Is Tungsten Carbide Magnetic? Find Out Now

In the precision processing workshop, the newly installed tungsten carbide cutting tools were suddenly attracted by the magnetic fixture, and the calibrated parameters were instantly disrupted. In the laboratory, a carefully selected tungsten carbide fixture was placed close to the instrument, but the screen data suddenly jumped. When purchasing, tungsten alloy workpieces that were repeatedly confirmed to be non-magnetic were firmly attracted by a magnet upon arrival…

If you have ever encountered a similar situation, you can’t help but wonder: It is said that tungsten carbide is non-magnetic, so why is the one in your hand magnetic? The problems behind this may directly lead to the scrapping of parts, delays in the construction period, and even affect the accuracy of experimental data.

Is Tungsten Carbide Magnetic? Yes Or No?

Let’s first draw a clear conclusion: Pure tungsten carbide itself has no magnetism. In terms of physical properties, pure tungsten carbide is a weak diamagnetic material, which means it is not only not attracted by magnets but even slightly repels magnetic fields. This characteristic can almost be ignored in daily applications and fully meets the requirement of being non-magnetic.

But the problem lies in the difference between industrial tungsten carbide and pure tungsten carbide. The tungsten carbide and hard carbide (commonly known as tungsten steel) we use in factories and laboratories are almost never pure tungsten carbide – they are composite materials made by sintering tungsten carbide powder (accounting for 80% to 95%) and metal binders (accounting for 5% to 20%) at high temperatures. Just as building a house requires cement to bond the bricks together, tungsten carbide particles also need a binder to form a high-strength whole.

It is the binders within these industrial tungsten carbide that make them magnetic, with cobalt being the most common – cobalt is a typical ferromagnetic metal and, like iron and nickel, can be strongly attracted by magnets. When cobalt is added as a binder to tungsten carbide, it makes the entire material magnetic. Moreover, the higher the cobalt content, the stronger the magnetism tends to be: for instance, a tungsten alloy containing 15% cobalt may be more easily “caught” by a magnet than one containing 5% cobalt. If the cobalt content drops below 1%, the magnetism will be significantly weakened. If cobalt is not used at all and nickel (non-ferromagnetic) is used as the binder instead, the magnetism will be greatly reduced or even disappear.

Of course, apart from cobalt, a few special grades of tungsten carbide may use iron or nickel-iron carbide as binders (such as some low-cost cutting tools), which can also bring magnetism – but the most mainstream in industry is still cobalt-based binders, and this is also the most common reason why tungsten carbide become magnetic.

How To Accurately Determine Whether Your Tungsten Carbide Is Non-Magnetic?

To avoid magnetic pits, the key is to learn to judge the true magnetism of materials. Several simple and practical methods can be referred to

When purchasing, don’t just ask “Is it tungsten carbide?” but be sure to ask “What is the binder?” and “What is the cobalt content?” Cobalt content is the core indicator for judging magnetism – the lower the content, the weaker the magnetism. Those with nickel as the binder are usually closer to being “non-magnetic”.

Clarify the requirements and make it clear in advance: Directly tell the supplier “I need non-magnetic/low-magnetic tungsten alloy”, and emphasize “low cobalt (for example, < 1%) or nickel-based binder”. Clear demands can reduce communication errors.

A simple test with a magnet: Find a strong neodymium iron boron magnet (a strong magnet that can be purchased daily will do) and bring it close to the workpiece. If it can be significantly attracted, it indicates that the cobalt content is not low. If there is almost no reaction, it is very likely to be a low-cobalt or nickel-based binder.

In extreme scenarios, professional reports are required: If the application has extremely high magnetic requirements (such as in medical or precision instruments), you can ask the supplier to provide a magnetic permeability test report. It is more reliable to rely on data.

How To Obtain Truly Non-Magnetic Tungsten Carbide?

If your requirement is to be non-magnetic, you can directly refer to these solutions:

• Choose low-cobalt or ultrafine-grained tungsten carbide: The lower the cobalt content (for example, < 3%, or even < 1%), the weaker the magnetism. Ultrafine grain technology can maintain material strength at low cobalt levels and is suitable for scenarios where both hardness and toughness are required.

• Give priority to nickel-based binder tungsten carbide: Using nickel instead of cobalt as the binder is the mainstream solution for achieving “non-magnetic” in industry. It can not only ensure the wear resistance of tungsten alloy, but also avoid magnetic interference, and has the highest cost performance.

• In special scenarios, consider binder-free tungsten carbide: A very small number of extreme demands (such as high-precision scientific research) may require pure tungsten carbide, but it is brittle, difficult to process, and extremely costly. It should not be chosen unless necessary.

• Surface coating assistance: If the substrate has a slight magnetic property but the surface needs to be absolutely non-magnetic, PVD/CVD coatings (such as TiN, DLC, etc.) can be applied. The coating itself is non-magnetic and can isolate the magnetic properties of the substrate while enhancing wear resistance.

Key Points To Note During Procurement And Application

To bid farewell to the “magnetic disturbance” completely, pay attention to these details when landing:

1. When making a purchase, ask one more question: In addition to confirming “non-magnetic”, be sure to ask the supplier to make a written commitment regarding the cobalt content (such as < 1%) or the type of binder (such as “nickel-based”) to avoid unreliable oral promises.
2. Remember to clean after processing: Even if low-cobalt or nickel-based tungsten carbide are selected, extremely fine iron filings may remain during processing (such as grinding), causing the surface to be slightly “magnetic”. Rinse it once with a non-magnetic cleaner before use to avoid misjudgment.
3. Demagnetization treatment in extreme environments: If the application scenario is extremely sensitive to magnetism (such as aerospace parts), demagnetization treatment can be carried out on the workpiece before use to further reduce risks.
4. Understanding that “non-magnetism is relative” : There is no industrial material that is absolutely “zero-magnetic”. The key is to clearly define how much magnetism your scenario can tolerate (such as the anti-interference threshold of the instrument), and then make targeted choices.

Final Thoughts

After all, the magnetic property issue of tungsten carbide lies in the “binder” : pure tungsten carbide is non-magnetic, while the magnetic property of industrial products mainly comes from cobalt. To avoid magnetic interference, it is more reliable to choose nickel-based binders or grades with ultra-low cobalt (<1%).

The next time you purchase or use tungsten alloy, remember to focus on the binder composition and cobalt content, and clearly express the non-magnetic requirement. If you choose the right materials, your precision tools and workpieces will no longer be stuck, and production and experiments will proceed more smoothly.

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