JP2013204151A - Two-phase stainless steel excellent in bulging workability and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of inexpensively manufacturing two-phase stainless steel having high ductility, excellent in bulging formability, and further excellent in surface property after forming.SOLUTION: A two-phase stainless steel excellent in bulging workability contains, by mass%, 0.001-0.03% C, 0.01-2.0% Si, 0.1-3.0% Mn, ≤0.045% P, ≤0.005% S, 19.0-25.0% Cr, 1.0-5.0% Ni, 0.05-0.5% Mo, 0.05-2.0% Cu, 0.0001-0.01% B, 0.06-0.25% N, at least one selected from 0.02-0.3% Sn, 0.05-0.2% Nb, and 0.05-0.2% Ti, and the balance Fe with inevitable impurities. In the two-phase stainless steel, the particle diameters of a ferrite phase are ≥10 μm, and the particle diameters of an austenite phase are ≥6 μm.

Description

  The present invention relates to a duplex stainless steel excellent in stretch workability and a method for producing the same, and more particularly to an alloy-saving duplex stainless steel (steel strip, steel plate) having a high ductility and good stretch formability and a method for producing the same. .

  Since the duplex stainless steel sheet has excellent corrosion resistance and high strength, it is used as various chemical industry apparatuses and devices. However, such a duplex stainless steel has a lower elongation than an austenitic stainless steel typified by SUS304, and thus has a problem that press working, particularly overhanging, is restricted.

  In this regard, in Patent Document 1, in order to improve the workability of the duplex stainless steel, hot-rolled sheet annealing is performed at an annealing temperature (T-100) ° C. or higher (T: temperature at which the ferrite single phase is formed), and cold rolling Then, the method of manufacturing the duplex stainless steel which is excellent in workability is proposed by performing cold-rolled sheet annealing in an annealing temperature range of 1000 to (T-150) ° C. Further, in Patent Document 2, by defining the rolling start temperature, end temperature, time between passes, the number of passes and the rolling reduction in hot rolling, and further by defining the hot rolled sheet annealing temperature and the cold rolled sheet annealing temperature, A method for producing duplex stainless steel with excellent workability has been proposed. Further, Patent Document 3 describes a technique in which the tensile fracture elongation is increased by the TRIP phenomenon of the austenite phase using a stainless steel having a main phase of a ferrite phase and having an austenite phase and a two-phase structure. Patent Document 4 describes a method for regulating the austenite phase stability and increasing the tensile elongation. Patent Document 5 discloses a technique for regulating the austenite phase fraction and the amounts of C and N in the austenite phase to increase the total elongation in a tensile test. In addition, some ferritic / austenitic stainless steels reduce Ni content and balance the austenitic phase with relatively cheap N and Mn, reflecting the recent resource savings, and achieve both balance of ductility and resource saving. The intended steel (alloy-saving) is described in Patent Document 6.

  However, in the case of Patent Document 1, since hot-rolled sheet annealing is performed at a high temperature of (T-100) ° C. or higher (T: temperature at which ferrite becomes a single phase), the hot-rolled sheet softens in the heating furnace, breaks, and operates. There is a problem that there is a danger of stopping. On the other hand, in Patent Document 2, no mention is made of the ferrite and austenite phase ratio at the start of heating and hot rolling, and the cause of the elongation characteristics of the duplex stainless steel sheet produced by this method is not clear. There was a problem that the variation was large.

  In Patent Document 3, the tensile elongation at break is 34 to 42% as shown in Examples, the tensile elongation at break is 46% at maximum in Patent Document 4, and the elongation at break is up to 71% in Example at Patent Document 5. Patent Document 6 describes a tensile elongation at break of ˜46%, but none of these documents describes the particle sizes of the austenite phase and the ferrite phase. In addition, although there is a description about the stretch formability using a part of Erichsen test, there is no description about molding that undergoes uniform deformation over a wide range such as hydraulic bulge forming. Moreover, when the unevenness | corrugation is large as the surface property after shaping | molding, since the manufacturability in a subsequent grinding | polishing process is reduced significantly, the surface property with a small unevenness | corrugation is calculated | required.

