Lesson 3: WELDING III – welding processes, fusion welding processes

In this lesson, we will delve into fusion welding processes, which employ various heat sources to create strong bonds between materials.

  1. GAS WELDING
  • Gas welding utilizes burning as a heat source.
  • Acetylene burned in oxygen produces a high flame temperature of 3160°C.
  • Caution is essential due to acetylene’s explosive nature.
  • Proper ventilation is crucial to prevent carbon monoxide formation.
  • Although less commonly used now, it was valued for its independence from electricity.

  1. THERMITE WELDING
  • This process relies on chemical energy as well.
  • It begins with a reaction initiated by a thermite igniter or an acetylene-oxygen flame.
  • Temperatures exceeding 2000°C are required.
  • The reaction produces thermite iron and significant heat.
  • Cooling is necessary, and steel pieces are added for this purpose.
  • Alloy quality is achieved through additives like coke, manganese, silicon, titanium, and vanadium.
  1. ELECTROSLAG WELDING
  • Electroslag welding is a mechanized process using Joule heat.
  • Initially, it starts as an arc welding on a cutoff plate.
  • The heat of the arc melts the welding flux to form slag.
  • Slag takes over current conduction, extinguishing the arc.
  1. SUBMERGED ARC WELDING
  • A high-power, automated process suitable for long seams on thick plates.
  • An electrical arc burns between the consumable wire electrode and the workpiece.
  • Welding flux is fed onto the workpiece, and a vacuum cleaner collects unused flux.
  1. MANUAL METAL ARC (MMA) WELDING WITH COATED ELECTRODE
  • An early arc welding process.
  • Arc forms under the protection of the electrode coating.
  • Versatile and cost-effective, used for various metals.
  • Limited deposition rate and quality affected by human factors.

  1. GAS METAL ARC WELDING
  • Gas Metal Arc Welding (GMAW) processes are highly productive and easily automated.
  • It utilizes a burning arc between a mechanically fed consumable wire electrode and the workpiece.
  • Protective gas flows through a nozzle to shield the weld and stabilize the arc.
  • Inadequate gas protection can lead to issues such as gas porosity and alloying element loss.
  • Shielding gas can be inert or active, e.g., Argon and Helium.
  1. TUNGSTEN INERT GAS (TIG) WELDING
  • TIG welding employs a non-fusing tungsten electrode and a shielding gas.
  • It is manually guided, similar to gas welding.
  • Arc can be ignited by lifting the electrode or using a high-frequency igniter.
  • Various electrode materials and diameters are available.
  1. PLASMA WELDING
  • Plasma is a medium with high temperatures and ionization.
  • Plasma welding uses an electric arc to create plasma.
  • Temperature can reach 5000-50000°C.
  • Various gases are used for plasma formation.
  • Plasma arc characteristics differ from regular arcs.

  1. LASER WELDING
  • Laser stands for Light Amplification by Stimulated Emission of Radiation.
  • Laser-active material is brought into a state of population inversion, resulting in amplified emission.
  • Laser welding involves an intense, focused laser beam.
  • Precise and efficient, it’s used for various applications.
  1. ELECTRON BEAM WELDING
  • High-speed electrons in an electron beam are converted into thermal energy on impact with the workpiece.
  • Welding is conducted in a vacuum chamber to avoid rapid electron deceleration due to air particles.
  • Precautions include demagnetization, radiation protection, and cleanliness.

Conclusion:

  • Fusion welding processes utilize diverse heat sources, from burning gases to laser beams, to create strong material bonds.
  • Each welding method has distinct advantages and is chosen based on factors like material type, thickness, and application.
  • Safety and precision are paramount in welding, as processes may involve high temperatures, potential hazards, and specific techniques.
  • Understanding these fusion welding processes equips professionals with the knowledge to select the right method for various welding applications.
  • Welding continues to play a critical role in industries ranging from construction to aerospace, underlining its importance in modern manufacturing.

In this lesson, you’ve explored a variety of fusion welding processes that use different heat sources to create strong bonds between materials. Each process has its advantages and applications, making them valuable tools in various industries.

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