Sheet Metal Welding: TIG, MIG, and Spot Welding Services
Professional sheet metal welding service offering TIG, MIG, spot, and seam welding for steel, stainless steel, and aluminum. Certified welders, distortion control, and full NDT inspection.
Sheet Metal Welding: TIG, MIG, and Spot Welding Services
Sheet metal welding permanently joins two or more metal sheets by melting the base material (with or without filler) to form a metallurgical bond. Welded joints achieve ≥85% of base material strength when properly executed, making welding essential for structural assemblies, sealed enclosures, and multi-part sheet metal fabrications.
At FIRMFG, we offer four welding processes: TIG for precision thin-sheet welding, MIG for high-efficiency production welding, spot welding for fast lap joints, and seam welding for leak-tight continuous joints. Our certified welders work with carbon steel, stainless steel, aluminum, and copper, with full distortion control and NDT inspection capabilities.
This guide covers welding methods, material compatibility, distortion control, quality inspection, and cost factors. Or, skip ahead and request a quote for an immediate price and lead time.
Welding Quick Specifications
Key specifications and capabilities of our sheet metal welding service.
| Specification | Value |
|---|---|
| Material Thickness | 0.5 – 12 mm |
| Max Weld Length | Unlimited (segmented) |
| Weld Strength | ≥ 85% of base material |
| Welding Position | Flat, horizontal, vertical, overhead |
| Max Part Size | 3000 × 1500 × 1000 mm |
| Weld Inspection | Visual, penetrant, X-ray available |
Welding Methods
We offer four welding processes, each suited for different thickness ranges, materials, and production volumes. Method selection depends on joint type, quality requirements, and cost.
TIG Welding (GTAW)
Tungsten Inert Gas welding uses a non-consumable tungsten electrode with separate filler rod. Produces the highest quality welds with precise heat control, ideal for thin sheets (0.5–3mm) and critical applications requiring aesthetic weld beads.
Typical use: Thin sheet 0.5–3mm; stainless steel, aluminum; precision joints
Advantage: Highest weld quality, precise heat control, clean welds
MIG Welding (GMAW)
Metal Inert Gas welding uses a continuously fed consumable wire electrode. High deposition rate and speed make it ideal for thicker sheets (2–12mm) and long weld seams. Most efficient for production welding of steel and stainless steel.
Typical use: Thick plate 2–12mm; steel, stainless steel; long production seams
Advantage: High efficiency, fast deposition, cost-effective for production
Spot Welding
Resistance spot welding joins overlapping sheets by passing current through copper electrodes at a single point. No filler material needed. Ideal for thin sheet lap joints (0.5–3mm) and high-volume production of enclosures and panels.
Typical use: Thin sheet lap joints 0.5–3mm; steel, galvanized steel; high volume
Advantage: No filler needed, very fast cycle, minimal heat distortion
Seam Welding
Continuous resistance welding that produces a leak-tight seam by overlapping spot welds. Ideal for sealed containers, tanks, and pipes where liquid or gas tightness is required.
Typical use: Sealed containers, tanks, pipes; thin sheet 0.5–3mm
Advantage: Leak-tight continuous seam, no filler material, fast production
Material Compatibility by Welding Process
Each material responds differently to each welding process. Difficulty and cost vary based on thermal conductivity, oxide formation, and cracking susceptibility.
| Material | Difficulty | TIG | MIG | Spot |
|---|---|---|---|---|
| Carbon Steel (SPCC) | Easy | Excellent, standard process | Excellent, high efficiency | Excellent, no issues |
| Stainless Steel (304/316L) | Moderate | Excellent, clean welds | Good, requires argon+CO₂ mix | Good, higher current needed |
| Aluminum (5052) | Moderate | Good, AC welding needed | Good, spray transfer mode | Difficult, high thermal conductivity |
| Aluminum (6061) | Challenging | Moderate, crack-sensitive HAZ | Moderate, needs pulsed MIG | Difficult, not recommended |
| Copper (C11000) | Challenging | Moderate, high thermal conductivity | Difficult, requires special wire | Very difficult |
| Brass (C26000) | Moderate | Good, braze welding preferred | Moderate, low fuming wire | Difficult |
Aluminum and copper require special welding procedures due to high thermal conductivity and oxide layer formation. Stainless steel requires argon backing gas for TIG welding.
Weld Distortion Control
Thermal expansion and contraction during welding cause distortion. We use four methods to minimize and correct warpage in sheet metal weldments.
Proper Weld Sequence
Welding in alternating or skip sequence to distribute heat evenly and prevent thermal accumulation in one area
Fixture & Clamping
Rigid fixturing holds parts in position during welding, resisting thermal expansion and contraction forces
Heat Input Control
Balancing amperage, voltage, and travel speed to minimize the heat-affected zone (HAZ) and thermal distortion
Post-Weld Correction
Mechanical straightening or flame straightening to correct residual distortion after welding is complete
Best Practices for Minimizing Distortion
- Design symmetrical weld joints to balance thermal stresses on both sides of the part.
- Use intermittent welds (stitch welding) instead of continuous welds where full strength is not required.
- Weld from the center outward to push thermal expansion toward free edges.
- Allow for post-weld machining on critical tolerance surfaces to correct residual distortion.
