JP2023150452A - Shearing work method and shearing workpiece - Google Patents

Abstract

To manufacture a shearing workpiece having a high percentage of a shear surface of a cut surface, while reducing a load on a metal mold.SOLUTION: In a shearing work method according to one embodiment of the present invention, a duplex phase stainless steel plate containing a ferrite phase and an austenite phase is shear-worked in a plate thickness direction. The shearing work method includes a compressive plastic deformation step of applying compressive plastic deformation to the duplex phase stainless steel plate in the plate thickness direction, and a shearing step of press-shear-working the duplex phase stainless steel plate by using a die and a punch.SELECTED DRAWING: Figure 1

Description

The present invention relates to a shearing method for shearing a duplex stainless steel plate containing a ferrite phase and an austenite phase in the thickness direction.

In addition to parts made of thin sheet steel materials that are formed by press, there are parts that are formed by shearing. In the shearing process, a sheared surface and a fractured surface are formed on the cut surface (fractured surface) formed by the shearing process. The sheared surface is a relatively smooth surface formed by punching, whereas the fractured surface is a surface with large irregularities. The fractured surface needs to be polished to make it smooth. Since the higher the ratio of fractured surfaces, the more the amount of polishing increases and the yield decreases, a cutting method with a smaller ratio of fractured surfaces, in other words, a higher ratio of sheared surfaces, is desired.

Patent Document 1 describes precision shearing as a technique for increasing the ratio of the sheared surface in the fracture surface. In the technique described in Patent Document 1, the ratio of the sheared surface in the fracture surface is improved by reducing the clearance between the punch and the die as much as possible.

Patent No. 6499571

However, in the technique of Patent Document 1, since the clearance is small, the load on the mold is high, and the life of the mold is shortened, especially when shearing a high-strength material such as duplex stainless steel.

An object of one aspect of the present invention is to realize a shearing method that can produce a sheared product with a high proportion of sheared surfaces in the cut surface while reducing the load on the mold.

In order to solve the above problems, a shearing method according to one aspect of the present invention is a shearing method for shearing a duplex stainless steel sheet containing a ferrite phase and an austenite phase in the thickness direction, The process includes a compression plastic deformation step of compressively plastically deforming the duplex stainless steel plate in the thickness direction, and a shearing process of pressing and shearing the duplex stainless steel plate using a die and a punch.

In order to solve the above problems, a sheared product according to one embodiment of the present invention is a sheared product manufactured by press shearing in the plate thickness direction from a duplex stainless steel plate containing a ferrite phase and an austenite phase. In a cut plane perpendicular to the rolling direction of the duplex stainless steel sheet, the interval between austenite phases in the shear direction is less than 4.0 μm, and the area ratio of the shear plane is 60% or more.

According to one aspect of the present invention, it is possible to manufacture a sheared product having a high proportion of sheared surfaces in the cut surface while reducing the load on the mold.

It is a figure for explaining the compressive plastic deformation process concerning one embodiment of the present invention. It is a figure for explaining the shearing process concerning one embodiment of the present invention. It is a photograph showing a cut surface of a punched product manufactured by a normal punching process. 1 is an optical microscope image of a cut surface obtained by cutting a duplex stainless steel plate on a plane parallel to the thickness direction of the duplex stainless steel plate before applying stress using a punch and a counter punch in an example. 1 is an optical microscope image of a cut surface obtained by cutting a region to which stress was applied using a punch and a counter punch along a plane parallel to the plate thickness direction in Example 1 of the present invention. 2 is an optical microscope image of a cut surface of the punched product of Example 1. 2 is an optical microscope image of a cut surface of a punched product of Comparative Example 1.

