KR20150086393A - Lubricant for dies - Google Patents

Abstract

It is an object of the present invention to provide a lubricant for a mold capable of further improving the service life of a mold as compared with a conventional lubricant. The lubricant for a mold according to the present invention contains a lubricating oil and calcium hydroxide (Ca (OH) ₂ ) and contains calcium hydroxide in a volume fraction of 20% or more.

Description

LUBRICANT FOR DIES}

The present invention relates to a lubricant for a mold to be coated on the surface of a mold.

As a means for extending the service life of a mold for press forming, there is a shot peening method in which a shot material such as a forcible is projected onto the surface of a mold. By performing the shot finishing method, numerous irregularities are formed on the surface of the mold, and the life of the mold is improved by the tribological effect. In addition, the shot pinning method generates residual compressive stress on the surface of the mold, thereby improving the fatigue life and the like of the mold.

For example, Japanese Patent Laying-Open No. 2007-56333 (Patent Document 1) discloses an example of a shot pinning method.

Patent Document 1: Japanese Patent Laid-Open No. 2007-56333

However, when shot peening is performed using a fine shot material (for example, a particle diameter of 50 탆 or less), the convex shape of the concavo-convex shape formed on the surface of the mold tends to be sharp. When the convex shape becomes sharp, the coefficient of friction of the surface of the mold becomes large, so that seizure occurs between the workpiece and the surface of the mold, resulting in a reduction in the life of the mold and a problem of molding cracks.

For this reason, a lubricant which improves the life of the mold by coating the surface of the mold is used. Conventionally, molybdenum disulfide (MoS ₂ ) and graphite are generally used as lubricants of this kind. When molybdenum disulfide is used, it is mixed with, for example, a work oil.

Use of a lubricant containing molybdenum disulfide can somewhat improve the service life of the mold, but it has not yet been achieved to achieve a desired lifetime improvement. Further, the lubrication effect by the graphite is high, but the graphite is expensive, has a cost problem, and is not preferable from the environmental standpoint.

The present invention has been made in view of the problems in the conventional lubricant for a mold, and it is an object of the present invention to provide a lubricant for a mold which can further improve the service life of the mold as compared with the conventional lubricant.

In order to achieve the above object, the present invention provides a lubricant for a mold comprising a lubricating oil and a calcium hydroxide (Ca (OH) ₂ ) mixed in the lubricating oil, wherein a lubricant for a mold containing the above- to provide.

In the lubricant for a mold according to the present invention, it is preferable that the calcium hydroxide has an average particle diameter determined according to the following formula.

log H ≥ log D and D <40 탆

H: Maximum irregularity of the mold surface

D: average particle diameter of calcium hydroxide

In the lubricant for a mold according to the present invention, it is preferable that the average particle diameter of the calcium hydroxide is not more than 1/2 of the initial particle diameter of the calcium hydroxide after the molding of the mold.

In the lubricant for a mold according to the present invention, it is preferable that the calcium hydroxide is produced from a baked shell as a raw material.

By applying the lubricant for a mold according to the present invention to the surface of a metal mold, it is possible to increase the internal galling load as compared with the case of using a conventional lubricant (molten metal with a working oil + molybdenous disulfide) The coefficient can be lowered.

Specifically, in the case of using a conventional lubricant (molybdenum disulfide + molybdenum disulfide), the internal golfering load was about 2600 kgf and the friction coefficient was about 0.13. In contrast, in the case of using the lubricant for mold according to the present invention, The maximum load was about 3600 kgf and the friction coefficient was about 0.08 at the minimum.

Since the lifetime of the mold increases as the internal rolling load becomes larger and the friction coefficient of the surface becomes smaller, the life of the mold can be surely increased by using the lubricant according to the present invention.

In addition, the inner gulling load refers to a load when a seizure occurs between the surface of the metal mold and the workpiece, as will be described later.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the relationship between the content (volume%) of calcium hydroxide and the internal golfering load (kgf) in a mold lubricant according to a preferred embodiment of the present invention;
Fig. 2 is a diagram showing an outline of a drawbead test performed when measuring the inner golring load. Fig.
3 is a graph showing the relationship between the maximum irregularity difference H on the surface of the mold and the average particle diameter D of calcium hydroxide.
4 is a graph showing the relationship between the pushing load (kgf) in the draw-bead test shown in Fig. 2 and the friction coefficient of the mold surface.
5 is a graph showing the relationship between the pushing load (kgf) in the drawbead test when the content of calcium hydroxide is changed and the friction coefficient of the surface of the mold.

The lubricant for a mold according to a preferred embodiment of the present invention contains a lubricant and calcium hydroxide (Ca (OH) ₂ ) mixed in the lubricant.

Any work can be used in the workshop. For example, a commercially available lubricating oil can be used.

