What is the melting point of bronze

Bronze melting point table

Bronze is a copper alloy alloyed with tin, aluminum, lead and other elements. Copper alloyed with zinc is brass, and with nickel is cupronickel. One of the ways to produce bronze products is casting. The molten metal is poured into a mold where it solidifies.

Classification

Bronze alloys according to their composition are divided into:

As the name implies, this refers to the presence or absence of tin in them. The latter are aluminum, silicon, beryllium and others, depending on the main alloying component.

Additives affect the quality of the alloy in different ways:

• Tin – adds strength and improves anti-friction properties. Large amounts of tin make metal brittle.
• Beryllium strengthens the material well; its properties are comparable to steel.
• Lead – improves corrosion resistance.
• Aluminum – again corrosion resistance and anti-friction qualities.
• Iron – improves structure and strength properties.

According to their technological properties, bronzes are divided into:

• Processable by pressure (deformable) - well stamped and forged.
• Foundry.

Marking

The marking principle is as follows:

• They write the letters Br (meaning “bronze”).
• Write letters denoting alloying elements:

• Write numbers indicating the percentage of each element. For wrought bronzes, the numbers are written at the end of the markings in the same order as the letters. For foundries, a number is written after each alloying component. For example:

BrOF10-1 – deformable bronze. Tin is approximately 10%, phosphorus is 1%, the rest is copper. Or:

BrA10Zh3 – cast bronze, where aluminum is 10%, iron is 3%, the rest is copper.

There may be other impurities, but their number is insignificant.

Melting temperature

The table shows the melting temperature of some brands of bronze, as well as the pouring temperature. The table shows that the melting and casting temperatures of the materials do not coincide. This is due to the fact that bronze is a viscous material. It needs to be melted, then heated well before pouring to achieve maximum melt fluidity.

Is it possible to cast bronze at home?

The good news is that this metal can be melted not only in industrial conditions, but also at home. True, “home” is a relative concept. You won't be able to pour in your kitchen. You need at least a separate room with good ventilation. This is for small things, such as small art castings. For large parts you will need a garage or hangar.

Bronze has low shrinkage - less than 1%, and is used to make precision castings. But in any case, it will not be possible to achieve industrial quality casting. And most importantly, you need to follow safety precautions and fire safety! They will be discussed at the end of the article.

Bronze scrap is used as a raw material; you can melt down plumbing parts with your own hands. The industry produces metal in ingots.

How to make a casting mold

The material for the mold (equipment) in non-industrial conditions is sand or clay mixture (casting into the ground) and gypsum.

Examples of mixtures for casting into the ground:

• sand, clay, coal dust in a ratio of 75% - 20% - 5%.
• clay, fireclay brick, thin sawdust, ratio 40% - 40% - 20%.

The components are mixed until a homogeneous consistency is obtained.

A model of a product made of wood or other material can also be used. It can also be a finished part, a sample.

A device for preparing sand equipment - a flask. It consists of two boxes without a lid, usually wooden. The lower one has a bottom, the upper one has no bottom (essentially a frame). The parts of the flask have centering elements for their precise location relative to each other. They are sometimes fastened together with clamps.

The equipment is made as follows:

1. Before work, the surface of the flask and the product sample are sprinkled with talc.
2. The sand mixture is poured into the bottom box to the edge and compacted.
3. The model parts are placed in a flask on the ground and pressed.
4. The upper frame is placed on the lower box of the flask.
5. A truncated cone is attached to the model with its narrow part to the product. This is a model of the sprue; the melt will be poured through it. It is desirable that the sprue location be the thickest part of the product. It must be taken into account that the finished part may have defects at the pouring site.
6. The upper flask is filled to the top with the mixture. They're ramming again.
7. A model of the sprue is taken out of the sand.
8. Use a sharp thin object to separate the upper and lower halves, marking the parting line. The upper flask with the sand mass in it is removed, and the product is carefully removed from the sand.
9. The mold parts are dried and put back together.

The parting line is chosen so that the part can be removed from the tooling without damaging it. In addition, sometimes an “air vent” is made in the part of the product opposite the sprue. This is the same hole in the tooling as the sprue. Air escapes from the cavity through it during the filling process.

Pouring metal

In order to melt the material you will need:

• Melting muffle furnace, preferably with a heating regulator. For large castings you need a forge. Sometimes the material is melted with an autogen, a blowtorch, a gas or gasoline burner.
• Crucible - a steel, cast iron or fireclay (fireclay) container for melting, preferably with a spout.
• Tongs and a hook for removing the hot crucible from the furnace and other manipulations.
• Casting shape. How to prepare it for work is described below.
• Flux. Needed to protect the alloy from oxidation by air. Charcoal, borax.
• Fuel for the forge, for example, is the same charcoal.
• Ceramic or birch stick for stirring the melt.

Casting technology

1. Pieces of raw material are placed in a crucible and heated in an oven to the desired temperature (50-100˚ Celsius above the pouring temperature) and held for 4-5 minutes. Overheating is undesirable, since some alloy components can burn at high temperatures. Before pouring, the melt is stirred several times with a stick. Melting is carried out under a layer of flux. It isolates the metal from the air and prevents oxidation.
2. The crucible with liquid metal is removed from the furnace using a hook and tongs. Be sure to use a spoon to remove the slag from the surface of the melt.
3. Using a thin continuous stream, the material is carefully poured into the tooling cavity through a special hole (sprue).
4. When the metal has cooled, the hardened product is removed.

