JPH0730406B2 - Method for producing Cr-Ni stainless steel sheet with excellent surface quality and material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses a so-called synchronous continuous casting process in which there is no relative speed difference between a slab and an inner wall surface of a mold, and the slab thickness is close to the product thickness. The present invention also relates to a method for producing a Cr-Ni-based stainless steel thin plate, which comprises refining the structure from the cast piece stage to produce a Cr-Ni-based stainless steel sheet having excellent surface quality and material.

(Prior Art) Conventionally, in order to produce a stainless steel thin plate using a continuous casting method, casting is performed on a slab with a thickness of 100 mm or more while vibrating the mold according to the production method, and surface treatment of the obtained slab is performed. After heating to 1000 ° C. or higher in a heating furnace, hot rolling was performed using a hot strip mill consisting of a rough rolling mill and a finishing rolling mill row to obtain a hot strip having a thickness of several mm.

When cold-rolling the hot strip thus obtained, the shape (flatness), material,
In order to secure the surface texture, hot-rolled sheet annealing is performed to soften the hot strip that has undergone strong hot working, and the surface scale and the like are removed by grinding after the pickling step. This conventional process requires a large amount of energy for heating and processing the material in a long hot rolling facility, and it is difficult to say that the manufacturing process is excellent in terms of productivity. Also, the final product develops a texture because many processes are made from a slab with a thickness of 100 mm or more, and the anisotropy is taken into consideration when the product is pressed by the user. There were also many restrictions on usage such as the necessity to do so.

In order to roll a slab with a thickness of 100 mm or more into a hot strip, a long hot rolling facility and a large amount of energy,
Recently, in order to solve the problem of requiring rolling power,
Research on a process for obtaining a slab (thin band) having a thickness equal to or close to that of a hot strip in the process of continuous casting is under way. For example, "Iron and Steel"'85, A197 to '85, A256
In the article featured in, a process for directly obtaining hot strip by continuous casting is disclosed. In such a continuous casting process, the twin drum system is used when the gauge of the slab (strip) to be obtained is in the level of 1 to 10 mm, and the gauge of the slab is 20 to 50 mm.
The twin-belt method is being considered when the level is.

However, it is said that there is still a problem in the casting stage in these continuous casting processes, and it has not reached the stage where the problem regarding the material and surface properties of the product has been solved.

(Problems to be Solved by the Invention) In a process that is being developed as a new process and is premised on obtaining a slab (thin band) having a thickness equal to or close to that of a hot strip by continuous casting, Since the process from casting to product is simplified,
The surface characteristics of stainless steel products will be sensitively affected by the slab properties. That is, in order to obtain a product having excellent surface properties, it is necessary to obtain an excellent slab.

The present invention has been made for the purpose of providing a simple manufacturing process capable of obtaining a Cr-Ni-based stainless steel sheet free from surface defects called uneven luster and roping phenomenon peculiar to stainless steel sheet products.

(Means for Solving the Problems) The features of the present invention are as follows.

(1) The cooling rate during solidification of Cr-Ni stainless steel represented by 18% Cr-8% Ni steel is 100 ℃ / s or more by the continuous casting machine in which the mold wall surface moves in synchronization with the slab. As a continuous casting to a strip-shaped slab having a thickness of 10 mm or less, hot working of 60% or less in a temperature range of 900 ° C. or more is performed, and γ grains are refined to average γ by promoting recrystallization inside the slab. After making the particle size 50 μm or less, cool it in the range of 900 ℃ to 550 ℃ at a cooling rate of 50 ℃ / s or more, and wind it in the temperature range of 650 ℃ or less, and then make a cold rolled sheet by the usual method. A method for manufacturing Cr-Ni stainless steel sheet with excellent surface quality and material.

