Welding Process Selection Guide

Understanding Welding Process Selection: A Critical Decision for Project Success

Selecting the appropriate welding process for a manufacturing project is one of the most consequential decisions engineers and fabricators face. The wrong choice can lead to structural failures, budget overruns, delayed timelines, and compromised safety standards. Conversely, the right welding process ensures optimal joint integrity, cost efficiency, and compliance with Canadian welding codes such as CSA W47.1 and CSA W59.

For manufacturers and fabricators across Nova Scotia and the broader Atlantic Canada region, understanding the nuances of welding process selection is particularly important given our diverse industrial landscape. From shipbuilding in Halifax to offshore energy structures, agricultural equipment in the Annapolis Valley, and structural steel fabrication throughout the Maritimes, each application demands careful consideration of process parameters, material compatibility, and environmental factors.

This comprehensive guide examines the key factors influencing welding process selection and provides practical frameworks for making informed decisions that align with your project specifications, quality requirements, and budgetary constraints.

The Six Primary Welding Processes: Capabilities and Limitations

Before selecting a welding process, engineers must thoroughly understand the capabilities, advantages, and limitations of each available option. The six most commonly used fusion welding processes in industrial manufacturing each serve distinct purposes.

Shielded Metal Arc Welding (SMAW)

Often referred to as "stick welding," SMAW remains one of the most versatile and widely used processes, particularly for field applications and repair work. This process operates at currents typically ranging from 50 to 300 amperes and can weld materials from 3mm to over 25mm in thickness.

• Advantages: Excellent portability, minimal equipment requirements, effective in windy outdoor conditions, suitable for all positions

• Limitations: Lower deposition rates (1-5 kg/hour), frequent electrode changes, higher skill requirements, slag removal necessary

• Best Applications: Structural steel erection, pipeline welding, maintenance and repair work, remote locations without power infrastructure

Gas Metal Arc Welding (GMAW/MIG)

GMAW offers significantly higher productivity than SMAW, with deposition rates reaching 3-8 kg/hour depending on wire diameter and amperage. Operating parameters typically range from 100 to 450 amperes with wire feed speeds from 2.5 to 20 metres per minute.

• Advantages: High deposition rates, minimal post-weld cleaning, easily automated, suitable for thin materials (0.6mm and above)

• Limitations: Shielding gas sensitivity to wind, higher equipment costs, porosity concerns with contaminated base metals

• Best Applications: Automotive manufacturing, sheet metal fabrication, robotic welding cells, production welding environments

Flux-Cored Arc Welding (FCAW)

FCAW combines the productivity of GMAW with improved tolerance for outdoor conditions. Self-shielded variants (FCAW-S) eliminate the need for external shielding gas entirely, while gas-shielded variants (FCAW-G) offer superior mechanical properties.

• Advantages: Highest deposition rates among semi-automatic processes (up to 11 kg/hour), excellent penetration, wind tolerance with self-shielded wires

• Limitations: Slag removal required, higher fume generation, limited to ferrous metals

• Best Applications: Shipbuilding, heavy structural fabrication, offshore construction, bridge building

Gas Tungsten Arc Welding (GTAW/TIG)

GTAW provides the highest quality welds with superior aesthetic appearance and precise heat control. This process operates at 5 to 300 amperes and excels with thin materials and critical applications requiring radiographic quality welds.

• Advantages: Exceptional weld quality, precise heat control, no spatter, welds all metals including aluminium, magnesium, and titanium

• Limitations: Lowest deposition rates (0.5-2 kg/hour), highest skill requirements, wind sensitivity

• Best Applications: Aerospace components, pressure vessels, food processing equipment, pharmaceutical piping, root passes on critical joints

Submerged Arc Welding (SAW)

SAW offers the highest deposition rates of any arc welding process, reaching up to 45 kg/hour with multiple wire configurations. Operating at 300 to 2000 amperes, this process is exclusively used for flat and horizontal fillet welds.

• Advantages: Exceptional productivity, deep penetration, excellent weld quality, minimal fumes and spatter

• Limitations: Flat and horizontal positions only, requires granular flux handling, high initial equipment investment

• Best Applications: Pressure vessel longitudinal and circumferential seams, structural beam fabrication, shipbuilding panels, wind tower manufacturing

Plasma Arc Welding (PAW)

PAW utilises a constricted arc to achieve higher energy density than GTAW, enabling keyhole welding techniques that can penetrate materials up to 10mm thick in a single pass without edge preparation.

