Are 304 & 316 stainless steel fasteners magnetic?

The question of whether or not certain stainless steel fasteners are magnetic can be an important one. 304 and 316 stainless steel are two grades of the metal that are commonly used to make fasteners. Are these magnetic?

What makes stainless steel magnetic?

The main constituent of stainless steel is iron. Different grades of stainless steel contain different amounts and forms of iron – and this is what determines the magnetism of the steel. There are two basic types of stainless steel: ferritic and austenitic. Ferritic steel contains a high concentration of iron. Austenitic steel contains a particular phase of iron called austenite or gamma iron. Austenite is non-magnetic, which means that austenitic steel is as well. Ferritic stainless steel, on the other hand, is magnetic.

304 and 316 stainless steel

The 304 and 316 stainless steel grades are both austenitic, which means that they are non-magnetic. However, it’s not quite as simple as that. Under certain circumstances, it is possible for objects made of 304 or 316 stainless steel to be magnetic – at least to some extent. When stainless steel items are cold worked or welded, or exposed to very low temperatures, the austenite can be converted to martensite or ferrite, which are both magnetic. The specific alloy composition of the steel is also a consideration: certain variations of nickel and chromium can lead to higher levels of magnetism. So it is possible that, even if your fasteners are made of 304 or 316 stainless steel, they may have magnetic properties.

Due to the processes used in the shaping and forming of steel to form fasteners, you may very well end up with screws or bolts that are magnetic despite being made of 304 or 316 stainless steel. Magnetic qualities in fasteners are not always desirable. It is possible to avoid making fasteners with these qualities  by reducing the amount of cold work used on a part during thread cutting. The finished fasteners can also be annealed after these processes to reduce magnetic properties. In this way, a 100% non-magnetic product can be created.

As a leading stainless steel fastener specialist; and partnered with manufacturers and suppliers of the full range of stainless steel and aluminum use across all industries; Marsh Fasteners can help you ensure that you use the best stainless steel fasteners with non-magnetic qualities.

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