The inclusion formation mechanism of the 409L stainless steel

Abstract

In order to solve the problem of the inclusion defects in the cold rolled 2B strip of 409L stainless steel, samplings have been taken from the cold rolled stainless steel strip, to facilitate the research for the forming process of the inclusions of TiN and MgO–Al₂O₃, etc., which presented in the hot steel of 409L and the submerged entry nozzle (SEN) clogging and flux floaters, with the aid of metallographic microscope and electron back scanner. It is revealed from the investigation that: the inclusions of 409L stainless steel consist of TiN inclusions, the complex inclusions nucleated upon MgO–Al₂O₃, enwrapped by TiN, and the complex inclusions from the mould flux picked up during the continuous casting process. The origins of the inclusions consist of the content of MgO–Al₂O₃ and the product [Ti]%×[N]%; The mould flux picked up during the hot metal surface fluctuation caused by the SEN clogging and flux floaters in the mould. To eliminate the above-mentioned inclusions, it is recommended that proper control shall be implemented for the composition of N, Al and Ti in the hot steel, the inclusion modification during the smelting process, soft blowing after refining, killing, minimisation of re-oxidation and well-adjusted mould flux, etc., to minimise the inclusion defects in the final stainless steel products.

Keywords:

• Defects
• Clogging
• Flux floater
• Product [Ti]%×[N]%
• Inclusion modification