Brass, properties, characteristics

Brass, which is well known and has been actively used for many years, is an alloy of copper and zinc. The inventor of this material with a number of unique characteristics is considered to be the Englishman James Emerson, who patented it in 1781.

Brass metal products have good corrosion resistance and high strength

Classification of brasses

Depending on the chemical composition there are:

Simple (two-component) brass. They contain only copper and zinc. Simple brass is marked with the letter “L” and a number that indicates the percentage of copper. For example: L85 contains 85% copper and 15% zinc.
Special (multi-component) brass. They contain copper, zinc, lead, aluminum, iron and other elements that improve the basic properties of the material. Such elements are called alloying elements. Special brass is marked with the letter “L”, as well as letters and numbers indicating additional alloying elements and their percentage. For example: LA77-2 contains 77% copper, 2% aluminum and 21% zinc.

Special brasses are divided into classes named after the main alloying element (manganese, aluminum, silicon, tin, nickel, lead).

According to the degree of processing of brass there are:

• deformable (brass tape, wire, pipe, brass sheet); • foundry (fittings, bearings, instrument parts).

There is also a classification based on the amount of zinc in the alloy:

• 5-20% zinc – red brass (tompak); • 20-36% zinc – yellow brass.

How to properly care

Under the influence of the external environment, brass becomes dull, losing its decorative qualities and brightness. To maintain the beauty and shine of the material, you need to properly and regularly care for it. Let's look at the main cleaning methods.

What is forbidden to wash

During production, copper alloy products are protected with a special coating. It is easy to damage a thin layer with sandpaper. Even the finest grain of abrasive material can scratch or completely remove the upper protective tier.

Prohibited means Source market.yandex.ru

To clean brass products, it is prohibited to use vinegar and acid-based products. The aggressive substance destroys the zinc in the alloy. As a result of dezincification, the metal acquires a poisonous red color.

Basic properties of brass

Brass lends itself well to pressure processing. Mechanical properties are relatively high, corrosion resistance is satisfactory. If we compare brass with bronze, then their strength, corrosion resistance and anti-friction properties are less. They are not very stable in air, in salt sea water, carbon dioxide solutions and solutions of many organic acids.

Brass has a beautiful color and, compared to copper, has better corrosion resistance. However, as the temperature increases, the corrosion rate also increases. This process is most noticeable in thin-walled products. Corrosion can be provoked by: humidity, traces of ammonia and sulfur dioxide in the air. To prevent this phenomenon, brass products are subjected to low-temperature firing after processing.

Almost all brasses, when the temperature drops (to helium temperatures), remain ductile and do not become brittle, which makes it possible to use them as a good structural material. Due to the higher recrystallization temperature (300-370°C) than copper, the creep of brasses at high temperatures will be less. At average temperatures (200-600°C), the phenomenon of brittleness occurs, since impurities insoluble at low temperatures (for example: lead, bismuth) form brittle intercrystalline layers. As the temperature increases, the impact strength of brass decreases. Compared to copper, the electrical conductivity and thermal conductivity of brass is lower.

How to distinguish gold from brass

Even though gold and brass look similar, there are ways to tell one from the other. This is checked as follows:

Gold has a more saturated color. In addition, over time, brass darkens because it oxidizes in air, but gold does not.
If you put a magnet near it, brass will be attracted, but gold will not.
Brass has a higher density, which means it is heavier. This is noticeable when throwing pieces of metal in your palms.
Availability of sample.
If you test with acid, the gold will not react and the brass will discolor.

Let's look at how alloying elements affect the properties of brass.

Tin significantly increases the anti-corrosion properties in sea water and increases the strength of the alloy. Brass with tin is often called marine brass.
Manganese increases strength and corrosion resistance. Manganese brasses are often combined with tin, iron and aluminum.
Nickel improves corrosion properties and strength in various environments.
Silicon reduces strength and hardness and also improves weldability. Brasses containing silicon and lead have good anti-friction properties. Such alloys can replace more expensive ones, such as tin bronze.
Lead significantly improves machinability, but at the same time degrades mechanical properties. Lead brass is called automatic, since it is processed on automatic machines. This alloy is the most common.
Aluminum reduces the volatility of zinc due to the formation of a protective film (aluminum oxide) on the surface of molten brass.

Properties and characteristics

The properties of brass are determined by its composition, both chemical and phase. Therefore, it is quite difficult to talk about general technical properties. Each alloy has its own characteristics.

The average data looks like this:

average density – 8300–8700 kg/cubic. m;
specific heat capacity at normal temperature - 0.377 kJ kg−1 K−1 resistivity - (0.07-0.08) 10−6 Ohm m;
thermal conductivity – 0.26–0.592 cal/cm sec, °C, the higher the proportion of copper, the higher the thermal conductivity;
The melting point is determined by the chemical composition and varies from 880–950 C. An increase in the proportion of zinc reduces the temperature;
the material can be welded, but not by fusion welding, but, for example, by contact welding.
Alloys of any composition are well polished.

