The Complete Guide to Welding
Everything a beginner or working technician needs in one place: welding processes and machine types, every major electrode and filler metal, welding positions, PPE and helmet shade selection, amperage/voltage/wire-speed settings, joint design, and a buying guide for building out a home or shop welding station.
Safety first. Welding produces intense UV/IR radiation, molten spatter, toxic fumes, and electric shock hazards. Never strike an arc without proper eye and skin protection, adequate ventilation, and a fire-safe work area. This guide is educational reference material, not a substitute for hands-on training, your machine's owner's manual, or your local electrical/fire code. When in doubt, take a certified welding course before working unsupervised.
Welding is a fabrication process that joins materials — almost always metals or thermoplastics — by using heat, pressure, or both to cause the pieces to fuse together, often with a filler material added to build up the joint. Unlike bolting or riveting, a properly made weld becomes part of the base metal itself: the joint can be as strong as, or stronger than, the surrounding material.
Most hobby and professional welding falls under arc welding: an electric arc is struck between an electrode and the workpiece, generating temperatures above 6,000 °F (3,300 °C) — hot enough to melt steel almost instantly. The molten pool is shielded from atmospheric oxygen and nitrogen (which would weaken and embrittle the joint) using a gas, a flux coating, or a flux core inside the wire itself. A separate family of processes, oxy-fuel welding and cutting, uses a burning gas mixture instead of electricity.
- A welding machine matched to your process, material and power supply
- A welding helmet with the correct shade range (auto-darkening recommended)
- Flame-resistant gloves and a leather jacket or sleeves
- A steel-top welding table or fire-safe work surface
- C-clamps, locking pliers, and magnetic welding squares for fit-up
- A wire brush, chipping hammer, and angle grinder for cleanup
- A properly sized ground clamp and clean grounding point
- A fire extinguisher (ABC or Class D for metal fires) within reach
- Fume extraction or adequate cross-ventilation
- Safety glasses to wear under the helmet and during grinding
This page is organized the way a technician would actually approach the trade — from choosing a process, to picking consumables, to running an actual bead safely and correctly.
| Process | Ease of learning | Typical cost | Best material range | Indoor / outdoor | Best for |
|---|---|---|---|---|---|
| MIG (GMAW) | Easiest | $$ | 24 ga – 1/2″ steel/aluminum | Indoor (shielding gas needs still air) | General fabrication, auto body, beginners |
| Stick (SMAW) | Moderate | $ | 1/16″ – 1″+ steel | Both — great outdoors/wind | Repair, farm/ranch, rusty or dirty metal |
| TIG (GTAW) | Hardest | $$$ | Foil – 1/4″ most metals | Indoor only | Precision welds, aluminum, stainless, thin sheet |
| Flux-Cored (FCAW) | Easy | $$ | 16 ga – 1″+ steel | Both (self-shielded works outdoors) | Construction, heavy equipment, thick steel |
| Oxy-Fuel | Moderate | $ | Thin sheet – medium plate | Both | Brazing, cutting, heating, pipe/HVAC work |
| Plasma Cutting | Easy | $$ | Up to ~1″ conductive metal | Both | Fast, clean cutting of any conductive metal |
Every welding process works the same basic way — melt the base metal, add filler, protect the puddle from air — but each gets there differently. The process you choose drives which machine, which consumables, and which skills you need.
Older welders use a heavy copper-wound transformer to step down mains voltage — reliable and simple, but large, heavy, and coarse in its control. Modern inverter machines convert power electronically at high frequency, giving a smaller, lighter unit with a much smoother, more precise arc, better performance on generator power, and often multi-process capability (MIG/TIG/Stick in one box). Inverters cost more but dominate the current market for good reason.
120V machines run off a standard household outlet but are limited to thin material (roughly up to 1/8″–3/16″). 240V single-phase is the sweet spot for a home shop, unlocking enough amperage for 1/4″+ steel. Industrial three-phase (208/230/460V) machines deliver a smoother arc and higher duty cycle for continuous production welding but require dedicated shop wiring.
Duty cycle is the percentage of a 10-minute period a machine can weld continuously at a given amperage before it needs to cool down (thermal overload shutoff). A machine rated 200A at 20% duty cycle can weld for about 2 minutes, then must rest roughly 8 minutes. Duty cycle rises sharply at lower amperage — the same machine might run 60% duty cycle at 120A. Higher-priced machines generally offer a higher duty cycle at their rated maximum amperage; buy more machine than you think you need if you plan to weld for long, continuous stretches.
- Clean the joint to bare metal and clamp the ground clamp to clean, bare metal as close to the weld as practical.
- Set amperage per the electrode's diameter and the manufacturer's chart, and hold the electrode at roughly a 20–30° travel angle.