   Sometimes the melting mold is opened and the part is knocked out or the equipment is destroyed if it is disposable.

If the part has complex geometry or is very small, the melt may not squeeze out all the air from the cavity, and defects may appear on the part. In this case, centrifugal casting is used. The equipment is installed in a rotating centrifuge.

Under the action of centrifugal force, the liquid metal is evenly distributed throughout the mold cavity. The centrifuge drive can be manual or electric.

Source: https://MyTooling.ru/instrumenty/temperatura-plavlenija-bronzy-tablica

Melting point of bronze and how to melt and cast at home

Bronze is a copper-based alloy that does not contain nickel and zinc as the main alloying components. Characterized by a relatively high melting point, the metal becomes liquid in the range from +940°C to +1300°C. The most refractory is tin-phosphorus.

Bronze alloys are used to produce long products, sheets and pipes, engine parts, elements of transmission devices, liners for shut-off valves, fittings, taps, souvenirs, instrument parts and much more. You can make casting at home. Bronze is smelted in muffle furnaces or furnaces.

At the melting temperature, bronze becomes thick and does not flow well into the mold; you need to know some tricks in order to do casting yourself.

Main characteristics of bronze alloys

The color of the bronze alloy depends on the quantitative composition of alloying elements. They influence the physical properties: ductility, wear resistance, melting point of bronze.

The alloying components are metals (tin, aluminum, beryllium, lead, manganese) and non-metals (phosphorus, silicon). You can melt any bronze alloy at home. Knowing the markings of the scrap, it is easy to determine the exact melting point of bronze.

But usually the composition of bronze pieces prepared for melting varies. Then the appearance of the metal is assessed.

Bronze alloys are classified into two categories:

1. tin ones are more ductile;
2. tinless ones are less easy to process:

• beryllium are characterized by high strength, maximum tensile strength and torsion;
• aluminum has a low melting point, is resistant to corrosion, and has good anti-friction properties;
• lead plastic, easy to machine;
• with additives of zinc and silicon, they are characterized by fluidity; when melted, they evenly fill the casting mold;
• the alloy with iron can be welded well, but its contact with aggressive environments is undesirable;
• manganese improves strength characteristics while maintaining the ductility characteristic of copper;
• Tin-lead bronzes are malleable, they are subjected to hot deformation, and the alloy is made into hot-rolled products.

For industrial casting, tin bronze with a low melting point, up to +1000°C is used.

Unlike brass, bronze is more viscous at its melting point. When filling forms of complex configurations in production shops, centrifuges are used. The alloy, heated above the melting point by 5°, is given additional acceleration so that it spreads evenly.

When making handicraft castings, it is advisable to take into account the viscosity of the bronze alloy at the melting point so that there is no defect on the surface. Foundry workers consider low shrinkage during cooling to be an advantage of non-ferrous metal. It is possible to obtain castings that do not require lengthy finishing to the specified geometric dimensions.

High-quality shaped castings are made from bronze alloys.

Is it possible to melt and cast bronze at home?

It is impossible to recreate industrial technology using a homemade method. The metal is overheated to improve fluidity. At a temperature above the melting point, a certain time interval is maintained, only after this the melt is poured into molds. Technologists calculate the temperature regime for each alloy.

Source: https://svarkaprosto.ru/tehnologii/temperatura-plavleniya-bronzy

Melting point of bronze

Many people today are trying to master industrial production technologies at home. Provided that the sequence of certain manipulations is followed and the necessary equipment is available, it is sometimes possible to solve very complex problems.

For example, you can easily melt metals and create bladed weapons or exclusive jewelry with your own hands. To do this, you need to know to what temperature the metal needs to be heated and how best to do it.

This article will tell you what the melting point of bronze is, what you need to take into account if you want to subjugate this metal.

What is bronze? This is an alloy consisting of a main component (copper) and an additional alloying element. Depending on what acts as an alloying additive, several grades of the material being described are distinguished, therefore each type of bronze has its own melting point. The physical and chemical properties of bronze depend on the percentage of additional components. Its marking helps to understand what impurities are contained in the alloy.

All bronze compositions can be divided into two large groups:

Tin alloys are a type of bronze that contains tin as an alloying element. This metal is stronger than copper, but it is fusible. The combination of copper (80%) and tin (20%) is the first alloy that humanity has learned to create. With its help, church bells were cast in Rus'. The metal sounded good, but was fragile. Therefore, there was a need to look for more advanced alloys.

Tin-free alloys do not contain brittle tin. Beryllium, silicon, lead and aluminum can be used as alloying additives. Depending on which of the listed metals is combined with copper, the alloy acquires its physical and chemical properties.

For example, beryllium makes it possible to create alloys whose strength characteristics are much superior to high-quality steel. The addition of silicon makes bronze more resistant to mechanical friction.

