JPS5950952A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To improve the heat resistance and wear resistance of a mold for continuous casting by plating Ni on the inside surface of a Cu or Au alloy plate forming the long side members of the mold and further covering the surface thereof with an Ni-W-Fe alloy plating layer having a specific compsn. CONSTITUTION:A set of long side plates and movable short side plates used in continuous casting of molten steel are manufactured from Cu or a Cu alloy, and Ni is plated on the inside surface side that contacts with the molten metal. A plating layer 8 of an Ni-W-Fe alloy consisting of 3-10% W, 2-10% Fe and the balance Ni is formed in the specific position on the Ni plating layer 6 formed on the surface of the Cu or Cu alloy plate material 4 forming the long side of the casting mold. The plating layer 8 is positioned in the range of at least 50mm. upper and 300mm. lower than the level of the molten steel in the mold. The heat resistance to the high temp. of the molten steel and the resistance to wear by the molten steel are improved by the presence of such plating layer 8 and the service life of the casting mold is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting mold, and more particularly to a continuous casting mold that has excellent heat resistance and abrasion resistance and can cope with increased casting speeds.

A continuous casting mold consists of a set of Q and long sides of the mold that are arranged opposite to each other, and a set of short sides of the mold that are held between the long sides of the mold and move forward and backward, and are forcedly cooled with water between them and the back plate. In order to quickly remove the heat from the molten steel poured into the mold, a mold base made of copper alloy or copper alloy is coated with nickel or a nickel alloy. It is well known that chromium plating is applied as a second layer to impart wear resistance that corresponds to the descent of the solidified shell.

However, as continuous casting equipment has recently become larger and casting speeds have increased, plastic deformation or softening occurs in the plated layer of nickel or nickel alloy.
Furthermore, deep horizontal flaws occur on the long side of the mold due to the descent of the solidified shell that forms the slab and the advancement and retreat of the short side of the mold due to the change in slab width.Furthermore, these flaws induce welding defects due to molten steel, significantly shortening the life of the mold. This creates the problem of shortening the .

An object of the present invention is to provide a continuous casting mold having excellent heat resistance and wear resistance, which eliminates the drawbacks of the prior art as described above, and which can cope with higher casting speeds. be.

The gist of the present invention is as follows.

That is, a mold base made of copper or a copper alloy constitutes a pair of mold long sides arranged to face each other and a set of mold short sides that move forward and backward while being held between the long sides of the mold, and a mold base of the mold base. In a continuous casting mold having a coating layer made of nickel or a nickel-based alloy plated on the surface, at least 50 rr above the molten steel surface in the mold.
rm, downward to 300°C mrl) region υ on the long side surface of the mold in weight ratio: 3 to 10 inches, iron: 2 to 1
This continuous casting mold is characterized in that it has a coating layer including nickel and the remainder made of nickel or a nickel-based alloy.

The present inventors investigated the cause of the shortening of mold life due to the increase in pouring speed υ with recent large-scale continuous casting equipment, and found that the meniscus of the mold is at the highest temperature, so the width of the slab slab It was found that horizontal drag was concentrated due to friction at the part where the short side of the long side of the mold was clamped as the short side of the mold moved back and forth due to the change, and that the flaw was deeper than other parts. Furthermore, it has become clear that these υ defects cause weld defects when they come into contact with high-temperature molten steel, which significantly shortens the life of the mold.

The inventors conducted research on this countermeasure and found that
In order to prevent problems that occur in the hot water surface area, which corresponds to the meniscus area around the length of the mold, it is necessary to develop a mold with excellent high-part properties that can withstand long-term use without causing plastic deformation or softening even when used continuously at high temperatures. We came to the conclusion that it is most effective to apply eutectoid-strengthening electroplating to the surface of the mold, at least to the long sides of the mold corresponding to the top and bottom of the meniscus υ.After conducting various experiments, we were able to complete the present invention. It is something that

The present invention is a plating layer made of nickel or nickel-based alloy applied on the surface of a conventional copper or copper alloy V mold substrate, and further contains W: 5 to 1o and Fe: 2 to 10, and the remainder is Ni or This mold has a eutectoid-strengthened electroplated coating layer made of an N1-based alloy. The reasons for limiting the composition of the coating layer according to the present invention are as follows.

The Ni-W photoelectroplated layer is a eutectoid-strengthened plating with fine crystal grains, and its effect is recognized when the W content is 3% or more in terms of weight fI: ratio, and the effect is saturated at 10 g. Therefore, it was limited to a range of 3 to 10 inches.

It has been found that the effect of achieving the object of the present invention becomes even more remarkable by eutectoiding Fe simultaneously with the eutectoiding of N1-W. For example, when two pieces of Fe are co-electrodeposited,
The hardness of the plating layer that does not eutectoid Fe is approximately 300 in Hv.
, it increases at about 38 QHv4. This F
The effect of co-depositing e is observed at 2 or more chips, and gradually increases, but the effect is saturated at 10 chips, and if it exceeds 10%, the deposited layer becomes brittle, so it is limited to 2 to 10 chips. did.

The effect of eutectoiding Fe is also remarkable in high-temperature strength; for example, a N1-W deposited layer starts to soften when the temperature exceeds 500°C, but when 2 to 10% Fe is eutectoid, the softening temperature It was found that the initial strength of about 60 degrees was maintained even at 600 degrees Celsius as the temperature rose to 600 degrees Celsius.

