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SOLUTIONS: Cast Iron

Build up of missing section Occasionally, it will be necessary to rebuild parts where sections have been worn down or broken off. In explaining the salvage process a broken-off cog on a wheel is taken as an example.

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Cut stress-relieving grooves in the area to be built up, using Unitor CH2 382. If the area is large enough to accept more than one groove, there should be a minimum of 6 mm (1/4") between the groves. Do not use a grinder for cutting stress relieving grooves. The groves will not be geometrically correct for the dispersion of stresses from the casting surface.

Fill in the grooves. Then "paint" on weld metal by using a long arc and fast zigzag movements. Apply thin deposits (1,5 mm) to seal in all contaminants. Do not quench. Built up section, use stringer beads. When repairing defects in raised areas, such as bosses, which must be machined after welding, it is unwise merely to chip out the defects and fill the defective areas. It is better to prepare the area for repair by machining to a dept slightly below the desired final surface. Then build up the surface 2 mm (1/16") above the required dimension to allow for machining. All machining will then be done on the solid weld metal deposit, which is fully machinable. Alternatively the parts may be rebuilt by braze welding, using Unitor Castiron 237 or Unitor FC-Wearbro 262.

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Filling holes that penetrate clear through the casting Begin to weld at one side and run straight stringer beads side by side until the hole is closed. Weld from one side only. Do not alternate sides or weld around the edges. Such action will create stress cracks. Peen each weld pass lightly to reduce shrinkage stresses. Remove slag.