How to get bronze - Metals and their processing

How to turn stone into gold with bronze powder

Paint containing bronze powder is successfully used by decorators, designers and ordinary people to transform interior items. This composition can give a metallic shine to almost any material. What kind of bronze powder is this that will turn a brick into metal?

Where is it used?

It is a dispersed powder that is obtained by grinding copper or copper-zinc alloys with a slight addition of iron and aluminum. Paraffin or stearic acid must be added to the powder, which prevent oxidation of the particles and their sticking together.

Based on their chemical composition and purpose, there are several brands of powder for:

paints (BOD);
offset printing (BPO);
tool making (BPI);
printing (BPP).

Bronze powder has a layered structure. Each layer is composed of scaly plates. Color - from yellow-golden to deep red or brass. The saturation of the shade is determined by the percentage of zinc.

Powder production

The production of powder takes place using industrial methods by repeatedly crushing bronze powder. After several stages of grinding, its separation is carried out in ball mills or pneumatic units.

Paints and varnishes based on bronze powder have significant hiding power. The quality of painting depends on the size of the fraction. The highest quality is powder, which, when sifted, forms a residue of no more than 1% (on sieve No. 0.045). To obtain a powder with maximum coverage, it is necessary to use bronze alloys rather than pure copper. With one gram of such powder you can cover up to 4500 cm² of surface.

Areas of application

Bronze powder is used in decoration, printing, in the production of paints and coatings, various labels, and in the cosmetics industry. With the help of paint, which has been injected with bronze powder, you can impart a metallic shine and a characteristic texture to products made of steel, plaster, cardboard, glass, concrete, and plastic.

This product is also used when painting components of systems that require additional protection:

tanks, system parts in industry;
radiator systems, heating batteries;
parts of boiler systems that protect against elevated temperatures;
various port structures and parts of ships that are constantly under water;
fences, bridges.

Methods for preparing formulations

It is necessary to mix the powder with the binder. The tincture will determine the main characteristics of the future coating, accordingly the possible areas of application, as well as the final cost. Tincture can be:

varnishes on metal or wood for exterior and interior use;
epoxy enamel;
some types of adhesives;
egg powder dissolved in water;
gelatin.

The binder component is selected based on the type of surface being treated. For example, when treating wood products that will be used indoors, the tincture should be a clear interior varnish.

The color depth of the finished coating is determined by the ratio of the amount of bronze powder and the binder base. The deeper the color, the more powder you need to take. The consistency of the ready-to-apply composition resembles thick sour cream. This paint, with a bronze powder content of about 40%, will provide a reliable and effective coating.

What proportions should be observed? If varnish or drying oil serves as a tincture, then take two parts of powder for 4 parts of the base. If the solution turns out to be too thick, then turpentine, white spirit or solvent are used for dilution.

When using a spray bottle to apply a bronze layer, mix the solvent and powder in equal proportions. When using a brush, you need to take two portions of foundation per serving of powder.

Coating

To give the product a metallic shine, you can make the composition yourself or buy it ready-made in aerosols.

Before applying the coating, any product must be cleaned of contaminants. Wooden surfaces are pre-sanded, and metal surfaces are treated to prevent rust. Often craftsmen prefer to remove the old coating:

by mechanical cleaning with a grinding attachment or brush (applicable to metal surfaces);
sandblasting (cleaning metal surfaces under the influence of grains of sand);
chemical cleaning (special compounds react with the old coating);
thermal cleaning using a hair dryer.

Then the varnish or paint is applied in a thin layer, which is literally rubbed over the surface. To obtain the thinnest possible layer, use a sponge or stiff brush.

When using nitro varnish as a tincture, apply bronze paint as quickly as possible until the composition sets.

If the coating is to protect the product from corrosion, then it must be primed before applying paint.

Coating of smooth products

There are usually no problems with applying paint to equal surfaces. The main issue in such work is the determination of the connecting component. If the product will be exposed to aggressive influences, then use varnishes for external use.

Such surfaces can be coated with a brush or even spray equipment. Compositions in aerosol cans are also suitable for applying a high-quality layer.

Sputtering

Products with simple relief can be decorated using the spraying method. It is worth starting staining with this method again with preparation. It is necessary to apply varnish or glue to the degreased surface of the product. When applying the binder component, care must be taken to ensure that no lint or other foreign bodies remain on the product.

Bronze powder is first poured onto gauze folded in several layers, which is then tied in a knot. When the bundle is shaken over a varnished product, small particles of powder are securely attached to it. This application allows you to obtain a very durable and beautiful metal-like coating.

Application on difficult terrain

To apply high-quality paint on products with complex relief, you need to have some skill.