JP-A-60-59017 JP-A-8-41594 JP-A-10-219407 JP-A-11-71643 JP 2006-169622 A WO2002 / 27056

  Conventional techniques for improving the workability of duplex stainless steels are techniques that focus on hot rolling conditions and subsequent annealing conditions, and use of work-induced transformation of the austenite phase. In these conventional technologies, even if the elongation in the tensile test is high, in the actual press working, the overhang workability is low due to the difference in the processing characteristics of each of the γ / α phases forming the two phases. There is a problem that the decrease in the polishing property becomes remarkable due to the large unevenness. Therefore, in order to widely use the duplex stainless steel for general press forming, it is necessary to overcome such problems.

  Therefore, the present inventors can analyze in detail the deformation behavior of the material particularly required during the press forming of duplex stainless steel, and clarify the method of relaxing the stress concentration by controlling the particle size of each phase. It is important to provide an inexpensive duplex stainless steel having high ductility, excellent stretch formability, and excellent surface properties after molding, and a technology for producing the same.

  In order to solve the above-described problems in the prior art, the present inventors have focused on the deformation behavior of the material required during press molding and the deformation difference of each phase, and as a result of earnest research, control the particle size of each phase. As a result, it was found that a duplex stainless steel having high ductility at room temperature and excellent stretch-formability and excellent surface properties after formability can be obtained.

  In order to improve the stretchability of the duplex stainless steel sheet, the influence of the microstructure, tensile properties, hydraulic bulge test, and surface properties after the hydraulic bulge test based on the component composition of the duplex stainless steel was determined by laboratory tests. As a result of intensive studies, the present inventors have found that there is a combination of the particle size of each phase and its size ratio as a duplex stainless steel having excellent overhanging formability and good surface properties after processing.

  The gist of the present invention is as follows.

(1) In mass%,
C: 0.001 to 0.03%,
Si: 0.01 to 2.0%,
Mn: 0.1 to 3.0%
P: 0.045% or less,
S: 0.005% or less,
Cr: 19.0 to 25.0%,
Ni: 1.0-5.0%,
Mo: 0.05-0.5%
Cu: 0.05-2.0%,
B: 0.0001 to 0.01%
N: 0.06 to 0.25%
And Sn: 0.02 to 0.3%,
Nb: 0.05-0.2%
Ti: 0.05 to 0.2%
Any one of the above, the balance being Fe and inevitable impurities, the ferrite phase particle size is 10 μm or more, and the austenite phase particle size is 6 μm or more. Excellent duplex stainless steel.

(2) By mass%
Ca: 0.003% or less,
Mg: 0.003% or less,
Zr: 0.5% or less,
Co: 0.2% or less,
REM: The duplex stainless steel as described in (1) above, containing at least one of 0.01% or less.

  (3) The duplex stainless steel as described in (1) or (2) above, which is excellent in stretch workability, characterized by having a breaking elongation of 33% or more in a mechanical test of JIS-Z2201.

  (4) The duplex stainless steel having excellent overworkability according to any one of the above (1) to (3), wherein a fracture limit molding height is 35 mm or more in a hydraulic bulge test of φ100 mm.

  (5) In the cold rolling step of the duplex stainless steel sheet comprising the component composition described in (1) or (2) above, the sheet temperature when the cold rolling is performed is in the range of 100 to 200 ° C. The method for producing a duplex stainless steel having excellent overworkability according to any one of (1) to (4), wherein the cold rolling rate is less than 80%.

  (6) Hot rolling is performed on the slab having the composition described in (1) or (2) above, the obtained hot-rolled sheet is annealed, and then cold rolling described in (5) is performed. Further, the method for producing a duplex stainless steel excellent in overhang processability according to any one of the above (1) to (4), further comprising cold-rolled sheet annealing.

  According to the present invention, duplex stainless steel excellent in overhanging workability can be produced at low cost. In addition, the duplex stainless steel sheet manufactured according to the method of the present invention can be processed in a shape that has not been possible so far, and since the processing process can be simplified, significant cost reduction can be achieved. .

It is a figure showing the relationship between the crystal grain size of each phase and the elongation at break It is the figure which showed the relationship between cold rolling temperature and breaking elongation in each cold rolling rate

  The present invention will be described in detail below.

  In order to obtain the effect aimed at by the present invention, it is necessary to control the grain sizes of the ferrite phase and austenite phase constituting the microstructure to a certain size or more. Duplex stainless steel has different stable phase fractions depending on the heat treatment temperature. Furthermore, since the recrystallization start temperature is also different, it is difficult to control the structure only by changing the heat treatment temperature. Therefore, it is important to control the structure by thermomechanical processing with work strain introduced by cold rolling, but there is a large difference in hardness between the ferrite phase and the austenite phase, and the composition of the present invention having the composition of alloy-saving is soft. Since processing strain is excessively introduced into the ferrite phase, the ferrite phase tends to be finer as the cold rolling ratio increases.

