JP2007144461A - Surface treatment method for die, and die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment method for a die where lubricity can be imparted to a die without performing the application of a lubricant. <P>SOLUTION: When the powder of a solid lubricant is sprayed on the surface of a die together with a high speed gas, and a solid lubricant layer is formed on the surface of the die, upon the spraying of the solid lubricant, a spray nozzle is vibrated to the forward/backward direction of the spraying direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface treatment method of a mold and a mold surface-treated by the method, and more specifically, a surface treatment method for imparting lubricity to the surface of the mold and a mold surface-treated by the method. About.

  Conventionally, in various moldings using molds, the processing load is reduced by imparting lubricity to the molds, the surface condition of the workpiece is improved, the transfer of the workpiece to the mold is prevented, A lubricant is used for the purpose of preventing wear of the mold.

  As such a mold lubricant, an oily or water-soluble resin in which a lubricating component is dispersed is generally used, and it is used by applying such a lubricant to the mold by spraying or the like. .

  In the lubricant used in this way, pyrolysis gas with bad odor and the like is likely to be generated by the heat of the mold, so that the pyrolysis gas is used for the purpose of preventing the generation of such pyrolysis gas. Without using an oily base that is easily generated, a mold lubricant composed of a solid lubricant, a water-soluble polymer, and a surfactant (see Patent Document 1), a powdered solid lubricant, and organic or A mold lubricant composed of an adhesion improver made of an inorganic compound and a volatile solvent (see Patent Document 2) has also been proposed.

  Also, although it is not a technique related to molds, a method of forming a solid lubricant film on machine element parts that require friction resistance and wear resistance, such as sliding products, instead of liquid lubricants such as lubricating oil is also available. As an example of such a method, a method of forming a molybdenum disulfide coating by spraying molybdenum disulfide powder onto a surface to be processed made of aluminum alloy by a high-speed air flow such as compressed air is proposed. (See Non-Patent Document 1).

  In the above-described method for forming a film by spraying molybdenum disulfide, since the solid lubricant film is formed on the surface to be treated by the collision energy of the molybdenum disulfide powder, the specific gravity is higher than that of molybdenum disulfide. When other solid lubricants such as graphite (specific gravity of molybdenum disulfide 4.8; specific gravity of graphite 2.24) are used, sufficient impact energy cannot be obtained. In view of the fact that it cannot be applied to processing objects that require high collision energy due to the formation of a coating, such as steel with higher hardness, a research report on spraying conditions for forming a solid lubricant coating with graphite powder (Non-Patent Document 2) The injection speed can be improved so that a high collision energy can be obtained even when used for injection of a solid lubricant having a low specific gravity. Specially designed proposed injection nozzle so that (see Patent Document 3) have been made.

Prior art document information of the present invention includes the following.
JP 2003-13085 A JP 2000-33457 A JP-A-2005-144666 "Tribologist" published by Japan Society of Tribologists, Vol. 47, No. 12 (2002) 895 Hidemi Sugawara "Surface modification of piston sliding part of internal combustion engine by fine particle peening of solid lubricant" "Tribology Conference Proceedings Tokyo 2003-5" (published April 18, 2003) P293-294, Kazunori Umeda, et al. "Creation of self-lubricating surface layer by high-speed injection of graphite powder"

  In the field of plastic working such as forging, by applying a lubricant as described above to a workpiece such as a mold or billet, the interface between the mold and the material is given lubricity, and the workpiece adheres to the mold. And wear of molds is prevented.

  However, as described above, when the lubricant is applied to a work material such as a mold or billet and applied to the mold or the work material and molded, the surface of the obtained molded product The lubricant adheres to the surface.

  For this reason, a process for removing the attached lubricant by washing the obtained molded product or the like is required, but the lubricant adheres extremely firmly and cannot be easily removed.

  In addition, labor and equipment for such cleaning are required, the cost for that is reflected in the price of the product, and wastewater treatment work and processing facilities used for cleaning are also required.

  In addition, in the case of the lubricant used by applying to the above-described mold, etc., if this is applied to the mold by spraying, etc., the lubricant will be scattered in the working environment, or due to the heat of the mold. Even if pyrolysis gas is generated by pyrolysis or the pyrolysis gas is reduced (for example, the one described in Patent Document 2), volatilization of the volatile solvent added to the lubricant May contaminate the work environment.