The introduction of alloying additives significantly affects the physical characteristics. The data given relate specifically to two-component brasses.

We will talk about the production of parts from brass and copper in bulk and to order, as well as the production of other products from it below.

Melting brass in an induction furnace without a graphite crucible is presented in the video below:

Methods of obtaining

The technology for producing brass involves the processes of the copper and zinc industries, as well as the processing of recyclable materials. The raw materials for the production of alloys are blanks of copper, zinc and other metals for the production of multicomponent alloys. We also use our own production waste and secondary raw materials. All blanks are manufactured in accordance with GOST.

For smelting brass, various types of smelting furnaces are used, which are used for smelting copper alloys. The most effective are electric induction low-frequency furnaces with a magnetic core. Melting is carried out under exhaust ventilation, since some elements of the alloy evaporate intensely and can harm human health. It is undesirable to overheat the alloy, due to the likelihood of some components igniting in air. Pure and recycled metals are used as charges for smelting brass.

The raw materials are first prepared and the ovens are cleaned. Copper heated to red heat is placed in a furnace, and then lumps of zinc are added. When melting copper-zinc alloys, the significant oxidation of zinc is taken into account. To reduce oxidation, a number of measures are carried out. To make multi-component alloys, copper is added first, followed by the remaining components carefully.

The homogeneous mass is poured into molds to produce foundry brass. The result is flat and round ingots. After casting, wrought alloys undergo a deformation procedure. The resulting products differ in the degree of hardening and aging, as well as the hardness of the material. Preliminary heat treatment of workpieces significantly increases the strength and corrosion resistance of brass.

How can you tell the difference between a brass alloy and a bronze alloy?

Sometimes it is necessary to distinguish bronze from brass. Bronze bushings are used as bearings.

There are methods for this:

Bronze is darker in color and significantly heavier. This is noticeable when tossing.
Bronze products are harder. The area of the chip will be coarse-grained. The fracture of the brass part will be smooth.
Take 2 test tubes with the reagent. Bronze shavings are placed in one, brass shavings in the other. After heating, a white precipitate will appear in the first. In the second, nothing will happen.
When brass shavings come into contact with sea salt, they change color. No bronze filings.

Brass is an alloy that is no longer possible to live without in everyday life. Metal is included in the technological process of many industrial parts, and it is not so easy to replace it.

Application

Cooling systems for motors, various bushings, and adapters are made from brass. The alloy is used in the construction industry. For example, for the manufacture of plumbing equipment and design elements. Fastening elements such as bolts and nuts are also made from brass. This alloy is used in shipbuilding and in the manufacture of ammunition.

There are several types of rolled brass:

A brass rod
is a long metal product that is a blank for various parts. The rod has different cross-sectional shapes: round, oval, rectangular, square, hexagonal, trapezoidal.
A brass plate
is a flat semi-finished product with a rectangular cross-section more than 25 mm thick, which is produced by rolling or casting. The slabs are soft, hard, semi-hard and extra hard. Brass plates are used in industry for decorative finishing of buildings.
Brass wire
is an elongated profile of small diameter. Wire is used in the production of electrical equipment and decorative elements, as well as in mechanical engineering, aircraft manufacturing, welding and the footwear industry.
Brass pipe
– has high ductility, resistance to corrosion and wear. Pipes are used in housing and communal services, mechanical engineering, instrument making, and electric power.
A brass circle
is a solid round profile. The product is used in the automotive industry, instrument making, and in the manufacture of machine tools and mechanisms.
Brass sheet
is indispensable in printing, automotive, electrical power, instrument making, electrical, construction and chemical industries.

Physicochemical characteristics

Brass has a yellow-golden hue, due to which the material is often used in the manufacture of artistic jewelry. The material is characterized by high ductility, corrosion resistance and anti-friction characteristics. Physical properties allow for polishing, forging, gas and arc welding, and plastic deformation of metal.

The melting point depends on the percentage of zinc content: as it increases, the melting point decreases. On average it is 880-940 degrees Celsius. In the open air, the surface of brass oxidizes and darkens, so it is often treated with a special protective varnish.

Products made of brass differ in their chemical properties from objects made of other metals. Resistance to oxidation and corrosion is much higher than that of copper, but the latter has better electrical and thermal conductivity. Brass alloys are easier to process, but they are inferior in strength to, for example, bronze products.

The special role of brass composition

Brass can look like bronze if the compositions and proportions are chosen correctly and the surface of the brass is treated. Today, due to their lower cost, copper-zinc alloys have begun to gain positions in the market. Once popular bronze chandeliers, sconces, decorative items and faucets are now increasingly made of brass.

And so that external differences in the alloys cannot be discerned, the surface of the brass is subjected to a special chemical composition. This is how they make plumbing brass.

The conquest of the decorative metals market does not end there. Now brass is a material for headboards, candlesticks, kitchen hoods and utensils, and other interior elements. It is not for nothing that alloys received the status of the most important metals in the world. And even typographic fonts are brass.

