JP5667504B2 - Nonmagnetic stainless steel - Google Patents

Description

  The present invention relates to a nonmagnetic stainless steel used in a strong magnetic field environment, and more particularly to a precipitation strengthened high strength nonmagnetic stainless steel having excellent corrosion resistance and strength.

  Recently, as a means of transportation to replace railway vehicles, such as Shinkansen, driven by electric motors, a magnetic motor is used to switch the magnetic field by a linear motor provided on the ground or on the vehicle side to provide propulsive force. A magnetically levitated vehicle (linear motor car) that attracts attention attracts attention. As a material for such a structure such as a superconducting magnet, for example, austenitic stainless steel is used (for example, Patent Document 1). In Patent Document 1, a composition and a controlled rolling method for increasing the strength and toughness of austenitic stainless steel at extremely low temperatures are disclosed, and the amount of C to be added is reduced to 0.03% by mass or less, By adding N: 0.10 to 0.40% by mass and Nb: 0.02 to 0.25% by mass, the recrystallization temperature of the steel is increased to facilitate controlled rolling, and a fine crystal structure after rough rolling. It is disclosed that it becomes easy to obtain.

  On the other hand, when a magnetically levitated vehicle travels, the magnetic force acting from the outside acts as a magnetic resistance. For example, a structure such as a bridge supporting a guideway to be laid has a conventional iron bridge and reinforced concrete. It is necessary to use a non-magnetic material. For the same reason, it is required to use a non-magnetic material for a member such as a bolt for fixing the ground electromagnetic coil to the guide way. The development of non-magnetic stainless steel used for such structures and bolts is being promoted recently.

  For example, Patent Document 2 discloses that in high-strength nonmagnetic high-Mn steel, the amount of Cr added to increase the magnetic permeability by forming a ferrite structure is reduced to 15% or less.

Japanese Patent Laid-Open No. 2-97649 JP-A-2-104633

  However, the conventional techniques described above have the following problems. Since the austenitic stainless steel of Patent Document 1 has increased strength by work hardening by controlled rolling and controlled cooling, it is necessary to uniformly and sufficiently work harden the inside of the stainless steel in the case of large diameter materials or large parts. However, there is a limit to improving the strength. Moreover, in the technique of patent document 1, there exists a problem that the shape and dimension of stainless steel which can be manufactured are restrict | limited and it is difficult to manufacture the stainless steel component of a complicated shape.

  In addition, the high-strength nonmagnetic high-Mn steel disclosed in Patent Document 2 cannot secure sufficient corrosion resistance, and is not suitable for applications where corrosion resistance such as bridges is desired.

  The present invention has been made in view of such a problem, and an object thereof is to provide a nonmagnetic stainless steel having high corrosion resistance under a strong magnetic field environment and having a high strength capable of withstanding a high load and a high load. To do.

  The nonmagnetic stainless steel according to the present invention has C: 0.20 to 0.55 mass%, Cr: more than 15.0 mass% and 20.0 mass% or less, N: 0.025 to 0.25 mass%, V: 1.0 to 2.5 mass%, Mn: 4.50 to 9.50 mass%, Ni: 3.0 to 10.0 mass%, Si: 0.01 to 1.00 mass%, and Al: Nonmagnetic stainless steel containing 0.001 to 0.050 mass%, the balance being Fe and inevitable impurities, and the total content of C and N is 0.3 to 0.6 mass% Yes, when the contents of Cr, N, C and V are [Cr], [N], [C] and [V], respectively, the N content [N] is expressed by the following formula 1. The ratio [N] / X to the numerical value X is 0.4 to 3.0, and the V content [V] corresponds to the numerical value Y represented by the following mathematical formula 2. The ratio [V] / Y is equal to or 0.7 to 1.5.

  This non-magnetic stainless steel further includes Cu: 0.05 to 4.00 mass%, Mo: 0.05 to 2.00 mass%, W: 0.05 to 2.00 mass%, and Nb: 0.01. To 1.00% by mass, Ti: 0.01 to 1.00% by mass, B: 0.0005 to 0.0200% by mass, and Mg: 0.0005 to 0.0200% by mass It is preferable to contain 1 type, or 2 or more types.

  The nonmagnetic stainless steel is further selected from the group consisting of P: 0.02 to 0.20 mass%, S: 0.005 to 0.300 mass%, and Se: 0.005 to 0.200 mass%. 1 type, or 2 or more types can be contained.

