JP4883400B2 - Casting parts - Google Patents

Description

  The present invention relates to a casting member used in contact with a molten metal, such as a die used for die casting and casting, or a casting pin, or a piston ring used for an injection machine for die casting.

  Conventionally, steels such as hot die steel, high-speed steel, and stainless steel have been used for casting members used for forming molten metal by casting. The metal to be molded most frequently used in molding by casting is an aluminum alloy. However, in the case of the above steel materials used for casting members such as molds, these steel materials are aluminum in the portion that comes into contact with the aluminum alloy. It melts with the molten alloy, increases the iron content in the molten aluminum alloy, and lowers the quality of the cast product. Furthermore, the melting damage of these molds and the like causes various inconveniences in operation.

  As the above countermeasure, since a deep hardened layer is obtained and the cost of the treatment is very low, nitriding treatment on the work surface has been often used. However, due to the increased strength of cast products, the use of high-melting-point aluminum alloys has increased as a material to be molded. Therefore, in nitriding, N in the treated layer easily diffuses into the molten aluminum at high temperatures. As a result of the disappearance of the treatment layer, the resistance to melt damage is reduced, and the melt damage phenomenon proceeds rapidly.

In order to solve the above problems, there is an increasing use of a mold in which a work surface is coated with a ceramic that is difficult to react with a molten metal by a physical vapor deposition method (hereinafter also referred to as a PVD method). For example, after carburizing or nitriding the mold base material, a method of applying a coating layer such as TiC or TiN by the PVD method (Patent Document 1), coating the Ti intermediate layer on the mold surface, then TiAlN A coating method (Patent Document 2) has been proposed. A method of applying CrN to the coating layer has also been proposed (Patent Documents 3 and 4).
JP 61-033734 A JP 07-112266 A Japanese Patent Laid-Open No. 10-137915 JP 2001-11599 A

  Due to the recent increase in the speed of the casting cycle, the molten metal temperature of the aluminum alloy is cast at a relatively high temperature, so that the use environment of the molten metal member such as a casting mold becomes more severe. In other words, the thermal expansion of molds and other members due to molten metal during casting, and shrinkage due to the application of a release agent after solidification of the work material, or deflection of the mold and members due to solidification shrinkage of the work material occurs significantly. It has become like this. As a result, in the coating layer having the composition proposed in Patent Documents 1 to 4, peeling of the coating layer occurred during use, and the molten metal penetrated into the member through this peeling portion as a route, and the mother layer just below the surface treatment layer. Reacts with iron in the material to form an alloy. And when the surface coating layer directly expanded due to the formation of this alloy, the treatment layer was peeled off at once, and a phenomenon in which the melting loss rapidly progressed was observed.

  In recent years, die casting products made of aluminum alloy or magnesium alloy have been applied to housings such as hard disks, personal computers, and mobile phones that are required to be lighter, and cast products have been made thinner. In order to reduce the thickness of the cast product, it is necessary to increase the injection speed of the molten metal into the mold, and the proposed coating layer does not have sufficient wear resistance against wear due to the molten metal. . In other words, if explained with a mold, wear due to fluid occurs at a site where the molten metal near the gate enters at a high speed, resulting in a mold correction cycle, a decrease in mold life, and a defective shape of the cast product. It becomes.

  An object of the present invention is to provide a casting member that solves the above-mentioned problems in a casting member such as a die-casting die or a casting pin that is used in contact with a high-temperature molten metal.

  The present inventors pay attention to the failure occurrence mechanism in the casting member that is the above-mentioned use, and in the melting resistance and wear resistance of the coating layer applied to the working surface (welded surface of the molten metal) of the member. The effects of the composition of the coating layer, the layer structure, and the film formation conditions were examined in detail.

  As a result, the coating layer that plays a role from the base material surface to the work surface in contact with the workpiece is a composite layer classified by its hardness distribution, and further by adjusting the thickness relationship between those layers, As a casting member, it has been found that extremely good resistance to melting and abrasion can be obtained. As a result, for example, in an aluminum alloy die-cast die-cast pin, melt damage due to peeling of the coating layer due to deflection of the pin that occurs during solidification shrinkage of the cast product, and wear when a high-speed molten metal collides are sufficiently suppressed. It was confirmed that the service life of the casting member was significantly improved.

