JPS62192235A - Direct production for two phase stainless steel thin strip having excellent superplasticity and surface property - Google Patents

Abstract

PURPOSE:To reduce production cost by solidifying molten steel for two phase stainless having the specified wt.% Ni, Cr, etc., after cooling rapidly on a rotating surface of roll, to form a thin strip. CONSTITUTION:The compositions of components for the molten two phase stainless steel consist of by weight <=0.02% C, <=2.0% Si, <=3.0% Mn, 3-10% Ni, 20-35% Cr, 0.5-6.0% Mo, 0.08-0.3% N, and a little specified quantities of the other elements, such as W, V, B, and Cu. Next, a tundish 3 and a molten metal vessel 1 are arranged to the cooling single roll 4, and the molten two phase stainless steel 2 in the vessel 1 is poured into the tundish 3. Then, the molten steel 2 is cooled rapidly and solidified on the rotating surface of the roll 4 rotated in counterclockwise direction, to form the continuous thin hoop having <=5 mm thickness. As the products, such as the thin strip is obtd. by only the casting process, the production cost is reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a duplex stainless steel FiA which has superior superplastic deformability and surface properties in casting than duplex stainless steel molten steel.
This invention relates to a method for directly manufacturing thin plate strips.

(Prior art) Certain duplex stainless steels exhibit superplastic phenomena.
(1968), 85. When plastic working is performed using this superplastic phenomenon, objects with complex shapes can be worked with a small number of times due to the low working stress and high ductility due to the superplastic deformability. It is known that in order to impart superplasticity to duplex stainless steel as described above, it is necessary to refine the structure.

In addition, Nikkei New Materials A 5.1986.30 describes that duplex stainless molten steel is made into a sheet with a thickness of 1 by the twin roll method.
Rapidly cooled and solidified to a degree of AS, resulting in a single phase of ferrite.
Further cold rolling was carried out at a reduction rate of 80%, resulting in 1050 t
It is stated that when annealed with: ', a fine two-phase structure is formed and a two-phase stainless steel having superplastic deformability is obtained.

(Problems to be Solved by the Invention) As mentioned above, the conventional manufacturing method for manufacturing a duplex stainless steel thin plate strip having superplasticity is to process it into a shape such as a plate in advance to obtain a fine grain structure, and then heat it at high temperature. Heat treatment is performed to form a single phase of ferrite or a form in which a small amount of austenite exists in the ferrite base, and a combination of heat treatment at high temperature and repeated processing (1, S-) is required, and the yield is poor (, The disadvantage was that it required a process of

Furthermore, according to the manufacturing method described in Nikkei New Materials, molten duplex stainless steel is rapidly cooled and solidified to about one plate thickness using the twin roll method to form a single ferrite phase, and then cold rolled at a high reduction rate and then heated to a high temperature. It requires annealing.

(Means for Solving the Problems) The present inventors have discovered that duplex stainless molten steel can be continuously quenched on the rotating surface of a single roll or twin rolls, which can solve the above-mentioned drawbacks or problems of conventional methods.・Research and experiments were conducted on a method for manufacturing duplex stainless steel thin plate strips with a thickness of 5 m or less that have excellent superplastic deformability and surface properties even when solidified and as cast.

First, 5US329Jl of molten steel was continuously rapidly cooled and solidified on the rotating surface of a single roll or twin rolls, and an as-built thin plate strip with a thickness of 5 mm or more was used to conduct an experiment on superplastic deformability. The strain rate sensitivity index m value at high temperatures was determined by performing the following steps. There wasn't. Therefore, a duplex stainless steel with excellent hot workability, i.e., composition C:
0.02% or less, Si: 2.0% or less, Mn: 3
．． 0% or less, N1:3~IO%, 0r=20~35%,
Mo: 0.5-6.0%, N: 0.08-0.
3%, at least one of WSv 0.03 to 2.0
%, B: 0.0005-0.01%, S: 0.
0.005% or less, the remainder substantially consisting of Fe, and a duplex stainless steel in which the component composition of the steel contains 2.0% or less of Cu, SUS 329
As in the case of J1, we conducted an experiment on superplastic deformability and found the strain rate sensitivity index m value at high temperatures, which was 0.
．． The present invention was completed based on a new finding that satisfies 3 or more.

