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What defects are prone to occur during the production of hot rolled seamless steel tubes?

Posted by:Rain Time:2020.03.17 21:39

1. Cracks

Features: The internal and external surfaces of seamless steel pipes are cracked in straight or spiral shapes, and some are reticulated, and the ends and bottom of the cracks are pointed.


(1)   Poor steel with subcutaneous stomata and subcutaneous inclusions.

(2)   The tube blank is not heated properly.

(3)   Excessive deformation pressure.


2. hairline

Features: continuous or discontinuous hairline fine lines on the outer surface of the seamless steel pipe, mostly spiral spiral direction opposite to the direction of rotation of the punch, larger pitch, and some are approximately linear.

(1)   Poor steel with subcutaneous stomata and subcutaneous inclusions.

(2)   The surface of the tube blank is not cleaned thoroughly.


3. Inward fold (commonly known as incision)

Features: Zigzag defects on the inner surface of the steel pipe are straight or spiral. For high-alloy steel pipes, this defect is irregularly shaped and distributed at the inlet. If the inner fold due to centering is generally half to one circle, and it is on the head.


(1)   Excessive reduction in front of the head.

(2)   Head wear is severe.

(3)   During the perforation process, the metal in the central part of the billet is subjected to strong alternating stress. Therefore, the inner wall of the rough tube is prone to inward folding during rolling.

(4)   The inward fold at the entrance of the high-alloy steel pipe is caused by the uneven force of the roll during perforation.


4. Outer Folding

Features: The spiral surface of the seamless steel pipe is folded in a spiral direction, the spiral direction of which is opposite to that of the waste pipe on the puncher, and the pitch is large.


(1)   Defects such as cracks or ears remain on the surface of the tube blank.

(2)   Poor steel, inclusions or severe looseness.


5. Rolling and folding

Features: Regular folding defects on the outer surface of seamless steel tubes.

It is mainly caused by the damage of the rollers of the piercing machine or the rolls of the pipe rolling machine.


6. folding

characteristics: During rolling, the metal enters the gap between the rolls or the pipe loses stability, causing it to form a zigzag. After sizing, it shows local convex and concave wrinkles on the surface of the steel pipe.


(1)   The diameter of the outlet pipe of the whole machine is larger than that of the fixed and reduced machine.

(2)   Incorrect adjustment, roll misalignment, inconsistent center line, etc.

(3)   The sizing rack is installed upside down.


7. Straight inward fold

characteristics: The inner surface of the seamless steel pipe is symmetrical or a single linear fold 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 larger than the width of the grooved hole, the inner diameter is too large or the tube wall is too thin.

(3)   The distribution of the reduction of punching and rolling mills is unreasonable.

Before the second rolling, the 90 ° flip was not turned

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