How to apply paint in this case? The secret is simple - it is better to use oil varnish as a binding base. To give it a noble golden brown hue, you can add a little brown oil-based paint.

This composition is applied to a fat-free product. The powder, as with spraying, is formed into a slide on gauze and a knot is tied.

Of course, this method allows you to achieve high-quality and effective coverage, but for beginners it is better to use a simpler method. To do this, prepare a coloring composition with bronze powder in advance, and then simply apply it with a cloth swab or sponge.

How to get a patina effect

The pinnacle of craftsmanship is considered to be giving relief products a patina effect. How to do it? First, the prepared composition is applied to a clean surface. Wait until the layer dries completely. Then you should apply a layer of stain or liquid bitumen varnish, also filling all the relief depressions.

Without waiting for this layer to dry, use a sponge or cotton cloth to wipe all convex surfaces. Excess varnish in the recesses must also be removed. After complete drying, the product can be used.

To achieve the effect of a polished surface, some craftsmen additionally tint the convex parts with a bronze composition.

Bronze powder in printing

Bronze fine powder is widely used in printing. Thanks to it, labels, advertising and packaging materials are produced with a unique shine and a particularly rich color. This technology is called bronzing.

The process involves applying flakes of bronze powder to a print that has been treated with adhesive paint. Due to the layered structure of the powder, as well as the large particle size, multiple refraction and reflection of light occurs. This reflection gives the enchanting mother-of-pearl effect.

Previously, foil, gold varnish or metallic paints were used to decorate labels. But bronzing gives an incomparably better effect at lower costs. The popular foil stamping is twice as expensive as bronzing.

Advantages and disadvantages

Advantages of bronze powder for paints:

This powder actually contains bronze, which means it can protect individual parts or entire surfaces from aggressive environments.
This coating has high resistance to ultraviolet radiation and resistance to moisture and, as a result, extends the service life of products and individual components. Objects treated with a bronze composition have a guaranteed service life of up to three years when used under water, and up to seven years when used in air.
You can coat brick, concrete, metal, wood, plaster, paper and other surfaces with bronze powder.
The bronze layer is very thin, but durable and resistant to abrasion. It's difficult to remove.
Bronze powder based paint is non-toxic, dries quickly and adheres well.
Thanks to this coating, you can decorate the interior without much expense.

Flaws:

This is an explosive substance that must be stored in a tightly closed container away from open flames.
The composition cannot be applied to surfaces treated with nitro enamel, acrylic and oil paints, or varnishes. After application, the base coating may peel off and bubble.
When applying acrylic paint with bronze powder, rust often occurs.

Ways to remove random paint stains

It is impossible to completely protect clothing or interior items from accidental paint. The most careful craftsmen need to know how to remove bronze composition. If the stain has already dried, it can be removed with the same solvent in which the powder was diluted.

If a ready-made composition was applied, the basis of which is unknown, then you can apply a drop of sunflower oil to the stain. Leave the applied oil on for about 10 minutes, then wipe the stain with a cotton napkin. Remove fresh stains with nail polish remover without acetone.

Source: https://tsvetmet.wordpress.com/2020/01/13/%D0%BA%D0%B0%D0%BA-%D0%BF%D1%80%D0%B5%D0%B2%D1% 80%D0%B0%D1%82%D0%B8%D1%82%D1%8C-%D0%BA%D0%B0%D0%BC%D0%B5%D0%BD%D1%8C-%D0% B2-%D0%B7%D0%BE%D0%BB%D0%BE%D1%82%D0%BE-%D0%B1%D1%80%D0%BE%D0%BD%D0%B7%D0% BE/

Bronze casting technology at home

Bronze is often used in the manufacture of decorative metal products. This material produces attractive products that retain their decent appearance for a long time.

Bronze casting is considered one of the most popular foundry processes and has been used for hundreds of years to make various products from this metal.

To understand how suitable this material is for casting and how to work with it correctly, you need to have general information about the metal itself and how it is processed.

General characteristics of the metal

Bronze is an alloy that may contain tin, copper and other components. Foreign impurities include zinc, aluminum, beryllium, lead, nickel or silicon. If we talk about composition, bronze can be divided into two groups:

Tin alloys. The material may consist of two or several components. Tin is the second most abundant component of the alloy.
Tin-free alloys. The composition may include aluminum, lead, silicon, lead or beryllium. These components change the characteristics of the alloy.

The characteristics of the bronze alloy include:

Density. This indicator depends on the tin content in the composition. Average number 9.1 kg/cu.m. cm.
The temperature at which metal melts. Varies depending on the components of the composition. Range 880–1060 degrees Celsius.
Heat capacity - 0.385 kJ / (kg*K).
Electrical conductivity - 0.176 μOhm*m.

