How to determine tungsten at home? —

We hope that the Bundesbank and of course the German people will use some of this in the near future (up to and including 2022).

Ultrasonic testing of gold bars

Application: Non-destructive testing of the physical integrity of gold bars.

Explanations:

Gold bars were fraudulently counterfeited by inserting bars of non-precious metal of similar density. Such inserts are difficult or impossible to detect by weighing, radiography, or X-ray fluorescence, so some metal technologists resort to drilling holes or cutting ingots to test for integrity. However, a simple ultrasonic test can quickly and reliably locate the inserts without having to drill, cut or otherwise modify the ingot.

Equipment:

Any Olympus flaw detector or phased array instrument such as: EPOCH XT, EPOCH 600, EPOCH 1000, OmniScan SX and OmniScan MX2. It is recommended to use a converter frequency of 2.25 MHz.

Principle:

A fake gold bar with another metal inside changes the path that ultrasonic waves take through the metal in a predictable way. Insertion of material other than gold, as well as voids within the ingot, will change the angles at which the waves are reflected. Large inserts that occupy most of the ingot can also be detected by changes in the speed of sound.

1. Pulse/echo reflection method

Ultrasonic waves passing through any medium will travel in one direction until they reach an interface with another material, causing them to be reflected in the direction of the source.

Ultrasonic flaw detectors and phased array instruments generate pulses of high-frequency sound waves from small hand-held transducers. Sound energy interacts with the test object, the device measures and displays a picture of the distribution of reflected signals. Signals reflected from the inside of the gold bar, rather than from its opposite surface, change the pattern and indicate the presence of either an insert of another metal or an internal cavity.

In this test, the sensor's reference signal, i.e., the signal reflected by the bottom surface of a known gold bar, is first recorded. Strobe pulses can be used to measure the time it takes for the ultrasonic wave to reach the bottom surface. All reflected signals from the area marked by the strobe pulse indicate that the sound stream is reflected from the boundary of the heterogeneity of the material, and further inspection of the ingot is necessary. Below are typical pictures on the screen.

Images on the flaw detector screen in cases of monolithic metal (above) and damaged metal (below).

Note. The signal appears in the interval marked in red.

Images of solid metal (above) and metal with heterogeneity (below), obtained using a phased array device. The heterogeneity appears in color where there should be a white background.

2. Speed ​​measurement method

The speed of sound in pure gold is 3.240 m/s or 0.1275 in/µs. In harder gold alloys used in jewelry, the speed is higher, but each alloy also has a specific speed value. If the speed of sound propagation is different from the expected value, this means that the composition of the metal has been changed.

Source: goldenfront.ru

Tungsten metal or non-metal

Read also: 10 interesting facts about pine resin

Tungsten also belongs to the group of metals characterized by high refractoriness. It was discovered in Sweden by a chemist named Scheele. It was he who was the first to isolate the oxide of an unknown metal from the mineral wolframite in 1781. The scientist managed to obtain tungsten in its pure form after 3 years.

Description

Tungsten belongs to a group of materials that are often used in various industries. It is designated by the letter W and has serial number 74 in the periodic table. It is characterized by a light gray color. One of its characteristic qualities is high refractoriness. The melting point of tungsten is 3380 degrees Celsius. If we consider it from the point of view of application, the most important qualities of this material are:

• density;
• melting temperature;
• electrical resistance;
• linear expansion coefficient.

When calculating its characteristic qualities, it is necessary to highlight the high boiling point, which is at the level of 5,900 degrees Celsius . Another feature is its low evaporation rate. It is low even in temperature conditions of 2000 degrees Celsius. In terms of electrical conductivity, this metal is 3 times superior to such a common alloy as copper.

Factors limiting the use of tungsten

There are a number of factors that limit the use of this material:

• high density;
• significant tendency to become brittle at low temperatures;
• low oxidation resistance.

In appearance, tungsten is similar to ordinary steel . Its main application is mainly related to the production of alloys with high strength characteristics. This metal can be processed, but only if it is preheated. Depending on the type of treatment chosen, heating is carried out to a certain temperature. For example, if the task is to forge rods from tungsten, then the workpiece must be preheated to a temperature of 1450-1500 degrees Celsius.

How to determine the type of metal at home?

Recycling and reusing items such as plastic bottles, worn-out clothing and newspapers is very important and forms part of everyday life, helping to increase your contribution to the green movement. One segment of the recycling industry that may not be as popular, but is no less important, is scrap metal recycling. The export of scrap metal is widespread in the Russian Federation and, by processing metal, we reduce the volume of ore production throughout the world.

Some of these metals include copper, steel, aluminum, iron and wire, but are often simply thrown into the trash due to a lack of knowledge and sources of metal recycling. We are here to help educate the public about the possibilities of collecting certain metals and taking them to the right place.

Scrap metal recycling makes money

What many people don't know is that most scrap metal can be recycled for a fee at local scrap metal collection points across the country, thus joining the green movement.

Scrap metal collection centers work with customers from the trade industry who deal with metal every day. Many of them are construction companies that have tons of metal beams from structures, electrical companies that have wires and electrical equipment, or plumbers that have copper piping and brass fixtures. While scrap yards receive a huge amount of such metals from the trading industry, ordinary people are also welcome and encouraged to bring their scrap metal, get paid and have the metal recycled at the right place.

