JP2001073164A - Metallic material in which oxidized passive film has been formed, formation of the oxidized passive film and die and parts in which the oxidized passive films have been formed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance, releasing properties, gas releasability, surface hardness, wear resistance or the like in the material and to repeately reuse the same by applying the surface of a metallic base material with chromium plating, thereafter executing heating in an oxidizing atmosphere and oxidizing and passivating the surface of the chromium plating layer at a specified thickness. SOLUTION: The surface of a metallic material is applied with chromium plating of about 1 to 50 μm, is, if required, subjected to degreasing cleaning, is thereafter heated at 20 to 400 deg.C in reactive gas, preferably, contg. halogen such as fluorine or a halogen compd. such as ClF3 to clean and activate the surface of the chromium plating layer. Next, the chromium plated metallic material is held under heating at <=700 deg.C, preferably, at about 400 to 700 deg.C for about 2 to 48 hr in an oxidizing atmosphere having an O2 concn. of about 10 ppm to 100% and is subsequently subjected to heat treatment, preferably, in an inert gas. In this way, the surface of the chromium plating layer is oxidized and passivated at a thickness of >=0.01 μm to improve its chemical and mechanical properties, by which the parts excellent in cost effectiveness and general applicability and having a long life can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal material having a chromium plating layer on the surface of a metal substrate and further having an oxidation passivation film formed on the surface, a mold and parts using the same,
Also, the present invention relates to a method for forming a chromium oxide film on a surface of a chromium-plated metal substrate to improve the surface hardness, abrasion resistance, corrosion resistance, releasability, and the like.

[0002]

2. Description of the Related Art Metal materials have improved surface hardness, wear resistance, corrosion resistance, fatigue strength, releasability, and other chemical and mechanical properties to enhance the surface characteristics of products, prolong the service life, and improve the material surface. Various methods have conventionally been proposed for the purpose of increasing the load.
That is, conventional methods for modifying the surface of a metal material are roughly classified into a method of changing the material surface itself and a method of providing a surface coating.

The former method is a method of modifying the surface of a material by directly changing the surface itself of the material to give a new target function. Methods belonging to this include a mechanical treatment method, a chemical change method, a laser surface treatment, a surface heat treatment, a surface diffusion heat treatment, an ion nitriding / carburizing treatment, a boring treatment, a metal diffusion treatment, and an ion implantation method. But,
When using these methods, it is important to note that the deteriorated layer has excellent adhesion, but when the modified surface becomes unusable due to wear or functional change, it must be reprocessed in relation to dimensional changes. It is often difficult.

[0004] The latter method is a method in which the surface of a material is coated with a film (metal, compound, ceramics, alloy, or the like) having a property of a desired property and different from the base material to achieve the desired purpose. Methods belonging to this include thermal spraying, plating, plating composite, and chemical vapor deposition (CVD).
Method), physical vapor deposition method (PVD method, vacuum vapor deposition method, sputtering method, ion plating method) and the like. However, when using these methods, it should be noted that the adhesion of the target coating to the base material becomes a problem, and it is necessary to devise a method for obtaining good adhesion.

[0005] In order to improve the problems of both surface modification methods, a method has been proposed in which a plating film having relatively high adhesion is further added with functionality by a gas diffusion heat treatment. In particular, hard chromium plating is well known for its excellent wear resistance and corrosion resistance, but this is because the chromium coating has high hardness and the surface oxide chromium oxide has high hardness. It is believed that this is due to the good adhesion to the chromium film and the excellent corrosion resistance. Focusing on the excellent physical properties of chromium oxide, various methods for forming a chromium oxide film have been proposed.

As a method of forming a chromium oxide film which has been known for a long time, there is a chromate treatment which is one of chemical conversion treatments. The chemical conversion treatment is a method in which a certain metal is chemically reacted with a corrosive solution (chemical conversion bath) adjusted under specific conditions to produce a water-insoluble corrosion product that is fixed to the surface of the metal. Utilizing the physical or chemical properties of the corrosion product film, it is used for rust prevention, paint base, lubrication base for plastic working, etc.

