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Tag: stick welding

  • Welding Science: MIG vs TIG vs Stick Cost per Foot

    Welding Science: MIG vs TIG vs Stick Cost per Foot

    The Science of Welding: MIG, TIG, and Stick Compared – Plus the Real Cost Per Foot of Weld

    Introduction

    In the world of metal fabrication, welding is both art and a science. Understanding not just how to weld but why certain processes work better—and cost less—in specific scenarios is essential for:

    • Welders are optimizing efficiency in the booth.
    • Engineers and designers make process-specific decisions during material selection.
    • Fabrication buyers and project managers estimate costs accurately and competitively.

    From the molecular thermodynamics of arc formation to the economic reality of consumables, each welding process—MIG (GMAW), TIG (GTAW), and Stick (SMAW)—brings trade-offs that can dramatically affect weld quality and cost per foot.

    In this guide, we’ll break down:

    • The science behind MIG, TIG, and Stick welding.
    • How variables like speed, consumable use, and labor affect cost per linear foot.
    • Real-world cost breakdowns and comparisons—to help you make informed decisions and reduce waste.

    The Science of Welding Processes

    🔌 MIG Welding (GMAW) – High Speed, Low Cost

    Science Behind the Process:

    • Arc Formation: A continuous solid wire is fed through a MIG gun, producing an electric arc between the wire and base metal.
    • Shielding Gas: Typically a mix of argon and CO₂ to protect the weld zone from atmospheric contamination.
    • Filler Metal Transfer: Spray or short-circuit transfer, depending on settings and thickness.

    Molecular Level Insight:

    • The arc melts both the electrode and base metal, fusing them at a localized point as electrons bombard the joint.
    • Shielding gas prevents oxygen and nitrogen from contaminating the weld pool, which is crucial for metallurgy.

    Strengths:

    • High deposition rate and travel speed.
    • Easy to learn and automate.
    • Ideal for production shops and thin to mid-thickness steel.

    Weaknesses:

    • Requires shielding gas, limiting portability.
    • Less suitable for windy outdoor environments or dirty/oxidized metal.

    TIG Welding (GTAW) – Precision and Cleanliness

    Science Behind the Process:

    • Non-Consumable Tungsten Electrode creates the arc without melting itself.
    • Filler rod is added manually (or autogenously).
    • Shielded with pure argon (and sometimes helium blends).

    Precision Metallurgy:

    • Arc is extremely focused—ideal for very thin materials and dissimilar metals.
    • Allows precise control of heat input, reducing heat-affected zones (HAZ) and distortion.

    Strengths:

    • Produces the highest quality and cleanest welds.
    • Ideal for aluminum, stainless steel, nickel alloys, and precision aerospace components.

    Weaknesses:

    • Slowest process—low deposition rate.
    • Skill-intensive; long arc-on time per weld.
    • Highest cost per foot.

    Stick Welding (SMAW) – Versatility and Ruggedness

    Science Behind the Process:

    • Uses a flux-coated consumable electrode.
    • An arc is created between the electrode tip and the base metal.
    • Flux burns off to create shielding gas and leaves a protective slag layer.

    Molecular Dynamics:

    • Flux deoxidizes and scavenges impurities in the weld pool.
    • Slag forms a protective crust, improves cooling rates, and must be chipped away after the weld.

    Strengths:

    • Works in windy/outdoor settings without shielding gas.
    • Lower upfront equipment costs.
    • Suitable for structural steel, piping, and field repairs.

    Weaknesses:

    • Slower than MIG, more cleanup.
    • Stub loss and slag introduce waste.
    • Arc-on time is lower than GMAW.

    Welding Variables That Impact Cost

    To get to the real cost per foot, consider these key variables:

    Variable MIG (GMAW) TIG (GTAW) Stick (SMAW)
    Travel Speed Fast Slow Medium
    Deposition Rate High Low Medium
    Consumable Efficiency High (~90–95%) Moderate (~75%) Lower (~60% with stub loss)
    Power Usage Moderate High Moderate
    Labor Skill Level Moderate High Moderate
    Cleanup/Rework Minimal Minimal Significant (slag chipping)

    Cost Breakdown Per Foot of Weld

    Let’s compute the average cost per linear foot using common practices, consumables, and hourly wage estimates.

