Copper is a transition metal with a high thermal and electrical conduction capacity; this characteristic makes it very precious for the realization of different objects. It can be cast into ingots to be stored, sold or to be forged again into other elements, such as jewelry.
Steps
Part 1 of 4: Prepare the Materials
Step 1. Gather everything you need
Systems for home smelting of metals include an oven, a layer of coating or insulation material, a crucible, a propane cylinder and a burner, as well as a lid. You will also need to procure personal safety devices, such as special gloves, a heat-resistant face mask, and a set of pliers to lift and move the crucible. Remember that while it is possible to build a safe oven, it is best to abound with the insulation layer to prevent you or someone else from getting hurt.
- Artisan furnaces are generally cylindrical and made of metal. Depending on the size of the one you want to build (which is determined by the amount of copper you want to melt), you can use a metal drum or a stainless steel pot for slow cooking.
- Kaowool (a ceramic fiber with high heat resistance) is ideal for lining melting furnaces.
- Crucibles are containers in which metal scraps are placed that must be melted. The liquefied copper will remain inside them, so it is necessary to build them with a material that does not break and does not melt at the temperatures you will have to reach to work the metal. Graphite is generally chosen.
- As for the propane burner, know that you do not need a tool similar to the one for cooking, but a tool that resembles the blowtorch and that will be placed outside and near the crucible. You can buy it online.
- As for the lid, you can make it with a small portion of the top of the container that you have decided to use as a furnace. Lids used in foundries have a small hole to allow ventilation and avoid dangerous pressure build-up.
Step 2. Make sure all safety devices are of high quality
It is recommended to use high temperature resistant gloves (such as those used in the metallurgical industry and foundries), as well as a face mask suitable for this type of work. It is also important to know that the flame itself is not able to reach the necessary temperature, but thanks to a correct insulation of the furnace, the crucible in the center of the same will be overheated to the point of melting the copper.
Step 3. Use an induction furnace
Since copper has a high melting point (1085 ° C), this type of equipment is generally needed. Although these are very expensive industrial machines, induction furnaces guarantee a high level of safety that is not obtainable with artisanal ones. The most common induction furnaces are tilting and double thrust furnaces.
- The double push ones quickly heat the metal in "sessions", or individual cycles. The advantage of this tool is that you can start and stop the melting process without difficulty, so that you don't waste energy when you only have to melt small amounts of metal.
- Tilting furnaces are often used in industry. They are able to melt large quantities of copper without interruption and pour the liquid metal automatically into ceramic containers or into any metal mold / mold.
Step 4. Get fuel
If you decide to build the furnace yourself, then you will need enough fuel to ensure a constant fire. Natural gas is indispensable in the metallurgical industry; however, you can also work with coal alone.
- Originally, foundry workers used coal and vegetable coal. Nowadays propane and natural gas are preferred because they save time and allow locksmiths to focus on their work.
- One of the disadvantages of charcoal is the emission of dangerous fumes and the need for more attention to ensure the right temperature.
Part 2 of 4: Building a Forge
Step 1. Create the outer body of the furnace
To melt only small quantities of copper, a furnace with a diameter between 15 and 30 cm will be sufficient. Typically these tools have the shape of a cylinder.
- Large "family size" cans in which food is stored (such as canned peaches and soups) may be suitable for your artisan furnace.
- If you need a larger container, then you can opt for a stainless steel pot and turn it into a foundry oven.
Step 2. Line the outside bottom of the forge with refractory tiles or bricks
They will serve to contain splashes or metal flow and will prevent damage to both people and surrounding material.
Step 3. Lining the interior walls and floor of the furnace
For this operation use the material "kaowool". It is a synthetic mineral wool (in some cases it is called ceramic fiber) very resistant to heat. It is not necessary to use glue to adhere the coating to the furnace. Slightly bend the ceramic fiber and then insert it into the container following its curve; it should keep the shape of the furnace itself.
Kaowool is a blend of aluminum, silica and kaolinite
Step 4. Cover the exposed part of kaowool (which now represents the inside wall of the furnace) with a refractory mortar or reflective product
This increases the strength of the material and at the same time allows your equipment to maintain the internal temperature necessary to melt copper and other metals.
- The reflective product is able to reflect 98% of the heat that hits it. You can use it to line the inside of the oven and other elements. If you use this material, you protect the furnace and save fuel.
- The refractory mortar must be mixed with water until it forms a pasty compound. Finally, you can spread it on the ceramic fiber using a brush.
Step 5. Drill a hole for the propane cylinder with a drill
Use an electric model with a hole saw and drill a hole in the outer wall of the furnace about 5cm from the bottom.
- The opening should be angled approximately 30 ° downwards. That way, if some of the metal leaked out of the furnace (or the furnace itself broke), splashes of hazardous material would not fall on the propane pipe.
- The diameter of the hole should be slightly larger than that of the burner in order for it to fit securely.
Step 6. Prepare the propane burner
Furnace templates are available online. This is a very important device that must be connected to the fuel bottle. Its purpose is to emit a constant flame to increase the internal temperature of the oven.
- Once the burner has been securely connected to the propane cylinder, insert it into the opening you made with the drill, so that it fits in.
