DIN 2391 Seamless Precision Tube

DIN 2391 Overview

DIN 2391 is a German industrial standard that specifies the dimensions, tolerances, delivery conditions, and inspection requirements for cold-worked seamless precision tube.

Part 2 of DIN 2391 specifies the dimensions of cold-worked seamless precision tubes and should be used in conjunction with Part 2 of DIN 2391 (which specifies the relevant technical delivery conditions). The preferred dimensions listed in the standard are primarily used in mechanical and automotive engineering. Steel tubes of the dimensions specified in this standard shall conform to the technical delivery conditions listed in Clause 1.2 of Part 2 of DIN 2391.

The main products of steel / steel grade: DIN2391-1(ST35, ST45, ST52).

Seamless carbon steel pipe for machine structural purposes.

DIN 2391 Equivalent Standards

DIN 2391 Quality Grades

DIN 2391 allows for the supply of seamless precision tubes in two quality grades: Grade A and Grade C.

All grades refer to Grade A and other high-quality steels. Grade A is the basic grade, fully compliant with the delivery conditions of DIN 2391. Grade C is the custom grade, produced according to the specific requirements of the project, and can use any material, delivery condition, and tube shape, including but not limited to DIN 2391.

1. Grade A

Suitable for precision tubes that do not require inspection certificates and are therefore not subject to special requirements.

St30Si (1.0211);

St30Al (1.0212);

St35 (1.0308);

St45 (1.0408);

St52 (1.0580)

2. Grade C

Precision tubes that meet special requirements.

DIN 2391 Seamless Precision Tube Chemical Composition

DIN 2391 Seamless Precision Tube Tolerances

DIN 2391 Seamless Precision Tube Mechanical Properties

DIN 2391 Seamless Precision Tube Dimensions

DIN 2391 dimensions typically meet the following requirements:

1. Outer diameter: 4 – 260 mm;

2. Wall thickness: 0.5 – 25 mm;

3. Length: 4-7 meters, random or precise length;

4. Surface smoothness: DIN 2391 requires the surface Ra value of the pipe to be less than or equal to 6.3 micrometers.

Delivery Conditions for DIN 2391 Seamless Precision Tube

The tubes shall be manufactured using cold drawing or cold rolling processes. The tubes shall be delivered in one of the following conditions:

Delivery Condition Symbol in accordance with EN10305 and DIN2391.

Surface Quality and Defect Requirements

1. Tube Surface Condition

Due to cold working, untreated pipes, i.e., those in the BK or BKW condition, typically have a layer of lubricant or grease film covering their inner and outer surfaces.

Heat-treated pipes, i.e., those in the BKS, GBK, or NBK condition, may show signs of scorching, but should not have loose oxide scale.

2. Defects

Minor surface imperfections resulting from the manufacturing process, such as scabs or dents, are permissible as long as the repaired inner and outer diameters still meet the specified requirements. Scabs, overlaps, or laminations are not allowed.

Inspection and Test List for DIN 2391 Seamless Precision Tube

DIN 2391 Seamless Precision Tube Application

DIN 2391 seamless precision tube is widely used in:

1. Hydraulic and pneumatic control systems;

2. Automotive driveshafts, shock absorbers, and steering systems;

3. Mechanical hydraulic cylinder barrels and piping;

4. Instruments, equipment frames, and construction machinery.

5. St52 NBK tubing, due to its combination of high strength and good weldability, is the most common choice for hydraulic cylinders and mechanical structural components.

FAQ

1. What is The Difference Between DIN 2391 And EN 10305?

DIN 2391 = Old German standard

EN 10305-1 = EU unified standard (new replacement)

2. DIN 2391 Precision Tube VS. Ordinary Seamless Steel Pipe?

DIN 2391 precision tube is more suitable for high-precision, dynamic sealing systems, while ordinary seamless tubing is more suited for structural or conveying applications.