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There are no gates and risers in liquid forging, so it is necessary to quantify the casting more accurately. The funnel is cast, and the funnel needs to be heated to a temperature close to the metal liquid phase to perform an "bottom" to avoid the metal liquid splashing onto the mold to cause defects. Due to the large plane size of the workpiece and the faster heat dissipation, the casting should be completed in the shortest possible time. The speed of the large hydraulic press is slow. It takes a certain time for the rapid downward transfer to the working pressurization. Therefore, after the pouring, the punch is lowered as soon as possible, so that the start The pressurization time is controlled at 5 to 8 s, and the pressurization speed is about 0.1 m/s. Too fast will cause the molten metal to splash out, causing insufficient pouring. The pressing pressure is greater than 100 MPa. This is because the rim has a certain height, the pressure is too low, and the pressure at the joint between the rim and the spoke is insufficient, and the mechanical properties are poor. The holding time is about 10s, the cooling time is 15~20s, the holding pressure cooling time is too long, the workpiece temperature is too low, the stripping force is greatly increased, the demoulding is difficult, and even the workpiece shrinkage and cracking.
 3. Treatment of annular cold partition
In the direct liquid die forging, part of the molten metal is moved up, and a cold gap is formed between the molten metal and the original molten metal surface. This cold partition is sometimes difficult to avoid, and the pouring temperature and the mold preheating temperature are increased, and the pressurization is shortened. After the time, the cold partition has been alleviated, but it cannot be completely avoided. There is still a 1~1.5mm deep cooling compartment, as shown in Figure 3. For this reason, a semi-circular arc of R2 is formed at a height formed by the cold partition on the mold, so that the cold partition is formed on the arc of the protrusion and cut off in the machining process, thus completely eliminating the influence of the cold partition.
In order to detect the mechanical properties of the hub, the heat treatment was first carried out. The heat treatment conditions were 515±5°C for 6h quenching, 175±5°C for 6h tempering, and processed into test pieces. The test results are listed in Table 1.
(1) The liquid die forging process of automobile aluminum alloy wheels is feasible, and the product performance is superior to the current manufacturing method.
(2) The process equipment is simple, the investment is small, the material utilization rate is high, and the product cost is low.
(3) The process is easy to automate and is suitable for mass production of auto parts.
references
[1] Shanghai Jiaotong University. Liquid Die Forging. Beijing: National Defense Industry Press, 1981.
[2] Qi Zhiying. Squeeze casting. Beijing: National Defense Industry Press, 1984.
[3] Zhou Dazhao et al. Application and new development of liquid die forging technology. Forging technology, 1993, 18 (5).
[4] Osawa Jialang. Current Status of Automotive Aluminum Alloy Forgings. Forging Technology. 1993, 18(6).
Application of New Process Liquid Die Forging in Automobile Aluminum Alloy Wheel Manufacturing (2)
(2) pouring and pressing
image 3
Fourth, the detection of mechanical properties of the hub
Table 1 Mechanical properties of liquid die forged wheels
-
Test piece number
Σb(MPa)
δ(%)
HB
Liquid die forging
1
314
7.4
110
2
327
7.1
104
3
321
7.0
113
average value
321
7.2
109
Low pressure casting
-
245
2.5
90
V. Conclusion
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