JPH0852536A - Mold for continuous casting coated with combined film and production method thereof - Google Patents

Abstract

PURPOSE:To advantageously form the surface treatment film, excellent in wear resistance, adhesion, further heat resistance and corrosion resistance on the inner wall of a mold. CONSTITUTION:The combined film which has on the inner wall of a copper mold main body 1, a first layer film 2 of a under layer film made of metal or its alloy, and on the first layer 2, a second layer film 3 of thermal spraying film made of carbide or cermet carbide and in which the surface of the second thermal spraying layer film 3 and pores in the thermal spraying film are coated and impregnated with Cr23C6 based carbide is formed and the mold for continuous casting is formed. Cr23C6 chromium carbide is generated on the upper surface of laminated films consisting of the first layer 2 and second layer film 3 and in the pores in the second layer film 3 by heat treatment in hydrogen containing hologenated chrome vapor generating atmosphere and a film 4 is modified.

Description

Detailed Description of the Invention

The present invention provides a composite coating on the inner wall surface of a mold body which has high hardness (wear resistance) and good adhesion in a high temperature environment, and which is also excellent in heat resistance, wear resistance and corrosion resistance. The present invention relates to a continuous casting mold coated with and a method for producing the same. Further, the present invention, in addition to iron and iron alloys, zinc, aluminum, titanium, nickel, cobalt, copper,
We propose a non-ferrous metal such as tin and its alloys that can be used as a member for molten metal resistance.

[0002]

2. Description of the Related Art Generally, a copper or copper alloy material having good thermal conductivity is used as a material for a continuous casting mold. However, this continuous casting mold (hereinafter simply referred to as "mold")
Since the molten steel injected into the furnace is extremely hot and the surface of the molten steel is in a semi-solid state, the contact area with the soft copper or copper alloy mold will be severely scratched or thinned due to wear. However, there is a problem that the life of the mold is extremely short for that reason.

As measures against this, conventionally, there is a technique for improving or changing the material of the mold (for example, Japanese Patent Laid-Open No. 56-59565), a technique for improving the water cooling passage and shape of the mold to extend the life (for example, KAISHO 50-60429, JP 50-97521
No. 50, No. 144632, No. 51-8124, No. 51
No. 20026, No. 51-141721, No. 52-47525, etc.), ultrasonic vibration or high-frequency vibration is applied to the mold (JP-A-54-11).
2336, 56-11156, 56-11154, 56-11152, 56-11150, etc.) have been proposed respectively. However, although any of the techniques has some improvement effects, the expected effect of extending the mold life has not been obtained.

Of these, the most proposed technique for preventing damage to the mold is the technique of forming various surface treatment films on the inner surface of the mold which is in direct contact with molten steel. The following is classified according to the type of each surface treatment film. Proposed application of plating film; JP-A-52-
52829, 52-54622, 53-45626, 54-2224, 54-4237, 54-4235.
No. 54-4236, No. 54-4240, No. 54-
4239 publication, 54-4238 publication, 54-5826 publication,
54-102236, 54-116227, 54-152626
Publication Nos. 55-11201, 55-40065, and
55-45514, 55-61355, 55-70425
No. 55, No. 55-156642, No. 56-59564, No.
56-68554, 56-152146, 57-60104
Publications, 57-31448, 57-31447, and
57-31446, 57-31445 and 57-82440
No. 58, No. 58-23539, No. 58-138541,
58-137546, 58-212841, 59-39449
Japanese Patent Publication No. 63-5176, which is modified by heat treatment after forming a plating film;
JP-A-52-52828, JP-A-54-102238, JP-A-54-
No. 124831, No. 57-32851, No. 57-32850, No. 57-32849, No. 54-114436, and a method for plating a mold; JP-A-56-47
No. 592, No. 57-1543, No. 58-13442, Proposals for applying a thermal spray coating; Japanese Patent Publication No. 35-5260, Japanese Patent Publication No. 49-24837, No. 53-45626. ,
54-28228, 55-156643 and 56-8665.
5, JP-A-56-86656, JP-A-58-81544, and JP-A-52-43726, JP-A-56-1978, and JP-A-55- 7045
No. 3, No. 56-68555, No. 58-13257,
No. 60-38222, No. 56-80356, No. 58-2954.
No. 7, 61-5819, those applying surface treatment methods other than plating and thermal spray coating; JP-B-49-3727, JP-A-54-71724, JP-A-54-116224 , JP-A-56-148441, JP-A-57-28656, and JP-A-57-103759.

