self-developed AOD nitrogen alloying patent technology. They overcame many technical difficulties such as difficult decarburation for high-Chrome and ultra-low-carbon stainless steel, and difficult surface quality control due to narrow hot-machining plastic zone. They successfully developed stainless steel medium plate with nitrogen content of 2700-3000ppm and thickness range from 5mm to 60mm.

Because of the complicated processing technology of this steel grade, our country has been depending upon importation from foreign countries with expensive price and long delivery period. This product fills the domestic blank in China, and forms a series of duplex stainless steel with various levels and TISCO's feature together with previously-developed steel grade such as 3Re60, S32304, S31803, S32205 and so on, and can meet various demands of different corrosion environments. It is of significance to enhance market competitiveness for TISCO.