TW202115267A - Mold and method for producing mold having excellent wear resistance and erosion resistance to molten metal - Google Patents

Abstract

The present invention is to provide a mold that has excellent wear resistance and erosion resistance to molten metal. The mold of the present invention is provided with an iron-based mold base material; a nitrogen diffusion layer provided on a top layer of the mold base material; a nitrogen compound layer provided on a top layer of the nitrogen diffusion layer; and an iron-based oxide layer that is provided on a top layer of the nitrogen compound layer becoming the outermost layer. The thickness LN of the nitrogen diffusion layer of the mold is 100 [mu]m or more, the maximum Vickers hardness HS of the nitrogen diffusion layer is 900 HV or more, and the thickness LO of the iron-based oxide layer is 1 [mu]m or more and less than 10 [mu]m.

Description

Mold and mold manufacturing method

The present invention relates to molds and mold manufacturing methods.

Metal processing methods that use molds made of steel include casting, forging, and extrusion. The molds used in such metal processing are subjected to various surface treatments on the surface of the mold base material. The surface treatment of the base material of the mold is as follows: the surface of the base material of the mold is treated by carburizing, nitriding and oxidation to form a surface modification layer; using chemical vapor deposition (CVD) Method and physical vapor deposition (Physical Vapor Deposition; PVD) method, etc., the surface of the mold base material is coated with a film such as nitrides, carbides, and borides.

For example, the mold used in forging the material to be processed by warm or heat (warm forging mold), most of the factors that affect the life of the mold are damage caused by wear or cracks (hot cracks) caused by thermal fatigue. Therefore, it has been reviewed to improve the abrasion resistance or thermal cracking resistance by applying surface treatment. The hot forging mold with excellent wear resistance proposed in Patent Document 1 is characterized by the presence of iron oxides in the surface of the mold with one or two of Si and Cr in a region where the concentration is thicker than that of the base. The main body and a layer with a thickness of 1-20μm. In addition, the warm forming mold proposed in Patent Document 2 diffuses and penetrates nitrogen in the surface layer, and At a depth of at least 100 μm from the surface, a wear-resistant layer with a hardness of 900 to 1100 Hv and an N concentration of 1.5% by weight or more is formed at any depth.

In addition, for die-casting molds, most of the causes that affect the life of the mold are cracks (hot cracks) caused by thermal fatigue, or the parts that are in contact with the molten metal (molten metal) are easily melted by the molten metal, so Some reviews have been conducted to improve the resistance to thermal cracking or melting damage by applying surface treatment. The die-casting mold proposed in Patent Document 3 is provided with: an iron-based mold base material, a nitrogen diffusion layer provided on the upper layer of the mold base material, a nitrogen compound layer provided on the upper layer of the nitrogen diffusion layer, and The lithium iron composite oxide layer with a specific thickness, which is the outermost layer on top of the nitrogen compound layer, has excellent resistance to melt loss in molten metal.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 9-279328

[Patent Document 2] Japanese Patent Laid-Open No. 2009-041063

[Patent Document 3] Japanese Patent Laid-Open No. 2016-221542

The above-mentioned Patent Document 3 discloses that a die-casting die in which a nitrogen diffusion layer, a nitrogen compound layer, and a lithium-iron composite oxide layer of a specific thickness are formed on the upper layer of the iron-based die base material exhibits excellent resistance to melt loss against molten metal . On the other hand, when improving the life of extrusion dies or forging dies with high surface pressures, and part of die casting dies, in addition to melt loss resistance, wear resistance is also important. Abrasion resistance can be considered to be obtained by using a deeper hardened layer, but it is customary Known methods require long-term processing in order to obtain a deeper hardened layer. However, due to long-term processing, there is a concern that the surface layer will peel off. That is, the conventional method is difficult to form a structure having a deep hardened layer with an iron-based oxide layer and a nitrogen compound layer having an optimal thickness, and it is considered that there is a limit to the application of a part of the mold.

The reason is that the present invention is to provide a mold having excellent wear resistance and resistance to melt loss in molten metal.

The inventors of the present invention have also found the best structure on the surface of the mold that can increase the life of the mold in the above-mentioned mold that requires a high level of wear resistance or surface pressure resistance, and completed the present invention.

That is, the mold provided according to the present invention is provided with an iron-based mold base material, a nitrogen diffusion layer provided on the upper layer of the mold base material, a nitrogen compound layer provided on the upper layer of the nitrogen diffusion layer, and The iron-based oxide layer that is the outermost layer above the nitrogen compound layer; wherein the thickness L _N of the nitrogen diffusion layer is 100 μm or more, and the maximum Vickers hardness H _S of the nitrogen diffusion layer is 900 HV or more; and, _{The thickness L O} of the iron-based oxide layer is 1 μm or more and less than 10 μm.

