Fine blanking dies are characterized by countertop, crimp and small gap, etc., with bright section, good perpendicularity and flatness, high precision, and can be directly assembled and applied. However, the fine blanking die is subject to high pressure, small gap between concave and convex die, thermal effect, friction and other influences, the service life is difficult to be guaranteed, and it is necessary to carry out appropriate appearance strengthening treatment for the fine blanking die, so PVD coating treatment can be carried out. the PVD coating accumulation process of the die will not produce deformation, and therefore it can be a very good enhancement of the characteristics of the fine blanking die.
Conditions of PVD coating for fine blanking dies
1) Hardness conditions
In order to make the PVD treatment get stable effect, the hardness of the base material of fine blanking die should not be lower than HRC48, otherwise it will constitute a collapse phenomenon when it is used, and the base material will produce plastic deformation, which will cause the coating to peel off.
2) Temperature conditions
The final processing temperature of the coating should be not less than 360℃, if the processing temperature is too low, it will lead to a significant decrease in the combined performance of the coating. Special attention should be paid to, when the material using low-temperature tempering process (tempering temperature <400 ℃), if the coating treatment temperature exceeds the material's tempering temperature, will lead to the substrate material secondary tempering softening phenomenon.
Surface treatment process selection as an example:
(1) carbon die steel, low alloy die steel by low temperature tempering (such as 200 ℃), is strictly prohibited to use PVD treatment. Because the PVD process temperature (usually 300-500 ℃) will exceed the material tempering temperature, resulting in a decline in hardness.
(2) Cr12MoV steel PVD treatment to meet specific conditions:
When adopting high quenching and high tempering process (1050℃ quenching +520℃×3 times tempering), the matrix tempering temperature (520℃) is higher than the PVD treatment temperature, so it can be used safely;
If low quenching and low tempering process (980℃ quenching + 200℃ tempering) is used, it is prohibited because the PVD treatment temperature is higher than 200℃ tempering temperature, which will lead to softening of the substrate.
3)Material conditions
The materials commonly used for PVD treatment on fine blanking molds are Cr12MoV, SKD11, DC53, SKD61 and so on.
Precautions for PVD coating on fine blanking dies
1) Due to the evaporated material is difficult to accumulate to the shape of complex grooves, narrow grooves and diameter less than 3mm deep hole, so these products are not easy to constitute a coating.
2) If oxidized, corroded and other metamorphic layers are formed on the appearance of the substrate, the coating with good bonding force will not be obtained.
3) The stacking temperature of 200 ℃ or so constitute the coating, the bonding force is very poor and does not stand. In order to form a strong PVD coating, it is necessary to make the stacking temperature above 360℃.
4) Under normal processing conditions, the coating bonding force is also related to the strength of the substrate material, if working under low-pressure strong sliding conditions, the requirements for the improvement of abrasion resistance, burn resistance and demolding, the substrate hardness HRC30 has been sufficient; if the operating pressure up to 50kgmm2 sliding pressure, this time the substrate material hardness needs to be HRC50.