KR102404122B1 - Wire rod for stainless steel wire, stainless steel wire and manufacturing method thereof, and spring parts - Google Patents

Abstract

C: 0.005 to 0.15%, Si: 0.1 to 4.0%, Mn: 0.1 to 8.0%, Ni: 1.0 to 10.0%, Cr: 13.0 to 20.0%, Mo: 0.01 to 3.00%, Cu: more than 0.80% to 4.00% , N: 0.005 to 0.20%, including V, etc. as necessary, the balance being Fe and unavoidable impurities, characterized in that Md30 represented by the following formula (a) is -20 to 40 Wire rod for stainless steel wire. From this wire rod, a high-strength stainless steel wire with excellent delamination resistance can be obtained. Md30=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo... (a) However, the element symbol in Formula (a) means content (mass %) in steel of the said element. In addition, when content of the element in Formula (a) is 0 %, "0" is substituted for the said symbol location, and it calculates.

Description

Wire rod for stainless steel wire, stainless steel wire and manufacturing method thereof, and spring parts

The present invention relates to a wire rod for a stainless steel wire, a stainless steel wire, a method for manufacturing the same, and a spring component.

Conventionally, high-strength stainless steel products, represented by coil springs, have been manufactured by processing and forming austenitic stainless steel wires and steel wires represented by SUS304 and SUS316 as raw materials. However, the strength characteristics and delamination resistance characteristics of stainless steel products processed and manufactured from the austenitic stainless steel wire as described above do not sufficiently correspond to precision parts, and there is a drawback that the use is limited.

For the said subject, the technique using the reinforcement|strengthening by a process induction martensite (Hereinafter, it may refer to process induction alpha' in this specification) is examined (for example, patent documents 1, 2, and 3) .

Japanese Patent Laid-Open No. 2001-262281 Japanese Patent Laid-Open No. 2005-290538 Japanese Patent Laid-Open No. 2005-298932

The invention of Patent Document 1 aims to provide a high-strength metastable stainless steel excellent in cold workability, and the inventions of Patent Documents 2 and 3 aim to provide a high-strength stainless steel wire excellent in a modulus of stiffness. Line) Longitudinal cracks (aging cracks) during machining are studied. Moreover, in patent document 3, although the improvement of drawing resistance longitudinal crack resistance is aimed at combining process induction martensite and the temperature-controlled wire-drawing, such a method raises manufacturing cost.

Here, the characteristic which is hard to peel when various force is provided, ie, a delamination-resistant characteristic is calculated|required by a stainless steel wire. In particular, in automobile parts, such as spring parts, it is calculated|required that it is excellent in the characteristic with respect to the delamination which generate|occur|produces in the vicinity of a torsional yield point. However, in the inventions of Patent Documents 1 to 3 described above, the delamination resistance characteristics are not studied at all.

An object of the present invention is to provide a high-strength stainless steel wire having excellent delamination resistance and a method for manufacturing the same.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the present inventors repeated examination, paying attention to the helical dislocation fraction of the austenite phase in 200 micrometers position from the surface layer of a stainless steel wire. The helical dislocation fraction is measured using CuKα ray by X-ray diffraction at a position 200 µm from the surface layer of the steel wire in the L section of the steel wire, and half of (111), (200), (220) (311) It can be obtained by measuring the width and using the modified Williamson-Hall equation from the obtained data.

And the present inventors discovered that the outstanding delamination-resistant characteristic could be acquired, when a helical dislocation fraction was 0.9 or less. The present inventors have investigated the wire drawing conditions for obtaining a steel wire having a helical dislocation fraction of 0.9 or less, and found that it is particularly important to appropriately manage the total area reduction ratio, the number of passes, and the reduction area in the final pass. did.

The gist of the present invention is as follows.

