Aluminum casting at home: making molds, technological process

Aluminum is a metal that is widely used in industry and everyday life.

It is used to produce not only aircraft and ship parts, but also dishes and other utensils. Therefore, there is often a need to independently manufacture aluminum parts that have failed.

The ability of aluminum to melt at relatively low temperatures makes it possible to produce cast products from it in artisanal conditions. In order to independently produce cast aluminum products, you need to know the behavior of this metal at high temperatures and its physical and chemical properties.

Characteristics of aluminum

The melting point of aluminum depends on the purity of the metal and is approximately 660 °C. Its boiling point is 2500 °C.

Aluminum is distinguished by its lightness and ductility, so it bends well and can be processed by stamping.

This metal is an excellent conductor of heat and actively enters into a chemical reaction at high temperatures with atmospheric oxygen, forming an oxide film on the surface. It protects aluminum from further oxidation, but when scrap melts, it significantly affects the composition of the alloy. During the metal smelting process, the structure of aluminum changes.

When it cools sharply, internal stresses and shrinkage of the resulting alloy may occur. This must be taken into account when working with aluminum at home.

Technologies for home aluminum casting and necessary equipment

The principle of casting aluminum at home should be based on the technology for its production in production, adjusted for conditions that can be used at home.

Aluminum products are produced by casting in several ways. In domestic conditions, the most common and convenient method is the technology of casting molten aluminum into specially made molds.

Therefore, to carry out the process, two things must be ensured:

• build a furnace for melting aluminum scrap;
• create the desired shape to produce a cast alloy or a separate part.

The casting process must include several stages:

1. Preparation of aluminum scrap, including cleaning from dirt, impurities and various fillers, as well as grinding it to a small size.
2. Carrying out the smelting process in the planned way. When the metal is completely melted, slag formations must be removed from its surface.
3. Filling the prepared mold with liquid aluminum melt. After solidification, the ingot is freed from the molding mass.

Let's consider how to melt aluminum at home, what designs of furnaces for melting metal can be used, as well as options for making molds yourself.

Homemade furnaces and methods for melting aluminum

In order to melt aluminum, you need to heat it to a temperature close to 660 °C. It is impossible to reach such a temperature on an open flame of a fire. Therefore, a closed space is needed, which a homemade stove can provide. It can be heated by burning coal and wood or using natural gas.

You can also use an electric muffle furnace if you have one on the farm.

With a self-made stove, forced ventilation must be provided to maintain the combustion process.

1. The simplest version of a homemade fireplace can be made from old pots.

Its design is as follows:

• As a frame, use a steel container, for example, an old pan, on the side of which you need to make a hole to supply air through a connected metal pipe.
• Air can be forced through the hose using a vacuum cleaner.
• Coal is placed inside the device.
• Then the coal is set on fire and air is supplied to keep the fire from going out.
• A container for melting aluminum is first placed inside an improvised furnace structure and lined with coal on its sides. When it burns, uniform heat distribution is ensured.
• To prevent heat from being lost to the surrounding air, the top of the “pan” stove should be loosely covered with a lid, leaving a small gap for the smoke to escape.

An ideal design would be a firebox with an oval arch made from a masonry mixture used for heat-resistant bricks. You can use a flower pot of the desired size as a frame to create an oval vault.

After the mixture dries, a good firebox is obtained that can withstand several heats.

Video:

2. The second version of the furnace involves using the flame of a household gas burner to heat aluminum.

It can only be used for piece products made of aluminum weighing no more than 150 grams. An imitation oven is created by using two containers inserted into each other with a small gap. These can be ordinary cans from canned food.

The outer jar should be larger. A hole with a diameter of about 4 cm is made in it to ensure the supply of flame to the inner can.

The flame jet should be directed towards the opening of the can. Only the inner container is heated directly, and the outer one serves as a shell that retains heat. The top of the structure must be covered with a simulated lid, leaving a gap for the removal of combustion products.