According to the present invention, it is possible to provide a mold excellent in both abrasion resistance and melting loss resistance to molten metal.

1: Mould

2: Mould base material

3: Nitrogen diffusion layer

4: Nitrogen compound layer

5: Iron-based oxide layer

100: Test device

101: Iron Bottle

102: Crucible

103: Melt

104: test piece

Fig. 1 is a schematic cross-sectional view of a layer structure on the surface side of a mold according to an embodiment of the present invention.

Fig. 2 shows the thickness (depth) direction distance (horizontal axis) of the mold (the iron-based oxide layer that becomes the outermost layer) of the present embodiment, and the Vickers hardness (vertical axis) from the nitrogen diffusion layer to the base material of the mold. ) A schematic diagram of an example of the relationship between.

Fig. 3 is a schematic diagram for explaining the test method of the melt loss resistance evaluation.

Hereinafter, the embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

A mold according to an embodiment of the present invention is provided with: an iron-based mold base material, a nitrogen diffusion layer provided on the upper layer of the mold base material, a nitrogen compound layer provided on the upper layer of the nitrogen diffusion layer, and a nitrogen compound layer provided The upper layer becomes the outermost iron-based oxide layer. The maximum Vickers hardness H _S L _N line thickness based nitrogen diffusion layer above 100μm, and the nitrogen diffusion layer than 900HV. In addition, the thickness L _O of the iron-based oxide layer is 1 μm or more and less than 10 μm. With these constitutions, the mold has excellent abrasion resistance and melt loss resistance to molten metal.

Hereinafter, referring to FIG. 1, the structure and manufacturing method of the mold of this embodiment will be described in detail. FIG. 1 is a diagram for explaining the structure of the mold of the present embodiment, and is a schematic diagram of a cross-section of the mold 1 of an example of the present embodiment. The mold 1 is provided with an iron-based mold base material 2, a nitrogen diffusion layer 3, a nitrogen compound layer 4, and an iron-based oxide layer 5 as the outermost layer.

The iron-based oxide layer 5 is the layer on the outermost surface of the mold 1 and is formed on the upper layer of the nitrogen compound layer 4. The iron-based oxide layer 5 is an oxide containing at least iron element (Fe) and oxygen element (O) Floor. The iron-based oxide layer 5 can be formed in a process in which the manufacturing method described later can be appropriately used when manufacturing the mold 1.

_{The thickness L O} of the iron-based oxide layer 5 is 1 μm or more and less than 10 μm. The iron-based oxide layer 5 with the specific thickness is provided on the nitrogen compound layer 4 provided on the specific nitrogen diffusion layer 3 to improve the wear resistance and the melt loss resistance. In order to fully obtain the improvement effect of the melting loss resistance, the thickness L _O of the iron-based oxide layer 5 is set to 1 μm or more, preferably 2 μm or more, more preferably 4 μm or more, and particularly preferably 5 μm or more. On the other hand, in order to fully obtain the effect of improving the abrasion resistance, the thickness L _O of the iron-based oxide layer 5 is set to be less than 10 μm, preferably 9.9 μm or less, more preferably 9.5 μm or less, especially preferred. Below 9μm.

_{The thickness L O} of the iron-based oxide layer 5 can be determined by adjusting, for example, the treatment temperature and treatment time of the nitriding treatment or oxidation treatment that can be suitably used in the manufacture of the mold 1. In addition, the thickness L _O of the iron-based oxide layer 5 can be measured by observing the side surface or cross section of the mold 1 with an optical microscope or an electron microscope, and the average thickness of about 3 to 10 points can be taken. The measurement of the thickness L _{O is} the same for the other layers described later.

The iron-based oxide layer 5 may be any one of an iron oxide layer and a composite iron oxide layer containing metal elements other than iron, and is preferably a composite iron oxide layer. The constituent elements of the iron-based oxide layer 5, in addition to iron (Fe) and oxygen (O), may also contain the constituent elements of the mold base material 2, and can be derived from the manufacturing method described later when the mold 1 is manufactured. Use the element of the salt bath. In addition to Fe, the constituent element system of the mold base material 2 may also include, for example, Si, V, Cr, Mn, Mo, Ni, W, and S. The preferable element system derived from the salt bath includes, for example, Li and the like. The constituent elements of the iron-based oxide layer 5 preferably contain Fe and O, and contain Si, V, One or more elements selected from the group consisting of Cr, Mn, Mo, Ni, W, S, and Li.

