2005 Volume 46 Issue 3 Pages 593-601
This work was carried out to investigate the effect of welding variables (includes wire feeding techniques, wire feeding rates and heat inputs) on the cooling rate, Δt8⁄5 (cooling time from 800 to 500°C), in the weld and heat affected zone (HAZ) areas of multi-pass weldments in a super duplex stainless steel. Furthermore, changes in thermal condition caused by welding variables can affect the microstructure and consequently the material properties. Therefore, supporting tests, including pitting corrosion resistance and microstructure analysis were investigated.
To establish the effect of welding variables on the cooling rate, a series of weldments using a semi-automatic welding process which is enable the control of welding variables such that one parameter can be varied at a time were completed. The method used for pitting resistance tests was the basic ASTM G48-76 standard, with reference to the ASTM A923-94 standard and recommended practice for pitting corrosion tests for duplex stainless steel weldments by the use of ferric chloride solution from The Welding Institute (TWI). Microstructure Analysis was carried out using a Buehler Omnimet Image Analysis System and a manual point counting technique with reference to ASTM E562-89 (Standard test method for determining volume fraction by systematic manual point count).
From these tests results, various empirical correlations have been proposed to relate the cooling rates and pitting corrosion resistance to the welding variables.