Clean out impurities
Farmers fail to prepare metals before welding adequately. This includes removing rust, paint, dust and other surface contaminants-it also means grinding out cracks. Metal preparation is the last thing on your mind when a weld repair at the height of the season.
Cleaning removes impurities that get absorbed into the metal during welding; if they get left behind, they compromise the repair. If cleaning is not possible, avoid mending a replacement with a welder. Slow your travel speed. This allows time for bubbles to boil out of the molten weld before impurities are trapped inside the weld.
Hydrogen is welding enemy number one #1
Hydrogen is the worst weld-destroying impurity around. Since its everywhere ( in the dirt, water, rust, paint, grease, manure), hydrogen is a considerable challenge for welders. What can be done to wipe out hydrogen? Clean, clean and clean some more. Along with high-residual stress and crack sensitive steel, may result in cracking hours or days after welding. High strength steels (commonly used on tillage implements), restrained and thick metal parts are more susceptible to hydrogen cracking.
Rules on direction, angle and speed
One of the fantastic aspects of welding is that even an amateur welder can experience some level of success. However, there are some hard-and-fast rules to produce lasting welding repair.
- *Pull or Push: Here, the rule is simple. If it produces a slag, you drag. In other words, you drag the wire or rod when welding with a flux-core wire or stick welder. Otherwise, you should push the wire with metal inert gas welding.
- *Wok angle: with wire welding hold the gun at a 10-15 degrees angle into the direction you are pushing the weld. With stick welding, maintain a 20-30 degrees lead angle in the dragging direction. With a fillet weld, hold the rod or wire at a 45 angle between the two pieces of metal.
- *Speed: watch the welding ridge and puddles (where the molten metal solidifies). A too slow travel speed produces a wide, convex bead with a too shallow penetration that also deposits too much metal. On the other hand, a high travel speed creates a shallow weld which produces a high and narrow crowned bead. Most travel speeds for various joints are below a 40 inches a minute.
Why do welds crack?
- * Not grinding cracks out to their bottom before welding.
- * Forming hollow or concave beads. Such welds may lead to cracking down the middle of the bead. Welds should always be humped up or convex.
- * Not properly reinforcing a weld repair.
- * Avoiding the use of hydrogen electrodes to repair hard-to-weld steels (high alloy or carbon content).
- * Not pre-heating prior to welding. This is required when the steel you are welding has a higher alloy or carbon content.
- * Failing to clean a repair properly. Leaving paint, rust, dirt, grease or moisture on a repair introduces hydrogen in the weld which promotes cracking.
- * Forming undersized beads. Weld must be wider than they are deep.
- Source: www.finconinstallations.com.au