JP5389474B2 - Spheroidal graphite cast iron material having hard coating, press mold, and method for producing spheroidal graphite cast iron material having hard coating - Google Patents

Description

  The present invention relates to a spheroidal graphite cast iron material having a hard coating that can be preferably used as a mold material for pressing a high-strength steel plate such as a high-tensile steel plate.

  In recent years, in the field of automobile manufacture, high-tensile steel sheets tend to be frequently used for the purpose of improving safety and reducing the weight of a vehicle body.

  High-tensile steel sheets have high tension and high strength. Therefore, compared with the press steel plate conventionally used, a high pressurizing force is required at the time of press forming.

  By the way, conventionally, steel materials have been widely used for dies used for press working of high-tensile steel plates. However, the steel material has a problem that the cutting resistance is high, the cutting volume required for die machining is large, and the cost of the steel material itself is relatively high. For this reason, a mold obtained from steel has a problem that the total cost becomes high.

  In order to solve the above-described problems, for example, a mold obtained from a cast iron material as shown in Patent Document 1 below is known. A mold base material obtained from a cast iron material is obtained by pouring cast iron previously heated and melted into a mold, cooling and solidifying, and then removing it from the mold. And it is finished by cutting only the surface. Therefore, the total cost can be reduced because cutting is relatively simple and the material cost is relatively low. However, a mold using a cast iron material as a base material has a drawback of poor wear resistance. Therefore, when a mold having a cast iron material as a base material is used as a mold for processing a high-tensile steel plate, there is a problem that wear tends to occur and the mold life is shortened.

  As a technique for improving the wear resistance of a cast iron material, for example, a method of forming a hard film such as a titanium film on the surface of the cast iron material is known. For example, Patent Document 2 below discloses a method in which at least a part of a surface layer of cast iron is chilled, the surface of the chilled layer is polished, and then a hard coating is formed on the surface of the chilled layer by PVD or CVD treatment. It is disclosed. Note that chilling is a surface treatment that forms a cast iron surface that has a structure composed of a reedbright layer and pearlite and does not contain graphite. Such surface treatment is performed, for example, by irradiating the surface of cast iron with high-density energy such as laser or plasma arc to remelt its surface layer portion and then rapidly solidify it.

JP-A-9-111395 JP 63-60270 A

  According to the method disclosed in Patent Document 2 described above, a chilled layer not containing graphite is formed in the surface layer portion. And the hardness of the chilled surface is increased. Therefore, when a hard film is formed on such a chilled surface, the surface hardness is relatively high. However, in a member obtained by such a method, since graphite does not exist on the surface, the slidability (slidability) due to the self-lubricating action of graphite is lost. Therefore, the member obtained by such a method has a high surface hardness, but also has a high friction coefficient on the surface. Therefore, when a mold obtained using such a member is used for pressing a steel sheet, the surface mold release resistance during pressing increases, so that the adhesion of the hard coating is low. Arise. In addition, in the case of chilling, since it requires a complicated process of rapidly re-solidifying after irradiating the surface of the base material with high-density energy, it is necessary to apply it to the manufacture of a large mold. It takes a lot of labor to chill the entire surface.

  The present invention solves the above-mentioned problems, and can be preferably used to press various steel plates, particularly high-tensile steel plates, and has a hard coating having a hard coating with a high adhesion formed on the surface. An object is to provide a graphite cast iron material.

  The spheroidal graphite cast iron material having a hard coating of one aspect of the present invention has a titanium-based hard coating formed on the surface of nitridized spheroidal graphite cast iron, and the average particle diameter of spheroidal graphite on the surface is 30 μm or less. It is characterized by being. According to such a configuration, a spheroidal graphite cast iron material having a titanium-based hard coating with extremely high adhesion can be obtained.

  In addition, the titanium-based hard coating includes a TiN layer from the surface and a Ti (CxNy) layer formed on the TiN layer surface (where x + y = 1, x <1, and as the distance from the TiN layer surface increases, x Is gradually increased so as to approach 1), and a TiC layer formed on the surface of the Ti (CxNy) layer is preferable from the viewpoint of obtaining a higher adhesion of the hard coating.

  The titanium-based hard coating is preferably a coating formed by a PVD method, preferably an arc ion plating method. According to the film formation by the PVD method, the film can be formed at a low temperature of 500 ° C. or less. By forming the film at a low temperature, since the distortion and thermal deformation after the film formation are small, a film with higher adhesion can be formed. Moreover, there is also an advantage that it can be used as it is without processing for dimensional correction after the coating is formed.

