Why does genuine stainless steel attract magnets?

Buyers often understand and believe that stainless steel grade 304 should not be attracted to magnets, but sellers and manufacturers explain that the non-magnetic property of stainless steel is not the same as placing a magnet on glass or plastic, which has no magnetic attraction at all, as stainless steel will have weak, slight magnetic attraction. Today BSF will explain this phenomenon, as stainless steel is divided into three groups as follows

Stainless Steel

1. Austenitic Stainless Steel contains chromium composition of 15% - 20% and nickel of 5% - 19%, which provides superior corrosion resistance properties compared to the other two types of stainless steel, with tensile strength ranging between 72,000 - 115,000 psi (500 - 800 MPa). Grade 18-8 stainless steel is widely used for manufacturing stainless steel screws and nuts, containing an average of 18% chromium and 8% nickel, and comprises stainless steel grades 302, 303, 304, and 316.

2. Martensitic Stainless Steel contains chromium composition of 12% - 18%, which provides magnetic properties and can be heat treated for hardening, but is not suitable for welding applications. Stainless steel screws and nuts with martensitic composition are commonly used in environments with moderate corrosive conditions, comprising stainless steel grades 410, 416, 420, and 431.

3. Ferritic Stainless Steel contains chromium composition of 15% - 18%, which provides magnetic properties similar to martensitic stainless steel, but cannot be heat treated for hardening or used in welding applications. This group of stainless steel comprises grades 430 and 430F.

Principles Behind Stainless Steel's Magnetic Response

    We must comprehensively understand all aspects of the information first. Stainless steel, or rust-resistant steel, is created through synthesis processes that maintain steel's hardness while preventing rust formation by incorporating chromium and nickel. The standard properties for Grade 304 stainless steel require 18% chromium and 8% nickel. Nickel is the key element that prevents magnetic attraction to stainless steel. Therefore, stainless steel containing nickel content of 3% or higher is classified almost entirely within the Austenitic category.

    According to documentation and explanations from European manufacturers, stainless steel exhibits minimal magnetic response, described as "slightly responsive to magnetic" attraction, but not adhering like iron. However, when using large industrial magnets, there is potential for magnetic attraction similar to iron. When stainless steel undergoes machining processes involving turning, drilling, or heat exposure with various contributing factors, there is potential for Austenitic stainless steel to transform into the Ferritic category or become magnetically attracted.

    Determining authentic stainless steel cannot be measured solely through magnetic attraction, as stainless steel includes both magnetic and non-magnetic categories. Stainless steel classified as non-magnetic does not mean complete non-attraction like paper or plastic, but rather exhibits slight magnetic response without firm adherence like iron. Certification of stainless steel grade authenticity, such as genuine Grade 304, must be verified through chemical composition analysis. Purchasers ordering products from certified manufacturers will receive grade certification and composition documentation from the factory.

BSF's stainless steel is genuine stainless steel manufactured from certified factories and comes with factory certification documents for grade verification and chemical composition. Therefore, customers can confidently trust the quality and products from BSF with complete assurance.