JP5245569B2 - Die casting mold - Google Patents

Description

The present invention relates to a die casting mold, and more particularly, Al, Mg, die casting mold melting loss of the Zn and the like, and to a mold surface treatment technique for improving the seizure resistance.

The die casting mold is generally manufactured using hot tool steel (for example, SKD61) as a material. Die casting molds are damaged mainly in three forms: heat check, seizure, and melting.
Here, “heat check” means that a crack is generated on the surface due to thermal stress generated by repeatedly receiving heating when the mold comes into contact with the molten metal and cooling when spraying the release agent. Say. Further, “seizure” means that the molten metal solidifies on the mold surface. The “melting loss” means that an element (mainly Fe) constituting the mold reacts with the molten metal and melts into the molten metal. When a heat check occurs, cracks are transferred to the product to cause rough skin, and when seizure or melting damage occurs, the solidified surface is transferred to the product or the mold itself is deformed.

  Paying attention to the initial stage of use of the mold, among these damages, seizure and the accompanying melt damage are likely to occur. This is because the mold release agent is not compatible with the mold at the initial stage of using the mold. As a result, the cast product adheres to the mold surface, causing deformation and damage of the die casting mold surface. In addition, if die cutting is performed while the casting is adhered to the mold surface, the die-cast product is deformed or damaged. When such deformation or damage occurs, the life of the die casting mold is reached, and the mold needs to be replaced. Therefore, in order to extend the life of the die casting die, it is important to suppress seizure and melting damage.

Therefore, various proposals have conventionally been made to solve these problems.
For example, in Patent Document 1, a nitride layer mainly composed of CrN is formed by nitriding the SKD61 material, and further, an oxidation treatment using oxygen gas (dry gas) not containing water vapor is performed on the nitride layer. An aluminum erosion resistant material having an oxide layer formed thereon is disclosed. In this document, as an example, a base material on which a nitride layer has been formed is placed, and oxygen gas (dry gas) is introduced under heating at 400 to 580 ° C. for 2 to 12 hours (with low oxygen concentration). And the second stage having a higher oxygen concentration) to form an oxide layer.

  Patent Document 2 discloses a casting mold having an excellent resistance to melting damage in which an iron-chromium oxide layer having a thickness of 1 to 30 μm is formed on the surface of steel having a predetermined composition. As an example, this document discloses that an oxide film is formed by heating in a steam atmosphere at 550 ° C. for 1 hour.

  Patent Document 3 discloses a mold in which a portion that is likely to be melted by hot tool steel is covered with a protective layer containing Nb / NbC having a thickness of 5 μm or more, and the protective layer is oxidized. Is disclosed. In the same document, as an example, SKD61 steel surface has Stellite 21 (Co-28Cr-5.5Mo-0.25C-2.5Ni), NbC, Nb, Nimonic 80A (73Ni-19.5Cr-1Co-2). .3Ti-1.4Al-1.5Fe-0.05C) is applied by plasma spraying / discharge overlaying / PVD, and heated in an air furnace and air-cooled to perform an oxidation treatment to form an oxide film. Is disclosed.

  In Patent Document 4, a ceramic film is formed on a part or all of a surface of a die casting mold for casting a molten metal that negotiates with the molten metal, and the ceramic film (TiN, TiAlN, TiCN, TiNO, TiAlCN, etc.) ) Is disclosed.

  In addition to the techniques disclosed in Patent Documents 1 to 4, as a general technique for suppressing seizure and melting damage when die casting Al, Zn, Mg, etc., these metals are formed on the die casting mold surface. It is known to form a film having low reactivity with molten metal or a film having low wettability.

JP2005-028398 JP 2000-234149 A JP-A-11-151563 JP2001-300711

As described in Patent Documents 1 to 4 above, various techniques have been proposed as techniques for suppressing damage to a die casting die. However, these conventional techniques all have seizure resistance (particularly, anti-seizure resistance). It was insufficient to ensure the aluminum seizure property. Further, even when a coating having low wettability is formed on the mold surface by using the above general technique, seizure and accompanying erosion may occur.
The present invention has been made in view of the above circumstances, and its purpose is to form a coating (functional coating) having excellent seizure resistance on the surface of the intermediate layer having excellent melt resistance, thereby preventing seizure resistance. An object of the present invention is to provide a die casting die that can improve the property and the resistance to melting damage.

