Overview of Stainless Steel Pipe Classification

Stainless steel pipes are classified into two main categories: seamless and welded (with seams). Based on the outer diameter, they can be further divided into round and shaped pipes. Round pipes are widely used, but there are also various shaped pipes such as square, rectangular, semicircular, hexagonal, equilateral triangular, and octagonal.

Pressure-Resistant Pipe Testing

All pipes that must withstand fluid pressure undergo hydraulic testing and X-ray inspection to ensure their pressure resistance and quality. Pipes are deemed qualified if they show no leakage, wetting, or expansion under specified pressure. Some pipes also undergo flaring, flanging, or flattening tests as required by standards or customer demands.

Seamless Stainless Steel Pipe

Also known as stainless steel seamless pipe, it is made by piercing a steel ingot or solid pipe billet to form a hollow pipe, followed by hot rolling, cold rolling, or cold drawing. The specification of seamless steel pipes is expressed in terms of outer diameter * wall thickness in millimeters.

SUS304 Stainless Steel Pipe

SUS304 stainless steel pipe corresponds to the U.S. standard stainless steel and is equivalent to 0Cr19Ni9 in China, commonly replaced with 0Cr18Ni9.

Corrosion Resistance Mechanism of Stainless Steel

Stainless steel resists rust due to a dense oxide film formed by alloy elements, which isolates oxygen and prevents further oxidation. Therefore, stainless steel is not entirely "stainless."

Reasons for Rust on 304 Stainless Steel

1. Presence of Chloride Ions: Chloride ions are widespread in environments such as salt, sweat, seawater, sea breeze, and soil. Stainless steel can corrode rapidly in the presence of chloride ions, even faster than ordinary low-carbon steel. Therefore, stainless steel must be used in environments that meet specific conditions and must be regularly cleaned to remove dust, keeping it dry and clean.

316 and 317 Stainless Steel

316 and 317 stainless steels contain molybdenum. 317 has a slightly higher molybdenum content than 316. Due to molybdenum, these steels perform better than 310 and 304 stainless steels. In high-temperature conditions, 316 stainless steel has a wide range of applications, especially when sulfuric acid concentration is below 15% or above 85%. It also has good resistance to chloride corrosion, making it suitable for marine environments.