An object of the present invention is to provide a method for manufacturing a duplex stainless steel thin plate having excellent superplastic deformability and surface properties as cast, which can solve the above-mentioned drawbacks or problems of conventional methods. The above object can be achieved by the method described in the claims. That is, the present invention involves continuously rapidly cooling and solidifying duplex stainless steel on the rotating surface of one type of roll, either a single roll or a twin roll, so that a small amount of austenite phase is precipitated in a matrix of ferrite phase. The present invention relates to a method for manufacturing a duplex stainless steel thin plate strip having excellent superplastic deformability and surface properties as cast, which is characterized by obtaining a thin plate strip having a texture of a similar structure.

Next, the present invention will be explained in detail.

According to the present invention, (3: 0.02% or less, Ni: 3 to
10%, Cr: 20-35%, Mo: 0.5-6.0
%, B: 0.0005-0.01%, W 17'c
Its V) (eiJ t'L i' Type 1 mata is 0.03 to 2.0% for type 2, s: o, oos% or less. Duplex stainless steel containing 0.2% or less is used, and the thin plate strip with a thickness of 5 mm or less, which is continuously rapidly cooled and solidified on a single roll or double roll A, is SUS 329Jt. Compared to the structure when using ferrite, a small amount of austenite exists in the ferrite base, making it easier for grain boundary sliding to occur and imparting excellent superplastic deformability. Based on this knowledge, t! ! A thin plate strip having a thickness of 5II or less is obtained by continuously rapidly cooling and solidifying duplex stainless molten steel having the composition described in claims 2 and 3 on the rotating surface of a single roll or twin rolls. Manufacture.

Figure 1 shows a method for producing a rapidly cooled plate strip using a single cooling roll 4.
FIG. 2 is a vertical cross-sectional explanatory view of an apparatus showing two embodiments. To explain the method of manufacturing a thin plate strip using this apparatus t1, first, duplex stainless molten steel 2 is poured into a tundish 3 from a molten metal container 1.

Three of the four side walls of Tanditsh 3 and the bottom are made of refractory material, and the remaining one side wall is made of single roll 4.
It is formed by a zero rotation surface.

Therefore, in the tundish 3, molten steel is accumulated by its bottom surface, 3 side wall surfaces, and the rotating surface of the single roll 40.

At this time, as the single roll 4 is rotated counterclockwise in the figure, the molten steel 2 that contacts the rotating surface of the roll 40 is rapidly solidified, and a continuous thin plate band of 5IlI11 or less is formed on the rotating surface of the roll 4 (? ) formed continuously on top.

FIG. 2 is an explanatory longitudinal sectional view of an apparatus showing one embodiment of manufacturing a rapidly quenched thin plate strip using water-cooled twin rolls 9, 9', and this apparatus is constructed as follows. That is, a nozzle 6 vertically installed at the bottom of the molten steel container l; an inclined plate 7 with which the lower end of the nozzle 6 abuts; a rotation axis substantially parallel to the upper edge of the inclined plate 7; The twin rolls 9.9 disposed below the edge of the
and; both side weirs slidably disposed on both end surfaces of the twin rolls 9 and 9' in a direction perpendicular to the rotation axis of the twin rolls 9 and 9'; and a lower end S of the nozzle 6. An opening 8 is formed in a portion of the cylinder side wall that corresponds to the downward direction of the slope of the inclined plate 7 surface, and includes a position where the lower end of the nozzle 6 contacts the inclined plate 7 surface and a position where the upper end thereof contacts the inclined plate 7 surface. The distance from the side is such that the molten steel 2 discharged from the opening of the nozzle 6 in a fan shape that spreads toward the end becomes a steady laminar flow having a uniform flow rate distribution on the surface of the slope plate 7 while flowing down on the surface of the slope plate 7. The distance between the upper end edge and the closest gap between the twin rolls 9, 9' is such that the molten steel 2 flowing down from the upper end edge can be This is a distance that does not cause disturbance on the surface and inside of the molten steel pool formed in the upward gap, and the molten steel 2 is solidified and formed in the gap closest to the twin rolls 9, 9'. This is a direct casting device for two-phase stainless steel thin plate strips, which is configured to discharge from the downward gap of .