The calcium hydroxide is contained at a ratio of 20% or more with respect to the volume of the entire lubricant.

That is, when the volume of the operation oil is V1 and the volume of the calcium hydroxide is V2,

[V2 / (V1 + V2)] x 100? 20

1 is a graph showing the relationship between the content (volume%) of calcium hydroxide in the lubricant for a mold and the internal golfering load (kgf).

The inner gulling load refers to a load when a seizure occurs between the surface of a metal mold and a workpiece. The larger the value of the inner gogging load is, the more the sticking is less likely to occur and the life of the mold becomes longer. Generally, it is said that the inner golring load is preferably 2800 kgf or more.

Fig. 2 is a diagram showing an outline of a drawbead test performed when measuring the inner golring load. Fig.

Two blocks 10 and 11 are arranged so as to oppose each other as shown in Fig. 2, and a cemented carbide tool 12 is placed in one block 10 and a mold sample SKD11 is placed in the other block 11. [ (13) are attached so that the cemented carbide tool (12) and the mold sample (13) face each other.

A high-strength cold-rolled steel sheet (SPFC440) 14 is disposed between the cemented carbide tool 12 and the mold sample 13.

The cemented carbide tool 12 and the mold sample 13 are pressed against the high-strength cold-rolled steel sheet 14 in the pushing direction 15 while increasing the pushing load by 200 kg. The high-strength cold-rolled steel sheet 14 is pulled out in the pull-out direction 16 at a speed of 1 m / minute (minute) while being pressed between the cemented carbide tool 12 and the mold sample 13 in both directions. At this time, the load on the high-strength cold-rolled steel sheet 14 which is pressed against the mold sample 13 is measured. Is the internal golfering load of the loaded load.

The following five kinds of lubricants were applied to the high-strength cold-rolled steel sheet 14, and the draw-bead test shown in Fig. 2 was carried out for each of them, and the internal golring load was measured.

(1) Lubricant 1 (content of calcium hydroxide: 0%)

(2) Lubricant 2 (content of calcium hydroxide: 15%)

(3) Lubricant 3 (content of calcium hydroxide: 25%)

(4) Lubricant 4 (content of calcium hydroxide: 35%)

(5) Lubricant 5 (content of calcium hydroxide: 45%)

With respect to the above-mentioned five kinds of lubricants, the measured inner golring loads were as follows.

(1) Lubricant 1: 2200 kgf

(2) Lubricant 2: 2600 kgf

(3) Lubricant 3: 3000 kgf

(4) Lubricant 4: 3400 kgf

(5) Lubricant 5: 3600 kgf

1, the maximum irregularity of the surface of the mold sample 13 was 17 mu m, and the average particle diameter of calcium hydroxide was 4 mu m.

Generally, it is said that the allowable minimum value of the inner gulling load is 2800 kgf, and that the inner gulling load of 3000 kgf or more is sufficient.

When each plot shown in Fig. 1 is made of a smooth curve (not shown), it can be seen that an inner golring load of 2800 kgf can be obtained when the content of calcium hydroxide is 20%.

In addition, when the content of calcium hydroxide is 25% or more, it can be understood that an inner golring load of 3000 kgf or more is reliably achieved.

As described above, in the lubricant for a mold according to the present embodiment, when the content of calcium hydroxide is 20% or more, an internal golring load of 2800 kgf or more can be obtained. When the content of calcium hydroxide is 25% A load can be obtained.

Further, by using calcium hydroxide as the particles contained in the lubricant for a mold according to the present embodiment, press molding is carried out by using a mold to which the lubricant for a mold according to the present embodiment is applied, after which the calcium hydroxide particles are cleaved and broken, The average particle diameter of calcium hydroxide is adjusted to be ½ or less of the initial particle diameter.

From the micro perspective, the surface of the mold is not flat, with minute irregularities scattered. According to the study by the inventors, whether or not the particles of the calcium hydroxide exert a large friction reducing effect on the surface of the mold when the lubricant is applied to the surface of the mold is determined by the height (irregularity) of these irregularities and the average particle diameter And the presence or absence of cleavage destructive properties.

For example, even if calcium oxide (CaO) is mixed with a lubricant instead of calcium hydroxide (Ca (OH) ₂ ), cleavage destructiveness can not be obtained, but cleavage destructibility can be obtained by mixing calcium hydroxide with a lubricant. For this reason, the lubricant for a mold according to the present embodiment comprises calcium hydroxide.

The height (ruggedness difference) of the concavo-convex shape on the surface of the mold can be controlled through factors such as the hardness, size, number, and impact speed of the shot material used for the shot peening process, for example.

For this reason, the inventors conducted a test in which the maximum irregularities (H) on the surface of the mold and the average particle diameter (D) of calcium hydroxide were changed to determine the internal golfering load at that time.

