Large-diameter stainless steel pipe prices, stainless steel pipe manufacturer

Hot-rolled seamless steel pipes are classified into ordinary steel pipes, steel pipes for low- and medium-pressure boilers, steel pipes for high-pressure boilers, alloy steel pipes, stainless steel pipes, steel pipes for petroleum cracking, geological steel pipes, and other types of steel pipes.

In addition to common steel pipes, low- and medium-pressure boiler tubes, high-pressure boiler tubes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other types of steel pipes, this category also includes carbon steel thin-walled pipes, alloy steel thin-walled pipes, stainless steel thin-walled pipes, and specially shaped steel pipes. The outer diameter of hot‑rolled seamless steel pipes generally exceeds 32 mm, with wall thicknesses ranging from 2.5 to 75 mm; the outer diameter of cold‑rolled seamless steel pipes can reach up to 6 mm, with wall thicknesses up to 0.25 mm; thin-walled steel pipes have an outer diameter of up to 5 mm and wall thicknesses less than 0.25 mm, and they offer higher dimensional accuracy than hot‑rolled seamless steel pipes.

Classification of stainless steel pipes: Stainless steel pipes are divided into two major categories—seamless steel pipes and welded steel pipes.

For stainless steel pipelines subjected to fluid pressure, a hydrostatic pressure test shall be conducted to verify their pressure‑resistance performance and quality. The pipe shall pass the test if, under the specified pressure, no leakage, blistering, or bulging occurs. In addition, certain steel pipes must undergo flange‑connection tests, flaring tests, flattening tests, and other examinations as required by the relevant standards or the purchaser.

Commonly used seamless steel pipes are manufactured from high‑quality carbon structural steels such as 10#, 20#, 35#, and 45#, as well as low‑alloy structural steels like 16Mn and 5MnV, or alloy steels such as 40Cr, 30CrMnSi, and 40MnB, through either hot rolling or cold rolling. Seamless pipes made from low‑carbon steels like 10# and 20# are primarily employed for fluid‑transport pipelines, while medium‑carbon seamless pipes such as 45# and 40Cr are used to fabricate mechanical components for automobiles, tractors, and other machinery. The quality of seamless steel pipes is typically assessed by tensile strength and flattening tests. Hot‑rolled steel pipes are delivered in the hot‑rolled condition or after heat treatment, whereas cold‑rolled steel pipes are supplied in a heat‑treated condition.

The key manufacturing processes for large-diameter stainless steel pipes are as follows:

1. Plate Flaw Detection: After thick steel plates used for manufacturing large-diameter steel pipes enter the production line, they undergo full‑plate ultrasonic flaw detection as a first step.

2. Milling: According to the milling machine’s specifications, both edges of the thick steel plate are machined to achieve the required plate width, edge flatness, and weld appearance quality.

3. Pre-bending of edges: A pre-bending machine is used to pre-bend the edges of the sheet metal, achieving the specified bending angle.

4. Forming: In the JCO forming machine, the pre‑bent front half of the thick steel plate is sequentially passed through multiple stamping dies driven by stepper motors, where it is pressed into a “J” shape; subsequently, the rear half of the plate is bent and pressed into a “C” shape, ultimately forming an open “O” shape.

5. Welding Treatment

8. Various Aspects of Testing

10. Diameter Expansion: By increasing the overall length of submerged-arc-welded straight-seam steel pipes, this process enhances dimensional accuracy and improves the distribution of thermal stresses within the pipe.