DIN 2391 standard specifies the Seamless steel tubes used forMechanical and Automobile.
The main products of steel / steel grade: DIN2391-1(ST35, ST45, ST52).
DIN 2391 is included in DIN Handbook 3 and 272. Gives dimensions for seamless precision steel tubes; these tube dimensions have been selected from the range of manufacturable tube dimensions which are mainly used as design elements.
DIN 2391 applies to seamless precision steel tubes and in compliance with ISO/DIN 3304, those tube dimensions have been selected from the range of manufacture dimensions which are mainly used as design elements.
DIN2391 Part 2 specifies dimensions for cold finished, seamless precision steel tubes and is to be used in conjunction with DIN2391 part2 which states the relevant technical delivery conditions. The preferred sizes listed in standard are mainly used in mechanical and automotive engineering.
Where steel tubes of dimensions specified in this standard are to comply with the technical delivery conditions listed in subclause 1.2 of DIN 2391 Part 2.
DIN 2391 seamless precision tubes applications – Used in Hydraulic & pneumatic cylinder, Mechanical and Automotive engineering.
| Standard | Grade | Chemical Components (%) | |||||
| Symbol | Material No. | C | Si | Mn | P | S | |
| DIN2391 | St 30 Si | 1.0211 | ≤0.10 | ≤0.10 | ≤0.55 | ≤0.025 | ≤0.025 |
| St 30 Al | 1.0212 | ≤0.10 | ≤0.05 | ≤0.55 | ≤0.025 | ≤0.025 | |
| St 35 | 1.0308 | ≤0.17 | ≤0.35 | ≥0.40 | ≤0.025 | ≤0.025 | |
| St 5 | 1.0408 | ≤0.21 | ≤0.35 | ≥0.40 | ≤0.025 | ≤0.025 | |
| St 52 | 1.058 | ≤0.22 | ≤0.55 | ≤1.60 | ≤0.025 | ≤0.025 | |
The 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. |
Delivery Condition Symbol in accordance with EN10305 and DIN2391.
| Symbol in accordance with EN 10305 | Symbol in accordance with DIN2391 |
| +C | BK |
| +LC | BKW |
| +SR | BKS |
| +A | GBK |
| +N | NBK |
| Steel Grade | Minimum values for the delivery condition | ||||||||||||
| Steel Name | Steel Number | BK | BKW | BKS | GBK | NBK | |||||||
| Rm | A % | Rm | A % | Rm | ReH | A % | Rm | A % | Rm | ReH | A % | ||
| Mpa | Mpa | Mpa | Mpa | Mpa | Mpa | Mpa | |||||||
| St 30 Si | 1.0211 | 430 | 8 | 380 | 12 | 380 | 280 | 16 | 280 | 30 | 290 to 420 | 215 | 30 |
| St 30 Al | 1.0212 | 430 | 8 | 380 | 12 | 380 | 280 | 16 | 280 | 30 | 290 to 420 | 215 | 30 |
| St 35 | 1.0308 | 480 | 6 | 420 | 10 | 420 | 315 | 14 | 315 | 25 | 340 to 470 | 235 | 25 |
| St 45 | 1.0408 | 580 | 5 | 520 | 8 | 520 | 375 | 12 | 390 | 21 | 440 to 570 | 255 | 21 |
| St 52 | 1.0580 | 640 | 4 | 580 | 7 | 580 | 420 | 10 | 490 | 22 | 490 to 630 | 355 | 22 |
| Inspection or test types | Test frequency | |
| Internal test | Acceptance test | |
| Chemical analysis | M | M |
| Tensile testing | M | One per tested batch |
| Flattening test or extension test | M | Two per tested batch |
| Dimension verification | M | M |
| Visual inspection | M | M |
| NDT in order to identify leaks | Individual | Individual |
The following marking shall be shown on a label attached to the bundle:
Ceramic lined pipe is made through self-propagating high-temperature synthesis (SHS) technique.
Cast basalt lined steel pipe is composed by lined with cast basalt pipe, outside steel pipe and cement mortar filling between the two layers.
Ceramic tile lined pipes have very uniform coating of specially formulated ceramic material that is affixed to the inner of the pipe.
The material of the rare earth alloy wear-resistant pipe is ZG40CrMnMoNiSiRe, which is also the grade of rare earth alloy steel.
Tubes Erosion Shields are used to protect boiler tubing from the highly erosive effects of high temperatures and pressures thereby greatly extending tube life.
The ASTM A213 T91 seamless tubes are primarily used for boiler, superheater, and heat-exchanger.