Hereinafter, one embodiment of the present invention will be described in detail. The shearing method in this embodiment is a shearing method in which a duplex stainless steel plate containing a ferrite phase and an austenite phase is sheared in the thickness direction. The duplex stainless steel plate to be processed by the shearing method in this embodiment has a structure in which ferrite phases and austenite phases are alternately laminated in layers in the plate thickness direction. First, in the shearing method according to the present embodiment, an example of the composition of a duplex stainless steel plate to be sheared will be described. The duplex stainless steel plate to be processed by the shearing method in this embodiment has a mass percentage of C: 0.08% or less, Si: 2.00% or less, Mn: 4.00% or less, P: 0. 040% or less, S: 0.030% or less, Ni: 1.50-8.00%, Cr: 17.00-28.00%, Mo: 5.00% or less, Cu: 0.05-3. 00% and N: 0.080 to 0.320%, with the remainder consisting of Fe and impurities. The significance and content of these elements will be explained in detail below.

<C: 0.08% or less>
When the C content exceeds 0.08%, corrosion resistance decreases due to Cr carbide precipitation. Therefore, it is desirable that the C content be lower, but since a C content of 0.08% or less is permissible, this is set as the upper limit. From the viewpoint of improving corrosion resistance, the upper limit of the C content is preferably 0.030%, more preferably 0.025%. The lower limit of the C content is not particularly limited, but from the viewpoint of cost, it is preferably 0.001%, more preferably 0.007%.

<Si: 2.00% or less>
Si acts as a deoxidizing agent and a desulfurizing agent. If the Si content exceeds 2.00%, the toughness will decrease, so the Si content should be 2.00% or less. The upper limit of the Si content is preferably 0.65%. In order for Si to sufficiently act as a deoxidizing agent and a desulfurizing agent, the lower limit of the Si content is preferably 0.05%. A more preferable lower limit of the Si content is 0.30%.

<Mn: 4.00% or less>
Although Mn is a relatively inexpensive element, it increases the amount of austenite phase in the stainless steel sheet and further increases the solid solubility of nitrogen, thereby having the effect of suppressing the precipitation of Cr nitrides. On the other hand, since excessive content causes deterioration of corrosion resistance, the upper limit is set to 4.00%. The upper limit of Mn content is preferably 2.50%. The lower limit of the Mn content is preferably 0.85%, more preferably 2.00%.

<P: 0.040% or less>
P is an element that is unavoidably contained in stainless steel sheets, but since it degrades hot workability, the P content is set to 0.040% or less. The P content is preferably 0.035% or less. Although the lower limit is not particularly limited, it is preferably 0.005% or more from the viewpoint of cost.

<S: 0.030% or less>
S, like P, is an element that is unavoidably contained in stainless steel sheets, but since it deteriorates hot workability, toughness, and corrosion resistance, the upper limit of the S content is set to 0.030%. The upper limit of the S content is preferably 0.020%. Although the lower limit of the S content is not particularly limited, it is preferably 0.0001% from the viewpoint of cost. A more preferable lower limit of the amount of S is 0.0005%.

<Ni: 1.50-8.00%>
Ni is an element that improves the crevice corrosion resistance of stainless steel sheets. Crevice corrosion is corrosion that occurs when the pH inside the crevice decreases and a passive film cannot be maintained. Ni suppresses the dissolution of stainless steel sheets in a low pH environment. If the Ni content is too low, no improvement in crevice corrosion resistance can be obtained. Therefore, the Ni content is 1.50% or more. The lower limit of Ni content is preferably 2.00%. On the other hand, if the Ni content is excessive, not only will the cost increase, but also the austenite phase will be excessive and hot workability will deteriorate. Therefore, the Ni content is 8.00% or less. The upper limit of the Ni content is preferably 6.80%, more preferably 2.50%.

<Cr: 17.00-28.00%>
Cr is an element that improves the corrosion resistance of stainless steel sheets. From the viewpoint of corrosion resistance, the Cr content is 17.00% or more. The Cr content is preferably 20.00%. On the other hand, Cr is an element that increases the ferrite phase, and when a stainless steel sheet contains too much Cr, the ferrite phase becomes excessive and the toughness deteriorates. Therefore, the upper limit of the Cr content is set to 28.00%. The upper limit of the Cr content is preferably 24.50%, more preferably 22.00%.

