JPH02133528A - Production of cr-ni stainless steel sheet having excellent surface quality and material quality - Google Patents

Abstract

PURPOSE:To produce the title stainless steel sheet having excellent surface quality and material quality with the simple process by continuously casting a Cr-Ni stainless steel to a thin strip-like ingot under specific conditions, then subjecting the ingot to hot working to form the finer recrystal grains, coiling the ingot after cooling and subjecting the same to cold rolling. CONSTITUTION:The Cr-Ni stainless steel represented by 18% Cr-8% Ni steel is continu ously cast to the thin strip-like ingot having <=10mm thickness by a continuous casting machine in which the wall surfaces of the casting mold moves in synchronization with the ingot while the cooling rate at the time of solidifying is kept at >=100 deg.C/sec, by which the smaller gamma grains are formed. The ingot is then subjected to <=60% hot rolling in a >=900 deg.C temp. region to accelerate the recrystallization in the ingot and to form the finer gamma grains until <=50mu average gamma grain size is attained. The ingot is further cooled at >=50 deg.C/sec cooling rate in a 900 to 500 deg.C range and after the ingot is coiled in a <=650 deg.C temp. region, the ingot is made into a cold rolled sheet by the conventional method. The finer structure is formed in this way and the Cr-Ni stainless steel sheet having the excellent surface quality and the material quality is obtd. in this way.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention uses a so-called synchronous continuous casting process in which there is no relative speed difference between the slab and the inner wall surface of the mold, so that the thickness of the slab can be reduced to a size close to the product thickness. The present invention relates to a method for manufacturing a Cr-Ni stainless steel sheet having excellent surface quality and material quality by refining the structure from the slab stage.

(Conventional technology) Conventionally, in order to manufacture stainless steel thin plates using the continuous casting method, the mold is vibrated in the casting direction and the thickness is 100 mm.
V on the above slab? The obtained slab is surface-treated, heated to 1,000°C or higher in a heating furnace, and then hot-rolled in a hot string mill consisting of a rough rolling mill and two finishing mill rows. It was a hot strip of several mm.

When cold rolling the hot strip obtained in this way, the shape (flatness), material, and
In order to secure the surface quality, hot-rolled sheets were annealed to soften the Honstrip, which had undergone intense hot processing, and surface sgale and the like were removed by grinding after the pickling process.

This conventional process requires a large amount of energy to heat and process the material in a long hot rolling facility, and cannot be said to be an excellent manufacturing process in terms of productivity. Also, the highest 8! The product is manufactured from cast slabs with a thickness of 100 mm or more, which undergoes many processes, so it is difficult to assemble.
With the development of textiles, there were many restrictions on use, such as the need to consider the anisotropy when applying press processing etc. to the product by the user.

Recently, in order to solve the problem that rolling slabs with a thickness of 100 mm or more into flat strips requires a long hot rolling facility and a large amount of energy and rolling power, a continuous rolling method has been recently developed. Research is underway on a process for obtaining slabs (thin strips) with a thickness equal to or close to that of hot strips during the casting process.

For example, "Tetsu to Hagane J'85, A197~'85, A2
The article featured in 56 discloses a process for obtaining hot strip directly by continuous casting. In such a continuous casting process, the twin drum method is used when the gauge of the strip to be obtained is 1 to 10 mm, and the twin drum method is used when the gauge of the strip to be obtained is 20 to B. A twin belt system is currently being considered.

However, in these continuous casting processes, there are still problems at the casting stage, and the problems regarding the material and surface quality of the product have not yet been resolved.

(Problem to be solved by the invention) In the tossle process, which is being developed as a new process, it is assumed that a slab (thin ribbon) having a thickness equal to or close to that of hot strip is obtained by continuous casting. In order to simplify the process from casting to products,
The surface properties of stainless steel FA products are sensitively affected by the properties of the slab. That is, in order to obtain a product with excellent surface properties, it is necessary to obtain an excellent slab.

The present invention has been made with the object of providing a simple manufacturing process capable of obtaining a Cr--Ni stainless steel thin plate free of surface defects called uneven gloss and roving phenomenon that are characteristic of stainless steel thin plate products.

(Means for solving problems) The features of the present invention are as follows.

(1) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/S during solidification.
As described above, a thin strip-shaped slab with a thickness of 10 m+n or less is continuously cast, and hot worked at a temperature of 900°C or higher to a depth of 60% or less to promote recrystallization inside the slab and refine each grain. After reducing the average γ grain size to 50 μm or less before cold rolling,
The surface quality and material are characterized by being cooled at a cooling rate of 50°C/s or more in the range from 0"C to 550°C, coiled in a temperature range of 650°C or less, and then made into a cold rolled sheet by a conventional method. Excellent Cr-
A method for manufacturing Ni-based thin stainless steel sheets.

