JPH04304298A - Lubricant for warm plastic working - Google Patents

Abstract

PURPOSE:To provide a lubricant which is used for forming a lubricating film by electrostatic spraying, reveals particularly excellent lubricating performance in warm plastic working, and is easy to remove after working. CONSTITUTION:20-80wt.% molybdenum disulfide is mixed with a non-glass insulant binder comprising, e.g. a polyester, fluororesin, rosin, sericite, sepiolite, talc, pyrophyllite, bentonite or fluorocarbon to give a powdery material. The powdery material is in the form ((1), (3), (4), (5), (7) or (8)) having a constitution wherein smaller particles adhere to the periphery of a central larger particle or in the form ((1) or (6)) having a constitution wherein a larger particle carries smaller particles in the inside thereof, and it is adjusted to a particle diameter of 30-50mum. Molybdenum disulfide alone cannot form a lubricating film in warm working temperature by electrostatic spraying; the use of the insulant binder enables good adhesion.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an electrostatic spray lubricant for forming a lubricant film that is sprayed in an electrically charged state toward a grounded workpiece, and in particular, the present invention relates to a lubricant for forming a lubricant film by electrostatic spraying, which is sprayed in a charged state toward a grounded workpiece. Regarding lubricants suitable for plastic working.

0002

BACKGROUND OF THE INVENTION In recent years, expectations for warm forging have increased due to the need to reduce the cost of various parts in a wide range of fields such as automobiles, electronics, electrical machinery, and construction. However,
Forging with difficult-to-work materials such as stainless steel was difficult because there was no effective lubricant for warm forging. On the other hand, even if a lubricant effective for warm forging of difficult-to-process materials was developed, there was no means to form a uniform and good lubricant film. Especially like headers and parts formers,
In the forging method that starts from a coil, there was no means to apply lubricant to the end face of the steel material.

Against this background, very recently a method of forming a lubricating film using electrostatic spraying has been developed (Japanese Patent Application No. 2-167497, Japanese Patent Application No. 2-184).
No. 988). Therefore, it can be said that the problem of how to form a good lubricating film has been solved separately.

[0004] Furthermore, in Japanese Patent Application No. 2-293350, a proposal was made that it would be better to use a powder made by blending a resin that melts with heat with glass or titanium oxide for these electrostatic sprays. It's arrived.

With these proposals, on the surface of the workpiece,
Compared to the lubricating oils previously used in forging, it was able to form a good and uniform lubricating film with far superior lubrication performance, making it possible to forge difficult-to-process materials.

[0006]

However, as a recent trend, so-called black lubricants such as molybdenum disulfide and graphite tend to be avoided because they pollute the environment. For these reasons, glass-based lubricants and polymer resin-based lubricants are attracting attention.

However, glass-based lubricants have the problem that they are difficult to remove from products during post-processing, and that they may remain in molds and cause so-called scum clogging. The difficulty of removing such glasses from products becomes a particular problem in warm plastic working where strong working is performed.

[0008] Therefore, when used in forming such an electrostatic spray-type lubricant film, a lubricant that exhibits particularly excellent lubrication performance for warm plastic working and that is easy to remove from products and molds after processing is needed. The present invention was completed with the first objective of providing the following.

[0009] In addition to achieving this first objective, the present invention was completed with the second objective of providing a form of lubricant that is easy to handle in electrostatic spraying and can exhibit stable lubricity. did.

0010

[Means and operations for solving the problem] In order to achieve the first object, there is provided a lubricant for forming an electrostatic spray lubricant film that is sprayed in a charged state toward a grounded workpiece, comprising: We have invented a lubricant for warm plastic working consisting of a powder containing molybdenum disulfide and a non-glass insulating binder.

Incidentally, like graphite, molybdenum disulfide is known to have excellent lubricating performance as a solid lubricant with a layered structure. Furthermore, molybdenum disulfide is a poor conductor at room temperature, but exhibits electrical conductivity when the temperature rises. On the other hand, in order to spray in a charged state by electrostatic spraying, the material must not be electrically conductive.

[0012] Therefore, the warm plastic working temperature (200 to 80
At 0°C, especially 400 to 600°C, it is impossible to form a lubricating film on the surface of a workpiece by electrostatically spraying only molybdenum disulfide.