[0007] Chromate treatment is mainly applied to surface treatment of zinc and aluminum. As an example, showing the film formation mechanism of a chromate film of aluminum,
The chemical conversion bath contains chromic acid and fluoride at a pH of 1.8 to 3.8.
(A) Corrosion of aluminum by hydrofluoric acid (b) Dissociation of dichromate ion and reduction of chromium
(c) Precipitation of trivalent chromium and hexavalent chromium (d) Amorphous film, Cr (OH ₂ ) ₂ .HCrO ₄ .Al (O
It is said that H ₃ ) · 2H ₂ O is produced. The aluminum chromate film is expected to have good paint adhesion and long-term durability as a base treatment for coating.

[0008] The coating component obtained by chromate treatment of zinc is said to be Cr (OH) ₃ · Cr (OH) CrO ₄ . It is considered that some of the coating components are further converted to chromium oxide, but no formation of a pure chromium oxide layer is observed. Therefore, in the chromate treatment, rust prevention and a paint base can be expected, but effects such as high corrosion resistance and wear resistance are not observed. In addition, the chromate film is inferior in heat stability, and the treatment requires a wastewater treatment facility, which is a major obstacle.

Further, a method has been proposed in which a ceramic coating containing chromium oxide applied by plasma spraying is irradiated with a laser to melt the ceramic coating entirely or partially (JP-A-63-24077). No.). This is a method in which the plasma-sprayed chromium oxide coating is porous with fine particles applied, and this is melted and solidified by laser irradiation to homogenize it.
Although the hardness and abrasion resistance are improved to some extent, it is difficult to completely homogenize the film, and it is not possible to form a coating having high corrosion resistance.

[0010] Further, a chemical densification method has been proposed. This is a method of precipitating and coating or densifying a surface modifying component on a substrate surface by a chemical decomposition or thermal decomposition reaction of a compound. At present, chromium oxide coating and densification are used. It is known that chromic acid or chromic anhydride undergoes thermal decomposition when heated, and changes as follows. In the CrO ₃ → Cr ₂ O ₃ + 3 / 2O ₂ chemical densification method, chromium oxide produced by this reaction is deposited on the surface to add a desired function.

For example, a liquid containing chromic acid as a main component is applied to the surface of the base material by coating or dipping, and then the base material is coated with 50%.
A baking treatment is performed at 0 to 600 ° C. to form a layer mainly composed of chromium oxide on the surface of the base material. There is a method of forming a strong chromium oxide layer by repeating this process a plurality of times (Japanese Patent Application Laid-Open No. 62-60766). Also, a method has been proposed in which the surface of a metal base material is smoothed to reduce the number of repetitions of chromic acid deposition and firing treatment, and to form a film having a thickness of 1 to 2 μm containing chromium oxide as a main component. (JP-A-11-29876). However, since the chromium oxide forming the coating layer obtained by these methods is in the form of fine particles having an average particle size of 0.1 to 1.0 μm, high corrosion resistance cannot be expected.

Further, a chromium nitride film is formed by an ion plating method using a pressure gradient plasma gun, and a chromium oxide film having excellent wear resistance is formed on the chromium nitride film so as to adhere to the base material. A method for forming a chromium oxide film having excellent properties has been proposed (JP-A-8-29603).
However, gas-phase coating such as an ion plating method has a problem that a high vacuum atmosphere is an indispensable condition, so that the processing cost is high and the shape and size of a processed object are restricted.

