Shaanxi Faste Automotive Transmission Group Co., Ltd. was founded in 1968 and produced and sold over 1 million transmissions in 2017. Fast Company requires 50 million gears annually, most of which are manufactured by Fast Forging. Faste Forging has the ability to produce 100000 tons of forgings annually, and has a very mature system and experience in forging technology, processing equipment, mold management, and other aspects.

　

Figure 1 Common Types of Forgings on Automatic Line

Application and Practice of Mold Cooling and Lubrication on Automatic Forging Line

As a manufacturer of automotive parts, Faster Company has a high demand for forgings. Whether on automatic forging lines or ordinary forging machines, the annual cost of tooling and auxiliary materials consumed is huge. The selection of release agents is directly related to the effective service life of forging molds. Therefore, how to choose a release agent with a higher "cost performance" has become a crucial link in energy conservation and consumption reduction for Faste forging.

For automatic forging lines, the main criteria for selecting release agents are to ensure continuous production, avoid frequent shutdowns, have a longer mold life, avoid frequent mold changes, and the main form of mold failure is wear and tear for mold reuse. Additionally, the production cost (including release agent costs and mold costs) of individual forgings is the lowest. Based on these principles, we conducted an experiment on the release agent for the automatic line.

Observing the common types of forgings in automatic forging lines (Figure 1), there are some abnormal failures in the mold, as shown in Figure 2. This type of "cavitation" opening failure has never appeared on ordinary forging machines. Why does the cavity design approach, which is basically the same as that of ordinary forging machines, result in such completely different failure forms on automatic forging lines when analyzing the process and mold design process? After a period of process validation, we found that it should be related to the formation of a closed cavity during the final forging process when the mold and pre forging come into contact (Figure 3). Due to the larger spray volume of the automatic line, the liquid inside the closed chamber rapidly vaporizes in a high-temperature environment. Under the action of thousands or tens of thousands of gas "cavitation" forces, the mold forms a special failure mode as shown in Figure 2. Based on this approach, we have improved the cavity design of the automatic forging line, basically avoiding abnormal failure of the mold due to "cavitation". The release agent experiment was conducted on such a forging variety.

Figure 2: Abnormal Failure of Automatic Line Mold

　　

Figure 3 Closed Chamber

experimental condition

Experimental equipment: 3500t automatic forging line.

(2) Using molds: The third and fourth layers are key molds, and when replacing the release agent, the entire set should be replaced with a new one; The fourth mold is the key monitoring mold, and all release agent brands use the same batch of molds; The first and second molds have no impact on the experimental results and are only replaced when necessary.

Evaluation criteria

(1) Release agent dosage: The daily production ratio is 10% to 15%, and the commonly used ratio is 12%. Each release agent manufacturer can recommend the ratio based on their own product performance.

⑵ Lower top output: The maximum lower top output is 10t. When it exceeds 10t, the equipment will alarm. If the alarm is frequent, production will be interrupted.

⑶ Mold status: compare the Surface states of the mold after the mold is offline.

experimental result

(1) Mold status.

1) Is there any "cavitation" opening in the mold and the occurrence time.

Six types of release agents were selected for this experiment, two of which are commonly used. Based on the results of this experiment, it was found that even though we have improved the mold cavity and basically eliminated "cavitation", molds using four types of release agents, 3 # to 6 #, still exhibit this abnormal failure. Molds using 5 # and 6 # release agents even exhibit "openings" when only 500 to 800 pieces are produced. The mold using 6 # release agent not only had early "opening", but also caused frequent mold jumping of forgings, resulting in production not being able to proceed normally. Finally, the experiment had to be terminated. It was observed that the offline mold using 6 # release agent had produced less than 3000 pieces, but its surface had already shown severe radial grooves, indicating poor lubrication. However, the mold with 1 # and 2 # release agents is produced to about 8000 pieces, and the Surface states is still good. See Figure 4 for comparison.

Figure 4 Comparison of "cavitation" failure of six release agents

2) Other mold Surface states.