  Another aspect of the present invention is a press die made of a spheroidal graphite cast iron material having any one of the hard coatings described above.

  Another aspect of the present invention is a nitriding treatment step of nitriding a base material made of spheroidal graphite cast iron, and a coating forming step of forming a titanium-based coating film on the surface of the nitriding base material by a PVD method, And an average particle diameter of spheroidal graphite on the surface of the base material is 30 μm or less, and a method for producing a spheroidal graphite cast iron material having a hard coating. According to such a method, a spheroidal graphite cast iron material having a titanium carbide-based hard coating with extremely high adhesion can be obtained.

Further, the film forming step supplies nitrogen gas into a vacuum chamber in which the base material and the titanium evaporation source are mounted, and generates plasma by evaporating titanium by arc discharge to the titanium evaporation source, Nitrogen ions and titanium ions ionized by the plasma are accelerated by a bias voltage to form a TiN film by depositing nitrogen ions and titanium ions on the surface of the mold base material, and supply of the nitrogen gas is gradually performed. And forming a TiCN film by supplying hydrocarbon gas while gradually increasing the supply amount; and
And a step of forming a TiC layer by stopping the supply of the nitrogen gas and supplying only the hydrocarbon gas. According to such a method, higher adhesion strength of the hard coating can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the spheroidal graphite cast iron material which has a hard film with high adhesive force which can be preferably used for pressing various steel plates, especially a high-tensile steel plate etc. is obtained.

FIG. 1 is a schematic cross-sectional view showing the configuration of a spheroidal graphite cast iron material having a titanium-based hard coating in an embodiment of the present invention. FIG. 2 is a conceptual diagram of the ion plating apparatus used in the embodiment of the present invention. FIG. 3 is an explanatory diagram of the shape of the test mold for bead drawing characteristics. FIG. 4 is an explanatory diagram of a method for evaluating the bead drawing characteristics. FIG. 5 shows the result of an indentation test in the titanium-based coating formed on the press die obtained in Example 1. FIG. 6 shows the result of an indentation test in the titanium-based film formed on the press die obtained in Comparative Example 2. FIG. 7 is a graph plotting the relationship between the average particle diameter of the spheroidized graphite particles on the surface and the scratch adhesion of the titanium-based hard coating in the press dies obtained in Examples and Comparative Examples.

  Preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a configuration in which a titanium-based hard coating 2 is formed on the surface of a nitridized spheroidal graphite cast iron 1 according to this embodiment. On the surface layer of the spheroidal graphite cast iron 1, a nitrided layer 1a formed by nitriding is formed. And the average particle diameter of the spherical graphite in the surface of the spheroidized graphite cast iron 1 is 30 micrometers or less.

  The spheroidized graphite cast iron is not particularly limited as long as it is cast iron in which graphite is spheroidized. Specific examples thereof include those represented by steel symbols FCD and the like. Among these, FCD540, FCD600, FCD700 and the like are particularly preferably used because of their excellent strength.

  The average particle diameter of the spheroidal graphite on the surface of the spheroidal graphite cast iron 1 in the present invention is 30 μm or less, preferably 20 to 30 μm. In the present invention, spheroidized graphite cast iron having a titanium carbide-based hard coating having excellent adhesion can be obtained by forming a titanium-based hard coating on the surface of such spheroidized graphite cast iron. When the average particle diameter exceeds 30 μm, the adhesion of the titanium-based hard coating is remarkably reduced. In addition, spherical graphite having an average particle size of 20 μm or less tends to be difficult to produce. The average particle diameter of the spheroidal graphite is determined by observing the surface of the nitrided spheroidal graphite cast iron with a metal microscope at a magnification of 100 times, arbitrarily selecting 100 spheroidal graphites, and determining the area of each spheroidal graphite. Is the average value of the diameter when converted to an equivalent circle.

  The surface of spheroidal graphite cast iron used in the present invention is nitrided. Such nitriding treatment hardens the surface of the spheroidal graphite cast iron. The hardened surface improves the backup force and can sufficiently increase the hardness and adhesion of the titanium-based hard coating formed on the surface.