(1) in mass %,

C: 0.005 to 0.15%;

Si: 0.1~4.0%,

Mn: 0.1~8.0%,

Ni: 1.0 to 10.0%,

Cr: 13.0~20.0%,

Mo: 0.01~3.00%,

Cu: more than 0.80%~4.00%,

N:0.005~0.20%,

V: 0~2.5%,

B: 0~0.012%,

Al: 0~2.0%,

W: 0-2.5%,

Ga: 0~0.0500%,

Co: 0~2.5%,

Sn: 0~2.5%,

Ti: 0~1.0%,

Nb: 0~2.5%,

Ta: 0~2.5%,

Ca: 0~0.012%,

Mg: 0~0.012%,

Zr: 0~0.012%,

REM: 0~0.05%,

the balance consists of Fe and unavoidable impurities,

Md30 represented by the following formula (a) is -20 to 40, the wire rod for stainless steel wire.

Md30=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo... (a)

However, the element symbol in Formula (a) means content (mass %) in steel of the said element. In addition, when content of the element in Formula (a) is 0 %, "0" is substituted for the said symbol location, and it calculates.

(2) in mass %,

C: 0.005 to 0.15%;

Si: 0.1~4.0%,

Mn: 0.1~8.0%,

Ni: 1.0 to 10.0%,

Cr: 13.0~20.0%,

Mo: 0.01~3.00%,

Cu: more than 0.80%~4.00%,

N:0.005~0.20%,

V: 0~2.5%,

B: 0~0.012%,

Al: 0~2.0%,

W: 0-2.5%,

Ga: 0~0.0500%,

Co: 0~2.5%,

Sn: 0~2.5%,

Ti: 0~1.0%,

Nb: 0~2.5%,

Ta: 0~2.5%,

Ca: 0~0.012%,

Mg: 0.012%,

Zr: 0~0.012%,

REM: 0~0.05%,

the balance consists of Fe and unavoidable impurities,

Md30 represented by the following formula (a) is -20 to 40,

The processed organic martensite phase has a metal structure of 20 to 95 vol.%,

The stainless steel wire whose helix dislocation fraction of the austenite phase in the position of 200 micrometers from the surface layer of a steel wire is 0.9 or less.

Md30=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo... (a)

However, the element symbol in Formula (a) means content (mass %) in steel of the said element. In addition, when content of the element in Formula (a) is 0 %, "0" is substituted for the said symbol location, and it calculates.

As for the stainless steel wire of said (2), it is preferable that the said metal structure contains an austenite phase. In addition, it is preferable that the stainless steel wire of (2) has a tensile strength of 1600 MPa or more and a shear strain rate of 3.0×10 ^-4 /s or more that causes delamination.

(3) A method of manufacturing the stainless steel wire of (2) by wire-drawing the wire of (1),

The method for producing a stainless steel wire, wherein the wire drawing is performed under the conditions of a total reduction in area: 40 to 90%, the number of passes: 7 or more, and a reduction in area in the final pass: 0.5 to 25%.

(4) A spring component using the stainless steel wire of (2) above.

ADVANTAGE OF THE INVENTION According to this invention, the high strength stainless steel wire excellent in the delamination resistance can be provided.

1. Wire rod for stainless steel wire

First, the chemical composition of the wire rod for stainless steel wire is demonstrated. In addition, (%) in the following description is mass (%) unless otherwise indicated.

C:0.005~0.15%

C is contained 0.005% or more in order to obtain high strength after wire drawing. However, when C is contained excessively, longitudinal cracks will occur at the time of wire drawing, and the delamination resistance will be lowered. Therefore, the C content is made 0.15% or less. A preferable lower limit is 0.06%, and a preferable upper limit is 0.13%.

Si: 0.1~4.0%

Si is contained 0.1% or more in order to obtain high strength after wire drawing. However, when Si is contained excessively, wire-drawing property will worsen, and since the delamination resistance property will be reduced, the content shall be 4.0 % or less. Preferably it is 1.0% or less.

