Honed Tube
Honed Tube - seamless steel tube
DIN 2391 seamless precision steel tubes are high-quality cold-finished pipes known for their superior dimensional accuracy and smooth surface finish, widely used in hydraulic systems, automotive engineering, and mechanical applications.
The main products of steel / steel grade: DIN2391-1(ST35, ST45, ST52).
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:
DIN steel heat exchanger tubes, meeting German Industrial Standards, are constructed from high-temperature and corrosion-resistant steel, specifically designed for efficient heat exchange applications.
With years of expertise, we provide a wide range of steel tube processing services. From basic sawing and machining to complex bending and upsetting operations, we support you at every stage of your project.
Our capabilities include eccentricity reduction and concentricity improvement through turning and grinding. We specialize in creating complex geometries using rotary swaging and axial forming, and offer property modifications through partial heat treatment to meet your exact requirements.
A range to meet your needs
High-quality steel solutions for diverse mechanical engineering applications – reliable, precise, and built for performance.
Premium steel products for demanding construction projects – from bridges to offshore structures, built to last.
Versatile components for the automotive industry – precision, quality, and processing expertise for every application.
Robust tubes for plant engineering and energy systems – designed for extreme conditions and long-term efficiency.
Versatile solutions for modern infrastructure – supporting reliable supply networks and large-scale construction projects.
Versatile solutions for hydraulic systems – durable, pressure-resistant, and engineered for maximum reliability.
| Condition | Typical Application |
|---|---|
| High Temperature | Boilers, superheaters, steam headers |
| Low Temperature | Cryogenic processing systems |
| High Pressure | Power & process piping |
| Corrosive Media | Chemical & petrochemical plants |
| Creep Service | Thermal power stations |
| Product | Specification |
|---|---|
| Seamless Pipes | ASTM A335 P1 / P5 / P9 / P11 / P22 / P91 |
| Butt Weld Fittings | ASTM A234 WP1 / WP5 / WP9 / WP11 / WP22 / WP91 |
| Forged Fittings & Flanges | ASTM A182 F1 / F5 / F9 / F11 / F22 / F91 |
Sunny Steel supplies alloy steel piping systems worldwide, supporting projects that demand certified materials, full traceability and long-term operational reliability.
Steel pipe delivery status(condition): cold / hard (BK), cold / soft (BKW), after cold stress relief annealing (BKS), annealing (GBK), normalized (NBK).
| Term | Symbol | Explanation |
|---|---|---|
| Cold-finished/hard (cold-finished as-drawn) | BK | No heat treatment after the last cold-forming process. The tubes therefore have only low deformability. |
| Cold-finished/soft (lightly cold-worked) | BKW | After the last heat treatment there is a light finishing pass (cold drawing). With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits. |
| Annealed | GBK | After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum. |
| Normalized | NBK | The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum. |
The general cold strip mills, volume should go through continuous annealing (CAPL unit) to eliminate cold hardening and rolling stress, or batch annealing reach the mechanical properties of the corresponding standard specifies. Cold rolled steel surface quality, appearance, dimensional accuracy better than hot-rolled plate, and right-rolled thin product thickness is about 0.18mm, so the majority of users favor.
Cold rolled steel coil substrate products deep processing of high value-added products. Such as electro-galvanized, hot dip galvanized, electro-galvanized fingerprint resistant, painted steel roll damping composite steel, PVC laminating steel plates, etc., so that the excellent quality of these products has a beautiful, high resistance to corrosion, has been widely used.
Cold rolled steel coil finishing after annealing, cut the head, tail, trimming, flattening, smooth, heavy volume, or longitudinal clipboard. Cold-rolled products are widely used in automobile manufacturing, household electrical appliances, instruments, switches, buildings, office furniture and other industries. Steel plate strapping package weight of 3 to 5 tons. Flat sub-volume typically 3 to 10 tons / volume. Coil diameter 6m.
Bare packing/bundle packing/crate packing/wooden protection at the both sides of tubes and suitably protected for seaworthy delivery or as requested.
There are probably hundreds of different methods for packing a pipe, and most of them have merit, but there are two principles that are vital for any method to work: prevent rusting and sea transportation security.
Our packing can meet any needs of the customers.
Commonly used alloying elements and their effects are listed in the table given below.
| Alloying Elements | Effect on the Properties |
|---|---|
| Chromium | Increases Resistance to corrosion and oxidation. Increases hardenability and wear resistance. Increases high temperature strength. |
| Nickel | Increases hardenability. Improves toughness. Increases impact strength at low temperatures. |
| Molybdenum | Increases hardenability, high temperature hardness, and wear resistance. Enhances the effects of other alloying elements. Eliminate temper brittleness in steels. Increases high temperature strength. |
| Manganese | Increases hardenability. Combines with sulfur to reduce its adverse effects. |
| Vanadium | Increases hardenability, high temperature hardness, and wear resistance. Improves fatigue resistance. |
| Titanium | Strongest carbide former. Added to stainless steel to prevent precipitation of chromium carbide. |
| Silicon | Removes oxygen in steel making. Improves toughness. Increases hardness ability |
| Boron | Increases hardenability. Produces fine grain size. |
| Aluminum | Forms nitride in nitriding steels. Produces fine grain size in casting. Removes oxygen in steel melting. |
| Cobalt | Increases heat and wear resistance. |
| Tungsten | Increases hardness at elevated temperatures. Refines grain size. |
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.
When you partner with Sunny Steel, you can stop worrying about meeting deadlines thanks to our responsive and timely service. You'll also say goodbye to unnecessary shopping around. Instead, you'll get white glove service from an expert who understands your needs and can get you the materials you need quickly.