Magnet evaluates the value of metal

Identifying and separating ferrous and non-ferrous metals is the first important step before you recycle the metal. The simplest and most accessible way to determine metal is to test it with a magnet.

Tip: If you don't have a portable magnet on hand, any magnet will do - even one from your refrigerator.

If a magnet is attracted to your metal: You are holding a ferrous (ferrous) metal, something as simple as steel or iron. Ferrous metals don't cost much at scrap yards, but they will be accepted to make sure the metal is recycled properly.

If the magnet does not stick to the metal: You have iron-free metal. Many common metals such as copper, aluminum, brass, stainless steel and bronze are classified as non-ferrous metals. These metals are very valuable for recycling and they pay more for them at scrap metal collection points.

So you've got your metal sorted, now call the metal collection center and ask what metals they accept to get an idea of ​​the procedure before you go there yourself. Homeowners are often apprehensive about going to scrap yards, but making sure your scrap metal is carefully sorted will take a step in the right direction. Some places recommend that you bring the scrap metal to them and put it on a scale, while others will remove it all themselves.

This will help you identify the metal:

The most difficult part of metal recycling is determining its grade and value. Knowing these basic metals will make the task much easier:

In good condition it has a reddish color, and if it is quite worn out, the color may be dark brown with green rust spots. Find out how to recycle copper and other scrap metals using the contact section. Copper is a common material in home construction. It can be found throughout the home as plumbing pipes, roof drainpipes, as well as internal parts of air conditioners and general electrical wiring. Copper can also be found in electrical wires: under black or colored braiding there is brightly colored copper wire. Copper is one of the most valuable materials to recycle, so collecting it and storing it separately from other metals can net you some monetary rewards.

Characteristics of nichrome and its application

The alloy consists of 50−80% nickel and 15−24% chromium with a small amount of additives in the form of aluminum, manganese and chromium. Alloying with rare earth components is possible to increase service life.

Cr20Ni80 is the most common type of material, and wire made from this alloy is the most popular. In second place are stripe and ribbon, and the least popular is the leaf shape.

Depending on the grade of the alloy, it has the following physical characteristics:

1. Melting point 1100 - 1400 °C, operating temperature 800−1100 °C.
2. Specific resistance depending on the alloy = 1.05−1.4 Ohmxmm²/meter.
3. Thermal conductivity coefficient = 11.3W/(mxK)

Nichrome has a number of advantages over wires made of other alloys:

Nichrome is used in most devices, such as:

As you can see, nichrome has good physical properties and is not subject to corrosion, which extends its service life compared to other types of similar materials used for the same purposes. The scope of its use in everyday life is also vast, so the question is often asked - where can you get nichrome thread. Most common options for obtaining nichrome will be listed below.

Tungsten and rhenium

The alloy of these two elements is quite widely used for the manufacture of high-temperature thermocouples. Tungsten - what metal? Like rhenium, it is a heat-resistant metal, and alloying the elements reduces this property. But what if you take two almost identical substances? Then their melting point will not decrease.

If rhenium is used as an additive, an increase in the heat resistance and ductility of tungsten will be observed. This alloy is produced by smelting in powder metallurgy. Thermocouples made from these materials are heat-resistant and can measure temperatures above 2000°C, but only in an inert environment. Of course, such products are expensive, because in one year only 40 tons of rhenium and only 51 tons of tungsten are mined.

Events

International geological and geophysical conference and exhibition “GeoEurasia-2021. Geological exploration in modern realities"

International conference and technical visit “Mining industry of Russia: construction and modernization”

Mining industry in Russia and the CIS

XXVII International Specialized Exhibition of Mining Technologies "COAL OF RUSSIA and Mining"/VI International Specialized Exhibition "Subsoil of Russia 2020"/XI International Specialized Exhibition "Security, Labor and Life Safety"

Areas of application

Tungsten wire is used in various fields of production and the national economy. It is used for the manufacture of spirals and spring elements intended for incandescent light bulbs.

Tungsten-rhenium variety (TRN) is used for the production of traverses.

Tungsten is a refractory metal, so wire products based on it are indispensable when creating resistance elements in heating devices. It is contained in thermoelectric converters and loop heaters.

The manufacturing process of tungsten rolled metal is quite complex, involving powder metallurgy techniques. It is very popular in the electrical and radio engineering industries. It is actively used in the creation of LCD television screens. The most popular wire products are tungsten anhydride and obtained from salts of this metal.

It is used to make parts of X-ray equipment, which during operation are subject to vibrations and strong heating. Meshes and filter mechanisms based on it are used in the chemical industry.

Tungsten rods

Of course, this is one of the most common types of products made from this metal. What kind of tungsten is used to make them? These are the posts described above, which are forged on a rotary forging machine. It is important to note that the process occurs in a heated state (1450-1500°C). The resulting rods are used in a wide variety of industries. For example, for the manufacture of welding electrodes. In addition, tungsten rods are widely used in heaters. They operate in furnaces at temperatures up to 3000 °C in vacuum, inert gas or hydrogen. The rods can also be used as cathodes of electronic and gas-discharge devices, radio tubes.

Interestingly, the electrodes themselves are non-consumable, and therefore during welding, the supply of filler material (wire, rod) is necessary. When melted with the material being welded, it creates a weld pool. These electrodes are usually used for welding non-ferrous metals.

