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?
To start the discussion, it must be understood that pure tungsten carbide has no magnetic properties at all. From a physical characteristic perspective, pure tungsten carbide is a weak diamagnetic material, therefore it does not get attracted to magnets. However, it can very slightly repel magnetic fields at the same time. In practice, this property is negligible and thus, tungsten carbide is considered more than adequate to be non-magnetic for the purpose.
Despite this, a discontinuity between industrial tungsten carbide and pure tungsten carbide is still persistent. Tungsten carbide or hard carbide (often referred to as tungsten steel) obtained from factories and laboratories are composite materials rather than the purest form of tungsten carbide; they are mostly composed of tungsten carbide powder (which can range from 80% to 95%) mixed with metal binders (which can range from 5% to 20%) and heated at extremely high temperatures to get sintered. To put it differently, just like a house requires cement to keep its bricks together, the tungsten carbide particles also require a binder to create a strong unit.
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 Check 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.
Comparing The Magnetic Differences of Different Types of Tungsten Carbides
Tungsten Carbide is typically formed by sintering tungsten carbide powder with metal binders (such as cobalt, nickel, iron, etc.) at high temperatures. Different types of hard alloys exhibit varying magnetic properties due to differences in composition and binder ratios
| Type of Tungsten Carbide | Primary Binder | Magnetic Properties | Typical Applications / Notes |
|---|---|---|---|
| Cobalt-bonded WC | Cobalt (Co) | Weakly magnetic / almost non-magnetic, slightly attracted by strong magnets | Most common type; widely used in cutting tools, dies, and industrial parts |
| Nickel-bonded WC | Nickel (Ni) | Nearly non-magnetic | Suitable for applications requiring strict non-magnetic properties, e.g., medical devices, electronics |
| Iron-bonded WC | Iron (Fe) | Strongly magnetic | Easily detectable in magnetic separation or recycling processes |
| Composite-binder WC | Cobalt + Nickel or other combinations | Magnetic strength varies between single-binder types | Binder ratio can be adjusted to tune magnetism for specialized industrial needs |
How To Obtain Truly Non-Magnetic Tungsten Carbide?
If your requirement is to be non-magnetic, you can directly refer to these solutions:
- Select low-cobalt or ultrafine-grained tungsten carbide: The less the cobalt is present (for instance, < 3%, or even < 1%), the fainter the magnetism will be. Ultrafine grain technology is able to keep material strength at low cobalt levels and is appropriate for situations where both hardness and toughness are required.
- ickel-based binder tungsten carbide is the top priority: The use of nickel as the binder instead of cobalt is the main technique in the industry to obtain “non-magnetic” tungsten alloy. This not only guarantees the wear-resistance of tungsten alloy but also rules out magnetic interference and has the best cost performance.
- Think about the application of binder-free tungsten carbide in rare cases: Only a very small number of extreme demands like high-precision scientific research may require pure tungsten carbide; however, it is brittle, difficult to process, and extremely expensive. It should not be an option unless absolutely necessary.
- Surface coating assistance: If the substrate has a little magnetic property bur the surface has to be totally non-magnetic, PVD/CVD coatings (like TiN, DLC, etc.) can be applied. The coating is non-magnetic and can separate the magnetic properties of the substrate while increasing the 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:
- 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.
- 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.
- 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.
- 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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