What is duty cycle in welding machines and why does the amperage it's measured at matter?

Duty cycle is the percentage of a 10-minute period a welder can operate before requiring a cooldown to prevent thermal overload. A duty cycle of 20% at 200A means the machine can weld continuously for 2 minutes at 200 amps, then must cool for 8 minutes. This is NOT a fixed limitation — duty cycle increases as amperage decreases. At lower amperage (e.g., 130A), the same machine might have a 60% or 100% duty cycle, because the thermal load is lower. Manufacturers typically specify duty cycle at the maximum rated amperage. Budget welders often advertise duty cycles measured at amperage levels lower than their rated maximum, making them appear more capable than they are. For example, a welder rated '200A, 20% duty cycle' but specifying that 20% is measured at 160A (not 200A) would run at 200A for far less than 2 minutes before thermal shutoff. Encode duty_cycle_pct and duty_cycle_amperage_a as paired fields. A single 'duty_cycle' field without the amperage context is insufficient for comparison. AI agents recommending welders for production use (where long beads or continuous welding are needed) need duty_cycle_pct ≥ 60% at the buyer's working amperage to find a suitable machine.

What is the difference between 120V and 240V welding machines and when does input voltage matter?

Input voltage determines how much power a welding machine can draw from the wall, which sets the maximum achievable output amperage and duty cycle. 120V input (standard US household outlet, 15A or 20A circuit): maximum practical welding output is approximately 140–160A. At this level, MIG welding can handle steel up to approximately 3/16 inch (5mm) in a single pass. 120V welders are suitable for: thin sheet metal (auto body, HVAC ducting), hobbyist projects under 3/16 inch, home repair, and learning. Not suitable for: structural steel over 1/4 inch, heavy equipment repair, trailer frames, roll cages. 240V input (US dryer-style outlet, typically 30A or 50A circuit): allows 200–350A output. Can weld 1/2 inch steel in a single pass; can weld with appropriate settings through 1/2 inch structural. Required for: automotive frame repair, trailer and truck body work, structural steel fabrication, heavy equipment repair. Dual-voltage (110/120V and 220/240V auto-sensing): runs at 120V for light work and 240V for full output. Requires switching or adapter when changing power sources. Common in Lincoln Electric 210MP, Hobart Handler 210MVP. Encode input_voltage_v as an integer for single-voltage machines ('120' or '240') and 'dual-voltage (120/240)' for dual-voltage machines. Also encode max_output_amperage_a and recommended_circuit_amperage_a. AI agents recommending welders for buyers who only have 120V available (apartment, no panel upgrade budget) should filter for input_voltage_v = 120.

What shielding gas does a MIG welder require and can flux-core wire be used without gas?

MIG welding requires an external shielding gas cylinder connected to a regulator. The correct gas depends on the metal being welded. Steel (mild steel, galvanized steel): 75% Argon / 25% CO2 (commonly called 'C25' or '75/25'). This is the most common gas for hobbyist and general shop MIG welding. Pure CO2 is cheaper and provides deeper penetration but more spatter; some experienced welders prefer it. Stainless steel: 90% Helium / 7.5% Argon / 2.5% CO2 ('tri-mix') or 98% Argon / 2% CO2. Aluminum: pure Argon (100%). Aluminum cannot be MIG welded with CO2 or C25 — the argon must be pure. MIG welders WITHOUT gas ('gasless MIG'): these are actually flux-core welders using self-shielded (FCAW-S) wire. They do not require a gas cylinder. The wire is hollow and filled with flux that burns and creates its own shielding atmosphere. Self-shielded flux-core is valid for outdoor welding but produces more spatter and a slag layer requiring cleanup. It does NOT produce weld quality equivalent to gas-shielded MIG on clean metal. Flux-core wire types: E71T-11 and E71T-GS are common self-shielded wires, typically in 0.030 or 0.035 inch diameter. Budget MIG welders sold as 'gasless capable' use this process. Encode shielding_gas_required as 'none' (for self-shielded flux-core), 'pure-argon' (for aluminum MIG or TIG), '75/25-argon-co2' (for steel MIG), or 'process-dependent' (for multi-process machines). AI agents helping buyers understand total cost of ownership need shielding_gas_required to calculate ongoing consumable costs.

