JP6109106B2 - Manufacturing method of continuous casting mold - Google Patents

Description

The present invention relates to a method of manufacturing a mold casting for continuous casting used in the production of such steel, more particularly, heat, corrosion, and a method of manufacturing a mold casting for continuous casting which is excellent in wear resistance.

  Conventionally, as a casting mold for continuous casting whose inner surface is thermally sprayed to improve wear resistance, for example, there is a mold disclosed in Patent Document 1. In the production of this mold, the surface of a base material made of a precipitation hardening type copper alloy (hereinafter also referred to as a base material copper plate) was subjected to base plating such as Ni, and a Ni—Cr based self-fluxing alloy was sprayed thereon. Thereafter, it is heated to about 1000 ° C. As a result, a diffusion layer is formed between the base copper plate and the base Ni plating layer and between the base Ni plating layer and the sprayed coating, and is bonded metallurgically, thereby providing a strong resistance on the base copper plate. A thermally sprayed coating having wear properties is formed.

However, as described above, when the base copper plate after thermal spraying is heated to about 1000 ° C., the base copper plate is deformed. For this reason, it is necessary to perform a strain relief operation on the base copper plate, but even if the strain relief is performed, it may not be incorporated into the back frame of the continuous casting mold. There is a problem that the flatness of the copper plate is inferior.
Furthermore, it is necessary to perform an age hardening heat treatment to recover the strength of the base copper plate, and there is a problem that the manufacturing process is extremely complicated and diverse. Here, it is conceivable that heat treatment is not performed after thermal spraying of a Ni—Cr self-fluxing alloy. In this case, the adhesion with the base copper plate is 0.20 to 0.29 MPa ( ^{2 to 3} kg / mm ^2). ) And is difficult to use for a long time.

For this reason, the inventor previously applied for a continuous casting mold that can be manufactured without performing heat treatment, as shown in Patent Document 2.
Specifically, the thermal spray coating includes 10 to 90% by mass of a Ni-based alloy material and wear-resistant ceramics, and is composed of 90 to 10% by mass of a cermet material corresponding to the proportion of the Ni-based alloy material. The mold was formed by simultaneously spraying the Ni-based alloy material and the cermet material at the same location using independent flame sprayers.
However, in the mold described in Patent Document 2, peeling of the sprayed coating due to toughness and thermal shock resistance occurred, and the life of the mold could not be further extended.

Therefore, the present inventor further applied for a continuous casting mold shown in Patent Document 3.
Specifically, the thermal spray coating is made of a granular cermet material A composed of Cr ₃ C ₂ : 10 to 30% by mass, Ni: 5 to 15% by mass, and the balance WC, and a granular material composed of Ni or a Ni-based alloy. B is a mold formed by mixing with B and sprayed with 5 to 30% by mass of the material B as a material B with a flame sprayer.
With this mold, it is possible to provide thermal shock resistance that meets the current needs, and to extend the service life of the mold.

Japanese Examined Patent Publication No. 61-15758 JP-A-10-71454 Japanese Patent Application Laid-Open No. 2011-31247

  However, in the above-mentioned Patent Document 3, Ni is used as the material B of the thermal spray coating. However, in corrosion, particularly in an S (sulfur) -based corrosive environment, the corrosion resistance (corrosion resistance) of Ni is very weak. In some cases, the life of the mold may be shortened due to corrosion rate control. In other words, the above molds may not be able to achieve both thermal shock resistance and corrosion resistance that meet current needs, and the mold life may be shortened.

The present invention has been made in view of such circumstances. For continuous casting, the toughness can be improved, the thermal shock resistance can be further improved, and the corrosion resistance can be improved. As a result, the life of the mold can be extended. and to provide a casting mold manufacturing method of.

A method for producing a continuous casting mold according to the present invention that meets the above-described object is a method for producing a continuous casting mold in which a surface plating layer and a sprayed coating are sequentially formed on the molten steel contact surface side,
Co: 5% by mass or more and 15% by mass or less, Cr: 2% by mass or more and 6% by mass or less, and a granular cermet material composed of the balance WC, and granular Ni—Al containing Al in excess of 0 and 8% by mass or less The thermal spraying particles formed by mixing the alloy with the Ni-Al alloy at 20% by mass or more and 60% by mass or less of the whole are sprayed by a flame spraying machine, and the Ni-- is applied to the grain boundaries of the cermet material. The sprayed coating in which an Al alloy is present is formed.

