A comparison between end milling cutters with a diameter of 10mm used for full slotting of Inconel 718 is used as an example (see table in image 4). The significantly higher feed rate provided by ceramic is an unbeatable advantage, despite the greater depth of cut provided by carbide. In this case, the metal removal rate using a ceramic cutting edge is 56% higher. In addition, the total volume of metal removed using the ceramic milling cutter is 180% higher than the carbide milling cutter. Metal removal rates and the total volume of metal removed per tool life are the parameters where ceramic offers clear advantages over carbide. The shorter machining time enables larger batch sizes to be machined using the same machinery; the option for users to configure their existing machinery enables them to get by with fewer machining centres. The high total machining volume reduces tool costs.

The measuring points on the slot were selected in order to determine and evaluate the maximum thermal load. The basic hardness of the material is 446 HV. The result: A hardening of up to 640 HV was detected within a depth of 100µm. No hardening could be detected at depths greater than 200µm – regardless of the wear of the tool or the direction of measurement. As the generally applicable roughing offset is between three- and five-tenths of a millimetre, it is therefore not expected that roughing using ceramic tools will result in any damage remaining after the finishing process.

11/32″ wrench 20′ tape measure The labels on the tape also use this notation Even the dumb decimal imperial stuff like 0.032″ drill bits

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The first step in releasing metallic tungsten is to decompose APT into various tungsten oxides using high temperatures:

“world’s tungsten reserve of 3.2 million tonnes” and “We produced almost 120,000 tonnes of tungsten in 2022”. So that means we only have less than 27 years to go before exhausting tungsten reserve ???

There’s no winning with local notations without getting very inconvenient. Sometimes I see numbers given like 100,234 instead of 100.234 and have to figure out whether they meant a hundred or a hundred thousand. Or if the word is a billion, is it a thousand million or is it more? Even with numbers like 1.00234E5 there’s always the chance that it gets garbled by text formatting or mistyped and misinterpreted.

US Air Force leaders and Northrop Grumman have provided updates on the B-21 Raider, the service’s newest bomber.

Correct, same with oil. There is a major economic factor in that nobody wants to fund discovering more of a mineral that is still relatively cheap

The primary causes of wear when milling nickel-based alloys with ceramic tools are chemical wear caused by the temperature and built-up edges. While chemical wear or diffusion wear continuously weakens the cutting tool material, wear caused by build-up on the cutting edge is unpredictable and occurs in sudden increments. As a result of the high machining temperature (see image 2) and the high toughness of high-temperature super alloys even at high temperatures (for example Inconel 718; Rm = 880N/mm² at 750°C), a large build-up of chips can form on the tool. These can fuse to the surface of the cutting material and cause parts of the ceramic to chip off when removed. The built-up edge on the tool can be clearly seen in image 3. Even though the high temperature resulting from machining of HRSAs has a negative impact on tool life, it is necessary. This is the only way to reduce the hardness of the material and to machine it efficiently.

Even though the age of the vacuum tube is long gone and the world has largely turned away from incandescent lighting, tungsten wire is still an important end product. A single ingot of tungsten can be drawn into almost 1,300 kilometers of wire, depending on the gauge. The drawing process starts with hot-rolling the ingot into a cylindrical shape and swaging to reduce its diameter. One end of the tungsten rod is tapered by dipping it into molten potassium nitrate, which dissolves the rod enough for it to fit into a die. Up to 50 passes through smaller and smaller dies, the smallest of which are made from diamond, may be required to get the wire to the proper size.

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APT, a free-flowing white crystalline salt, is convenient to handle and contains a lot of tungsten — twelve atoms per molecule. APT is the main raw material produced at most tungsten mines, and is generally shipped out to refineries for further processing into metallic tungsten and fabrication of metal products, such as wire, sheet stock, and billets, not to mention the all-important tungsten carbides.