  As described above, in the conventional mold lubricant used by being applied to a mold or the like, even if a device for reducing the generation of pyrolysis gas or the like has been devised, it still does not contaminate the processing work site. It cannot be completely prevented and the work environment cannot be improved.

  On the other hand, if a solid lubricant film can be formed on the surface of the mold by injecting the solid lubricant powder into the mold and causing it to collide, the application of the lubricant by spraying or the like can be omitted. At the same time, product cleaning and post-processing are not required. Furthermore, the processing surface accuracy can be improved, the cleaning can be improved, and the working environment can be improved, and the product cost can be reduced by simplifying these working steps.

  And as shown in the above-mentioned non-patent document 2, even when a solid lubricant powder having a relatively low specific gravity such as graphite is injected, depending on the processing conditions, the surface of the solid lubricant It has been confirmed that a film can be formed.

  However, according to the conditions described in Non-Patent Document 2, it was confirmed that a graphite layer could be formed on the surface to be treated. However, there was uneven formation of the graphite layer on the surface to be treated on which the graphite layer was formed. Appearing as striped spots, it was not possible to form a homogeneous graphite layer throughout the object to be treated.

  Further, the conditions described in Non-Patent Document 2 show the formation conditions of the solid lubricant film on the flat surface, but do not show the examination of the injection treatment conditions on the curved surface.

  Furthermore, when the surface treatment was performed on the actual mold by the above method, the surface of the mold became a satin finish instead of a glossy surface, and the friction resistance was high. Therefore, the surface treatment method described in Non-Patent Document 2 does not show any advantage as a mold surface treatment method.

  Thus, the surface treatment method described in Non-Patent Document 2 shown as the prior art can form a solid lubricant film by spraying solid lubricant powder such as graphite other than molybdenum disulfide. Although an excellent technique is disclosed in terms of what is shown, even if this is directly applied as a surface treatment method for a mold, a desired effect cannot be obtained.

  Therefore, the present invention obtains the lubricity to the mold without applying the lubricant as described above by obtaining the injection conditions of the solid lubricant powder that can be practically applied to the mold. An object of the present invention is to provide a surface treatment method of a mold that can be used, and the above-mentioned surface-treated mold, thereby making it unnecessary to apply a lubricant, wash a molded product, and to improve the working environment. For the purpose.

In order to achieve the above object, the mold surface treatment method according to the present invention forms a solid lubricant layer on the mold surface by injecting a powder of solid lubricant together with a high-speed gas onto the mold surface. In the mold surface treatment method to
When injecting the solid lubricant, the injection nozzle is vibrated back and forth in the injection direction and / or in the left-right direction (Claim 1).

  In the surface treatment method of the mold, one reciprocal movement of the nozzle is set as one vibration, and the nozzle is vibrated at a frequency of 30 or more per minute (Claim 2).

  Furthermore, in the surface treatment method of the mold, the injection of the solid lubricant powder is performed in two steps. In this case, it is preferable that the second injection is performed with a lower injection pressure than the first injection ( (Claim 4) For example, the first injection is carried out with an injection pressure of 0.8 to 1.0 MPa, an injection distance of 30 to 70 mm, an injection time of 20 to 40 sec, a nozzle amplitude of 80 to 120 mm, and a nozzle frequency of 30 to 30. The second injection is performed at 60 cpm, injection pressure: 0.05 to 0.2 MPa, injection distance: 30 to 70 mm, injection time: 20 to 40 sec, nozzle amplitude: 80 to 120 mm, nozzle frequency: 30 to 60 cpm (Claim 5).

  In addition, as the powder of the solid lubricant, graphite having a particle size of 5 to 30 μm can be suitably used (Claim 6).

  Moreover, the metal mold | die of this invention is a metal mold | die characterized by the surface treatment by one of the methods mentioned above (Claim 7).

  According to the configuration of the present invention described above, it is possible to impart lubricity to the mold itself by performing the surface treatment by the above-described method, thereby eliminating the need to apply a lubricant to the mold and the workpiece. .

  As a result, there is no deterioration of the working environment due to the scattering of the lubricant into the working environment, the volatilization of the volatile solvent, and the generation of decomposition gas accompanying the heating of the mold when the lubricant is applied, and the working environment can be improved. It was.

  Further, by imparting lubricity and releasability to the mold by the surface treatment of the above configuration, there is no adhesion of the lubricant to the surface of the molded product obtained by the mold, so that the molded product can be removed after molding. The steps for washing and the like can be omitted, and the treatment work of the washing water used for washing, the treatment facility, and the like can be omitted.

