DIN 1629 St37 St52 Seamless Steel Pipes

What is DIN 1629 Standard?

DIN 1629 is a German industrial standard primarily used for the manufacture of seamless steel pipes for chemical equipment, piping, vessels, mechanical engineering components, and steel structures, requiring high strength. It includes three base material grades (St37.0, St44.0, and St52.0) and covers mechanical properties, chemical composition, and manufacturing requirements. In simple terms, it specifies high-quality seamless carbon and alloy steel tubes for pressure-bearing applications.

Standard Overview:

DIN 1629 - "Seamless Circular Tubes of Non-alloy and Alloy Steels with Special Quality Requirements - Technical Delivery Conditions"

Standard Status: DIN 1629 has been superseded by the European standard (EN 10216-1). However, it is still widely referenced and used in many older equipment, on older drawings, and in specific industries. EN 10216-1 includes steel grades with similar properties to DIN 1629 St 37.0, St 44.0, and St 52.0, but uses a new designation system (e.g., P235TR1, P355TR1, etc.).

Manufacturing Process: Seamless process. Manufactured by hot rolling or cold drawing (cold rolling), without welds.

Scope of Application: Pressure-Retaining Components. Used in the manufacture of vessels, boilers, pressure piping systems, and other mechanical engineering structures subject to internal pressure.
Quality Level: Special Quality Requirements. This means that requirements for material chemical composition, mechanical properties, and non-destructive testing are higher than those for ordinary piping.

Key Features of the DIN 1629 Standard:

1. Seamless Structure: The absence of welds eliminates potential weld defects (e.g., slag inclusions, lack of fusion, etc.), resulting in greater reliability and safety when subjected to pressure, especially cyclic pressure and high temperatures.
2. Broad Material Range: Covers both unalloyed (carbon steel) and alloy steels, subject to specific chemical composition controls.
3. Stringent Inspection Requirements: The standard mandates a series of tests, such as hydrostatic testing, nondestructive testing (eddy current testing is often mandatory), tensile testing, and impact testing, to ensure material uniformity and integrity.
4. Processability: These tubes are suitable for subsequent processing, such as bending, coiling, and welding.

Material Grades:

The DIN 1629 standard classifies materials based on their minimum tensile strength. The standard includes three main grades, with St 37.0 and St 52.0 being the most common. Their mechanical properties are as follows:

St 37.0: Tensile strength 350–480 MPa, yield strength ≥ 235 MPa, elongation ≥ 25%.

St 44.0: Tensile strength 420–550 MPa, yield strength ≥ 275 MPa, elongation ≥ 21%. 

St52.0: Tensile strength 500–650 MPa, yield strength ≥ 355 MPa, elongation ≥ 21%.

Equivalent steel grades in similar standards:
St37.0: ASTM A106 Gr. B, ASTM A53 Gr. B, EN 10216-1 Grade P235 T1
St52.0: ASTM A106 Gr. C, EN 10216-3 Grade P355N

Chemical Composition Requirements:
Carbon (C): St37.0 ≤ 0.17%, St44.0 ≤ 0.21%, St52.0 ≤ 0.22%. Ensures good weldability.
Silicon (Si): St52.0 ≤ 0.55%.
Manganese (Mn): St52.0 ≤ 1.60%. -- Provides excellent hardenability
Phosphorus (P) and Sulfur (S): ≤ 0.035% each. -- Improves material purity

This balanced alloy design enables the steel pipe to maintain high strength while also achieving excellent ductility and toughness.

Dimensions and Tolerances:

The DIN 1629 standard itself primarily specifies technical specifications, and its dimensions are generally referenced to another standard, DIN 2448.

DIN 2448: Seamless steel pipes for normal wall thicknesses. Its full name is "Seamless Steel Pipes — Dimensions and Mass per Unit Length."

DIN 2448 specifies seamless steel pipe dimensions expressed as a combination of outside diameter and wall thickness. It covers a wide range of diameters, from small to large.
Dimensions are typically expressed as "outer diameter x wall thickness," for example: "114.3 x 6.3" (meaning an outside diameter of 114.3 mm and a wall thickness of 6.3 mm).

Analysis of the Innovative Production Process:
This product utilizes a three-step production process of "hot rolling + cold drawing + bright annealing," which offers significant technical advantages. First, hot-rolling at 1000°C creates a uniform initial tube billet. Dimensional accuracy is then controlled through a precision cold drawing process. Finally, a bright annealing treatment at 650°C for 4 hours effectively eliminates processing stresses and optimizes the crystal structure. This process combination ensures the steel pipe achieves excellent mechanical properties, with a yield strength of ≥235 MPa and an elongation of ≥25%.

Applications of DIN 1629 seamless pipes:

Due to their high strength and reliability, DIN 1629 seamless pipes are widely used in various pressure-bearing and critical structural applications:

1. Boiler and pressure vessel manufacturing.
2. Process piping in the petrochemical industry.
3. Steam and water pipes in the energy and power industry.
4. Hydraulic cylinders and bearing sleeves in mechanical engineering.
5. Structural applications, where a higher safety factor than welded pipe is required.

Conclusion:

DIN 1629 is a technical standard representing high-quality seamless pressure steel pipes. Although it has been superseded by the more modern EN 10216 series, its technical requirements and quality philosophy have been continued and developed in the new standard.

Read more: Seamless Steel Pipe Sizes and Weights