Quick Answer
Choose 4.0 mm E6013 only if a suitable joint and approved procedure accommodate the larger core and the welder can sustain its published current. A 3.2 mm option can be more manageable for smaller welds, limited access or lower-output equipment. Compare the actual manufacturer’s size-specific settings, rod length, position and accepted welds rather than assuming the larger diameter is inherently better.
Key Takeaways
- The nominal electrode diameter describes the metal core, not the outside of the coating.
- Lincoln Fleetweld 37 publishes a higher AC current range for 4.0 mm than for 3.2 mm.
- A published deposition rate does not prove a higher rate of accepted welds on the buyer’s joint.
What Actually Changes With Diameter?
A larger core generally calls for more current and can deposit more metal under suitable conditions. It can also add unwanted heat on a small or poorly supported joint. Compare the same named product and polarity before drawing a conclusion.
| Named product | 3.2 mm example | 4.0 mm example |
|---|---|---|
| Lincoln Fleetweld 37 | AC 110–140 A; DC± 100–135 A | AC 160–200 A; DC± 145–180 A |
| ESAB Weld 6013 | 3.2 × 350 mm: 80–130 A | 4.0 × 400 mm: 150–200 A |
The ESAB examples differ in rod length as well as diameter; its published deposition figures depend on specified test conditions. Do not transfer these values to an unnamed supplier’s rod.
When Is 4.0 mm Worth a Trial?
Consider it for a suitable larger weld or thicker part where access permits controlled placement and a higher sustained current. Check machine duty cycle, polarity and the actual manufacturer’s operating row.
Use the real joint, fit-up, operator and position in a comparative trial. Count acceptable welds and time spent changing rods, cleaning and reworking—not only deposited kilograms.
When Should 3.2 mm Stay in the Order?
Keep 3.2 mm when the specified weld is small, access is restricted, equipment cannot sustain 4.0 mm settings, or the WPS does not permit a size change. It may offer easier control in some positions.
That does not make 3.2 mm a universal thin-sheet solution: a smaller diameter or another approved process may be needed. If vertical-down travel is required, check the named product and procedure separately.
What Belongs on Two Comparable Quote Lines?
RFQ checklist:
- Base metal, thickness and joint drawing: define the work each size must perform.
- WPS and acceptance criteria: establish whether both diameters are permitted.
- Exact product, core diameter and rod length: avoid comparing different configurations.
- Machine output, duty cycle and polarity: verify sustained operation.
- Current row and datasheet revision: tie settings to the quoted product.
- Pack, lot documents and sample plan: compare deliverables and accepted-weld cost.
Buyer FAQ
Is 4.0 mm automatically stronger?
No. Diameter alone is not a weld-quality or strength grade.
Can an AC welder’s maximum current prove suitability?
No. Check usable duty cycle and the named rod’s AC range.
Can a successful shop trial change a tender WPS?
No. Obtain the required procedure approval first.
Inquiry: Send the joint drawing, machine data and required sizes through your established inquiry route to request size-specific sheets and comparable quotes.
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