The most refractory metal. Metal Characterization

Metals are the most common material (along with plastics and glass) that has been used by people since ancient times. Even then, a person was aware of the characteristics of metals, he used all their properties to advantage to create beautiful works of art, utensils, household items, structures.

One of the main features when considering these substances is their hardness and refractoriness. It is these qualities that make it possible to determine the area of ​​use of one or another metal. Therefore, we consider all physical properties and pay special attention to issues of fusibility.

Physical properties of metals

The physical characteristics of metals can be expressed as four main points.

1. Metallic luster - all have about the same silver-white beautiful characteristic luster, except for copper and gold. They have a reddish and yellow tint, respectively. Calcium - silver blue.
2. The state of aggregation is all solid under ordinary conditions, except for mercury, which is in the form of a liquid.
3. Electrical and thermal conductivity is characteristic of all metals, but is expressed to varying degrees.
4. Durability and ductility are also a common parameter for all metals, which can vary depending on the particular representative.
5. Melting point and boiling point - determines which metal is refractory and which is low melting. This parameter is different for all elements.

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

Fusible and refractory metals

This parameter is very important when it comes to the areas of application of the substances in question. Refractory metals and alloys - this is the basis of machine and shipbuilding, smelting and casting of many important products, obtaining high-quality working tools. Therefore, knowledge of the melting and boiling points plays a fundamental role.

Characterizing metals by strength, they can be divided into hard and brittle. If we talk about refractoriness, then there are two main groups:

1. Fusible ones are those that are capable of changing the state of aggregation at temperatures below 1000 ° C. Examples include tin, lead, mercury, sodium, cesium, manganese, zinc, aluminum, and others.
2. Refractory are those whose melting point is higher than the specified value. There are not so many, but in practice even less is used.

A table of metals having a melting point in excess of 1000 ° C is presented below. It is in it that the most refractory representatives are located.

This table of metals includes all representatives whose melting point is above 1000 ° C. However, in practice, many of them are not used for various reasons. For example, due to economic benefits or due to radioactivity, too high a degree of fragility, susceptibility to corrosion.

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

The most refractory metal is tungsten

In the periodic system it is located under serial number 74. The name was received by the name of the famous physicist Stephen Wolfram. Under ordinary conditions, it is a solid refractory silver-white metal. It has a pronounced metallic sheen. Chemically practically inert, reluctantly enters into the reaction.

It is found in the form of minerals in nature:

• wolframite;
• sheelitis;
• gubernite;
• ferberite.

Scientists have proven that tungsten is the most refractory metal of all existing. However, there are suggestions that the siborg is theoretically able to break the record of this metal. But it is a radioactive element with a very short period of existence. Therefore, to prove this is not yet possible.

At a certain temperature (above 1500 ° C), tungsten becomes malleable and ductile. Therefore, it is possible to manufacture a thin wire based on it. This property is used to make incandescent filaments in ordinary household light bulbs.

As the most refractory metal withstanding temperatures above 3400 ° C, tungsten is used in the following fields of technology:

• as an electrode in argon welding;
• to obtain acid-resistant, wear-resistant and heat-resistant alloys ;
• as a heating element;
• in vacuum tubes like a filament and so on.

In addition to metallic tungsten, its compounds are widely used in technology, science and electronics. As the most refractory metal in the world, it forms compounds with very high quality characteristics: durable, resistant to almost all types of chemical attack, not subject to corrosion, able to withstand low and high temperatures (wins, tungsten sulfide, its single crystals and other substances).

Niobium and its alloys

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

• rocket science;
• aviation and space industry;
• nuclear power;
• chemical engineering;
• radio engineering.

This metal retains its physical properties even at very low temperatures. Products based on it are characterized by corrosion resistance, heat resistance, strength, excellent conductivity.

This metal is added to aluminum materials to increase chemical resistance. Cathodes and anodes are made from it , non-ferrous alloys are alloyed with it. Even coins in some countries are made with the content of niobium.

Tantalum

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

1. At temperatures above 1000 ° C it becomes a superconductor.
2. It is the most refractory metal after tungsten and rhenium. The melting point is 3017 ^about C.
3. Perfectly absorbs gases.
4. It is easy to work with it, as it rolls into layers, foil and wire without much difficulty.
5. It has good hardness and is not brittle, retains ductility.
6. Very resistant to chemical agents (not soluble even in aqua regia).

Thanks to these characteristics, he managed to gain popularity as the basis for many heat-resistant and acid-resistant, anti-corrosion alloys. Its many compounds are used in nuclear physics, electronics, and computing devices. Used as superconductors. Previously, tantalum was used as an element in incandescent lamps. Now his place was taken by tungsten.

Chrome and its alloys

One of the hardest metals in its natural form, a bluish-white color. Its melting point is lower than that of the elements considered so far, and amounts to 1907 ° C. However, it is still used everywhere in engineering and industry, as it lends itself well to mechanical stress, is processed and molded.

Chrome is especially valuable as a sprayer. It is applied to products to give them a beautiful shine, protection against corrosion and increase wear resistance. The process is called chrome plating.

Chrome alloys are very popular. Indeed, even a small amount of this metal in the alloy significantly increases the hardness and resistance of the latter to impacts.

Zirconium

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

Under normal conditions, it is a beautiful silver-white metal. It has a fairly high melting point - 1855 ° C. It has good hardness and corrosion resistance, since it is chemically inactive. It also has excellent biocompatibility with the skin of a person and of the whole organism. This makes it a valuable metal for use in medicine (tools, prostheses, and so on).

The main applications of zirconium and its compounds, including alloys, are as follows:

• nuclear energy;
• pyrotechnics;
• alloying of metals;
• the medicine;
• production of biological dishes;
• construction material ;
• like a superconductor.

Even jewelry can be made of zirconium and alloys based on it, which can affect the improvement of human health.

Molybdenum

If you find out which metal is the most refractory, then, in addition to the indicated tungsten, molybdenum can also be called. Its melting point is 2623 ^about C. Moreover, it is quite hard, ductile and amenable to processing.

It is used mainly not in its pure form, but as an integral component of alloys. They, thanks to the presence of molybdenum, are significantly strengthened in wear resistance, heat resistance and anticorrosion.

Some molybdenum compounds are used as technical lubricants. Also, this metal is an alloying material, which simultaneously affects both strength and anticorrosion, which is very rare.

Vanadium

Gray metal with a silver sheen. It has a fairly high fusibility index (1920 ). It is used mainly as a catalyst in many processes, due to its inertness. It is used in energy as a chemical current source, in the production of inorganic acids. The main value is not pure metal, but precisely some of its compounds.

Rhenium and alloys based on it

What is the most refractory metal after tungsten? This is rhenium. Its melt index is 3186 ° C. It is superior in strength to both tungsten and molybdenum. Its ductility is not too high. Demand for rhenium is very high, but production is difficult. As a result, it is the most expensive metal available today.

It is used for the manufacture of:

• jet engines;
• thermocouples;
• filament for spectrometers and other devices;
• as a catalyst in oil refining.

All applications are expensive, so it is used only in case of emergency, when there is no possibility to replace it with anything else.

Titanium alloys

Titanium is a very light silver-white metal that is widely used in the metallurgical industry and metal processing. May explode when in a finely divided state, therefore it is fire hazard.

It is used in aircraft and rocket science, in the manufacture of ships. It is widely used in medicine due to biocompatibility with the body (prostheses, piercings, implants, etc.).