One、What are the different types of stainless steel pipe materials?
Stainless steel pipes can be classified based on their composition into Cr-based (400 series), Cr-Ni-based (300 series), Cr-Mn-Ni-based (200 series), and precipitation hardening-based (600 series).
200 Series – Chrome-Nickel-Manganese Austenitic Stainless Steel300 Series – Chrome-Nickel Austenitic Stainless Steel
301-----Excellent workability, suitable for forming products. Can also be rapidly hardened through mechanical processing. Good weldability. Superior wear resistance and fatigue strength compared to 304 stainless steel.
302-----Offers corrosion resistance comparable to 304, with improved strength due to its higher carbon content.
303-----By adding small amounts of sulfur and phosphorus, it is easier to machine than 304.
304-----Equivalent to 18/8 stainless steel. GB standard is 0Cr18Ni9. 309—Offers better temperature resistance compared to 304.
316-----Following 304, 316 is the second most widely used stainless steel grade, primarily used in the food, pharmaceutical, and surgical instrument industries. The addition of molybdenum imparts a unique corrosion-resistant structure. Due to its superior chloride corrosion resistance compared to 304 stainless steel, it is also used as "marine-grade" steel. 316 is commonly used in nuclear fuel recovery systems. 18/10 grade stainless steel tubes typically meet this application level.
Model 321 – Other performance characteristics are similar to 304, except that the addition of titanium elements reduces the risk of corrosion in welds.
400 series – Ferritic and Martensitic Stainless Steels.
408 — Good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.
409—The most affordable grade (in the US and UK), commonly used for automotive exhaust pipes, is chromium-molybdenum steel (chromium steel).
410—Martensitic (High-Strength Chromium Steel), Excellent Wear Resistance, Relatively Poor Corrosion Resistance.
416—The addition of sulfur improved the processing performance of the material.
420—“Tool Steel Grade” Molybdenum Steel, similar to early grades of chromium-containing stainless steel. Also used in surgical instruments, producing a very bright finish.
430—Stainless steel, for decorative purposes, such as automotive trim. Offers good workability, but has poor temperature resistance and corrosion resistance.
440 – High-strength blade steel with slightly higher carbon content, which, after appropriate heat treatment, can achieve high yield strength and hardness up to 58 HRC, making it one of the hardest stainless steels. A common application is in "razor blades." Common models include 440A, 440B, 440C, and 440F (a version for easier machining).
500 Series – Heat-Resistant Chromium Alloy Steel.
600 Series – Martensitic Stainless Steel Pipe with Cementitious Hardening.
Second, can 304 stainless steel be used for water pipes?
Not all 304 stainless steel is suitable for potable water pipes. only food-grade 304 stainless steel is approved for use in potable water pipes. Currently, there are many products on the market that use 304 stainless steel decorative pipes as potable water pipes, which is a deceptive practice that misleads consumers.
Food-grade 304 stainless steel pipes meet the standard GB/T29038-2012 "Technical Specifications for Thin-Walled Stainless Steel Pipes." Stainless steel decorative pipes conforming to GB/T18705-2002 "Welded Stainless Steel Pipes for Decorative Purposes" are not intended for direct contact with food or use as potable water pipes.
The minimum wall thickness for 304 stainless steel water pipes, with a diameter of DN15 and food-grade, is 0.6mm – 0.8mm. The allowable deviation is ±10% of the nominal wall thickness. The welds require a high quality, and the pipes must pass tests for flattening, expanding, bending, and stretching. The test water pressure must be 2.5Mpa or higher. The wall thickness of 304 stainless steel decorative pipes is not explicitly specified, and the weld quality requirements are not stringent. There are no specific pressure requirements for the pipes.