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May 20, 2021

When you see an aircraft or any machinery, welds may not be the first thing that comes to your mind. Our modern world heavily relies on welding, making it one of the most economical and efficient construction processes. Since welding is a skill that is open to everyone, finding a cheap welder for a small investment may sound attractive, but it has many associated risks. Industries such as aircraft manufacturing cannot afford such risks, and therefore aviation welding technicians are highly trained and skilled.

Aircraft manufacturing processes employ several sophisticated welding techniques that depend on their materials and applications. However, one thing that is common when selecting a method is the effectiveness and durability of the final product. A good weld is strong and durable, with a neat appearance that sets it apart from a bad weld.

Every manufacturer and industry has to follow certain quality standards to obtain ISO certification. In this blog, we have enlisted the criteria to identify the quality of a weld and some signs to identify good and bad welds in different welding methods.

Common Criteria To Identify Weld Quality

Penetration: How far does the weld penetrate the joint. It is possible to have both too little (weak joint) and too much (poor finish in the backside of the joint) penetration.

Defects: Including porosity caused by contamination of the weld due to inadequate preparation/cleaning or shielding, craters caused by rapid current reduction at the end of a run, and cold.

Undercutting: Thinning of the parent metal at the edges of the weld is usually caused by less filler metal relative to the current.

Appearance: Welds should have a consistent, smooth, and uniform appearance.

Profile: Depending on the application, welds need to be flat, concave, or convex.

Coloration: A good weld will have a color-free appearance that indicates no oxidation has occurred.

MIG Welding

MIG or metal inert gas welding, also known as gas metal arc or GMAW welding, is one of the most common techniques used for large-scale aircraft manufacturing. In this method, a welding gun feeds a wire electrode, a filler material, to join two metal pieces. It is used on thin types of metals such as mild or stainless steel and aluminum. Here are some indicators to help you identify if a MIG weld has been done right.

Signs Of A Good MIG Weld

  • A smooth, consistent weld with no patterns or discoloration
  • No cracks, slags, or holes on the weld bead
  • Some coloration on the base metal
  • Flat bead profile that is neither concave nor convex
  • Straight and uniform appearance with no dips or craters

Signs Of A Bad MIG Weld

  • An overly thin welding bead or line
  • Parent metal has no discoloration
  • The appearance of cracks along with the bead
  • Lack of uniformity and straightness on the welding line
  • Joined structure lacks strength

TIG Welding

TIG or tungsten inert gas welding, also known as gas tungsten arc welding or GTAW, often finds its use in aircraft assembly and repair. It is a technique that is considerably harder to perfect and requires more skill to produce quality welds than MIG welding. It is used on various metals, including stainless steel, aluminum, magnesium, and copper alloys.

Although it is known for its aesthetically pleasing welds, it can easily create an illusion of a good weld. The following signs can help you differentiate between a good and a bad TIG weld.

Signs Of A Good TIG Weld

  • No signs of tungsten metal particles in the weld
  • A distinct pattern of smooth beads
  • Lack of pores on the surface of the weld
  • No visible signs of slag or burnout
  • Tiny and neatly layered welds
  • Visually appealing

Signs Of A Bad TIG Weld

  • Not enough filler metal used
  • Flat and wide beads with no distinct pattern
  • Inclusion of tungsten in the weld
  • Signs of burnout and undercutting

Conclusion

Welding is one of the most vital processes of any construction or manufacturing project today. It’s a useful skill that requires a lot of learning and experience to master. A professional welder will have the knowledge about its functioning and other aspects, including identifying a good quality weld from a bad one, the differences between various welding processes, and how to weld different types of metals.

The ability to spot a bad weld is crucial to any welder, especially for an aviation welding technician, as the strength of this industry lies in its quality and effective welding techniques.

About Acorn Welding

Acorn Welding is a trusted and highly qualified aviation welding company in Edmonton. We have the latest product designs and manufacturing capabilities required for safe aircraft welding. To get the most reliable and best services related to aviation welding, click here.