Basic knowledge of square pipe

Basic knowledge of square pipe

Introduction to square tube

As the name suggests, the square tube is a square tube shape. Many kinds of materials can form a square tube body. It is used as a medium, what it is used for, and where it is used. Most square tubes are made of steel pipes. After unpacking, Flattened, crimped, welded to form a round tube, and then rolled into a square tube from the round tube and then cut to the required length. Generally, there are 50 pieces of square tubes per package. In terms of spot stock, the large specifications are mostly 10*10*0. 8-1.5~~ 500*500*10-25. Square tubes are divided into structural square tubes, decorative square tubes, architectural square tubes according to their uses Square tube, mechanical square tube, etc. The square tube is a hollow square cross-section light-weight thin-walled steel tube, also known as steel cold-formed profile. It is a section steel with square cross-section shape and size made of q235 hot-rolled or cold-rolled strip or coil as the base material, which is formed by cold bending and then high-frequency welding. Except for the thickened wall thickness of the hot-rolled extra-thick-walled square tube, the corner size and edge straightness reach or even exceed the level of the resistance-welded cold-formed square tube.

Classification of square tube

Craft classification

Square tubes are divided according to the production process: hot-rolled seamless square tubes, cold-drawn seamless square tubes, extruded seamless square tubes, and welded square tubes.
Among them, the welded square tube is divided into:
(a) According to the process - arc welded square tube, resistance welded square tube (high frequency, low frequency), gas welded square tube, furnace welded square tube
(b) According to the welding seam - straight seam welded square pipe, spiral welded square pipe

Material classification
Square tubes are divided according to material: plain carbon steel square tubes, low alloy square tubes. Common carbon steel is divided into: q195, q215, q235, ss400, 20# steel, 45# steel, etc.; low alloy steel is divided into q345, 16mn, q390, st52-3, etc.

Production Standard Classification
Square tubes are divided according to production standards: national standard square tubes, Japanese standard square tubes, imperial square tubes, American standard square tubes, European standard square tubes, and non-standard square tubes.

Section shape classification
Square tubes are classified according to the cross-sectional shape:
(1) Square tube with simple cross-section - square tube, rectangular tube
(2) Square tubes with complicated cross-sections - flower-shaped square tubes, open-shaped square tubes, corrugated square tubes, special-shaped square tubes

Surface treatment classification
Square tubes are classified according to surface treatment - hot-dip galvanized square tubes, electro-galvanized square tubes, oil-coated square tubes, pickling square tubes
Square tubes are classified according to their uses - square tubes for decoration, square tubes for machine tools, square tubes for machinery industry, square tubes for chemical industry, square tubes for steel structures, square tubes for shipbuilding, square tubes for automobiles, square tubes for steel beams and columns Tube, square tube for special purpose
Square tubes are classified by wall thickness - super thick-walled square tubes, thick-walled square tubes and thin-walled square tubes

Square tube forming method

1. Solid bend
Solid bending, as the name implies, is compacted bending. During solid bending, the inner and outer rollers and the inner and outer walls of the tube blank are compacted in two directions.
1) The advantages of solid bending are small rebound and accurate forming, and as long as the roll shape is accurate, the r of inner angle forming is more accurate.
2) The disadvantage of solid bending is the stretching/thinning effect. First, solid bending will cause stretching at the bend, and the stretching effect will shorten the longitudinal length of the bending line; second, the metal at the bend will become thinner due to stretching.

2. Empty bend
Air bending is to bend the strip material through the one-way contact between the outer roller and the outer wall of the tube blank. The empty bending will cause the bending line to be compressed. The compression effect will make the bending line elongate longitudinally, and the metal at the bending place will accumulate and thicken. This is the compression/thickening effect of the empty bend.
1) The advantage of empty bending is that it can bend the side length when real bending cannot be performed, such as simultaneous bending and finishing of the upper side/side side of the square tube. The empty bend can also bend the inner angle of r<0. 2t without breaking the pipe wall.

2) The disadvantage of air bending is that when the top/side synchronous air bending, due to the pressure generated by the upper roller and the lower roller at the same time, the forming force is easy to exceed the critical point, causing the edge to be unstable and concave, and it will also affect the stable operation of the unit and molding quality. This is also the difference between rectangular tubes and round tubes when they are air-bent.