Dimensions
Product shapes
Heavy plates.
Cut lengths, slit strips and coils.
Cut lengths with mill edges.
| Steel grade |
Thickness mm |
Width mm |
Length m |
| COR-TEN A |
2-12 |
1000 - 1860 |
2-12 |
| COR-TEN B |
2-15 |
1000 - 1860 |
2-12 |
Maximum width of each steel grade depends on the thickness of the cut length.
Heavy plates.
| Steel grade |
Thickness mm |
Width mm |
Length m |
| COR-TEN A |
6-12 |
1901 - 3300 |
2-15 |
| COR-TEN B |
6-40 |
1901 - 3300 |
2-15 |
Maximum length of each steel grade depends on the thickness.
The thickness ranges for heavy plates and cut lengths manufactured from weathering steel grades as per EN 10025-5 are the same as those of the approximately equivalent COR-TEN grades.
Steel grades and their approximate correspondence for weather resistance
| Steel grade |
EN 10025-5:2004 |
| COR-TEN A |
S355J0WP |
| COR-TEN B |
S355J0W and S355J2W |
For exact comparisons, original data sheets and standards must be used. The yield strength is guaranteed as ReL for COR-TEN steels and as ReH for the EN 10025-5:2004 weathering steel grades. A Charpy V impact test is carried out on standard steels equivalent to COR-TEN B.
More detailed information on dimensions is provided in the following technical brochures:
Properties
The anticorrosive properties of weather-resistant steels are better than those of other structural steels in many applications. The enhanced weather resistance is based on the oxide layer, i.e. patina. The use of uncoated weather-resistant steel in steel structures saves surface treatment costs. The elegantly brown patinated surface is architecturally distinguished. The patina-type surface can be obtained in weather-resistant steels using the Rust Brown method, which extends the scope of application of weather-resistant steels to indoor structures. Weather-resistant steel in flue gas structures prolongs the service life of chimneys and flue gas ducts.
Materials testing
An inspection lot of COR-TEN steel grades at the steel works consists of a maximum of 40 tonnes of plates or coils from the same cast. One series of tests per inspection lot shall be carried out: a tensile test with transversal samples and, if required, a Charpy V impact test with longitudinal samples. Inspection and sampling of steel grades as per EN 10025-5:2004 shall be carried out in compliance with the standard.
Mechanical properties
If agreed upon separately, COR-TEN B can be delivered with a guaranteed longitudinal impact strength of 27 J at the temperature of -20 °C, in which case it is marked with COR-TEN B-D.
COR-TEN
|
Yield strength
ReL N/mm2 Minimum |
Tensile strength
Rm N/mm2 Minimum |
Elongation A50%
Minimum |
| COR-TEN A |
345 |
485 |
20 |
| COR-TEN B |
345 |
485 |
19 |
EN 10025-5:2004
|
Yield strength
ReH N/mm2 Minimum
Thickness mm |
Tensile strength
Rm N/mm2 Minimum
Thickness mm |
Elongation A80%
Minimum
Thickness mm |
A5
Minimum
Thickness mm |
|
2 –16 |
(16) – 40 |
2 – (3) |
3 – 40 |
2 |
(2) – 2.5 |
(2.5) – (3) |
3 – 40 |
| S355J0WP |
355 |
- |
510 – 680 |
470 – 630 |
14 |
15 |
16 |
20 |
| S355J0W |
355 |
345 |
510 – 680 |
470 – 630 |
14 |
15 |
16 |
20 |
| S355J2W |
355 |
345 |
510 – 680 |
470 – 630 |
14 |
15 |
16 |
20 |
Chemical composition
|
Content, % (ladle analysis) |
|
C
Maximum |
Si |
Mn |
P |
S
Maximum |
Al |
V |
Cu |
Cr |
Ni
Maximum |
| COR-TEN A |
0.12 |
0.25 – 0.75 |
0.20 – 0.50 |
0.07 – 0.15 |
0.030 |
0.015 – 0.06 |
– |
0.25 – 0.55 |
0.50 – 1.25 |
0.65 |
| COR-TEN B |
0.19 |
0.30 – 0.65 |
0.80 – 1.25 |
0.035 max. |
0.030 |
0.020 – 0.06 |
0.02 – 0.10 |
0.25 – 0.40 |
0.40 – 0.65 |
0.40 |
The chemical composition of weathering steels as per EN 10025-5 complies with the standard.
Carbon equivalent CEV
CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15
|
Thickness mm |
CEV typical |
Product |
| COR-TEN A |
2 – 12 |
0.35 |
Strip products |
| COR-TEN A |
6 – 12 |
0.39 |
Plate products |
| COR-TEN B |
2 – 15 |
0.38 |
Strip products |
| COR-TEN B |
6 – 20 |
0.48 |
Plate products |
| COR-TEN B |
(20) – 40 |
0.50 |
Plate products |
Carbon equivalents for grades as per EN 10025-5 are in line with the standard.