<Mo: 5.00% or less>
Although Mo has a higher corrosion resistance improvement effect than Cr, it is a very expensive element, and excessive Mo content increases manufacturing costs. Moreover, if the Mo content is excessive, the stainless steel sheet becomes hard and the workability deteriorates. Therefore, the upper limit of the Mo amount is set to 5.00%. The upper limit of Mo content is preferably 2.95%, more preferably 0.60%. The corrosion resistance improving effect of Mo is poor when the Mo content is less than 0.01%, so the Mo content is set to 0.01% or more. The lower limit of the Mo content is preferably 0.05%, more preferably 0.20%.

<Cu: 0.05-3.00%>
Cu, like Ni, is an element that suppresses the dissolution of stainless steel sheets in a low pH environment. However, if the stainless steel sheet contains excessive Cu, hot workability is significantly impaired, so the upper limit of the Cu content is set to 3.00%. The upper limit of Cu content is preferably 1.40%. On the other hand, the above effects cannot be expected so much when the Cu content is less than 0.50%. Therefore, the lower limit of Cu content is set to 0.50%. The lower limit of the Cu content is preferably 0.60%, more preferably 0.70%.

<N: 0.080-0.320%>
N is an element that significantly increases corrosion resistance and increases the amount of austenite phase. In order to obtain this effect, the lower limit of the N content is 0.080%. The lower limit of the N content is preferably 0.150%, more preferably 0.155%. On the other hand, if the N content exceeds 0.320%, nitrides are formed in the steel and the corrosion resistance and toughness are reduced, so the upper limit of the N content is set to 0.320%. The upper limit of the N content is preferably 0.200%.

An example of the basic components of the duplex stainless steel plate to be sheared in the shearing method of the present embodiment has been described above, but in the present invention, it is preferable to appropriately contain other elements described below.

<Al: 0.003-0.050%>
Al is an element with a strong deoxidizing effect. For the deoxidizing effect of Al, the Al content is preferably 0.003% or more. The lower limit of the Al content is more preferably 0.005%. On the other hand, Al tends to form nitrides together with N, and when nitrides are formed, the toughness is greatly reduced. Therefore, the upper limit of the Al content is preferably 0.050%. The upper limit of the Al content is more preferably 0.040%.

<Nb: 0.005-0.20%>
Nb is an element that fixes C and N, prevents a decrease in corrosion resistance due to Cr carbide precipitation, and improves corrosion resistance. If the Nb content is 0.005% or more, the effect will be exhibited, so the lower limit of the Nb content is preferably 0.005%. On the other hand, if the Nb content exceeds 0.20%, the α phase may become hard due to solid solution strengthening and workability may be reduced, so the upper limit of the Nb content is preferably 0.20%.

<Ti: 0.005-0.20%>
Ti is an element that fixes C and N, prevents sensitization due to Cr carbide precipitation, and improves corrosion resistance. If the Ti content is 0.005% or more, the effect will be exhibited, so the lower limit of the Ti content is preferably 0.005%. On the other hand, if the Ti content exceeds 0.20%, the ferrite phase becomes hard and the toughness decreases, and Ti-based precipitates may cause a decrease in surface roughness. is preferably 0.20%.

<Co:0.005-0.25%>
Co suppresses precipitation of Cr carbide and suppresses deterioration of corrosion resistance. If the Co content is 0.005% or more, Co exhibits the above effects, so the lower limit of the Co content is preferably 0.005%. On the other hand, since Co is a rare element and expensive, the upper limit of the Co content is preferably 0.25%.

<V: 0.005-0.15%>
V is a strong carbide forming element. Therefore, when V, which tends to form carbides in a high temperature range, is contained, precipitation of Cr carbides is suppressed, and a decrease in corrosion resistance can be suppressed. If the V content is 0.005% or more, V exhibits the above effects, so the lower limit of the V content is preferably 0.005%. On the other hand, since a large V content causes hardening, the upper limit of the V content is preferably 0.15%.

<Sn: 0.005 to 0.20%, Sb: 0.005 to 0.20%>
Sn and Sb are elements that improve corrosion resistance, but are also elements that strengthen the solid solution of the ferrite phase. Therefore, it is preferable that the upper limit of the content of each of Sn and Sb is 0.20%. The lower limit of each content of Sn and Sb is more preferably 0.030%. When the content of either Sn or Sb is 0.005% or more, the effect of improving corrosion resistance is exhibited, so the content of each of Sn and Sb is preferably 0.005% or more. The upper limit of each content of Sn and Sb is more preferably 0.10%.

