JP6809325B2 - Duplex stainless steel shaped steel and its manufacturing method - Google Patents

Description

The present invention relates to duplex stainless steel shaped steel and a method for producing the same. The shaped steel refers to a steel material having a shape such as an angle, a channel, an H-shaped steel, or a round steel. Generally, in the production of shaped steel, there are a method of forming a shaped steel shape by rolling and a method of bending a thin plate manufactured by rolling or the like to form a shaped steel shape, but the subject of the present invention is the former. Regarding shaped steel whose shape is created by rolling.

Since stainless steel has excellent corrosion resistance, it is used in many applications such as building materials, automobiles, and home appliances. Among stainless steels, duplex stainless steel is used as a building material and a structural material because it has particularly high strength. Among the hot-rolled stainless steel sheets and strips, examples of duplex stainless steels include SUS329J1 and SUS329J4L described in JIS G 4304. Since conventional duplex stainless steels have a large amount of additive elements and are relatively expensive, lean duplex stainless steels having a reduced amount of additive elements have been developed. Patent Document 1 discloses duplex stainless steel having a relatively small amount of Ni. Further, Patent Document 2 discloses an inexpensive two-phase stainless steel having a small amount of Ni and utilizing an austenite-forming element such as Mn or N.

On the other hand, as building materials and structural materials, not only plates but also stainless steel having the shape of shaped steel is required. The types of hot-formed stainless steel shaped steels are described in JIS G 4317. However, as the duplex stainless steel, as described above, only relatively expensive stainless steels such as SUS329J1 and SUS329J4L are used. Recently, a manufacturing technique for duplex stainless steel with a small amount of Ni has been reported. Non-Patent Document 1 describes a technique for defining S in order to produce an EN1.4362 standard duplex stainless steel (representative component: 23Cr-4Ni-0.3Mo (Mn: ≦ 2.00)) shaped steel. It is disclosed. Duplex stainless steel generally has higher strength than austenitic stainless steel and is in high demand. However, a major problem in producing duplex stainless steel is the generation of hot cracks and dents due to poor hot workability.

Hot cracking is eliminated by reducing impurity elements such as S, as described in Non-Patent Document 1. However, the current situation is that a complete control method has not been established for hesitation defects. Especially in the case of shaped steel products, baldness is more likely to occur than steel materials. This is considered to be due to the manufacturing method.
In the case of a material having poor hot workability, cracks are likely to occur on a surface that is not constrained during deformation, that is, a rolled end portion. In the case of steel sheets, the thickness is reduced by rolling, that is, the upper and lower surfaces are in contact with the rolling rolls, and the unconstrained surfaces are limited to the ends. Width rolling under width to make the width uniform may be added, but basically only the plate thickness is reduced. However, in the case of hot rolling of shaped steel, the rolled steel material is rolled in the first half, which includes a process of rotating the steel material to be rolled by 90 ° about the rolling direction multiple times, and in the latter half of the rolling, it passes between rolls restrained in all directions. It is made into a shape such as an angle or a channel. Therefore, in the first half of rolling, the plate thickness direction and the plate width direction change for each rolling path. Therefore, if a crack occurs at the end, it becomes a rolled surface in the next pass and is stretched, so that it tends to remain as a bald defect. Above all, in a component system having a large amount of Mn, the occurrence of baldness becomes remarkable, so that a duplex stainless steel shaped steel product containing Mn does not exist.

Japanese Unexamined Patent Publication No. 61-56267 Japanese Patent No. 5366609

Aichi Steel Technical Report Vol. 29 (2012), pp. 30-34

In recent years, it has been desired to develop a steel grade that satisfies the required characteristics of high strength and high corrosion resistance in building materials and structural materials and has a low alloy content. Duplex stainless steel has sufficient characteristics, so if a technology for manufacturing by reducing the alloy content, especially the Ni content, can be established, it can be expected to spread to modern society. In order to reduce the Ni content, it is necessary to produce a duplex stainless steel shaped steel containing Mn having a similar effect. However, in the production of shaped steels, duplex stainless steel shaped steels containing Mn have not been conventionally manufactured because they are prone to blemishes.

