EN 10305-1 defines the technical requirements for cold-drawn seamless precision tubes with a circular cross-section and an outer diameter up to 380 mm. These tubes feature tight dimensional tolerances, excellent surface finish, and high precision, making them ideal for use in the automotive, furniture, and general engineering industries.
Manufacturing Process of EN 10305-1Seamless Precision Tube
EN 10305-1 seamless precision tubes are produced by cold drawing from hot-rolled seamless steel tubes. Other cold-forming methods may also be applied. After the final cold-drawing operation, the tubes are normalized (+N condition) in a controlled atmosphere to achieve uniform mechanical properties and dimensional stability.
Material Grades of EN 10305-1Seamless Precision Tube
The EN 10305-1 standard includes both non-alloy and alloy steels, categorized as follows:
Non-alloy steels: E215, E235, E255, E355, E410, 26Mn5, 10S10, 15S10, 18S10, 37S10
Non-alloy special steels: C35E, C45E
Alloy steels: 26Mo2, 25CrMo4, 42CrMo4
(Note: BS EN 10305-1 and DIN EN 10305-1 are equivalent designations used in different regions.)
Key Features of EN 10305-1Seamless Precision Tube
High dimensional accuracy and straightness
Superior surface quality and smoothness
Consistent mechanical properties after normalization
Suitable for machining, bending, and hydraulic applications
EN 10305-1 Equivalent
|
BS |
DIN |
DIN |
GB |
ASTM |
|
BS EN 10305-1 |
DIN EN 10305-1 |
DIN 2391 |
GB/T 3639 |
ASTM A519 |
EN 10305-1 Seamless Precision Tube Dimensions
The EN 10305-1 standard specifies the dimensional requirements for cold-drawn seamless precision tubes with an outer diameter of up to 380 mm, ensuring tight tolerances and controlled surface roughness for precision engineering applications.
1. Outer and Inner Diameter Tolerances
When tubes are ordered by outer or inner diameter, tolerances must comply with the tube’s delivery condition, as defined below:
Applicable for +C and +LC (cold-finished) conditions.
Applicable for +SR, +A, and +N (stress-relieved, annealed, and normalized) conditions.
2. Wall Thickness Tolerance
For tubes ordered by outer diameter and wall thickness or inner diameter and wall thickness, the wall thickness tolerance shall be:
±10% or ±0.1 mm, whichever is greater.
3. Length Tolerance
According to EN (DIN) 10305-1, tube lengths may be supplied in one of three forms:
Random Length: Minimum 3 m; difference between the longest and shortest tube in an order ≤ 2 m.
Approximate Length: Specified length with a tolerance of ±500 mm. Up to 10% of the order may include shorter tubes (≥2 m), which should be bundled separately.
Exact Length: Supplied to the precise length agreed upon in the order, within specified tolerances.
Exact Length:
|
Length L, mm |
Tolerance, mm |
|
≤ 500 |
0 – + by agreement |
|
500 ＜ L ≤ 2000 |
0 – + 3 |
|
2000 ＜ L ≤ 5000 |
0 – + 5 |
|
5000 ＜ L ≤ 8000 |
0 – + 10 |
|
＞ 8000 |
0 – + by agreement |
EN 10305-1 Seamless Precision Tube Chemical Composition
|
Steel grade |
Steel |
C(% max) |
Si(% max) |
Mn(% max) |
P(% max) |
S(% max) |
|
E215 |
1.0212 |
0.10 |
0.05 |
0.70 |
0.025 |
0.015 |
|
E235 |
1.0308 |
0.17 |
0.35 |
1.20 |
0.025 |
0.015 |
|
E355 |
1.0580 |
0.22 |
0.55 |
1.60 |
0.025 |
0.015 |
EN 10305-1 Seamless Precision Tube Mechanical Properties
1. Mechanical Properties Chart
|
Yield strength |
Tensile strength |
Elongation |
|
E215 |
290-430 |
30 |
|
E235 |
340-480 |
25 |
|
E355 |
490-630 |
22 |
2. Flattening Test
The flattening test is applicable to precision tubes conforming to EN 10305-1 with a wall thickness less than 15% of the outer diameter.
