What is the Advantage and Disadvantage of exothermic welding mould

Exothermic welding is also known as exothermic bonding, thermite welding, or thermite welding. It was developed around by Hans Goldschmidt. The process was refined by Dr. Charles Cadwell, who performed the first non-ferrous application. Exothermic welding was first used to weld signal bonds to railroad tracks.

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Exothermic welding is often used to join copper conductors. The welding process joins two electrical conductors by use of superheated copper alloy. An exothermic reaction requires no external heat or current source. The reaction occurs between a copper thermite composition that heats the copper. The chemical reaction is aluminothermic, occurring between aluminum powder and copper oxides. The reaction reaches very high temperatures. Reactant powders and a spark is all that is needed for a high energy reaction.

How it Works

Molten copper produced by an exothermic reaction flows through a semi-permanent graphite crucible mold. The mold goes over and around conductors to be joined and the weld is electrically conductive. The mold can be broken off or left in place when the copper cools. Handheld graphite crucibles are portable, reusable, and flexible for field applications.

A common formula for the reaction is five parts iron oxide powder to three parts aluminum powder, by weight. The combination is ignited at high temperatures. The heat-generating reaction produces a white hot mass of molten iron and a slag of refractory aluminum oxide (through reduction and oxidation). The molten iron is the welding material. The aluminum oxide floats to the top of the reaction. When working, you must remember that the actual molten metal is below, at the bottom of the crucible and covered by floating slag.

When Exothermic Welding is Used

Exothermic welding is most commonly used for permanently joining copper conductors. It is the only acceptable means of bonding copper to galvanized cable. It can also be used on stainless steel, cast iron, steel, brass, bronze, and more. If joining two dissimilar metals, exothermic welding is a good option. You’ll find thermite welding under the names of Ultraweld, Cadweld, Techweld, and Thermoweld.

Thermite welding is a common method for joining railway rails, though it is not chemically pure thermite. For sound welds the ends of the rails are preheated with a torch. When they reach orange heat, the molten steel will not be chilled during the pour. Without preheating, the low heat penetration into the joining metals would not create the quality weld needed. Also, because exothermic bonding yields mostly iron (not stronger steel) pellets or rods of high-carbon alloying metal are added to the thermite mix. The added materials melt from the heat and mix into the weld metal.

Advantages and Disadvantages

Compared to other forms of welding, exothermic bonds have a higher mechanical strength. The weld is also resistant to corrosion. You will not see an increase in electrical resistance despite repeated short circuit pulses; the weld is highly stable. The process is more costly, however. The process requires replaceable molds, is not easily repeatable, and can be hindered by poor weather conditions when the work is done outdoors.

Exothermic welding can also be done remotely. This reduces risks to operators. An igniter is used with standard graphite molds or a consumable sealed drop in weld metal cartridge, semi-permanent graphite crucible mold, and an ignition source that connects the cartridge with a cable.

When you have a project that requires grounded connections, will you use Burndy HYGROUND® compressions or nVent ERICO Cadweld exothermic welds? Both connections are high-quality and long-lasting, so how do you select the best option for your location?

In this article, we’ll provide an overview of nVent ERICO Cadwelds and demonstrate when they are the most suitable option.

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What is a nVent ERICO Cadweld?

nVent ERICO Cadweld is the brand name of an exothermic weld, which means that it uses molten metal to permanently join conductors. Typically, thermite powder (powdered aluminum and iron oxide) is poured into a graphite mold, then ignited. The thermite becomes molten, reaching temperatures in excess of °F. When the metal cools, you remove the mold and are left with an exothermically welded joint.

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Modern exothermic welds have been an industry standard since the late 19th century. Like all exothermic welds, nVent ERICO Cadwelds create a low-impedance, durable connection that resists corrosion. It’s a common weld because it is relatively easy to complete, it lasts decades, and you don’t need any outside heat or power to create it.

Advantages of a nVent ERICO Cadweld

Exothermic welds are suitable for connecting copper to copper or connecting copper to steel, cast iron, brass, and bronze. It’s especially useful when connecting two different types of metal because it resists galvanic corrosion. When welding two dissimilar metals, they often corrode preferentially, meaning that one metal corrodes quicker than the other. nVent ERICO Cadwelds help limit preferential corrosion, which is just one reason that they’re used frequently.  

Without an exothermic weld to reinforce connection joints, the connection can degrade from soil corrosion. With an exothermic weld, the joint resists corrosion from soil so it can be buried underground or under concrete with no risk of deterioration. In fact, the weld may even outlast the wire.

The applications for nVent ERICO Cadwelds are nearly endless. With the right graphite mold, you can use exothermic welds to join multiple copper wires to each other. They can be used to connect wire to rebar or ground rods. You can also use nVent ERICO Cadwelds to install ground grids or to connect new equipment to existing grids.

nVent ERICO Cadwelds won’t loosen over time. They can carry electrical currents at the same capacity as the conductor, sometimes more. When done properly, they can withstand multiple fault currents without failing. They’re so sturdy that they can withstand natural and manmade vibrations without loosening, so Cadwelds are an excellent option in many different circumstances.

Disadvantages of nVent ERICO Cadweld

The primary disadvantage of a nVent ERICO Cadweld is that environmental conditions must be ideal for a successful weld. It’s not safe to do exothermic welds in explosive environments or near flammable components. When used outdoors, exothermic weld completion can be limited by weather. Exothermic welds cannot be completed when there is high wind, rain or other moisture in the vicinity of the connection. However, the conditions won’t suffer from exposure to moisture after a successful installation.

If you need a connection done immediately, an exothermic weld may prove to be a challenge in some locations and climates. Unfortunately, delays to your project can be costly. However, if you have flexibility in your schedule, you can wait and create the nVent ERICO Cadweld when the conditions are suitable.

Compared to compression welds, exothermic welds take quite a bit more time. It’s likely that your labor costs will be much higher for a project with nVent ERICO Cadwelds than one with Burndy HYGROUND® connections. It’s also difficult to inspect the quality of an exothermic weld to be sure that there are no “pits” in the weld interior. The quality of the weld can also vary from one installer to another.

Get a nVent ERICO Cadweld with Wetherbee

High-quality, durable connections are essential to the safety of your employees and facility. Choosing the right weld for your location helps avoid liability issues, plus it reduces the time and money that you have to spend on maintenance. If you’re not sure which type of weld is best for your location, get in touch with Oklahoma’s Certified nVent ERICO Cadweld Installers. We can discuss your options and then move forward with creating expert welds that will last for decades. 

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