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Cold formed welded hollow sections according to EN 10219

05 July 2015
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Hollow sections are internationally accepted term in steel industry, which means round, square and rectangular pipes made according to the standard EN 10219 - Cold formed welded structural hollow sections of non-alloy and fine grain steels and the standard EN 10210 - Hot finished structural hollow sections of non-alloy and fine grain steels.

Their versatility in shape and characteristics allows them wide used the industry nowadays.

What are the advantages of steel hollow section in relation to the open sections?
- better static characteristics
- lighter construction (about 30% less weight)
- smaller surface (it is necessary to protect about 40% less surface area)
- less resistance to air and liquids
- usable interior space (concrete, cables, wires, pipes ...)
- better visual effect

Cold formed hollow sections for steel construction ensure high mechanical resistance and high yield strength. They are used as a fixed load-bearing structures in the building and civil engineering, are suitable elements in mechanical engineering because of its static advantages, and are also used in aerospace and automotive industry. They are not suitable for dynamic loads.

They are produced at room temperature, by cold forming the sheet which is longitudinally welded at the ends, and therefore also known as welded hollow sections. (At the request and the technical possibilities, the inner weld can be removed or smoothed, while the outer weld is already processed in most cases.) Due to the process of cold forming, there is a high level of residual stress remaining in the hollow sections which the can cause cracks during workload.


Unlike warm-formed hollow sections, cold-formed have considerably greater accuracy of wall thickness, and they are visually more attractive thanks to the flat and smooth surface.

Cold formed hollow sections are defined by the European standard EN 10219:
EN 10219-1: 2006 - defines the technical requirements for the delivery of round, square and rectangular cold formed welded hollow sections
EN 10219-2: 2006 - specifies tolerances, dimensions and sectional
properties

The greatest advantage of cold formed hollow sections is the way they are made that enables the production of round, square or rectangular pipes from almost any material at an affordable price. (approximately 10-20% cheaper than pipes manufactured according to EN 10210)

There are uniform names prescribed to facilitate the administrative work with these or other types of hollow sections, so that everyone would know which product it is when seeing the specification. According to EN 10219-1 the following denotements are defined:
CFCHS - cold formed circular hollow sections
CFRHS - cold formed square or rectangular hollow sections

Common materials of which cold-formed hollow sections are made according to EN10219

Non-alloy steel

Material

EN 10027-2

DIN

JUS

S235 JRH

1.0039

R St 37-2

Č0361

S275 JOH

1.0149

St 44-2

Č0451

S275 J2H

1.0138

St 44-3

 Č0452

S355J2H

1.0576

St 52-3

Č0563

Fine-grained structural steel

Material

EN 10027-2

DIN

S275 NH

1.0493

StE 285 N

S275 NLH

1.0497

T StE 285 N

S355 NH

1.0539

StE 355 N

S355 NLH

1.0549

T StE 355 N

S460 NH

1.8953

StE 460 N

Tolerances - Cold formed welded structural hollow sections of non-alloy and fine grain steels

Size (mm) Tolerance

Outside

Dimension

(OD)

CFCHS +/- 1%  - min. +/- 0,5 mm, max. +/- 10 mm
CFRHS  H, B < 100 mm +/- 1%, min. +/- 0,5 mm
100 mm H, B 200 mm +/- 0,8%
V, Š > 200 mm +/- 0,6%

Thickness

(t)

CFCHS

OD 406,4mm

t 5 mm  +/- 10%
t > 5 mm  +/- 0,50 mm
OD > 406,4 mm  +/- 10%, max. 2 mm
CFRHS  t 5 mm  +/- 10%
t > 5 mm  +/- 0,50 mm
Length - 0 mm, + 50 mm
Concavity / Convexity

CFRHS

max. 0,8% mm, min. 0,50 mm
Squarness CFRHS 90° +/- 1° 

External

Corner

Profie

CFRHS  t ≤ 6 mm 1,6T to 2,4T
6 mm < t 10 mm 2,0T to 3,0T
10 mm < t 2,4T to 3,6T
 Ravnost  CFCHS 0,20% of total length*
CFRHS 0,15% of total length*
3 mm on any arbitrarily 1 m dužine**
Težina +/- 6% on individual length

* - This tolerance on the flatness of cold formed hollow sections refers to the total produced length and it is not valid after cutting

Example:
The square hollow section of total produced lenght of 12.20 m, is obviously curved. It was measured that the flatness deviation is 16 mm. Tolerated deviation on the length of 12,200 mm is 18.3 mm, which means that the square pipe is within the acceptable limits. Measurement can be made on a meter in length from an arbitrary starting point, and find out that at one point deviation is 3.05 mm per meter length. No matter that the total length of the deviation is within the limits, more precise measurements determined impermissible deviation, and the product can be declared as defective and to be reclaimed.

** - This tolerance is calculated on certain arbitrary meter in length regardless of the length of the tube

Example:
Round tube in a fixed length of 3.75 m deviates 6 mm from flatness. The tolerance on the total lenght is not considered in this case (which is beyond the allowed limits), but the deviation is measured for every meter away from any arbitrary point. All measurements have shown that the deviation from flatness is within the allowed 3 mm per meter of length. Therefore, the product is correct though not flat.

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