What are the Most Common Types of Stainless Steel?

One of the most useful and most commonly used materials in the world, stainless steel is a name that is meant to be taken seriously. From cooking pots to surgical instruments and building materials to automotive parts, stainless steel permeates modern life. Few people, however, know that stainless steel exists in numerous forms, each designed specifically to perform a specific function. Knowing the most in-demand grades of stainless steel will assist you in selecting the perfect material for your application if you are an engineer, a manufacturer, or a discerning purchaser.

In this post, we will be posting about the most in-demand grades of stainless steel, their attributes, uses, and what makes each better than the others as per the discussion with the Stainless Steel Parts Manufacturer in India.

What is Stainless Steel?

Let us get a feel of stainless steel before proceeding to the different types. Stainless steel is simply a form of steel with over 10.5% weight of chromium. When you include chromium, a surface protective layer of passive chromium oxide is formed that does not permit rusting and corrosion to occur. That is the wonder of stainless steel being "stainless."

Depending on the alloying elements to which the iron-carbon base composition is alloyed, there are a number of types of stainless steel—each with varying physical, chemical, and mechanical properties.

Classification:

The stainless steels are conventionally classified into five families, and there are numerous grades in a family

• Austenitic
• Ferritic
• Martensitic
• Duplex
• Precipitation Hardening (PH)

We will now enumerate the most commonly encountered types in each group.

1. Austenitic Stainless Steel

Description:

Austenitic stainless steels are the most prevalent and make up around 70% of total stainless steel production. Austenitic steels are corrosion-resistant, highly ductile, and non-magnetic.

Typical Grades:

• 304 Stainless Steel: Also "18/8" stainless with 18% chromium and 8% nickel. Very corrosion-resistant and used in kitchen sinks, food processing equipment, and building frames.
• 316 Stainless Steel: Essentially 304 with molybdenum content (2-3%), which is chloride and seawater resistant. Find extensive application in chemical processing, marine, and surgical uses.

Key Characteristics:

• Good corrosion resistance
• Non-magnetic (in annealed state)
• Good formability and weldability
• Withstands high and low temperatures alike

Uses:

• Food and drink industry
• Chemical processing
• Naval equipment
• Architectural design

2. Ferritic Stainless Steel

Description:

Ferritic stainless steels are less ductile than austenitic steels but are adequate in corrosion resistance and are also less expensive. They have high chromium and low carbon and are usually magnetic.

General Grades:

• 430 Stainless Steel: Has approximately 17% chromium and is most widely used for application in automotive trim, kitchen hardware, and for architectural use.
• 409 Stainless Steel: Due to its higher content of high-temperature corrosion, it is utilized most widely in automotive exhaust applications.

Most Significant Features

• Excellent corrosion and oxidation resistance
• Worse weldability compared to austenitic grades
• Lower cost compared to austenitic stainless steels

Applications:

• Motor vehicle components
• Domestic appliances
• Industrial components
• Architectural panels

3. Martensitic Stainless Steel

Definition:

Martensitic stainless steels are a range of hard alloys that can be heat-treated for the sake of acquiring hardness. They contain more carbon than ferritic and austenitic grades and are therefore stronger and harder but hard.

General Grades

• 410 Stainless Steel: Contains approximately 11.5–13.5% chromium. Used in cutlery, pumps, and valves.
• 420 Stainless Steel: Mainly used in knives and surgical instruments due to excessive hardness.

Major Characteristics:

• Can be heat-treated for added strength
• Excellent corrosion resistance More hard than other stainless

Applications:

• Cutlery and blades
• Instrumentations utilized in medical
• Shafts and valves
• Industrial equipment

4. Duplex Stainless Steel

Characteristics:

Duplex stainless steels are the fusion of ferritic and austenitic stainless steels' strengths. They have a duplex microstructure of the two phases with superior strength and stress corrosion cracking resistance.

Common Grades:

• 2205 Duplex Stainless Steel: Contains approximately 22% chromium, 5-6% nickel, and 3% molybdenum. Typical for chemical processing, marine, and oil and gas.
• 2507 Super Duplex: Higher corrosion and strength resistance; application in hostile environments.

Key Features

• Stronger than austenitic and ferritic steel
• Enhanced corrosion resistance against stress in chloride
• Magnetic
• Weldable

Uses:

• Oil and gas sector
• Chemical processing
• Offshore and marine platforms
• Pulp and paper

5. Precipitation Hardening (PH) Stainless Steel

Description

Precipitation-hardened stainless steel alloys are designed to provide corrosion resistance and strength. Precipitation-hardening substances such as copper, aluminium, or titanium may be heat-treated to make the steels stronger.

Average Grades:

• 17-4 PH (Grade 630): It consists of 17% chromium and 4% nickel. It has very extensive use for aircraft components and high-strength gears.

Key Characteristics:

• High strength-to-weight ratio
• Hard, corrosion-resistant
• May be heat-treated for utmost strength
• Magnetic Applications:
• Aviation and space machinery
• Nuclear reactors War equipment High-duty shafts and gears

Selecting the Correct Stainless Steel Grade 

When selecting a stainless steel for an application, be sure to take the following into consideration:

• Corrosion resistance—Will the material come into contact with water, chemicals, or salt?
• Mechanical properties—Will strength, hardness, or ductility be required in the application?
• Magnetic properties—Non-magnetic materials are required in some applications.
• Cost—Austenitic grades are much more expensive than the ferritic and martensitic grades, which are economical.
• Fabrication requirements—Is the steel required to be formed, bent, or welded? Each stainless steel grade is unique in its advantages and disadvantages, and, thus, selecting a corresponding one between grade and environment and the end use requirement is necessitated.

Conclusion 

Stainless steel is not something of a general nature, anyway. There are too many grades and kinds to keep up with, so there is a stainless steel for just about every application—you're at home, on a building, or on an oil rig. Knowing the most common kinds—austenitic, ferritic, martensitic, duplex, and precipitation hardening—you can now make informed choices on what to use for what. The next time you see a shiny appliance or rustproof railing, you'll be wiser to the process and science behind that reliable shine of stainless steel.

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