Lead is a waterproof metal that melts easily and is less prone to corrosion, making it an ideal choice for many welding projects. Although lead is often used for automobile parts and pipes, it is highly toxic when handled improperly.
Take precautions by ventilating the area and wearing safety gear before turning on your torch. Then, use an oxyacetylene torch and a rod of lead solder to complete the bond. Whether you work with old or new pieces of lead, weld them to create a strong, long-lasting bond.
What is Lead Welding?
Lead burning is a welding process used to join lead sheets. It is a manual process carried out by gas welding, usually oxy-acetylene.
This process joins sheets of lead together manually with the use of a torch flame, the only difference being it doesn’t require flux. Flux is a chemical cleaning agent used mainly before soldering electronics, but never for lead welding.
The welding of other metals, however, does require the use of flux. Similar to copper, lead has its own fluxing agent and therefore does not need any additional flux for welding.
Lead can be identified by the color of an unfinished surface (white to gray), the color and structure of a newly fractured surface (light gray, crystalline), the color of a freshly filed surface (white).
MORE: What is Welding?
Which Gas Used for Lead Welding?
Three combinations of gases are commonly used for lead welding:
- Oxygen-natural gas
The oxyhydrogen and oxyacetylene processes work for all positions. Overhead welding does not use oxygen-natural gas. Normally a low gas pressure that ranges from 1-1/2 to 5 psi (or 10.3 to 34.5 kPa) is used, depending on the kind of weld that is being made.
Lead Welding Torch
Welding torches are fairly small. The flammable gas and oxygen valves are on the forward part of the handle. This makes it easy to adjust them by using the thumb of your holding hand.
The drill size of the torch tip ranges from 78 up to 58. Bigger tips are used for heavier lead and smaller tips are used with 6-pound (2.7 kg) lead.
Which Welding Rods use for Lead Welding?
Your filler rods should have the same composition that the lead does that you are welding. The diameters of these rods range from 1/8 up to 3/5 inches (or 3.2 to 19.1 mm). Bigger sizes are used for heavier lead and smaller sizes for lightweight lead.
How to Weld Lead – Step By Step Process
Lead burning is an autogenous welding process. Two sheets of lead are formed mechanically to lie close against each other. They are then heated with the torch flame and flow together. No filler rod is required, the sheets form their own filler (autogenous welding). Neither is a flux used.
Soldering, by contrast, uses a solder alloy that is some compatible alloy showing eutectic behavior. This gives a melting point lower than the base metal, allowing a soldering process rather than welding. A filler rod may be needed for some welds if there is no convenient way to form sufficient close overlap at a sheet edge.
Offcuts of the same lead sheet are used as this filler. Excessive use of a filler, rather than an initial close fit, is considered a sign of poor technique.
The torch used for lead burning is a small, hot, gas flame. Oxy-acetylene is most commonly used, as it is easily portable. A small size #0 nozzle is usually used, sometimes with a miniature torch body, but the torch is otherwise the same as that used for steel or copper work.
A variety of fuel gases may be used, but to achieve the high temperature needed, an oxygen supply is always used. Fuel gases may be acetylene, natural gas, or hydrogen. Oxy-hydrogen is considered to be the best but is not easily portable.
Oxy-natural gas is the cheapest and is often used on fixed workbenches. As it is less hot, it cannot be used for some awkward positional (overhead) welding. Oxy-acetylene is the most common, as much leadwork is carried out on-site and this is easily portable.
A neutral flame is used. A reducing flame (fuel-rich) gives trouble with soot deposits in the weld. An oxidizing flame burns the lead and creates lead oxide dross, leading to poor welds with low malleability.
Application of Lead Welding
Lead burning is carried out for roofing work in sheet lead, or for the formation of custom-made rainwater goods: gutters, downspouts, and decorative hoppers. Decorative lead working may also use lead burning, particularly where a waterproof joint is required as for planters.
Lead burning is thus part of a traditional plumber’s work, in its original sense of a worker in lead (Latin: plumbum). Although rare and specialized, this work is still carried out today and not just for the restoration of historical buildings.
Most lead sheet work is formed and sealed by bossing, a mechanical fold, or crimp. This is adequate for roofing that sheds water but is insufficiently watertight when standing water sits upon it and so an impermeable burned joint is needed.
Lead burning is not used as part of plumbing work for installed pipework. Lead piping has long been considered obsolete, owing to the health aspects. Even where lead piping, or lead-sheathed cable, still needs to be jointed, this is carried out with a wiped joint, rather than a burned joint.
Wiping a lead joint is a soldering process, using a plumber’s solder (80% lead / 20% tin) and is carried out at a low temperature, with a natural-draught propane blowtorch. Today, even wiped joints are rare and where an existing lead pipe must be connected to, a proprietary mechanical joint is more likely to be used.
In some rare cases within the chemical industry, lead burning is used for pipework, where acid-resistant tanks and pipes are required to be made of lead rather than steel. Niche uses for lead burning include the manufacture of lead plates for lead-acid batteries and for electro-plating electrodes.