This design is disposable and can only be used for one melt, since the tin is thin and can quickly burn out.

Video:

Aluminum: characteristics

Before the discovery and implementation of an accessible method of industrial production, this metal was considered precious. At a certain historical stage, it was more expensive than gold. Its properties could be used in many industries. Aluminum is a lightweight and ductile material. It can be stamped, bends, and molds well into complex shapes, especially under pressure. Its melting point is 660 °C, which can be achieved without industrial equipment. This means that casting aluminum at home is quite possible.

Who will benefit from this? Aluminum is a proven material. It was used to make dishes and parts for the aviation and space industries. Castings with good thermal conductivity, corrosion resistance and acceptable strength are valued by tinkerers. The material is suitable for making souvenirs, decorative elements of utensils, for repairing or restoring parts and components in equipment.

Technical features of aluminum

Aluminum is considered one of the most popular metals. It is very convenient to work with, the melting point is 658 degrees. It has excellent heat and electrical conductivity and is resistant to corrosion.

Today we will cast a cover for the car's water pump.

Materials used:

• Sand.
• Aluminum.
• Gypsum.
• Plasticine.
• Silicone Grease.
• Steel wire.
• Lego constructor or any children's construction set.

Necessary tools for work:

• Lathe.
• Screwdriver.
• Muffle furnace.
• Drill.
• Pliers.
• Dremel engraver.

Aluminum casting at home

The melting point can be reached without the use of industrial technologies in various ways. In the old days, blacksmiths forged steel and heated it with the energy of burning coal. This is the first option, but to implement it you will need a forced air furnace.

The second option is the use of natural or liquefied gas. The process can be organized in a homemade oven. There is another possibility if the melting volumes are insignificant. In this case, you can use a household gas stove.

Aluminum casting at home can also be organized if the household has an acetylene generator and a cutter. An option with an electric muffle furnace is also suitable. Such equipment can already be classified as industrial. But if you don’t want to make a stove, it’s quite possible to rent it and order the service of an operator.

Interesting facts about aluminum

Aluminum can bend like paper or be as hard as steel. Aluminum is everywhere, even inside us.

Every adult gets about 50 mg of aluminum every day through food, this is not some kind of diet, it just cannot be avoided.

Aluminum is the most common metal on the planet. Its content in the earth's crust is 8%, but it is not easy to extract, at least in its pure form.

Unlike gold and silver, aluminum is not found in nuggets or whole veins. Aluminum is 3 times lighter than iron or copper.

Aluminum in its original form does not look like metal at all, this is all because of aluminum’s special “love” for oxygen.

In fact, the first use of aluminum in history occurred when Eastern potters added aluminum-rich clay to their wares to make them stronger..

Sufficient for the production of beer cans, strong for racing cars, flexible for the skin of airplanes, capable of being turned into anything, aluminum is an indispensable material for the modern world.

And these are not all the features that this useful metal stores.

Technological process

In principle, the situation of industrial casting should be modeled with a reservation for home conditions. In any case, it is necessary to prepare the raw materials. Aluminum scrap is cleaned of dirt, foreign impurities, and all kinds of fillers. Large parts are crushed to the desired size.

Aluminum casting technology consists of several stages. The prepared scrap is melted using the chosen method. When the fluid phase is reached, the slag is removed from the surface of the melt. In the final phase, the mold is filled with liquid metal. The disposable form breaks after cooling.

First you need to decide what is to be cast. Even if this is a trial attempt at melting, it makes sense to prepare at least some form. What if it is possible to reach the desired temperature? It is interesting to see the result of melting and evaluate the results: appearance, porosity, cleanliness. Any experience, even a bad one, will be beneficial.

Casting process

Thanks to casting, you can quickly make various devices based on aluminum for domestic or industrial needs.

The process can be performed under pressure or using molds. In the first case you will need:

1. Special equipment;
2. Specialized technological knowledge;
3. Press forms.

The process is also performed using conventional molds, which are made on the basis of a special homemade mixture. The production technology is quite easy to master. Aluminum has high ductility, thanks to which it can take on any shape. Its melting point is more than 600 degrees.

