The most refractory metal. Characteristics of metals

Metals are the most common material (along with plastics and glass), which is used by people since ancient times. Even then, the man was a well-known characteristic of metals, it also benefited all of their properties to create beautiful works of art, glassware, household items, construction.

One of the main features in the consideration of these materials is their hardness and refractoriness. These qualities allow us to define the scope of use of a particular metal. Therefore, we consider all physical properties and pay special attention to the issues of fusibility.

Physical properties of metals

Characteristics of metals on the physical properties can be expressed in the form of four main points.

1. Metallic luster - all have roughly the same silvery-white beautiful characteristic luster, except copper and gold. They have a reddish and yellow tide, respectively. Calcium is a silvery blue.
2. Physical state - all solids under normal conditions except for mercury which is in liquid form.
3. Electrical and thermal conductivity characteristic of all metals, but expressed in different ways.
4. Malleability and ductility are also common for all metals the parameter, which can vary depending on the particular representative.
5. Melting point and boiling point determines which refractory metal, and some fusible. This parameter is different for all elements.

All the physical properties are due to the special structure of the metal crystal lattice. Its spatial arrangement, shape and strength.

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Fusible and refractory metals

This parameter is very important when it comes to applications of the substances in question. Refractory metals and alloys is the basis of mashino - and shipbuilding, smelting and casting of many important products, acquiring high quality working tool. Therefore knowledge of the melting points and boiling plays a fundamental role.

Describing the metals for strength, you can divide them into hard and brittle. If you talk about refractoriness, here there are two main groups:

1. Fusible - are those that are capable of changing the aggregate state at temperatures below 1000 ^OS. Examples include: tin, lead, mercury, sodium, cesium, manganese, zinc, aluminum and others.
2. Refractory are those whose melting temperature is above the indicated value. Not so much, but in practice is used even less.

Table of metals having melting point over 1000 ^OC below. It and are the most refractory representatives.

This table of metals includes all representatives, whose melting point is above 1000 ^OC. However, in practice many of them will not apply for various reasons. For example, because of economic benefits or due to radioactivity, too high degree of brittleness, susceptibility of corrosion.

Also from the table it is obvious that the refractory metal in the world is tungsten. The lowest level of gold. When working with metals it is important softness. Therefore, many of the above are not used for technical purposes.

The Most refractory metal tungsten

In the periodic system located under the serial number 74. The name given by the name of the famous physicist Stephen Wolfram. Under normal conditions, is a solid refractory metal silver-white color. Has a pronounced metallic sheen. Chemically almost inert in the reaction enters reluctantly.

In nature, found In the form of minerals:

• Wolframite;
• Scheelite;
• Hubnerite;
• Ferberite.

Scientists have proved that tungsten - the most refractory metal of all. However, there are suggestions that cyborgy theoretically able to break the record this metal. But it is a radioactive element with a very short period of existence. So to prove it is impossible.

At a certain temperature (over 1500 ^OC), the tungsten becomes ductile and plastic. Therefore, it is possible to manufacture a thin wire on its basis. This property is used for the manufacture of filaments in a regular household electricbulbs.

As the most refractory metal that can withstand temperature of more than 3400 ^OC, tungsten is used in the following engineering fields:

• As the electrode with argon welding;
• To retrieve acid-resistant, wear-resistant and heat-resistant alloys;
• The heating element;
• Vacuum tubes as filament and so on.

In Addition to the metal tungsten, are widely used in engineering, science and electronics its compounds. As the refractory metal in the world and the connection he forms with very high quality characteristics: durable, resistant to virtually all types of chemical exposure, corrosion, withstand low and high temperatures (win, a sulfide of tungsten, its single crystals and other substances).

Niobium and its alloys

Nb, or niobium, - under normal conditions, silver-white shiny metal. It is also refractory, since the transition temperature to a liquid state for him is 2477 ^OC. it is this quality, as well as the combination of low chemical activity and superconductivity allows the niobium to become more and more popular in practical human activity every year. Today, this metal is used in such industries as:

• Rocket science;
• Aviation and space industry;
• Nuclear energy;
• Chemical apparatus building;
• Radio.

