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Common problems and treatment of steel pipe internal burr removal II

Residual height of internal burr exceeded the standard

In production, the contents of steel pipe are prone to remain bumps after burr removal in small diameter welded pipe, as shown in the following figure. This problem is often caused by inadequate scraping of burr knives or inadequate adjustment of burr knives.


Internal burr removal is not clean


1 The burr knife should be readjusted. If the blade is worn out, the burr knife should be re-sharpened. When using cylinder feed tool, if the cylinder piston does not rise in place and the seal ring is damaged, the high quality fluororubber seal ring should be replaced.


2 If the oil quality is poor, the high temperature resistant oil should be replaced, and the oil pressure and the operation of the oil pump station should be checked.


The weld is peach-shaped

the weld is peach-shaped after welding the steel pipe smaller than 165mm, as shown in the following figure:


Peach-shaped in weld seam


Four-roll extrusion or three-roll extrusion is adopted. When producing steel pipe with wall thickness of 4-14 mm, the first deformation roll should make the edge of strip fully deformed, and the billet after the extrusion roll should be flat ellipse, so that the edge of strip can be welded horizontally. When producing steel pipe with 0.4-2mm wall thickness, the first deformation roll should fully deform the edge of the strip, forming the bottom arc vertical ellipse at six guide sheets, forming the bottom arc flat ellipse at seven and eight guide sheets; when extruding with two rolls, the tube blank arc after the extrusion roll is flat ellipse.


The knife bar can’t lift up and can’t de-burrs

Cause: The lower roller rack has metal oxide slag stuck and can not rise and fall.


1 Clean the lower roller rack or replace the new lower roller rack to make it rise and fall flexibly;

2 Check whether the hydraulic system, tubing and relief valve are blocked, whether the reversing valve is reversed, whether the hydraulic pump is working, etc.

If the above two conditions are completely normal, the knife rod can not be raised and burrs can not be scraped. The main causes of such problems are as follows:

(1) The outer diameter of the guide blade is too large to support the knife rod so that the knife rod can not be raised.


Reduce the outer diameter of the guide blade

(2) The fixed plate fixed on the adjusting device at the end is raised too high.


Lower the fixed plate on the adjustment unit to a reasonable position.


The internal burr is periodic, scaly or spiral in shape.

The internal burr scraping changes periodically, and the causes of this problem are as follows:

1 There are iron nodules in the middle groove of the lower roller, which make the lower roller run periodically when it rotates.

2 The breakdown of relief valve and hydraulic pump makes the pressure change periodically.


Replace the lower roll; Replace the new relief valve and hydraulic pump.

The internal burr of scraping is scaly and the cause of the problem is as follows:

1 The lower roller has a flat surface. Solve the problem of replacing the new lower roller.

2 Hydraulic pressure varies between (+0.2 MPa).


Replace a new relief valve.


The shape of the inner burr scraped out is spiral or tower spiral. The causes of the problem are as follows:

1 The weld deflects to one side and the strip steel sickle bends greatly.


Adjust the pressure of the upper roll supported by the flat roll of the right and left bench of the sizing machine to make the weld force twist.

2 The weld seam swings left and right, and the bending of the strip sickle is large, especially the serious wave bending of the head and tail of the strip.


Improve strip quality and reduce sickle bending and wave bending.


Internal burr scratch deviation

In the actual production process, the phenomenon of internal burr scratching deviation (as shown in the figure below) is quite common.


Internal burr scratch deviation

The main causes of this problem are:

1 Because the center position of the mandrel is deviated from the weld, or the weld is uneven.


The position of the mandrel can be adjusted by the adjusting bolt of the connecting plate until the scraping phenomenon disappears;


2 Because the temperature of the working environment of the mandrel is high, the cooling of the mandrel is deformed and the blade is deformed.


The mandrel needs to be straightened and the mandrel cooling system is processed until it meets the production requirements;


3 Because the outer weld burr can be leveled under the adjustment of the operator, and the weld is not flat, the inner weld is just scratched.


To adjust the welding squeeze roller to make the inner weld flat, take the weld seam in the pipe as the standard.


However, there are often intermittent offsets on the sides of the inner burr scraping in production for two reasons:

1 The mandrel support wheel is not in good contact with the pipe wall, causing the mandrel to drive the cutter head to oscillate;

2 The mandrel link lock nut is loose, causing intermittent offset on both sides. This can be solved by adjusting the relative height of the cutter head and the support wheel; relock the lock nut.


Other problems and handling

When producing 42mm welded pipe with a wall thickness of 1.5 to 3.5mm, since the strip is a longitudinal strip, and because the roll hole shape design is conventionally designed. Therefore, the positive and negative V-shaped butt welding will cause uneven size of internal burr and poor quality of internal burr scraping.


The roll shape design adopts multiple radii, the 6th frame with guide piece is designed as a vertical ellipse, and the 7th and 8th frames are designed as flat ellipse. At the same time, in the production adjustment, when the two rolls are pressed, the upper rod of the pressing roller can be tightened and the lower shaft rod can be loosened, so that the inner burr is stable and uniform.


The burr removal in small diameter HFW welded pipes is a key process in the production of high quality small diameter welded pipes. However, in the production process, the use of the device and the removal of the inner burr often cause problems such as slow welding speed, weld seam welding, collapse, internal burr residual height, internal burr scraping, fish scale or spiral, internal burr scraping, etc. To the quality and normal production of welded pipes. Therefore, regardless of the reasons for these problems, specific analysis should be carried out according to specific problems, and corresponding solutions should be taken to produce high-quality small-diameter welded pipe products.


Post time: May-16-2019

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