The tube is flattened between two parallel plates. When the distance H between the plates meets the specified requirement, the tube is inspected for cracks.
H = (1 + C) × T / (C + T/D)
H is the distance between the plates measured under load, in millimeters;
D is the specified outer diameter, in millimeters;
T is the specified wall thickness, in millimeters;
C is a factor: 0.09 for E215 and E235, and 0.07 for E355.
3. Drift Expansion Test
The test shall be conducted according to EN ISO 8493, using a 60° tapered mandrel, provided the outer diameter is less than 150 mm and the wall thickness is less than 10 mm.
EN 10305-1 requires three tests for mechanical properties, of which the tensile test is mandatory, while the flattening test and drift expansion test are optional.
EN 10305-1 Seamless Precision Tube: Non-destructive Testing (NDT)
To ensure the integrity of EN 10305-1 seamless precision tubes, non-destructive testing for longitudinal defects must be carried out using one or more of the following standardized methods:
Eddy Current Testing
According to EN ISO 10893-2, acceptance level E3
Magnetic Flux Leakage Testing
According to EN ISO 10893-3, acceptance level F3
Ultrasonic Testing
According to EN ISO 10893-10, acceptance level U3B
All NDT procedures shall comply with EN ISO 10893-1 to confirm tightness and sealing integrity of the tubes.
Appearance Requirements of EN 10305-1Seamless Precision Tube
1. Surface Finish
The inner and outer surfaces of EN 10305-1 tubes must reflect the typical finish of the manufacturing and heat treatment processes.
The surface condition should be clean and uniform, allowing for the identification of any defects that may require correction.
2. Surface Roughness (Ra)
The EN 10305-1 standard sets limits on maximum surface roughness based on pipe diameter and delivery condition:
For tubes with outer diameter D ≤ 260 mm:
In delivery conditions +SR, +A, and +N: outer surface roughness ≤ 4 μm.
In delivery conditions +C and +LC: both inner and outer surface roughness ≤ 4 μm.
Inner surface requirement applies when the inner diameter (specified or calculated) ≤ 15 mm.
For tubes with outer diameter D > 260 mm:
Both inner and outer surface roughness ≤ 6 μm.
EN 10305-1 Pipe Delivery Conditions
|
Yield strength |
Tensile strength |
Elongation |
|
Cold-finished/hard |
BK |
No heat treatment after the last cold-forming process. The tubes therefore have only low deformability. |
|
Cold-finished/soft |
BKW |
After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits. |
|
Annealed |
GBK |
After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum. |
|
Normalized |
NBK |
The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum. |
Note:
For annealed (GBK) tubes, the yield point should be at least 50% of the ultimate tensile strength. In cold-drawn hard (BK) and cold-drawn soft (BKW) conditions, depending on the degree of deformation during drawing, the yield point may increase to nearly match the tensile strength.
When estimating the yield point, it is recommended to use:
≥80% of tensile strength for cold-worked/hard-state tubes
≥70% of tensile strength for cold-worked/soft-state tubes
EN 10305-1 Seamless Precision Tube Applications
EN 10305-1 seamless precision tubes are widely used in applications requiring high dimensional accuracy and smooth surface finish, including:
Heat exchangers and gas cylinders
Elevator guide tubes and maintenance station supports
HPL tubes (phosphated or galvanized)
Cable conduits and pump tubes
Motorcycle and bicycle frames
Rivets, piston, telescopic, and stabilizing tubes
Textile machinery and general structural components
These tubes offer excellent mechanical performance and surface quality, making them ideal for precision engineering, automotive systems, and industrial equipment manufacturing.
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