Various methods have been proposed for forming an oxidized passivation film having a chromium oxide film as a main component on the surface of stainless steel. For example, by forming a work-strained layer made of microcrystals on the surface of a stainless steel base material and performing a heat treatment under a low oxygen partial pressure and a weakly oxidizing atmosphere, chromium is selectively diffused from the inside of the stainless steel to the surface, By oxidizing
A method for forming a chromium oxide passivation film containing no Fe has been proposed (JP-A-6-116632). In addition, by dissolving and removing a colored oxide film mainly composed of an iron-based oxide formed by oxidizing a stainless steel surface, a film mainly composed of a chromium-based oxide having a thickness of 50 to 100 mm is formed. (Japanese Unexamined Patent Application Publication No. 10-140)
323), a method of forming a passivation film in a high-purity gas pipe at a low temperature using high-concentration ozone (Japanese Patent Laid-Open No. 9-1)
95031), after degreasing and cleaning stainless steel,
A method in which heat treatment is performed at 1000 to 1200 ° C. in a mixed gas atmosphere of an inert gas, hydrogen, carbon monoxide, carbon dioxide, and oxygen (Japanese Patent Application Laid-Open No. 10-237651) has been proposed.

[0014] It has been reported that an oxide film formed on the surface of stainless steel and containing chromium oxide as a main component and having a low content of iron oxide has properties such as corrosion resistance, improved gas release, and reduced elution of metal ions. But with these methods,
Since the diffusion of chromium to the surface is used, only a few to several hundreds of thin films can be formed as the chromium oxide layer. Therefore, it is impossible to improve mechanical functionality such as high hardness and wear resistance. Naturally, it cannot be applied to a material containing no chromium. Further, there has been proposed a timepiece dial in which a chromium oxide film is forcibly formed after chromium plating, and the color is developed with the interference color of the oxide film (JP-A-60-82677).
However, this method is intended only for decorative use, is very thin, and does not show any improvement in mechanical properties.

[0015]

The present invention has been made under such a background, and the problem to be solved by the present invention is not particularly limited to stainless steel.
A metal material having a chromium plating layer on the surface of a metal substrate, and further having an oxidized passivation film formed on the surface thereof, a mold and parts using the same, and chromium oxide on a surface of a chromium-plated metal material. In the method of forming a passivation film, a passivation film having excellent corrosion resistance, mold release properties, and gas release properties, and having a mechanical property such as high hardness and abrasion resistance is provided with a thick film. And a metal material having a chromium oxide film which is excellent in adhesion to a metal material substrate and which can be easily reprocessed repeatedly, a mold and a part using the same, and a method for forming the chromium oxide passivation film. On offer.

[0016]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have provided a chromium plating layer on the surface of a metal substrate, and further provided an oxidation passivation film on the surface. Formed metal materials, molds and parts using the same,
Further, the present inventors have found that the above problem can be solved by using a method of forming a chromium oxide passivation film by applying chromium plating to the surface of a metal substrate and then heating in a oxidizing atmosphere to complete the present invention. The present invention provides the following (1) to (1)
Metal material having a chromium plating layer on the surface of the metal substrate shown in 3) and further having an oxidation passivation film formed on the surface, molds and parts using the same, and chromium-plated metal material And a method for forming a chromium oxide passivation film on the surface of the substrate.

(1) A metal material having a chromium plating layer on the surface of a metal substrate, wherein the chromium plating layer has a thickness of 0.01 μm or more and is passivated by oxidation. (2) A method for forming a chromium oxide film, which comprises applying chromium plating to the surface of a metal substrate and heating the metal substrate in an oxidizing atmosphere to oxidize the surface of the chromium plating layer. (3) The method for forming a chromium oxide film according to the above (2), wherein the thickness of the chromium oxide film is 0.01 μm or more. (4) The chromium oxide according to the above (2) or (3), wherein the metal substrate having the surface subjected to chromium plating is heated in a halogen compound or a reactive gas containing halogen before being heated in an oxidizing atmosphere. The method of forming the coating. (5) The method for forming a chromium oxide film according to (4), wherein the halogen compound or the reactive gas containing halogen is a fluorine compound or a fluorine-containing reactive gas. (6) The method for forming a chromium oxide film according to the above (5), wherein the fluorine-containing reactive gas is a reactive gas containing ClF ₃ .

