Welding

Welding

1. Manual Arc Weldung

   • Consumable electrode (stick electrode wire coated in chemicals)
     • Shields the weld pool from the oxidising effects of the atmosphere
     • fluxing elements helps the weld form
     • slows down the rate at which the weld cools
     • helps to maintain the arc
     • filler for the weld pool
   • Applications
     • repairs
     • structural steel joinery
   • Process
     • It involves striking an arc between a covered metal electrode and a workpiece. The heat of the arc melts the parent metal and the electrode which mix together to form, on cooling, a continuous solid mass.

2. Oxy-acetylene Welding

   • flames
     • Oxidising
       • excess oxygen
       • welding brass to prevent fuming
     • Carburising
       • excess acetylene
       • really protect specialist welds from oxidation
     • Neutral
       • equal quantities of oxygen and acetylene
       • most commonly used
   • Process
     • In oxy-fuel welding, a welding torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal. The molten pool is generally supplied with additional metal called filler.
   • safety features
     • O2 tank = white shoulder
     • acetylene tank = maroon shoulder
     • opposite threads on both tanks
     • flashback arrestors
     • pressure regulators

3. MAGS Welding

   • continuous feed electrode
     • bare wire
       • fed from spool through a weld gun
   • inert gas supply
     • shields the weld pool
     • Argon/Nitrogen/carbon dioxide or Helium
   • applications
     • semi automatic assemblies
     • robotic
   • process
     • A consumable bare wire electrode is fed continuously into the weld pool area through the welding torch. An inert gas, such as Argon, creates a protective shield around the weld pool giving a fluxing action. The feed rate and flow rate of the gas are set by the operator. This allows the operator to guide the torch along the weld once the arc is generated between the electrode and the work.

4. TAGS Welding

   • Non- consumable tungsten electrode
   • inert gas supply
     • shield the weld pool
     • Argon/Nitrogen/Carbon dioxide or Helium
   • filler metal is required and is fed in by hand to the weld pool
   • Applications
     • aluminium
     • stainless steel
   • Process
     • Argon is used and it flows over the electrode preventing oxygen in the air contacting the weld joint. A high frequency generator provides a path for the welding current through the shielding gas. Because the welder must maintain a short arc length, great care and skill are required to prevent contact between the electrode and the work. .

5. Resistance Spot Welding

   • The components to be joined are placed between the electrodes and then pressed together. A nugget weld is achieved as current is passed through the electrodes generating a large heat between the metals.

6. Resistance Seam Welding

   • copper roller electrodes to provide a continuous run of overlapping spot welds as the current is activated at set intervals. One of the electrodes may be driven by an electric motor. The workpiece is moved between the rollers and pulses of current are supplied. Each pulse is set to last long enough to produce a spot weld. The time interval is controlled so that these spots overlap by approx. 40% of their length along the seam

7. Submerged arc welding

   • In submerged arc welding, a bare wire electrode is used. It is fed automatically from a spool and generates an electric arc to heat the metal. The flux in powder form is fed from a hopper to completely cover the joint and the tip of the electrode. The arc creates the heat to melt the joint, flux and electrode. A slag is formed to provide a protective coating for the weld. The excess flux powder can be collected and used again. Submerged arc welding is a fully automated process.

8. Electro slag welding

   • Electro-slag welding is automatic welding process used to join thicker plates. The gap between the plates to be welded can be quite large as it is filled with molten metal. Water cooled copper shoes prevent this molten metal escaping from the joint. The carriage, shoes and electrode all move together leaving the solidified weld behind.