Deposits and production

Wolframites (Hübnerite, Ferberite) and scheelite are suitable for industrial mining.

Classification of deposits:

• stockwork wolframite;
• stockwork scheelite;
• vein wolframite;
• skarn-scheelite.

The largest reserves of tungsten ores are:

• China;
• Canada;
• Russia;
• Australia;
• USA.

Russian reserves of tungsten ores originate from primary deposits.

Being in nature

The tungsten Clarke of the earth's crust is (according to Vinogradov) 1.3 g/t (0.00013% of the content in the earth's crust). Its average content in rocks, g/t: ultrabasic - 0.1, basic - 0.7, intermediate - 1.2, acidic - 1.9.

Main article:
Tungsten ores
Tungsten occurs in nature mainly in the form of oxidized complex compounds formed by tungsten trioxide WO3 with oxides of iron and manganese or calcium, and sometimes lead, copper, thorium and rare earth elements. Wolframite (tungstate of iron and manganese n)

FeWO4
m
MnWO4 - ferberite and hübnerite, respectively) and scheelite (calcium tungstate CaWO4). Tungsten minerals are usually embedded in granite rocks, so the average tungsten concentration is 1-2%.

Place of Birth

Kazakhstan, China, Canada and the USA have the largest reserves; deposits are also known in Bolivia, Portugal, Russia, Uzbekistan and South Korea. World tungsten production is 49-50 thousand tons per year, including 41 in China, 3.5 in Russia; Kazakhstan 0.7, Austria 0.5. Main exporters of tungsten: China, South Korea, Austria. Main importers: USA, Japan, Germany, UK. There are also tungsten deposits in Armenia and other countries.

History of discovery

Miners of Saxony in the XIV-XVI centuries. noticed that after processing tin ores a lot of slag remains. Workers in the local mines called it a by-product that “devours” the tin, likening it to “a wolf devouring a sheep.” This is how the name of the slag “wolfrahm” (“wolf foam” from German) was formed.

When chemist Karl Scheele treated “tungsten” (“heavy stone” in Swedish) with nitric acid, he was able to isolate a new metal, which received the same name. The event occurred in 1781. Later, a series of analyzes were carried out that showed that the Swedish chemist managed to discover not tungsten itself, but its oxide. Therefore, the mineral was renamed “scheelite”.

Two years after the discovery made by Karl Scheele, chemists from Spain, the Eluard brothers, announced that they were able to isolate pure tungsten from wolframite mines in Saxony. It should be noted that neither Scheele nor the Eluard brothers insisted that they were the discoverers of tungsten.

Until the beginning of the 20th century, the chemical element was called “tungsten” and was designated by the symbol “Tu”. The term “tungsten” and the symbol “W” were approved only in the middle of the last century.

Applications and Uses of Tungsten

Back in the 16th century, the mineral wolframite was known, which translated from German ( Wolf Rahm

) means "wolf's cream". The mineral received this name due to its characteristics. The fact is that tungsten, which accompanied tin ores, during the smelting of tin turned it simply into foam of slag, which is why they said: “devours tin like a wolf devours a sheep.” Over time, it was from wolframite that the name tungsten was inherited by the 74th chemical element of the periodic system.

Characteristics of elements

When considering the lower elements of the subgroup, attention is drawn to the growth of the ionization potential with a practically unchanged atomic and ionic radius. This means densification of the electron shells of atoms. The proximity of the radii makes molybdenum more similar to tungsten than these metals are to chromium. The stability of their oxidation states is different than that of chromium. The +2 state is almost never found in it, and +3 is uncharacteristic for W; +4 and +6 are more stable.

The similarity with elements of the VIA subgroup is manifested in the formation of compounds SF6, WF6 and SO ions, the bonds in which are largely covalent.

How much does a meter of nichrome wire cost?

Page 1

Element properties

As mentioned earlier, tungsten is one of the most refractory metals. It has a shiny light gray color. Its melting point is 3422°C, its boiling point is 5555°C, its pure density is 19.25 g/cm3, and its hardness is 488 kg/mm². It is one of the heaviest metals and has high corrosion resistance. It is practically insoluble in sulfuric, hydrochloric and hydrofluoric acids, but quickly reacts with hydrogen peroxide. What kind of metal is tungsten if it does not react with molten alkalis? Reacting with sodium hydroxide and oxygen, it forms two compounds - sodium tungstate and ordinary water H2O. Interestingly, as the temperature rises, tungsten self-heats, and then the process occurs much more actively.

Main characteristics of tungsten

For practical use, high levels of the following characteristics are most important:

• electrical resistance;

• linear expansion coefficient;

• melting temperature.

Pure tungsten has high ductility and does not dissolve in a special acid solution without preheating to at least 500 0 C. It easily reacts with carbon, which results in the formation of tungsten carbide, known for its high strength. The metal is also known for its oxides, the most common of which is tungsten anhydride. Its main advantage over the others is the ability to restore the powder to the state of a compact metal, with the by-product formation of lower oxides.

Sandvik Coromant cutting inserts using tungsten carbide

Among the main characteristics that make the use of tungsten difficult are the following:

• high density;

• fragility and tendency to oxidize at low temperatures.

In addition, the high boiling point as well as the evaporation point make it difficult to extract the compact material.

Peculiarities

For the manufacture of tungsten wire - GOST 18903-73 - forged rods are used. During the drawing process, a gradual decrease in temperature is performed. The product is then cleaned by annealing and electrolytic polishing.

