The Generation And Elimination Of Scratches On The Surface Of Square Tubing

Surface scratches are also called scrapes, scratches, and scratches. It is a single or multiple parallel linear mechanical damage that appears in the axial direction of the surface of the square tubing. The bottom of the trench can be seen visually or under a magnifying glass. Due to the different temperatures of the scratches, the grooves will appear in different colors. Therefore, it can be used to determine the approximate process location where scratch defects occur.

Generally, for scratches formed under high temperature, the entire groove mark is oxidized; for scratches formed in the blue brittle temperature zone, the groove mark will be blue; when scratched at low temperature, the iron matrix will appear bright white in the groove mark. The depth of the iron sheet can be seen to be several millimeters, the length ranges from several millimeters to more than several meters, and the width varies. Most of the scratches and grooves are of the same width and appear intermittently on part or the entire length of the steel. Under the microscope, the bottom of the scratched groove is smooth, and there is basically no decarburization on the edge and bottom of the groove. Generally, the use of steel pipes for turning will not be affected when the depth of scratches does not exceed half of the tolerance specified in national standards.

Obvious scratches have a certain impact on the square tubing used for drawing. During the cold drawing process, scratches and grooves on the surface will worsen the lubrication state between the round steel and the drawing grinding tool, aggravating the surface damage of the rectangular tube after drawing, and in severe cases, causing damage to the drawing die. For steel pipes used for cold heading, scratches are one of the defects that are not allowed. During the cold heading process, surface damage and stress concentration caused by scratches will directly cause cracks in the cold heading and result in waste products.

The locations and processes that may cause scratches in high-temperature areas are scratches caused by poor processing of the guide device, skewed installation, severe wear, or sticky iron oxide scale; the roughness of loopers, runners, etc. due to installation and processing factors The surface or protrusions will cause the rolled piece to be scratched when jumping; the locations and processes that may cause scratches in medium or low-temperature areas are: the steel comes into contact with rough rollers, floors, cooling beds and other equipment during production and transportation, etc.

Wherever scratches occur in places and processes, sparks or sharp sounds often occur, and residual filamentous metal objects can be found. Based on this, the location of the scratches on the square and rectangular pipe can be found, and then dealt with according to the specific situation.