In order to confirm this, we investigated molybdenum disulfide (Mo), which changes between a poor conductor and a good conductor depending on the temperature.
S2 ), boron nitride (BN), which is always a bad conductor,
Table 1 shows the observation results of the adhesion state when graphite (C), which is always a good conductor, was electrostatically sprayed with a single powder. As the electrostatic spray, a commercially available electrostatic spray for painting was used, and the adhesion status was visually observed.

[0014]

[Table 1]

In this way, molybdenum disulfide alone has 2
The adhesion condition worsened at 00°C, and no adhesion occurred at temperatures above 400°C. Therefore, we used various insulating materials as binders and
Table 2 shows the results of checking the adhesion status when electrostatically spraying a blended powder containing 0% by weight at 400°C. Regarding this, the results of similarly checking the adhesion status of boron nitride and graphite are shown as a comparative example.

[0016]

[Table 2]

As can be seen from this table, since boron nitride has the property of adhering even as a single substance, good adhesion was achieved even when mixed with any insulating binder. On the other hand, molybdenum disulfide and graphite showed good adhesion when sericite, rosin, and polytetrafluoroethylene were used as binders;
No adhesion occurred when lead glass was used as the binder. Furthermore, when polyester was used as the binder, a small amount of molybdenum disulfide was attached. This adhesion condition was also determined by visual inspection, but when the surface was observed after an extrusion test, it was found that very small amounts of disulfide were present even in mixtures of molybdenum disulfide and phosphate glass or lead glass. It was confirmed that there was molybdenum attached.

In this way, in order to apply molybdenum disulfide as a lubricant for warm plastic working by electrostatic spraying,
It is effective to add an insulating binder, but for some reason glass-based binders did not work. In other words, it has been found that even if the material is an insulator, it is necessary to incorporate a non-glass type material as a binder. Furthermore, molybdenum disulfide has superior lubricating performance compared to graphite and boron nitride.

From this viewpoint, the present invention having the above-mentioned structure was completed as a lubricant for warm plastic working. As a result of being able to adhere molybdenum disulfide well to the end face of the workpiece, it is possible to prevent it from scattering to the surroundings, and it does not cause environmental pollution despite its black color.

In other words, by providing a new form of lubricant in which molybdenum disulfide, which is avoided due to its black color, is blended with a non-glass-based insulating binder, it can be used for electrostatic spray type lubrication. When used in a film forming method, it exhibits good lubrication performance during warm plastic working, has little adhesion to molds, and does not cause environmental pollution.

In the lubricant for warm plastic working of the present invention, the blending ratio of molybdenum disulfide is preferably 20 to 80% by weight. This is because if the blending ratio of molybdenum disulfide is less than 20% by weight, the lubricating performance of molybdenum disulfide itself cannot be fully exhibited. Furthermore, if the blending ratio of molybdenum disulfide exceeds 80% by weight, the amount of the insulating binder becomes insufficient, making it impossible to properly adhere molybdenum disulfide to the surface of the workpiece.

In addition to the above-mentioned sericite, polyester, fluororesin, and rosin, the non-glass insulating binder used in the present invention may include various insulating resins, sepiolite, talc, pyrophyllite, bentonite, and other insulating resins. Minerals can be used. Another option is carbon fluoride, although it is expensive. Both are common non-glass insulating materials.

In addition, in order to achieve the second objective, in the above-mentioned lubricant for warm plastic working, the powder after blending is composite particles containing a non-glass insulating binder and molybdenum disulfide. It is desirable that it be adjusted to

Specifically, as shown in FIG. 1, particles have a two-layer structure in which one of a non-glass-based insulating binder or molybdenum disulfide is attached at the center, and the other is attached around it (as shown in the figure). (■, ■, ■, ■, ■, It is recommended to adjust to (■, ■).

From the viewpoint of ease of handling and no variation in properties such as concentration and composition, the
, ■ It is desirable to prepare composite particles with the following shapes. Moreover, regardless of the form, each composite particle is desirably adjusted to a particle diameter of approximately 30 to 50 μm so that it can be easily electrostatically sprayed and transported.

For example, the illustrated particles (■) and (■) are prepared in advance by 30
It can be adjusted by mixing insulating binder particles granulated to ~50 μm with fine molybdenum disulfide particles. Since molybdenum disulfide has a very sticky property, it is sufficient to simply mix it. This is thought to be due to the arrangement of S in its molecular structure.

