JPS62207534A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To lengthen service life of a mold and to improve the casting billet quality by forming the first layer composing Ni on the inner wall face of the Cu-made mold body and the second layer having the specified thickness, composing cermet thermal spraying layer with the specified composition on the lower half part of the first layer. CONSTITUTION:The first layer 2 composing of Ni or Ni-Fe alloy, in which Fe content is about 2-7wt%, is formed on the inner wall face of the mold body 1, composing Cu or Cu alloy. Then, the thickness of the first layer 2 is desirable to be thicker toward lower part. Next, the cermet thermal spraying layer, which contains 20-50wt% metallic binder, composing about 15-26wt% Cr, about 5-13wt% A$;, about 0.5-2wt% Y and the balance Ni or Co, is formed at the second layer 3 having 0.05-0.5mm thickness on the lower half part of the first layer 2. In this way, the mold for the continuous casting having about two times of service life of the conventional mold is obtd.

Description

[Detailed Description of the Invention] <Industrial Application Field> The continuous casting mold of the present invention, more specifically, the wear resistance of the lower half in the longitudinal direction of the mold body is enhanced, and its life can be extended. This invention relates to a continuous casting mold that improves the quality of the cast side.

<Prior art and its problems> Continuous casting molds have a main body made of copper or its alloy, which has good thermal conductivity from the viewpoint of heat removal, and various types of coatings are applied to the inner wall surface to prevent the inner wall surface from abrasion. Generally, a surface layer with wear resistance of 100% is formed.

Examples of wear-resistant materials used as the surface layer include metal plating layers such as Ni and Ni-Cr, and spray-sprayed Ni-Cr self-fluxing alloys. However, metal plating layers lack hardness or, depending on their composition, cannot be plated to the required thickness in a healthy state, and unidirectionally soluble alloy sprayed layers have sufficient wear resistance. However, in the solution treatment after thermal spraying, it must be heat-treated to a temperature of approximately 1000°C, and the distortion caused by this heat treatment is large, causing distortion in the mold dimensions, and copper alloys whose composition can withstand such high-temperature heat treatment. There are problems such as having to use the main body as the main body.

In recent years, a technique has been proposed in which a cermet or ceramic coating layer is applied to the inner wall surface of a continuous casting mold. For example, JP-A-56-80356 and JP-A-55-1513.
This is the technique disclosed in Publication No. 64:11.

However, the cermets used in the techniques disclosed in these two publications contain Ni and C as binder metals.

Alternatively, Cr can be used and any ceramic can be used to mix it with it, but according to the experiments of the present inventors, there is a large difference in the adhesion strength depending on the composition of the cermet, which is shown in the above two publications. It was found that cermets with a composition of Another example is a technique disclosed in Japanese Patent Application Laid-Open No. 60-221151, in which a metal layer is applied in two stages as a base treatment before applying a ceramic or cermet layer to improve adhesion. The particle flight speed during thermal spraying of ceramics and cermets is regulated to 400 m/s or more, but although it is natural that higher flight speeds are more desirable, the adhesion of the ceramics and cermets used is still limited. There is a problem of lack of sexuality. Also, JP-A-56-86655 and JP-A-56-86656
In the publication, an example is shown in which a specific refractory layer is applied on the upper surface of a metal intermediate layer, but since the refractory layer used in these does not include a binder layer, the refractory layer is fragile. Moreover, there is a problem that the adhesion is not sufficient.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention more strictly examines the composition of the cermet used as the wear-resistant surface layer, and also limits the locations where the cermet layer is applied. In addition, the purpose is to provide a continuous casting mold having a cermet layer that is difficult to peel off, and the gist thereof is to provide nickel or nickel-iron alloy plating on at least the lower half of the inner wall surface of the copper or copper alloy mold body. forming a first layer of layers;
On the surface of the first layer, in a portion corresponding to the lower half of the mold body,
N1-Cr-Aj for chromium carbide or titanium carbide
A second layer consisting of a cermet sprayed layer containing 20 to 50% by weight of Y or Co-Cr-Y alloy as a binder metal is coated with a thickness of 005 to 05 m.
This is a continuous casting mold characterized in that it is formed as much as possible.

