The Delivery Conditions Of ST52 Seamless Steel Tubes
Standard ST52 seamless steel tubes are produced using the cold drawn process. Seamless precision tubes can be supplied as cut tubes and bent tubes. Cut tubes are designed especially for manufacturers of automotive components.
Precision seamless steel tubes from our production satisfy the requirements for the following applications: components for the vehicle drivetrain, cars suspension systems, fuel injection, components for engine and transmission, components for body and chassis, vehicle control systems and others.
Stress relieving is carried out on seamless cold drawn tubes in order to minimise residual stresses in the structure thereby reducing the risk of dimensional changes during further manufacturing or final use of the component.stress relieving does not change the hydraulic tube’s structure and does not significantly affect its hardness.
Hardened and tempered steel tube to be stress relieved must be treated at a temperature around 50°C below the temperature used for previous tempering to avoid an impact on the hardness.
Delivery Conditions Of ST52 Seamless Steel Tubes
The seamless precision steel tubes shall be manufactured from cold drawn or cold rolled processes. The tubes will be supplied in one of the delivery conditions as follows:
| Designation | Symbol | Description |
| Cold finished (hard) | BK | Honed cylinder tubes do not undergo heat treatment following the final cold forming and thus, have a rather high resistance to deformation. |
| Cold finished (soft) | BKW | The final heat treatment is followed by cold drawing involving limited deformation. Appropriate further processing allows a certain degree of cold forming (e.g. bending, expanding). |
| Cold finished and stress-relieved | BKS | Heat treatment is applied following the last cold forming process. Subject to appropriate processing conditions, the increase in the residual stresses involved enables both forming and machining to a certain degree. |
| Annealed | GBK | The last cold forming process is followed by annealing in a controlled atmosphere. |
| Normalized | NBK | The last cold forming process is followed by annealing above the upper transformation point in a controlled atmosphere. |