  In a duplex stainless steel composed of a ferrite phase and an austenite phase, it is important to suppress the generation of voids while interpolating the deformation of each phase in the deformation process accompanying the processing, or to prevent the generated voids from growing. Here, when comparing the ductility of the ferrite phase and the austenite phase, the ferrite phase is generally lower in ductility, so it is important to improve the deformability of the ferrite phase. Further, when only the ferrite phase is coarsened, the difference in hardness between the ferrite phase and the austenite phase is expanded, and thus the coarse and softening of the austenite phase is also required. FIG. 1 is a graph showing the relationship between the crystal grain size of each phase and the elongation at break. The horizontal axis shows the crystal grain size of the ferrite phase (○ mark) and austenite phase (△ mark) in the steel measured by the EBSD method, and the vertical axis shows the elongation at break corresponding to each crystal grain size. Yes. Therefore, for one elongation value, there are a ferrite phase particle size and an austenite phase particle size, respectively. As is apparent from FIG. 1, when the ferrite phase particle size is 10 μm or more (● mark) and the austenite phase particle size is 6 μm or more (▲ mark), the elongation at break is stable at 33%. Can be achieved. On the other hand, the ferrite phase and the austenite phase have a lamellar structure in the thickness direction. Here, the particle size of each phase was measured by the EBSD method. The measurement condition of the grain size is a measurement magnification of 2000 times and a 0.2 μm step, and the obtained data is equivalent to a circle by setting one grain size with a crystal grain boundary of orientation difference of 15 ° or more by TSL OIM analysis software. The diameter was calculated. The value obtained by arithmetic average of the obtained equivalent circle diameter was defined as the crystal grain size. Therefore, in order to increase the crystal grain size, a form in which each phase is divided and scattered is required. However, enormous energy is required to divide and grow the layered structure when the thermomechanical treatment is performed, and the upper limit is about 25 μm for the ferrite phase and about 15 μm for the austenite phase in consideration of the manufacturing cost. Become. In addition, the test method of FIG. 1 was described in the Example. In FIG. 1, the elongation at break of 33% or more is No. in Example Table 1. 1-15 steel.

  There is a hydraulic bulge test as a molding method in which the influence of elongation at break is significant. Using a die with a lock bead with a height of 2 mm on a circular blank sheet with a diameter of 160 mm, the overhang processability was evaluated under the condition of a cushion pressure of 37 tons. As a result, it was found that when the elongation at break exceeds 33%, the forming limit height exceeds 35 mm even in a hydraulic bulge test of φ100 mm. Therefore, not only general duplex stainless steel but also high purity ferritic stainless steel It is understood to indicate a higher value. Accordingly, the breaking elongation is 33% or more and the molding limit height is 35 mm or more. Here, since there is an upper limit on the coarsening of the crystal grain size depending on the structure and manufacturing conditions, the effect is reflected in the breaking limit and the molding limit height of the hydraulic bulge, and the breaking limit is 50% or less. The upper limit is 40 mm in height.

  In order to control the particle size of each of the ferrite phase and austenite phase, it is effective to increase the plate temperature before starting cold working and soften both the ferrite phase and the austenite phase to reduce the difference in hardness. I understood that. It was found that when the cold rolling temperature is raised, the introduction of processing strain is reduced and recrystallization nuclei are reduced, so that coarsening can be achieved. FIG. 2 is a diagram showing the relationship between the cold rolling temperature (cold rolling start temperature / ° C.) and the breaking elongation at each cold rolling rate. As in FIG. 1, the test method and the composition of the test material are described in the examples. The test material was Steel No. 1. The elongation at break increases as the cold rolling temperature rises and the cold rolling rate decreases. In addition, the raw material used for cold rolling heated the ingot produced by the laboratory melt | dissolution to 1200 degreeC, made it 5 mmt by hot rolling, and then implemented the solution treatment at 1050 degreeC. The plate thickness of the cold-rolled plate was 1.0 mmt, and the final heat treatment temperature was 1050 ° C. When the cold rolling temperature is less than 100 ° C., the introduction of processing strain is significant. Moreover, when the total cold rolling rate exceeds 80%, even if the cold rolling temperature is set to 100 ° C. or higher, the introduction of processing strain is not suppressed and the elongation at break is reduced. On the other hand, when the cold rolling temperature exceeds 200 ° C., the effect of the lubricant necessary for cold rolling is reduced, and a problem arises in surface properties such as roll seizure. The cold rolling temperature is preferably in the range of 140 to 180 ° C.