In view of the above circumstances, it is an object of the present invention to provide a duplex stainless steel shaped steel satisfying high strength and low cost (low Ni content) and a method for producing the same.

In order to solve the above-mentioned problems, the present inventors diligently conducted experiments and studies on the composition of Mn-containing duplex stainless steel, the relationship between the heating conditions before hot rolling and the surface scratches after hot rolling. Overlapping, the present invention was completed.
The findings obtained in the present invention will be described below.

(I) Duplex stainless steel containing Mn tends to cause scabs, but scabs can be suppressed by controlling the heating temperature and heating time.
(Ii) Appropriate heating conditions that do not cause blemishes are affected by the components. It depends not only on the amount of Mn but also on the amount of Cr and Si.
(Iii) In the case of hot rolling of shaped steel as described above, in the case of manufacturing a two-phase stainless steel, the steel material to be rolled is rolled in the first half including a step of rotating the steel material by 90 ° about the rolling direction a plurality of times. The metallographic structure is a mixed structure of ferrite phase and austenite phase when microscopically observed in a cross section perpendicular to the rolling direction, and shows a characteristic metallographic structure (crystal grain shape) when no baldness occurs. The aspect ratio of the austenite phase is large.
The detailed results of the above (ii) are shown below.
Using four kinds of materials with different components, the heating temperature was changed and the flaws after rolling were investigated. In order to simulate hot rolling of shaped steel using a material with a thickness of 120 mm and a width of 120 mm, rolling in the thickness direction and the width direction is repeated for each pass, and finally rolled to a thickness of 35 mm and a width of 35 mm. It was cooled and the presence or absence of surface defects was investigated. As for the surface defects, four surfaces of thickness and width were investigated, and when there was a dent defect of 5 mm or more that could be confirmed by appearance, it was judged as "rolling defect". FIG. 1 shows the results obtained in this experiment. The horizontal axis is an equation considering the components (Cr, Si, Mn), and the vertical axis is the heating temperature. By considering the components and heating temperature, the range in which rolling flaws do not occur becomes clear.
In addition, FIG. 2 shows the metallographic structure of the bald defect-generated portion and the non-wedge-defected portion after heat treatment. The metallographic structure is micro-observed in a cross section perpendicular to the rolling direction. In the structure, the white part shows the austenite phase and the blackish part shows the ferrite phase. In the (a) non-heavy flawed portion, the crystal grains of the austenite phase are close to equiaxed crystals, whereas in the (b) hege flawed portion, the crystal grains of the austenite phase are flattened.

The present invention has been made based on the above findings, and the gist of the present invention is as follows.

