The welding elbow is a "xiami bend". It can be cut down on the pipe or steel plate and then welded. The specification can be large. The number of bending and bending radius is determined by the creator. The bending radius of the welded bend is not very good, and it is generally about 1 times the diameter of the pipe.
The classification method of welding elbow is divided according to its radius of curvature.
Can be divided into long radius elbow and short radius elbow. The radius of the long radius is equal to 1.5 times the diameter of the tube, that is R= 1.5d. The radius of curvature of the short radius is equal to the diameter of the tube, which is R= D. D is the diameter of bend, R is the radius of curvature. The most commonly used one is 1.5d elbow. If the contract does not indicate 1D or 1.5d, it should be optimized to choose 1.5d. The most common implementation standards in China are GB/t12459-2005, GB/ 13401-2005, GB/t1072-1995.
Class of pressure grade
According to the stress level, there are about a dozen of them, which are the same as the American pipe standards, including: Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS; Sch
80, Sch100, Sch120, Sch140, Sch160, XXS, the most commonly used are STD and XS. According to bend Angle, has 45 ° elbow, and 180 ° 90 ° elbow bend. So there are a lot of kinds of elbow, an order when the order is often said to take the following methods: such as "LRSTD90 ° 8", said the long radius, pressure rating for STD, 90 ° 8 "elbow; Another example, "SRXS45 ° 4" said short radius, pressure rating for XS, 45 ° 4 "elbow. The above is the approximate classification of the elbow. There are usually two kinds. Three diameters of three diameters are equal to three diameters with diameters of the same diameter, but the diameter of the confluence is different from that of the other two diameters. The method is as follows: for equal diameter tee, such as "T3", the outer diameter is 3 inches. For different diameters, such as "T4 x 4 x 3.5", the same diameter has a diameter of 3.5 inches. The pressure level and the stress level of the elbow are the same, and the range of the specifications is the same.
It's the same as the size head. The method of representation of the size head is the head diameter times the diameter of the small head, for example, "8 by 6" means the head diameter is 8 inches and the small head is 6 inches in diameter.
The material of welding elbow is divided
Carbon steel: ASTM/ASME A234 WPB, WPC
Alloy: ASTM/ASME A234 WP 1-WP 12-wp 11-WP 22-WP 5-WP 91- WP911, 15Mo3 15CrMoV, 35CrMoV
Stainless steel: ASTM/ASME A403 WP 304-304-304l-304lln -304n
ASTM/ASME A403 WP 316-316 l - 316 - h - 316 ln - 316 - n - 316 ti
ASTM/ASME A403 WP 321-321h ASTM/ASME A403 WP 347-347h
Low temperature steel: ASTM/ASME A402 wpl3-wpl 6
High performance steel: ASTM/ASME A860 WPHY 42-46-52-60-65-70
Welding process flow,
If the long radius bend, you should select the specifications, and put forward the pipe material. The expansion ratio is calculated by theoretical calculation, and the general expansion rate is between 33% and 35%. Short radius 219 mm general hole enlargement rate was 50%. The chosen materials, the bend materials specifications, then consider the radius of curvature, for example, the 90 ° elbow, through its curvature can calculate how much material can work out the 90 ° elbow. It can be calculated by theoretical calculation and then cut by the length. And then we're going to heat it up. You might have seen it, but it's pretty simple. It is a bullhorn core or mandrel bar, the core rod is thickened by thin, and the process of pushing is a process of expanding and winding. After the back is supported, the lower material pipe section is inserted into the mandrel bar, which is fixed with the core rod in the back. There is a small car in the middle, the car some through hydraulic transmission, some through mechanical drive namely the screw drive, then push the car forward. The car pushes the pipe along the core bar, and there is an induction loop that heats the tube and heats it up. Then the car pushes the pipe down, and then it is processed. After push, bend the head to be in this hot condition to undertake plastic surgery. Because some of the corners are handled improperly, it will be distorted, which is not allowed. In addition, the front end of the head is usually large external diameter, to be done by the shaping model. The shaping mold is actually a press machine, with a set of moulds, two and a half arcs, each one. The outside diameter of the plastic surgery has reached the size requirement of the finished product. The wall thickness is controlled by the thickness of the incoming material. Elbow and pipe wall thickness tolerance is the same, all is plus or minus 12.5% in the process of driving system, under normal circumstances wall thickness should not be changed, but if for tool reason, some local wall reduction happens, so generally refer to material, wall thickness to add some allowance, such as the elbow is 8.18 mm wall thickness, pipe of the 8.5 mm or so commonly, to prevent the push system error due to the local reduction of thickness. After the good shape, the outer diameter of the elbow and the thickness of the wall meet the requirements. In the following, the finishing process is carried out and the oxide sheet is removed from the inner and outer surface of the elbow, and the two ends are treated with groove for welding. After inspection, steel word, painting, packaging and other procedures, we can leave the factory. The above is the production method of the elbow with seamless steel tube as the raw material. After more than 24 words, it is more than 600mm, and the elbow is between 2.032 meters and 2.80 meters. It is made of steel plate. After pressing the steel plate according to the requirement, like UOE molding, it is also made into a circle by punching die stamping. It's two and a half and then it's pieced together and welded. Because of the existence of the weld, it is required to carry out non-destructive inspection. Due to the existence of welding stress, heat treatment is also necessary. The welding elbow has two more processes: one is flaw detection, one is heat treatment. Other programs are the same.
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