Is stainless steel magnetic?

It’s one of the most common questions we hear, and the answer is “it depends.” Whether a stainless steel is magnetic comes down to two things: the alloy family and the temper, or how much the material has been cold worked.

Why some stainless steels are magnetic

Stainless steels are grouped by their internal crystal structure, and that structure decides how they respond to a magnet.

• Austenitic grades (300 series). Their structure is not magnetic, so in the annealed condition these grades barely react to a magnet.
• Ferritic and martensitic grades (400 series). Their structure is magnetic, so they’re attracted to a magnet in every condition.
• Precipitation-hardening grades such as 17-7PH®. These change structure as they’re hardened and become magnetic in the hardened condition.

How cold rolling changes the 300 series

Cold rolling is what turns annealed strip into Quarter Hard, Half Hard and Full Hard tempers. As 300 series stainless is cold rolled, part of its nonmagnetic structure converts to a magnetic one. The harder the temper, the more of that change takes place, and the more strongly the strip is drawn to a magnet.

How much the magnetism increases depends on the alloy:

• 301 changes the most. That’s what lets it reach high strength through cold rolling, and it’s also why Half Hard and Full Hard 301 are noticeably magnetic.
• 302 and 304 become moderately magnetic in the harder tempers.
• 305 and 316 / 316L are more stable and stay only weakly magnetic, even after significant cold work.

Alloys we stock at a glance

For the other alloys we stock: 1008 / 1010 low carbon steel is magnetic, while Alloy 625 nickel alloy and C17200 beryllium copper are nonmagnetic.

This article is educational information only. Magnetic response varies with chemistry, temper and processing; always design to the requirements of your drawing or specification.