If the used high frequency tube mills refers to the chemical composition and mechanical properties of welded tube blanks that require certain inspection methods to be known as invisible defects; then, those defects that can be seen only by vision are called tube blanks. Overt defect.

The dominant defects of the welded tube blank of the used high frequency tube mills generally include cracked edges, broken edges, sawtooth, pitting, scratches, roll marks, dark spots, edge burrs, sickle bends, wrinkles, waves, edge warping, and points. Layers, warped skins, pinholes, sticky rolls, soft spots, rust, oxide layers, towers, loose rolls, etc. Let me introduce you to the causes of cracked edges and the impact of cracked edge billets on welded pipes.

Rust

Corrosion refers to the phenomenon that the surface of the tube blank is damaged by the wetness of rainwater, acid, lye and other liquids or air oxidation.

Rust can be divided into slight corrosion and severe corrosion. Slightly rusted tube blanks, gently wipe with 240 grit sandpaper, after blowing off the rust powder, there is no trace on the surface of the tube blanks. After wiping off the severely corroded blank tube with sandpaper, the surface of the blank tube still has corroded dent marks. Corrosion is one of the common defects of tube blanks.

Causes of corrosion:

(1) The tube blank is exposed to the air for a long time, and is oxidized in contact with moisture and oxygen in the air.

(2) Directly corroded by water, acid, alkali and other liquids.

The effect of corrosion on the quality of welded pipe:

(1)Even if it is slightly rusty, after the welded pipe is formed, welded, and rolled by the sizing roll, the surface of the welded pipe will be impressed by the rust powder, which will damage the surface quality of the welded pipe and increase the subsequent surface treatment cost of the welded pipe.

(2)The weld seam strength is low, and the weld seam structure is not dense. The chemical expression of rust powder is mFe203,·nH2O. The rust in the thickness direction of the tube blank will undergo a series of chemical reactions during high-temperature welding to generate CO gas and H2, and stay in the weld during solidification to form pores and structure. loose.

(3) Severe corrosion will thin the pipe wall and reduce the pressure-bearing capacity of the pipe.

Raw materials are critical to product quality, and we must keep the raw materials in check.

Regarding the defects of welded pipe blanks of used high frequency tube mills(11), the causes of corrosion and the influence of corrosion on the quality of welded pipes, I hope it can help you.