JP4135835B2 - Mold for continuous casting overlay welding - Google Patents

Description

【００１１】
実施条件は、母材として機械構造用鋼管（ＳＴＫＭ）−１３Ａを用い、肉盛り材質は１．７５重量％Ｃ−１３．０重量％Ｃｒ−５．５重量％Ｖの鋳鉄とし、モールド径φ３２５ｍｍ、胴長７９００ｍｍとした。以上の条件で本発明材４材質と試験材２材質及び比較材として黒鉛ライニングによる連続鋳掛け肉盛溶接を行った。実施結果を表１のように、実施後のモールドの耐用度、摩耗量、ロール表面のクラック数で示す。まず、モールドの耐用度を調査した。その結果、従来の黒鉛ライニングの耐用度１回に対し本発明材１〜４の耐用度は２回であった。試験材５、６、比較材７については、モールドの摩耗及び鋳肌欠陥の増大から複数回の使用は不可能であった。モールドの摩耗量については、従来の黒鉛ライニングの摩耗量３ｍｍに対し、本発明材１〜４は、いずれも摩耗量０．５ｍｍ以下で耐摩耗性は良好である。次に連続鋳掛け肉盛溶接後のロールをスキンカットして、染色浸透探傷試験によって鋳肌表面のクラックを調査した。
【００１２】
その結果、本発明材１〜４には、従来の黒鉛ライニングのクラック数７個に対し欠陥が発生しておらず鋳肌性状は良好であった。２チャージ目の実施結果でもクラックは発生していなかった。また、試験材５、６についてはクラック個数が従来の黒鉛ライニングと同様多数発生していた。以上の結果より、摩耗量、クラック発生数共に良好であることから、本発明材は十分に複数回の使用に耐え、良製品を製造できることが判明した。
【００１３】
【発明の効果】
以上述べたように、請求項１〜３の連続鋳掛け肉盛溶接用モールドにおいては、組合せモールドの内側上部に設けられた冷却緩衝型の消耗度が極めて少なく、安定して複数回の使用が可能になり、かつ良製品を供給できる等経済的効果は極めて大である。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る連続鋳掛け肉盛溶接用モールドの概略説明図である。
【図２】従来例に係る連続鋳掛け肉盛溶接用モールドの概略説明図である。
【符号の説明】
１０ 組合せモールド １１ 中空式冷却型
１２ 冷却緩衝型 １３ 電磁誘導加熱コイル
１４ 耐火枠
１５ 連続鋳掛け肉盛溶接用モールド １６ 被溶接母材
１７ 溶湯 １８ 引抜き方向を示す矢印
１９ 肉盛層 ２０ ガラスコーティング層
２１ 予熱用の電磁誘導加熱コイル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cooling mold for continuous cast overlay welding.
[0002]
[Prior art]
As shown in FIG. 2, a continuous casting overlay welding mold 50 used for conventional continuous casting overlay welding disclosed in Japanese Patent Publication No. 52-2848 is a hollow type cooling made of metal such as steel. It has a combination mold of a mold 51 and a cooling buffer mold 52 provided on the inside upper part thereof. Then, a hollow annular fireproof frame 54 having an electromagnetic induction heating coil 53 is combined thereabove, and continuous casting overlay welding is performed on a base material 55 to be welded provided in the center.
The to-be-welded base material 55 is always lowered and cooled and solidified downward to form a build-up welded article 56. However, since the descending speed is slow, cooling directly with metal such as steel will have an excessive cooling effect. Then, a crack is generated in the built-up layer 57. Therefore, a graphite lining is used as the cooling buffer mold 52 for the purpose of suppressing the heat removal of the built-up layer 57 to a predetermined level. The main characteristics required for the cooling buffer mold 52 used for such a purpose are that it does not get wet with the molten metal 58 and has excellent corrosion resistance and erosion resistance, and has excellent wear resistance and does not deteriorate mechanical strength up to high temperatures. In addition, the thermal expansion coefficient is small and the thermal shock resistance is high.
[0003]
[Problems to be solved by the invention]
The inner surface of the graphite lining constituting the cooling buffer type 52 is in contact with the build-up weld layer, and when the build-up weld layer is in a molten state, the contact surface is hardly worn, but the solidified shell is formed on the build-up weld layer. When this occurs, sliding damage flaws are generated on the inner surface of the graphite lining, and the resistance during descending increases sequentially. That is, the cooling buffer type 52 using the conventional graphite lining is inferior in corrosion resistance, erosion resistance, and wear resistance. As the increase progresses, the resistance during descent tends to occur and defective products tend to occur.
In addition, the cooling buffer mold 52 that was consumed every time the overlay welding was to be replaced, which was inefficient. Due to the flaws on the inner surface of the graphite lining, sliding flaws are generated on the surface of the built-up layer 57, and the sliding flaws conversely enlarge the flaws of the graphite lining, and both combine to form a flesh. Damaged flaws on the surface of the built-up layer 57 gradually increased, resulting in defective products. Therefore, the graphite lining always needs to be replaced for each charge, and has many drawbacks such as generation of defective products and reduced work efficiency.
The present invention has been made in view of such circumstances, and provides a cooling mold for continuous casting overlay welding that eliminates the above-described drawbacks, can be used for a long period of time, and is less likely to cause scratches on the product. With the goal.
[0004]
[Means for Solving the Problems]
The continuous casting overlay welding mold according to the present invention that meets the above-mentioned object is a combination mold having a cooling buffer mold on the upper inner surface of a hollow cooling mold made of metal such as steel, and above the combination mold. In the continuous casting overlay welding mold having a hollow annular fireproof frame encased by an electromagnetic induction heating coil, the cooling buffer mold is a non-graphite type mold, which is more resistant to corrosion and melting than graphite. It is made of a ceramic having damage resistance and wear resistance.
The ceramic is similar to the conventional graphite lining material in terms of thermal conductivity and linear expansion coefficient, and has other characteristics such as excellent oxidation resistance, corrosion resistance and thermal shock resistance against molten metal. Much better than graphite lining. Therefore, according to the continuous casting overlay welding mold according to the present invention, the degree of wear is extremely small and it can be used stably over a long period of time, and the economic effects such as improvement of quality and efficiency of work are remarkable.
Here, for example, composite ceramics having 10 to 60% by weight of boron nitride and 40 to 90% by weight of sialon can be used as the ceramic.