On the other hand, in the case of ① and ② shown in the figure, similar to the granulation of ceramics, a fine insulating binder and molybdenum disulfide are mixed in a slurry state dissolved in a medium, sprayed and granulated, and dried. It can be manufactured by

Furthermore, by mixing or coating large molybdenum disulfide particles with a fine slurry of an insulating binder and drying the mixture, lubricant powders having the shapes of (1) and (2) shown in the figure can be obtained. At this time, if the insulating binder is sparsely adhered, it is possible to obtain the objects shown in the figure (■) and (■).

[0029]

[Example] Next, in order to further clarify the present invention, as shown in FIG.
A lubricant was applied to the end face 1a of a cylindrical SUS304 steel test piece 1 with a height of 30 mm by electrostatic spraying, and this was set in the mold 3 and pressed under warm plastic working conditions at a working temperature of 400°C. Extrusion was performed and lubrication performance etc. were confirmed. The lubrication performance is determined by the extruded portion 5a of the T-shaped product piece 5 after extrusion processing.
The size of the height h and the circumferential roughness at the 1/2h position (
This can be determined from the magnitude of Rmax). Hereinafter, the method for evaluating the lubrication performance by this extrusion process will be referred to as a spike test, and the extruded portion 5a will be referred to as the spike portion 5a, and the height h thereof will be referred to as the spike height h. In addition, in this spike test, extrusion processing was performed while commercially available auxiliary lubricating oil was dripped to cool the mold 3.

[0030] The lubricant contains a lubricant such as molybdenum disulfide (MoS2), boron nitride (BN), or graphite (C), and sericite, phosphate glass, polyester, rosin, lead glass, or polyester. Tetrafluoroethylene with any insulating binder in a weight ratio of 50:
The mixture was used at a temperature of 50°C. As for molybdenum disulfide, due to its tendency to stick together, the blended powder is in the form of ■ or ■ in FIG. Also,
The particle size is in the range of 30 to 50 μm.

Table 3 shows the measurement results of the spike height h for each combination of lubricant and insulating binder in two cases. The unit is mm, and it means that the larger the spike height h is, the better the lubrication performance is.

Table 4 also shows the measurement results of the circumferential roughness Rmax at 1/2 h for each combination of lubricant and binder, two examples each. The unit is μ, and the smaller the value, the smaller the friction during the spike test, that is, the better the lubrication performance.

[0033]

[Table 3]

[0034]

[Table 4]

As can be seen from Table 3, molybdenum disulfide (
MoS2) had the best lubricity in combination with any binder. Furthermore, when using phosphate glass or lead glass as a binder, almost no molybdenum disulfide was attached, but these low-melting glasses themselves adhered well, and the lubrication performance of these glasses is expressed as the spike height h. ing. Therefore, it is shown in parentheses as mere reference information.

Looking more closely, molybdenum disulfide has a spike height of approximately 13 mm when a non-glass insulating material such as polyester, rosin, polytetrafluoroethylene or sericite is used as a binder. From the above, it was found that the combination with polytetrafluoroethylene resulted in a spike height of approximately 14 mm, and the warm lubrication performance was considerably better than other examples using boron nitride or graphite as the lubricant.

On the other hand, according to Table 4, when boron nitride is used as a lubricant, the circumferential roughness Rmax is the largest regardless of the combination with the binder, and the lubricating performance is inferior among the three. Do you get it.

On the other hand, when molybdenum disulfide is used as a lubricant, the roughness Rmax in the circumferential direction is extremely small.
It was found that the lubrication performance was also good from this point of view.

The specimen using graphite as the lubricant also had a small circumferential roughness Rmax, indicating good lubrication performance. In addition, in this table as well, items using phosphate glass or lead glass as a binder are shown in parentheses because these are just the properties of the binder itself, and are reference information that cannot be compared. It means.

Next, each lubricant was compared from the viewpoint of post-treatment of the product piece 5 and the mold 3 after processing. First, Table 5 shows the adhesion force of the lubricant to the mold 3. The weaker the adhesion force, the easier the post-processing is, and the less likely it is that clogging will occur during actual processing. Regarding the strength of adhesion, the lubricant that adhered to the tapered hole 3a of the mold 3 is judged to be "weak" if it can be removed by simply rubbing it with a cloth, and the amount of effort required to remove it with sandpaper is judged as "weak". They were rated on a three-point scale, ``strong'' or ``very strong.'' Here, too, examples of low-melting point glass-based binders to which lubricating substances could not be adhered well are shown in parentheses.

