Stainless steel is an alloy of iron that resists corrosion and rust. It is also known as inox, corrosion-resistant steel, or rustless steel. According to its specific use and cost, stainless steel contains iron combined with chromium, molybdenum, carbon, nickel, and nitrogen. The 10.5% or more chromium in stainless steel forms a passive film that protects and self-heals when exposed to oxygen, resulting in stainless steel’s corrosion resistance.

Luster and corrosion resistance of stainless steel benefit many applications. The alloy can be rolled into sheets, plates, bars, wires, and tubing. It can also be used to make major appliances, vehicles, construction materials in large buildings, industrial equipment, and chemicals and food storage tanks and tankers.

Stainless steel is superior to aluminum and copper in biological cleanability and comparable to glass. It is commonly labeled with AISI three-digit numbers, such as AISI304, AISI316, and AISI430.

Properties of Stainless Steel Materials

Magnetism

People often ask, “Is stainless steel magnetic?” Stainless steels like martensitic, duplex, and ferritic are magnetic, whereas austenitic stainless steels are usually non-magnetic. Through work hardening, austenitic stainless steel can be slightly magnetic. As a result of the crystal structure rearranging itself, magnetism can sometimes occur along the edge of austenitic steel when bent or cut.

Corrosion resistance

Stainless steel does rust, but it only affects the outer few layers of atoms, as its chromium content protects deeper layers from oxidation.

Also, nitrogen improves mechanical strength and resistance to pitting corrosion. Thus, there are numerous grades of stainless steel with varying chromium and molybdenum contents to suit the environment the alloy must endure. The following methods can enhance further corrosion resistance:

Increasing chromium content to over 11%
Nickel should be added to at least 8%
By adding molybdenum (which also improves corrosion resistance)

Strength

Stainless steel exhibits high tensile strength, which refers to its ability to resist stretching or pulling forces without breaking. The tensile strength of stainless steel can vary depending on the grade and specific alloy composition. Additionally, stainless steel exhibits good impact strength, which refers to its ability to resist sudden, high-energy forces or shock loads.

Yield strength is the maximum stress that stainless steel can withstand before it begins to deform permanently. It is an essential parameter for structural design and determining the working load capacity of components. Stainless steel typically has a higher yield strength than many other materials, making it suitable for applications requiring structural integrity and deformation resistance.

In terms of fatigue strength, stainless steel exhibits excellent fatigue strength, allowing it to withstand repeated stress cycles without experiencing fatigue failure. This property is fundamental in cyclic or dynamic loading applications, such as aerospace and structural components.

It’s important to note that stainless steel’s specific strength properties can vary depending on the grade, heat treatment, and manufacturing processes. For example, stainless steel 304 has a tensile yield strength of around 210 MPa in the annealed condition. It can be strengthened by cold working to a strength of 1,050 MPa in the full-hard condition.

Higher Melting Point

Stainless steel’s melting point is similar to ordinary steel’s but much higher than aluminium’s or copper’s. It is determined by a range of temperatures, not a single temperature. This range ranges from 1,400 to 1,530 °C, depending on the alloy’s consistency.

Various Stainless Steel Materials

Stainless steel comes in various types, each with unique properties and characteristics. Overall, the key to selecting the right stainless steel materials lies in understanding the specific needs and requirements of your project or application.

Types of Stainless Steel

According to their crystalline structure, stainless steel materials are classified into austenitic, ferritic, martensitic, duplex, and precipitation hardening.

Austenitic stainless steel

Main article: Austenitic stainless steel

Known for its high corrosion resistance and durability, austenitic stainless steel accounts for about two-thirds of all stainless steel production.

Steels with austenitic microstructures are alloyed with nickel, manganese, and nitrogen so that they remain austenitic at all temperatures, from cryogenic to melting. This makes them a popular choice for applications where the material will be exposed to harsh environments or chemicals.