Mn:0.1~8.0%

Mn is an element effective as a replacement element for expensive Ni and is effective for obtaining high strength after wire drawing. For this reason, Mn is made to contain 0.1% or more. However, when Mn is contained excessively, in order to deteriorate the delamination resistance characteristic of a steel wire, the content is limited to 8.0 % or less. Preferably it is made into 3.0 % or less.

Ni: 1.0~10.0%

Ni is contained 1.0% or more in order to ensure a delamination resistance characteristic. Preferably, the amount of Ni is made into 4.0% or more. However, when it is contained excessively, the Md30 value in γ is lowered and the generation of processing induction α′ effective for strength is suppressed, so the content is made 10.0% or less. Preferably, it is 9.0% or less.

Cr: 13.0~20.0%

In order to ensure corrosion resistance, Cr is made to contain 13.0% or more. Preferably, the amount of Cr shall be 15.0% or more. However, when Cr is contained excessively, in order to deteriorate the delamination resistance characteristic of a steel wire, the content is made into 20.0 % or less. Preferably, it is 19.0% or less.

Mo: 0.01~3.00%

Mo is made to contain 0.01% or more in order to acquire corrosion resistance and delamination resistance characteristic. However, when Mo is contained excessively, the effect is saturated, and since the delamination resistance property falls conversely, an upper limit is made into 3.00 % or less. Preferably it is 1.00% or less.

Cu: more than 0.80%~4.00%

Cu has an effect of reducing the fraction of helical dislocations of the steel wire, and is contained in an amount exceeding 0.80%. However, when Cu is contained excessively, in addition to deterioration of hot workability, since intensity|strength will fall, the content is made into 4.00 % or less. Preferably, it is 3.00% or less, More preferably, it is 2.00% or less, More preferably, it is 1.50% or less.

N:0.005~0.20%

In order to obtain high strength after wire drawing, N is made to contain 0.005% or more. However, when N is contained excessively, longitudinal cracks will occur at the time of wire drawing, and since the delamination resistance property will be reduced, the amount of N shall be 0.20 % or less. Preferably it is 0.10% or less. The amount of N is preferably 0.02 or more.

V: 0~2.5%

V forms a carbonitride to make a crystal grain size fine, and since it improves the strength and wire drawing property of a wire rod and a steel wire, you may contain it. However, when V is contained excessively, coarse inclusions are produced|generated, and since wire-drawing property and a delamination-resistant characteristic fall, let the upper limit in the case of containing it be 2.5 %. A preferable range is 1.0% or less, and a more preferable range is 0.5% or less. In order to express the said effect, it is preferable to make the V amount into 0.001 % or more.

B: 0~0.012%

Since B is effective for improving grain boundary strength and improving the strength of a wire rod and a steel wire, you may contain it. However, when B is contained excessively, since the wire-drawing property and the delamination resistance property fall conversely by coarse boride formation, the upper limit in the case of making it contain is made into 0.012 %. Preferably it is 0.005% or less. In order to express the said effect, it is preferable to make B amount into 0.001 % or more.

Al: 0~2.0%

Since Al promotes deoxidation and improves the cleanliness level of inclusions, it may be contained. However, when Al is contained excessively, the effect is saturated, and since the strength and delamination resistance properties of the material itself deteriorate, the upper limit in the case of containing Al is made 2.0%. Preferably it is 1.0 % or less, More preferably, it is 0.3 % or less. In order to express the said effect, it is preferable to make Al amount into 0.001 % or more.

W: 0~2.5%

Since W is an element effective in improving corrosion resistance, you may contain it. However, when W is contained excessively, the effect is saturated, and there exists a possibility that delamination-resistant characteristic may deteriorate conversely. Therefore, the upper limit in the case of containing it shall be 2.5 %. More preferably, it is 2.0 % or less, More preferably, it is 1.5 % or less. In order to express the said effect, it is preferable to make W amount into 0.05 % or more. More preferably, it is 0.10% or more.