That is, the first invention of the present invention is a casting member having a coating layer formed by physical vapor deposition on at least a work surface of a casting member made of a metal as a base material, and the coating layer is formed on the outermost layer. a layer, c layer directly above the base material, and at least three layers of b layer are coated between the a layer and c layer, and the a layer, b layer, and c layer are the same metal-based compound, and the hardness symbol HV0 The hardness of each layer according to .025
2500> (hardness of layer a)> 1000,
3500> (b layer hardness)> 2300,
2500> (hardness of c layer)> 1000 and
(500 + a layer hardness) <(b layer hardness),
(500 + c layer hardness) <(b layer hardness),
The casting member is characterized in that the layer thickness is b layer <c layer, and the total thickness of the coating layers is 5 to 15 μm.

The a layer which is the outermost layer of the present invention and the c layer immediately above the base material are composed of a nitride, carbide or carbonitride mainly composed of Ti or Cr, and the outermost layer a layer. and b layer covering between the c layer directly preform is either a nitride, carbide, carbonitride of a metal element portion Ti, mainly one or two chosen C r or al It is desirable. Alternatively, the a layer and the c layer are composed of any one of a nitride, carbide, and carbonitride in which the metal element portion is mainly composed of Cr, and the b layer is a nitride in which the metal element portion is mainly composed of Cr and Al, It is desirable to be either carbide or carbonitride.

  It is desirable that the outermost layer a has a layer thickness of 1 to 5 μm, the b layer has a layer thickness of 1 to 5 μm, and the c layer immediately above the base material has a layer thickness of 2 to 7 μm.

  Further, the base material on which the coating layer is formed has a hardness symbol HV0.2 that has a hardness at a depth of 25 μm from the outermost surface of the base material compared to a hardness at a depth of 500 μm from the outermost surface of the base material. It is desirable that it is 100 or more.

  Conventional casting members coated with TiN, TiCN, and CrN have been unable to obtain a sufficient life against the severe use environment in recent years. By using the casting member to which the surface coating layer structure of the present invention is applied, it is possible to achieve improvement in the mold resistance and wear resistance of the mold, so that the life can be drastically improved.

  The hard coating on the working surface of the casting member does not have to be examined only by paying attention to the characteristics only for the molten metal that comes into contact with it. It is necessary to consider this. Therefore, the coating film according to the present invention is a composite coating layer that can impart both the required characteristics for the outermost surface in contact with the molten metal and the required characteristics for the base material to the maximum extent. The outermost layer of the present invention has a main role of imparting melt resistance and wear resistance to the casting member, and its presence is extremely important. Therefore, it is necessary that the film has these characteristics in a high dimension and in a well-balanced manner.

According to the examination results of the present inventors, at least three layers on the mold work surface, such as the outermost layer a layer, the layer c immediately above the base material, and the layer b existing between the layer a and the layer c, It is coated by physical vapor deposition. And the boundary of the three layers is classified according to the hardness characteristics that each has, and the hardness of each layer is a hardness symbol HV0.025,
2500> (hardness of layer a)> 1000,
3500> (b layer hardness)> 2300,
2500> (hardness of c layer)> 1000 and
(500 + a layer hardness) <(b layer hardness),
(Hardness of 500 + c layer) <(Hardness of b layer)
In order to improve the adhesion of the coating layer, it has been confirmed that it is extremely important to make the structure as follows. The hardness symbol HV0.025 is a hardness value with a test load of 0.2452N in the Vickers hardness test method specified by JIS-Z-2244.

  As the hard material is a relatively soft substance, the aggressiveness to the work piece that is a cast product is lower, and cracks in the coating layer due to thermal cycle and bending of the member are less likely to occur. Further, in the case of physical vapor deposition, the adhesion of the coating material is also improved. Therefore, although a certain degree of hardness is required for the outermost layer, applying a layer of a relatively soft substance reduces the aggression on the workpiece, that is, the covering layer reduces the workpiece. Sudden galling caused by scratching can be suppressed. In addition, since the coating layer is covered with a soft material that does not easily generate cracks, peeling and melting damage starting from the cracks can be suppressed, and as a result, the adhesion of the entire coating layer can be improved. At this time, although a certain degree of hardness is required, the reason for applying a soft substance to the c layer immediately above the base material is to improve the essential adhesion between the base mold material and the coating layer. This is to make it happen.

