Tungsten rings have been increasing in popularity over the past 5 years due to the strength, durability and lower price point over precious metals. In the past the tungsten metal has been popular with men. In specific men that worked with their hands in professions such as mechanics, construction or welding. The men that worked in these industries desired the metal for the scratch resistance and durability while the ring was getting beat up at work. Now, men of all professions purchase tungsten due to the endless style possibilities, uniqueness of the metal and it being economically friendly. Not only are retailers noticing more men purchase the rings but women as well. Women are making up approximately 25% of all tungsten ring purchases for themselves. With this in mind there are many styles that accommodate women which are listed below.

Abalone Shell Inlay Tungsten Rings:

Abalone Shell Tungsten Bands are ideal for women as it brings a delicate shell which is bright in color in with the durable tungsten. Abalone shell inlays have an array of colors consisting of blues, greens, grays and sometime a swirl of white. The inlay is protected on each side with tungsten and coated in a liquid crystal for durability. The rings are ideal for men and women and are commonly used as a unique wedding band.

Diamond or Gemstone Set Tungsten Wedding Bands:

Diamond set tungsten rings can be worn by both men and women. The diamond or gemstone is carefully set in a tungsten ring and protected by a bezel. Tungsten rings can have one stone or many depending on the specifications of the customer. Many can find exactly what they are looking for with in stock rings however if not many companies offer a customization option.

Celtic Claddagh Carbide Rings:

Celtic rings have always been popular with couples due to the symbolic meaning the rings hold. The symbols represent love, friendship, family and life all within the intricacy of a knotwork pattern or symbol. The Celtic rings are ideal to be worn as a fashion piece, engagement ring or wedding band for both men and women.

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With the Holidays quickly approaching many people are beginning to shop the internet for ideas on what to buy the special people in their lives. The top internet searching criteria consist of clothing, toys and electronics. Another top category is jewelry. With the economy taking a turn for the worse many people are looking to get high quality, fashionable jewelry at prices they can afford. This does not typically include the expensive diamonds, gold and platinum. With this in mind many are seeking out alternative metals as an affordable choice. Alternative metals typically consist of silver, titanium and tungsten carbide. Among these 3 metals tungsten carbide has the best lasting quality. While silver and titanium are great metals they can scratch over time. Tungsten Carbide can also scratch however it is very hard to do and this particular metal is popular among those that work with their hands for its lasting quality. Some new jewelry trends popular for the 2012-13 season consist of following below.

Heritage Rings: Heritage ring consist of typically Irish and Greek rings. Tungsten rings companies manufacture many heritage rings in a large array of styles including symbolic designs, knot work ring and rings with unique phrases on them. Many tungsten ring manufacturers can even laser engrave personalization for a small fee.

Wide Width Rings: Wide width ring are popular to wear as a fashion ring or wedding band. Wide width tungsten rings consist of any width beyond a 9mm width. Many tungsten wedding band companies can manufacture to a 12mm width, some manufacturers design rings even wider, at times to a 16mm width. Anything wider can become too large and heavy and could crack under severe force.

Black Tungsten Rings: Colored tungsten rings consist of a black and gold plating coating a tungsten ring. Tungsten retailers suggest that colored tungsten be used as fashion purposes only due to the fragility of the outer coating. Black and gold plated rings can fade and slightly scratch over time, happening even quicker with those that work with their hands.

Carved Tungsten Carbide: Carved tungsten carbide rings is a fairly new technology, only being found at a few retailers. Carved tungsten is unique and the intricate designs are carefully carved into the metal. Many Celtic rings are found in a carved design, where the detail is more prominent. Carved tungsten tends to be sold at a slightly higher price point due to the detail that goes into manufacturing one ring.

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Both tungsten and fluorescent lighting are widely used in professional photography. Each has unique characteristics that enhance the image output with color temperature ranging between 3200-3500K. However, there are a few differences between the two, the specifics of which are beneficial to know if you are practicing or learning photography.

Light Color
The most obvious difference between tungsten and fluorescent lights is their color; at first glance, photos using these lights turn out with yellow or blue casts. This is because tungsten light shifts the light spectrum towards red, which comes out as yellow or orange, while fluorescents shift light towards blue.

