JP3460160B2 - Manufacturing method of mold for continuous casting - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a casting mold manufacturing method for continuous casting of forming a thermal sprayed wear resistant coating.

[0002]

2. Description of the Related Art A casting mold for continuous casting of steel or the like is required to have wear resistance, high thermal conductivity and high strength from its mission. Particularly, from the viewpoint of wear resistance, Cr plating, Ni plating, Alternatively, a Ni alloy plating film is used. In recent years, for the purpose of further improving wear resistance, a mold has been proposed in which a Ni—Cr-based self-fluxing alloy or the like is sprayed on Ni plating or the like, and after spraying, heat treatment is performed to form a sprayed coating. There is.

[0003]

However, the formation of the sprayed coating in the conventional continuous casting mold is performed by a spraying method called an ultra-high speed flame spraying (HVOF) in which the working pressure of the spraying gun is 0.5 MPa (megapascal) or less. And
Since the thermal spray material is wholly melted by the heat of the thermal spray frame, a strong bite into the copper or copper alloy substrate (hereinafter abbreviated as "copper substrate") is hardly obtained,
Therefore, the adhesion strength between the substrate and the thermal spray coating was low, and it could not be used in the state of thermal spraying.

Therefore, in the conventional thermal spraying method, after thermal spraying, for the purpose of forming a denser coating and improving the adhesion strength by forming a diffusion layer between the thermal sprayed coating and the substrate (Cu or [Cu + plating]). It was essential to perform a high temperature heat treatment (fusing treatment) at about 900 to 1000 ° C.

However, when the copper substrate is a non-precipitation hardening type material (pure copper system such as deoxidized copper), it is about 900 to 10 after thermal spraying.
When the high temperature heat treatment at 00 ° C. is performed, there is a drawback that the material strength to be provided as a copper substrate is significantly reduced. That is, a non-precipitation hardening type substrate whose material strength is increased by cold working strain is remarkably deteriorated in material strength by recrystallization and cannot be used as a mold material, which is a fatal problem in terms of materials. was there. Therefore, conventionally, it has been necessary to use a precipitation hardening type substrate capable of recovering the strength as a mold material by heat treatment.

Therefore, even when a precipitation hardening type material is used for the copper substrate, in the conventional method, a high temperature heat treatment of about 900 to 1000 ° C. is performed as a heat treatment after the thermal spraying, and then it is rapidly cooled for the above-mentioned reason. It was necessary to perform a heat treatment as a precipitation hardening treatment at about 400 ° C. However, in the solution treatment for recovering the material strength of the copper base, the rapid cooling (water cooling) that should be originally performed has a large difference in the coefficient of thermal expansion between the thermal spray coating and the copper base, resulting in peeling of the thermal spray coating, or in the thermal spray coating. Due to problems such as cracking, rapid cooling was impossible and sufficient heat treatment was not performed. Therefore, there is also a fatal problem as a mold that the material strength of the copper substrate cannot be obtained.

In addition, in the conventional thermal spraying method, a grid material such as alumina is sprayed at a high speed before the thermal spraying to remove stains on the copper substrate surface and oxide films such as Cu ₂ O, and to roughen the substrate surface. It was necessary to perform a so-called blasting process for making the surface more uneven (making unevenness).

As described above, in the conventional thermal spraying method, there are many working steps such as blast treatment before thermal spraying and heat treatment after thermal spraying.
The work content is also complicated, and as a result, there is a drawback that the cost becomes high. Also, in order to maintain wear resistance, it is better to increase the thickness of the thermal spray coating, but in the conventional ultra-high speed flame thermal spraying method, the thickness of the thermal spray coating is about 0.5 to 1 mm at maximum, and more If it is too thick, there is a problem such as cracks in the film.

The present invention has been made in view of the above circumstances and requires no blast treatment before thermal spraying and heat treatment after thermal spraying, is dense, has excellent adhesion strength due to the anchor effect, and is resistant to wear. and its object is to provide a manufacturing <br/> method for producing superior type cast for continuous casting in a sustained sex.