  In the nonmagnetic stainless steel of the present invention, the contents of C, N, V and Cr are optimized. Thereby, MC type carbonitride precipitates preferentially by the aging treatment, and the hardness and strength can be increased in the nonmagnetic stainless steel containing a large amount of Cr to ensure corrosion resistance.

It is a figure which shows the appropriate addition range of N and Cr in this invention.

  Hereinafter, the nonmagnetic stainless steel according to the embodiment of the present invention will be specifically described. The nonmagnetic stainless steel of the present embodiment includes C: 0.20 to 0.55 mass%, Cr: more than 15.0 mass% and 20.0 mass% or less, N: 0.025 to 0.25 mass%, V: 1.0 to 2.5 mass%, Mn: 4.50 to 9.50 mass%, Ni: 3.0 to 10.0 mass%, Si: 0.01 to 1.00 mass%, and Al: It is a nonmagnetic stainless steel containing 0.001 to 0.050 mass% with the balance being Fe and inevitable impurities, and the total content of C and N is 0.3 to 0.6 mass% . Further, when the contents of Cr, N, C, and V are [Cr], [N], [C], and [V], respectively, the N content [N] is expressed by the following Equation 3. The ratio [N] / X to the numerical value X is 0.4 to 3.0, and the content [V] of V is the ratio [V] / Y to the numerical value Y represented by the following formula 4 is 0.7 to 1.5.

In nonmagnetic stainless steel, in order to provide high corrosion resistance even in an environment with a strong magnetic field, Cr may be contained in a larger amount than in the past. However, the inclusion of a large amount of Cr means that the magnetic permeability increases due to the formation of a ferrite structure in the steel, and the M ₂₃ C ₆ type Cr carbonitride is formed. When aging the stainless steel, a sufficient amount of hardening due to precipitation strengthening cannot be obtained. The inventor of the present application has conducted various experimental studies in order to solve this problem. And in high Cr stainless steel, in order to maintain nonmagnetism, it discovered that Mn and C which contribute to nonmagnetism should just be added. In addition, in this non-magnetic stainless steel, in order to obtain high strength that can withstand high loads and high loads, it is found that an appropriate amount of C and N may be added to Cr and V, and the configuration of the present invention is found. It was.

  That is, in the present invention, the addition of Cr suppresses an increase in the magnetic permeability of stainless steel by adding Mn and C while maintaining high corrosion resistance. By adding N, C and N are preferentially set to V. To form MC type carbonitride, and precipitation of MC type carbonitride improves the strength of nonmagnetic stainless steel.

  That is, in the present invention, the ingot having a predetermined composition is subjected to rolling processing and straightening processing, and then subjected to solution heat treatment, and then the material after the solution treatment is used for, for example, a bolt or the like, Cut to predetermined dimensions. And after processing shapes, such as diameter expansion, jaw processing, and a hexagon bolt head, by cold processing or cutting, an aging treatment is given. In this aging treatment, in the present invention, MC type carbonitride in which C and N are preferentially bonded to V is precipitated. Thus, in the present invention, the hardness and strength can be increased in the nonmagnetic stainless steel containing a large amount of Cr to ensure corrosion resistance only by precipitation hardening by heat treatment. Therefore, compared to the case where the strength is increased by work hardening by controlled rolling and controlled cooling, etc., sufficiently high strength is obtained up to the inside of the stainless steel, and there are almost no restrictions due to dimensions and shapes, so non-magnetic stainless steel A great degree of freedom can be obtained for products that can be applied. In particular, in the case of large-diameter jaw bolts and parts having complicated shapes, precipitation strengthening by heat treatment is optimal as in the present invention in order to obtain sufficient strength uniformly from the surface to the inside of the steel.

  Hereinafter, the reason for the numerical limitation in the nonmagnetic stainless steel of this embodiment will be described.

C: 0.20 to 0.55 mass%
C combines with V to produce MC-type carbonitrides and contributes to precipitation strengthening in the aging treatment. That is, the carbonitride produced between C and V has the effect of increasing the hardness and strength of stainless steel. C contributes to non-magnetism as an austenite former. If the C content is less than 0.20% by mass, the effect of sufficient precipitation strengthening due to the aging treatment cannot be obtained, and if it exceeds 0.55% by mass, the carbonitride produced is coarsened and the toughness is deteriorated. To do. Therefore, in the present invention, the C content is defined as 0.20 to 0.55 mass%.