[0005]

[Problems to be Solved by the Invention]

a. Most of the technologies that have been proposed for plating films are Cr plating, Ni plating, Fe-Ni plating on the water-cooled surface of the mold.
Plating and Co plating films can be used individually or in combination, or a film in which metal silicide particles are dispersed in this kind of plating layer, a combination of electroplating film and Ni-P electroless film, etc. Is. However, these plating films lose their hardness in high temperature environments (especially Cr plating), peel off from the water-cooled surface of the mold, and the film hardness is usually 500 Vickers hardness or less. There are problems such as insufficient wear. b. The heat treatment plating film developed as a measure against the peeling of the plating film is heated at 600 to 1000 ° C after the plating film is formed and diffused into the copper base material on the water-cooled surface of the mold to improve the adhesion of the film. However, this technique has not solved the reduction of hardness of the plating film and the deterioration of wear resistance. c. The technique related to the method of plating on the mold has the same problem as the above a. d. The technique of applying a thermal spray coating is directly on the water-cooled surface of the mold.
Spray cermet consisting of Cr alloy and Al ₂ O ₃ or JIS
After spraying a Ni-based self-fluxing alloy specified by H 8303, this is subjected to a fusing treatment, and MgO-on the undercoat of the Ni-Cr-Al alloy.
A technique of spraying ZrO ₂ and a technique of spraying a chromium carbide cermet have been proposed respectively, but both have a problem that the sprayed coating is easily peeled off. e. The technology of forming a thermal spray coating on the plating film is based on chromium carbide, tungsten carbide, Co
-Mo-Cr alloys are individually formed into films. However, this technique has exactly the same problem as the above d, in which the sprayed coating formed to protect the soft plating coating often peels off during use. f. Continuous casting molds that use surface treatment coatings other than plating coatings and thermal spray coatings can be used for firing colloidal substances containing Al ₂ O ₃ fine particles at 1000 ° C, lining Ni, Ni-Cu alloys, and heat- and wear-resistant firing. We are proposing a technique to line the body. However, these methods have a problem that the coating and the lining material are often peeled off, and a stable casting operation cannot be maintained for a long period of time.

Therefore, the present invention is mainly aimed at overcoming the problems of the above-mentioned respective prior arts. In particular, the inner wall surface of the mold has high hardness, excellent abrasion resistance and adhesion, and heat resistance. The present invention proposes a method for advantageously forming a mold surface treatment film having excellent corrosion resistance. Another object of the present invention is to propose a casting mold for continuous casting having a composite coating excellent in the above various properties.

[0007]

The features of the continuous casting mold coated with the composite coating proposed in the present invention are as follows: First, as a first layer, the inner wall surface of a copper mold is subjected to metal plating by electroplating, electroless plating or thermal spraying. By forming a coating, a carbide or carbide cermet spray coating as a second layer on the surface, and further by heat treating the laminated coating consisting of the first and second layers in an atmosphere of chromium halide vapor containing hydrogen, Promote the metallurgical diffusion reaction to the metal components constituting the first layer and the second layer, in addition, in the coexistence with hydrogen gas, using active and fine metal Cr particles precipitated by the reduction of chromium halides with covering the surface of the carbide thermally sprayed coating of the second layer, by entering into the pores unit, to generate Cr ₂₃ C ₆ type carbide chromium hard into the surface and pores This fact, have a dense and high hardness, excellent wear resistance, and in addition to excellent adhesion, in that it further forming an excellent continuous casting mold in heat resistance and corrosion resistance.

That is, the present invention has the following constitution. (1) At least a part of the inner wall surface of the copper mold body has, as a first layer, an undercoating film of a metal or an alloy thereof that is alloyed with copper by a metallurgical reaction, and a carbide is formed on the first layer film. Or, it has a sprayed coating of carbide cermet as the second layer coating, and the surface of the second layer sprayed coating and the pores of the coating are coated with Cr ₂₃ C ₆ type carbide and impregnated to form a composite coating. Casting mold. (2) The first layer coating is made of Ni, Cr, Fe, Al, Mo, Nb, Ta or Co or their alloys by electroplating, electroless plating or thermal spraying in the range of 0.1-5 mm. It is preferably formed to have a thickness. (3) The second layer coating is ZrC, MnC, HfC, TaC, TiC, Nb
C, CrC, BC, WC, FeC, MnC, SiC or VC carbides or carbide cermets containing one or more of Ni, Cr, Fe, Al, Mo and Co in these carbides by thermal spraying
The coating is preferably formed to a thickness of 0.01 to 3 mm. (4) The Cr ₂₃ C ₆ type carbide formed in the pores of the upper surface of the laminated film consisting of the first layer film and the second layer film and the second layer film is a chromium halide vapor generating atmosphere containing hydrogen gas, It is preferably formed by a reaction between activated metal chromium and carbon in the film, which is deposited by heat treatment under the conditions of 600 to 1000 ° C. and 0.5 to 20 hours. (5) On at least a part of the inner wall surface of the copper mold body, a first layer coating is formed on the metal or its alloy that is alloyed by copper and metallurgical reaction, and a carbide or a carbide cermet is formed on the first layer coating. The thermal spray coating is applied as the second layer coating, and then the formed second thermal spray coating is heat treated in a chromium halide vapor generating atmosphere containing hydrogen gas to generate hydrogen reduction reaction during this heat treatment. Continuous casting characterized in that it is formed on the surface and in the pores of the second layer sprayed coating in the form of Cr ₂₃ C ₆ type chromium carbide formed by the reaction between activated fine metal Cr fine particles and carbon in the coating. Of manufacturing casting mold. (6) The first layer film formed on at least a part of the inner wall surface of the copper mold body is Ni, Cr, Fe, Al, Mo, Nb, Ta or Co.
Alternatively, those alloys are preferably formed by electroplating, electroless plating or thermal spraying so as to have a thickness in the range of 0.1 to 5 mm. (7) The second layer coating formed on at least a part of the inner wall surface of the copper mold body is ZrC, MnC, HfC, TaC, TiC, NbC, C
Carbide that is rC, BC, WC, FeC, MnC, SiC or VC,
Or Ni, Cr, Fe, Al, Mo and Co can be added to these carbides.
It is preferable that a carbide cermet containing one or more of the above is sprayed to a thickness of 0.01 to 3 mm to form a coating. (8) a laminated coating consisting of the first layer coating and the second layer coating formed on at least a part of the inner wall surface of the copper mold body,
The heat treatment in a chromium halide vapor generating atmosphere containing hydrogen gas is preferably carried out under the conditions of 600 to 1000 ° C. and 0.5 to 20 hours. (9) It is preferable to form the interdiffusion layers at the boundary between the base material and the first layer coating and the boundary between the first layer coating and the second layer coating by the heat treatment.

