JPS6034639B2 - Manufacturing method of continuous casting mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a mold for continuous casting, and in particular to a method for manufacturing a mold for continuous casting, in particular a mold made of copper or steel alloy, which has a coating layer of Ni-Fe alloy containing 1 to 20% Fe on the surface of the mold. , relates to a method for manufacturing a continuous casting mold of steel with excellent wear resistance, seizure resistance, and thermal shock resistance.

Conventionally, molds for continuous casting of steel have been made of steel or steel alloys with excellent thermal conductivity. However, if such a continuous casting mold (hereinafter referred to as the mold) is used as is,
Because the molten steel injected into the mold is extremely hot, the molten steel injection surface is severely damaged, and the mold reaches its lifespan in an extremely short period of time. At the same time, some of the scraped copper enters the grain boundaries from the surface of the coin. Star-shaped cracks occur on the surface of coin coins, resulting in major quality defects. Conventional attempts have been made to protect the inner surface of the mold with chrome plating, but the plating peeled off early due to thermal shock, making the plating ineffective.

The cause of this is the difference in thermal expansion coefficient, Cu: 16.5×10
-6 (20oo), Cr: 6.2×10-6(
This is because the chrome plating is small (20 qo) and easily peels off from the copper base due to thermal shock. To solve this problem, Ni or Ni alloy plating such as Ni-P or Ni-B was applied.

This material has a coefficient of thermal expansion of 13.3 x 10-6 (20℃)
Compared to Cr, which is relatively similar to Cu and has excellent malleability, it has lower hardness and is more prone to wear, so it is necessary to make it thicker. This Ni plating has a lifespan several times longer than that of Cr plating, but Ni tends to weld with the molten steel, and in severe cases, breakage of the coin piece called breakout occurs during casting. Splashing may cause serious damage to equipment.

Furthermore, Ni plating is done once for three ribs of total thickness because cracks occur due to repeated thermal shocks near the scratched surface of the molten steel injected into the mold, and the cracks open wide in a short period of time, eventually making it unusable. It is necessary to cut down 0.3 to 0.5 skin per inch, and there is a drawback that the cutting is performed at least twice or more during the service life, which significantly shortens the service life. An object of the present invention is to overcome the drawbacks of the conventional continuous casting molds and to provide a method for manufacturing a continuous casting mold having a coating layer with excellent hardness, wear resistance, seizure resistance, and thermal shock resistance. be.

The gist of the method for manufacturing a continuous casting mold according to the present invention is as follows.

First, the mold to be manufactured is a mold for continuous casting of steel made of copper or a steel alloy.
The mold has a coating layer of a Ni-Fe alloy containing ~20% Fe. The manufacturing method for obtaining such a continuous casting mold involves depositing a Ni coating layer on the surface of the copper or brocade alloy that constitutes the continuous casting mold using an electrolytic solution containing nickel sulfamate as the main component. In the method for manufacturing a continuous casting mold, the electrolytic solution does not contain organic sulfur compounds other than sulfamate salts, and contains ferrous ions and oxycarboxylic acids, and the Ni coating layer contains 1 to 20 % of Fe is contained in the continuous casting mold. Generally, the characteristics required of a mold are related to the movement of the fin pieces within the mold, and are as follows.

The material to be plated near the upper meniscus of the mold must have excellent corrosion resistance, thermal shock resistance, and seizure resistance against molten steel. 'o} Excellent abrasion resistance against the sliding of coins at the bottom of the mold, and peeling resistance due to the difference in thermal expansion coefficient between plating and copper when exposed to heat.

The molds to be used in the manufacturing method of the present invention are the above-mentioned 'i}, {o}
In particular, the wear resistance was approximately twice as high as that of the Nj-plated secondary mold, and cracks were also reduced in the mold. Specifically, the content of Fe in the Ni--Fe coating layer may be set to 1 to 20%, and this is for the following reason.

In other words, if the Fe content is less than 1%, the wear resistance and hardness cannot be guaranteed to be higher than the values required for the lining material.
This is because if it exceeds 0%, the plating layer becomes brittle and peels off and cracks at an early stage, and the residual stress generated during plating increases and peels off from the copper base. Next, a method of manufacturing a mold made of copper or a copper alloy having a coating layer of a Ni--Fe alloy containing 1 to 20% Fe according to the present invention will be described.