Cr: more than 15.0% by mass and not more than 20.0% by mass Cr is added to ensure high corrosion resistance, oxidation resistance, and non-magnetism in non-magnetic stainless steel. Moreover, Cr has an effect of suppressing martensite formation during cold working. When the content of Cr is 15.0% by mass or less, these effects cannot be sufficiently obtained. When the content of Cr exceeds 20.0% by mass, the M ₂₃ C ₆ type is used in the aging treatment. Thus, the production of Cr carbonitride of V is inhibited, and the production of MC type carbonitride having V as a main component is inhibited, and the effect of precipitation strengthening by aging treatment cannot be sufficiently obtained. Therefore, in the present invention, the Cr content is specified to be more than 15.0 mass% and not more than 20.0 mass%.

N: 0.025 to 0.25% by mass
N, like C, is combined with V to form MC-type carbonitrides and contributes to precipitation strengthening by aging treatment. In stainless steel with a high Cr content, MC type carbonitride is added during the aging treatment so as to be preferentially produced over other carbonitrides. When the N content is less than 0.025% by mass, the carbonitride precipitated by aging treatment is not MC type, but becomes M ₂₃ C ₆ type Cr-based carbonitride, and the effect of precipitation strengthening by aging treatment Becomes insufficient, and the strength decreases. Moreover, corrosion resistance falls by the reduction | decrease of Cr content in a matrix. By adding N in an amount of 0.025% by mass or more, the precipitate formed by the aging treatment becomes a V-type MC carbonitride, and the effect of precipitation strengthening can be sufficiently obtained without reducing the corrosion resistance. On the other hand, when the addition amount of N exceeds 0.25% by mass, a huge eutectic carbonitride crystallizes during solidification and the toughness deteriorates. Therefore, in the present invention, the N content is defined as 0.025 to 0.25% by mass.

C and N: 0.3 to 0.6% by mass in total
As described above, in the present invention, C and N are components that contribute to the production of MC-type carbonitrides. By making these contents 0.3 to 0.6% by mass in total, MC type carbonitride can be produced at an optimum ratio by both components. That is, when the total content of C and N is less than 0.3% by mass, the amount of MC-type carbonitride produced is reduced, and the effect of precipitation strengthening in the aging treatment is insufficient. On the other hand, if the total content of C and N exceeds 0.6% by mass, the produced carbonitride becomes coarse and the toughness deteriorates.

[N] / X: 0.4 to 3.0 (where X = [Cr] /100−0.10)
The non-magnetic stainless steel of the present invention is a high Cr precipitation strengthened stainless steel to which C and N are added. When a large amount of Cr is added in excess of an appropriate amount, M ₂₃ C ₆ is used during aging treatment. When a type of Cr carbonitride is produced and a large amount of N is added in excess of an appropriate amount, a huge eutectic carbonitride is crystallized. Thereby, the generation of MC type carbonitrides mainly composed of V during the aging treatment is inhibited, and the effect of precipitation strengthening by the aging treatment may not be sufficiently obtained. Therefore, as described above, in addition to defining the contents of C and N by the total amount, both Cr and N are added in combination in an optimum amount. That is, in the present invention, the effect of precipitation strengthening can be sufficiently obtained by aging treatment by adding N in an optimum amount according to the Cr amount. When the ratio [N] / X is less than 0.4, the content of N is reduced with respect to the amount of Cr, and it is difficult to obtain the effect of preferential production of MC type carbonitride by adding N. Strength decreases. On the other hand, when the ratio [N] / X exceeds 3.0, the content of N increases with respect to the amount of Cr, and during the solidification, huge eutectic carbonitrides crystallize and toughness deteriorates. It becomes like this.

  The relationship between the optimum addition amounts of N and Cr in the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a proper addition range of N and Cr in the present invention, and a portion surrounded by a solid line shows the range of the present invention. Note that the white circle plots in FIG. 1 to No. An example in which the content of N and Cr of 10 was shown and the tensile strength, ductility, corrosion resistance, and non-magnetism were good. The black circle plot indicates the comparative example No. which does not satisfy the scope of the present invention. 39, no. 42, no. 45-No. 48, no. 53 and no. A comparative example in which one or more items of tensile strength, ductility, corrosion resistance, and non-magnetic properties are deteriorated is shown. In FIG. 1, the numbers given to the plots indicate the numbers of the examples or comparative examples. As shown in FIG. 1, in the present invention, N: 0.025 to 0.25% by mass, Cr: more than 15.0% by mass and 20.0% by mass or less, and the value of the ratio [N] / X Is 0.4 to 3.0, a nonmagnetic stainless steel having excellent tensile strength, ductility, corrosion resistance and nonmagnetic properties can be obtained.

