DIN 1629 - Seamless Unalloyed Steel Tubes for Special Requirements
DIN 1629 is a German standard for seamless circular tubes made from unalloyed (plain carbon) steel that must meet special mechanical property requirements. These tubes are used for mechanical engineering, pressure purposes, and general applications.
Key Features
| Feature | Description |
|---|---|
| Material | Unalloyed (Carbon) Steel |
| Process | Seamless (SMLS) only |
| Key Focus | Guaranteed mechanical properties |
| Primary Use | Mechanical parts, low-pressure systems, structural |
Material Grades
| Grade | Similar to | Yield Strength (MPa) | Key Characteristic |
|---|---|---|---|
| St 35.0 | 1020 | ≥ 235 | Standard mild steel |
| St 45.0 | 1045 | ≥ 265 | Medium carbon steel |
| St 52.0 | Similar to 1026 | ≥ 355 | Higher strength steel |
| St 55.0 | - | ≥ 380 | Special high-strength grade |
Note: The ".0" suffix indicates special property requirements (unlike DIN 1628 which has less strict requirements).
Chemical Composition
Typical Ranges:
| Element | St 35.0 (%) | St 45.0 (%) |
|---|---|---|
| Carbon (C), max | 0.17 | 0.22 |
| Manganese (Mn) | 0.40-0.80 | 0.40-0.80 |
| Silicon (Si) | ≤ 0.35 | ≤ 0.35 |
| Phosphorus (P), max | 0.045 | 0.045 |
| Sulfur (S), max | 0.045 | 0.045 |
Key Point: Chemistry is less critical than guaranteed mechanical properties.
Mechanical Properties
Minimum Requirements:
| Property | St 35.0 | St 45.0 | St 52.0 |
|---|---|---|---|
| Yield Strength (MPa) | ≥ 235 | ≥ 265 | ≥ 355 |
| Tensile Strength (MPa) | 340-470 | 410-530 | 490-630 |
| Elongation (%) | ≥ 25 | ≥ 22 | ≥ 22 |
Manufacturing & Processing
Production Methods:
Hot-finished seamless (most common)
Cold-drawn seamless (for tighter tolerances)
Heat Treatment Options:
As-rolled/hot-finished (no additional treatment)
Normalized (for property refinement)
Stress-relieved (for dimensional stability)
Testing Requirements
| Test | Requirement | Purpose |
|---|---|---|
| Tensile Test | Mandatory per batch | Verify mechanical properties |
| Flattening Test | Required for OD ≤ 100mm | Check ductility and weld quality |
| Ring Tensile Test | For OD > 100mm | Alternative to flattening test |
| Hydrostatic Test | Optional (if specified) | For pressure applications |
| Hardness Test | Optional | For material verification |
Dimensional Tolerances
| Parameter | Standard Tolerance |
|---|---|
| Outside Diameter | DIN 2448 or special agreement |
| Wall Thickness | Typically ±12.5% |
| Length | Standard: +100mm / -0mm |
| Straightness | 1.5mm per meter typically |
Applications
Mechanical Engineering:
Machine frames and structures
Drive shafts and axles
Rollers and cylinders
Bearing housings
Low-Pressure Systems:
Hydraulic lines (low pressure)
Pneumatic systems
Lubrication oil lines
Cooling water circuits
Structural Applications:
Support columns and pillars
Handrails and guardrails
Scaffolding components (when specified)
Agricultural equipment frames
General Industry:
Conveyor system components
Material handling equipment
Tool and die applications
Prototype and development parts
Comparison with Related Standards
| Standard | Key Difference from DIN 1629 |
|---|---|
| DIN 1628 | Less strict property requirements |
| DIN 17175 | For elevated temperature service |
| DIN 2391 | Cold-drawn precision tubes |
| EN 10216-2 | European pressure tube standard |
| DIN 2448 | Seamless steel tubes for general use |
Advantages
Guaranteed Properties: Mechanical properties are verified
Cost-Effective: Unalloyed steel is economical
Good Weldability: Low carbon content enables easy welding
Versatility: Suitable for wide range of applications
Good Machinability: Easy to machine and fabricate
Limitations
Not for High Pressure: Limited pressure capability
Not for High Temperature: Maximum ~350°C
Corrosion Susceptible: Requires protection in corrosive environments
Limited Strength: Compared to alloy steels
Ordering Information
Typical Designation:
text
DIN 1629 - Grade - Dimensions - Additional Requirements Example: DIN 1629 - St 45.0 - 88.9 x 4.0 mm
Common Specifications:
DIN 1629 Part 1: General requirements
DIN 1629 Part 2: Tubes for pressure purposes
DIN 1629 Part 3: Tubes for mechanical engineering
Quality Documentation
Required Certificates:
2.2 Certificate: Declaration of compliance with order
3.1.B Certificate: Test report with property values
3.1.C Certificate: Full test report with traceability
Marking Requirements:
Manufacturer's name or trademark
Material grade (e.g., St 45.0)
Heat number or batch identification
Standard designation (DIN 1629)
Equivalent Standards
| Region | Equivalent Standard | Notes |
|---|---|---|
| ISO | ISO 2937 | Similar mechanical property tubes |
| ASTM | A53 Type S (partial) | Different testing philosophy |
| Japan | JIS G3445 | Similar mechanical tubes |
| China | GB/T 8162 | Structural seamless tubes |
Design Considerations
Pressure Applications:
Maximum pressure must be calculated based on actual properties
Safety factors typically 4:1 for mechanical applications
Consider corrosion allowance for long-term service
Mechanical Applications:
Yield strength is design-limiting property
Fatigue considerations important for cyclic loading
Weldability excellent for fabrication
Future Status
Note: DIN 1629 has been largely superseded by EN 10216-2 for pressure applications and EN 10297-1 for mechanical applications, but it remains specified in some existing designs and legacy equipment.
In summary: DIN 1629 provides quality seamless carbon steel tubes with guaranteed mechanical properties for applications requiring more than basic material performance but not needing the specialized capabilities of alloy or precision tubes. It represents a reliable, cost-effective solution for a wide range of mechanical and low-pressure applications in German and European industry.