Ferritic stainless steel

Main article: Ferritic stainless steel

Ferritic stainless steel contains 10.5% and 27% chromium and has a body-centred cubic crystal structure like carbon steel.

Due to the chromium addition, this microstructure is present at all temperatures, so heat treatment cannot harden it. Hence, it is ideal for applications requiring a solid material that can tolerate high temperatures.

Martensitic stainless steel

Main article: Martensitic stainless steel

Martensitic stainless steel is known for its high hardness and wear resistance. It has a body-centred cubic crystal structure and offers a wide range of properties, making it an excellent choice for engineering, tool, and creep-resistant steels.

Due to their low chromium content, they are magnetic and less corrosion-resistant than ferritic and austenitic stainless steels.

Duplex stainless steel

Main article: Duplex stainless steel

Duplex stainless steels have an ideal ratio of austenite to ferrite, although commercial alloys may have a ratio of 40:60. In contrast to austenitic stainless steels, they contain more chromium (19–32%), molybdenum (up to 5%), and less nickel.

Compared to austenitic stainless steel types 304 and 316, their mixed microstructure improves chloride stress corrosion cracking resistance.

Grades of Stainless Steel

Over 150 different grades of stainless steel are available for various applications. Each grade offers a unique balance of properties, such as corrosion resistance, strength, and machinability. The most common grades of stainless steel include 201, 304, 316, and 430. See all steel grades.

200 Series

In the 200 series, manganese and nitrogen are maximized to minimize nickel use so they can be hardened through cold working. Stainless steel grade 201 is hardenable through cold working, whereas grade 202 has a decreasing nickel content and an increasing manganese content, resulting in weak corrosion resistance. Therefore, it is a general-purpose stainless steel.

300 Series

As the largest group and most widely used stainless steel, the 300 series is the most common. SS304, 18/8 or 18/10, contains 18% chromium and 8 or 10% nickel, respectively. SS316 is another ordinary austenitic stainless steel. Molybdenum is added at 2%, which enhances resistance to acids and corrosion caused by chloride ions locally. To prevent corrosion problems caused by welding, low-carbon versions such as 316L and 304L have carbon contents below 0.03%.

Application of Stainless Steel in Construction

Regarding construction, stainless steel is a versatile material offering aesthetic appeal and structural integrity. From sleek modern buildings to intricate architectural details, stainless steel can be found in various applications.

One key use of stainless steel in construction is for cladding and facades. Its corrosion resistance and low maintenance requirements make it an ideal choice for exterior surfaces that need to withstand harsh weather conditions. Additionally, its reflective properties can create a striking visual impact, especially when paired with other materials like glass or concrete.

Stainless steel is also commonly used in structural components such as beams, columns, and reinforcement bars. Its high strength-to-weight ratio makes it an excellent choice for supporting heavy loads while maintaining a slim profile. This allows architects and engineers the flexibility to design innovative structures that are both durable and visually appealing.

From structural beams to decorative finishes, stainless steel offers endless possibilities for architects and builders to create durable, aesthetically pleasing structures that stand the test of time. Its sleek appearance and long-lasting performance make it an attractive option for any construction project.

Standard Finishes

The following names are used to describe stainless steel surface finishes that conform to ASTM A480/A480M-18 (DIN) standards:

No. 1 (1D): Hot-rolled, annealed and passivated
No. 2D (2D): Cold rolled, annealed, pickled and passivated
No. 2B (2B): Cold rolled, annealed, pickled, passivated, polished
No. 2BA (2R): Cold rolled, annealed, pickled, passivated, polished, then bright annealed under oxygen-free atmospheric condition
No. 3 (G-2G:) Coarse abrasive finish applied mechanically
No. 4 (1J-2J): Brushed finish
No. 5: Satin finish
No. 6 (1K-2K): Matte finish (brushed but smoother than #4)
No. 7 (1P-2P): Reflective finish
No. 8: Mirror finish
No. 9: Bead blast finish
No. 10: Heat colored finish – offering a wide range of electropolished and heat colored surfaces

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