------ | ---------------- | --------- | ----------------------------------------------------------------- | | A36 | A36 | E70XX | 70 ksi overmatches 58 ksi base metal Fu | | A36 | A572 Gr 50 | E70XX | Match the higher-strength side | | A572 Gr 50 | A572 Gr 50 | E70XX | 70 ksi vs 65 ksi Fu -- acceptable overmatch | | A572 Gr 50 | A913 Gr 65 | E80XX | Match the higher-strength side (80 ksi vs 80 ksi Fu) | | A36 | A514 Gr 100 | E110XX | Match the quenched-and-tempered steel -- undermatching prohibited | | A992 | A572 Gr 50 | E70XX | Both are 65 ksi Fu grade -- E70XX acceptable | | A36 | 304L (stainless) | E309L | Dissimilar metal -- controlled ferrite content |
The governing rule from AWS D1.1 Table 3.1: the filler metal classification tensile strength shall equal or exceed the lower of the two base metal tensile strengths.
Process Selection by Project Type
| Project Type | Preferred Process | Reason |
|---|---|---|
| High-rise building (30+ stories) | FCAW (shop) + SMAW (field) | Shop production volume justifies FCAW. Field connections are standard shear tabs |
| Industrial building / PEMB | FCAW self-shielded (field) | Metal building erectors use E71T-8 almost exclusively -- fast, all-position, no gas bottles |
| Bridge fabrication | SAW (shop, main girders) + FCAW (shop, stiffeners) | Bridge girder welds are long continuous seams -- SAW is the only economical process |
| Bridge erection | SMAW E7018 (field splices) | Field splices are CJP groove welds in all positions |
| Seismic retrofit | SMAW E7018 or FCAW E71T-8 JD | Access is often restricted -- stick welding is most adaptable |
| Architectural exposed steel (AESS) | GMAW ER70S-6 (pulse spray) | AESS requires smooth, uniform welds with minimal spatter. Often followed by grinding smooth |
Worked Example -- Specifying Electrodes for a Complete Project
Project: 4-story office building, steel moment frame (SMF) in one direction, braced frame (BRBF) in the other. Shop fabrication in a controlled facility. Field erection in a temperate climate (Pacific Northwest, wet winters).
Shop Welding Specification
| Connection | Process | Electrode | Notes |
|---|---|---|---|
| Beam/shear tab fillet weld | FCAW | E70T-1 | CO2 shielding, 70 ksi, production shop standard |
| Column base plate to column fillet weld | FCAW | E70T-1 | Same as above, 5/16 in. min fillet |
| Moment connection CJP (beam flange to column flange) | FCAW | E71T-8 JD | Demand-critical, self-shielded, 40 ft-lb at -20F |
| Brace gusset to beam/column fillet weld | FCAW | E70T-1 | Standard fillet |
| Column splice PJP weld | FCAW | E70T-1 | Partial joint penetration |
Field Welding Specification
| Connection | Process | Electrode | Notes |
|---|---|---|---|
| Shear tab to column flange | SMAW | E7018 H4R | All-position, low hydrogen |
| Moment connection backup bar removal + back-weld | SMAW | E7018 H4R | Overhead position, CVN required |
| Miscellaneous field fixes | SMAW | E7018 H4R | Standard field stick electrode |
| Embed plate field adjustments | SMAW | E7018 H4R | Wet conditions -- preheat and dry surface required |
QC Notes for Project Specification
Electrode certification: All electrodes to be supplied with mill test reports (MTRs) showing chemical composition and mechanical properties per the applicable AWS specification. CVN test reports required for E71T-8 JD.
Storage and handling: E7018 electrodes to be stored in a holding oven at 250-300 F in both shop and field. Maximum atmospheric exposure: 4 hours (shop), 2 hours (field, due to higher ambient humidity in the Pacific Northwest).
WPS availability: Welding Procedure Specifications for each electrode/base metal/position combination to be available at the point of welding. Prequalified WPS per AWS D1.1 Clause 3 is acceptable except for demand-critical moment connection CJP welds, which require PQR-qualified WPS per Clause 4.
Inspector qualifications: All welding inspection to be performed by an AWS Certified Welding Inspector (CWI) or an engineer with equivalent documented training.
Common Selection Mistakes
Specifying E7018 for sheet metal (t < 16 ga). The deep penetration of E7018 blows through thin material. Use E6013 or GMAW short-circuit transfer.
Using E70T-1 outdoors without a windscreen. The CO2 gas shield dissipates in wind over 5 mph, causing porosity. Either shelter the weld or switch to self-shielded E71T-8.
Forgetting to specify CVN requirements for seismic welds. E7018 without supplemental CVN testing may not meet the AISC 341 toughness requirements. Specify "E7018 with CVN testing per AWS A5.1, minimum 20 ft-lb at 0 degrees F" on the contract drawings.
Allowing E7024 for out-of-position welding. E7024 is a high-deposition flat/horizontal electrode. The heavy slag is too fluid for vertical or overhead welding. Specify E7018 for all-position work.
Mixing E6010 root pass with insufficient E7018 fill. The E6010 root introduces hydrogen. The subsequent E7018 passes must be deposited with sufficient heat input and interpass temperature to allow hydrogen diffusion. A single thin E7018 pass over an E6010 root with a fast cooling rate traps hydrogen in the HAZ.
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Related Tools and References
- Weld Electrodes Reference
- Steel Connection Design Guide
- End Plate Connection Design
- Steel Grades Reference
- How to Verify Calculations
Disclaimer
This page is for educational and reference use only. It does not constitute professional welding engineering advice. Electrode selection, welding procedure qualification, and inspection criteria must be established by a qualified welding engineer or CWI for the specific project. The site operator disclaims liability for any loss arising from the use of this information.