JP2001105103A - Mold for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the surface structure of a mold, on which both of high wear resistance and high thermal conductivity are obtained even under the conditions of high speed casting and high cycle oscilation. SOLUTION: The surface of the casting space side of the mold for continuous casting molten metal is coated with e.g. the thermal-sprayed layer of an amorphous alloy composed of iron alloy or nickel alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for continuous casting of molten metal, and more particularly to a mold for suppressing abrasion of a casting surface in contact with a molten metal and the like for a long period of time even under high speed casting or high cycle oscillation. The present invention relates to a continuous casting mold capable of maintaining casting.

[0002]

2. Description of the Related Art Continuous casting of molten metal such as molten steel is usually performed by
A molten metal (hereinafter referred to as “melted steel”) is supplied into a mold (casting space) that is open in the vertical direction and is formed of a water-cooled copper plate on all four sides, and heat is removed from the outer surface by the copper plate. While solidifying (primary cooling), the slab is subjected to secondary cooling while continuously being drawn downward. In such a casting method, so-called oscillation, in which the mold body is moved up and down periodically, is added in order to reduce the frictional resistance with the inner wall surface of the mold when the formed solidified shell (slab) is pulled downward. is necessary. However, in this oscillation, since the solidified shell and the copper plate constituting the mold wall are slid with each other, there is a problem that the copper plate having a lower hardness than steel is significantly worn and has a shorter life. . In addition, a component of copper, which is a constituent material of the mold, infiltrates the surface of the slab, and a slab surface defect called star crack may occur on the surface of the steel slab.

On the other hand, Japanese Patent Laid-Open Publication No.
No. 23 proposes a method of improving the wear resistance of a mold by plating Ni or a Ni alloy on the inner surface of the mold.
However, according to this conventional technique, for example, when the casting speed is 1.4 m / min. And the oscillation is several tens of cycles / min., The life of the copper plate forming the mold wall is remarkably improved. However, under the conditions of high speed casting (casting speed of 1.5 m / min. Or more) and high cycle oscillation (several hundred cycles / min), which have been aimed at in recent years, it was still insufficient.

[0004] Among other prior arts, there is a proposal aimed at further improving the wear resistance of the mold.
For example, Japanese Patent Application Laid-Open Nos.
Japanese Patent Publication No. 175044 proposes a method of forming a sprayed coating of a self-fluxing alloy or cermet on the inner wall surface of a mold. However, although these thermal spray coatings certainly improve the wear resistance of the mold, there is a problem that the thermal conductivity is reduced due to the inclusion of the ceramic. In other words, if the thermal conductivity of the mold decreases, the growth of the solidified shell of the molten steel at an early stage is delayed, and as a result,
The solidified shell thickness of the slab in the (secondary cooling zone) becomes insufficient,
There was a danger of breaking out because the steel could not withstand the static pressure of the molten steel. Therefore, in the case of these conventional techniques, there remains a problem that the casting speed cannot be increased.

[0005]

As described above, the conventional continuous casting mold, especially the coating technique for the surface of the copper mold in contact with molten steel, is not suitable for high-speed casting or casting under high cycle oscillation conditions. Was not fully tolerated. Therefore, an object of the present invention is to propose a surface structure of a mold that can achieve both high wear resistance and thermal conductivity even under high-speed casting and high cycle oscillation conditions.

[0006]

Means for Solving the Problems In a study aimed at solving the above-mentioned problems in the prior art, the inventors found that when forming a protective coating on the surface of a copper plate forming the inner wall surface of a mold, The coating layer should be a metal layer instead of ceramic etc. to ensure high thermal conductivity, an amorphous alloy layer to make the metal layer excellent in wear resistance, and a sufficient thickness It has been concluded that it is effective to achieve this by adopting a thermal spraying method in order to form the film of amorphous by making it amorphous without impairing the adhesion to the underlying copper plate, and to complete the present invention. It is a thing.

That is, the present invention proposes a continuous casting mold characterized in that a surface of a casting space side of a continuous casting mold of molten metal is coated with a sprayed layer of an amorphous alloy. . In the present invention, the amorphous alloy is preferably an iron alloy containing 70% or more of Fe, and in particular, an alloy of Fe and one or more elements selected from C, Si, P and B It is preferred that In addition, the amorphous alloy has N
A nickel alloy containing 70% or more of i is preferable, and an alloy of Ni and one or more elements selected from C, Si, P, and B is particularly preferable.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The type of continuous casting of molten metal which is the subject of the present invention is not limited as long as the slab and the mold move relative to each other. For example, in addition to a continuous casting machine that supplies molten metal from above the mold and pulls out the slab from the bottom of the mold, such as a vertical continuous casting machine, a vertical bending continuous casting machine, a curved continuous casting machine, and a horizontal continuous casting machine. It is also applicable to casting machine molds. Also, depending on the shape of the slab to be manufactured, it can be applied to any continuous casting machine such as a slab continuous casting machine, a bloom continuous casting machine, a billet continuous casting machine, a beam blank continuous casting machine, and a round cast slab continuous casting machine. is there.

As the molten metal to be cast, molten steel is advantageous as long as the effects and effects of the present invention can be utilized, but it is not particularly limited to the molten steel. In the case of the molten steel, any of ordinary steel, alloy steel, stainless steel and the like may be used.

The material of the copper plate constituting the mold is not particularly different from the Cu alloy conventionally used as the mold copper plate. It is preferable to use a precipitation hardening type copper alloy such as Cr copper or Cr.ZrO2 copper.