Table 1 is a statistical table of the usage of the molds after the completion of the six release agent experiments. It can be seen that except for the obvious comparison of "cavitation" failure in the final forging upper mold, there are also significant differences in the surface conditions of other molds. For example, using release agents 3 # and 6 #: severe radial grooves on the surface of the pre forged upper and lower molds are scrapped; The first piece of the final forging lower die was abnormally cracked, and the second piece was replaced. Using release agents 4 # and 5 #: Both the final forging lower die inserts have deep ring grooves and cannot be used again.

⑵ Lower jacking force.

When the output force of the 3500t automatic forging line exceeds 10t, it will alarm and stop, and it is necessary to replace the pre and final forging lower die inserts. In this experiment, molds using release agents 3 #, 4 #, and 6 # were all replaced with lower mold inserts, and even cracked lower mold inserts.

⑶ Release agent dosage.

The six demolding agents used in the experiment were all set at a mixing ratio of 12% for 1 # to 5 #, while 6 # was gradually adjusted from 12% to 20% and 24%, and finally barely produced at 24%. Therefore, theoretically speaking, the amount of release agent 6 # is greater when producing the same number of forgings.

Table 1 Mold Usage on Automatic Forging Line

Summary of lubrication for automatic forging lines.

According to the experimental results, priority is given to selecting 1 # release agent and 2 # release agent as a backup.

It should be noted that for automatic lines, due to their high level of automation and fast production pace, in order to ensure the service life of the mold and avoid abnormal failure forms such as "cavitation", the cooling and lubrication requirements for the mold are also higher. That is, not only is the spray volume higher, but for the release agent itself, in addition to basic parameters such as viscosity and concentration, the following two aspects need to be mainly considered.

1) The impact of gas production: Under the same batch of molds and the same spray state, why do the four varieties of 3 # to 6 # unexpectedly have mold cavitation openings at 500-800 pieces? The release agent 6 # even causes frequent mold jumping of forgings, which is closely related to the vaporization rate of the release agent itself at high temperatures.

2) Whether it is easy to mix evenly: The initial setting of the 6 # release agent in the experiment was 12% (the measured concentration at the outlet was only 6%), but the ejection force was too high to produce. After gradually increasing to 20% and 24%, the measured outlet concentration was only 8.8% and 11%, and ultimately produced at 24%. The observed decrease in the original solution was also abnormal, and at a 24% mixing ratio, it did not decrease as quickly as expected, but rather extremely slowly. Observing the mold, about 800 pieces showed openings, and when used for 3000 pieces, the mold had deep and long radial grooves. The poor inhalability and miscibility of 6 # lead to poor final lubrication effect.

Application and Practice of Cooling and Lubrication for Dies on Forging Machines

There are many types of forgings on forging machines, with significant changes in size and shape. Common types are shown in Figure 5. However, for different types of forgings, the main form of mold failure is normal wear and tear. The common abnormal failure forms are rapid wear, collapse, and early cracking as shown in Figure 6.

In addition to ensuring normal production, the main inspection items for lubricants used in forging machines include three points: offline mold status (considering mold reuse), residual release agent, and single piece forging cost (including release agent and mold cost). Therefore, this round of forging press release agent experiment also starts from these aspects.

Figure 5 Common Forging Shapes on Forging Press

Figure 6 Common Abnormal Failure Forms of Forging Press Dies

experimental condition

Experimental equipment: 4000t hot die forging press.

⑵ Use of molds: The second and third layers are key molds, and when replacing the release agent, the entire set should be replaced with a new one; The second upper mold and the third lower mold are the key monitoring molds, and each release agent brand uses the same batch of molds.

Evaluation criteria

(1) Mold status: Considering the subsequent surface renovation of the mold, cracking is not allowed; Compare the surface wear status of the mold after it is taken offline.

(2) Residual release agent: It is not allowed to have large scale scabs between the lower mold insert and the inner core of the lower mold.

⑶ Cost of release agent for single piece forging: Release agent manufacturers can recommend the usage ratio based on product performance.

(4) Mold cost: The difference in mold costs incurred in producing the same quantity of forgings.

——This article is excerpted from the 3rd and 5th issues of "Forging and Stamping" in 2019