The method for producing a rapidly cooled thin plate strip using the above-mentioned apparatus M is as follows. That is, the lower end of the nozzle 6, which is vertically installed in the lower part of the molten steel container l, is brought into contact with the inclined surface of the inclined plate 7 made of refractory material, and the downward direction of the inclined surface of the inclined plate 7 of the circumferential side wall of the lower end of the nozzle is brought into contact with the inclined surface of the inclined plate 7 made of refractory material. The molten steel 2 is discharged from an opening provided in the side wall of a portion corresponding to the area in a fan shape that spreads toward the end, and a steady laminar flow having a uniform flow rate distribution on the surface of the slope plate 7 is created while flowing down the surface of the slope plate 7. Next, an upward gap is formed by an internal water-cooled twin roll 9.9' disposed on the upper end of the inclined plate 7 so that the axis of rotation is substantially parallel to the lower end. The steady laminar flow is continuously and non-impact supplied to the part to form a molten metal pool with no turbulence on the surface or inside, and the molten steel 2 is supplied near the gap closest to the twin rolls 9, 9'. 9. Solidify and form the twin rolls.
A quenched thin plate strip can be produced by discharging the downward gap area of 9'.

FIGS. 3(a) to 3(C) are longitudinal cross-sectional explanatory views of an apparatus showing another embodiment of the twin roll method used in the method of the present invention, in which water-cooled twin rolls 9 with different relative positions and heights of the rotation axes An induction nozzle 6 having a width equal to or shorter than the roll width is horizontally brought into contact with the gap formed on the entrance side of the roll 9', and while the roll 9.9''i is rotated, the molten steel is injected through the nozzle 6. 2 is supplied (~) and is rapidly cooled and solidified on the rotating surface of the roll, while being discharged from the roll exit side.

FIG. 4 is an explanatory longitudinal cross-sectional view of an apparatus showing another embodiment of the twin roll method used in the method of the present invention, in which water-cooled twin rolls 9°9' with equal relative positions and heights of the rotation axes are placed on the lower entry side. The guide nozzle 6, which is the same as or shorter than the roll width, is brought into contact with the gap formed in the twin rolls 9 from below.
, 9''k, the molten steel 2 may be supplied from the nozzle 6, rapidly solidified on the rotating surface of the roll, and then discharged from the exit side of the roll.

The continuous thin plate band obtained in this way is as shown in the micrograph (200x magnification) showing the longitudinal cross-sectional structure of the beat 5 diagram.
A structure is obtained in which a small amount of austenite phase precipitates at the grain boundaries with the ferrite phase and within the ferrite phase grains. The equipment N shown in FIG. 1, FIG. 2, FIG. 3 (a) to (C), and FIG.
In the case of twin rolls, the plate thickness can be changed by changing the roll diameter, material, rotational speed, and roll gap and roll cooling conditions used to produce thin plate strips. When the thickness of the produced thin plate strip is 5 mm or less, the structure consists of a small amount of austenite phase precipitated at the grain boundaries with the ferrite phase and within the ferrite phase grains.

f ノ,? ) Claims 2 and 3 stated in the Examples
The duplex stainless steel having the composition described in section 1 has excellent superplastic deformability and surface properties up to the level of casting.

Next, the present invention will be explained with reference to examples.

(Example) Table 1 shows the composition of ingredients used in this example.

