Stainless steel welded pipe production process:

Raw material–slitting–welding pipe–repairing–polishing–inspection (printing)–packaging–shipping (warehousing) (decorative welded pipe).

Raw material–slitting–welding pipe–heat treatment–correction–straightening–end trimming–pickling–water pressure test–inspection (printing)-packaging–shipping (warehousing) (Welded pipes for industrial piping).

Material classification

Stainless steel pipes can be divided into Cr series (400 series), Cr-Ni series (300 series), Cr-Mn-Ni (200 series) and precipitation hardening series (600 series) according to the composition.

200 Series—Chromium-Nickel-Manganese Austenitic Stainless Steel 300 Series—Chromium-Nickel Austenitic Stainless Steel.

301—–Good ductility, used for molding products. It can also be hardened by mechanical processing. Good weldability. Wear resistance and fatigue strength are better than 304 stainless steel.

302—–The corrosion resistance is the same as 304, and the strength is better because of the relatively high carbon content.

303—–By adding a small amount of sulfur and phosphorus, it is easier to cut than 304.

304—–that is, 18/8 stainless steel. The GB grade is 0Cr18Ni9. 309—Compared with 304, it has better temperature resistance.

316—–After 304, the second most widely used steel grade is mainly used in the food industry, pharmaceutical industry and surgical equipment. Adding molybdenum element makes it obtain a special corrosion-resistant structure. Because it has better resistance to chloride corrosion than 304 stainless steel pipes, it is also used as “marine steel”. SS316 is usually used in nuclear fuel recovery units. Grade 18/10 stainless steel pipe is also generally suitable for this application class.

Model 321—Similar to 304 except that the risk of material weld corrosion is reduced due to the addition of titanium.

400 Series—Ferritic and martensitic stainless steels.

408—good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.

409—The cheapest model (British and American), usually used as an automobile exhaust pipe, is a ferritic stainless steel (chrome steel).

410—Martensitic (high-strength chromium steel), good wear resistance and poor corrosion resistance.

416—The addition of sulfur improves the processing properties of the material.

420 – “Knives grade” martensitic steel, similar to the earliest stainless steels such as high chromium brinell steels. It is also used for surgical knives and can be made very shiny.

430—Ferritic stainless steel, for decoration, such as for car accessories. Good formability, but poor temperature resistance and corrosion resistance.

440—High-strength cutting tool steel, with slightly higher carbon content, higher yield strength can be obtained after proper heat treatment, and the hardness can reach 58HRC, which belongs to the hardest stainless steel. The most common application example is “razor blades”. There are three commonly used models: 440A, 440B, 440C, and 440F (easy to process).

500 Series—Heat resistant chromium alloy steel.

600 Series—Martensitic precipitation-hardening stainless steel tubing.