(1) In terms of mass%, C: 0.001% or more and 0.060% or less, Mn: more than 2.00% and 15.00% or less, Si: 0.01% or more and 1.50% or less, P: 0. 050% or less, S: 0.0050% or less, Cr: 19.0% or more and 23.0% or less, Ni: 1.00% or more and 4.00% or less, N: 0.050% or more and 0.250% or less , Al: 0.003% or more 0.050% or less, the balance being a two-phase stainless steel section steel Ru Fe and impurities der, an area ratio of austenite phase of 30% to 70%, the remainder Austenite phase crystal grains having a metallographic structure that is a ferrite phase, located at a depth of 100 μm from the outer surface of the bent or curved portion of the two-phase stainless steel shaped steel, and located in a cross section perpendicular to the rolling longitudinal direction. It is a two-phase stainless steel shaped steel characterized in that the average aspect ratio of is 0.40 to 1.00 and the 0.2% withstand strength of the tensile test is 350 MPa or more.
(2) In terms of mass%, Ti: 0.010% or more and 0.050% or less, Nb: 0.020% or more and 0.150% or less, Mo: 0.05% or more and 2.00% or less, Cu: 0. 05% or more and 3.00% or less, W: 0.05% or more and 2.00% or less, Mg: 0.0002% or more and 0.0050% or less, Ca: 0.0002% or more and 0.0050% or less, REM: 2. The duplex stainless steel according to (1), which contains any one or more of 0.005% or more and 0.300% or less, and B: 0.0003% or more and 0.0040% or less. It is a shaped steel.
(3) After heating the steel material to a temperature range of 1100 ° C. or higher and T ° C. or lower specified by the following formula (1) for 1 hour or more and 24 hours or less, the material to be rolled is rotated 90 ° around the rolling direction. The method for producing a two-phase stainless steel shaped steel according to (1) or (2), which comprises performing hot rolling including a plurality of steps to form a shaped steel shape.
T = 800 + 18 [Cr] + 73 [Si] -0.5 [Mn] ... (1)
However, [Cr], [Si] and [Mn] indicate the contents (mass%) of Cr, Si and Mn, respectively.

According to the present invention, a duplex stainless steel shaped steel having a high Mn amount can be produced.

It is a graph which shows the relationship between the heating temperature and the defect after rolling in duplex stainless steel. It is an optical microscope image of an arbitrary cross section of duplex stainless steel cut perpendicular to the rolling direction.

Hereinafter, each requirement of the present invention will be described in detail. The "%" indication of the content of each element means "mass%".
The two-phase stainless steel shaped steel of the present invention has C: 0.001% or more and 0.060% or less, Mn: more than 2.00% and 15.00% or less, Si: 0.01% or more and 1. 50% or less, P: 0.050% or less, S: 0.0050% or less, Cr: 19.0% or more and 23.0% or less, Ni: 1.00% or more and 4.00% or less, N: 0. A two-phase stainless steel shaped steel containing 050% or more and 0.250% or less and Al: 0.003% or more and 0.050% or less, in which the area ratio of the austenite phase is 30% to 70% and the balance is ferrite. Austenite phase crystal grains having a metal structure that is a phase, located at a depth of 100 μm from the outer surface of the bent or curved portion of the two-phase stainless steel shaped steel, and located in a cross section perpendicular to the rolling longitudinal direction. It is a two-phase stainless steel shaped steel having an average aspect ratio of 0.40 to 1.00 and a 0.2% strength of a tensile test of 350 MPa or more.
Further, the duplex stainless steel shaped steel of the present invention has Ti: 0.010% or more and 0.050% or less, Nb: 0.020% or more and 0.150% or less, Mo: 0.05% or more in mass%. 2.00% or less, Cu: 0.05% or more and 3.00% or less, W: 0.05% or more and 2.00% or less, Mg: 0.0002% or more and 0.0050% or less, Ca: 0.0002 % Or more and 0.0050% or less, REM: 0.005% or more and 0.300% or less, B: 0.0003% or more and 0.0040% or less, whichever one or more may be contained.

(I) The reasons for limiting each component will be described below.

Mn is an important element constituting duplex stainless steel, and since it behaves similarly to Ni, the Ni content can be reduced by adding Mn. When the Mn content is 2.00% or less, the effect of cost reduction is small and the strength of the material is lowered. Therefore, the Mn content is set to more than 2.00%. Mn is an element that stabilizes the austenite phase, and if the content is large, the austenite phase ratio increases, making it difficult to form a two-phase structure or reducing the strength. Therefore, the upper limit of the Mn content is set to 15.00% or less. In order to achieve both stable manufacturability and cost, the Mn content is preferably 2.50% or more and 9.00% or less. More preferably, the Mn content is 3.00% or more and 6.50% or less.

