ALTA cold drawn welded tubes RTU H9 (+C, +SR, +N)
Precise dimensional tolerances, high concentricity, and an excellent surface finish: these are the distinctive properties of cold drawn welded tubes with H9 (ISO) inner diameter tolerance, which meet the UNI EN 10305-2 standard and are marketed by ALTA Spa.
These characteristics are attained using a production process in which the thickness of the strip is obtained by a rolling process and is strictly controlled. Next, the ends of the strip are prepared to attain better contact during the welding operation. Here is where the cold deformation of the strip begins until the desired circular cross section is attained.
The high frequency welding operation carried out after deformation causes the strip edges to fuse without using any additional material. This produces a continuous tube with no change in chemical composition in the weld zone, ensuring a welding factor of V=1.
The end result is a tube with a clean, defect-free surface as well as optimal thickness and concentricity tolerances, which are ideal for the subsequent drawing operation. This process consists of cold plastic deformation of the tube and ensures an excellent surface finish for the product by obtaining precise dimensional tolerances with a ready-to-use inner surface with 0.8 micron Ra roughness. The excellent quality of the rough tube, together with a specially designed heat treatment, gives the drawn tube exceptional mechanical properties, including resilience. Finally, the highest quality in cold drawn welded tubes is also guaranteed by regular destructive and non-destructive tests in the laboratory, along with size checks and surface finish measurements.
To date, cold drawn tubes have proven to be the best product for constructing high quality oil hydraulic cylinders at low costs.
TUBES TO EN 10305 STANDARDS
ALTA cold drawn welded tubes meet the UNI EN 10305-2 standard, a detailed item of the more generic EN 10305. The EN 10305-2 in particular characterizes cold drawn welded tubes equipped with high dimensional accuracy, excellent surface quality and definable mechanical properties. They are therefore highly suitable tubes for precision applications.