Lead helps to form high resistance to corrosion, aluminum improves the friction characteristics of the alloy.

The process of melting bronze must begin with studying its composition. All tin grades melt at a temperature of 900–950°C, tin-free grades melt at a temperature of 950–1080°C.

Note! When casting, another indicator of the alloy is taken into account - its viscosity. Tin bronze has a higher temperature than brass, so when heating it it must be very overheated. Then, after cooling, the described brand gives minimal shrinkage, so this type of bronze is ideal for shaped casting.

Many of us wonder whether the process of melting the described alloy is possible at home. It is impossible to recreate industrial casting. Since bronze has a high melting point, special conditions are required to work with hot metal.

You can try to master small casting, which allows you to create jewelry or small crafts. To carry out this process, you will have to allocate a separate room, as well as take all fire safety measures and provide high-quality ventilation.

Large bronze parts can be made where there is an earthen or concrete floor (this could be a garage with good forced ventilation).

To work you will need certain equipment and special tools. Only a muffle furnace will allow casting (the presence of a thermostat will greatly simplify the solution of the task). For large pours, you will have to install a forge. You can melt metal in a cast iron container that is shaped like a spout. It helps to gently pour the molten metal into the mold. This cast iron container is called a crucible.

The crucible is removed from the furnace using long tongs and a special hook. There should be a casting mold at hand. Charcoal is best suited for lighting a muffle furnace, and coke for a forge.

Casting process

The process of casting bronze is extremely simple. The oven heats up to certain parameters. Let us remind you once again that to melt tin alloys it is necessary to heat the furnace to a temperature of 900–950°C; the melting temperature of tin-free alloys is an order of magnitude higher – 950–1080°C.

Melting of any bronze composition must begin with calcination of the mold for pouring in a muffle furnace or in a forge. To do this, the oven is first heated to a temperature of 600°C. Then the mold is immersed in it, after which the temperature in the oven must be increased to 900°C. The mold should spend a couple of hours in the oven. After the timer ends, the mold is removed from the oven and cooled to a temperature of 500°C.

The bronze is placed in a cast iron tray and sent straight into a well-heated oven. After the alloy has melted, the metal must be kept in the oven for another five minutes. This way it will warm up well, which means it will be easy to ensure high-quality filling of the casting mold. The crucible is removed from the furnace using a hook, and the process of pouring the molten alloy into the mold is ensured with tongs. It is important to pour the metal in a thin, continuous stream. This is the only way to prevent the process of blurring the shape.

How to properly pour molten bronze into a casting mold

Pouring molten bronze into a mold is a real science. Filling out a large form will be easy. The liquid alloy, under the influence of gravity and its own weight, will itself be evenly distributed throughout the container and displace all existing air.

There will be a certain problem with filling out small forms. The fact is that air prevents the uniform redistribution of the alloy over all planes.

Therefore, often melting bronze at home does not allow creating high-quality products.

Is it possible to solve a similar problem on my own? Yes, if you have a centrifuge at hand. Centrifugal force will displace the air and allow the alloy to be evenly redistributed over the entire area of ​​the mold. It is necessary to act according to this plan very quickly, before the bronze has time to harden.

You need to remove the pouring from the mold when the alloy has completely hardened. The surface of the workpiece will be rough, and in some places metal deposits will definitely appear. Such defects are eliminated by mechanical grinding. If the oven has been heated correctly, the amount of mechanical grinding will be minimal.

Creating a casting mold

Given the fact that each type of bronze has its own melting point, it is important to have on hand a mold that can withstand the highest heating point of the alloy being described. It is difficult to create it with your own hands at home, but you can try if you carefully study the following instructions.

First you need to create a molding box (foundry workers call it a flask). Its dimensions are one and a half times larger than the dimensions of the future part. The flask is assembled from unplaned boards according to the following scheme: first, the upper frame is knocked down (outwardly it looks like an ordinary box without a bottom and top, but with two crossbars in the middle), then the lower frame (box with a bottom) is knocked down.

Then they begin to create the molding soil. It has a special composition: 75% fine-grained sand, 20% clay and 5% coal dust. All ingredients are combined and mixed thoroughly.

The next stage is making a model that will help form a mold for future casting. Experts recommend making it from wood. The further process is reproduced according to the following algorithm.

1. The wooden model is first generously sprinkled with talcum powder, and then carefully placed exactly halfway in the bottom drawer of the flask.
2. Then it is filled to the top with ready-made molding soil.
3. The entire resulting composition is generously sprinkled with graphite.
4. After this, the lower part of the flask (with a bottom) is covered with an upper frame (without a bottom).
5. A metal cone is inserted into the upper frame, the narrow part of which should touch the surface of the wooden model. The cone will allow you to form a sprue - a part through which molten bronze will be poured.
6. The top box is also filled to the top with molding soil. The filling is carefully compacted with a special mortar.
7. After this, the metal cone is carefully removed. Using a sharp knife, the upper flask is removed from the lower frame along with the molding sand. A wooden blank is removed from it. After all the manipulations performed, there should be indentations on both flasks that accurately copy the geometry of one half of the wooden model.