[0009]

The function of the coating of the mold according to the present invention will be described below in the order of the manufacturing steps. (1) Formation of a first-layer coating as an underlayer covering the inner wall surface of the mold A part of or the entire inner wall surface of the copper mold (hereinafter simply referred to as the “mold surface”) is coated with, for example, an electro-Ni plating as a first layer. Apply as a film. The first layer coating plays a role of improving the adhesion of the carbide or the carbide cermet thermal spray coating of the second layer coating formed thereon. Also,
This first layer coating, after forming the second layer coating, when subjected to heat treatment in a chromium halide vapor containing high-temperature hydrogen gas from above, passes through the pores of the thermal spray coating which is the second layer coating, It has a function of performing a metallurgical reaction with the invading fine Cr particles to more firmly bond with the second layer film. Further, this first layer film also functions to cause a metallurgical reaction with the copper mold of the base material to form a Ni-Cu alloy and strongly bond with it.

From the above, as the plating metal for the first layer coating, in addition to the above-mentioned electric Ni plating, alloys such as Co, Cr and Ni-Cr, Ni-Fe which form an alloy with copper as the template material are used. Plating can be applied, and electroless Ni-P and Ni-B alloy plating can also be used. At the same time, a plating film obtained by combining these plating methods is also effective. In addition, Ni, Al, Cr, Mo, Co, Fe, by the thermal spraying method using the combustion flame of plasma or combustible gas as the first layer coating,
Spraying of simple substances such as Nb and Ta or alloys of these is applicable.

The thickness of the first layer film is preferably in the range of 0.02 to 5 mm, and more preferably 0.5 to 3 mm. The reason is that when the film thickness is less than 0.02 mm,
It may be destroyed by the blasting treatment performed as a pretreatment of the second layer carbide sprayed coating. On the other hand, if it is thicker than 5 mm, the mechanical strength of the first layer coating itself deteriorates and it is economically disadvantageous. is there.

(2) Formation of a second layer film to be coated on the first layer film First, in forming (spraying) this second layer film, there is a first layer film such as electroplating or electroless plating. In this case, the surface of the first layer coating is roughened by Al ₂ O ₃ , blasting or the like. If the first layer coating is a thermal spray coating,
Since this thermal spray coating itself is in a rough state, it is applied as it is. That is, a carbide or carbide cermet coating is formed on the above-mentioned base coating (first layer coating) by a thermal spraying method using a combustion flame of plasma or a combustible gas as a heat source. Carbides as thermal spray materials are ZrC, MnC, HfC, Ta
C, TiC, NbC, CrC, BC, WC, FeC, MoC, SiC, etc. can be used.
Metals such as Ni, Co, Cr, Mo, Fe and Al may be used alone or as a mixture in an alloy state.

The thickness of the above-mentioned carbide or carbide cermet film, which is the second layer film, is preferably 0.01 to 3 mm, and particularly preferably 0.
05-0.5 mm is suitable. When the film thickness is less than 0.01 mm, not only is it difficult to form a second layer film, but also the film function is not sufficient. On the other hand, when it is more than 3 mm, it takes a long time to form the film, which is economical. Is disadvantageous.

(3) Heat treatment on the above coatings in a chromium halide vapor generating atmosphere containing high-temperature hydrogen gas. After forming the first and second layer coatings, high-temperature hydrogen gas is applied to these coatings. Heat treatment is performed in a chromium halide vapor containing the same. This heat treatment causes the following chemical reaction in the atmosphere, and active and minute metal Cr particles are deposited. For example, if a chloride is used as the halogen, the reaction will be as shown in the following formula (1). CrCl ₂ + H ₂ → Cr + 2HCl (1) Since the metal Cr particles generated here are usually fine particles of 0.1 μm or less, they can easily penetrate into the pores of the second layer coating. Moreover, if the reaction of the formula (1) occurs in the thermal spray coating or on the surface of the second layer coating, the heat treatment will be performed more effectively. Furthermore, since the deposited metal Cr fine particles are extremely rich in chemical activity, in addition to performing a metallurgical reaction with the first layer coating, they adhere to the surface of the second layer sprayed coating and penetrate into the pores. It is densified and further reacts with carbides (free carbon etc.) in the film components to produce hard Cr ₂₃
This produces C ₆ type chromium carbide. In particular, when free carbon is contained in the carbide of the second layer sprayed coating, it reacts as in the following formula (2) to produce Cr ₂₃ C ₆ . _{23Cr + 6C → Cr 23 C 6} ... (2) In addition, according to the inventors' knowledge, carbides Cr ₃ C _2, Cr ₇
Carbide of a metal that is C ₃ type chromium carbide or has a weaker carbon affinity than Cr (for example, FeC, SiC, WC, B ₄ C, CoC,
In the case of MnC, MoC, NiC, etc., thermodynamic conversion to Cr ₂₃ C ₆ type chromium carbide occurs easily even if free carbon is not contained.

