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Stainless Steel Castings Are Actually Magnetic?

Update On Dec 19.2022

Many customers will ask why the purchased stainless steel castings can be sucked by a magnet? Is it the wrong material or alloy elements do not meet the standard? Stainless steel castings can be magnetized that the product is not qualified?

In fact, no, magnetism is generated in the casting process, natural cooling molding of stainless steel castings are basically magnetic, all the chemical composition is in line with the standard, but still will produce magnetic.

This article we share the following topics for you

1. The magnetic difference between austenitic stainless steel and ferritic stainless steel

2. Why austenitic stainless steel castings are magnetic

3. Whether the magnetism of austenitic stainless steel castings is important

4. How to produce non-magnetic austenitic stainless steel castings


Magnetic Difference Between Austenitic Stainless Steel and Ferritic Stainless Steel

Not magnetic-Austenitic grades 200 and 300 series are generally not magnetic.

Magnetic - All ferritic grades such as 430, 444, all duplex grades such as 2205, 2304, 2101, 2507, all martensitic grades such as 431, 416, 420, 440C, and all precipitation hardening grades such as 17-4PH, are magnetic.

Duplex grades are a mixture of austenite and ferrite, and they are strongly attracted to magnets.


Why Austenitic Stainless Steel Castings Are Magnetic

As we all know, theoretically austenitic stainless steel is not supposed to be magnetic, but the products produced are magnetic, some manufacturers think it is the material, but after the third-party spectral testing, the material qualified and did not appear abnormal, so many people can not find the problem and can not solve the problem.

we have a new discovery after consulting a lot of information and exchange with the relevant technical personnel to discuss The reason why the natural cooling forming of stainless steel castings with magnetic is because the internal structure of austenitic stainless steel in the cooling forming process has changed, part of the austenite transformation to martensite, and body-centered structure of martensitic stainless steel is magnetic.

In the production of stainless steel castings, the stability of austenitic stainless steel, the amount of processing deformation, processing methods, etc. may affect its transformation into martensitic stainless steel.


Does the Magnetism of Austenitic Stainless Steel Castings Matter

When realizing that 300 series stainless steel castings are magnetic, the bottom line for our customers is that this magnetic reaction does not negatively affect any properties.

Ferritic stainless steels have some drawbacks that typically only affect those castings used for specific applications. For example, equipment that uses magnetic coupling must be made of non-magnetic materials, and the Navy mandates the use of non-magnetic materials for minesweepers. 

At ultra-low temperatures (below -180 degrees Celsius) and high temperatures (above 500 degrees Celsius), increased ferrite can reduce impact toughness, although the latter rarely occurs.

At the same time, cast austenitic stainless steels containing some degree of ferrite are stronger and more corrosion resistant than forged parts because ferrite is inherently stronger than base austenite. This is because the ferrite itself is stronger and tougher than the underlying austenitic phase of the metal.

Some of the most highly corrosion-resistant stainless steels are strongly magnetic, for example, duplex and super duplex steels and highly alloyed ferritic grades.


How to Produce Non-magnetic Austenitic Stainless Steel Castings

Even though 99% of our customers do not require non-magnetic stainless steel castings, there are still individual customers who, in 20 years of experience in the industry, place extreme emphasis on the non-magnetic properties of their products. We at Bayside Casting have also developed a process for casting non-magnetic stainless steel products.

According to the causes and factors affecting the martensite, in order to avoid magnetic stainless steel castings, in general, we can add "alloy demagnetizing agent" in the casting process, "alloy demagnetizing agent" can transform the iron elements in stainless steel castings into Austenite, so as to achieve the purpose of demagnetization.

As "alloy demagnetizer" is expensive, if the customer does not have special requirements for the magnetic properties of stainless steel castings, we will not add "alloy demagnetizer" in the casting process. Therefore, the price of non-magnetic stainless steel castings will be relatively high.

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