Lifetime and Wattage
Another difference between tungsten and fluorescent is their efficiency in terms of lifetime and wattage. In this regard, fluorescent lighting may be considered more effective as it only consumes an average of 85 watts, compared to tungsten which consumes about 500 watts. In addition, fluorescent lights' lifespan extends up to 7500 hours while tungsten bulbs only last for an average of 50-60 hours.

Temperature
Tungsten is referred to as "hot lights" because it emits a red, warmer look which varies depending on the voltage. On the other hand, fluorescent lights are known to be cooler and skewed towards the blue end of the spectrum. Although the temperature differences are not that great, during long working hours fluorescent lights prove to be a lot cooler, which is beneficial those working with them. Similarly, using tungsten lights for long photography sessions may make it uncomfortably hot for the people you are photographing.

Operational Cost
When it comes to operational costs, tungsten and fluorescent lights may differ depending on your usage requirement. In terms of energy efficiency, fluorescent lights, being cooler, have many benefits over tungsten, especially in a small-to-medium sized studio. Tungsten emits more heat than light energy -- at a ratio of 95:5 -- in comparison with fluorescent lights, which emit more light than heat energy at a 5:95 ratio.

Power
Tungsten lights are more powerful than fluorescents and may be a better lighting option for larger photo studios. Also, some flash photography effects come out better with tungsten than fluorescent lighting. For shorter photography sessions that require powerful lighting, tungsten is a better choice.

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Why Tungsten Carbide Jewelry?
What is Tungsten? Tungsten is a metal found in several ores and has robust physical properties. It has the highest melting point of all the non-alloyed metals and is second to carbon of the elements.

Tungsten carbide is one of the most durable and scratch resistant jewelry available.
What gives Tungsten Carbide it's hard, scratch resistant property?

The way tungsten carbide is made is so interesting. Tungsten, carbon and other elements like cobalt or nickel are ground into a powder. They are compressed with high-pressure dyes to form a round blank (for rings). The blank is then fired in an oxygen free furnace at 2400 degrees Fahrenheit to form an extraordinarily hard ring. Rings are then cut and shaped using diamond tools with approximately 30 steps required for completion. The cutting and shaping of a tungsten carbide ring is similar in many ways to the cutting and polishing of a rough diamond. The rings can then be inlaid with gold, silver, platinum, Mokume, or Shakudo. The inlay is created by grinding a channel in the center of the ring and compressing the metal into it under extreme pressure. The ring is then polished with diamond polishing tools and wheels. This creates a permanent luster and polish that is not possible with other metals.

There are many different kinds of tungsten carbide jewelry. Tungsten carbide can be changed significantly within the carbide manufacturers sphere of influence, determined by grain size, cobalt content, dotation and carbon content. Some people have shown an allergy to cobalt. Thus, many of the tungsten carbide Jewelry manufacturers have cobalt free jewelry replacing the cobalt with nickel.

So why Tungsten Carbide?

Tungsten Carbide is the only rare and exotic metal that can promise a permanence in polish and finish that will endure as long a the wearer bears it. Rings made from gold, platinum, and even titanium all become significantly less attractive over time. The patterns and design in many gold rings will all but disappear after several years. For me, it didn't take several, but two years for the brushed finish on my gold wedding band to rub off. I take it back and get it re-brushed every few years so that it looks like it did when my wife gave it to me.

Tungsten carbide jewelers are able to guarantee that their ring's shine for life. The reason why? The chance of it ever getting scratched or dulled is extremely low. Tungsten Carbide rings will and do maintain a lasting, beautiful, shiny finish. To the wearer tungsten carbide jewelry speaks of commitment and security to the couples who choose Tungsten Carbide for their wedding bands due to it everlasting nature.

What Mokume Gane and Shakudo? I mentioned a few inlays commonly used in Tungsten Carbide rings, Mokume Gane and Shakudo. These two inlays are really the same thing just with different metals used in the manufacturing process. Mokume Gane (moh-ku-may Gah-nay) is ancient Japanese metalworking developed in feudal Japan by master sword smiths. This is a technically difficult and time-consuming process. The process begins by stacking layers of different colored metals and heating them to 1400 degrees under extreme pressure for 10 hours. This allows the atom from gold and other metals to fuse together, forming distinctive patterns. The metal is then forged and rolled to set the crystal structure. Finally the Gold and other metal ate manipulated by twisting and curving to expose the multiple layer, thereby forming unique ring patterns. No Mokume Gane or Shakudo rings will look alike!