A suitable temperature for the heat treatment is 600 to 1000 ° C. The reason is that if the temperature is lower than 600 ° C, not only the reactions of the above formulas (1) and (2) become significantly slower, but also the metallurgy of the first layer coating and the base material or the first layer coating component and the second layer carbide sprayed coating. This is because the reaction is extremely weak and not practical. On the other hand, 1000
Although the precipitation reaction of Cr and the diffusion reaction of metal become active at a temperature higher than ℃, it is not practical because it becomes close to the melting point of the copper base material (1084.5 ℃) and the softening and deformation of the base material become large. It is preferably in the range of 750 to 980 ° C.

The processing time of this heat treatment is 0.5 to 20.
Time is appropriate. The reason is that if it is shorter than 0.5 hours, the reaction is not sufficient, while if it is longer than 20 hours, the production cost is high and it is economically disadvantageous.
The range of 4 to 15 hours is preferable.

As the halogen compound for increasing the main component in the heat treatment atmosphere, any of chromium bromide, chromium iodide and chromium fluoride can be used in addition to chromium chloride. This allows fine particles of active metal Cr coexisting with hydrogen gas to be deposited by a reduction reaction. It is important to keep the heat treatment atmosphere reductive.

FIG. 1 shows a coating structure on the inner wall surface of a mold having a composite coating according to the present invention. (A) in the figure
Is a first layer coating on the copper base material 1 and the electroplating layer 2
And a carbide cermet coating 3 formed by plasma spraying as the second layer coating thereon.
And, (B) is a laminated film having the structure of (A),
It shows the situation after heat treatment in a vapor of chromium halide containing high temperature hydrogen gas. Due to the reducing action of hydrogen gas, a large amount of active and minute metal Cr particles are deposited from the chromium halide inside and outside the second-layer sprayed coating, and these particles adhere to the surface and pores of the second-layer sprayed coating. However, a part of the metal reaches the surface of the first electroplated layer film, where an alloying reaction of Cr and Ni occurs, and the two are metallurgically bonded. The fine particles of metal Cr attached to the surface and pores of the second layer sprayed coating are extremely chemically active in the reducing atmosphere, and therefore are contained in excess in the carbides or carbides that make up the sprayed coating. Cr ₂₃ C _{6 which is} very hard and thermodynamically stable by reacting with free carbon
Form type chromium carbide. This reaction eliminates voids in the pores of the thermal spray coating, and also eliminates the roughness specific to the thermal spray coating on the surface and makes the surface smooth.

Since the above heat treatment is carried out at 600 to 1000 ° C., the electroplating layer of the first layer causes mutual diffusion with the base material, and here again, the adhesion of the coating film by metallurgical bonding contributes to improvement. It will be. In FIG. 1 (B), reference numeral 4 is a modified layer composed of fine metal Cr particles adhered to the surface of the second-layer carbide cermet sprayed coating 3, the main component of which is Cr ₂₃ C ₆ . Reference numeral 5 in the figure shows a group of metal Cr particles that has penetrated into the interior from the surface of the carbide cermet sprayed coating (second layer) through the pores of the sprayed coating. When the pores penetrate, the first The electroplating layer 2 of the layer has also been reached. Reference numeral 6 has penetrated the pores of the thermal spray coating 3.
Interdiffusion layer of Cr particles and electroplating layer, and 7
Shows an interdiffusion layer between the electroplated layer and the copper base material.

As shown in FIG. 2, the surface of the inner wall surface of the continuous casting mold having the composite coating according to the present invention, as shown in FIG. You may provide the intermediate layer 8 which has a metal as a main component. However, the present invention is not limited to such a multilayer structure. In the figure, 9 is an interdiffusion layer of the intermediate layer 8 and the first layer plated metal, and 10 is an interdiffusion layer of Cr particles that have penetrated through the pores of the intermediate layer metal and the thermal spray coating. . The intermediate layer is preferably a so-called gradient compounding film in which the carbide content is increased toward the outside and the metal component ratio is increased toward the base material.

