Brass, as you know, is an alloy of copper with zinc, in which other chemical elements can be added in small quantities. The chemical composition determines the properties of brass, which must be taken into account, selecting material to solve specific technological problems.
Brass rod - one of the semi-finished products, supplied to various industries
general properties
Adding zinc to copper (that's exactly what brass is made of) allows you to get an alloy, which differs from the base metal not only in its properties and color, but also lower cost. The density of the final alloy, in which zinc may be contained in an amount 5-45%, slightly different from a similar parameter of the base metal - copper. To increase the hardness of brass, as well as improving its antifriction and other mechanical properties in the production process, it is subjected to various types of additional processing.
The main types of brass. Alloys are highlighted in yellow, used for soldering and welding
If we talk about the most significant properties of brass, then they should be attributed:
- high corrosion resistance under normal operating conditions;
- quite good resistance to aggressive environments, such as aqueous saline solutions, carbon dioxide, organic acids;
- beautiful light golden color, which allows you to use this material for the manufacture of decorative items (which even in the photo look very attractive);
- tendency to processing by methods of plastic deformation as in hot, and in the cold state (with, which is important, the color of the finished product does not change);
- low electro- and thermal conductivity;
- simplicity and low cost of production;
- the ability to apply solder using as soft, and brazing.
Due to its high decorativeness and practicality, brass is often used for kitchen furniture
Some brands of brass, in particular those, in the chemical composition of which contains more 20% zinc, poorly tolerate high humidity: in such conditions the surface of products from them can crack. The situation is even more complicated, if in a humid atmosphere, in which such products are operated, contains a significant amount of ammonia. Then the brass not only cracks and loses its original color, but also loses its good performance.
Meanwhile, you can improve the properties of brass alloys in this category, if products from them after production by one of methods of plastic deformation to be subjected to annealing at temperature 240-260 °. Such a procedure, which is often called hardening, leads to increased strength and hardness of brass, as well as the removal of residual stresses in its internal structure.
Improving performance
To improve such properties of brass alloys, as density, color, hardness, corrosion resistance and others, they, except copper and zinc, add alloying elements, which include tin, iron, arsenic, aluminum, nickel, manganese, etc.. The number of such elements, added to the composition of brass, very slightly. Usually, it does not exceed a few percent. The most significant properties, which can be improved in the process of alloying brass, there is a cavitation density, wear resistance and corrosion resistance.
The diagrams show, how brass is stronger and harder than copper due to alloying elements
Alloying elements, added to the chemical composition of brass, affect its properties in different ways. So, silicon in excess of its content in the alloy, reduces its density and, in accordance, worsens its characteristics. If in addition to silicon in brass add lead, then it will be painted in a beautiful color, and its antifriction properties will increase.
To improve this property of brass, as a temporary resistance to rupture, tin is added to its composition, aluminum or manganese. If the brass is alloyed with manganese and iron, the number of which should not exceed 2-3%, it is possible to significantly improve its coefficient of elongation. What is characteristic, other chemical elements, used for alloying brass, worsen this figure.
Physical properties of simple brass (click to enlarge)
To increase the corrosion resistance of brass, the following elements are added to its composition, like nickel, aluminum, tin and manganese. Nickel-plated brass is especially noteworthy, which is called white because of its color. The surface of products from such alloys due to the content of nickel in their composition is not prone to cracking, even when operating in conditions of high humidity.
Adding tin to the composition of brass can increase its density and, in accordance, such is its property, as strength. Products from such alloys can be successfully operated in salt water. Among the great variety of brands of brass are specially designed for use in conditions of constant exposure to sea water.
Chemical composition and examples of brass, containing tin (click to enlarge)
Lead is added to brass mainly for this purpose, to ensure good machinability by cutting. This element provides the formation of short and well-breaking chips during machining on a lathe, milling or drilling equipment. in addition, the content of lead in the processing of brass with metal-cutting tools ensures a surface with low roughness.
Quite a rare element, by means of which carry out alloying of brass, there is arsenic. Ware, made of such brass, successfully operated in fresh highly aggressive liquid media, in a state of normal or elevated temperature. If the chemical composition of brass, doped with arsenic, add iron and nickel, then its products can be successfully operated in acidic and alkaline environments.
Well amenable to cutting, including laser, brass with less zinc content 42%
Advantages and disadvantages of foundry brass
Brass, belonging to the category of multicomponent, are divided into two large groups:
- foundries;
- processed by methods of plastic deformation.
Copper-zinc alloys, belonging to the foundry category, are actively used in modern industry. The high popularity of such materials contributes to that, that they show a low tendency to gas-saturated, what, in turn, allows to receive from them castings with high density and worthy resistance to corrosion. Good deoxidation of such brass, which occurs during casting, contributes to that, that some of the zinc evaporates during melting.
Chemical composition of foundry brass (click to enlarge)
To the most significant properties of brass, belonging to the foundry category, should be credited:
- high fluidity in the molten state;
- slight shrinkage during casting;
- mechanical characteristics, in many respects similar to similar parameters of tin and aluminum bronzes;
- simplicity and low cost of production, if we compare with the technology of obtaining bronze alloys.
Areas of application of foundry brass
Metals in this category have some disadvantages.
- In the process of casting in the products can be formed crystallization shells of fairly large size.
- Special fluxes must be added to the brass, to minimize zinc loss, which occur as a result of evaporation of this metal.
Correction of such shortcomings, associated with the melting of brass, associated with significant financial costs. If you do not take such measures, increasing the cost of the finished alloy, then most of it will have to be recycled.
Deformable brass alloys
Brass, finished products from which and blanks for further processing, produced by methods of plastic deformation, can relate to one thing- or two-phase. Alloys of the first category contain no more in their chemical composition 30% zinc, second - 40-45%.
Areas of application are deformable double brass
Two-phase brass lends itself well to plastic processing only in the hot state, while the color of their surface remains unchanged. In the cold state, they show very low ductility. Brass single-phase group, also differ in color consistency, can be subjected to processing by plastic deformation as in the cold, and hot.
Areas of application of deformable multicomponent brass
Brass items differ not only in their attractive appearance, which can be judged even by the photo, but also excellent mechanical properties, which allows you to successfully use them not only in decorative, but also for practical purposes.
In conclusion, a short video about the features of brass and the nuances of its production.