Moreover, it is also possible to use the composite ceramics which contain 10 to 50 weight% boron nitride and 50 to 90 weight% silicon nitride for the said ceramic, for example.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a sectional view of a continuous casting overlay welding mold according to one embodiment of the present invention.
As shown in FIG. 1, the combination mold 10 has a hollow cooling mold 11 made of a metal such as steel and a cooling buffer mold 12 which is a non-graphite mold, and the cooling buffer mold 12 is a hollow cooling mold. 11 and is cooled from the outside by the hollow cooling die 11. A continuous cast-in overlay welding mold 15 is formed by integrally arranging a hollow annular refractory frame 14 enclosed by an electromagnetic induction heating coil 13 above the combination mold 10.
In the center of the continuous casting overlay welding mold 15, the base material 16 to be welded is set up vertically, and the molten metal 17 is injected into the gap between the base material 16 to be welded and the continuous casting overlay welding mold 15. And continuous overlay welding. The base material 16 to be welded descends slowly as indicated by an arrow 18 at all times, but the poured molten metal 17 is fused to the base material 16 to be welded that has been heated by high-frequency induction heat. It is gradually cooled by the cooling buffer mold 12 and solidifies from the surface to form a built-up layer 19. In FIG. 1, 20 is a glass coating layer, and 21 is a preheating electromagnetic induction heating coil.
[0006]
Here, as the cooling buffer mold 12, a composite ceramic having 10 to 60% by weight of boron nitride and 40 to 90% by weight of sialon is used. The reasons for limiting the components of the cooling buffer mold 12 will be described below.
Sialon has high strength at high temperatures and excellent oxidation resistance, erosion resistance, and wear resistance. Boron nitride has the same crystal structure as graphite, has the effect of improving thermal conductivity, corrosion resistance and thermal shock resistance, and has the effect of making it difficult to get wet with molten metal, so the combination of sialon and boron nitride is a cooling buffer. It is effective for improving the properties as a mold. In the compounding, the proportion of sialon is set to 40% by weight or more because the strength at high temperature is remarkably lowered if it is less than 40% by weight. When the ratio of boron nitride is less than 10% by weight, not only the effects of sufficient thermal shock resistance and corrosion resistance cannot be obtained, but also the characteristics that make it difficult to wet the molten metal cannot be obtained. If it exceeds 60% by weight, the mechanical strength is remarkably lowered, causing problems in wear resistance and corrosion resistance, resulting in conspicuous wear and irregular casting surface properties. Therefore, boron nitride is 10 to 60% by weight. The main components are as described above, but an improving component such as a sintering aid can be added as long as the target characteristics are not impaired.
[0007]
Next, as the cooling buffer mold 12 of the continuous casting overlay welding mold according to another embodiment of the present invention, a composite ceramic having 10 to 50% by weight of boron nitride and 50 to 90% by weight of silicon nitride is used. Yes. The reason for limiting this component will be described in detail below.
Silicon nitride is excellent in mechanical strength and wear resistance at high temperatures, but has a drawback of low thermal conductivity and inferior melt resistance. For this reason, the disadvantage is eliminated by combining with boron nitride having high thermal conductivity and excellent resistance to erosion and thermal shock. In compounding, the ratio of silicon nitride is 50% by weight or more in order to obtain high temperature strength. If the proportion of boron nitride is less than 10% by weight, the effect of the erosion resistance is small, and if it exceeds 50% by weight, a problem occurs in the wear resistance, resulting in a disturbed casting surface property. Therefore, boron nitride is 10 to 50% by weight. The main components are as described above, but an improving component such as a sintering aid can be added as long as the target characteristics are not impaired.
[0008]
As described above, as the cooling buffer mold 12, (1) a composite ceramic having 10 to 60% by weight of boron nitride and 40 to 90% by weight of sialon, and (2) 10 to 50% by weight of boron nitride and 50 to 90% of silicon nitride. By using a composite ceramic having a weight percent, the following characteristics are obtained. That is, in the cooling buffer mold 12 made of the material according to this embodiment, the molten metal is in a molten state, there is almost no damage to the contact surface, the contact with the solidified shell layer is extremely smooth, and both have sliding resistance. There is almost no generation of sliding wrinkles due to. Accordingly, an excellent overlay layer 19 can be obtained, and the number of times the mold is used increases.
[0009]
【Example】
Then, the Example which concerns on the mold for overlay welding containing this invention and the comparative example below is described.
Overlay welding was performed by continuous casting using a combination mold in which a composite ceramic of sialon and boron nitride and silicon nitride and boron nitride was used as a cooling buffer type. The components of the examples are shown in Table 1.
[0010]
[Table 1]