[0021]

【Example】

Example 1 In this example, general characteristics of the composite coating formed on the inner wall surface of the mold according to the present invention were confirmed by conducting X-ray diffraction, micro hardness and thermal cycle tests. Test conditions: (1) Base material: JIS H 3100 (1992) C1020P pure copper 50 × 100
The one processed to a size of 8 mm was used. The following coating was formed on the base material. (2) Composite coating formed on the surface of the mold and conforming to the present invention (first layer / second layer plasma spraying process to a thickness of 0.2 mm) Electro Ni plating 0.1 mm / 73 wt% Cr ₃ C ₂ -20 wt% Ni -7
wt% Cr Electric Ni plating 3mm / 83wt% WC-17wt% Co Electric Ni-8wt% Fe alloy plating 3mm / 100wt% TiC
(Including 0.01 mwt% free carbon) Thermal spray 80 wt% Ni-20 wt% Cr 0.15 mm / 73 wt% Cr ₃ C ₂ −
20 wt% Ni-7 wt% Cr Spraying 90 wt% Ni-10 wt% Al 0.30 mm / 83 wt% WC-17 wt
% Co Sprayed 55wt% Ni-20wt% Cr-25wt% 0.2mm / 80wt%
TiC -20wt% Ni

After applying the second layer coating on each of the above-mentioned test materials, heat treatment was performed at 900 ° C. for 10 hours in CrCl ₂ gas containing hydrogen gas using the apparatus shown in FIG. (At 900 ° C
CrCl ₂ vapor pressure is about ₂ mmHg, and the same amount of H ₂ gas is mixed.) In FIG. 3, 31 is a processing container made of Ni, 32 is a CrCl ₂ gas introduction pipe, 33 is an Ar gas introduction pipe, and 34 is H ₂ The gas introduction pipe, 35 is a gas discharge pipe, and each pipe is equipped with a valve capable of supplying or discharging gas. The entire processing container is placed in an electric furnace and is heated from the outside. Reference numeral 36 is a temperature measuring tube inside the processing container. Reference numeral 37 denotes an object to be processed, which can be installed on a porous plate 38 made of an alumina sintered body.

(3) A coating used as a comparative example (first layer /
Second layer) a. Electro Ni plating 3mm / Electro Cr plating 1mm b. Electro-Ni plating 3 mm / electroless 95 wt% Ni-5 wt% P c. Electricity 92wt% Ni-8wt% Fe plating 3mm / 73wt% Cr ₃ C ₂
-20wt% Ni-7wt% Cr 0.2mm d. 73wt% Cr ₃ C ₂ -20wt% Ni-7wt% Cr 0.3mm Sprayed coating e. 83wt% Cr ₃ C ₂ -17wt% Co 0.3mm sprayed coating f. JIS H 8303 MSFNi5 1mm fusing after spraying

(4) Evaluation test a. X-ray diffraction test of coating surface: RINT-1 manufactured by Rigaku Denki Co., Ltd.
Diffraction test of the coating surface was performed using 500. b. Measurement of microhardness of coating surface: Five points were measured with a load of 100 g using a micro Vickers meter. c. Thermal cycle test: 800 ℃ x 15 minutes heating in air ← →
After the operation of pouring in water at 25 ° C. was repeated 5 times, the appearance of the film was observed and the microhardness (Hv) of the film after the test was measured.

Table 1 summarizes the results of the above evaluation tests.
It is a thing. First-layer electroplating used conventionally
/ Second layer electroplating (test piece No.7), first layer electroplating
/ Second layer electroless plating (test piece No.8) or first layer
Composite coating of electro-alloy plating / second layer spraying (test piece No. 9)
According to the X-ray diffraction results,
It was detected as it was. The hardness of these coatings is
In o.7, it is relatively hard at 800 to 900 Hv, but thermal cycle test
The hardness after that has dropped to 280-300 Hv,
It was found that the film was softened and the wear resistance was lost. test
The No. 8 Ni-P second layer coating has a hardness after the heat cycle test.
Increased to 430-580Hv, but with this level of hardness, wear resistance
Attrition is insufficient. Cr as the second layer₃C₂Cermet
The thermal sprayed test piece No. 9 had a high thermal hardness,
The film peels off in the icle test, so it can be put to practical use.
Absent. Such film peeling is caused by
As in No. 11, a carbide cermet is directly formed on the copper base material.
It was also recognized by those who did. However, Ni-based self-fluxing directly on the copper base material
Fused coating after thermal spraying of alloy (test
Specimen No. 12) remained healthy after the thermal cycle test.
However, the hardness is about 500 to 630 Hv, and the wear resistance is
Not enough to exert. In contrast, the composite leather of the present invention
The films (test pieces No.1 to No.6) are made of CrCl containing hydrogen gas. ₂gas
Most of the film surface is heated by heat treatment in
Stable Cr_{twenty three}C₆Type chrome carbide
The microhardness of all reaches over 1000Hv and the thermal cycle
It does not peel off even in the
No change was observed, and sufficient adhesion and wear resistance were maintained.
It turned out.