- The burner must not fully enter the hole. The flame must be 4 cm from the center of the melting chamber to protect the tool from damage caused by high temperatures.
- Remember to always close the valve on the propane bottle when you are not using it.
Step 7. Make the lid
If you have decided to use a large can as a furnace, simply cut out a 5 cm piece from the top and cover the inside with the kaowool and the appropriate lining. Drill a hole in the lid to ensure a way out of the pressure and to safely add the metal pieces into the furnace when it reaches maximum temperature.
Step 8. Add the crucible
This container is made of steel, silicon carbide and often graphite. It is very resistant to high temperatures and is intended to contain and heat the copper you want to melt. Remember that you will also need proper tongs to grab it, if you are going to pour liquid copper into the molds. The tongs must allow a firm grip to prevent the crucible from slipping.
If you want to build one yourself, you can recycle old materials, such as a completely empty fire extinguisher
Part 3 of 4: Prepare the Metal Samples
Step 1. Get some copper to melt
Copper waste is very common in household appliances and electronic devices.
- This metal is used to make wiring, electronics, motors and appliances, so it's not uncommon to find it around the house. It can be present in cookware, furniture, cables and pipes.
- Appliances that use copper include air conditioners, dishwashers, heat pumps, freezers, refrigerators, washing machines, dryers, garbage disposals, dehumidifiers and ovens. There are also decorative objects of various usefulness that contain this material, such as chimney nets, large clocks, bells, jewels and so on.
- Remember that it is illegal to melt one, two and five euro cent coins.
Step 2. Transfer the copper pieces to the place where you set up your craft "foundry"
Depending on the size of the scrap metal this could mean carrying just a couple of electrical cables into the garden or carrying large, heavy plates of metal that will require a lot of effort.
You may need a van or truck, conveyor belts, and even mobile or stationary cranes, depending on the size of your project
Step 3. Break and separate the copper
Since the various scrap pieces can have very different shapes, it is sometimes physically complicated to insert them efficiently into the furnace. If you have to deal with large sheets of metal, then a lot of hard manual work will be waiting for you. Many people choose the "wrecking ball" method which involves using a strong machine to hit metal at high speed and break it apart.
Be aware that the process can be dangerous to security. Fragments that shoot at high speed can become a threat to safety. Make sure no one is around during this phase of the work. All people who help you should be protected by some form of shield, such as walls, to avoid blows and injuries
Step 4. Cut the copper pieces with the blowtorch
When you have reduced the larger objects to easily manageable material, you can use the blowtorch to shape the fragments, so that they enter the furnace without problems. Oxyhydrogen flames that use compressed gas are the most commonly used for this type of work.
- Always wear a mask to protect your face from hot debris.
- Copper is very heat resistant and is very difficult (though not impossible) to cut with a blowtorch. Plasma torches and iron powder torches are often used when cutting superconducting metals such as copper and bronze.
Step 5. Compact the scrap metal
Use an automated metal press to compact large quantities of copper into small pieces. The presses are generally made of steel and use a hydraulic jack to crush the material in question.
Part 4 of 4: Melting the Copper
Step 1. Place the furnace on the sand or ground
Splashes of molten metal may explode on contact with concrete, so your craft foundry is best placed on earth or sand. Both substances are able to absorb materials at high temperatures.
Step 2. Place the crucible inside the furnace
Inspect the interior of the furnace to be sure there are no other materials that could interfere with the stability of the crucible or the melting process. Remember to check that the inside of the crucible is completely dry. If molten metal comes into contact with water or a foreign material, it could explode. Before lighting the flame, check that the crucible is stable inside the furnace.
Step 3. Turn on the propane burner
This starts the heat build-up process up to a temperature high enough to melt the copper. If you have used charcoal, know that when it starts to burn, the furnace is almost ready to accept the pieces of metal.
Step 4. Cover the furnace with the lid
With just one hole, your oven is practically almost completely closed. The internal space that houses the crucible is ready to retain heat, reach a high temperature and overheat all the copper pieces you have stored there.
Step 5. Place the metal fragments in the crucible
Since they were compacted and cut in the previous stages, you shouldn't have a hard time blending a large amount of them at once, making blending even more efficient. Be careful not to insert so many pieces of copper into the crucible that the metal overflows from the rim of the vessel once it is liquefied.
Always wear heat resistant gloves and a face mask when starting the fusion phase
Step 6. Check the temperature
Copper melts at 1085 ° C; to know if your furnace is hot enough, you need to check it with a high temperature thermocouple. There are both disposable and reusable models and you can buy them from various suppliers of materials for the metallurgical industry.
Step 7. Pour the molten copper into a mold or cast
When the amount of metal you want to use is ready, prepare a mold on a safe surface (preferably sand or some other heat-resistant grainy material). Grab the crucible with tongs and slowly pour the liquefied metal into the mold.
Warnings
- Do not attempt to melt copper without using the proper safety devices, as it is an extremely dangerous process.
- Extracting copper from ore is much more difficult than smelting products made from this metal, because the ore contains other substances within it that need to be removed. Furthermore, it is difficult for a private individual to be able to obtain the mineral directly from a mine.