(2) Cr-N represented by 18%Cr-8%Ni1i
I-series stainless steel is cooled at a cooling rate of 100°C/100°C during solidification using a continuous casting machine in which the mold wall moves in synchronization with the slab.
Continuously cast into thin strip slabs with jI of 10 mm or less, and after solidification, start cooling from the high temperature range as much as possible without causing reheating of the slab, and average cooling rate up to 1100 ° C. The slab surface temperature is set at 100 °C/S or higher to suppress the growth of γ grains, and the temperature difference between the surface and the inside of the slab is 60% or lower within 10 seconds after casting in a temperature range of 900 °C or higher. Performing machining to promote recrystallization inside the slab and improve the T of the slab.
After refining the grains so that the average grain size before cold rolling is 50 μm or less, the grains are rolled at 50”C/
A method for producing a Cr-Ni stainless thin steel sheet with excellent surface quality and material quality, characterized by cooling at a cooling rate of s or more, coiling at a temperature of 650°C or less, and then forming a cold-rolled sheet by a conventional method. .

(3) Cr − represented by 18%Cr-8%N1fi
A continuous casting machine in which the mold wall moves in synchronization with the slab is used to reduce the cooling rate of Ni-based stainless steel to 100% during solidification.
℃/s or more into a thin strip slab with a thickness of 10 mm or less, δ-Fe, cal (χ) = 3 (Cr + 1.5
Si+Mo+Nb+Ti) 2.8(Ni+0.5M
n+0.5Cu) 84(C+N)-19,8 δ-Fe, cal(χ) is set to -2 to 10%, the primary crystal of solidification becomes the δ phase, and the crystallization and transformation of the γ phase starts. The growth of γ grains during solidification is suppressed by lowering the temperature, and after solidification, cooling is started from as high a temperature as possible without causing reheating of the slab, and the average cooling rate is increased to 1100℃. Hot heating of 60% or less in a temperature range of 900°C or higher within 10 seconds after casting where there is a temperature difference between the surface and inside of the slab while suppressing the growth of γ grains by setting the slab surface temperature to 100°C/s or higher. Processing is performed to advance recrystallization inside the slab to refine each grain of the slab so that the average grain size before cold rolling is 50 μm or less, 9
It has excellent surface quality and material quality, as it is cooled at a cooling rate of 50°C/s or more in the range from 00°C to 550°C, rolled up in a temperature range of 650°C or less, and then made into a cold-rolled sheet by a conventional method. A method for manufacturing a Cr-Ni stainless thin steel sheet.

(4) Cr- represented by 18%Cr-8%Ni1jl
Ni-based stainless steel is cooled at a cooling rate of 100°C during solidification using a continuous casting machine in which the mold wall moves in synchronization with the slab.
/s or more into thin strip-shaped slabs with a thickness of 10 mm or less, subjected to hot working of 60% or less in a temperature range of 900 ℃ or higher, and then 50 '' in a temperature range of 900 '' to 550 ℃.
After cooling at a cooling rate of C/s or higher and coiling in a temperature range of 650°C or lower, hot-rolled sheet annealing is performed at 950°C or higher with controlled temperature and time so that the average γ grain size is 50tIm or lower. A method for producing a Cr-Ni stainless thin steel sheet with excellent surface quality and material quality, characterized by cooling at a cooling rate of 10° C./S or more and then forming a cold-rolled sheet by a conventional method.

(5) Cr-N represented by 18%Cr-8%NiwA
I-series stainless steel is cooled at a cooling rate of 100°C/100°C during solidification using a continuous casting machine in which the mold wall moves in synchronization with the slab.
Continuously cast into thin strip slabs with a thickness of 10 mm or less as s or more, and after solidification, start cooling from the high temperature range as possible without causing reheating of the 51 pieces, and average cooling rate up to 1100"C. The surface temperature of the slab is set at 100℃/S or higher to suppress the growth of γ grains, and the temperature difference between the surface and the inside of the slab exists within 10 seconds after casting. Temperature processing is performed, and then the temperature range from 900°C to 550°C is
After cooling at a cooling rate of 0"C/s or higher and coiling at a temperature range of 650°C or lower, hot-rolled sheet annealing is performed by controlling temperature and time at 950°C or higher so that the average grain size is 50 μm or lower. A method for producing a Cr-Ni stainless thin steel sheet with excellent surface quality and material quality, characterized by subjecting the sheet to cold rolling, followed by cooling at a cooling rate of 10° C./s or more, and then forming a cold-rolled sheet by a conventional method.

