Why Alloy Bend Processing Speed Is Low?
During the processing of alloy bends, the temperature in the metal deformation zone rises during the extrusion process, leading to the potential formation of cracks or surface fissures in brittle regions of the alloy. As a result, the speed at which the metal flows out is restricted. In the rolling process, deformation and friction are relatively minimal, and therefore, there is little generation of frictional heat during hot deformation. The probability of an alloy bend transitioning from the plastic region to the brittle region due to a temperature increase is also very low. Hence, the speed of development through extrusion for alloy bends is not practically time-limited.
Furthermore, within a single extrusion cycle, the presence of multiple auxiliary processes, which can be time-consuming, results in a lower production speed compared to rolling.
The heating methods in the forming process include flame heating and induction heating with medium or high-frequency induction (the heating coil may consist of multiple or single loops). The selection of the heating method depends on the specific product requirements, process conditions, and the prevailing environmental factors that determine the development of the technology.
For carbon steel and alloy steel bends, hot pushing bending is the primary method, but hot forming has also been applied to standard stainless steel bends. The hot push bending process exhibits characteristics such as a refined appearance, uniform thickness, and continuous operation, making it suitable for mass production.
The high cost of materials processing and the fabrication of extrusion tools, especially for advanced heat-resistant alloys, means that the cost of extruded products is negligibly affected. In summary, extrusion remains the only viable forming method for producing complex or thin-walled pipes and profiles, as well as for processing materials like brittle non-ferrous metals and steel.
While extrusion was initially used for mass production of bends made from carbon steel and alloy steel, it has also found applications for standard stainless steel bends. The hot extrusion process uses specialized pusher machines to heat the blank during forward movement. It is suitable for producing bends with a diameter-to-wall thickness ratio of up to 2.
Press forming, as employed in alloy bend production, has initially replaced or supplemented the conventional hot-forming process. However, for some standard alloy bends with low production quantities or excessively thick or thin walls, traditional production methods are still employed due to specific quality requirements.
Press forming processes typically involve using a blank with the same outer diameter as the finished bend. The bend is pressed directly under the constraints of a hydraulic press. Prior to the operation, the pipe is placed onto a die, and the upper die, inner core, and end die are mounted to begin restricting downward motion. This method enforces external constraints in the bending process.
In the case of alloy bends, the outer arc is subject to stretching during forming, and there is no additional metal material left to compensate economically for thinning in the outer arc section. However, the bending press process is still suitable for manufacturing heavy-walled alloy bends, especially due to its single-piece production and cost-efficiency characteristics.