Alloys, grades

Based on their composition, brass is divided into two-component (zinc alloy) and multi-component. These metal alloys may contain tin Sn, Pb (lead), Al (aluminium), nickel Ni, manganese Mn.

Using the marking formula, it is easy to determine which metals the alloy contains and in what quantities.

The marking of two-component alloys consists of the letter L, to which a number is added - the percentage of copper. Example: L59, L75.

The markings of multi-component brasses indicate the first letters of the metal and its percentage. Example: LTs16K4 - zinc content 16%, silicon 4%, the rest copper.

Microstructure of ground and etched brass alloy under 400x magnification

Main areas of use of brass alloys

In mechanical engineering, brass alloys are used for the production of adapters, bushings, and cooling systems for engines. In construction, this alloy is often used in the manufacture of pipe fittings and individual elements of plumbing equipment.

Brass often becomes a material popular in the design environment: its presentable appearance allows numerous interior components to be made from alloys.

April 16, 2017

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Story

Brass production was practiced in ancient Rome, and later in Egypt, Greece and China. According to information presented in SBIE, the ancient Romans made brass by fusing copper and the mineral gallium in the form of carbon ZnCO3. The purity of such an alloy was not great, so real high-quality brass appeared much later, when in 1746 Andreas Sigismund Maggraf found a way to extract pure zinc by calcining zinc oxide in a retort made of refractory clay without access to air, and condensing the zinc in the gas phase in a refrigerator.

The word zinc goes back to the German zinke (tooth), probably this name is associated with the shape of sphalerite crystals (zinc blende) from which zinc was subsequently mined on an industrial scale. Sphalerite contains zinc sulfide ZnS. Concentrates are obtained from it using a pyrometallurgical scheme. First, the mineral is crushed and then placed in a selective flotation apparatus, where other concentrates are recovered along with the zinc concentrate. Next, zinc concentrates are enriched and reduced by roasting in a fluidized bed, and then by sintering. The distillation method is not currently used to obtain pure zinc. The most widely used method in our time is the hydrometallurgical method of producing Zn by electrolysis.

Metal production

Since the main component of brass is copper, the material is classified as a copper alloy. The production scheme is quite simple. However, from a technological point of view, the process turns out to be complex, since it requires very strict adherence to temperature conditions and processing of raw materials and workpieces.

In general, the production of the alloy looks like this:

melting copper in special crucibles;
introduction of zinc;
introduction of additional components - iron, nickel;
pouring into molds;
hardening - by stamping or drawing.

The matter is further complicated by the fact that the conditions for obtaining alloys largely depend on the composition of the alloy and its purpose.

Below is a video about melting brass at home.

The video below explains how to produce and melt brass at home:

Technologies

The production of brass should begin with the extraction of copper from copper ore. In fact, this is a complex polymetallic raw material, in which the proportion of copper is small. The main components are waste ore, iron and copper, and the first step in obtaining brass is to separate the copper from the other components.

Receiving raw materials

The process is extremely complex, since its goal is to transfer raw materials from a single multicomponent mixture into a heterogeneous system consisting of several phases with different compositions and different properties. Only after this the phases can be separated from each other and compositions suitable for further use can be obtained. A variety of methods are used for this: in some cases, the extracted phase is additionally enriched with the “main” metal, in others, on the contrary, it is depleted, in others they resort to mechanical separation methods when the phases, for example, differ in solubility, and so on.

The following two methods are most often used.

Pyrometallurgical technology involves processing copper ore with subsequent refining of blister copper. It includes smelting, converting copper matte, fire refining - essentially removing large impurities, and electrolytic refining. The latter allows not only deep purification of copper, but also the extraction of any associated components if they are of value.
The hydrometallurgical method is used when using low-grade copper ore. Its essence comes down to leaching - the effect of sulfuric acid, iron sulfate. To do this, the ore is crushed and dissolved in solvents, and then the copper is extracted either by cementation - the deposition of pure copper on iron, for which ordinary scraps of sheet and wire are used, or by electrolysis.

In this way, it is possible to completely extract copper from even the poorest ore.

Obtaining zinc also has its own characteristics, but, in general, is a simpler process.

We will tell you below whether it is possible to weld brass at home and how it is produced at a factory.

Alloy production method

Smelting of brass depends on the composition of the alloy. Here it is necessary to take into account both the different boiling temperatures of metals and different oxidation abilities.

Melting with pure metal - when using recycled metals, the charge can be loaded in any order. If there is pure metal in the charge, then copper is melted first, and then the circulating metals. Zinc and lead, if any, are introduced into the melt last, pre-heated to 100–120 C. Melting is carried out under a layer of charcoal, which is loaded with the first portion of the charge.
Melting silicon brass - this composition tends to absorb reducing gases, so charcoal is not used here. Melting is carried out under a covering flux - glass or borax - to prevent interaction with oxygen. Copper is loaded into the furnace first, then waste and copper-silicon master alloy. Zinc is loaded into the melt last, after the slag has been removed.
Melting of manganese brass is carried out under charcoal or glass flux. In this case, manganese is introduced last along with alloys, after all other ingredients are melted.