The carbon steel elbow forming process uses a dedicated elbow pushing machine, core mold, and heating device to achieve the forward movement of the billet covered in the mold under the push of the pushing machine, which is heated, expanded, and bent into shape during the movement. The deformation characteristics of carbon steel elbows are determined based on the law of constant volume before and after plastic deformation of metal materials. The diameter of the pipe blank used is smaller than the diameter of the elbow, and the deformation process of the blank is controlled by a core mold, allowing the compressed metal at the inner arc to flow and supplement other parts that have been thinned due to expansion, thus obtaining a carbon steel elbow with uniform wall thickness.
The forming process of carbon steel elbows has the characteristics of beautiful appearance, uniform wall thickness, and continuous operation, which is suitable for mass production of products. Therefore, it has become the main production method for carbon steel and alloy steel elbows, and is also applied in the manufacturing of certain specifications of stainless steel elbows. The heating methods for the forming process include medium frequency or high-frequency induction heating (the heating coil can be multiple or single coils), flame heating, and reflection furnace heating. The heating method used depends on the requirements of the formed product and the energy situation.
Carbon steel elbows have poor rigidity and are suitable for applications with pressure p ≤ 4MPa; The national standard carbon steel elbow has high rigidity and is suitable for occasions with high pressure and temperature. The basic process of carbon steel elbow forming technology is to first weld a polygonal multi ribbed ring shell or a closed multi ribbed fan-shaped shell at both ends. After the internal pressure medium is filled, internal pressure is applied. Under the action of internal pressure, the cross-section gradually changes from a polygon to a circle, and finally becomes a circular ring shell. There are three types of flange sealing surfaces: flat sealing surfaces, suitable for occasions with low pressure and non-toxic media; The concave convex sealing surface is suitable for slightly higher pressure situations.
Carbon steel elbow technology is suitable for manufacturing with working pressure less than 10MPa and inner diameter d of carbon steel elbows? 125mm, the ratio of pitch diameter D of carbon steel elbow to inner diameter d of carbon steel elbow D/d? Any carbon steel elbow with a diameter of 1.5, and the size of the pitch diameter of the carbon steel elbow is not limited. For example, large national standard carbon steel elbows with an inner diameter of 12m and a pitch diameter of over 60m can be processed. The pipeline system for industries such as petroleum, natural gas, chemical, hydropower, construction, and boiler with national standard carbon steel elbows. The tenon groove sealing surface is suitable for flammable, explosive, toxic media, and high pressure situations. A gasket is a circular ring made of a material that can produce plastic deformation and has a certain strength.
The production of carbon steel elbows (HG20600, GB/T9121, JB/T83) is relatively simple and mainly suitable for pipeline systems with corrosive media; Different materials can be used for elbows and flat welding rings to reduce elbow costs and improve performance. The sealing surface of the elbow has convex, concave convex, and tenon groove surfaces.
The component that connects pipes to each other, connected to the end of the pipe. There are holes on the elbow, and the bolts make the two elbows tightly connected. Seal the elbows with gaskets. Flanged pipe fittings refer to fittings with elbows (flanges or adapters). It can be made by casting (not shown in the figure), or it can be formed by threaded connections or welding. The elbow joint consists of a pair of elbows, a gasket, and several bolts and nuts. The gasket is placed between the sealing surfaces of the two elbows. After tightening the nut, the specific pressure on the gasket surface reaches a certain value, causing deformation and filling the uneven areas on the sealing surface to ensure a tight connection without leakage. Elbow connection is a detachable connection.