Weathering steel of common metal materials for landscape

Metals generally have high strength, good plasticity, unique metallic luster and other properties. It has distinctive characteristics, wear resistance and durability, easy maintenance, and can match with soil, wood, stone, cement and other materials harmoniously. Compared with stone, it is lighter, can reduce load, and has certain ductility. It is easy to process on a factory scale, has high machining accuracy, is more convenient in the construction process, can reduce labor costs, shorten the construction period, and is also a material with high recycling rate, which is a truly environment-friendly material.

1. Material introduction

Weathering steel, namely atmospheric corrosion resistant steel, originated from Cowton steel in North America, is a low alloy steel series between ordinary steel and stainless steel. Weathering steel is made of ordinary carbon steel with a small amount of corrosion-resistant elements such as copper and nickel. It has the characteristics of high quality steel, such as strength, toughness, plastic ductility, molding, welding, cutting, abrasion, high temperature, etc; The weather resistance is 2~8 times of that of plain carbon steel, and the painting performance is 1.5~10 times of that of plain carbon steel. At the same time, it has rust resistance, so that the components have the characteristics of corrosion resistance, life extension, thinning and consumption reduction, labor saving and energy saving.
Weathering principle: After adding phosphorus, copper, chromium, nickel and other weathering elements into the steel, the steel will form a dense and highly adherent oxide layer between the rust layer and the substrate. This special dense oxide layer has the characteristics of stable and uniform natural rust red, which can prevent oxygen and water in the atmosphere from penetrating into the substrate, protect the substrate below the rust layer, and slow down its corrosion rate.

2. Material properties

(1) Unique performance characteristics: it has outstanding visual expression, and the rusted steel will change with time. Its color, lightness and saturation are higher than ordinary building materials, so it is easier to highlight in the background of green plants.
(2) Strong shaping ability: weathering steel is easy to shape into various shapes, and can maintain excellent integrity.
(3) Distinctive space definition ability: use very thin steel plates to separate the space clearly and accurately, making the site simple, bright and powerful.

3. Product process and classification

Rust stabilization treatment method: the rust stabilization treatment method is to use chemical method (rust liquid) to slowly dissolve the surface film of steel plate, so that it can produce rust stabilization and form a uniform rust layer. This rust layer has a protective effect and can inhibit the rust from the initial use of steel.

                       (Color change caused by rust treatment)

Note: It will take at least 1~2 years from the new weathering steel plate to the formation of stable and dense rust red protective layer in South China, and it may take another 5~6 years for some dry areas. Therefore, rust promoters are mostly used in the market to accelerate the formation of rust layer, and proper rust promoters and processing methods should be selected.
Classification: weathering steel is divided into high weathering steel (high P content: 0.07~0.15 wt%) and welding weathering steel (low P content: ≤ 0.04 wt%).

4. Common parameters

The thickness of weathering steel sheet is generally 1.5mm~4mm, the thickness of medium plate is 4mm~20mm, the thickness of thick plate is 20mm~60mm, the thickness of extra thick plate can reach 80mm, and the width is 0.5m, 1m, 1.2m, 1.5mm, 2m, etc.

5. Price range

Price of weathering steel=price of steel plate raw materials+price of rust treatment.
The price of rust treatment is 90~200 yuan/m2 according to different processes. The weathering steel takes 3mm thick weathering steel plate as an example, and the raw material is about 110 yuan/m2. Therefore, the price of weathering steel plate is 200~400 yuan/m2. Of course, the price of weathering steel will be affected by the change of plate thickness and plate quality. (This price is the price of ordinary mid tier products, for reference only)

6. Design considerations

(1) Pay attention to the natural conditions of the site. The salt content, air humidity, sunshine, building shape and orientation in the air at different locations in different areas, indoor and outdoor, inland and coastal areas, will affect the growth rate and composition of the rust layer of weathering steel, so it will more or less show uneven rust state. If the color is required to be uniform, attention shall be paid to the setting of the drain and the uniformity of the whole workpiece lighting and water collection.
(2) Avoid water accumulation. In the water environment, the rust layer is prone to delamination corrosion, and attention should be paid to the drainage design near the bottom of the weathering steel. For example, if weather resistant steel is used as the planting bed, attention shall be paid to the filling height and internal drainage channel during the design to prevent muddy water from pouring out to pollute and corrode the steel when it rains.
(3) The color reference of the sample plate of weathering steel is not significant. Because it takes 6 months to 1 year (with rust promoter) to generate a stable and dense rust red protective layer from a brand new steel plate in general natural environment, it may be longer in some dry areas or indoors. And even if you want to generate a simple uniform rust yellow, it will take about 1 month. In this process, the color of components gradually transits from bright yellow, earthy yellow, orange, orange red, reddish brown and brown.
Therefore, when designing the weather resistant steel landscape, the last color should be used for design, and the color changes that will be experienced at the initial stage should be communicated with Party A.
(4) Weathering steel is not non corrosive, but rather slow in corrosion. The service life of high-quality weathering steel is 8 times that of ordinary steel (the annual corrosion rate of one side is 0.097mm). A little thickness corrosion allowance should be considered in design.