  When the solid lubricant powder is sprayed twice and the second spray is performed at a lower spray pressure than the first spray, the surface of the formed solid lubricant layer becomes smoother and glossy. Became a face. As a result, the frictional resistance on the surface of the solid lubricant layer could be further reduced.

  Hereinafter, the surface treatment method of the mold of the present invention will be described.

  The surface treatment method for a mold according to the present invention involves injecting a solid lubricant into the surface of the mold from the surface to the inside by injecting the powder of the solid lubricant onto the surface of the mold at a high speed. The solid lubricant, the injection device, the injection conditions, and the like are as follows.

[Solid lubricant]
In general, solid lubricants include “soft metal” such as gold (Au), silver (Ag), tin (Sn), zinc (Zn), indium (In), graphite (C), molybdenum disulfide (MoS ₂ ), Tungsten disulfide (WS ₂ ), boron nitride (BN) and other “layered structures”, diamond and sapphire “super-hard”, PTFE, nylon and other “organic polymer” solid lubricants However, among these, as the solid lubricant used in the present invention, a layered structure type solid lubricant excellent in lubricity is used.

  The surface treatment method of the present invention is effective particularly when a solid lubricant powder having a small specific gravity such as graphite is used.

  The shape of the solid lubricant to be used is not particularly limited, and various shapes can be used. However, the above-mentioned layered structure type solid lubricant, for example, graphite is stable up to a high temperature (about 400 ° C). In addition, it is a plate-like layered structure belonging to the hexagonal system, and the in-plane of each layer constituting this layered structure is bonded between carbons by strong covalent bonds. Since the bonds between the two are bonded by a relatively weak force, they usually have a scaly shape. In this embodiment, such a scaly member is used.

  The particle size of the solid lubricant to be used is in the range of 20 to 30 μm, preferably 10 to 20 μm in the long side or the long diameter of the solid lubricant.

[Injection device and injection conditions]
As the solid lubricant injection device, a known blasting device can be used, and a configuration example of such an injection device is shown in FIG.

  The injection device shown in FIG. 1 includes an injection nozzle, an air compressor, an injection chamber, a powder supply device, a classifier, a recovery unit, and a pressure pipe, and compression from the air compressor in the powder supply device. The solid lubricant powder combined with air is injected from the nozzle in the injection chamber to collide with the mold, and the injected solid lubricant powder is recovered and reusable by the classifier. The body is recovered and re-introduced into the powder feeder, and the solid lubricant powder that is crushed and cannot be reused can be recovered by the recovery unit.

  In the mold surface treatment method of the present invention, with such a blast processing apparatus, an injection pressure of 0.05 to 1.0 MPa, an injection speed of 240 m / sec, and an injection distance (distance between the nozzle tip and the mold surface) are set. The solid lubricant powder is sprayed at 25 to 150 mm.

The spraying time is 5 to 10 seconds per 0.0001 m ^{2 of} processing area, and the nozzle is vibrated during spraying in order to prevent the formed solid lubricant film from becoming striped spots.

  The nozzle is vibrated with an amplitude of 50 to 150 mm before and after the jetting direction, and the reciprocating vibration of the nozzle is defined as 1 frequency, and this frequency is set as 20 to 80 cpm (cycle per minute).

  In order to make the surface of the surface-treated mold an excellent lubricating surface, in particular, the solid lubricant powder is sprayed in two portions, and the second spray is performed at a lower level than the first spray. It is effective to perform the injection at a pressure or a low injection speed. Thus, when the injection of the solid lubricant is performed in two stages, preferable injection conditions in each stage are as follows.

1st injection pressure: 0.8-1.0MPa
Injection distance: 30-70mm
Injection time: 20-40sec
Nozzle amplitude: 80-120mm
Nozzle frequency: 30-60cpm

2nd injection pressure: 0.05-0.2MPa
Injection distance: 30-70mm
Injection time: 20-40sec
Nozzle amplitude: 80-120mm
Nozzle frequency: 30-60cpm

[Action etc.]
As described above, when the powder of the solid lubricant is sprayed onto the surface of the mold at a high speed, the injected solid lubricant collides with the surface of the mold and is solid lubricated from the surface to the inside of the mold. The agent penetrates and a high-performance and solid solid lubricating layer is created on the surface of the mold.

