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SOLUTIONS: Cast Iron

A way to reduse shrinkage stress In order to reduce the shrinkage stresses, do not put down a complete root bead first, before proceeding to build up. "Stack" the beads stepwise as shown in the sketch, advancing each bead (starting always with the root bead) 2 - 3 cm forward at a time. Take care to keep the heat down (hand warm before proceeding each new bead!) and hammer each bead while still hot. A small pneumatic hammer is suitable for this kind of hammering.

Hammering

Stacking

Steel insert technique

It is sometimes desirable to insert a steel patch in the centre section of a large housing or motor block. A gear may have shattered and pushed out an area in the housing. A frozen block may have suffered the same damage. Usually the pushed-out section has been broken in so many pieces that it is not practical to try to join the pieces. The least expensive method or repairs is to fit a steel patch into the hole. This is done as follows:

cracks. Grind the edges of the casting at an angel of 45° halfway down its wall thickness. Remember to file the ground area to remove surface graphite. Seal in the contaminants, using Unitor NICKEL-334N. Using a piece of cardboard cut a template to obtain the correct shape for the steel patch.

Select a piece of low carbon steel, one half the thickness of the casting's wall. Using the template as a guide cut the patch out of the piece of steel. It should fit the hole with a clearance of 2 - 3 mm. Grind the edge of the patch 45°. The patch should be "doomed" slightly by striking with a ball-peen hammer until a bulge is formed.

2.07

Place the patch in the hole and secure it in position but do not tackweld it. As this will prevent the patch from expanding to heat. Now weld the patch to the casting, using the backstep technique as indicated in the sketch. Be careful to let each bead of 2 - 3 cm cool off before proceeding with the next bead. Use Unitor NIFE-334N for the build-up. Bevel edges to 45°.

Casting

steel-patch

Remove all damage material on the casting. Avoid leaving sharp corners, round off wherever possible. Clean off dirt, paint, oil and grease from the area where the repairs is to take place. Use a Crack Detection kit to make sure there are no hidden 93