Ga: 0~0.0500%

Since Ga is an element effective in improving corrosion resistance, you may contain it. However, when Ga is contained excessively, hot workability is reduced. Therefore, the upper limit in the case of making it contain is made into 0.0500 %. In order to express the said effect, it is preferable to make the amount of Ga into 0.0004% or more.

Co:0~2.5%

Since Co has the effect of improving the intensity|strength of a steel wire, you may contain it. However, when Co is contained excessively, the effect is saturated, and conversely, there exists a possibility that the delamination resistance characteristic of a steel wire may deteriorate. Therefore, the upper limit in the case of containing it shall be 2.5 %. More preferably, it is 1.0 % or less, More preferably, it is 0.8 % or less. In order to express the said effect, it is preferable to make Co amount into 0.05 % or more, and it is more preferable to make it contain 0.10 % or more.

Sn: 0~2.5%

Since Sn is an element effective in improving corrosion resistance, you may contain it. However, when Sn is contained excessively, the effect is saturated, and there exists a possibility that delamination-resistant characteristic may deteriorate conversely. Therefore, the upper limit in the case of containing it shall be 2.5 %. More preferably, it is 1.0 % or less, More preferably, it is 0.2 % or less. In order to express the said effect, it is preferable to make the amount of Sn into 0.01 % or more. More preferably, it is 0.05 % or more.

Ti: 0~1.0%

Nb: 0~2.5%

Ta: 0~2.5%

Ti, Nb, and Ta may be contained in order to form carbonitrides to make the grain size fine and to improve the strength and delamination resistance of the steel wire. However, when each of these elements is contained excessively, there exists a possibility that a coarse inclusion may generate|occur|produce and the delamination resistance characteristic of a steel wire may fall. Therefore, the upper limit in the case of containing is made into 1.0% for Ti, 2.5% for Nb, and 2.5% for Ta. It is preferable to set it as 0.7 % or less, and, as for Ti, it is more preferable to set it as 0.5 % or less. It is preferable to set it as 1.5 % or less, and, as for Nb, it is more preferable to set it as 0.9 % or less. It is preferable to set it as 1.5 % or less, and, as for Ta, it is more preferable to set it as 0.9 % or less. In order to express the said effect, it is preferable to contain 0.01% or more of Ti, 0.01% or more of Nb, and 0.01% or more of Ta. It is preferable to set it as 0.03 % or more, and, as for Ti, it is more preferable to set it as 0.05 % or more. It is preferable to set it as 0.04 % or more, and, as for Nb, it is more preferable to set it as 0.08 % or more. It is preferable to set it as 0.04 % or more, and, as for Ta, it is more preferable to set it as 0.08 % or more.

Ca: 0~0.012%

Mg: 0~0.012%

Zr: 0~0.012%

REM: 0~0.05%

Ca, Mg, Zr, and REM may be contained as needed for deoxidation. However, there is a fear that coarse inclusions are generated and the delamination resistance properties and wire-drawing properties of the steel wire are deteriorated. Therefore, the upper limit in the case of containing it is made into 0.012% for Ca, 0.012% for Mg, 0.012% for Zr, and 0.05% for REM. It is preferable to set it as 0.010 % or less, and, as for Ca, it is more preferable to set it as 0.005 % or less. It is preferable to set it as 0.010 % or less, and, as for Mg, it is more preferable to set it as 0.005 % or less. It is preferable to set it as 0.010 % or less, and, as for Zr, it is more preferable to set it as 0.005 % or less. The REM is preferably set to 0.05% or less. In order to express the said effect, it is preferable to contain 0.0002% or more of Ca, 0.0002% or more of Mg, 0.0002% or more of Zr, and 0.0002% or more of REM. It is preferable to set it as 0.0004 % or more, and, as for Ca, it is more preferable to set it as 0.001 % or more. It is preferable to set it as 0.0004 % or more, and, as for Mg, it is more preferable to set it as 0.001 % or more. It is preferable to set it as 0.0004 % or more, and, as for Zr, it is more preferable to set it as 0.001 % or more. It is preferable to set it as 0.0004 % or more, and, as for REM, it is more preferable to set it as 0.001 % or more.