[0010]

That is, the method for producing a casting mold for continuous casting according to the present invention is a method for producing a casting mold for continuous casting, wherein a sprayed coating is formed on the inner surface of a casting mold having copper or a copper alloy as a base. By injecting a sprayed coating having a coating thickness of 0.01 to 6 mm on at least the copper substrate surface by a high pressure / ultra high speed flame spraying method in which the working pressure of the spray gun is 0.55 MPa to 1.04 MPa on the inner surface of the substrate mold. As one layer, it is characterized in that it is formed of one or more kinds of tungsten-carbide-based wear resistant materials, and that blast treatment before thermal spraying and heat treatment after thermal spraying are not performed.

Further, between the thermal spray coating and the copper substrate, N
The operating pressure of the spray gun is 0.55MPa to 1.04M with an i-plated or Ni-Fe plated layer interposed.
1 or 2 or more types of tungsten / carbide-based wear resistance as a first layer that penetrates at least the surface of the plating layer with a sprayed coating having a coating thickness of 0.01 to 6 mm by a high pressure / ultra high speed flame spraying method of Pa It is characterized in that it is made of a conductive material and is not subjected to blast treatment before thermal spraying and heat treatment after thermal spraying.

The tungsten-carbide wear-resistant material is a powder having a diameter of 5 to 53 μm and a micro Vickers hardness (load 300 g) HV _0.3 of 1000 to 1.
It is preferably 400.

Here, the high pressure / ultra high speed flame spraying method means that when the working pressure of the spraying gun is set to 0.55 MPa or more, the spraying material digs into the surface of the sprayed substrate and has excellent adhesion and is precise. This is a thermal spraying method for forming a thermal spray coating.

Conventional super high speed flame spraying (HVOF) and high pressure / super high speed flame spraying (HP / HVO) according to the present invention
The difference in F) is that not only the operating pressure of the spray gun described above, but also the particle velocity, the jet Mach, and the fuel supply pressure and the oxygen supply pressure are higher in high-pressure / ultra-high-speed flame spraying. The jet temperature is low (see Table 2). As a result, in the high-pressure / ultra-high-speed flame spraying method, particles in a semi-molten state in which the hardness that can penetrate into the base material is maintained without being melted entirely by the heat of the spraying flame are sprayed onto the base material at an ultra-high speed, It is possible to obtain excellent adhesion strength.

The operating pressure of the thermal spray gun of the high pressure / ultra high speed flame spraying method is theoretically 0.55 MPa or more, but preferably 0.55 MPa to 1.04 MPa. At 0.55 MPa or less, sufficient kinetic energy cannot be given to the thermal spray material. On the other hand, 1.04MP
If it is a or more, the bite into the surface of the substrate does not increase in spite of the increase in the operating pressure, and on the contrary, a large residual stress may remain on the surface of the substrate.

Further, as a wear-resistant material of at least the first layer having a hardness capable of digging into the copper substrate or the above-mentioned plating layer (exhibiting the anchor effect), the above-mentioned preferable spray gun operating pressure range 0.55 MPa. ~ 1.04
At MPa, tungsten carbide (hereinafter "WC")
Abbreviation) -based wear-resistant material, and when its powder is used, the micro Vickers hardness (load 30
0 g) HV _0.3 : 1000 to 1400 is preferable, and the diameter of the powder is preferably 5 to 53 μm.

If the diameter of the powder is smaller than 5 μm, the above kinetic energy cannot be obtained sufficiently and the powder does not completely adhere to the substrate. Further, if the diameter of the powder is larger than 53 μm, the penetration into the substrate becomes shallow and the adhesion strength decreases.

When the hardness of the powder becomes lower than HV _0.3 : 1000, the bite of the powder becomes shallow, and HV _0.3 :
If it is higher than 1400, there is a problem that the strain generated in the thermal spray coating becomes large. Needless to say, the preferable diameter of this powder depends on the material and shape of the powder.

As the first layer of WC-based wear resistant material,
WC-12Co (WC with 12 wt% Co) or WC-27NiCr (27 wt% Ni and Cr (Ni
The WC) containing 4: 1) and the compounding ratio of Cr and Cr can be mentioned.