The iron-based oxide layer 5 is preferably a lithium-iron composite oxide layer containing lithium as another metal element. The lithium iron composite oxide is more preferably formed to have a crystal structure of _{(Li,Fe)O, Li 5} Fe ₅ O ₈ , Li ₂ Fe ₃ O ₄ , Li ₂ Fe ₃ O ₅ , LiFe ₅ O ₈ , or LiFeO ₂ Any one of the composite oxides or mixtures thereof. The lithium iron composite oxide layer can be formed, for example, by performing a salt bath nitrocarburizing treatment ^{using a molten salt bath to which Li + has been added.}

The nitrogen compound layer 4 is formed on the lower layer of the iron-based oxide layer 5 and on the upper layer of the nitrogen diffusion layer 3. The nitrogen compound layer 4 is a compound layer containing at least nitrogen element (N). The nitrogen compound layer 4 can be formed in the process of appropriately adopting the manufacturing method described later when manufacturing the mold 1.

_{The thickness L C of the} nitrogen compound layer 4 is preferably 1 μm or more and 25 μm or less, more preferably 2 μm or more and 20 μm or less, particularly preferably 5 μm or more from the viewpoint of improving the wear resistance and melt loss resistance of the mold 1 15μm or less.

Furthermore, regarding the relationship between the thickness of the iron-based oxide layer 5 and the nitrogen compound layer 4, the ratio _{of the thickness L O of the iron-based oxide layer 5 to the thickness L C of the nitrogen compound layer 4 (L O} /L _C ) , Preferably 0.1 or more and 5.0 or less. Thereby, in addition to improving the abrasion resistance and melt loss resistance of the mold 1, it is also possible to easily suppress uneven gloss on the surface (the surface of the iron-based oxide layer 5). From this viewpoint, L _O / L _C based more preferably 0.2 or more, and particularly preferably 0.5 or more lines, and based more preferably 3.0 or less, particularly preferably 1.5 or less based.

The constituent elements of the nitrogen compound layer 4, in addition to containing nitrogen (N), may also contain carbon (C), the constituent elements of the mold base material 2, and the constituent elements derived from the mold 1, which can be appropriately used in the manufacturing method described later. Elements of the salt bath. The constituent elements of the mold base material 2 are, as described above, for example, Fe, Si, V, Cr, Mn, Mo, Ni, W, and S. The preferable element system derived from the salt bath includes, for example, Li and the like. The constituent elements of the nitrogen compound layer 4 preferably contain N and C, and contain one or two selected from the group consisting of Fe, Si, V, Cr, Mn, Mo, Ni, W, S, and Li The above elements.

The nitrogen diffusion layer 3 is formed on the lower layer of the nitrogen compound layer 4 and on the upper layer of the mold base material 2. The nitrogen diffusion layer 3 can be formed in a process in which the manufacturing method described later can be appropriately adopted when the mold 1 is manufactured, and is formed by at least the diffusion of nitrogen elements. The nitrogen diffusion layer 3 may also be formed in a manner that contains either or both of carbon and oxygen as diffusion elements in addition to nitrogen. The constituent elements of the nitrogen diffusion layer 3 preferably contain nitrogen (N) and carbon (C), and contain the constituent elements of the mold base material 2 (Fe, Si, V, Cr, Mn, Mo, Ni, W, and S, etc.) ) One or more elements.

_{The thickness L N} of the nitrogen diffusion layer 3 can be a mold excellent in abrasion resistance, and must be 100 μm or more. From the viewpoint of further improving the wear resistance of the mold 1, the thickness L _{N of the} nitrogen diffusion layer 3 is preferably 110 μm or more, more preferably 130 μm or more, and particularly preferably 150 μm or more. _{The upper limit of the thickness L N} of the nitrogen diffusion layer 3 is not particularly limited. From the viewpoint of the productivity of the mold 1, it is preferably 500 μm or less, more preferably 400 μm or less.

In addition, the maximum Vickers hardness H _{S of the} nitrogen diffusion layer 3 is required to be a mold with excellent wear resistance, and must be 900 HV or more. The Vickers hardness of the nitrogen diffusion layer 3 is different according to the thickness (depth) direction of the nitrogen diffusion layer 3. In the thickness (depth) direction of the nitrogen diffusion layer 3, the closer to the nitrogen compound layer 4, the higher and the closer The mold base material 2 is lower (refer to FIG. 2 described later). It is known from this phenomenon that the Vickers hardness of the nitrogen diffusion layer 3 near the interface with the nitrogen compound layer 4 (within the area from the interface to the depth of 10 μm of the nitrogen diffusion layer 3) is regarded as the nitrogen diffusion layer 3 The maximum value of Vickers hardness is called the maximum Vickers hardness H _S. In addition, the position of the maximum Vickers hardness is set within the 10 μm area from the interface of the nitrogen diffusion layer 3 and the nitrogen compound layer 4 to the depth of the nitrogen diffusion layer 3, and it is assumed that the Vickers hardness near the interface can be measured. .