In order to solve the above problems, the present inventors conducted extensive research on various surface treatment techniques, and formed a film (functional film) having excellent seizure resistance on the surface of the intermediate layer having excellent resistance to melting damage. As a result, it was found that a mold surface and a tool surface excellent in seizure resistance and resistance to erosion could be obtained. The present invention has been made based on such knowledge.

In order to solve the above problems, a die casting die according to the present invention is:
A mold base;
Formed on the surface of the mold base material, from IVa group elements (Ti, Zr, Hf), Va group elements (V, Nb, Ta), VIa group elements (Cr, Mo, W), Al, and Si A metal or alloy of at least one selected from the above, or a group IVa element (Ti, Zr, Hf), a group Va element (V, Nb, Ta), a group VIa element (Cr, Mo, W), Al, and Ri Do a single layer or multiple layers of compounds containing at least one element selected from Si, an intermediate layer is 1~10μm thickness formed by ion plating,
A film formed on the surface of the intermediate layer, having a thickness of 0.5 to 2.0 μm, containing 20% by mass or more of Fe, and having an Fe oxide formed thereon ;
The gist is that
Here, “at least one element selected from group IVa elements (Ti, Zr, Hf), group Va elements (V, Nb, Ta), group VIa elements (Cr, Mo, W), Al, and Si” "Is preferably Cr, Ti, or Al. As the “alloy”, CrAl and TiAl are preferable. The “compound” is preferably CrN, CrC, TiN, TiC, CrAlN, CrAlC, TiAlN, or TiAlC.

In this case ,
Surface of the mold base material is desirably being nitriding treatment,
The coating desirably includes a high oxygen portion having an oxygen concentration of 10 times or more that of the non-oxidized portion in a range from the surface to 0.5 μm.

  (Delete)

The die casting mold according to the present invention includes a coating film containing Fe of 20% by mass or more and having an Fe oxide formed thereon , so that seizure resistance can be improved, and the coating film and the mold surface Since the intermediate layer formed between the two is provided, there is an effect that the resistance to melting loss can be improved. Furthermore, the die-casting mold according to the present invention has an effect that the coating formed on the surface of the intermediate layer can contribute to the resistance to melting damage.
If the thickness of the intermediate layer is 1 to 10 μm, it is further effective in improving the resistance to melting .
Since the surface of the mold base is subjected to nitriding treatment, it is further effective in improving the melt resistance.
Since the coating has a high oxygen part in which the oxygen concentration is 10 times or more that of the non-oxidized part in the range from the surface to 0.5 μm, there is an effect of further improving seizure resistance.

  (Delete)

(Die casting mold)
A die casting mold according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, “%” means mass%.
FIG.1 and FIG.2 shows the cross-sectional schematic diagram of the metal mold | die for die-casting which concerns on one Embodiment of this invention.
In these drawings, a die casting mold 1 includes a mold base KK, an intermediate layer CS , and a film containing Fe in an amount of 20% by mass or more and having an Fe oxide formed thereon (hereinafter referred to as “functional film”). KH ”) . The intermediate layer CS is composed of a single layer or a plurality of layers. As shown in FIG. 1, the intermediate layer CS is composed of 1 to 3 layers, but as shown in FIG. 2, 1 to m layers (m is a natural number of 2 or more). It may be. Moreover, as shown in FIG. 2, the functional coating KH may be composed of 1 to n layers (n is a natural number of 2 or more).
The die-casting die 1 may be any one that can die-cast various materials generally used for die casting such as Al, Zn, and Mg.

The material of the mold base KK is not particularly limited, but hot tool steels such as SKD4, SKD5, SKD6, SKD7, SKD8, SKD61, and SKD62 are suitable. This is because hot tool steel has a particularly high operating temperature range.
The mold base KK may be in a state where the hardness is tempered by quenching and tempering, or a state in which nitriding treatment is further performed thereafter. If the nitriding treatment is performed, the thermal expansion coefficient of the surface is lowered, so that the peeling of the intermediate layer CS and / or the functional coating KH and the occurrence of cracks can be suppressed. In addition, when Al, Zn, Mg, or the like is die-cast, it becomes difficult to dissolve in these molten metals.

