General Lead Burning Instructions
Flame. With all the lead burning outfits, it is possible to adjust the pressures of the gases so as to get extremely hot, medium, and soft flames. With the oxygen-acetylene, or oxygen-hydrogen flame, each gas should have a pressure of about two pounds. With the oxygen-illuminating gas flame, the oxygen should have a pressure of 8 to 10 pounds. The city gas then does not need to have its pressure increased by means of a pump, the normal pressure (6 to 8 ounces) being satisfactory.
Various makes of lead-burning outfits are on the market, and the repairman should choose the one which he likes best; since they all give good results. All such outfits have means of regulating the pressures of the gases used. With some the gases are run close to the burning tip before being mixed, and have an adjusting screw where the gases mix. Others have a Y shaped mixing valve at some distance from the burning tip, as shown in Figure 78. Still others have separate regulating valves for each gas line.
With these adjustments for varying the gas pressure, extremely hot, hissing flames, or soft flames may be obtained. For the different welding jobs, the following flames are suitable:
1. A sharp, hissing flame, having a very high temperature is the one most suitable for the first stage in welding terminals and connectors to the posts.
2. A medium flame with less of a hiss is suitable for welding plates to strips and lengthening plate lugs.
3. A soft flame which is just beginning to hiss is best for the finishing of the weld between the posts and terminals or connectors. This sort of a flame is also used for finishing a sealing job, drying out the cover channels before sealing, and so on.
In adjusting the burning flame, 4 the oxygen is turned off entirely, a smoky yellow flame is obtained. Such a flame gives but little heat. As the oxygen is gradually turned on the flame becomes less smoky and begins to assume a blue tinge. It will also be noticed that a sort of a greenish cone forms in the center portion of the flame, with the base of the cone at the torch and the tip pointed away from the torch. At first this inner-cone is long and of almost the same color as the outer portion of the flame. As the oxygen pressure is increased, this center cone becomes shorter and of a more vivid color, and its tip begins to whip about. When the flame is at its highest temperature it will produce a hissing sound and the inner cone will be short and bright. With a softer flame, which has a temperature suitable for welding plates to a strap, the inner cone will be longer and less vivid, and the hissing will be greatly diminished.
The temperature of the different parts of the flame varies considerably, the hottest part being just beyond the end of the inner cone. Experience with the particular welding outfit used will soon show how far the tip of the torch should be held from the lead to be melted.
Cleanliness. Lead surfaces which are to be welded together must be absolutely free from dirt. Lead and dirt will not mix, and the dirt will float on top of the lead. Therefore, before trying to do any lead welding, clean the surfaces which are to be joined. The upper ends of plate lugs may be cleaned with a flat file, knife., or wire brush. The posts and inter-cell connectors should be cleaned with a knife, steel wire brush, or triangular scraper. Do not clean the surfaces and then wait a long time before doing the lead burning. The lead may begin to oxidize if this is done and make it difficult to do a good job.
The surfaces which are to be welded together should also be dry. If there is a small hole in the top of a post which is to be welded to a connector or terminal, and this hole contains acid, a shower of hot lead may be thrown up by the acid, with possible injury to the operator.
Do not try to save time by attempting to weld dirty or wet lead surfaces, because time cannot be saved by doing so, and you run the risk of being injured if hot lead is thrown into your face. Remove absolutely every speck of dirt — you will soon learn that it is the only way to do a good job.
Safety Precautions. Remove the vent plugs and blow down through the vent holes to remove any gases which may have collected above the surface of the electrolyte. An explosion may result if this is not done. To protect the rubber covers, you may cover the whole top of the battery except the part at which the welding is to be done, with a large piece of burlap or a towel which has been soaked in water. The parts covered by the cloth must be dried thoroughly if any welding on them. Instead of using a wet cloth, a strip of asbestos may be laid over the vent holes, or a small square of asbestos may be laid over each vent hole.