KR20090067541A - Casting roll surface plating method of twin type strip caster - Google Patents

Abstract

A plating method of a casting roll surface of a two roll-typed strip caster is provided to stabilize surface quality of a cast material and to improve durability of a mold by preventing micro-crack of a plating layer. A plating method of a casting roll surface of a two roll-typed strip caster includes a step for plating a surface of a casting roll of the strip caster with a plating solution of which temperature is 50°C or more, pH is 5.5~7.5, and electric current density is 7A/dm or less. The casting roll is dipped and plated with completely the plating solution(110).

Description

Casting roll surface plating method of twin roll sheet casting machine {CASTING ROLL SURFACE PLATING METHOD OF TWIN TYPE STRIP CASTER}

The present invention relates to a method for plating a cast roll surface of a twin roll sheet caster, and more particularly, to a cast roll surface of a twin roll sheet caster to improve durability by preventing microcracks of a plated layer. It relates to a plating method.

In general, as shown in Figure 1, the twin roll type sheet casting method, the molten steel accommodated in the ladle (1) flows into the tundish (2) and then the edges provided at both ends of the casting roll (6) through the injection nozzle (3) Solidification is initiated by supplying between the dams 5, that is, between the casting rolls 6, and at this time, the molten portion between the casting rolls 6 is protected by the meniscus shield 4 to prevent oxidation and a suitable gas. It is injected into the atmosphere to be appropriately adjusted, and exiting the roll nip (7) where both casting rolls (6) is made of a thin plate (8) and drawn while being cooled, it is made in the form of being wound in the winder (9).

As such, in the twin roll type sheet casting method of directly manufacturing a sheet having a thickness of 10 mm or less from molten steel by using a sheet casting machine, an important part is through the injection nozzle 3 between the water-cooled casting rolls 6 rapidly rotating in opposite directions. It is to supply molten steel quickly and manufacture thin plate of desired thickness with high real rate without cracking.

On the other hand, the casting surface for the continuous casting adopts an electrolytic plating method, as shown in Figure 2, the casting roll 6 to be plated becomes a cathode, the anode connects the metal 10 to be plated, The object to be plated is completely immersed in the plating solution to flow an appropriate current to obtain a plating layer having a desired thickness.

At this time, the casting roll 6 to be plated is rotated to improve the plating quality, and in the case of a flat surface, the plating solution 30 is rotated so that the plating can be uniformly performed. After plating, a hardness gold layer such as Ni-W or Ni-Co, which is a hardness gold layer, is coated as a secondary plating layer to improve durability.

Such a conventional mold plating method is mainly plated with nickel, and the following techniques have been disclosed regarding plating conditions such as current density and temperature of a plating solution.

That is, JP 1989-254357 discloses Ni plating on the mold surface first, followed by Cr plating secondarily to improve durability and quality, and JP 2001-205399 discloses high hardness Ni-W after primary Ni plating. It is disclosed to improve the durability by applying a plating layer, such as Ni-Co.

However, these conventionally disclosed technologies are applied to the plating or the spray coating layer for secondary durability, after performing the most basic Ni plating, and most of them adopt a hard gold layer for durability improvement, eventually high internal stress plated table Microcracks would sometimes form on the cotton.

Therefore, the microcracks of the hardness gold layer caused a problem of lowering the durability of the mold and deteriorating the surface quality of the cast material.

Here, reference numeral '20', which is not described in FIG. 2, is a plating bath and '40' is a rectifier.

The present invention has been proposed to solve the conventional problems as described above, and the plating is applied as part of the surface treatment of the mold, in applying the primary plating such as nickel and the secondary plating layer of a high hardness layer on the base material of the copper alloy The main problem is to provide the casting roll surface plating method of the twin roll type sheet casting machine to improve the durability of the mold and to stabilize the surface quality of the casting material by deriving the appropriate plating condition to prevent the micro crack of the hardness gold layer. There is.

The present invention is a means for achieving the above-described problems, when forming a hardness gold layer by electroplating Ni, W on the surface of the casting roll of the twin-roll sheet caster, a plating solution temperature of at least 50 ℃, pH 5.5 ~ 7.5, current The present invention provides a casting roll surface plating method of a twin roll thin plate casting machine, wherein the plating is performed while maintaining the density at 7 A / dm 2 or less.

At this time, the casting roll is also characterized by being plated in a state completely bathed in the plating liquid.

According to the present invention, it is possible to prevent the micro-cracks generated during the surface hardness of the thin cast roll, thereby improving the durability of the plating layer, it is possible to obtain the effect of improving the surface quality of the cast material.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment according to the present invention.