When the second layer wear-resistant thermal spray coating is formed on the surface of the first layer, a Ni-based self-fluxing alloy can be used as the second layer thermal spray material. Ni
Base self-fluxing alloys are Ni-Cr-Si-B based alloys with F
e, Cu, C, Mo, etc. are added, and the preferable composition is Si of 1.25 to 5.50% by weight and B of 2.
00 to 4.50 wt%, Cr 8.0 to 18.0 wt%, C 0.30 to 1.00 wt%, Fe 1.25 to
5.50% by weight, Cu is 0 to 5% by weight, Mo is 0 to 5% by weight, and Ni is the rest. Further, the composition may be sequentially changed to form the third and subsequent layers.

In addition to the above second layer, when a third layer wear-resistant thermal spray coating is formed, a Co-based self-fluxing alloy is used as the third layer wear-resistant thermal spray material. However, like the Ni-based self-fluxing alloy, it may be used as the wear-resistant thermal spraying material for the second and subsequent layers. The Co-based self-fluxing alloy is a Co-Cr-Si-B based alloy containing Fe, C,
Ni, Mo, W, etc. are added, and the preferable composition is 1.5 to 4.5% by weight of Si and 1.5 to 4.
0 wt%, Cr 16.0 to 24.0 wt%, C 0.
25 to 1.50% by weight, Fe 1.25 to 5.00% by weight, Mo 0 to 7.00% by weight, Ni 0 to 30% by weight, W 4 to 15% by weight, and the balance Co. is there.

If the thickness of the sprayed coating formed on the surface of the copper substrate or the surface of the above-mentioned plating layer by the high pressure / ultra high speed flame spraying method is 0.01 mm or less, it is not sufficient to maintain the wear resistance on the inner surface of the mold. is there. In order to maintain abrasion resistance, it is preferable to increase the film thickness, but increasing the thickness to 6 mm or more impairs the heat removal effect which is the mission of the mold due to the decrease in heat conduction of the film, or There is an inconvenience such that there is a risk of cracking due to the strain. Therefore, the film thickness is 0.01 to 6 mm.

[0023]

[Operation] The above-mentioned wear-resistant material forming at least the first layer used in the present invention does not melt entirely by the heat of the thermal spraying frame, and has a hardness capable of biting into the substrate. . The operating pressure of the spray gun used in the high-pressure / high-speed flame spraying method (HP / HVOF, etc.) is the pressure that causes the above-mentioned bite, and is the pressure of the spray gun used in the conventional ultra-high-speed flame spraying method (HVOF). Greater than operating pressure. Therefore, the powder of the wear resistant material sprayed by the high pressure / ultra high speed flame spraying method bites into the substrate and is firmly fixed (adhered).
At the same time, when forming this sprayed coating, dirt (hand marks, various markings, etc.) on the surface of the substrate or an oxide coating such as Cu ₂ O is also removed.

Therefore, the oxide film on the surface of the substrate can be removed and good adhesion strength can be obtained without performing the blasting of the substrate as the pretreatment for thermal spraying unlike the conventional method. Also,
A large operating pressure can give a large kinetic energy to the powder, and it becomes possible to form a very dense and thick sprayed coating. Therefore, the heat treatment for improving the adhesiveness and coating quality of the thermal spray coating and for recovering the material characteristics of the copper substrate, which has been performed by the conventional method, is completely unnecessary.

[0025]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows an enlarged vertical cross section of a short side copper plate of a mold of the present invention, and FIG. 2 shows an enlarged vertical section of a short side copper plate of another embodiment. Showing the face.
In these figures, reference numeral 1 denotes a mold body (base body) made of copper or a copper alloy, and a sprayed coating 2 or a plating layer 3 made of a wear resistant material is formed on the inner wall surface of the mold body.

In the embodiment shown in FIG. 1, a wear-resistant material that does not melt entirely due to the heat of the thermal spray frame and has a hardness that allows it to dig into the inner wall surface of the substrate 1 is used.
A thermal spray coating 2 directly formed on the inner wall surface of the substrate is formed by a high pressure / ultra high speed flame spraying method. Reference numeral 4 is the bite layer.

