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Manufacturing process of the carbide wire drawing dies

1. Die blank processing
The core of the carbide wire drawing will shrink during the sintering process, and the shrinkage amount varies greatly depending on the composition, pressing and sintering process; Due to the different shrinkage of each part of the mold blank, it often forms a “saddle” or “flare” shape. The fluctuation of the shape and size of the mold blank, although it meets the mold standard, far exceeds the interference amount requirements of the mold set, resulting in serious uneven prestress of the mold core during mounting, and the service life of the mold is greatly reduced. Therefore, the mold blank must be externally ground, and special fixtures must be used on the grinding machine and ground with diamond grinding wheels.


2. Interference amount of mounting setting
To obtain a certain prestress of the mold core during mounting, the diameter of the inner hole of the mold sleeve should be smaller than the outer diameter of the mold core. The difference between the two is called the interference amount. The amount of interference should be determined according to the mold core size and deviation, pulling stress and sleeve method. Table 1 shows the actual interference amount when the mold is mounted. The mold set is set with two kinds of hot pressing method and cold pressing method, the amount of interference of the cold pressing method is small, and the pre-compression stress obtained is also small. It is mostly used to manufacture wire drawing dies with smaller specifications and drawing soft metals.


3. Mold sleeve processing
The molded sleeve is formed by turning on a lathe, and the control points in the processing are as follows:
(I) The roughness of the inner diameter of the mold sleeve must reach 0.80-I.6 m, which is conducive to a close fit with the mold sleeve;
(2) The inner diameter of the mold sleeve should correspond to the outer diameter of the mold blank to ensure that the interference amount of each mold is accurate;
(3) The bottom surface of the inner hole of the mold sleeve must be parallel to the outer end of the mold, and ensure that it is perpendicular to the center line of the mold hole after installation;
(4) The ovality of the inner hole of the mold sleeve should be as small as possible, not greater than 0.02 mm. During hot installation, the outer surface of the mold sleeve should be polished to ensure uniform cooling after installation.

4 Mounting Process
The cold-pressing mounting process involves pressing the blank into the mold sleeve with a press at room temperature. The cold pressing method requires an accurate interference amount and high dimensional accuracy requirements for the mold core and sleeve. The advantage is that no heating equipment is required, saving energy and reducing costs.

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