• Advantages: Deep penetration capability, high travel speeds, reduced distortion, excellent for automated applications

• Limitations: Complex equipment, higher maintenance requirements, limited manual applications

• Best Applications: Automated pipe welding, thin gauge stainless steel, aerospace applications, electronic component manufacturing

Material Considerations in Process Selection

The base material composition fundamentally influences welding process selection. Different materials respond uniquely to thermal cycles, require specific shielding atmospheres, and demand particular filler metal compositions to achieve sound welds.

Carbon and Low-Alloy Steels

These materials, comprising the majority of structural and mechanical applications in Atlantic Canada, offer the broadest process compatibility. For carbon steels with carbon content below 0.30%, virtually all arc welding processes perform satisfactorily. However, higher carbon equivalents (CE > 0.45) necessitate controlled hydrogen processes and preheating protocols to prevent hydrogen-induced cracking.

Maritime fabricators working with weathering steels (such as those used in bridge construction and outdoor structures) should select low-hydrogen processes like GMAW, GTAW, or SAW to maintain the material's atmospheric corrosion resistance in our humid coastal climate.

Stainless Steels

Process selection for stainless steels must address sensitisation concerns, particularly in the 300-series austenitic grades commonly used in food processing and marine applications. Heat input control becomes critical, with maximum interpass temperatures typically limited to 175°C for 304L and 316L grades.

GTAW remains the preferred process for root passes and thin-gauge applications, while GMAW with pulsed current transfer provides improved productivity for heavier sections. For fabricators serving Nova Scotia's growing food processing and aquaculture industries, proper process selection ensures compliance with sanitary welding requirements and prevents corrosion failures.

Aluminium Alloys

Aluminium's high thermal conductivity, oxide layer characteristics, and crack sensitivity limit suitable processes to GMAW and GTAW. The 5000-series marine grades used extensively in Maritime boat building require filler metals carefully selected to avoid hot cracking, typically ER5356 or ER5183 alloys.

Pulsed GMAW has become increasingly popular for aluminium fabrication, offering reduced heat input and improved control over the weld pool compared to conventional spray transfer.

Production Volume and Economic Considerations

Economic analysis must accompany technical evaluation in welding process selection. The total cost of welding encompasses direct costs (labour, consumables, power, shielding gas) and indirect costs (equipment depreciation, maintenance, quality assurance, rework).

Low-Volume and Prototype Production

For job shop environments handling diverse, low-volume work—common among engineering firms and fabricators across Nova Scotia—process flexibility often outweighs maximum productivity. SMAW and GMAW provide the versatility needed to address varying material types, joint configurations, and quality requirements without excessive equipment investment.

A typical small fabrication shop can establish comprehensive GMAW and GTAW capabilities for $15,000 to $30,000 in equipment, compared to $150,000 or more for automated SAW or robotic GMAW cells.

High-Volume Production

Production environments with repetitive weld joints should prioritise processes amenable to automation and mechanisation. The labour component typically represents 70-85% of total welding costs; therefore, processes with higher deposition rates deliver significant cost advantages when production volume justifies capital investment.

Consider that a welder using SMAW might achieve an arc-on time of 20-30%, while automated GMAW systems can reach 60-80% arc-on time. This productivity differential translates directly to labour cost savings of 40-60% for suitable applications.

Calculating Welding Costs

Engineers should analyse welding costs using the following framework:

• Labour cost per metre: (Labour rate × Time per metre) / Efficiency factor

• Consumable cost per metre: Weight of weld metal × Filler metal cost per kg / Deposition efficiency

• Power cost per metre: (Voltage × Amperage × Arc time) / 1000 × Power rate

• Shielding gas cost per metre: Flow rate × Arc time × Gas cost per litre

Joint Design and Position Requirements

Joint configuration and welding position significantly influence process selection. Not all processes perform equally in all positions, and joint accessibility often dictates viable options.

Positional Capability

SMAW, GMAW, FCAW, and GTAW can weld in all positions (flat, horizontal, vertical, and overhead) with appropriate technique modifications and parameter adjustments. SAW is limited to flat and horizontal fillet positions due to the granular flux required for shielding.