Mokume is usually made with white Palladium and either silver or 18k green gold. Shakudo usually has 90-95% copper and 5-10% pure gold, layered with either sterling silver or 14k yellow Gold. Shakudo tends to have a darker and more deliberate pattern than Mokume. However, both of them are equally gorgeous!
 
  from http://www.ehow.com

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Wedding bands are traditionally created out of gold of varying purities. Platinum has often been an alternative, albeit a more costly one due to the difficulty in working with the metal, while silver has also been an alternative but not as favorable due to the softness of the metal. Another alternative wedding band material that has emerged is tungsten, but one must consider the pros and cons of this metal before choosing it for a wedding band.

Durability
Tungsten wedding bands are very strong and show a resistance to bending that gold, silver, platinum and titanium can not come close to attaining.

Tungsten rings actually do not bend under pressure, instead it takes an extreme amount of pressure to shatter them. For this reason this metal is viewed favorably by those who perform manual labor since the rings do not wear during heavy loads. Scratch resistance is another advantage for tungsten rings as it takes a material with an abrasion capacity near that of a diamond to put a scratch in tungsten.

Resizing
Since wedding bands are intended to be items with a lifetime usable capacity, it is important to be able to re-size these rings as a person's weight can fluctuate throughout his life. It is nearly impossible to re-size a tungsten wedding band which is a disadvantage of the material for this application.

Engraving
Many people elect to have a special sentiment or date engraved on the inside of their wedding band to solidify the sentimental nature of the item. Due to the strength of tungsten engraving is not optional. A jeweler can attempt to engrave the band but these markings will be faint at best.

Maintenance
Tungsten is a popular choice for wedding bands as the metal does not require polishing to keep its original luster. Oils from the skin and outside chemicals do not have an effect on tungsten's sheen so it is a popular choice for those who desire a low maintenance band.

Allergic Reactions
Some jewelers use cobalt in the tungsten alloy for their bands. Many people are allergic to cobalt and experience rashes as a result of exposure. To negate the risk of this happening it is advised to buy a tungsten wedding band that uses nickel in its alloy composition. When nickel is used in tungsten alloys it actually becomes hypoallergenic, even to those who suffer from nickel allergies.

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Tungsten(VI) oxide, also known as tungsten trioxide or tungstic anhydride, WO3, is a chemical compound containing oxygen and the transition metal tungsten. It is obtained as an intermediate in the recovery of tungsten from its minerals.Tungsten ores are treated with alkalis to produce WO3. Further reaction with carbon or hydrogen gas reduces tungsten trioxide to the pure metal.

    2 WO3 + 3 C + heat → 2 W + 3 CO2
    WO3 + 3 H2 + heat → W + 3 H2O

Tungsten(VI) oxide occurs naturally in form of hydrates, which include minerals: tungstite WO3·H2O, meymacite WO3·2H2O and hydrotungstite (of same composition as meymacite, however sometimes written as H2WO4). These minerals are rare to very rare secondary tungsten minerals.

History
Tungsten has a rich history dating back to its discovery during the 18th century. Peter Woulfe was the first to recognize a new element in the naturally occurring mineral, wolframite. Tungsten was originally known as wolfram, explaining the choice of "W" for its elemental symbol. Swedish chemist Carl Wilhelm Scheele contributed to its discovery as well with his studies on the mineral scheelite.

In 1841, a chemist named Robert Oxland gave the first procedures for preparing tungsten trioxide and sodium tungstate. He was granted patents for his work soon after, and is considered to be the founder of systematic tungsten chemistry.

Preparation
Tungsten trioxide can be prepared in several different ways. CaWO4, or scheelite, is allowed to react with HCl to produce tungstic acid, which decomposes to WO3 and water at high temperatures.

    CaWO4 + 2 HCl → CaCl2 + H2WO4
    H2WO4 + heat → H2O + WO3

Another common way to synthesize WO3 is by calcination of ammonium paratungstate (APT) under oxidizing conditions:

    (NH4)10[H2W12O42]•4H2O → 12 WO3 + 10 NH3 + 11 H2O

Structure
The crystal structure of tungsten trioxide is temperature dependent. It is tetragonal at temperatures above 740 °C, orthorhombic from 330 to 740 °C, monoclinic from 17 to 330 °C, and triclinic from -50 to 17 °C. The most common structure of WO3 is monoclinic with space group P21/n.

