At a Glance: DIN 1629
Full Title: DIN 1629: Seamless circular steel tubes for special requirements.
Key Feature: Seamless construction, meaning no welded seam, making it stronger and more reliable for pressure.
Primary Use: Pressure vessels, boilers, high-pressure piping systems, and mechanical engineering applications.
Material: Primarily unalloyed carbon steels and carbon-manganese steels.
Detailed Breakdown
1. Scope and Application
DIN 1629 covers seamless steel tubes that are intended for applications where the integrity of the tube is critical. They are designed to withstand internal pressure, mechanical loads, and elevated temperatures. Common applications include:
Power Generation: Boiler tubes, superheater tubes, and high-pressure steam lines.
Petrochemical Industry: Process piping, heat exchangers, and pressure vessels.
Mechanical Engineering: Hydraulic cylinders, high-pressure fluid systems, and structural components under stress.
2. Material Grades
The standard specifies several material grades, primarily based on German standard DIN 17175 (for heat-resistant steels) and its successor, the European standard EN 10216. The most common grades for carbon steel are:
St 35.8 / P235GH: A common low-carbon steel with good weldability and formability, suitable for lower temperature and pressure services.
St 45.8 / P265GH: A medium-carbon steel with higher strength than St 35.8.
17 Mn 4 / P355GH: A carbon-manganese steel offering significantly higher yield and tensile strength, used for more demanding pressure conditions.
Note: With the harmonization of European standards, DIN 1629 has been largely superseded by EN 10216-1 and EN 10216-2. The material grades from DIN are now mapped to equivalent grades in EN.
| Common DIN 1629 Grade (Old Designation) | Equivalent EN 10216-2 Grade | Key Characteristics |
|---|---|---|
| St 35.8 | P235GH | Good weldability, low temperature strength. |
| St 45.8 | P265GH | Higher strength than P235GH. |
| 17 Mn 4 | P355GH | High-strength carbon-manganese steel. |
3. Manufacturing Process
As per the standard, these tubes are manufactured using a seamless process, typically:
Hot Rolling/Forging: A solid steel billet is pierced and hot-rolled to form a hollow shell, which is then stretched and sized to the final dimensions.
Cold Drawing: For tighter tolerances, smoother surface finish, and higher strength, the hot-finished tubes can be cold-drawn.
4. Technical Requirements
DIN 1629 specifies strict requirements for:
Chemical Composition: Limits for Carbon (C), Manganese (Mn), Silicon (Si), Phosphorus (P), and Sulfur (S) are defined for each grade.
Mechanical Properties: Minimum values for:
Yield Strength (Rp0.2): The stress at which the material begins to deform plastically.
Tensile Strength (Rm): The maximum stress the material can withstand while being stretched.
Elongation (A): A measure of ductility.
Pressure Test (Hydrostatic Test): Each tube must be tested to a specified hydraulic pressure without leaking or showing defects.
Non-Destructive Testing (NDT): Tubes can be subjected to ultrasonic or eddy current testing to ensure internal and external soundness.
Dimensional Tolerances: Strict limits on outer diameter (OD), wall thickness (WT), and length.
5. Comparison with Other Standards
It's helpful to compare DIN 1629 with other common pipe standards:
| Feature | DIN 1629 | ASTM A106 (USA) | ASTM A53 (USA) |
|---|---|---|---|
| Type | Seamless | Seamless | Seamless & Welded |
| Primary Use | High-pressure, temp. | High-temperature service | General Purpose |
| Common Grades | St 35.8, St 45.8 | A106 Grade B | A53 Grade B |
| Key Focus | European conformity, specific material properties | High-temperature yield strength | General service, cost-effective |
Summary and Key Takeaways
DIN 1629 is a historical German standard for high-quality seamless carbon steel pipes.
It has been largely replaced by the European standard EN 10216-1 (for non-alloy steels) and EN 10216-2 (for alloy steels).
Its primary use is in pressure applications across power plants, oil & gas, and heavy industry.
When sourcing or specifying, you will likely encounter the EN 10216 grades (e.g., P235GH, P265GH, P355GH) rather than the old DIN designations (St 35.8, etc.), but they refer to the same type of product.
If you are working on a project with German engineering roots, you may still see references to DIN 1629, but the material supplied today will conform to the EN standard.
When procuring this material, always confirm the exact grade, dimensions, and delivery condition (e.g., normalized, +N) with your supplier to ensure it meets your specific project requirements.