Note! At this stage, you can use a knife to correct slightly crumbling lines. If some of the earth sticks to the model, its deficiency in the flask is made up for. The excess is simply removed.

1. We leave the lower and upper parts of the flask until completely dry, and then connect them together so that there is no gap between them. The bronze casting mold is ready.

Using this form, it is possible to create bronze products that do not have a clear pattern and small details.

How to get better quality castings

Even at home, you can produce higher-quality casting if you use a special method for creating a mold for casting. The basis is a model that exactly resembles the one that will need to be smelted from bronze. It is made from wax or paraffin.

• First, a plaster cast consisting of two halves is taken from the model. The parts of the cast are connected to each other with gypsum mortar.
• After drying, the resulting form is filled with liquid paraffin through a specially left hole.
• When the paraffin hardens, the gypsum shell is removed. A figure of frozen paraffin should remain.
• It is placed in a heat-resistant mass and a one-piece mold is formed for casting. Foundry masses are sold today in construction stores. Be sure to leave a hole in the mold for draining paraffin and pouring bronze.
• Then the one-piece mold must be placed in boiling water. It will heat up and melt the paraffin or wax. Through a special hole designed for pouring liquid alloy (future sprue), you need to drain the molten wax. After this, the mold for creating a higher-quality casting will be ready. Making a mold in this way allows you to obtain a bronze casting that has a clearer outline and finer details.

Recreating the process of melting bronze at home is not so easy, but if you are faced with a similar task, this article will help you solve it. The main thing is to always remember safety precautions, be able to distinguish between types of alloys, and know at what temperature each of them melts.

Source: https://svarkalegko.com/materials/bronza-i-eyo-svojstva-temperatura-plavleniya.html

Technology and melting temperature of bronze at home

Bronze is a copper alloy alloyed with tin, aluminum, lead and other elements. Copper alloyed with zinc is brass, and with nickel is cupronickel. One of the ways to produce bronze products is casting. The molten metal is poured into a mold where it solidifies.

Preparing the form

Before work, the mold is warmed up. The oven is heated to 500-600˚C, the equipment is placed there and the temperature in the oven is increased to 900˚C. Calcinate for 2-5 hours. The time depends on the size of the mold. Then it is taken out and cooled to 500-600˚C. After this, the metal can be cast.

Production of high quality castings

It is possible to obtain products of higher quality than by casting into the ground. For this purpose, lost wax casting is used.

The equipment is made of gypsum. It is disposable and destructible. To make a mold, you need a model of the product made of wax, paraffin or other fusible material. This material should be lighter than water. The following will explain why this is important.

A wax model is also made by casting into plaster casting. Models of complex configuration are made from several parts. And plaster equipment for the model is made according to the original product or its model, similar to equipment made from sand. The result is a chain: original product - plaster mold for wax model - model - plaster mold for metal - finished product.

When the tooling for the product is ready, a wax model is melted from it by immersing the mold in hot water or simply heating it. The melted wax flows out of the cavity through the same hole into which the metal will then be poured. That is why the material of the model must be lighter than water - so that when smelted in water it rises to the surface.

You can familiarize yourself with the process by following the instructions in the video provided.

Precautionary measures

To cast bronze in non-industrial conditions, you need a separate room with forced ventilation. For small parts, a room is suitable; for large parts, a garage or hangar is needed.

The floor in the workshop is made of non-combustible material. A working fire extinguisher must be installed. It is prohibited to store flammable substances in the workshop.

You should work in special clothing, gloves, a mask and a respirator. Some materials release harmful substances when melted. You should be especially careful when melting antique metal, as it sometimes releases arsenic when heated.

Source: https://oxmetall.ru/metalli/bronza/tehnologiya-i-temperatura-plavleniya

Melting point of bronze and features of casting at home - Turner Master

Bronze is a copper alloy alloyed with tin, aluminum, lead and other elements. Copper alloyed with zinc is brass, and with nickel is cupronickel. One of the ways to produce bronze products is casting. The molten metal is poured into a mold where it solidifies.

Melting point and bronze casting at home

The melting point of a certain brand of bronze depends on what chemical elements are included in the composition of this alloy. In order to cast bronze products at home, you need to equip your workshop with appropriate equipment and strictly follow technological recommendations.

Melting bronze at home

Types of bronze alloys and differences in their melting points

The basis of an alloy such as bronze is copper, and the alloying additives are tin, aluminum, silicon, lead and beryllium. Bronze of any brand also contains small quantities of elements such as phosphorus, zinc, etc. In addition to bronze, modern industry also produces other copper-based alloys - cupronickel, copel, constantan and nickel silver (the main alloying element in them is nickel), brass (alloy of copper and zinc).

The amount of main alloying additives in bronze determines not only its physical and chemical properties, but also its color.

Each grade of bronze, the melting point of which is in the range of 930–1140°, is indicated by its own marking. Depending on their chemical composition, all bronze alloys are divided into:

Man has learned to combine copper and tin to make bronze since ancient times. Tin, which is added to such an alloy, makes it harder when compared to pure copper, and also lowers its melting point.

One of the striking examples of such an alloy is bell bronze, from which bells have long been made by casting. It contains 80% copper and 20% tin.