<Ga: 0.001-0.050%>
Ga is an element that contributes to improving corrosion resistance. If the Ga content is 0.001% or more, the effect of improving corrosion resistance will be exhibited, so the Ga content is preferably 0.001% or more. On the other hand, if the Ga content exceeds 0.050%, the effect of improving corrosion resistance is saturated, which only leads to an increase in cost. Therefore, the upper limit of the Ga content is preferably 0.050%.

<Zr: 0.005 to 0.50%>
Zr is an element that contributes to improving corrosion resistance. If the Zr content is 0.005% or more, the effect of improving corrosion resistance will be exhibited, so this is set as the lower limit. If the Zr content exceeds 0.50%, the effect is saturated, so the upper limit thereof is preferably 0.50%.

<Ta: 0.005-0.100%>
Ta is an element that improves corrosion resistance by modifying inclusions. When the Ta content is 0.005% or more, the above effects are exhibited. Therefore, the lower limit of the Ta content is preferably 0.005%. On the other hand, if the Ta content exceeds 0.100%, it may lead to a decrease in ductility or toughness at room temperature. Therefore, the upper limit of the Ta content is preferably 0.100%. The upper limit of Ta content is more preferably 0.050%.

<B: 0.0002 to 0.0050%>
B is an element that has the effect of suppressing secondary processing embrittlement and deterioration of hot workability. Further, B is an element that does not affect corrosion resistance. If the B content is 0.0002% or more, B exhibits the above effects, so the B content is preferably 0.0002% or more. On the other hand, if the B content exceeds 0.0050%, hot workability may deteriorate, so the upper limit of the B content is preferably 0.0050%. The upper limit of the B content is more preferably 0.0020%.

<O: 0.0070% or less>
O exists as an impurity, and when present in excess in steel, it produces oxides and reduces toughness. Therefore, the upper limit of the O content is preferably 0.0070%. The upper limit of the O content is more preferably 0.0050%. Although the lower limit of the O content is not particularly limited, it is preferably 0.0005% from the viewpoint of cost.

In an example of the basic components of the duplex stainless steel sheet to be subjected to shearing in the shearing method of the present embodiment, the remainder other than the above-mentioned elements is Fe and impurities, but other elements other than the above-mentioned elements may also be present. , can be contained within a range that does not impair the effects of this embodiment.

(Shear processing method)
The shearing method in this embodiment includes a compression plastic deformation step and a shearing step. Below, the compression plastic deformation step and the shearing step will be explained in detail.

<Compression plastic deformation process>
The compression plastic deformation process is a process of compressively plastic deforming the duplex stainless steel plate in the thickness direction. The present inventors compressively plastically deform a duplex stainless steel plate in the thickness direction to reduce the interval between austenite phases in the thickness direction of the duplex stainless steel plate, thereby creating a shearing process created by the shearing process described below. It has been found that the area ratio of the sheared surface on the cut surface (fracture surface) of the product can be increased.

FIG. 1 is a diagram for explaining an example of a compressive plastic deformation process in this embodiment. As shown in FIG. 1, in the compression plastic deformation process in this embodiment, a punch 1 and a counter punch 2 arranged to correspond to the punch 1 are used to deform the duplex stainless steel plate 10 in the thickness direction. The means for deforming can be selected. Specifically, the duplex stainless steel plate 10 fixed to the die 3 and the holding member 4 is pressed onto the punch 1 side and the counter punch 2 side as shown by the arrows in FIG. 1 using a press machine (not shown). Stress is applied in the thickness direction of the duplex stainless steel plate 10 from both sides. At this time, an equivalent stress σ of 400 MPa or more is applied to the duplex stainless steel plate 10 for a predetermined time (for example, 5 seconds or more). Thereby, the duplex stainless steel plate 10 can be compressively plastically deformed in the thickness direction in the region where stress is applied, and as a result, the interval between austenite phases can be reduced in the thickness direction. The equivalent stress σ of 400 MPa or more is a stress that is 17 times or more the shearing force applied when punching the duplex stainless steel plate 10 in the shearing process described later. The equivalent stress σ can be calculated using the formula shown in Equation 1 below.
In the above equation, σ ₁ is the maximum principal stress, σ ₂ is the intermediate principal stress, and σ ₃ is the minimum principal stress.

