Requirements on pipe billet for hot-rolled seamless tube is related to and pipe varieties, uses and piercing methods. For general-purpose steel pipe tube quality requirements can be relaxed more, but the quality of important applications of tube steel and high-alloy steel pipe requirements must be strictly. Stress conditions better or lesser amount of deformation perforation method, without affecting pipe performance conditions, the tube surface and internal quality requirements may be slightly lower. Stress disadvantaged two-roll rotary piercing, if a large amount of deformation perforation, then the tube surface and internal quality have strict requirements. In short, steel tube technical condition is to ensure the quality and smooth production process as the basis to determine, and with different methods vary perforation, with the technical conditions of steel to improve and increase. Technical conditions can be found on a variety of tube standards and technical protocols. Such as general automatic rolling machine for tube requirements are as follows:
(1) Deviation in Table 1 tube diameter Dp. Tube bending of any part of the ≤6mm / m, tube end face of the cut slope ≤6 ~ 8mm, flattened tube end face of ≤8% Dp;
(2) Tube surface without cracks, hairline, scarring, scaly layer, folding, non-metallic inclusions and residual shrinkage. Not allowed height or depth of more than 0.5mm small grooves, pitting, ears and height of more than two-sided ears of 1mm. Cleanup tube defects deeper than 0.05Dp;
(3) Low magnification tube: not allowed ≥1 level of residual shrinkage, bubbles, anti-leather, white spots and cracks. For the average carbon structural steel billet, which generally loose ≤3 level, center porosity ≤3 level, segregation ≤3 level, subcutaneous bubbles ≤2.