In the method for producing a casting mold for continuous casting according to the present invention, the base plating layer is made of Ni, Co, Fe, or an alloy based on any one or two of these, and the base plating layer includes the above-described base plating layer. After the surface roughening treatment is performed to make the surface roughness (Rz) 50 μm or more and 150 μm or less, the sprayed coating is preferably formed.
In the method for producing a continuous casting mold according to the present invention, a high-speed flame sprayer may be used as the flame sprayer, and the velocity of the spray particles may be 600 m / second or more.
In the method for manufacturing a continuous casting mold according to the present invention, the thickness of the sprayed coating may be 0.05 mm or more and 1 mm or less.

Method for producing a mold casting for continuous casting according to the present invention, a thermal spray coating, Co adjusted to a predetermined ratio, Cr, and particulate consisting balance WC and cermet materials, particulate containing a predetermined amount of Al Ni- The sprayed particles, which are formed by mixing with an Al alloy and the Ni-Al alloy is 20% by mass or more and 60% by mass or less of the whole, are sprayed by a flame sprayer, and the Ni-Al alloy is present at the grain boundary of the cermet material. Therefore, the toughness can be improved as compared with the prior art, the thermal shock resistance can be improved, and the corrosion resistance (particularly, the corrosion resistance against sulfur) can be improved. Therefore, peeling and corrosion of the sprayed coating to be formed can be suppressed, and the life of the mold can be further extended.

  Further, when the base plating layer is made of Ni, Co, Fe, or an alloy based on any one or more of these, a part of the sprayed particles sprayed by the flame spraying machine is It can penetrate into the surface layer and secure the retention force of the spray particles. Here, since the roughening treatment is further performed, the adhesion strength of the sprayed coating can be improved. In addition, since this roughening process has a roughness of 50 μm or more and 150 μm or less, the adhesion of the sprayed coating can be enhanced while suppressing variations in the thickness of the sprayed coating.

When the thickness of the thermal spray coating is 0.05 mm or more and 1 mm or less, the thickness of the thermal spray coating can be set to an optimum thickness that can suppress the peeling of the thermal spray coating and further extend the life of the mold.
Furthermore, when the flame sprayer is a high-speed flame sprayer that makes the speed of the spray particles 600 m / sec or more, the adhesion of the sprayed coating to the underlying plating layer can be further increased.

It is explanatory drawing which shows the thermal spraying condition in the manufacturing method of the casting mold for continuous casting which concerns on one embodiment of this invention. (A) is the partial expansion schematic diagram of the thermal spray coating of the same casting mold, (B) is the partial expansion schematic diagram of the thermal spray coating formed only with the cermet material. It is explanatory drawing of the evaluation method of a thermal shock resistance.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIGS. 1 and 2A, a continuous casting mold manufactured by a manufacturing method according to an embodiment of the present invention has a cooling member 10 in which a space portion penetrating in the vertical direction is formed. Then, molten steel is supplied to the space and the slab is manufactured while cooling. The cooling member 10 includes a base material 11 made of copper or a copper alloy (for example, Cu—Cr—Zr), and a base plating layer 12 and a thermal spray coating 13 are sequentially formed on the molten steel contact surface side. ing. This will be described in detail below.

As shown in FIG. 1, a base plating layer 12 that has been subjected to a roughening treatment is formed on the molten steel contact surface side of the base material 11. The base plating layer 12 has an anchor effect, which is the principle of adhesion of thermal spraying, obtained from a soft base material made of copper or a copper alloy, and in particular, Ni, Co, Fe, or any one or two of these It is preferable to consist of an alloy having the above as a base material.
In the roughening treatment performed on the base plating layer 12, the surface roughness (Rz) of the base plating layer 12 is 50 μm or more and 150 μm or less (preferably, the lower limit is 70 μm, the upper limit is 120 μm, and further 100 μm). Is preferred. Here, when the roughness is out of the range of 50 μm or more and 150 μm or less, the adhesion of the thermal spray coating to the base plating layer becomes less than 98 MPa (10 kg / mm ² ), and the thermal spray coating is easily peeled from the base plating layer. .

A thermal spray coating 13 is formed on the base plating layer 12.
The thermal spray coating 13 is formed by spraying a thermal spray particle formed by mixing a granular cermet material made of Co, Cr, and the balance WC and a granular Ni-Al alloy containing a predetermined amount of Al with a flame sprayer 14. And formed.
The reason why the Ni—Al alloy was selected as the spray particles is that Al tends to be an oxide (easily passivated), and Ni is easily alloyed with Al. The Ni—Al alloy may contain inevitable impurities.