Weld Quality Inspection
We provide multiple inspection methods from basic visual to advanced X-ray radiography, ensuring weld integrity for any application.
| Inspection Method | Description | Standard |
|---|---|---|
| Visual Inspection | 100% of welds inspected for bead appearance, width, height, undercut, cracks, and surface porosity | AWS D1.1 / ISO 5817 |
| Dye Penetrant Testing (PT) | Fluorescent or color-contrast penetrant applied to detect surface-breaking cracks and porosity | ASTM E165 |
| X-Ray Radiography (RT) | Internal weld inspection for volumetric defects: porosity, slag inclusion, lack of fusion | ASME V |
| Tensile Strength Testing | Destructive testing of weld coupons to verify joint strength ≥ 85% of base material | AWS B4.0 |
Visual and penetrant testing are included as standard. X-ray radiography and tensile testing are available for critical applications at additional cost.
What Drives Welding Cost?
Welding is priced by weld length, process type, and material difficulty. Batch size and weld position also affect the total cost.
Priced by Weld Length
Cost calculated per linear meter of weld, with TIG costing 30–50% more than MIG per meter
Material Affects Difficulty
Aluminum and copper require special processes and gases, increasing cost 40–80% over carbon steel
Position Premium
Overhead and vertical welding positions require more time and skill, adding 20–30% to cost
Volume Discount
Per-part cost decreases at 25+ parts due to shared fixture setup and batch welding optimization
Cost by Weld Type and Thickness
| Weld Type | Thickness | Cost | Lead Time |
|---|---|---|---|
| TIG Welding | 0.5–3mm (thin sheet) | $15 – $35 | 3 – 5 days |
| TIG Welding | 3–6mm (medium plate) | $30 – $60 | 5 – 7 days |
| MIG Welding | 2–6mm (standard) | $10 – $25 | 3 – 5 days |
| MIG Welding | 6–12mm (thick plate) | $20 – $45 | 5 – 7 days |
| Spot Welding | 0.5–3mm (lap joint) | 2 – 4 days | |
| Seam Welding | 0.5–3mm (continuous) | $12 – $30 | 3 – 5 days |
Pricing includes welder time, consumables (wire, gas), and basic visual inspection. NDT testing, fixturing, and post-weld correction are quoted separately.
Sheet Metal Welding FAQ
Answers to the most common questions about our welding service at FIRMFG.
QWhat is the maximum material thickness you can weld?
For MIG welding, we can handle steel up to 12mm thick in a single pass, with multi-pass welding possible for thicker sections. TIG welding is typically used for materials up to 6mm, as the lower deposition rate makes thicker welds time-prohibitive. Spot and seam welding are limited to 3mm per sheet for reliable lap joints. For materials thicker than 12mm, we recommend our CNC machining or plasma cutting services.
QCan you weld aluminum sheet metal?
Yes, we weld aluminum using both TIG (AC) and pulsed MIG welding. Aluminum 5052 is the most weldable grade with excellent results. Aluminum 6061 is weldable but requires careful heat management due to its susceptibility to hot cracking in the heat-affected zone. We use 4043 or 5356 filler wire depending on the base alloy and application. All aluminum welding requires thorough cleaning to remove the oxide layer before welding.
QHow do you control weld distortion?
We use four key methods: (1) Proper weld sequencing — alternating or skip welding to distribute heat evenly across the part. (2) Rigid fixturing — custom clamps and jigs hold parts in position during welding, resisting thermal expansion forces. (3) Heat input control — balancing amperage, voltage, and travel speed to minimize the heat-affected zone. (4) Post-weld correction — mechanical straightening or flame straightening to correct any residual distortion. For critical tolerance parts, we can pre-distort parts to compensate for expected warpage.
QWhat weld inspection methods do you offer?
All welds undergo 100% visual inspection per AWS D1.1 / ISO 5817 standards. Additional inspection methods available include: dye penetrant testing (PT) for surface crack detection, X-ray radiography (RT) for internal defect inspection, and tensile strength testing of weld coupons. For aerospace and medical applications, we provide full weld documentation including welder qualifications, WPS/PQR, and inspection reports.
QWhat is the minimum batch size for welding?
We have no minimum order quantity — single prototypes and one-off parts are welcome. However, per-part costs are higher for small batches due to fixture setup and welder preparation time. Batch pricing becomes cost-effective at 10+ identical parts. For spot welding and seam welding of high-volume enclosures, per-part cost drops significantly at 100+ parts.
QWhat is the lead time for sheet metal welding?
Standard lead time is 3–5 business days for simple weldments (1–3 welds per part) in small batches. Complex assemblies with 5+ welds or multi-position welding take 5–7 days. For batches of 50+ parts, lead time extends to 7–10 days. Rush service (2-day turnaround) is available for single-part prototypes with standard materials. Lead time includes fixturing, welding, post-weld correction, and quality inspection.
Applications of Sheet Metal Welding
Welding is used to create permanent structural joints, sealed assemblies, and multi-part fabrications across industries.
Chassis Assembly
Equipment chassis, frame assembly, base plates
Pipe & Tube Joints
Exhaust pipes, ductwork, fluid lines
Bracket Connections
Mounting brackets, support gussets, reinforcement
Enclosure Sealing
Sealed boxes, waterproof housings, tanks
Structural Parts
Load-bearing weldments, supports, frames
Automotive Parts
Body panels, subframes, exhaust components
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Learn MoreStart Your Welding Project
Upload your CAD files and get a free welding quote within 24 hours. Our certified welders provide DFM feedback, process selection, and distortion control recommendations at no cost. AWS D1.1 compliant, NDT inspection available, 3-day turnaround.