Picture of lead welding. Photo courtesy of Siegbert Pinger // Pixabay
Although the practice has declined over the years, lead welding (also, and somewhat erroneously, referred to as lead burning) is commonly used in applications like roofing, pipework and in the manufacture of acid-resistant tanks where conventional steel tanks may be susceptible to corrosion.
Jump to a section: Types of Lead | Tools and Materials | Preparing for Lead Welding | Safety | Common Methods | Uses | Step-by-Step | Post-Welding Process | Troubleshooting Common Issues | FAQ
Types of Lead Used in Welding
There are two types of lead found in commercial welding:
Pure Lead
Pure lead is lead in its natural state, not mixed with any other alloys. This type of lead is commonly found in radiation shielding, lead-acid batteries, certain types of pipes, and cable sheathing due to its high density and malleability.
Lead Alloys
Lead alloys are made by alloying lead with antimony, which increases corrosion resistance due to its stability and resistance to oxidation. These alloys are often used in wheel weights, bearings, and various types of ammunition. Lead alloys are known for their durability and strength.
Essential Tools and Materials
Since lead has a low melting point, it is most commonly welded with oxy-acetylene or in the TIG (or GTAW) welding process.
Welding Equipment
To weld lead using the oxy-acetylene process, use a set of oxygen and acetylene tanks with regulators and a torch fitted with a brazing tip.
ATIG machine capable of welding at very low amperages on the DC + polarity is a must For the TIG welding process. Since lead’s low melting point (621 F) makes it easy to burn through, low amperage and a long arc are recommendable.
Lead Welding Rods
Lead welding filler rods are available at many welding supply distributors and online. However, it’s also possible to make filler metal by shearing or cutting thin strips of the base metal.
Personal Protective Equipment (PPE)
Proper ventilation is required for any welding process, but it is especially important for welding lead. High, prolonged lead exposure may have serious and long-lasting health effects.
When welding lead, wear proper respiratory equipment, such as a respirator with a filter of the appropriate rating.
Additional Tools and Supplies
A wire brush and/or sanding pads (either on a grinder or hand-held, depending on the size of the parts you will be welding) are necessary to clean surface oxidation and other impurities before welding.
Preparing for Lead Welding
Workspace Setup
Use a steady metal workbench to fit up and weld lead sheets together, choosing an appropriate size based on the parts you will be joining. Since lead most commonly comes in thin sheets, you can make lap joints and square butt joints on a sturdy welding bench.
Lead Material Preparation
Like most welding processes, it is crucial to clean the parts before welding to minimize the risk of weld defects caused by impurities in the base metal.
You can accomplish this by using a wire brush or fine-grit sandpaper. When clean, lead should have a bright, silvery luster. A dull gray surface is evidence of oxidation.
Safety Considerations
The health risks involved in working with lead may be one of the main reasons for its decline in commercial use. For situations where welding lead is necessary, there are some important safety considerations to take into account.
Health Risks of Lead Exposure
Lead exposure poses significant health risks, particularly with prolonged exposure. Lead can enter the body through various pathways, including inhalation, ingestion, and direct contact with the skin. This exposure, often referred to as heavy metal poisoning, can lead to health issues such as:
Anemia: Lead interferes with the production of hemoglobin, the protein in red blood cells that carries oxygen. This can result in anemia, characterized by fatigue, weakness, and shortness of breath.
Kidney Damage: The kidneys filter waste from the blood, and prolonged lead exposure can lead to decreased kidney function.
Stomach Ulcers: Lead can irritate the gastrointestinal tract, causing abdominal pain, cramps, and ulcers.
Brain Damage: Lead exposure can cause cognitive deficits, behavioral issues, and developmental delays, particularly in children.
Nervous System Complications: Lead disrupts the normal functioning of the nervous system, which can result in numbness, pain, and in severe cases, seizures or encephalopathy.
Reducing exposure to lead by implementing safety measures and ensuring proper handling and disposal of lead-containing materials is crucial for protecting health.
Ventilation
Use local exhaust ventilation systems to remove fumes, gasses, and any airborne particulates from the welders’ breathing zone. Always work in a well-ventilated area when possible.
Safe Disposal of Lead Waste
Collect any waste generated from lead welding operations in heavy-duty trash bags or containers. Check the local regulations for the disposal of lead materials. Contact waste management or recycling facilities for guidance on the proper disposal. When cleaning the work area after cutting, grinding, and welding lead, use a respirator to avoid breathing in dust and debris. You should also wet down dust with water before sweeping to keep airborne particulates to a minimum.
Common Lead Welding Methods
Oxy-acetylene welding is the most common method for welding lead. The low melting point of lead means the welder can easily melt the base metal and filler metal with an oxy-acetylene torch to achieve a solid weld.
TIG welding is also suitable for welding lead due to the capability of this process to weld at very low amperages.
Stick welding is unsuitable for welding lead because the SMAW process is too hot. The lead base metal would likely melt, if not vaporize, before forming any bond.
Selecting the Appropriate Method
Among the welding processes discussed, oxy-acetylene welding is the preferred method for welding lead due to its relatively low heat, ease of use, simplicity, and the low cost of the required equipment.
Uses of Lead Welding
Although it is less common than it was just 50 years ago, some applications still use lead welding.
Plumbing and Pipework
Lead is still used in pipe assembly, as, unlike steel and iron, it prevents the formation of rust.
Battery Manufacturing and Repair
Lead welding is used extensively in the production of lead-acid batteries for automotive, marine, and industrial applications. Resistance welding with AC current is commonly used to weld the lead castings that form the core of individual battery cells.