The chemical composition of the wire rod for stainless steel wire contains each of said elements, and remainder consists of Fe and an unavoidable impurity. As typical unavoidable impurities, O, S, P, etc. are mentioned, and it mixes normally as an unavoidable impurity in the range of 0.0001 to 0.1 % in the manufacturing process of steel.

In addition to each element described above, it can be contained within a range that does not impair the effects of the present invention. Although other components are not specifically stipulated in the present invention, it is preferable to reduce the general impurity elements P, S, Zn, Bi, Pb, Se, Sb, H, etc. as much as possible. To the extent that these elements solve the problems of the present invention, the content ratio is controlled, and if necessary, P≤400ppm, S≤100ppm, Zn≤100ppm, Bi≤100ppm, Pb≤100ppm, Se≤100ppm, At least one of Sb ≤ 500 ppm and H ≤ 100 ppm is contained.

Md30 value: -20~40

The Md30 value is an index obtained by examining the relationship between the volume fraction and component of the processed organic martensite after wire drawing, respectively, and it is necessary to control it in order to stably secure the relaxation characteristics between high strength and temperature resistance of the steel wire.

Md30 value is a value calculated|required from following formula (a), and when this value in an austenite phase is less than -20, it will become difficult to produce|generate processing-induced (alpha)', and strength characteristic is inferior. On the other hand, when the Md30 value exceeds 40, the austenite phase becomes unstable, and the processed organic martensite phase initially produced by wire drawing deteriorates wire-drawing properties and delamination resistance properties. Therefore, the Md30 value is limited to -20 or more and 40 or less. Preferably, the lower limit of the Md30 value is set to zero. The upper limit is 20.

Md30=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo... (a)

However, the element symbol in Formula (a) means content (mass %) in steel of the said element. In addition, when content of the element in Formula (a) is 0 %, "0" is substituted for the said symbol location, and it calculates.

The wire rod according to the present embodiment has the above-described chemical composition, and the Md30 value satisfies -20 to 40. Therefore, when a stainless steel wire is manufactured using the wire rod, the stainless steel wire has a volume fraction of a processing-induced martensite phase of 20 to 95 vol.%, and it is easy to obtain a high strength stainless steel wire excellent in delamination resistance. .

2. Stainless steel wire

Since the chemical composition and Md30 value of the stainless steel wire according to the present embodiment are the same as the chemical composition and Md30 value of the wire rod, description thereof is omitted.

Processed organic martensite phase: 20-95 vol.%

With respect to the volume fraction of the processing-induced α' of the steel wire, if it is less than 20 vol.%, the strength characteristics cannot be obtained. Therefore, the processing-induced α' fraction of the steel wire of the present invention is set to 20 vol.% or more. On the other hand, when the volume fraction of processing induction alpha' exceeds 95 vol.%, in order to reduce wire-drawing property and delamination resistance, an upper limit is made into 95 vol.% or less. Preferably, it is 30 vol.% or more. Moreover, Preferably, it is 70 vol.% or less.

In addition, since the processed martensite phase has ferromagnetic properties, while the austenite phase is phasic magnetism, the electromagnetic measurement method is used to measure the phase rate, and the processed induction martensite phase can be obtained in vol.%. have. Although the unavoidable precipitate phase exists, it is 1.0 vol.% or less, and it is extremely small compared with the processed organic martensite phase and an austenite phase. Accordingly, since 1.0 vol.% of the unavoidable impurity phase is negligible, the vol% of the austenite phase becomes a value obtained by subtracting the vol.% of the processed organic martensite phase from 100%.