(6) Using a continuous casting machine in which the mold wall surface moves in synchronization with the slab, Cr-old stainless steel, such as 18% Cr-8% Ni steel, is cooled at a cooling rate of 100°C/S or more during solidification. Continuously cast into thin strip slabs with a thickness of 10 mm or less,
δ-Fe, cal(χ)=3(Cr+1.5Si+Mo
+Nb+Ti) 2.8(Ni+0.5Mn+0.5
Cu) −84(C+N)−δ− defined as −19,8
By setting Fe, cal (χ) to -2 to 10%, the primary crystals for solidification are made into 6 phases, and the starting temperature for crystallization and transformation of the γ phase is lowered to suppress the growth of a single grain in the middle of solidification. After that, without causing reheating of the slab, start cooling from the high temperature range as possible, and increase the average cooling rate to 1100°C by 10% at the slab surface temperature.
900°C within 10 seconds after casting when there is a temperature difference between the surface and the inside of the slab while suppressing the growth of γ grains at 0°C/S or higher.
After hot working at a temperature of 60% or less in a temperature range of 650°C or higher, cooling at a cooling rate of 50°C/S or higher from 900°C to 550°C, and winding in a temperature range of 650°C or lower, the average Hot-rolled plate annealing is carried out at 950°C or higher, controlling the temperature and time so that the grain size is 50 μm or less, and then annealing is performed at 10°C/s.
Cr-Ni with excellent surface quality and tensile quality characterized by being cooled at the above cooling rate and then made into a cold rolled sheet by a conventional method.
A method for manufacturing stainless steel FilJ steel sheets.

The present invention will be explained in detail below.

Molten steel containing 5US304 steel as a basic component was cast into a thin ribbon with a thickness of 2 to 4 mm using an internal water-cooled twin-roll (twin-drum) continuous casting machine, which was cooled and wound up.

The thus obtained slab (thin ribbon) was descaled, directly cold rolled, finally annealed, and pickled to obtain a 2B product. The surface quality of these products can be improved by conventional continuous casting of molten steel into slabs with a thickness of 100 mm or more, which are then reheated and hot rolled using a hot strip mill.
A detailed comparison was made with the surface properties of products obtained by cold rolling.

As a result, the molten steel was cast into a thin strip with a thickness of 2 to 4 bars using an internal water-cooled twin-roll (twin-drum) continuous casting machine, which was then cooled and wound, which was then descaled and cold-rolled. It has been found that the following surface defects may occur in 2B products that have been subjected to final annealing and pickling.

(1) Roving and orange beer: Fine irregularities occur on the surface during cold rolling or product processing.

(2) Unevenness in gloss: Unevenness in gloss occurs due to the sensitization of the structure of the material during winding of the slab (thin ribbon), grain boundary oxidation, or coarsening of γ grains.

Problems regarding the surface properties of these products are unique to the process, which does not occur in conventional processes, and involves the process of obtaining thin slabs (thin strips) directly by continuous casting.

The inventors examined the causes of these surface defects in detail (■) and found that they occur when the γ grain size of the material before cold rolling is large or when the slab is insufficiently cooled in the Cr carbide precipitation temperature range. We found that these surface defects occur significantly.

Thus, as a countermeasure against roving, it is necessary to set the grain size of the material before cold rolling to a grain size number of 6 or more, that is, 50 μm or less, and as a countermeasure against gloss unevenness, it is necessary to control the cooling of the slab in the high temperature range. However, it has been shown that it is desirable to employ a process that involves obtaining thin slabs directly by continuous casting.

Below, these measures will be explained in detail.

There are various ways of thinking as follows as a means of making a material for cold rolling with a grain size of 50 μm or less. In other words, 1) reducing the size of each grain of the thin slab itself, 2) hot working the thin slab after casting to recrystallize it into fine grains, 3) cold working the thin slab. , annealing and recrystallization to make the grain finer. Of course, each of 1), 2), and 3) is effective alone, but it has been found that the effect is significantly greater when 1), 2), and 3) are combined with each other.

In the present invention, in particular, the following two methods are used: 1) reducing the size of each grain of the thin slab itself; and 2) hot working the thin slab after casting to recrystallize it to fine grains. The structure is designed to prevent roving from occurring on the surface of the stainless steel fiEl plate, and to obtain a product with excellent surface properties without uneven surface gloss.

First, when obtaining thin slabs by a continuous casting process such as the twin roll (twin drum) method in which the mold wall surface moves in synchronization with the slab, in order to make each grain of TR51 piece smaller, the slab It is important to reduce the size of a single grain from the time of its formation and to cool the slab from a high temperature range in order to suppress subsequent growth. It is also important to hot-roll the slab immediately after casting and recrystallize it to make each grain finer.

Following this idea, the inventors cast 18Cr aNi steels of various compositions using a small twin-roll continuous casting machine in the laboratory, and varied the conditions immediately after casting, cold and hot rolling, and cold rolling. We manufactured thin stainless steel plates and investigated ways to prevent roving, focusing on the surface properties of the product, especially roving. As a result, as mentioned earlier, the γ grain size of the material before cold rolling was changed to the average grain size N
It has become clear that it is desirable to have a particle size of 6 or more, that is, 50 or less.