On the other hand, in the embodiment shown in FIG. 2, a Ni plating layer 3 having a thickness of 0.01 mm is formed on the surface of the copper substrate 1, and the Ni plating layer 3 is cut into the plating layer 3 by a high pressure / ultra high speed flame spraying method. The obtained wear resistant material is sprayed to form the sprayed coating 2. Then, the plating layer 3 and the thermal spray coating 2
A biting layer 4 is formed between and.

Next, in order to examine the adhesion, cracking susceptibility, and thermal effect on the copper substrate of the sprayed coating sprayed on copper or copper alloy, the mold material of the embodiment structure of FIG.
A test piece shown in (1) was prepared and a thermal shock test was conducted. In FIG. 3, 1a is a copper or copper alloy substrate, 2a is a thermal spray coating, and 5 is a mounting hole.

The compositions and types of copper and copper alloys constituting the substrate of the test piece are as shown in Table 1. In addition, the high-pressure / high-speed flame spraying method (HP / HVOF) used for the test
Table 2 shows the details of the process (equipment) for performing the conventional ultra high-speed spray flame method (HVOF).

[Table 1]

[Table 2]

The "gun operating pressure" in Table 2 means
It is a value obtained by measuring the pressure in the combustion chamber of the spray gun with a pressure sensor. In addition, "jet temperature" is a calculated value of the temperature of the flame due to each fuel, and "jet mach" is calculated from the angle of the diamond pattern shock due to the shock wave generated when the velocity of the flame exceeds the speed of sound. Frame rate. Further, the "particle velocity" is a value obtained by measuring the particles in the flame of the spray gun injection port with a laser Doppler particle velocity meter.

A wear-resistant thermal spray coating 2a was formed on the surface of a substrate 1a made of copper or a copper alloy having the composition and type shown in Table 1 under the thermal spray conditions shown in Table 2. At this time, a tungsten carbide powder containing 12% by weight of Co or 27% by weight of Ni and Cr was used as the wear-resistant thermal spray material of the first layer to form a thermal spray coating having a thickness of about 0.8 mm. . Powder composition and particle size (powder diameter) of the thermal spray material used in the test examples
And hardness are as shown in Table 3.

[Table 3]

In the thermal shock test, first, four bolts are inserted into the mounting holes 5 at four positions on both ends of the test piece shown in FIG. 3, and it is securely fastened to a predetermined fixed block with a tightening torque of 1000 kgf · cm. Fixed After that, the test piece is heated in an annular electric furnace to 300 ° C., and immediately after reaching 300 ° C., rapid cooling with water to 100 ° C. is performed as one heating / cooling cycle. Was repeated 500 times. 50 heating / cooling cycles
After 0 times, the surface cracks of the protective layer made of the sprayed coating 2a were observed, and then the sprayed coating 2a was cut, and the presence or absence of peeling and cracking of the sprayed coating 2a was observed from the cross section.

[Test Example 1] In Table 4, pure copper shown in Table 1 is used as a typical example of the non-precipitation hardening type material, and a spray coating is formed on the substrate under a predetermined test piece manufacturing method. The presence or absence of the influence of the heat treatment after thermal spraying on the material strength (hardness) of the substrate, the adhesion strength of the thermal spray coating, and the evaluation of the thermal spray coating by the thermal shock test are shown.

[Table 4]

From the results shown in Table 4, when the pure copper substrate was subjected to the blasting treatment and the post-spraying heat treatment by the conventional ultra-high speed flame spraying method (HVOF) to form the sprayed coating, the material strength of the substrate ( Hardness) is significantly reduced,
It is less than 2. Due to this decrease in material strength, pure copper (non-precipitation hardening type material) has traditionally been used as a substrate for thermal spray coatings.
Could not be used. On the other hand, if the heat treatment after thermal spraying is not performed, the hardness of the substrate does not decrease, but the adhesion strength of the thermal spray coating is about 1.5 kgf / mm ^2, which is about 1/10 of that of the examples of the present invention. is there. Also,
Even if the blasting treatment and the heat treatment after the thermal spraying are performed, the adhesion strength is only about ½ of that of the embodiment of the present invention. This indicates that even when the thermal spray material is sprayed by the conventional ultra-high speed flame spraying method, the operating pressure of the spray gun is low and the bite into the substrate is insufficient.