AI+ &2 is a comparative component example, SUS 329Jt
This is the composition of the ingredients. Ya3 to A7 are examples of bosses used in the present invention.

Table 2 shows the casting conditions, strain rate sensitivity index m values, and maximum elongation % for A1 to A7.

(/ri) Publication No. 62-192235 (5) The test method is to use the high-temperature tensile test piece shown in the photograph in Figure 6 (magnification: 1.1 times) with the direction perpendicular to the casting direction parallel to the tensile force direction. , standard distance5. 5. Take the sample so that it turns on, and hold it at that temperature for 5 minutes at a high temperature. OX 10～
5. OX 1. Tensile tests were conducted at constant strain rates in the OSeC range.

Figure 7 shows the strain rate (s) at 1000 C using sample A4.
The relationship between ea"") and elongation (%) is shown.

Furthermore, the strain rate (sec) at 1000t:'
Table 3 shows the relationship between deformation resistance f kg7m'').

Table 3 Next, when calculating the strain rate sensitivity index mW1 shown by formula (1), σ=K ;m ・・・・・・・・・(1)
Te, σ: deformation resistance (kg7m2), K: constant.

;: Obtain the strain constant (See), m=0.51.

Similarly, samples AI, A2. A3. A5. The strain rate sensitivity index m values for A6 and A7 were found to be 0.22, respectively, as shown in Table 2. 0.18. 0.33°0.3
3. 0.44. 0.31 was obtained. Table 2 shows the maximum elongation values (%) obtained. 80.0%, 63.0%, 311.0%, 4 for samples A1 to A7, respectively.
04.0%.

210.0%, 313.0%, and 307.0% were obtained.

Mat, Sci, and Tech, Vo
l, 1. 5up8rpl, asticityancl 5upe described in p925NOV, 1985
plastic forming process
It is known that in the case of a superplastic phenomenon using fine grains, the strain rate sensitivity index m value is 0.3 or more.

Therefore, A3. A4. A5+
A6 and 11 (z7 indicate that superplastic deformability was obtained, respectively.

The reason for this superplastic phenomenon is that crystal grains are fragmented by strain during deformation, and recrystallization proceeds at the same time as the deformation due to thermal energy, resulting in fine crystal grains, and this fine crystal structure exhibits superplastic deformability. It is something.

(Effects of the Invention) As described above, the duplex stainless molten steel used in the present invention can be easily and cost-effectively fabricated into thin plate strips having either single-roll or double-roll properties. can be manufactured.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of an apparatus for producing a quenched thin plate strip by the method of the present invention using a single roll; Fig. 2 is a longitudinal sectional view of an apparatus for producing a quenched thin plate strip by the method of the present invention using twin rolls; Figures 3(a) to (C) and Figure 4 are longitudinal cross-sectional views of an apparatus showing other embodiments for producing rapidly cooled thin plate strips by the method of the present invention using twin rolls; A micrograph (200x magnification) showing the longitudinal cross-sectional structure of the manufactured thin plate strip, Figure 6 is a photograph (1.1x magnification) of the specimen used in the tensile test, and Figure 7 is a micrograph showing the longitudinal cross-sectional structure of the manufactured thin plate strip (magnification 1.1x). Strain rate (sec-1) and elongation (
FIG. DESCRIPTION OF SYMBOLS 1... Molten steel container, 2... Molten steel, 3... Tundish, 4... Single roll, 5... Thin plate strip, 6... Induction nozzle, 7... Refractory inclined plate, 8... opening,
9.9'...Twin roll. Patent applicant Nippon Yakin Kogyo Co., Ltd. Agent Patent attorney Mura 1) Politics (/ta)
) Figure 5 (200x) Corrected Figure 7 Procedure Master Hosho Seishobo Ceremony) May 9, 1985 Director General of the Patent Office Mr. Michibe Uga 1, Indication of Case Patent Application No. 33981 of 1988 2, Name of the invention Direct production method for duplex stainless steel thin plate strips having excellent superplastic deformability and surface properties 3, Amendment person 4, Agent 104 6, Number of inventions increased by amendment None 7, Amendment Subject 8, Contents of amendment (1) “Photograph (1.1x magnification)” on page 16, line 1 of the specification
” will be deleted. (2) Insert the description ``metal'' between ``longitudinal section'' and ``structure'' on page 18, line 17 of the same book. (3) The statement in lines 18-19 of the same page of the same book is corrected as follows. "Figure 6 is a plan view of the specimen used in the tensile test." (4) Figure 6 of the drawing is amended to the drawing attached to the written amendment.

