JPS6039455B2 - Mold for continuous casting equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a mold for continuous casting equipment.

For example, in a mold for continuous forging equipment that automatically changes the width of the strand during casting, a pair of long pieces 1, 1 and a pair of short pieces 2, 2 are formed in a plane, as shown in Figs. 1 and 2. It is roughly constructed to have a rectangular shape when viewed, and a mold wall surface 3 is formed by the surface of each mold piece.

These mold pieces are made of steel plates, and are subjected to surface treatments using a variety of methods in order to improve the surface properties of the strands and extend their lifespan. As this type of surface treatment, there is an example in which a single layer or a multilayer plating layer is formed on the entire mold wall surface 3, and on the other hand, when the mold disk surface 3 is partially treated, a plating layer is formed only on the lower half thereof. There is an example in which a plating layer is not formed on the upper half. In the former example, the wear resistance in the lower part of the mold wall surface 3 is satisfied to some extent, but the thermal conductivity in the upper part is not satisfactory. In the latter example,
Compared to the former example, the wear resistance in the lower part and the thermal conductivity in the upper part are relatively satisfactory. However, even in this example, inconveniences arise in those in which the width of the strand is automatically changed during casting. In other words, the automatic width change of the strand is performed by sliding the short pieces 2, 2 shown in FIGS. 1 and 2 against the pair of long pieces 1, 1, so that If the upper part does not have a plating layer, this part will be damaged and the life of the mold will be shortened as a result. In view of the above points, the present invention simultaneously ensures the thermal conductivity of the upper part of the mold wall surface and the abrasion resistance of the lower part, and also prevents the adhesion of welding during the initial stage of casting. The purpose is to provide a mold for continuous machining that can prevent damage during width changes and extend its life.One embodiment of the mold will be described below with reference to the drawings.

In Fig. 3, 4 is a pair of outermost pieces 1, 1 constituting the mold.
and a nickel plating layer (hereinafter referred to as Ni plating layer) with a thickness of 300 to 1000 mm formed over the entire surface of the pair of short pieces 2, 2, that is, the mold wall surface 3, and the N
A nickel-iron alloy plating layer (hereinafter referred to as Ni-Fe plating layer) 5 with a thickness of 500 to 1500 mm is formed on the i-plating layer 4 over a range of approximately 1/2 in the height direction from the lower end of the mold wall surface 3. has been done. The nickel-iron alloy constituting this Ni-Fe plating layer 5 contains iron in an amount of 5 to 2% by weight. Further, on each of the plating layers 4 and 5, a chromium plating layer (hereinafter referred to as Cr plating layer) 6 having a thickness of 10 to 100 m is formed over a range of at least 2/3 in the height direction from the upper end of the mold wall surface 3. . By the way, the temperature of the mold wall surface 3 during continuous casting differs by about 5,000 degrees or more between the upper and lower sides, as shown in FIG. It makes a big difference in performance.

In FIG. 4, the boundary A-A', where the temperature of the mold wall surface 3 transitions from the high-temperature part to the flat part, changes depending on the structure and operating conditions of the continuous casting machine, but this boundary A-A' If we define the area above A' as the upper side and the area below as the lower side, what determines the lifespan of the mold pieces 1 and 2 on the upper side is... and wear on the lower side. Therefore, the surface treatment layer applied to the mold wall surface 3 in order to improve the surface quality of the strands and extend the life of the mold pieces 1 and 2 is required to have thermal fatigue resistance on the upper side and wear resistance on the lower side.
It is important to select and combine surface treatment materials that satisfy these properties. Therefore, first, as a plating layer formed over the entire mold wall surface 3 to break direct contact between the strand and the mold pieces 1 and 2, a Ni plating layer 4, which has excellent adhesion to the mold pieces 1 and 2 made of steel plates, is used. Using. However, this N
The i-plated layer 4 has a lower thermal conductivity than copper and is more susceptible to thermal fatigue.As a result of examining the relationship between the thickness of the Ni-plated layer 4 on the upper part of the mold wall surface 3 and the degree of crack occurrence due to thermal fatigue, As shown in Figure 5, it has been found that cracks become more noticeable when the thickness exceeds 1000× skin.
Note that FIG. 5 shows the results when the number of anchor constructions was 25 ratio h.
Therefore, the thickness of the Ni plating layer 4 was set to 1000 m or less. The lower limit of the thickness of the Ni plating layer 4 is the thickness necessary to prevent the mold pieces 1 and 2 from being exposed during a predetermined number of castings, and this thickness is approximately 300 mm. The predetermined number of castings is determined or restricted by matters unrelated to the selection of the surface treatment material, such as deformation or replacement of the crab.
In terms of operation of continuous casting equipment, the ratio is approximately 25 ratio h or a multiple thereof, and in the present invention, it is set to 25 ratio h. Since the Ni plating layer 4 alone does not maintain sufficient wear resistance against the wear caused by the strands during casting at the lower part of the mold wall surface 3, surface treatment with further attention to wear resistance is required.

