Wolfram crucible

Types of Wolfram crucible

Wolfram crucible is made of tungsten to provide the most heat and temperature resistance for a crucible. These crucibles mainly handle the smelting of high-temperature metals like nickel and cobalt.

Whether it's a tungsten alloy crucible for holding molten material to prevent contamination or one with a thin wall for high-efficiency heating, knowing the right kind is essential in modern forges and workshops.

Occasionally, manufacturers need a crucible made of tungsten composites. These include tungsten and copper or tungsten and molybdenum, one of the more common alloys, to save on the weight and expense of pure tungsten while still allowing for a safe work environment around high-temperature metals like cobalt or nickel.

Here is a rundown of some common types of tungsten crucibles that suppliers have in stock:

• Machinable tungsten crucibles: Pure tungsten is a very dense metal. It can also be hard to work with. Hence, machinable tungsten crucibles are made from slightly softer tungsten alloys. These alloys are more machinable and can be easily hunted or welded even in their alloyed state. Molybdenum is also often added to the mix to lower the melting point and add workability. It will still be able to resist the typical hell of any crucible in the forge, though.
• Tungsten copper alloy crucibles: Often called copper-infiltrated tungsten, tungsten copper alloys are used where one needs the strength and density of tungsten but with increased machinability. The copper fills in the gaps between the tungsten grains, making a more workable alloy. Sometimes a little silver is added to increase electrical conductivity, which is often the purpose of such alloys.
• Tungsten alloy crucibles: The most common is copper tungsten alloy made by mixing copper and tungsten together for crucibles where electrical conductivity and strength are both required. These are often used in electrical discharge machining, where the tool needs to make a lot of fine electrical cuts in a workpiece. Silver is also sometimes added for better conductivity.
• Molybdenum tungsten alloy: Molybdenum is often added to tungsten alloys to lower the melting point and make the alloy easier to work with. Even pure tungsten can be hard to shape or cut. Molybdenum's lower melting point also affords the worker greater flexibility, as it can be melted and recast to repair or reshape tools that would otherwise be very difficult to work with.
• Patented tungsten alloy composites: There are also many proprietary tungsten alloys where manufacturers add other metals or modify how the alloy is formed to increase strength, workability, electrical properties, or other desired traits. Examples are alloys containing nickel or silver to give them more desirable properties for electric motors or making tools in a foundry for machining metal parts.

Industrial application of wolfram crucible

There are some general-purpose crucibles around that are made from other materials, such as graphite or ceramics, but most crucibles tend to be made from tungsten or one of its alloys. Therefore, it's better to use one of those in industries that regularly melt or forge tungsten alloys from high-temperature metals.

• Electrical Engineering: As mentioned before, copper tungsten alloys are used in the electrical engineering industry for machining electrical contacts and other parts. These furnace parts go through enormous stresses, law, and wear. They should be made from material that can hold up to a lot of heat as well as the electric currents passing through the parts. This industry frequently uses tungsten crucibles to hold workpieces through machining, welding, or other finishing to make items such as electric motors, relays, and other components.
• Metalworking: The metalworking industry will use crucibles to both hold metal alloys that are being shaped by machining and to contain the molds into which newly smelted metals will be poured. The molybdenum crucible is often used to hold metals with high melting points like tantalum, niobium, molybdenum itself, and refractory metals.
• Aerospace: The aerospace industry makes many parts using tungsten alloy and refractory metal due to its strength, density, and resistance to heat. It is commonly used on afterburner flame holders, jet engine lube oil pumps, and other parts exposed to extreme conditions. Parts in the aerospace industry need to be very tough yet lightweight.
• Nuclear: Tungsten crucibles can also be used in the nuclear industry due to their low viscosity and refractory nature. Tungsten alloys are used on several parts in this industry that need to resist temperature or other wear and tear that is not seen elsewhere. An example of such parts is the AERD nozzle tip used in the Aerospace Nuclear Engine.
• Chemical: The chemical industry also makes use of tungsten alloys for parts that need to resist corrosion. This is especially true if any of the chemicals involved are highly caustic or might dissolve metals. In this industry, tungsten alloys are often used for sensors and other parts that undergo chemical processes.
• High-temperature furnaces: Tungsten and molybdenum alloying crucibles are often used in high-temperature furnaces to carry out zone melting. This method produces high-purity single crystals used in the semiconductor industry or to make piezoelectric and other components. Non-contact heating, such as induction heating, requires a material with low thermal conductivity to contain the material without contaminating it.