The thermal spray coating 13 is preferably formed densely (with a filling rate of 90% or more, more preferably 95% or more) in a range of 0.05 mm to 1 mm.
Here, when the thickness of the thermal spray coating is less than 0.05 mm, the thickness of the thermal spray coating is too thin and the service life of the mold becomes too short. On the other hand, when the thickness of the thermal spray coating exceeds 1 mm, the thermal spray coating is too thick and the thermal spray coating is easily peeled off from the cooling member.
From the above, the thickness of the sprayed coating 13 to be formed is preferably 0.05 mm or more and 1 mm or less, but it is more preferable that the lower limit is 0.1 mm, further 0.2 mm, and the upper limit is 0.7 mm. .

The spray particles are formed by mixing a granular cermet material and a granular Ni—Al alloy (20 mass% or more and 60 mass% or less of the entire spray particles are Ni—Al alloy). FIG. 2 (A) shows an enlarged schematic view of a sprayed coating formed by spraying the sprayed particles, and FIG. 2 (B) shows an enlarged schematic view of a sprayed coating formed by spraying only a granular cermet material. , Respectively. 2A and 2B are each formed on a base plating layer.
As shown in FIG. 2A, a Ni—Al alloy is present at the grain boundary of the cermet material by forming a thermal spray coating with thermal spray particles obtained by mixing granular cermet material and Ni—Al alloy. For this reason, compared with the case where a sprayed coating is formed only by the cermet material shown in FIG. 2 (B), the brittleness of the sprayed coating can be reduced and the toughness can be improved.

That is, when the amount of Ni—Al alloy in the spray particles is less than 20% by mass, the amount of Ni—Al alloy present at the grain boundary of the cermet material is too small, and the effect of improving toughness is obtained, and Corrosion resistance deteriorates. On the other hand, when the amount of the Ni—Al alloy in the spray particles exceeds 60% by mass, the amount of the cermet material contained in the spray coating is too small, resulting in a decrease in the hardness of the spray coating and an increase in the volume wear rate. The Ni—Al alloy is preferably present at all grain boundaries of the cermet material, but may be partial.
From the above, the amount of Ni—Al alloy in the spray particles is set to 20% by mass or more and 60% by mass or less, but the lower limit is 25% by mass, further 30% by mass (more preferably more than 30% by mass), and the upper limit. Is preferably 55 mass%, more preferably 50 mass%.

The cermet material is Co: 5% by mass or more and 15% by mass or less (preferably, lower limit is 6% by mass, further 7% by mass, upper limit is 14% by mass, further 13% by mass), Cr: 2% by mass or more 6 It is composed of not more than mass% (preferably, the lower limit is 3 mass%, the upper limit is 5 mass%) and the balance WC. The cermet material may contain, for example, Fe as an unavoidable impurity.
By making the cermet material as described above, the hardness is comparable and the thermal shock resistance at a high temperature is 5-7 compared with WC / 12% Co which is generally used as a wear-resistant material. Can be doubled. Therefore, the crack resistance of the thermal spray coating 13 can be improved.

In addition, the Ni-Al alloy has an Al content exceeding 0 and not more than 8% by mass.
When the Al content is 0% by mass (when Al is not included), since only Ni is obtained, the corrosion resistance is deteriorated as described above. On the other hand, when the Al content exceeds 8% by mass, Ni cannot dissolve Al (Al solid solubility limit: about 8% by mass), an intermetallic compound is formed, and the thermal shock resistance of the sprayed coating is reduced. There is a risk.
From the above, the Al content of the Ni-Al alloy is set to be more than 0 and 8% by mass or less, but the lower limit is 3% by mass, further 4% by mass, and the upper limit is 7% by mass, and further 6% by mass. It is preferable.

The thermal spray coating 13 shown above is formed by spraying thermal spray particles with a flame sprayer 14.
The flame sprayer 14 is a high-speed flame sprayer that makes the velocity of spray particles 600 m / second (preferably 700 m / second) or more, but a flame sprayer that is usually used can also be used. In addition, when a high-speed flame sprayer is used, the adhesive force of the thermal spray coating 13 to the base plating layer 12 can be further increased.
For the reasons described above, the upper limit of the velocity of the spray particles is not defined, but in reality, for example, it is about 1000 m / second.

Next, the manufacturing method of the casting mold for continuous casting which concerns on one embodiment of this invention is demonstrated.
First, as shown in FIG. 1, a base plating layer 12 is formed by performing base plating having a thickness of about 100 μm on the inner surface of the molten steel contact surface side of the base material 11 constituting the continuous casting mold.
As an electrolytic solution in this case, a solution in which 350 g of S-Ni (nickel sulfamate), 5 g of nickel chloride, and 30 g of boric acid are dissolved in 1 liter is used. the density 3A / dm ^2. Here, the base plating layer is formed of Ni, but may be formed of, for example, Co or Fe, or may be formed of an alloy based on any one or more of Ni, Co, and Fe. Also good.

