Surface Quality Analysis of High Precision Cold Drawn Seamless Steel

Cold-drawn pipe wall defects
High-precision cold-drawn tube inner surface roughness Ra ≤ 0.8μm, precision can reach diameter size ~ H9 H10, only to ensure that the honed H7 ~ H8 hole size and RA ≤ 0.2μm internal surface roughness requirements. In addition to the precision of the honing machine, the surface quality of the cold drawn tube is another key point. The internal surface defects of the cold drawn tube are classified by actual measurement data from a domestic manufacturer. There are mainly three types of honing tube surface roughness.


1. Pitting
After rough drawing, many pit-like defects can be found on the surface. Such defects do not seriously affect the smoothness of the cylinder bore because the cylinder is waste.
2. Scratches
Scratch defects are cold drawn, generally along the direction of the steel pipe along the axis of the scratches, must have more than the scratch depth of the honing margin, it may be worn off such defects, processing qualified cylinders.
Three. Not round
When the cold-drawn seamless steel pipe is produced, the inner mold fixed on the mandrel floats up and down, so the diameter of the cold-drawn pipe is not as straight as the blank. In addition, some hot-rolled pipes, due to the large wall thickness difference, cold drawing deformation due to the presence of uneven tube deformation, easy to produce cold-drawn pipe no point. The honed tube, if the grinding amount is small, can find a hole on the reflecting surface to a different degree even without removing the phosphate layer. Severely affect the cylinder surface quality.


These measures are as follows:
(1) The cold-drawn seamless steel pipe directly enters the cylinder, and the quality is not guaranteed. It is better to stay at 0.2 mm (wall thickness) for honing, grinding and reprocessing.
(2) The main reason for the surface quality of the cylinder bore is the bore defects in the cold drawn seamless steel tube.
(3) Pitting pitting defects caused by hot-rolled steel pipes. Cold drawing can reduce the depth of defects and cannot eliminate defects.
(4) increase the amount of cold-drawn deformation, preferably hot-rolled seamless steel billet, hot-rolled tube defects in the hole to clean up, can improve the quality of cold drawn seamless steel pipe wall surface, reduce honing.




Reduce honing costs and improve honing production efficiency.