My mothers home town has a wolframium mine that was very active during WW2. The demand fell after the war and the mine was closed

Image 3: Despite high levels of build-up edge and chipping, the ceramic milling cutter is still good for use after machining five blades. The discolouration of the chips adhered to the tool indicates a high machining temperature

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Because of the relative rarity of tungsten ores and the geological processes that tend to sequester it, a lot of overburden has to be removed to gain access. Open-pit mining techniques are often used, at least when exploiting a new find, but once the ratio of waste to payable ore gets too high, underground mining becomes favored, since it allows miners to work along ore veins and ignore the waste rock that encases them. Because tungsten ores are associated with mountain-building geology, many underground tungsten mining operations actually mine up into the core of mountains rather than down. This was the case with the Pine Creek Mine in the Sierra Nevada mountains outside Bishop, California, where miners had a 3,000′ elevator ride up from the mine entrance to work the scheelite veins. That one mine produced most of the tungsten used in the United States for nearly 60 years before closing in 2001.

The toughness and high melting point of tungsten also make it suitable for cutting tools, especially in the form of tungsten carbide (WC). Tungsten carbide is made either by reacting powdered tungsten metal with graphite at high temperatures, or by blowing a mixture of hot carbon monoxide and carbon dioxide through a bed of tungsten trioxide. Either way, the tungsten and carbon bind to each other, creating a material that’s twice as stiff and twice as dense as steel, with a melting point of about 2,800 °C. Tungsten carbide can be mixed with various binders and additives and pressed into complex shapes that can be sintered into solid cutting tools tough enough to withstand the punishing requirements of CNC cutting.

The liquid sodium tungstate then moves on to a series of purification steps using a combination of hydrometallurgical processes. The exact steps taken depend on the source ore and tungsten concentration, but include filtration, extraction with organic solvents like decanol or even kerosene, or precipitation with salt solutions such as calcium chloride. The goal is to form increasing pure solutions that can be treated with hot hydrochloric acid to form tungstic acid, a hydrated form of tungsten trioxide (WO3). Tungstic acid, a vibrant yellow compound that was once used as a fabric dye, is washed repeatedly until as pure as possible before being dissolved with ammonium hydroxide. This solution is filtered and then heated, driving off the ammonia and water to leave behind ammonium paratungstate (APT), a salt with a complex chemical formula:

Cutting tool specialist, Walter explains how the machining of heat-resistant super alloys can be achieved with the same feed rates as aluminium. Walter’s aerospace component manager, Stefan Benkóczy reports.

Of course, it’s a bit less than perfectly accurate when we say incandescents have been discontinued – mainly what was discontinued was standard screw-in bulbs. Halogen lamps are just an incandescent that can run at a higher temperature without burning out too soon, and is therefore a bit more efficient. And we still have plain non-halogen filament bulbs in automotive use, or for heat, or in other carve-outs that weren’t discontinued. They’re cheap, and the efficiency doesn’t matter as much in other uses.

The two main ores of tungsten are scheelite, which is calcium tungstate (CaWO4), and wolframite, which is a combination of iron tungstate (FeWO4) and manganese tungstate (MnWO4). About 70% of the world’s tungsten reserve of 3.2 million tonnes is locked up in wolframite, which is often found in granitic formations and is often associated with quartz. Scheelite is also often found in quartz veins and tends to be found along with commercially important amounts of tin, as well as sometimes with gold. Both tungstate minerals also tend to be found near molybdenate minerals, making molybdenum another valuable byproduct of tungsten mining.