  By creating this solid lubricating layer, it is possible to obtain lubricity in the mold without applying a lubricant or the like.

  Next, test examples using graphite as a solid lubricant will be described below.

1. Basic data test In order to make the film formation method by high-speed injection of solid lubricant powder practical as a mold surface treatment technology, as a preliminary step, first, the basis for identifying suitable injection conditions for curved surfaces A test was conducted to investigate the data.

  In this test, the optimum conditions for obtaining a uniform and glossy graphite layer on the circumferential surface of the cylindrical sample were obtained, and the treatment conditions with excellent characteristics were adopted as the surface treatment conditions for the actual mold described later. did.

1-1. Test conditions (cylindrical sample)
The following was used as a cylindrical sample.
Material: SKD11
Size: Diameter 20mm x Height 25mm

[Solid lubricant]
Graphite (graphite) was used as a solid lubricant. The graphite used is a product name “CPB” manufactured by Nippon Graphite Trading Co., Ltd., and an SEM photograph thereof is shown in FIG.

The graphite used is a scaly powder, and its characteristics are a fixed carbon content of over 97%, an ash content of less than 2%, a volatile content of over 1%, an average particle size of 19 μm, and an apparent specific gravity of 0.2 g / m ³ . .

[Injection device]
The spraying device used for spraying the graphite powder is the above-described direct pressure blasting device described with reference to FIG.

  In addition, the thing as described in patent document 3 (Unexamined-Japanese-Patent No. 2005-144566) shown as a prior art was used as an injection nozzle. This nozzle has a divergent flow path derived from ultra-high speed theory. In this embodiment, the diameter of the narrowest part (throat part) of the nozzle flow path is 5 mm, and the length is compared with the throat part. 11 was used. This injection nozzle has a maximum injection speed of about 450 m / sec, whereas conventional injection nozzles have a maximum injection speed of about 180 to 200 m / sec, depending on the material, specific gravity, shape, etc. of the injection material. It was made feasible.

1-2. Test for checking the effectiveness of nozzle vibration during injection Checking the change in the formation state of the graphite layer when the nozzle is vibrated (Example) and when the nozzle is not vibrated (Comparative Example) did.

  In Examples 1 to 3 and the comparative example, the other conditions were the same except for the nozzle frequency.

  The cylindrical sample was placed on a rotating turntable, and solid lubricant powder (graphite) was injected under the conditions shown in Table 1.

  In addition, the vibration of the nozzle moved the nozzle back and forth by 100 mm, and thereby the ejection distance (distance between the cylindrical sample and the nozzle tip) was periodically displaced by 50 to 150 mm. One reciprocal movement at this time was defined as one frequency.

  As a result of the above, in the cylindrical sample of Comparative Example 1 in which the injection distance was fixed at 50 mm and graphite was injected without vibrating the nozzle, it was confirmed that a graphite layer was formed, The formed graphite layer was uneven, and this formation unevenness appeared as striped spots.

  On the other hand, in the cylindrical samples described in Examples 1 to 3 in which the nozzle was vibrated when graphite was injected, in Example 3 in which the frequency was 10 cpm, the formation of striped spots was still observed, It was confirmed that the striped spots formed as compared with those of Comparative Example 1 were thin, and the uniformity of the formation of the graphite layer was eliminated and the uniformity was improved.

  When the frequency was further increased, the striped spots were further thinned, and the striped spots could not be confirmed at a frequency of 30 cpm or more. Thereafter, the same state was maintained even when the frequency was increased to 60 cpm.

  From the above results, in the formation of the graphite layer on the curved surface, it can be confirmed that it is effective for the formation of a uniform graphite layer to vibrate the nozzle back and forth during the injection of the graphite powder. It was confirmed that setting the frequency to 30 cpm or more is effective for forming a uniform graphite layer.

1-3. Effectiveness confirmation test of two-stage injection The change in the formation state of the graphite layer was confirmed when the graphite powder was injected in two portions and when it was performed by one injection.

  About each cylindrical sample obtained on the above injection conditions, the difference in the formation state of a solid lubricant film was confirmed visually.

  In the cylindrical samples treated under the spraying conditions of Examples 4 and 5, formation of a uniformly glossy graphite layer was confirmed.

  In contrast, in the cylindrical sample of Example 6 in which the nozzle frequency was reduced to 10 cpm, although the formed graphite layer showed gloss, there was some unevenness in the formation state, and this unevenness was It was confirmed as striped spots.

