Precision Arc Welding Processes

A brief summary

Welding small parts does not mean a stampede to the laser welding equipment store. Many welding processes exist that may be capable of performing the given task and each could form the basis for a lengthy discussion. The challenge is to weigh the cost of each method against the benefits and select the process that will most efficiently and cost effectively accomplish the required weld.

• Soldering & Brazing: An economical means of applying filler metal to join components in low volume. Soldering or brazing may be used when the assembly can endure the high temperature rise these processes present.
  
  
• Resistance Welding: This process applies large current flow to heat the components at the point of highest resistance - at the weld joint. Hermetic seals may be produced but weld integrity is always a question as the weld itself may not be always be visually inspected because the true weld joint is hidden from view under the external material surface.
  
  
• Electron Beam Welding: This is a fusion process performed in a vacuum chamber where a high velocity beam of electrons is focused on the surface to be welded. The resultant welds are deep and narrow with low heat input. Because of the equipment expense and set up times, a compelling reason must exist to justify this process.
  
  
• Laser Welding: Laser welding is appropriate where the parts demand such extreme requirements and where the weld joint can be positioned with no tolerance for gaps or mismatch. If the weld joint cannot be that precise, the laser beam can be defocused, however in these cases, new technology now allows less expensive processes to be used.This process offers two benefits:
  • Extremely small welds with low heat input.
  • High speed welding possible with large power systems.
    
    
• Gas Tungsten Arc Welding: Gas Tungsten Arc Welding (GTAW, also known as Tig Welding) is the most commonly used precision arc welding process. A welding arc is established between a Tungsten electrode and the part to be welded. The metal of the part is melted by the intense heat of the arc and fuses together either with or without a filler metal. Advances in power supplies, welding techniques and process controls have allowed for greater weld accuracy and the process is now used in even more precision welding applications.
  
  
• Plasma Arc Welding: Plasma arc welding, basically an advancement of the GTAW process uses a copper nozzle to surround the Tungsten electrode. A pilot arc is first established between the electrode and copper nozzle and then transferred to the part to be welded. Among other advantages, this offers some enhancements to the arc process:
  • The orifice of the copper nozzle tends to constrict the arc passing through it, concentrating the power of the arc for smaller weld sizes and faster welding.
  • The welding torch keeps a pilot arc established. This provides for more controllable arc starting/transfer to give gentle consistent arc starting for low heat input seam welds. This also allows for short duration weld times for accurate spot welding.
  • Long electrode life offers many more hours of welding than Tig before contamination occurs

The two most popular methods used for precision joining are the Tig and Plasma weld processes. Advances in power supplies, welding techniques and process controls have allowed for greater weld accuracy and the process are now used in even more precision applications.