[0026]

[Table 1]

Example 2 In this example, the source of CrCl ₂ gas was Cr powder (70 wt.
%) And NH ₄ Cl (1 wt%), and alumina (29 wt
%) Is added to the sample to immerse the test material on which the composite film according to the present invention is formed, and the heat treatment time is kept constant at 10 hours while flowing hydrogen gas, and the temperature is 500 ° C.
The hardness of the film was examined by changing from 1 to 1100 ° C. FIG.
Shows an outline of the heat treatment apparatus used in this example. In FIG. 4, 41 is an Ni-made processing container, 42 is an H ₂ gas supply pipe, 43 is a gas discharge pipe, 44 is an object to be processed (test piece), 45 is a temperature measuring pipe, and the processing container itself is an electric furnace. It is installed inside and heated from outside. Also, 46 is Cr
It is a penetrant for generating Cl ₂ . (1) Composite coating of the present invention in this example (a second layer sprayed coating was formed on the copper test piece used in Example 1 to a thickness of 0.2 mm by the plasma spraying method) Electric Ni plating 3 mm / 73 wt% Cr ₃ C ₂ -20wt% Ni-7
wt% Cr (2) No comparative example

FIG. 5 shows the results of this test. That is, the average of the micro-hardness of the composite coating processed in the temperature range of 600 to 1000 ° C. all shows Vickers hardness of 1000 or more, and becomes harder as the temperature rises, especially the coating processed at 1000 ° C. has an average of 1300. Had reached above. Cr ₂₃ C ₆ type chromium carbide was found in all of these films by X-ray diffraction. On the other hand, in the film treated at 500 ° C., the presence of Cr ₂₃ C ₆ is unclear, and the hardness is low, and it is considered that sufficient results cannot be obtained even when applied to the application of the present invention. On the other hand, the composite coating treated at 1100 ° C is significantly deformed because it exceeds the melting point of the base material copper, and from this point it is considered difficult to put it into practical use. From the above, it is considered appropriate to perform the heat treatment in the CrCl ₂ gas containing hydrogen within the range of 600 to 1000 ° C.

The reaction for forming fine metal Cr particles when a powdery penetrant is used is as follows. That is,
When the penetrant is heated to 330 ° C or higher, NH ₄ Cl contained in the penetrant is decomposed. NH ₄ Cl → NH ₃ + HCl (3) The HCl generated here reacts with the Cr powder in the penetrant. _{Cr + 2HCl → CrCl 2 + H} 2 ... (4) (4) equation Although the reaction is a reversible reaction, the H ₂ gas to flow from the outside of the processing chamber for the vessel is maintained in a reducing atmosphere, the CrCl ₂ Most of the H ₂ gas precipitates minute metallic Cr. CrCl ₂ + H ₂ → Cr + 2HCl (5) The fine metal Cr particles generated by the formula (5) are chemically active and highly reactive as compared with the metal Cr powder that constitutes the penetrant. I'm out. As a result, due to the reaction of equation (2), Cr
_It produces ₂₃ C ₆ type chromium carbide. Since the reaction of formula (2) also occurs in the carbide cermet spray coating, in this case the deposited fine metal Cr particles are easy to adhere to the pores of the spray coating and the first layer coating. , Cr ₂₃ C ₆ formation and metallurgical diffusion reaction proceed rapidly.

Example 3 In this example, the denseness and corrosion resistance of a composite coating formed according to the present invention was investigated. Generally, thermal spray coating is 1% to 10
Since it has a porosity of about 10%, various corrosive media penetrate into the interior through these pores and corrode the base metal to eliminate the adhesion of the thermal spray coating and remove it. There are many. Therefore, in this embodiment, SS400 (50 × 100 × 5 mm), which has poor corrosion resistance, is used as the base material and directly applied to it.
wt% Cr ₃ C ₂ −20 wt% Ni −7 wt% Cr was deposited by plasma spraying to a thickness of 0.2 mm and then 900 ° C. was measured using the apparatus shown in FIG.
A heat treatment of × 10 hours was performed. Using this test piece, a salt spray test (JIS Z 2371 (1988)) was performed, and the appearance change of the composite film was observed every 24 hours, 48 hours, and 96 hours. Also, for this test, as a comparison, a plasma spray coating of the same composition that was not heat-treated by the apparatus of FIG. 4 was used. Table 2 summarizes the results. In the non-heat treated film of the comparative example, 5 to 6 points of red rust had already been observed after 24 hours, and this increased the area over time, resulting in 96 hours.
Later, 30% of the total area was covered with red rust. In contrast,
The composite film formed according to the method of the present invention is such that the metal Cr fine particles active during the heat treatment fill the pores of the film, and the Cr particles are evenly attached to the surface to cover the entire film. Therefore, the intrusion of salt water was completely prevented, the base material was not corroded, and the sound state was maintained even after 96 hours.

[0031]

[Table 2]

Example 4 In this example, the wear resistance of the composite coating formed by the present invention was investigated. FIG. 6 shows an outline of the test part in the Taber tester used for the abrasion test of the coating. That is, a copper disk having a diameter of 120 mm and a thickness of 2 mm was used as a base material 61, and various test films 62 were formed on the upper surface thereof. Two pairs of SiC disc type grindstones 63 are arranged on the sample coating on the disk so that they can be pressed against the sample coating surface with a load of 1 kgt. In this state, the copper disk rotates to the right (30 times per minute), while the grinding wheel itself rotates while rotating to the left, so that the test film is forcibly rubbed by the grinding wheel. The evaluation of wear resistance is based on the number of rotations of the copper disk,
It was carried out by measuring the weight loss of the test film. (1) Test film (first layer / second layer applied by plasma spraying method to a thickness of 0.2 mm) Electro Ni plating 0.2 mm / 73 wt% Cr ₃ C ₂ -20 wt% Ni-7
wt% Cr This composite film was heat-treated at 900 ° C for 10 hours in CrCl ₂ containing H ₂ gas. Electro Ni plating 0.2mm / 73wt% Cr ₃ C ₂ -20wt% Ni-7
wt% Cr Electro-Ni plating 0.3mm Electro-Ni plating 0.3mm / Electroless Ni-P plating 0.1mm Electro-Ni plating 0.3mm / Electro-Cr plating 0.1mm The film of is the composite film of the present invention, and ~ are for comparison. It is a film.