(7) The method for forming a chromium oxide film according to any one of the above (4) to (6), wherein the heating temperature in the halogen compound or the reactive gas containing halogen is 20 to 400 ° C. (8) The temperature at which the surface of the chromium plating layer is oxidized is 7
The method for forming a chromium oxide film according to any one of (2) to (7), wherein the temperature is not higher than 00 ° C. (9) The method for forming a chromium oxide film according to any one of the above (2) to (8), wherein after the surface of the chromium plating layer is oxidized, heat treatment is further performed in an inert gas. (10) A rubber molding die comprising a chromium plating layer on the surface of a metal substrate, wherein the chromium plating layer surface is passivated by oxidation. (11) The rubber molding die according to the above (10), wherein the surface of the chromium plating layer is passivated by oxidation to a thickness of 0.01 μm or more. (12) An injection-molded part comprising a chromium plating layer on the surface of a metal substrate, wherein the chromium plating layer surface is passivated by oxidation. (13) The injection molded part according to the above (12), wherein the surface of the chromium plating layer is passivated by oxidation to a thickness of 0.01 μm or more.

That is, the present invention provides a metal material having a chromium plating layer on the surface of a metal substrate and further having an oxidation passivation film formed on the surface, a mold and parts using the same, and a metal substrate. In a method capable of quickly and uniformly forming a chromium oxide film on the surface, a metal material excellent in economy, versatility, corrosion resistance, and excellent releasability, molds and parts using the same, This is a method of forming a chromium oxide film that has a certain thickness to improve high hardness and abrasion resistance, has excellent adhesion to a metal material base, and is easy to repeat reprocessing.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a metal material having a chromium plating layer on the surface of a metal substrate of the present invention and further having an oxidation passivation film formed on the surface, a mold and a part using the same, A method of forming a chromium oxide passivation film on the surface of a chromium-plated metal substrate will be described.

First, a description will be given of a metal material in which a chromium plating layer is provided on the surface of a metal base material and an oxidation passivation film is formed on the surface. The metal substrate used in the present invention is not particularly limited as long as it is a material that can be subjected to chrome plating. For example, iron, steel, and non-ferrous metals can be used. Although the thickness of the chrome plating layer is not particularly limited,
It is preferably 50 μm, more preferably 1 to 20 μm.
Further, the thickness of the chromium oxide passivation film is preferably 0.01 μm or more, and more preferably 0.1 μm or more, and it is excellent in corrosion resistance and releasability, and has high hardness and improved wear resistance. Can be.

Next, a method for forming a chromium oxide passivation film on the surface of a chromium-plated metal material will be described. The metal substrate used in the present invention is not particularly limited as long as it is a material that can be subjected to chromium plating.For example, iron, steel, and non-ferrous metals can be used. And high corrosion resistance chrome plating, micro-porous chrome plating,
Special chrome plating such as amorphous chrome plating containing 2-4% carbon is available. The thickness of the chromium plating layer is not particularly limited, but is preferably 1 to 50 μm,
1-20 μm is more preferred. The plating process is 2
It is also possible to carry out the combination of the two methods.

More specifically, a method of forming a chromium oxide passivation film on the surface of a chromium-plated metal material will be described. A chromium-plated workpiece is degreased and cleaned and then inserted into a heating furnace. It is desirable that the chromium-plated object is continuously degreased and cleaned after plating, and then inserted into a heating furnace. However, the method of the present invention does not impede the use of a stored product that has passed time. Next, set the heating furnace to N
_2. Replace with an inert gas such as argon. Further, if necessary, the temperature is raised to about 400 ° C. In this case, the flow of the inert gas may be continued, or the flow of the inert gas may be stopped, and the heating furnace may be evacuated by a vacuum pump. This operation is intended to sufficiently remove and desorb water and oxygen which interfere with the subsequent halogen pretreatment or chromium oxide film formation treatment.