V: 1.0 to 2.5% by mass
V has the effect of generating MC type carbonitrides by combining with C and N during the aging treatment and increasing the strength of the nonmagnetic stainless steel by precipitation strengthening. If the V content is less than 1.0% by mass, the effect of precipitation strengthening cannot be sufficiently obtained. If the V content exceeds 2.5% by mass, the precipitated carbonitrides become coarse and toughness Deteriorates. Therefore, V is added in an amount of 1.0 to 2.5% by mass.

[V] / Y: 0.8 to 1.5 (Y = 4.25 × [C] + 3.64 × [N])
In the present invention, in high Cr stainless steel, in order to preferentially produce MC type carbonitride over other carbonitrides during aging treatment, an appropriate amount of C and N is added and combined with V. Yes. Therefore, not only the content of V but also the content of V is defined by the ratio to the respective contents of C and N, so that the amount of MC type carbonitride produced can be optimized. That is, when the ratio [V] / Y is less than 0.8, the amount of MC type carbonitride produced is not sufficient, and the effect of precipitation strengthening by aging treatment cannot be obtained sufficiently. On the other hand, when [V] / Y exceeds 1.5, the content of V becomes excessive with respect to the contents of C and N, toughness deteriorates, and cold workability deteriorates.

Mn: 4.50 to 9.50 mass%
Mn is added as a component that generates austenite, and suppresses the generation of martensite during cold working. Mn is important for increasing the strength of nonmagnetic stainless steel, promotes the solid solution of carbonitride during the solution treatment, increases the precipitation amount of carbonitride during the aging treatment, Has the effect of increasing strength. Moreover, Mn contributes to the nonmagnetic property of stainless steel. In order to obtain these effects, 4.50% by mass or more of Mn is added in the present invention. Industrially, when non-magnetic stainless steel is manufactured using a mass-produced arc-type electric furnace, the amount of Mn added is generally 9.50% by mass or less for ease of manufacturing. .

Ni: 3.0 to 10.0% by mass
Ni is important as an austenite forming element and is a basic element of stainless steel. That is, by adding Ni, the cold workability and corrosion resistance of the nonmagnetic stainless steel are improved, and the formation of martensite during cold working is suppressed. However, since Ni is expensive, the upper limit of the amount added is 10.0% by mass.

Si: 0.01 to 1.00% by mass
Si is added to molten steel as a deoxidizer. That is, if the addition amount of Si is less than 0.01% by mass, the molten steel cannot be sufficiently deoxidized, and if the addition amount of Si exceeds 1.00% by mass, the cold workability of nonmagnetic stainless steel and Corrosion resistance deteriorates.

Al: 0.001 to 0.050 mass%
Al is added to molten steel as a deoxidizing agent in the same manner as Si. That is, if the addition amount of Al is less than 0.0001% by mass, the molten steel cannot be sufficiently deoxidized, and if the addition amount of Al exceeds 0.050% by mass, oxide inclusions increase, The toughness and fatigue properties of magnetic stainless steel deteriorate.

Cu: 0.05 to 4.00 mass%
Cu can be added in an appropriate amount in place of Ni as a component that improves the ductility of the nonmagnetic stainless steel and improves the cold workability. However, if a large amount of Cu exceeding 4.00% by mass is added, the nonmagnetic stainless steel tends to become brittle, so Cu can be added in the range of 0.05 to 4.00% by mass.

Mo: 0.05 to 2.00% by mass
Mo can be added as a component that enhances corrosion resistance. However, when a large amount of Mo exceeding 2.00% by mass is added, coarse carbides are generated, and the toughness tends to decrease. It can be added in the range of 0.05 to 2.00% by mass.

W: 0.05 to 2.00% by mass
W, like Mo, can be added in the range of 0.05 to 2.00% by mass as a component that improves corrosion resistance. If added in a large amount, coarse carbides are generated as in the case of Mo, and the toughness tends to be lowered. Therefore, W can be added in the range of 0.05 to 2.00% by mass.

