JP3088186B2 - Manufacturing method of Ni-based alloy sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal plate of high quality made of a Ni-base alloy on which a Laves phase is precipitated, with good yield.

[0002]

2. Description of the Related Art Ni alloys having better heat resistance and corrosion resistance than stainless steel are used in harsh environments where stainless steel cannot be used, such as chemical equipment and seawater resistant parts.

[0003] In general, Ni-base alloys have higher hot deformation resistance than stainless steel.
Annealing and rolling must be repeated many times before a sheet is obtained from the ingot. In particular, a Ni-based alloy on which a Laves phase compound precipitates has extremely poor hot workability.

[0004] That is, the γ 'phase or MC in the matrix
In a Ni-based alloy in which high-temperature strength is improved by precipitating type carbides, for example, a Ni-based alloy to which a large amount of Mo or Nb is added, a Laves phase (intermetallic compound) is precipitated by segregation at the end of solidification. Since the Lavas phase has a low melting point, the temperature at which ductility develops is lowered in the Ni-based alloy in which the Laves phase is precipitated, and cracks are likely to occur during hot working due to so-called liquid film embrittlement.

[0005] Therefore, Ni having the Laves phase precipitated
When hot working a base alloy ingot, it was necessary to lower the working temperature to a temperature at which liquid film embrittlement did not occur. As a result, in order to obtain a thin plate from the ingot, machining was required in a region having high deformation resistance, and the machining cost was inevitably increased.

[0006]

For such a material which is difficult to hot work, a technique of directly manufacturing a thin plate from a molten metal, such as a twin roll method or a single roll method, may be applied. That is, if it becomes possible to directly obtain a thin plate by rapid solidification from a molten metal, it is possible to expect not only the merit of saving steps but also an improvement in quality, such as fine dispersion of precipitates (Laves phase compound) in the material. .

However, N which precipitates the Laves phase compound
When an i-based alloy is manufactured into a thin plate by applying the twin-roll method, cracks are more likely to occur during casting than other Ni-based alloys. In other words, alloys that are liable to cause liquid film brittleness have a problem that cracks are likely to occur on the sheet surface during casting even in the twin-roll method, and in severe cases, tearing occurs. Therefore, even if a melt quenching method such as a twin roll method or a single roll method is applied to the alloy without any technical improvement, it is extremely difficult to obtain a good plate without defects such as cracks.

An object of the present invention is to solve the above-mentioned problem when a thin plate is directly produced from a molten metal by a twin-roll method using a Ni-based alloy in which a Laves phase is precipitated.

[0009]

According to the present invention, a twin-roll type in which a solidified shell formed on both circumferential surfaces of a pair of internally cooled rolls is pressure-bonded in a gap between the roll pairs and directly cast into a thin plate. Ni that precipitates Laves phase compound using continuous caster
A method of manufacturing a base alloy metal plate, in which the circumferential surface of the roll to be cooled from the inside is made of copper or a copper alloy, and the surface is made of a material with a thermal conductivity of 10 to 90 W / mK A heat transfer resistance layer having a thickness of more than 1.0 mm and not more than 3.5 mm is formed, and the surface of the heat transfer resistance layer has a center average roughness (Ra) of 5 to 25 μm.
m using a twin-roll type continuous caster with a roughened surface, and controlling the pressing load per unit plate width on the thin plate passing through the gap between the pair of rolls to a range of 20 to 100 N / mm width. A method for producing a Ni-based alloy plate, characterized by casting a Ni-based alloy.

[0010]

The present inventors cast a Ni-base alloy in which a Laves phase is precipitated under various conditions by a twin roll method, and investigated in detail the relationship between cracks on the sheet surface and the casting conditions. as a result,
First of all, we found that the crack location was the position corresponding to the high temperature part of the temperature unevenness (cooling unevenness) of the sheet surface generated during casting. It was also found that cracks were more likely to occur as the temperature unevenness on the plate surface became more remarkable. Therefore, in order to prevent cracking of the alloy sheet, it is important to reduce the temperature unevenness of the sheet surface generated during casting.