If the equivalent stress σ applied to the duplex stainless steel plate 10 in the compression plastic deformation process is smaller than 400 MPa, the duplex stainless steel plate 10 cannot be sufficiently compressed. In addition, in this specification, when the plate thickness of the duplex stainless steel plate 10 is compressed by 0.5% or more, it is defined that compression plastic deformation has been performed. Further, the equivalent stress σ applied to the duplex stainless steel plate 10 in the compressive plastic deformation process is greater than 880 MPa (in other words, it is 40 times greater than the shear force applied when punching the duplex stainless steel plate 10 in the shearing process described later). (also large), the tensile strength becomes greater than the tensile strength of the duplex stainless steel plate 10, and there is a concern that the processed product may be damaged. Therefore, in the compressive plastic deformation step in this embodiment, an equivalent stress σ of 400 MPa≦σ≦880 MPa is applied to the duplex stainless steel plate 10. In the compressive plastic deformation process in this embodiment, the stress applied to the duplex stainless steel plate 10 is 40 times or less the shear force applied when punching the duplex stainless steel plate 10 in the shearing process described later.

In the shearing method in this embodiment, an equivalent stress σ in the above range is applied to the duplex stainless steel plate 10 so as to compress it in the thickness direction, so that the duplex stainless steel plate 10 is The interval between austenite phases in the thickness direction of the stainless steel plate 10 is set to be less than 4.0 μm.

In addition, in this embodiment, although the structure which applies stress to the duplex stainless steel plate 10 using the punch 1 and the counter punch 2 was demonstrated, this invention is not limited to this. One aspect of the present invention may be configured to apply stress to the duplex stainless steel plate 10 only by the punch 1, or may be configured to apply stress to the duplex stainless steel plate 10 using other methods such as rolling. It's okay. Note that the area to which stress is applied may be in the vicinity of where the shearing process is performed, and it is not necessarily necessary to apply stress to other areas that are not used for manufacturing the processed product.

<Shearing process>
The shearing process is a process of press-shearing the duplex stainless steel plate 10 that has been compressively plastically deformed in the compressive plastic deformation process using the punch 1 and the die 3. Hereinafter, a case where press punching is performed will be described as an example of the shearing process.

FIG. 2 is a diagram for explaining the shearing process in this embodiment. As shown in FIG. 2, in the shearing step in this embodiment, the duplex stainless steel plate 10 fixed to the die 3 and the restraining member 4 is Then, the punch 1 presses the duplex stainless steel plate 10 to perform a punching process.

FIG. 3 is a photograph showing a cut surface of a punched product manufactured by a normal punching process. In the punching process using a punch and die, as shown in FIG. 3, on the cut surface of the punched product in the punching direction, a sag, a sheared surface, and a fractured surface are formed in this order from the side pressed by the punch. Ru. The fracture surface is a surface formed by the progression of cracks that occur when pressing a duplex stainless steel plate with a punch.

Here, in the shearing method in this embodiment, as described above, before performing the punching process, an equivalent stress σ of 400 MPa or more is applied to the duplex stainless steel plate 10 in the compressive plastic deformation process in the plate thickness direction. There is. As a result, the distance between austenite phases becomes smaller in the thickness direction. Therefore, in the shearing step, when the duplex stainless steel plate 10 is pressed with a punch, the austenite phase makes it difficult for cracks to develop, and as a result, the progression of cracks can be suppressed. Thereby, the area ratio of the fractured surface in the cut surface of the sheared product 20 to be manufactured can be reduced, and as a result, the area ratio of the sheared surface can be increased. Specifically, after the compression plastic deformation step, the interval between austenite phases in the thickness direction of the duplex stainless steel sheet 10 is set to less than 4.0 μm, so that the area ratio of the sheared surface in the cut surface is 60% or more. be able to. When the distance between austenite phases in the thickness direction of the duplex stainless steel sheet 10 is 4.0 μm or more, the effect of suppressing the progression of cracks by the austenite phase is not efficiently expressed.