(2) The cooling rate during solidification of Cr-Ni stainless steel represented by 18% Cr-8% Ni steel is 100 ℃ / s or more by the continuous casting machine in which the mold wall surface moves in synchronization with the slab. As a continuous casting into a strip-shaped slab with a thickness of 10 mm or less, after solidification, start cooling from the high temperature range as much as possible without causing reheating of the slab
The average cooling rate up to 1100 ° C is set to 100 ° C / s or more at the slab surface temperature and the temperature of 900 ° C or more within 10 seconds after casting where there is a temperature difference between the slab surface part and the inside while suppressing the growth of γ grains. After 60% or less hot working in the region, the recrystallization inside the slab is promoted to refine the γ grains of the slab to an average γ grain size of 50 μm or less, and then the range of 900 ℃ to 550 ℃ is 50 Cooled at a cooling rate of ℃ / s or more, wound in the temperature range of 650 ℃ or less, and then cold-rolled by a conventional method. Manufacturing method.

(3) The cooling rate during solidification is 100 ℃ / s or more for Cr-Ni stainless steel represented by 18% Cr-8% Ni steel by a continuous casting machine in which the mold wall surface moves in synchronization with the slab. As a continuous casting to a strip-shaped slab with a thickness of 10 mm or less, δ-Fe.cal
(%) = 3 (Cr + 1.5Si + Mo + Nb + Ti) -2.8 (Ni + 0.5M
n + 0.5Cu) -84 (C + N) -19.8 defined as δ-Fe.c
al (%) is set to -2 to 10% to set the primary crystal of solidification as the δ phase, and the crystallization of the γ phase and the start temperature of transformation are lowered to control the growth of γ grains during the solidification. The average cooling rate up to 1100 ° C by starting the cooling from the highest possible temperature range without causing reheating of the slab and the average slab surface temperature of 100 ° C / s or more γ
There is a temperature difference between the surface of the slab and the inside of the slab, while suppressing the growth of grains. Within 10 seconds after casting, 60% or less hot working is performed in the temperature range of 900 ° C or more to recrystallize the inside of the slab. We proceeded to refine the γ grains of the cast slab to make the average γ grain size 50 μm or less, then 90
Cool in the range of 0 ℃ to 550 ℃ at a cooling rate of 50 ℃ / s or more,
A method for producing a Cr-Ni-based stainless steel sheet having excellent surface quality and material, which is characterized by rolling in a temperature range of 650 ° C or less and then forming a cold-rolled sheet by a conventional method.

(4) The cooling rate during solidification of Cr-Ni stainless steel represented by 18% Cr-8% Ni steel is 100 ℃ / s or more by the continuous casting machine in which the mold wall surface moves in synchronization with the slab. As a continuous casting to a strip-shaped slab with a thickness of 10 mm or less, hot working 60% or less in the temperature range of 900 ℃ or more, then 900 ℃ to 550
After controlling the temperature in the range of ℃ at a cooling rate of 50 ℃ / s or more and winding it in the temperature range of 650 ℃ or less, heat that controls the temperature and time at 950 ℃ or more so that the average γ particle size is 50 μm or less. A method for producing a Cr-Ni-based stainless steel sheet with excellent surface quality and material, characterized by performing annealing of a rolled sheet, then cooling at a cold angular velocity of 10 ° C / s or more, and then forming a cold rolled sheet by a conventional method. .

(5) The cooling rate during solidification of Cr-Ni stainless steel represented by 18% Cr-8% Ni steel is 100 ℃ / s or more by a continuous casting machine in which the mold wall surface moves in synchronization with the slab. As a continuous casting into a strip-shaped slab with a thickness of 10 mm or less, after solidification, start cooling from the high temperature range as much as possible without causing reheating of the slab
The average cooling rate up to 1100 ° C is set to 100 ° C / s or more at the slab surface temperature and the temperature of 900 ° C or more within 10 seconds after casting where there is a temperature difference between the slab surface part and the inside while suppressing the growth of γ grains. After hot working 60% or less in the temperature range, then cooling in the range of 900 ℃ to 550 ℃ at a cooling rate of 50 ℃ / s or more, and winding in the temperature range of 650 ℃ or less The hot rolled sheet is annealed at a temperature of 950 ° C. or higher to suppress the temperature and time to 50 μm or less, then cooled at a cooling rate of 10 ° C./s or higher, and then a cold rolled sheet is prepared by a conventional method. A method for manufacturing Cr-Ni stainless steel sheet with excellent surface quality and material.