  The intermediate layer CS is formed on the surface of the mold base KK. That is, it is formed between the functional coating KH and the surface of the mold base KK. The intermediate layer CS may be formed over the entire surface of the mold base KK, or may be formed on at least a part of the surface of the mold base KK. The intermediate layer CS may be formed on a part that is liable to be damaged or seized, such as the surface of a mold cavity, the surface of a runner communicating with the cavity, or the surface adjacent to the cavity.

The intermediate layer CS is made of at least one selected from IVa group elements (Ti, Zr, Hf), Va group elements (V, Nb, Ta), VIa group elements (Cr, Mo, W), Al, and Si. Or a metal or alloy, or at least one selected from group IVa elements (Ti, Zr, Hf), group Va elements (V, Nb, Ta), group VIa elements (Cr, Mo, W), Al, and Si What consists of a single layer or multiple layers of a compound containing a seed element may be used.
Here, “single layer” refers to one type of layer composed of a single element or a plurality of elements, and “multilayer” refers to a laminate of two or more types of layers having different compositions. If the intermediate layer CS is a multilayer, the hardness can be adjusted according to the positions of the mold side and the surface side. The intermediate layer CS was formed in this manner when the functional coating KH having excellent seizure resistance on the outermost surface was peeled off, and the intermediate layer having excellent melt resistance on the surface of the mold base KK. This is because by providing a single layer or multiple layers as CS, further melting damage can be prevented.
As the “metal”, each of the above metals can be used as a single layer or multiple layers.
As the “alloy”, CrAl and TiAl can be used as a single layer or a multilayer. “Compounds” include carbides (eg, CrC, TiC, CrAlC, TiAlC, VC, Mo ₂ C, WC, TaC), nitrides (eg, TiN, ZrN, HfN, NbN, TaN, CrN, CrAlN, TiAlN, TiAlSiN) and carbonitride (for example, TiCN) can be used in a single layer or multiple layers.

Fig.1 (a) shows the cross-sectional schematic diagram of the metal mold | die 1 for die-casting in case the intermediate | middle layer CS consists of a single layer. Specifically, the intermediate layer CS can be composed of CrN, Cr, TiN, Ti, TiAlN, TiAl, CrAlN, CrAl, or the like.
FIG.1 (b) shows the cross-sectional schematic diagram of the die-casting die 1 in case the intermediate | middle layer CS consists of two layers of intermediate | middle layers CS1 and CS2 in order from the lower layer side. Specifically, the intermediate layers CS1 and CS2 are composed of the intermediate layer CS1 of Cr and the intermediate layer CS2 of CrN, the intermediate layer CS1 of Ti and the intermediate layer CS2 of TiN, the intermediate layer CS1 of CrN and the intermediate layer CS2 of the intermediate layer CS2. TiAlN or the like can be used.
FIG.1 (c) shows the cross-sectional schematic diagram of the die-casting die 1 in case the intermediate | middle layer CS consists of three layers of intermediate | middle layers CS1, CS2, and CS3 in order from the lower layer side. Specifically, the intermediate layers CS1, CS2, and CS3 are composed of the intermediate layer CS1 of Cr, the intermediate layer CS2 of CrN, and the intermediate layer CS3 of TiAlN, the intermediate layer CS1 of CrN, the intermediate layer CS2 of TiAlN, and the intermediate layer CS3. It can be composed of Cr or the like.

  The layer thickness of the intermediate layer CS is preferably 1 to 30 μm as a whole in either case of a single layer or multiple layers. The reason why the thickness of the intermediate layer CS is preferably 1 μm or more is that the resistance to melting can be improved. Moreover, if the layer thickness of the intermediate layer CS becomes too thin, the melt resistance becomes insufficient. On the other hand, the reason why the thickness of the intermediate layer CS is preferably 30 μm or less is that if it exceeds this, the melt resistance may deteriorate due to peeling of each layer or the like.