From the viewpoint of further improving the wear resistance of the mold 1, the maximum Vickers hardness H _{S of the} nitrogen diffusion layer 3 is preferably 920 HV or more, more preferably 950 HV or more, and particularly preferably 980 HV or more. The upper limit of the maximum Vickers hardness H _S of the nitrogen diffusion layer 3 is not particularly limited, and it can be set to 1500 HV or less, for example. In addition, the maximum Vickers hardness Hs of the nitrogen diffusion layer 3 is preferably higher than the Vickers hardness H _{B of the} core of the mold base material 2 by 300 HV or more (H _S- H _B ≧300), and more preferably 400 HV or more ( H _S -H _B ≧400), the special best series is higher than 420HV (H _S -H _B ≧420). In addition, the Vickers hardness of the nitrogen diffusion layer 3 uses a method based on the "micro Vickers hardness test" described in JIS Z 2244:2009 or a method based on the "measurement method of diffusion layer depth" described in JIS G 0562:1993. The value measured by a micro Vickers hardness tester.

As described above, the Vickers hardness of the nitrogen diffusion layer 3 depends on the thickness (depth) direction of the nitrogen diffusion layer 3. Figure 2 shows the distance in the thickness (depth) direction from the surface of the mold 1 (the iron-based oxide layer 5 that becomes the outermost layer) (the horizontal axis in Figure 2), and the Vickers hardness from the nitrogen diffusion layer 3 to the mold base material 2 ( A schematic diagram of an example of the relationship between the vertical axis in FIG. 2). As shown in FIG. 2, the Vickers hardness of the nitrogen diffusion layer 3 is higher in the nitrogen diffusion layer 3 toward the nitrogen compound layer 4 side. On the other hand, the Vickers hardness of the diffusion layer 3 containing nitrogen in the nitrogen diffusion layer 3 closer to the mold base material 2 side is lower, the mold base material becomes Vickers hardness H _B 2 of the same degree.

From the viewpoint of further improving the wear resistance and melt loss resistance of the mold 1, the nitrogen diffusion layer 3 is at the interface side with the nitrogen compound layer 4, and the distance in the thickness (depth) direction from the surface of the mold 1 is the same as the nitrogen diffusion layer 3. The relationship between the Vickers hardness of, it is better to have the relationship as described below. First, the mold 1 from the outermost layer (iron oxide layer 5) surface to a depth of nitrogen diffusion layer 3 exhibits a maximum Vickers hardness H _S of the position, set D _S (μm). As described above, nitrogen diffusion layers maximum Vickers hardness H _S-based nitrogen diffusion layer 3, 3 from the Vickers hardness within 10μm of the region depth and interfacial nitrogen compound layer 4 to, whereby said depth D _S (μm) lines L _O +L _C (μm)≦D _S ≦L _O +L _C +10(μm). Also, the depth from the surface of the outermost layer (iron-based oxide layer 5) of the mold 1 to the above-mentioned depth D _S +30 μm in the _{nitrogen diffusion layer 3 is set to D X} (μm), then (L _O +L _C +30( _{μm) ≦ D X ≦ L O} + L C +40 (μm)), the Vickers hardness of said depth D _X at the nitrogen diffusion layer 3 to H _X (HV). In this case, it is preferable to satisfy the following formula (1) (refer to FIG. 2).

0<(H _S -H _X )/(D _X -D _S )<4‧‧‧(1)

The above-mentioned "(H _S -H _X )/(D _X -D _S )" means the depth of the nitrogen diffusion layer 3 in the region from the interface with the nitrogen compound layer 4 to the position with a depth of 30-40 μm in the nitrogen diffusion layer 3 The relationship with Vickers hardness, and shows the slope of the curve in this area in Figure 2. (H _S -H _X )/(D _X -D _S ) in the specific range shown in the above formula (1) represents the dimension of the nitrogen diffusion layer 3 from the interface with the nitrogen compound layer 4 to the position at a depth of 30 μm The change (decrease) of the hardness is moderate. The value (HV/μm) of (H _S -H _X )/(D _X -D _S ) is more preferably 3 or less, particularly preferably 2 or less.

Furthermore, the difference between the maximum Vickers hardness H _{S of the nitrogen diffusion layer 3 and the Vickers hardness H B} of the mold base material 2 _{(H S} -H _B ), the thickness L _{N of the} nitrogen diffusion layer 3 and the difference between the nitrogen compound layer 4 The total of the thickness L _{C and the thickness L O} of the iron-based oxide layer 5 _{(L N} +L _C +L _O ) preferably satisfies the relationship of the following formula (2).

0.3<(H _S -H _B )/(L _N +L _C +L _O )<4‧‧‧(2)

The value (HV/μm) of (H _S -H _B )/(L _N +L _C +L _O ) is within the specific range shown in the above formula (2), which can further improve the mold 1 Wear resistance and melt loss resistance. From this viewpoint, _{the value (HV/μm) of (H S} -H _B )/(L _N +L _C +L _O ) is preferably 0.5 or more, more preferably 3 or less, particularly preferably 2 or less.

