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Quality Defects Analysis of Seamless Steel Pipes
May 14, 2021
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As for the seamless steel pipe production, we should follow the main points and matters of the production process to avoid defects of seamless steel pipes, which will have a fatal impact on the quality of our products. Then, how do you avoid these defects? We believe that it is important to understand the causes of them as follows.
1. The folding of seamless steel pipes
It exists on the outer surface or inner surface of seamless steel pipes with a straight line or spiral shape, in a continuous or discontinuous state. The main reasons for the folding are as follows: 1. The quality of the pipe material is not good. 2. The folding itself exists. 3. There are inclusions on the surface, serious scratches and cracks. 3. There are edges and corners in the grinding place. And, the folding appears after extension after drawing. In order to avoid folding, the quality of pipe material should be improved and attention should be paid to inspection and grinding.
2. Cracks of seamless steel pipes
It refers to the small cracks of a straight line or spiral distribution on the inner and outer surface of seamless steel pipes. The depth is 1mm or more, which is continuous and discontinuous. According to the relevant analysis, the causes are as follows: there are subcutaneous bubbles and subcutaneous inclusions in the hot rolled pipe billet, cracks or deep pit-spots on the steel pipe before drawing, and longitudinal scratches or abrasions in the hot rolling or cold drawing processes. Preventing the formation of cracks also lies in improving the quality of pipe billets, strengthening the inspection and grinding of pipe materials. At the same time, the pipe should avoid pitting, scratching and abrasion in the process of cold drawing.
3. Abrasions of seamless steel pipes
The defect is characterized by longitudinal linear scratches of varying lengths on the inner and outer surfaces of the seamless pipe. The shapes of those scratches are mostly grooves, but some of them may also be raised streaks. The main reasons for scratching (scratching) are as follows: there is an inner scratch on the pipe material, which can not be eliminated during drawing. There is residual iron oxide mold sticking steel on the steel pipe. The strength and hardness of the mold are not enough or uneven. The mold is broken and worn. The hammer head is bad, and the sharp edges and corners of the transition part of the hammer head damage the mold. In order to prevent scratches, the quality of each preparation process before drawing should be improved, and the mould with high strength and hardness and good finish should be used.
4. Pits of seamless steel pipes
This is one of the common surface defects of seamless pipes. The part of sunken areas is distributed on the surface of the steel pipe. Some are periodic and some are irregular. The pits are caused by iron oxide or other hard dirt pressed into the surface of the steel pipe during the drawing or straightening process, or by peeling off the warped skin that originally existed on the surface of the steel pipe. Datang Steel Pipe held the view that the measures to prevent pits are to carefully check the pipe material and remove defects such as warping skins, keep the work site, tools and lubricants clean, and prevent iron oxide and dirt from falling on the surface of the steel pipe.
When there are smooth or sharp spiral marks on the outer surface of seamless steel pipes, the straightener should be checked. Due to the incorrect position and angles of the straightening roller, the shoulder of steel pipes at the edge of the straightening roller during straightening is brushed, and there are worn grooves on the straightening roller. Excess bending at both ends of the steel pipe may cause pits on the outer surface of the steel pipe.
5. The pitting surface of seamless steel pipes
It is characterized by small pits on the surface of the steel pipe. The main reason for producing pitting surface is that the pitting corrosion during pickling and the pitting surface is formed after the iron oxide sheet is pressed into the steel pipe surface after being too thick and straightened. The storage environment of the steel pipe is wet. Even after the water, the punctate corrosion occurs, and the pitting surface is formed after the removal of rust spots.
1. The folding of seamless steel pipes
It exists on the outer surface or inner surface of seamless steel pipes with a straight line or spiral shape, in a continuous or discontinuous state. The main reasons for the folding are as follows: 1. The quality of the pipe material is not good. 2. The folding itself exists. 3. There are inclusions on the surface, serious scratches and cracks. 3. There are edges and corners in the grinding place. And, the folding appears after extension after drawing. In order to avoid folding, the quality of pipe material should be improved and attention should be paid to inspection and grinding.
2. Cracks of seamless steel pipes
It refers to the small cracks of a straight line or spiral distribution on the inner and outer surface of seamless steel pipes. The depth is 1mm or more, which is continuous and discontinuous. According to the relevant analysis, the causes are as follows: there are subcutaneous bubbles and subcutaneous inclusions in the hot rolled pipe billet, cracks or deep pit-spots on the steel pipe before drawing, and longitudinal scratches or abrasions in the hot rolling or cold drawing processes. Preventing the formation of cracks also lies in improving the quality of pipe billets, strengthening the inspection and grinding of pipe materials. At the same time, the pipe should avoid pitting, scratching and abrasion in the process of cold drawing.
3. Abrasions of seamless steel pipes
The defect is characterized by longitudinal linear scratches of varying lengths on the inner and outer surfaces of the seamless pipe. The shapes of those scratches are mostly grooves, but some of them may also be raised streaks. The main reasons for scratching (scratching) are as follows: there is an inner scratch on the pipe material, which can not be eliminated during drawing. There is residual iron oxide mold sticking steel on the steel pipe. The strength and hardness of the mold are not enough or uneven. The mold is broken and worn. The hammer head is bad, and the sharp edges and corners of the transition part of the hammer head damage the mold. In order to prevent scratches, the quality of each preparation process before drawing should be improved, and the mould with high strength and hardness and good finish should be used.
4. Pits of seamless steel pipes
This is one of the common surface defects of seamless pipes. The part of sunken areas is distributed on the surface of the steel pipe. Some are periodic and some are irregular. The pits are caused by iron oxide or other hard dirt pressed into the surface of the steel pipe during the drawing or straightening process, or by peeling off the warped skin that originally existed on the surface of the steel pipe. Datang Steel Pipe held the view that the measures to prevent pits are to carefully check the pipe material and remove defects such as warping skins, keep the work site, tools and lubricants clean, and prevent iron oxide and dirt from falling on the surface of the steel pipe.
When there are smooth or sharp spiral marks on the outer surface of seamless steel pipes, the straightener should be checked. Due to the incorrect position and angles of the straightening roller, the shoulder of steel pipes at the edge of the straightening roller during straightening is brushed, and there are worn grooves on the straightening roller. Excess bending at both ends of the steel pipe may cause pits on the outer surface of the steel pipe.
5. The pitting surface of seamless steel pipes
It is characterized by small pits on the surface of the steel pipe. The main reason for producing pitting surface is that the pitting corrosion during pickling and the pitting surface is formed after the iron oxide sheet is pressed into the steel pipe surface after being too thick and straightened. The storage environment of the steel pipe is wet. Even after the water, the punctate corrosion occurs, and the pitting surface is formed after the removal of rust spots.