It is well known that in the conventional manufacturing of molds made of Ni-plated steel or steel alloys, a method of using an electrolytic solution containing nickel sulfonate as a main component for open deposition is explored, but the manufacturing method of the present invention In the method, the following two items 'a} and 'b' are essential requirements in the plating step.

(a) Adding both oxycarboxylic acids such as tartaric acid, citric acid, malic acid, and their ammonium salts, and ferrous ions to an electrolytic solution of nickel sulfamate. Use an electrolyte that does not contain organic sulfur compounds such as saccharin, which are commonly used as stabilizers.

That is, in the present invention, one of the features of the present invention is to use an oxycarboxylic acid in combination with a sulfamate salt bath, which inherently has lower electrodeposition stress than other solutions, in place of the conventional organic stabilizer. It is a characteristic.

The action of this oxycarboxylic acid stabilizes the ferrous ions by converting them, and according to the stress measurement results by the present inventors, it has been confirmed that the stress reducing effect is not as great as that of organic compounds, but is sufficient to be usable. There is. Further, the reason why organic sulfur compounds other than sulfamate salts were not included is as follows. That is, an organic sulfur compound such as saccharin is added to a normal nickel or nickel alloy plating solution. This is to reduce the internal stress (strain) of the plating film, prevent it from peeling or cracking from the base material, and use it to smooth out the plating. However, when used to plate continuous casting molds, the molds are exposed to high temperatures for long periods of time and are heated, so it was discovered that the plating film would develop large cracks due to the effects of heat. It is. In other words, a decrease in tensile strength and elongation was observed in the sticky coating obtained by using an organic sulfur compound such as saccharin.
It was observed that there was no decrease in tensile strength or elongation in the damped coating obtained without using the combination. It is clear that organic sulfur compounds are the cause of the above-mentioned adverse effects on the gluing of high-temperature heated components, and in fact, not only saccharin but also other organic sulfur compounds used for stress reduction and smoothing purposes. It is known that, for example, sodium naphthalene sulfonate, P-toluenesulfonamide, etc. behave similarly to saccharin. Based on these results, it was decided not to contain organic sulfur compounds. In addition, sulfamic acid and sodium lauryl sulfate also contain sulfur in their molecules,
Although they are considered organic sulfur compounds, they are added as components of the plating solution, and their presence does not cause extreme deterioration of the plating film, so sulfamates were excluded. Considering the above plating solution composition, Table 1 shows the composition range of the plating solution used in the present invention.

Table 1 Plating conditions pH 2-5 Current density 0.5-200 A/d ordinary temperature
Room temperature to 70 qo Next, examples of the manufacturing method according to the present invention will be described.

Example 1 In order to examine the liquid suitable for mold dew-bonding, the second
A total of six types of plating solutions as shown in the table were prepared, and the electrodeposition stress of each solution was measured using a spiral stress meter. After that, it was immersed in a constant temperature bath maintained at 50 qo for 10 days, and the appearance and composition of the solution were determined. The stability was investigated by examining changes in

Table 2 In Table 2, all nickel ions and ferrous ions were added as sulfamate salts.

The results of measurement of tortoise stress and liquid stability are shown in Table 3. Table 3 Electrodeposition stress measurement conditions: Current density 3A/d〆, 30 minutes 3rd
From the results in the table, it is clear that the stress reduction effect of citric acid addition and the stabilizing effect of ferrous ions, and that saccharin has a large stress reduction effect, but even the E solution without saccharin according to the present invention It was found that the stress reduction effect was observed to the extent that it could be used.

Example 2 The liquids A to F of Example 1 were newly prepared, a buffed SUS304 stainless steel of 300 mm diameter x 40 mm length x 1 sail thickness was prepared, and a current density vessel / d〆After applying to a thickness of 0.1 at a liquid temperature of 50 qo, and then peeling off the plating film from the stainless steel, ASTM standard E8 was applied.
A tensile test piece according to -66 was prepared and tested at room temperature, 4000x
lhr, and the tensile strength and elongation of those subjected to 700q0×lhr heat treatment were determined.