7. Key points of construction

(1) Corrosion of welding points: oxidation rate of welding points must be the same as that of weathering steel, which requires special welding materials and technologies. Although ordinary welding rods can also weld weathering steel plates normally, and there will be no serious color difference after welding, the life of the weld will be much shorter than that of the weathering steel plate, or the weathering steel plate may be polluted by the downflow of rust water due to the rapid corrosion rate of the weld. Therefore, special welding rods with similar chemical composition and matching strength and toughness shall be selected.
(2) Water corrosion: the weathering steel is not stainless steel. If there is water in the depression of the weathering steel, the corrosion rate will be faster. Pay attention to drainage during construction.
(3) Salt rich air environment: weathering steel is sensitive to salt rich air environment. In such an environment, the surface protective film may not prevent further oxidation inside.
(4) Construction temperature: too high (over 35 ° C) and too low (below 5 ° C) surface temperatures of weathering steel workpieces, as well as high temperature exposure will have a negative impact on the rust formation effect, especially for the coating of rust fixative, avoid construction under the above conditions.
(5) Sequence of installation and rusting: generally for better overall effect, it is recommended to install the weathering steel plate before rusting. To avoid the pollution (such as oil stain, fingerprints, etc.) or scratch of the rusty layer during transportation and installation; Second, welding and other methods are usually used for installation, which not only destroys the original rust layer, but also does not cover the weld seam, which looks very incongruous.
However, if the shape of weathering steel workpiece is very complex, it is difficult to rust construction after installation or construction is not allowed on the site, it can be considered to rust before installation. However, the premise is that the rust shall be fixed first after it is rusted, so as not to worry about pollution, and the fastener installation or screw installation shall be used as far as possible to avoid the problem of new welds caused by welding.
(6) Correct construction posture: For the case that the workpiece is rusted after installation, the following construction posture should be adopted for the case that the corrosion agent will flow from top to bottom during the facade rust treatment: gradually reduce the direct spraying dosage from the top to the bottom, and basically do not need to spray (the rust promoter flowing from the top rusts), otherwise the top is prone to rust free, and the bottom is prone to excessive corrosion.

8. Distinguish between genuine and fake weathering steel

To distinguish the truth from the falsehood of weathering steel, we must first understand the rust formation process of weathering steel and ordinary steel,The rust appearance of ordinary steel and weathering steel is not significantly different within 6 months after the rusting, because the dense protective rust layer of weathering steel has not really grown 6 months ago. Therefore, it is difficult to distinguish the authenticity of weathering steel with the naked eye in the early stage, which is also an important reason for the phenomenon of mixed fish and pearl in the market.

(The left side is made of weathering steel, and the right side is made of ordinary steel. The color and texture are almost the same after 7 days of rusting)

                        (Dense rust spots are formed in the later stage of weathering steel)

                     (Flaky fluffy rust layer is formed in the later stage of ordinary steel)

To sum up, the weathering steel can not be identified by ordinary observation in the early stage, so the following methods can be adopted for detection.
Detection method for authenticity of weathering steel:
First, the content of several precious metal elements, such as Cu (copper), Ni (nickel) and Cr (chromium), shall be tested by a third-party testing agency through spectral testing, and shall be compared with the warranty. The content of several precious metal elements, such as Cu, Ni and Cr, in ordinary steel plates will be 10 times or more less than the corresponding content in the warranty.
Second: sample and inspect the weathering steel plate, divide the sample plate into two parts, use a sander or sandpaper to destroy the original rust surface, and then spray the water for observation. Because the real weathering steel plate is made of excellent materials, even if a layer is knocked off, good rust will still grow naturally inside.

9. Application of weathering steel in landscape

Weatherproof steel landscape wall

Weathering steel retaining wall

Weathering Steel Pieces

Weathering steel planting pool

Weathering steel signboard

Weatherproof steel seat

Shandong Kuai Ma Steel Co., Ltd. is located in Liaocheng City in the west of Shandong Province. Mainly produce and process stainless steel products, carbon steel series, color-coated steel and galvanized steel products, honing series and seamless steel pipe series,etc.
Our products have been exported to 30 countries and regions. Europe, USA, Canada, United Kingdom, United Arab Emirates,Russia, Australia, South America, Middle East, Africa, India, etc. and our company has rich experience in freight forwarding,We can export to any country that shipping company can reach.
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