(6) The cooling rate during solidification of Cr-Ni stainless steel represented by 18% Cr-8% Ni steel is 100 ℃ / s or more by the continuous casting machine in which the mold wall surface moves in synchronization with the slab. As a continuous casting to a strip-shaped slab with a thickness of 10 mm or less, δ-Fe.cal
(%) = 3 (Cr + 1.5Si + Mo + Nb + Ti) -2.8 (Ni + 0.5M
n + 0.5Cu) -84 (C + N) -19.8 defined as δ-Fe.c
al (%) is set to -2 to 10% to set the primary crystal of solidification as the δ phase, and the crystallization of the γ phase and the start temperature of transformation are lowered to suppress the growth of γ grains during solidification, and after solidification, A slab that suppresses γ grain growth by starting cooling from the highest possible temperature range without causing reheating of the slab and setting the average cooling rate up to 1100 ° C at a slab surface temperature of 100 ° C / s or more Within 10 seconds after casting, where there is a temperature difference between the surface and the inside, 60% or less hot working is performed in the temperature range of 900 ℃ or more, and then the range of 900 ℃ to 550 ℃ is 50 ℃ / s.
After cooling at the above cooling rate and winding in a temperature range of 650 ° C or lower, hot-rolled sheet annealing in which the temperature and time are controlled at 950 ° C or higher so that the average γ grain size is 50 μm or lower, and then 10 ℃
A method for producing a Cr-Ni-based stainless steel sheet having excellent surface quality and material, which is characterized by cooling at a cooling rate of / s or more and then forming a cold-rolled sheet by a conventional method.

The present invention will be described in detail below.

Molten steel containing SUS304 steel as a basic component was cast by an internal water-cooling twin roll (twin drum) continuous casting tester into a ribbon having a thickness of 2 to 4 mm, cooled and wound.

The cast piece (thin band) thus obtained was descaled, then directly cold-rolled, finally annealed, and pickled to obtain a 2B product. The surface texture of these products was obtained by continuously casting molten steel into a slab with a thickness of 100 mm or more, reheating it, hot rolling it with a hot slip mill, and cold rolling. The surface properties of the products were compared and examined in detail.

As a result, molten steel was cast by an internal water-cooled twin roll (twin drum) continuous casting tester into a ribbon of 2 to 4 mm in thickness, which was cooled and wound, followed by descaling and cold rolling, It was found that the following surface defects may occur in the 2B product obtained by final annealing and pickling.

(1) Roping or orange peel ... Fine irregularities are generated on the surface during cold rolling or during product processing.

(2) Uneven gloss: Uneven luster occurs due to sensitization of the structure of the material during winding of the cast slab (thin band), oxidation of grain boundaries or coarsening of γ grains.

The problem regarding the surface texture of these products is a process-specific problem that includes a process of directly obtaining a thin ingot (strip) by continuous casting, which is not found in a conventional process.

The inventors, as a result of detailed examination of the causes of these surface defects, when the γ grain size of the material before cold rolling is large, or when the cooling of the Cr carbide precipitation temperature range of the slab is insufficient, these It was clarified that the surface defects are remarkable.

Thus, as a roping measure, the γ grain size of the material before cold rolling is set to a grain size No. 6 or more, that is, 50 μm or less, and as a measure for uneven gloss, control the cooling of the slab in the high temperature range. Have found that it is desirable when taking a process including a process of directly obtaining a thin slab by continuous casting.

Hereinafter, these measures will be described in detail.