The most significant disadvantage of bronzes of this type, due to the tin content, is the increased fragility of products made from them.

Processing temperature and technical properties of tin bronzes

Tin-free bronzes, as their name suggests, do not contain tin. Alloys of this type are presented on the modern market in one of the following categories of bronzes:

• beryllium - the most durable, superior to high-quality steel in many respects;
• silicon-zinc, which are particularly resistant to abrasion (a great advantage of bronzes in this category is that in the molten state they have increased fluidity);
• alloys with the addition of lead, which are characterized by increased resistance to corrosion;
• made on the basis of copper and aluminum, the distinctive characteristics of which are increased resistance to corrosion and good anti-friction properties.

Melting point and other physical properties of cast tin-free bronzes

Although bronzes with the addition of tin are highly fragile, as mentioned above, they are still the most common today. To mark bronzes of any grade, regardless of their chemical composition, the letters “Br” are used, after which the designations of additives are listed, as well as their percentage content.

As an example, we can decipher the designation of bronze grade Br OTsSN3-7-5-1. This bronze, which belongs to the tin type, contains 2.5–4% tin, 6–9.5% zinc, 3–6% lead, 0.5–2% nickel.

The chemical composition of any bronze, as mentioned above, may also include other elements, which are designated by the following letters:

• A – aluminum;
• B – beryllium;
• F – iron;
• K – silicon;
• Mts – manganese;
• F – phosphorus.

Chemical composition and purpose of common grades of bronze (click to enlarge)

If we talk about the most common brands of bronze, they include:

• casting alloys BrO5, BrO19, BrOTs8-4, BrOTs10-2, BrOF10-1;
• malleable bronze alloy BrOS5-25.

For a technological operation such as casting, especially when performed at home, the temperature at which the metal can be melted is of great importance. Bronzes containing tin melt at a lower temperature - 900–950°, and those that do not contain this metal melt at a temperature of 950–1080°.

Bronze casting alloys, when heated to the melting point, have higher viscosity when compared with brass. That is why, in order to perform high-quality casting from such alloys, they must be overheated. A significant advantage of using cast bronzes is that the shrinkage of products made from them is very insignificant. This makes it possible to produce shaped castings from such alloys.

Pouring a mold with cast bronze

Is it possible to cast bronze at home?

In order to cast bronze products at home, you need to create all the necessary conditions for this. The most important of these conditions is good ventilation in the work area, as well as the use of fire safety equipment.

If you are going to make small-sized bronze products, the area of ​​a small room will be enough for this, but if you plan to produce large castings, then you will need a spacious room (for example, a garage).

A mandatory requirement for such premises is a floor made of non-combustible material.

To melt a material like bronze, you will need a muffle furnace. It is advisable that this device be equipped with a heating temperature regulator. If you don’t have such a furnace at your disposal, then an ordinary forge is suitable for melting bronze at home.

Homemade forge with a fan from an old hood

In addition to the furnace, which will melt the metal, for casting bronze products you will need:

• crucible - a steel or cast iron vessel with a spout (for melting and pouring metal into molds);
• tongs with which the crucible is removed from the furnace;
• hook;
• a mold into which molten metal is poured;
• charcoal used as fuel (if a forge is used to smelt metal).

A crucible for melting can be easily made from scraps of thick-walled steel pipe

The procedure for casting bronze products is as follows.

• The metal to be melted is crushed and placed in a crucible.
• The crucible is placed in the furnace and heated to the required temperature.
• After the metal has completely melted in the crucible, it is left in the furnace for another 4–5 minutes to warm up. Such heating is necessary so that the metal acquires maximum fluidity and fills all the cavities in the mold well.
• The crucible with molten metal is removed from the furnace using a hook and tongs.
• Liquid metal is poured into the mold through a special sprue hole. In this case, it is important to ensure that the stream of the poured alloy is thin and not interrupted.

Pouring bronze melt should be carried out quickly and carefully

The mold for casting must first be prepared, which involves calcining it in an oven. To carry out this procedure, the furnace is heated to a temperature of 550–600°, and only after that the casting mold is placed in it. Then the temperature in the oven is increased to 900° and the mold is kept under its influence for 2–4 hours.

The larger the mold, the longer it must be kept in a hot oven. After the casting mold is completely calcined, it must be removed from the furnace and cooled to a temperature of 500°, only then can it be used for casting.

A video of this process allows you to become more familiar with the rules of bronze casting and the equipment used for these purposes.

How to properly pour metal into a mold

If molten metal is poured into large casting molds, then its own weight is quite enough to displace all the accumulated air from them. If casting is performed in small molds, then it is almost impossible to displace air from all the internal cavities of such structures due to the mass of molten metal. In order to obtain high-quality castings in such cases, it is necessary to use special technological techniques.

Casting molds are placed in special centrifuges, powered by manual or electric drive. During rotation, centrifugal forces are created that evenly distribute the molten metal throughout all the internal cavities of the molds. This technology is effective only if the metal is still in a liquid and not a solidified state.

Homemade centrifuge for casting small parts

After the casting process is completed and the metal has cooled, the casting is removed using simple mechanical devices. It should be borne in mind that the surface of products freshly removed from the molds is not of high quality, so they must be subjected to various types of mechanical processing.

