The Manufacturing Process of Cemented Carbide Wire Drawing Die
1. Mold Blank Processing
The core of the cemented carbide wire drawing die will shrink during the sintering process, and the amount of shrinkage varies greatly due to the difference in composition, pressing, and sintering process; due to the different shrinkage rates of each part of the mold blank, it often forms a "saddle" or "trumpet" shape.
Although the fluctuation of the shape and size of the mold blank meets the mold standard, it far exceeds the interference requirement of the mold group, which leads to serious uneven prestress of the mold core during mold loading, and greatly reduces the service life of the mold.
Therefore, the mold blank must be ground externally, and a special fixture must be used on the grinding machine to grind it with a diamond grinding wheel.
2. Interference Amount of Installation Settings
In order to obtain a certain prestress of the mold core during installation, 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 size and deviation of the mold core, the draft stress, and the method of the sleeve.
There are two types of mold sets: hot pressing method and cold pressing method. The cold pressing method has a small interference and a small precompression stress.
It is mostly used to make wire drawing dies with smaller specifications and draw soft metals.
3. Mold Sleeve Processing
The molded sleeve is formed by turning on a lathe, and the control points during processing are as follows:
(1) The roughness of the inner diameter of the mold sleeve must reach 0.80-I.6m, which is conducive to close cooperation 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 of each mold is accurate;
(3) The bottom surface of the inner hole of the mold sleeve must be parallel to the outer end surface of the mold, and ensure that it is perpendicular to the center line of the mold hole after installation;
(4) The ellipticity of the inner hole of the mold sleeve should be as small as possible, not more than 0.02mm. When hot-loading, the outer surface of the mold sleeve should be polished and smooth to ensure uniform cooling after installation.
4. Mounting Process
The cold press mounting process involves pressing the blank into a mold sleeve with a press at room temperature.
The cold pressing method requires accurate interference between the mold core and the sleeve, and high dimensional accuracy. The advantage is that no heating equipment is required, which saves energy and reduces costs.