The high volume of orders in the aviation industry places great pressure on the capacity of engine manufacturers and their suppliers. Therefore, a reduction in component machining times would be highly beneficial. For heat-resistant super alloys, the cutting speed of carbide milling cutters is approx. 50m/min. Ceramic milling cutters offer a different approach, with cutting speeds of up to 1,000m/min. The Walter product range includes two series of ceramic milling cutters: The MC275 with universal geometry is suitable for most applications; the MC075 is designed as a high-feed milling cutter. Both product ranges (see image 1) are available with cutting diameters of 8 to 25mm. Tools with diameters of 8 to 12mm are available as integral milling cutters, while tools with diameters of 12 to 25mm are available as ConeFit milling cutters. In both cases, only the head of the tool is made from ceramic. This head is brazed onto either a carbide shank or a carbide ConeFit base body. In principle, the entire milling cutter could be manufactured from ceramic, but a carbide shank increases the strength and damping of the tool. This enables increased projection lengths and higher material removal rates in comparison to solid ceramic tools. Image 2: MC275 ceramic milling cutter used for a slot milling in Inconel 718 with a cutting speed of 670m/min Dynamic with ceramic The range of applications of ceramic cutting tool materials includes nickel-based, cobalt-based and iron-based heat-resistant alloys in the ISO S group. Typical alloys are for example Inconel 718, René 80, Nimonic 80A, Haynes 556, Mar-M-247 and Stellite 31. These heat-resistant super alloys (HRSAs) are the preferred choice for use in the hot section of aircraft engines. The ceramic cutting tool material is tailored for use in milling applications. SiAlON ceramics are more resistant to temperature fluctuations than whisker-reinforced ceramics. This makes them the ideal choice for milling operations. The interrupted cut causes the temperature on the cutting edge to vary, and the use of coolant media can further increase the temperature difference, resulting in a thermal shock effect. For this reason, Walter recommends dry machining when machining high-temperature super alloys with ceramic milling cutters. An additional benefit for users is the environmental and economic advantage they gain from avoiding use of cooling lubricants. The primary causes of wear when milling nickel-based alloys with ceramic tools are chemical wear caused by the temperature and built-up edges. While chemical wear or diffusion wear continuously weakens the cutting tool material, wear caused by build-up on the cutting edge is unpredictable and occurs in sudden increments. As a result of the high machining temperature (see image 2) and the high toughness of high-temperature super alloys even at high temperatures (for example Inconel 718; Rm = 880N/mm² at 750°C), a large build-up of chips can form on the tool. These can fuse to the surface of the cutting material and cause parts of the ceramic to chip off when removed. The built-up edge on the tool can be clearly seen in image 3. Even though the high temperature resulting from machining of HRSAs has a negative impact on tool life, it is necessary. This is the only way to reduce the hardness of the material and to machine it efficiently. Image 4: The comparison demonstrates the significantly higher cutting speed, higher metal removal rate and higher total volume of metal removed provided by the ceramic milling cutter in comparison to the carbide milling cutter The cutting data is predetermined by the cutting tool material and the material to be machined. A brittle yet heat-resistant cutting tool material can be used at high temperatures, but the low impact strength demands low feed rates per tooth of 0.02 to 0.05mm and small tool engagement of ap = 5% of Dc for full slotting operations and ae = 5% of Dc for contour milling with maximum cutting-edge length. The exception to this is the MC075 with high-feed geometry where fz = 0.15mm for ap ≤ apf. The cutting speed for both product ranges are between 400 and 1,000m/min. The results for milling cutters with carbide cutting edges and milling cutters with ceramic cutting edges could not be more different. The wear photos in image 3 show why ceramic milling cutters are only used for roughing. Signs of wear such as chipping on the cutting edge and wear mark widths of over 0.5mm, which for carbide milling cutters would indicate end of tool life, are no reason to stop using a ceramic cutting tool. The differences between the two cutting tool material types are also made clear by comparing the cutting parameters. A comparison between end milling cutters with a diameter of 10mm used for full slotting of Inconel 718 is used as an example (see table in image 4). The significantly higher feed rate provided by ceramic is an unbeatable advantage, despite the greater depth of cut provided by carbide. In this case, the metal removal rate using a ceramic cutting edge is 56% higher. In addition, the total volume of metal removed using the ceramic milling cutter is 180% higher than the carbide milling cutter. Metal removal rates and the total volume of metal removed per tool life are the parameters where ceramic offers clear advantages over carbide. The shorter machining time enables larger batch sizes to be machined using the same machinery; the option for users to configure their existing machinery enables them to get by with fewer machining centres. The high total machining volume reduces tool costs. A classic example of a component made from a nickel-based alloy is a blisk for aircraft engines. This rotating integral component is a disc with a large number of blades. The spaces between the blades can be milled out using carbide milling cutters via a roughing process. The machining time for this is approximately 30 minutes. The MC075 ceramic milling cutter with high-feed geometry can carve out the same spaces in 10 minutes. For this application, it achieves feed rates of 9,500mm/min in a heat-resistant nickel-based alloy with a hardness of 44 HRC and a tensile strength of 1400N/mm². Feed rate values such as these are generally expected for machining aluminium, rather than nickel-based alloys. Image 3: Despite high levels of build-up edge and chipping, the ceramic milling cutter is still good for use after machining five blades. The discolouration of the chips adhered to the tool indicates a high machining temperature While ceramic tools present excellent machining opportunities, it is nevertheless worth considering whether the high machining temperatures that ceramic milling cutters reach could result in damage to the material. As ceramic tools are only used for roughing operations, the only thing that needs to be ensured is that the depth of the damage to the material is less than the offset for finishing. In collaboration with Fraunhofer IPT in Aachen, Germany, the depth and extent of hardening was measured – for ceramic milling cutters with different levels of wear, in a full slotting operation in Inconel 718. The hardness measurement was carried out after the ceramic tools had been used to mill 13 or 14 slots with medium wear, or 23 slots with very high wear, in each case. The measuring points on the slot were selected in order to determine and evaluate the maximum thermal load. The basic hardness of the material is 446 HV. The result: A hardening of up to 640 HV was detected within a depth of 100µm. No hardening could be detected at depths greater than 200µm – regardless of the wear of the tool or the direction of measurement. As the generally applicable roughing offset is between three- and five-tenths of a millimetre, it is therefore not expected that roughing using ceramic tools will result in any damage remaining after the finishing process. www.walter-tools.com

