Introduction and Application of Stainless Steel Pipes

1. Material Classification

• Ferritic Stainless Steel: It contains 12% - 30% chromium. With the increase in chromium content, its corrosion resistance, toughness, and weldability improve. It has better resistance to chloride stress corrosion than other types of stainless steel. For example, the 430 stainless steel pipe is often used in the decoration field.

• Austenitic Stainless Steel: It contains more than 18% chromium, about 8% nickel, and small amounts of elements such as molybdenum, titanium, and nitrogen. It has excellent comprehensive properties and can resist corrosion from a variety of media. Stainless steel pipes like 304 and 316 are widely used in the food and medical industries.

• Austenitic - Ferritic Duplex Stainless Steel: It combines the advantages of austenitic and ferritic stainless steels and has superplasticity. For instance, the Sandvik SAF3207HD duplex stainless steel pipe is suitable for pipeline systems in harsh subsea environments.

• Martensitic Stainless Steel: It has high strength, but poor plasticity and weldability. Examples include 410 and 420 stainless steel pipes. The 420 stainless steel pipe can be used to manufacture surgical knives.

2. Production Process

• Raw Material Preparation: High - quality raw materials containing at least 10.5% chromium, such as iron, chromium, and nickel alloy elements, are selected. These raw materials are melted in an electric furnace at a high temperature of about 1500°C and then cast into steel billets.

• Forming: Seamless pipes are formed through hot extrusion or cold drawing processes. Hot extrusion involves extruding a heated steel billet through a die to form a pipe, while cold drawing pulls the steel billet to reduce its diameter and improve precision. Welded pipes are made by rolling a stainless - steel strip into a pipe shape and then welding it using processes such as TIG welding.

• Heat Treatment: After forming, the steel pipes are annealed. They are heated to a certain temperature and then cooled to eliminate internal stress and improve strength and toughness.

• Surface Treatment: Pickling is carried out to remove the surface oxide scale, and then passivation treatment is performed to form a dense oxide film, enhancing corrosion resistance.

• Quality Inspection: The dimensions, wall thickness, surface quality, and strength of the steel pipes are strictly inspected to ensure they meet the standards.

3. Performance Characteristics

• High Corrosion Resistance: Chromium reacts with oxygen to form a dense chromium oxide film, which can effectively block oxygen and moisture, making it not easy to rust in humid, acidic, alkaline, and other environments.

• High Strength: It has good tensile, compressive, and bending resistance, and can withstand large pressures and external forces.

• Good High - Temperature Resistance: It can maintain its structure and mechanical properties in high - temperature environments, and is not easy to deform or be damaged.

• Excellent Hygiene: The surface is smooth and easy to clean, and will not contaminate food, medicine, etc., meeting hygiene standards.

4. Application Fields

• Civilian Applications: It is often used for the low - pressure fluid transportation of cold and hot water, direct - drinking water, heating, gas supply, and fire - sprinkler systems. For example, the water pipes in home decoration and the fire - protection pipes in buildings.

• Industrial Applications: It is widely used in the low - pressure fluid transportation systems of industries such as medicine, beverage, food, brewing, electricity, and chemical engineering. For instance, the material - transportation pipes in food and beverage factories and the pipelines for transporting corrosive media in chemical plants.