  Incidentally, the hardness of the intermediate layer CS is preferably 1000 HV or less in terms of micro Vickers hardness. This is because if the hardness of the intermediate layer CS becomes too high, stress relaxation due to plastic deformation becomes insufficient when a cooling cycle is applied to the mold. That is, it is for improving heat check resistance. On the other hand, the hardness of the intermediate layer CS is preferably 400 Hv or more, more preferably 600 Hv or more in terms of micro Vickers hardness. The lower the hardness of the intermediate layer CS, the higher the stress relaxation effect can be obtained. However, the intermediate layer CS is easily deformed by a slight external force, and other intermediate layers CS (in the case of multiple layers) formed on the intermediate layer CS and functions It is because there exists a possibility of promoting peeling and the generation | occurrence | production of a crack of the conductive film KH.

  The intermediate layer CS can be formed by an ion plating method, a vapor deposition method, or the like.

  The functional coating KH is formed on the surface of the intermediate layer CS. That is, it is formed on the outermost surface of the die casting mold 1. The functional coating KH may be formed over the entire surface of the intermediate layer CS, or may be formed on at least a part of the surface of the intermediate layer CS. The functional coating KH may be formed on a portion that is liable to be damaged or seized, such as the surface of a mold cavity, the surface of a runner communicating with the cavity, the surface adjacent to the cavity, or the like.

The functional coating KH only needs to be made of a material containing Fe in an amount of 20% by mass or more and having an Fe oxide formed thereon. This is for obtaining sufficient seizure resistance. Further, the functional coating KH may be either a single layer or multiple layers. Specifically, the functional coating KH can be composed of a single layer or multiple layers containing at least one of Fe ₂ O ₃ , FeO, and Fe ₃ O ₄ as Fe oxide. The thickness of the functional coating KH is preferably 0.5 to 2.0 μm. This is because if the film is too thin, sufficient seizure resistance cannot be obtained, while if it is too thick, the film may be peeled off.

  The functional coating KH can be formed by coating with a coating material by an ion plating method, a vapor deposition method, or the like, followed by an oxidation treatment. For the coating of the coating material, a target material containing Fe and / or Cr may be used. The target material preferably contains 20% by mass or more of Fe. The reason is to form 20 mass% or more of Fe oxide effective for improving seizure resistance. Specifically, SUS201, SUS303, SUS304, SUS305, SUS316, SUS321, or the like can be used as the target material. The method for the oxidation treatment is not particularly limited, but can be performed in an atmospheric furnace, a homo-treatment furnace, or a salt bath. This is because Fe oxide is formed. The functional coating KH preferably includes a high oxygen portion where the oxygen concentration is 10 times or more that of the non-oxidized portion in the range from the surface to 0.5 μm. The reason is that in the absence of such a high oxygen part, the Fe oxide is worn away due to wear or the like, and the seizure resistance may be deteriorated.

  In the above embodiment, the example of the method of forming the intermediate layer CS and the functional coating KH on the surface of the die base material KK of the die casting die 1 has been described. However, the method is not limited to the die casting die. First, it is within the scope of the present embodiment to be applied to the surface treatment of base materials such as parts attached to the mold, such as core pins, water jackets, shut-off valves, runner inserts, and the like.

(Die-casting die film forming method and target material)
Next, a method for forming a coating film on a die casting mold according to an embodiment of the present invention will be described. The film forming method of the die casting mold according to this embodiment is as follows:
(1) Production / preparation of mold base KK / tool base,
(2) Step of forming intermediate layer CS,
(3) Step of forming a film to be the functional film KH,
(4) It consists of a process of forming a functional coating KH by oxidation of the coating H.

Hereinafter, each process of these (1)-(4) is demonstrated.
(1) Preparation / preparation of mold base material KK / tool base material Mold base material / tool made of the above materials, that is, hot tool steel (SKD4, SKD5, SKD6, SKD7, SKD8, SKD61, SKD62, etc.) As a base material, the thing which carried out quenching and tempering and tempered hardness, or the state which performed the nitriding process after that is produced or prepared.
The nitriding method in the case of performing nitriding is not particularly limited, and various methods can be used depending on the purpose. Specifically, as the nitriding method, a gas nitriding method, a liquid nitriding method, an ion nitriding method, a radical nitriding method, or the like can be used. The nitriding treatment may be omitted, but when the nitriding treatment is performed, the surface hardness of the mold base material / tool base material is increased, and at the same time, the thermal expansion coefficient is lowered, so that the heat check resistance is further improved. . Moreover, it contributes to the improvement of the melt resistance and can further extend the mold life.