FIG. 4 is a photograph and a diagram showing this fact. WC-Ni was formed by the conventional ultra-high speed flame spraying method.
FIG. 3 is a photograph and an explanatory view showing a microscopic metallographic structure of a cross section at the interface between the thermal spray coating and the substrate after thermal spraying of a Cr-based thermal spray material. As can be seen from the microstructure, the bite of the thermal spray material is extremely insufficient.

On the other hand, FIG. 5 shows a case where the present invention is carried out by a high pressure / ultra high speed flame spraying method, and is WC-NiC.
FIG. 3 is a photograph and an explanatory view showing a microscopic metal structure of a cross section at the interface between the sprayed coating of the mold and the substrate when the r-based sprayed material is sprayed. As can be seen from this microstructure, it is understood that the bite into the substrate is sufficient. Note that FIG.
The first layer is a WC-NiCr-based thermal spray material, and the second layer is
The layer is a Ni-based self-fluxing alloy.

Test Example 2 Table 5 shows Cr-Zr- as a typical example of the precipitation hardening type material.
A thermal spray coating was formed on a Cu substrate, and the thermal spray coating was evaluated in comparison with the conventional method.

[Table 5]

As can be seen by comparing the results of Table 4 and the results of Table 5, as in the case of pure copper, the adhesion strength of the thermal spray coating according to the example of the present invention and the thermal shock test were evaluated in comparison with the conventional example. It is extremely excellent. Further, from the results of Tables 4 and 5, the adhesion strength between the thermal spray coating and the substrate is higher when the substrate is a precipitation hardening material, Cr-Zr-Cu, than in the case of pure copper. It turns out that it is preferable as. Further, as shown in FIG. 6, surface cracks occurred in the thermal spray coating in the conventional example, but no such cracked state occurred in the examples of the present invention.

[Test Example 3] Table 6 is based on the fact that WC-12Co is sprayed on the first layer as a base, and a Ni-based self-fluxing alloy is sprayed thereon as a sprayed coating for the second layer. By adding an example and performing a thermal shock test, the "relationship between film thickness and film cracking susceptibility" is shown.

[Table 6]

According to Table 6, as the thermal spray coating becomes thicker, surface cracking of the coating occurs, and when the substrate is pure copper, surface cracking occurs when the total coating thickness becomes 5 mm. Also, the base of the precipitation hardening type material, namely Cr-Z
In the case of the r-Cu substrate, surface cracking was slightly observed when a 7 mm-thick coating was formed from a WC-12Co single layer having high hardness. However, the first layer is WC-1 with a thickness of 0.05 mm.
No cracks were observed in the case of 2Co and the total film thickness of the second layer was a 5.95 mm thick Ni-based self-fluxing alloy having a thickness of 6 mm.

Therefore, it is better to increase the thickness of the coating to maintain the abrasion resistance, but cracks may occur if the thickness is increased to 4 mm or more depending on the constitution of the abrasion resistant material. If the film thickness is 0.01 mm or more,
It acts as a wear resistant film, but 0.015 mm is required to maintain wear resistance due to the unevenness of the surface of the substrate.
The above is necessary. From this, the preferable film thickness is
It can be said to be 0.015 to 4 mm.

[0043]

As described above, according to the present invention,
It is possible to remove dirt on the surface of the substrate or an oxide film such as Cu ₂ O at the same time when the sprayed film is formed without performing a blasting process as a pre-spraying process. At the same time, due to the sufficient penetration of the thermal spray material into the substrate (anchor effect), a dense thermal spray coating with high adhesion strength can be formed. Therefore, it is possible to obtain an excellent effect that the heat treatment after the thermal spraying for improving the characteristics of the base material, which has been performed in the conventional example, becomes unnecessary.

On the other hand, in the conventional example, the heat treatment after the thermal spraying is indispensable. Therefore, the material strength of the non-precipitation hardening type material (pure copper type) mold is lowered, which is a major drawback in the use as a thermal spray substrate. It was However, due to the practice of the invention,
Even in the case of a non-precipitation hardening type material (pure copper type), a sprayed coating can be applied to the inner surface of the mold.

