Selection of steel types and coatings for color coated steel used in construction
2020年10月29日
Selection of steel types and coatings for color coated steel used in construction
The material requirements of the building itself (roof panel and exterior wall panel) can be divided into safety properties (impact resistance, wind resistance, and fire resistance), housing performance (water resistance, heat insulation, and sound insulation), durability (pollution resistance, weather resistance, and appearance retention), production and processing type (economy, easy to process, easy to maintain and repair)
Safety and service life are of utmost importance to the ultimate owner of the building. For the design corporation, service life, carrying capacity, appearance, and so on are more important. For the molding process of building walls and roofing, the machinability (surface hardness, wear resistance, plate shape, and steel plate strength) of the color coating plate is the first choice.
Performance indexes of color-coated steel plate include:
Substrate: yield strength, tensile strength, elongation clad layer: Coating weight and binding force Coating: color difference, gloss, T - bend, impact, hardness, anti - powdery, anti-humidity, and heat. Surface: surface defect visible to the naked eye. Plate type: tolerance, roughness, etc.
Firstly we will talk abourt the steel grade,for buildings, the design of bearing weight (wind load, snow load, construction personnel's machinery), span and purlin distance of buildings, etc. all depend on the strength of steel plates. For building maintenance structure with color coating and aluminum-zinc plating, there are corresponding standards at home and abroad. Such as China GB/T 12754-2006 USA ASTM653, ASTM792, Japan JISG3302, JISG3321, Europe EN10215, EN10147 and so on. It is divided into CQ (general commercial grade), DQ (general stamping) and HSS (high strength structural steel) FH Full-hard steel by steel types.
CQ
Now the most commonly used, such as the TDC51 produced by baosteel, yield strength between 260 mpa and 320Mpa, tensile strength between 350 and 400Mpa, relative to the structural steel, its buckling ratio is slightly higher.
DQ
As the general building color plate are roll forming or composite sandwich, the stamping requirements of materials are not high, so DQ is mainly used in doors, Windows, pipelines and other industries
HSS
High-strength structural steel: according to European standard HSS, it can be divided into 4-5 kinds of steel with different strengths. However, because ordinary CQ grade material has been able to replace HSS steel with low strength, more steel types with a yield strength of 290MPa and 345MPa are used in the market. The TS280GD and TS350GD produced by Baosteel are these two kinds of steel.
Compared with ordinary CQ, HSS steel has several advantages:
1) The steel has good fire resistance and earthquake resistance due to its low buckling. 2) Compared with thick steel plates, it can make large-span arched plates. 3) For general exterior walls and roof panels, it can be thinner than CQ material, so as to save material consumption.
1.Plating Layer
The common coating used in construction is hot-dip galvanizing and hot-dip aluminum-zinc. For color coating, the application fields of the two kinds of substrates are not very different. In the relatively acidic environment, aluminum-zinc substrates are a better choice. And for the use of the wet, alkaline environment, galvanized substrate incisions corrosion resistance can be reflected. For coating thickness, on the roof panel and cladding the general requirements for hot-dip galvanized 180 g/m2 or about 26 (um), 100 g/m2 or zinc with aluminum plated (about 27 um) when using the environment in heavy industry or the beach, the foreign-related association will have a minimum amount of galvanized, as the Australian standard ECCA specification request content of 275 g/m2 or galvanized layer (about 38 um), aluminum zinc plating (about 40 um) 150 g/m2。
2.The coating
To meet the user's color needs and durability requirements. For the processor, it has to meet its processing performance. Therefore, it is necessary to specify coating types, colors and gloss and coating thickness when ordering.
The choice of color is mainly to consider the match with the surrounding environment and the owner's interest, but from the practical technical point of view, light color thermal reflection ability, small contrast after daub differentiation, if the cleaning and maintenance of proper, long service life, will be more beautiful.
For gloss, in the outdoor use of color coating board, light loss is the earliest phenomenon, especially for high gloss products, the initial light loss will be very fast. It lasts for a long time when the gloss drops to about 20, which can now be used for a few months, because outdoor building paints are generally low-light.
In addition in the same building should use the same color coating factory production of products. Because the color coated steel plate of different manufacturers in the outdoor use of a certain number of years after the speed of coating powder is different, even if the building seems to be the same when the completion of a time regret the appearance of different colors of visual effects and affect the beauty.
At the microscopic level, a coating is a porous tissue. Water in the air, corrosive media (chloride ions, etc.) will be through the weak parts of the coating invasion, resulting in submembrane corrosion, and then coating bubbles and peeling. In addition, even with the same coating thickness, the secondary coating is denser than the primary coating.
According to the relevant corrosion test results, only the front coating below 20UM can effectively prevent the intrusion of corrosive media. PVDF products require thicker coatings. On the back of the coating depends on the use, the sandwich board only requires a shell bonding primer, and the molding steel plate due to the indoor corrosion environment is also required to be coated with two, the thickness of at least 10um above.
- Get In Touch: +86-18115459757
