When you’re sourcing metal parts for a project, magnetic properties might feel like a niche technical detail—until a component fails to hold a magnet where it needs to, or a sensitive assembly picks up unwanted ferromagnetic debris. As a metal parts supplier who’s worked with engineers, fabricators, and hobbyists for over a decade, I’ve seen how small oversights in magnetic behavior can derail timelines, raise costs, or even compromise product performance. In this post, I’ll break down the magnetic traits of the most common metal parts we produce, explain why they matter, and share how we tailor our manufacturing to match your needs. Metal Parts
First, let’s start with the basics: magnetism in metals stems from the alignment of unpaired electrons in atomic structures, plus external factors like heat, processing, and impurities. Most metals fall into three categories: ferromagnetic (strongly magnetic), paramagnetic (weakly magnetic), and diamagnetic (non-magnetic). But it’s not that simple—many parts we supply are made of alloys, and their magnetic properties shift with composition, heat treatment, and finishing.
Ferromagnetic metals are the workhorses for applications that require consistent magnetic attraction. The core here is iron, and alloys built around it. Carbon steel, for example, is one of the most common parts we make—think structural brackets, fasteners, and gear shafts. Low-carbon steel (A36, 1018) has a soft magnetic structure, meaning it’s easy to magnetize but also easy to demagnetize. That makes it perfect for parts like lifting hooks that need to hold heavy loads with magnetism, then release when the current cuts off. On the other hand, high-carbon steel (1095, O1 tool steel) is much harder and forms a harder magnetic domain structure. That’s why we use it for things like screwdriver tips or magnetic drill bits—they stay magnetized longer, so they don’t slip out of a magnetic chuck mid-use.
But there’s a catch with ferromagnetic steels: heat and processing change their magnetism. If you’re making parts for high-temperature environments, like furnace components, standard carbon steel will lose its ferromagnetism above the Curie temperature (around 770°C for pure iron). That’s a problem—if you’re relying on a sensor that detects a magnetic part, it’ll stop working at those temps. So for those applications, we use alloys like Invar, which is an iron-nickel alloy with a Curie temperature around 230°C, making it stable at lower high-heat settings. We also have to watch out for cold working—bending or machining steel too much can disrupt its magnetic domains, making it less responsive to magnets. That’s why we stress-quench many of our steel parts after machining, to restore consistent magnetic properties and prevent warping.
Next, stainless steel is a big one—many of our clients ask if all stainless parts are non-magnetic, and the short answer is no. Austenitic stainless steel (304, 316) is the most common type for food processing, medical equipment, and marine parts, and it’s technically paramagnetic—meaning it’s very weakly attracted to magnets, but not enough to count as magnetic for most practical uses. Wait, why? Austenitic steel has a crystal structure with high nickel content, which suppresses strong magnetic alignment. But if you machine or bend 304 too aggressively (cold working), it can transform a small portion of the austenite into martensite, a ferromagnetic phase. That’s why you might see a 304 bolt that sticks weakly to a magnet—don’t worry, that’s not a defect; it’s just a side effect of forming. We can mitigate that by using annealed austenitic stainless, which is heated to 1050°C and slowly cooled to remove residual martensite, making it as non-magnetic as possible.
Then there’s ferritic stainless steel (430, 409), which is magnetic. These have lower nickel and higher chromium content, with a body-centered cubic crystal structure that supports strong magnetic domains. We use 430 for things like automotive exhaust brackets and kitchen appliance trim because it’s corrosion-resistant like austenitic stainless, but cheaper and magnetic. 409 is even more magnetic—we source it for catalytic converter components where magnetic sensors need to detect the part’s position.
The third common stainless type, martensitic stainless (410, 420), is also magnetic. These have higher carbon content, so they harden with heat treatment, just like carbon steel. We supply 410 for things like pump shafts and valve stems, where we need a part that’s strong, corrosion-resistant enough for water applications, and can hold a magnet for alignment during installation.
Beyond steels, we work with non-ferrous metals that have their own magnetic traits. Aluminum is paramagnetic—very weakly magnetic, so a magnet won’t stick to aluminum parts. That makes it ideal for things like electronic chassis or aircraft components where you don’t want magnetic interference. But here’s a quirk: if you move a magnet quickly past aluminum, you’ll feel a drag force from eddy currents—this is how magnetic brakes work, and it’s a property we leverage when we make custom aluminum parts for testing equipment that relies on magnetic damping.
Copper is diamagnetic—so it’s actually repelled by magnets, though the effect is tiny. We use copper parts for things like bus bars in electrical systems, where magnetic attraction would cause unwanted vibration or heat. Brass, which is a copper-zinc alloy, is also diamagnetic. We get requests often for brass fasteners for sensitive medical devices because they won’t interfere with MRI machines, which is a huge plus.