  The nitriding method in the present embodiment is not particularly limited, and conventionally known ion nitriding method, pulse plasma diffusion (PPD) nitriding treatment, tuftlite treatment, gas nitriding treatment and the like are used without particular limitation. Among these, the ion nitriding method and the PPD nitriding treatment can perform nitriding treatment at a temperature of about 500 to 550 ° C., which is a temperature below the transformation point of the base material. It is preferable from the point which can be performed.

  As the thickness of the nitrided layer, the depth from the surface of the spheroidized graphite cast iron before film formation is preferably 50 to 300 μm, more preferably 100 to 200 μm. If the nitride layer is too shallow, the surface hardness will not be sufficiently high. On the other hand, even if the nitrided layer is made too deep, the backup force due to the improvement of the surface hardness with respect to the surface of the spheroidal graphite cast iron reaches a peak, and a nitriding treatment for a long time is required, which is not economical.

  Further, the thickness of the compound layer in the surface layer portion constituting a part of the nitride layer is preferably 5 to 20 μm, more preferably 10 to 15 μm.

  The surface roughness (Ra) of the spheroidized graphite cast iron 1 on which the titanium-based hard coating 2 is formed is preferably 0.1 μm or less, and more preferably 0.05 μm or less. When the surface roughness is in such a range, a surface having excellent slipperiness and low frictional resistance can be obtained. In particular, when a titanium-based hard coating is formed by the PVD method, a dense and highly smooth coating is obtained, so that the surface state of the spheroidized graphite cast iron 1 is easily reflected in the coating.

  The titanium-based hard coating is a coating containing titanium as a main component, and specific examples thereof include titanium nitride, titanium carbide, titanium carbonitride, and the like.

  Such titanium-based hard coatings are conventionally known physical plating methods (PVD methods) such as ion plating methods such as arc ion plating methods, reactive sputtering methods such as magnetron sputtering methods, and chemical vapor deposition. It is formed using a method (CVD) or the like. Among these, the film formation by the PVD method is preferable because the film can be formed at a low temperature of 500 ° C. or less. By forming the film at a low temperature, distortion and thermal deformation after the film formation can be reduced, so that a film with higher adhesion can be formed.

The titanium-based hard coating is particularly preferably a coating in which the nitrogen concentration gradually decreases as the distance from the surface of the spheroidized graphite cast iron 1 increases, while the carbon concentration gradually increases. Specifically, a TiN layer having good adhesion to the nitride layer 1a is formed on the surface of the nitrided layer 1a of the spheroidal graphite cast iron 1, and the nitrogen atoms in the TiN layer are gradually replaced with carbon. Ti (C _x N _y ) layer whose carbon concentration gradually increases (however, when x + y = 1, x <1, x gradually increases so that x approaches 1 as the distance from the TiN layer surface increases) It is preferable that a TiC layer having excellent hardness and slipperiness is formed on the outermost layer of the mold surface. Such a titanium-based hard coating, particularly excellent in hardness, adhesion, and slipperiness.

  The thickness of the titanium-based hard coating 2 is not particularly limited, but is preferably about 1 to 5 μm, and more preferably about 2 to 4 μm, from the viewpoint of maintaining a higher adhesive force while maintaining the internal stress balance of the coating.

  As an example of a method of forming a titanium-based hard coating, the nitrogen concentration gradually decreases as the distance from the surface of the spheroidized graphite cast iron 1 as described above using the arc ion plating method, while the carbon concentration gradually increases. A method of forming an increasing film will be described in detail with reference to FIG.

  FIG. 2 shows an example of an arc type vacuum film forming apparatus using an arc ion plating method.

First, the spheroidal graphite cast iron 1 on which the nitride layer 1 a is formed is placed on the turntable 11 in the vacuum chamber 10. The inside of the vacuum chamber 10 is heated to 250 to 550 ° C. and further depressurized to about 10 ⁻² to 10 ⁻³ Pa, and then argon (Ar) gas is introduced from the gas introduction port 12a. In order to improve the adhesion of the titanium-based hard coating, the spheroidized graphite cast iron 1 is preferably heated to about 400 to 500 ° C. Then, a bias voltage is applied to the spheroidized graphite cast iron 1 by a bias power source 15 to cause Ar ions to collide with each other, thereby activating the surface of the spheroidized graphite cast iron 1.

