How do I read AWS electrode classifications like E7018 and E70T-1?

AWS electrode classifications follow a standardized system. For SMAW stick electrodes like E7018: 'E' designates an electrode, '70' is the minimum tensile strength in ksi (70,000 psi), '1' indicates all-position usability (1=all positions including overhead, 2=flat/horizontal only, 4=flat/horizontal/vertical-down), and '8' identifies the flux coating type (8=low hydrogen with iron powder). For flux-cored FCAW electrodes like E70T-1: 'E' is electrode, '70' is 70 ksi tensile strength, 'T' denotes tubular (flux-cored) wire, '-1' is the usability designation indicating rutile flux with CO2 or 75Ar/25CO2 shielding gas for all-position welding. For GMAW solid wires like ER70S-6: 'ER' is electrode/rod, '70' is 70 ksi tensile, 'S' is solid wire, and '-6' indicates the chemical composition with higher deoxidizer content (silicon and manganese) for welding over mill scale.

Which electrode should I use for A36 and A992 structural steel?

E7018 is the standard choice for welding A36 (Fy=36 ksi, Fu=58 ksi), A572 Gr 50 (Fy=50 ksi, Fu=65 ksi), and A992 (Fy=50 ksi, Fu=65 ksi) structural steel. The rule of thumb is to match the electrode tensile strength to the base metal tensile strength, not the yield strength. Since A36 has Fu=58 ksi and A992 has Fu=65 ksi, E70XX electrodes (70 ksi tensile) provide adequate matching with the 0.60 factor for fillet weld shear: φRn = 0.75 × 0.60 × 70 ksi × 0.707w × L = 0.928 kips/inch per 1/16 inch of fillet leg. For higher-strength steels: use E8018 electrodes for A913 Gr 65 (Fu=80 ksi) and A588 weathering steel (Fu=70 ksi), E8018-W specifically for weathering steel to match the patina color, and E11018-M for A514 quenched and tempered steel (Fy=100 ksi, Fu=110 ksi). E70XX electrodes are the default for approximately 85% of structural steel applications.

What is the difference between SMAW, FCAW, and GMAW for structural welding?

The three main structural welding processes differ in deposition rate, field suitability, and quality control. SMAW (stick welding, E7018) has low deposition rates of 2-5 lb/hr but excellent wind tolerance, making it ideal for field repairs, short welds, and tack welds where portability matters. FCAW (flux-cored, E70T-1 or E71T-8) achieves high deposition rates of 5-15 lb/hr — 3 to 4 times SMAW — and is the preferred process for production structural welding. Gas-shielded FCAW (E70T-1) requires CO2 or 75Ar/25CO2 shielding and is used in shops. Self-shielded FCAW (E71T-8) needs no external gas and handles moderate wind, making it ideal for field erection. GMAW (MIG, ER70S-6) with 3-10 lb/hr deposition is mainly used for shop fabrication where wind is not a concern and joint fit-up is precise. AWS D1.1 permits all three processes for structural welding provided qualified WPS procedures are followed. For seismic demand-critical welds, FCAW and GMAW with appropriate filler metals are preferred because they consistently produce high-toughness weld metal.

Why is low-hydrogen electrode storage critical?

Hydrogen in weld metal causes hydrogen-induced cracking (HIC or cold cracking), a delayed brittle fracture that can occur hours or days after welding. This is especially critical for high-strength steels (Fu > 65 ksi), thick sections (> 3/4 inch), highly restrained joints, and low-temperature service. Low-hydrogen electrodes like E7018 must be stored in a holding oven at 250°F ± 25°F after the sealed container is opened. At the welding station, electrodes must be kept in a portable heated quiver at minimum 150°F for no more than 4 hours. Electrodes exposed to atmosphere beyond the allowed time (typically 4-8 hours depending on the specification) must be rebaked at 650°F for 1-2 hours — but only one rebake is permitted. Electrodes showing moisture damage (cracked flux coating, rust on the core wire) must be discarded. AWS D1.1 Clause 5.3 requires that low-hydrogen electrodes for demand-critical welds be stored in holding ovens at all times and documented in the WPS. Skipping these requirements is a leading cause of weld failures in seismic and fatigue-critical connections.