(2) Intermediate layer CS forming step The intermediate layer CS is formed on the surface of the mold base material / tool base material, group IVa elements (Ti, Zr, Hf), group Va elements (V, Nb, Ta), group VIa. A metal or alloy comprising at least one element selected from the elements (Cr, Mo, W), Al, and Si, or a group IVa element (Ti, Zr, Hf), a group Va element (V, Nb, Ta), By forming a single layer or a multiple layer of a compound (for example, carbide, nitride, carbonitride) containing at least one element selected from Group VIa elements (Cr, Mo, W), Al, and Si It is formed.

The method for forming the intermediate layer CS is not particularly limited, and various methods can be used depending on the purpose. Specifically, an ion plating method, a vapor deposition method, or the like can be used as the intermediate layer forming method. In the case of forming a compound, carbonization treatment, nitriding treatment, or carbonitriding treatment may be performed as necessary.
Here, the composition of the intermediate layer CS can be controlled by the target composition, the electrolyte composition, and the like.
The layer thickness of the intermediate layer CS can be controlled by adjusting the electrolysis voltage and the processing time.
In addition, the hardness of the intermediate layer CS can be controlled by optimizing its composition and formation method.
When the intermediate layer CS is formed into a multilayer, these processes may be performed on the already formed intermediate layer.

(3) Formation process of film H that becomes functional film KH Film H that becomes functional film KH covers the surface of intermediate layer CS with a target material (coating material) containing 20 mass% or more of Fe. It is formed. The method for coating the target material is not particularly limited, and various methods can be used depending on the purpose. Specifically, as a method for coating the target material, an ion plating method, a vapor deposition method, or the like can be used.
The composition of the coating H, and thus the functional coating KH, can be controlled by the composition of the target material, the atmosphere during coating, and the like.
The layer thickness of the coating H, and hence the functional coating KH, can be controlled by adjusting, for example, the arc current and the processing time.
The hardness of the coating H, and hence the functional coating KH, can be controlled by optimizing its composition and formation method.

(4) Step of forming functional film KH by oxidation of film H The functional film KH is formed by oxidizing the film H. That is, by this oxidation treatment, a functional coating KH not only containing 20% by mass of Fe but also containing at least one kind of Fe oxide (Fe ₂ O ₃ , FeO, Fe ₃ O ₄ ) is formed.
The method for oxidizing the coating H is not particularly limited, and various methods can be used depending on the purpose. As a method for oxidizing the coating H, specifically,
(A) A method of holding a sample for a predetermined time in an atmospheric furnace at 400 to 600 ° C.,
(B) a method of holding a sample for a predetermined time in a furnace of an oxidizing atmosphere (for example, a homoprocessing furnace) at 400 to 600 ° C.,
(C) A method of immersing a sample for a predetermined time in a salt furnace (for example, a salt bath nitriding furnace) at 400 to 600 ° C. can be used.

Examples of the present invention and comparative examples will be described below.
(Preparation of test piece)
Since the test piece was produced in the following procedures (1) to (4), this will be described.
Tables 1 and 2 show the presence / absence of substrate nitriding in Examples ( Comparative Example 25 in Table 1) and Comparative Examples, the composition and film thickness of the intermediate layer, and the functional coating (or coating). The amount of Fe, film thickness, and oxidation treatment method are shown together.

(1) Preparation of test piece A columnar (φ11 × 70 mm) specimen made of SKD61 was prepared, and the hardness was tempered to 44 HRC by quenching and tempering. Thereafter, it was precisely processed into a cylindrical shape (φ10 × 60 mm) to obtain a test piece.
Radical nitriding treatment was performed on some test pieces (see the column of base material nitriding in Tables 1 and 2). The conditions for radical nitriding were 500 ° C. × ₃ hr in 20 vol% NH ₃ gas-80 vol% H ₂ gas.

(2) Formation of intermediate layer, etc. Next, 1 to 3 single layers or multiple layers are formed as intermediate layers on the surface of some test pieces (excluding Comparative Examples 22 to 26) by ion plating. It was. Each layer thickness was controlled by adjusting the electrolysis voltage and the treatment time. Moreover, when forming carbide, nitride, or carbonitride (only examples of nitride in Tables 1 and 2), a reaction gas (methane, nitrogen, etc.) was introduced into the reaction vessel. The partial pressure of the reaction gas was 1 to 10 Pa. In Comparative Examples 22 to 26, no intermediate layer was formed.

