Welding Buyer's Guide
Looking to upgrade your welder to a unit with more features and versatility? What exactly is the difference between MIG and TIG welding? See our Welding Buyer.s Guide for information on selecting the right welder for your repair or metal fabrication needs. You.ll find a quick overview on the welding process, what to consider when choosing a welder and commonly used welding terms.
The Welding Process
Welding is a process for joining or fastening two pieces of similar metals (workpieces) by melting and fusing 1) the base metals being joined and 2) the filler metal applied. Most commonly, workpieces are welded by melting both of them and adding more molten metal or plastic to form a pool that cools to form a strong joint. The energy to form the joint between metal workpieces most often comes from a flame (e.g. oxy-acetylene) or an electric arc. Most welding involves ferrous-based metals such as steel and stainless steel. Welding covers a temperature range of 1500º F - 3000º F. Weld joints are usually stronger or as strong as the base metals being joined.
Whereas soldering uses solder, a lower-melting-point material, welding applies enough heat to melt the materials being joined.
Plasma cutters are ideal for cutting and fabricating metal from thin sheets, to thick beams. Plasma cutting employs a torch which uses a powerful electric arc to create plasma, made by boosting a gas (nitrogen, argon or oxygen) to a very high temperature. This creates a stream, or cone, of directed plasma that can reach a temperature of 30,000°F. Handheld torches can usually cut up to 1/2 in (13 mm) thick steel plate, and stronger computer-controlled torches can pierce and cut steel up to 12 inches (300 mm) thick. Unlike laser cutting, for example, the process of plasma cutting is only effective on materials that conduct electricity.
Understanding the Welding Process
Shielded Metal Arc Welding (SMAW) - Stick
This process uses a consumable electrode to support the arc. Shielding is achieved by the melting of the outer flux coating on the electrode. Filler metal is obtained from the electrode core.
- Good for windy, outdoor conditions
- OK to use on dirty or rusty metal
Recommended metal: Steel, stainless steel, cast iron
Skill Level: Moderate
Gas Metal Arc Welding (GMAW) - MIG
A process used with a wire feed welding machine. Metals are joined by heating them with an arc, which is between the continuously fed filler metal electrode (solid wire) and the workpiece. Externally supplied gas or gas mixture provide shielding.
- Easy process to learn
- Better control on thinner metals
- Cleaner welds with less slag to clean
- Equipment can be used for Flux Cored welding
Recommended metal: Steel, stainless steel, aluminum, cast iron
Skill Level: Low
Flux Cored Arc Welding (FCAW) - Gasless
Process that uses a wire-fed welding machine. Metals are melted and joined by heating them with an arc between a continuous, consumable electrode wire and the workpiece. The weld is tubular with flux material contained inside the shielding. Added shielding may or may not be supplied from external gas or gas mixture, depending on the type of flux cored wire being used.
- Works well on dirty or rusty material
- Deep penetration for welding thick sections
- Can be used with or without shielding gas
- Self-shielded wire are best for windy conditions
Recommended to weld: Steel, stainless steel
Skill Level: Low
Gas Tungsten Arc Welding (GTAW) - TIG
This process uses welding equipment with a high-frequency generator. The arc is created between a nonconsumable tungsten electrode and the workpiece. Filler metal may or may not be used, and argon inert gas or inert gas mixtures are used for shielding.
- Provides high-quality, precise welds
- Highly aesthetic weld beads
Recommended metal (AC TIG): Aluminum, magnesium alloys(DC TIG): Steel, stainless steel, copper, brass, titanium
Skill Level: High
Resistance Spot Welding (RSW)
Two separate pieces of metal are joined by passing current between electrodes positioned on opposite sides of the workpieces. No arc is used; rather, it is the resistance of the metal to the current flow that fuses the pieces.
- Portable and easy to operate
- Ideal for light industrial applications
Recommended metal: Steel, stainless steel
Skill Level: Low
What to look for when choosing a welder
Consider the most common uses and applications for your welder: construction, farm/ranch, general maintenance/repair, home, auto body/repair, etc. Welders are designed for certain applications, depending on rated output, duty cycle and other features. For example, heavy-duty repairs in the field requires a welding package that can handle different types and sizes (thickness) of metal, whereas repairing a wrought iron railing can be done using a stick welder.