The maximum irregularities (H) on the surface of the mold used in the tests were as follows. The maximum irregularities on the surface of the mold indicate the difference in height between the bottom (lowest position) of the concave portion of the mold surface and the top (highest position) of the convex portion.

(1) 2 탆

(2) 8 탆

(3) 17 탆

(4) 63 탆

For these four metal molds having the maximum concavo-convex difference, calcium hydroxide having the following three average particle diameters was used.

(1) 4 탆

(2) 13 탆

(3) 40 탆

3 is a graph showing the correlation between the maximum irregularity difference H on the surface of the mold and the average particle diameter D of calcium hydroxide.

In the test shown in Fig. 3, a lubricant having a calcium hydroxide content of 20% was used.

In Fig. 3, &quot; o &quot; indicates that the inner gulling load was 2800 kgf or more, and &amp; &amp; cir &amp; indicates that the inner gulling load was less than 2800 kgf.

In Fig. 3, the boundary line 20 represents a line in which the following equation (1) is established.

log H = log D ... (One)

The region above the boundary line 20 (including the boundary line 20) is the region where the following inequality (2) is established and the region below the boundary line 20 is the region where the following inequality (3) .

log H ≥ log D ... (2)

log H <log D ... (3)

As is apparent from Fig. 3, &quot; o &quot;, which indicates that the inner golfering load was 2800 kgf or more, exists only in the regions where both inequality (2) &Amp; cir &amp; &amp;le; &amp;le; indicating that the internal golfering load was less than 2800 kgf exists in the region where?

From this, it was proved that the above inequality (2) and D <40 占 퐉 were satisfied in order to secure the inner golring load of 2800 kgf or more.

log H &amp;ge; log D (D &lt; 40 mu m)

As described above, by changing the average particle diameter of calcium hydroxide according to the conditions of inequality (2) and D < 40 mu m in response to the maximum irregularities on the surface of the mold, it is possible to always secure an internal golfer load of 2800 kgf or more It becomes.

The calcium hydroxide used in the lubricant according to the present embodiment can be, for example, a calcined shell.

According to the "Recycling of Shells by Highly Integrated Technique and Improving the Quality of Charcoal (Part 1)" (Reporter: Armed and Amphibious), published in Iwate Industrial Technology Center Research Report 15 (2008), scallops, oysters, (CaCO ₃ ), which is a main component of the shell, is calcined at a ratio of almost 100% in the case where shellfish such as shellfish, mackerel shell, clam, shellfish, etc. are fired in an electric furnace under conditions of 1000 ° C. and 5 hours. ).

In addition, by calcining the shell under any of the following conditions, calcium oxide (CaO) can be efficiently produced.

(1) More than 900 degrees Celsius, 1 hour (when firing time is emphasized)

(2) 750 degrees Celsius, 5 hours or more (when firing temperature is emphasized)

The calcium oxide thus produced is, for example, in the form of a powdery calcium oxide having an average particle diameter within a certain range by being hung on a pulverizer. Thereafter, the powdery calcium oxide is subjected to a hydroxide treatment to obtain calcium hydroxide. Further, by using this ultra-fine dispersion device and slurrying this calcium hydroxide together with the working oil, a lubricant in which calcium hydroxide having an average particle diameter of nano order is dispersed can be obtained.

The shell is now being abolished in large quantities as industrial waste. As described above, by using the shell as a raw material of calcium hydroxide, the industrial waste can be reduced in weight and effectively used. In addition, the shell powder is totally harmless to the human body and contributes to the reduction of the environmental load.

As described above, according to the lubricant for a mold according to the present embodiment, by setting the content of calcium hydroxide to 20% by volume or more, it is possible to obtain an undergrowing load of 2800 kgf or more and, at the same time, It is possible to do.

Fig. 4 is a graph showing the relationship between the pushing load (kgf) in the draw-bead test shown in Fig. 2 and the friction coefficient of the mold surface.

As Sample 1, when a workpiece coated with molybdenum disulfide (MoS ₂ ) of 30% by volume was applied to the surface of the mold as sample 2 when only the workpiece was applied to the surface of the mold (In Fig. 4, indicated by &quot;&quot;). In the case of applying the mold lubricant (the content of calcium hydroxide was 45%) of the present embodiment to the surface of the mold The friction coefficient on the surface of the mold when the pushing load was increased from 200 kgf to 3600 kgf by 200 kgf was measured. The friction coefficient was measured by the draw-bead test shown in Fig.

As shown in Fig. 4, with respect to Samples 1 and 2, the friction coefficient gradually decreased with the increase of the pushing load, but the sample 1 caused the sticking when the pushing load was 2200 kgf . Further, Sample 2 caused sticking when the pushing load was 2600 kgf. That is, the sample 1 had an internal golfering load of 2200 kgf and the sample 2 had an internal golfering load of 2600 kgf, both of which were below the minimum allowable load of 2800 kgf.