As a material for cold rolling, there are various ideas as follows as means for making the material having a γ particle diameter of 50 μm or less. That is, 1) reduce the γ grain of the thin slab itself, 2) subject the thin slab to hot work following casting to recrystallize the fine grain, 3) cold work the thin slab, Annealing to recrystallize the grains, and so on. Of course, 1), 2) and 3) are also effective respectively, but it has been found that the combination of 1), 2) and 3) significantly increases the effect.

In the present invention, in particular, both of the above-mentioned 1) reducing the γ grains of the thin slab itself, and 2) subjecting the thin slab to hot working subsequent to casting to recrystallize the fine slab are used. It is configured to prevent roping that occurs on the surface of a stainless steel thin plate, and also to obtain a product with excellent surface properties without uneven surface gloss.

First, when obtaining a thin cast piece by a continuous casting process in which the mold wall surface moves in synchronization with the cast piece, such as a twin roll (twin drum) method, in order to reduce the γ grain of the thin cast piece,
It is important to reduce the γ grains in the slab from the time of generation and to cool the slab from a high temperature range in order to suppress subsequent growth. In addition, it is important to hot-roll the slab immediately after casting and recrystallize it to refine the γ grains.

According to such an idea, the inventors have
18Cr-8Ni steel is cast by a small twin-roll continuous casting machine in a laboratory, and the conditions of quenching immediately after casting, hot rolling, and cold rolling are changed to produce a stainless steel thin plate, and the surface texture of the product, in particular, The prevention method was investigated by paying attention to roping which causes undulations on the surface. As a result, as described above, it became clear that it is desirable that the γ grain size of the material before cold rolling is 6 or more, that is, 50 μm or less in the average grain size No. of the γ grain. It was

FIG. 1 shows the temperature history of the slab until the molten steel is continuously cast by the twin roll method and wound up.

In FIG. 1, the case (3) is the case where the material is air-cooled after being cast, and in the casting machine, the material is rapidly cooled by the casting drum, but when it leaves the casting machine, it reheats and rises in temperature to cool from directly below the drum. Cooling is slower than in the case of not performing it, and if wound as it is, the growth of γ grains will proceed during cooling after winding, and sensitization by Cr carbide precipitation during roping and cooling, surface characteristics due to grain boundary oxidation The above problem occurs.

In FIG. 1, case (1) is hot-rolled after casting,
This is a product in which the slab is recrystallized to make the γ grains fine, and a process of quenching after hot rolling to prevent sensitization due to precipitation of Cr carbide is shown.

Similarly, in case (2), in order to further reduce the grain size of the slab from case (1), rapid cooling is performed after casting and then hot working is performed, and the γ grains after casting become finer than in case (1). Therefore, when hot rolling recrystallization is performed, very fine γ grains can be obtained, and after hot rolling, a quenching process is shown to prevent sensitization due to precipitation of Cr carbide.

In addition, when hot working is performed, recrystallization may not occur sufficiently and a partially processed microstructure may occur. In this case, it was also clarified that the hot rolled sheet was annealed and recrystallized sufficiently to obtain a product having excellent surface characteristics.

Further, in addition to the control of cooling and hot rolling, fine adjustment of the alloy composition of the starting material is also effective.

Figure 2 shows Cr eq in the equilibrium diagram of the Fe-Cr-Ni ternary system.
+ Ni eq ≈ 30% cross-sectional state diagram corresponding to
It is quoted from action of JWRI, Vol.14, No.1,1985, p.125. Cr eq and Ni eq are calculated from the components as follows.

Cr eq ＝ Cr (%) ＋ 1.5 × Si (%) ＋ Mo (%) ＋ Nb (%) ＋ Ti (%) Ni eq ＝ Ni (%) ＋ 1/2 (Mn (%) ＋ Cu (%)) ＋ 30 (C (%) ＋ N (%)) First, Cr eq is small (Cr eq = 17.3%), and the primary crystal γ
It solidifies and is in the complete γ phase. In this case, the γ phase crystallizes at a high temperature just below the liquidus line and grows thereafter.

