Elbow is to change the direction of the pipe fittings. Angularly points, 45 ° and 90 ° 180 ° three most commonly used, according to project needs in addition also includes other non-normal 60 ° angle bend. Elbow materials are cast iron, stainless steel, alloy steel, malleable iron, steel, nonferrous metals and plastics. Way tube connection are: direct welding (the most common way) flange connection, hot melt connection, fused connection, threaded connections and socket-type connections. According to the production process can be divided into: welding elbow, pressing elbow, push the system elbow, casting elbow. Plumbing installation in a common connection with fittings for connecting pipes at the corner, used to change the direction of the pipe. Other names: 90 ° elbow, right angle bend, bend love, stamping elbow, pressing elbow, elbow mechanism, welding elbow. Purpose: to connect two of the same or different nominal diameter pipe, so that the pipe for 90 °, 45 °, 180 ° and various degrees of turn. Bending radius less than or equal to 1.5 times the diameter of belonging to elbow, is greater than 1.5 times the diameter of belonging elbow 1. Material classified: 2. production methods can be divided into pushing, pressing, forging, casting and so on. 3. manufacturing standards can be divided into GB, electricity standard, ship standard, technology standard, water standard, American Standard, the German standard, Japanese standard, the Russian standard and so on. 4. It is the radius of curvature of points: can be divided into long and short radius bend radius elbow. Long radius elbow refers to its radius of curvature is equal to 1.5 times the outer diameter of the tube, that R = 1.5D; short radius elbow refers to its radius of curvature is equal to the pipe diameter, namely R = 1.0D. (D is the diameter of the bend, R is the radius of curvature). 5. In terms of pressure levels to points: about seventeen species, and the US standard pipe is the same, there are: Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS; Sch80, SCH100, Sch120, Sch140, Sch160, XXS; one of the most common STD and XS are two kinds. 6. The use of different shapes can be divided into: grooved elbow, elbow card sets, double socket elbows, flanges elbows, reducers elbow, elbow seat stay, both inside and outside the tooth elbow, pressing elbow push the system elbow, socket elbow, welded elbow, female thread elbow. Seamless elbow: elbow pipe for a pipe bend of. All fittings in piping systems used in the largest proportion, about 80%. Typically, the thickness of different materials or choose a different bend forming process. At present, the factory used seamless elbow hot push forming process, stamping, extrusion. Elbow hot push forming process is the use of special elbow pushing machine, mandrel and the heating device, so set in the blank mold under the impetus pushing machine forward movement, is heated in the movement, expanding and bending process. Picks elbow tube diameter deformation characteristics are determined according to the law of constant volume before and after plastic deformation of the metal material, the use of the elbow tube diameter smaller than the diameter of the mandrel by controlled deformation of the blank, at the inner arc is compressed metal flow to other parts of the compensation due to the enlarged diameter and thinned, thereby obtaining a uniform wall thickness of the elbow. Elbow hot push forming process has a beautiful appearance, uniform thickness and continuous operation, suitable for mass production characteristics, and thus become carbon steel, alloy steel elbow primary forming method, and also used in certain types of stainless steel elbow The forming. Heating process of forming intermediate frequency or high frequency induction heating (heating coil may be a multi ring or lap), flame heating and reflection furnace heating, depending on what kind of heating the shaped product and energy requirements of decisions. When the product is still in use with special requirements. Stamping elbow bend is first used in mass production seamless elbow forming process, now commonly used in the production specifications of the elbow has been replaced by extrapolation or other hot forming process, but in some of the specifications of the elbow because a small number of production, the thickness is too thick or too thin. Forming punch with the use of the elbow tube outer diameter equal to, direct compression using a press molding in a mold. Before stamping, tube placed on the lower mold, the inner core and the end of the tube into the mold, the mold pressing downward movement began, through binding and supporting role within the mold so that the outer mold forming elbow. Compared with hot push technology, visual quality not as good as the former stamping; stamping elbow when forming outside the arc in tension, no other parts of the excess metal to compensate, so the wall thickness of the outer arc about thinning at around 10% . However, due for single piece production and low cost, it is used for stamping elbow craft small batch manufacturing thick-walled elbow. Stamping elbow cold stamping and hot stamping points two, is usually cold stamping or hot stamping based on material properties and equipment capacity. Cold extrusion molding process is to use a dedicated elbow elbow forming machine, the tube into the outer mold, after the upper and lower mold clamping, push in the push rod, tube along the inner and outer dies reserved movement gap forming process is completed. Use elbow appearance inside and outside for the cold extrusion process manufacturing, uniform thickness, small size deviation, so especially for thin-walled stainless steel elbow stainless steel elbow forming more using this process. This inner and outer molding process used precision high; tube wall thickness deviation requirements are more demanding.