If you want to change any of the characteristics of the alloy, a certain amount of foreign impurities is added to its composition.

History of technology

Historians and archaeologists claim that bronze casting began to develop more than 10 thousand years ago. At the beginning of the history of the appearance of this alloy, it was used for the production of tools and primitive jewelry. Previously, the alloy was used only for industrial purposes. At the moment, bronze is used for the manufacture of decorative items, fences, movable fences, chandeliers, sconces, and sculptural compositions.

The moment of the most important peak in the manufacture of bronze products is the European Baroque period. During this period, people decorated their homes and estates with decorative elements made from this alloy.

Main stages

Bronze casting involves a technological process that requires the use of special equipment and compliance with certain production stages:

First of all, a drawing of the future workpiece is prepared.
A connection to the gating system model is created. This is done by soldering or gluing.
An injection mold is made from refractory mixtures.
The form is freed from the model composition. To do this, it is heated with steam or lowered into a container with hot water.
Using a centrifugal machine, molten bronze is poured into a mold.
The future workpiece is allowed to cool on its own.

For further processing of the bronze part, the mold is broken. The workpiece is washed using chemical compounds.

Bronze casting technologies

Bronze casting can be divided into several types depending on the technological process and the use of casting machines. Induction furnaces are used to melt the alloy. The metal itself is coated with flux.

Injection molding

During the vacuum suction process, the molten metal begins to be drawn into the mold. Next, the workpiece begins to cool, which occurs from the edges to the center. It uses a container with thin walls as a crystallizer. It is cooled with water. After cooling, the workpiece itself moves away from the mold.

Centrifugal casting

Centrifugal casting of bronze is used for the manufacture of cylindrical and cone-shaped parts. These include O-rings, bushings for industrial equipment and other parts. Worm wheels and gears are manufactured using centrifugal technology. The technological process involves rotation of the mold, due to which the molten metal is compacted.

Artistic casting

Bronze artistic casting technology is used to create decorative elements. These include various sculptures, lamps, grilles, fences, and souvenirs. Stages of artistic bronze casting:

Initially, a drawing of the future workpiece is made.
Next, the master creates a mold into which the molten metal will be poured.
The feedstock—the charge—is melted.
The casting mold is filled with molten metal.
Cooling process.
Removing the workpiece from the mold.

The last stage is the cleaning and further processing of the part. If the design is composite, individual parts are initially created and processed. After this, they are combined into one structure. The seams are cleaned and treated with protective compounds. By correctly performing the technological process of creating decorative elements from bronze, you can avoid mistakes and reduce the quality of the finished product.

Casting at home

Experienced metallurgy masters practice bronze casting at home. To carry out this process you need to purchase:

bugle;
forceps;
charcoal or coal;
crucible in which metal will be melted.

A gas burner is often used as a heating element for melting a bronze alloy. This is due to the fact that bronze can be melted at a low temperature. This way you can save on the purchase of an induction furnace.

Casting at home

Creating a casting mold

Casting bronze at home requires the correct production of casting molds. The molding mixture should consist of a mixture of sandstone, coal dust, and clay. Stages of mold making:

The molding mixture is poured into a wooden box called a flask. It is compacted from above with weak blows.
Next, a model of the future workpiece is immersed in the molding mixture.
On top there is another box (flask). The molding mixture is poured into it. It's being compacted.
Next, the master divides the form into lower and upper halves.

How to properly pour molten bronze into a casting mold

Bronze casting at home requires special preparation of casting molds. It is necessary to remove air from them in order to obtain durable castings without defects. The molds must be spun in an electrically driven centrifuge. After this, the molten metal can be poured.

How to get better quality castings

The casting quality can be improved. You need to use another modified technology. In this case, wax is used. It is used to make molds into which the castings will be poured. You can use paraffin. To make such a model, you need to use a ready-made mold that is heated in boiling water.

Casting bronze into a steel mold at home
Bronze casting has been known for many hundreds of years. Using this technological process, decorative elements, fences, lamps and sculptures are made. The composition of bronze includes various components that affect the characteristics of the alloy.

There are different types of making bronze castings, which involve different technological processes.

Source: https://metalloy.ru/obrabotka/lityo/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.

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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.

The wooden model is first generously sprinkled with talcum powder, and then carefully placed exactly halfway in the bottom drawer of the flask.
Then it is filled to the top with ready-made molding soil.
The entire resulting composition is generously sprinkled with graphite.
After this, the lower part of the flask (with a bottom) is covered with an upper frame (without a bottom).
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.
The top box is also filled to the top with molding soil. The filling is carefully compacted with a special mortar.
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.

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

Bronze casting

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.

Bronze casting

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