How do I calculate the design strength of a fillet weld for different electrodes?

The design shear strength of a fillet weld per AISC 360 is φRn = 0.75 × 0.60 × FEXX × (0.707 × w) × L, where FEXX is the electrode classification strength, w is the fillet leg size, and L is the weld length. For E70XX electrodes (FEXX=70 ksi): the shear strength is 0.75 × 0.60 × 70 × 0.707 × w = 22.3w ksi, giving 0.928 kips per inch per 1/16 inch of fillet leg. For E80XX electrodes (FEXX=80 ksi): 1.060 kips/inch per 1/16 inch. For E90XX (FEXX=90 ksi): 1.193 kips/inch per 1/16 inch. Example: a 1/4 inch fillet weld using E7018 provides 0.928 × 4 = 3.71 kips per inch of length. The minimum fillet weld size is governed by the thicker connected part per AISC Table J2.4, ranging from 1/8 inch for material up to 1/4 inch thick to 5/16 inch for material over 3/4 inch thick. The maximum fillet size at edges is limited to the base metal thickness minus 1/16 inch for material 1/4 inch thick or greater to prevent edge melting.

Welding Electrode Selection -- Practical Guide for Structural Engineers

This page provides practical guidance for selecting the right electrode for structural steel applications. It covers how to match electrodes to specific conditions: field vs. shop, seismic vs. non-seismic, thin vs. thick material, and position constraints. For the electrode classification system, mechanical properties tables, and AWS specification cross-references, see the Weld Electrodes Reference.

The Selection Decision Tree

When specifying an electrode for a structural weld, answer these five questions in order:

What is the base metal? (Determines the tensile strength class: E70XX, E80XX, etc.)
What is the welding process? (SMAW, FCAW, GMAW, SAW)
Is the weld demand-critical? (Seismic, fatigue, fracture-critical -- requires notch toughness)
Where is the welding performed? (Shop vs. field -- affects process selection, preheat, hydrogen control)
What is the welding position? (Flat, horizontal, vertical, overhead -- limits electrode usability)

Scenario-Based Selection Guide

Scenario 1: Shop Welding of Standard Structural Steel (A36/A992)

Recommendation: FCAW E70T-1 with CO2 shielding gas.

This is the most common scenario in structural fabrication shops. The shop environment provides controlled conditions: no wind (gas shielding is reliable), ambient temperature above 50 F, and material that is clean and dry. FCAW with CO2 shielding produces high-quality welds at deposition rates of 8-15 lb/hr (compared to 3-5 lb/hr for SMAW E7018).

Alternative: GMAW ER70S-6 with 75%Ar/25%CO2 shielding. GMAW (hard wire) is increasingly common in structural shops with robotic or mechanized welding equipment. The argon blend produces less spatter than pure CO2 and is preferred for single-pass fillet welds under 5/16 in.

Do not use: Self-shielded FCAW (E70T-4, E70T-7) indoors without adequate ventilation. The self-shielding flux generates significant fumes. Self-shielded wires are designed for outdoor/windy conditions.

Scenario 2: Field Welding -- General Structural

Recommendation: SMAW E7018 (stick welding).

Field conditions are uncontrolled: wind, cold, wet surfaces, variable fit-up. SMAW E7018 is tolerant of these conditions. The electrode coating provides its own shielding, so wind does not affect weld quality. The manual process allows the welder to adjust technique for variable root openings and fit-up.