In the shearing method in this embodiment, the clearance, which is the distance between the punch 1 and the die 3 in the direction perpendicular to the punching direction, is set to a value used in normal punching (specifically, the clearance is the distance between the punch 1 and the die 3 in the direction perpendicular to the punching direction). 7 to 10% of the plate thickness), the area ratio of the sheared surface is larger than that of conventional punched products (specifically, when the sheared surface area ratio is A punched product 20 (having a cross-sectional area ratio of 60% or more) can be manufactured. As a result, the punched product 20 has a high area ratio of sheared surfaces while reducing the load on the mold without performing precision shearing that imposes a high load on the mold (that is, punch and die) as in Patent Document 1. can be manufactured.

The sheared product 20 in this embodiment, which is manufactured by the above-described shearing method, is a sheared product that is manufactured by punching out a duplex stainless steel plate 10 by shearing in the thickness direction. The sheared product 20 has an interval between austenite phases in the punching direction of less than 4.0 μm in a cut plane parallel to a plane perpendicular to the rolling direction of the duplex stainless steel plate 10, and an area ratio of the sheared plane in the cut plane. is 60% or more. Therefore, the processing amount for polishing the sheared product 20 can be reduced, and the polishing yield can be improved.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

An embodiment of the present invention will be described below.

In this example, C: 0.001%, Si: 0.40%, Mn: 3.1%, P: 0.020%, S: 0.003%, Ni: 2.1%, Cr: 21 .2%, Mo: 0.40%, Cu: 0.60%, N: 0.17%, with the balance consisting of Fe and unavoidable impurities, a duplex stainless steel plate with a thickness of 1.0 mm was used. Thus, punched products (sheared products) of Examples 1 to 10 and Comparative Examples 1 to 10 were produced.

The punched product of Example 1 was produced as follows. First, a load of 329 tons was applied from both sides of the duplex stainless steel plate in the thickness direction using a punch and a counter punch. This load is 21.9 times the shear load (punching load) applied in the punching process of 15, resulting in an equivalent stress of 560 MPa.

Next, the stress-applied duplex stainless steel was subjected to punching by applying a shear load of 15 tons to produce a disk-shaped punched product of Example 1 with a diameter of 60 mm.

The punched products of Examples 2 to 10 and Comparative Examples 1 to 10 were produced in the same manner as the punched product of Example 1, except that the magnitude of the stress applied using the punch and counter punch was changed. In addition, for the punched product of Comparative Example 1, no load was applied using a punch or a counter punch. The loads applied in the production of the punched products of Examples 1 to 10 and the punched products of Comparative Examples 1 to 10, the load ratio of the load to the shear load applied in the punching process, and the value of the equivalent stress. It is shown in Table 1 below.

For Examples 1 to 10 and Comparative Examples 1 to 10, the spacing between austenite phases in the thickness direction of the duplex stainless steel plates after applying stress using a punch and a counter punch was measured. Specifically, a cut surface obtained by cutting a region to which stress was applied using a punch and a counter punch along a plane parallel to the plate thickness direction was observed using an optical microscope. FIG. 4 is an optical microscope image of a cut surface of the duplex stainless steel plate of Comparative Example 1 to which no stress was applied, cut along a plane parallel to the plate thickness direction. FIG. 5 is an optical microscope image of a cut surface obtained by cutting a region to which stress was applied using a punch and a counter punch on a plane parallel to the plate thickness direction in Example 1. The distance between the austenite phases in the thickness direction of a duplex stainless steel plate is determined by dividing the optical microscope image into four equal parts so as to divide the fibrous austenite phase at the cut plane, as shown in Figures 4 and 5. The interval with the longest distance between austenite phases on the line was extracted, and the average value of the intervals was taken as the interval between austenite phases. In addition, the optical microscope image was acquired for three fields of view, the above-mentioned operation was performed in each field, and the average value was calculated. Table 1 shows the calculated spacing between austenite phases for Examples 1 to 10 and Comparative Examples 1 to 10.

