Analysis of common faults of used welded pipe units: tube billet scratches

Publish Time: 2025-03-10

In the production process of used welded pipe units, tube billet scratches are a common fault. This fault not only affects the quality of the product, but also may threaten the continuous operation of the production line. The scratches are mainly caused by two key parts: the guide mechanism and the extrusion welding mechanism.

Guide mechanism scratches

1. Scratches location and characteristics

Guide mechanism scratches mainly occur on both sides of the tube billet. When the guide sleeve is not adjusted properly, friction scratches may also occur on the upper and lower surfaces of the tube billet. The characteristics of this scratch are that the wound surface is large and the continuity is strong, which has a significant impact on product quality.

2. Causes of scratches

(1) Incorrect height position of the guide sleeve: The height position of the guide sleeve is crucial to controlling the movement trajectory of the tube billet. If the height position is set improperly, the tube billet may have unnecessary friction with the guide sleeve during transportation, resulting in scratches.

(2) Guide roller bearing damage: Damage to the guide roller bearing will cause the guide roller to be unable to stably control the tube billet, causing it to shake or deviate from the predetermined trajectory during movement, thereby increasing the chance of friction with the guide sleeve.

(3) Guide roller deviates from the rolling center line: When the guide roller deviates too much from the rolling center line, the relative difference between the axis of the guide sleeve and the guide roller will also increase, which will also increase the chance of friction between the tube billet and the guide sleeve, resulting in scratches.

Scratches in the extrusion welding mechanism

1. Scratching location and characteristics

Scratches in the extrusion welding mechanism mainly occur at the bottom of the tube billet. This type of scratch is usually caused by poor contact or improper matching between the extrusion roller and the tube billet.

2. Causes of scratches

(1) Hole mismatch: The hole design of the weld extrusion structure is crucial to ensuring welding quality. If the hole mismatch, such as bearing damage, roller axial movement, inconsistent hole size, different height positions of the two rollers, shaft bending, and unstable assembly, may lead to poor contact between the extrusion roller and the tube billet, resulting in scratches.

(2) Height matching problem: The lower edge of the extrusion roller hole should be consistent with the height of the rolling line. If the height of the guide roller is reduced to a certain limit, the edge radius of the extrusion roller hole will scratch the bottom of the tube. Especially after the R radius of the extrusion roller hole is sharpened, scratches are more likely to occur.

(3) Insufficient extrusion force on the extrusion roller: For the extrusion roller device with a two-roller structure, when the upper extrusion force is insufficient, the tube will cause the roller shaft to have an upward tilt angle under the action of tension, resulting in the protrusion of the R radius of the hole edge. This will also cause scratches on the lower part of the tube. When the R radius of the extrusion roller hole is sharpened, the incidence of scratch accidents will increase further.

Fault handling suggestions

For the above scratch faults, we put forward the following handling suggestions:

Regularly inspect and maintain the guide mechanism and extrusion welding mechanism to ensure that all components are in good condition.

Adjust the height position of the guide sleeve and the position of the guide roller to ensure that the tube will not have unnecessary friction with the guide sleeve during transportation.

Optimize the hole design of the extrusion welding mechanism to ensure good hole fit and avoid scratches caused by hole mismatch.

Strengthen the training and management of operators to improve their ability to judge and handle equipment failures.
Through the implementation of the above measures, the incidence of pipe blank scratch failures in used welded pipe units can be effectively reduced, and production efficiency and product quality can be improved.