Figure 1 shows the temperature history of a slab from continuous casting of molten steel to rolling up by the twin roll method.

In Figure 1, case (3) is a case in which the material is air-cooled after casting.In the casting machine, the material is rapidly cooled by the casting drum, but when it leaves the casting machine, it regenerates and rises in temperature. Cooling is slower than when no cooling is performed, and if the winding is continued as it is, the growth of γ grains will progress during cooling after winding, resulting in roving, sensitization due to Cr carbide precipitation during cooling, and grain boundary oxidation. Problems arise in terms of surface properties.

In Figure 1, case (1) is hot rolled after casting.
It is made by recrystallizing a cast slab to make each grain finer, and shows the process of rapid cooling after hot rolling to prevent sensitization due to precipitation of Cr carbides.

Similarly, in case (2), in order to make the slab grain finer than in case (1), the cylinder is cooled after casting and then hot worked, and each grain after casting is finer than in case (1). Therefore, when hot-rolling recrystallization is performed, very fine grains can be obtained, and this shows the process of cooling after hot rolling to prevent sensitization due to precipitation of Cr carbides. .

Further, when hot working is performed, recrystallization may not occur sufficiently and a partially processed structure may be formed. In this case, it has also become clear that a product with excellent surface properties can be obtained by annealing the hot rolled sheet and sufficiently promoting recrystallization.

Furthermore, in addition to the cooling control and hot rolling described above, delicate adjustment of the alloy composition of the starting material is also effective.

FIG. 2 is a cross-sectional phase diagram of a portion corresponding to Creq + N1eq #30% in the equilibrium phase diagram of the Fe Cr Ni ternary system, as described in the literature Transaction of Jf
4R1, Vo! , 14. No. I, 1985゜p, 12
This is quoted from 5. Creq and N1eq are calculated from the components as follows.

Cr eq −Cr (χ) +1.5XSi(X)
+Mo(χ)+Nb(χ) 10Ti(χ)Nieq=Ni
(χ) + 1/2 (Mn (χ)+Cu(χ))+
30(C(χ)×N(χ)) First, Creq is small (
■Creq=17.3χ), solidified with primary γ, and is a 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, Creq increases, and Creq = 19.5
When χ (■) or more, the primary crystals complete solidification in the δ phase,
As a solid phase reaction, the γ phase begins to precipitate at about 1370° C. and then begins to grow, but compared to the case where Creq is small, the growth of γ grains is greatly suppressed. This is entirely conceivable since the high temperature region immediately after casting dominates the growth of a single grain.

When Creq is between the above three, the peritectic reaction is added and the situation becomes complicated, but in order to suppress the growth of a single grain, it is advantageous to have a composition system that solidifies the δ phase. It is effective to rapidly cool the material. Furthermore, the effect of δ-phase solidification is that the δ-phase obstructs the growth of a single grain even in a solid-phase reaction. As a result of experimenting with effects based on the component system, we found that δ-Fe, cal(χ)=3(Cr+1.5
Si + Mo + Nb + Ti) -2,8 (Ni + 1/2
Mn+1/2Cu) 84(C+N) 19.8(
δ-Fe. It has been found that it is effective to set cal (χ) to -2% or more and up to 10%. In particular, δ-Fe. cal(χ): 1 to 5% is good.

FIGS. 3(a) to 3(c) show a comparison of the microstructures of slabs having a thickness of 2 mm by continuous casting of molten steel with various compositions of δ-Fe and cal(χ). From Figure 3, δ−F
It can be seen that in the case where e, cal (χ) is −2.3%, γ grains grow due to γ phase solidification.

In the case where δ-Fe and cal(χ) are -1.1%, δ ferrite remains and one grain is small. δ-Fe,
In the case where cal(χ)) is 3.0%, the solidification is clearly in the δ phase, and the γ grains remain extremely small.

In this way, in conjunction with the aforementioned grain refinement using slab cooling control and hot rolling, the composition selection of Cr-Ni stainless steel has a large effect on the refinement of each grain. ,
It is extremely important to control δ-Fe, cal(χ) to -2% or more and 10% or less.

Figure 4 shows the reduction ratio when a slab cooled with δ-Fe, cal (χ) of about 1% is hot rolled at 1100°C, and then descaled and cold rolled. This shows how the rolling reduction affects the roving height on the product surface.

From FIG. 4, the influence appears from the reduction ratio of 20% in hot rolling, and as the reduction ratio increases to 30% or more, the roving height of the product becomes smaller, and "waviness" on the surface is no longer recognized.

Recrystallization is observed inside the slab at a reduction rate of 20% or more during hot rolling, and recrystallization occurs almost entirely at a reduction rate of 30% or more. In this way, the average particle size of one particle was 50 μm or less.

