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what is the carbon steel elbow?

Carbon Steel Pipe Fittings

Let us learn what is the carbon steel elbow in this article

Carbon steel elbow

Carbon steel elbows are metal fittings that change the direction of the pipe on the carbon steel pipe. Connections are threaded and welded. Divided by angle, there are 45 ° and 90 ° 180 ° the three most commonly used, in addition to other engineering needs also include 60 ° and other abnormal angle elbow. Elbow materials are cast iron, stainless steel, alloy steel, malleable iron, carbon steel, non-ferrous metals and plastics. The connections to the tube are: direct welding (the most common method) flange connection, hot melt connection, electrofusion connection, screw connection and socket connection. According to the production process can be divided into: welding elbow, stamping elbow, pushing elbow, casting elbow and so on.Carbon steel elbow is a kind of carbon steel pipe fittings.

Varieties classification

Carbon steel elbow is first divided into its radius of curvature, which can be divided into long radius elbows and short radius elbows. The long-radius elbow refers to its radius of curvature equal to 1.5 times the outer diameter of the tube, ie R = 1.5D. A short-radius elbow means that its radius of curvature is equal to the outer diameter of the tube, ie R = 1.0D. (D is the diameter of the elbow, and R is the radius of curvature. D can also be expressed in terms of folds.) If there are 17 levels depending on the pressure rating, the same standards as in the U.S. tube are: Sch5s, Sch10s, Sch10 , Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS; Sch80, Sch100, Sch120, Sch140, Sch160, XXS, the most commonly used are STD and XS. According to the angle of the elbow, there are 45° elbows, 90° elbows and 180° elbows.

The material classification

Carbon steel can be divided into
10# 20# A3 Q235A 20g Q345B 20G 16Mn ASTM A234 ASTM A105 st37 ASTM A403 etc
The elbows made of these materials as raw materials can be called carbon steel elbows.
90° carbon steel elbow
90° carbon steel elbow
According to the angle: 45°, 90°, 180°, these three commonly used elbows, and other engineering needs, can be specially customized such as 60 ° or other angles.
Connection with carbon steel pipe: welding, flange connection, screw connection, socket connection and other forms.
According to the process form can be divided: welding elbows, stamping elbows, casting elbows and so on.
Uses: Connect two tubes to change the direction of the tube, turning to 45° or 180° and 90° or other angles.
Manufacturing standards: national standard, American standard, Japanese standard, German standard, and Russian standard.
The basic process of a carbon steel elbow is to first weld a multi-prism ring shell with a polygonal cross-section or a polygonal prismatic shell with both ends closed. After the interior is filled with pressure medium, internal pressure is applied and the cross-section under internal pressure is applied. From a polygon to a circle, it eventually becomes a circular shell. According to need, a circular ring shell can be cut into 4 90° elbows or 6 60° elbows or other size elbows. The process is suitable for manufacturing any elbow diameter and elbow ID ratio greater than 1.5 times. Specifications Large elbows are an ideal way to make large carbon steel elbows.
The advantages of the carbon steel elbow production process are mainly manifested in the following aspects:
(1) Tube blanks are not needed as raw materials, which can save the cost of the tube equipment and molds, and can obtain carbon steel elbows with any large diameter and relatively thin wall thickness.
(2) The blank is a flat or developable surface, so the material is simple, the accuracy is easy to ensure, and the assembly and welding are convenient.
(3) Due to the above two reasons, the manufacturing cycle can be shortened and the production cost can be greatly reduced. Because it does not require any special equipment, it is especially suitable for on-site processing of large-scale carbon steel elbows.
(4) Carbon steel elbows are suitable for the pipeline series of petroleum, natural gas, chemical, hydropower, construction and boiler industries.


The process flow

Seamless elbows: Elbows are a kind of pipe fittings used for turning pipes. Of all the pipe fittings used in the piping system, the largest share is about 80%. In general, different forming processes are selected for different materials or wall thickness bends. Manufacturers commonly used seamless elbow forming process hot push, stamping, extrusion and so on.
Heat forming
The hot-bending bending head forming process adopts a special elbow pushing machine, a mandrel and a heating device, so that the billet placed on the die is moved forward by the pushing machine, heated, expanded and bent during the movement. the process of. The deformation characteristics of the thermal pusher elbow is to determine the diameter of the blank according to the law of constant volume before and after the plastic deformation of the metal material. The diameter of the blank used is smaller than the diameter of the elbow. The deformation process of the blank is controlled by the core die, so that the internal arc is compressed. The metal flow is compensated to other parts that are thinned due to the expansion, so that an elbow with a uniform wall thickness is obtained.
The hot-pushing head forming process has the characteristics of beautiful appearance, uniform wall thickness and continuous operation, and is suitable for mass production. Therefore, it has become a main shaping method for carbon steel and alloy steel elbows, and is also applied to certain specifications of stainless steel elbows. The formation of.
Heating methods in the forming process include medium-frequency or high-frequency induction heating (multi-turn or single-turn heating coils), flame heating, and reverberatory furnace heating. The heating method used depends on the product requirements and energy conditions.
Stamping
Press forming elbow is the earliest forming process used for mass production of seamless elbows. It has been replaced by hot extrusion method or other forming process in the production of elbows with common specifications, but the number of production in some elbows Little, thick or thin wall thickness.
When the product has special requirements, it is still in use. The stamping of the elbow uses a tube blank with an outer diameter equal to that of the elbow and is pressed directly into the mold using a press.
Before punching, the tube blank is placed on the lower mold and the inner core and the end mold are loaded into the tube blank. The upper mold moves downwards to start pressing. The bend is formed by the constraint of the outer mold and the supporting function of the inner mold.
Compared with the hot-pushing process, the appearance quality of stamping is not as good as the former; the outer arc of the stamping elbow is in the stretched state during forming, and there is no excess metal in other parts to compensate, so the wall thickness at the outer arc is reduced by about 10%. . However, due to the characteristics of single-piece production and low cost, the stamped elbow process is mostly used for the manufacture of small batches and thick-walled elbows.
Stamping elbows are divided into cold stamping and hot stamping. Cold stamping or hot stamping is usually selected according to material properties and equipment capabilities. The forming process of the cold extrusion elbow is the use of a special elbow forming machine. The tube blank is placed in the outer mold. After the upper and lower molds are closed, the blank is reserved along the inner mold and the outer mold under the push of the push rod. Gap movement to complete the forming process.
The elbows produced by the internal and external die cold extrusion process have beautiful appearance, uniform wall thickness, and small dimensional deviation. Therefore, the stainless steel elbows, especially the thin-walled stainless steel elbows, are formed using this process. The inner and outer molds used in this process require high precision; and the wall thickness deviation of the tube blanks is also more demanding.
Plate welding
Half of the elbow profile was made with a press using a press plate, and then the two profiles were welded together. This process is generally used for DN700 above the elbow.
Other methods
In addition to the above-mentioned three commonly used forming processes, the seamless elbow forming method also employs a forming process of extruding the tube blank to the outer mold and shaping the ball through the inside of the tube blank. However, such a process is relatively complicated and cumbersome to operate, and the forming quality is not as good as that of the aforementioned processes and is therefore less frequently used.

Someone want to know what is hot bends.well ,we will introduce that next time.


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