Handbook-Welding Ferrous Metals

The building up of a lug, a small boss, or an incomplete edge is something of an art, but an art that any welder can

master with experience. The trick is to keep the molten metal in the mushy range, not let it get really fluid, and to learn how to control the puddle with the flame. As in normal welding try always to let the puddle do the actual melting of the filler metal. Before trying to fill a hole which extends all the way through a section of the casting, always find a way to shape the sides of the hole, either by countersinking or actual melting, so that at the bottom of the hole you have something sharper than a square corner to start work on. Then run a bead around that bottom edge, and add weld metal in progressively narrowing circles until the hole is closed at the bottom. Then add metal, a layer at a time, until the hole is completely filled. Always make certain that every layer is thoroughly fused to the layer below. When the hole goes all the way through a thick section, and it is possible to work on it from both ends, countersink or shape it from both sides, and then fit a small piece of steel into the center of the hole. Finally, weld from each side, making sure, when starting the second side, that the steel insert is completely melted. High Carbon Steels Almost every item made from high-carbon steel must be heat-treated after forming or fabrication to achieve the right combination of hardness and toughness required in service. Welding high-carbon steel by the oxy- acetylene process, even when filler metal of high carbon is employed, will always result in substantial modification of those properties in the base metal. Therefore, high-carbon steel items can seldom be repaired by welding unless facilities

for correct heat-treating after welding are available. If, in an emergency, you ever feel the need to weld something

which is probably made of high-carbon steel (such as a knife blade or spring) use the best steel filler metal you have, use an excess-acetylene flame (to cause carbon pickup by the molten metal), and try to work as fast as you can, melting no more of the base metal than is absolutely necessary to insure complete fusion.