Use cases ·

Importance of graphite as a mold for exothermic welding

Exothermic welding uses the high temperatures generated as a result of the reaction of materials to join different materials.

Importance of graphite as a mold for exothermic welding

Exothermic welding uses the high temperatures generated as a result of the reaction of materials to join different materials.

Because the process generates extreme heat, a mold is required to contain the flux and the elements to be joined. The mold for exothermic welding offers excellent properties such as thermal shock resistance and self-lubricating properties, making it excellent for this task.

Exothermic welding is used to join copper to copper; copper to steel; steel to steel; aluminum to steel and aluminum to aluminum. For example for joining copper cables.

The exothermic welding mold has many uses, which we will look at below to understand what it is, what it is for and why graphite is used in this process.

What is exothermic welding?

Exothermic is a chemical term used when there is a chemical reaction that generates heat while the reaction is taking place.

Thus, welding is a process that creates the molecular bonding of two or more metallic conductors that through a chemical reaction melt together. Also, it improves mechanical, electrical and corrosion properties over any mechanical joint resulting in strong joints with a host of advantages.

The advantages are:

  1. The material has a long durability, equal to or greater, than other materials used in joining.
  2. The connections are not damaged when there are current peaks, causing the conductor to melt and not the connection.
  3. It does not deteriorate with time, since the connections do not loosen or suffer corrosion.
  4. The exothermic connection becomes part of the conductor.
  5. It has the ability to conduct current equally or more than the conductors.
  6. Withstands electrical damage repeatedly.
  7. The reaction is terminated in a few seconds, and is important in the connection of insulated conductors or thin-walled tubes.
  8. It has a low cost.
  9. It only requires soldering skill.
  10. The quality of the work is visually checked.

Procedure 1.

  1. Cleaning Cleans and removes any impurities from conductors and mold, so that no unacceptable welds or welds with dangerous reactions are made.
  2. Heats the mold. Heat the exothermic welding mold to 120ºC with a torch. It is important that it be made of graphite, to absorb the moisture from the temperature and not make porous welds. Also, so that the work is done only once.
  3. Place the conductors in the mold The conductors must be well fastened, closing hermetically the mold with the clamps. And you must check that the conductors have the standard diameter to be able to work with them.
  4. Place the flux tablets in the mold hopper The number of tablets will depend on the type of connection to be made. It is important to mention that it is not necessary to use metallic discs to make the soldering.
  5. After closing the lid, the electronic initiator must be placed and any movement must be blocked with the safety lever.
  6. Open the electronic ignition equipment. Place the other end of the cable in the side connector of the exothermic welding mold. Connect the clamp to the contact of the electronic ignitor. It is very important to ensure electrical contact between the clamp and the filament. Move away from the mold and turn on the equipment.
  7. Move away from the mold for exothermic welding At the maximum distance offered by the connection cable which is 2 m.
  8. Start weldingPress both ignition buttons at the same time until the reaction starts.
  9. Wait 15 seconds Before opening the mold to make sure that the solidification of the melt is done, wait 15 seconds.
  10. Once the mold is clean, a new weld can be made without reheating the mold, as long as the new connection is made within 10 to 15 minutes.

Why a mold is needed for exothermic graphite welding?

Precision in this process is vital, which is why exothermic welding molds are used. Since they are made of graphite, to the size of the conductors and of course arranged by the customer's needs.

Due to the high temperatures, a material that can withstand them is required. Graphite offers excellent thermal shock resistance, is easy to machine, does not burn and can be used repeatedly.

Each mold has specifications of type and quantity of flux to be used, which must be checked by the operator. Graphite exothermic welding molds usually have a nameplate: mentioning the technical specifications of the mold as well as the flux volume.

The molds vary in their machining for the union of two conductors determined as cable-cable; plate-plate; cable-spike, among others. They have exact dimensions such as 50mm2; 70mm2, etc., and are joined in specific ways such as T-shaped or cross-shaped.

Conclusions

To conclude, the exothermic welding mold is an important tool in electrical work and for joining parts by fusion.

In ESGRAF we have a wide inventory of graphite grades for the production of exothermic welding molds such as iso molded or extruded grades. Do not hesitate to contact us to offer you the best solution.