(3) Ion plating Each test piece (Examples 1 to 30) using a target of 65 vol% or more Fe residual Cr as a target of an ion plating apparatus (multi-arc PVD apparatus M500C-600 manufactured by Nissin Electric Co., Ltd.). And the film of the single layer or the multilayer (only the example of a single layer in Table 1 and Table 2) was formed on the surface of comparative example 4) by ion plating. Moreover, when forming nitride, nitrogen gas was introduce | transduced in reaction container. The partial pressure of the reaction gas was 1 to 5 Pa.

(4) Oxidation treatment Under the conditions shown in Tables 1 and 2, each test piece (Examples 1 to 30, Comparative Examples 4 to 21, 23, 24, 26) in an atmospheric furnace, a homo-treatment furnace, or a salt bath. The oxidation treatment was performed. Thereby, while forming the functional film in the surface of each test piece of an Example, the surface of each test piece of the comparative example used as object was oxidized.

(Analysis of functional coating: composition analysis)
Next, for Example 12, the amount of Fe element contained in the functional coating and the oxygen concentration of the functional coating KH were analyzed. These analyzes were performed by examining the composition from the surface layer of the functional coating using a high frequency glow discharge spectroscopic analyzer (GD-OES) manufactured by Horiba, Ltd. The results are shown in FIGS.
FIG. 3 is a graph showing the amount of each element contained in the functional coating KH in relation to the distance from the surface. As shown in FIG. 3, the functional coating KH was found to have an Fe content of about 78% by mass to about 38% by mass.
FIG. 4 is a graph showing an enlarged portion of 0 to 1 μm indicated by the horizontal axis of the graph shown in FIG. 3 in order to verify the amount of O (oxygen) among the elements included in the functional coating KH. is there. As shown in FIG. 4, it was found that the functional coating KH had a range in which the oxygen concentration was 10 times or more that of the non-oxidized portion between 0.5 μm from the surface.

(Analysis of functional coating: oxide formation)
Next, Example 12 was analyzed whether or not Fe oxide was formed. This analysis was performed by structural analysis using an X-ray diffractometer (XRD) manufactured by Rigaku Corporation. The result is shown in FIG.
Based on empirical structural analysis data, it was confirmed that the peak of the oxide (Fe ₂ O ₃ ) appeared according to the results shown in the figure. Therefore, it was confirmed that the functional coating KH was formed with an oxide. In other examples, it was confirmed that oxides such as Fe ₂ O ₃ , FeO, and Fe ₃ O ₄ were formed by the same method.

(Evaluation test: seizure resistance)
Since the seizure resistance of the test pieces of each Example and each Comparative Example was examined, this will be described.
A φ10 test piece subjected to surface treatment was immersed in a molten aluminum alloy for casting (JIS ADC12) heated to 750 ° C. for 30 seconds. The specimen was pulled up from the molten metal and cooled to room temperature, and then the solidified film of the aluminum alloy adhering to the surface was removed with a waste as much as possible. The seizure property was evaluated by visually observing whether a solidified film remains. The results are shown in Tables 1 and 2. The result is that the solidified film does not remain as good (indicated by “◯”), the solidified film remains somewhat poor (indicated by “△”), and the solidified film that is hardly removed is bad. (Indicated by “x”).

(Evaluation test: resistance to erosion)
The melt resistance of the test pieces of each Example and each Comparative Example was examined and will be described.
The erosion rate was measured using the aluminum erosion tester shown in FIG. In the figure, an aluminum erosion tester 10 includes a support column 11 standing vertically from a floor FL, an arm 13 supported by the support column 11 through a slider 12 so as to be movable up and down, and hanging from the vicinity of the tip of the arm 13. The rotating shaft 14 is rotated by the motor M, and the disc 15 is fixed to the lower end of the rotating shaft 14. On the lower surface of the disc 15, a holder 16 is provided for fixing the test piece downward at a position eccentric from the center of the disc 15 and protecting the base of the test piece from the molten aluminum. A holding furnace 17 in which the molten aluminum alloy L is held is provided below the disk 15. A heater h is spirally wound around the outer peripheral surface of the holding furnace 17, and the holding furnace 17 is accommodated in a heat insulating tank 18.
The surface-treated φ10 test piece p was attached to the holder 16 with the tip 30 mm out. In this state, the slider 12 was lowered, the tip 30 mm of the test piece p was immersed in the molten aluminum L for casting (JIS ADC12) heated to 750 ° C., and the disk 15 was rotated at 200 rpm for 1 to 5 hours.
The weight of each test piece p before and after the test was measured, and the erosion rate (weight difference ratio before and after the test) was calculated. The results are shown in Tables 1 and 2.

