"Porous" is widely recognized in the industry as "porous mold." The extrusion process using the "one-mode porous" technology represents an advanced manufacturing method that enhances yield, production efficiency, and profile quality. This technique significantly contributes to energy savings, labor reduction, land conservation, and cost control, aligning with national policies on energy conservation and emission reduction. It plays a crucial role in promoting sustainable development.
1. Mold Design and Manufacturing
In the design of "one-mode porous" molds, optimization is key. When placing the pores, it's essential to consider the steel’s strength and avoid spacing that is either too large or too small. A symmetrical layout is recommended, with holes typically placed horizontally. If a top-and-bottom arrangement is necessary, staggered placement is advised. High-precision machining equipment is critical for mold production. For example, splitting holes and welding chambers are best processed using CNC machining centers, while cavities are cut via slow wire cutting to ensure verticality, parallelism, and smoothness of the working belt.
2. Extrusion Production Process Control
2.1 Process Parameters
2.1.1 Bar Temperature: The temperature range for the bar in porous dies is generally between 390°C and 480°C. A step-cooling method is used, starting from the upper limit and gradually decreasing by 10°C until reaching the lower limit.
For the split-mode porous die, the bar temperature usually ranges between 430°C and 500°C, following a similar cooling approach.
2.1.2 Mold Temperature: Typically maintained between 430°C and 480°C.
2.1.3 Ingot Cylinder Temperature: Usually controlled between 410°C and 440°C, with the upper limit adjustable based on actual conditions.
2.1.4 Outlet Port Temperature: Normally kept between 520°C and 580°C. Too high or too low can affect material hardness and profile quality.
2.2 Process Operation Requirements
2.2.1 Aluminum Rod Heating: Heated in a rod furnace, with partition control heating methods commonly used. For porous molds, the heating mode is generally from high to low, ensuring even heating.
2.2.2 Mold Heating: Typically takes 6 hours, with the mold heated together with the pad and sleeve. Overheating should be avoided to prevent surface and material issues.
Molds should be placed in the center of the furnace, away from walls and fans, with at least 5 cm clearance between them. The furnace must remain clean to prevent dust contamination.
2.3 Extrusion Process Control
2.3.1 The time between removing the mold and extrusion should not exceed 3 minutes.
2.3.2 The first rod should be short (200–300 mm) and extruded under the “0†section.
2.3.3 The extrusion speed should be gradually increased after initial material output.
2.3.4 Use high-temperature pads and graphite plates to prevent scratches and damage.
2.3.5 Adjust the tractor pulling force to maintain dimensional accuracy.
2.3.6 Normal extrusion speed is around 30–40 m/min.
2.3.7 Quenching, air cooling, or water cooling must follow alloy requirements.
2.3.8 Avoid random shutdowns. If the machine stops for more than 3 minutes, the mold must be reheated to 500°C. It's better to remove and reinsert the mold to ensure consistent profile quality.
2.4 Outlet Profile Temperature and Speed Control
2.4.1 Adjust rod temperature based on outlet profile temperature.
2.4.2 The discharge profile temperature should be between 520°C and 580°C. Below 520°C may cause insufficient hardness; above 580°C risks defects.
2.4.3 If the profile turns black, immediately reduce rod temperature and extrusion speed.
2.4.4 Operators must constantly monitor temperatures, profile surfaces, and equipment status. Any issue must be addressed immediately to prevent mold damage.
3. "One-mode Porous" Extrusion Equipment
Achieving "one-mode porous" technology requires advanced equipment such as twin-tractor machines, flying saws, mold systems, rod heating furnaces, and long-spindle hot-shear technology. These tools are essential for improving extrusion yield, production efficiency, and output stability.
4. Conclusion
With continuous improvements in the extrusion process, the efficiency and yield of "one-mode porous" technology are steadily increasing. However, due to variations in equipment, mold materials, and extrusion processes among companies, the development of this technology varies across industries.
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