The advantages of patina in different conditions
Thanks to their patina layer, weathering steels can be used in outdoor structures without any separate surface treatment. At its best, weathering steel can save the costs of all the surface treatment and the repairs necessary later. The cost advantage in comparison to painted structures is emphasised in environments where regular repainting is required.
The Rust Brown method extends the architectural use of weathering steels in indoor structures. It is recommended to make all markings in all applications during construction using chalk or water soluble colours.
Open air structures and patina
Weather resistance is based on the oxide layer, i.e. patina, which forms on the surface of the steel, and which, as a result of the alloying elements, is dense and nearly impervious to oxygen. Under normal weather conditions the patina will form in about 18–36 months, if the surface is alternately wet and dry. At first, the patina is a reddish brown colour, but with time takes on a darker hue.
In industrial environments, the patina forms more quickly and is darker in colour than in rural areas. In marine environments, the formation of the protective patina may be slower due to chloride exposure. For open air structures, the slow corrosion rate is taken into account by adding corrosion allowance to the nominal thickness.
Example of corrosion allowance for untreated COR-TEN B steel
| Type of atmosphere |
Corrosion allowance to be added for one side of the nominal thickness for each 10-year period of working life |
|
First 10 year period mm |
Each following 10 year period mm |
| Rural |
0.10 |
0.05 |
| Urban 1) |
0.20 |
0.05 |
| Industrial 2) |
0.20 |
0.10 |
1) With the chief impurity in the air being sulphur dioxide, SO2.
2) In addition to SO2 the air also contains chloride. Also for locations in the immediate vicinity of salt water.
In order to ensure the uniform colour of the patina, all impurities must be cleaned from the steel surface. Organic impurities such as oil or protective greases must be removed by washing. Surface oxidation, oxides or rust can be removed by either shot-blasting or pickling. This will also accelerate the patina formation process. The surface of clean weathering steel can be pre-patinated by allowing the surface to get wet and dry or to use suitable acid solutions.
Indoor structures
The patina formed on structural parts which are not directly exposed to weather will not be as uniform as that on parts which are alternately made wet and dried. Small variations in colour may also occur on parts which are subjected to strong local variation in temperature. An example of this is a wall block under eaves.
The Rust Brown method has been developed for indoor structures. It produces an instant patina-type layer on the surface of the weather-resistant steel. The method is easy to use. Steel surfaces must be cleaned before the Rust Brown treatment and finally the patina layer is fixed on the surface with a varnish. Further information is available from our Customer Service.
Submerged structures
Steel surfaces which are continually wet do not form a protective layer. These may be, for example, the surfaces of structures which are in contact with the ground or submerged in water. In these cases, it is recommended to paint the weathering steel surface.
Exposure to waste gases and high temperature conditions
Weathering steels resist the corrosive effect of sulphur-containing stack gases very well, even better than stainless steel. Weathering steels are at their best in construction, and are mainly used at temperatures above the dew point of sulphuric acid but are occasionally cooled down to temperatures below the dew point. These conditions prevail in many waste gas structures which cool down below the dew point during shutdowns.
The life expectancy of the weathering steel is extended under conditions of alternate wetting and drying. At temperatures constantly below the dew point an excessive amount of acid is condensed on the steel surface, which may be detrimental to the resistance to corrosion.
The special alloying of the steel, especially with chromium, improves in addition scaling resistance at high temperatures, even up to as high as 600–650 °C. However, when using weathering steels at temperatures over 425 °C, both the creep resistance requirements and, in phosphorus alloyed steel, possible thermal embrittlement of the material must also be taken into account.
Painted structures
The surface of weathering steel can be painted using the same methods applied in painting ordinary steels. As a result of the special alloying of the steel, a coat of paint can last twice as long as a coating on ordinary steel. If weathering steel is continuously exposed to water, it is usually always recommended to be painted.
Prefabrication services
The range of prefabrications available includes bending, shape cutting, precision cutting and bevelling.
Cutting
Wide flats from plate and strip that are ready for assembly and dimensionally accurate speed up the manufacture of steel structures and assembly, and avoid wasting material. Thanks to the extensive range available, steel grades best suited for the application in question can be used.
Read more about cutting wide flats from plates and strip
Manufacture and the throughput time of installation will decrease using flat cut shapes. The customer will receive the needed components ready for installation, and can thus avoid unnecessary material and storing costs. If ordered, the products are delivered as shop-primed, bevelled and bent.
Read more about flat cut shapes
Bevelling
Precision cut lengths and precision cut plates with a bevelled edge are components that can be delivered directly to the installation site, which saves time and reduces transport and storage costs. The dimensionally accurate groove ensures uninterrupted automated welding and fitting.
Read more about precision cut lengths and precision cut plates with bevelled edge
Bent plate products
Bent plate products are components that are ready to be delivered to the installation site, which is beneficial in terms of schedule as well as transport and storing costs. If needed, the products can also be ordered as shop-primed, furnished with welding bevels, and cut to shape. Premarked matchmarks facilitate installation.