The iron-based mold base material 2 is the base material of the mold 1. The material of the mold base material 2 is an iron-based material, specifically, a steel material. A preferable material of the mold base material 2 includes, for example, JIS standard (JIS G4404: 2006) hot mold steel. The better material of the mold base material 2 can include, for example, SKD4 material, SKD5 material, SKD6 material, SKD61 material, SKD62 material, SKD7 material, SKD8 material, SKT3 material, SKT4 material, and SKT6 material of JIS specifications, and the equivalent Such steel materials, etc. Therefore, the mold 1 is preferably used for warm forming (for example, for warm forging or warm extrusion, etc.) or for casting (for example, for die casting, etc.), and more preferably for warm forging or for die casting.

The manufacturing method of the mold 1 is not specifically limited. By performing, for example, salt bath nitrocarburizing treatment with oxidation; gas nitriding treatment with oxidation; and nitriding treatment or nitrocarburizing treatment, and oxidation treatment, or nitriding treatment with oxidation, or The mold 1 can be manufactured by any combination of soft nitriding treatment and other treatments. Among these manufacturing methods, a combination of nitriding treatment or nitrocarburizing treatment, oxidation treatment, or nitriding treatment accompanied by oxidation, or nitrocarburizing treatment is preferred, and the following manufacturing method is more preferred.

A method of manufacturing a mold according to an embodiment of the present invention includes: a first step of nitriding or nitrocarburizing an iron-based mold base material using a gas or molten salt bath; and after the first step, The second step of oxidation treatment, nitridation treatment with oxidation, or nitrocarburizing treatment is performed. In this manufacturing method, by the first step and the second step, are sequentially formed on the die base material 2 L _N of a thickness of 100μm or more and a maximum Vickers hardness of 900HV or more H _S nitrogen diffusion layer 3, a nitrogen compound layer 4, And the iron-based oxide layer 5 having a thickness L _O of 1 μm or more and less than 10 μm.

According to the manufacturing method of the mold 1 including the first and second steps described above, the surface of the mold base material 2 can be nitrided or nitrocarburized in two stages: the first and second steps (below Including soft nitriding treatment, abbreviated as "nitriding treatment"). Therefore, precise control of conditions such as the temperature and time of the nitriding treatment can be facilitated. That is, the first step and the second step, the mold can be easily in the base material 2, L _N having a thickness of 100μm or more and a maximum Vickers hardness of 900HV or more H _S nitrogen diffusion layer 3, a nitrogen compound layer 4, And the iron-based oxide layer 5 having a thickness L _O of 1 μm or more and less than 10 μm.

The gas that can be used in the nitridation treatment in the first step can be any gas that has been used in gas nitridation treatment since the prior art. Preferable gas systems include, for example, ammonia (NH ₃ ) gas, nitrogen, and mixed gases of these, and mixed gases of NH ₃ gas, nitrogen, hydrogen, and carbon dioxide gas. When using gas for nitriding treatment, the treatment temperature is preferably 430 to 590°C, more preferably 480 to 580°C. In addition, the processing time is preferably 60 minutes or more, more preferably 600 to 6000 minutes.

The molten salt bath that can be used in the nitriding treatment in the first step can be any molten salt bath that has been used in salt bath nitrocarburizing since the prior art. The salt bath nitrocarburizing treatment system can employ, for example, a salt bath nitrocarburizing method disclosed in Japanese Patent Laid-Open No. 2002-226963 and Japanese Patent Laid-Open No. 2004-91906. A preferable molten salt bath system includes, for example, a molten salt bath containing cyanate or carbonate. More preferably, for example, a molten salt bath ^{containing one or more of Li +} , Na ⁺ , and K ⁺ as a cationic component, and one or more of CNO ^- and CO ₃ ^{2- as an anion component} . In the case of nitriding treatment using a molten salt bath, the treatment temperature is preferably 480 to 600°C, more preferably 530 to 580°C. Moreover, the processing time is preferably 30 to 600 minutes, more preferably 60 to 180 minutes.

The oxidation treatment in the second step is preferably in a molten salt bath of nitrates such as sodium nitrate and potassium nitrate, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, and carbonates such as sodium carbonate and potassium carbonate. A process of contacting the mold base material 2 that has undergone the nitriding process in the first step. The treatment temperature is preferably 280 to 600°C, more preferably 350 to 500°C. The processing time is preferably 10 to 180 minutes, more preferably 20 to 120 minutes.