[0011]
The working conditions are steel pipe for machine structure (STKM) -13A as the base material, the build-up material is cast iron of 1.75 wt% C-13.0 wt% Cr-5.5 wt% V, and mold diameter φ325mm The body length was 7900 mm. Under the above conditions, continuous casting overlay welding by graphite lining was performed as the material 4 of the present invention, the material 2 of the test material, and the comparative material. As shown in Table 1, the results are shown in terms of the durability of the mold after execution, the amount of wear, and the number of cracks on the roll surface. First, the durability of the mold was investigated. As a result, the durability of the present invention materials 1 to 4 was twice that of the conventional graphite lining. Test materials 5 and 6 and comparative material 7 could not be used a plurality of times due to mold wear and increased casting surface defects. With respect to the wear amount of the mold, the present invention materials 1 to 4 have a wear amount of 0.5 mm or less, and the wear resistance is good, compared with the wear amount of 3 mm of the conventional graphite lining. Next, the roll after continuous casting overlay welding was skin-cut and the cracks on the casting surface were investigated by a dye penetration test.
[0012]
As a result, the inventive materials 1 to 4 were free from defects with respect to the number of cracks of the conventional graphite lining, and the casting surface properties were good. Cracks did not occur even in the results of the second charge. Further, the test materials 5 and 6 had many cracks as in the conventional graphite lining. From the above results, it was found that the amount of wear and the number of occurrence of cracks are good, so that the material of the present invention can sufficiently withstand multiple uses and can produce a good product.
[0013]
【The invention's effect】
As described above, in the continuous cast overlay welding mold of claims 1 to 3, the cooling buffer type provided in the upper part of the inner side of the combination mold has very little wear and can be used multiple times stably. The economic effects such as being able to supply good products are extremely large.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of a continuous casting overlay welding mold according to an embodiment of the present invention.
FIG. 2 is a schematic explanatory diagram of a continuous casting overlay welding mold according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Combination mold 11 Hollow cooling die 12 Cooling buffer type 13 Electromagnetic induction heating coil 14 Fireproof frame 15 Continuous casting overlay welding mold 16 Welded base material 17 Molten metal 18 Arrow indicating the drawing direction 19 Overlay layer 20 Glass coating layer 21 Electromagnetic induction heating coil for preheating

Claims (3)

A combination mold having a cooling buffer mold on the upper inner surface of a hollow cooling mold made of metal such as steel, and a hollow annular fireproof frame that is above the combination mold and is encased by an electromagnetic induction heating coil In a continuous casting overlay welding mold,
The cooling buffer mold is a non-graphite mold, and is made of ceramics having excellent corrosion resistance, melt resistance, and wear resistance compared to graphite, and is a continuous casting overlay welding mold characterized by the above. The continuous cast overlay welding mold according to claim 1, wherein a composite ceramic having 10 to 60 wt% boron nitride and 40 to 90 wt% sialon is used as the ceramic. Mold. The continuous casting overlay welding mold according to claim 1, wherein the ceramic is a composite ceramic having 10 to 50% by weight boron nitride and 50 to 90% by weight silicon nitride. Mold for welding.

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