- Strike the arc with a scratching motion (like striking a match) rather than a straight tap, to avoid the rod sticking to the plate.
- Once the arc starts, immediately lift to a 1/8″ arc length (roughly the electrode's own diameter) and hold it steady.
- Travel smoothly and steadily along the joint, watching the puddle rather than the arc flash, and maintain a consistent arc length throughout.
Every stick electrode is stamped with a code like E7018. Each part of that code tells you exactly how to use the rod:
Electrode for arc welding.
Minimum tensile strength of the weld in thousands of psi — "70" = 70,000 psi.
Welding position: 1 = all positions, 2 = flat & horizontal only, 4 = all positions incl. vertical-down.
The final digit (8 in E7018) identifies the flux coating type and the current the rod runs on — this is what actually determines how the rod behaves, its penetration, and its ease of use.
| Classification | Coating | Current | Positions | Typical use |
|---|---|---|---|---|
| E6010 | Cellulosic (sodium) | DCEP | All | Deep penetration; pipeline root passes; cuts through rust, mill scale & paint |
| E6011 | Cellulosic (potassium) | AC or DCEP | All | Like 6010 but runs on AC — the classic farm/ranch welder rod |
| E6012 | Rutile (sodium) | AC or DCEN | All | Bridges poor fit-up and gaps; general-purpose, low cost |
| E6013 | Rutile (potassium) | AC/DC either polarity | All | Easiest rod to run; smooth arc, light penetration; great for beginners and thin sheet |
| E7014 | Rutile + iron powder | AC/DC either polarity | All (best flat/horiz.) | Faster deposition than 6013 while staying easy to run |
| E7016 | Low-hydrogen (potassium) | AC or DCEP | All | Higher-strength steel; X-ray-quality welds |
| E7018 | Low-hydrogen (iron powder) | AC or DCEP | All | The structural/pressure-vessel workhorse; store in a rod oven — moisture causes hydrogen cracking |
| E7024 | Iron powder rutile | AC/DC either polarity | Flat & horizontal only | Very high deposition rate; "drag rod" for heavy flat-position welding |
| E308L-16 | Stainless rutile | AC or DCEP | All | 304-series stainless steel fabrication and repair |
| ENiFe-CI | Nickel-iron | DCEP | Flat / horizontal | Cast iron repair — minimizes cracking in a hard-to-weld base metal |
| Wire | Metal | Notes |
|---|---|---|
| ER70S-6 | Mild steel | The default MIG wire — extra deoxidizers tolerate light rust/mill scale |
| ER70S-3 | Mild steel | General purpose; needs cleaner base metal than S-6 |
| ER308L | Stainless (304) | Low carbon avoids carbide precipitation at the weld |
| ER316L | Stainless (316) | Marine and chemical-resistant applications |
| ER4043 | Aluminum | Forgiving, general-purpose; lower crack sensitivity |
| ER5356 | Aluminum | Higher strength; better color match after anodizing |
Wire diameter by thickness: 0.023–0.030″ for sheet metal (18–24 ga), 0.035″ as the do-everything default (18 ga – 1/4″), 0.045″ for 1/4″+ material.
| Classification | Shielding | Current | Notes |
|---|---|---|---|
| E71T-11 | Self-shielded (no gas) | DCEN | Windy/outdoor jobsites; more spatter and smoke than gas-shielded |
| E71T-1 | Gas-shielded (CO₂ or 75/25) | DCEP | Cleaner welds, higher deposition; shipbuilding & heavy fabrication |
| Color | Type | Current | Tip prep | Best for |
|---|---|---|---|---|
| Green | Pure tungsten (EWP) | AC | Balled | Aluminum & magnesium on transformer AC machines |
| Red | 2% Thoriated (EWTh-2) | DC only | Pointed | Steel & stainless DC work (grind wet; mildly radioactive dust) |
| Blue | 2% Lanthanated (EWLa-2) | AC or DC | Pointed or balled | The modern all-purpose replacement for thoriated — non-radioactive |
| Gray | 2% Ceriated (EWCe-2) | DC (light AC) | Pointed | Thin material, low-amperage precision & orbital tube welding |
Colors and blends vary slightly by manufacturer — confirm against the box, but green/red/blue/gray cover the vast majority of TIG work.
| Gas | Process | Effect |
|---|---|---|
| 100% CO₂ | MIG, mild steel | Deepest penetration, more spatter, cheapest |
| 75/25 Ar/CO₂ (C25) | MIG, mild steel | Best all-around — smoother arc, less spatter |
| 100% Argon | TIG (all metals); MIG aluminum | Smooth, stable arc; required for aluminum |
| Argon/Helium blends | TIG, thick or heat-hungry metal | Helium adds heat/penetration and travel speed |
| 98/2 Ar/O₂ | MIG stainless & low-alloy | Improves puddle wetting and bead appearance |
Position codes describe the orientation of the joint relative to gravity — not the welder's own posture. The number identifies the position; the letter identifies the joint type (G = groove, F = fillet).
