this welding is a thin paste and is applied by brush to all parts of the joint and to the welding rod. Adjust the torch to give a slightly carburizing flame; the tip of the inner cone should just touch the base metal. Do not melt the base metal any more than necessary to ensure good fusion. Keep the end of the filler rod within the protective envelope of the flame, adding the filler metal without disturbing the molten pool of weld metal. If possible, run the weld from one end of the joint to the other without stopping. After you complete the weld, cool the part slowly and remove the remaining traces of flux with warm water.
Nickel and High-Nickel Alloys
Oxygas welding of nickel and high-nickel alloys is similar to that for copper-nickel alloys. Good mechanical cleaning of the joint surfaces is essential. The joint designs are basically the same as steel of equivalent thickness. The included angle for V-butt welds is approximately 75 degrees. You may weld plain nickel without a flux, but high-nickel alloys require a special boron-free and borax-free flux. The flux is in the form of a thin paste and should be applied with a small brush. You should flux both sides of the seam, the top and bottom, and the filler rod. Adjust the torch to give a very slightly carburizing flame; the tip selected should be the same size or one size larger than for steel of the same thickness. The flame should be soft and the tip of the cone kept in contact with the molten pool. Use a rod suitable for the base metal, and always keep the rod well within the protective envelope of the flame. After the weld is completed, postheat the part and cool it slowly. Then remove the flux with warm water.
Oxygas welding of lead requires special tools and special techniques. Although you do not require a flux, you must ensure that the metal in the joint area is scrupulously clean. You may accomplish this by shaving the joint surfaces with a scraper and wire brushing them to remove oxides and foreign matter. In the flat-welding position, a square butt joint is satisfactory. In other positions, a lap joint is used almost exclusively. When you use a lap joint, the edges should overlap each other from 1/2 of an inch to 2 inches, depending upon the thickness of the lead.
To weld lead, use a special, lightweight, fingertip torch, with tips ranging from 68 to 78 in drill size. Adjust your torch to a neutral flame with the gas pressure ranging from 1 1/2 psig to 5 psig, depending on the thickness of the lead. The length of the flame varies from about 1 1/2 inches to 4 inches, depending upon the gas pressures used. When you are welding in the horizontal and flat positions, a soft, bushy flame is most desirable. But, when you are welding in the vertical and overhead positions, better results are obtained with a more pointed flame.
For oxygas welding of lead, you should ensure that the filler metal has the same composition as the base metal. The molten puddle is controlled and distributed by manipulating the torch so the flame moves in a semicircular or V-shaped pattern. Each tiny segment of the weld is made separately, and the torch is flicked away at the completion of each semicircular or V-shaped movement. Joints are made in thin layers. Filler metal is not added during the first pass, but it is added on subsequent passes.
When welding lead or lead alloys, you should wear a respirator of a type approved for protection against lead fumes.
LEAD FUMES ARE POISONOUS.
Aluminum and Aluminum Alloys
When assigned to work with nonferrous metals, you can expect jobs that involve the welding of aluminum and aluminum alloys. Pure aluminum has a specific gravity of 2.70 and a melting point of 1210°F. Pure aluminum is soft and seldom used in its pure form because it is not hard or strong enough for structural purposes; however, the strength of aluminum can be improved by the addition of other elements to form aluminum alloys.
Aluminum alloys are usually 90-percent pure. When elements, such as silicon, magnesium, copper, nickel, and manganese, are added to aluminum, an alloy stronger than mild steel results; whereas pure aluminum is only about one fourth as strong as steel.
A considerable number of aluminum alloys are available. You may use some of the aluminum alloys in sheet form to make and repair lockers, shelves, boxes, trays, and other containers. You also may have to repair chairs, tables, and other items of furniture that are made of aluminum alloys.
Oxygas welding of aluminum alloys is usually confined to materials from 0.031 of an inch to 0.125 of an inch in thickness. Also, thicker material can be weldedContinue Reading