On the other hand, in the sample (Sample 3) coated with the lubricant for a mold according to the present embodiment, the pushing load at the time of occurrence of sticking was 3600 kgf. That is, the sample 3 had an inner growing load of 3600 kgf. The internal golfering load of Sample 3 was larger than the pushing load of 2600 kgf at the occurrence of seizure in Sample 2 and larger than the minimum allowable load of 2800 kgf.

4, the friction coefficient of Sample 3 is lower than the friction coefficient of Samples 1 and 2 in the entire range of the pushing load measured.

5 is a graph showing the relationship between the pushing load (kgf) in the draw-bead test when the content of calcium hydroxide is changed and the friction coefficient of the mold surface, similarly to the graph shown in Fig.

In Fig. 5, the following three sample values are shown.

(1) Sample 1: Lubricant (content of calcium hydroxide: 15%)

(2) Sample 2: Lubricant (content of calcium hydroxide: 25%)

(3) Sample 3: Lubricant (content of calcium hydroxide: 45%)

The test results of Sample 1 are shown as &quot; &quot;, the test results of Sample 2 are shown as &quot; DELTA &quot;, and the test results of Sample 3 are shown as &quot; O &quot;.

In the test shown in Fig. 5, the friction coefficient was measured on the surface of the mold when the pushing load was increased from 200 kgf to 3600 kgf by 200 kgf as in the case of the test shown in Fig. The friction coefficient was measured by the draw-bead test shown in Fig.

As apparent from the content of calcium hydroxide, Sample 1 is not included in the lubricant for a mold according to the present embodiment, but Samples 2 and 3 are included in the lubricant for a mold according to the present embodiment.

With respect to Sample 1, the friction coefficient gradually decreased with the increase of the pushing load, but the sticking occurred when the pushing load was 2600 kgf. That is, the sample 1 had an internal golfering load of 2600 kgf and a minimum allowable load of 2800 kgf or less.

On the other hand, in Sample 2, which is one of the lubricants for the mold according to the present embodiment, the pushing load at the time of occurrence of sticking was 3000 kgf. That is, the inner growing load of Sample 2 was 3000 kgf. The internal golfering load of Sample 2 was larger than the internal golfering load of Sample 1 of 2600 kgf and was larger than the minimum allowable load of 2800 kgf.

As is apparent from Fig. 5, the coefficient of friction of Sample 2 is lower than the coefficient of friction of Sample 1.

In Sample 3, which is one of the lubricants for the mold according to the present embodiment, the pushing load at the time of occurrence of sticking was 3600 kgf. That is, the sample 3 had an inner growing load of 3600 kgf. The internal golfering load of Sample 3 was larger than the internal golfering load of Sample 1 of 2600 kgf and larger than the minimum allowable load of 2800 kgf.

5, the friction coefficient of the sample 3 is lower than the friction coefficient of the sample 1 and the sample 2 in the entire range of the pushing load measured.

As can be seen from the comparison of Sample 2 and Sample 3, the larger the content of calcium hydroxide is, the lower the friction coefficient of the surface of the mold.

As described above, by coating the mold lubricant according to the present embodiment on the surface of the metal mold, it is possible to increase the internal golfering load as compared with the case of using the conventional lubricant (molten metal with a disulfide + molybdenous disulfide) It is possible to reduce the coefficient of friction of the rotor. Since the lifetime of the mold increases as the inner gulling load becomes larger and the friction coefficient of the surface of the mold becomes lower, the lifetime of the mold can be surely extended by using the lubricant for the mold according to the present embodiment.

In the above-described embodiment, an example of performing press molding using a mold coated with a lubricant for a mold according to the present invention has been described. However, the lubricant for a mold according to the present invention can be used for plastic molding, die casting molding or other molding using a die .

10, 11: Block
12: Carbide Tools
13: mold sample
14: Cold rolled steel plate
15: pushing direction
16: Drawing direction
20: Boundary line

Claims (3)

A lubricant for a mold comprising a lubricating oil and calcium hydroxide (Ca (OH) ₂ ) mixed in the lubricating oil,
The calcium hydroxide is contained in a proportion of 20% or more and 40% or less in volume fraction,
Wherein the calcium hydroxide has an average particle diameter determined according to the following formula:
log H ≥ log D Also 28 탆 <D <40 탆
H: Maximum irregularity of the mold surface
D: average particle diameter of calcium hydroxide The method according to claim 1,
Wherein the calcium hydroxide has a characteristic that an average particle diameter after molding of the mold becomes 1/2 or less of the initial particle diameter. The method according to claim 1,
The lubricant for a mold according to claim 1, wherein the calcium hydroxide is produced by using a baked shell as a raw material.

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