1. The Panic: "Why does the magnet stick?!"
Hello, this is Global Steel Insight.
We often get angry calls from customers:
"I bought 304 Stainless Steel pipe, but my magnet sticks to it! You sent me fake iron!"
Stop worrying. This is completely normal.
2. The Science: It's "Work Hardening"
Originally, Grade 304 has an Austenite structure, which is non-magnetic. However, when we bend, draw, or cold-roll the steel to make a seamless pipe, the internal structure undergoes a "Phase Transformation."
Under physical stress, some Austenite transforms into Martensite. Martensite is extremely hard and Strongly Magnetic.
This means: Magnetism = Evidence of Hard Work (Cold Working), not low quality.
3. Why the "Magnet Test" is Dangerous
If you rely only on a magnet, you will fall into a bigger trap. Unethical sellers know this and use it against you.
| Grade | Magnetism | Quality Verdict |
|---|---|---|
| 304 (Sheet) | None | Standard |
| 304 (Pipe/Bar) | Slightly Magnetic | Normal (Work Hardened) |
| 201 (Cheap) | None | Risk (Rusts easily) |
| 430 (Ferritic) | Strong Magnetic | Good (But distinct from 304) |
As you can see, Grade 201 (the fake one) is also non-magnetic! If you only trust the magnet, you might end up buying cheap 201 thinking it's premium 304.
4. Forget Magnets, Test the Strength
Instead of playing with magnets, professional engineers check the Mechanical Properties. We verify quality by checking Tensile Strength and Yield Strength.
5. Expert Tip: How to remove magnetism?
Does your application require 100% non-magnetic properties (e.g., MRI rooms, Sensitive Electronics)?
There is a solution: Solution Annealing.
Heat the pipe to 1050°C and cool it rapidly. This transforms the structure back to pure Austenite, removing all magnetism. (Note: This costs extra).
NEXT STRATEGIC STEP ➤
[STS Tip #3] The Art of Surface: 2B, BA & PVC
"We solved the magnet mystery. Now, let's choose the right look.
What is the difference between 2B (Matte) and BA (Mirror)?"
🚀 Need Verified Stainless Steel?
"Stop guessing with magnets."
We supply Prime Quality STS 304/316 with full MTC & Lab Data.
Get the real steel from a real partner.
Direct Email: rongzhai69@gmail.com