USA Piping Solution is a trusted ST30 precision tubes supplier who stocks and exports mill certified materials ready for immediate shipment to customers in North America, Europe and Asia. We have full material test reports (MTR), EN 10305 compliance certificates and third party inspection capabilities available to supply precision tubes for ST30 with OD ranging from 4 mm to 120 mm and wall thickness from 0.5 mm to 15 mm. Our customers range from automotive Tier 1 manufacturers to deep-draw press shops to precision engineering OEMs, which require the softest grade under DIN 2391 for applications that require forming. Get a competitive quote with lead time of less than 24 hours.
DIN 2391 ST 30 seamless precision steel tubes represent the softest grade within the DIN 2391 precision tube standard. ST30 is the most suitable type of tube for all applications where the tube has to be cold-formed, deep-drawn or bent without cracking, with carbon max 0.07% and elongation min 30%. Some ST30 precision tube supplier confuse ST30 with ST35 and provide their tubes with a designation of E195, which is actually EN 10305-1 E155. Purchasers should take special note of this difference when ordering ST30. ST30 is designed for use in applications where formability is more important than load-bearing strength, such as deep-drawing, thin-wall tube forming and automotive body pressing. All our tubes have tight OD and WT tolerances according to DIN 2391 and EN 10305 standards.
DIN 2391 ST 30 Seamless Precision Steel Tubes Specifications
| Property | Standard | Value (MPa) | Value (ksi) |
|---|---|---|---|
| Standard | DIN 2391 / EN 10305-1 | ST 30 | E155 Equivalent |
| C max | Carbon | 0.10% max | 0.10% max |
| Mn | Manganese | 0.25 to 0.50% | 0.25 to 0.50% |
| Yield Strength (min) | Mechanical | 215 MPa | 31 ksi |
| Tensile Strength (min) | Mechanical | 320 MPa | 46 ksi |
| Elongation (min) | Mechanical | 30% | 30% |
Note: The DIN 2391 yield value of 195 MPa (28 ksi) applies to tubes in NBK (bright annealed) delivery condition. The EN 10305-1 designation E155 reflects the European grade reference; when tested per DIN 2391 protocol, the same material achieves 195 MPa minimum yield.
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DIN 2391 ST 30 Seamless Precision Steel Tubes Grade Comparison
Selecting the correct DIN 2391 grade is critical for performance and cost optimisation. ST30 occupies the softest, most formable position in the grade ladder. Buyers who require higher strength for structural or hydraulic applications should review DIN 2391 ST44 seamless precision tubes or ST52, while those needing a general-purpose precision tube may find that ST35 tubes satisfy most mechanical requirements at a lower material cost than ST44. The table below places all four grades in direct comparison.
| Grade | C max (%) | Yield (MPa / ksi) | Tensile (MPa / ksi) | Primary Application |
|---|---|---|---|---|
| ST 30 | 0.07 | 195 MPa / 28 ksi | 320 MPa / 46 ksi | Deep drawing, forming |
| ST 35 | 0.17 | 235 MPa / 34 ksi | 340 MPa / 49 ksi | General precision tubing |
| ST 45 | 0.21 | 295 MPa / 43 ksi | 440 MPa / 64 ksi | Structural, mechanical |
| ST 52 | 0.22 | 355 MPa / 51 ksi | 520 MPa / 75 ksi | Hydraulic cylinders, high stress |
ST30 is the only DIN 2391 grade with C max at 0.07%, making it uniquely suited for operations involving extreme forming ratios. Any supplier listing ST30 with E195 equivalent is incorrectly cross-referencing the ST35 grade.