Precautions:

Store E7018 electrodes in a portable rod oven at the job site (250-300 F minimum)
Remove electrodes from the oven one handful at a time -- do not leave the can open
If the electrode has been out of the oven for more than 4 hours, return it for rebaking
In rain or snow: shelter the weld area with a tent or welding blanket. The base metal must be dry at the point of welding
Preheat with a rosebud torch if the base metal temperature is below 50 F (for A36) or 70 F (for A572 Gr 50)

Scenario 3: Seismic Moment Frame -- Demand-Critical CJP Weld

Recommendation: FCAW E70T-6 or E71T-8 (self-shielded, high toughness).

Seismic moment connections (SMF, IMF per AISC 341) require the highest level of quality control. The CJP weld at the beam flange must develop the full tensile capacity of the beam with sufficient ductility to accommodate post-yield rotation without fracture. The electrode must supply minimum Charpy V-notch toughness of 20 ft-lb at 0 F (for AISC 341 moderate ductility) or 40 ft-lb at 70 F (for AISC 341 high ductility).

E71T-8 with the JD (demand-critical) designation provides 40 ft-lb at -20 F and is prequalified for the AISC 358 prequalified connections (RBS, WUF-W, and end plate moment connections). This electrode produces weld metal with upper-shelf toughness exceeding 80 ft-lb -- far above the minimum and suitable for the highest seismic demand.

Critical QC requirements for seismic welds:

WPS must be qualified by PQR testing per AWS D1.1 Clause 4 (not prequalified per Clause 3)
The electrode lot must be tested for CVN toughness per contract specification
UT inspection of the completed CJP weld per AWS D1.1 Table 6.2 (Class A -- zero rejectable discontinuities over 1/8 in.)
Weld tabs must be removed and the ends ground smooth (notch-free surface)
The backup bar at the bottom flange must be removed, back-gouged, and back-welded with a reinforcing fillet (per AISC 358)

Scenario 4: Thin Material -- Cold-Formed Steel or Light Gage Plate (t < 1/4 in.)

Recommendation: SMAW E6013 or GMAW ER70S-6 (short-circuit transfer mode).

For thin material, the heat input must be low to prevent burn-through. E6013 (titania potassium coating) provides a soft arc with shallow penetration -- ideal for sheet metal and light plate. The slag is easy to remove and the bead appearance is excellent.

For GMAW on thin material, short-circuit transfer mode (low voltage, low wire feed speed) limits the heat input and produces a small, controllable weld pool. Typical parameters: 16-18 V, 150-250 in/min wire feed, 0.035 in. wire diameter.

Do not use: E7018 on material thinner than 1/8 in. The deep penetration and high heat input will blow through.

Scenario 5: Thick Material -- Heavy Plate (t > 2 in.)

Recommendation: SAW (submerged arc welding) in the shop; SMAW E7018 + E8018-C3 in the field.

For plate thicknesses exceeding 2 inches, SAW in the shop provides the highest deposition rate (up to 40 lb/hr with multiple wires) and the deepest penetration. The granular flux blankets the arc, eliminating spatter and fumes. Preheat and interpass temperature control are critical: thick plate acts as a massive heat sink, and the cooling rate must be controlled to prevent martensite formation in the HAZ.

In the field, where SAW equipment is impractical, SMAW E8018-C3 (1% Ni) provides the low-temperature toughness needed for thick-section restraint. The nickel addition refines the weld metal grain structure and improves CVN toughness without excessive strength increase (E8018 = 80 ksi tensile, E8018-C3 = 80 ksi with improved toughness at low temperature).

Hydrogen control for thick plate:

Minimum preheat 225 F for A572 Gr 50 plate over 1-1/2 in. (per D1.1 Table 3.2)
Interpass temperature: maximum 550 F (excessive interpass temperature degrades CVN toughness)
Post-weld hydrogen bake-out: 450-600 F for 1 hour per inch of thickness (D1.1 Annex H)
H4 electrodes are mandatory for plate over 2 in.

Electrode Selection by Base Metal Combination

Base Metal 1	Base Metal 2	Electrode	Rationale
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.

Related Tools and References

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.