Previously, to make aluminum parts they used molds that were inserted into the ground, then homemade plaster molds began to be used. Now there are special molds from which parts are made under pressure.

At large enterprises, casting is carried out under high pressure and shrinkage is practically absent. Special machines and equipment are used for the work. The technological process is quite complex:

1. The required working pressure is created due to the operation of the piston, and it is driven by compressed air;
2. Oil and emulsion help speed up movement;
3. The material, heated to the melting temperature, quickly enters the mold under pressure and fills it completely.

Products produced in this way rarely have any defects and are highly accurate. This technology is relevant in the manufacture of parts for aircraft manufacturing and instrument making. Molds allow the use of molten metal at any temperature.

Conditions and necessary equipment

When melting secondary raw materials, the coating burns, fumes are released, and there is smoke. Working in an enclosed space without an intensively functioning hood is problematic. The best option is open space.

Even in this case, an additional source of ventilation will be useful. Molding casting of aluminum into foam plastic is accompanied by intense release of combustion products. A fan with side ventilation of the work area will remove acrid smoke, which will ensure normal conditions for casting.

A well-equipped and well-organized workplace is also important. It is advisable to have sheet metal or another surface as a base on the table that is not susceptible to the high temperature of molten aluminum. The likelihood of splashes and spills of liquid mass is high. With this in mind, you should think about the need to carry out work in a residential environment.

Homemade smelting furnace

The easiest way is to take a few refractory bricks and build a fireplace out of them. It is convenient to do this in a suitable metal container (an old pan), which will be used as a frame. A hole is made on the side for connecting the air supply pipe. You can adapt a piece of metal pipe of suitable diameter. A vacuum cleaner hose, hair dryer or other air supply device is connected to it.

Charcoal (stone) charcoal is placed inside. The fire is lit and the air supply is turned on. The vessel where the aluminum will be melted is installed inside the furnace. It is also lined with coal on the sides. It is advisable to put a lid on the stove so that the heat does not go away in vain, but leave only a hole for the smoke to escape.

Ideally, the firebox is made solid with an oval arch. Special mixtures are used for laying heat-resistant bricks and lining furnaces. Such a structure can easily be built from an old bucket. The inner vault is formed using plastic flower pots of a suitable size. A metal mesh can be embedded inside the reinforcement mass. After the mixture hardens, you will get a high-quality furnace that can withstand more than one heat.

Using a stove

Piece casting of aluminum can be organized without the manufacture of a special furnace. The required temperature is achieved using domestic gas. The smelting process itself takes about half an hour if the volume of aluminum does not exceed 100-150 grams.

A tin of condensed milk, for example, is used as a container. Cleaned and crushed aluminum scrap is poured into it. But you won’t be able to melt it by placing a tin can on the grate over the burner - there won’t be enough temperature. To reduce the loss of thermal energy, the inventors came up with a clever design.

A can of raw materials for smelting is placed inside another tin and placed on spacers so that there is a gap of 5-10 mm from the bottom to the bottom and from the sides to the walls. The second jar, accordingly, should be of a larger diameter. A hole (3-4 cm in diameter) is made in it from below to supply a jet of flame. The divider is removed from the gas stove burner.

The flame is ignited. The structure is installed strictly above its wick. The flame should go inside and heat only the tin with the crowbar. A larger diameter jar acts as a shell and retains heat inside. The opening is covered from above, leaving only a gap for the combustion products to escape. The combustion intensity is adjustable.

Die casting of aluminum and aluminum alloys

The mold is a reusable form (up to 10,000 pours) and is ideal for organizing serial and large-scale production. Basic operations and processes: cleaning the mold from the old lining, heating it to 200-300°C, covering the working cavity with a new layer of lining, installing rods, closing parts of the mold, pouring metal, cooling and removing the finished casting.

