What is the significance of pickling large-diameter steel pipes?

Release date:

2021-01-16

Author:

Source:

Category:

Steel Pipe Knowledge

Pickling of large-diameter steel pipes is a process that uses acidic solutions to remove scale and rust from the steel surface. Common pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, and mixed acids. The primary purpose of pickling is to eliminate surface oxide scales, followed by lubrication—carbon steels are treated with phosphating soap, stainless steels with oil‑lime, and copper or aluminum tubes with oil coating. Subsequently, the traditional copper‑plating process is applied, after which the material undergoes further deep‑drawing operations.

　　 Large-diameter steel pipe The selection of a welding process should be based on the material and wall thickness of the large-diameter steel pipe, as different welding methods exhibit varying arc heat and arc force characteristics. Moreover, each welding method possesses distinct properties.

　　Pickling of large-diameter steel pipes is a process that uses acidic solutions to remove scale and rust from the steel surface. Common pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, and mixed acids. The primary purpose of pickling is to eliminate surface oxide scale, followed by lubrication—carbon steel is treated with phosphating soap, stainless steel with oil‑lime, and copper or aluminum tubes with oil coating—and then subjected to an older technique: copper plating, before proceeding to drawing and further deep‑processing operations.

　　If large-diameter steel pipes are not pickled, their surfaces may be covered with oxides and oil residues. These contaminants cannot be removed by the phosphating solution, leading to degraded phosphating quality. Moreover, during manufacturing, after undergoing multiple processing steps, even slight carelessness can leave surface defects on the pipes, reducing the corrosion resistance of components and directly shortening their service life.

　　To enhance the corrosion resistance of large-diameter steel pipes and extend their service life, these pipes undergo pickling and passivation surface treatments to form a protective oxide film on the surface. The steel exhibits high hardenability, good machinability, and moderate cold‑working ductility and weldability. Moreover, its toughness decreases only slightly during heat treatment, while it maintains relatively high strength and wear resistance; notably, it retains considerable toughness even after water quenching. However, this steel is highly susceptible to white‑spot defects, tends to exhibit temper embrittlement and overheating sensitivity during heat treatment, and offers high strength and hardenability along with good toughness. It shows minimal distortion during quenching and possesses high creep strength and long‑term strength at elevated temperatures. Consequently, it is well suited for manufacturing forgings that demand higher strength than 35CrMo steel and have larger cross‑sections subjected to tempering, such as large gears for locomotive traction, supercharger drive gears, rear axles, heavily loaded connecting rods, and spring clips. It can also be used for drill‑pipe joints and fishing tools in oil wells shallower than 2,000 meters, as well as for dies in bending machines.

Protection of Anti-Corrosion Spiral Steel Pipes During Construction

Corrosion Mechanism of Steel Plate Coiled Pipes

More News

■

What are the product categories offered by spiral pipe manufacturers?

—

2023-05-11