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SMAW welding electrodes parameters

The SMAW (Shielded Metal Arc Welding) process uses a consumable coated electrode between 1,6 mm and 6,4 mm (1/16 in and 1/4 in) in diameter, whose electric arc generates melting temperatures above 1500 °C / 2732 °F. The electrode coating decomposes forming a protective gas atmosphere and a slag layer that insulates the weld pool. Typical current intensity ranges from 40 A to 400 A depending on the electrode diameter and type, usually working with direct current electrode positive (DCEP) or alternating current (AC).

Operating Parameters

Section titled “Operating Parameters”

The current selection for a given electrode diameter directly influences penetration and deposition rate. The recommended amperage ranges according to AWS classification and diameter are summarized below. The arc voltage is usually maintained between 18 V and 30 V, with a travel speed of 150 mm/min to 350 mm/min (6 in/min to 14 in/min) for root and fill passes.

Electrode (AWS) Diameter Recommended Current (DCEP or AC) Typical Polarity
E6010 2,4 mm / 3/32 in 40 – 70 A DCEP
E6010 3,2 mm / 1/8 in 70 – 110 A DCEP
E6010 4,0 mm / 5/32 in 100 – 160 A DCEP
E7018 2,4 mm / 3/32 in 65 – 100 A DCEP, AC
E7018 3,2 mm / 1/8 in 90 – 130 A DCEP, AC
E7018 4,0 mm / 5/32 in 120 – 180 A DCEP, AC
E7018 5,0 mm / 3/16 in 180 – 260 A DCEP, AC
E6011 3,2 mm / 1/8 in 75 – 120 A AC, DCEP
E6013 3,2 mm / 1/8 in 80 – 125 A AC, DCEN, DCEP

The cooling rate is controlled by adjusting the heat input between 0,5 kJ/mm and 2,5 kJ/mm (12,7 kJ/in to 63,5 kJ/in), which influences the joint microstructure.

Tolerances and Dimensional Quality

Section titled “Tolerances and Dimensional Quality”

SMAW welded joints can maintain weld bead position tolerances of ±0,8 mm (±0.031 in) on sheet thicknesses up to 5 mm (0.197 in). The weld reinforcement is controlled not to exceed 3,0 mm / 0.118 in above the base metal surface, and complete penetration on 1,5 mm / 0.059 in sheet is achievable with 1,6 mm / 1/16 in electrodes. Final dimensional accuracy depends on operator skill and edge preparation, allowing a maximum angular misalignment of 3° to 5° in butt joints.

Applicable Materials

Section titled “Applicable Materials”

The process is suitable for welding carbon steels with carbon content up to 0,30 %C, low alloy steels such as ASTM A36 and A572, austenitic stainless steels 304/316, and gray or ductile cast irons using nickel-based electrodes. Thicknesses from 1,5 mm / 0.059 in to more than 50 mm / 1.97 in can be joined with multiple passes. Compatibility extends to copper and nickel alloys, although with less frequent use.

Advantages and Limitations

Section titled “Advantages and Limitations”
  • Advantages:
    • Simple and low-cost equipment, with initial investment under 1000 USD for basic 150 A units.
    • Outdoor operation with moderate wind, no need for external shielding gas.
    • Wide variety of electrodes for different materials (more than 50 AWS classifications).
    • Suitable for maintenance and repair work in the field.
  • Limitations:
    • Deposition rate limited to 1 – 3 kg/h (2 – 6 lb/h) in high-production electrodes.
    • Productivity lower than GMAW and FCAW in continuous production.
    • Requires slag removal between passes, increasing cycle time.
    • Sensitive to coating moisture; low-hydrogen electrodes must be stored at 120 °C / 248 °F.

Electrode Selection Guide

Section titled “Electrode Selection Guide”
  1. E6010/E6011: deep penetration, fine slag and rapid solidification; ideal for root passes in pipes and maintenance in difficult positions. Deposit tensile strength: ~430 MPa / 62 ksi.
  2. E7018: low hydrogen, excellent low-temperature toughness (−30 °C / −22 °F), deposit with 490 MPa / 70 ksi tensile strength. Use in high-strength steel structures and pressure vessels.
  3. E7016: similar to E7018 but with sodium coating, suitable for alternating current, deposited metal efficiency of 95%.
  4. E308L-16: stainless steel electrode for 304L steels, deposit with intergranular corrosion resistance, current of 70–110 A for 3,2 mm / 1/8 in diameter.
  5. E Ni-Cl: nickel electrode for dissimilar joints and cast iron welding; preheating to 150 °C / 302 °F for thicknesses >10 mm / 0.394 in.

