Welding stainless steels

Introduction

Austenitic stainless steels are readily welded with or without filler wire. They are by far the most common family of stainless steels used in fabrications.

Super-austenitic (i.e. with a pitting resisting number greater than 40), ferritic, super-ferritic, martensitic and austenitic-ferritic (duplex/super-duplex) stainless steels require more control when being welded and may involve post weld heat treatment or special welding consumables.

The prime objectives when producing a welded joint are:

  1. To ensure sound welds which match the corrosion and mechanical properties of the parent material.
  2. To choose a welding process that meets productivity requirements, but which will result in as little distortion as possible and need a minimum of post weld dressing.

 

Considerations to be taken when choosing a welding process are:

  • Joint type and material thickness.
  • Welding position and working environment, e.g. fabrication shop or on-site.
  • Manual or mechanised methods to increase productivity and repeatable quality.
  • Availability of suitable filler materials which are often over-alloyed to enhance the corrosion resistance of the weld deposit, and may be essential in the prevention of weld bead cracking.

 

 

General guidelines

 

  • Avoid excessive heat input and high weld interpass temperature. Austenitic grades have a high coefficient of thermal expansion and low conductivity, so high heat input will result in excessive distortion and residual stress.
  • Design criteria and/or metallurgical transformation due to welding may necessitate the selection of a non matching welding consumable, to achieve toughness levels at cryogenic temperatures or increased weld metal corrosion resistance.
  • It is important, where possible, to reserve a fabrication facility exclusively for stainless steels. In addition, use protective handling equipment and tools which are dedicated to stainless steel fabrication to avoid contamination from contact with carbon steels.
  • If in doubt about welding and fabrication techniques, then consultation of the parent material or welding consumable supplier / manufacturer is recommended.
  • When shielding gas is required, consult your supplier for updated information on recommended gas compositions.
  • When new grades of materials are to be welded, especially ferritic, martensitic and duplex alloys, contact your consumable manufacturer for weld procedure information and filler material recommendations.
  • Post weld dressing may require the use of pickling pastes or other corrosive substances. Consult your material supplier before use.

 

Health and safety in welding

Welding Manufacturers Association Publication No. 236, 1994 HAZARDS FROM WELDING FUME states: It is advised that where stainless steel welding takes place in a building or a confined space, the provision of adequate fume extraction is especially important. Ask your welding consumables supplier for information and recommendations.

top

Office and Postal Address: BSSA, Regus, Blades Enterprise Centre, John Street, Sheffield S2 4SW

Registered Office: Pegasus House, 463A Glossop Road, Sheffield S10 2QD

Tel: +44 (0)114 292 2636    |     Email: admin@bssa.org.uk

Copyright © 2017 British Stainless Steel Association

web design sheffield by Llama Digital