In a twin-roll continuous caster using an internally cooled twin roll, the solidified shell growing from the roll surface is not uniform but grows with a certain degree of shell thickness unevenness. In the region where the shell thickness unevenness is large, the shells that have grown from both roll surfaces are rolled against each other earlier than the others, so that the adhesiveness with the roll is rapidly improved only in that region, and the heat transfer resistance is significantly reduced. The temperature drops.

That is, the temperature unevenness of the plate surface becomes more remarkable as the shell thickness unevenness becomes larger. Also, as the pressure load increases, the temperature difference between the area where the adhesion between the solidified shell and the roll is rapidly improved and the temperature decreases and the area where the other adhesion is not improved becomes larger. Temperature unevenness becomes significant.

Therefore, in order to reduce the temperature unevenness of the plate surface that causes cracks on the plate surface, the thickness unevenness of the shell growing on the circumferential surface is reduced, the pressure load is reduced, and It is important to suppress the sudden heat removal even when the properties are improved.

Roll sleeve (circumferential surface of roll body)
In general, copper or a copper alloy having high thermal conductivity is used as the material for the thermal expansion of the roll to reduce the thermal expansion of the roll. In the present invention, the material of the sleeve is copper or copper alloy in this sense.

Then, a layer (heat transfer resistance layer) having thermal resistance is separately provided on the surface (circumferential surface) of the sleeve made of copper or copper alloy. That is, a metal layer having a lower thermal conductivity than copper is formed on the surface of the copper or copper alloy sleeve by, for example, plating. More specifically, if a heat transfer resistance layer made of a material with a thermal conductivity of 10 to 90 W / mK and having a thickness of more than 1.0 mm and less than 3.5 mm is formed on the sleeve surface, even if the adhesion becomes better, Heat removal can be suppressed.

The material of the heat transfer resistance layer has a thermal conductivity of 90 W / m.
Use those below K. A material having a higher thermal conductivity does not sufficiently function as a heat transfer resistor. However,
If the thermal conductivity is less than 10 W / mK, the solidification rate will be too slow, which will hinder productivity and other aspects.

The thickness of the heat transfer resistance layer is preferably in the range of more than 1.0 mm and not more than 3.5 mm. If the thickness is less than 1.0 mm, the thickness becomes too thin, making it difficult to achieve the original function as a heat transfer resistance layer. If the thickness exceeds 3.5 mm, the solidification rate becomes slow, which impairs productivity and other problems. Become like

On the other hand, the surface roughness of the surface of the heat transfer resistance layer is determined by blasting or the like to determine the center average roughness (Ra).
Adjust to 5-25 μm with. With such a surface roughness, unevenness of the shell thickness at the time of initial solidification when solidifying from the molten metal to the circumferential surface can be suppressed. On a surface having a surface roughness of less than 5 μm, even if the above-mentioned condition of the thermal conductivity of the heat transfer resistance layer is satisfied, the slow cooling effect is small, so that the unevenness of the shell thickness cannot be suppressed, and the temperature unevenness of the plate surface is reduced. It is promoted, and as a result, cracks easily occur. However, if the surface is roughened to a value exceeding 25 μm, surface irregularities will be transferred to the cast plate, which will cause defects such as poor gloss in the subsequent cold rolling process of the cast thin plate, which is not desirable. .

In addition to adjusting the roll sleeve material and surface roughness as described above, in the present invention, the pressure applied to the thin plate during casting per unit plate width is 20 N / mm width or more and 100 N / mm width or more.
Control within the width or less. When the pressing load exceeds 100 N / mm width, temperature unevenness is promoted and the roll surface is also abraded. On the other hand, if the width is less than 20 N / mm, the center of the sheet thickness is not solidified, and the sheet is likely to crack due to bulging or reheating after the roll is released. Such control of the crimping load is performed by, for example, Japanese Patent Application No. 2-214041 or Japanese Patent Application No.
This can be achieved by employing the crimping load control technology proposed in 214042.

As described above, according to the present invention, the
In a Ni-base alloy in which an s-phase compound precipitates, a good metal plate free of surface defects such as cracks can be directly produced from the molten metal, and a good effect is provided in terms of quality such as fine dispersion of precipitates (Laves phase). .

