Stainless Steel Alloy is an iron-based alloy named for its excellent corrosion resistance in air, steam, water and chemical environments. By adding elements such as chromium, nickel, molybdenum and titanium, stainless steel exhibits a unique combination of properties and is widely used in construction, industrial, medical and catering applications.
Major Elements:
Iron (Fe): Base material, providing structural strength.
Chromium (Cr): ≥10.5%, forming a protective oxide layer to improve corrosion resistance.
Nickel (Ni): Enhances corrosion resistance and toughness, improves processability.
Molybdenum (Mo): improves resistance to pitting and crevice corrosion.
Carbon (C): affects strength and hardness, but too high a level reduces corrosion resistance.
Other elements (manganese, silicon, titanium, etc.): improve mechanical properties or oxidation resistance.
Core characteristics:
Corrosion resistance: exhibits very high corrosion resistance in most environments.
Mechanical strength: high strength and toughness for highly loaded structures.
High temperature resistance: able to maintain stable performance in high temperature environments.
Ease of processing: Suitable for welding, stretching, bending and other processing methods.
Non-magnetic (some types): especially austenitic stainless steel.
Classification of stainless steel
According to the metallographic organisation and properties, common stainless steels can be divided into the following categories:
1. Austenitic stainless steel
Characteristics: non-magnetic, superior corrosion resistance, good toughness and workability.
Composition: chromium (16-26%), nickel (6-22%), some containing molybdenum or nitrogen.
Applications: food processing equipment, medical devices, chemical installations.
Representative grades: 304, 316, 310S.
304: general-purpose stainless steel, good corrosion resistance and processing performance.
316: add molybdenum, acid and alkali resistance is better than 304, suitable for marine environment.
2. ferritic stainless steel
Characteristics: high chromium content, little or no nickel, low cost, good oxidation resistance.
Composition: chromium (10.5-30%), low carbon content.
Applications: automotive exhaust systems, appliance shell.
Representative grades: 430, 409.
3. Martensitic stainless steel
Characteristics: high carbon content, high hardness, low corrosion resistance.
Composition: chromium (11-18%), high carbon content.
Applications: knives, bearings, medical tools.
Representative grades: 410, 420.
4. Duplex stainless steel
Characteristics: mixed organisation of austenite and ferrite, high strength, excellent corrosion resistance.
Composition: chromium (19-28%), nickel (4.5-8%), usually containing molybdenum or nitrogen.
Applications: chemical equipment, marine engineering.
Representative grades: 2205, 2507.
5. precipitation hardening stainless steel
Characteristics: Through heat treatment to achieve high strength and hardness, while maintaining a certain degree of corrosion resistance.
Composition: chromium (15-17.5%), nickel (3-7%), plus titanium, aluminium, copper and other elements.
Applications: aerospace, nuclear industry.
Representative grade: 17-4PH.
Advantages and disadvantages of stainless steel
Advantages:
Strong corrosion resistance: suitable for a variety of acids, alkalis, salts and other chemical media.
High strength: with good impact resistance and load-bearing capacity.
High and low temperature resistance: suitable for extreme environments.
Aesthetics: smooth surface, suitable for decorative purposes.
Long life: low maintenance cost.
Disadvantages:
Higher costs: especially for grades with high nickel and molybdenum content (e.g. 316).
Complicated machining: machining and welding of some grades requires specialised skills.
Possible corrosion in certain environments: e.g. pitting may occur in high chloride ion environments.
Typical applications
Construction: curtain walls, roofs, handrails.
Food and pharmaceuticals: storage tanks, pipelines, cleaning equipment.
Transport: automotive, marine and aviation components.
Chemical and energy: heat exchangers, reactors, pipework.
Daily necessities: tableware, kitchenware, electronic product housings.
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