  On the other hand, the b layer is a relatively hard substance having a hardness exceeding 2300HV0.025 and is coated for the purpose of improving the wear resistance. Poor adhesion. At this time, it is recognized that the b layer is not easily peeled by sandwiching the b layer between the soft a layer and the c layer. Further, in a portion where the wear due to the molten metal of the casting member is severe, the outermost layer a The layer wears preferentially, but since a hard b layer appears from below, it was confirmed that the coating layer exhibited a function of improving the wear resistance at a necessary site.

  Regarding the thickness of each layer, if the hard b layer is made thicker than the c layer, the balance of the characteristics of each layer is lost and the adhesion of the b layer is deteriorated even in the above-described hardness relationship. Therefore, the layer thickness of the b layer and the c layer has a relationship of b layer <c layer. Also, if the film thickness of the entire coating layer is less than 5 μm, sufficient melt resistance cannot be obtained as a casting member, and if the coating layer exceeds 15 μm, the adhesiveness is extremely reduced. The total thickness is 5 to 15 μm. Furthermore, it is good to set it as 7-12 micrometers.

  The physical vapor deposition method is prescribed | regulated about the coating method of the member for casting of this invention. This is for the purpose of suppressing the thermal effect on the base material that coats the hard material, thermal distortion and deformation generated in the mold, for example, below the tempering temperature of the hot die steel or high-speed steel that is the base material. This is because the film can be formed and the compressive stress can remain in the film. Although there is no particular limitation on the type of physical vapor deposition method, it is desirable to be a physical vapor deposition method such as an arc ion plating method or a sputtering method in which a Bias voltage is applied to the coating base material side.

  The metal material of the base material is not particularly defined, and for example, hot die steel, high speed steel and cemented carbide as described above can be used. In this regard, improved metal types that have been proposed as steel types that can be used in conventional molds, including standard metal types (steel types) according to JIS and the like, can also be applied.

In the working surface of the casting member of the present invention, the a layer which is the outermost layer of the formed coating layer and the c layer immediately above the base material satisfy the relationship between the hardness and the layer thickness with the b layer. good. However, it is desirable that the a layer and the c layer are any of nitride, carbide, and carbonitride whose metal element portion is mainly Ti or Cr depending on the use of the casting member. In addition, regarding the main component, Ti or Cr is 70 (atomic%) or more, and further 90 (atomic%) or more in the ratio of only the metal (including semimetal) composition part excluding nitrogen and carbon. (Essentially 100 (atomic%) included).

Further, in the working plane of the casting member of the present invention is coated between a layer and the layer c, b layer, the metal element portion Ti, Cr, 1 kind or 2 or more species selected from Al, more In a limited manner, it is desirable to use any one of nitride, carbide, and carbonitride mainly composed of one or two selected from Ti and Cr . In addition, about making it the main body, it is the same as that of said a and c layer, It is good to set it as 70 (atomic%) or more, Furthermore, it is good to set it as 90 (atomic%) or more (substantially 100 (atomic%) is included. ). At this time, in order to satisfy the hardness relationship with the a layer and the c layer, for example, when the a layer and the c layer are TiN, a TiAlN-based hard material that is harder than TiN is used as the b layer. Select and coat using the component ratio of Ti and Al that satisfies the hardness relationship of each layer or film forming conditions, or hard carbide or carbonitride compared to TiN such as TiC and TiCN of the hardness of each layer It is necessary to coat under film forming conditions that satisfy the relationship.

In the present invention, the a layer, the b layer, and the c layer are more preferably, in terms of adhesion between the respective layers, and are limited to this. For example, in the case of Cr-based nitride, it is desirable that the a layer is CrN, the b layer is CrAlN, and the c layer is CrN. That is, the a layer and the c layer are composed of any one of a nitride, carbide, and carbonitride whose metal element portion is mainly Cr, and the b layer is a nitride whose metal element portion is mainly Cr and Al. It is desirable to be either carbide or carbonitride.

