Surface Defects on the Inner Wall of Cold Drawn Pipe
The surface roughness Ra of high precision cold-drawn tube is less than 0.8 micron, and the diameter dimension accuracy can reach H9~H10. Only the requirement of honing to H7~H8 aperture and Ra less than 0.2 micron inner surface roughness can be guaranteed. In addition to the accuracy of honing equipment, the surface quality of cold-drawn pipe is another key point. The surface defects of cold-drawn pipe are classified by the measured data of A factory in China. There are three kinds of surface roughness of main honing pipe.


pitting
After rough machining, many pit-like defects can be found on the surface, which will not seriously affect the smoothness of the cylinder bore, because the cylinder is a waste.
2. Scratches
Scratch defect is cold drawn. Generally along the axis of the steel pipe along the scratch direction, there must be more than the honing depth of the scratch. It is possible to wear out such defects and produce qualified cylinders.
3. Not round
Cold-drawn seamless steel pipe can float up and down on the mandrel fixed in the internal die in production, so the diameter of cold-drawn pipe is not as straight as that of the processed pipe. In addition, some hot-rolled pipes differ greatly from the wall thickness. The cold drawing deformation is due to the uneven deformation in the pipes, which is easy to produce cold-drawn pipes. The honed tube will find a hole in the hole, which will be worn to varying degrees with other parts of the reflective surface. If the grinding amount is small, the phosphate layer will not be removed even when it is cooled. It seriously affects the surface quality of cylinder.


The measures are as follows:
(1) Cold-drawn seamless steel tube directly into the cylinder, the quality can not be guaranteed, it is best to leave 0.2 mm (wall thickness) honing, grinding and reprocessing use.
(2) The inner hole defect of cold-drawn seamless steel tube is the main reason affecting the surface quality of cylinder hole.
(3) The pitting defect of hot-rolled pipe can be reduced by cold drawing, and the defect can not be eliminated.
(4) Increasing cold-drawn deformation, optimizing hot-rolled seamless steel tube blank and cleaning up defects in hot-rolled pipe holes can improve wall quality of cold-drawn seamless steel tube and reduce honing.




Profit margin, reduce honing cost, improve honing production efficiency.