Making molds for casting

The quality of products produced by casting from bronze alloys is seriously influenced by the correct manufacturing of the casting mold, which makes it possible to create a part of the required configuration and with given geometric parameters from molten metal. For the manufacture of casting molds, special devices are traditionally used - flasks. The flask, the dimensions of which should be approximately one and a half times greater than the parameters of the finished product, consists of:

• top frame;
• bottom drawer.

The casting mold is made for a specific product

The upper and lower parts of the flask, into which the molding mixture is poured, can be reliably connected to each other for greater reliability, for which special clamps are used on their side surfaces.

The composition of the most commonly used molding sand includes:

• fine sand – 75%;
• clay – 20%;
• coal dust – 5%.

As a result of mixing these components, a homogeneous mass should be obtained.

To make a casting mold, you will also need a model that is made from wood or other soft material (you can use a finished product of the required quality in its role).

A homemade casting mold consists of two halves

The production of the casting mold itself is carried out as follows.

• The molding mixture is poured into the bottom drawer of the flask and lightly compacted.
• A model is placed into the resulting compacted mass, the surface of which must first be coated with talc or powdered graphite.
• Place the upper frame on the lower part of the flask and fill it to the top with molding mixture, also compacting it. Before filling the upper half of the flask, it is necessary to form a sprue hole in the future shape, for which a special conical plug is used.
• After compacting the molding mixture, you need to divide the finished mold into two halves - upper and lower, for which you can use any sharp object.
• After removal from the resulting casting mold, the internal cavities of the model are carefully inspected and any defects that may be present are corrected.

The finished mold must be dried, after which it can be assembled and started to be used for casting bronze products. The production of a casting mold is shown more clearly in the video below.

The plaster mold should be covered with a thin graphite layer

Technology for casting bronze products of higher quality

To obtain a higher quality bronze product by casting or to produce a part of a complex configuration, you can use another technology that involves the use of a model made of a low-melting material. In this case, to create a one-piece casting mold, a model made of paraffin, wax or any other low-melting material is used. Such a model is simply melted from the finished mold by heating it or placing it in boiling water.

A wax model of complex configuration is made of several parts, which are then modified and soldered

To ensure high accuracy of the shape and geometric parameters of the model, a finished product can be used to create it. With its help, a plaster mold is obtained, into which the copy is cast.

You can also get acquainted with the technology that allows you to perform high-quality casting of even very complex products by watching numerous videos on the Internet.

Source: http://met-all.org/cvetmet-splavy/bronza/temperatura-plavleniya-bronzy-lite-domashnih-usloviyah.html

Bronze casting

from here

Bronze casting has been used since ancient times. For many centuries, copper alloys (bronze, brass) were used to make tools, hunting and jewelry.

Improvements in foundry technology have led at the present stage to the emergence of many methods for casting metals, especially non-ferrous ones. The technological capabilities of bronze casting make it possible to obtain not just objects, but works of art, which have been considered the height of perfection since ancient times.

The developed technologies make it possible to melt copper alloys not only in industrial production conditions, but also at home, in small workshops.

Main stages

To obtain high-quality cast products, strict adherence to the technological sequence is required. The casting process is as follows:

1. Making a model or copy according to a sketch or drawing. Materials for the model are easily melting at low temperatures: stearin, paraffin, wax and others. The ability to completely fill the volume of internal space in a mold has made these materials widely used.
2. The gating system is attached to the model by gluing, soldering or mechanical fastening. Thus, feeders, channels, vents and other elements are formed.
3. The production of injection molds is made from a refractory mixture. The main composition of the mixtures is fireclay or alumina clay and quartz sand.
4. The mold is released from the model composition by heating with steam or immersion in heated water.
5. Typically, bronze casting is carried out by free pouring using centrifugal machines, excess or insufficient pressure (vacuum).
6. Cooling is done in air or using a thermostat.
7. After cooling, the model form collapses. The gating system is cut off. The workpiece is sent for cleaning using washing or chemical compounds.

Foundry models

Artistic casting of bronze and brass involves obtaining the smoothest possible surface, so fairly hard materials are used to recreate the model:

1. • wood;
   • gypsum;
   • Ivory.

To obtain the smoothest possible surface, it is subjected to elimination of porosity by puttying, priming and varnishing.
Casting models are made split; one-piece - suitable for casting products of simple shapes; special for parts with a rather complex configuration.

Casting molds

There are two types of casting molds: disposable and reusable. It all depends on the material from which they are made. If a clay-sand mixture is used for manufacturing, then to maintain its shape, metal flasks are required to prevent the destruction of the mixture.

Reusable molds are made of steel with a horizontal or vertical parting line. To increase the casting ability of a copper alloy, lubricants are used to prevent the occurrence of welds, burns and other defects.

Melting points

The melting point of bronze directly depends on the filling of the alloy with chemical elements. After all, refractory elements can act as alloying components. Thus, the maximum temperature for casting bronze is 1350 °C.

Marking of alloying elements added to copper alloys:

• aluminum (A);
• beryllium (B);
• iron (F);
• silicon (K);
• manganese (Mc);
• nickel (N);
• lead (C);
• selenium (O);
• titanium (T);
• zinc (Z).