Here, the halogen pretreatment will be described.
I do. The chrome-plated metal substrate was degreased and washed
Later, before heating in an oxidizing atmosphere, the halogen compound or
Is treated with a reactive gas containing halogen,
Halogen pretreatment to clean and activate the surface
No. This may be either a liquid phase or a gas phase, but is preferably
Before processing the chromium oxide film, remove the workpiece
Or 20 to 40 in a reactive gas atmosphere containing halogen.
It is carried out while maintaining at 0 ° C. This pretreatment allows
Destruction and removal of inorganic and organic contaminants adhering to the surface layer
To clean the surface, and furthermore,
Dozens of natural oxide films and O _TwoRemove adsorbent coating
The chrome-plated surface is activated. acid
In forming the chromium oxide film, the activated chrome
The surface of the jack has oxygen atoms compared to the untreated chrome-plated surface.
Easily adsorbs, penetrates, and diffuses.
A uniform chromium oxide film is formed. Thus, at low temperatures
Even if the chromium oxide film is formed quickly,
However, due to the problem of heat resistance, there is no distortion or distortion
This is particularly effective when the following processing is desired.

Examples of the halogen compound or a reactive gas containing a halogen include chlorine-based gases such as Cl ₂ , HCl and CH ₃ Cl, F ₂ , HF, ClF ₃ , NF ₃ , BF ₃ and CF.
₄ , a fluorine-based gas such as SF ₆ can be used, and a fluorine-based gas is preferably used. The halogen compound or the reactive gas containing a halogen is diluted with an inert gas such as N ₂ or argon, and the concentration of the reactive gas containing the halogen compound or the halogen can be 0.1 to 100%. A temperature of 20 to 400 ° C. and a processing time of 10 to 480 minutes are generally used. More specifically, among the above compounds, ClF is highly reactive even at a low temperature and can be treated at a lower concentration.
₃ is preferably used.

In this halogen pretreatment, the heating furnace is adjusted to a pretreatment temperature (20 to 400 ° C.) if necessary.
A halogen compound or a reactive gas containing halogen, for example, a mixed gas of Cl ₂ and N ₂ or a mixed gas of ClF ₃ and N ₂ is introduced. Cl ₂ or ClF ₃ generates Cl and F as active groups, and removes dirt remaining on the surface.
Reacts quickly with the oxide film and adsorbed O ₂ present on the chromium plating surface to activate the surface. In this way, the pretreated object is subjected to a chromium oxide film forming treatment after replacing the remaining halogen compound or the reactive gas containing halogen with a non-oxidizing atmosphere of an inert gas such as N ₂ or Ar. I do.

The chromium oxide film forming process is performed at 400 to 70
At a processing temperature of 0 ° C, preferably at about 500 ° C
Hold for some time_TwoOr H_TwoOxidizing atmosphere containing O
For example, O_TwoAnd N_TwoIs carried out by introducing a mixed gas of
O_TwoThe concentration is in the range of 10 ppm to 100%
And preferably in the range of 0.1 to 20%.
Also, H_TwoThe O concentration is preferably in the range of 1 ppm to 1%.
Appropriately used. O_TwoAnd H _TwoO can coexist
is there.

Here, in order to efficiently form an active chromium layer, it is also possible to carry out a treatment with a reducing atmosphere gas containing H ₂ or NH ₃ after the halogen pretreatment to form a chromium oxide film. . Since an active chromium layer is formed on the chromium plating surface, O, which is an active group generated by the decomposition of O ₂ , is adsorbed and easily penetrates and diffuses into the metal. It is formed. It is also possible to form a deep chromium oxide film by maintaining an oxidizing atmosphere under pressure.

Further, in the present invention, after the chromium oxide film is formed, heat treatment may be performed in an inert atmosphere or a weakly reducing atmosphere after the chromium oxide film is formed in order to promote crystallization and form a stronger passive film. It is possible.

In the present invention, the shape and size of the object to be treated are not particularly limited. However, industrially, a mold for a semiconductor sealing material, a mold for rubber molding, an injection molded part, a cylinder and a liner, a piston and It can be used for piston rods, piston rings, tools, shafts and journals, rolls, mechanical parts, etc.

