Due to this difference, ferritic stainless steels are generally magnetic while austenitic stainless steels usually are not. A ferritic stainless steel owes its magnetism to two factors: its high concentration of iron and its fundamental structure. The metallic atoms in an austenitic stainless steel are arranged on a face-centered cubic fcc lattice. The unit cell of an fcc crystal consists of a cube with an atom at each of the cube's eight corners and an atom at the center of each of the six faces.
In a ferritic stainless steel, however, the metallic atoms are located on a body-centered bcc lattice. The unit cell of a bcc crystal is a cube with one atom at each of the eight corners and a single atom at the geometric center of the cube.
Alloying the stainless steel with elements such as nickel, manganese, carbon and nitrogen increases the likelihood that the alloy will possess the fcc crystal structure at room temperature. Chromium, molybdenum and silicon make it more likely that the alloy will exhibit the bcc crystal structure at room temperature. The most popular stainless steel is Type , which contains approximately 18 percent chromium and 8 percent nickel.
At room temperature, the thermodynamically stable crystal structure of stainless steel is bcc; nevertheless, the alloy's nickel concentration, as well as the small amounts of manganese about 1 percent , carbon less than 0.
If the alloy is mechanically deformed, i. Popular ferritic stainless steels are iron-chromium binary alloys with 13 to 18 percent chromium. These alloys are ferromagnetic at room temperature. Like all ferromagnetic alloys, when heated to a high enough temperature--their Curie temperature--the ferritic stainless steels lose their ferromagnetism and become paramagnetic--that is, they do not retain their own magnetic field but continue to be attracted to external ones.
A piece of ferritic stainless steel is typically unmagnetized. When subjected to a magnetic field, however, it will become magnetized and when this applied magnetic field is removed the steel remains magnetized to some degree.
A ferritic stainless like stainless steel, on the other hand, is ferromagnetic. Magnets stick to it. We tested a few different thicknesses of steel vs. We simulated a lot more. We considered disc magnets of various diameters and thicknesses. The steel it sticks to was always much larger than the magnet diameter, but we varied the thickness. It varies depending on the exact stainless steel.
We only covered a few in this article. We found:. Try it! Finding good magnetic data on all the kinds of steel out there turns out to be surprisingly hard. For some less common varieties, the magnetic specification information can be hard to find, and harder to know if it's trustworthy.
Prototype and test! In these cases it is often necessary to agree to maximum magnetic permeability between customer and supplier. It can be as low as 1. Here at Mead Metals, we stock series stainless steels, which are austenitic. Why is Stainless Steel Not Magnetic? Posted by: Brian Rothstein on October 24, How does a steel become classified as stainless? Steel alloys composed with a minimum of What Makes Something Magnetic? Is Stainless Steel Magnetic or Not? From the British Stainless Steel Association : For example, cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel.
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