Stainless steel pipe is a hollow, long, circular steel section, mainly widely used in industrial pipelines for oil, chemical, light industry, and mechanical instruments, as well as for mechanical structural components. Additionally, with the same bending and torsional strength, it is lighter in weight, making it also extensively used in the manufacturing of mechanical parts and engineering structures.
Stainless steel pipes can be categorized by composition into Cr-series (400 series), Cr-Ni-series (300 series), Cr-Mn-Ni (200 series), and precipitation hardening-series (600 series). 200 Series — Chromium-Nickel-Manganese Austenitic Stainless Steel; 300 Series — Chromium-Nickel Austenitic Stainless Steel.
301 - Excellent formability for molding products. Can be rapidly hardened through mechanical processing. Good weldability. Higher wear resistance and fatigue strength than 304 stainless steel.
302 - Corrosion resistance similar to 304; higher carbon content results in better strength.
303——Easier to machine than 304 by adding a small amount of sulfur and phosphorus.
304 - 18/8 stainless steel. GB grade: 0Cr18Ni9. 309 - Has better temperature resistance compared to 304.
316 - Following 304, a widely-used steel grade, primarily for industrial and equipment purposes. The addition of molybdenum elements imparts a special corrosion-resistant structure. Due to its superior chloride corrosion resistance compared to 304 stainless steel tubes, it is also used as "shipboard steel." SS316 is typically used in nuclear fuel recovery systems. 18/10 grade stainless steel tubes usually meet this application level as well.
Model 321—Similar to 304 in performance, except that the addition of titanium elements reduces the risk of weld seam rust.
400 Series – Ferritic and Martensitic Stainless Steel.
408 — Good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.
409 - Inexpensive model (US/UK), commonly used for car exhaust pipes, belongs to ferritic stainless steel (chrome steel).
410—Martensitic (high-strength chromium steel), good wear resistance, poor corrosion resistance.
416 – Added sulfur to improve the material's workability.
420—"Tool Steel" Martensitic steel, similar to early stainless steels like Beryllium Chrome steel. Also used for cutting tools, which can be highly polished.
430—Ferritic stainless steel, decorative, e.g., for automotive accessories. Good formability, but poor temperature resistance and corrosion resistance.
440—High-carbon, high-strength tool steel, with higher carbon content. After appropriate heat treatment, it can achieve high yield strength, with hardness up to 58HRC, placing it among the hardest stainless steels. Common applications include "razor blades." There are three commonly used grades: 440A, 440B, and 440C, with an additional 440F (easy-to-machine).
500 Series — Heat Resistant Chromium Alloy Steel.
600 Series - Martensitic precipitation hardening stainless steel tubes