Scheelite, or rather the calcium tungstate crystals within the ore, have interesting properties that make them valuable aside from being a source of tungsten. Calcium tungstate is a scintillator, which means it will fluoresce at a specific wavelength when excited by ionizing radiation, such as X-rays. This made the material very valuable for manufacturing intensifying screens, which were used with traditional film-based radiography to reduce the dose of radiation received by the patient. Large crystals of calcium tungstate, which can be produced synthetically using the Czochralski process, have also been used as scintillators in nuclear medicine procedures.

A classic example of a component made from a nickel-based alloy is a blisk for aircraft engines. This rotating integral component is a disc with a large number of blades. The spaces between the blades can be milled out using carbide milling cutters via a roughing process. The machining time for this is approximately 30 minutes. The MC075 ceramic milling cutter with high-feed geometry can carve out the same spaces in 10 minutes. For this application, it achieves feed rates of 9,500mm/min in a heat-resistant nickel-based alloy with a hardness of 44 HRC and a tensile strength of 1400N/mm². Feed rate values such as these are generally expected for machining aluminium, rather than nickel-based alloys.

The range of applications of ceramic cutting tool materials includes nickel-based, cobalt-based and iron-based heat-resistant alloys in the ISO S group. Typical alloys are for example Inconel 718, René 80, Nimonic 80A, Haynes 556, Mar-M-247 and Stellite 31. These heat-resistant super alloys (HRSAs) are the preferred choice for use in the hot section of aircraft engines.

But even a king needs someone to keep him in check, and while steel can be used to make tools hard enough to cut itself, there’s something even better for the job: tungsten, or more specifically tungsten carbide. We produced almost 120,000 tonnes of tungsten in 2022, much of which was directed to the manufacture of tungsten carbide tooling. Tungsten has the highest melting point known, 3,422 °C, and is an extremely dense, hard, and tough metal. Its properties make it an indispensible industrial metal, and it’s next up in our “Mining and Refining” series.

