ER70S-6 filler metal

Hobart's HB-28 ER70S-6 gives typical as-welded GMAW results with 100% CO₂ of 85,000 psi tensile, 70,000 psi yield and 29% elongation in 2 in. Its listed minima are 70,000 psi, 58,000 psi and 22%. Verify procedure and test conditions before comparing this wire with another product or a finished joint. HB-28 data sheet, p. 1

Identity and classification

In ER70S-6, ER means electrode or rod, 70 the 70,000 psi tensile class and S solid construction. The suffix identifies the chemistry and shielding category. Qualify position separately. Hobart, solid-wire selection, updated February 20, 2025

AWS A5.18/A5.18M:2025 is the current edition identified here: its preview records ANSI approval on August 5, 2025 and identifies it as the tenth edition, replacing 2023. For solid electrodes and rods, classification addresses electrode chemistry and as-welded weld-metal mechanical properties, with additional manufacturing, size and packaging requirements. AWS says its customary and SI systems must be used independently. A classification therefore describes specified tests; it does not establish the strength of every production joint. Use the edition invoked by the project and the supplied product's certification. AWS A5.18/A5.18M:2025 preview, pp. 1–2

Chemistry, deoxidation and surface condition

Manganese and silicon help scavenge oxygen during welding. Silicon also promotes weld-pool fluidity and toe wetting; reaction products can rise to the surface as silicate islands. These deposits are distinct from the continuous slag covering associated with flux-bearing consumables. Their amount depends on the wire formulation, base-metal condition and shielding gas. Manufacturers can vary deoxidizer additions within a classification, so two ER70S-6 products need not behave identically. Compare bead shape, cleanup and feeding in the actual operation rather than selecting on classification alone. Hobart, understanding deoxidizers, updated July 14, 2023

Deoxidizer tolerance does not make contamination irrelevant. Hobart's selection guidance favors clean base material, while identifying ER70S-6 as helpful where light rust or mill scale remains. It also calls for removal of silicon islands before painting or surface conditioning. Include that cleanup in the finishing process instead of assuming a smooth-looking bead is ready for coating. Hobart, solid-wire selection

As one product-specific chemistry example, Hobart HB-28 lists typical wire values of 0.08% carbon, 1.52% manganese and 0.80% silicon. These are that sheet's typical results, not target values that every spool must reproduce. The same sheet specifies DCEP for its GMAW use, allows CO₂ or listed argon/CO₂ mixtures, and recommends dry enclosed storage in intact original packaging. Re-drying is not recommended. Treat wire storage differently from a covered-electrode baking procedure. HB-28 data sheet, pp. 1–2, printed revision code 201001

Process, shielding and transfer mode

The product form and process matter. Midalloy supplies ER70S-6 for both GMAW and GTAW, with spooled MIG wire and packaged TIG rods. Its bulletin lists argon for GTAW, while its GMAW recommendations use different shielding selections. A CO₂ recommendation for MIG wire is consequently not a TIG shielding recommendation. Specify process, diameter and package as well as alloy classification when ordering. Midalloy ER70S-6 technical bulletin, undated

For GMAW, distinguish how metal crosses the arc:

Conventional short-circuit, globular and spray modes can use the same wire, but depend on gas and electrical settings. Pulsed operation requires a source with suitable pulse capability. Wire classification alone cannot select the waveform or establish its operating window. Miller, guide to pulsed MIG welding

Miller identifies 75% argon/25% CO₂ as an option for short-circuit MIG and 90% argon/10% CO₂ for spray or pulse. These are process examples, not interchangeable cylinder specifications. Short circuit can suit thin material or positional work, but an unsuitable setup on thicker material can leave inadequate fusion. Joint access, travel speed, wire feed, voltage, work angle and electrode extension all affect the result. A flat bead or low spatter level does not independently demonstrate root fusion. Miller, reducing weld rework

Reading product data: bounded examples

Lincoln's SuperArc L-56 sheet gives this typical short-circuit operating point: 0.025-inch wire, DC+, 100% CO₂, 9–12 mm contact-tip-to-work distance, 2.5 m/min wire feed, 17 V and approximately 35 A. It is a documented starting point for that product and configuration, not a thickness-to-amperage rule or a qualified joint procedure. The sheet also supports other transfer modes and lists multiple gas families; do not combine a current from one row with the gas or extension from another. Lincoln explicitly warns that test results vary with procedure, plate chemistry, temperature and weldment design. SuperArc L-56, publication C4.10.5, issue 06/17, pp. 2–3

The HB-28 sheet separates its CO₂ test results from specification minima. Assess the actual joint using its qualified procedure and test evidence. HB-28 data sheet, p. 1

For selection, record the base-metal grade, required strength and toughness, service temperature, joint geometry, process/transfer mode, gas, wire diameter and any heat treatment before comparing products. Keep manufacturer typical results separate from purchasing acceptance requirements and procedure qualification results. The useful deliverable is a compatible filler and welding procedure with demonstrated joint performance, rather than the highest tensile number in a catalog. Lincoln test-results limitations, p. 3

Related reference

Welding methods