  Although the above is given as an example, each of the a layer and the c layer is mainly composed of Ti or Cr in the metal element portion, but if necessary, such as IVa, Va, VIa group and Al, Si, B, Other metal (semi-metal) elements, even in the b layer, the metal element part is mainly composed of one or more selected from Ti, Cr, Al, but if necessary, IVa, Va, VIa group Further, other metal (metalloid) elements such as Si and B may be added in a small amount of 10 atomic% or less in each layer.

  Next, the thickness of each layer constituting the coating layer of the present invention will be described. The layer a which is the outermost layer of the present invention preferably has a layer thickness of 1 to 5 μm. When the layer thickness is less than 1 μm, the melt resistance is not sufficient and the layer is lost at an early stage, and the effect of suppressing the initial sudden galling, which is one of the roles of the a layer, may not be obtained. On the contrary, if the coating exceeds 5 μm, it may be peeled off early depending on the use conditions. Therefore, the layer thickness of the a layer that is the outermost layer among the coating layers on the work surface of the present invention is preferably 1 to 5 μm.

  Moreover, it is desirable that the b layer coated between the outermost layer a and the layer c immediately above the base material has a layer thickness of 1 to 5 μm. If the layer thickness is less than 1 μm, the abrasion resistance, which is the purpose of coating the b layer, may not be sufficient. Conversely, if the layer thickness exceeds 5 μm, the adhesion may be poor and peeling may occur early. Therefore, the layer b of the present invention desirably has a layer thickness of 1 to 5 μm.

  And as for c layer which is the base material layer of this invention, it is desirable that the layer thickness is 2-7 micrometers. Depending on the use conditions, if the layer thickness is less than 2 μm, it is difficult to obtain sufficient adhesion with the base material because it is too thin. On the other hand, when the coating exceeds 7 μm, the effect of improving the adhesion is not changed, and depending on the use conditions, it may be peeled off early. Therefore, the layer thickness of the c layer, which is the layer immediately above the base material of the present invention, is desirably 2 to 7 μm.

  Further, the casting member of the present invention has a hardness at a depth of 25 μm from the outermost surface of the base material on which the coating layer is formed for the purpose of further improving the resistance to melting and abrasion. It is desirable that the Vickers hardness defined by JIS-Z-2244 is 100HV0.2 or more higher than the hardness at a depth of 500 μm to 500 μm. The hardness symbol HV0.2 is a hardness value with a test load of 1.961N in the Vickers hardness test method. As a specific example, it is desirable to apply in advance a surface hardening process using diffusion such as nitriding or carburizing. At this time, a nitride layer called a white layer formed by nitriding treatment and a compound layer called a carbide layer recognized by carburizing cause a decrease in the adhesion of the c layer directly above the base material. It is desirable not to form the film by controlling the thickness or to remove it by polishing or the like.

  Next, the present invention will be described in detail based on examples. However, the present invention is not limited by the following examples, and can be arbitrarily changed without departing from the gist of the present invention. Included in the technical scope.

Example 1
Hot die steel SKD61 prescribed by JIS was prepared, oil-quenched from 1030 ° C, and tempered to 47HRC by tempering at 550-630 ° C. Thereafter, a cylindrical test piece having a diameter of 10 mm and a length of 100 mm was evaluated for the evaluation of the melt resistance, and a plate-shaped test piece having a thickness of 3 mm and a side of 30 mm was evaluated for the evaluation of adhesion. Then, a coating treatment was performed using these test pieces as a base material. Before the coating treatment, ion nitriding treatment was performed on all test pieces under the following conditions as surface hardening treatment.

The surface hardening treatment before the coating treatment is performed by ion nitriding treatment at 500 ° C. for 10 hours in an atmosphere with a flow rate ratio of 5% N ₂ (remaining H ₂ ), and then finishing each test surface by polishing. It was. Since the hardness at a depth of 25 μm from the finished surface was 680 HV0.2 in all the test pieces subjected to this nitriding treatment, the hardness at a depth of 500 μm was 47 HRC (= 471 HV0.2 ) Has been confirmed to be cured to 100HV0.2 or higher. And the coating process of the following conditions was performed with respect to the base material surface after finishing.