Table 4 shows the results, and also includes the Fe content of the foils obtained from liquids A to F.

As is clear from Table 4, the elongation rate of the film obtained from the liquid E of the present invention, which does not contain organic sulfur compounds other than sulfamate, is superior to that obtained from the conventional liquid A, even when treated at high temperatures. It can be seen that it has

Example 3 Using the two liquids A and E of Example 1, a medium size of 30 mm x length of 40 mm was prepared.
Liquid temperature 50qo, current density 3A on a saddle steel plate of 1 side x 1 thickness
A sample for the Taber type abrasion test was prepared by welding to a rib thickness of 0.1 under the condition of /d, and the abrasion loss was compared under the following test conditions for the sample which was subjected to the same heat treatment as in Example 2. .

Table 4 and Table 5 of Window Chapter show the test results. It was found that the wear resistance was improved and good results could be expected even when applied to actual molds.

As shown in the attached drawing, Table 5 shows that the copper mold coated with the Ni-Fe alloy according to the present invention was superior to the secondary mold coated with only Ni at the same plating thickness. It was found that the lifespan was approximately twice that of the previous one.

Example 4 Considering the application to actual molds, actual mold materials were prepared using the E liquid of Example 1 under conditions of a liquid temperature of 50℃ and a current density of 3A/d. A cape x thickness 1 ratio was cut, and a sample was placed on one side of the cape for 4 hours to obtain a thickness of 1.
A test piece having a dew-diagnosed membrane of 0 to 1.5 ribs was obtained.

For comparison, a test piece was also prepared from Solution A of Example 1 under the same conditions. The external appearance of test strips obtained from liquid E according to the present invention is no different from that of liquid A except that the color tone is darker than that obtained from the conventional liquid A using only nickel. A, E
The test pieces from the solution were combined and heat treated at room temperature, 400°C x lhr and 700°C x lhr in this order, and the surface hardness was determined, and the results shown in Table 6 were obtained.

As is clear from Table 6 and the Examples, F according to the present invention
Continuous casting molds made of copper or steel alloys with a Nj-Fe alloy coating layer containing ~20% ei can be made from conventional Ni
It was found that the mold had better high-temperature properties and wear resistance than a single-plated mold.

1 to 20% F on the surface of the copper or steel alloy according to the present invention.
A continuous casting mold having a coating layer of Ni--Fe alloy containing e has the following effects.

{i} Since the coefficient of thermal expansion is not much different from that of the single Ni coating layer, the peeling resistance is comparable.

'Row Ni-Fe alloy has a high melting point of about 1400q0 and has excellent high-temperature strength and elongation, so it has excellent seizure resistance and thermal shock resistance even when it comes into contact with molten steel.

Since the hardness at room temperature and high temperature is superior to that of Ni plating, it has high wear resistance.

This fact is also supported by the wear test results. As a result, the service life can be extended to about twice that of conventional coin molds with a single Ni coating layer, and the productivity of continuous casting can be significantly improved.

The method of manufacturing a Ni--F8 coating layer by electroplating according to the present invention has the following effects.

A Nj-Fe alloy coating layer with an arbitrary Fe content can be formed on the surface of a copper or copper alloy mold.

The coating layer of 'o'Ni-Fe alloy can be plated thickly, and according to the method of the present invention, a sulfamate bath and an oxycarboxylic acid can be used without using an organic stabilizer such as saccharin. By doing so, plating with low bonding stress can be achieved, so cracks will not occur even when thickly plated.

[Brief explanation of drawings]

The attached drawing shows the number of heats used during continuous casting, comparing the wear loss of the Ni-Fe alloy coating layer mold according to the present invention (black circles) and the conventional Ni coating layer mold (white circles) at the same plating thickness in an actual machine. FIG.

Claims (1)

[Claims] 1. A method for manufacturing a continuous casting mold in which a Ni coating layer is electrodeposited on the surface of copper or a copper alloy constituting the continuous casting mold using an electrolyte containing nickel sulfamate as a main component, wherein the electrolyte contains sulfamine. A continuous casting mold that does not contain organic sulfur compounds other than acid salts, contains ferrous ions and oxycarboxylic acids, and contains 1 to 20% Fe in the Ni coating layer. manufacturing method.