FIG. 7 shows the wear test results of the above-mentioned test film.
It is shown. The film of the comparative example is of the rotational speed of the copper disk.
As the wear increases, the wear amount increases, especially for the electric Ni plating layer.
Weight loss is large. Ni-P and Cr on the electroplated Ni layer
A plating layer that is generally called hard is formed.
The amount of weight loss is smaller than that of the Ni plating layer alone.
Although the amount is small, the amount of decrease is considerably larger than that of the thermal spray coating.
Of the test films of the comparative example, the one that showed the most wear resistance was the electrode.
Cr on the Ni plating layer₃C ₂It is a coating sprayed with cermet
It The hardness of this film is 680-780 (Vickers hardness) (Table
(See No. 1, No. 9 and No. 10))
It was the one that demonstrated its ability. On the other hand, the
In the case where the coating film is formed, the same composition of Cr is used as the thermal spray material.
₃C₂Even if a cermet film is used, Cr containing hydrogen gas
Cl₂Since the film is heat treated in gas, the film surface is thermally
Stable and high hardness (Vickers hardness 1100 to 1280, Table 1
(See test piece No. 1)_{twenty three}C₆Because it has been modified to
The amount of wear is extremely small, and it has the highest wear resistance of the test film.
It was confirmed that

Example 5 In this example, the type of carbide or carbide cermet coating of the second layer constituting the composite coating of the present invention was investigated. These were prepared by using the copper base material of Example 1 and applying an electric Ni plating layer thereon to a thickness of 1 mm, and then subjecting the following carbides to a plasma spraying method or in an argon gas containing substantially no air (atmospheric pressure 100 ~ 200 hPa) by plasma spraying method
CrC containing hydrogen gas under the conditions of Example 1 with a thickness of 0.2 mm.
Heat treatment was performed in l ₂ gas. Types of test carbides (1) 90wt% ZrC −10wt% Ni (2) 90wt% MnC −10wt% Cr ₃ C ₂ (3) 90wt% HfC −10wt% Fe ₃ C (4) 99.5wt% NbC −0.5 wt % C (5) 99.8 wt% TaC −0.2 wt% C (6) 80 wt% B ₄ C −10 wt% Ni −8 wt% Mo −2 wt% Al (7) 90 wt% SiC −10 wt% Cr ₃ C ₂ After heat treatment It was confirmed that Cr ₂₃ C ₆ type chromium carbide was formed in all of the coatings, and that the microhardness was 1000 or more in Vickers hardness.

Example 6 In this example, the composite coating of the present invention was applied to a part of an actual continuous casting mold, and a conventional surface treatment coating (for example, electric Ni plating, electric Ni plating / electric Cr plating, Electric Ni plating / Cr ₃ C ₂ cermet spray coating) and its practicality were confirmed. FIG. 8 shows an outline of the mold used in this example and a coating applied portion. As molten steel injected from the upper ladle (not shown) enters the mold being water-cooled, the surface of the molten steel that comes into contact with the mold gradually begins to solidify, and this hardened molten steel surface comes into contact with the mold. Apply the test film at the position (hatched area). Then, the durability of the film was examined by setting 1 operation as the operation of completely injecting 120 ton of molten steel into the mold. The composite coating formed according to the method of the present invention was applied with an electric Ni plating coating of 3 mm as the first layer, a 73 wt% Cr ₃ C ₂ -20 wt% Ni cermet thermal spray coating as the second layer, and 7 wt% Cr + hydrogen. 9 in CrCl ₂ gas containing gas
It was heat-treated in an atmosphere of 30 ° C x 20h. As a result, the electric Ni plating of the comparative example, the electric Ni plating / electric Cr
The plating disappeared after 100 to 120 charges. Also,
Electro Ni plating / Cr ₃ C ₂ cermet spray coating is up to 250
Some of them were able to withstand charging, but some of them were unreliable, such as only the thermal spray coating peeled off after 100 charges. On the other hand, the composite film of the present invention is 50
No peeling of the coating was observed, which could withstand use for 00 charges or more, and which hinders practical use.

As described above, the composite film formed on the surface of the mold based on the method of the present invention has the carbide cermet film forming the second layer densified by the heat treatment in CrCl ₂ containing hydrogen gas. Cr with high hardness
It has been modified to ₂₃ C ₆ type chromium carbide, and because the entire composite coating adheres firmly due to the mutual diffusion reaction, it exhibits excellent wear resistance and adhesion, as well as heat resistance and corrosion resistance. As a result, great effects can be expected in stabilizing the quality by the stable operation of the steelmaking process, reducing the repair cost, and reducing the product cost by reducing the maintenance personnel.

