Die steel material selection and surface treatment

During the production process, we encountered some problems affecting production efficiency. In the process of punching the parts, due to the wear and tear of the punching die or breakage of the punching die, and there is a great randomness, it is necessary to stop the machine to change the needle more frequently, which greatly affects the production. To this end, we tested two die steels, ASP23 from Sweden ASSAB and SKD11 from Taiwan. ASP23 has high hardness, so it is not easy to wear, but its toughness is slightly worse; SKD11 has good toughness and is not easy to break, but its hardness is low, and it is easy to wear and fail. In terms of price, ASP23 is significantly more expensive than SKD11, ASP23 is several hundred yuan per kilogram, and SKD11 is tens of yuan per kilogram.

In order to better improve the performance of die punching needles, we have found many companies engaged in surface treatment. Among them is a company in Shenzhen that is coated with titanium nitride (TiN), and a Hong Kong company is coated with diamond-like carbon (DLC) film, and there is also a Beijing company that provides amorphous diamond (ta-C) coating. We are all familiar with titanium nitride (TiN).

It is a mature technology with a wide range of applications. In recent years, the application of diamond-like carbon (DLC) films has gradually emerged. Amorphous diamond (ta-C) ) Coating is a brand new technology. For the test results of the three companies, we have made a comparison: the effect of titanium nitride (TiN) coatings is not obvious, not as advertised in the market; the effect of diamond-like carbon (DLC) coatings is slightly better than that of titanium nitride (TiN); We are quite satisfied with the effect of amorphous diamond (ta-C) coating.

In the first amorphous diamond (ta-C) coating test, the average life of all SKD11 plating parts has been increased by 3 times, and the average life of ASP23 plating parts The average life span has doubled, and the life span of all plated parts has been increased evenly. Usually, the new technology has the problem that the process is not stable enough. In order to verify the stability of this technology, we conducted a second test.

The same use of ASP23 and SKD11 die steel, and the number of plated parts is more than the first test, the test results surprised us, the average life of ASP23 plated parts increased by 2 times, and the average life of SDK11 plated parts increased We asked the company’s technicians about this by nearly 7 times. They explained that the coating process has been optimized and adjusted, so the coating effect is better.

Since the cost of SKD11 is significantly lower than ASP23, and the coating effect is better than ASP23, we adopted SKD11 coating products provided by this surface treatment company in Beijing.

We later asked the technicians of this company in Beijing why the effects of diamond-like carbon (DLC) and titanium nitride (TiN) were not ideal. They said that their technical working temperature is at room temperature, usually below 80 degrees Celsius. The film forming temperature of diamond-like carbon (DLC) and titanium nitride (TiN) is usually several hundred degrees.

The higher temperature causes the steel to produce an annealing or tempering effect, which reduces the quality of the original steel; the combination of the film and the substrate Force is also an important factor affecting the effect. Diamond-like carbon (DLC) and titanium nitride (TiN) coatings are usually chemical vapor deposition (CVD) methods. The film is only deposited on the surface of the plated part. Amorphous diamond coatings use advanced surfaces.

Ion activation technology, so that the coating penetrates into the substrate surface, and the film-base bonding force is significantly improved. During the stamping process, the film layer is not easy to fall off; in terms of surface hardness, the hardness of diamond is higher than that of titanium nitride (TiN). The content of pure diamond in the crystalline diamond film is more than 70%, and the content of the diamond-like film is usually only 20%, and the highest is only 60%. Therefore, the hardness of the amorphous diamond film is the highest among the three; in terms of surface finish, non- The friction coefficient of the crystalline diamond film is lower than 0.10, the titanium nitride (TiN) film is 0.55, and the diamond-like carbon (DLC) film is 0.15.

After starting to use the amorphous diamond film punching needle, we carried out the coating test of the tap again. The test results are roughly as follows: the effect of coating the tap with oxide layer is not obvious, while the life of the tap without oxide coating is increased by an average of 3 times. The effect is evident.