The underlying plating layer 12 is subjected to a roughening treatment, and the roughness of the surface of the underlying plating layer 12 is set to 50 μm or more and 150 μm or less.
Here, the roughening treatment is performed by blasting using alumina or steel grit. In addition, as an alumina to be used, for example, alumina having a grid size of # 24 can be used, and the air pressure at the time of blasting is set to about 0.49 MPa (5 kg / cm ² ). When steel grit is used, steel grit having a particle size of # 50 can be used, and the air pressure during blasting is about 0.49 MPa (5 kg / cm ² ).
And it forms by mixing the granular cermet material which consists of Co, Cr, and the remainder WC, and granular Ni-Al alloy on the base plating layer 12 by which the roughening process was carried out, and also 20 mass% of the whole Thermal spray particles having a Ni—Al alloy content of 60 mass% or less are sprayed by the flame sprayer 14.

Here, each particle size distribution of the cermet material and the Ni—Al alloy is, for example, about 5 μm to 60 μm (preferably, the lower limit is 10 μm and the upper limit is 55 μm) in consideration of the strength of the sprayed coating to be formed. Note that the particle size distributions of the cermet material and the Ni—Al alloy before thermal spraying may be the same or different.
As the spray particles, a cermet material and a Ni—Al alloy can be purchased separately and mixed in the above-described proportions. Alternatively, premixed particles can be purchased and used.

As the flame sprayer 14 for spraying the sprayed particles, a high-speed flame sprayer that makes the speed of the sprayed particles 600 m / second (preferably 700 m / second) or more is used, but a conventionally known flame sprayer is used. You can also
Thereby, as shown in FIG. 2A, the thermal spray coating 13 in which the Ni—Al alloy is present can be formed at the grain boundary of the cermet material. The thickness of the sprayed coating 13 is not particularly limited, but is preferably formed densely in the range of 0.05 mm to 1 mm.
The surface side of the sprayed coating 13 formed in this way is finished as necessary, and then used as a continuous casting mold.

Next, examples carried out for confirming the effects of the present invention will be described.
First, an underlying plating layer made of Ni was formed on the surface of a base material made of Cu—Cr—Zr by the method described in the above embodiment. In this roughening treatment, steel grit was used, and the air pressure at that time was about 0.49 MPa.
Then, a sprayed coating having a thickness of about 0.8 mm was formed on the base plating layer using a high-speed flame spraying machine. Table 1 shows the types and ratios of materials constituting the thermal spray coating.

In the reference examples shown in Table 1, WC / 12% Co, which is generally used as a wear-resistant material, was used as the cermet material (the compound metal was not used).
Comparative Examples 1 to 4 are the thermal spray particles described in Patent Document 3 (Japanese Patent Laid-Open No. 2011-314747) with improved thermal shock resistance, and WC / Cr ₃ C ₂ / Ni is used as a cermet material. Ni or Ni-Cr alloy was used as a compound metal.
In Examples 1 to 4, WC / Co / Cr was used as the cermet material, and a Ni—Al alloy having an Al content of 5 mass% was used as the compound metal.

Further, as shown in FIG. 3, the thermal shock resistance in Table 1 was evaluated based on the number of times the plasma spraying machine was moved at a constant speed to the surface side of the formed sprayed coating, and cracks were generated in the sprayed coating. Specifically, the number of occurrences of cracks in Comparative Examples 1 to 4 and Examples 1 to 4 was divided by the number of occurrences of cracks in the reference example, and the reciprocal number is shown in Table 1 as thermal shock resistance. The thermal shock resistances of Comparative Examples 1 to 4 and Examples 1 to 4 are ratios when the thermal shock resistance of the reference example is 1.0.
Furthermore, the degree of extension of the mold life in Table 1 is determined by measuring the use time of the actually used mold, setting the time of the reference example to 1.0, and the ratio of Comparative Examples 1 to 4 and Examples 1 to 4 Asked.

As is clear from Table 1, the thermal shock resistance of Examples 1 to 4 can be increased to 5 times or more (up to about 8 times) of the thermal shock resistance of the reference example, and the thermal shock resistance is improved. It was possible to raise it to be equal to or higher than those of Comparative Examples 1 to 4.
Therefore, it has been confirmed that the mold life resulting from the thermal shock resistance can be extended to be equal to or greater than that of Comparative Examples 1 to 4.