As a coating method, an arc ion plating apparatus was used. First, a bias voltage of −400 V was applied to the base material in an Ar atmosphere at a pressure of 0.5 Pa, and plasma cleaning with a hot filament for 60 minutes was performed. After that, various metal targets that are evaporation sources of the metal components and N ₂ gas as a reaction gas, using CH ₄ gas as necessary, a base material temperature of 500 ° C., a reaction gas pressure of 3.0 Pa, − Film formation was performed at a Bias voltage of 50V.

  The obtained test piece was subjected to the measurement of the layer thickness for each layer of the coated surface, the hardness test, the adhesion evaluation test applying the Rockwell hardness test, and the melt resistance evaluation. Each evaluation test method is shown below.

(1) Measurement of layer thickness After cutting the test piece in the thickness direction so that the cross section of the coating layer appears, the sample is embedded in a resin and polished for structure observation, and the thickness of each layer is measured with an optical microscope (1000 times magnification). It was measured.

(2) Hardness test The same test piece as the layer thickness was used, and the hardness of each layer cross section was measured with a micro Vickers tester (HM-115 manufactured by Mitutoyo Corporation).

(3) Adhesion evaluation test Indentation was made on the coated surface (30 mm × 30 mm) with a C scale with a Rockwell hardness tester (Mitutoyo AR-10), and the portion was observed with an optical microscope. The peeling that occurs around the indentation was evaluated according to the criteria shown.

(4) Melt resistance test for molten metal The test piece was tested in a molten metal of 750 ° C. of aluminum alloy AC4C for 90 hours per minute with a vertical motion of 30 mm amplitude for 3 hours. The melt resistance was compared with the mass ratio before and after.

Table 1 shows the details of the coating layers relating to the inventive examples and comparative examples (subscript coefficients attached to the metal (semi-metal) composition part are atomic ratios) and the results of various evaluations. In the conventional example, since the configuration of the coating layer of the present invention is not satisfied, it is difficult to define the formed outermost layer, the layer immediately above the base material, and the intermediate layer.

  As shown in Table 1, the examples of the present invention satisfy the prescribed range of the present invention, so that the adhesion is remarkably excellent regardless of the thickness of the layer. 2 and 3 are examples of the present invention. 3 and no. 4 is a photomicrograph showing the adhesion evaluation test result of 4 (state around the Rockwell indentation). Compared to other examples of the present invention, the present invention example No. Even if it is 4, sufficiently excellent adhesion is achieved. Moreover, since adhesiveness is favorable, it turns out that all are excellent also about melt-resistance.

  On the other hand, for the evaluation results of the comparative example and the conventional example, comparative example No. No. 11 satisfies the present invention with respect to the hardness of each layer, but the b layer and the c layer are too thick, so that the adhesion and the erosion resistance are extremely poor. Comparative Example No. For Nos. 12 and 15, the hardness relationship of each layer does not satisfy the present invention, and the hardness balance is lost due to the coating of a relatively hard layer directly on the base material and the outermost layer. As a result, the melt resistance was poor. Comparative Example No. Although the adhesiveness of 13 and 14 was favorable compared with the other comparative examples, since the layer thickness of c layer was thinner than b layer, the adhesiveness was inferior to the example of this invention. In FIG. 13 shows a micrograph of the adhesion evaluation test result 13 (state around the Rockwell indentation).

  Further, the conventional example No. different from the basic covering structure. Nos. 21 and 23 are remarkably inferior in adhesion in a region where the layer thickness is relatively thick as in the present invention. FIG. It is the microscope picture which showed the adhesive evaluation test result of 23 (state around Rockwell impression). Conventional example No. coated with relatively soft CrN No. 22 is excellent in adhesion even when the layer thickness is thick, but since the hardness is extremely low, early wear is expected when applied to a mold.

(Example 2)
Next, the invention example No. 1 in Table 1 was used. 4, no. 5, conventional example No. 2 in Table 2. A die-cast core pin having a surface coating layer configuration equivalent to that of No. 22 was produced and evaluated based on the life of the actual mold.