  In addition, in the cylindrical sample processed under the spraying conditions of Example 3, it was not possible to confirm the presence of striped spots, that is, the formation of unevenness in the graphite layer, by applying vibration to the nozzle. The gloss was dull compared to those of other examples, and the surface of the graphite layer was confirmed to have a satin finish. From this surface state, it is predicted that the cylindrical sample of Example 3 has a higher surface frictional resistance than the cylindrical samples obtained in other Examples.

  Therefore, the graphite is sprayed in two steps, and the second graphite injection is performed at a lower injection pressure than the first graphite injection. It was confirmed that it was effective in giving (smoothing).

1-4. Friction Test A friction test was performed on each cylindrical sample on which the solid lubricant powder was injected as described above using the two-wire tribometer shown in FIG.

  In the friction test, a block sample (4 x 3 x 10 mm) made of the same magnesium alloy (AZ61) as the material of the molded product used in the extrusion test using a mold, which will be described later, is placed in the center of the side of the rotating cylindrical sample (SKDl1). Were pressed from both sides at 24.5 N, and the cylindrical sample was rotated.

  The load cell for measuring the frictional force is in contact with a torque bar connected to a free rod to which a block sample is attached. When the frictional force changes, the torque bar changes to pressurize the load cell.

  The composition of the magnesium alloy (AZ61) used in this test is shown in Table 3, and the photomicrograph is shown in FIG.

  From this micrograph, the crystal grains of the magnesium alloy (AZ61) are about 10 to 20 μm in size.

  FIG. 5 shows the results of the two-wire tribo test. This shows the friction behavior at room temperature when the circular surface of a cylindrical SKD11 sample was subjected to high-speed graphite injection treatment. The round plot shows a cylindrical sample obtained under the injection conditions of Example 5 in which the nozzle vibration was 30 cpm. The square plot is the test result of the cylindrical sample obtained by the injection of Example 4 with the nozzle frequency set at 60 cpm.

  In the cylindrical sample of Example 5 having a good gloss surface (round plot), the friction coefficient was 0.17 at the start of the experiment, but increased with the number of rotations and reached a maximum value of 0.24 at about 800 times. .

  However, after that, the coefficient of friction decreased with an increase in the number of revolutions, and when it exceeded 10,000 times, it became about 0.208, and this state was maintained until 33,000 times. The friction coefficient increased rapidly after 33,000 times, which is considered to be due to the life of the graphite layer.

  Since it was confirmed that the cylindrical sample (square plot) obtained by the injection according to Example 4 in which the nozzle frequency was 60 cpm also showed the same tendency as the cylindrical sample (round plot) obtained under condition 2 up to 20000 times, The experiment was interrupted here.

  From this result, the cylinder sample obtained by the injection of Example 5 with the nozzle frequency of 30 cpm and the cylinder sample obtained by the injection condition of Example 4 obtained by the injection of frequency 60 cpm have substantially the same friction. The coefficient and the life were predicted, and in any case, it was confirmed that a graphite layer having a low friction coefficient and excellent wear resistance was formed.

  On the other hand, a cylindrical sample obtained under the injection conditions of Example 6 in which the nozzle frequency was 10 cpm, and the injection conditions of Example 3 performed by one injection without dividing the injection process twice. Although not shown in the figure for the cylindrical sample, the friction coefficient is higher when compared with the cylindrical sample obtained under the injection conditions of Examples 4 and 5, and the lifetime was short. In the relationship with the cylindrical sample obtained under the conditions of Comparative Example 1 manufactured without vibrating the nozzle during body injection, the friction coefficient was low.

2. Extrusion test (magnesium alloy billet)
2-1. Materials and equipment used (1) Extruded material A commercially available magnesium alloy (AZ61) billet was used as the extruded material. The composition and structure of the extruded magnesium alloy (AZ61) are the same as those in Table 3 and FIG.

  The magnesium alloy billet used has a cylindrical shape with a diameter of 16 mm and a length of 50 mm.

(2) Processing machine A multi-axis material testing machine was used as an extruder. The multi-axis material testing machine used here has four horizontal moving rams and one vertical moving ram. The horizontal capacity is 500 kN, the displacement is ± 125 mm, the vertical capacity is 2500 kN, and the displacement is 150 mm.