Subsequently, each of the sprayed particles of Comparative Example 1 and Example 1 described above was used to investigate the corrosion resistance using a test piece on which a sprayed coating was formed by the method described above.
First, after placing the above-described test piece in a furnace, a mixed gas adjusted to H ₂ S (hydrogen sulfide) gas: 2% and Ar gas: 98% was flowed into the furnace at a flow rate of 200 (milliliter / Min). Then, the furnace was heated to 500 ° C. at a rate of temperature increase of 250 ° C./hour, held at this temperature for 16 hours, and then cooled at a temperature decrease rate of 100 ° C./hour.
After cooling the inside of the furnace to room temperature, the supply of the mixed gas to the furnace is stopped, the test piece is taken out from the furnace and cut, and then the cross section is observed with EPMA, and the thickness direction of the thermal spray coating is observed. The corrosion status of was confirmed.

As a result, the corrosion thickness due to sulfur (the thickness of the sulfurization reaction layer) ranged from the surface of the thermal spray coating to 19.8 μm in the case of Example 1, but in the case of Comparative Example 1, the thickness from the surface of the thermal spray coating. It was found that the corrosion had progressed to a depth of about 4 times compared to Example 1 over a range of up to 80.0 μm.
Therefore, it was confirmed that the corrosion resistance can be significantly improved as compared with Comparative Example 1. That is, it was confirmed that the mold life caused by the corrosion resistance can be significantly extended from that of Comparative Example 1. In addition, the other Examples 2 to 4 showed the same tendency as Example 1.

In addition, as a result of investigating about abrasion resistance (Vickers hardness) using the test piece which formed the thermal spray coating using each thermal spray particle of above-mentioned comparative example 1 and Example 1, the comparative example 1 was 726. However, Example 1 was 941.
Therefore, it was confirmed that the wear resistance can be improved as compared with Comparative Example 1.

From the above, by using the method of the type cast for continuous casting production present invention, Hakare is a further improvement in thermal shock resistance model improves toughness, and Hakare also corrosion resistance, as a result, the mold It has been confirmed that the service life can be extended.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, when a part or the method of type casting for continuous casting production combination present invention all of the respective embodiments and modified example is also included in the scope of the present invention.
The thermal spray coating and the base plating layer shown in the above embodiment may be formed at least on the molten steel contact surface side on the lower side (downstream in the casting direction) of the cooling member where corrosion due to sulfur is likely to occur. You may form over the molten steel contact surface side.

  In addition, the cooling member for forming the thermal spray coating to which the present invention is applied includes a combination of four composed of a pair of short sides and a pair of long sides, but is not limited thereto. The tube-shaped thing which manufactures a billet (for example, width and thickness is about 100-200 mm) or a bloom (for example, width and thickness is about 200-400 mm) may be sufficient. Therefore, as for the mold configuration, for example, a mold for producing a slab, billet, bloom, or beam blank (used for H-shaped steel), and further, a block mold in which water conduction holes are drilled in a forged or forged copper block, Of course, it is possible to apply the present invention.

10: Cooling member, 11: Base material, 12: Undercoat layer, 13: Thermal spray coating, 14: Flame sprayer

Claims (4)

In the method for producing a casting mold for continuous casting, in which a base plating layer and a sprayed coating that have been roughened are sequentially formed on the molten steel contact surface side,
Co: 5% by mass or more and 15% by mass or less, Cr: 2% by mass or more and 6% by mass or less, and a granular cermet material composed of the balance WC, and granular Ni—Al containing Al in excess of 0 and 8% by mass or less The thermal spraying particles formed by mixing the alloy with the Ni-Al alloy at 20% by mass or more and 60% by mass or less of the whole are sprayed by a flame spraying machine, and the Ni-- is applied to the grain boundaries of the cermet material. A method for producing a casting mold for continuous casting, comprising forming the sprayed coating in which an Al alloy is present. The method for manufacturing a casting mold for continuous casting according to claim 1 , wherein the base plating layer is made of Ni, Co, Fe, or an alloy based on any one or more of these, and the base plating layer A method for producing a casting mold for continuous casting, wherein the thermal spray coating is formed after the surface roughening treatment is performed to set the surface roughness (Rz) to 50 μm or more and 150 μm or less. 3. The continuous casting mold according to claim 1 , wherein a high-speed flame sprayer is used as the flame sprayer, and the velocity of the spray particles is 600 m / second or more. Manufacturing method.   The method for manufacturing a continuous casting mold according to any one of claims 1 to 3, wherein the sprayed coating has a thickness of 0.05 mm to 1 mm.

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