The smaller the amount of C, the more preferable it is because it deteriorates the corrosion resistance, and the upper limit of the C content is preferably 0.060% or less. However, since excessive reduction leads to an increase in refining cost, it is preferable to set the lower limit of the C content to 0.001% or more. From the viewpoint of manufacturability, the more preferable range of the C content is 0.010% or more and 0.045% or less.

Si is an element that improves oxidation resistance and affects the heating conditions during the production of duplex stainless steel shaped steel of the present invention. In order to obtain the effect of improving the oxidation resistance, the lower limit of the Si content is preferably 0.01% or more. On the other hand, excessive addition reduces the toughness and workability of the steel, so the upper limit of the Si content is preferably 1.50% or less. From the viewpoint of manufacturability, the Si content is more preferably 1.00% or less.

P is an element that inhibits manufacturability and weldability, and the smaller the content, the better. Therefore, the upper limit of the P content is preferably 0.050% or less. However, since excessive reduction leads to an increase in refining cost, it is preferable to set the lower limit of the P content to 0.003% or more. From the viewpoint of manufacturability and weldability, the more preferable range of the P content is 0.005% or more and 0.040% or less, and the more preferable range is 0.010% or more and 0.030% or less.

S is an unavoidable impurity element contained in steel, which lowers hot workability. Therefore, the lower the S content, the more preferable, and the S content is preferably 0.0050% or less. From the viewpoint of hot workability, the lower the S content is, the more preferable it is. However, since an excessive reduction leads to an increase in raw materials and refining costs, the lower limit of the S content is preferably 0.0001% or more. From the viewpoint of manufacturability, the more preferable range of the S content is 0.0001% or more and 0.0020% or less, and the more preferable range is 0.0002% or more and 0.0010% or less.

Cr is an element that improves oxidation resistance and corrosion resistance. In order to ensure sufficient corrosion resistance as duplex stainless steel, the lower limit of Cr content is preferably 19.0% or more. However, excessive Cr content promotes the formation of the embrittled phase σ phase when exposed to a high temperature atmosphere, and also causes an increase in alloy cost. Therefore, the upper limit of Cr content is 23.0%. The following is preferable. From the viewpoint of manufacturability, the more preferable range of Cr content is 19.5% or more and 22.0% or less.

Ni improves corrosion resistance and stabilizes the austenite phase in duplex stainless steel. In order to improve the corrosion resistance, the lower limit of the Ni content is preferably 1.00% or more. Since the alloy cost of Ni is high, it is preferably low, and the upper limit of the Ni content is preferably 4.00% or less. From the viewpoint of manufacturability, the more preferable range of Ni content is 1.50% or more and 3.00% or less.

N is an element that improves corrosion resistance and, like Ni, stabilizes austenite, so it can be used as a substitute for Ni. When the N content is low, sufficient corrosion resistance cannot be obtained. Therefore, the lower limit of the N content is preferably 0.050% or more. A larger N content is more effective for corrosion resistance, but it is preferable that the upper limit of the N content is 0.250% or less because nitrogen gasification may occur during melting to generate bubbles. From the viewpoint of stable manufacturability, the more preferable range of the N content is 0.100% or more and 0.200% or less.

Al is used as a deoxidizing element. Since it is effective to contain 0.003% or more of the deoxidizing element, it is preferable to set this as the lower limit of the Al content. On the other hand, since excessive content causes hardening, the upper limit of Al content is preferably 0.050% or less. From the viewpoint of manufacturability, the more preferable range of Al content is 0.005% or more and 0.030% or less.

In addition to the above basic composition, one or more of the following elements may be selectively added.

Ti combines with C and N and contributes to corrosion resistance and high strength of the welded portion. Since the effect of Ti is exhibited when the content is 0.010% or more, it is preferable to set this as the lower limit of the Ti content. On the other hand, since excessive content causes a decrease in corrosion resistance and an increase in alloy cost, it is preferable to set the upper limit of the Ti content to 0.050% or less.