Read more about bent plate products
Processing instructions
Welding
Weathering steels can be welded under workshop conditions using all the common welding processes. Low-hydrogen welding procedures and consumables are recommended. Before welding, the patina must be removed, down to the bare steel, from the steel surface over a band of approximately 10–20 mm wide along the welded joint. It is also equally important to remove any moisture, grease, oil and other impurities from the surface.
Download information about welding
Working temperature
The carbon equivalent values are slightly higher in weathering steel than in S355 structural steel, which increases the preheating need correspondingly. In practice this difference applies only to COR-TEN B and the corresponding steels because, thanks to their lower material thickness, steel grades alloyed with phosphorus do not usually require an elevated working temperature. When welding those steels, it is recommended that for plates of over 15 mm thickness the working temperature should be increased to 100–200 °C. In multi-pass welding the temperature between different passes must not exceed 200 °C in order that the toughness of the heat affected zone (HAZ) remains good.
Choice of welding consumables
- The weather resistance of welded joints can be ensured by using filler materials corresponding to the alloying of the base material.
- The mechanical properties of the welded joint have to be at least equivalent to those of the base material. Unnecessary over-strength is to be avoided as an increase in strength also increases residual stress.
- The impact strength of the welded joint must meet the set requirements, which are usually the same as those.
- If the base and filler materials mix sufficiently to provide good weathering resistance, ordinary non-alloyed consumables can be used. Sufficient mixing is achieved in single run welding of under 4 mm plates for butt joints, and for fillet welds with a design throat thickness of up to approximately 4 mm.
- Generally there is a small colour difference between a non-alloyed consumable material used in a weld and the weathering steel base material.
- In the multi-run welding of thick plates at least the final runs should be made using weathering consumables if the weld metal is also intended to be weather-resistant.
- Welding consumables of sufficient deformation capacity must be used for the sealing and root runs.
- Low-hydrogen consumables must be used, stored and dried in accordance with the manufacturer’s instructions.
Download welding consumables guide
Forming
Weathering steels can be cold-formed in the same manner as S355 structural steels. The table [table 6] shows the smallest allowable bending radii to be used for flanging. Successful forming requires good workshop technology from the producer of the steel product. Worn tools, insufficient lubrication, surface defects on plates, and cutting burrs may all reduce the quality. Shot-blasting may also be unfavourable. Plates stored outside under cold conditions must be taken inside to warm up sufficiently before being formed. The formability of EN 10025-5:2004 weathering steels is in accordance the standard.
| |
Thickness mm |
|
|
|
|
|
|
|
|
|
| |
(2) - 3 |
(3) - 4 |
(4) - 5 |
(5) - 6 |
(6) - 7 |
(7) - 8 |
(8) - 10 |
(10) - 12 |
(12) -14 |
(14) - 16 |
(16) - 18 |
18 - 20 |
| |
Smallest allowable internal bending radius mm |
| COR-TEN A |
6 |
8 |
10 |
12 |
21 |
24 |
30 |
36 |
42 |
– |
– |
– |
| COR-TEN B |
6 |
8 |
10 |
12 |
21 |
24 |
30 |
36 |
42 |
48 |
54 |
60 |
Values apply to all forming directions.
Download information about flanging and forming
Heat treatment
Weathering steel applications do not normally require post-weld heat treatment. If, however, this is required by the customer or the authorities, it is recommended that stress relieving or normalising is carried out in accordance with the table below.
| Heat treatment |
Temperature °C
|
Treatment time
Manner of cooling
|
| Stress relieving |
550 – 600
(target 580) |
2 minutes / millimetre thickness, minimum 30 minutes.
Slow cooling in the furnace. |
| Normalising |
860 – 940
(target 910) |
1 minute / millimetre thickness, minimum 15 minutes.
Free cooling in air atmosphere outside the oven. |
Cutting
Weathering steels can be cut thermally and mechanically in almost the same manner as the S355 structural steels. When flame cutting thick plates, the working temperature recommendations concerning welding can be used as a guideline. Due to thin plate thickness CORTEN® A and corresponding steels do not normally need an elevated working temperature for thermal cutting. Slowing down the cutting speed and increasing the working temperature have a similar effect on cutting: the cooling rate of the cutting point decreases and so does the risk of thermal cracks. When handling weathering steels, it should be remembered that a plate taken directly from cold outside storage needs adequate time to warm up before mechanical cutting.
Download information about thermal cutting and flame straightening
Download information about mechanical cutting
Order & delivery
Delivery conditions
Heavy plates: Hot-rolled, normalised rolled or normalised in furnace.
Cut lengths, slit strips and coils: Controlled rolled or thermomechanical rolled.
Inspection documents
The inspection document shall be specified at the time of order. The European types of inspection documents are defined in the EN 10204:2004 standard.
Download information about inspection documents
General delivery information for hot-rolled steels
General delivery information for hot rolled steels can be found from documents Markings and packing, Ultra-sonic testing and General terms of sale.
Download information about markings and packing
Download information about ultrasonic testing
Download general conditions of sale