JPS60145247A - Mold for continuous casting and its production - Google Patents

Abstract

PURPOSE:To improve the life in the lower part where heavy wear arises by subjecting the inside wall surface of a base body to specific ternary alloy plating as metallic plating for said wall surface. CONSTITUTION:An electronickel plating layer 2 having excellent adhesion is formed on the inside wall surface of a base body 1 of a casting mold which contacts with the molten metal to be poured therein. A ternary alloy plating layer 3 consisting of (60-98wt%) Ni, (1-20wt%) W and (1-20wt%) Fe is formed on the layer 2. A chrome plating layer 4 is further formed thereon. The layer 3 is preferably formed on the lower part of the casting mold where heavy wear arises and is formed preferably of the layer having the hardness gradient at which the hardness increases gradually from the body 1 toward the inside wall surface in contact with the molten steel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting mold and a method for manufacturing the same, and in particular, the invention relates to a continuous casting mold and a method for manufacturing the same, in particular, the inner wall surface in contact with molten metal (explained below using an example of molten steel) is coated with a heat-resistant and wear-resistant metal plating. We propose a unique technology for the mold and the plating method for its production. In view of the fact that severe wear occurs especially in the lower part of the continuous casting mold, a Ni-W-Fe 8-component alloy plating that is resistant to such wear is formed as part of the mold inner wall surface plating layer. It's technology.

In general, continuous casting molds are made of steel or its alloy with good thermal conductivity, and the inner wall surface that comes into contact with the injected molten steel is coated with heat-resistant and wear-resistant metals such as nickel plating and chromium plating. A plating layer is formed to protect the inner surface of the mold and to prevent the copper from entering the slab.

Even with such an N-plated mold, the wear is severe, especially in the lower part, and the bare surface (copper) of the mold base is exposed after a relatively rapid number of uses, resulting in the above-mentioned problems. Conventionally, attempts have been made to solve this problem by applying a high-hardness alloy plating to areas subject to severe wear, or by thermal spraying a wear-resistant metal onto the underlying nickel plating.

However, these methods using high-hardness alloy coating layers have a significant difference in mechanical properties (mainly elongation) between the copper and base nickel constituting the mold base and the alloy plating layer, which causes thermal fatigue in the vicinity of the meniscus, which is highly affected by heat. The disadvantage was that cracks frequently occurred due to That is, when Ni-W alloy plating is performed in a sulfamate bath, as the W content increases, the columnar structure becomes more prominent and the hardness increases.
At 00Hy or higher, cracks are more likely to occur due to internal stress.

On the other hand, when Ni-Fe plating is applied in a sulfamine i salt bath, a layered structure is formed, but by increasing the Fe content, 500 H
It has been known that when the hardness is increased beyond y, the layered structure collapses and becomes extremely brittle, causing local defects to occur at the interface between the base and the coating layer, or between each coating layer.

Therefore, an object of the present invention is to provide a long-life mold structure that can overcome the above-mentioned eight problems of the conventional technology of coating high-hardness binary alloy plating, and also to provide a method for manufacturing such a mold. The purpose of this report is to make proposals regarding the The gist of the present invention to achieve this object is as described in the claims at the beginning of this specification. The details of its configuration will be explained below.

As shown in FIG. 1, the mold of the present invention has a mold base J made of copper or the like.
First, an electrolytic nickel plating layer 2P with excellent adhesion of approximately 11ll+ thickness is formed on the inner wall surface of the nickel plating layer 2. S~3 thick (80~98% by weight)
) Ni and (1 to 20% by weight, preferably 5 to 7% by weight)
)W and (]~20% by weight, preferably 1~5% by weight)Fe
An 8-element alloy plating layer 3 consisting of the above is formed. This 8-component alloy plating layer 8 is preferably formed only in the lower part of the mold where wear is severe, and the hardness gradually increases in the range of 800 to 700 Hy from the base to the inner wall surface in contact with the molten steel. A preferred embodiment is a layer with a hardness gradient. Note that 4 in the figure is a chromium plating layer.

Figure 2 shows Ni-W (5-7%)-Fe(]~5%
) according to the present invention and the conventional N1-(7%)
The hardness of the Ni-W-Fe octa-alloy plating according to the present invention is superior to that of the binary Fe alloy in terms of hardness. This difference in hardness between the two is explained by the difference between Fe and W in the case of an 8-element alloy.
acts as a promoter for the precipitation effect of w ; Fe
3 plays a precipitation hardening function in Ni plating, and N
While i plating has a face-centered cubic lattice structure, Ni, -
It is thought that this occurs because the w-yea original alloy plating has a dense structure with a close-packed hexagonal lattice.

