JPH0716775B2 - Support for continuous casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a continuous casting facility for steel, in which a support used as a slab guide device immediately below a mold, that is, a surface such as a cooling grid or a wear plate has a long life. The present invention relates to a support for continuous casting equipment, which has a lining layer for the purpose of conversion.

<Prior Art> Generally, in continuous casting equipment for steel, molten steel in a tundish is molded into a slab of a certain shape and size by passing through a copper or copper alloy mold, but immediately after passing through the mold. The cast slab solidifies only in the vicinity of its surface (hereinafter referred to as a solidified shell), and its thickness is also nonuniform, so that there is a possibility that so-called breakout occurs in which the shell breaks and molten steel flows out. Therefore, mainly for the purpose of preventing this breakout, a support composed of a cooling grid or a wear plate is arranged immediately below the mold as a slab guide device. As such a support, one made of cast iron FCD60 has been conventionally used, paying attention to lubricity with a cast piece. However, the FCD60 support was subject to wear and heat cracks due to contact with the slab at a temperature just below the freezing point, and it was necessary to replace it in a short period of time. Further, there is a problem that scratches are generated on the surface of the slab due to abrasion and the like, for example, the surface of the cooling grid being roughened.

In a continuous casting facility, powder composed of CaO, SiO ₂ and Al ₂ O ₃ is added to the mold for the purpose of preventing the molten steel in the mold from being oxidized and lubricating the mold and the slab. However, by attaching these powders to the surface of a support such as a cooling grid or a wear plate,
It was found that the surface of the slab was flawed.

<Problems to be solved by the invention> Conventionally used cast iron FCD60 support is low in hardness at high temperature, because it does not have heat crack resistance, contact with the cast piece causes wear and heat cracks. However, it was replaced within a short period of time. Also, due to abrasion, the cooling grid or wear plate surface becomes rough, and thermal deformation causes scratches on the center layer of the movable surface, causing flaws on the surface of the slab. It was

Further, in the continuous casting equipment, for the purpose of preventing oxidation of molten steel in the mold and lubricating between the mold and the slab, a powder made of CaO, SiO ₂ and Al ₂ O ₃ is added to the mold,
The problem that the powder adheres to the surface of the support consisting of the cooling grid or the wear plate and the surface of the slab is flawed due to lack of high temperature hardness of the support or damage to the surface due to wear or heat cracks. Was also occurring.

Furthermore, even if it is attempted to repair the damaged support by overlay welding, it is difficult because the material is cast iron FCD60, and even if it can be implemented, it is difficult to maintain the performance that can withstand use. Met.

In order to solve the above problems, the present invention provides a support for continuous casting, in which a lining layer having excellent wear resistance and durability is formed on the surface of a support body composed of a steel cooling grid or a wear plate. The purpose is to do.

<Means and Actions for Solving the Problems> The above object of the present invention can be achieved by the following means. That is, the gist is to form an intermediate lining layer made of austenitic stainless steel on the surface of the steel body, and to add 23 to 28% by weight of Cr and Mo to the surface of the intermediate lining layer.
4-7% by weight, Ni3% by weight or less (excluding O), C0.15-
A support for a continuous casting facility, characterized in that a lining layer comprising 0.3% by weight and the balance being Co is formed.

The main body material of the support composed of the cooling grid or the wear plate according to the present invention is not cast iron FCD60 but steel. This means that overlay welding or thermal spraying is adopted to form the lining layer, but cast iron FCD60 has problems in weldability and adhesion with the lining layer. Therefore, in addition to the weldability and adhesion with the lining layer, we decided to use a steel body that is excellent in economic efficiency and workability.

Therefore, by using the steel main body, if the support of the present invention is damaged, it can be easily repaired and regenerated.

Next, in the lining layer, oxidation resistance, high temperature abrasion resistance and heat crack resistance are important due to the environment of use. And, as a lining layer that is considered to have these characteristics, in general, Fe-based alloy, Ni-based alloy and
Co-based alloys can be mentioned, but in cooling grids or wear plates that come into contact with slabs at temperatures just below the freezing point, Fe-based alloys have low oxidation resistance and high-temperature wear resistance, and Ni-based alloys have low melting points. In addition, there is a problem that it is expensive, so a Co-based alloy was used. Furthermore, the range of each chemical composition of Cr, Mo, Ni, and C contained in the Co-based alloy was determined from the viewpoint of coexistence of high temperature wear resistance and heat crack resistance. If the heat resistance is deteriorated, the heat crack resistance is deteriorated, and the opposite phenomenon is likely to occur.As a content of alloy elements having high temperature wear resistance and heat crack resistance suitable for a cooling grid or a wear plate, Cr23 to 28% by weight, Mo4
~ 7 wt%, Ni3 wt% or less (0 is not included) C0.15 ~ 0.3
We have found that the chemical composition range consisting of wt% and the balance being Co has sufficient high-temperature wear resistance and decided to adopt it.