Product specifications and features of wolfram crucible

Technical specifications/key features

• Size: Wolfram crucibles can be produced in a range of sizes from 50ML to 1000ML. Smaller individual crucibles usually don't hold more than 100ML but can be as small as 10ML. The larger ones are typically in the range of 500ML to 1000ML. However, there are also larger crucibles over 1000ML but not in single units. Often they are in sets of several together.
• Material: Wolfram's crucible is made from tungsten. Tungsten is a metal known for its opposing combination of extremely high density yet high melting point. This makes it ideal for the crucible used in high-temperature environments. Tungsten usually comes with an atomic number of 74 on the periodic table. It is classified as a transition metal because it tends to have very high melting and boiling points and extreme density compared to other metals. Its toughness and rigidity also mean it can withstand extreme battering without shattering or cracking.
• Surface finish: Tungsten crucibles are polished to make them shiny to remove impurities and allow for more homogenous mixing. Other types of surface treatments include shot blasting to roughen and improve mechanical interlocking or reduce solder wetting in mass solder application.
• Max working temperature: The melting point of pure tungsten is 3422 degrees centigrade. However, most tungsten alloys have slightly lower melting points. Nevertheless, it still means they can withstand extreme temperatures and hold up to at least 99% of what the tungsten alloy is made for. Note that the crucible may become brittle at or near the melting point. Therefore, it is not meant to be worked at this temperature for an extended period. The alloying with other metals that have lower melting points than tungsten also helps with this. It will never reach that point in normal scenarios. However, if it does, then the workability of the crucible is not affected.
• Shape: Crucibles are commonly spherical, ellipsoidal, cylindrical, conical, or cuboids. This allows the molten metal to move freely within the container. They are also designed in such a way as to provide easy pouring of the content once it is molten without the risks of contamination or easily having a difficult time pouring it out. Note that some crucibles have greater than 1:1 aspect ratios. They can be egg-shaped or other shapes that are not typical geometrical shapes.

How to install or use

The tungsten crucible is often installed in furnace space or used alone in a furnace to smelt metal alloys. The furnace will have a heating element around the crucible to provide the temperature needed to melt the metal.

Maintenance and repair

There are some general maintenance tips and recommendations for repairing or taking care of Wolfram's crucible. Tungsten is very dense and hard and cannot be easily manipulated. It actually has one of the highest densities after osmium among all the known metals. Therefore, traditional repair techniques for softer metals do not work.

That said, here are some ways to maintain or repair wolfram crucibles:

• Replacement: The most effective way to maintain a wolfram metal crucible is to replace it entirely when it wears or develops a hole. As an extremely tough metal, it's virtually impossible to sand or grind down a tungsten crucible to make it flat and the right shape as it was originally.
• Preventive measures: However, there are some tips to help prevent wear and tear on the crucible itself. These include minimizing thermal shock by heating the crucible slowly when starting and cooling it gradually. Avoid contact with tools in the furnace to minimize scratches.
• Welding: If the crucible develops small cracks or spalling, welding them together might be a solution if done carefully enough. However, this will only be as good as it will be.

Quality and safety considerations of wolfram crucible

Quality considerations

Some key quality considerations when purchasing tungsten crucibles include:

• Purity: Make sure the tungsten is at least 99.95% pure or higher for very critical applications such as semiconductor manufacturing. Lower purity alloys may be acceptable for less sensitive industries like aerospace or medical.
• Alloy composition: If using an alloy, ensure the proportions of other metals like copper or molybdenum are within recommended ranges. Too much of these could weaken the structure or contaminate molten metals.
• Tolerance and finish: Roughness, dimensionally accurate, tightly measured to ensure proper fit in furnaces and minimize contamination by trapping impurities. However, not too smooth like a mirror finish that doesn't allow for proper molten metal to wet the crucible surface for effective casting.
• Test reports: Reliable suppliers will be able to provide test reports (preferably third-party certified) showing the alloy's chemical composition, purity, mechanical properties, and maybe even thermal conductivity and expansion tests.

Safety considerations

Safety risks generally are related to:

• Handling: Tungsten is a very heavy metal with a very high density. Hence, it can potentially cause crushing or blunt force trauma if not handled properly. It can also cause injury if welded and touched due to its tendency to retain heat even after cooling.
• Spillage: Handling molten metals are dangerous and can result in severe burns, spillage, or contamination if allowed to escape the crucible.
• Tungsten dust: Welding or machining tungsten can release fine dust that is a respiratory hazard if inhaled. It can also cause skin irritation upon contact.
• Combination with other materials: Sometimes tungsten alloy safes and crucibles are manufactured with other materials like copper. This can also cause fume generation that can be toxic if not properly ventilated during melting or machining.

Q&A

Q1: Is wolfram the same as tungsten?

A1: Yes, wolfram and tungsten are the same. Tungsten is the English name for the metal that comes from the Swede word tungsten. However, wolfram is the name for tungsten in most other languages, such as wolfram in Spanish and French. It is known as wolframite when combined with iron or manganese.

Q2: What is lasalle metal?

A2: Lasalle metal is also known as lasalle alloy or Russell light alloy, made with approximately 15% tungsten, 15% nickel, and 70% steel. It was invented by Lesalle and hence the name lasalle metal. Compounded with refractory metals and high nickel content, it has superior strength and corrosion resistance yet is lighter than common metals.

Q3: What is the advantage of tungsten?

A3: Tungsten is very dense and keeps heat better than most metals. Hence, it provides better weight, temperature, and burn time for the user. Tungsten also does not vaporize as easily as other metals. This makes it good for holding very molten metals without contaminating them.

Q4: Does tungsten have radiation?

A4: Yes, tungsten does have some radiation, although it is not alpha nor beta particles that are harmful to the body. Tungsten does emit some low-level gamma rays due to its atomic number and structure. It is also used as shielding against rays in x-ray machines.

Q5: What are some common uses of tungsten?

A5: Tungsten has a lot of uses froms medical to aerospace to automotive. In industries, it is used to make parts that deal with a lot of pressure and temperature. For example, Wolfram metal is used in rocket fuel ignition nozzle, jet engine parts, and afterburner flame holders.