Furthermore, for the punched products of Examples 2 to 10 and Comparative Examples 1 to 10, the area ratio of the sheared surface in the cut surface was measured. Specifically, the cut surface of the punched product was observed using an optical microscope. FIG. 6 is an optical microscope image of a cut surface of the punched product of Example 1. FIG. 7 is an optical microscope image of the cut surface of the punched product of Comparative Example 1. The area ratio of the sheared surface is determined by measuring the shortest distance between the boundary between the sheared surface and the fractured surface and the surface of the punched product, and then converting the distance to the surface of the punched product, as shown in Figures 6 and 7. It was calculated by dividing by the thickness. Table 1 shows the calculated area ratios of sheared surfaces for the punched products of Examples 1 to 10 and Comparative Examples 1 to 10.

As shown in Table 1, in Examples 1 to 10 in which an equivalent stress of 400 MPa or more was applied to the duplex stainless steel plate, the duplex stainless steel plate was The distance between the austenite phases was 3.2 μm or less. Therefore, in the punched products of Examples 1 to 10, the area ratio of the sheared surface in the cut surface was as large as 63.0% or more.

On the other hand, in Comparative Examples 1 to 10 in which an equivalent stress of less than 400 MPa was applied to the duplex stainless steel plate, the austenite in the thickness direction of the duplex stainless steel after applying stress using a punch and a counter punch was The spacing between the phases was 4.0 to 4.2 μm. Therefore, in the punched products of Comparative Examples 1 to 10, the area ratio of the sheared surface in the cut surface was as small as 54.0% to 55.0%.

1 Punch 2 Counter punch 3 Die 10 Duplex stainless steel plate 20 Sheared product

Claims (7)

A shearing method for shearing a duplex stainless steel plate containing a ferrite phase and an austenite phase in the thickness direction, the method comprising:
a compression plastic deformation step of compressively plastic deforming the duplex stainless steel plate in the thickness direction;
A shearing method comprising a shearing step of pressing and shearing the duplex stainless steel plate using a die and a punch. In the compressive plastic deformation step, the duplex stainless steel plate is compressively plastically deformed in the thickness direction by applying an equivalent stress of 400 MPa≦σ≦880 MPa to the duplex stainless steel plate. Shearing method. 3. The method according to claim 1, wherein in the compressive plastic deformation step, the duplex stainless steel plate is compressively plastically deformed in the thickness direction so that the interval between austenite phases in the thickness direction is less than 4.0 μm. Shearing method. Any one of claims 1 to 3, wherein in the compressive plastic deformation step, the duplex stainless steel plate is compressively plastically deformed in the thickness direction using the punch and a counter punch arranged to face the punch. or the shearing method described in item 1. The duplex stainless steel plate has, in mass %, C: 0.08% or less, Si: 2.00% or less, Mn: 4.00% or less, P: 0.040% or less, S: 0.030% or less. , Ni: 1.50-8.00%, Cr: 17.00-28.00%, Mo: 5.00% or less, Cu: 0.05-3.00%, and N: 0.080- The shearing method according to any one of claims 1 to 4, wherein the shearing method contains 0.320%, with the remainder consisting of Fe and impurities. A sheared product produced from a duplex stainless steel plate containing a ferrite phase and an austenite phase by press shearing in the plate thickness direction,
In the cut plane perpendicular to the rolling direction of the duplex stainless steel plate,
the spacing between austenite phases in the shear direction is less than 4.0 μm,
A sheared product with an area ratio of sheared surfaces of 60% or more. In mass%, C: 0.08% or less, Si: 2.00% or less, Mn: 4.00% or less, P: 0.040% or less, S: 0.030% or less, Ni: 1.50~ Contains 8.00%, Cr: 17.00 to 28.00%, Mo: 5.00% or less, Cu: 0.05 to 3.00%, and N: 0.080 to 0.320%. The sheared product according to claim 5, wherein the remainder consists of Fe and impurities.

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