Then, arc discharge is generated by the arc power supplies 13a, 14a and the anodes 13b, 14b, and the titanium of the titanium evaporation sources 13, 14 is evaporated. At the same time, for example, nitrogen gas is supplied as a nitrogen source from the gas inlet 12a. Then, nitrogen and titanium are ionized in plasma generated by arc discharge, and ions are accelerated by a bias voltage, thereby depositing the ionized product on the surface of the spheroidized graphite cast iron 1 to form a TiN film. Next, a TiCN film is formed by supplying hydrocarbon gas as a carbon source from the gas inlet 12a. At this time, the supply of nitrogen gas is gradually decreased and the supply of hydrocarbon gas is increased. Finally, supply of nitrogen gas is stopped and only hydrocarbon gas is supplied. In this way, as the source gas supplied into the system, a large amount of nitrogen gas is initially supplied, and the nitrogen gas is gradually replaced with hydrocarbon gas, thereby forming a TiN film on the surface of spheroidal graphite cast iron 1 Next, a Ti (C _x N _y ) layer is formed so that the amount of nitrogen in the film gradually decreases and the amount of carbon increases, and finally, a TiC layer is formed as the outermost layer. In this way, a TiN layer with excellent adhesion is formed so as to be in contact with the mold surface, and the composition in the layer thickness direction is gradually changed so that nitrogen is replaced with carbon. By forming a TiC layer excellent in the above, a hard film having excellent durability can be formed on the surface of the spheroidal graphite cast iron 1.

  The surface hardness (Vickers hardness) of the spheroidized graphite cast iron material having the hard coating formed as described above is preferably about 3000 to 3800 HV because of high wear resistance.

  The spheroidized graphite cast iron material on which such a titanium-based hard coating is formed has excellent adhesion to the titanium-based hard coating and also has excellent slipperiness. Accordingly, such a spheroidized graphite cast iron material is preferably used for a die for press-working various steel plates, particularly for high-strength steel plates.

  The present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

Example 1
C: 3.5%, Si: 2.3%, Mn: 0.5%, P: <0.05%, S: <0.02%, Mg: 0.05%, Cu: 0.4% A molten metal was prepared by melting 500 kg of a blend (both mass%) in a high frequency induction electric furnace. Then, the molten metal is poured into a sand mold for obtaining a shape as shown in FIG. 3 at 1350 to 1450 ° C., and the temperature range of 1150 to 950 ° C. is cooled at a cooling rate of about 350 ° C./min. A casting was obtained after cooling. And the male side metal mold | die base material 20a and the female side metal mold | die base material 21a as shown in FIG. 3 were produced by cutting the surface of the obtained casting.

  Next, ion nitriding treatment was performed on the male side mold base material 20a and the female side mold base material 21a. Specifically, the male mold base 20a and the female mold base 21a were placed in an ion nitriding furnace set at a temperature of 550 ° C. and a pressure of 250 Pa. Then, while applying a DC voltage of −400 V to the male side mold base material 20a and the female side mold base material 21a, a mixed gas of air having a nitrogen gas content of 50% and nitrogen was flowed at a flow rate of 2 L / min. This treatment was performed for about 20 hours to form a nitride layer having a depth of 150 μm. At this time, 13 μm of the surface layer portion of the nitride layer was a compound layer. Then, a mirror-finished surface having a surface roughness (Ra) of about 0.05 μm was formed by blast polishing several μm of the surface of the compound layer. When the obtained surface was observed with a metallographic microscope, spherical graphite having a particle diameter range of 23 to 28 μm and an average particle diameter of 25 μm was observed.

  Next, an arc ion plating method as shown in FIG. 2 is used on the surfaces of the mirror-finished male die base material 20a and female side die base material 21a to perform the following by an arc ion plating method. A titanium-based hard coating was formed by the procedure described above.

First, the male mold base 20a and the female mold base 21a were placed on the turntable 11. And the pressure inside the vacuum chamber 10 was reduced to 3 × 10 ⁻³ Pa. Each temperature of the male side mold base material 20a and the female side mold base material 21a was controlled to 450 ° C. by a heater (not shown). Next, while supplying Ar gas from the gas introduction port 12a, the internal pressure was maintained at 2.7 Pa by exhausting from the exhaust port.

  Next, after the supply of Ar gas was stopped, nitrogen gas was supplied at a flow rate of 3000 mL / min for 7 minutes. At this time, the internal pressure was maintained at 2.7 Pa. At the same time, the arc was discharged to the titanium evaporation sources 13 and 14 to evaporate titanium. In the plasma generated by the arc discharge, nitrogen and titanium are ionized, and ions are accelerated by the bias voltage applied by the bias power source 15 to the male side mold base material 20a and the female side mold base material 21a. A TiN film was formed on the surface.