(3) Mold The mold used is a two-branch mold as shown in FIG. 6, and a mold having a predetermined shape is formed by superposing an upper mold and a lower mold which are divided vertically. Yes.

  Each of the upper and lower molds is formed with a semicircular groove in cross section, and two vertical and horizontal grooves intersect at a right angle at the center of each mold to form a cross-shaped groove.

In this embodiment, two types of molds having different groove widths are prepared, and one mold has a horizontal groove width of 16 mm and a vertical groove width of 11.3 mm. Is twice the cross-sectional area of the transverse groove, that is, the area reduction rate is 50%
The other mold had a vertical groove and a horizontal groove with a width of 16 mm, and the vertical and horizontal grooves had a common cross-sectional area.

  The mold materials are all high-speed steel (SKH51) and the hardness is 62HRC.

  The mold is heated by 8 space heaters (plate-shaped) and 4 pipe heaters (columnar shape; not shown), and 100 V and 300 W space heaters on the outer peripheral surfaces of the upper and lower molds. And 100V and 800W pipe heaters were accommodated in mounting holes formed in the mold.

  The temperature was measured with an alumel-chromel thermocouple thermometer placed on the upper and lower mold surfaces at a position of about 20 mm from the mold center.

  The surface treatment conditions for the mold used in each test are as shown in Table 4 (4-1, 4-2).

(4) Test method Warm side extrusion was performed using the above-mentioned multiaxial material testing machine at a mold temperature of 190 ° C.

  The mold was clamped by a vertically moving ram at the center of the work surface of the multi-axis material testing machine, and the billet as an extruded material was set in the groove of the mold, and then heated to the extrusion temperature.

  After reaching the extrusion temperature, side extrusion was performed by a horizontal moving ram of a multi-axis material testing machine using two punches.

2-2. Extrusion test example 1
Using the surface-treated mold II and the untreated mold 1, warm side extrusion was performed.

  The billet to be filled in the untreated mold 1 was coated with graphite powder as a lubricant and then filled into the mold. Lubricant is not applied to the billet filled in the surface-treated mold.

  Each of the vertical grooves of each mold is filled with the respective billets and heated to a heating temperature, and then two punches are pushed from both ends of the vertical groove toward the center, and FIGS. 7A and 7 ( Two types of cross-type parts shown in B) were manufactured.

  In any example, the extrusion speed is 50 mm / min.

  The cross-type component shown in FIG. 7A is one in which the total length of the trunk and branches is 35 mm and 46.5 mm, respectively, and the branches are relatively simple (hereinafter referred to as “short-branch cross-type components”). The cross-type component shown in FIG. 7 (B) has a trunk and a branch of 20 mm; 76.5 mm respectively, and the branch is relatively long (hereinafter referred to as “long-branch cross-type component”). is there.

Test results Comparing the short-branched cloth parts formed as described above, the short-branched cloth parts molded by the surface treatment mold IV have a metallic luster on the entire surface, and solid lubricant (graphite) It was not possible to confirm the adhesion of.

  On the other hand, in the short branch cloth type part obtained by molding a billet coated with graphite powder with the untreated mold 1, a solid lubricant (graphite) is attached to the entire surface, Overall it was dark.

  The same result was obtained for the long-branched cloth-type part. In the long-branched cloth-type part obtained by molding a billet coated with graphite powder using the untreated mold 1, the solid lubricant (graphite) adhered. However, in the long-branch cloth type part molded by the surface treatment mold V, adhesion of the solid lubricant (graphite) could not be confirmed.

2-3. Extrusion test example 2
Using two types of molds (surface treatment molds I and VII) with different graphite injection conditions, cross-type parts were manufactured.

  In any example, the extrusion speed is 50 mm / min.

  In each of the above-mentioned surface-treated molds I and VII, the entire surface of the mold was not a glossy surface, and many satin-like surfaces were observed.

  Stress-displacement characteristics during extrusion performed using surface-treated molds I and VII, and stress during extrusion using billets coated with graphite powder using untreated mold 1 as a comparative example -Both displacement characteristics are shown in FIG.

  In an example in which a billet coated with graphite powder is molded using the untreated mold 1, the stress increases rapidly to a value of 789 MPa, and when the material flows in the branch direction, it decreases by 18 MPa and the increase disappears until the end of processing. It was a constant value of 771 MPa.

