Cold Bending Method and Quality of Pipe Bends, as well as Forging Methods
In the manufacturing process of pipe bends, hydraulic forces play a significant role, providing the necessary strength and power. Hydraulic forces drive the rotation angle and feed rate, controlled by servo motors, ensuring high speed and precision. Multiple processing sequences can be stored and switched flexibly, enhancing production efficiency significantly.
Typically, cold bending is employed for bending pipes. In cases where there's no cold bending equipment available, hot bending can be allowed, but it should not be used for gas pipes. It's worth noting that the bending of No. 20 steel pipes is not suitable for mid-frequency bending. Stainless steel pipes and alloy steel pipes should be cold-bent. If hot bending is necessary, it is essential to avoid carburization of stainless steel pipes during the heating process. Alloy steel pipes with a high tendency for hardening should not be water-cooled. Copper pipes should undergo local annealing before cold bending.
When using pipe bends, the bending radius should generally be no less than three times the pipe's diameter. In compact piping arrangements, where quality of bends is maintained, smaller bend radii may be used, provided they are not less than three times the pipe's outer diameter. Operators working with pipe bends should be familiar with the structure, performance, operating procedures, and regulations related to bending.
Pipe bends must be lubricated appropriately at their inner diameters and valve stem working areas. The end sleeve of the mandrel should be cut at the mandrel's end and should extend beyond the mandrel's centerline vertically. The mandrel's front-end value is typically determined through testing and can be selected as a reference based on newly installed and calibrated bending machines.
Quality requirements for pipe bends are generally high during production. However, traditional oil-based lubricants are not easy to clean, leading to pollution in the production environment and work conditions for labor. In traditional applications of oil-based lubricants, production efficiency is often significantly limited due to issues with the flow and cleaning of lubricants.
Pipe bends take on a bent shape after bending, and they have found applications across numerous industries. Various production and processing methods are employed, but as long as they meet the requirements, they are considered suitable.
As for forging methods, they can be described as follows:
1. The raw material for the pipe fittings is a round pipe blank, which should be cut into small square billets of approximately 1 meter in length using a cutting machine. These billets are then sent to the furnace for heating. The pipe blanks are heated to a temperature of around 1200°C in the furnace, with hydrogen or acetylene used as the fuel source. Precise temperature control inside the furnace is critical. After exiting the furnace, the round pipe blanks should be pierced using a piercing machine.
2. A commonly used piercing machine is the conical cross-rolling piercing machine. It offers advantages like high production efficiency, excellent product quality, a large piercing expansion capability, and compatibility with various pipe fittings. After piercing the steel pipes, they go through a series of rolling processes, such as three-roll cross-rolling, continuous rolling, or extrusion, to progressively shape the round pipe blanks. Following extrusion, the pipes are cut and their diameters are set. A sizing machine uses a conical drill head to rapidly drill into the steel blank, forming the pipe fittings.
Forging the pipes enhances their performance, making them ideal for various applications. As long as the quality of the pipes meets the requirements, they can be considered suitable for use.
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