Figure 3 is a schematic configuration diagram of a plating apparatus for plating according to the present invention, Figure 4 is an enlarged photograph of the surface of the hardness gold layer according to the present invention.

As shown in FIG. 3, the apparatus for plating according to the present invention includes a plating bath 100, a plating liquid 110 filled in the plating bath 100, and a plated body immersed in the plating bath 100. A casting roll 120, a driving motor M installed on one side of the plating bath 100 to rotate the casting roll 120, and a metal to be plated installed on the bottom surface of the plating bath 100 ( 130, a plating liquid circulation tank 140 provided below the plating tank 100, a pipe 150 connecting the plating liquid circulation tank 140 and the plating tank 100, and the pipe 150 on the pipe 150. It consists of a pump (P) installed in.

Thus, the casting roll 120 is rotated slowly in the state bathed completely in the plating bath 100, and at the same time it is energized so that the electroplating is performed.

At this time, the casting roll 120 to be plated is connected to the cathode of the rectifier 160, the metal 130 to be plated is connected to the anode of the rectifier 160.

In addition, the metal 130 to be plated is preferably Ni, W.

In addition, when a current is applied, Ni and W ions are separated from the anode and attached to the surface of the casting roll 120, which is the cathode, so that plating proceeds.

Here, the temperature condition of the plating liquid 110 during plating is very important.

The temperature conditions of the plating liquid 110 according to the present invention should be maintained at least 50 ℃ to prevent microcracks.

This is because when the temperature of the plating solution 110 becomes less than 50 ° C., microcracks are generated in the hardness gold layer. When the temperature of the plating solution 110 is low, stress concentration of the hardness gold layer occurs and cracks are sensitive. to be.

This fact was confirmed through the experimental example of Table 1.

division Plating solution temperature (℃) Microcracks Experimental Example 1-1 30 ○ Experimental Example 1-2 40 ○ Experimental Example 1-3 50 × Experimental Example 1-4 60 × Experimental Example 1-5 70 × Experimental Example 1-6 80 ×

In addition, it was confirmed that the microcracks of the hardness gold layer are sensitively changed even by the pH conditions of the plating solution 110.

PH conditions for preventing the occurrence of microcracks according to the present invention should be maintained at 5.5 ~ 7.5.

This was also confirmed through the experimental example of Table 2.

division Plating solution pH Microcracks Experimental Example 2-1 4.5 ○ Experimental Example 2-2 5.0 ○ Experimental Example 2-3 5.5 × Experimental Example 2-4 6.0 × Experimental Example 2-5 6.5 × Experimental Example 2-6 7.0 × Experimental Example 2-7 7.5 × Experimental Example 2-8 8.0 ○

In addition, it was confirmed that the microcracks of the hardness gold layer are also sensitively changed by the current density applied to the plating solution 110.

The current density for preventing the occurrence of microcracks according to the present invention should be maintained at 7 A / dm 2 or less.

This was also confirmed through the experimental example of Table 3.

division Current density (A / dm²) Microcracks Experimental Example 3-1 One × Experimental Example 3-2 3 × Experimental Example 3-3 5 × Experimental Example 3-4 7 × Experimental Example 3-5 10 ○ Experimental Example 3-6 15 ○

Through this, the plating solution 110 during plating according to the present invention is maintained at a temperature of 50 ° C. or more, pH of 5.5 to 7.5, and a current density of 7 A / dm 2 or less, thereby preventing microcracks in the hardness gold layer after plating and durability. It was confirmed that this is improved, and through this it was confirmed that the surface quality of the cast (material) can also be improved.

That is, as shown in Figure 4, (a) can be seen that there is no micro-crack in the tissue picture according to the present invention, (b) can be seen that the micro-crack occurs in the existing tissue picture.

1 is an exemplary conceptual view showing a general sheet casting process,

Figure 2 is an exemplary device configuration showing a plating method of a conventional casting roll,

3 is a schematic configuration diagram of a plating apparatus for plating according to the present invention;

Figure 4 is an enlarged photograph of the surface of the hardness gold layer according to the present invention.

♧ description of the symbols for the main parts of the drawing ♧

100..Plating tank 110..Plating amount

120 .... casting roll 130 .... metal

140 .... Plating solution circulation tank 150 .... Plumbing

160 .... Rectifier

Claims (2)

When electroplating Ni and W on the casting roll surface of a twin roll sheet casting machine to form a hard gold layer, Plating roll surface plating method of a twin-roll thin plate casting machine characterized in that the plating while maintaining at a plating solution temperature of at least 50 ℃, pH 5.5 ~ 7.5, current density of 7A / dm 2 or less. The method according to claim 1; The casting roll surface plating method of a twin roll thin plate casting machine, characterized in that the plated in a state completely bathed in the plating liquid.

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