The thickness of the thermal spray coating of the conventional ultra-high speed flame spraying method is 0.5 to 1 mm at maximum, and there is a problem that cracks are generated in the coating if it is thicker than that. However, in the present invention, the film thickness can be increased to a maximum of 6 mm as compared with the conventional method, and the abrasion resistance can be remarkably improved.

[Brief description of drawings]

FIG. 1 is an enlarged vertical cross-sectional view of a main part of a copper plate on a short side of a mold according to an embodiment of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view of a main part of a copper plate on the short side of another embodiment of the mold.

FIG. 3 is an explanatory view of a test piece for a thermal shock test, FIG. 3 (a) is a plan view thereof, and FIG. 3 (b) is a front view thereof.

FIG. 4 is a photograph and a diagram showing a microscopic metallographic structure of a cross section at an interface between a sprayed coating of a conventional example mold and a substrate.
(A) is the photograph (magnification: 150), and FIG. 4 (b) is an explanatory diagram showing it in a graphic form.

FIG. 5 is a photograph and a diagram showing a microscopic metallographic structure of a cross section at an interface between a sprayed coating of a mold of an example of the present invention and a substrate,
FIG. 5 (a) is the photograph (magnification 150), and FIG. 5 (b) is an explanatory diagram illustrating it.

FIG. 6 shows the condition of the surface of the sprayed coating in the conventional mold as 1.
The figure which expanded and demonstrated 2 times.

[Explanation of symbols]

1,1a Copper base 2,2a Thermal spray coating 3 plating layer 4 bite layer 5 mounting holes

Front page continuation (72) Inventor Takayuki Tanaka 1 in Nishi-Ashihara, Tateyama-machi, Nakashinkawa-gun, Toyama Prefecture 1 Chuetsu Alloy Foundry Co., Ltd. Address 1 Chuetsu Alloy Casting Co., Ltd. (72) Inventor Masahiro Adachi 1-13-8 Ginza, Chuo-ku, Tokyo Inside Welding Rod Co., Ltd. (72) Ryoji Miki 1-chome, Ginza, Chuo-ku, Tokyo No. 13-8 Japan Welding Rod Co., Ltd. (72) Inventor Takeo Owari 2-7-2 Tsukushigaoka, Kashiwa-shi, Chiba (72) Inventor Toru Morishita 8-25-1-206, Takashimadaira, Itabashi-ku, Tokyo ( 56) References JP-A 1-186245 (JP, A) JP-A 1-233047 (JP, A) JP-A 4-325668 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/059 110 C23C 4/06

Claims (3)

(57) [Claims] 1. A method for producing a casting mold for continuous casting, comprising forming a thermal spray coating on the inner surface of a copper or copper alloy base mold, wherein the operating pressure of the thermal spray gun is 0.5 on the inner surface of the copper base mold.
By a high pressure / ultra high speed flame spraying method of 5 MPa to 1.04 MPa, a sprayed coating having a coating thickness of 0.01 to 6 mm is at least formed as the first layer that digs into the surface of the copper substrate.
1. A method for producing a continuous casting mold, which is characterized in that it is formed of one or more kinds of tungsten / carbite-based wear-resistant materials and is not subjected to a blast treatment before thermal spraying and a heat treatment after thermal spraying. 2. A method of producing a casting mold for continuous casting, comprising forming a sprayed coating on the inner surface of a mold having copper or a copper alloy as a base, wherein Ni plating or Ni-Fe plating is performed between the sprayed coating and the copper base . High pressure that the operating pressure of the spray gun is 0.55 MPa to 1.04 MPa with the plating layer interposed.
Ultra-high speed flame spraying method, coating thickness 0.01-6m
The thermal sprayed coating of m is formed of at least one type of tungsten / carbide-based wear-resistant material as a first layer that bites at least the surface of the plating layer, and blasting is performed before thermal spraying and heat treatment is performed after thermal spraying. A method for producing a continuous casting mold, which is characterized in that it does not exist. 3. A tungsten / carbite-based wear-resistant material is a powder having a diameter of 5 to 53 μm, and a micro Vickers hardness (load 300 g) HV _{0.3 of} 1000 to 1400.
The method for producing a continuous casting mold according to claim 1 or 2, wherein