(Test results)
While both the seizure resistance and the melt resistance were good in the examples, none of the comparative examples was good in both. Overall, when an intermediate layer is formed on the mold base, and a functional film is formed thereon,
(1) The functional coating is effective in improving seizure resistance and contributes to resistance to erosion, and
(2) It was found that the intermediate layer was effective in improving the resistance to melting.
These results are discussed in more detail below.

(Consideration of test results: Functional coating)
This result is considered from the viewpoint of the presence or absence of a functional coating.
Comparative Examples and Examples with or without Functional Coating (Comparative Example 1 and Examples 10 and 11 in which the intermediate layer is TiN, Comparative Example 2 and Examples 1 to 6, 23 to 25 in which the intermediate layer is CrN, intermediate Comparing Comparative Example 3 in which the layer is Cr and Examples 7 to 9), all of the examples have good seizure resistance, but the comparative example has an Al seizure that can hardly be removed even by rubbing with a waste cloth. The seizure resistance was poor. From this, it was found that the functional coatings of the examples had an effect of improving the seizure resistance. In these examples, the intermediate layer has a thinner thickness than the comparative examples (Examples 7 to 9 and 23). However, if the functional film is formed even if the intermediate layer is thin, it is resistant to fire. It was found that the adhesion was good.

By the way, when the intermediate layer which is the outermost layer is only Cr as in Comparative Examples 9 and 10, when this intermediate layer is directly oxidized, the seizure resistance is different even if the oxidation method is the same. Became. The cause is considered to be that a small amount of Fe oxide in the salt furnace was attached to the surface.
From the above, it was found that the functional coating is effective in improving the seizure resistance.

Next, the above results will be considered from the viewpoint of the specific configuration of the functional coating.
Comparing Comparative Example 4 with each Example, Comparative Example 4 has an intermediate layer formed, and further, a coating film is formed but no oxidation treatment is performed, so that no oxide is formed. Seizure was observed. Therefore, it was confirmed that an oxide should be formed on the film in order to improve the seizure resistance. In addition, according to the structural analysis of Example 12 (see FIG. 5), the formed oxide is Fe ₂ O ₃ or the like, and therefore the oxide formed in the functional film may be Fe oxide. I was able to confirm.
Moreover, although Examples 1-22 employ | adopt any one of an atmospheric furnace, a salt furnace, and an atmospheric furnace as an oxidation processing method, and oxidation time is 1h or 5h, in any case, seizure does not occur and favorable seizure resistance Showed sex. From this, it has been confirmed that the oxidation treatment method for forming the Fe oxide is not limited.
Furthermore, according to the composition analysis of Example 12 (see FIG. 3), the Fe element amount of the functional coating was about 38 mass% to about 78 mass%.
Further, according to the figure, it was confirmed that the functional coating had a range in which the oxygen concentration in the range from the surface to 0.5 μm was 10 times or more the oxygen concentration in the non-oxidized part.

  The reason why the seizure resistance is improved by forming the functional film is considered as follows. To cause seizure in a state in which a functional film is formed, “Al molten metal (a) separates the bond between oxygen and iron in the Fe oxide, and (b) bonds with the oxygen”. However, considerable energy is required to cause (a) and (b) in the state where the functional film is formed. Therefore, since the test pieces on which the functional film is formed do not cause (a) and (b), seizure does not occur, and as a result, it can be said that seizure resistance is improved.