The raw material for the manufacture of this type of wire products is the most refractory metal. This material is heat-resistant and durable, and is not afraid of acidic and alkaline environments. Such characteristics make it possible to use tungsten wire for the manufacture of parts intended to operate under heating conditions, as a result of which they do not lose their original properties.

The characteristic mechanical parameters of this type of wire products (higher hardness, wear resistance when heated, low coefficient of thermal expansion), superior to many similar materials, make tungsten products very popular.

This type of laminated metal is characterized by a high modulus of elasticity, excellent ohmic resistance and good thermal conductivity. It is a durable and reliable material that can withstand extreme operating conditions, making it indispensable in various manufacturing industries.

There are several brands of such wire. The classification is based on the cross-sectional diameter and the percentage of tungsten in the material.

The wire diameter can vary from 12.5 to 500 microns.

The most popular brand is VA. The BPH grade is used to produce cathodes for electronic devices.

Tungsten laminates of the VM and VT brands are also in demand.

It is the brand that determines the scope of application of the material.

Tungsten and wire

Here is another type of widespread product. Tungsten wire is made from the forged rods we discussed earlier. Drawing is carried out with a gradual decrease in temperature from 1000°C to 400°C. The product is then cleaned by annealing, electrolytic polishing or electrolytic etching. Since tungsten is a refractory metal, the wire is used in resistance elements in heating furnaces at temperatures up to 3000°C. Thermoelectric converters are made from it, as well as spirals of incandescent lamps, loop heaters and much more.

Tungsten - properties and applications

Of all the metals known today, tungsten is the most refractory. It occupies position 74 in the periodic table and has a number of properties similar to molybdenum and chromium, which are in the same group with it. In appearance, tungsten is a gray solid with a characteristic silvery tint.

Main characteristics of tungsten

For practical use, high levels of the following characteristics are more important:

• electrical resistance;

• linear expansion coefficient;

Pure tungsten has high ductility and does not dissolve in a special acid solution without preheating to at least 5000C. It reacts easily with carbon to form tungsten carbide, known for its high strength. The metal is also known for its oxides, the most common of which is tungsten anhydride. Its main advantage over others is the ability to reduce dust to a compact metallic state with the lateral formation of lower oxides.

Sandvik Coromant tungsten carbide inserts

Among the main features that make it difficult to use tungsten are the following:

• fragility and tendency to oxidize at low temperatures.

In addition, the high boiling point as well as the evaporation point make it difficult to extract the compact material.

Alloys containing tungsten

Today, single-phase tungsten alloys are distinguished. This involves the introduction of one or more elements. The best known compounds are tungsten and molybdenum. An alloy with this element increases the tensile strength of tungsten. In addition, single-phase alloys include the following systems: tungsten-titanium / zirconium, niobium, hafnium.

However, rhenium gives tungsten greater ductility, while maintaining other properties at its characteristic high level. But the practical application of such compounds is limited by the difficulties in extracting Re.

Since tungsten is the most refractory material, it is difficult to obtain its alloys using the traditional method. At the melting point of tungsten, other metals already boil or even go into the gas phase. Modern technologies make it possible to produce a number of alloys by electrolysis. For example, tungsten-nickel-cobalt, which is used not for the manufacture of entire parts, but for applying a protective layer to less durable metals.

In addition, the method of producing tungsten alloys using powder metallurgy methods is still relevant in industry. This requires the creation of special process conditions, including the presence of a vacuum. The peculiarities of the interaction of metals with tungsten make it preferable for compounds of a non-combined nature, but using 3, 4 or more components. Such alloys are especially hard, but the slightest deviation from the percentage of one or another element leads to an increase in the fragility of the finished alloy.

Tungsten, like many other rare elements, does not occur in nature. Therefore, metal mining is not accompanied by the construction of large industrial complexes. The process of obtaining the material is conditionally divided into the following stages:

1. Extraction of rare metal ores.
2. Creation of conditions for the possible separation of tungsten from the processed mass.
3. The concentration of a material in the form of a solution or precipitate.
4. Purification of the resulting chemical compound.
5. Get a pure substance.

Tungsten Ore

The process of creating a compact metal such as tungsten wire is more complex. The main difficulty is that even the slightest impurity should not be allowed to enter, which sharply worsens the properties of the fuse and resistor.

Application area of ​​tungsten

This metal is used to make filaments, X-ray tubes, heaters, and screens for vacuum furnaces intended for use in high-temperature conditions.

X-ray tube with tungsten filament

Alloy tungsten steel has high strength properties. Products from these types of alloys are used for the manufacture of tools for a wide range of purposes: medicine, well drilling, products for processing materials in mechanical engineering (cutting inserts, as in the photo above). The advantage of the connection is its resistance to abrasion and the unlikely occurrence of cracks during operation. The most well-known type of steel in tungsten construction is called “win-win.”

Tungsten scrap

The chemical industry has also found use for tungsten. It is used to make paints, catalysts and pigments.

The nuclear industry uses crucibles made of this metal, as well as special containers for storing radioactive waste.

Tungsten coating has already been discussed briefly. Used for materials operating at high temperatures in reducing and neutral environments, as a protective film.

Rods used in arc welding are also known. Since tungsten is invariably a refractory metal during welding, it is used with filler wire.

