We use cookies to offer a better browsing experience, analyze site traffic, and personalize content. By using this site, you agree to our use of cookies.

Accept
Decline

Pipe Knowledge

Sharing China-Made with Global Customers

seamless pipe suppliers,inconel 825 tube,smls pipe

Pipe Knowledge

Sharing China-Made with Global Customers

Common welded pipe surface defects - pipe surface scars,alloy steel seamless pipe,FBE Coating Pipe,carbon steel tubing suppliers
BackYou are in :  Home  >  News  >  Pipe Knowledge

Common welded pipe surface defects - pipe surface scars

Date:2023-04-28View:240Tags:seamless pipe suppliers,inconel 825 tube,smls pipe

Pipeline scar is a common defect of welded pipe, and its specific manifestations include crush, indentation and scratch.

Crush: refers to the damage of roll pass to the surface of tube blank. There are many kinds of crush, but the causes are as follows:

1.The bottom line of an opposite roll pass is adjusted higher than the rolling bottom line, which makes the rolling line uneven.

2.The vertical roll is too tight.

3.The vertical roller has elevation angle.

4.The new pass may be that the edge chamfer of pass is too small or the chamfer angle does not meet the requirements.

5.High strength tube blank has large springback and deformation resistance, and the edge of pass is easy to bite the tube blank.

6.The vertical roll in front of the flat roll does not exert enough transverse force on the tube blank, resulting in the wide tube blank entering the flat roll pass with fixed width, and the tube blank is "sheared" by the pass.

7.The flat roll is too low, resulting in the tube billet being crushed by the bottom edge of the vertical roll pass.

8.The vertical roll deviates from the rolling center line, resulting in the tube billet being crushed in the flat roll.

Indentation and dark line:

Indentation and dark line are actually the products of indentation. The formation mechanism is roughly the same, but it is more hidden. It can not be seen without careful observation, and the handle is not obvious, but it has an impact on the surface quality of welded pipe.

Generally, there is a reflective band of 5 ~ 10 mm in the indentation, especially for the light source. The refractive index of the light at the indentation is different from other parts.

The essence of the dark line is that the linear scar occurred in front of the pipe was not found in time, and was "flattened" by the subsequent roll. After a rough look, nothing wrong can be seen. However, after careful inspection, wiping with sandpaper and drawing along the circumference of the pipe surface with nails, the existence of the dark line can still be seen or felt. The dark line is more hidden and difficult to find than the indentation.

Scratch:

It mainly refers to the damage to the running tube billet caused by the roller that does not move or has a large relative speed difference. The characteristic is related to the speed difference. The damage to the running tube billet, such as the damage to the vertical roller bearing, causes the vertical roller rotation to be blocked, scratches the tube surface, the linear speed of the rolling diameter position on the pass is different from other parts, and the position with a large speed difference is related to the moving formed tube When the friction reaches a certain degree, the surface of the tube will be scratched. The former is characterized by a straight longitudinal line on the surface of the tube, while the latter is characterized by an irregular arc on the surface of the tube, which is like a "nail print". The "nail print" often occurs at the two edges, bottom and middle of the tube, and at the edge and bottom of the tube The middle part corresponds to the position where the velocity difference of the forming vertical roll pass is large, while the middle part corresponds to the position where the velocity difference of the forming flat roll pass is large.

The removal of "nail marks" can be done from two aspects: pass and adjustment

From the point of view of pass design, the bold removal of pass without affecting the overall deformation effect is not only harmless to forming, but also can avoid the trouble of scratch in the future.

From the point of view of adjustment, if there is an indentation under the tube blank of the vertical roll, lower the vertical roll; if there is an indentation on both sides of the tube blank of the flat roll, tighten the vertical roll before the flat roll or loosen the flat roll properly; if there is an indentation on one side of the tube blank after the flat roll, correct the vertical roll rolling center line before the flat roll.