Vertical and overhead welding demand reduced heat input to maintain weld pool control. This requirement favours processes with precise current control, such as pulsed GMAW and GTAW, particularly for critical applications in shipbuilding and structural steel where positional welding is unavoidable.

Joint Access and Configuration

Restricted joint access, common in pipe welding and vessel fabrication, may eliminate processes requiring bulky equipment. GTAW's compact torch design makes it ideal for root passes in pipe welding, where GMAW guns cannot access the joint. Conversely, deep groove welds in thick plate benefit from processes offering high deposition rates and deep penetration characteristics.

For narrow groove applications, processes capable of operating in tight joint configurations—such as GTAW with extended tungsten electrodes or GMAW with slim-line torches—provide access impossible with conventional equipment.

Quality Requirements and Code Compliance

Welding quality requirements vary dramatically depending on application criticality, governing codes, and end-user specifications. Process selection must align with these requirements while remaining economically viable.

Radiographic and Ultrasonic Inspection Standards

Applications requiring volumetric inspection (radiography or ultrasonic testing) demand processes capable of producing defect-free welds. GTAW and properly executed GMAW with appropriate shielding gas coverage consistently achieve radiographic quality results. SMAW and FCAW, while capable of producing acceptable results, require higher welder skill levels and more rigorous cleaning between passes.

Canadian Welding Code Requirements

Projects governed by CSA W59 (Welded Steel Construction) or CSA W47.1 (Certification of Companies for Fusion Welding of Steel) impose specific requirements regarding welding procedure specifications, welder qualification, and process approval. Engineers must verify that selected processes meet code requirements and that qualified welding procedures exist or can be developed.

For pressure-retaining applications under ASME Boiler and Pressure Vessel Code or CSA B51, process selection must consider the additional requirements for procedure qualification testing, including mechanical testing of weld samples at specified thicknesses and positions.

Environmental and Safety Considerations

Working conditions, environmental factors, and safety requirements increasingly influence process selection, particularly for field construction and outdoor fabrication common throughout Atlantic Canada.

Weather and Atmospheric Conditions

Nova Scotia's coastal environment presents challenges for gas-shielded processes. Wind speeds exceeding 8 km/h can disrupt GMAW and GTAW shielding, causing porosity and oxidation. For outdoor construction, SMAW and self-shielded FCAW provide reliable alternatives that maintain weld quality despite atmospheric interference.

During winter months, low ambient temperatures require preheat considerations regardless of process selection. Base metal temperatures below 0°C generally require heating to at least 20°C before welding to prevent thermal shock and hydrogen-related cracking.

Fume Generation and Ventilation Requirements

Occupational health regulations mandate control of welding fumes, with Canadian exposure limits set at 5 mg/m³ for general welding fumes and significantly lower for specific metal constituents. FCAW generates substantially higher fume levels than GMAW or GTAW, requiring enhanced ventilation systems that add to operational costs.

For enclosed space welding—common in ship repair, tank fabrication, and confined industrial applications—processes with lower fume generation rates reduce ventilation requirements and improve working conditions.

Making the Final Selection: A Systematic Approach

Effective welding process selection requires systematic evaluation of all relevant factors. We recommend the following decision framework:

• Step 1: Identify base material type, thickness range, and joint configurations

• Step 2: Determine quality requirements, inspection criteria, and applicable codes

• Step 3: Assess production volume and establish target cycle times

• Step 4: Evaluate environmental conditions and positional requirements

• Step 5: Analyse available equipment and welder qualifications

• Step 6: Calculate comparative costs for viable process options

• Step 7: Select process and develop qualified welding procedures

This systematic approach ensures all technical and economic factors receive appropriate consideration, leading to optimised process selection that balances quality, productivity, and cost.

Partner with Sangster Engineering Ltd. for Your Welding Engineering Needs

Selecting the optimal welding process requires deep technical expertise combined with practical manufacturing experience. At Sangster Engineering Ltd. in Amherst, Nova Scotia, our engineering team brings decades of experience in welding process selection, procedure development, and quality assurance across diverse industries throughout Atlantic Canada.

Whether you require welding procedure specifications for a new fabrication project, assistance evaluating process alternatives for improved productivity, or expert guidance navigating Canadian welding code requirements, our team provides the professional engineering support your project demands.

Contact Sangster Engineering Ltd. today to discuss your welding engineering requirements. Let our expertise ensure your next manufacturing project achieves optimal results through informed process selection and sound engineering practices.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.