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SOLUTIONS: Cast Iron

Preparation of the work piece First clean off all oil, grease, rust and paint from the surface, using a brush or by chemical means. Then remove casting skin to a width of 20 mm on both sides of the edges to be welded. A grinding machine may be used for this work. Remove imperfections in the weld area, such as blowholes, cracks, fatigue areas and porosities down to sound metal.

2.07

If the damage is in the form of a crack in the material, it may be difficult to determine where the crack actually

ends. The use of a crack detector set to find the complete extent of the crack is absolutely recommended (see "Inspection of welds"). When this has been established, drill a 3 mm hole at a distance of 3 mm in front of the crack. This will prevent the crack from opening further during the repair.

Cracks should be "V-ed" or "U-ed" out, using either a grinding machine or by gouging electrodes. Suitable groove profiles for various material thicknesses can be as follows:

Preventing crack propagation

Material thickness up to 20 mm

Material thickness 20–40 mm

Material thickness above 40 mm

Alternative shape, thickness above 40 mm

Groove preparation by grinding Grind a 90° V-groove as indicated in the sketches. If the part has broken into two or more pieces, the sides of the fracture should be ground to a 45° bevel.

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Sharp corners and edges should be rounded of wherever possible, particularly on surfaces to be machined or filed later. This is necessary to prevent excessive melting of the base material in these