When using nickel-iron alloy plating as the first layer, the optimum iron content is 2 to 7% by weight. In other words, the purpose of adding iron to nickel is to increase its hardness and strength, but this effect cannot be expected if it is less than 2% by weight, and on the other hand, if it exceeds 7% by weight, it becomes brittle and prone to cracking. It is from. The alloy used as a binder for the second cermet layer contains C "15 to 26% by weight,
A15-13% by weight, Yo, 5-2% by weight and the balance Ni
Or C.

Use one with the following composition. As shown in the experimental results shown in detail later, this metal binder is required to be at least 20% by weight in order to maintain the adhesion of the second layer, but 50% by weight is required.
If it exceeds 20 to 20, the abrasion resistance of the second layer itself will decrease.
50% by weight.

The continuous casting mold of the present invention has a mold body (
1) in which the first layer (2) is formed on the entire surface;
As shown in Figure 2, the first layer (2) may be formed only in the lower half of the mold body, and preferably the thickness of the first layer (2) decreases as it goes downward. Keep it large.

The second layer (3) is applied only to the lower half of the mold body, because the upper half of the mold body is still in the molten state, so it is hardly susceptible to damage caused by wear. No, but
Particularly near the mesonicus part, the thermal cycle of heating and cooling is intense, so even if the second layer (3) consisting of a cermet sprayed layer is applied, it is easy to peel off, and if peeling occurs in one part, it will spread throughout the area. This is because there is a risk that even the second layer in the lower half will peel off.

Although not shown, in the continuous casting mold of the present invention, a chromium layer with a thickness of 10 to 50 μm may be applied to the outermost surface to prevent splash adhesion during the initial stage of casting.

<Examples> The present invention will be described in detail below with reference to Examples and Comparative Examples.

First, in order to examine the adhesion and other properties of various cermets, a Ni plating layer was applied to the surface of a copper base material to a thickness of 100 ml, and then various ceramics and binder metals shown in Table 1 below were applied onto the Ni plating layer by plasma spraying. A cermet layer consisting of the following combinations was formed to have a thickness of 0.3 mm. In this case, the binder metal in the cermet layer is 30% by weight.
and Ni-Cr is Ni80wt%, Cr2Owt%
Cr-kl-Y is an alloy of 16% by weight of Cr, 16% by weight of Ni, and 0.8% by weight of Y with the balance Ni, and also Co-C
r-A R-Y11' An alloy containing 23% by weight of Cr, 13% by weight of AJ, and 7% by weight of Y0 with a balance of Co was used. Table 1 shows the results of examining the adhesion, thermal shock resistance, and peelability of the cermet layer of the obtained samples. Thermal shock resistance in Table 1 indicates the number of times each sample was held at 600°C for 30 minutes and then immediately put into water until cracks appeared, with the maximum number of times being 20.
Regarding peelability, the state of peeling of the cermet layer was observed when each sample was bent approximately 180 degrees. In the table, O indicates no peeling and X indicates peeling. The overall evaluation was determined based on all the characteristics shown in the table, with 0 indicating good, ◯ fair, △ very poor, and × indicating poor.

From the expected results, Cr5Cz or TiC is preferable as the ceramic used for the cermet, and Ni-Cr-Y or Co- as the binder metal.
It was found that Cr-AJ-Y is preferable.

Next, specific examples of the present invention will be shown.

11 N
An i-plating layer was applied. The conditions for this old plating are metal Ni
80g/l, H3B0330g/J, sodium lauryl sulfate < 0.1g/l, plr4. The plating bath was conducted using a plating bath with a liquid temperature of 50°C. On the Ni plating layer obtained in this way, Cr3 C280 weight, old -
〇A cermet layer consisting of 20% by weight of r-AJ-Y alloy was sprayed to a thickness of 0.3+ nm by plasma spraying.
r16 weight% weight 16 weight%, Yo, 8 weight% balance N1
An alloy with the following composition was used. The hardness of the cermet sprayed layer of the mold obtained was in the range of Hv750 to Hv850, and as a result of an actual machine test as a continuous casting mold that processes 150 tons of molten steel per charge, it was possible to operate up to 800 charges without any problems. At that point, the surface of the mold was observed, and no peeling or cracking had occurred.