Spiral dislocation fraction of the austenite phase at a position of 200 µm from the surface layer of the steel wire: 0.9 or less

The fraction of helical dislocations of the austenite phase at a position of 200 µm from the surface layer of the steel wire contributes to the delamination resistance characteristic. And since it becomes difficult to deform|transform when a helical dislocation fraction becomes high excessively and the delamination resistance property falls, the upper limit is made into 0.9 or less. Preferably it is 0.8 or less, More preferably, it is 0.7 or less, More preferably, it is 0.6 or less. Although it is not necessary to determine the lower limit of the fraction of helical dislocations, if it is too low, the strength may deteriorate. Therefore, the fraction of helical dislocations is preferably 0.001 or more. A preferable lower limit is 0.01, and a more preferable lower limit is 0.05.

Tensile strength: 1600 MPa or more

When the tensile strength of the steel wire is less than 1600 MPa, since the strength deteriorates, the effect of the present invention is not expressed. Therefore, the lower limit of the tensile strength is set to 1600 MPa or more. Preferably it is 1700 MPa or more, More preferably, it is 1800 MPa or more, More preferably, it is 1900 MPa or more.

Shear strain rate causing delamination: 3.0×10 ^-4 /s or more

Next, when the shear strain rate causing delamination of the steel wire is less than 3.0 × 10 ^-4 /s, since the delamination resistance is lowered, the effect of the present invention is not expressed. Therefore, the lower limit is set to 3.0 x 10 ^-4 /s or more. Preferably it is 7.0x10 ^-4 /s or more, More preferably, it is 2.0x10 ^{-3 /s or more, More preferably, it is 3.5x10 -3 /} s or more.

The steel wire according to the present embodiment has the same chemical composition as that of the wire rod according to the present invention described above, and has an Md30 value of -20 to 40. In addition, the volume fraction of processing induced α' is 20 to 95 vol.%, and the fraction of the austenite helical dislocation at a position 200 μm from the surface layer of the steel wire is 0.9 or less, so a high-strength stainless steel wire with excellent delamination resistance is obtained. . In addition, the tensile strength becomes 1600 or more, and the shear strain rate causing delamination becomes a steel wire of 3.0×10 ^-4 /s or more.

3. Manufacturing method of stainless steel wire

Next, the manufacturing method of the high-strength stainless steel wire and a wire which concerns on this embodiment is demonstrated. In addition, it goes without saying that the manufacturing method of the high-strength stainless steel wire and wire rod of this invention is not limited to the conditions described below.

After the steel having the above-mentioned composition is melted and cast into a slab having a predetermined diameter, the slab is subjected to hot wire rolling. Next, if necessary, solution treatment and pickling are performed appropriately to make a wire rod.

The stainless steel wire according to the present embodiment can be obtained by cold drawing the above-described wire rod. Specifically, a stainless steel wire is manufactured by wire-drawing a steel wire or a steel wire under the following conditions.

Total reduction rate: 40~90%

The total reduction in area in wire drawing is set to 40% or more in order to secure the amount of processing induced α' and to increase the strength. On the other hand, if the total reduction ratio is too large, the amount of processing induced α' increases too much and the delamination resistance property deteriorates. Therefore, the upper limit of the total reduction ratio is set to 90%. The lower limit of the total reduction rate is preferably 50%, and the upper limit is preferably 80%.

Number of passes: 7 or more

The wire-drawing is performed by multi-pass wire-drawing in which the number of passes is 7 or more. The number of passes means the number of times a workpiece such as a wire rod passes through the die. When the number of passes is too small, the number of passes is set to 7 or more in order to increase the fraction of the austenite phase helical dislocations in the 200 µm position from the surface layer of the steel wire and deteriorate the delamination resistance. Preferably, it is set as 15 times or more, More preferably, it is set as 21 times or more.

Final pass reduction rate: 0.5 to 25%

In order to improve the delamination resistance characteristic, it is important to reduce the area of the final pass within a predetermined range. That is, if the area reduction ratio of the last pass is too large, the fraction of the austenite helical dislocation at a position 200 µm from the surface layer of the steel wire is increased, and the delamination resistance property is deteriorated, so it is set to 25% or less. Preferably, it is set as 20 % or less, More preferably, it is 10 % or less, More preferably, it is 5 % or less. On the other hand, when the reduction in area of the final pass is less than 0.5%, the fraction of the spiral dislocations of the austenite phase at a position 200 μm from the surface layer of the steel wire increases, and the improvement of the delamination resistance becomes insufficient. .

