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77 & 72 Electrodes
77/72 Comparison
| Compare |
77 Electrode |
72 Electrode |
| Sizes available |
5/32", 3/32", 1/8" |
5/32", 3/32", 1/8" |
| Arc - TIG - Braze |
Arc - TIG |
Arc - TIG |
| Works on engine blocks |
Yes |
Yes |
| Works on large cast iron holes |
Yes |
Yes |
| Joins cast iron to steel |
Yes |
Yes |
| Joins cast iron to metals other than steel |
No |
No |
| Works on exhaust manifolds, woodstoves, or other burnt cast iron |
Good |
Great |
| Works on thin cast iron |
Yes |
Yes |
| Color match? |
Fair |
Fair |
| All position? |
Yes |
Yes |
| Machineable? |
Yes |
No |
| Paintable? |
Yes |
Yes |
| Works over existing welds? |
Fair-- better on unwelded surface |
Fair |
| Depth to bevel cracks |
3/4 through |
3/4 through |
| Crack resistant? |
Yes |
No |
72 Information
Available in 1/8", 5/32", 3/32"
There are occasions in industry where exceedingly dirty cast iron is encountered. 77, which bonds well to most cast iron does have a limitation. Since 77 has controlled penetration, which is ideal for non-cracking and machinability, it may not be able to bond exceptionally dirty cast iron. 72 should be used instead. It has a high penetration, can anchor deep into the subsurface of dirty cast iron, and seals in porosity generating contaminates prior to finish welding with 77. 72 is used for a cladding operation, then the weld is completed with 77.
72 is our recommendation for welding cast iron exhaust manifolds.
Welding positions: flat, vertical (up), horizontal, vertical (down), overhead
Welding techniques: Use stringer or moderate weave technique. When cladding, cover the entire base surface prior to finish welding.
Applications: for non-machinable welds on exhaust manifolds, furnace grates, cast iron stoves, machine bases etc.
How to Apply
Begin by beveling the joint. Drill holes 1/2" from each end of the crack to prevent further cracking while welding. Tack weld to retain alignment. Use AC or DC with reverse polarity. (70-110 amps for 1/8" rods, 95-140 amps for 5/32" rods) Maintain a short to medium arc and make short passes and peen each pass promptly to chip off slag before cooling. Continue back whipping and overlapping until all deposits are connected. Cool naturally.
77 Information
Available in 1/8", 5/32", 3/32"
| Tensile (as welded): |
52,500 - 55,000 PSI |
| Tensile (slightly worked): |
56,100 - 58,250 PSI |
| Elongation (in red zone): |
71% |
| Elongation (in weld room temp. 70): |
59% |
| Yield (as welded): |
44,550 PSI |
| Yield (slightly worked): |
45,750 PSI |
| Color match (Grey Iron): |
Good |
| Machinability: |
Excellent |
| Weld Appearance: |
Excellent |
| Weldability: |
Excellent |
| Cross Strength (Build up area) |
* |
Points |
| (In total Sq. Ins. Area) |
Thickness |
100 Index |
| 8 sq. ins. |
1/4" |
90 |
| 16 sq ins. |
3/8" |
88 |
| 32 sq ins. |
1/2" |
87 |
| 64 sq ins. |
1-1/2" |
84 |
How to Apply
Begin by beveling the joint. Drill holes 1/2" from each end of the crack to prevent further cracking while welding. Tack weld to retain alignment. Use AC or DC with reverse polarity. (60-110 amps for 1/8" rods, 90-140 amps for 5/32" rods) Maintain a short to medium arc and make short passes and peen each pass promptly to chip off slag before cooling. Continue back whipping and overlapping until all deposits are connected. Cool naturally.
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