The general requirements for castings obtained in molds are a streamlined configuration without sharp corners, sharp transitions from one surface to another, without high ribs and protrusions, deep holes and pockets.

• The minimum permissible wall thickness of aluminum castings is 3 mm;
• The weight of produced aluminum castings is from 20 g to 50 kg;
• Surface roughness of castings according to GOST 2789-73 Ra = 4 - 20 microns;
• Accuracy class of the resulting aluminum castings according to GOST R 53464-2009: 6-10.

Crucible and auxiliary equipment

A tin can can withstand one heat. Its further use is possible, but with the risk of being burned through. In this case, molten aluminum runs the risk of getting inside the stove, which can not only lead to clogging of the burner nozzles.

To work in a furnace running on coal or liquefied gas, and indeed for reusable melts, it is advisable to make a special container - a crucible. It is made of steel. A piece of pipe with a welded bottom will do. A good option is made from a cut-off fire extinguisher or a small-sized oxygen cylinder with an oval arch. It is advisable to make a side gutter for easy pouring of a thin stream.

What additional equipment may be needed for aluminum casting? Reliable pliers or their version with clamp fixation will come in handy. Ideally, the crucible can be equipped according to the principle of industrial designs: with side grips of a removable suspension and a lower fixed stop for ease of turning it over. You need a spoon with a long handle to remove slag from the surface of the melt.

Simple forms

What are the methods for casting aluminum? The easiest way is to pour the molten metal into a metal mold: an old mug, a frying pan, a tin can. After cooling, the blank is removed. It’s easier to do this if you tap the mold while it’s not yet cooled down. If it had grooved sides or reverse corners, the frame will have to be cut. You can simply pour a slightly cooled drop of metal onto a prepared fireproof surface. Such methods are called open.

If there is a need to make a special casting, you first need to prepare a mold to fit it. In order for the metal to acquire clear outlines after cooling, closed molds are made from two or more component parts. One of them is the main one, and the other usually forms the arch or lateral surface. Holes are made in it. Often another part of the form is added above them - funnel-shaped flyers for convenience.

Material

Aluminum casting molds, depending on the method, can be produced using different technologies. There are several simple options. For open pouring into a simple mold, sifted earth (silica) is often used. It is laid in layers and compacted. After removing the forming element, the earth holds its shape and withstands pouring. This material is simple and cheap to use.

There are craftsmen who pour aluminum into sand. When mixing, use liquid glass (silicate glue). There is information about the use of cement. The mixture is mixed, oddly enough, with brake fluid. Knead with your hands and rub through a sieve to avoid lumps. The consistency should be such that when clenched in a fist, a lump forms. When tamping, sand and cement are well held inside the flask and even repeat small details of the workpiece shape.

Burnout casting: technology features

Manufacturing a part from aluminum using burn-out casting has its own characteristics, which will be discussed below. The work is performed in the following sequence:

• Foam plastic is used as a material for the model at home. Using cutting elements and glue, make a figure that resembles the required shape in outline.

• Prepare a container for making the model. You can use an old shoe box. Mix alabaster with water. Pour the mixture into the box. Place the foam model. Level it out. Give the material time to harden well. Due to the rapid hardening process of alabaster, perform the work at an accelerated pace.

• Remove the box. Heat the mold in the oven to dry the alabaster and remove any remaining moisture. Otherwise, all the water from the alabaster will enter the aluminum and turn into steam, which will lead to pores in the metal and aluminum splashing out of the mold during work.
• Melt the aluminum. Remove molten slag from the liquid surface. Pour the metal into the mold in place of the foam. Due to the high temperature, the latter will begin to burn out and aluminum will take its place.

• After the metal has cooled, break the mold and remove the resulting cast aluminum model. You can watch the process in more detail in the video.

Manufacturing of complex shapes

Castings of complex configurations are made using a different technique. The most common material is gypsum (alabaster). Forms without reverse corners and undercuts can be collapsible and consist of two or more parts. They won't last long, but it's quite possible to get a few castings.