A feature of the mold according to the present invention is that the surface of the mold copper plate on the casting space side, that is, the inner wall surface in contact with the molten steel or the solidified shell is covered with a sprayed coating of an amorphous alloy. That is, when the surface in contact with the molten steel is covered with the sprayed coating of the amorphous alloy, the hardness of the inner wall surface of the mold is increased, the wear resistance can be improved, and the life of the mold copper plate is improved. Therefore, as such an amorphous alloy, it is preferable to use an alloy mainly composed of Fe or Ni as an alloy effective to impart sufficient hardness and wear resistance to the casting surface of the mold. In particular, Fe or Ni
It is important that the content of Fe or Ni is 70% or more. If the content of Fe or Ni is less than 70%, it may be difficult to impart sufficient hardness and wear resistance to the cast surface. .

[0012] Fe and Ni are hard to be amorphous by themselves and need to be added with other elements. There are several known additive elements that make Fe and Ni amorphous, but C, Si, P
And B are preferable, and it is appropriate to contain at least one of these elements. The content of each of these elements is preferably set to 6% or less.

Next, a method of forming such an amorphous alloy sprayed coating will be described. The above-mentioned amorphous alloy contains elements such as C, Si, P and B. However, all of these components are easily oxidized, and if oxidized, an amorphous layer is not easily formed, and an oxide layer that hinders heat conduction is mixed in the coating film, which is not preferable. Therefore, at the time of thermal spraying, while maintaining the atmosphere under reducing conditions,
It is necessary to adjust the atmosphere so that the sprayed and applied film does not touch the atmosphere or is reheated to be transformed into crystalline. From such a viewpoint, in the present invention, it is advantageous to apply a method using reduced pressure plasma spraying. Note that Fe, Ni
Spraying alloys of the above is an extremely effective means for making the alloy amorphous by receiving heat and quenching when droplets of these alloys collide with the adherend surface.

[0014] The thickness of the sprayed amorphous alloy film is set at 0.1 mm.
It is preferable to set it to about 1 to 5 mm. If the thickness of the sprayed coating is less than 0.1 mm, the effect of improving the wear resistance of the mold is poor. On the other hand, if the thickness of the coating exceeds 5 mm, the heat transfer resistance of the coating increases, which may cause a solidification delay of the cast metal. Because there is. In addition, more preferably 0.2 to
3 mm is appropriate.

[0015]

EXAMPLE In this example, a two-strand vertical bending type slab continuous casting machine was used.
This is an example of continuous casting of molten steel using a mold incorporating a copper plate subjected to i-alloy electroplating and using a mold incorporating a copper plate provided with an amorphous spray coating according to the present invention on the other strand. is there. The details of the plating and the thermal spray coating are shown in Table 1 below. The composition of the continuously cast steel types was approximately 40% for ultra-low carbon steel, 40% for medium and low carbon steel, 10% for high carbon steel, and 10% for low alloy steel in terms of the number of charges. And casting conditions are mold size,
The thickness was 260 mm x 100 to 1900 mm, the casting speed was 1.5 to 2.2 m / min, and the oscillation cycle was 60 to 180 cycle / min. As a result, with respect to the mold of the comparative example, at the time of 600 charge casting, the nickel coating on the lower end of the mold was worn, and it was necessary to recoat. However, in the mold on which the amorphous sprayed coating of the present invention was formed, the coating on the lower end of the mold was only worn out at the 1800th charge. Therefore, according to the present invention, under the high-speed and high-cycle pouring conditions as described above, it is possible to achieve a three-fold increase in the life of the mold as compared with the related art.

[0016]

[Table 1]

[0017]

As described above, according to the continuous casting mold of the present invention, the copper plate forming the mold can be formed under severe casting conditions such as high-speed casting and high cycle oscillation of molten metal, especially molten steel. An extremely excellent effect that wear can be significantly reduced can be obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Kuroki 1st Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Chiba Works of Kawasaki Steel Corp. (72) Koichi Hayashi 1st Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Chiba Works (72) Inventor Satoru Satoru Midorikawa 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Chiba Works (72) Inventor Masaya Kumagawa 1-1-1 Gyoda, Funabashi City, Chiba Prefecture No. Talkaro Co., Ltd. Tokyo Plant (72) Inventor Mitsuru Yoshida 1-1-1 Gyoda, Funabashi City, Chiba Prefecture Tokaro Co., Ltd. Tokyo Plant (72) Inventor Shinichi Kubo 1-1-1 Gyoda, Funabashi City, Chiba Prefecture No. 1 Tokaro Corporation Tokyo factory F-term (reference) 4E004 AB04 AD00 4K031 AA03 AB08 CB21 CB25 CB28 CB29 DA04

Claims (5)

[Claims] 1. A continuous casting mold characterized in that a surface of a casting space side of a continuous casting mold for molten metal is coated with a sprayed layer of an amorphous alloy. 2. The amorphous alloy contains 70% of Fe.
2. The continuous casting mold according to claim 1, wherein said casting is an iron alloy. 3. The method according to claim 1, wherein the amorphous alloy comprises Fe, C, and S.
3. The continuous casting mold according to claim 2, wherein the casting mold is an alloy with at least one element selected from i, P and B. 4. The amorphous alloy contains 70% of Ni.
2. The continuous casting mold according to claim 1, wherein the alloy is a nickel alloy containing the above. 5. The method according to claim 1, wherein the amorphous alloy comprises Ni, C, and S.
The continuous casting mold according to claim 4, which is an alloy with any one or more elements selected from i, P, and B.