Cold drawn seamless tubes for cylinders

Seamless cold drawn tubes for cylinders produced by ALTA spa have very high mechanical properties and are available also in special steel grades. Dimensional tolerances, surface quality and eccentricity values are standardized according to UNI EN ISO 10305-3 requirements, and can be provided for a wide range of sizes on request.

The surfaces obtained in the drawn tube depend on the condition of the rough-hewn tube, as during hot drilling, the tube takes on a spiral shape (fig. A), which it retains, albeit to a reduced degree, after hot rolling and drawing (Fig. B).

Traditional honing and rolling processes follow this spiroidal pattern and, while achieving the required tolerance, achieve the result of not changing the spiral defect of the tube in contrast to the coaxiality principle of the STEM/PISTON/SLEEVE assembly. The photo demonstrates the extreme straightness of the internal processing of ALTA’s finishing system (see fig. C).

Producing a tube with reduced internal machine allowance leaves spots of rough appearing (darker spots in the photo) because those areas are outside the maximum tolerated straightness due to the spiral shape of the tube.
To overcome this, ALTA uses tubes with greater oversize than required by the standard (up to 3mm in diameter) by removing the necessary amount, ensuring greater straightness, roundness and surface cleanliness than traditional methods.