Selection of welding electrodes
1.) Section Basis:-
To ensure compatible property with base material
Strength / toughness related compatibility
Environment / specific environment related compatibility – e.g.. Corrosion / high or low temperature related application
Welding procedure / position related compatibility – e.g.. V-up / v-down / oh welding
Crack resistant weld during welding in specific cases – SS / cast iron / dissimilar welding
2.) Section of Welding Electrode for Different Metallurgy:-
A.) Selection of Welding Electrode for C-Mn Steels:-
Group contains:- Mild steels (IS 2062), Boiler quality steel (IS: 2002), Micro-alloyed steels (IS: 8500), Weathering steels (IS : 11587)
E6013 medium coated electrodes: – For mild steel non-critical applications in static loading up to 40 mm combined thickness,
E6013 heavy coated electrodes:- For mild / boiler quality steel semi-critical applications in dynamic loading up to 40 mm combined thickness
E 7018 electrodes + pre-heat as required:- For higher thicknesses for mild / boiler quality steel for all applications above 40 mm combined thickness –
B.) Selection of Welding Electrode for Micro-alloyed steels
- These are medium & high tensile steels developed for improved strength and toughness without impairing weldability. (Covered by IS:8500 – 1991)
- They contain small amounts of carbide forming elements e.g.. Nb, V, Ti etc. (Total 0.20% max). They are characterized by very fine grain size (ASTM 12 – 14)
- Properties :
- UTS 450 – 600 MPa
- YS 400 – 500 MPa
- Elongation 20 – 22 %
4. Weld all sections with E7018 / E8018 G electrodes depending on minimum yield requirements
C.) Selection of Welding electrode for weathering steels
- These are medium tensile steels with Cu, Cr & small amount of P added to improve atmospheric corrosion resistance. However, P gives hot shortness and lower impacts and latest grades have reduced P levels.
Example – Corten A, B & C and Sailcor HR & CR steels used for rolling stock in railways and other transportation sectors. Corten B & C with lower P levels have better weldability
- For the lower strength Corten A & B type use E7018 – W1 electrodes
- For higher strength Corten C use E8018 – W2 electrodes.
- Note the electrode weld metal does not contain P
D.) Selection of electrodes for Creep Resisting steels
- These steels have additions of Cr, Mo & V for improving their creep / stress rupture properties at high temperature.
- They are used in turbines, boiler tubes and associated piping that carry superheated steam at elevated temperatures.
- These are called chrome-moly steels and the higher grades are alloyed with Vanadium for higher strength
- These are welded by electrodes of equivalent compositions.
3.) Electrode used for Steel Applications:-