Furthermore, δ-Fe, cal (X) is set to about 3%, and the slab is cooled directly under the twin rolls (cooling drum) to create a temperature difference between the surface layer and the inside of the slab, and hot rolling is performed. When this was done, good roving properties were obtained even at a rolling reduction of about 10%. It can be seen that the effect of cooling the slab directly under the twin rolls (cooling drum) is large.

Next, reasons for limiting the constituent elements of the present invention will be explained.

Regarding the molten steel components, C: 0.01 to 0.08%, Si
: 0.25-1.50%, nn: 0.15-3.0%
, P: 0.015~o, o, io%, S: 0.
001~0.008%, Cr:1G, O~28.0%,
Ni:6. O~24.0%, N: 0.015~0
．． 33%, AZ: 0.001-0.050%, Mo
: 0.01-3.0%, Cu: 0.01-2.
0%, Ti: 0.01-0160%, Nb: 0
．． 01 to 0; 80%, balance: In the component range consisting of Fe and unavoidable impurities, it is necessary to control δ-Fe, cal (%) in the range of 2% to 10%, that is, to perform δ phase solidification. . δ-Fe, cal (%) is 1
If it exceeds 0%, the δ phase remains in the product, which is unfavorable in terms of material quality.

On the other hand, if the thickness of the slab exceeds 10111I11, it becomes difficult to refine one grain, and if intense hot working is attempted to refine the γ grains, the rolling mill will become too large, which is impractical.

Cooling of the slab after casting is done by suppressing heat recovery of the slab at the outlet of the casting machine and increasing the average cooling rate as much as possible to 100℃/s or more in the T grain growth temperature range up to 1100℃. It is effective to do so.

Hot rolling is performed in a region where the surface temperature of the slab is 900° C. or higher to promote recrystallization inside the slab. In particular, when the inside of the slab is in a high temperature range (within 10 seconds after casting),
It is sufficient to hot-roll the slab using a rolling reduction of 0% or less. The effect is saturated even if a reduction rate of more than 60% is applied. On the other hand, at a timing exceeding 10 seconds after casting, the temperature difference between the surface layer and the inside of the slab becomes small, and the effect of refining each grain is significantly reduced.

Thereafter, the slab is heated in a temperature range of 900 to 550°C.
After being cooled at a cooling rate of 50°C/s or more, 650°C
If these conditions are not met, carbides will precipitate at the grain boundaries, causing intergranular corrosion when the material is pickled, reducing the surface gloss of the product.

Hot-rolled sheet annealing is performed at a temperature of 950° C. or higher to advance recrystallization. In particular, by controlling temperature and time, the average γ particle size is 50μ
Annealing is performed so as not to exceed m. On the other hand, during cooling after annealing a hot rolled sheet, since δ-Fe decreases from the slab stage during annealing, the precipitation of Cr carbides precipitated at the δ/T interface is delayed, resulting in The cooling rate of the Cr carbide precipitation region was set to 10"C/s or more because the cooling rate can be slower than that of the Cr carbide precipitation region.

(Example) Example 1 Cr-Ni stainless steel 24 having various components based on 18Cr-f3Nifi as shown in Table 1 was produced. 1
In order to make the pseudo-solid initial phase δ phase, δ −Fe, cal (X)=3(Cr+1.5Si+
Mo+Nb+Ti)2.8(Ni+1/2Mn+1/2
Cu)-84(C+N)-]9.8(X), as shown in Table 2, δ-Fe, cal(χ) is -
It 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 using a vertical twin-roll continuous casting machine with internal water cooling. Roll cooling and water spray cooling were applied from directly below the casting machine to cool the slab and prevent heat recovery. 1300-1
In a temperature range of 100°C, an average cooling rate exceeding 120°C/s was obtained.

The slab is then heated to a temperature of 1100 to 950 within 8 seconds after casting.
Hot rolling was carried out in the temperature range of ℃. The rolling reduction rate at this time is 10
% to about 50% (Table 2). Thereafter, the slab was cooled between 900 and 550°C at a cooling rate of 60°C/s or more, and wound up at 600°C or less.

The comparative material was insufficiently cooled between 900 and 550°C, resulting in a temperature of 7.
Some are wound at high temperatures of around 50°C.

Thereafter, the material was pickled, descaled, cold rolled, and then conventionally annealed or bright annealed.

The surface properties of the product thus obtained were investigated.

In particular, we focused on the roving height and gloss on the product surface. As shown in Table 2, the product shown in this example utilizes δ ferrite to lower the temperature of crystallization and precipitation of the T phase in the slab. In addition to the effect of inter-rolling, all exhibited excellent surface properties.