On the other hand, when Cr eq becomes large and Cr eq = 19.5% () or more, the primary crystal completes solidification in the δ phase and a solid-phase reaction occurs.
The γ phase begins to precipitate from 1370 ° C., and the growth starts thereafter, but the growth of γ grains is greatly suppressed compared to the case where Cr eq is small as described above. This is fully considered because the high temperature region immediately after casting controls the growth of γ grains.

When Cr eq is in the middle of the two, peritectic reaction is added and it becomes complicated, but in order to suppress the growth of γ grains, a component system that solidifies the δ phase is advantageous, and high temperature It is effective to quench the material in the area. Further, the effect of the δ-phase solidification is that the δ-phase hinders the growth of γ grains even in the solid phase reaction. As a result of experimenting the effect based on such a component system, δ-Fe.cal (%) = 3 (Cr + 1.5Si + Mo + Nb + Ni) -2.8 (Ni + 1 / 2Mn + 1 / 2Cu) -84 (C + N) -19.8 (%) It was found that it is effective to set the δ-Fe.cal (%) to be -2% to 10%. In particular, δ-Fe.cal
(%): 1 to 5% is good.

FIGS. 3 (a) to 3 (c) show a comparison of the microstructures of molten steels of various compositions with various .delta.-Fe.cal (%) continuously cast into 2 mm thick slabs. From Fig. 3, δ-Fe.cal
It can be seen that when the (%) is -2.3%, the γ grains grow due to the γ phase solidification.

When the δ-Fe.cal (%) is -1.1%, the δ ferrite remains and the γ grains are small. δ-Fe.cal (%))
Of 3.0% is clearly δ phase solidification, and γ grains remain extremely small.

Thus, in combination with the grain refining utilizing the cooling control and hot rolling of the slab described above, the selection of the composition in the Cr-Ni stainless steel greatly affects the refinement of the γ grains. , Δ−
To control Fe.cal (%) to -2% or more and 10% or less,
Extremely important.

Fig. 4 shows the reduction rate when hot rolling was performed at 1100 ° C on the slab cooled to δ-Fe.cal (%) of about 1%, and then descaling and cold rolling. It shows how the rolling reduction influences the roping height of the product surface.

As shown in FIG. 4, the rolling reduction of 20% in hot rolling has an effect. The higher the rolling reduction is, the lower the roping height of the product becomes, and the "waviness" of the surface is not observed.

Recrystallization was observed inside the slab at a reduction of 20% or more in hot rolling, and almost complete recrystallization at 30% or more. Thus, the average grain size of the γ grains was 50 μm or less.

Further, the δ-Fe.cal (%) is set to about 3%, the slab is cooled immediately below the twin rolls (cooling drum), and there is a temperature difference between the surface layer of the slab and the inside, and hot rolling is performed. When it was carried out, good roping characteristics were obtained even when the rolling reduction was about 10%. It can be seen that the amount of δ and the effect of cooling the slab just below the twin rolls (cooling drum) are large.

Next, the reasons for limiting the constituent features of the present invention will be described.

Regarding molten steel components, C: 0.01 to 0.08%, Si: 0.25 to 1.50
%, Mn: 0.15-3.0%, P: 0.015-0.040%, S: 0.001-0.0
08%, Cr: 16.0 to 28.0%, Ni: 6.0 to 24.0%, N: 0.015 to 0.
33%, Al: 0.001-0.050%, Mo: 0.01-3.0%, Cu: 0.01-
2.0%, Ti: 0.01 to 0.60%, Nb: 0.01 to 0.80%, balance: Fe and δ-F in the composition range consisting of inevitable impurities.
It is necessary to control e.cal (%) in the range of -2% to 10%, that is, to perform δ phase solidification. δ-Fe.cal
If the (%) exceeds 10%, the δ phase remains in the product, which is not preferable in terms of material.

On the other hand, if the thickness of the slab exceeds 10 mm, it becomes difficult to refine the γ grains, and if strong hot working is performed to refine the γ grains, the rolling mill becomes enormous, which is not practical.

