Surface Quality Analysis of High Precision Cold Drawn Seamless Steel

Surface defect of cold drawn tube inner wall
High precision cold drawn tube surface roughness Ra ≤ 0.8μm, diameter size accuracy can reach H9 ~ H10, only to ensure that after honing to H7 ~ H8 bore size and Ra ≤ 0.2μm of the internal surface roughness requirements. In addition to the honing machine equipment precision, the cold drawn tube surface quality is another key point, cold drawn tube internal surface defects by the domestic A factory measured data classification, there are three kinds of main honing pipe surface roughness.

1. Pitting
After rough drawing, the surface can be found by many pits-like defects, such defects will not seriously affect the smoothness of the cylinder bore, for the cylinder is a waste.
2. Scratch
Scratch defects are cold drawn, generally along the axis of a steel pipe along the direction of the scratches, there must be more than the depth of the scratches honing margin, it is possible to grind away such defects, processing a qualified cylinder.
3. Not round
Cold drawn seamless steel pipe in the production, fixed on the mandrel of the internal model can be floating up and down, so cold drawn tube diameter is not as straight as the machining tube. In addition, some hot-rolled tube, with the wall thickness difference between the larger, cold drawing deformation due to the existence of deformation within the tube is not uniform, easy to produce cold drawn tube does not dot. The tube after honing will find a hole in the hole with other parts of the reflective surface of different degrees, if the grinding volume is small, where even the cold drawn when the phosphate layer is not removed. Seriously affecting the cylinder surface quality.

The measures are as follows:
(1) Cold drawn seamless steel pipe directly into the cylinder, the quality can not be guaranteed, it is best to stay 0.2mm (wall thickness) honing, grinding and then processing use.
(2) Cold drawn seamless steel pipe inner hole defect is the impact of the cylinder bore hole surface quality of the main reasons.
(3) Pitting defects produced by the hot-rolled tube, cold drawing can reduce the depth of the defect can not eliminate the defect.
(4) To increase the amount of cold drawn deformation, preferably hot-rolled seamless steel tube blank, hot-rolled tube defects in the hole clean-up, can improve the cold drawn seamless steel pipe wall surface quality, reduce honing 


margins, reduce honing costs and improve Honing production efficiency.