Submerged Arc Welders vs. GMAW: Which Cuts Your Per-Pass Cost in Half?
In industrial welding, choosing the right process directly impacts productivity, quality, and costs. Two popular methods are submerged arc welding (SAW) using submerged arc welders and gas metal arc welding (GMAW), also known as MIG welding. Both processes join metals using an electric arc, but their designs, capabilities, and costs differ significantly. A key question for manufacturers and fabricators is: which process reduces per-pass costs—submerged arc welders or GMAW? This guide compares the two, analyzing factors like deposition rates, material usage, labor, and energy costs to determine which option can cut per-pass expenses in half.
Understanding Submerged Arc Welders and GMAW
Submerged Arc Welders
Submerged arc welders use a continuous electrode wire fed into the weld joint, with the arc and molten weld pool shielded by a layer of granular flux. The flux melts to form a protective slag, preventing contamination from air and improving weld quality. Submerged arc welders are known for high deposition rates, deep penetration, and suitability for thick materials (6 mm and above). They are often used in heavy industries like shipbuilding, pipeline construction, and structural steel fabrication.
GMAW (Gas Metal Arc Welding)
GMAW uses a continuous electrode wire fed through a welding gun, with the arc shielded by a shielding gas (like argon or carbon dioxide). The gas protects the weld pool from oxygen and nitrogen, ensuring clean fusion. GMAW is versatile, used for thin to medium-thick materials (0.5–12 mm), and is popular in automotive, manufacturing, and repair work due to its portability and ease of use.
Key Cost Factors: Per-Pass Comparison
Per-pass cost is calculated by combining expenses like consumables, labor, energy, and equipment wear. Let’s break down how submerged arc welders and GMAW perform in each category.
1. Deposition Rate and Productivity
Deposition rate—the amount of filler metal deposited per hour—directly affects per-pass costs. Higher rates mean fewer passes are needed to fill a joint, reducing labor and time expenses.
- Submerged Arc Welders: These machines excel in deposition rates, typically ranging from 5 to 20 kg per hour. Some high-power submerged arc welders can reach 30 kg/hour for thick materials. This high output means a single pass can fill large joints, reducing the number of passes required compared to GMAW. For example, welding a 20 mm thick steel plate may take 2–3 passes with a submerged arc welder versus 5–7 passes with GMAW.
- GMAW: Deposition rates are lower, usually 1 to 8 kg per hour. The process is slower because the shielding gas limits how much current can be applied without causing spatter or porosity. Thicker materials require more passes, increasing total time and labor costs per joint.
Higher deposition rates make submerged arc welders more productive, cutting per-pass time and labor expenses significantly.
2. Consumable Costs: Electrode, Flux, and Gas
Consumables (electrode wire, flux, shielding gas) are a major part of per-pass costs.
- Submerged Arc Welders: Consumables include electrode wire and flux. Flux is relatively inexpensive, and a portion of unused flux can be recovered and reused (up to 50–70% in some setups), reducing waste. Electrode wire for SAW is often cheaper per kilogram than GMAW wire because it doesn’t require special coatings for gas compatibility.
- GMAW: Consumables include electrode wire and shielding gas. Shielding gas is a recurring cost; a typical cylinder can cost $50–$100 and lasts 8–12 hours of continuous use. GMAW wire is also more expensive than SAW wire due to specialized coatings. Additionally, GMAW produces more spatter, which wastes wire and requires post-weld cleanup, adding indirect costs.
Submerged arc welders have lower consumable costs per kilogram of deposited metal, especially with flux recovery.
3. Labor Costs
Labor costs depend on how long a welder spends on each pass and the skill level required.
- Submerged Arc Welders: SAW is often automated or semi-automated, reducing the need for highly skilled operators. Once parameters are set, the machine can run continuously, with operators monitoring progress rather than manually guiding the arc. This lowers labor costs per pass, as one operator can oversee multiple machines.
- GMAW: GMAW is often manual, requiring skilled welders to control the gun, maintain travel speed, and adjust for joint variations. Manual operation is slower and more labor-intensive, especially for large joints needing multiple passes. Skilled GMAW welders also command higher hourly wages, increasing per-pass costs.