  First, a high-speed steel-based toughness improving material having the chemical composition shown in Table 3 is roughly processed into an approximate shape of a cast pin in an annealed state, subjected to oil quenching at 1080 ° C., and tempered to 55 HRC by tempering at 600 ° C. did. Thereafter, finishing was performed, and coating treatment was performed under the same conditions as in (Example 1). In addition, these cast pins that were not subjected to surface hardening treatment before the coating treatment had a hardness at a depth of 25 μm and a depth of 500 μm from the outermost surface of the base material before and after the coating treatment. Both maintained the above-mentioned tempered hardness 55HRC (= 595HV0.2).

  The core pin produced above has the shape shown in FIG. Then, casting was performed using a 300-ton die casting machine using an aluminum alloy AC4C having a molten metal temperature of 700 ° C. Table 4 shows the life of each core pin.

  The cast pin to which the present invention is applied has improved the mold life by more than twice as compared with the conventional pin. Finally, the pin applied to the present invention had a lifetime due to seizure, but the pin applied to the conventional example eventually had a lifetime due to breakage after wear at the tip. As described above, it has been confirmed that the life of the pin is dramatically improved by applying the present invention to a die-cast core pin.

  The present invention describes a casting member used in contact with molten metal, such as a die or a die pin used for die casting and casting, or a piston ring used for an injection machine for die casting. The molten metal (casting material) is not limited to aluminum and aluminum alloys, but can be applied to casting of magnesium alloys. Further, the casting member of the present invention is used for metal plastic processing such as forging and pressing in cold and warm conditions, and can be diverted as a hard material-covered plastic processing die that requires wear resistance. Is possible.

It is a figure which shows the evaluation criteria of the peeling generation | occurrence | production situation of the adhesiveness evaluation test which applied the Rockwell hardness tester used in the Example. Invention Example No. 3 is a photomicrograph showing the result of 3 adhesion evaluation test (state around the Rockwell indentation). Invention Example No. 4 is a photomicrograph showing the adhesion evaluation test result of 4 (state around the Rockwell indentation). Comparative Example No. It is the microscope picture which showed the adhesive evaluation test result of 13 (state around Rockwell impression). Conventional Example No. It is the microscope picture which showed the adhesive evaluation test result of 23 (state around Rockwell impression). It is a figure which shows the shape of the core pin used in (Example 2).

Claims (5)

A casting member having a metal as a base material, a casting member having a coating layer formed by physical vapor deposition on at least a work surface, the coating layer having an a layer as an outermost layer, a c layer directly above the base material, At least 3 layers of b layer are coat | covered between a layer and c layer, a layer, b layer, and c layer are the same metal type compounds, and the hardness of each layer by hardness symbol HV0.025,
2500> (hardness of layer a)> 1000,
3500> (b layer hardness)> 2300,
2500> (hardness of c layer)> 1000 and
(500 + a layer hardness) <(b layer hardness),
(500 + c layer hardness) <(b layer hardness),
A casting member, wherein the layer thickness is b layer <c layer, and the total thickness of the coating layers is 5 to 15 μm. The a layer and the c layer, nitride metal element portion is composed mainly of Ti or Cr, carbides, either as carbonitride, the b layer is selected metallic element portion Ti, C r or al 2. The casting member according to claim 1, wherein the casting member is any one of nitride, carbide, and carbonitride mainly composed of one or two kinds . The a layer and the c layer are any one of a nitride, carbide, and carbonitride in which the metal element portion is mainly Cr, and the b layer is a nitride in which the metal element portion is mainly Cr and Al, The casting member according to claim 1, wherein the casting member is one of carbide and carbonitride. Thickness of the layer a is 1 to 5 [mu] m, the layer thickness of the b layer is 1 to 5 [mu] m, the layer thickness of the c layer according to any one of claims 1 to 3, characterized in that a 2~7μm Casting member. The base material on which the coating layer is formed has a hardness at a depth of 25 μm from the outermost surface being 100 or more higher at a hardness symbol HV0.2 than a hardness at a depth of 500 μm from the outermost surface. The casting member according to any one of claims 1 to 4 , characterized in that: