How to Test Stainless Steel: Use a Magnet or Alloy Gun for Accurate Element Analysis?

You think your material is genuine stainless steel, but a magnet sticks to it. You start to worry that you've received a low-quality or fake product.

The most reliable way to test stainless steel is with a handheld spectrometer, also called an alloy gun. A magnet test is often misleading because manufacturing processes can make high-quality stainless steel, like grade 304, magnetic. The alloy gun accurately analyzes the chemical elements to confirm the grade.

I remember a client who received one of our stainless steel mesh belts. They used a magnet on the cross rods, and it stuck. They immediately sent us an anxious email, believing the belt wasn't real stainless steel. We understand their concern. So, we used our own alloy gun to test the belt and sent them the report showing the chemical elements were perfect for stainless steel. To be absolutely sure, they cut off a piece and sent it to an independent lab. The lab results confirmed what we knew all along: the material met all the requirements. This experience highlights a common misunderstanding. Let me break down the right way to test stainless steel so you don't face the same uncertainty.

What is the magnetic test for stainless steel?

You have a magnet and want to check your stainless steel. You've heard this is a valid test, but you're unsure what the result really means. Here’s the simple truth.

A magnetic test¹ simply checks if the steel is attracted to a magnet. Generally, austenitic stainless steels like 304 and 316 are not magnetic. Other types, like ferritic and martensitic steels², are magnetic. However, this test is not a reliable quality check.

![A magnet being held near a stainless steel surface](https://www.yiyimeshbelt.com/wp-content/uploads/2025/07/qq图片20250704111254-副本.jpg
"Magnetic Test on Stainless Steel")

To understand this, you need to know about stainless steel's internal structure, its microstructure. Stainless steel comes in several families based on this structure.

The most common types used in applications like our conveyor belts are austenitic, specifically grades 304 and 316. In their original, fully annealed state, they are not magnetic because of their high nickel and chromium content, which creates a stable, non-magnetic austenitic structure. So, a magnet test is a very basic first step, but it doesn't tell the whole story.

Will a magnet work on genuine stainless steel?

Your brand new 304 stainless steel product is magnetic. This goes against what you've been told, making you question if you received the right material. Let me explain why this happens.

Yes, a magnet can definitely stick to genuine stainless steel like grade 304. This often happens after the steel has been "cold-worked." Processes like bending, drawing, or forming the steel at room temperature can change its internal structure and make it magnetic.

This is a very important point for our products at YIYI Mesh Belt. To make a durable metal conveyor belt, the wire and cross rods must be drawn and formed. This is a type of cold working¹. During this process, some of the non-magnetic austenite structure in 304 steel transforms into magnetic martensite.

Here's why:

1. Starting Material: We begin with high-quality 304 stainless steel², which has a non-magnetic austenitic structure.
2. Cold Working: To make the belt components, we draw the wire and bend the rods. This mechanical stress forces a change in the steel's crystal structure.
3. Transformation: A portion of the austenite turns into deformation-induced martensite.
4. Result: The martensite structure³ is strongly magnetic.

This means the final product, like the cross rods my client tested, can become magnetic. It is not a sign of poor quality or fake steel. In fact, this process can increase the strength of the material.

What impact do magnets have on stainless steel?

You've tested your steel and found it's magnetic. Now you're worried. Does this test itself harm the steel or change its properties, like its ability to resist rust?

A magnet has absolutely no physical or chemical impact on stainless steel. It does not change the steel's composition, its strength, or its corrosion resistance. The only impact is on your perception; it is a misleading test that can cause unnecessary worry.

Think of the magnet as just a detector. The magnetism it detects was already present in the steel's microstructure due to how it was made. The magnet didn't create it. The properties that truly matter, especially corrosion resistance, come from the steel's chemical makeup. Specifically, the amount of chromium and nickel in the alloy. These elements form a passive, protective layer on the surface that stops rust. A magnetic field has no effect on this protective layer or the elements that create it. So, while a magnet can tell you if a piece of steel has a magnetic structure, it tells you nothing about its quality or its ability to perform its job.

What are the methods to test the quality of stainless steel?

You need to be certain about your stainless steel's quality. A simple magnet test is not enough and leaves you with unanswered questions. So, let’s explore the professional methods for a clear answer.

Beyond a magnet, you can use a chemical test kit for a quick check. For professional, accurate results, a handheld spectrometer gives instant elemental analysis. The most thorough method is sending a sample to a third-party lab for testing.

Each method has its pros and cons. At YIYI Mesh Belt, we need fast and accurate results to guarantee our quality, which is why we rely on our handheld spectrometer.

For any business where material quality is critical, the handheld spectrometer is the industry standard. It gives us and our clients peace of mind by providing a complete chemical breakdown in seconds.

What is the Difference Between 304 and 316 Stainless Steel?

You need to choose between 304 and 316 stainless steel. They look identical, but 316 costs more. Understanding the key difference will help you make the right investment for your needs.

The main difference is that 316 stainless steel contains an element called molybdenum; 304 does not. This single addition gives 316 much better corrosion resistance, especially against salts and chlorides, making it essential for harsh environments.

![Two identical-looking conveyor belts, one labeled 304 and one 316]( "Difference Between 304 and 316 Stainless Steel")

While both are excellent materials, that 2-3% of molybdenum in grade 316 makes a world of difference. It specifically helps prevent "pitting corrosion," which is a type of localized damage that can create small holes in the steel when exposed to chloride solutions, like saltwater or industrial chemicals.

Here's a simple guide for when to use each:

We often recommend 304 for general-purpose conveyor belts, especially in the food industry. But if a client's process involves high salt content, cleaning chemicals, or operates near the ocean, we always advise upgrading to 316 to ensure the belt's longevity and performance.

What is the chemical composition standard of SUS304 and SUS316 stainless steel?

You need the exact technical specifications for 304 and 316 steel. Vague descriptions are not enough for engineering or critical quality control. Here are the numbers that define these materials.

The key elements for 304 stainless steel are approximately 18% chromium and 8% nickel. For 316, the composition is about 16-18% chromium, 10-14% nickel, and, most importantly, 2-3% molybdenum. These percentages are what define their grade.

An alloy gun or lab test measures these elements to verify the steel's identity. The specific ranges can vary slightly based on the standard (e.g., ASTM, JIS), but they are generally very close. Understanding what each element does helps explain why these formulas work so well.

This is why we trust our alloy gun. It confirms these exact percentages, ensuring that the raw material we use for your conveyor belt has the precise chemical foundation to deliver the performance you expect.

Conclusion

Don't rely on a simple magnet. For a true measure of stainless steel, use a handheld spectrometer to ensure you get the quality and performance you paid for.