Hot Elbow Forming Technology Reliability

1.?The forming process of the seamless elbow produced by the hot push method includes loading the cut tube blank into the core mold, and using a special push machine to carry out continuous heating, diameter expansion, bending forming, and other processes. The hot push elbow forming process has the characteristics of uniform wall thickness, beautiful appearance, and continuous production, so it has become the preferred process for the production of carbon steel and alloy steel seamless elbows by many pipe fitting manufacturers in the world. In addition to the inherent factors of the raw material seamless steel pipe, the factors affecting the forming quality of the hot push elbow are mainly related to the geometry of the core mold, the heating temperature, and the diameter of the tube blank. Elbow is a widely used accessory in equipment or process pipelines in many industries such as petroleum, chemical, power station, shipbuilding, etc. Its reliability is of great significance to the safe operation of the entire equipment. The reliability of the elbow is determined by its strength. An important factor affecting the strength of the elbow is the wall thickness of the elbow, and the selection of the appropriate tube blank diameter is the key to ensuring the wall thickness of the hot push elbow. Generally speaking, when ordering, the buyer determines the material, structural size, and wall thickness of the elbow, which cannot be changed. The scope of the manufacturing plant process design. How to make the selected wall thickness and outer diameter of the pipe not only ensure the production of products that meet the strength requirements but also minimize the cost is a problem that engineers and technicians must consider when carrying out process design, especially in the case of mass production. important.

2. Stress Analysis

Analyze the stress of the elbow when it is subjected to internal pressure by using the hoop stress calculation formula of the constant internal pressure of the ring pipe and find out the stress concentration of the elbow.

R: ELBOW RADIUS

T: ELBOW WALL THICKNESS

r： ELBOW INSIDE RADIUS

P: WORKING PRESSURE

σ: Hoop stress

According to the above analysis, the stress at the boundary of the inner and outer arcs is the same as that of the straight pipe, the stress at the outer arc is less than that of the straight pipe, and the stress at the inner arc is greater than that of the straight pipe. Therefore, for the elbow, the part that affects its strength is the inner arc..

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