Nb combines with C and N and contributes to corrosion resistance and high strength of the welded portion. Since the effect of Nb is exhibited when the content is 0.020% or more, it is preferable to set this as the lower limit of the Nb content. On the other hand, excessive content causes a decrease in corrosion resistance and an increase in alloy cost. Therefore, the upper limit of the Nb content is preferably 0.150% or less.

Mo, Cu and W may be added as corrosion resistance improving elements. Since the corrosion resistance improving effect is exhibited when the contents of Mo, Cu and W are 0.05% or more, it is preferable to set these as the lower limits of the Mo content, the Cu content and the W content. On the other hand, excessive content causes an increase in cost and a decrease in hot workability. Therefore, the upper limit of the Mo content is preferably 2.00% or less, the upper limit of the Cu content is preferably 3.00% or less, and the upper limit of the W content is 2.00% or less. Is preferable.

Mg, Ca, REM and B are elements that improve hot workability and diformability, and are contained as necessary. However, excessive content leads to inhibition of manufacturability. Therefore, the upper limit of the Mg content is preferably 0.0050% or less, the upper limit of the Ca content is preferably 0.0050% or less, and the upper limit of the REM content is 0.300% or less. The upper limit of the B content is preferably 0.0040% or less. In order to exert the above effects, the lower limit of the Mg content is preferably 0.0002% or more, the lower limit of the Ca content is preferably 0.0002% or more, and the lower limit of the REM content is 0.005. % Or more, and the lower limit of the B content is preferably 0.0003% or more.

REM (rare earth element) is a general term for two elements, scandium (Sc) and yttrium (Y), and 15 elements (lanthanoids) from lanthanum (La) to lutetium (Lu). These elements may be contained alone or may be a mixture.

The rest of the chemical composition of steel is Fe and impurities.
Here, the impurity is a component mixed by various factors in the manufacturing process, including raw materials such as ore and scrap, when steel is industrially manufactured, and does not adversely affect the present invention. Means what is acceptable in the range.

Next, the metal structure will be described.
The metal structure of the two-phase stainless steel shaped steel of the present invention is a metal structure in which the area ratio of the austenite phase is 30% to 70% at room temperature and the balance is substantially a ferrite phase. If the austenite phase ratio is less than 30%, the 0.2% proof stress described later becomes low. On the other hand, when the austenite phase ratio exceeds 70%, cracks are likely to occur during molding. The area ratio of the austenite phase is more preferably 40% to 60%.

Next, a method for measuring the phase ratio of austenite will be described.
Since the austenite phase has a different crystal structure from the ferrite phase, it is preferable to measure it with an analytical instrument capable of discriminating the crystal structure, for example, Electron Backscatter Diffraction (EBSD) or the like. Further, an apparatus such as a ferrite scope that measures the ferrite phase ratio from the magnetic force may be used.
The average aspect ratio of the austenite phase crystal grains is 0.40 to 1.00. When the aspect ratio was less than 0.40, rolling defects were observed, and these were set as the lower limit. The measurement position of the aspect ratio is from the outer surface of the bent portion of the cross section perpendicular to the rolling longitudinal direction of the duplex stainless steel shaped steel (in the case of the shaped steel having no bent portion, the curved portion having the smallest curvature). The position is set to a depth of about 100 μm. The cross section is polished and then etched to allow grain boundaries to appear. At this time, if coloring etching is performed, the austenite phase can be easily discriminated. For the aspect ratio, 30 crystal grains of the austenite phase at the above positions were arbitrarily selected, and the maximum length X and the maximum length Y in the direction orthogonal to the measurement direction of X were measured for each crystal grain, and the following (2) Calculate from the formula.
Aspect ratio = Y / X ... (2)
The arithmetic mean value of the aspect ratio calculated by Eq. (2) for 30 crystal grains is used as the average aspect ratio.
The reason why the occurrence of scabs and the average aspect ratio are not clear is clear, but it is presumed that the surface scale generated during pre-rolling heating and the recrystallization behavior during rolling are correlated. The oxide scale involved in the baffle is generated by pre-rolling heating, and its morphology depends on the heating temperature and components. On the other hand, whether or not it remains as a burr defect during deformation is considered to depend on how strain is applied during rolling deformation and the recrystallization behavior between passes.