Claims (1)

[Claims] 1. Casting characterized by continuously rapidly solidifying duplex stainless steel on the rotating surface of one type of roll, either a single roll or a twin roll, to obtain a thin plate strip. A method for the direct production of duplex stainless steel thin strips with excellent superplastic deformability and surface properties. 2. The composition of the duplex stainless steel molten steel is C: 0.0
2% or less, Si: 2.0% or less, Mn: 3.0% or less,
Ni: 3-10%, Cr: 20-35%, Mo: 0.5
~6.0%, N: 0.08-0.3%, at least one of W or V 0.03-2.0%, B: 0.0005
~0.01%, S: 0.005% or less, remainder substantially F
The method according to claim 1, characterized in that the method comprises: e. 3. The composition of the duplex stainless steel is C: 0.0.
2% or less, Si: 2.0% or less, Mn: 3.0% or less,
Ni: 3-10%, Cr: 20-35%, Mo: 0.5
~6.0%, N: 0.08-0.3%, at least one of W or V 0.03-2.0%, B: 0.0005
~0.01%, S: 0.005% or less, Cu: 2.0%
2. The method according to claim 1, wherein the remaining portion consists essentially of Fe. 4. The method according to claim 1, wherein the thickness of the thin plate band is 5 mm or less. 5. While continuously pouring and accumulating duplex stainless steel in a tundish that is in slidable contact with a part of the rotating surface of the single roll, the single roll is moved from the bottom of the tundish toward the free surface of the molten steel. 2. The method according to claim 1, wherein the molten steel is rapidly solidified on the rotating surface of the single roll while rotating toward . 6. Bring the lower end of the nozzle vertically installed at the lower part of the duplex stainless steel molten steel container into contact with the inclined surface of the inclined plate made of refractory material, and place the lower end of the nozzle on the circumferential side wall of the lower end of the nozzle in the downward direction of the inclined plate surface. The molten steel is discharged from an opening provided in the side wall of the corresponding portion in a fan shape that spreads toward the end, and while flowing down on the inclined plate surface, a steady laminar flow having a uniform flow rate distribution is formed on the inclined surface, and then the The steady laminar flow is formed in the upward gap formed by the internal water-cooled twin rolls arranged at the lower end of the inclined plate so that the axis of rotation is approximately parallel to the lower end. The molten steel is continuously and non-impact fed to form the molten steel pool with no disturbance on the surface or inside, and the molten steel is rapidly solidified in the vicinity of the gap closest to the twin rolls so that the molten steel flows downwardly between the twin rolls. The method according to claim 1, characterized in that the liquid is discharged from a gap. 7. Rotate the twin rolls by horizontally abutting an induction nozzle with a diameter equal to or shorter than the width of the rolls in the gap formed on the inlet side of the water-cooled twin rolls having different relative positions and heights of the rotation axes. 2. The method according to claim 1, wherein the molten steel is supplied from the nozzle while the molten steel is rapidly solidified on the rotating surface of the roll, and then discharged from the exit side of the roll. 8. An induction blow-out nozzle having the same width or shorter than the roll width is brought into contact with the gap formed on the lower entry side of the water-cooled twin rolls having the same relative position and height of the rotation axes from below,
2. The method according to claim 1, wherein the molten steel is supplied from the nozzle while rotating the twin rolls, is rapidly solidified on the rotating surface of the rolls, and is then discharged from the exit side of the rolls.