On the other hand, in the comparative method, there was no effect of δ ferrite, cooling of the slab was insufficient, and the winding temperature was high, resulting in large roving on the product surface and poor surface gloss.

(Effects of the Invention) Since the present invention is constructed and operated as described above, it is possible to directly obtain a strip with a thickness close to that of the product by continuous casting, and the surface It is possible to obtain a Cr-Ni stainless thin steel sheet with excellent quality and material.

[Brief explanation of drawings]

Figure 1 shows how Cr is cast using a twin-roll (water-cooled) continuous casting machine.
A diagram showing the temperature/time relationship of the ribbon when casting a Ni-based stainless steel ribbon. Figure 2 is a cross-sectional phase diagram of a portion corresponding to 30% of Cr light + Nl four ζ in the FeCr-Ni ternary system equilibrium phase diagram. , Fig. 3(a) to (C) are δFe, cal
Continuous casting of molten steel with various compositions with different (χ)
Fig. 4 is a metallurgical micrograph showing a comparison of the structures of J¥-sized cast slabs. It is a diagram showing the influence of the rolling reduction when hot rolling is applied and the rolling reduction when descaling and cold rolling is subsequently applied without affecting the roving height of the product surface. /8 20 Crgin ( %) Figure 8 Roasted )) Figure 8 Procedural Amendment (Voluntary) Fin thread, -) Reduction rate (%) 1. Indication of the incident Patent Application No. 221471 of 1988 2. Name of the invention Surface quality and material Excellent Cr-Ni stainless thin steel sheet manufacturing method 3, relationship with the amended case Patent applicant 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Nippon Steel Corporation Representative Saito Yu 4, Agent Address: 2-4-1-5 Marunouchi, Chiyoda-ku, Tokyo 100 Date of the amendment order: Month, Day 6, 1939, Subject of amendment (1) The scope of the patent claims is revised as shown in the attached sheet. (2) ``Before cold rolling'' is deleted from page 10, line 4, page 11, line 1, and page 12, line 3 of the specification. (3) Revise Figure 2 as shown in the attached sheet. Claims (1) Cr- represented by 18%Cr-8%N1jiQ
Ni-based stainless steel is cooled at a cooling rate of 100% during solidification using a continuous casting machine in which the mold wall moves in synchronization with the slab.
"C/s or more, it is continuously cast into a thin strip slab with a thickness of 10M or less, and hot worked at a temperature of 900℃ or higher to a rate of 60% or less to promote recrystallization inside the slab, resulting in 7 grains. @, I
After converting into II and making the average particle size 50 μm or less, 900
Excellent surface quality and material quality, characterized by cooling at a cooling rate of 50"C/s or more in the range from ℃ to 550℃, coiling in a temperature range of 650℃ or less, and then forming it into a cold-rolled sheet by a conventional method. (2) Cr-Ni stainless steel, represented by i%Cr-8%Nii, is produced using a continuous casting machine in which the mold wall moves in synchronization with the slab. , Continuously cast into a thin IP-shaped slab with a thickness of 10 or less with a cooling rate of 100 ° C / s or more during solidification, and after solidification, the slab is kept in the high temperature range as much as possible without causing reheating. After casting, the average cooling rate from 1100°C to 1100°C was set to 100°C or higher at the slab surface temperature to suppress the growth of γ grains and create a temperature difference between the slab surface and the inside.
After performing hot working of 60% or less in a temperature range of 900°C or higher within seconds to advance recrystallization inside the slab and refine the γ grains in the slab to an average γ grain size of 50 μm or less, ℃
to 550°C at a cooling rate of 50°C/s or more, coiled in a temperature range of 650°C or less, and then made into a cold-rolled sheet by a conventional method.C with excellent surface quality and material quality.
Method for producing r-Ni stainless thin steel sheet. (Cr represented by 3118%Cr-8%Nit1gI)
- The cooling rate of Ni-based stainless steel during solidification is increased to 100% by using a continuous casting machine in which the mold wall moves in synchronization with the slab.
℃/s or more into a thin strip slab with a thickness of 10 mm or less, δ-Fe, cal (χ) = 3 (Cr + 1.5S
i+MofNb+Ti)-2,8(Ni+0.5Mn+