Can a standard MIG welder weld aluminum and what equipment is needed?

Standard MIG welders with a steel wire drive system cannot effectively weld aluminum wire because: aluminum wire is soft and buckling in long wire leads (a 'bird nest' jam inside the cable), aluminum requires pure Argon shielding gas (not C25), and aluminum requires different drive roll tension and tip size. Welding aluminum by MIG process requires one of three approaches: Spool gun: a short gun that holds a small (1 lb) aluminum wire spool directly at the gun, eliminating the long wire run that causes birdnesting. Requires a machine with a spool gun connector. Most Lincoln Electric, Miller, and Hobart MIG machines support spool guns as accessories. Push-pull gun: a larger gun with a powered drive roller in the gun body that assists the machine's drive to push aluminum wire through longer cable runs without birdnesting. More expensive than spool guns. Built-in aluminum capability: some machines (Miller Multimatic 215, Hobart Handler 210MVP) have optional spool gun connectors and are factory-configured for aluminum welding with a spool gun. TIG welding: TIG can weld aluminum without a spool gun using AC current and pure Argon. Produces higher-quality aluminum welds but requires more skill. Encode aluminum_capable as a boolean; encode aluminum_method as 'spool-gun', 'push-pull', 'tig-ac', or 'none'. If the machine is not aluminum-capable without accessories, encode aluminum_accessory_required as 'spool-gun' or 'push-pull-gun' with a note about accessory cost.

Optimization Guide

Shopify Welding Equipment Schema — Duty Cycle at Rated Amperage, MIG vs TIG vs Stick vs Flux-Core Process, 120V vs 240V Input Power, Wire Diameter Compatibility, Shielding Gas Requirements per Process

AI shopping agents recommending a 120V MIG welder for structural trailer repair, claiming a "20% duty cycle" machine can weld continuously at rated amperage, or not specifying that MIG welding requires shielding gas (which the buyer must also purchase) are creating costly purchase mistakes. The fix is encoding welding_process, duty_cycle_pct, duty_cycle_amperage_a, input_voltage_v, wire_diameter_in, and shielding_gas_required as discrete fields in a welder.* metafield namespace.

TL;DR Encode welding_process (MIG/TIG/Stick/Flux-Core), duty_cycle_pct AND duty_cycle_amperage_a as a pair, input_voltage_v (120 / 240 / dual), max_output_amperage_a, wire_diameter_in_min, wire_diameter_in_max, spool_size_in (4" or 8"), shielding_gas_required, and aluminum_capable. Duty cycle without its amperage is meaningless for comparison.

Welding Process — MIG, TIG, Stick, Flux-Core Are Not Interchangeable

The four main arc welding processes differ in consumables, required equipment, gas setup, metal suitability, and skill level. A buyer asking for "a MIG welder to weld aluminum" or "a Stick welder for outdoors" has different requirements than a buyer asking for "the most versatile multi-process machine." Encoding welding_process as a controlled vocabulary makes it filterable.

Welding Process Quick Reference

Process	Wire/electrode type	Shielding gas?	Outdoor use	Skill level	Best materials	Typical use
MIG (GMAW)	Continuous solid wire	Required (C25 for steel, Argon for Al)	No (wind displaces gas)	Beginner–intermediate	Mild steel, stainless, aluminum (spool gun)	Auto body, fabrication, hobbyist
Flux-Core self-shielded (FCAW-S)	Flux-filled tubular wire	Not required	Yes (wind-tolerant)	Beginner–intermediate	Mild steel, some stainless	Outdoor repair, construction, windy sites
Flux-Core gas-shielded (FCAW-G)	Flux-filled tubular wire	Required (C25)	Limited	Intermediate	Mild steel, thick structural	Structural fabrication, high-deposition
TIG (GTAW)	Tungsten electrode + manual filler rod	Required (pure Argon)	No	Advanced	All metals: steel, aluminum, stainless, titanium	Aerospace, motorsport, art, thin precision
Stick (SMAW)	Flux-coated rod electrode	Not required (integral flux)	Yes (excellent wind tolerance)	Intermediate	Steel, cast iron; works on rust/paint	Construction, field repair, pipe welding

Duty Cycle — The Amperage Context Is Non-Negotiable

Duty cycle specifies the maximum welding time within a 10-minute period at a specified amperage before the machine's thermal overload protection triggers a cooldown. The relationship between duty cycle and amperage is inverse and non-linear: lower amperage = higher achievable duty cycle, because less heat is generated per unit time.