Lead welding is widely employed in the production of lead-acid batteries for automotive, marine, and industrial applications. Resistance welding with AC current is commonly used to weld the lead castings that form the core of individual battery cells.
Radiation Shielding
Lead provides vital protection from various sources of radiation. Sheet lead is not structurally self-supporting, but lead sheeting is often used in a frame of a material to provide enclosures and barriers in X-ray labs and other facilities where there are radiation hazards.
Roof Sections in Buildings
Lead was historically used in various building applications because of its durability and resistance to corrosion. It was commonly used for flashing, gutters, and other roofing components. However, due to its toxicity and the health risks associated with lead exposure, its use has significantly decreased. Regulations and safety standards have limited or banned the use of lead in many applications, leading to the use of safer alternatives.
Lead sheets are still used in some restorative and decorative applications, particularly in historical buildings where maintaining the original materials is crucial for authenticity and preservation.
Step-by-Step Lead Welding Process
Lead welding needs a steady hand and attention to detail. Getting the joint set up right and checking the weld afterward are key to making it work.
Preparing the Joint
Lead can be welded in a lap, butt, or groove joint configuration. It is important to place the pieces you are joining in firm contact with minimal gaps. challenging to fill in lead welding compared to other metals. Holding the heat and adding filler metal in one spot for too long can lead to burn-through or excessive melting of the lead.
Thoroughly clean the base metal of any surface impurities and remove oxidation to produce a bright, shiny surface.
Setting Up the Welding Equipment
If you will be using the oxy-acetylene welding process, use a small brazing tip in the torch to maintain a small, neutral flame and provide focused, localized heat to the weld joint.
Preheating the Lead
Since welding lead in normal working conditions requires minimal heat, preheating is usually not necessary. In colder than normal conditions (including when frost or moisture is present), you may need to apply heat to the weld joint to ensure the base metal is clean, dry, and ready to weld.
Welding the Joint
It is best to weld lead by moving the torch in a back-and-forth motion, adding filler metal to the molten puddle. You must maintain a fairly rapid and consistent travel speed to avoid burn-through and excessive melting of the base metal.
Post-Welding Process
Cooling the Weld
When you have completed the lead welding operations, allow the weld to cool to ambient temperature before cleaning or carrying out any further processing.
Cleaning the Welded Joint
Clean the completed weld joint with a wire brush. Any debris from the welding process should fall away.
Inspecting and Testing the Weld
Thoroughly inspect the completed lead weld for defects like lack of fusion, porosity, or cracks.
Troubleshooting Common Issues
Preventing Lead Oxidation
Excessive amounts of oxygen may oxidize the surfaces of the lead parts being joined and impair weldability. For this reason, you should clean lead pieces thoroughly before welding. You should also maintain a small neutral flame during the welding process to avoid introducing excessive amounts of oxygen into the weld puddle
Incomplete Fusion
Incomplete fusion may occur for a variety of reasons, including poor joint prep or poor welding technique. Make sure that you bring all parts within the weld joint into firm contact and that they are free from dirt, debris, and any surface-level impurities that may result in fusion defects.
Welding too quickly or with insufficient heat to properly fuse the base metal and filler metal may also result in fusion defects.
Porosity
Porosity is a defect that often occurs due to moisture or the presence of other surface-level impurities. For this reason, cleanliness is important for achieving a weld free of porosity defects. You should completely remove any paint, dirt, grease, or oils before welding. You can remove any moisture by applying a small amount of preheat to the affected area.
Cracks, Distortions, and Leaks
Cracks often result from stress in the metal over long periods, especially if the metal is under excessive amounts of stress due to insufficient support. Since lead has little structural rigidity on its own, you should adequately support it with a proper substructure.
Distortion may also result from a lack of supporting structure. This is likely to worsen with poor welding technique. To minimize distortion, take care to ensure a consistent weld joint. Any lack of uniformity or inconsistency in the joint may result in you applying excessive heat to the immediate vicinity or an inconsistent area in the joint, which may lead to distortion in the completed part.
Leaks may result from cracking or from fusion and/or porosity-type defects. If you discover a leak in a completed weld, it may be necessary to remove the weld material from the joint with a file or grinder and attempt the weld again. You should employ all the steps described above for cleaning and joint preparation to ensure a quality weld joint.
FAQ
Can I use a regular welding torch for lead welding?
For lead welding, an oxy-acetylene torch with a brazing tip is commonly used because it provides the low, controlled heat necessary for welding lead’s low melting point. A TIG welding machine capable of welding at very low amperages is also suitable. Stick welding is not recommended for lead due to the high heat output that can easily vaporize lead.
How should I prepare lead materials for welding?
To prepare lead for welding, clean the parts to be joined to remove any surface impurities and oxidation. This can be done using a wire brush or fine-grit sandpaper until the lead has a bright, silvery luster. Preparation is crucial to prevent weld defects and ensure a strong weld joint.
What are the common applications of lead welding today?
Although less common than in the past, lead welding is still used in several applications, including roofing, plumbing and pipework, battery manufacturing and repair, radiation shielding, and some restoration and decorative projects. Lead’s corrosion resistance and ability to form a strong, durable joint make it usable for these specific applications.
What are the health risks associated with welding lead?
Welding lead can pose health risks due to prolonged exposure to lead fumes and particles. These risks include anemia, kidney damage, stomach ulcers, brain damage, and nervous system complications. Proper ventilation and the use of the right personal protective equipment (PPE), such as respirators, are essential to minimizing exposure.
Featured Photo by Jimmy Nilsson Masth on Unsplash
Leave a comment 0 comments, be the first!