The thus obtained chromium oxide film of the present invention has a thickness of 1 to 5 between the metal material base and the chromium oxide film.
A laminated structure having a chromium plating layer of 0 μm is formed, and a chromium oxide film having a thickness of 0.01 μm or more is formed on the surface layer. This structure is effective for obtaining strong adhesion between the metal base material and the chromium oxide layer. In addition, since a strong and stable passive chromium oxide film is formed, it exhibits high corrosion resistance and good releasability from resin or rubber.
Further, since an unprecedented thick film can be formed and high adhesion to a metal material substrate can be exhibited, mechanical properties such as surface hardness and abrasion resistance can be improved.

[0032]

The present invention will be described in more detail with reference to the following Examples, but the present invention is not limited to these Examples. (Example 1) Test piece SKD61 (15 × 30 × 2
mm) was subjected to ultrasonic treatment in acetone for 60 seconds to degrease it. The degreased sample is placed in a reaction furnace (30 mmφ × 400
mm), and the atmosphere was replaced twice with N ₂ gas, and then the temperature was raised to 50 ° C. Thereafter, 1% ClF ₃ diluted with N ₂ was introduced and kept for 1 hour. Then, the remaining ClF ₃ containing gas was replaced by flowing N _2, diluted with N ₂ 2
0% O ₂ gas was introduced, the temperature was raised to 500 ° C, and 500 ° C
For 24 hours. afterwards,
After replacing the remaining O ₂ gas by flowing N ₂ ,
By holding at 500 ° C. for 12 hours, a stabilization treatment of the chromium oxide film was performed. After the treatment, the sample was taken out by air cooling. The chromium oxide film of the obtained sample was uniform and 2 μm, and an 8 μm chromium plating layer was formed between the SKD61 substrate and the chromium oxide film. The hardness of the obtained sample is 1500 to 1600 Hv and the base material SK
D61 was 500 to 600 Hv, and that of only chromium plating was 900 to 1000 Hv. In addition, the result of the reciprocating motion wear test was 740 ds / μm, and that of only the chromium plating treatment was 360 ds / μm. Furthermore, the result of the releasability test with the acrylic resin was 30 N / cm ²
And a release force of 95 N /
Good releasability was shown for cm ² . In addition, a corrosion resistance test in a hydrochloric acid atmosphere showed twice the corrosion resistance of the sample subjected to the chromium plating treatment alone, and no peeling of the film was observed in the result of a repeated scratch test (100 cycles) under a load of 50 g.

Example 2 In the same manner as in Example 1, a test piece SKD61 (15 × 30 × 2 mm) plated with 10 μm of industrial chromium was coated with acetone in acetone for 6 hours.
Ultrasonic treatment was performed for 0 seconds to perform degreasing. The degreased sample is inserted into a reaction furnace (30 mmφ × 400 mm), and N ₂
After the gas was replaced twice, the temperature was raised to 100 ° C. afterwards,
10% Cl ₂ diluted with N ₂ was introduced and held for 1 hour.
Then, the Cl ₂ containing gas remaining after substitution by flowing N _2, introducing 1% H ₂ diluted with N _2, 500 ° C.
Then, 1% O ₂ gas diluted with N ₂ was introduced, and a chromium oxide film forming treatment was performed at 500 ° C. for 24 hours. Then, after the remaining O ₂ gas was replaced by flowing N ₂ , the chromium oxide film was stabilized by holding at 500 ° C. for 12 hours. After the treatment, the sample was taken out by air cooling. The chromium oxide film of the obtained sample was uniform and 1.8 μm, and a 8.2 μm chromium plating layer was formed between the SKD61 substrate and the chromium oxide film. The hardness of the obtained sample is 1400-1600
Hv, and the result of the reciprocating motion wear test was 720 ds / μ.
m. Further, in the result of the repeated scratch test (100 cycles) under a load of 50 g, no peeling of the film was observed.

