To increase the durability of the working surfaces of dies and molds, as well as to obtain a glossy shine on punches and dies, they are subjected to chrome plating. This process involves saturating or precipitating the workpiece area with a chromium layer using electric current. It not only increases the strength and durability of structures, but also prevents adhesion of the press material, protects them from the formation of corrosion.
FEATURES OF CHROMINATION
For the stability of the metal to any load and other production purposes, choose the thickness of the applied layer is 0.02 or 0.06 millimeters. If you want to create a reliable protection against rust and its spread, these values are significantly reduced from hundredths to thousandths. Too thick coating is fraught with the fact that it can be deformed. It often cracks and flakes. To avoid damage, it is better to follow the generally accepted rules and regulations, choosing the appropriate thickness.
In addition, it should be borne in mind that working areas are coated with chromium only after heat treatment. In other words, punches and dies must first be quenched. Then they are subjected to grinding and pre-polishing. As soon as these operations are observed, you can start chrome plating. Carrying out all these effects, you need to remember about the features of machining. It is always carried out taking into account the applied layer. As for the chromium itself, it should also be uniform (even in the corners). For hard-to-reach places, special anodes and screens are used. They are placed above the sharp and convex parts of the work items. After coating, the treated area is carefully polished. As a result of all manipulations, the wear resistance of the mold increases at least three, maximum six times.
Processing of matrices is almost always takes place using an anode. Moreover, for maximum accuracy, its shape should repeat the shape of the recesses and holes. During installation, it must be centered with respect to all chrome cavities. Defective coatings are removed with a 50% aqueous solution of hydrochloric acid. It adversely affects the quality of steel, therefore, a 20% alkali solution is often used instead. After it, the mirror surface is not deformed and remains unharmed.
The technology works the same for all stamps and as follows. To begin with, select the most suitable shaped anodes, they can be equipped with individual current control. In this case, for ease of installation and further action, a brass rod is placed in the middle of the element, it is fixed by means of a lead alloy and current is conducted to the projecting end.
As mentioned above, the process of such processing is regulated by the relevant norms and standards of GOST. They, in turn, recommend the use of sulfate little concentrated electrolyte for chrome plating of press forms. For more complex instruments, the electrolyte temperature is raised. This makes it possible to reduce the risk of burning the substance on the ledges. At the very beginning, a current boost is given for about 10-15 seconds. During work with complex structures, the distance between the electrodes is reduced to 1 or 1.5 centimeters. It remains the same throughout the treated surface.
Very often, for convenience, experts use special suspension devices. They are universal and allow you to fix the anode well using different positions.