Cooling of the slab after casting is performed by suppressing reheating of the slab at the exit of the casting machine and increasing the average cooling rate in the γ grain growth temperature range up to 1100 ° C to 100 ° C / s or higher as much as possible. And is effective.

Hot rolling is performed in a region where the surface temperature of the slab is 900 ° C or higher, and promotes recrystallization inside the slab. Especially, 60% when the inside of the slab is in a high temperature range (within 10 seconds after casting)
It is sufficient to subject the slab to hot rolling in which the following reduction ratios are applied. The effect is saturated even if a rolling reduction of more than 60% is applied. On the other hand, at a timing that exceeds 10 seconds after casting, the temperature difference between the surface layer portion and the inside of the cast slab becomes small, and the effect of refining γ grains is significantly diminished.

After that, the slab is 50 ℃ / s in the temperature range of 900 ~ 550 ℃.
After being cooled at the above cooling rate, it is wound up at 650 ° C or lower. If these conditions are not met, carbides will precipitate at the grain boundaries, causing intergranular corrosion when the material is pickled and impairing the surface gloss of the product.

The hot-rolled sheet annealing is performed at a temperature of 950 ° C. or higher to promote recrystallization. In particular, the temperature and time are controlled and annealing is performed so that the average γ grain size does not exceed 50 μm. On the other hand, cooling after hot-rolled sheet annealing is because δ-Fe decreases during annealing from the slab stage,
Since the precipitation of Cr carbide precipitated at the / γ interface is delayed, and as a result, it can be slower than the cooling of the slab and the hot rolled sheet, the cooling rate in the Cr carbide precipitation region was set to 10 ° C / s or more.

(Example) Example 1 C of various components based on 18Cr-8Ni steel shown in Table 1
r-Ni stainless steel was melted. According to the relation of δ−Fe.cal (%) = 3 (Cr + 1.5Si + Mo + Nb + Ti) −2.8 (Ni + 1 / 2Mn + 1 / 2Cu) −84 (C + N) -19.8 (%), the first phase of solidification should be δ phase. As shown in Table 2, δ-Fe.cal
(%) Was changed from -3.55% to 7.81%. These molten steels were cast into slabs of various thicknesses between 1.6 and 7.5 mm by an internal water-cooled vertical twin roll continuous casting machine.
Roll cooling and water spray cooling were applied from directly below the casting machine to cool the slab and prevent recuperation. The average cooling rate of over 120 ℃ / s was obtained in the temperature range of 1300〜1100 ℃.

Then, the slab was hot-rolled within a temperature range of 1100 to 950 ° C. within 8 seconds after casting. The rolling reduction at this time was between about 10% and about 50% (Table 2). After that, the slab is cooled between 900 and 550 ℃ at a cooling rate of 60 ℃ / s or more,
It was wound up at 0 ° C or lower.

The comparative material was insufficiently cooled between 900 and 550 ° C, and some of the comparative materials were wound at a high temperature of about 750 ° C.

After that, the material was pickled, descaled, cold-rolled, and then bright-annealed in the usual annealing region.

The surface properties of the products thus obtained were investigated. Particular attention was paid to the roping height and gloss of the product surface. As shown in Table 2, in the example shown in the present example, δ ferrite was utilized to lower the temperature of crystallization and precipitation of the γ phase in the slab, thereby cooling and heat the slab thereafter. In addition to the effect of hot rolling, all of them showed excellent surface properties.

On the other hand, in the comparative method, the effect of δ-ferrite was not obtained, the slab was insufficiently cooled, and the winding temperature was high. As a result, the product surface had a large roping and the surface gloss was poor.

(Advantages of the Invention) Since the present invention is configured and operated as described above, a simple process for directly obtaining a thin ribbon having a thickness close to the product thickness by continuous casting, It is possible to obtain a Cr-Ni-based stainless steel sheet with excellent material.