    📌 Assumptions:

    • Labor rate: $40/hour
    • Electricity: $0.12/kWh
    • Mild steel or stainless steel applications
    • Weld size: 1/4” fillet weld, 12” long

    🧮 MIG Welding Cost Example

    Consumable & Indirect Costs:

    Item Cost Estimate
    Wire (ER70S-6) $2.50/lb; ~0.035 lb/ft = $0.09
    Shielding gas $1.00/CFH; ~35 CFH ≈ $0.12/ft
    Power 4 kW/hr @ 12 in/min = ~0.067 kWh = $0.01
    Labor 12 in/min = 1 ft/min = $0.67/ft
    Total per Foot ⚙ $0.89/ft

    🧮 TIG Welding Cost Example

    Consumable & Indirect Costs:

    Item Cost Estimate
    Filler (ER308L rod) $12/lb; ~0.045 lb/ft = $0.54/ft
    Argon (pure) $1.10/CFH @ 20 CFH = $0.18/ft
    Power 5 kW/hr @ 6 in/min = ~0.167 kWh = $0.02
    Labor 6 in/min = 2 min/ft = **$1.34/
  • Welding with 7018: Should You Use AC or DC Current? When to Use 7018AC

    Welding with 7018: Should You Use AC or DC Current? When to Use 7018AC

    Introduction

    Welding with 7018 electrodes is a staple in shielded metal arc welding (SMAW), also known as stick welding. Known for creating strong, smooth welds, the 7018 is frequently used in critical applications such as structural steel work. A common question among welders is whether to use AC or DC current with this electrode, and when to opt for the 7018AC variant. Understanding these choices is crucial for welders, fabricators, and students striving for optimal performance.

    Types / Variants / Models

    The primary variants include:

    • 7018 Electrode: Typically used with direct current electrode positive (DCEP).
    • 7018AC Electrode: Specifically designed for alternating current (AC) applications.

    Each variant excels under different conditions, making the choice between them vital depending on the available equipment and project requirements.

    Key Features or Specifications

    • Coating Composition: Low hydrogen, iron powder which minimizes the risk of cracking.
    • Current Type:
      • 7018: Best with DCEP for stability and penetration.
      • 7018AC: Optimized for AC, offering good arc stability even with lower voltage machines.
    • Sizes: Available from 3/32″ to 1/4″, depending on thickness needs.
    • Certifications: Meets AWS A5.1 standards ensuring quality and reliability across structural applications.

    The differences in current compatibility directly affect arc stability and penetration, essential for achieving robust, high-quality welds.

    Usage & Compatibility

    Welding Processes:

    • SMAW (Stick Welding): The preferred method for 7018, ensuring strength in welds.

    Machine Compatibility:

    • DC Machines: Offer stable arcs with deeper penetration for the standard 7018.
    • AC Machines: Enable the use of 7018AC, overcoming limitations of older or less robust machines prone to arc interruptions.

    Pros and Cons:

    • 7018 with DC:
      • Pros: Deeper penetration, better arc stability.
      • Cons: Requires DC-compatible equipment.
    • 7018AC:
      • Pros: Usable with AC machines, improved arc stability on fluctuating AC power.
      • Cons: Slightly different handling required due to AC characteristics.

    Common Applications

    Welding with 7018 electrodes is prevalent in:

    • Structural Steelwork: Essential for beams and columns due to its strength.
    • Pipeline Welding: Ensures solid joints crucial for durability.
    • Shipbuilding: Vital in combating metal fatigue and environmental pressures.

    The 7018AC variant is particularly useful in field repairs and projects where only AC power sources are available, providing necessary flexibility and reliability.

    Tips & Best Practices

    • Setup: For AC use, ensure a stable power supply to reduce fluctuations.
    • Handling: Maintain dry storage for electrodes to prevent moisture absorption, particularly for low-hydrogen types.
    • Troubleshooting: If experiencing arc blow on DC, try adjusting the grounding position or switch to 7018AC for better control.

    Avoid common mistakes such as incorrect polarity settings and improper storage, which can compromise weld quality.

     Conclusion

    Choosing between AC and DC currents for 7018 electrodes hinges on equipment availability and project needs. The 7018AC variant provides a viable option for those restricted to AC machines without sacrificing weld quality. Welders and students should assess their equipment and project requirements to make informed decisions, ensuring efficiency and optimal results in their welding tasks.

    In summary, understanding when and why to use the 7018 or 7018AC can significantly impact the success of your welding projects, guiding you toward making the best choices for each unique scenario.