Tungsten Characteristics

Tungsten is a light gray transition metal. Has an external resemblance to steel. Due to its rather unique properties, this element is a very valuable and rare material, the pure form of which does not exist in nature. Tungsten has:

• a fairly high density, which equates to 19.3 g/cm 3 ;
• high melting point of 3422 0 C;
• sufficient electrical resistance – 5.5 μOhm*cm;
• normal indicator of the linear expansion parameter coefficient equal to 4.32;
• the highest boiling point among all metals, equal to 5555 0 C;
• low evaporation rate, even despite temperatures exceeding 200 0 C;
• relatively low electrical conductivity. However, this does not prevent tungsten from remaining a good conductor.

Table 1. Properties of tungsten

All this makes tungsten a very durable metal that is not susceptible to mechanical damage. But the presence of such unique properties does not exclude the presence of disadvantages that tungsten also has. These include:

• high fragility when exposed to very low temperatures;
• high density, which makes its processing difficult;
• low resistance to acids at low temperatures.

Definition - tungsten

Determination of tungsten by the thiocyanate method, E. B. Sendel, Colorimetric determination of trace metals, Goskhimizdat, 1949, p. [1]

The determination of tungsten by the oxidation-reduction method is complicated by the low normal potential of the WVI / WV system. The conditions for the reduction of tungsten (VI) with ascorbic acid are described in the Vanadium section (see page [2]

The determination of tungsten in pure products is a relatively simple task and can be accomplished by treatment with acids alone. Sodium, potassium, ammonium salts, phosphorus, molybdenum, arsenic, fluorine and organic substances, such as tartaric acid, interfere with the precipitation of tungsten by treatment with acids when heated. These elements also slow down the precipitation of cinchonin to a certain extent. [3]

The determination of tungsten by the oxidation-reduction method is complicated by the low normal potential of the WVI / WV system. The conditions for the reduction of tungsten (VI) with ascorbic acid are described in the Vanadium section (see page [4]

The determination of tungsten in pure products is a relatively simple task and can be accomplished by treatment with acids alone. In the case of analyzing complex materials, the isolation of tungstic acid with acids alone is not reliable enough and at the end of the operation, cinchonin should be added, which forms an insoluble compound with tungsten a. Sodium, potassium, ammonium salts, phosphorus 3, molybdenum, arsenic, fluorine and organic substances, such as tartaric acid, interfere with the precipitation of tungsten by treatment with acids when heated. These elements also slow down the precipitation of cinchonin to a certain extent. [5]

The determination of tungsten is based on its isolation from a sample solution in the form of acid-soluble tungstic acid H2W04 - yellow H2O; in this case, the tungsten is simultaneously separated from most of the associated components. The formation of tungstic acid precipitate occurs as a result of the oxidation of carbide and metal tungsten by the action of nitric acid. Tungsten is usually not all precipitated; a small part of it remains in solution. The tungstic acid precipitate is capable of coprecipitating impurities from the solution (silicic acid, iron, phosphorus, chromium, vanadium, molybdenum, niobium, etc.), therefore titrimetric and photometric methods have certain advantages, since contaminants do not have a significant effect here, as happens in gravimetric method. [6]

Determination of tungsten by the thiocyanate method, E. B. Sendel, Colorimetric determination of trace metals, Goskhimizdat, 1949, p. [7]

It is better to determine tungsten in the form of WO3, which is brought to a constant weight by calcination no higher than 900. [8]

Determination of tungsten Determination is carried out in the same way as in the pobedite mixture. [9]

The determination of tungsten (VI) by the oxidation-reduction method is complicated by the low standard potential of the WVI / WV system. Therefore, for amperometric determination it is necessary to resort to very strong reducing agents, for example, chromium (II) [I], which is associated with certain inconveniences due to the fact that solutions of chromium (II) are unstable during storage. [10]

Gold or tungsten? Here's how to find out...

We hope that the Bundesbank and of course the German people will use some of this in the near future (up to and including 2022).
Ultrasonic testing of gold bars

Application: Non-destructive testing of the physical integrity of gold bars.

Explanations:

Gold bars were fraudulently counterfeited by inserting bars of non-precious metal of similar density. Such inserts are difficult or impossible to detect by weighing, radiography, or X-ray fluorescence, so some metal technologists resort to drilling holes or cutting ingots to test for integrity. However, a simple ultrasonic test can quickly and reliably locate the inserts without having to drill, cut or otherwise modify the ingot.

Equipment:

Any Olympus flaw detector or phased array instrument such as: EPOCH XT, EPOCH 600, EPOCH 1000, OmniScan SX and OmniScan MX2. It is recommended to use a converter frequency of 2.25 MHz.

Principle:

A fake gold bar with another metal inside changes the path that ultrasonic waves take through the metal in a predictable way. Insertion of material other than gold, as well as voids within the ingot, will change the angles at which the waves are reflected. Large inserts that occupy most of the ingot can also be detected by changes in the speed of sound.

1. Pulse/echo reflection method

Ultrasonic waves passing through any medium will travel in one direction until they reach an interface with another material, causing them to be reflected in the direction of the source.

Ultrasonic flaw detectors and phased array instruments generate pulses of high-frequency sound waves from small hand-held transducers. Sound energy interacts with the test object, the device measures and displays a picture of the distribution of reflected signals. Signals reflected from the inside of the gold bar, rather than from its opposite surface, change the pattern and indicate the presence of either an insert of another metal or an internal cavity.