The 0.2% proof stress of the tensile test shall be 350 MPa or more. When duplex stainless steel shaped steel is used as a structural material, it is often designed using 0.2% proof stress. The higher this is, the stronger the structural material can be secured or the thinner the steel material can be, so 350 MPa is set as the lower limit. Since 0.2% higher is more advantageous for design, it is preferably 400 MPa or more. On the other hand, if the proof stress is too high, the deformability is lowered and the impact characteristics are deteriorated. Therefore, the upper limit of the proof stress is set to 800 MPa or less.

Next, the manufacturing method will be described.
When producing a shaped steel having the above chemical composition, the heating temperature before hot rolling is set to 1100 ° C. or higher. If the temperature is lower than 1100 ° C., the material may become hard and not bite into the roll due to the temperature drop during rolling. In addition, the increase in deformation resistance causes baldness.
The upper limit of the heating temperature is the temperature determined by the following formula (1).
T = 800 + 18 [Cr] + 73 [Si] -0.5 [Mn] ... (1)
However, [Cr], [Si] and [Mn] indicate the contents (mass%) of Cr, Si and Mn, respectively.

This condition is a condition clarified by the studies of the present inventors, and is a condition applicable to duplex stainless steel containing 2% or more of Mn. If the heating temperature exceeds the heating temperature T of the formula (1), a dent is generated during rolling, so this is set as the upper limit. The reason why the upper limit of the heating temperature T is determined by the equation (1) is under consideration, but at present, it is considered as follows. It is probable that the hesitation defects in the section steel rolling are caused by the surface scale formed during heating before rolling being involved during rolling. Since Cr and Si stabilize the scale and suppress scale growth, the coefficients of these elements are positive, and the higher the content, the higher the temperature of heating. On the other hand, Mn is an element that generally improves oxidation resistance, but in the present invention, the smaller the Mn content, the higher the temperature, that is, the coefficient of Eq. (1) is negative. The reason why duplex stainless steel shaped steel with a high Mn content has not been produced so far is that the effect of the Mn content on baldness has not been clarified and the heating conditions were not appropriate. Inferred.

Further, if the heating time is too short, the temperature of the material will not be uniform, so it is necessary to hold the material for 1 hour or more. On the other hand, if the heating time is too long, the scale thickness increases and the scale tends to remain during rolling. Therefore, the upper limit of the heating time is set to 24 hours. From the viewpoint of manufacturability and scale homogenization, the heating time is preferably 3 to 8 hours.

The shape steel is manufactured by rolling the material to be rolled by 90 ° around the rolling direction a plurality of times, and then performing hot rolling a plurality of times after the above heating. The shape of the rolling roll is not particularly specified, and may be suitable for obtaining a desired shape. In the present invention, the steel is formed into a predetermined shape by rolling a shaped steel including a step of rotating the material to be rolled by 90 ° about the rolling direction. This is because, unlike plate rolling, the material is not rotated around the rolling direction, and is intended for defects that are not seen in the rolling process. The rolled material may be heat-treated or pickled for the purpose of softening or the like. In the case of heat treatment, since the γ phase ratio changes depending on the heat treatment temperature, the heat treatment is performed in the range of the ultimate temperature of 920 ° C to 1080 ° C. Further, shape correction and surface treatment (polishing, etc.) for obtaining the desired surface texture may be performed.

The shape of the material used for section steel rolling is not particularly specified. Any shape such as billet, bloom, slab, etc. does not change the effect of the present invention.
The two-phase stainless steel shaped steel of the present invention is shaped by rolling, such as H-shaped steel, I-shaped steel, angle steel (angle material), flat steel, channel steel (channel material), Z-shaped steel, and round steel. It can be applied to shaped steel to be built.