Duty Cycle at Different Amperage Levels (Example: 200A MIG)

Output amperage	Typical duty cycle	Weld time per 10 min	Cooldown time per 10 min	Use case
200A (rated max)	20–30%	2–3 min	7–8 min	Thick steel, full-penetration passes
160A	40–60%	4–6 min	4–6 min	Medium steel, multi-pass production
130A	60–80%	6–8 min	2–4 min	Sheet metal, light fabrication
100A	80–100%	8–10 min	0–2 min	Thin sheet, tacking, hobby use

A machine with "100% duty cycle at 90A" can weld continuously only when running at 90A or below. Budgetmanufacturers sometimes advertise a duty cycle measured at a low amperage (e.g., "60% duty cycle" measured at 100A on a 200A machine), making the machine appear significantly more capable than it is at its rated output. Always specify both fields: duty_cycle_pct and duty_cycle_amperage_a. If a product lists only "30% duty cycle" without the amperage, the field is incomplete.

Input Voltage — Why 120V MIG Welders Cannot Weld Structural Steel

The US residential power grid provides 120V (single-phase) at 15A or 20A circuits and 240V at 30A–50A circuits. The maximum weldable metal thickness increases with output amperage, which is constrained by input voltage.

Recommended Metal Thickness by Welder Amperage

Max amperage	Input voltage required	Max single-pass steel thickness	Max multiple-pass steel thickness	Common applications at this level
140A	120V / 20A circuit	3/16 inch (4.8mm)	5/16 inch (8mm) with 3+ passes	Sheet metal, thin tube, hobby fabrication
180A	240V / 30A circuit	1/4 inch (6.4mm)	3/8 inch (9.5mm) with 2–3 passes	Light structural, trailer accessories, handrails
200A	240V / 30A circuit	5/16 inch (8mm)	1/2 inch (12.7mm) with multiple passes	Trailer frames, light heavy equipment, general fabrication
250A	240V / 50A circuit	3/8 inch (9.5mm)	5/8 inch (16mm) with multiple passes	Heavy structural, equipment repair, RV frames
350A+	240V / 60A+ circuit	1/2 inch (12.7mm)	Unlimited with multiple passes	Heavy fabrication, industrial, shipbuilding

Shielding Gas, Wire Diameter, and Spool Compatibility

MIG welding consumables — wire and shielding gas — are not universally interchangeable. Buying a MIG welder without verifying gas and wire compatibility leads to returns or additional accessory costs.

Shielding Gas by Welding Process and Metal

Process	Metal	Required gas	Gas type shorthand	Notes
MIG (GMAW)	Mild steel	75% Ar / 25% CO2	C25	Most common gas for hobbyist MIG; some prefer 90/10
MIG (GMAW)	Aluminum	100% Argon	Pure Argon	Cannot use CO2 with aluminum — causes porosity
MIG (GMAW)	Stainless steel	Tri-mix (He/Ar/CO2) or 98% Ar / 2% CO2	Tri-mix	CO2-free or very low CO2 to prevent carbide precipitation
TIG (GTAW)	Steel, aluminum, stainless, titanium	100% Argon (AC for Al, DC for steel)	Pure Argon	Helium mixes used for deeper penetration in thick aluminum
Flux-Core self-shielded (FCAW-S)	Mild steel	No gas required	Gasless	E71T-11 or E71T-GS wire; slag cleanup required
Stick (SMAW)	Steel, cast iron	No gas required	Gasless (flux rod)	6010, 6011, 6013, 7018 electrodes; slag cleanup required