For comparison, we conducted a similar actual test on a conventional copper mold body surface with only a Ni plating layer to a thickness of 5.0 mm, and the results were as follows: After 400 charges, the surface N1 plating layer wore out and it could no longer be used.

In Example I, the above-mentioned actual machine test was conducted in which the amount of binder metal in the cermet layer was varied.
It cracked and peeled off after 50 charges, and its lifespan was only 200 charges at 10 weight. In addition, regarding the thickness of the cermet layer, in the case where the binder metal is contained in 35% by weight, if the thickness is 1.0 mm, the thickness is 10%.
Cracks occur as early as the 350th charge for 1.6 mm, and 5 for 0.5 mm.
There were no abnormalities even at 0.00 charge, and it was confirmed that the thickness of the cermet layer should be 0.5 mm or less. However, in actual thermal spraying, in order to achieve a uniform thickness and to provide a certain level of wear resistance required, a minimum of 3.0
5mm is necessary.

115I Ni-, 5% by weight Fe alloy is applied to the inner wall surface of the copper mold body, with a thickness of 0.5 mm in the upper half of the mold body,
Plating was performed so that the thickness of the lower half was 2.0 mm. Plating conditions are metal Ni90g/J, metal Fe
5g/l, ■, BO330g/J, lauryl sulfate (
0.1 g/I.

The pH was 4, 2p, and the liquid temperature was 50°C. On this old -Fe alloy plating layer and in the lower half of the mold body, a cermet layer consisting of 65% by weight of TiC and 35% by weight of -Cr-1-Y alloy was applied to a thickness of 0.3 mm by explosive spraying. It was sprayed as much as possible. Co-Cr-Human 1-Y alloy is Cr
23% by weight, A4 13% by weight, Yo, 7% by weight balance Co
An alloy with the following composition was used. The hardness of the cermet layer of the obtained mold was in the range of Hv 750 to 830. The mold of Example 2 was also tested on an actual machine similar to that shown in Example I above, and as a result, it could be used up to 800 charges without any problem.

Note that TiC and Co-Cr-AI- shown in this Example ①
In the case of a cermet made of Y, it has been confirmed that cracks are likely to occur if the sprayed layer is too thick, and the desirable thickness is also found to be 0.05 to 0.5 mm.

<Effects of the Invention> As described above, according to the continuous casting mold of the present invention, the combination of the ceramic and metal binder constituting the cermet used as the second layer is limited to a limited range, and it is possible to achieve strong In addition, Cr3C2 and TiC have superior properties compared to other ceramics in terms of seizure resistance and oxidation scale reactivity to steel, so they can be used for a long time. This results in a mold that can be used stably over time. Furthermore, in the present invention, the cermet layer is made thinner so that cracks are less likely to occur, and wear resistance is not so required for actual functionality; on the other hand, if the cermet layer is present at that location, it can become a starting point for peeling. There is no need to apply a cermet layer to the upper half of the mold, and as a result, the required lower half of the cermet layer is prevented from peeling off.As shown in the example above, the lifespan is approximately twice as long as that of conventional molds. There is.

[Brief explanation of drawings]

1 and 2 are cross-sectional explanatory views of the present invention, respectively. In the figure, (1) ``Mold body (2): 1st layer (3)・Second layer

Claims (1)

[Claims] 1. A first layer consisting of a nickel or nickel-iron alloy plating layer is formed on at least the lower half of the inner wall surface of the copper or copper alloy mold body, and the surface of the first layer is applied to the lower half of the mold body. In corresponding parts, Ni-Cr-Al-Y or Co-Cr-A is added to chromium carbide or titanium carbide.
A second layer consisting of a cermet sprayed layer containing 20 to 50% by weight of l-Y alloy as a binder metal,
A mold for continuous casting, characterized in that the mold is formed to have a thickness of 0.05 to 0.5 mm.