Example 3 In the same manner as in Example 1, a test piece SKD61 (15 × 30 × 2 mm) plated with 10 μm of industrial chromium was treated with acetone in acetone for 6 hours.
Ultrasonic treatment was performed for 0 seconds to perform degreasing. The degreased sample is inserted into a reaction furnace (30 mmφ × 400 mm), and N ₂
After the gas was replaced twice, a 20% O ₂ gas diluted with N ₂ was introduced, the temperature was raised to 500 ° C., and a chromium oxide film forming treatment was performed at 500 ° C. for 24 hours. After that, the remaining O ₂ gas was replaced by flowing N ₂ ,
By holding for 2 hours, the chromium oxide coating was stabilized. After the treatment, the sample was taken out by air cooling.
The chromium oxide film of the obtained sample was uniform and 1.3 μm.
8.7 between the SKD61 substrate and the chromium oxide coating.
A μm chromium plating layer was formed. The hardness of the obtained sample was 1300 to 1500 Hv, and the result of the reciprocating wear test was 700 ds / μm. Also, 50
Repeated scratch test with g load (100 cycles)
As a result, no peeling of the film was observed.

Example 4 In the same manner as in Example 1, a test piece SKD61 (15 × 30 × 2 mm) plated with 10 μm of industrial chromium was treated with acetone in acetone for 6 hours.
Ultrasonic treatment was performed for 0 seconds to perform degreasing. The degreased sample is inserted into a reaction furnace (30 mmφ × 400 mm), and N ₂
After the gas was replaced twice, N ₂ gas containing 10 ppm of H ₂ O was introduced, the temperature was raised to 500 ° C., and a chromium oxide film forming treatment was performed at 500 ° C. for 12 hours. Then, the remaining H
After replacing ₂ O by flowing N ₂ , the chromium oxide film was stabilized by holding for 12 hours. After the treatment, the sample was taken out by air cooling. The chromium oxide film of the obtained sample was uniform and 1.0 μm, and S
9.0 μm Cr between KD61 substrate and chromium oxide film
A plating layer was formed. The hardness of the obtained sample is 13
00 to 1400 Hv, and the result of the reciprocating motion wear test was 600 ds / μm. Further, in the result of the repeated scratch test (100 cycles) under a load of 50 g, no peeling of the film was observed.

Comparative Example 1 In the same manner as in Example 1, a test piece SKD61 (15.times.30.times.2 mm) plated with 2 .mu.m of industrial chromium was cast in acetone for 60 hours.
Ultrasonic treatment was performed for 2 seconds to perform degreasing. The degreased sample is inserted into a reaction furnace (30 mmφ × 400 mm), and N ₂
After the gas was replaced twice, the temperature was raised to 50 ° C. Then N
1% ClF ₃ diluted in ₂ was introduced and kept for 1 hour. Then, the remaining ClF ₃ containing gas was replaced by flowing N _2, to introduce 20% O ₂ gas diluted with N _2, 5
The temperature was raised to 00 ° C., and a chromium oxide film forming treatment was performed at 500 ° C. for 24 hours. Then, after the remaining O ₂ gas was replaced by flowing N ₂ , the chromium oxide film was stabilized by holding at 500 ° C. for 12 hours. After the treatment, the sample was taken out by air cooling. The chromium oxide film of the obtained sample was uniform and 2 μm, and SKD6
1 No chromium plating layer remained between the substrate and the chromium oxide film. The hardness of the obtained sample is 1500 to 16
00Hv, and the result of the reciprocating motion wear test is 640 ds.
/ μm, but as a result of a repeated scratch test (100 cycles) under a load of 50 g, peeling of the film was observed.

(Comparative Example 2) Test piece SKD61 (1
5 × 30 × 2 mm) by ion plating.
A μm chromium oxide coating was applied. There was no chromium plating layer between the SKD61 substrate and the chromium oxide coating.
The hardness of the obtained sample was 1400 to 1600 Hv and the result of the reciprocating motion wear test was 650 ds / μm, but the repeated scratch test (100
As a result of the (cycle), peeling of the film was observed.