Uses
Tungsten trioxide is used for many purposes in everyday life. It is frequently used in industry to manufacture tungstates for x-ray screen phosphors, for fireproofing fabrics and in gas sensors. Due to its rich yellow color, WO3 is also used as a pigment in ceramics and paints.

In recent years, tungsten trioxide has been employed in the production of electrochromic windows, or smart windows. These windows are electrically switchable glass that change light transmission properties with an applied voltage. This allows the user to tint their windows, changing the amount of heat or light passing through.

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Tungsten carbide (WC)
Tungsten carbides are divided into two categories. The first is the cemented tungsten carbides, also called hard metals, which are essentially WC produced from sintering a mixture of carbon black and hydrogen-reduced tungsten powder at 1,500° C (2,700° F). These are cemented using a cobalt or nickel binder, with or without other refractory carbides. The major uses of cemented carbides are for cutting and drilling tools, forming and drawing dies, and tire studs.

The second group is called fused or cast carbide, consisting of W2C and a eutectic mixture of WC and W2C. Harder but more brittle than the cemented carbide, it is used in wear-resisting applications such as anvils, guide sleeves in machines, and teeth and jaws for excavators.

Other compounds
Tungsten bronze, composed of tungstates of the alkali and alkaline-earth metals, is employed as a substitute for bronze in ornamental paints. Sodium tungstate is also used to produce phosphotungstic acid-type organic dyes and pigments, which are brilliant, light-resistant, and insoluble in water and linseed oil. Calcium and magnesium tungstates are used as phosphors in fluorescent light and television tubes. Ammonium tungstate and other compounds are used as catalysts in the petroleum industry for hydrotreating, hydrocracking, and polymerization.

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Tungsten Powder
When APT is decomposed to tungsten oxides, it displays different colours according to its composition: the trioxide is yellow, the dioxide is brown, and the intermediate oxide is purple-blue. APT can be decomposed to yellow oxide when heated to above 250° C (480° F) in a furnace under a flow of air. In the industrial production of tungsten, however, APT is usually decomposed to the intermediate oxide in a rotary furnace under a stream of hydrogen, which partially decomposes the ammonia in the crystals into nitrogen and hydrogen while maintaining a reducing atmosphere. The rotary furnace is divided by partitions into three zones maintained, respectively, at 850°, 875°, and 900° C (1,550°, 1,600°, and 1,650° F). The furnace is tilted at a small angle and rotated to provide a continuous flow of powder through the central holes of the partitions.

The blue oxide is then reduced by hydrogen to metallic tungsten powder in stationary furnaces at temperatures ranging from 550° to 850° C (1,025° to 1,550° F). In this process the oxide is loaded into “boats” made of Inconel, a nickel-based alloy noted for its strength at high temperatures. These are stoked into tubes, usually arranged in two rows, and the tubes are heated in three separate zones along their lengths.

APT may also be reduced by carbon, although the powder is usually contaminated with tungsten carbide and some mineral elements contained in the carbon. When APT and carbon are mixed and reacted at 650°–850° C (1,200°–1,550° F), the product is a blue oxide. When heated in the range of 900°–1,050° C (1,650°–1,925° F), the brown oxide is formed. For complete reduction to metal, a temperature higher than 1,050° C is required. The purity of the metal is about 95 percent.

Consolidation
Tungsten powder is compacted into bars or billets with a mechanical or isostatic press prior to sintering. The “green,” or unfired, density of these compacts, obtained from powder particle sizes ranging from 1 to 10 micrometres, is usually 65 to 75 percent of the theoretical. After being presintered at 1,000°–1,200° C (1,800°–2,200° F), tungsten bars of small diameter are sintered in a hydrogen atmosphere, with heat being provided by the direct-resistance method—that is, by an electric current passed through the bar. A spring attachment to the water-cooled clips holding each bar is necessary so that one end is free to move as the bar shrinks during sintering. The current is gradually increased to raise the temperature from room temperature to 2,700°–3,100° C (4,900°–5,600° F). After holding at the final temperature for 30 to 60 minutes, the density reaches 88.5 to 96 percent of the theoretical.

