What Is The Difference Between Stainless Steel And Mild Steel? Which Is Stronger?

By Author: Ashish Shah
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STEEL :

Alloy steel refers to a type of steel that is alloyed with various elements. In theory, every steel can be referred to as alloy steel since the simplest steel is iron alloyed with up to 2.06% of carbon. However, the term “alloy steel” commonly refers to steels that are alloyed with elements other than carbon. The total weight of alloying elements can amount up to 50% to give the material improved properties such as better wear protection or ductility. A distinction is made between low-alloyed and high alloyed steels. Low-alloyed steels are characterized by their low amount of alloys, which in summation make up to less than 5%. The number of elements in high-alloyed steels can be greater or equal to 5%, making the material more expensive by tendency. Aside from those two groups, there are also unalloyed steels which carry an extremely small amount of alloys.

STEEL GRADES AND PROPERTIES:
According to the World Steel Association, there are over 3,500 different grades of steel, encompassing unique physical, chemical, and environmental properties.
In essence, steel is composed of iron and carbon, ...
... although it is the amount of carbon, as well as the level of impurities and additional alloying elements that determine the properties of each steel grade.
The carbon content in steel can range from 0.1-1.5%, but the most widely used grades of steel contain only 0.1-0.25% carbon. Elements such as manganese, phosphorus, and sulfur are found in all grades of steel, but, whereas manganese provides beneficial effects, phosphorus and sulfur are deleterious to steel's strength and durability.
NOTE: Different types of steel are produced according to the properties required for their application, and various grading systems are used to distinguish steels based on these properties.

According to the American Iron and Steel Institute (AISI), steel can be broadly categorized into four groups based on their chemical compositions:

1. Mild Steels

2.Stainless Steels

1. Low Carbon Steels:

Carbon steels contain trace amounts of alloying elements and account for 90% of total steel production. Carbon steels can be further categorized into three groups depending on their carbon content:

1. Low Carbon Steel (Mild Steel): Typically contain 0.04% to 0.30% carbon content. This is one of the largest groups of Carbon Steel. It covers a great diversity of shapes; from Flat Sheet to Structural Beam. Depending on the desired properties needed, other elements are added or increased. For example, Drawing Quality (DQ) – The carbon level is kept low and Aluminum is added, and for Structural Steel the carbon level is higher and the manganese content is increased.

2. Stainless Steels
Stainless steels generally contain between 10-20% chromium as the main alloying element and are valued for high corrosion resistance. With over 11% chromium, steel is about 200 times more resistant to corrosion than mild steel. These steels can be divided into three groups based on their crystalline structure:

• Austenitic: Austenitic steels are non-magnetic and not heat-treatable, and generally contain 18% chromium, 8% nickel, and less than 0.8% carbon. Austenitic steels form the largest portion of the global stainless steel market and are often used in food processing equipment, kitchen utensils, and piping.

• Ferritic: Ferritic steels contain trace amounts of nickel, 12-17% chromium, less than 0.1% carbon, along with other alloying elements, such as molybdenum, aluminum or titanium. These magnetic steels cannot be hardened by heat treatment but can be strengthened by cold working.

• Martensitic: Martensitic steels contain 11-17% chromium, less than 0.4% nickel, and up to 1.2% carbon. These magnetic and heat-treatable steels are used in knives, cutting tools, as well as dental and surgical equipment.

STEEL CLASSIFICATIONS

Types of Steel can also be classified by a variety of different factors:

1. Composition: Carbon range, Alloy, Stainless.
2. The production method: Continuous cast, Electric furnace, Etc.
3. Finishing method used: Cold Rolled, Hot Rolled, Cold Drawn (Cold Finished), Etc.
4. Form or shape: Bar, Rod, Tube, Pipe, Plate, Sheet, Structural, Etc.
5. De-oxidation process (oxygen removed from steelmaking process): Killed & Semi-Killed Steel, Etc.
6. Microstructure: Ferritic, Pearlitic, Martensitic, Etc.
7. Physical Strength (Per ASTM Standards).
8. Heat Treatment: Annealed, Quenched & Tempered, Etc.
9. Quality Nomenclature: Commercial Quality, Drawing Quality, Pressure Vessel Quality, Etc.

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