  Next, in the supply of nitrogen gas and the supply amount of methane gas, the internal pressure of nitrogen gas and methane gas is maintained at 2.7 Pa while controlling so that the supply amount of nitrogen gas gradually decreases and the supply amount of methane gas increases. For 20 minutes. And finally, supply of nitrogen gas was stopped and only methane gas was supplied for 20 minutes.

By the method as described above, a TiN layer of about 1 μm on the surface of each of the male mold base 20a and the female mold base 21a, and a Ti (C _x N _y ) layer of about 2 μm on the surface of the TiN layer Then, a TiC layer having a thickness of about 1 μm was formed on the surface of the Ti (CxNy) layer.

  The micro Vickers hardness, scratch adhesion, Rockwell indentation test, and bead pulling characteristics of the surfaces of the male mold 20 and the female mold 21 formed with the titanium-based hard coating were evaluated.

  In addition, the adhesive force was evaluated by a scratch measurement value using a scratch tester (Automatic Scratch Tester REVETEST) manufactured by CSEM. Moreover, the Rockwell indentation test and the bead drawing characteristics were evaluated by the following methods.

[Rockwell indentation test]
A Rockwell indentation test (indenter: Rockwell C scale, pressing load: 1470 N (150 kgf)) was performed, and the adhesion was evaluated according to the following criteria from the state of the film around the indentation. An optical micrograph of the indentation at this time is shown in FIG.
Excellent: No defect such as peeling was found around the indentation at the test site. Good: One defect was found around the indentation at the test site. Inferior: At least two peelings around the indentation at the test site. [Bead pulling characteristics]
As shown in FIG. 4, a steel plate 30 made of 20 × 300 × 1.4 mm high-tensile steel CR980Y (100 k class high tensile) was sandwiched between a male mold 20 and a female mold 21. Then, a pressing die composed of a male die 20 and a female die 21 sandwiching the steel plate 30 was set in a fixed small press. Then, one end of the sandwiched steel sheet 30 was pulled at a constant speed (500 mm / min) while gradually pressing the male mold 20 and the female mold 21 with a small press. And the drawing load F when the steel plate 30 broke and the pressing load P of a small press machine were measured.

  Then, the friction coefficient was measured from the pull-out load F and the pressing load P at the initial stage of tension and at the time of breakage by the formula of “friction coefficient μ = pull-out load F / pressing load P”.

  The results are shown in Table 1.

(Example 2)
In Example 1, the same as in Example 1 except that the cooling rate in the temperature range of 1150 to 950 ° C. was set to about 290 ° C./min when the male mold base 20a and the female mold base 21a were created. Thus, a male mold base 20a and a female mold base 21a having a surface roughness (Ra) of about 0.05 μm on which a nitride layer was formed were obtained. When the obtained surface was observed with a metal microscope, spherical graphite having a particle diameter range of 28 to 32 μm and an average particle diameter of 30 μm was observed. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, the same as in Example 1 except that the cooling rate in the temperature range of 1150 to 950 ° C. was set to about 160 ° C./min when the male mold base 20a and the female side mold base 21a were created. Thus, a male mold base 20a and a female mold base 21a having a surface roughness (Ra) of about 0.05 μm on which a nitride layer was formed were obtained. When the obtained surface was observed with a metal microscope, spherical graphite having a particle diameter range of 38 to 42 μm and an average particle diameter of 40 μm was observed. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1. Moreover, the optical microscope photograph of the impression in the Rockwell impression test obtained at this time is shown in FIG.

(Comparative Example 2)
In Example 1, the same procedure as in Example 1 was performed except that the cooling rate in the temperature range of 1150 to 950 ° C. was set to about 60 ° C./min when the male side mold base material 20a and the female side mold base material 21a were created. Thus, a male mold base 20a and a female mold base 21a having a surface roughness (Ra) of about 0.05 μm on which a nitride layer was formed were obtained. When the obtained surface was observed with a metallurgical microscope, spherical graphite having a particle diameter range of 53 to 58 μm and an average particle diameter of 55 μm was observed. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1.