In this test, the sensor's reference signal, i.e., the signal reflected by the bottom surface of a known gold bar, is first recorded. Strobe pulses can be used to measure the time it takes for the ultrasonic wave to reach the bottom surface. All reflected signals from the area marked by the strobe pulse indicate that the sound stream is reflected from the boundary of the heterogeneity of the material, and further inspection of the ingot is necessary. Below are typical pictures on the screen.

Images on the flaw detector screen in cases of monolithic metal (above) and damaged metal (below).

Note. The signal appears in the interval marked in red.

Images of solid metal (above) and metal with heterogeneity (below), obtained using a phased array device. The heterogeneity appears in color where there should be a white background.

2. Speed ​​measurement method

The speed of sound in pure gold is 3.240 m/s or 0.1275 in/µs. In harder gold alloys used in jewelry, the speed is higher, but each alloy also has a specific speed value. If the speed of sound propagation is different from the expected value, this means that the composition of the metal has been changed.

Use based on ability to protect against radiation

Tungsten collimators in surgery.

• According to this criterion, tungsten alloys are ahead of cast iron, steel, lead and water, which is why collimators and protective screens that are used in radiotherapy are made from metal. Tungsten alloys are not subject to deformation and are highly reliable. The use of multi-leaf collimators makes it possible to direct radiation to a specific area of ​​the affected tissue. During therapy, X-rays are first taken to localize the location and determine the nature of the tumor. Then the collimator blades are moved by an electric motor to the desired position. 120 petals can be used, with the help of which a field is created that follows the shape of the tumor. Next, high radiation rays are directed to the affected area. In this case, the tumor receives radiation by rotating a multileaf collimator around the patient. To protect neighboring healthy tissues and the environment from radiation, the collimator must be highly accurate.
• Special ring collimators made of tungsten have been developed for radiosurgery, the irradiation of which is directed to the head and neck. The device provides high-precision focusing of gamma radiation. Tungsten is also included in plates for computed tomographs, shielding elements for detectors and linear accelerators, dosimetric equipment and non-destructive testing instruments, and containers for radioactive substances. Tungsten is used in drilling devices. Screens are made from it to protect submersible instruments from X-ray and gamma radiation.

Production

Tungsten wire, like thread, is made by drawing. The starting material for its production is rods with a diameter of 2.75 mm. Due to the properties of the metal, drawing must be carried out in conjunction with heating the workpiece. At room temperature, this material cannot be processed by pressure due to its brittleness, but when heated, W acquires sufficient ductility. Tungsten filament is a wire of small diameters. As a rule, its size is 0.1 mm or less. The starting material for production is wire. Despite the fact that the GOST 25501-82 standard, which defines the names of semi-finished products, does not contain a definition of thread, this term is quite often used in the professional environment. Depending on the brand and product group, it may be additionally subjected to heat treatment, such as annealing and chemical treatment, such as etching.

Tungsten thread and wire, or rather, their dimensions, properties, delivery condition and other technological parameters must meet the requirements of a number of standards. Among them are GOST 18903-73, TU 48-19-39-85, TU 48-19-309-79 and others.

Making tungsten jigs at home

Tungsten jigs are deservedly in demand among fishermen who love winter fishing, both with a jig and a float rod. Due to the high density of the material, the jig is heavy with a small size, which is very important when fishing from great depths. Moscow fishermen can easily purchase such jigs, but what should a fisherman do if he lives far from a large city. In addition, store-bought jigs are not always presented in the required range. That is, there are no smallest, or vice versa, the largest. Since I have been engaged in the industrial production of jigs from heavy alloys for many years, I consider it useful to share with my colleagues my old experience of making jigs using an artisanal method at home.

The easiest way to make a jig is from tungsten-nickel-iron (TNI) and tungsten-nickel-copper (TNM) alloys. These alloys have a specific gravity of about 15 g/cc, which is already significantly higher than that of lead or tin. At the initial stage of manufacturing waste electrical stamps and current collector brushes, tetrahedral columns must be cut using a hacksaw with a fine tooth or a disk cutter. The side of the workpiece should be 0.5-1 mm larger than the size of the jig. Next, you can clamp the post into the chuck of an electric drill, use a needle file to give the end of the workpiece the shape of a jig, leaving a jumper between the workpiece and the post (Fig. 1)

.
Then a hole for the hook is drilled from the end of the workpiece, and a hole for the fishing line is drilled on the side (Fig. 2)
. After this, the jig blank is cut off from the post. To drill holes, you can use drills with a diameter of 0.7 to 1.5 mm; during drilling, it is useful to use a lubricating emulsion (for example, you can use milk at home). Drill speed: 300-500 rpm. In this way it is quite easy to make any jig that has the shape of a rotation. If you have access to a lathe, then it is easier to grind the posts, turning them into cylindrical blanks, then use a cutter to give the jig the desired shape. It is better to use cutters of brands VK3-VK8, and drills R13-R18, but R6M5 are also suitable.

However, it is more interesting to make an irregularly shaped jig (Fig. 3)

. Then you need to be patient and use a needle file (not a diamond one) to cut out the workpiece, drill it and cut it off from the post. Abrasive stones can also be used for rough processing of the workpiece. It is better to process tungsten alloys with conventional needle files, since when using a diamond tool, tungsten carbide may form, which will make manual processing very difficult. Also, don’t be surprised if one needle file is used to make one or three jigs.