In the second step, a nitriding gas may be used during the oxidation treatment, and a gas nitriding treatment accompanied by oxidation may be performed. The gas system that can be used in this treatment can be any gas that has been used in gas nitriding treatment since the prior art. Preferable gas systems include, for example, water vapor, oxygen, nitrogen, hydrogen, ammonia, and mixed gases of these. In the oxidation treatment using gas, the treatment temperature is preferably 350 to 600°C, more preferably 500 to 560°C. Moreover, the processing time is preferably 30 to 600 minutes, more preferably 30 to 120 minutes.

Furthermore, the nitriding treatment (soft nitriding treatment) accompanied by oxidation in the second step is preferably contained in In a molten salt bath containing cyanate, carbonate, and lithium salt, the mold base material 2 that has undergone the nitriding treatment in the first step is brought into contact (soft nitriding treatment). The treatment temperature and treatment time of the soft nitriding treatment can be set within the range of the treatment temperature and treatment time described in the nitriding treatment (soft nitriding treatment) that can be used in the first step. More preferably, the present embodiment includes: a first step of performing a nitriding treatment on the mold base material 2 using the aforementioned gas; and a second step of performing a nitrocarburizing treatment accompanied by oxidation after the first step.

The mold 1 of this embodiment described in detail above is because the mold base material 2 is sequentially provided with a nitrogen diffusion layer 3 having a thickness of 100 μm or more and a maximum Vickers hardness of 900 HV or more, a nitrogen compound layer 4, and a thickness of 1 μm or more and no The iron-based oxide layer 5 having a thickness of 10 μm is excellent in both abrasion resistance and melt loss resistance. Therefore, the mold 1 exhibits a long life, and this result contributes to reducing the manufacturing cost of metal products manufactured by using the mold 1.

In addition, the mold system according to an embodiment of the present invention can adopt the following configuration.

[1] A mold comprising: an iron-based mold base material, a nitrogen diffusion layer provided on the upper layer of the mold base material, a nitrogen compound layer provided on the upper layer of the nitrogen diffusion layer, and the nitrogen compound provided on the the upper layer and the outermost layer becomes iron-based oxide layer; wherein the thickness of the above-described line L _N of the nitrogen diffusion layer 100 m or more, and a maximum Vickers hardness H _S is the above 900HV or more of the nitrogen diffusion layer; and the iron oxide The thickness L _O of the material layer is 1 μm or more and less than 10 μm.

[2] The mold according to the above [1], wherein the thickness L _C of the nitrogen compound layer is 1 μm or more and 25 μm or less.

[3] The mold described in [1] or [2] above, wherein the ratio (L _O /L _C ) _{of the thickness L O of the iron-based oxide layer to the thickness L C} of the nitrogen compound layer is 0.1 or more and 5.0 or less.

Depth [4] The above [1] to [3] according to any one mold, wherein the outermost layer from said surface to a nitrogen diffusion layer is present above the position of the maximum of the Vickers hardness is defined as D H _{S S} (μm), the depth from the surface of the outermost layer to the depth of _{D S +30 μm in the nitrogen diffusion layer is D X} (μm), and the Vickers hardness at the _{D X in the nitrogen diffusion layer is H When X} (HV), the following formula (1) is satisfied:

0<(H _S -H _X )/(D _X -D _S )<4‧‧‧(1)

[5] above [1] mold to [4] according to any one of claims, wherein the Vickers hardness H _S maximum nitrogen diffusion layer and the above-described difference between the Vickers hardness H _B of the mold base material (H _S -H _B ), and the total of the thickness L _{N of} the nitrogen diffusion layer, the thickness L _{C of the nitrogen compound layer, and the thickness L O of} the iron-based oxide layer (L _N +L _C +L _O ), which satisfies The relationship of the following formula (2):

0.3<(H _S -H _B )/(L _N +L _C +L _O )<4‧‧‧(2)

[6] The mold as described in any one of [1] to [5] above, which is used for warm forming or casting.

[7] A method of manufacturing a mold, comprising: applying a gas or molten salt bath to the iron-based mold base material, and performing a first step of nitriding treatment or soft nitriding treatment; and after the first step, performing oxidation The second step of treatment, or nitriding treatment or nitrocarburizing accompanied by oxidation; wherein, using the first step and the second step, the mold base material is sequentially formed with a thickness L _N of 100 μm or more and a maximum A nitrogen diffusion layer having a Vickers hardness H _S of 900 HV or more, a nitrogen compound layer, and _{an iron-based oxide layer having a thickness L O} of 1 μm or more and less than 10 μm.

[Example]

Hereinafter, the effects produced by the present invention will be specifically explained based on test examples, but, The present invention is not limited to these test examples. In addition, the "%" in the test example refers to the quality standard (% by mass) unless otherwise stated.