[0021]

EXAMPLE A Ni-base alloy thin plate was cast using a twin-roll continuous caster using an internal water-cooled roll made of a copper alloy having a width of 300 mm and a diameter of 400 mm. Table 1 shows the chemical component values of the tested Ni-based alloys. Both are Ni-base alloys in which the Laves phase is crystallized at the end of solidification. Ni plating or Ni-2.5% Fe plating was applied to the surface of the rolled copper alloy as a heat transfer resistance layer to the thickness shown in Table 1, and the surfaces of these plating layers were subjected to sand blasting to obtain the results shown in Table 1. The center average roughness (Ra) was adjusted to a roughness. Both Ni plating and Ni-2.5% Fe plating layer have thermal conductivity of 90W / mK
It is as follows.

For casting, the roll gap was set so that the molten metal amount was 110 kg and the sheet thickness was more than 1 mm and not more than 6.0 mm. Then, by detecting the pressure applied to the plate during casting and controlling the rotation speed of the roll, the pressure applied was adjusted to fall within the range shown in Table 1 for each heat. That is, when the crimping load was likely to be larger than the specified range, the rotation speed of the roll was increased, and when it was likely to be smaller, the rotation speed of the roll was decreased.

Table 1 shows the casting conditions in each example,
The results of investigating the occurrence of cracking and bulging of the obtained plate are also shown.

[0024]

[Table 1]

From the results in Table 1, it can be seen that even with a Ni-base alloy in which a Laves phase compound is precipitated, according to the twin-roll method satisfying the conditions specified in the present invention, a thin sheet having good surface quality without causing cracking or bulging is obtained. Is obtained.

On the other hand, if at least one of the conditions specified in the present invention is deviated as seen in the comparative example, cracks and bulging occur, and a good thin plate cannot be obtained. That is, No.
Cracks occurred with no plating or with a plating thickness of 1.0 mm or less, as in 8, 9, and 12. When the crimping load included a small range such as No. 11, bulging occurred due to unsolidification. Thermal conductivity less than 90W / mK and thickness 1mm
Even when plating was performed in excess of the above, a large number of cracks occurred on the surface of the cast plate with a roll having a center average roughness of 5 μm or less as shown in No. 10.

When the appearance of the thin plate obtained in the example of the present invention is compared with the appearance of the thin plate obtained in the comparative example, the former shows no uneven temperature pattern, whereas the latter shows no uneven temperature pattern. A pattern of uneven temperature occurred in the casting direction, and cracks occurred on the surface at positions corresponding to the high-temperature part.

[0028]

As described above, according to the present invention, a thin plate having a good surface quality without cracking or bulging can be directly produced from a molten metal with respect to a Ni-base alloy in which a Laves phase having a hot workability is precipitated. Became. In addition, the precipitate (La
ves phase) is finely dispersed, so that quality is also improved.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Morihiro Hasegawa 4976 Nomura Minami-cho, Shinnanyo-shi, Yamaguchi Prefecture Inside of the Iron and Steel Research Laboratory of Nisshin Steel Corporation (56) References JP-A-4-293754 (JP, A) JP-A Heihei 3-166345 (JP, A) JP-A-64-17823 (JP, A) JP-A-5-154616 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/06 330 B22D 11/00

Claims (3)

(57) [Claims] 1. A twin-roll continuous caster, in which a solidified shell formed on both circumferential surfaces of a pair of internally cooled rolls is pressed in a gap between the pair of rolls and is directly cast into a thin plate, is used as a Laves.
A method for producing a Ni-based alloy metal plate on which a phase compound precipitates, wherein the circumferential surface of the roll cooled from the inside is made of copper or a copper alloy, and the surface has a thermal conductivity of 10 to 90%.
Twin rolls formed of a W / mK material having a thickness of more than 1.0 mm and less than 3.5 mm and having a rough surface having a center average roughness (Ra) of 5 to 25 μm. Using a continuous caster, and casting the Ni-base alloy by controlling the pressing load per unit plate width of the thin plate passing through the gap between the roll pairs to a range of 20 to 100 N / mm width. Characteristic method for producing Ni-based alloy sheets. 2. The thickness of a metal plate to be cast exceeds 1.0 mm.
2. The method for producing a Ni metal alloy sheet according to claim 1, which is not more than 6.0 mm. 3. The heat transfer resistance layer is a Ni plating layer or a Ni-Fe layer.
3. The method for producing a Ni-based alloy plate according to claim 1, which is a plating layer.