Because the amount of tungsten in either ore is so low — a tonne of tungsten ore contains only about four kilograms of either scheelite or wolframite — tungsten mines have to concentrate it considerably before it can be refined. This beneficiation is usually performed right at the mine site, starting with the usual crushing and grinding steps. Jaw crushers and ball mills turn the ore into a fine powder, which is classified by a series of sieves to achieve the correct grain size. The powdered ore is then transferred to a digester, where hot sodium hydroxide reacts with the tungstate minerals to form sodium tungstate, liberating it from the gangue, or waste rock.

Image 4: The comparison demonstrates the significantly higher cutting speed, higher metal removal rate and higher total volume of metal removed provided by the ceramic milling cutter in comparison to the carbide milling cutter

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I think my comment disappeared, but anyway – Carbon sublimates at that temperature rather than melting, unless you put it under very high pressure. Tungsten filaments at the same (incandescent bulb) temperatures last longer than carbon, especially with the benefit of a bit of inert gas or in a halogen bulb.

Image 2: MC275 ceramic milling cutter used for a slot milling in Inconel 718 with a cutting speed of 670m/min

The aerospace sector’s push for net-zero flight will result in an aviation revolution that will be as influential as Whittle’s jet engine, a conference has heard.

The results for milling cutters with carbide cutting edges and milling cutters with ceramic cutting edges could not be more different. The wear photos in image 3 show why ceramic milling cutters are only used for roughing. Signs of wear such as chipping on the cutting edge and wear mark widths of over 0.5mm, which for carbide milling cutters would indicate end of tool life, are no reason to stop using a ceramic cutting tool. The differences between the two cutting tool material types are also made clear by comparing the cutting parameters.

Precious metal and jewellery specialist Cooksongold has launched a new industrial division to pioneer the use of precious metal additive manufacturing (AM) for a range of performance-critical applications such as those found in aerospace.

I’ve used thousands of those inserts, and seeing the automated process was so enlightening. Well done! :-)

Tungsten is a rare metal, making up only a fraction of a percent of the Earth’s crust, about 1.25 parts per million. It has never been found in its elemental form in nature; instead, it appears as several mineral-bearing ores. The physical and chemical properties of tungsten, which make it such a useful metal, also ensure that the formation of these ores is limited to geologies where tremendous heat and pressure are exerted, such as where sections of continental crust collide to build mountain ranges. These orogenic belts, located mainly around the Pacific basin but also across the Alpine-Himalayan belt that stretches from southern Spain to Indonesia, are the main source of tungsten ore.

The high volume of orders in the aviation industry places great pressure on the capacity of engine manufacturers and their suppliers. Therefore, a reduction in component machining times would be highly beneficial. For heat-resistant super alloys, the cutting speed of carbide milling cutters is approx. 50m/min. Ceramic milling cutters offer a different approach, with cutting speeds of up to 1,000m/min.

The resulting fine powder of metallic tungsten is washed, dried, and sifted before going to ingot production, or consolidation. Here the powdered metal is placed in thick-walled molds and put into a hydraulic press, which forms the metal into an ingot. The ingot is referred to as “green” at this point and needs to be handled carefully so it doesn’t break apart during sintering, a two-step process where the ingot is first heated to 650 °C in a furnace, then up to 3,000 °C by passing an electric current through it in a water-cooled tube filled with hydrogen. The result is a solid ingot of tungsten, ready to be worked into products.

Our metallurgical history is a little bit like a game of Rock, Paper, Scissors, only without the paper; we’re always looking for something hard enough to cut whatever the current hardest metal is. We started with copper, the first metal to be mined and refined. But then we needed something to cut copper, so we ended up with alloys like bronze, which demanded harder metals like iron, and eventually this arms race of cutting led us to steel, the king of metals.

