Four important steps in the production of cemented carbide wire drawing dies

1. Cemented carbide die blank processing

Carbide wire drawing die cores will shrink during the sintering process. Different batch numbers have different shrinkage due to differences in composition, pressing and sintering processes. Each part of the die blank often forms a "saddle" or "saddle" due to the difference in shrinkage. "Bell mouth" shape. Although the fluctuations in the dimensions of the die blanks meet the standards of the die blanks, they far exceed the interference requirements during die set mounting, resulting in serious unevenness in the prestress of the die core during mounting and greatly reducing the service life of the mold. Therefore, the die blanks must For external cylindrical grinding, a special fixture is required on the grinder and a diamond wheel is used for grinding.

2. The interference of cemented carbide die steel set inserts

In order to obtain a certain prestress of the mold core during installation, the inner hole diameter of the mold sleeve should be smaller than the outer diameter of the mold core, and the difference between the two is called the interference. The amount of interference should be determined according to the die core size and deviation, drawing stress and inserting method. Table 1 shows the actual interference when the mold is installed. The die set is inlaid with hot pressing and cold pressing. The cold pressing method has a small interference and a small pre-pressing stress. It is mostly used to make small-sized wire drawing dies for drawing soft metals.

3. Cemented carbide die set processing

The die sleeve is formed by turning on a lathe, and the control points during processing are as follows:

(I) The inner diameter roughness of the die sleeve must reach 0.80-I. 6 m, which is conducive to close cooperation with the mold sleeve;

(2) The inner diameter of the mold sleeve must correspond to the outer diameter of the mold blank to ensure the accuracy of the interference of each mold;

(3) The bottom surface of the inner hole of the mold sleeve and the outer end of the mold must be parallel, and ensure that it is perpendicular to the center line of the mold hole after the sleeve is installed;

(4) The ovality of the inner hole of the die sleeve should be as small as possible, and should not be greater than 0.02 mm. The outer surface of the mold sleeve should be polished during hot assembly to ensure uniform cooling after assembly.

Table 1 Mould set with interference

4. Hard alloy mold assembly process

The assembling process of the cold pressing method is to press the mold blank into the mold sleeve with a press at room temperature. The cold pressing method requires accurate interference and high dimensional accuracy of the mold core and mold sleeve. The advantage is that it does not require heating equipment, saves energy and reduces costs.