Nb: 0.01 to 1.00% by mass
Nb can be added as a component that generates carbonitrides, refines crystal grains, and increases strength. However, when a large amount of Nb exceeding 1.00% by mass is added, coarse carbides are generated. Nb can be added in the range of 0.01 to 1.00% by mass.

Ti: 0.01 to 1.00% by mass
Ti, like Nb, can be added as a component that generates carbonitrides, refines crystal grains, and increases strength. However, if added in a large amount, coarse carbides are generated similarly to Nb, and the toughness tends to be lowered, so Ti can be added in the range of 0.01 to 1.00% by mass. .

B: 0.0005 to 0.0200 mass%
B can be added in the range of 0.0005 to 0.0200 mass% in order to improve hot workability. When a large amount of B exceeding 0.0200 mass% is added, hot workability is lowered.

Mg: 0.0005 to 0.0200 mass%
Mg, like B, can be added to improve hot workability. When a large amount of Mg is added, the hot workability decreases as in the case of B.

P: 0.02 to 0.20 mass%
P can be added in the range of 0.02 to 0.20 mass% in order to improve the machinability of the nonmagnetic stainless steel. When a large amount of P exceeding 0.20% by mass is added, the nonmagnetic stainless steel becomes brittle.

S: 0.005 to 0.300 mass%
S, like P, can be added in the range of 0.005 to 0.300 mass% in order to improve the machinability of nonmagnetic stainless steel. When a large amount of S exceeding 0.300 mass% is added, the nonmagnetic stainless steel becomes brittle.

Se: 0.005 to 0.200 mass%
Se, like P and S, can be added in the range of 0.005 to 0.200 mass% in order to improve the machinability of the nonmagnetic stainless steel. When a large amount of Se exceeding 0.200% by mass is added, the nonmagnetic stainless steel becomes brittle.

  Hereinafter, the effect of the Example of this invention is demonstrated compared with the comparative example which remove | deviates from the scope of the present invention. First, co-test materials having various compositions were prepared. The composition of this test material is shown in Table 1-1 to Table 2-2. In addition, specimen No. shown in Table 1-1 thru | or Table 1-3. 1 to No. No. 34 is an example whose composition satisfies the scope of the present invention, and specimens No. 34 and No. 2-2 shown in Table 2-1 and Table 2-2. 35 thru | or No. 56 is a comparative example whose composition does not satisfy the scope of the present invention. In Tables 1-2 and 1-3, a blank in the content of Cu, Mo, W, Nb, Ti, B, Mg, P, S, and Te means that the content is at an impurity level. To do. That is, in a mass production furnace, for example, C, Mo, W, etc. are mixed at an inevitable impurity level of C: 0.1 mass% or less, Mo: 0.05 mass% or less, and W: 0.05 mass% or less. There are things to do. About each sample material, Md30 value computed from the composition is shown to Table 3-1 and Table 3-2. The Md30 value is a parameter indicating the ease of work-induced martensite transformation in which the metastable austenite phase after solution heat treatment is transformed into a martensite phase by cold working. The temperature at which 50% of the structure is transformed into martensite when a tensile strain of 0.3 is applied is defined as in the following formula 5. That is, the smaller the Md value is, for example, −100 or less, the austenite structure is stable, and it is difficult to transform into martensite having a high magnetic permeability, so that nonmagnetism can be maintained.

  About each sample material of the Example and comparative example shown in Table 1-1 thru | or 2-2, after casting each molten steel into a predetermined | prescribed casting_mold | template and shape | molding in an ingot, it is by hot forging (forging heating temperature: 1150 degreeC). The steel bar was forged into a steel bar having a diameter of 44 mm, and then the steel bar was formed into a bar-shaped member having a cross-sectional shape of 24 mm square (24 mm × 24 mm) by hot rolling and used as a specimen for a hardness test. Thereafter, the test piece was subjected to a solution treatment that was held at a treatment temperature of 1150 ° C. for 1 hour using an electric muffle furnace, and the Rockwell hardness (HRB hardness) of the test piece after the solution treatment was measured. Tables 3-1 and 3-2 show the HRB hardness after the solution treatment of each test piece.