<Test Examples 1-13>

Assuming that the steel system of the base material of the mold uses steel equivalent to SKD61 (containing: C: 0.37%, Si: 0.97%, Mn: 0.43%, Cr: 5.30%, Mo: 1.22%, and V: 0.81%, the rest is A steel material that is substantially made of iron) is subjected to quenching and tempering treatment (quenching and tempering) so that the Vickers hardness (H _{B) becomes 480HV.} A cylindrical base material test piece A with a diameter of 16 mm and a height of 100 mm processed from this steel material was used for a melt loss test, and a disc-shaped base material test piece B processed with a diameter of 32 mm and a height of 3 mm was used for abrasion tests and the like.

Test examples 1 to 13 were performed on the above-mentioned base material test pieces A and B, respectively, and subjected to the nitriding treatment shown in Table 1 below, to prepare test pieces 1 to 13 (test pieces A-1 to 13 and test pieces B-1 to 13). The "gas nitriding treatment" in Table 1 is a nitriding treatment performed by heating the above-mentioned base material test piece in a mixed gas atmosphere of ammonia, nitrogen, and hydrogen. The "salt bath nitrocarburizing treatment" is a nitrocarburizing treatment performed by immersing the above-mentioned base material test piece in a molten salt bath containing cyanate, carbonate, and lithium salt. "Salt bath nitrocarburizing treatment without added Li" is a nitrocarburizing treatment performed by immersing the above-mentioned base material test piece in a molten salt bath containing no lithium salt but containing cyanate and carbonate. "Post-oxidation treatment" is performed by immersing the test piece after the nitriding treatment in a molten salt bath of nitrates such as sodium and potassium, and alkali hydroxides such as sodium and potassium. Oxidation treatment. In Test Examples 8 to 11, after the "gas nitriding treatment" was performed under the conditions described in Table 1 in the first step, the "salt bath nitrocarburizing treatment" was performed under the conditions described in the same table in the second step.

(Type and thickness (depth) of surface treatment layer)

For the test pieces B-1 to 13 produced, the cross-sections of the test pieces were measured and analyzed by X-ray diffraction device (XRD). By this XRD measurement, the type of surface treatment layer formed by nitriding treatment or the like was confirmed for each test piece. _{In addition, the thickness (depth) L O (μm) of the iron-based oxide layer, the thickness (depth) L C} (μm) of the nitrogen compound layer, and the thickness (depth) of the nitrogen diffusion layer were measured for each test piece by observation with an optical microscope. )L _N (μm). The thickness measurement of each layer is carried out at three places randomly selected in each layer, and the average value of these is taken. These results and L _O /L _{C are} shown in Table 2. In addition, in Table 2, where the thickness (depth) is "0.0 μm", it means that no layer conforming to it has been confirmed.

(Maximum Vickers hardness of nitrogen diffusion layer)

For the prepared test specimens B-1 to 13, cut the test specimens and prepare the cross sections of the test specimens, and measure the maximum Vickers hardness H _S (HV) of the nitrogen diffusion layer and the depth of the nitrogen diffusion layer D _X ( μm) Vickers hardness H _X (HV). The maximum Vickers hardness H _S of the nitrogen diffusion layer is in the depth direction of the nitrogen diffusion layer, from the outermost surface of the nitrogen diffusion layer to a depth of 10 μm (the depth from the outermost surface of the test piece D _S (L _O +L _C) (μm)≦D _S ≦L _O +L _C +10 (μm)) position). In addition, the Vickers hardness H _X is in the depth direction of the nitrogen diffusion layer, from _{the position where the maximum Vickers hardness H S} is measured to a depth of 30 μm (the depth from the outermost surface of the test piece D _X (D _X = D _S +30μm)) to perform the measurement. The measurement of Vickers hardness is based on the method of "micro Vickers hardness test" described in JIS Z 2244:2009, using a Vickers hardness tester (manufactured by MITUTOYO, trade name "micro Vickers hardness tester HM-103"), Implemented under the conditions of a test force of 0.980N. The measured value of the maximum Vickers hardness H _S (HV), and the value of "(H _S -H _X )/(D _X -D _S )", and "(H _S -H _B )/(L _N +L _C) +L _O )" is shown in Table 2.

(Uneven surface)

For each of the test pieces B-1 to 13 produced, the outermost layer was visually confirmed, and the unevenness of the surface gloss (peeling of the surface layer or the difference in the fine structure) was confirmed, and those with no unevenness were rated as good (○) , And those who have confirmed unevenness will be rated as bad (×). The results are shown in Table 2.

