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Seamless pipe defects and causes

There are some common defects of seamless pipe for sharing.

1 Abscission
Characteristics of defects: in the steel pipe inner surface of the vertical distribution was raised spiral separation or rupture of bulk metal-like sandwich.
Causes: the material is caused by poor non-metallic inclusions, residual shrinkage, or severe osteoporosis.

2 Straight within the fold
Characteristics of defects:in the steel pipe inner surface of the vertical distribution is showing a symmetrical or single linear folded a long pass even local.
Causes:poor lubrication of the mandrel, the mandrel surface defects or surface with the oxide scale, scrap iron to make steel pipe inner surface of the program into the channel, the shortage of pipe in the rolling process, too full of rolling mill pass.

3 Wall contraction
Characteristics of defects:steel pipe horizontal thinnest section is surface depression located on the inner surface of the steel pipe and is local thinning of the wall thickness, even severe contraction of tear. Causes:rolling mill extension in the hole sidewall part of the local pulled thin strip mill each rack pressure adjustment is improper and unreasonable extension coefficient distribution.

4 Within the rolling scars
Characteristics of defects:inner surface of steel pipe is vertical to nail-shaped scar, raised or block folding.
Causes:poor mandrel lubrication state is causing the mandrel local wear, damage, sticky metal, immediate serious wear and tear, stick the metal, the lack of meat or large cracks perforated ears were pressed on the steel pipe wall.

5 Rolling fold
Characteristics of defects:located on the partial or total length of the inner surface steel pipe was apparent grooves of the outer concave, convex folds or in the pipe outer surface longitudinal long pass prescribe symmetry is generally linear, individual slash-shaped.
Causes:rolling waste pipe outside diameter or waste pipe ovality is too large, bamboo control is not strong enough or lubrication conditions is poor, traverse device rolling touch the flat, rolling mill speed is error.

6 Double seam fold
Characteristics of defects:cracks in the steel pipe surface are sometimes scattered in the tube park weeks sometimes symmetrical.
Causes:Perforation capillary outside diameter is too large or irregular diameter is caused by folding.

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