  Below, the component composition of the duplex stainless steel preferable in the present invention will be described in detail. Here, “%” for the component means mass%.

C: 0.001 to 0.03%
C is not only an element that lowers the corrosion resistance of stainless steel, but also causes hardening during cold rolling, making subsequent processing difficult. Therefore, C is 0.03% or less, preferably 0.02% or less. However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.001%.

Si: 0.01 to 2.0%
Si is known as an extremely effective element for improving the corrosion resistance, but promotes the precipitation of the σ phase and causes embrittlement. Therefore, Si is 2.0% or less, preferably 0.5 to 1.0%. However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.01%.

Mn: 0.1 to 3.0%
Mn acts as a deoxidizing element during melting and refining, but if it is contained in a large amount, deterioration of corrosion resistance is caused. Therefore, Mn is 3.0% or less, preferably 0.5 to 2.0%. . However, excessive reduction leads to an increase in refining costs, so the lower limit was made 0.1%.

P: 0.045% or less Since P is an element harmful to corrosion resistance, the smaller the better. However, in order to reduce the content excessively, a special smelting technique is required, leading to an increase in production cost. Therefore, P needs to be controlled to 0.045% or less.

S: 0.005% or less S is an element that precipitates at the ferrite-austenite grain boundaries to deteriorate the hot workability and also adversely affects the corrosion resistance. In particular, when the amount of S exceeds 0.005%, the influence becomes significant, so S is made 0.005% or less. Preferably, it is 0.002% or less.

Cr: 19.0 to 25.0%
Cr is one of the ferrite forming elements contributing to the improvement of corrosion resistance and is also a σ phase constituent element. When the Cr content is less than 19.0%, the corrosion resistance is insufficient. On the other hand, when the Cr content exceeds 25.0%, the elongation is reduced by hardening and the toughness is deteriorated. Therefore, Cr is 19.0 to 25.0%, preferably 20.0 to 22.0%.

Ni: 1.0-5.0%
Ni is an austenite forming element, and when it is less than 1.0%, if a γ phase ratio is adjusted by other ferrite forming elements or austenite forming elements, a large amount of N is required, which causes bubbles and hardening. On the other hand, if it exceeds 5.0%, on the contrary, not only the γ phase ratio is more than necessary, but also a significant cost increase is caused. Therefore, Ni is 1.0 to 5.0%, preferably 1.5 to 2.5%.

Mo: 0.05-0.5%
Mo is an element that contributes to improvement of corrosion resistance such as pitting corrosion resistance and crevice corrosion resistance and also to solid solution strengthening. If the Mo content is less than 0.05%, there is no effect of addition. On the other hand, if it exceeds 0.5%, the ductility is lowered and the toughness is deteriorated with hardening, and the production cost is increased. Therefore, Mo is 0.05 to 0.5%, preferably 0.08 to 0.2%.

Cu: 0.05-2.0%
Cu is an element that contributes to the improvement of corrosion resistance. However, when the Cu content is less than 0.05%, there is no effect of addition, and when it exceeds 2.0%, hot workability is significantly deteriorated. Therefore, the Cu content is 0.05 to 2.0%, preferably 0.05 to 1.0%.

B: 0.0001 to 0.01%
B is an element that exists at the grain boundary of the alloy with a small amount of addition and improves hot workability. However, at the same time, it is an element that deteriorates corrosion resistance such as intergranular corrosion. Therefore, the B content is 0.0001 to 0.01%, preferably 0.001 to 0.005% or less.

N: 0.06 to 0.25%
N is an austenite-forming element like C. Therefore, the N content needs to be determined from the composition in consideration of other ferrite-forming elements. N also has an effect of improving pitting corrosion resistance, and the N content needs to be at least 0.06%. However, if it exceeds 0.25%, the hot workability is deteriorated, so 0.06 to 0.25%, preferably 0.08 to 0.18%.

