ER70S-2 MIG / GMAW filler metal is a solid carbon steel wire used as a forgiving starting point for mild steel and general carbon steel work. It is commonly considered when fit-up is not perfect, mill scale is present, or surface condition is less than ideal. That said, it is not a substitute for the weld procedure specification. Before ordering wire or striking an arc, verify the WPS, code requirements, base metal grade, service conditions, and the manufacturer data sheet.

Key Takeaways

• ER70S-2 is a solid wire for MIG / GMAW carbon steel applications.
• Use the filler metal page as a selection starting point only, not a procedure approval.
• Confirm base metal, joint design, shielding gas, and wire diameter with the WPS.
• When fit-up or surface condition is questionable, inspect the joint before you assume the wire will solve the problem.
• If a requirement is unclear, mark it as Unknown (Verify) and check the governing document.

What the Filler Metal Finder Page Does

The ER70S-2 MIG / GMAW filler metal page and the filler metal finder are useful starting points for narrowing a wire choice. They help you move from a general application to a candidate filler metal, but they do not replace the WPS, engineer approval, or code review.

For this wire, the known basics are limited to the following: classification ER70S-2, AWS specification AWS A5.18, process MIG / GMAW, and intended use on mild steel and carbon steel. Any other detail such as recommended gas mix, weld position limits, current range, or diameter selection must be verified from the actual manufacturer data sheet or the project WPS. If that data is not available, record it as Unknown (Verify).

Practical Selection Checks

Use these checks before you put ER70S-2 into service:

1. Check the WPS. Verify that solid wire carbon steel filler is allowed for the joint and material group.
2. Inspect the base metal. Confirm the parent metal is mild steel or carbon steel as expected.
3. Verify service conditions. If the part sees low temperature, pressure, fatigue, or code-controlled service, do not assume this wire is acceptable without review.
4. Inspect joint prep. Look for rust, oil, paint, heavy scale, moisture, and dimensional mismatch.
5. Verify shielding gas. Do not guess. The correct gas and flow settings are Unknown (Verify) unless the WPS and manufacturer sheet state them.
6. Confirm wire diameter. Common sizes may exist, but use only the diameter specified for the job. If not specified, Unknown (Verify).

Troubleshooting and Support

If weld quality is inconsistent, work through the problem in order. Do not start by changing wire type unless the procedure allows it.

1. Verify the joint condition

• Inspect for contamination on both sides of the joint.
• Verify that loose mill scale, rust, and paint are removed to the level required by the WPS.
• Check root opening, land, and fit-up consistency.

Poor joint condition often looks like a wire problem when it is actually a preparation problem.

2. Verify the machine setup

• Check wire feed consistency and drive roll condition.
• Inspect liner wear, tip wear, and contact tip size.
• Verify polarity and gas delivery against the WPS. If not stated, Unknown (Verify).

Erratic feed can cause stubbing, spatter, and poor bead appearance. Do not treat these symptoms as proof that ER70S-2 is the wrong filler.

3. Verify the weld outcome

• Inspect bead profile, tie-in, and edge wetting.
• Check for undercut, porosity, and visible lack of fusion.
• Verify that the finished weld meets the acceptance criteria for the job.

If defects repeat, stop and compare the actual setup to the WPS line by line.

How to Use This Page in Purchasing

For maintenance buyers and welding support teams, the right workflow is simple: identify the application, pull the WPS, confirm the filler classification, and then compare the wire page to the manufacturer documentation. The filler metal finder page narrows the field, but it does not authorize substitution by itself.

When a detail is missing from the job packet, do not fill the gap with assumptions. Record the missing item as Unknown (Verify) and request the source document. That includes shielding gas, wire diameter, polarity, and any approval for out-of-position or restricted-service work.

Safety Notes

• Follow the WPS and site safety rules before welding.
• Use ventilation, fume control, and appropriate PPE.
• Do not weld on unknown or unverified base metal without clearance.
• Handle wire spools carefully to avoid contamination and damage.
• If the weld is for code work, pressure work, or critical service, verify the procedure and inspection plan first.

FAQ

Is ER70S-2 the same as ER70S-6?

No. They are different classifications. If either can be used on a job, that must come from the WPS or engineering direction, not from assumption.

Can I use ER70S-2 on rusty steel?

It may be considered when fit-up or surface condition is less than ideal, but that does not mean dirty steel is acceptable. Clean the joint to the required level and verify the WPS. If the required prep is unclear, Unknown (Verify).

What shielding gas should I use?

Unknown (Verify) unless the WPS or manufacturer data sheet states it. Do not guess gas type or flow rate.

Can I select wire from the filler metal finder without a WPS?

No. Use the finder page only as a starting point. It helps identify a likely filler family, but it does not replace procedure approval or code compliance.

Sources Checked

• ER70S-2 MIG / GMAW filler metal page
• WSP filler metal finder

Reviewed details were limited to the provided WSP pages and the information supplied in the draft brief. Any unlisted technical detail remains Unknown (Verify).

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