According to the above manufacturing method, the high strength stainless steel wire excellent in the delamination resistance which concerns on this embodiment can be obtained.

Example

Examples of the present invention will be described below, but the conditions in the examples are examples of conditions employed to confirm the practicability and effects of the present invention, and the present invention is limited to the conditions used in the following examples. it's not going to be Various conditions can be employ|adopted for this invention, as long as the objective of this invention is achieved without deviating from the summary of this invention.

Tables 1 and 2 show the chemical compositions (steel grades A to AR) of the steels of Examples and the Md30 values in the austenite (γ) phase. In addition, underlined in Table 2 indicates that it is outside the scope of the present invention.

[Table 1]

[Table 2]

The steel of these chemical compositions was melted in a vacuum melting furnace of 100 kg, assuming an AOD flux, which is a cheap melting process for stainless steel, and cast into a slab of φ180 mm. After heating the obtained cast steel at 1100 degreeC for 200 minutes, hot wire rolling (reduction of area ratio: 99.9%) was performed to (phi) 5.5 mm, and hot rolling was complete|finished at 1050 degreeC. Immediately thereafter, as a solution treatment, inline heat treatment was performed at 1050° C. for 3 minutes, cooled with water, and pickled to obtain a wire rod. Then, it cold-wired to (phi) 4.0 mm. The obtained stainless steel wire of (phi)4.0mm was subjected to intermediate strand annealing at 1050°C for 3 minutes, and then, it was subjected to cold wire drawing to a diameter of 2.0mm to obtain a high-strength stainless steel wire. In that case, the total reduction rate was 75%, the number of passes was 7 times, and the reduction rate of the last pass was 10%.

And, with respect to the steel wire manufactured by the above method, according to the following method, the processing-induced martensite fraction (α' fraction) of the steel wire, the austenite phase dislocation fraction at 200 µm from the surface layer of the steel wire, the tensile strength , the shear strain rate of delamination generation was evaluated.

[fraction of processed organic martensite (processed organic α' fraction)]

The processing-induced α' fraction of the steel wire was determined by measuring the saturation magnetization value when applying a magnetic field of 1.0×10 ⁴ Oe to “steel wire” and “material obtained by heat-treating steel wire at 1050° C.×3 minutes” with a DC magnetic flux meter, and It calculated|required by Formula (B). For the measurement of the saturation magnetization value, a DC magnetization characteristic tester (manufactured by Metron Machinery Co., Ltd.) was used.

α' fraction (vol.%)={(σ _s -σ ₁₀₅₀ )/σ _s (bcc)}×100 … (B)

Here, σ _s is the saturation magnetization value of the product (T), σ ₁₀₅₀ is the saturation magnetization value of the material heat treated at 1050°C × 3 minutes (T), σ _s (bcc) is γ is 100% martensite ( [alpha]') The saturation magnetization value (calculated value represented by the following formula (C)) at the time of deformation|transformation is shown. Creq in the following formula (C) is represented by the following formula (D).

σ _s (bcc)=2.14-0.030×Creq … (C)

Creq=Cr+1.8×Si+Mo+0.5×Ni+0.9×Mn+3.6(C+N)+1.25×P+2.91×S … (D)

[fraction of helical dislocations in the austenite phase at 200 µm from the surface layer of the steel wire]

The fraction of helical dislocations of the austenite phase at a position of 200 µm from the surface layer of the steel wire was measured by X-ray line profile analysis. In the L section of the steel wire, at a position 200 μm from the surface layer of the steel wire, measurement is performed using CuKα ray by X-ray diffraction, and the half widths of (111), (200), (220) (311) are measured, Substitute the obtained half width into the following modified Williamson-Hall equation (E).