0.5Cu) δ-Fe defined as 84(C+N)-19,8, cal (X) is set to -2 to 10% to make the primary crystal of solidification the δ phase, and the crystallization of the γ phase and the start of transformation. The growth of γ grains during solidification is suppressed by lowering the temperature, and after solidification, cooling is started from as high a temperature as possible without causing reheating of the slab, and the average cooling rate is increased to 1100℃. Hot heating of 60% or less in a temperature range of 900°C or higher within 10 seconds after casting where there is a temperature difference between the surface and inside of the slab while suppressing the growth of γ grains by setting the slab surface temperature to 100°C/s or higher. After processing and recrystallizing the inside of the slab to make each grain of the slab fine and the average γ grain size to 501Im or less, it is cooled in the range from 900 °C to 550 °C at a cooling rate of 50 °C / s or more. cool,
Cr- with excellent surface quality and material quality, characterized by being rolled in a temperature range of 650°C or less and then cold-rolled by conventional methods.
A method for manufacturing Ni-based stainless thin steel sheets. (4) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/s during solidification.
As described above, a thin strip slab with a thickness of 10 mm or less is continuously cast, subjected to hot working of 60% or less in a temperature range of 900 °C or more, and then cooled in a range of 900 °C to 550 °C at a rate of 50 °C/S or more. After cooling at a high speed and winding in a temperature range of 650°C or less, 950
It has excellent surface quality and material quality, which is characterized by subjecting the hot-rolled plate to annealing at a temperature and time controlled above ゛C, then cooling at a cooling rate of 10℃/s or above, and then forming it into a cold-rolled plate using a conventional method. A method for manufacturing a Cr-Ni stainless thin steel sheet. (5) C represented by 18%Cr-8%N1jllil
A continuous SR molding machine, in which the mold wall surface moves in synchronization with the slab, reduces the cooling rate of r-Ni stainless steel to 1 during solidification.
Continuously cast into a thin strip slab with a thickness of 10 mm or less at a rate of 00°C/s or more, and after solidification, start cooling in the high temperature range as much as possible without causing reheating of the slab, and average up to 1100°C. The cooling rate is set to 100 °C/S or more at the slab surface temperature to suppress the growth of γ grains, and the cooling rate is reduced to 60% or less in the temperature range of 900 °C or higher within 10 seconds after casting when there is a temperature difference between the slab surface and the inside. hot working, and then cooled at a cooling rate of 50"C/s or more in the range of 900°C to 550°C, and then cooled to 650"
After coiling in a temperature range of 10°C or lower, hot-rolled plate annealing is performed at a temperature of 950°C or higher and for a controlled time so that the average γ grain size is 50 μm or lower, and then at a cooling rate of 10°C/s or higher. A method for manufacturing a Cr--Ni stainless thin steel sheet with excellent surface quality and material quality, which comprises cooling and thereafter forming a cold-rolled sheet by a conventional method. (6) Cr-N represented by 18%Cr-8%Nti4
I-series stainless steel is cooled at a cooling rate of 100°C/100°C during solidification using a continuous casting machine in which the mold wall moves in synchronization with the slab.
s or more into a thin strip slab with a thickness of 10 mm or less, δ-Fe, cal (X) = 3 (Cr + 1.5 Si
10Mo+Nb+Tj)-2,8(Ni+0.5Mn+0
．． 5Cu) δ-Fe defined as 84(C+N)-19,8, cal(χ) is -2 to 10%, the initial solidification product is δ phase, and the starting temperature of crystallization and transformation of γ phase is After solidification, cooling is started from as high a temperature as possible without causing reheating of the slab, and the average cooling rate is maintained at 1100℃. 9 within 10 seconds after casting when there is a temperature difference between the surface and the inside of the slab while suppressing the growth of γ grains by setting the surface temperature to 100℃/S or higher.
After applying hot working of 60% or less in a temperature range of 00°C or higher, then cooling in a range of 900°C to 550°C at a cooling rate of 50°C/S or higher, and winding in a temperature range of 650"C or lower. , hot-rolled sheet annealing is performed at 950°C or higher with controlled temperature and time so that the average grain size is 50 mm or less, and then 10 mm
Cr- with excellent surface quality and material quality, characterized by being cooled at a cooling rate of ℃/S or higher and then made into a cold-rolled sheet by a conventional method.
A method for manufacturing Ni-based stainless thin steel sheets. Crgin (%)