Nb: 0.05 to 0.2%, Ti: 0.05 to 0.2%
Nb and Ti are both stabilizing elements in the ferrite phase, and are effective elements for improving local corrosion resistance. However, the addition of 0.05% or less is not effective, and on the other hand, if it exceeds 0.2%, a large amount of precipitates are precipitated. Become. Therefore, the addition amounts of Nb and Ti are both 0.05 to 0.2%, preferably 0.08 to 015%.

Sn: 0.02-0.3%
Sn is a solid solution strengthening element in the ferrite phase, and is an element effective for hardening the ferrite phase by adding a small amount and reducing the strength difference from the austenite phase. In order to acquire this effect, 0.02% of content is required. On the other hand, it is also an element that remarkably lowers the hot workability of the austenite phase, and if it exceeds 0.3%, the productivity is significantly lowered. Preferably, it is 0.05 to 0.15%.

Ca: 0.003% or less, Mg: 0.003% or less Ca may be slightly contained for desulfurization and deoxidation. However, the content of over 0.003% tends to cause hot working cracks and lowers the corrosion resistance, so this was made the upper limit. In order to obtain the effect stably, 0.0005% or more is desirable. Mg has not only deoxidation but also an effect of refining the solidified structure. In order to stably exhibit these effects, the content is preferably 0.0005% or more. Moreover, since content exceeding 0.003% brings about the cost increase in a steelmaking process, this was made into the upper limit.

Zr: 0.5% or less Zr can be contained in an amount of 0.5% or less as required in order to improve the corrosion resistance. In order to obtain a stable effect, it is preferable to contain 0.05% or more of Zr.

Co: 0.2% or less Co can be contained in an amount of 0.2% or less as required in order to improve secondary workability and toughness. In order to obtain a stable effect, it is preferable to contain 0.02% or more of Co.

REM: 0.01% or less REM is an element useful for scouring because it has a deoxidizing effect and the like, and can be contained by 0.01% or less as necessary. In order to obtain a stable effect, it is preferable to contain REM 0.001% or more.

  The balance other than the components described here is Fe and inevitable impurities.

  Next, the manufacturing method of this invention is demonstrated.

  In the method for producing a duplex stainless steel having excellent overworkability according to the present invention, it is important that the plate temperature during cold rolling is in the range of 100 to 200 ° C. and the total cold rolling rate is less than 80%. It is.

That is, when the cold rolling temperature is less than 100 ° C., the introduction of processing strain is significant. In addition, when the total cold rolling rate exceeds 80%, even if the cold rolling temperature is set to 100 ° C. or higher, the introduction of processing strain is not suppressed, and the elongation at break is reduced. . On the other hand, if the cold rolling temperature exceeds 200 ° C., the effect of the lubricant necessary for cold rolling is reduced, and problems arise in the surface properties such as roll seizure. Therefore, the plate temperature when performing cold rolling is set to 100. Within the range of ~ 200 ° C.

  Moreover, the duplex stainless steel excellent in the stretch workability of the present invention is obtained by hot rolling a slab of the duplex stainless steel having the component composition of the present invention, annealing the obtained hot rolled sheet, and then described above. Is cold rolled, and further cold-rolled sheet annealed.

  Specifically, the slab of the duplex stainless steel having the component composition of the present invention is heated to 1150 to 1250 ° C. (1200 ° C. is an example) and then hot-rolled, and the obtained hot-rolled sheet is obtained at 1050 to 1100 ° C. After annealing, the cold rolling described above is performed, and further cold-rolled sheet annealing is performed at 1000 to 1100 ° C. (1050 ° C. is an example).

  Since the slab heating temperature affects the deformation resistance during hot rolling, it is desirable that the slab heating temperature be high. However, when the slab heating temperature is increased, the ratio of the ferrite phase increases and significant softening occurs, which causes problems such as wrinkles. Similarly, since the high temperature of the hot-rolled sheet annealing causes the generation of soot, heat treatment is required at a limit temperature at which recrystallization proceeds and softening occurs. On the other hand, the cold-rolled plate annealing temperature needs to suppress the temperature rise because the plate thickness is thin and the rigidity is lowered. It is also necessary to optimize these conditions in producing the duplex stainless steel having excellent overhang workability according to the present invention.

  The effects of the present invention will be described below based on examples.

