Lead is a waterproof metal that melts easily and has a low corrosion rate as such, there are many welding applications where lead can be appropriately used. While lead is often used for automobile parts and pipes, it is also highly toxic when not handled in an appropriate way.
Be sure to ventilate the area and wear appropriate safety gear before lighting your torch. After you ventilate the area and put on your appropriate safety gear, you can turn on the oxyacetylene torch and use a rod of lead solder to complete the bond.
Whether you are welding with old or new pieces of lead, it is a good practice to weld as them together to give it a strong enduring bond.
What is Lead Welding?
Lead burning is a welding process for joining lead sheets. It is a manual process that utilizes gas welding, typically oxy-acetylene.
This process is manual and joins lead sheets with a torch flame, and the only difference is that it doesn’t require flux. Flux is a chemical cleaning agent used primarily for soldering electronics, but is never used for lead welding.
Flux is required for the welding of other metals however. Again, lead has its own fluxing agent like copper and therefore does not require additional flux to weld.
Lead can be differentiated from other metals based on the color of the unfinished surface (white to gray), color and condition of the newly fractured surface (light gray, crystalline) and the color of a newly filed surface (white).
MORE: What is Welding?
Which Gas is Used for Lead Welding?
Three combinations of gases are commonly used for lead welding:
- Oxyacetylene
- Oxyhydrogen
- Oxygen-natural gas
The oxyhydrogen and oxyacetylene processes are applicable to any position. Overhead welding actually does not use oxygen or natural gas. Generally, a low gas pressure is used from 1-1/2 to 5 psi (10.3 to 34.5 kPA), depending on the type of weld it is.
Lead Welding Torch
Welding torches are fairly compact devices. The flammable gas and oxygen valves are located on the front end of the handle with the adjustable gas and oxygen valves. You can easily manipulate these valves with the thumb of your holding hand.
Welding torch tip drill size runs from 78 up to 58. Much larger tips are to be used for heavier lead, while lighter tips are to be used with 6-pound (2.7 kg) lead.
Which Welding Rods are used for Lead Welding?
Your filler rods should match the composition of the lead you are welding. The diameters of these filler rods will range from 1/8 to 3/5 inches (or 3.2 to 19.1 mm). The larger sizes are used for heavier lead and smaller sizes are used for lighter weight lead.
How to Weld Lead – Step-By-Step Process
The process of lead burning is an autogenous welding process. Two sheets of lead are deliberately formed to lie in proximity to one another. They are heated with the torch flame and flow together. There is no filler rod used; the sheets create their own filler (autogenous welding). Neither is there a flux used or required.
In contrast, soldering would also require a solder alloy, which is some compatible alloy showing eutectic behaviour. This lower melting point must be lower than the base metal to allow for a soldering process rather than a welding process. A filler rod can be used for some attachments if for example; there was no convenient way of achieving some close overlap on a sheet edge.
Offcuts of the same lead sheet would be used as a filler. An excessive filler rather than an initial close fit is looked down upon or at least interpreted as poor elusiveness.
The torch used for lead burning is small hot gas. Oxy-acetylene is the most common, and it is portable. A nozzle size of #0 is used, sometimes with a miniature torch body, but otherwise is the same as a torch used for steel or copper work.
A number of different fuel gases could be used, but to reach the high temperature needed, an oxygen supply is always used. Fuel gases could be acetylene, natural gas, or hydrogen. Oxy-hydrogen is thought to be the best but not convenient for site work as noted.
Oxy-natural gas is the cheapest and is commonly used on fixed workbenches. Its less hot flame means that it cannot be used for awkward positional (overhead) welding. Oxy-acetylene has to be the most common source as the majority of leadwork is carried out onsite and this is quite portable.
A neutral flame is used. A reducing flame (fuel rich) causes trouble with soot deposits in the weld. An oxidising flame burns the lead and adds lead oxide dross which creates poor welds with poor malleable joints.
Application of Lead Welding
Lead burning is used for roofing work using sheet lead or for the purposes of making custom rainwater goods: gutters, downpipes, and decorative hoppers.
Some decorative lead work will be carried out with lead burning, especially where and when a waterproof joint is required, like for planters.
Lead burning is therefore part of a traditional plumber’s work, in the original sense of a worker in lead (Latin: plumbum). Though rare and specialized, such work still happen today, and not just for historic building restoration work.
Most lead sheet work is formed and sealed using bossing, a mechanical fold, or crimp. Why this is adequate for roofing that drains water, it is not satisfactory for being watertight when water accumulates on it, so an impermeable burned joint is necessary.
Lead burning has no longer been accepted as part of plumbing work for installed pipework. Lead piping is now long been considered antiquated, for health reasons.
Even if lead piping, or lead sheathed cable, has to be jointed when it still exists, it is carried out using wiped joints, not using burned joints.
Wiping, using a low melting temperature plumber’s solder (80% lead / 20% tin) is a soldering process carried out using a natural draught propane blowtorch.
Even wiping joints are now outside of common practice, and if a lead pipe has to be connected to in order to a run off it, a proprietary mechanical joint would be the norm today.
In some rare chemicals industry cases, lead burning is being used for pipework, where acid resistant tanks and pipework have to be made of lead, rather than say steel.
Niche areas for lead burning uses include making lead plates for lead-acid batteries and the use of lead-burning for electrodes for electro-plating.
FAQs
What is lead welding used for?
Lead welding is used for pipe joints, preventing the rust of steel and iron, as well as for the construction of chimneys. This is where lead flashing comes in. Whilst lead welding is mainly for professional construction, it can also be used for DIY purposes.
How hard is it to weld lead?
Lead welding is a skilled trade that requires years of training and experience. In order to become a lead welder, one must first gain a thorough understanding of the properties and characteristics of lead, as well as the techniques and tools used in lead welding.
Can lead be welded to steel?
You generally need to stick to the same type of metal in welding. Since lead melts so quickly, it’s hard to get it to bond properly with something like steel. You might be able to melt the lead, then dip the steel into it to coat it.
Can you weld lead with a blowtorch?
No. The flame is not hot enough to melt most metals. Yes, a butane or propane torch will make the joint “hot”, so don’t touch it after you do so. It is not a “welding joint” since no “welding” will occur.
How toxic is lead welding?
When welding lead, workers can come into contact with lead oxide fumes leading to chronic health issues. Extremely high lead exposure can be fatal and smaller amounts can lead to anaemia, kidney damage and brain damage. This is also known as heavy metal poisoning.
Can I use propane for lead welding?
The correct Lead Welding (Lead Burning) equipment is essential for getting good results. Whilst Oxygen + Acetylene are the traditional gasses used, Oxygen + Propane or Polypropylene are well worth considering.