Next, the mold position where the Ni-W-FeQ eutectoid is applied will be described. V) N i -W -Fe (
QIt is effectively best to apply the eutectoid layer to the entire long side and short side υ of the mold, but it is very expensive, so consider the cost and decide the most effective position to apply the eutectoid layer. I decided to do so.

First, the surface of the mold copper plate is 20mm deep, Q the casting speed is 1, 0.
When the temperature distribution at m/n1in was investigated, the results shown in FIG. 1 were obtained. As is clear from Figure 1, the temperature is highest at about 2ooITII'rl from the upper end of the mold and about 10011'+m from the meniscus, at about 250 m.
The seismic intensity of the copper plate decreases as it reaches C and reaches the bottom of the mold, and when changing the width of the slab during pouring, the friction caused by moving the short side of the mold back and forth causes horizontal resistance on the long side of the mold. Due to the fact that the anti-mirror high u1 molten steel causes defects in the welded fastening layer and significantly shortens the mold life, the effective plating area of the N1-W-FeD eutectoid plating layer according to the present invention is on the long side of the mold. Plating should be applied within an area of at least 50 mm above the meniscus of the molten steel surface and 300 mm below.

If a further minimum is desired within this υ region, it may be limited to the advancing and retreating portions of the short sides of the mold, as shown in FIG. The thickness of the Ni-W-Fe plating layer according to the present invention is 50 μm.
About n is sufficient.

In the continuous casting of a slab slab with a row cross-sectional shape of 17 mm in thickness and 1.800 mm in width, a conventional conventional mold with Ni plating after 320 castings and a mold according to the present invention were used. %Ni-71W-4%Fe (7)
Plating the second [? 21 (A), (B), 50 mm above and 20 mm below the meniscus part of long side 2 of the mold.
01TllTIO was applied to the advancing and retracting parts of the short sides of the mold except for the center part, and the width of the slab slab was changed from 1800 mm to 12
Reduction to 00mm and 1200mm to 1800+T
The depth of the flaws generated on the long side 2 of the mold and the amount of flaws generated after 50 times of zero-width expansion to Im were compared and investigated.

In the case of plating according to the present invention, a constant thickness of υNi is applied to the minimum area on the copper plate of the mold base 4 as shown in FIG.
Plating 6 is applied, and N1-W according to the present invention is applied to the 0 surface.
-Fe plating 8 was carried out on 5Q7annoq, and other υ parts! (This is one that has been plated with N1 to make the surface uniform.

The N1-W-Fe plating layer 8 according to the present invention can be applied in addition to the above-mentioned υ, as shown in FIG.

As a result of the above comparative test, many defects with a maximum depth of approximately 0.5 to 1.0 mm were created in the case of only Ni plating using the conventional method, whereas in the case of the mold according to the present invention, there were 8/8 defects.
) The maximum depth was approximately 0.02nrm, and it was observed that the amount generated was also halved. Although the mold according to the present invention continued to be used after that, its lifespan was finally extended to 2 can plates-H compared to the conventional mold.

As is clear from the above examples, the continuous casting mold according to the present invention has Ni plating applied directly to or on the copper plate of the conventional mold base, and further has a W of 3 to 1 on the surface.
0%, Fe: 2 to 10%, balance Ni or Ni-based alloy eutectoid-strengthened electroplating is applied, and the application area is at least 50 IrIITl above the mold surface and 30 IrIITl below.
By setting it to 0 mm, the following effects could be achieved.

(stomach)@! Even though the width of the slab slab to be manufactured is changed frequently and the width of the short side is moved back and forth, the occurrence of horizontal drag as in the conventional method is extremely small, and the life of the mold can be extended by more than twice that of the conventional method.

Oki) The mold according to the present invention completely eliminates the occurrence of plastic deformation and softening of the plating layer Q as in the past, and has excellent heat resistance and wear resistance. It can also fully cope with the increase in loading speed.

(c) If the area where the N1-W-Fe plating layer is applied according to the present invention is limited to the minimum necessary area on the long side of the mold, the cost of implementation can be relatively small and can be fully compensated for by the effect.

[Brief explanation of drawings]

Figure 1 is a temperature distribution diagram measured from the upper end of the mold in the mold copper plate during continuous casting, Figure 2 (5), (B), (C)
(A) is a front perspective view thereof, (CB) is a sectional view taken along the line B-B four times, ( C) is B-B
Another aspect of the line arrow sectional view is shown. 2... Mold long side, 4... Mold base 6...
Ni-metsuki layer 8...N1-W-Fe-metsuki layer agent Patent attorney Takeo Nakaji Figure 1 i 1 kosi! P gold dougou 3F shi1 taedami (0C) (A)

Claims (1)

[Claims] (1) A mold base made of copper or copper alloy, which constitutes a pair of mold long sides arranged to face each other and a set of mold short sides that move forward and backward while being sandwiched between the long sides of the mold, and the mold base a continuous casting mold having a coating layer made of nickel or a nickel-based alloy plated on the surface of the continuous casting mold, at least 50 m in the -F direction from the molten steel surface in the mold.
m, downwardly on the long side surface of the mold in the region of 300 cylinders, a coating layer containing 3 to 10% by weight, iron: 2 to 10%, and the remainder consisting of nickel or a nickel-based alloy. A continuous casting mold comprising: