Decorative bronze: casting
To give the interior associations with the aristocratic style of the Middle Ages, brass was used by the masters of the decor, and bronze was especially common. Casting from these alloys and now makes it possible to create monumental masterpieces that can decorate any house. Bronze: properties In art casting, alloys are more often used than pure metal
To give the interior associations with the aristocratic style of the Middle Ages, brass was used by the masters of the decor, and bronze was especially common. Casting from these alloys and now makes it possible to create monumental masterpieces that can decorate any house.
In art casting, alloys are more often used than pure metal. The most popular is bronze - an alloy of copper with tin (additive and alloying element) in various proportions. If zinc is added instead of tin, the result is brass, and if nickel is nickel silver. Copper in combination with aluminum, beryllium or silicon is also considered bronze. The alloying element is indicated in the designation:
- BrO5, where tin is 5%;
- BrOS5-25: composed of 5% tin and 25% lead.
What technological properties does bronze have? Casting is possible when the material reaches yield. The temperature at which copper is melted is 1083 ° C. When tin is added to it, the threshold drops to 800 ° C, which greatly simplifies the process of heating the raw material. After solidification, the product shrinks to 1%. Depending on the components, bronze products will differ in hardness. With a minimum amount of tin, they can be forged, with a concentration of 20% or more, they become hard and become brittle. Plasticity adds an introduction to the composition of lead. The addition of zinc makes the material more resistant to corrosion.
Melting of metals is preceded by significant preparatory work. One part of it is related to the manufacture of the model. At this stage, the sculptor molds a sample on a scale of plastic material. Then translates it in full size in a cast or clay. With this transitional model, the reverse cast is taken. The complex form has several components and is assembled in parts. Heated wax is poured into it. Wrapping the form, achieve its uniform distribution over the entire surface. After cooling, a model of the future sculpture, made in wax, is formed. The author refines the details, corrects the shortcomings.
The overwhelming majority of art casting in bronze and brass is carried out according to such casting molds ("waxes"). The sculpture turns hollow with a wall thickness of 2 - 5 mm. Otherwise, if the metal filled the entire form, then the massive casting would be too heavy, and the material would be required a lot. And it's not just his high cost. When pouring, it would be necessary to melt all its quantity at once, and this automatically increases the size of the hearth and furnace, complicates the process of feeding the alloy to the mold. In addition, the shrinkage of the material will give inevitable deformation, which will lead to a distortion of the forms and individual parts of the composition.
After creating the wax form, the next stage begins. The caster is accepted for business. He creates his form for pouring molten metal. Stencil is covered with a special heat-resistant composition in several layers. At first such liquid ceramics is poured inside a wax mold. At this stage, the core is created - "blockhead". After it hardens with the same composition, the model is carefully coated on the outside, setting the required number of years to which the bronze will go.
Casting becomes possible after sintering (calcining) the mass at high temperature. As a result of this process, a strong ceramic shell is formed. The wax is evaporated through the letniki and holes for air release. The result is a hollow form. After pouring the metal, it is broken. The inner layer of ceramics can be left or also removed through the technological hole.
Casting bronze at home
It is possible to get a product from an alloy and in an earthen form. At home, if you have a template in this way, you can make a bronze casting. But you need to be prepared for the fact that it will not be possible to achieve exact copying of small parts and there is a lot of work ahead. The form turns out disposable, but the earth itself (a mixture of clay and sand) can be used repeatedly. Usually make split forms, consisting of two parts. But you can make and whole, if you use a wax model. After sintering the clay form is boiled in water, the wax floats on its surface through the letnik.
High-quality casting can be obtained if the form is preheated. Copper and tin are heated in a steel crucible. Use a coal forge or muffle furnace. After complete melting, the metal is kept at a high temperature for a few more minutes and poured into the letnik in a thin continuous stream. After cooling, the product is additionally processed. First, the metal is frozen, frozen in annals. Places are cleaned. Thin parts are formed in the process of embossing. The product is polished, polished, if necessary, covered with patina.