[Brief description of drawings]

Fig. 1 shows Cr-using a twin roll (water cooling) type continuous casting machine.
Temperature of ribbon when casting Ni-based stainless steel ribbon
Fig. 2 is a diagram showing a time relationship, Fig. 2 is a sectional state diagram of a portion corresponding to Cr eq + Ni eq ≈ 30% in the Fe-Cr-Ni ternary system equilibrium state diagram,
FIGS. 3 (a) to 3 (c) are metal micrographs showing a comparison of the structures of molten steels of various component types with various δ-Fe.cal (%) continuously cast into 2 mm thick slabs. , FIG. 4 shows δ−
Fe.cal (%) to about 1% and cast and cooled,
It is a figure which shows the influence which the rolling reduction at the time of hot-rolling at 1100 degreeC, and the rolling reduction at the time of performing descaling and cold rolling after that on the roping height of a product surface.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Suehiro 3434 Shimada, Hikari City, Yamaguchi Pref. Nippon Steel Co., Ltd. Inside the Hikari Works, Ltd. (56) JP-A-60-224715 (JP, A) JP-A-60-255921 (JP, A) JP-B-63-27407 (JP, B2)

Claims (6)

[Claims] Claims: 1. A Cr-Ni type stainless steel represented by 18% Cr-8% Ni steel is cooled by a continuous casting machine in which the wall surface of the mold moves in synchronism with the slab and the cooling rate during solidification is 100 ° C / s or more continuously cast into a thin strip-shaped slab having a thickness of 10 mm or less, and hot-worked at 60% or less in a temperature range of 900 ° C. or more, and promotes recrystallization inside the slab to refine γ grains. After setting the average γ grain size to 50 μm or less, cool it in the range of 900 ° C to 550 ° C at a cooling rate of 50 ° C / s or more, wind it in the temperature range of 650 ° C or less, and then form a cold rolled sheet by a conventional method. A method of manufacturing Cr-Ni-based stainless steel sheet with excellent surface quality and material. 2. A Cr-Ni type stainless steel represented by 18% Cr-8% Ni steel is cooled by a continuous casting machine in which the wall surface of the mold moves in synchronism with the slab and the cooling rate during solidification is 100 ° C. / Continuously cast into a strip-shaped slab having a thickness of 10 mm or less as s or more, and after solidification, the average cooling rate up to 1100 ° C. is started by cooling from the high temperature region without causing reheat of the slab. 100 ° C / at surface temperature
s or more, while suppressing the growth of γ grains, there is a temperature difference between the surface and the inside of the slab. Within 10 seconds after casting, 60% or less hot working is performed in the temperature range of 900 ° C or more, After refining the γ grains of the slab to make the average γ grain size 50 μm or less, cool it in the range of 900 ° C to 550 ° C at a cooling rate of 50 ° C / s or more, A method for producing a Cr-Ni-based stainless steel sheet having excellent surface quality and material, which is characterized by winding in a zone and then forming a cold-rolled sheet by a conventional method. 3. A continuous casting machine in which a Cr-Ni-based stainless steel typified by 18% Cr-8% Ni steel moves in synchronization with a slab, and the cooling rate during solidification is 100 ° C. / s-Fe.cal
(%)-3 (Cr + 1.5Si + Mo + Nb + Ti) -2.8 (Ni + 0.5M
n + 0.5Cu) -84 (C + N) -19.8 defined as δ-Fe.c
al (%) is set to -2 to 10% to set the primary crystal of solidification as the δ phase, and the crystallization of the γ phase and the start temperature of transformation are lowered to suppress the growth of γ grains during solidification, and after solidification, The average cooling rate up to 1100 ° C by starting the cooling from the highest possible temperature range without causing reheat of the slab and the average slab surface temperature of 100 ° C / s or more γ
There is a temperature difference between the surface of the slab and the inside of the slab, while suppressing the growth of grains. Within 10 seconds after casting, 60% or less hot working is performed in the temperature range of 900 ° C or more to recrystallize the inside of the slab. We proceeded to refine the γ grains of the cast slab to make the average γ grain size 50 μm or less, then 90