Therefore, on the part corresponding to the lower half of the mold wall surface 3 on the Ni plating layer 4, we added a layer of N, which has excellent wear resistance and strength at commercial temperatures (200 to 300°C) and excellent adhesion to the Ni plating layer 4.
An i-Fe plating layer 5 was formed. In order to improve the wear resistance, it is desirable to increase the thickness of the Ni-Fe plating layer 5, but if this thickness is too thick, the surface temperature will rise and the difference in physical strength between the Ni-Fe plating layer 4 and the Ni plating layer 4 will increase. This causes problems of peeling and thermal fatigue cracks, which would normally not be a problem. Ni-F at the lower part of the mold wall surface 3
As a result of examining the relationship between the thickness of the e-plated layer 5 and the degree of crack occurrence due to thermal fatigue, as shown in FIG.
It has been found that cracking becomes noticeable when the surface exceeds 0. Note that FIG. 6 shows the results when the thickness of the Ni plating layer 4 was 800 μm. Therefore, the Ni-Fe plating layer 5
The thickness was set to 1500 Buddhas or less. In addition, if the thickness of the Ni-Fe plating layer 5 is too thin, the wear resistance will be weakened, so in order to withstand the predetermined number of castings (25 ratio h), it is necessary to
It is necessary to have a thickness greater than zero. In addition, the wear resistance of the nickel-iron alloy constituting the Ni-Fe plating layer 5 decreases if the iron content is less than 5% by weight, and if it exceeds 20% by weight, the Ni-F
Since cracks are likely to occur in the e-plating layer 5,
Preferably, the iron content is between 5 and 2% by weight. By multi-layer plating of each Ni plating layer 4 and Ni-Fe plating layer 5, a surface treatment layer with sufficient thermal fatigue resistance and wear resistance was obtained. It is necessary to prevent scattered droplets from adhering to the surface treatment layer during unsteady conditions. For this reason, the upper part 2/of the mold wall surface 3 on the Ni plating layer 4 and the Ni-Fe plating layer 5 is
A Cr plating layer 6 was formed on a portion corresponding to 3. This C
It is sufficient to form the r plating layer 6 only on the upper two-thirds. Further, since the Cr plating layer 6 has the above-mentioned purpose, it has been confirmed through experiments that the thickness of 10 to 10 W is sufficient. Next, the experimental results will be explained.

A Ni plating layer 4 is formed on the entire mold wall surface 3 to a thickness of 700 mm, and a Ni-Fe plating layer 5 containing 15% by weight of iron is formed on the Ni plating layer 4 to a thickness of 1000 mm. A mold is formed in a portion corresponding to the lower half of the wall surface 3, and a Cr plating layer 6 is formed on each of these plating layers 4 and 5 with a layer thickness of 40 mm in a portion corresponding to the entire area of the mold wall surface 3. using
When the slab is cast at a casting speed of about 1.2 m/min, each plating layer 4, 5,
There was no need to repair 6. On the other hand, when using a conventional mold in which a nickel plating layer with a thickness of 200 cm is formed over the entire mold wall surface, and a chrome plating layer with a thickness of 5 cm is formed over the nickel plating layer over the entire area. ,
Repair of the plating layer was required after approximately 15 ratio h of casting. In the above embodiments, a mold for automatically changing the width of the strand has been described, but it goes without saying that the present invention can be applied to molds for any other type of continuous casting equipment.

As explained above, according to the mold for continuous casting equipment according to the present invention, the nickel plating layer and the nickel-iron alloy plating layer are formed to have an appropriate thickness, thereby improving thermal conductivity in the upper part and wear resistance in the lower part. At the same time, the chromium plating layer prevents adhesion of weld metal during the early stages of casting, so it is possible to improve the surface quality of the strand and extend the life of the mold. Moreover, a nickel plating layer with excellent adhesion to the mold wall is first formed over the entire mold wall, and then a nickel-iron alloy plating layer is applied on the lower part of the nickel plating layer, and then a chromium plating layer is applied on the upper part. As a result, good adhesion can be obtained and peeling of the nickel-iron alloy plating layer and chromium plating layer can be strongly prevented, and the lower end of the upper chromium plating layer is attached to the upper end of the lower nickel-iron alloy plating layer. By partially overlapping, it is possible to avoid early peeling that may occur at the boundary between the chromium plating layer and the nickel-iron alloy plating layer.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the mold, Fig. 2 is a sectional view taken along the Rolo line in Fig. 1, Figs. 3 to 6 show an embodiment of the present invention, and Fig. 3 is a sectional view of a mold piece. , Fig. 4 is an explanatory diagram of the temperature distribution on the mold wall surface during the lotus period, Fig. 5 is an explanatory diagram of the relationship between the layer thickness of the nickel plating layer on the upper mold wall surface and the degree of crack occurrence, and Fig. 6 is an explanatory diagram of the relationship between the crack occurrence degree and the thickness of the nickel plating layer on the upper mold wall surface. FIG. 2 is an explanatory diagram of the relationship between the layer thickness of the nickel-iron alloy plating layer and the degree of crack occurrence in FIG. 3... Mold wall surface, 4... Nickel plating layer, 5... Nickel-iron alloy plating layer, 6...
...Chrome plating layer. Figure 1 Figure 2 Figure 3 Figure 5 Figure 4

Claims (1)

[Claims] 1. A nickel plating layer with a thickness of 300 to 1000 μm is formed over the entire area of the mold wall surface, and a nickel-iron alloy with a thickness of 500 to 1500 μm is formed on the nickel plating layer from the lower end of the mold wall surface to approximately 1/2 in the height direction. A plating layer is formed, and a layer of 10 to 10
A mold for continuous casting equipment, characterized by forming a chrome plating layer with a thickness of 0 μm.