Lesson 5: Methods that meet today’s requirements – repair welding of iron casting, and reconditioning of aluminium castings

In this lesson, we will explore two important methods for repair and reconditioning of castings – Repair Welding of Iron Castings and Reconditioning of Aluminium Castings.



  • Iron castings come in various sizes and shapes, making replacement challenging for specially designed and large castings.
  • Repair welding offers a solution for professional repair, but it involves specific methods.

Welding Methods for Cast Iron

  • Three primary methods for repairing cast iron are Cold Welding (no preheating), Semi-Hot Welding (preheating to 300-400°C), and Hot Welding (preheating to 500-600°C).
  • Cold welding is preferred for custom repair welding due to its simplicity and effectiveness.


  • Part preparation involves cleaning, defect type inspection, extent assessment, and disassembly planning.
  • Preparing the surface by rounding edges, corners, and marking the crack trace.
  • Grooving the electrode and engraving.
  • Grinding to remove stone residue.

Performing a Repair Weld

  • Using a thin 2-2.5 mm diameter nickel-based electrode with 40-60 A current to minimize heat input.
  • Applying the weld sections sequentially to avoid concentrated heat.
  • Preventing crack propagation with two auxiliary welds perpendicular to the weld section.
  • Hammering to reduce the brittle cementitious fabric structure and weld zone stresses.
  • Continuous removal of slag residues.
  • Quality control methods depend on the part’s function, including paint penetration tests, ultrasonic testing, or radioisotope testing for high-value or high-risk equipment.



  • Aluminium castings are widely used, and their repair and reconditioning are common procedures.
  • Several methods are employed for reconditioning aluminium castings.

Possible Methods

  • Coated Electrode Arc Welding
    • Drying the highly hygroscopic electrode coating at 200°C for at least two hours before use.
    • Coating includes alloys (Mg, Cu), excess silicon, and a fluxing agent.
    • Cleaning and defect site preparation, which can include grooving or drilling.
    • Preheating the area around the fault location (150-200°C).
    • Using a 2.5 mm diameter electrode with 50 A current and reverse polarity to break down the oxide layer and access the base metal.
  • AWI (Argon Shielded Tungsten) Welding
    • Similar preheating requirements as electrode arc welding.
    • For up to 15 mm wall thickness, a 4 mm diameter electrode, 220 A welding current, 10 mm arc length, and left-hand welding are used.
    • Continuous monitoring of melt penetration, with immediate repairs on the hot workpiece if insufficient.


  • Repair welding of iron castings and reconditioning of aluminium castings are essential techniques in maintenance.
  • These methods allow for the cost-effective restoration of components, extending their useful life.
  • The choice of method depends on factors such as material, part size, and desired results.
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