  After that, the material after the solution treatment is roughly processed into test pieces for each evaluation test, subjected to aging treatment at 650 ° C. and 700 ° C. for 8 hours, and then finished into test pieces for each evaluation test. And subjected to an evaluation test. That is, the HRC hardness after aging treatment at 650 ° C. and 700 ° C. was measured with a Rockwell hardness meter. The measurement results are shown in Table 3-1 and Table 3-2.

  Moreover, about the test piece of each Example and comparative example which performed the aging treatment at 700 degreeC aging temperature, ductility, corrosion resistance, and nonmagnetic were evaluated on condition of the following. That is, each specimen was processed into a No. 14A test piece specified in JIS Z2201, and the tensile strength and drawing (ductility) were measured by the tensile test method specified in JIS Z2241. And when each tensile strength of 900 MPa or more (HRC: 28.0 or more) was obtained at each aging treatment temperature, it was determined that the tensile strength was good. Also, when the aperture was 40% or more, the ductility was very good (（), when the aperture was 30% or more and less than 40%, the ductility was good (◯), and the aperture was less than 30%. In some cases, the ductility was evaluated as poor (x). For corrosion resistance, 5% NaCl was sprayed for 8 hours at a temperature of 35 ° C. on a test piece processed to a diameter of 20 mm and a length of 15 mm according to the salt spray test method specified in JIS Z2371, and the cross section of the test piece was applied. The number of island-like rusts produced was visually evaluated by the rating number method. That is, the rust generated in the circular cross section of the test piece, excluding those generated from the edge of the circular cross section, was checked against the rating number standard chart specified in JIS H8502, and the occurrence of rust in the cross section of each test piece was checked. The score was evaluated. And when the rating number is 8 or more (area corrosion rate in the cross section of the test piece is 0.25% or less), the corrosion resistance is very good (（), and the rating number is 6 or more and less than 8 points (area corrosion rate) Of 0.25% to 1.00% or less) was evaluated as having good corrosion resistance (O). For non-magnetism, the permeability in the cross section of each test piece was measured with a permeability meter so as not to be affected by the surface scale. And the thing whose magnetic permeability was 1.02 or less and whose Md30 value was -100 or less was evaluated as favorable non-magnetic ((circle)).

  As shown in Table 3-1, Example No. 1 to No. Since each composition of the nonmagnetic stainless steel No. 34 satisfies the scope of the present invention, Comparative Example No. 34 having a composition that does not satisfy the scope of the present invention. Compared to 35 to 56, the corrosion resistance is high, and the nonmagnetic property and ductility are improved. In this Example No. 1 to No. 34, no. 11, no. 12 and no. Since 31 contains an appropriate amount of Cu, the ductility of nonmagnetic stainless steel was improved. In addition, Example No. 13 to No. 16 and no. No. 32 contained a suitable amount of Mo or W, thereby improving the corrosion resistance of the nonmagnetic stainless steel. Example No. 17-No. 20 and no. No. 33 contained an appropriate amount of Nb or Ti, thereby improving the tensile strength of nonmagnetic stainless steel.

  Comparative Example No. In No. 35, since the contents of Cr and N were less than the range of the present invention, the corrosion resistance was lowered, and the ratio [N] / X exceeded the range of the present invention, so the ductility was lowered. This Comparative Example No. Although the amount of Cr was small, the Md30 value of −100 or less was obtained with other elements, and the nonmagnetic property was good. Comparative Example No. In No. 35, although the N content was less than the range of the present invention, the C and V contents were large, and no decrease in tensile strength was observed. Comparative Example No. No. 36 had a low N content, and the ratio [N] / X was less than the range of the present invention, so the tensile strength decreased. This Comparative Example No. In No. 36, although the N content was less than the range of the present invention, the Cr and Si contents were large, and no deterioration in corrosion resistance was observed.

  Comparative Example No. 37, no. 38 and no. In No. 40, the N content was small and the ratio [N] / X was less than the range of the present invention, so the tensile strength decreased, and the corrosion resistance deteriorated due to the lack of Cr and N. Of these, Comparative Example No. 38 and no. No. 40 has a large Md30 value due to insufficient Cr amount, and nonmagnetic properties deteriorated. Although the amount of Cr was small, Md30 value of −100 or less was obtained by other elements, and the nonmagnetic property was good. Comparative Example No. In No. 40, since the Al content exceeded the range of the present invention, the ductility decreased. Comparative Example No. 39 and no. In No. 41, since the Cr content was less than the range of the present invention, the corrosion resistance was deteriorated, the Md30 value was increased, and the nonmagnetic property was also deteriorated.

