Steel is a ferrous metal alloy composed mainly of iron and carbon whose magnetic property is primarily influenced by composition and microstructure. The ferromagnetic behavior of steel is attributed to the iron presence.
Factors Influencing Magnetism in Steel
The following factors are cause for the various degrees of magnetism exhibited by steel:
- Iron Content
Iron is one of the primary materials that makes steel alongside carbon. As a ferromagnetic material, iron’s atomic structure allows development of significant magnetic moments in the presence of a magnetic field.
Alloying iron with other elements, like carbon to form steel, results in the material retaining iron’s ferromagnetic properties. The ferromagnetic properties are more pronounced especially when the iron content is high.
- Carbon Content
The carbon content in steel affects its magnetic properties. Steels with low carbon content display more magnetic qualities than high-carbon steels. The microstructure in high-carbon steels reduces their overall magnetic behavior.
- Heat Treatment
Carrying out heat treatment processes like annealing or quenching on steel can alter its magnetic properties. Heat treating steel changes its microstructure which ultimately influences magnetic behavior.
Annealing involves heating the steel to a specific temperature before gradually cooling, often to reduce hardness, increase ductility, and refine grain structure. Annealing can reduce the magnetic susceptibility of steel by realigning the magnetic domains such that it reduces overall magnetism.
In quenching, the steel is rapidly cooled by immersing in a cooling medium after heating it to a specific temperature. It is often used to increase steel hardness and strength. The rapid cooling can lock the magnetic domains in a particular orientation, enhancing overall steel magnetic behavior.
- Alloying Elements
Adding certain alloying elements like cobalt and nickel to steel can modify its magnetic properties. For instance, adding nickel to steel can enhance the resulting alloy’s magnetic properties with strength depending on concentration.
Magnetic Steel Alloys
There are several magnetic steel alloys with specific magnetic properties tailored for different applications. The magnetic properties of these steel alloys vary with factors like composition and heat treatment resulting in different magnetic strengths.
Some of these alloys include:
i. Carbon Steel: Carbon steel can be classified as low or high-carbon steel depending on the carbon content. Steel alloys with a low carbon content exhibit pronounced ferromagnetic properties compared to high-carbon steel.
ii. Alloy Steels: These include various alloying elements to enhance its properties. For instance, the alloy steel 4140 contains chromium and molybdenum which alongside other elements enhances the alloy’s magnetic properties.
iii. Permalloy: This steel alloy combines nickel and iron alloy resulting in high magnetic permeability and low coercivity. It is useful where high sensitivity to magnetic fields is required.
iv. Stainless Steels: Depending on the stainless steel type, the magnetic properties here can vary from weak to strong. While austenitic stainless steel can be non-magnetic, ferritic and martensitic stainless steel can display magnetic properties.
Just like it has several capabilities in the application, steel exhibits diverse magnetic behaviors. You can find non-magnetic steel, strongly ferromagnetic, and weakly paramagnetic. This depends on composition especially carbon content and alloying elements, and heat treatment.