TWI Industrial Member Report Summary 957/2010
by D Howse and S Baclet
The need for fabrication in duplex stainless steel using automated welding processes is becoming the more common due high strength and corrosion resistance. Higher strength allows designers to reduce material thickness for large scale production whilst maintaining static strength and can offer a subsequent weight and primary material cost saving against structures designed in austenitic stainless steels. There are applications in the nuclear containment, oil and gas, petrochemical and domestic heating markets which use high volumes of duplex stainless steel.
The need for manufacture in large volumes impacts on the economics of production, necessarily driving the unit cost down if parts are to be manufactured at a realistic price, but quality must be maintained as suitable for service. Designs using duplex stainless steels usually require long term corrosion performance alongside other criteria such as impact performance and strength. Dimensional stability may be important and distortion potential will need to be considered.
There is therefore a research need to evaluate existing welding processes capable of producing relatively low cost, structures in stainless steels that meet high level quality requirements and operate at high speed to meet productivity requirements and also result in low distortion.
Arc welding processes such as conventional MIG, controlled deposition MIG and TOPTIGTM show promise for applications but need further work to demonstrate their relative capabilities for producing high quality welds with controlled heat input in stainless steel components. Similarly, laser processes are available capable of producing welds at high speeds and associated low distortion potential and are also worthy of consideration for these products.
- Identify current high-productivity options for welding duplex stainless steel components in terms of technical and economic suitability.
- Further develop and demonstrate low cost, high productivity welding procedures suitable for automated welding, controlled-deposition MIG, TOPTIG TM and laser to deliver high quality welds in duplexstainless steel.
- Make recommendations regarding the use of these processes for fully integrated, automatic manufacturing in duplex stainless steel.