To divide bronze alloys, two definitions are used: tin-bearing and tin-free bronzes. The melting point of a material suitable for casting, depending on its chemical composition, is given in the table.

Alloy, designation	Temperature for casting, °C
BrOF4-0.25	1300
BrOTs4-3	1250
BrOTsS4-4-4	1200
BrAZH9-4	1200
BrA9Mts2L	1150
BrA10Zh8L	1190
BrA11Zh6N6	1185
BrAZhS7-1.5-1.5	1150
BrS3O	975
BrA5	1200
BrKN1-3	1050
BrBNT1.7	1050
BrAMts10-2	1150
BrKMts3-1	1150
BrMts5	1150
BrB2	1100
BrSN60-2.5	1100

This is not a complete list of cast bronze alloys.

If bronze smelting is done at home, then special attention should be paid to the melting point of the alloy. Tin bronzes do not need to overcome the thousand-degree threshold. They need 900°C - 950°C. Tin-free alloys already require 950 °C - 1100 °C.

parts produced from bronze by centrifugal casting

When smelting bronze parts, it is worth considering their high viscosity. Therefore, for high-quality casting, they should be heated above the melting point by about 100 degrees. Bronzes have minimal shrinkage, which does not exceed 1.5%. This characteristic is an advantage over brass and makes it possible to obtain shaped castings.

For comparison, you can look at the melting point of brass. There are two categories of brass: two-component and multi-component brass. The two component alloys contain zinc in addition to copper. Its amount affects the melting point, which is in the range 880°C - 965°C.

For multi-component temperature conditions increase to 895 °C - 1070 °C due to the introduction of alloying components with a high melting point.

Bronze casting technologies

Melting, like cutting, is a widespread operation for producing parts. For melting, it is recommended to use induction melting or crucible heating furnaces. The choice is determined by economical electricity consumption.

To preserve the chemical composition of alloys, fluxes are used. With their help you can:

• Protect the outer layer of the melt surface:
  1. from oxidation;
  2. increase the volume of suitable melt;
  3. exclude non-metallic components;

• Degas the composition due to which the formation decreases:

To obtain smooth surfaces on the casting and ease its removal after cooling, non-stick paints are used. Their use ensures:

• mold lubrication;
• protection from destruction upon contact with the melt;
• no burns.

Injection molding

Injection molding occurs when exposed to excess or insufficient (vacuum) pressure. The press principle is used to supply the melt under excess pressure. The piston is subject to force from a hydraulic or pneumatic system. The high feed rate coupled with high viscosity creates high pressure to completely fill the mold. The resulting castings have high precision and a fine-grained structure.

Due to vacuum suction, the melt is drawn into the mold of the crystallizer. Cooling occurs towards the center of the mold. The required amount of melt is drawn in over a certain period of time.

A crystallizer is a container with thin walls that are cooled with water.

After normal (atmospheric) pressure is restored, the excess melt drains off. After cooling due to shrinkage, the part is independently removed from the mold. Automation of the vacuum suction process allows you to fill the mold in a minimum amount of time, down to 0.1 seconds.

Centrifugal casting

It is advisable to use centrifugal casting, pouring bronze and brass in the manufacture of parts such as rotating bodies. The formation of parts occurs on machines with horizontal and vertical axes of rotation. On machines with horizontal pouring the following is cast:

• bushings;
• inserts;
• rings.

On machines with vertical pouring the following is cast:

• gears;
• worm wheels;
• propellers.

centrifugal casting

The technology is based on centrifugal force, which is generated when the mold rotates. The melt is compacted under the influence of forces, displacing third-party components.

Artistic casting

Modern trends dictate the use of casting not only in the production of parts for mechanisms and assemblies, but also in the production of interior elements. Thus, using artistic casting technology it is possible to produce:

• bas-reliefs, sculptures;
• elements of fences, gratings, gate fences;
• souvenirs;
• lamps, sconces;
• interior elements.

The stages of technology for producing castings are as follows:

• making a model;
• mold making;
• preparing the form;
• melting of the charge;
• preparing the melt for pouring;
• cooling;
• demolding;
• stump;
• cleaning and presentation.

Finished castings, according to the master’s plan, are combined into a single product if it is multi-component. After which they can be chrome-plated, nickel-plated, covered with patina and other metals.

Casting at home

Many craftsmen cast bronze products at home. These are mainly interior parts and figure casting. In addition to the basic devices, you need to purchase auxiliary tools and materials. Among them:

• forceps;
• coal (wood, stone);
• crucible;
• horn

The forge supplies the air necessary to maintain the combustion of coal, which creates the necessary temperature for melting bronze. Using tongs, the crucible is removed from the heating chamber and the melt is poured. Due to the fact that bronze melts at low temperatures, the melting furnace can be replaced with a gas cutter (autogen) or a blowtorch.

Artistic bronze casting involves carrying out work in a separate room, which must be equipped with fire extinguishing equipment and supply and exhaust ventilation. In addition, it is necessary to organize storage areas for tools, devices, materials, as well as organize conditions for personal hygiene.