An indirect sintering process is used for large tungsten billets. The heating elements of the furnace are constructed of molybdenum strips and supported by molybdenum or tungsten frames, and they are surrounded by molybdenum heat shields. A slow heating in the early stage of sintering is essential for deoxidizing the material and releasing gases at a controlled rate. At higher temperatures—i.e., from 800° C up to the final sintering temperature of 2,400° C (4,350° F)—the heating rate also should be controlled, since too fast a temperature buildup within the billet would cause thermal stresses and would result in the cracking of the material. A final sintering for 10 hours is required for densification.

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HS Code of Tungsten and Tungsten Products

Tungsten processing, preparation of the ore for use in various products.

Tungsten exhibits a body-centred cubic (bcc) crystal lattice. It has the highest melting point of all metals, 3,410° C (6,170° F), and it has high conductivity for electricity. Owing to this unique combination of properties, it is used extensively as filaments for incandescent lamps, as electric contacts, and as electron emitters for electronic devices. Tungsten also has found wide application as an alloying element for tool steels and wear-resistant alloys. Tungsten carbides are used for cutting tools and hard-facing materials owing to their hardness and resistance to wear. The metal is brittle at room temperature but ductile and strong at elevated temperatures. Its alloys are employed in rocket-engine nozzles and other aerospace applications.

Tungsten Ores
Major minerals of tungsten are essentially of two categories. The first is wolframite [(Fe, Mn)WO4], which contains iron and manganese tungstates in all proportions between 20 and 80 percent of each. The second is scheelite (CaWO4), which fluoresces a bright bluish colour under ultraviolet light.

Tungsten deposits occur in association with metamorphic rocks and granitic igneous rocks. The most important mines are in the Nan Mountains in the Kiangsi, Hunan, and Kwangtung provinces of China, which possesses about 50 percent of the world’s reserves. In Russia, mines are located in the northern Caucasus and around Lake Baikal. There are also deposits in Kazakhstan. About 90 percent of South Korea’s tungsten is at Sang Dong. Canada’s Northwest Territories is home to the largest tungsten mine in the Western world, and a mine at Chojlla, Bol., is the largest producer in South America. Deposits in the United States are spread along the Rocky Mountains.

Extraction and refining - Ammonium paratungstate

Tungsten ores frequently occur in association with sulfides and arsenides, which can be removed by roasting in air for two to four hours at 800° C (1,450° F). In order to produce ammonium paratungstate (APT), an intermediate compound in production of the pure metal, ores may be decomposed by acid leaching or by the autoclave-soda process. In the latter process, the ground ore is maintained for 11/2 to 4 hours in a solution of 10–18 percent sodium carbonate at temperatures of 190° to 230° C (375° to 445° F) and under a pressure of 14.1–24.6 kilograms per square centimetre (200–350 pounds per square inch). Prior to the removal of unreacted gangue by filtration, the acidity is adjusted to pH 9–9.5, and aluminum and manganese sulfates are added at 70°–80° C (160°–175° F) and stirred for one hour. This can eliminate phosphorus and arsenic and reduce silica to a level of 0.03–0.06 percent. Molybdenum is removed by adding sodium sulfide at 80°–85° C (175°–185° F) at a pH of 10, holding for one hour, and then acidifying the solution to pH 2.5–3 and stirring for seven to nine hours to precipitate molybdenum sulfide. The remaining sodium tungstate solution can be further purified by a liquid ion-exchange process, using an organic extractant consisting of 7 percent alamine-336, 7 percent decanol, and 86 percent kerosene. During the countercurrent flow of the extractant through the solution, tungstate ions transfer from the aqueous phase to the organic phase. The tungsten is then stripped from the extractant into an ammonia solution containing ammonium tungstate. The resultant APT solution is sent to an evaporator for crystallization.

In the acid-leaching process, scheelite concentrate is decomposed by hydrochloric acid in the presence of sodium nitrate as an oxidizing agent. This charge is agitated by steam spraying and is maintained at 70° C (160° F) for 12 hours. The resultant slurry, containing tungsten in the form of a solid tungstic acid, is diluted and allowed to settle. The tungstic acid is then dissolved in aqueous ammonia at 60° C (140° F) for two hours under stirring. Calcium from the resulting solution is precipitated as calcium oxalate, while phosphorus and arsenic may be removed by the addition of magnesium oxide, which forms insoluble phosphates and arsenates of ammonium and magnesium. Iron, silica, and similar impurities that form colloidal hydroxides are removed by adding a small amount of activated carbon and digesting for one to two hours. The solution is clarified through pressure filters and evaporated to obtain APT crystals.

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