Various factors decide the methods and techniques of gas welding to be used while maintaining and repairing an aircraft, such as the item, to be welded, thickness of the alloy, joint, and placement of the weld. When it comes to welding a light-gauge metal, the expert aircraft welders usually hold the torch with the hose draped over the wrist. While combining heavy materials, the professional aircraft welders prefer the more usual grip that provides better control of the flame.
Keep in mind to hold the torch in the most comfortable position allowing the tip of the flame to be in line with the join that needs welding. It should also be angled between 30° and 60° from perpendicular. This position helps in preheating the edges before the molten puddle. The most suitable angle depends on the kind of weld, the amount of preheating needed, and the type and thickness of metal. For an alloy with increased thickness, the torch should be held in a more vertical position to aid in proper heat penetration.
Forehand welding is the method of gas welding during which the torch flame is pointed in the direction in which the welding process is proceeding. It’s the most commonly utilized technique for sheet metal and lighter tubing. Expert welders keep the filler rod ahead of the tip in the direction in which the welding procedure is progressing and then add it to the puddle.
Backhand welding is primarily used to weld heavy plates or thick metals. During this gas welding technique, aviation welding technicians point the torch flame back toward the already finished weld, followed by adding the filler rod between the flame and the welded part. This approach provides a higher intensity of heat for welding thicker pieces of metals, as is occasionally used in aircraft maintenance.
Holding the torch in an accurate position creates a small puddle of molten metallic forms. This puddle needs to be centered in the joint and must consist of equal components of the pieces being welded. After the pool becomes visible, the tip of the torch must be shifted in a circular or semicircular equally between the welded parts to ensure a balanced heat distribution.
How To Add Filler Rod To The Puddle
As the metal piece melts and the puddle starts to develop, the filler rod is required to replace the metal piece that will flow out from around the joint. Care should be taken to add a rod to the puddle in a required quantity that can assist in building up the finished fillet around one-fourth of the thickness of the base metal. Also, the selected filler rod must be fully compatible with the base metal that’s being welded.
Importance Of An Accurate Weld Formation
The welded metal form has tremendous significance upon a joint’s strength and fatigue resistance. The strength of an inadequately welded metal part usually is less than the strength of an intended joint design. These low-strength metallic welds are often the byproducts of the followings:
- Insufficient penetration
- Impairment of the base metal at the toe of the weld
- A weak fusion of the weld metal with the base metal
- Overlapping of the weld metal on the base metal
- Trapped gas pockets, slags, or oxides in the weld
- Too little or too much reinforcement
- Overheating of the weld
Properties Of A Good Weld
A well-finished weld has the following characteristics:
- The bead ripples must be evenly spaced and of a uniform thickness, and the seam should be smooth
- The weld should be made slightly convex to provide additional depth at the joint
- The weld should absorb smoothly into the base metal
- There should be no oxides formation on the base metal near weld
- There should be no signs of blowholes, projecting globules, or porosity on weld
- There should be no signs of pits, burns, cracks, or distortion on the base metal