(Comparative Example 3)
In Example 1, the surface on which the nitride layer was formed in the same manner as in Example 1 except that the cooling rate at the time of creating the male mold base 20a and the female mold base 21a was about 30 ° C./min. A male mold base 20a and a female mold base 21a having a roughness (Ra) of about 0.05 μm were obtained. When the obtained surface was observed with a metal microscope, spherical graphite having a particle diameter range of 65 to 73 μm and an average particle diameter of 70 μm was observed. And it evaluated similarly to Example 1. FIG. The results are shown in Table 1. Moreover, the graph which plotted the evaluation result of the adhesive force in Examples 1 and 2 and Comparative Examples 1-3 is shown in FIG.

  As shown in Table 1 and FIG. 7, according to the present invention, an example 1 in which a titanium-based hard coating was formed on the surface of nitriding-treated spheroidal graphite cast iron having an average particle diameter of spheroidal graphite of 30 μm or less and In Example 2, extremely high scratch adhesion was shown. In the Rockwell indentation test, almost no peeling was observed. On the other hand, in the comparative example 1 of 40 μm, the average particle diameter of the spherical graphite exceeding 30 μm, the comparative example 2 of 55 μm or less, and the comparative example 3 of 70 μm or less, the adhesion force suddenly decreased.

  From the above results, a titanium-based hard coating having excellent adhesion can be obtained by forming a titanium-based hard coating on the surface of nitrided spheroidal graphite cast iron having an average particle diameter of spheroidal graphite of 30 μm or less. I understand that.

  Further, in the bead drawing characteristic evaluation, the drawing load of Comparative Examples 1 to 3 is 14 to 18 kN, whereas in Examples 1 and 2, it is as high as 27 kN or more, and the spheroidal graphite cast iron material of Examples 1 and 2 is used. It can be seen that the hard coating formed on the surface of the press mold obtained from No. 1 is excellent in slipperiness and therefore also excellent in bead drawing characteristics. Furthermore, in both the initial friction coefficient and the friction coefficient at break as measured in the bead drawing characteristic evaluation, the press die of the example is lower than the press die of the comparative example, and is excellent in slipperiness. I understand that

DESCRIPTION OF SYMBOLS 1 Spheroidal graphite cast iron 1a Nitrided layer 2 Titanium hard coating 10 Vacuum chamber 11 Rotary table 12a Gas inlet 12b Gas exhaust port 13,14 Titanium evaporation source 13a, 14a Arc power source 13b, 14b Anode 15 Bias power source 20 Male side mold 20a Male side mold base material 21 Female side mold 21a Female side mold base material 30 Steel plate

Claims (7)

A titanium-based hard coating is formed on the surface of nitriding spheroidal graphite cast iron,
A spheroidal graphite cast iron material having a hard coating, wherein the average particle diameter of spheroidal graphite on the surface is 30 μm or less.   The titanium-based hard coating is a TiN layer from the surface, and a Ti (CxNy) layer formed on the TiN layer surface (where x + y = 1, x <1, and as the distance from the TiN layer surface increases, x becomes 1 The spheroidized graphite cast iron material having a hard coating according to claim 1, comprising a TiC layer formed on the surface of the Ti (CxNy) layer.   The spheroidal graphite cast iron material having a hard coating according to claim 1 or 2, wherein the titanium-based hard coating is a coating formed by using a PVD method.   The spheroidal graphite cast iron material having a hard coating according to claim 3, wherein the PVD method is an arc ion plating method.   A press die made of a spheroidal graphite cast iron material having the hard coating film according to any one of claims 1 to 4. A nitriding treatment step of nitriding a base material made of spheroidal graphite cast iron, and a coating forming step of forming a titanium-based coating film on the surface of the nitrided base material by a PVD method,
A method for producing a spheroidal graphite cast iron material having a hard coating, characterized in that an average particle diameter of spheroidal graphite is 30 μm or less on the surface of the base material. In the film forming step, nitrogen gas is supplied into a vacuum chamber in which the base material and the titanium evaporation source are placed, and arc is discharged to the titanium evaporation source to generate titanium, thereby generating plasma, and the plasma A step of accelerating nitrogen ions and titanium ions ionized by a bias voltage to deposit nitrogen ions and titanium ions on the surface of the mold base material to form a TiN film;
Forming the TiCN film by gradually reducing the supply of the nitrogen gas and supplying the hydrocarbon gas while gradually increasing the supply amount;
The method for producing a spheroidal graphite cast iron material having a hard coating according to claim 6, further comprising a step of forming a TiC layer by stopping the supply of the nitrogen gas and supplying only the hydrocarbon gas.