| Code | Pipe orientation | What it tests |
|---|---|---|
| 1G | Axis horizontal, pipe rotates | Welder stays in one spot; easiest pipe test |
| 2G | Axis vertical, fixed | Continuous horizontal welding around a fixed pipe |
| 5G | Axis horizontal, fixed (no rotation) | Welder moves around the pipe through all positions in one weld |
| 6G | Fixed at a 45° incline | The industry-standard "qualifies all positions" pipe certification |
| 6GR | 6G plus a restriction ring | Simulates a tight-access joint — one of the toughest common code tests |
An arc emits intense visible light plus UV and infrared radiation. Without the correct filter shade, unprotected eyes develop "arc eye" (photokeratitis) — a painful, sunburn-like injury to the cornea — often hours after exposure.
Passive (fixed-shade) helmets use a single dark lens you flip down before striking the arc — inexpensive and reliable, but you must stop and lift the helmet to see your work between welds.
Auto-darkening helmets (ADF) stay clear until a sensor detects the arc's flash and darken in a fraction of a second, letting you keep the helmet down to see the joint, strike the arc, and weld without interruption. Look for a fast switching speed, adjustable shade range, and a "grinding" mode.
| Process | Amperage | Shade |
|---|---|---|
| Stick (SMAW) | <75A | 10 |
| Stick (SMAW) | 75–200A | 12 |
| Stick (SMAW) | 200–400A | 14 |
| MIG / Flux-Cored | <100A | 11 |
| MIG / Flux-Cored | 100–500A | 12–14 |
| TIG (GTAW) | <50A | 10 |
| TIG (GTAW) | 50–500A | 12–14 |
| Plasma cutting | 20–60A | 4–6 |
- TIG gloves — thin, soft leather for maximum dexterity and rod-feeding feel.
- MIG/Stick gloves — heavier gauntlet-style leather for more heat and spatter protection.
- Leather jacket, sleeves or apron — stops spatter burns and radiant heat, especially overhead.
- 100% cotton or FR clothing — never synthetic fabric, which can melt onto skin.
- Leather boots, high-top and laced under the pant leg to keep sparks out.
- Ear protection or ear plugs when grinding or in a loud shop.
Welding fume contains fine metal-oxide particulate — manganese from mild steel, and hexavalent chromium and nickel compounds from stainless steel, both of concern with prolonged exposure. Position a fume extractor arm or ensure strong cross-ventilation with your head out of the fume plume. For stainless, galvanized (zinc-coated — never weld galvanized without ventilation, due to "metal fume fever"), or confined-space work, step up to a powered air-purifying respirator (PAPR) built into the helmet.
- Clear a minimum 35 ft (10 m) radius of flammable materials, or use fire-resistant welding curtains/blankets.
- Keep an appropriate fire extinguisher within reach and know where it is before striking an arc.
- Never weld on sealed containers or drums that may have held fuel or flammable residue.
- Inspect cables and connections for damage; wet gloves, wet ground, or damaged insulation dramatically raise shock risk.
- In confined or metal-enclosed spaces, use insulating mats and extra ventilation — sweat plus a metal floor is a serious shock hazard.
- Post a dedicated fire watch for at least 30 minutes after hot work in any area with hidden combustibles.
Arc UV can sunburn exposed skin in minutes and cause arc eye in anyone nearby who glances at an uncovered arc, not just the welder. Use welding curtains or screens to shield coworkers and passersby, keep all skin covered, and warn anyone working nearby before striking an arc — arc eye is a genuinely common, entirely preventable injury on shared shop floors.
| Polarity | What it means | Effect | Used by |
|---|---|---|---|
| DCEN | Direct current, electrode negative ("straight") | Electrode stays cooler; less penetration, more filler build-up | Most TIG on steel; self-shielded flux-core |
| DCEP | Direct current, electrode positive ("reverse") | Deeper penetration; more heat driven into the work | Most stick rods; all MIG (GMAW); gas-shielded flux-core |
| AC | Alternating current | Cycles between EN and EP each half-cycle | TIG on aluminum/magnesium — the EP half "cleans" the tenacious oxide layer |
| Thickness | Wire diameter | Voltage | Wire feed speed | Approx. amperage |
|---|---|---|---|---|
| 24 ga (0.6mm) | 0.023–0.030″ | 14–15V | 100–150 ipm | 30–50A |
| 18 ga (1.2mm) | 0.030″ | 15–17V | 150–250 ipm | 50–90A |
| 14 ga (2mm) | 0.030–0.035″ | 17–19V | 250–350 ipm | 90–130A |
| 1/8″ (3.2mm) | 0.035″ | 19–21V | 350–450 ipm | 130–180A |
| 3/16″ (4.8mm) | 0.035–0.045″ | 20–23V | 400–500 ipm | 180–220A |
| 1/4″+ (6.4mm+) | 0.045″ | 22–26V | 450–600 ipm | 220–280A |
Treat this as a starting point, then fine-tune by ear and by eye: a correctly set arc sounds like steady, crisp "frying bacon" — a hissing or popping sound usually means the voltage is too high or too low, respectively.