[0041]

[Table 5]

As can be seen from this table, boron nitride (BN) was slightly superior to others only when using sericite as a binder in terms of adhesion to the mold 3, but when using other binders, Molybdenum disulfide (M
There was no difference between oS2) and boron nitride (BN).

Next, Table 6 shows the adhesion force of the lubricant to the product piece 5. Similar to the case with the mold 3, the weaker the adhesive force is, the simpler the post-processing is. The strength of the adhesion is determined by the lubricant adhering to the spike portion 5a of the product piece 5.
Those that could be removed by alkaline degreasing were rated as "weak," and those that required cleaning with fluoronitric acid (HF/HNO3) were rated as "strong." Here, too, examples of low-melting point glass-based binders to which lubricating substances could not be adhered well are shown in parentheses.

[0044]

[Table 6]

From this table, it was found that when polyester is used as a binder, when boron nitride (BN) is used as a lubricant, the adhesion to the product is strong and post-treatment is troublesome. On the other hand, molybdenum disulfide (M
It was found that when oS2) was used as a lubricant, alkaline degreasing was sufficient and post-treatment was simple.

[0046] Comprehensive evaluation of the results shown in Tables 3 to 6 shows that a lubricant made of a combination of molybdenum disulfide and a non-glass insulating material is superior to other lubricants in the post-treatment of molds and products. It is not inferior in particular, and the spike height h is about 10% better than the others, and the circumferential roughness Rmax is also the best at about 1/2 that of boron nitride, and it is the best in terms of comprehensive evaluation of post-treatment and lubrication performance. I understand.

Furthermore, as is clear from Table 2, it was found that it is inappropriate to use a glass-based insulating material as a binder for electrostatic spraying. Conversely, if the binder is an insulating material such as sericite, polyester, rosin, or polytetrafluoroethylene,
Since molybdenum disulfide can be adhered well to the end face of the workpiece and does not scatter into the environment, it does not cause environmental pollution even if it is black in color.

As a result, by using molybdenum disulfide as a lubricant and forming a lubricating film on the workpiece using electrostatic spraying of a powder containing a mixture of molybdenum disulfide and a non-glass insulating material,
It was found that good lubrication performance was obtained during plastic processing such as warm forging and extrusion, and that it could be used without causing the environmental pollution problems peculiar to molybdenum disulfide.

It goes without saying that the present invention is not limited to these embodiments, and can be realized in various forms without departing from the spirit thereof.

[0050]

According to the lubricant for warm plastic working according to claim 1 or 2, molybdenum disulfide can be adhered well to a workpiece by electrostatic spraying,
It exhibits particularly excellent lubrication performance during warm plastic processing, making it easy to remove from products and molds after processing. As a result, even difficult-to-work materials can be plastically worked well by warm plastic working, and processing costs can be significantly reduced. In addition, because end face lubrication can be performed without dispersing molybdenum disulfide into the environment, there is no need to consider environmental pollution even if the molybdenum disulfide itself is black.

Furthermore, according to the lubricant for warm plastic working as composite particles according to claims 3 to 5, especially claims 4 and 5, it is convenient to handle when performing electrostatic spraying. With this, a lubricating film with uniform concentration and properties can be formed, and the good properties as a lubricant for warm plastic working according to claim 1 or 2 can be stably exhibited.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram illustrating the form of lubricant powder.

FIG. 2 is an explanatory diagram showing the contents of a spike test as a method of evaluating lubrication performance.

[Explanation of symbols]

1... Test piece, 3... Mold, 5... Product piece.

Claims (5)

[Claims] [Claim 1] An electrostatic spray lubricant for forming a lubricant film that is sprayed in a charged state toward a grounded workpiece, which is a mixture of molybdenum disulfide and a non-glass-based insulating binder. A lubricant for warm plastic processing made of powder. 2. The blending ratio of the molybdenum disulfide is 2.
The lubricant for warm plastic working according to claim 1, characterized in that the content is 0 to 80% by weight. 3. The blended powder is adjusted to composite particles containing a non-glass insulating binder and molybdenum disulfide. Lubricant for warm plastic processing. 4. The composite particle according to claim 3, wherein the composite particle has a two-layer structure in which one of a non-glass-based insulating binder and molybdenum disulfide is centered and the other is attached around it. The lubricant for warm plastic working described above. 5. The composite particles are characterized in that they have a mixed structure in which particles of one of the non-glass-based insulating binder and molybdenum disulfide are dispersed and supported therein. 3. The lubricant for warm plastic working according to 3.