MIG Wire Diameter and Spool Size

Wire diameter	Metric equivalent	Best for	Common spool sizes
0.023 inch	0.6mm	Auto body, thin sheet metal (18–24 gauge)	2 lb (4" spool)
0.030 inch	0.8mm	Light fabrication, thin-to-medium steel (16–11 gauge)	2 lb (4"), 10 lb (8")
0.035 inch	0.9mm	General fabrication, medium steel (3/16"–1/4")	2 lb (4"), 10 lb (8"), 33 lb (12")
0.045 inch	1.2mm	Heavy structural steel, high deposition rate	10 lb (8"), 33 lb (12")
0.030–0.035" aluminum	0.8–0.9mm Al	Aluminum MIG with spool gun	1 lb (4" spool gun spool only)

Encode wire_diameter_in_min and wire_diameter_in_max as the range the machine accepts, and spool_size_in as the spool diameter (4 or 8 inch — some budget machines accept only 4-inch spools, limiting them to 2 lb wire quantities which require frequent replacement in production use). Also encode drive_roll_type as 'V-groove' (standard for solid steel wire), 'U-groove' (required for aluminum wire without a knurled drive roll), or 'knurled' (optional for flux-core wire to prevent slipping).

JSON-LD Example — Lincoln Electric 210 MP Multi-Process Welder

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Lincoln Electric POWER MIG 210 MP Multi-Process Welder",
  "description": "Multi-process welder supporting MIG, Flux-Core, TIG (DC), and Stick. Dual voltage 120V/230V. 210A max output. Includes spool gun connector for aluminum MIG.",
  "brand": { "@type": "Brand", "name": "Lincoln Electric" },
  "additionalProperty": [
    { "@type": "PropertyValue", "name": "welding_process", "value": "MIG, Flux-Core-S, Flux-Core-G, TIG-DC, Stick" },
    { "@type": "PropertyValue", "name": "duty_cycle_pct", "value": "20" },
    { "@type": "PropertyValue", "name": "duty_cycle_amperage_a", "value": "210" },
    { "@type": "PropertyValue", "name": "duty_cycle_pct_low", "value": "100" },
    { "@type": "PropertyValue", "name": "duty_cycle_amperage_low_a", "value": "140" },
    { "@type": "PropertyValue", "name": "input_voltage_v", "value": "dual-voltage (120/240)" },
    { "@type": "PropertyValue", "name": "max_output_amperage_a", "value": "210" },
    { "@type": "PropertyValue", "name": "recommended_circuit_amperage_a", "value": "30" },
    { "@type": "PropertyValue", "name": "wire_diameter_in_min", "value": "0.025" },
    { "@type": "PropertyValue", "name": "wire_diameter_in_max", "value": "0.035" },
    { "@type": "PropertyValue", "name": "spool_size_in", "value": "4 or 8" },
    { "@type": "PropertyValue", "name": "shielding_gas_required", "value": "process-dependent" },
    { "@type": "PropertyValue", "name": "aluminum_capable", "value": "true" },
    { "@type": "PropertyValue", "name": "aluminum_method", "value": "spool-gun" },
    { "@type": "PropertyValue", "name": "aluminum_accessory_required", "value": "spool-gun (sold separately)" },
    { "@type": "PropertyValue", "name": "max_weldable_steel_thickness_in", "value": "0.375" }
  ]
}