  Comparative Example No. No. 42 has a low N content, the total amount of N and C is also less than the range of the present invention, and the ratio [N] / X is also less than the range of the present invention. The Md30 value increased and the non-magnetic property also deteriorated. Comparative Example No. In No. 43, the C content was less than the range of the present invention, so the tensile strength was lowered. On the other hand, Comparative Example No. Since No. 44 had much C content, ductility fell.

  Comparative Example No. No. 45, since the Cr content was less than the range of the present invention, the corrosion resistance deteriorated, the N content was large, and the total amount of C and N and the value of the ratio [N] / X exceeded the range of the present invention. As a result, the ductility decreased. This Comparative Example No. No. 45 also had a small amount of Cr, but with other elements, an Md30 value of −100 or less was obtained, and the nonmagnetic property was good. Comparative Example No. In No. 46, the Cr content exceeded the range of the present invention, so the tensile strength decreased. Comparative Example No. In No. 47, since the N content was less than the range of the present invention, the tensile strength decreased and the corrosion resistance also deteriorated. In addition, the Md30 value increased and the nonmagnetic property deteriorated. Comparative Example No. In No. 48, the amount of N was excessive, and the ductility decreased.

  Comparative Example No. No. 49 had a small amount of V and a reduced tensile strength. In No. 50, the amount of V was excessive and the ductility decreased. Comparative Example No. 51 and no. No. 52 is a comparative example No. 52, although the content of each component of the nonmagnetic stainless steel satisfies the scope of the present invention. No. 51 had a small total amount of C and N, and the tensile strength decreased. In No. 52, the total amount of C and N was excessive, and the ductility decreased.

  Comparative Example No. 53, the content of each component of the nonmagnetic stainless steel satisfies the range of the present invention, but the ratio [N] / X defined by the content of N and Cr is less than the range of the present invention. As a result, the tensile strength of the nonmagnetic stainless steel decreased. On the other hand, Comparative Example No. For No. 54, the value of the ratio [N] / X exceeded the range of the present invention, so the ductility of the nonmagnetic stainless steel was lowered.

  Comparative Example No. 55, the content of each component of nonmagnetic stainless steel satisfies the scope of the present invention, but the ratio [V] / Y defined by the contents of C, N and V is within the scope of the present invention. Therefore, the tensile strength of the nonmagnetic stainless steel was lowered. Comparative Example No. In No. 56, since the value of the ratio [V] / Y exceeded the range of the present invention, the ductility of the nonmagnetic stainless steel was lowered.

Claims (3)

C: 0.20 to 0.55 mass%, Cr: more than 15.0 mass% and 20.0 mass% or less, N: 0.025 to 0.25 mass%, V: 1.0 to 2.5 mass %, Mn: 4.50 to 9.50 mass%, Ni: 3.0 to 10.0 mass%, Si: 0.01 to 1.00 mass%, and Al: 0.001 to 0.050 mass% It is a non-magnetic stainless steel containing the balance of Fe and inevitable impurities, and the total content of C and N is 0.3 to 0.6% by mass, and Cr, N, C and V When the contents are [Cr], [N], [C], and [V], the ratio [N] / X of the N content [N] to the numerical value X represented by the following formula is 0. .4 to 3.0, and the V content [V] is such that the ratio [V] / Y to the numerical value Y represented by the following formula is 0.7 to 1.5. Non-magnetic stainless steel characterized by and.

Further, Cu: 0.05 to 4.00 mass%, Mo: 0.05 to 2.00 mass%, W: 0.05 to 2.00 mass%, Nb: 0.01 to 1.00 mass%, One or more components selected from the group consisting of Ti: 0.01 to 1.00 mass%, B: 0.0005 to 0.0200 mass%, and Mg: 0.0005 to 0.0200 mass% The nonmagnetic stainless steel according to claim 1, which is contained. Further, one or two components selected from the group consisting of P: 0.02 to 0.20 mass%, S: 0.005 to 0.300 mass%, and Se: 0.005 to 0.200 mass% are used. The nonmagnetic stainless steel according to claim 1, wherein the nonmagnetic stainless steel contains at least one species.

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