Is Bohler A31 to BS 2901 Pt1 A31 capable of giving impact value of min 27J at -46 degree Celsius?
If the filler metal is used with GTAW using pure argon shielding, and relatively low dilution, then the low temperature toughness requirement can be achieved. 27J is generally achievable at -20 degrees celsius, using careful welding procedures, providing clean weld metal. Metallurgically, steel toughness requires low inclusion content, fine grain size and minimised residual stress.
A preferred filler metal, which closely resembles A31 but which is far superior is ER80S-D2 (TIG/MIG) to AWS A 5.28 Release. It has a higher beneficial manganese content and more tightly controlled carbon content, tramp and impurity element control.
This version provides excellent low temperature toughness.
Welding Tips & Techniques
Optimum weld deposit mechanical properties including low temperature toughness are obtained by using:
- ER80S-D2 which is superior to A31 available and used in the aerospace industries
- GTAW
- Argon shielding from a full cylinder, rather than bulk argon sourcing
- Maximisation of weld deposit volume and thus minimising dilution from base material
- Top grade base steel material
- A welding procedure that prevents air contamination, preheat to warm ambient (not straight out from an external stock-yard)
- Controlled humidity by welding in perfectly dry conditions (no condensed moisture on the component to be welded, clean dry filler metal, warm weld area, war filler metal from a closed storage area)
- Good fusion
- The method of protecting the weld area from cross draughts and bulk air movement from open loading doors
- Toughness which is a function of inclusion content. A clean metal is necessary with minimum oxygen and other impurities present in the weld deposit
- The ideal metallurgy in 2Mn, 0.5Mo and clean weld metal