A complex knot or decorative three-dimensional model can be made once, but the mold will have to be broken. There are two methods at work. You can make a wax (paraffin) model and fill it with plaster. Later, during the intensive drying process, this material will melt and flow out through the flaps.

Casting aluminum into a plaster mold using foam plastic involves making a model of the future casting from this material. It is filled with the prepared mixture and cannot be removed. Molten aluminum is poured over the top. The temperature of the metal melts the foam, it evaporates in the process, and liquid aluminum fills the space vacated.

Materials for casting molds

With the open pouring method, the simplest material that is always at hand is often used, this is silica. First, the earth is laid with layer-by-layer compaction. A casting model is placed between the layers, which, after careful compaction, leaves an imprint in the silica. This mold is carefully removed and aluminum is poured in its place.

Some craftsmen use river sand with the addition of liquid glass when preparing the base of the mold. A mixture of cement and brake fluid is also sometimes used.

Plaster molds

When making a model of a complex shape, gypsum is often used, which can mainly be used for a one-time casting process. When casting aluminum into a plaster mold, paraffin or foam plastic is used as models.

The wax model of the product is filled with plaster and, after drying it at high temperature, it is melted and drained through a special hole.

If the model is made from foam plastic, it is filled with gypsum mixture and left in it until the mold completely hardens. Hot aluminum melt is poured directly onto the foam. Due to the high temperature of the metal, the foam melts and evaporates, and its place is taken by an aluminum melt, taking the shape specified by the foam.

When using polystyrene foam as a model, work must be carried out in an open space or the room must be well ventilated, since the combustion products of polystyrene foam are harmful to humans.

Typical mistakes and tips for proper casting

1. When working with plaster, you should avoid common mistakes. Despite the fact that plaster molds are a convenient way to cast the desired configurations of parts, this material is very sensitive to moisture. During normal air drying, it remains part of the gypsum. This is detrimental to the quality of the aluminum casting, as it can cause the formation of small shells and bubbles. Therefore, plaster molds need to dry for several days.
2. The metal must be hot enough before pouring to fill the entire mold before it begins to harden. Therefore, after reaching the melting temperature, taking into account the rapid cooling of aluminum, there is no need to delay pouring it into the mold.
3. It is not recommended to immerse the resulting casting in cold water to speed up the hardening process. This can disrupt the internal structure of the metal and lead to cracks.

As an option, I can suggest making a mold for pouring from plaster or alabaster.

Provided that your part is not of complex shape and does not have intricate reliefs or internal cavities.

We prepare a container slightly larger in size than your part, you can use any ready-made cardboard box or make it yourself from any cardboard or corrugated cardboard, you can half a plastic bottle, dishes, the main thing is to then remove the resulting form for filling.

Coat the part with technical Vaseline or other thick lubricant.

We prepare two dowels for centering the shape of two halves, for example, saw off two 2 cm pieces from a pencil, coat them with Vaseline.

We choose alabaster to make the mold.

We dilute alabaster as follows: add the required amount of alabaster to a container with cold water, wait until the water is completely absorbed into the powder and then stir until a homogeneous consistency is obtained.

The solution should look like medium thick sour cream.

A viscous solution is obtained from the proportion of 1 part alabaster to 1 part water.

Dilute such an amount of solution to use it in one go, since the mixture will harden quite quickly and will need to be thrown away; there is no point in restoring it; the properties of alabaster are not restored.

Pour enough solution into the container so that your part is immersed halfway in it. This will be half of your shape.

It is important to position the part so that after the solution hardens, it can be removed from this half of the mold.

Along the diagonal of the mold, separately from the part, vertically immerse two dowels halfway.

When the solution hardens, we will try to carefully remove the part and return it to its place. Everything worked out, let's continue.

We make a gasket for the frozen mold from available materials: plastic film, tracing paper, thin paper, close only the mold, do not close the part. You can also lubricate it with Vaseline.