| Diameter | Amperage range |
|---|---|
| 1/16″ (1.6mm) | 20–40A |
| 3/32″ (2.4mm) | 40–90A |
| 1/8″ (3.2mm) | 75–130A |
| 5/32″ (4.0mm) | 100–180A |
| 3/16″ (4.8mm) | 140–240A |
TIG rule of thumb: roughly 1 amp per 0.001″ of steel thickness — a 1/8″ (0.125″) plate needs about 125A DC.
| Process | Flow rate |
|---|---|
| MIG (indoor, still air) | 20–25 CFH |
| MIG (windy/outdoor) | 30–35 CFH |
| TIG (small cup) | 12–18 CFH |
| TIG (large cup) | 18–25 CFH |
| Gas-shielded flux-core | 25–35 CFH |
Too little flow lets air contaminate the puddle (porosity); too much causes turbulence that pulls air back in — more gas is not always better.
| Defect | What it looks like | Common causes | Fix |
|---|---|---|---|
| Porosity | Small holes/pits in the bead | Contaminated metal, lost gas coverage, wet electrodes | Clean the joint, check gas flow, block drafts, use dry rods |
| Undercut | A groove melted into the base metal at the weld toe | Travel too fast, amperage too high, wrong angle | Slow down, reduce amperage, pause slightly at the edges |
| Lack of fusion | Filler sits on top without bonding to the base metal | Amperage too low, travel too fast, dirty joint | Increase heat, clean the joint, slow down, adjust angle |
| Excess spatter | Scattered droplets around the weld | Voltage too high, dirty contact tip, wrong gas mix | Adjust voltage/wire speed, clean the tip, check gas |
| Warping/distortion | Base metal bends or twists | Excess heat input, poor clamping, weld sequence | Tack strategically, backstep or skip-weld, clamp firmly |
| Cracking | Fracture in the weld or heat-affected zone | Hydrogen (wet rods), rapid cooling, high restraint | Preheat, use low-hydrogen rod, control cooling rate |
| Joint | Description | Common weld type |
|---|---|---|
| Butt | Two edges meet flush in the same plane | Groove weld |
| Lap | One piece overlaps another | Fillet weld (one or both edges) |
| Tee | One piece meets another at 90°, forming a "T" | Fillet weld |
| Corner | Two pieces meet at an outside edge, forming an "L" | Fillet or groove weld |
| Edge | Edges are parallel and adjacent | Edge/seal weld |
Butt joints (via a groove weld) carry load through the full thickness of the joint and dominate pressure vessels and piping. Tee and lap joints (via a fillet weld) are far more common in general structural and sheet-metal fabrication, since they don't require precision edge prep — just a consistent leg length on each side of the joint.
- Clean to bare metal — grind or wire-brush away paint, rust, mill scale, and oil/grease before striking an arc.
- Bevel thicker material (typically 3/16″+) to open a V- or U-groove so the arc can reach full penetration through the joint.
- Leave a controlled root gap as specified by the joint design — too tight starves penetration, too wide risks burn-through.
- Tack weld at intervals to hold alignment before running the full weld, checking square/alignment before committing.
- Fixture or clamp the assembly so it can't move or warp out of position mid-weld.
- Stringer beads (straight line, no weaving) suit thinner material and multi-pass welds; weave patterns (zig-zag, figure-8) fill wider gaps and vertical joints.
- Multi-pass welding builds thick joints in layers — clean slag between stick/flux-core passes before running the next one.
- Backstepping (welding short segments backward along the joint) and skip welding (alternating segments) both spread heat out to reduce warping on long seams.
- Let assemblies cool between passes on heat-sensitive material, and consider preheating thick or high-carbon steel to slow the cooling rate and reduce cracking risk.
Chip and wire-brush slag off stick and flux-core welds before inspecting or painting. A good weld bead is uniform in width and height, free of visible porosity or cracks, with smooth transitions ("toes") into the base metal and no undercut. For anything structural or safety-critical, follow the applicable code's visual inspection criteria (such as AWS D1.1) and consider dye-penetrant or other non-destructive testing before the piece goes into service.
A practical shopping list for a home or small-shop welding setup, organized the way you'd actually buy it — machine first, then protection, then consumables, then the small tools that make every job faster.
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