Hainan Steel Wholesale

1. Roll imprint defect

Defect characteristics:It is a group of periodic, roughly consistent in size and shape concave convex defects, with an irregular appearance.


Cause of occurrence:



(1) On the one hand, due to fatigue or insufficient hardness of the rollers, some of the surface may have fallen off and the edges may be concave. On the other hand, it may be due to foreign objects adhering to the surface of the rollers, causing the surface to appear protruding;


(2) During steel rolling or finishing, concave and convex defects are formed by pressing into the surface of the steel plate.


2. Surface inclusions


Defect characteristics:There are irregular non-metallic inclusions in the shape of dots, blocks, or strips on the surface of the steel plate, and their colors are generally reddish brown, yellow brown, gray white, or gray black.


Cause of occurrence:


(1) The subcutaneous inclusions in the slab are exposed after rolling, or the original surface inclusions of the slab remain on the surface of the steel plate after rolling;


(2) Refractory materials and non-metallic substances such as mud and sand from the heating furnace fall on the surface of the slab, and are pressed into the slab surface during rolling.


3. Iron oxide scale


Defect characteristics:Iron oxide scale generally adheres to the surface of the steel plate, distributed locally or entirely on the surface of the plate, appearing black or reddish brown; Some iron sheets are loose and fall off, while others are not easy to fall off when pressed into the board surface; According to the different appearance shapes, there are:red iron sheet, block iron sheet, strip iron sheet, linear iron sheet, wood grain iron sheet, meteor shaped iron sheet, spindle shaped iron sheet, drag shaped iron sheet, and scattered iron sheet, with different depths of pressing.


Cause of occurrence:


(1) The generation of pressed iron oxide scale depends on the heating conditions of the slab. If the heating time exceeds a certain time, the higher the heating temperature and the stronger the oxidation atmosphere, the more iron oxide scale will be generated, and it is not easy to fall off. The iron scale produced once is difficult to remove completely, and is pressed into the surface of the steel plate during rolling;

(2) The setting of the large vertical roller is unreasonable, and the iron sheet is not squeezed loose, making it difficult to remove;

(3) Due to the low water pressure of the high-pressure descaling water pipe, water blockage, incorrect water angle, and improper use, the iron sheet on the surface of the steel plate has not been completely removed and is pressed into the surface of the steel plate after rolling;

(4) Iron oxide scale occurs more frequently in boiling steel, and it is easy to produce red iron scale in steel with higher silicon content.

4. Uneven thickness

Defect characteristics:The uneven thickness of each part of the steel plate is called uneven thickness. For steel plates with uneven thickness, it is generally due to excessive deviation, with local steel plate thickness exceeding the specified allowable deviation.


Cause of occurrence:


(1) Improper adjustment of roller gaps and configuration of roller profiles;


(2) The wear of the bearing shells on both sides of the rolling mill is different;


(3) The heating temperature of the slab is uneven.

5. Pockmarks

Defect characteristics:The surface of the steel plate shows local or continuous pits called pits, which vary in size and depth.

Reason:During the heating process, the slab oxidizes severely, and during rolling, the iron sheet is pressed into the surface, forming small pits after falling off.