The heaviest jigs are obtained if tungsten electrodes are used as the starting material. Such electrodes are used when welding in argon. On an emery machine, the end of the electrode is shaped into the body of a jig. Then, using a diamond-coated disk with a thickness of 0.27 to 0.80 mm, a groove is cut into the workpiece to such a depth that its end is located at the location of the future hole for the fishing line (Fig. 4)

. The disk rotation speed must be at least 3000 rpm. The workpiece is broken off from the electrode and the end is cleaned.

Jig blanks are copper-plated using any galvanic method described in the literature, for example, in the book “300 Practical Tips”, or any other. After copper plating, nichrome, or even better, tungsten wire is inserted into the slot or hole for the fishing line, a hook is inserted into the workpiece, and the whole assembly is soldered with tin solder. During soldering, it is important not to overheat the workpiece, otherwise the copper coating may peel off from the workpiece and the hook may become loose. After the jig has cooled, the wire is pulled out and the jig is ready.

Source: www.ohotniki.ru

Heavy tungsten alloys

All tungsten-based alloys that have a high density are called heavy. They are obtained only using powder metallurgy methods. Tungsten is always the basis of heavy alloys, where its content can be up to 98%. In addition to this metal, nickel, copper and iron are added to heavy alloys. However, they may also include chromium, silver, cobalt, and molybdenum. The most popular alloys are VMF (tungsten - nickel - iron) and VNM (tungsten - nickel - copper). The high level of density of such alloys allows them to absorb dangerous gamma radiation. Wheel flywheels, electrical contacts, and rotors for gyroscopes are made from them.

Tungsten compounds with carbon

Tungsten carbides are considered very important from a practical point of view. They are used for the manufacture of hard alloys. Compounds with carbon have a positive electrical resistance coefficient and good metal conductivity. Tungsten carbides are formed in two types: WC and W2C. They differ in their behavior in acids, as well as in their solubility in other carbon compounds.

Two types of hard alloys are made based on tungsten carbides: sintered and cast. The latter are obtained from a powdered compound and carbide with a deficiency of C (less than 3%) by casting. The second type is made from tungsten monocarbide WC and a cementitious binder metal, which can be nickel or cobalt. Sintered alloys are produced only by powder metallurgy. The cementitious metal powder and tungsten carbide are mixed, pressed and sintered. Such alloys have high strength, hardness and wear resistance.

In the modern metallurgical industry they are used for metal cutting and for the manufacture of drilling tools. One of the most common alloys are VK6 and VK8. They are used for the manufacture of cutters, cutters, drills and other cutting tools.

The scope of application of tungsten carbides is quite extensive. So, they are used to make:

• armor-piercing supplies;
• engine parts, aircraft, spacecraft and rockets;
• equipment in the nuclear industry;
• surgical instruments.

In the West, tungsten carbides are especially widely used in jewelry, especially for making wedding rings. Metal looks beautiful, aesthetically pleasing, and is easy to process.

This is because they are incredibly durable. To scratch such a product, you will have to make a lot of effort. Even after a few years, the ring will look like new. It will not fade, the relief pattern will not be damaged, and the polished part will not lose its shine.

Production of tungsten

Tungsten, along with molybdenum, rubidium and a number of other substances, is part of a group of rare metals that are characterized by a very low distribution in nature. Due to this, it cannot be extracted in the traditional way, like many minerals. Thus, the industrial production of tungsten consists of the following stages:

• extraction of ore, which contains a certain proportion of tungsten;
• organizing appropriate conditions in which metal can be separated from the processed mass;
• concentration of a substance in the form of a solution or precipitate;
• purifying the resulting chemical compound from the previous step;
• isolation of pure tungsten.

Thus, the pure substance from the mined ore containing tungsten can be isolated in several ways.

1. As a result of beneficiation of tungsten ore by gravity, flotation, magnetic or electrical separation. In this process, a tungsten concentrate is formed, consisting of 55-65% tungsten anhydride (trioxide) WO3. In concentrates of this metal, the content of impurities is monitored, which can include phosphorus, sulfur, arsenic, tin, copper, antimony and bismuth.
2. As is known, tungsten trioxide WO3 is the main material for the extraction of metal tungsten or tungsten carbide. The production of WO3 occurs as a result of the decomposition of concentrates, leaching of an alloy or sinter, etc. In this case, the output is a material consisting of 99.9% WO3.
3. From tungsten anhydride WO3. It is by reducing this substance with hydrogen or carbon that tungsten powder is obtained. The use of the second component for the reduction reaction is used less frequently. This is due to the saturation of WO3 with carbides during the reaction, as a result of which the metal loses its strength and becomes more difficult to process. Tungsten powder is produced by special methods, thanks to which it becomes possible to control its chemical composition, grain size and shape, as well as particle size distribution. Thus, the fraction of powder particles can be increased by rapidly increasing the temperature or by low hydrogen supply rate.
4. Production of compact tungsten, which has the form of bars or ingots and is a blank for the further production of semi-finished products - wire, rods, tape, etc.

The latter method, in turn, includes two possible options. One of them is associated with powder metallurgy methods, and the other is with smelting in electric arc furnaces with a consumable electrode.