[Brief description of drawings]

FIG. 1 shows an outline of a cross-sectional structure of a composite film of the present invention.

FIG. 2 shows a cross-sectional view structure in the case where an intermediate layer is provided between the first layer and the second layer in the composite film of the present invention.

FIG. 3 is a schematic diagram of Cr containing hydrogen gas obtained by a chemical vapor deposition method.
This is an outline of an apparatus for performing heat treatment in a Cl ₂ gas atmosphere.

FIG. 4 shows an outline of a heat treatment apparatus for producing a composite coating of the present invention using a powder penetrant.

5 is a graph showing the relationship between temperature and film hardness when the composite film having the film structure of the present invention is heat-treated by the apparatus shown in FIG.

FIG. 6 shows how the test piece and the grindstone come into contact with each other in the abrasion test of the coating and how they rotate.

FIG. 7 shows the relationship between the excess number of discs and the wear loss of the coating in the coating wear test.

FIG. 8 shows an outline of a continuous casting mold on which the composite coating of the present invention is applied.

[Explanation of symbols]

 1 Mold Body 2 Electroplating Layer 3 Carbide Cermet Coating 4 Modified Layer 5 Cr Particle Group 6 Mutual Diffusion Layer between Cr Particles and Electroplating Layer 7 Mutual Diffusion Layer between Electroplating Layer and Copper Base Material 8 Intermediate Layer 9 Intermediate Layer and first layer metal interdiffusion layer 10 Intermediate layer metal and Cr particle interdiffusion layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C23C 28/00 B // C25D 3/56 B

Claims (8)

[Claims] 1. An undercoating film of a metal or an alloy thereof which is alloyed with copper by a metallurgical reaction is provided as a first layer on at least a part of an inner wall surface of a copper mold body, and the first layer film is formed on the undercoating film. Has a sprayed coating of carbide or carbide cermet as a second layer coating, and further coats Cr ₂₃ C ₆ type carbide on the surface of the second layer sprayed coating and in the pores of the coating,
A continuous casting mold that is impregnated to form a composite film. 2. The first layer coating is Ni, Cr, Fe, Al, M
0.1 to 5 mm of o, Nb, Ta or Co or their alloys by electroplating, electroless plating or thermal spraying
The mold according to claim 1, which is formed to have a thickness in the range of. 3. The second layer coating is ZrC, MnC, HfC, Ta.
C, TiC, NbC, CrC, BC, WC, FeC, MnC, SiC or VC
Carbides, or these carbides with Ni, Cr, Fe,
The mold according to claim 1, wherein a carbide cermet containing at least one of Al, Mo and Co is coated and formed to a thickness of 0.01 to 3 mm by a thermal spraying method. 4. The Cr formed on the upper surface of the laminated coating composed of the first-layer coating and the second-layer coating and in the pores of the second-layer coating.
₂₃ C ₆ type carbide is deposited by the reaction between activated metal chromium and carbon in the film, which is deposited by heat treatment at 600 to 1000 ° C for 0.5 to 20 hours in a chromium halide vapor generating atmosphere containing hydrogen gas. It is what was produced | generated, The template of Claim 1, 2 or 3 characterized by the above-mentioned. 5. A first layer film of a metal alloyed with copper by a metallurgical reaction or a first layer film of the alloy is formed on at least a part of an inner wall surface of a copper mold body, and a carbide or a carbide is formed on the first layer film. The thermal spray coating of cermet is applied as the second layer coating, and then the deposited second layer thermal spray coating is subjected to heat treatment in a chromium halide vapor generating atmosphere containing hydrogen gas, whereby the hydrogen reduction reaction during this heat treatment Characterized in that it is formed on the surface and in the pores of the second layer sprayed coating in the form of Cr ₂₃ C ₆ type chromium carbide formed by the reaction between activated fine metal Cr fine particles generated by Manufacturing method of continuous casting mold. 6. The first layer coating formed on at least a part of the inner wall surface of the copper mold body is formed of Ni, Cr, Fe, Al, Mo, Nb, Ta.
Alternatively, Co or an alloy thereof is formed by electroplating, electroless plating or thermal spraying so as to have a thickness in the range of 0.1 to 5 mm. 7. The second layer coating formed on at least a part of the inner wall surface of the copper mold body is formed of ZrC, MnC, HfC, TaC, T.
Carbides that are iC, NbC, CrC, BC, WC, FeC, MnC, SiC or VC, or Ni, Cr, Fe, Al,
0.01 to 3 carbide cermets containing at least one of Mo and Co
The manufacturing method according to claim 5, wherein the coating is formed by spraying to a thickness of mm. 8. A heat treatment is applied to a laminated coating consisting of the first coating and the second coating formed on at least a part of an inner wall surface of a copper mold body in a chromium halide vapor generating atmosphere containing hydrogen gas, 600 to 1000 ° C, 0.5 to 20
The production method according to claim 5, 6 or 7, wherein the production is performed under the condition of time.