  A lab ingot of duplex stainless steel having the composition shown in Table 1 is heated to 1200 ° C. and then hot rolled to 5 mmt, then hot-rolled sheet annealed at 1050 ° C., followed by cold rolling at 1050 ° C. Thus, a cold-rolled sheet having a thickness of 1.0 mm was obtained by cold-rolled sheet annealing. Table 2 shows the temperature conditions during cold rolling. For temperature control during cold rolling, a constant temperature furnace was installed in the vicinity of the entry side of the cold rolling machine, and it was confirmed with a contact-type thermometer that the plate temperature reached a predetermined temperature. If the plate temperature is in the range of ± 5 ° C. with respect to the target temperature, cold rolling was performed. The measured value of elongation (%) is a numerical value obtained by performing a mechanical test in a direction perpendicular to the rolling direction using a No. 13 B test piece defined in JIS-Z2201. In the hydraulic bulge test, a fracture height is measured by using a mold having a lock bead of φ100 mm and a height of 2 mm and a cushion pressure of 37 tons. The particle size of each phase was measured by the EBSD method. The particle size was measured under the condition of a measurement magnification of 2000 times and a 0.2 μm step, and the obtained data was analyzed and calculated by OSL analysis software of TSL. One grain boundary was set with an orientation difference of 15 ° or more as the crystal grain boundary, and the equivalent circle diameter was calculated. The value obtained by arithmetic average of the obtained equivalent circle diameter was defined as the crystal grain size. The obtained results are shown together in Table 2. As is apparent from the results shown in Table 2, the duplex stainless steels (steel Nos. 1 to 18) produced according to the present invention were tested Nos. As shown to 1-18, it turned out that elongation and overhang workability are improved compared with the comparative example (test No. 19-43) which does not satisfy | fill the requirements of this invention. That is, by applying the method of the present invention, it is possible to produce a duplex stainless steel having excellent overhanging workability.

  That is, test no. Nos. 19 to 22 satisfy the requirements of the steel component of the present invention, but the grain size of the ferrite phase, the grain size of the austenite phase, and the plate temperature (cold rolling temperature) when performing cold rolling, Any requirement of the cold rolling rate was outside the scope of the present invention, and the elongation (%) and the bulge breaking height were inferior. In addition, Test No. Nos. 19 to 22 do not satisfy the requirements of the steel component of the present invention, and any of the cold rolling temperature), the total cold rolling rate, the ferrite phase particle size, and the austenite phase particle size is outside the present invention. The elongation (%) and the bulge break height were inferior.

Claims (6)

% By mass
C: 0.001 to 0.03%,
Si: 0.01 to 2.0%,
Mn: 0.1 to 3.0%
P: 0.045% or less,
S: 0.005% or less,
Cr: 19.0 to 25.0%,
Ni: 1.0-5.0%,
Mo: 0.05-0.5%
Cu: 0.05-2.0%,
B: 0.0001 to 0.01%
N: 0.06 to 0.25%
And Sn: 0.02 to 0.3%,
Nb: 0.05-0.2%
Ti: 0.05 to 0.2%
Any one of the above, the balance being Fe and inevitable impurities, the ferrite phase particle size is 10 μm or more, and the austenite phase particle size is 6 μm or more. Excellent duplex stainless steel. % By mass
Ca: 0.003% or less,
Mg: 0.003% or less,
Zr: 0.5% or less,
Co: 0.2% or less,
The duplex stainless steel according to claim 1, comprising at least one of REM: 0.01% or less.   3. The duplex stainless steel according to claim 1, wherein the duplex stainless steel according to claim 1 or 2 is excellent in stretch workability characterized by having a breaking elongation of 33% or more in a mechanical test of JIS-Z2201.   The duplex stainless steel excellent in stretch workability according to any one of claims 1 to 3, wherein a fracture limit forming height is 35 mm or more in a hydraulic bulge test of φ100 mm.   In the process of cold rolling of the duplex stainless steel sheet comprising the component composition according to claim 1 or 2, the sheet temperature when cold rolling is performed is in a range of 100 to 200 ° C, and the total cold rolling rate is 80. 5. The method for producing a duplex stainless steel excellent in overhanging workability according to claim 1, wherein the duplex stainless steel is excellent in stretch workability.   Hot rolling is performed on the slab having the component composition according to claim 1 or 2, the obtained hot rolled sheet is annealed, then cold rolling according to claim 5 is performed, and further cold rolled sheet annealing is performed. The method for producing a duplex stainless steel having excellent overworkability according to any one of claims 1 to 4, wherein the method is performed.

Images