Examples of the present invention will be described below.

Duplex stainless steel having the components shown in Table 1 was melted, heated under various conditions, and then hot-rolled. At this time, in order to simulate rolling in shaped steel, a steel material having an initial cross-sectional size of 100 mm × 100 mm was rotated by 90 ° every two rolling passes, and the plate thickness direction and the plate thickness direction were exchanged and rolled to 20 mm × 20 mm ( Surface reduction rate 96%). Some were annealed and pickled.
Then, the ferrite phase ratio F (%) was measured using a ferrite scope, and the austenite phase ratio was calculated as 100 −F (%).

Tensile test pieces were collected in parallel with the rolling direction of the obtained steel and subjected to a tensile test by a method conforming to JIS Z 2241, and 0.2% proof stress was measured. It was investigated whether or not a dent was formed on the surface of the product having a 0.2% proof stress of 350 MPa or more. For hege defects, the appearance evaluation of whether or not a covering-like defect is observed from the surface observation and the optical microscope observation of an arbitrary cross section cut perpendicular to the rolling direction are performed so that the total surface length is 200 mm. Carried out. The number of places where covered scabs as shown in FIG. 2 was observed was counted.
Using this material, rolling was performed to reduce the thickness only in the plate thickness direction from 100 mm thickness to 4.0 mm thickness (surface reduction rate 96%), but no surface defects were observed in any of them. From this, it can be seen that defects that do not occur in plate rolling but occur in shaped steel rolling are targeted.
In the examples of the present invention, no hesitation defects were observed at all, whereas in the comparative examples, hesitation defects occurred or the proof stress was low by 0.2%, which did not reach the standard.

Claims (3)

By mass%, C: 0.001% or more and 0.060% or less, Mn: more than 2.00% and 15.00% or less, Si: 0.01% or more and 1.50% or less, P: 0.050% or less , S: 0.0050% or less, Cr: 19.0% or more and 23.0% or less, Ni: 1.00% or more and 4.00% or less, N: 0.050% or more and 0.250% or less, Al: containing 0.050% 0.003% or more or less, the balance being a two-phase stainless steel section steel Ru Fe and impurities der,
The austenite phase has an area ratio of 30% to 70%, has a metal structure in which the balance is a ferrite phase, and is located at a depth of 100 μm from the outer surface of the bent or curved portion of the two-phase stainless steel shaped steel, and has a rolling length. Two phases characterized in that the average aspect ratio of austenite phase crystal grains located in a cross section perpendicular to the hand direction is 0.40 to 1.00, and the 0.2% withstand strength of the tensile test is 350 MPa or more. Stainless steel shaped steel. By mass%, Ti: 0.010% or more and 0.050% or less, Nb: 0.020% or more and 0.150% or less, Mo: 0.05% or more and 2.00% or less, Cu: 0.05% or more 3.00% or less, W: 0.05% or more and 2.00% or less, Mg: 0.0002% or more and 0.0050% or less, Ca: 0.0002% or more and 0.0050% or less, REM: 0.005 The duplex stainless steel shaped steel according to claim 1, wherein it contains any one or more of% or more and 0.300% or less, and B: 0.0003% or more and 0.0040% or less. After heating the steel material to a temperature range of 1100 ° C or higher and T ° C or lower specified by the following formula (1) for 1 hour or more and 24 hours or less, the process of rotating the material to be rolled by 90 ° around the rolling direction is performed. The method for producing a two-phase stainless steel shaped steel according to claim 1 or 2, wherein hot rolling including a plurality of times is performed and the shape is formed into a shaped steel shape.
T = 800 + 18 [Cr] + 73 [Si] -0.5 [Mn] ... (1)
However, [Cr], [Si] and [Mn] indicate the contents (mass%) of Cr, Si and Mn, respectively.