(Consideration of test results: about intermediate layer)
The above results are considered from the viewpoint of the presence or absence of an intermediate layer.
Comparing comparative examples with different intermediate layers (specifically, comparative examples 22 to 26 without an intermediate layer and comparative examples 5 to 7 and 14 to 19 with an intermediate layer) Was relatively low at 0.5 to 12%, while those without an intermediate layer had a high rate of 85 to 100% regardless of the presence or absence of nitriding of the base material. From this, it was confirmed that the melt resistance can be improved by forming the intermediate layer.

Here, according to Comparative Examples 14 to 19, when the intermediate layer is thin, an increasing tendency of the erosion rate is assumed. However, even if the intermediate layer was thin, it was confirmed that the melting rate could be kept relatively low when there was a functional coating as in Examples 23 and 30. This is supported by the fact that Examples 1 to 30 have the same or longer immersion time as compared with the comparative example, but the melting rate still tends to be as low as 3% or less. However, when Examples 23 and 30 are compared with other Examples, it is feared that the melting rate increases if the intermediate layer is too thin. Therefore, it was determined that the intermediate layer thickness is preferably 1 μm or more. On the other hand, when Reference Example 25 was compared with other examples, it was feared that the melt loss rate would be increased even if the intermediate layer was too thick. Therefore, the intermediate layer thickness was determined to be preferably 30 μm or less.
Accordingly, it was confirmed that the formation of the intermediate layer as in the Examples can improve the resistance to melting loss, and if a functional film is further formed in addition to the intermediate layer, it contributes to the improvement of the resistance to melting loss.

  Incidentally, in Comparative Example 4, even when a film having an Fe element amount of 65% by mass was formed on the surface of the intermediate layer, the erosion rate was 90% with a soaking time of 2 hours. Therefore, it has been confirmed that even if only the coating film on which the oxide is not formed is formed on the surface of the intermediate layer, it does not contribute to the improvement of the melt resistance.

(Consideration of test results: About substrate nitriding)
The above results will be considered from the viewpoint of the presence or absence of substrate nitriding.
When Examples 4 and 26, Examples 2 and 27, Examples 6 and 28, Examples 11 and 29, and Examples 7 and 30 with or without substrate nitridation are compared, It was confirmed that the melting loss rate tends to be lower than that of the material without nitriding. From this, it has been confirmed that if an oxide is formed on the surface of the intermediate layer and further the nitriding of the base material is performed, it contributes to the resistance to melting damage.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the above embodiment.

  The die casting die according to the present invention can be implemented as a die casting die used for die casting of Al, Mg, Zn or the like. Moreover, the target material for a film and the method for forming a film according to the present invention can be used for producing a die casting tool in addition to a die casting die according to the present invention.

The cross-sectional schematic diagram of the die-casting die 1 is shown. FIG. 5A shows a case where the intermediate layer CS is composed of a single layer (one layer), and FIG. (C) shows a case where the intermediate layer CS is composed of three layers. It is the cross-sectional schematic diagram which generalized and showed the cross section of the metal mold | die 1 for die-casting. 10 is a graph showing the composition analysis result of the functional coating obtained in Example 12. It is a graph which expands and shows the 0-1 micrometer part of a horizontal axis among the composition analysis results of FIG. 10 is a graph showing an XRD pattern of a functional coating obtained in Example 12. It is a schematic block diagram of an aluminum erosion tester.

Explanation of symbols

1 Die casting mold KK Mold base CS Intermediate layer KH Functional coating

Claims (3)

A mold base;
Formed on the surface of the mold base material, from IVa group elements (Ti, Zr, Hf), Va group elements (V, Nb, Ta), VIa group elements (Cr, Mo, W), Al, and Si A metal or alloy of at least one selected from the above, or a group IVa element (Ti, Zr, Hf), a group Va element (V, Nb, Ta), a group VIa element (Cr, Mo, W), Al, and Ri Do a single layer or multiple layers of compounds containing at least one element selected from Si, an intermediate layer is 1~10μm thickness formed by ion plating,
A film formed on the surface of the intermediate layer, having a thickness of 0.5 to 2.0 μm, containing 20% by mass or more of Fe, and having an Fe oxide formed thereon ;
A die casting mold characterized by comprising: Surface of the mold base material, die casting mold according to claim 1 you characterized in that nitriding is. 3. The die casting die according to claim 1 , wherein the coating includes a high oxygen portion having an oxygen concentration of 10 times or more of the non-oxidized portion in a range from the surface to 0.5 μm.

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