(Melting loss rate)

For the prepared test pieces A-1 to 13, respectively, an evaluation test of the melting loss resistance of the aluminum alloy melt was performed. The test system uses the test device 100 shown in Fig. 3, in an alumina crucible 102 with an inner diameter of about 90 mm and a depth of about 200 mm contained in an iron bottle 101, the Al-Si-Cu-based alloy of aluminum alloy The JIS standard ADC12 (Si: 11.4%, Cu: 1.9%, the rest: Al) was heated and melted at 680°C. In the melt 103, each test piece 104 in a group of two was immersed in a state of about 30 mm , While rotating at about 200rpm, while keeping for 120 minutes. The melting loss of each test piece (melting loss rate) is measured by measuring the mass of the test piece before and after the test, and then from the formula: (W ₀ -W ₁ )/W ₀ ×100 (%) (W ₀ : the mass of the test piece before the test ; W ₁ : the mass of the test piece after the test) calculated value. The results are shown in Table 2. In addition, the base material test piece A that was not subjected to any nitriding treatment or the like was similarly measured for the melt loss rate. As a result, the base material test piece A had a melt loss rate of 11.667%.

(Wear resistance)

The abrasion resistance evaluation test was performed on the prepared test pieces B-1 to 13 respectively. Specifically, a ball-to-disc friction and wear tester (manufactured by RHESCA, model "FPR-2100"), based on the dry type, object material: aluminum ball (A1050), load: 50g, speed: 0.1m/s, and Test time: After the test was performed under the condition of 1 hour, the amount of wear (m ³ ) on the disc side (each test piece) was measured. The results are shown in Table 2.

It is confirmed from Table 2 that the test pieces 6-10 obtained in test examples 6-10 (special test pieces 7-10 obtained in test examples 7-10) are below the test pieces obtained in other test examples , Low melting loss rate and less wear. Therefore, confirmed by a thickness L _N on a base material of the test piece is 100μm or more and a maximum Vickers hardness of 900HV or more H _S nitrogen diffusion layer, a nitrogen compound layer, and a thickness of 1μm or more L _O iron and less than 10μm The oxide layer can improve abrasion resistance and melt loss resistance. Therefore, it was confirmed that by adopting such a structure, a mold excellent in both abrasion resistance and melt loss resistance can be provided.

1: Mould

2: Mould base material

3: Nitrogen diffusion layer

4: Nitrogen compound layer

5: Iron-based oxide layer

Claims (7)

A kind of mold, which has: Iron-based mold base material, The nitrogen diffusion layer provided on the upper layer of the mold base material, A nitrogen compound layer provided on the upper layer of the nitrogen diffusion layer, and The iron-based oxide layer that is disposed on the upper layer of the nitrogen compound layer and becomes the outermost layer; Wherein the Vickers hardness of the maximum line thickness L _N H _S is the above nitrogen diffusion layer of 100 m or more, and said nitrogen diffusion layer of 900HV or more; and, a thickness of the iron-based L _O-based oxide layer is 1μm or more and less than 10μm. The mold according to claim 1, wherein the thickness L _C of the nitrogen compound layer is 1 μm or more and 25 μm or less. The mold of Item 1 requests, wherein a thickness L _O of the iron-based oxide layer thickness ratio of L _C with respect to the nitrogen compound layer (L _O / L _C), Department of 0.1 or more and 5.0 or less. The mold of claim 1, wherein the depth from the surface of the outermost layer to the position where the _{maximum Vickers hardness H S in the nitrogen diffusion layer is exhibited is D S} (μm), Let the depth from the surface of the outermost layer to _{the depth of D S +30 μm in the nitrogen diffusion layer be D X} (μm), _{When the Vickers hardness at the D X} in the nitrogen diffusion layer is set to H _X (HV), the following formula (1) is satisfied: 0<(H _S -H _X )/(D _X -D _S )<4‧‧‧(1). The mold of claim 1, wherein the difference between the maximum Vickers hardness H _{S of} the nitrogen diffusion layer and the Vickers hardness H _B of the mold base material (H _S -H _B ) and the thickness L of the nitrogen diffusion layer _{The total of N} , the thickness L _{C of the nitrogen compound layer, and the thickness L O} of the iron-based oxide layer (L _N +L _C +L _O ), satisfies the relationship of the following formula (2): 0.3<(H _S -H _B )/(L _N +L _C +L _O )<4‧‧‧(2). Such as the mold of any one of claims 1 to 5, which is used for warm forming or casting. A method of manufacturing molds includes: Use a gas or molten salt bath for the iron-based mold base material to perform the first step of nitriding or nitrocarburizing; and After the above-mentioned first step, the second step of oxidation treatment, or nitriding treatment accompanied by oxidation, or soft nitriding treatment is performed; Wherein, using the first step and the second step, the base material on the mold, L _N are sequentially formed to a thickness of 100μm or more and a maximum Vickers hardness of 900HV or more H _S nitrogen diffusion layer, a nitrogen compound layer, and thickness L _O is an iron-based oxide layer of 1 μm or more and less than 10 μm.

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