What is a rectangular tube?
Rectangular tube is a kind of hollow strip steel, also known as flat tube, square tube or square flat tube (as the name implies). A large number of pipelines are used to transport fluids, such as oil, natural gas, water, gas, steam and so on. In addition, under the same bending and torsion strength, it is light in weight, so it is also widely used to manufacture mechanical parts and engineering structures. It is also often used to produce various conventional weapons, barrels, shells and so on.
Classification of rectangular tubes
Classification of rectangular pipes: Steel pipes are divided into seamless steel pipes and welded steel pipes (slotted pipes), hot-rolled seamless square pipes, cold-drawn seamless square pipes, extruded seamless square pipes and welded square pipes.
Welded square pipes are divided into:
(a) according to the process is divided into arc welding square tube, resistance welding square tube (high frequency and low frequency), gas welding square tube and furnace welding square tube.
(b) Weld the square pipe and spiral weld the square pipe according to the weld seam.
The use of rectangular tubes
1, rectangular tube product description
Rectangular tube is a kind of light thin-walled steel tube with hollow square cross section, also known as cold-formed steel. It is made of Q235 hot-rolled or cold-rolled strip or coil as the base material, which is processed by cold bending and then welded by high frequency. In addition to the wall thickness thickening, the corner size and edge flatness of hot-rolled extra-thick-walled square tubes reach or even exceed the level of resistance welding cold-formed square tubes.
2. The use of rectangular tube
Construction, machinery manufacturing, steel structure engineering, shipbuilding, solar power bracket, steel structure engineering, power engineering, power plant, agrochemical machinery, glass curtain wall, automobile chassis, airport, etc.
Note: Q345 seamless rectangular pipe has a high utilization rate, but the general construction party should carry out visual inspection on pipes, fittings and rubber rings. Before construction, if problems are found, give up the use.
1. Cleaning the nozzle of Q345 seamless rectangular pipe: clean all the sundries in the socket and scrub them.
2. Cleaning apron and upper apron: clean the glue on apron, bend apron into plum blossom shape or figure 8, put it into socket slot, press it once along apron by hand, or tamp it with rubber hammer to ensure that all parts of apron are not warped or twisted and evenly stuck in the slot.
3. Brush the lubricant on the outer surface of the socket and the guard plate: brush the lubricant evenly on the inner surface of the guard plate installed on the socket. When brushing the lubricant on the outer surface of the socket, brush all the socket parts except the socket wire.
4. Pipeline laying: Q345 seamless rectangular pipe should be laid to the bottom of the tank according to the requirements of pipeline laying, generally by manual or mechanical laying.
5. Installation of machines and tools: Install the prepared machines and tools in place, and be careful not to pollute the cleaned Q345 seamless rectangular tube again during installation.
6. Push the Q345 seamless rectangular tube into the socket: When installing, it is easier and smoother to insert the socket into the socket. Firstly, put the socket into the socket, press the socket on the apron in the socket, connect the steel wire rope and the inverted chain, and tighten the inverted chain; Until the socket is completely inserted into the socket, there should be a gap of about 2mm between the sockets, and the distance from the outer edge around the socket to the skirt should be consistent.
During installation, the axes of the fixed tube and the movable tube should be in a straight line, otherwise the apron will pop out easily, which will affect the installation quality and speed. Q345 seamless rectangular pipe should be installed horizontally, and the seamless rectangular pipe should be in a straight line. Watch the tilt angle. Align the interface connecting Q345 seamless rectangular tube with the socket. If the insertion resistance is too high, do not forcibly insert it to prevent the rubber ring from twisting. Rubber ring lubricating oil should use vegetable oil; In cold winter, you can preheat the rubber ring with hot water to reduce the hardness and install it quickly.
Identification method of rectangular steel
1, fake rectangular pipes are easy to fold.
Folding is a variety of broken lines formed on the surface of rectangular tube, and this defect often runs through the longitudinal direction of the whole product. The reason for folding is that fake and shoddy manufacturers pursue high efficiency, and the reduction is too large, resulting in ears, which will fold in the next rolling, and the folded products will crack after bending, greatly reducing the strength of steel.
2. The appearance of fake rectangular pipes often has pits.
Pockmarked surface is an irregular and uneven defect of steel surface caused by serious groove wear. Because the manufacturers of fake and inferior rectangular tubes often exceed the standard in order to pursue profits.
3. The surface of fake rectangular tube is easy to scar.
There are two reasons: (1), the quality of fake and inferior rectangular pipes is uneven and there are many impurities. (2)。 The guide equipment of fake and inferior manufacturers is simple and easy to stick to steel. These impurities
4. The surface of fake and inferior wood is easy to crack, because its blank is adobe with many pores. Bricks crack due to thermal stress during cooling, and then crack after rolling.
5. Fake and inferior rectangular pipes are easy to be scratched, because the manufacturers of fake and inferior rectangular pipes have poor equipment and are prone to burrs and scratch the steel surface. Deep scratches will reduce the strength of steel.
6. The fake rectangular tube has no metallic luster and is reddish, or there are two reasons. Second, its blank is adobe. There is no standard for the rolling temperature of fake and inferior materials, and their steel temperatures are all visual, so it is impossible to roll according to the specified austenite region, and the properties of steel naturally cannot meet the standard.
7. The transverse reinforcement of fake rectangular pipes is thin and low, which often leads to dissatisfaction. The reason is that the negative tolerance of the manufacturer is large, and the first few passes of the finished product are pressed.
8. The cross section of the false rectangular tube is oval, because the finished product is rolled twice before, and the reduction is too large to save materials, so the strength of this rebar is greatly reduced, which does not meet the shape and size standards of rebar.
9. High-quality steel has uniform composition, high cold shear tonnage, smooth and tidy end face of cutting head, and the end face of cutting head often loses meat due to poor material, that is, it is uneven and has no metallic luster. And because the manufacturer's products are cut less, there will be a situation of big ears at the head and tail.
10, the fake rectangular pipe contains many impurities, the steel density is too small and the size is out of tolerance. You can weigh and check without vernier caliper. For example, the national standard stipulates that the maximum negative tolerance of rebar 20 is 5%, and its theoretical weight is 120kg when the length is 9M, and its minimum weight should be:120x (L-5%) = 14kg, and the actual weight ratio of a single thread is1. Generally speaking, the effect of integer proportional quantity will be better, mainly considering cumulative error and probability theory.
1 1. The inner diameter of fake rectangular pipes fluctuates greatly because: 1. The temperature of steel is unstable, with positive and negative sides. 2. The composition of steel is uneven. 3. Due to poor equipment and low foundation strength, the rolling mill bounces greatly. There will be great changes in the same week, and such steel bars are easy to break due to uneven stress.
12, trademark and printing comparison specification for high-quality pipes.
The spacing between the diameters of rectangular tubes above 13 and 16 is above IM.
14, the longitudinal reinforcement of fake and shoddy rebar is often wavy.
Rectangular steel pipe specification sheet
Theoretical weight table of rectangular tube
computing formula
2 [(a-d-2r+π (r+d/2)/2+(b-d-2r+π (r+d/2)/2] x7.85d (kg) a, where b is the length and width (m) of the rectangular tube, and r is the arc radius (m) of the four corners of the tube cavity.