Available Power Input
- Single-phase products require single-phase input power usually found in homes and garages (Welders operate off either 115 or 230 Volts)
- If electrical hook-up is not available, a gas-powered, engine-driven welding generator can supply welding and auxiliary power.
- Can the welder be brought to the workpieces, or do the workpieces need to be brought to the welder?
- Accessories can be used to make most welders portable
- Hand-portable welders are typically 70 lbs. or less
What to look for in a welding helmet
Auto-Darkening vs. Standard Glass Lens
Auto-darkening allows easy starting and positioning in welding. With standard glass, the welder needs to be able to flip the helmet down at the moment the weld starts, and flip the helmet up to view the workpiece before beginning again. The downside of this type of helmet is a potential loss of torch position on starts, and at times the helmet cannot be flipped because of space restrictions.
Solar Power vs. Battery (how about both?)
Most solar-powered helmets have either a rechargeable or nonreplaceable battery, or they maintain the lens in the shade mode. Solar-powered helmets typically require a charging period prior to their first use as well as after extended periods of storage. Dual-powered lens (solar with replacement battery) enable users to weld right out of the box and can last up to 2000 hours of use on MIG.
Lens Reaction Time/Switching Speed
The switching speed is the time it takes the lens to react to the weld arc. The sooner a welder.s eyes are shaded from the highly intense light, the better. Too slow a reaction time will cause eye discomfort. Some switching speeds are 1/12,000, 1/16,000, even 1/25,000 of a second.
Adjustable Sensitivity and Delay Controls
Sensitivity will set the helmet to trigger on the amount of light hitting the helmet. Delay sets the lens to stay dark after the weld arc goes out.
A lighter weight helmet can minimize strain on the user's neck.
Fixed vs. Adjustable Shade
If welding on one type of material with the same thickness, a welder may opt for a fixed-shade helmet. If welding using multiple processes, for example stick, MIG and TIG, a welder will want to adjust the helmet shade to get the best view of the puddle.
ANZI Z87.1-2003 Standard
Make sure the helmet meets ANSI Z87.1-2003 standards. This means the helmet will filter out ultraviolet (UV) and infrared (IR) rays, even in a nonshaded state. This standard requires helmets to be tested through an independent laboratory. The testing includes impact testing with pointed/ball-shaped objects at speeds of up to 150 ft./second, ultraviolet and infrared testing, and switch speed testing in extreme temperatures (-5° to 131°F).
Glossary of Welding Terms:
Arc [Arc Length] - The physical gap between the end of the electrode to the point where the arc makes contact with the base metal.
Duty-cycle - The minutes out of a 10-minute period an arc welder can be operated at maximum rated output. For example, a 60% duty cycle @ 300 Amps means that the welding machine can be used for 6 minutes (at 300 Amps) and then must be allowed to cool with the fan running for 4 minutes. This reduces the chance of heat damage to the system.
Electrode - A coated metal wire having the same composition as the material being welded.
Flux - The coating on arc-welding rods and in flux-cored welding wire that is consumed in the arc to produce a shielding gas. The gas displaces air and impurities from around the weld.
Ground Lead/ Workpiece Lead - The conductor cable or electrical conductor between the arc welding machine and the work.
Rated Output - The Amps and voltage the power source will produce for a given duty-cycle period. For example, 300 Amps, 32 load volts @ 60% duty-cycle.
Shielding Gas - Protective gas used to prevent atmospheric contamination of the weld pool. Usually a mixed gas or CO2.
Slag - A layer of flux soot protects the weld from oxides and other contaminants while the weld is solidifying (cooling). Slag is to be removed after cooling.
Spatter - Metal particles thrown from the weld, often cooling and hardening on the work surface. A spatter-resistant spray applied to the workpiece can minimize spatter.
Torch - A device in the TIG process to control the position of the electrode, to transfer current to the arc and to direct the flow of shielding gas.
Tungsten - A rare metallic element with extremely high melting point used for manufacturing TIG electrodes.
Wire Feed Speed - Expressed as in//min. or mm/s and refers to the speed and amount of filler metal fed into a weld. The higher the wire feed speed, the higher the amperage.
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