This metal retains its physical properties even at very low temperatures. Products based on it differ in corrosion resistance, heat resistance, durability, excellent conductivity.

This metal is added to the aluminum materials to improve chemical resistance. From it produce cathodes and anodes, they are alloyed with non-ferrous alloys. Even coins in some countries do with the content of niobium.

Tantalum

Metal, in free form and, under normal conditions, covered with an oxide film. Has a set of physical properties that allow it to be a widespread and very important to humans. Its main features are as follows:

1. When the temperature is over 1000 ^OC it becomes a superconductor.
2. This is the most refractory metal after tungsten and rhenium. The melting point is 3017 ^oC.
3. Absorbs gases.
4. Easy to work With, as it is rolled in layers, foil and wire easily.
5. Has good toughness and not brittle, maintains flexibility.
6. Very resistant to chemical agents (does not dissolve even in Aqua Regia).

Owing to these characteristics, has managed to gain popularity as the basis for many high-temperature and acid-resistant, corrosion-resistant alloys. Numerous compounds find application in nuclear physics, electronics, computing devices plan. Are used as superconductors. Before the tantalum was used as an element in incandescent lamps. Now his place was taken by tungsten.

Chromium alloys

One of the hardest metals in the natural bluish-white color. Its melting point is lower than that considered until now the elements, and is 1907 ^OC. However, it is still used in engineering and industry everywhere, as well to mechanical stress, processed and molded.

Chromium is Particularly valuable as applied napylitelem. It is applied to products to give them beautiful Shine, protection from corrosion and improved wear resistance. The process called chrome plating.

The Alloys of chromium very popular. Even a small amount of this metal in the alloy greatly increases the toughness and resistance to impact.

Zirconium

One of the most expensive metals, so its use in technical applications is difficult. However, the physical characteristics make it indispensable in many other industries.

Under normal conditions it is a beautiful silvery-white metal. Has a fairly high melting point - 1855 ^OC. Has good toughness, resistance to corrosion, as chemically active. Also has excellent biological compatibility with the human skin and the whole organism. This makes it a valuable metal for use in medicine (equipment, prostheses and so on).

The Main applications of zirconium and its compounds, including alloy, the following:

• Nuclear energy;
• Pyrotechnics
• The alloying of metals;
• Medicine;
• Manufacturer bioposy;
• Construction material;
• As a superconductor.

Made of zirconium and alloys on its basis are made even jewelry, can influence the improvement of the health of a person.

Molybdenum

If you find out what metal the refractory, that, in addition to the aforementioned tungsten, you can call and molybdenum. Its melting point is 2623 ^OC. thus it is quite solid, ductile and workable.

It is Used mostly not in pure form, and as component alloys. They are due to the presence of molybdenum greatly strengthens the wear resistance, heat resistance andcorrosion.

Some molybdenum compounds are used as technical lubricant. Also, this metal is a dopant material, at the same time affect the strength and corrosion resistance that is very rare.

Vanadium

Gray metal with a silvery sheen. Has a fairly high rate of fusion (1920 ^OC). Mainly used as catalyst in many processes, due to its inertia. It is used in energy as the chemical current source, in the production of inorganic acids. The main importance is not the pure metal, namely some of its compounds.

Rhenium and alloys based on it

What is the refractory after the metal of tungsten? Is rhenium. His record of fusibility is 3186 ^OC. strength exceeds tungsten, and molybdenum. Plasticity it is not too high. Demand for rhenium is very large, but the production is complexity. As a result, it is the most expensive metal available today.

Used to manufacture

• Jet engines;
• Thermocouple;
• Filaments for spectrometers and other devices;
• As a catalyst in oil refining.

All applications is expensive, so it is only used in case of emergency, when to replace anything else is not possible.

Titanium alloys

Titanium is very light metal with a silvery-white color that is widely used in metallurgical industry and Metalworking. Can explode when in fine condition, so is a fire hazard.

Used in aircraft and rocket construction, in production of ships. Widely used in medicine due to biological compatibility with the body (prostheses, piercings, implants, etc.).