1. ST37-2 - The Base Material (Historical DIN Grade)
ST37-2 is a steel grade defined in the now largely superseded DIN 17100 standard (and also found in the older DIN 1629 for tubes).
Decoding "ST37-2":
St: Stands for "Stahl" (German for Steel) used for structural purposes.
37: Indicates the minimum tensile strength is 370 MPa (≈ 54 ksi). Crucially, this is tensile strength, not yield strength. The minimum yield strength (ReH) is approximately 235 MPa.
-2: This suffix is critical. It indicates the impact energy (toughness) requirement:
"2" means the steel is tested for impact energy (Charpy V-notch) at a temperature of +20°C. A "1" would mean no impact test, and a "3" would mean testing at -20°C.
Modern Equivalent: The direct successor in the European EN system is S235J0 (or S235J2 for better toughness) from EN 10025-2.
S235J0 has a minimum yield strength of 235 MPa and is impact tested at 0°C, making it a slightly tougher and more controlled modern equivalent.
2. Longitudinally Submerged Arc Welded (L-SAW) Pipe - The Process
The process remains the same: high-quality longitudinal seam welding via submerged arc. The choice of ST37-2 implies the use of this process to create a reliable pipe from a basic, weldable structural steel.
3. Governing Product Standards
The pipe itself would be manufactured to a product standard. For ST37-2, the most relevant historical and still-referenced standard is:
DIN 2458: "Longitudinally welded steel tubes for mechanical and general engineering purposes." This standard explicitly lists and governs tubes made from steel grades like St 37-0, St 37-2, St 44-2, St 52-3.
Other Contexts: ST37-2 was also used as a tube material grade under the old DIN 1629 (seamless and welded tubes).
Complete Technical Specification (Legacy Format)
A classic specification, still seen in many technical datasheets and orders, would look like this:
Longitudinally Submerged Arc Welded (L-SAW) Steel Pipe
Product Standard: DIN 2458
Steel Grade: DIN 17100 / DIN 1629 St 37-2
Dimensions: Ø 323.9 mm x 8.0 mm WT (or as per DIN 2458 size table)
Delivery Condition: Usually as welded (+U for unglüht, unannealed). For better properties, normalized (+N) can be specified.
Testing: According to DIN 2458, typically including:
Tensile test (Rm ≈ 370 MPa, ReH min. 235 MPa)
Bend test on the weld seam (mandatory proof of weld ductility).
Flattening test or ring expansion test.
Non-destructive testing (e.g., eddy current) might be specified, but Ultrasonic Testing (UT) is an extra requirement.
Certification: Works Certificate (Werkzeugnis) per old DIN 50049, or its modern EN 10204 equivalent.
Key Comparisons & Modern Context
| Feature | ST37-2 (DIN 17100) | Modern Equivalent S235J0/J2 (EN 10025-2) | Note |
|---|---|---|---|
| Key Strength | Tensile: 370 MPa Min | Yield: 235 MPa Min (Tensile: 360-510 MPa) | ST37 is named for tensile; EN grades are named for yield. |
| Yield Strength | ~235 MPa (derived) | 235 MPa (guaranteed min.) | Essentially identical in practice. |
| Impact Test | +20°C (for "-2") | 0°C (J0) or -20°C (J2) | Modern grades often have stricter toughness requirements. |
| Standard | DIN 17100 (historic) | EN 10025-2 (current) | All new projects should specify the EN grade. |
Typical Applications
ST37-2 L-SAW pipes are used in general structural and mechanical applications where high strength is not the primary concern, but reliable weldability and formability are:
General Construction: Fencing posts, handrails, light structural supports.
Mechanical Engineering: Guards, frames, housings for industrial machinery.
Low-Pressure Fluid Conveyance: Water lines, irrigation pipes, non-critical process lines.
Piling and Foundation: For light to moderate loads.
Important Caution for Modern Projects
Obsolete Specification: While ST37-2 pipe is still produced and available, it is an obsolete designation. For new construction or projects requiring modern certification (CE marking, etc.), the EN 10219 (S235J2H) or EN 10217 (P235) standards with their respective EN 10025 steel grades should be specified.
Translation is Key: When you see "ST37-2," you can confidently translate it to "S235J0" for material equivalence, but you must also find the correct modern product standard (e.g., EN 10219 for structural tubes).
Summary
"ST37-2 Longitudinally Submerged Arc Welding Pipe" refers to:
A general-purpose structural pipe made from basic carbon steel, longitudinally welded via the SAW process, conforming to legacy German standards like DIN 2458 and DIN 17100, with a minimum tensile strength of 370 MPa and impact toughness tested at room temperature.
While still a valid and understood commercial product, for engineering, procurement, and construction in the 21st century, this specification should be updated to its modern EN equivalent (e.g., S235J2H to EN 10219-2) to ensure compliance with current codes, material traceability, and performance guarantees.
