TWI Industrial Member Report Summary 1035/2013
By Stephen Cater
This report considers the recent advances in the friction stir welding of steels arising from improved tool materials and developments in the process parameters and equipment used. The report contains preliminary data that indicates that FSW of steel is now not only technically possible, but that it may now be economically viable for some applications requiring high quality welds.
Developments in the use of FSW for steel have until recently been stalled by the lack of suitable tools able to withstand the high temperatures and forces experienced in the FSW process. Recent tool material developments, combined with greater insight into the FSW process, now enable industrially useful lengths of friction stir weld to be made in steel with weld properties that can in some cases justify their cost premium over conventional fusion welding techniques.
Key findings from this work include:
- All grades of steel can be friction stir welded, including Duplex and ODS steels
- FSW produces lower distortion than fusion welding
- FSW grain refines the microstructure of steel, producing stronger, tougher and more fatigue resistant welds than fusion welding
- Corrosion resistance of FSW steel seems greater than that of fusion welding
- Friction stir welding of steel can be performed underwater
- The process is less prone to operator error than fusion welding