Cold-formed steel refers to a finished steel product of various cross-sectional shapes bent by a steel plate or a strip in a cold state. Cold-formed steel is an economical thin-section thin-walled steel, also known as steel-refrigerated curved or cold-formed profiles. Cold-formed steel is the main material for making lightweight steel structures. It has a variety of extremely thin, well-shaped and complex sections that cannot be produced by hot rolling. Compared with hot-rolled steel, the radius of gyration can be increased by 50-60% and the moment of inertia of the section can be increased by 0.5-3.0 times in the same cross-sectional area, so that the material strength can be used reasonably; That is to say, compared with the traditional steel structures made of I-beam, channel steel, angle steel, and steel plate, it can save about 30 to 50% of steel.
Classification and application
1. Cold-formed steel is classified according to size specifications and is divided into four types: large, medium, small and wide in terms of product thickness and expansion width.
(1) Large-scale cold-formed steel: the thickness of the product is 6-16mm, and the product has a width of 600-2000mm.
(2) Medium-sized cold-formed steel: the product thickness is 3-6mm, and the product expansion width is 200-600mm.
(3) Small cold-formed steel: the product thickness is 1.5-4mm, and the product expansion width is 30-200mm.
(4) Wide-width cold-formed steel: the thickness of the product is 0.5-4mm, and the product has a width of 700-1600mm.
2. Cold-formed steels are classified according to their shape and can be divided into open and closed.
(1) Universal open-formed cold-formed steel with equilateral and unequal angles, inner and outer bead angles, equilateral and unequal channel steel, inner or outer bead channel, Z-beam, coil Side Z-shaped steel, special shaped open-section steel, etc.
(2) Closed cold-formed steel is a cold-formed steel with a closed section of welded shape, which is round, square, rectangular and shaped according to its shape.
3. Cold-formed steel is classified according to the application.
Different industries have different requirements for cold-formed steel. The production of cold-formed steel can meet the different requirements of various industries and produce various special cold-formed steels. The main items can be listed below.
(1) Cold-formed steel for automobile manufacturing; small passenger cars, mostly with irregular-shaped open-shaped steel, such as windows, rain gutters, seat machine pulleys. Most of the buses use closed rectangular steel, and most of the freight cars use open-cold steel; special vehicles such as fire trucks, engineering vehicles mostly use rectangular and shaped cold-formed steel. Bosj offerred cold roll forming machine can meets all kinds of industry requirements.
(2) Railway vehicles: Most of the passenger cars and freight vehicles use special shaped cold-formed steel, for example, cold-formed middle beams instead of hot-rolled middle beams. Open for a long time.
The middle beams used in the chassis of the car, the caravan, and the tanker are all hot-rolled steel-welded welded structures. They are welded by two hot-rolled sheets of steel with a height of 310. Since the middle beam is welded with a hot-rolled steel, it exists. The utility model has the advantages of large weight, high welding quality requirement (need to be non-destructive testing), and high comprehensive cost. Therefore, the railway department hopes to develop a high-efficiency cold-formed steel with integral shape, lightweight, high strength and good rigidity instead of hot-rolled steel. The cold-formed middle beam developed by WISCO uses hot-rolled coiled sheets as raw materials, and the integral middle beam is obtained by continuous molding. Another example: Qiqi Group developed cold-formed steel for end wall transverse belts and hat-shaped steel side columns in 1985. In 1993, cold-formed steel for upper side beams of rectangular tubes with sharp corners was developed. The material is cold-formed steel 09CuPTiRE-A The yield strength is 295 MPa. The application of cold-formed steel in China's railway wagons will be more and more.
(3) Elevator: hollow guide rail for the elevator, structural frame for the automatic elevator and cold-formed steel for other special-shaped members
(4) Shelf: Cold-formed steel for small supermarket shelves and large warehouse-style supermarket shelves.
(5) Transmission tower: Focus on the study of replacing the traditional hot-rolled angle steel with cold-formed steel to improve the overall performance of the tower and reduce costs. In the high-voltage long-distance transmission tower, high-strength and anti-corrosion structural steel pipes have been tried in various places. The triangular tower structure made of cold-formed steel for the communication tower is also under development.
(6) Construction machinery: crane lifting arm, support arm, cold-formed steel for tower crane frame.
(7) Electrical equipment manufacturing industry: electrical cabinets, cold-formed steel for cable trays.
(8) Agricultural machinery: cold-formed steel for tractors, plows, hoes, and harvesters, and cold-formed steel for agricultural vehicle beams.
(9) Construction industry: steel structure (beam, column) maintenance structure, roofing, wall, door and window, cold-formed steel for decoration.
(10) Furniture: Stools, chairs, cabinets, beds, etc. are special cold-formed steel.