The seamless precision steel pipes and tubes which suit hydraulic, mechanical, and general engineering applications. Amardeep Steel offers the ST45 precision tubes in conditions where the higher strength is required in comparison to ST35. The ST52 tubes are used where higher strength than ST45 is required. This makes ST45 suitable for components that require a balance of strength, machinability, and dimensional accuracy. See our ST35 precision tubes and ST52 pipes and tubes for other strength levels, or browse our range of precision tubes for additional cold drawn grades.
Each order is supplied with mill test certificates and dimensional inspection records to verify material quality and the close dimensional tolerances required for precision applications.
What Are ST45 Pipes and Tubes?
ST45 is a non alloy carbon steel grade from DIN 2391, with material number 1.0408. DIN 2391 tubes are cold drawn to very close tolerances on outside diameter, inside diameter and wall thickness, which is why they are used where parts must fit without further machining.
DIN 2391 has been withdrawn and replaced by EN 10305-1, where ST45 corresponds to grade E255. Many drawings and buyers still order by the DIN name, so we supply to either standard.
ST45 vs St45.8: Not the Same Tube
St45.8 is a boiler tube grade from DIN 17175, made for pressure service at high temperature, and it has since been replaced by EN 10216-2 P265GH tubes. ST45 under DIN 2391 is a precision tube for mechanical use. Check which one your drawing calls for before ordering.
ST45 Pipes and Tubes Specifications
Parameter | Details |
|---|---|
Standard | DIN 2391-1 / DIN 2391-2 (EN 10305-1 E255 for current orders) |
Grade | ST45 |
Material Number | 1.0408 |
Type | Seamless, cold drawn |
Outside Diameter | 4 mm to 120 mm as per DIN 2391-1 |
Delivery Conditions | BK, BKW, BKS, GBK and NBK |
Length | Random lengths, fixed lengths and cut lengths |
Surface | Bright, phosphated or oiled on request |
Test Certificate | EN 10204 3.1, with 3.2 available on request |
ST45 Chemical Composition
Element | Content (%) |
|---|---|
Carbon (C) | 0.21 max |
Silicon (Si) | 0.35 max |
Manganese (Mn) | 0.40 min |
Phosphorus (P) | 0.050 max |
Sulphur (S) | 0.050 max |
ST45 Mechanical Properties
Delivery Condition | Tensile Strength | Yield Strength, min | Elongation, min |
|---|---|---|---|
BK (cold finished, hard) | 580 MPa min | Not specified | 5% |
BKW (cold finished, soft) | 520 MPa min | Not specified | 8% |
BKS (cold finished, stress relieved) | 520 MPa min | 375 MPa | 12% |
GBK (annealed) | 390 MPa min | Not specified | 21% |
NBK (normalized) | 440 to 570 MPa | 255 MPa | 21% |
Choosing the Right Delivery Condition
BK tubes are the strongest but have little ductility, so they suit parts that will not be bent or formed. BKW allows limited forming, and BKS adds stress relief for better stability during machining. GBK is soft and easy to form, while NBK gives the best balance of strength and toughness and is the usual choice for hydraulic cylinders and welded parts.
ST45 Equivalent Grades
Standard | Equivalent Designation |
|---|---|
DIN 2391 | St45 |
EN 10305-1 | E255 |
Material Number | 1.0408 |
JIS | STKM 13A (close match) |
ST35 vs ST45 vs ST52 (NBK Condition)
Property | ST35 | ST45 | ST52 |
|---|---|---|---|
Material Number | 1.0308 | 1.0408 | 1.0580 |
Tensile Strength | 340 to 470 MPa | 440 to 570 MPa | 490 to 630 MPa |
Yield Strength, min | 235 MPa | 255 MPa | 355 MPa |
Elongation, min | 25% | 21% | 22% |
Need more strength? Our ST52 tubes and EN 10305-1 E355 tubes are the next step up. For general purpose work, see our ST37 pipes and tubes.
Applications of ST45 Precision Tubes
- Hydraulic and pneumatic cylinder barrels
- Hydraulic lines and fittings, alongside our SAE J524 hydraulic tubing
- Automotive parts such as shafts, sleeves and steering components
- Bushings, spacers and machined mechanical parts
- Machine building and general engineering
Testing and Documentation
Every order of ST45 tubes goes through the checks below at our testing facility or approved third party labs.
- Chemical analysis
- Tensile test for the ordered delivery condition
- Flattening and flaring tests
- Eddy current testing
- Close tolerance dimensional checks on OD, ID and wall
- Visual and surface inspection
Mill test certificates are issued to EN 10204 3.1, with 3.2 available on request. You can view our approvals on the certificates page.
Packing and Marking
Each bundle is tagged with the standard, grade, size, delivery condition and heat number. Tubes are oiled or protected against rust, end capped and packed in bundles or wooden boxes to protect the precision finish. Read more about our packing and despatch process.
Request a Quote for ST45 Pipes & Tubes
Send us the outside diameter, wall thickness or inside diameter, delivery condition, length and quantity, and our team will reply with price and delivery. Use the enquiry form or reach us through the contact page.
Frequently Asked Questions
What is ST45 material?
ST45 is a non alloy carbon steel grade for seamless precision tubes under DIN 2391, with material number 1.0408. In the normalized NBK condition it has a tensile strength of 440 to 570 MPa and a minimum yield strength of 255 MPa.
What is the EN equivalent of ST45?
The EN equivalent of DIN 2391 ST45 is E255 under EN 10305-1, which replaced DIN 2391. Both share the material number 1.0408.
What is the difference between ST45 and St45.8?
ST45 is a precision tube grade from DIN 2391 for mechanical use. St45.8 is a boiler tube grade from DIN 17175 for high temperature pressure service, now replaced by EN 10216-2 P265GH. They are different products.
What does NBK mean for ST45 tubes?
NBK means the tube is normalized after the last cold drawing pass, by heating above the upper transformation point in a controlled atmosphere. NBK tubes have the best balance of strength and toughness and are widely used for hydraulic cylinders.
