When designing future-facing architecture or developing precision instruments requiring long-term stability, material selection becomes the foundation that determines a project's success. Among metal materials, stainless steel stands out as the preferred choice for engineers and designers due to its exceptional corrosion resistance and versatile properties. But with numerous stainless steel plates available in the market, how does one select the most suitable option? This article examines the types, characteristics, and applications of stainless steel plates to facilitate informed decision-making.

True to its name, stainless steel resists rusting, but this represents just one facet of its advantages. As an alloy steel, stainless steel contains at least 10.5% chromium added to iron. The chromium reacts with oxygen to form an ultra-thin, dense chromium oxide protective layer called the "passive film." This self-healing layer regenerates quickly even when scratched, effectively preventing corrosion. Beyond chromium, stainless steel may incorporate elements like nickel, molybdenum, or titanium to enhance properties such as strength, heat resistance, or workability.

The applications of stainless steel span nearly all industrial sectors, from building facades and kitchenware to medical equipment and aerospace components. Its excellent corrosion resistance, aesthetic appeal, and good workability make it an ideal engineering material.

In stainless steel terminology, SUS represents a common classification system. Standing for "Stainless Used Steel," SUS serves as the material designation in Japanese Industrial Standards (JIS), effectively functioning as stainless steel's identification card. The SUS numbering system allows quick recognition of a stainless steel's type, composition, and properties. For instance, SUS304 denotes the most commonly used austenitic stainless steel, while SUS430 represents a typical ferritic stainless steel.

Stainless steel varieties are numerous, categorized primarily into three types based on their metallographic structure: martensitic, ferritic, and austenitic. Each type possesses distinct properties and application areas.

Martensitic stainless steels offer high strength, hardness, and good wear resistance. Their defining characteristic is the ability to undergo strengthening through heat treatment. However, they exhibit relatively poor weldability and corrosion resistance. Common martensitic types include SUS410 and SUS403. SUS410 provides good hardenability and machinability, frequently used in cutlery, valves, and fasteners. SUS403 demonstrates better corrosion resistance, suitable for components requiring both high-temperature and corrosion resistance, such as steam turbine blades.

Ferritic stainless steels deliver good workability, heat resistance, and oxidation resistance at relatively lower costs. Their nickel-free or low-nickel composition makes them more affordable than austenitic varieties, though they offer lower strength, toughness, and weldability. SUS430 represents the most common ferritic stainless steel, widely used in kitchenware, household appliances, and architectural decoration materials. Its magnetic properties also enable applications requiring magnetic materials.

Austenitic stainless steels constitute the most widely used type, offering excellent corrosion resistance, weldability, and workability. Characterized by high chromium and nickel content, they maintain good performance across various environments. SUS304 stands as the most prevalent austenitic stainless steel, often called the "versatile workhorse" of stainless steels, with applications spanning food processing, chemical industries, medical devices, and architectural decoration. SUS316 enhances SUS304 by adding molybdenum, further improving corrosion resistance, particularly in chloride-containing environments.

To better understand different stainless steel plate grades, we examine several common SUS steel plates:

SUS304 serves as a general-purpose stainless steel widely used for equipment and components requiring good comprehensive properties (corrosion resistance and formability). Containing 18% chromium and 8% nickel, it offers excellent corrosion resistance, heat resistance, and workability. Easy to form, weld, and polish with an attractive surface finish, SUS304 finds applications in:

• Architectural decoration: Elevator panels, facade cladding, railings
• Food industry: Processing equipment, storage tanks, piping
• Medical devices: Surgical instruments, equipment, implants
• Chemical industry: Reactors, storage tanks, piping
• Household appliances: Kitchenware, washing machines, refrigerators

SUS430, a ferritic stainless steel containing 16%-18% chromium with little or no nickel, offers cost-effectiveness, good heat resistance, and magnetic properties. While its corrosion resistance falls short of austenitic grades, it suffices for many applications. Primary uses include:

• Kitchenware: Cutlery, cookware, sinks
• Household appliances: Washing machine drums, water heater exteriors
• Building materials: Roofing, exterior panels
• Automotive components: Exhaust system parts

SUS303, an austenitic stainless steel enhanced with sulfur and phosphorus for improved machinability, facilitates easier cutting compared to SUS304, though with reduced corrosion resistance and weldability. It primarily serves components requiring extensive machining, such as:

• Bolts, nuts, and other fasteners
• Valves, fittings, and other piping components
• Mechanical parts

SUS310, an austenitic stainless steel containing 24%-26% chromium and 19%-22% nickel, excels in high-temperature and oxidation resistance, maintaining strength and corrosion resistance even in extreme heat. Typical applications include:

• Industrial furnace and boiler components
• Heat treatment equipment
• Aircraft engine parts

SUS316 enhances SUS304 by adding 2%-3% molybdenum, significantly improving corrosion resistance, particularly against pitting and crevice corrosion in chloride environments. Applications include:

• Marine engineering equipment
• Chemical processing equipment
• Medical implants

Beyond material composition, surface treatment significantly impacts stainless steel plates' performance and appearance. Different methods create varying levels of gloss, texture, and roughness to meet diverse application needs.

The No.1 finish represents stainless steel's original state after hot rolling, annealing, and pickling—rough, non-reflective, and silver-white. Primarily used for industrial applications not requiring surface gloss, such as structural components and rolling stock.

No.2D treatment involves cold rolling followed by annealing, pickling, passivation, and light rolling with matte rollers, producing a soft silver-gray sheen with relatively smooth texture. Commonly used for general-purpose materials, building materials, and aircraft structures.

No.2B treatment applies light rolling (or temper rolling) to No.2D surfaces to enhance flatness and gloss. As the market's most common stainless steel finish, it sees widespread application.

BA treatment involves bright annealing in a protective atmosphere after cold rolling, creating a highly reflective, smooth surface. Used where high reflectivity and aesthetic appeal are priorities, such as automotive parts, appliances, and kitchenware.

Dull treatment employs rough rollers or sandblasting to create fine surface irregularities, producing a non-reflective, pearlescent appearance. Ideal for applications requiring glare reduction, including building materials, cameras, and electronic devices.

Etching uses chemical corrosion to create patterns and textures on stainless steel surfaces, enabling highly personalized customization for art, architectural decoration, and kitchenware.

HL treatment grinds continuous, fine hairline patterns into the surface, creating a matte effect that conveys sophistication. Widely used in architectural decoration for elevator panels, walls, and doors.

No.4 treatment involves grinding to produce uniform satin finishes, offering good wear resistance and visual appeal. As the most common abrasive finish, it appears in kitchenware, building materials, vehicles, and food equipment.

Selecting stainless steel plates involves complex considerations of material type, properties, surface treatment, and cost. This guide aims to clarify stainless steel varieties and characteristics to support informed material selection decisions.