Claims (6)

[Claims] (1) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/s during solidification.
As described above, a thin strip-shaped slab with a thickness of 10 mm or less is continuously cast, hot-worked to a temperature of 60% or less in a temperature range of 900°C or higher to promote recrystallization inside the slab, refine the γ grains, and cool it. After making the average γ grain size 50 μm or less before rolling,
to 550°C at a cooling rate of 50°C/s or more, coiled in a temperature range of 650°C or less, and then made into a cold-rolled sheet by a conventional method.C with excellent surface quality and material quality.
Method for producing r-Ni stainless thin steel sheet. (2) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/s during solidification.
As described above, a thin strip-shaped slab with a thickness of 10 mm or less is continuously cast, and after solidification, cooling is started from as high a temperature as possible without causing reheating of the slab, and the average cooling rate is maintained at an average cooling rate of 1100℃. Hot working of 60% or less in a temperature range of 900°C or higher within 10 seconds after casting where there is a temperature difference between the surface and the inside of the slab while suppressing the growth of γ grains at a single surface temperature of 100°C/s or higher. After recrystallizing the inside of the slab and refining the γ grains in the slab to make the average T grain size before cold rolling 50μm or less, the rolling process is carried out at 50℃/s or more in the range from 900℃ to 550℃. A method for producing a Cr--Ni stainless thin steel sheet with excellent surface quality and material quality, characterized by cooling at a cooling rate of , coiling in a temperature range of 650° C. or lower, and then forming a cold-rolled sheet by a conventional method. (3) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/s during solidification.
As described above, a thin strip-shaped slab with a thickness of 10 mm or less was continuously cast, and δ-Fe. cal(%)=3(Cr+1.5Si+M
o+Nb+Ti)-2.8(Ni+0.5Mn+0.5
δ-F defined as Cu)-84(C+N)-19.8
e. Cal (%) is -2 to 10% and the primary crystal of solidification is δ
The growth of γ grains during solidification is suppressed by lowering the starting temperature of crystallization and transformation of the γ phase, and after solidification, the slab is heated as much as possible from the high temperature range without causing reheating. The average cooling rate from the start of cooling to 1100℃ is 100℃ at the slab surface temperature.
900°C within 10 seconds after casting, where there is a temperature difference between the surface and the inside of the slab while suppressing the growth of γ grains at ℃/s or higher.
After performing hot working of 60% or less in the above temperature range to advance recrystallization inside the slab and refine the γ grains in the slab to make the average γ grain size before cold rolling 50 μm or less, ℃ to 5
Cooling the range of 50°C at a cooling rate of 50°C/s or more, 6
Cr-N with excellent surface quality and material quality, characterized by being rolled in a temperature range of 50°C or less and then made into a cold-rolled sheet by a conventional method.
A method for manufacturing i-series thin stainless steel sheets. (4) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/s during solidification.
As described above, a thin strip slab with a thickness of 10 mm or less is continuously cast, subjected to hot working of 60% or less in a temperature range of 900 °C or higher, and then cooled at a cooling rate of 50 °C/s or higher in the range of 900 °C to 550 °C. After cooling and coiling at a temperature range of 650°C or less, hot-rolled plate annealing is performed at 950°C or higher with controlled temperature and time so that the average γ grain size is 50 μm or less, and then 1
Cr with excellent surface quality and material quality, which is cooled at a cooling rate of 0°C/s or more and then made into a cold-rolled sheet by a conventional method.
-Production method of Ni-based stainless thin steel sheet. (5) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/s during solidification.
As described above, a thin strip-shaped slab with a thickness of 10 mm or less is continuously cast, and after solidification, cooling is started from as high a temperature as possible without causing reheating of the slab, and the average cooling rate is maintained at an average cooling rate of 1100℃. Hot working of 60% or less in a temperature range of 900°C or higher within 10 seconds after casting where there is a temperature difference between the surface and the inside of the slab while suppressing the growth of γ grains at a single surface temperature of 100°C/s or higher. 50℃/50℃ in the range of 900℃ to 550℃.
After cooling at a cooling rate of s or more and winding in a temperature range of 650°C or less, the average γ grain size is 95 μm or less.
Excellent surface quality and material quality characterized by hot-rolled sheet annealing at a temperature and time control of 0°C or higher, then cooling at a cooling rate of 10°C/s or higher, and then a cold-rolled sheet using conventional methods. A method for manufacturing a Cr-Ni stainless thin steel sheet. (6) Cr-Ni represented by 18%Cr-8%Ni steel
A continuous casting machine, in which the mold wall surface moves in synchronization with the slab, cools the stainless steel at a cooling rate of 100°C/s during solidification.
As described above, a thin strip-shaped slab with a thickness of 10 mm or less was continuously cast, and δ-Fe. cal(%)-3(Cr+1.5Si+M
o+Nb+Ti)-2.8(Ni+0.5Mn+0.5
δ-F defined as Cu)-84(C+N)-19.8
e. Cal (%) is -2 to 10% and the primary crystal of solidification is δ
The growth of γ grains during solidification is suppressed by lowering the starting temperature of crystallization and transformation of the γ phase, and after solidification, the slab is heated as much as possible from the high temperature range without causing reheating. The average cooling rate from the start of cooling to 1100℃ is 100℃ at the slab surface temperature.
900°C within 10 seconds after casting, where there is a temperature difference between the surface and the inside of the slab while suppressing the growth of γ grains at ℃/s or higher.
Hot working of 60% or less in the above temperature range, then 9
The average γ
The hot-rolled sheet is annealed by controlling the temperature and time at 950° C. or higher so that the grain size is 50 μm or less, and then cooled at a cooling rate of 10° C./s or higher, and thereafter made into a cold-rolled sheet by a conventional method. A method for manufacturing Cr-Ni stainless thin steel sheets with excellent surface quality and material quality.