Forming an intermediate lining layer of austenitic stainless steel between the steel body and the lining layer reduces strain thermal expansion that occurs in the steel body and reduces cracking of the uppermost layer due to stress. . Further, the heat from the slab, which is the temperature just below the freezing point, is prevented from being conducted to the steel body, and the body is prevented from being oxidized. Further, when the overlay welding is adopted as a method for forming the lining layer, it is effective for preventing dilution from the steel main body as the base material and securing the chemical composition of the lining layer.

Next, the reason why high temperature wear resistance and heat cracks occur on the support consisting of the cooling grid or the wear plate is because it comes into contact with the slab having a temperature just below the freezing point. As a method of reducing the contact area with the slab without lowering the guide function, as shown in FIGS. 1 (a) and 1 (b),
Alternatively, it is conceivable to form a plurality of grooves a.
As the shape of, a V groove, a U groove, a dovetail groove, etc. were considered. By forming such a groove a on the surface of the lining layer (2) of the support (1) made of a cooling grid or a wear plate, the contact area with the slab can be reduced and the slab can be reduced. Cooling water can pass through this groove during contact with, thus suppressing the temperature rise on the surface of the support, thus preventing deformation of the center part of the groove and preventing scratches on the slab. To do. Furthermore, damage due to high temperature wear and heat cracks can be suppressed.

Forming such a groove may facilitate the generation of heat cracks in terms of shape, so the material of the place where the groove is formed is the heat crack resistance described in the present invention. It is necessary to have an excellent lining layer.

<Examples> Examples of the present invention will be described below.

As shown in FIG. 2, an intermediate lining layer (4) having a layer thickness of 3 mm was formed on the surface of the steel body (3) by a covered arc welding method using austenitic stainless steel as a weld overlay material. Next, the above intermediate lining layer (4)
A Co-based alloy consisting of 27 wt% Cr, 6 wt% Mo, 2 wt% Ni, 0.2 wt% C, and the balance Co on the surface of was used as a weld overlay material by the TIG welding method and a lining layer with a layer thickness of 6 mm ( 2) was formed.

In this way, the lining layer (2) is formed on the surface of the steel body (3), and the wear plate O of this example, a wear plate □ made of FCD60 as a comparative example, and Ni 50 wt% and Cr 50 wt% on the steel surface. The result of a high temperature hardness characteristic test conducted with a wear plate Δ having a lining layer formed of is shown in the graph of FIG.

As a result of the above high-temperature hardness characteristic test, the wear plate □ made of FCD60 has a hardness that decreases as the temperature becomes higher.
The 50% by weight wear plate Δ was found to retain sufficient hardness at high temperatures.

Therefore, the results of a thermal shock test using an acetylene oxygen gas flame (1000 ° C.) on the surface of each of the above wear plates are shown in Table 1 below.

From the above results, in this example ○, the thermal shock 100
A subtle crack of the turtle's back occurred at the second time, but I was convinced that it was not an open crack and there was no concern of damaging the product. Further, with respect to the wear plate Δ containing 50% by weight of Ni and 50% by weight of Cr, cracks are likely to occur due to thermal shock, and it is considered unsuitable immediately under the mold where thermal shock is severe due to cooling water or the like.

Next, Table 2 below shows the results of FEM analysis of the wear plate having one groove, the wear plate having a plurality of grooves, and the wear plate without grooves shown in FIGS. 1 (a) and 1 (b), respectively. Shown in.

From the above results, it was found that the wear plate having one or a plurality of grooves suppresses the temperature rise of the surface thereof, thereby suppressing the maximum displacement and the maximum surface thermal stress.

<Effects of the Invention> As described above, according to the present invention, the high-temperature slab has excellent and stable high-temperature wear resistance and heat crack resistance, and can sufficiently withstand long-term continuous use. Is. Also during repair, the main body of the support consisting of the cooling grid or wear plate is made of steel, so overlay welding is easy to perform, and maintenance is greatly reduced compared to the conventional support consisting of the cooling grid or wear plate. At the same time, a great effect can be obtained in improving productivity of continuous casting and improving and stabilizing slab quality.

[Brief description of drawings]

1 (a) and 1 (b) are perspective views showing the shape of the support of the present invention, FIG. 2 is a cross-sectional explanatory view of the wear plate of the present invention, and FIG. 3 is a graph of a high temperature hardness characteristic test. is there. In the figure a: groove (1): support (2): lining layer (3): steel body (4): intermediate lining layer

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Tadashi Baba 3-4-20 Jinyama, Hachimannishi-ku, Kitakyushu, Fukuoka Prefecture Kuroki Industry Co., Ltd. (72) Ichiro Goto 3-4, Jinyama, Hachimannishi-ku, Kitakyushu, Fukuoka No. 20 Kuroki Industry Co., Ltd. (56) Reference JP-A-1-148445 (JP, A)

Claims (2)

[Claims] 1. An intermediate lining layer made of austenitic stainless steel is formed on the surface of a steel body, and the surface of the intermediate lining layer contains 23 to 28% by weight of Cr and Mo.
4-7% by weight, Ni3% by weight or less (0 is not included), C0.15-
A support for a continuous casting facility, comprising a lining layer having 0.3% by weight and the balance being Co. 2. The support for continuous casting equipment according to claim 1, wherein at least one groove is formed on the surface of the lining layer.