  In an example in which a billet is molded without using a lubricant by using a surface-treated mold VII (conventional example), the stress change and displacement when using the untreated mold 1 are approximately equal to 5.2 mm. However, it continued to rise from this displacement to the end of machining, and the value at the end of machining was 900 MPa, which was the maximum value.

  In the example using the surface-treated mold I (example of the present application), the tendency of the stress change is almost the same as that when the untreated mold 1 is used, and the value becomes almost constant when the material flows in the branch direction. However, the value was about 275 MPa higher than the stress when the untreated mold 1 was used.

  The cross-type parts obtained with the surface-treated mold I showed relatively many burrs on the outer periphery of the end face of the trunk, and this burr showed a higher stress than when the untreated mold 1 was used. It seems to be the cause.

2-4. Extrusion test example 3
Using the surface-treated mold II and the untreated mold 2 in which the widths of the longitudinal grooves and the lateral grooves are both 16 mm, a cross-type part having the same diameter as the trunk and branches was manufactured. In the example in which the untreated mold 2 was used, a billet coated with graphite powder was molded.

  Unlike cross-type parts manufactured in the previous test example where the diameter of the branch was 11.3 mm, the cross-type molded product with the same trunk and branch diameters cracked due to lower extrusion pressure. It becomes easy.

  Therefore, in this test example, it was not possible to process at the same temperature (190 ° C.) as in the manufacturing test of a cross-type part having a branch of 11.3 mm, and the mold temperature was increased to 260 ° C.

  In any example, the extrusion speed is 50 mm / min.

  In a cross-type part obtained by using an untreated mold 2 and molding a billet coated with graphite powder, a solid lubricant (graphite) is fixed, and it is difficult to remove it. It was.

  On the other hand, when the surface-treated mold II was used, the surface of the obtained cloth-type part had a metallic luster, and solid lubricant (graphite) was not fixed.

  Moreover, if the stress-displacement figure at the time of the extrusion process by said 2 types of metal mold | die (surface treatment metal mold II-1 and untreated metal mold 2) is shown, it is as shown in FIG.

  In the molding example using the unprocessed mold 2, the stress is 1.56 mm after the punch contacts the billet, and the maximum stress is 255 MPa. When the material flows into the branch, the stress is reduced to 220 MPa, and this value is finished. It continued until.

  On the other hand, in the example using the surface treatment mold II, the displacement increased to 2.1 mm and once yielded at 457 MPa, but then increased slightly but increased to a maximum value of 475 MPa at a displacement of 5.1 mm. After that, it gradually decreased until completion, and reached 400 MPa at the end of machining.

  In the maximum stress, when the surface-treated mold II was used, it was 1.86 times that when the untreated mold 2 was used.

  When the state after extrusion molding of the surface-treated mold II was confirmed, the magnesium alloy was fixed to the outer peripheral portion of both punches with a width of about 10 mm, and the magnesium alloy was also fixed to the groove of the die. When high pressure is applied, the material flow in this portion does not become smooth, and it is considered that the material is pressed and fixed in the circumferential direction.

2-5. Extrusion test example 4
Using a surface-treated mold III, a cross-type part was manufactured.

  FIG. 10 is a stress-displacement diagram at the time of extrusion molding by the surface treatment mold III. Cross-type parts are extruded twice, and the stresses of the two punches (Punches A and B) at each time are shown.

  In the first processing, after the peak value of the stress, the stress decreased because the branch tip cracked. However, cracking occurred only at the tip and not after that, so the stress increased again and the material flowed in the direction of the branches, forming the branches.

  In order to prevent this crack at the tip, the second extrusion was carried out by changing the extrusion speed from 75 mm / min to 50 mm / min.

  Compared to the first time, the yield value was slightly higher, but the displacement was approximately equal after 4.7 mm.

  FIG. 11 shows a stress-displacement diagram at the time of short-branch cloth type product extrusion processing by each surface treatment mold. Here, the extrusion temperature was 190 ° C.

  In any example, the extrusion speed is 50 mm / min.

  When an untreated mold 1 is used and a billet coated with molybdenum disulfide powder is molded, the stress yields at 501 MPa, and this value is constant until the end of processing.

  In the example using the surface treatment mold II, the stress yields at 891 MPa and takes the maximum value, and then gradually decreases to 819 MPa at the end of processing, which is smaller than the surface treatment mold VII (conventional example). As shown, the untreated mold 1 was used and the value was almost equal to the value when the billet coated with graphite powder was molded.