Cool in the range of 0 ℃ to 550 ℃ at a cooling rate of 50 ℃ / s or more,
A method for producing a Cr-Ni-based stainless steel sheet having excellent surface quality and material, which is characterized by rolling in a temperature range of 650 ° C or less and then forming a cold-rolled sheet by a conventional method. 4. A continuous casting machine in which a Cr-Ni-based stainless steel typified by 18% Cr-8% Ni steel moves in synchronization with a slab, and the cooling rate during solidification is 100 ° C. / s or more, it is continuously cast into a strip-shaped slab with a thickness of 10 mm or less, hot-worked at 60% or less in a temperature range of 900 ℃ or more, and then cooled in the range of 900 ℃ to 550 ℃ to 50 ℃ / s or more. Cooling at speed, 650 ℃
After winding in the following temperature range, hot-rolled sheet annealing that controls the temperature and time at 950 ° C or higher is performed so that the average γ grain size is 50 μm or less, and then cooled at a cooling rate of 10 ° C / s or higher. A method for producing a Cr-Ni-based stainless steel sheet having excellent surface quality and material, which is characterized by forming a cold-rolled sheet by a conventional method. 5. A cooling machine for solidifying the cooling rate of Cr-Ni stainless steel typified by 18% Cr-8% Ni steel by a continuous casting machine in which the wall surface of the mold moves in synchronization with the slab. Continuously cast into a strip-shaped slab having a thickness of 10 mm or less as s or more, and after solidification, the average cooling rate up to 1100 ° C. is started by cooling from the high temperature region without causing reheat of the slab. 100 ° C / at surface temperature of slab
s or more, while suppressing the growth of γ grains, there is a temperature difference between the surface and the inside of the slab. Within 10 seconds after casting, 60% or less hot working is performed in the temperature range of 900 ° C or more, and then 900 ° C. From 5
After cooling the range of 50 ℃ at a cooling rate of 50 ℃ / s or higher, and winding it in the temperature range of 650 ℃ or lower, control the temperature and time at 950 ℃ or higher so that the average γ particle size becomes 50μm or lower. Manufacture of Cr-Ni-based stainless steel sheet with excellent surface quality and material, which is characterized by performing hot-rolled sheet annealing, then cooling at a cooling rate of 10 ° C / s or more, and then forming a cold-rolled sheet by a conventional method. Law. 6. A continuous casting machine in which a Cr-Ni-based stainless steel typified by 18% Cr-8% Ni steel moves in synchronization with a slab, and the cooling rate during solidification is 100 ° C. / s-Fe.cal
(%) = 3 (Cr + 1.5Si + Mo + Nb + Ti) -2.8 (Ni + 0.5M
n + 0.5Cu) -84 (C + N) -19.8 defined as δ-Fe.c
al (%) is set to -2 to 10% to set the primary crystal of solidification as the δ phase, and the crystallization of the γ phase and the start temperature of transformation are lowered to suppress the growth of γ grains during solidification, and after solidification, The average cooling rate up to 1100 ° C by starting the cooling from the highest possible temperature range without causing reheat of the slab and the average slab surface temperature of 100 ° C / s or more γ
There is a temperature difference between the surface of the slab and the inside of the slab while suppressing grain growth. Within 10 seconds after casting, 60% or less hot working is performed in a temperature range of 900 ° C or higher, then in the range of 900 ° C to 550 ° C. To 50 ° C
After cooling at a cooling rate of / s or more and winding in a temperature range of 650 ° C or less, hot-rolled sheet annealing is performed to control the temperature and time at 950 ° C or more so that the average γ grain size is 50 μm or less, Then 10
A method for producing a Cr-Ni-based stainless steel sheet having excellent surface quality and material, which is characterized by cooling at a cooling rate of ℃ / s or more and then forming a cold-rolled sheet by a conventional method.