Can 1018 steel be welded?
Yes. 1018 welds easily by MIG, TIG, stick or flux-core with ER70S-6 or E7018, needs no preheat below about 38 mm (1.5") and no post-weld heat treatment.
1018 is a low-carbon steel, 0.15-0.20% carbon and 0.60-0.90% manganese, with a carbon equivalent of about 0.3. At that level the heat-affected zone cannot quench to anything brittle, hydrogen cracking is not a practical concern in normal sections, and every common arc process works: GMAW (MIG) with ER70S-6, GTAW (TIG) with ER70S-2 or ER70S-6, SMAW (stick) with E6010 or E7018, and FCAW with E71T-1. These fillers overmatch the base metal, so a sound weld is stronger than the 1018 around it. Preheat is only needed on heavy sections, roughly above 38 mm (1.5"), where 65-110 °C (150-225 °F) keeps the cooling rate and stress down, and in a cold shop, where the joint should be warmed above about 20 °C (70 °F) and dried. No post-weld heat treatment is needed for strength.
The issues with 1018 weldments are dimensions and strength, not cracking. Most 1018 is bought as cold-drawn bar (ASTM A108), which carries residual stress from drawing and a yield strength of about 370 MPa (54 ksi). Welding releases that stress locally, so a bar that was straight and a machined feature that was in tolerance can move, and the heat-affected zone recrystallizes back toward the hot-rolled yield of about 220-250 MPa (32-36 ksi). For precision weldments the order is weld, stress relieve at 595-650 °C (1100-1200 °F) if the part must hold tight tolerances, then finish machine. Hot-rolled 1018 and plate carry mill scale that should be ground or blasted off for GMAW and GTAW; E6010 stick electrodes tolerate it better.
Watch what 1018 is welded to, and what it has been through. 1018 welded to 4140 or another hardenable steel takes the preheat and post-weld treatment of the hardenable side. 1018 welded to stainless steel takes an ER309L filler. Carburized or case-hardened 1018 must not be welded through the case: the 0.8-1.0% carbon surface cracks like tool steel, so grind the case off or mask the area during carburizing. Zinc-plated or galvanized 1018 needs the coating removed near the joint to avoid porosity and zinc fume. And check the cert: free-machining grades such as 12L14 and 1215 look identical on the rack and are sometimes substituted on screw-machine parts, but they weld with porosity and hot cracks.
Welding for 1018 parts: where to send them
What to specify
- Process and filler: ER70S-6 (AWS A5.18) for GMAW, ER70S-2 or ER70S-6 for GTAW, E7018 (AWS A5.1) for SMAW, E71T-1 (AWS A5.20) for FCAW
- Weld symbols per AWS A2.4 with size, length, and whether groove welds are complete joint penetration
- Preheat only where it applies: 65-110 °C (150-225 °F) above about 38 mm (1.5"), and no welding on stock below 0 °C (32 °F)
- Sequence for precision parts: weld, stress relieve at 595-650 °C (1100-1200 °F) if needed, then finish machine; mark the features machined after welding
- Material: 1018 per ASTM A108 (cold-finished bar) with a mill cert, and "no free-machining (leaded or resulfurized) substitutes" on weldments
- Acceptance: visual per AWS D1.1 or an ISO 5817 quality level, with dye penetrant or magnetic particle on critical joints
Pitfalls
- Machining a precision part completely before welding: the weld releases cold-drawn stress and pulls features out of tolerance
- Designing to cold-drawn strength at the weld: the heat-affected zone drops back toward hot-rolled strength
- Welding through a carburized case: the high-carbon surface cracks; grind it off or mask it before case hardening
- Welding over zinc plating or galvanizing: porosity and zinc fume; strip the coating from the joint area
- A shop substituting 12L14 or 1215 for easier machining: the weld cracks and fills with porosity
- Long single-side welds on thin bar and plate: they bow; sequence and fixture, or alternate sides
Frequently asked questions
- Is 1018 steel good for welding?
- Yes. It is one of the easiest steels to weld. Its low carbon (0.15-0.20%) means no brittle heat-affected zone, no preheat on normal sections and no post-weld heat treatment, with any common process and filler.
- What welding rod or wire should I use on 1018?
- ER70S-6 wire for MIG, ER70S-2 or ER70S-6 rod for TIG, E7018 or E6010 electrodes for stick, and E71T-1 for flux-core. All overmatch the strength of 1018.
- Can you weld 1018 to 4140?
- Yes. Preheat and post-weld treat for the 4140 side, typically 200-300 °C (400-575 °F) preheat and a slow cool or stress relief, and use a low-hydrogen filler such as E7018 or ER70S-6. The joint strength is then set by the 1018.