  FIG. 12 shows a stress-displacement diagram at the time of extruding a long-branch cross-type part using a die surface-treated according to each injection condition.

  In any example, the extrusion speed is 50 mm / min.

  The stress of the untreated metal mold 1 (graphite coated on the billet) once decreased slightly after yielding at 690 MPa, decreased from about 7 mm, and reached 730 MPa at the end.

  In the case of using the surface treatment molds VII, I, III, V, and VI, the yield of stress is 920 MPa to 1000 MPa in all cases. To 1320 MPa.

  The stress when using surface-treated molds I, III, V, and VI is higher than that when using untreated mold 1 (with billet coated with graphite powder). Compared to the treated mold VII (conventional example), the maximum values were all smaller, indicating an improvement in the injection process.

3. Extrusion test (aluminum alloy billet)
As an example of application to a metal other than a magnesium alloy, an aluminum alloy (A6061) was extruded at a temperature of 140 ° C. The mold used was a 16 mm diameter cross mold (surface-treated mold IV, untreated mold 2) with the same branches and trunks. In addition, the billet molded by the untreated mold 2 is a billet that has been subjected to a bonde treatment (phosphate treatment) in advance, and no solid lubricant is applied.

  FIG. 13 shows a stress-displacement diagram at the time of processing an aluminum alloy (A6061) using the mold.

  The stress when extruding a billet treated billet using the untreated mold 2 yields at 179 MPa and the processing is finished at this value, but the stress due to the surface treated mold IV is a displacement of 3.1 mm. Yields loosely at around 500 MPa, but increases with increasing displacement thereafter, reaching the maximum value of 821 MPa at the end of machining. This value is compared with the case of using untreated mold 2 (bonded to billet). It was 4.6 times.

The schematic explanatory drawing of the injection device used with the method of the present invention. Electron micrograph of graphite Schematic explanatory drawing of the friction test by a two-wire tribometer. Electron micrograph of magnesium alloy (AZ61). The table | surface which shows the friction test result by a two-wire type tribometer. The top view of the metal mold | die used for the extrusion test. Cross type parts manufactured by an extrusion test. (A) is a short-branch cross-type part and (B) is a long-branch cross-type part. The figure which shows the stress-displacement characteristic (magnesium alloy) of surface treatment metal mold | die I, VII. The figure which shows the stress-displacement characteristic (magnesium alloy) of surface treatment metal mold II-1. The figure which shows the stress-displacement characteristic (magnesium alloy) of the surface treatment metal mold | die III. The figure which shows the stress-displacement characteristic (magnesium alloy) of surface treatment metal mold | die I, II, VII. The figure which shows the stress-displacement characteristic (magnesium alloy) of surface treatment metal mold | die I, III, V, VI, and VII. The figure which shows the stress-displacement characteristic (aluminum alloy) of the surface treatment metal mold IV.

Claims (7)

In the mold surface treatment method of injecting solid lubricant powder onto the surface of the mold together with high-speed gas to form a solid lubricant layer on the surface of the mold,
A surface treatment method for a mold, wherein the injection nozzle is vibrated in the front-rear direction and / or the left-right direction during the injection of the solid lubricant.   The mold surface treatment method according to claim 1, wherein the reciprocating movement of the nozzle is a single vibration, and the nozzle is vibrated at a frequency of 30 or more per minute.   3. The surface treatment method for a mold according to claim 1, wherein the nozzle is vibrated in an injection distance range of 25 to 150 mm and an amplitude of the nozzle in a range of 75 to 100 mm.   The mold surface treatment method according to claim 1, wherein the injection of the solid lubricant powder is performed twice. The first injection is performed at an injection pressure of 0.8 to 1.0 MPa, an injection distance of 30 to 70 mm, an injection time of 20 to 40 sec, a nozzle amplitude of 80 to 120 mm, and a nozzle frequency of 30 to 60 cpm.
The second injection is performed at an injection pressure of 0.05 to 0.2 MPa, an injection distance of 30 to 70 mm, an injection time of 20 to 40 sec, a nozzle amplitude of 80 to 120 mm, and a nozzle frequency of 30 to 60 cpm. The mold surface treatment method according to claim 4.   The mold surface treatment method according to claim 1, wherein the solid lubricant powder is graphite having a particle size of 5 to 30 μm.   The metal mold | die surface-treated by the method of any one of Claims 1-6.