Adjusting your techniques and tools to your materials is one of the most important and challenging lessons you’ll learn as a welder. Each material comes with its own coatings, melting temperatures, and gas requirements. Welders for any job only achieve sterling results by understanding their metal’s properties. Lincoln Electric welding products demonstrate different uses for a variety of commonly used metals in welding.
Aluminum is notoriously difficult to work with. It’s lightweight and has a natural oxide coating that melts at a hotter temperature than its lower layers, so it requires electrode-positive or chemical cleaning. Acetone works, but it’s harsh on the lungs, so denatured alcohol is now preferred. The base metal should be prepared to avoid residue and an unattractive weld bead. Argon is the go-to gas, but helium offers more power and control.
Rare earth tungsten will give you a better arc without increasing your burn-off rates. You’ll need to use AC power sources as DC cannot penetrate the oxide layer.
Carbon and Alloy Steels
Low alloy steels will harden in tandem with the amount of carbon they contain. This can cause brittleness that destroys your weld entirely. Even if the metal survives the welding process, breakage can still happen at a later date. Steels that contain chromium or nickel can withstand loading more reliably. Preheating will prevent brittleness, but joints need to be correctly prepared, too. The surface must be cleared of oil, scale, and rust. If you’re working with a thick plate, brace the joints to prevent your metal from distorting.
Carbon steel responds well to Co2 or c25 gas. It’s relatively unfussy about tools and is easy to work with, but its thickness requires tool adjustments. You’ll also need to avoid cold lap.
Copper needs about twice the heat of steel. It’s an excellent conductor, so heat loss needs to be controlled. A larger tip and supplementary heating will help you to overcome this problem, especially when you’re working with a thick sheet. An oxidising flame provides extra protection, but it’s best to back up the seam to ensure even penetration. Ideally, your metal should cool slowly, so cover both sides of the joint to prevent heat radiation. If you’re working with thin sheets, forehand welding will give you better control.
Stainless steel is rust and stain resistant, so it’s a popular metal to work with. Filler metals should be limited to avoid extra heat application, but if you do need them, use a slimmer diameter than that of your base metal. They’d need to have similar properties and be chemically compatible. Your electrode size will depend on your polarity, thickness, and joint size—all of which can vary enormously. Regardless of those qualities, your taper needs a maximum of 2.5 times your electrode diameter or you will lose control. If your arc fans out too much, your penetration will be insufficient and spread heat too broadly. Pulsed gas tungsten arc welding with a negative current lets you prevent warping and brittleness.
General Rules for Tungsten
Pure tungsten electrodes melt at low temperatures, so they’re prone to developing a rounded tip. This can reduce your visibility and create an unstable arc. Ceriated tungsten works well at high temperatures and can be used with inverter or squarewave machines. They offer excellent control at low amperages. Thoriated tungsten offers incredible stability and resists weld pool contamination. Lanthanated tungsten is similar, so it’s an adequate replacement. If you can’t risk contamination, zirconiated tungsten is ideal. It offers exceptional arc starting.
Stick welding techniques can only be performed well if five facets are well selected:
- Current setting
- Arc length
- Electrode angle
- Electrode manipulation
- Travel speeds.
The better you prepare, the more forgiving your experience will be. Stick welding might offer you more freedom and less fussiness, but it should nonetheless be cleaned thoroughly. A grinder or wire brush will remove most grime, evading porosity, lack of fusion, and cracks.
When you work, you should be able to see the weld puddle easily. This will ensure that your arc remains on the puddle edge. No matter how practised your technique is, poor tools will never produce a satisfactory result. Choose trusted brands like Lincoln Electric welding products for their even diameter and the consistent, smooth finish they will achieve.