Bronze products, after they are removed from the mold, look like a black, charred, melted piece of metal. To give it a presentable appearance, at the initial stage, use a metal brush or a machine with attachments made of abrasive material.

The fairly good fluidity of bronze, unlike brass, does not contribute to complete filling of the mold when manually casting at home, as a result of which the pattern on the surface of the casting is unclear.

To eliminate this defect, craftsmen use embossing. It helps to give the final look to the product if it has a lot of openwork ornaments. Minting takes quite a lot of time.

Source: https://tsvetmet.wordpress.com/2018/09/17/%D0%BB%D0%B8%D1%82%D1%8C%D0%B5-%D0%B1%D1%80%D0% BE%D0%BD%D0%B7%D1%8B/

Bronze melting point: types of alloys and casting molds, features and pouring technology

The temperature at which bronze melts depends on its composition. In order to independently cast products from this material, you need to equip your workplace with all the necessary equipment and strictly adhere to technological rules.

Bronze contains copper and alloying additives (beryllium, lead, aluminum, silicon and tin). All its alloys also contain components such as zinc, phosphorus, etc. In addition to bronze, the modern industrial industry is engaged in the production of other alloys from copper - constantan, copel, nickel silver, cupronickel, brass, etc.

The amount and type of alloying components in a bronze alloy determines its chemical and physical characteristics, as well as the color of the material.

Brands of bronze alloys, the melting point of which lies in the range from 930 to 1140 degrees Celsius, have their own markings. , bronze-based alloys

People learned to combine tin with copper to produce bronze a long time ago. Tin makes the material stronger and also reduces its melting temperature. A striking example of this type of alloy is bell bronze. It contains twenty percent tin and eighty percent copper. However, products made on the basis of bell bronze are characterized by high fragility.

Tin-free bronzes, as the name suggests, do not contain tin. Such alloys today are classified into separate categories of bronzes:

1. Beryllium is the strongest and has many characteristics superior to steel;
2. Silicon-zinc - have increased resistance to abrasion (the advantage of such bronzes of this group is that when molten they have high fluidity);
3. Based on aluminum and copper, they have high anti-corrosion protection and excellent anti-friction properties.

Currently, the most common bronzes are those containing tin. For the purposes of marking the material, regardless of the composition, the designation “Br” is used, after which the additives used and their content in the material are indicated.

For example, you can decipher the bronze “BR OTSSNZ-7−4−2-. This tin alloy contains tin, zinc, lead and nickel. The numbers indicate their percentage in bronze.

The composition of any brand of bronze may contain other elements having the following designations:

1. A - aluminum alloys;
2. B - beryllium-based alloys;
3. F - ordinary iron;
4. K - silicon element;
5. Mts - ordinary manganese;
6. F - phosphorus.

Filling Features

If a molten metal alloy is cast into a large mold, then its mass will be sufficient to displace the accumulated air. If small molds are used for casting, then you should resort to special technological methods.

In this case, the forms are placed in centrifuges that operate either electrically or manually. During the rotation process, centrifugal energy is generated, ensuring uniform distribution of the metal alloy over the inner surface of the mold. However, this technology is only effective in a situation where the metal alloy is still liquid and not frozen.

After the casting is completed and the material has cooled, the product is removed using ordinary devices (tweezers and a hook). It must be remembered that the surface of recently removed structures cannot boast of a high level of quality, so they need to be subjected to special mechanical processing.

Manufacturing of casting molds

The level of quality of the resulting products is also influenced by the correctness of the casting mold, which allows the product to be endowed with the necessary geometric parameters and configuration. To create molds, a special tool is often used - a flask. The flask, the dimensions of which should be approximately one and a half times larger than the dimensions of the finished structure, includes a lower drawer and an upper frame.

The parts of the device can be connected to each other using side clamps.

The composition of the standard molding mixture includes:

1. Clay;
2. Fine sand;
3. Stone dust.

When these components are mixed, a homogeneous mixture is obtained. To make a mold, you also cannot do without a model made of wood or other fairly soft material.

The production of the molding structure itself is carried out as follows.

1. The molding mixture is placed inside the bottom drawer of the flask, which needs to be tamped down a little.
2. The model is placed in the prepared composition, which must be coated in advance with powdered graphite or talc.
3. The upper frame is attached to the bottom of the flask, after which it is filled with molding solution. Before backfilling, you need to make a hole for the future sprue. To do this, you can use a special conical plug.
4. After the molding mixture has been compacted, the mold must be divided in two. To do this, you can use any sharp device.
5. The final stage involves eliminating defects and leveling out unevenness.

The made form must be dried, only then can it be used.

In order to make a complex structure or a high-quality part, you can use another method, which involves using a model made of fusible materials. In such a situation, you can use paraffin or wax to make a casting mold. This model is simply melted and placed in boiling water.

To ensure the accuracy of the geometric characteristics and shapes of the model, you can use the finished product. Using it, a plaster mold is obtained, which will be used to cast an exact copy.

Source: https://tokar.guru/metally/temperatura-plavleniya/temperatura-plavleniya-bronzy-i-osobennosti-litya-v-domashnih-usloviyah.html