The Process For Powder Coating Stainless Steel
Is Surgical Steel Magnetic?
Most people aren't sure whether surgical stainless steel is a magnetic or non-magnetic metal alloy. Some believe that it's magnetic due to the presence of iron, which is the base metal for all steel alloys, or some magnetic solutes introduced to the alloy's chemical composition. But which one is right?
In this article, we'll discuss whether surgical stainless steel is magnetic, why, and how magnetism can be avoided for special applications. So, without further ado, let's dive right in.
What is Surgical Steel?
Surgical steel is a type of stainless steel that's used to produce medical and surgical instruments, as well as dental and orthopedic implants. It's used in biomedical applications due to its high chromium content and low nickel content, which grant it exceptional corrosion resistance, and a low chance of casing metal allergies.
However, not all surgical stainless steel grades are suitable for implants; some are just used to produce surgical tools. A good example of this is a medical-grade SAE 630, which has exceptional wear resistance making it suitable for surgical tools. Its corrosion resistance is comparable to that of 304 stainless steel.
Magnetic Properties of Surgical Steel
During application, magnetism has an impact on the material's functionality and intended usage. Magnetic materials can make the processes being used during fabrication and other operations, such as welding, more difficult. Electric currents can behave differently when passing through magnetic materials.
It's important to note that all grades of stainless steel contain iron. And for stainless steel to be magnetic, it has to contain iron (which it already does), and the crystal structure of the alloy has to be ferritic or martensitic.
Ferritic Stainless Steel
Ferritic stainless steel is magnetic primarily due to late concentrations of ferrite in its chemical composition, which is basically a compound of iron and other chemical elements. The material's microstructure is susceptible to the effects of the magnetic field, which makes these types of stainless steel magnetic. They generally have a low carbon content.
Martensitic Stainless Steel
Martensitic steel is formed by the creation of martensite within the crystal structure of the material. This type of steel is created during quenching, which prevents the formation of cementite and traps the carbon atoms within the material. However, the high iron content makes the material ferromagnetic.
Austenitic Stainless Steel
Austenitic stainless steels are physically solid stainless steel alloys but with the properties of an iron solution. This form of stainless steel is non-magnetic because the magnetic properties associated with iron atoms cancel out.
Electrons possess a quantum mechanical property called spin, and in ferromagnetic materials, the spin aligns with an applied magnetic field, making the material susceptible to the effects of magnetism. In austenitic stainless steel, the spin of electrons in each iron atom is arranged in an alternating pattern, which cancels out any net magnetic moments.
However, this can be disrupted by cold working the steel, as it breaks the symmetry of magnetic moments within the material. This can be reversed by heat treating the steel to 400°C, which would relax the internal stresses, allowing the material to regain the symmetry of its internal crystalline structure.
Summary
In conclusion, iron plays a significant role in whether stainless steel is magnetic or not. However, the crystalline structure of the material also plays a crucial role in the magnetic properties of surgical steel and other types of steel as well.
If you want to learn more about stainless and surgical steel, visit Reid Supply, and refer to their Engineer Resource Guides or some of their guides on Surgical and Stainless steel.