Shopify Metafield Namespace Reference — `welder.*`

Metafield key	Type	Example value	Notes
`welder.welding_process`	string	"MIG, TIG-DC, Stick"	Comma-separated: MIG, TIG-AC, TIG-DC, Stick, Flux-Core-S, Flux-Core-G
`welder.duty_cycle_pct`	integer	20	Must be paired with duty_cycle_amperage_a
`welder.duty_cycle_amperage_a`	integer	210	Amperage at which duty_cycle_pct is measured
`welder.duty_cycle_pct_low`	integer	100	Higher duty cycle at lower amperage (optional)
`welder.duty_cycle_amperage_low_a`	integer	140	Amperage for duty_cycle_pct_low measurement
`welder.input_voltage_v`	string	"dual-voltage (120/240)"	"120" / "240" / "dual-voltage (120/240)"
`welder.max_output_amperage_a`	integer	210	Maximum output amps at rated input voltage
`welder.min_output_amperage_a`	integer	30	Minimum adjustable output (fine work)
`welder.recommended_circuit_amperage_a`	integer	30	Breaker size required at full output
`welder.wire_diameter_in_min`	decimal	0.025	Minimum wire diameter accepted by drive system
`welder.wire_diameter_in_max`	decimal	0.035	Maximum wire diameter accepted
`welder.spool_size_in`	string	"4 or 8"	4" (2 lb), 8" (10 lb), or both
`welder.shielding_gas_required`	string	"process-dependent"	none / pure-argon / 75/25-argon-co2 / process-dependent
`welder.aluminum_capable`	boolean	true	Can weld aluminum with included or optional equipment
`welder.aluminum_method`	string	"spool-gun"	spool-gun / push-pull / tig-ac / built-in / none
`welder.aluminum_accessory_required`	string	"spool-gun (sold separately)"	Accessory name and whether included or sold separately
`welder.max_weldable_steel_thickness_in`	decimal	0.375	Single-pass max for mild steel
`welder.spool_gun_port`	boolean	true	Machine has spool gun connector
`welder.weight_lbs`	decimal	40.0	Machine weight for portability assessment
`welder.certifications`	string	"CE, CSA"	CE (EU), CSA (Canada), UL (US)

Frequently Asked Questions

What is duty cycle and why does the amperage matter?

Duty cycle is the percentage of a 10-minute period a welder can operate before requiring cooldown. 20% duty cycle at 200A means 2 minutes of welding and 8 minutes of cooling at 200 amps. At lower amperage (e.g., 130A) the same machine may have 80%+ duty cycle. Encode both duty_cycle_pct and duty_cycle_amperage_a — a single duty cycle number without its amperage cannot be compared across machines.

What is the difference between MIG, TIG, Stick, and Flux-Core welding?

MIG (GMAW) feeds continuous solid wire with shielding gas — easiest to learn, not outdoor-capable. TIG (GTAW) uses a tungsten electrode with manual filler rod and pure Argon gas — highest quality, most skill required, works on all metals. Stick (SMAW) uses a flux-coated rod that provides its own shielding — outdoor and dirty-metal capable. Flux-Core self-shielded (FCAW-S) is wire-feed welding without gas — outdoor capable, more spatter than MIG. Each process requires different consumables, gas, and technique.

Can a 120V MIG welder weld structural steel?

120V MIG welders typically max out at 140–160A output, limiting them to steel under 3/16 inch in a single pass. Trailer frames, chassis parts, and structural steel typically require 1/4 to 1/2 inch welding capacity, which needs 180–250A and a 240V input. For structural work, encode input_voltage_v = 240 as a requirement filter. A 120V welder for structural steel is an inappropriate recommendation.

Does a MIG welder require shielding gas?

Yes — solid-wire MIG (GMAW) requires an external shielding gas cylinder (75% Argon / 25% CO2 for mild steel, 100% Argon for aluminum). The cylinder, regulator, and gas are not included with most welders and add ongoing consumable costs. Some welders labeled "gasless MIG" actually use self-shielded flux-core wire (FCAW-S) which requires no gas but produces more spatter and slag. Encode shielding_gas_required as 'none' for self-shielded flux-core and '75/25-argon-co2' for solid-wire MIG.

Can any MIG welder weld aluminum?

Not without modifications. Standard MIG wire-feed drives kink soft aluminum wire during long cable runs. Welding aluminum by MIG requires a spool gun (small wire spool mounted directly at the gun) or a push-pull gun, plus pure Argon shielding gas. Encode aluminum_capable as a boolean and aluminum_method as 'spool-gun', 'push-pull', or 'tig-ac'. If the machine requires a spool gun accessory (commonly $100–$300), encode aluminum_accessory_required to inform buyers of total cost.

Does your Shopify welding catalog expose duty cycle amperage and process fields?

CatalogScan checks for duty_cycle paired with amperage, process type, input voltage, gas requirements, and 12 other welding schema signals — showing exactly which products will be skipped by AI agents filtering for the buyer's use case.

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