The obvious solution is for the U.S. to say goodbye to their SAE fractional inch units and embrace metric like literally the rest of the entire world has! Lol

The Walter product range includes two series of ceramic milling cutters: The MC275 with universal geometry is suitable for most applications; the MC075 is designed as a high-feed milling cutter. Both product ranges (see image 1) are available with cutting diameters of 8 to 25mm. Tools with diameters of 8 to 12mm are available as integral milling cutters, while tools with diameters of 12 to 25mm are available as ConeFit milling cutters. In both cases, only the head of the tool is made from ceramic. This head is brazed onto either a carbide shank or a carbide ConeFit base body. In principle, the entire milling cutter could be manufactured from ceramic, but a carbide shank increases the strength and damping of the tool. This enables increased projection lengths and higher material removal rates in comparison to solid ceramic tools.

The ceramic cutting tool material is tailored for use in milling applications. SiAlON ceramics are more resistant to temperature fluctuations than whisker-reinforced ceramics. This makes them the ideal choice for milling operations. The interrupted cut causes the temperature on the cutting edge to vary, and the use of coolant media can further increase the temperature difference, resulting in a thermal shock effect. For this reason, Walter recommends dry machining when machining high-temperature super alloys with ceramic milling cutters. An additional benefit for users is the environmental and economic advantage they gain from avoiding use of cooling lubricants.

Golden metal resources a British company has a new large discovery in Nevada. Is the largest undeveloped resource in the USA

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“Even though the age of the vacuum tube is long gone and the world has largely turned away from incandescent lighting, tungsten wire is still an important end product.” Indeed.

It took me a while to understand that. IMO “3,000 feet” would be much easier for those coming from metric world. (I assume that metric hacker can handle feet and pounds just fine, it’s just the unusual notation that’s confusing.)

Depending on the requirements for the finished metal, the tungsten oxide is sometimes doped with silicon, aluminum, or potassium before undergoing reduction. Reduction is performed in refractory vessels called boats, which are usually made of Monel, in tube furnaces called pusher furnaces. The tubes are filled with hydrogen gas and heated to about 850 °C, which reduces the oxide powder for about 20 minutes.

While ceramic tools present excellent machining opportunities, it is nevertheless worth considering whether the high machining temperatures that ceramic milling cutters reach could result in damage to the material. As ceramic tools are only used for roughing operations, the only thing that needs to be ensured is that the depth of the damage to the material is less than the offset for finishing. In collaboration with Fraunhofer IPT in Aachen, Germany, the depth and extent of hardening was measured – for ceramic milling cutters with different levels of wear, in a full slotting operation in Inconel 718. The hardness measurement was carried out after the ceramic tools had been used to mill 13 or 14 slots with medium wear, or 23 slots with very high wear, in each case.

The cutting data is predetermined by the cutting tool material and the material to be machined. A brittle yet heat-resistant cutting tool material can be used at high temperatures, but the low impact strength demands low feed rates per tooth of 0.02 to 0.05mm and small tool engagement of ap = 5% of Dc for full slotting operations and ae = 5% of Dc for contour milling with maximum cutting-edge length. The exception to this is the MC075 with high-feed geometry where fz = 0.15mm for ap ≤ apf. The cutting speed for both product ranges are between 400 and 1,000m/min.

Fascinating article. The video at the end showing how tungsten carbide inserts are made was great, also.

I realize not everyone in a metric county will have encountered this notation, but it is used in every place I just looked.

Another important industrial use for tungsten is welding electrodes. The high melting point of tungsten makes it perfect for TIG welding — the “T” is for tungsten, after all — which uses a high electric current to create a super hot plasma that melts the base metal and filler. Tungsten electrodes may look like pieces of thick wire, but they’re actually formed in much the same way as tungsten ingots are. Powdered tungsten is mixed with various additives, especially rare earth oxides like lanthanum and thorium, before being pressed and sintered into solid rods. The rare earth oxides serve to reduce the energy needed to remove electrons from the electrode, which makes it easier to strike an arc and makes the electrode last longer.