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Defects that May Occur in the Production of Hot-rolled Seamless Steel Pipes

Date:2020-11-18    keywords:hot-rolled seamless steel pipes,defects
Hot-rolled seamless steel pipe is a kind of round, square and rectangular steel with a hollow section and no joints on the periphery. When the bending and torsion strength is the same, the weight is lighter. It is an economical section steel. What defects are easy to appear in the production process of steel pipe? Let me explain it to you.

1). Cracks (also called cracks). Features: The inner and outer surfaces of seamless steel pipes are linear or spiral cracks, and some are mesh-shaped and both ends and bottom of the cracks are sharp.
1. Poor steel, with subcutaneous pores and subcutaneous inclusions.
2. Improper heating of the tube.
3. The deformation pressure is too large.

2). Hairline, features: continuous or discontinuous hair-like fine lines appear on the outer surface of seamless steel pipes. Most of the spiral spiral direction is opposite to the rotation direction of the perforator, the pitch is large, and some are similar to straight lines.
1. Poor steel, with subcutaneous pores and subcutaneous inclusions.
2. The surface of the tube blank is not cleaned thoroughly.

3). Folding inward, features: straight or spiral zigzag defects on the inner surface of the steel pipe. For high-alloy steel pipes, such defects are irregular blocks and distributed at the entrance. If the fold is caused by centering, it is usually half a circle to a circle, and it is on the head.
1. The amount of pressing down the head is too large.
2. Serious head wear.
3. During the piercing process, the metal in the central part of the blank bears strong alternating stress, so the inner wall of the waste tube is prone to inward bending during rolling.
4. The inward folding at the entrance of the high-alloy steel pipe is caused by the uneven force of the roll during piercing.

4). External folding, features: the outer surface of the seamless steel pipe is spirally folded, and the spiral direction is opposite to the spiral direction of the waste pipe on the puncher, and the pitch is relatively large.
1. Defects such as cracks or ears remain on the surface of the tube blank.
2. Poor steel quality, inclusions or serious looseness.

5). Rolling and folding, features: there are regular folding defects on the outer surface of the seamless steel pipe.
It is mainly caused by damage to the roll of the piercing machine or the roll of the tube mill.

6). Bending, characteristics: During rolling, the metal enters the gap between the rolls or the tube loses its stability, causing it to form twists and turns. After sizing, the surface of the steel pipe shows local convex and concave wrinkles.
1. The outlet pipe diameter of the equalizing machine is larger than the hole type of the fixed and reducing machine.
2. Incorrect adjustment, misalignment of rolls, inconsistent center lines, etc.
3. The sizing frame is installed upside down.

7). Straight inward folding, characteristics: the inner surface of the seamless steel pipe is symmetrical or a single straight line folded, distributed over the entire length or part of the steel pipe.
1. The head is severely worn or stuck to metal.
2. The outer diameter of the capillary is greater than the width of the grooved hole, the inner diameter is too large or the tube wall is too thin.
3. Unreasonable distribution of reduction of piercing machine and tube rolling mill.
4. Before the second pass of rolling, the 90° flip was not completed.

The above is the content of the defects in the production process of hot-rolled seamless steel pipes. I hope it will be helpful to you. If you have other things you want to know, you can consult us, and we will have professional people to answer you.

Tips: ASTM A53/SA53 seamless and welded steel pipe is a general, all-purpose pipe used in generator plants, refineries, compressor stations, natural gas transmission, and steam conduction.

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