Element

Content Range

Role of Each Element

Iron (Fe)

Base element

Iron is the base metal that makes up the majority of 304 stainless steel.

Chromium (Cr)

18% - 20%

Chromium is the most important alloying element in 304 stainless steel. It provides corrosion and oxidation resistance.

Nickel (Ni)

8% - 10.5%

Nickel enhances corrosion resistance, improves hardness and strength at high temperatures, and improves low temperature impact toughness.

Carbon (C)

≤ 0.08%

Carbon increases the strength of the steel, but higher levels can reduce its corrosion resistance, which is why it's kept low in 304 stainless steel.

Manganese (Mn)

≤ 2%

Manganese improves hot working characteristics like machinability and ductility.

Silicon (Si)

≤ 1%

Silicon increases corrosion and oxidation resistance.

Sulfur (S)

≤ 0.03%

a small amount of sulfur is intentionally added to improve machinability.

Physical Property

Value

Role

Density

~7.93 g/cm³

Determines part weight, crucial for weight - sensitive applications like aerospace, and aids in handling and transport planning.

Melting Point

1398 - 1454 °C

Sets processing temperatures for manufacturing and indicates high - temperature performance for heat - resistant applications.

Thermal Conductivity

~16.2 W/(m·K) at 100 °C

Enables efficient heat transfer in cookware and heat exchangers, and helps manage heat in machining.

Specific Heat Capacity

~500 J/(kg·K)

Governs heat - energy requirements for temperature changes, important in heat - treatment and rapid - temperature - change applications.

Electrical Resistivity

~72.0 μΩ·cm at 20 °C

Allows for controlled electrical conductivity in applications where some resistance is needed, like heating elements.

Young's Modulus

~193 GPa

Represents material stiffness, ensuring shape maintenance under load in structural applications.

Poisson's Ratio

~0.29

Helps predict lateral and longitudinal deformation under stress, vital for precision - machined parts.

Tensile Strength

515 - 795 MPa

Indicates maximum pulling stress tolerance, essential for components under tension like cables and fasteners.

Yield Strength (0.2% offset)

≥ 205 MPa

Defines stress for permanent deformation, used to set allowable stress in design for elastic - range operation.

Elongation at Break

≥ 40%

Measures ductility, enabling material to be formed into shapes and providing a safety margin in deformation.

Surface Treatment Method

Process Description

Characteristics and Effects

Applications

Polishing

Mechanical polishing uses abrasives or polishing wheels to remove surface imperfections and make the surface shiny; electrochemical polishing uses electrochemical principles to dissolve and level the surface.

Achieves a smooth and shiny surface, improves corrosion resistance, and enhances aesthetic appearance. It can also reduce surface roughness, which is beneficial for applications requiring low friction.

Commonly used in decorative applications such as architectural decoration, kitchenware, and bathroom fittings. Also used in some precision mechanical parts where a smooth surface is required.

Sandblasting

High-pressure air is used to spray abrasive particles onto the surface of the stainless steel to roughen or clean the surface.

Creates a matte or textured surface, which can improve the surface adhesion for subsequent coating or painting. It can also remove rust, scale, and other impurities on the surface.

Often used in the pretreatment of stainless steel surfaces before painting or coating, as well as in some decorative applications where a matte or textured effect is desired, such as in signage and architectural facades.

Anodizing

The stainless steel is used as the anode in an electrolyte solution, and an oxide film is formed on the surface through electrochemical reaction.

Forms a hard and dense oxide film on the surface, which significantly improves corrosion resistance and wear resistance. The anodized film can also be dyed in various colors to achieve different decorative effects.

Widely used in the electronics industry, aerospace, and automotive fields, such as for the surface treatment of electronic components, aerospace parts, and automotive decorative parts.

Passivation

The stainless steel is immersed in a passivating solution, usually containing chromium compounds or nitric acid, to form a passive film on the surface.

The passivating film can enhance the corrosion resistance of the stainless steel by isolating the metal from the outside environment. It helps to prevent rust and other forms of corrosion.

Commonly used in the manufacturing of chemical equipment, food processing equipment, and medical devices, where high corrosion resistance is required.

Painting

Organic coatings such as epoxy paint, polyurethane paint, etc., are applied to the surface of the stainless steel through spraying, brushing, or dipping.

Provides additional protection against corrosion and wear, and can also achieve various colors and decorative effects. The paint film can prevent the stainless steel from being in direct contact with the corrosive medium in the environment.

Used in a wide range of applications, including architectural exterior walls, industrial equipment, and consumer products, to protect the surface and enhance the aesthetic appearance.

Electroplating

A layer of metal such as nickel, chrome, or copper is deposited on the surface of the stainless steel through an electrochemical process.

Can improve the surface hardness, wear resistance, and corrosion resistance of the stainless steel. The electroplated layer can also give the stainless steel a bright and shiny appearance.

Commonly used in decorative parts, such as door handles, bathroom fixtures, and automotive trim, to enhance the aesthetic and durability.

Feature

SUS 304

SUS 303

SUS 316

SUS 201

Corrosion Resistance

Excellent (oxidation-resistant)

Poor (due to sulfur)

Superior (chloride-resistant)

Moderate (prone to pitting)

Machinability

Good (balanced for CNC)

Excellent (free-machining)

Fair (requires tool optimization)

Fair (high work-hardening)

Weldability

Excellent

Good

Excellent

Good

Applications

Food equipment, medical devices

Fasteners, screws

Marine components, chemical tanks

Architectural trim, consumer goods