Automation with submerged arc welders reduces labor expenses, a key factor in lowering per-pass costs.
4. Energy Efficiency
Energy usage affects operational costs, especially for high-volume welding.
- Submerged Arc Welders: SAW uses higher current (300–1000 amps) but is highly efficient at converting energy into heat for welding. The flux helps concentrate heat in the weld pool, reducing energy waste.
- GMAW: GMAW uses lower current (100–400 amps) but is less energy-efficient. More energy is lost as spatter or heat dissipation, and the need for multiple passes increases total energy consumption per joint.
While submerged arc welders use more power per hour, their higher deposition rates mean less total energy is used per kilogram of weld metal, lowering energy costs per pass.
5. Post-Weld Cleanup and Rework
Costs from cleanup and rework add to per-pass expenses.
- Submerged Arc Welders: SAW produces minimal spatter and forms a slag layer that protects the weld as it cools. The slag is easily removed with a chipping hammer, reducing cleanup time. Weld quality is high, with fewer defects like porosity or lack of fusion, lowering rework costs.
- GMAW: GMAW produces more spatter, which requires grinding or chipping to remove. Poor gas coverage can cause porosity, and inconsistent travel speed may lead to uneven beads, increasing rework needs. These extra steps add time and labor costs per pass.
Submerged arc welders reduce post-weld expenses, further cutting per-pass costs.
Real-World Cost Comparison: Case Study
To illustrate the difference, let’s compare per-pass costs for welding a 15 mm thick steel plate joint (1 meter long) using both processes. With a submerged arc welder, the deposition rate is 10 kg/hour, requiring 2 passes to complete the joint. Labor costs are $30 per hour due to automation, and consumables (wire and flux) cost $1.20 per kg. Energy costs are $0.15 per kWh, and minimal cleanup keeps additional expenses low. The total per-pass cost for the submerged arc welder comes to $18.50.
For GMAW, the deposition rate is lower at 3 kg/hour, needing 5 passes for the same joint. Labor costs are higher at $45 per hour because of manual operation, and consumables (wire and gas) cost $2.50 per kg. More spatter means extra cleanup time, and energy usage is higher due to the increased number of passes. The total per-pass cost for GMAW is $42.30.
In this scenario, submerged arc welders cut per-pass costs by over 50% compared to GMAW, driven by higher productivity, lower consumable costs, and reduced labor needs.
When Does GMAW Offer Better Cost Savings?
While submerged arc welders excel in heavy-duty applications, GMAW may be cheaper in specific scenarios:
- Thin Materials: For materials under 6 mm, GMAW requires fewer setup steps and can complete joints in 1–2 passes, avoiding the higher initial setup costs of SAW.
- Small, Complex Joints: GMAW’s portability and manual control make it better for intricate joints or small parts where automation is impractical.
- Low-Volume Production: For occasional welding tasks, GMAW equipment is cheaper to purchase and maintain than a submerged arc welder, lowering overall costs.
FAQ
Is a submerged arc welder more expensive to buy than a GMAW machine?
Yes, initial investment for submerged arc welders is higher ($10,000–$50,000) compared to GMAW machines ($2,000–$15,000). However, for high-volume production, the per-pass cost savings quickly offset the upfront expense.
Can submerged arc welders be used for thin materials?
They are not ideal. SAW’s high heat input can cause burn-through on materials under 6 mm. GMAW is better for thin metals.
Does flux recovery really reduce costs for submerged arc welders?
Yes. Recovering and reusing flux can lower consumable costs by 30–40%, making SAW more cost-effective for large projects.
Is GMAW faster for small jobs?
Yes. GMAW requires less setup time than SAW, making it faster for short, simple joints or low-volume work.
Do submerged arc welders require more maintenance than GMAW machines?
No. SAW has fewer moving parts than GMAW guns, which need regular nozzle cleaning and liner replacement. SAW maintenance focuses on flux systems and wire feeders, which are less frequent.
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