저널

The aim of this paper is to determine the proper heat treatment temperature for SDSS tube production without ${sigma}$-phase precipitation. When Mother steel tube was heat treated at $800^{circ}C$ temperature, relatively a large amount of ${sigma}$-phase precipitated and grain refinement of ferrite phase occurred simultaneously. However, in Pilgered and Drawn steel tubes, grain refinement of the ferrite phase did not occur and a small amount of ${sigma}$-phase precipitated. For all three types of steel tubes, the pitting potential was reduced to 2/5 or less compared with the untreated one and corrosion also occurred in the salt spray test due to the precipitation of ${sigma}$-phase. When heat treatment temperature was $900^{circ}C$, grain refinement of the ferrite phase occurred and very little ${sigma}$-phase precipitated in Pilgered and Drawn steel tubes. But when heat treatment was done at $1,000^{circ}C$ temperature, all three types of steel tubes had a similar corrosion properties of that of untreated one and also corrosion did not occur in the salt spray test, as ${sigma}$-phase did not precipitate. Therefore, the optimum heat treatment temperature range is determined to be more than $1000^{circ}C$ for the SDSS at which corrosion does not occur.

${sigma}$-phase precipitation;corrosion resistance;hardness;super duplex stainless steel;