Abstract:
This document presents an overview of the findings of several investigations into the
susceptibility of 12% chromium type 1.4003 ferritic stainless steel to heat-affected zone
sensitization and intergranular stress corrosion cracking. A description of the sensitization
behaviour of these steels is complicated by the partial transformation of d-ferrite to austenite
on cooling. During slow cooling or annealing below the A1 temperature, this austenite
decomposes to form desensitized ferrite and M23C6-type carbide precipitates. The rapid
cooling rates associated with welding, however, prevent the transformation of austenite to
ferrite at lower temperatures, and any austenite formed on cooling transforms to martensite
below the Ms-temperature. Four distinct modes of heat-affected zone sensitization have
been identified to date. Sensitization of the martensite phase may occur on welding material
inadvertently annealed above the A1 temperature (Mode 1), or when multiple welds are
positioned in such a way that the heat-affected zone of the 2nd pass overlaps the heataffected
zone of the 1st pass (Mode 2). Rapid cooling after very low heat input welding may
sensitize the ferrite phase (Mode 3), whereas very slow cooling after welding at excessively
high heat input levels may lead to sensitization of the austenite phase (Mode 4). Results
examining the influence of Modes 1 and 2 heat-affected zone sensitization on the incidence
of intergranular stress corrosion cracking are presented.
Description:
Professor Madeleine du Toit of the University of Pretoria has won the Harvey Shacklock Gold Medal. Prof du Toit works in the Department of Materials Science and Metallurgical Engineering.
The decision to declare her a winner was made at a recent meeting of the council of the Southern African Institute of Welding (SAIW).
This award is made to the author of an outstanding paper presented to a SAIW conference or technical meeting. The award was first presented as long ago as 1949 and is donated by Afrox in recognition of Harvey Shacklock – the former managing director of Afrox and the first President of SAIW in 1948.
Du Toit presented this paper to the SAIW meeting held in Johannesburg. Her paper was titled: ‘Failure of type 1.4003 welds due to intergranular stress corrosion cracking and pitting corrosion in the HAZ’.
“I know the award is well earned in this our 60th anniversary year– many congratulations,” said Jim Guild, Executive Director of SAIW.
Du Toit said that she feels very honoured to be the recipient of the Harvey Shacklock Gold Medal in the 60th anniversary year of the Southern African Institute of Welding (SAIW).
“Over the last 60 years, the Southern African Institute of Welding has grown into South Africa's leading provider of internationally accredited training and certification programmes in the field of welding. It is a privilege to be recognised by the Institute on occasion of such a milestone,” she said.
Du Toit will receive her award at the annual dinner to be held at the Balalaika Hotel on the 25th July 2008.