We make a cylinder with a funnel on the edge from plasticine at the distance from the part to the edge of the mold and place it in the mold, this will be the filling channel. Decide on the thickness yourself.

We dilute the required amount of solution and fill the part completely and wait for the second half of the mold to completely harden.

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Then we remove the resulting form from the container, carefully separate it into two halves, take out the part and plasticine, and clean up the defects.

We connect the form, the funnel goes to the top, that’s it, you can pour aluminum.

After pouring and removing from the mold, it will be necessary to modify the poured part manually using sandpaper, needle files, a cutter, etc. to the size of the original.

For many, the term “foundry” is closely associated with back-breaking labor and specialized professional skills. In fact, casting a part from the required metal is possible for the most ordinary person without professional training at home. The process has its own subtleties, but it can be done at home with your own hands. Outwardly it resembles the production of lead weights for fishing. Features of the aluminum casting process are related to the technical characteristics of the material.

Casting errors

Making molds from plaster is a convenient and inexpensive way. But there is moisture in the material. With natural drying it remains. When molten metal is poured, moisture begins to evaporate rapidly. Even intensive oven drying does not guarantee its complete absence. Depending on the amount of moisture remaining in the mold, the aluminum casting may have small pits or large frozen bubbles and craters.

If the metal was not heated up enough or it had time to cool before pouring, the aluminum does not pour out well and does not fill the volume of the mold. In fact, a drop is formed that does not have sufficient fluidity. The same thing can happen when using a small amount of metal in a cold form. Aluminum gives off heat quickly and does not have time to spread.

Experienced craftsmen do not recommend immersing the casting in water to speed up its cooling. In such a material, damage to the internal structure and the appearance of microcracks is possible. Such workpieces may not be suitable for subsequent turning.

How to cast a complex-shaped part from aluminum

Industrial enterprises often use metal molds. Aluminum casting molds can be made from a variety of materials. Most often, gypsum is used. Gypsum can be purchased at any hardware store at any price acceptable to you. It is recommended to use sculptured or white plaster.

An excellent option is sculptural, which is marked G-16. Due to the high price, it can be replaced with G-7 - ordinary white plaster. It is strictly forbidden to replace it with alabaster, despite the fact that they are often interchangeable in construction work.

Let's look at a simple way to cast an aluminum part with your own hands at home.

To cast an aluminum part we need:

• melting vessel;
• scrap metal;
• melting mold.

Main stages of the process:

1. Prepare a vessel for melting (you can use a vessel from part of a steel pipe).

2. We make a mold for melting. If the part has a complex structure, then the shape may have several components.

In our version, the form will consist of two parts. First, think about how to simplify the part for convenience (we recommend strengthening the holes with tape).

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The mold is very easy to make from sculpting plaster (do not use alabaster!). You can use plasticine.

3. Before pouring plaster, you should lubricate the container with oil so that the plaster cannot stick to the container.

4. Carefully pour the plaster, shaking the mold periodically to release the bubbles.

It is important to know:

The hardening process of plaster is quite fast, so be careful and try to install the model in plaster in time.

In addition, it is recommended to install an object (for example, a small stick) in the plaster, which will become a channel for pouring our part.

5. A primary layer is required for the upcoming filling.

Take a drill and make 4 small holes, treat the shape with oil. This is necessary to ensure that the finished mold parts lie as stable as possible during the casting process.

6. Fill the second layer.

7. After hardening occurs, you need to carefully remove the mold from the container and separate the halves.

8. Before casting, we treat the mold with soot to avoid sticking of liquid aluminum. The form must be dried. The natural drying process takes place all day long. It is advisable to dry the gypsum blank in the oven. Start at a temperature of 11 0 0 C - one hour and two hours at a temperature of 300 0 C. It is necessary to provide holes in the plaster for pouring aluminum and removing residual air.

This is how we melt aluminum.

9. Then we place the liquid metal in the mold and wait for it to cool completely.

As a result, we obtain the desired workpiece, then we grind it and make special holes.