Powder metallurgy method

Due to the fact that thanks to this method it is possible to more evenly distribute the additives that give tungsten its special properties, it is more popular.

It includes several stages:

1. Metal powder is pressed into bars;
2. The workpieces are sintered at low temperatures (so-called pre-sintering);
3. Welding of workpieces;
4. Obtaining semi-finished products by processing blanks. The implementation of this stage is carried out by forging or mechanical processing (grinding, polishing). It is worth noting that mechanical processing of tungsten becomes possible only under the influence of high temperatures, otherwise it is impossible to process it.

At the same time, the powder must be well purified with a maximum permissible percentage of impurities of up to 0.05%.

This method makes it possible to obtain tungsten rods with a square cross-section from 8x8 to 40x40 mm and a length of 280-650 mm. It is worth noting that at room temperatures they are quite strong, but have increased fragility.

This method is used if it is necessary to obtain tungsten blanks of fairly large dimensions - from 200 kg to 3000 kg. Such blanks are usually needed for rolling, drawing pipes, and manufacturing products by casting. Melting requires the creation of special conditions - a vacuum or a rarefied atmosphere of hydrogen. The output is tungsten ingots, which have a coarse-crystalline structure and are also highly brittle due to the presence of a large amount of impurities. The impurity content can be reduced by pre-melting tungsten in an electron beam furnace. However, the structure remains unchanged. In this connection, to reduce the grain size, the ingots are further melted, but in an electric arc furnace. At the same time, during the smelting process, alloying substances are added to the ingots, giving tungsten special properties.

To obtain tungsten ingots with a fine-grained structure, arc skull melting is used with metal casting into a mold.

The method of obtaining the metal determines the presence of additives and impurities in it. Thus, several grades of tungsten are produced today.

Where is tungsten used?

Thanks to its unique properties, chemical element 74 has become indispensable in many industrial sectors.

1. The main use of tungsten is as a basis for the production of refractory materials in metallurgy.
2. With the obligatory participation of tungsten, incandescent filaments are produced, which are the main element of lighting devices, picture tubes, and other vacuum tubes.
3. Also, this metal underlies the production of heavy alloys used as counterweights, armor-piercing cores of sub-caliber and swept-finned projectiles of artillery guns.
4. Tungsten is the electrode used in argon-arc welding;
5. Its alloys are highly resistant to various temperatures, acidic environments, as well as hardness and abrasion resistance, and are therefore used in the production of surgical instruments, tank armor, torpedo and projectile casings, aircraft and engine parts, as well as nuclear storage containers. waste;
6. Vacuum resistance furnaces, the temperature in which reaches extremely high values, are equipped with heating elements also made from tungsten;
7. The use of tungsten is popular to provide protection against ionizing radiation.
8. Tungsten compounds are used as alloying elements, high-temperature lubricants, catalysts, pigments, and also for converting thermal energy into electrical energy (tungsten ditelluride).

Source: mining-prom.ru

Tungsten based alloys

Tungsten alloys can be produced exclusively by powder metallurgy. This is caused by the large difference in melting temperatures of the metals included in the alloy. The powders of the original components, after mixing, are pressed and then sintered. As a result of capillary forces, more fusible metals fill the space between the tungsten grains, forming a monolithic alloy. Solid solutions of alloy components are formed at grain boundaries.

The most widespread are alloys of tungsten with copper, iron and nickel. The most common VNZH and VNM alloys include tungsten-nickel-iron and tungsten-nickel-copper.

To achieve special characteristics, the composition may also include silver, chromium, cobalt and molybdenum.

Tungsten alloys are used for the manufacture of parts and devices in which high density with small overall dimensions is important. These are all kinds of counterweights, flywheels, weights of centrifugal regulators, cores of bullets and shells.

There are not very many brands of tungsten known. First of all, this is technically pure tungsten - HF.

Tungsten grades used in industry typically include some additives. Material doped with lanthanum is designated as VL, and with yttrium - VI. These alloying additives further improve the mechanical and technological properties of the metal.

Alloys with rhenium - VR5, VR20 - are used in the production of high-temperature thermocouples.

Doping with thorium increases the emissive properties of tungsten, which is especially important in the manufacture of cathodes for high-power vacuum tubes. This additive also improves the ability to ignite an electric arc during argon-arc welding.

Tungsten alloys with copper and silver are used to make contacts for high-current switching equipment. Copper and silver, although highly electrically conductive, do not have high mechanical strength. When passing high currents, the contact groups may melt. Contacts made of tungsten alloys are free from these disadvantages, despite their slightly higher electrical resistance.

The high density of the alloys will make it possible to use them for the manufacture of containers for storing radioactive substances and screens for protection against γ-radiation.

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Tungsten grades

1. HF – pure tungsten, which does not contain any additives;
2. VA is a metal containing aluminum and silica-alkali additives, which give it additional properties;
3. VM is a metal containing thorium and silica-alkali additives;
4. VT – tungsten, which contains thorium oxide as an additive, which significantly increases the emissive properties of the metal;
5. VI – metal containing yttrium oxide;
6. VL – tungsten with lanthanum oxide, which also increases emission properties;
7. VR – alloy of rhenium and tungsten;
8. VРН – there are no additives in the metal, however impurities may be present in large volumes;
9. MV is an alloy of tungsten with molybdenum, which significantly increases strength after annealing, while maintaining ductility.