Titanium is another paramagnetic metal—magnetically neutral for most purposes, and it’s lightweight and corrosion-resistant. We supply titanium brackets for aerospace and medical implants, where both non-magnetism and strength are critical. The only time titanium gets a bit magnetic is if it’s alloyed with iron, but we use grade 5 titanium (6Al-4V) which has very low iron content, so it stays non-magnetic.
Now, why does all this matter for your metal parts project? Let’s walk through a few real examples from our work. Last year, a medical device client came to us with a problem: their new portable blood analyzer had a sensor that failed because the 304 stainless sample tray was weakly magnetic from machining, pulling a small magnetic component out of alignment. We swapped their tray material to annealed 304 stainless, and also adjusted the machining process to use slower cutting speeds that reduced cold working, so the tray was 95% non-magnetic, eliminating the sensor issue entirely.
Another client was a construction company lifting steel beams with magnetic cranes. They were using standard 1018 steel hooks, but the hooks would lose magnetism after a few months of heavy use because the heat from outdoor welding in summer raised their temperature above the Curie point temporarily. We switched them to a low-carbon steel with a modified alloy that has a slightly higher Curie temperature, so it stays magnetic through seasonal temperature swings, and also added a post-manufacturing demagnetization step that removed residual magnetism from machining, improving the crane’s lifting efficiency by 12%.
We also recently worked with a food processing equipment maker. They needed conveyor belts that would attract small stainless steel food scraps so they could be easily separated, but they didn’t want the belts to attract other debris like plastic. We supplied a custom ferritic stainless steel (430) belt, which is magnetic enough to catch the steel scraps but not so magnetic that it pulls in plastic bits, and the corrosion resistance of stainless meant the belt wouldn’t rust in frequent washdowns.
A common question we get is about finishing: does plating or coating change a part’s magnetic properties? The short answer is almost never. Plating with zinc, nickel, or chrome is a thin layer of non-magnetic (or very weakly magnetic) metal, so it won’t affect the base part’s magnetism. The only exception is if you plate a non-magnetic part with a ferromagnetic material—for example, plating aluminum with nickel. If you need a non-magnetic part, we’ll make sure to use a non-magnetic plating material. Anodizing aluminum (a common surface finish) is non-conductive and non-magnetic, so it doesn’t change magnetism at all.
When we ship parts, we also handle demagnetization for free on request. Machining and forming processes often leave residual magnetism, which can be a problem for parts that need to pass through a manufacturing process without picking up debris, or for sensitive equipment. Our demagnetization process uses alternating current to flip the magnetic domains in the part, gradually reducing their strength until the part is as non-magnetic as its composition allows.
If you’re not sure which metal part is right for your magnetic needs, here’s a quick checklist to reference before you order:
- If you need a part that will hold a magnet, or magnets will hold it, go with low or high carbon steel (depending on if you need temporary or permanent magnetism).
- If you need a non-magnetic part, stick to annealed austenitic stainless (304, 316), aluminum, brass, or grade 5 titanium.
- If you need a part that’s magnetic but corrosion-resistant, use ferritic (430) or martensitic (410) stainless.
- For high-temperature applications where ferromagnetism is required, check the Curie temperature of the alloy—standard carbon steel won’t work above 770°C.
At the end of the day, magnetic properties aren’t an afterthought—they’re a core part of a part’s functionality. Too many suppliers treat all metal parts as generic, but we don’t. Every part we make is tested for magnetic strength, composition, and surface finish to make sure it fits exactly what your project needs.
If you’re working on a project where magnetic properties matter—whether it’s a medical device, industrial equipment, aerospace component, or anything in between—we’re here to help. We can run custom magnetic tests on your prototype parts, adjust alloys or heat treatments to match your requirements, and deliver parts on your timeline without compromising on quality. Reach out to our team today to discuss your sourcing needs, and let’s make sure your metal parts work as hard as your project does.
Door and Window References
- ASTM International. (2020). Standard Test Methods for Magnetic Properties of Ferrous Alloys. ASTM A34/A34M-20.
- Cullity, B. D., & Graham, C. D. (2011). Introduction to Magnetic Materials (2nd ed.). Wiley-IEEE Press.
- ASM International. (2018). Magnetic Properties of Stainless Steels. ASM Handbook, Volume 4: Heat Treating.
- Brandes, E. A., & Brook, G. B. (1998). Smithells Metals Reference Book (7th ed.). Butterworth-Heinemann.
Taiwan Hardware Corp.
Taiwan Hardware Corp. is one of the most experienced metal parts manufacturers and suppliers in Taiwan, featured by quality products and good service. Please feel free to buy ISO certified metal parts from our factory. For customized service and OEM service, contact us now.
Address: 7th Floor, No. 270, Section 1, Fuxing Road, South District, Taichung City
E-mail: silviatsai@panutw.com
WebSite: https://www.taiwanhardware-en.com/
