The Application Of DIN 2391 ST35 NBK Seamless Tubes
DIN 2391 ST35 NBK Seamless Tubes come under AISI, DIN, EN, GB and other international standard specifications. they range from 4mm to 219mm in outer diameter with wall thicknesses ranging from 0.5mm to 20mm. ST35 Seamless tubes are frequently used for high heat and pressure applications in oil and gas(high pressure oil pipes) petrochemical, hydraulic cylinders & pneumatic cylinder,mechanical and Automotive engineering petroleum, and other industries. They come in various sizes and forms, including round, square, and U-shaped. Furthermore, these stainless steel tubes’ strength and corrosion resistance are well known. They are frequently produced with a seamless finish and can be used in many different sectors. ST35 is one of the best choices among the various types of steel tubes for low-cost, low-corrosion pipes. It has muscular tensile and yield strength and may be formed into round, square, or oval tubes. These stainless steel tubes’ ability to be welded without any pre-heating is their principal benefit. It makes them very simple to use and facilitates more straightforward manufacturing procedures.
Chemical Composition
| Standard | Grade | Chemical Components (%) | |||||
| Symbol | Material No. | C | Si | Mn | P | S | |
| DIN2391 | St 35 | 1.0308 | ≤0.17 | ≤0.35 | ≥0.40 | ≤0.025 | ≤0.025 |
Delivery Conditions
The ST35 seamless tubes shall be manufactured from cold drawn or cold rolled processes. The tubes shall be supplied in one of the delivery conditions as follows:
| Designation | Symbol | Description |
| Cold finished (hard) | BK | 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. |