DIN 2391 ST30 Equivalent Grade
| Equivalent | Steel number | EN | GB |
|---|---|---|---|
| DIN 2391 St30Al | 1.0212 | EN 10305-1 E215 | GB/T 3639 Grade 10 |
| DIN 2391 St30Si | 1.0211 | — | — |
DIN 2391 ST 30 Seamless Precision Steel Tubes Size Range
USA Piping Solution supplies DIN 2391 ST30 seamless precision steel tubes across a broad dimensional range to cover automotive, industrial, and instrumentation applications. All tubes are produced to the tight OD and wall thickness tolerances specified in DIN 2391 and EN 10305-1. For dimensional reference across related grades, visit our carbon steel pipes and tubes section.
| Parameter | Details |
|---|---|
| Outer Diameter (OD) | 4 mm to 120 mm |
| Wall Thickness (WT) | 0.5 mm to 15 mm |
| Standard Length | 6 metres (custom cut lengths available on request) |
| Tolerance Class | Per DIN 2391 Table 1 and Table 2 as applicable |
| End Finish | Plain ends as standard; deburred and chamfered ends on request |
| Surface Condition | Bright (NBK standard); oiled for corrosion protection during transit |
DIN 2391 Seamless Precision Tubes Tolerances
| Parameter | Tolerance |
|---|---|
| Outside Diameter (OD) | ± 0.01mm |
| Wall Thickness (WT) | ± 0.1 mm of the specified wall thickness |
| Ovality (Ovalness) | 0.1 mm |
| Length | ± 5 mm |
| Straightness | Max 1 mm per meter |
| Surface Finish | As per customer specification (Commonly:Anti-rust Oil,Hard chrome plating,Nickel chromium plating, or other Coating) |
| Squareness of Ends | ± 1° |
DIN 2391 ST30 Tubes Applications
DIN 2391 ST30 tubes are selected by engineers and procurement teams when the primary design requirement is cold formability rather than tensile strength. The following applications consistently specify ST30 or its EN 10305-1 E155 equivalent.
- Deep-Draw Forming: ST30 is the benchmark grade for progressive die and transfer die deep-drawing presses. The low carbon content and 30% minimum elongation allow extreme draw ratios without intermediate annealing.
- Automotive Body Pressings: Lightweight, thin-wall ST30 tubes are pressed into structural brackets, cross-members, and body panels where formability and weight reduction are equally important.
- Thin-Wall Low-Pressure Fluid Lines: ST30 is used for low-pressure brake pre-fill lines, coolant tubes, and instrumentation lines where tight bending is required and pressure loads are below 70 bar.
- Bicycle and Leisure Equipment Frames: The ductility of ST30 allows mandrel bending and hydroforming of complex frame geometries without wall thinning failures.
- Furniture and Structural Pressing: Cold-pressed furniture components and decorative structural parts specified in thin-wall precision tube commonly use ST30 for its surface quality after annealing.
Buyers who mistakenly source ST52 or ST45 for deep-drawing operations frequently encounter cracking at tight bend radii. Our precision steel tubes blog guide provides a detailed grade selection reference for procurement and engineering teams.
Frequently Asked Questions: DIN 2391 ST30 Seamless Precision Steel Tubes
ST30 vs ST35: Which grade is softer and why does it matter?
ST30 is the softer grade with C max 0.07% and yield 195 MPa (28 ksi) versus ST35 at C max 0.17% and yield 235 MPa (34 ksi). For deep-drawing, ST30 is the correct specification. ST35 suits general precision tubing where moderate strength is needed.
What is the EN 10305-1 equivalent for DIN 2391 ST30?
The EN 10305-1 equivalent for DIN 2391 ST30 is E155. The designation E155 reflects a 155 MPa yield reference in the EN system. When manufactured and tested per DIN 2391, the same material achieves 195 MPa minimum yield. This is not the same as EN 10305-1 E195, which corresponds to the harder ST35 grade. Buyers should confirm EN 10305-1 E155 when cross-referencing ST30 to European standards.
Is DIN 2391 ST30 suitable for hydraulic cylinder applications?
No. ST30 is not suitable for hydraulic cylinders. With a tensile strength of 320 MPa (46 ksi) and yield of 195 MPa (28 ksi), ST30 lacks the load-bearing capacity needed for hydraulic pressure containment. Hydraulic cylinder applications require ST52 (355 MPa yield, 520 MPa tensile). ST30 is specified exclusively for forming-critical, low-pressure, and deep-drawing uses.
Mill-certified stock. NBK delivery condition. OD 4 to 120 mm. Full MTR and EN 10305-1 compliance documentation.
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