Parameter Tables by Material

Section titled “Parameter Tables by Material”

Carbon Steel ASTM A36 – butt joint at 6 mm (0.236 in)

Section titled “Carbon Steel ASTM A36 – butt joint at 6 mm (0.236 in)”
Parameter Value for E6010 Value for E7018
Electrode diameter 3,2 mm / 1/8 in 3,2 mm / 1/8 in
Current (A) 85 – 105 A 100 – 120 A
Voltage (V) 20 – 24 V 22 – 26 V
Travel speed 200 mm/min / 7.9 in/min 250 mm/min / 9.8 in/min
Heat input 0,6 – 1,0 kJ/mm / 15 – 25 kJ/in 0,7 – 1,1 kJ/mm / 18 – 28 kJ/in
Welding positions All All, except vertical-down

Stainless Steel 304L – thickness 3 mm (0.118 in)

Section titled “Stainless Steel 304L – thickness 3 mm (0.118 in)”
Parameter E308L-16
Electrode diameter 2,4 mm / 3/32 in
Current 55 – 75 A (DCEP)
Voltage 21 – 25 V
Travel speed 180 mm/min / 7.1 in/min
Backing gas Pure argon (not always needed)
Post-weld treatment Normally not required

Gray Cast Iron – repair with Ni-Cl electrode

Section titled “Gray Cast Iron – repair with Ni-Cl electrode”
Parameter Recommendation
Preheating 150 – 260 °C / 302 – 500 °F
Electrode diameter 3,2 mm / 1/8 in
Current 70 – 100 A (AC or DCEN)
Post-weld cooling Slow, wrapped in ceramic blanket

Frequently Asked Questions (FAQ)

Section titled “Frequently Asked Questions (FAQ)”
Section titled “What is the recommended amperage for a 3,2 mm E7018 electrode?”

For a 3,2 mm (1/8 in) E7018 electrode, a current range of 90 to 130 A is recommended, operating with DCEP or AC polarity, depending on the base material thickness and welding position.

What penetration difference exists between E6010 and E7018 at 100 A?

Section titled “What penetration difference exists between E6010 and E7018 at 100 A?”

At 100 A, an E6010 electrode produces up to 30% greater penetration than an E7018 of the same diameter, due to the composition of its cellulosic coating that generates a more intense and directed arc.

What is the maximum storage temperature for a low-hydrogen electrode?

Section titled “What is the maximum storage temperature for a low-hydrogen electrode?”

Low-hydrogen electrodes, such as E7018, must be stored in ovens at a temperature between 120 °C and 150 °C (248 °F – 302 °F) to avoid moisture absorption, which could introduce up to 5 ml/100 g of diffusible hydrogen in the deposited metal.

What minimum thickness can be welded with SMAW electrode without backing?

Section titled “What minimum thickness can be welded with SMAW electrode without backing?”

With a 1,6 mm (1/16 in) electrode, it is possible to weld 1,5 mm (0.059 in) sheet in a butt joint without backing, maintaining a current of 30 to 50 A and a square edge preparation.

How much material does a 4,0 mm E7018 electrode deposit per arc minute?

Section titled “How much material does a 4,0 mm E7018 electrode deposit per arc minute?”

A 4,0 mm (5/32 in) E7018 electrode operating at 150 A deposits approximately 1,4 kg/h (3.1 lb/h), which is equivalent to 0.025 kg per minute of continuous arc, with a deposition efficiency close to 70% including the coating.

What is the typical tensile strength of an SMAW weld bead with E6013 electrode?

Section titled “What is the typical tensile strength of an SMAW weld bead with E6013 electrode?”

The deposited metal with an E6013 electrode has a minimum tensile strength of 430 MPa (62 ksi), with an elongation of 17% and a toughness of 27 J at −20 °C (20 ft·lbf at −4 °F), suitable for light structural applications.

References

Section titled “References”