Example 5 Extrusion Screw for Injection Molding
ー (20mmφ × 600mm) 20μm industrial black
And then sonicate in acetone for 60 seconds.
Degreasing was performed. The degreased screw is placed in a reaction furnace (700
mmφ × 2000mm) and N _TwoReplace with gas twice
After that, the temperature was raised to 50 ° C. Then N_Two1 diluted with
% ClF _ThreeWas introduced and held for 1 hour. Then survive
ClF_ThreeGas containing N_TwoAfter replacing by circulating,
10 ppmH_TwoO and 10 ppm O_TwoContaining N_TwoLed
And raise the temperature to 500 ° C.
A rom film formation process was performed. Then, the remaining H_TwoO and
And O_TwoGas N_TwoAfter being replaced by distribution, 500
Stabilization of chromium oxide film by holding at 12 ℃ for 12 hours
Processing was performed. After processing, remove sample by air cooling
did. Single screw extruder lab using the obtained screw
Flame-retardant A in a plast mill at 200 ° C. and 50 rpm
As a result of the extrusion test of BS resin, it was found that
Volume when using a chrome plating screw
Chromium oxide with ± 10% variation in torque and torque
Discharge volume and torque vary with processing screw
Showed a stability of ± 4% or less.

[0039]

The oxidation passivation film formed according to the present invention is
It is excellent in corrosion resistance, release property and gas release property, and can be formed into a thick film in order to have mechanical properties such as high hardness and abrasion resistance. Further, by having a chromium plating layer between the metal material base and the oxidation passivation film, the adhesion to the metal material is excellent, and the repetitive treatment is easy. The metal material used in the present invention is not particularly limited as long as it can be subjected to chromium plating, and its shape and dimensions are not limited. Therefore, it can be widely used for rubber molding dies, injection molded parts, and the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C23G 5/00 C23G 5/00 F term (reference) 4K044 BA02 BA15 BB03 BC01 BC02 BC06 CA02 CA04 CA12 CA18 CA62 CA64 4K053 PA09 QA04 RA02 RA42 TA06 4K057 DA01 DB08 DB11 DD10 DE01 DE06 DE08 DK10 WA01 WB08 WB11 WK10

Claims (13)

[Claims] 1. A metal material comprising a chromium plating layer on a surface of a metal substrate, wherein the chromium plating layer has a thickness of 0.01 μm or more and is passivated by oxidation. 2. A method for forming a chromium oxide film, comprising: applying chromium plating to a surface of a metal substrate; and heating the metal substrate in an oxidizing atmosphere to oxidize the surface of the chromium plating layer. 3. The chromium oxide film has a thickness of 0.01 μm.
The method for forming a chromium oxide film according to claim 2, wherein the thickness is not less than m. 4. The chromium oxide film according to claim 2, wherein the metal substrate whose surface is subjected to chromium plating is heated in a halogen compound or a reactive gas containing halogen before being heated in an oxidizing atmosphere. Formation method. 5. The method for forming a chromium oxide film according to claim 4, wherein the halogen compound or the reactive gas containing halogen is a fluorine compound or a fluorine-containing reactive gas. 6. The method according to claim 5, wherein the fluorine-containing reactive gas is a reactive gas containing ClF ₃ . 7. The method for forming a chromium oxide film according to claim 4, wherein the heating temperature in the halogen compound or the reactive gas containing halogen is 20 to 400 ° C. 8. The method according to claim 2, wherein a temperature at which the surface of the chromium plating layer is oxidized is 700 ° C. or less. 9. The method for forming a chromium oxide film according to claim 2, wherein after the surface of the chromium plating layer is oxidized, heat treatment is further performed in an inert gas. 10. A rubber molding die comprising a chromium plating layer on the surface of a metal substrate, wherein the chromium plating layer surface is oxidized and passivated. 11. The chromium plating layer has a surface of 0.01
The rubber molding die according to claim 10, which is passivated by oxidation to a thickness of at least μm. 12. An injection-molded part comprising a chromium plating layer on the surface of a metal substrate, wherein the surface of the chromium plating layer is oxidized and passivated. 13. The chromium plating layer having a surface of 0.01
The injection-molded part according to claim 12, which is passivated by oxidation to a thickness of at least μm.