As shown in Fig. 2, the method of creating a hardness gradient in the ternary alloy plating layer 8 is to gradually increase the Fe dissolution 11 in the plating bath (nickel sulfamate solution), and eventually increase the hardness at the cathode (mold). This is carried out by a method of gradually increasing the amount of reduced and precipitated Fe ions. FIG. 8 shows the relationship between the amount of Fe added to the plating bath and the hardness, and it is clearly seen that the hardness increases as the amount of Fe increases.

Figure 4 shows the hardness gradient of the present invention as described above.
The hardness distribution of the i-w-ire a base alloy plating layer in the plating thickness direction is shown, and the hardness increases toward the surface.

A chromium plating is formed on the 8-component alloy plating layer 8 to prevent chemical discoloration, etc.Next, a method for forming the above-mentioned plating layer will be explained. FIG. 5 is a route map for explaining the mold manufacturing method of the present invention, the so-called plating method.

The plating bath is a nickel sulfamate solution (pH +2 to 8).
), connect the mold substrate to the cathode side and N1 to the anode side, 45-55°C, ], 5-3.5 A/dm"
Under these conditions, first perform base nickel plating. Next, during the above plating process, W is added in an amount such that the W content in the plating layer is in the range of 5 to 7%, and then as time passes, y
e is gradually added until the Ire content in the plating layer reaches a maximum of 10% to form a Ni-W-Fe a-based composite plating layer. By the gradual addition of 11, mi-w
-Fe eutectoid-strengthened electroplated layer cannot be obtained.

(Example) On the short side mold base of a continuous casting mold for a slab slab with a cross-sectional shape of 200mm thick and 180Q+u+ width, conventional ordinary Ni plating was applied to the upper end of the mold by 0.5mm and the lower end] , 5 coats of uneven thickness, and then Or plating 'Fr-
Conventional mold with a thickness of 0.05wn Ni according to the invention of Atsugi
-w -ye The a-based alloy plating is applied only to the lower half of the base, in the range of about 40-0+u+, on the normal N1 plating, and the plating thickness is 0.5 mm at the #-shaped upper end and 0.5 mm at the lower end. 1
．． A comparative investigation was conducted of the wear condition of a mold which was machined to a separation distance of 5 and further subjected to Or plating (1.05 m+++) after 400 channels of use.

As a result of the above comparative test, Qr immediately after N1 plating was applied.
In the case of a conventional mold with plating, the exposed copper base on the surface of the Chibe mold base has a width of 2 to 15 N from the lower end in the direction of molten steel injection.
However, in the mold according to the present invention, the maximum wear amount was approximately Q, 2 mm.
Also, no copper base material was observed. Although the mold according to the present invention was continued to be used after that, it was finally able to be used for ] 6' +100 hours, and its lifespan was extended nearly four times as compared to the conventional mold.

As explained above, according to the present invention in which composite plating including in-w-Fe a-based alloy plating is applied, the life of the # mold for continuous casting is significantly improved, especially in the lower portion where wear is severe. Furthermore, the method for forming such a composite plating layer is extremely easy.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the short side wall of a continuous casting mold, and Figure 2 is a perspective view of the short side wall of a continuous casting mold.
This chart shows a comparison of the hardness of each plating layer. Figure 8 is a graph showing the relationship between the amount of Fe added in the plating bath and the hardness. Figure 4 shows the actual values of the hardness distribution in the plating layer direction of the 8-element alloy plating layer of the present invention. The graph shown in FIG. 5 is a conceptual diagram of a plating apparatus used in the manufacturing method of the present invention. 1...Mold base 2...Nickel plating 8...N
i -W -Fe a-base alloy plating 4... Ripm plating. Fig. 1 Fig. 2 = erpiix * ccxzt-t, f4 Fig. 3 Fig. 4 Plating eyebrow surface button 3f mm)-

Claims (1)

[Claims] 1. A continuous casting mold in which a heat-resistant and wear-resistant metal plating layer is provided on the inner wall surface of the base in contact with the injected molten metal. A mold for continuous casting, characterized in that it is formed by plating a Ni-W-Fe 8-component alloy having the following composition, and further plating the top of the plating. Ni: 60 to 98% by weight W: 1 to 20% by weight Fe: 1 to 20% by weight The intermediate 8-element alloy plating layer of the above metal plating layer gradually becomes hardness holes toward the inner wall surface. The mold according to claim 1, having a hardness gradient in the plating thickness direction. & In a method for manufacturing a continuous casting mold in which a heat-resistant and wear-resistant metal plating is provided on the inner wall surface of the base that is in contact with the injected molten metal, in forming the metal plating layer, first, the surface of the cast m base is coated.
A base nickel plating is applied to the nickel sulfamate bath, and then tungsten and iron are added to the nickel sulfamate bath for plating, and the amount of iron added is gradually increased over time.
-w-Fe A method for manufacturing a continuous casting mold, characterized in that a composite plating layer is formed on the inner wall surface of the mold by plating the a-based alloy and then applying transfer chromium plating.