ΔK=0.9/D+√((πM ² b ² ρ)/2)KC ^1/2 +O(K ² C) … (E)

In addition, in the formula (E), D is the crystallite size (nm), ρ is the dislocation density (m ^-2 ), b is the size of the Burgers vector (nm), M is the dislocation density ρ and the interaction distance between the dislocations Re constant in (nm), and C is the average contrast factor of the dislocation. In addition, K and (DELTA)K are as follows.

K=2 sinθ/λ,

ΔK=2βcosθ/λ

In the above formula, β, θ, and λ are the half width (rad), the Bragg reflection angle (rad), and the X-ray wavelength (CuKα=0.15405 nm) of each diffraction ray, respectively.

Here, by multiplying both sides of Equation (E) to the square, ignoring the higher-order term O(K ² C), and α=(0.9/D) ² , γ=πM ² b ² ρ/2, Equation (F ) can be obtained.

[(ΔK) ² -α]/K ² =γC … (F)

In the above formula, C=C ^h00 (1-qH ² ). And, q is a parameter including the type of dislocation and its ratio, H(=(h ² k ² +h ² l ² +k ² l ² )/(h ² +k ² +l ² ) ² ) is the index h of the diffraction line, It is a function of k and l. C _h00 is a constant obtained from the elastic constant.

By measuring said q value, the helical dislocation fraction S of austenite can be calculated from the following formula (G).

S=(qq ^e )/(q ^s -q ^e ) … (G)

In the above formula, q ^e and q ^s are q values in the case of 100% blade dislocation and spiral dislocation, respectively, and are constants determined from the elastic constant.

[The tensile strength]

The tensile strength of the steel wire was evaluated by the tensile strength in the tensile test of JIS Z 2241.

[Shear strain rate of occurrence of delamination]

The shear strain rate of generation|occurrence|production of the delamination of a steel wire was evaluated by the torsion test. The torsion test is a torsion test by making the wire diameter d of the steel wire 2.0 mm and the distance L between chucks 150 mm, changing the rotation speed R (rpm), controlling the shear strain rate γ' (/s) of the outermost layer, and did At various shear strain rates, what a torque fall generate|occur|produced after 0.3% proof stress was made into delamination generation|occurrence|production, and the shear strain rate which generate|occur|produced the delamination was made into the index|index of the delamination resistance characteristic.

The evaluation results are shown in Tables 3 and 4.

[Table 3]

[Table 4]

As shown in Table 3, in the steel wires of Examples 1 to 33 of the present invention, the processing-induced α' fraction was 20 to 90 vol.%, the tensile strength was 1600 MPa or more, and the austenitic phase at a position 200 μm from the surface layer of the steel wire. The helical dislocation fraction was 0.9 or less. Moreover, the shear strain rate of generation|occurrence|production of the delamination of Examples 1-33 of this invention was 3.0 x 10 ^-4 /s or more. On the other hand, in the steel wires of Comparative Examples 34 to 48, any one of the performance of tensile strength and delamination resistance was deteriorated. Moreover, in Comparative Example No. 41, since corrosion resistance was poor, evaluation was not carried out about tensile strength and delamination.

Next, the influence of manufacturing conditions was investigated.

Using the steel type R shown in Table 1, stainless steel wires having various diameters produced in the same manner as described above were drawn by wire drawing under the wire drawing conditions shown in Table 5 to produce a steel wire having a diameter of 2.0 mm. In any example, the steel wire diameter used for wire drawing and the steel wire diameter before a final pass were adjusted so that the final wire diameter of a steel wire might be set to (phi) 2.0 mm. Then, with respect to the obtained steel wire, in the same manner as described above, the volume fraction of processing-induced martensite (α'), the fraction of helical dislocations in the austenite phase at a position 200 μm from the surface layer of the steel wire, tensile strength, and shear of delamination generation The strain rate was measured and evaluated. The evaluation results are shown in Tables 5 and 6.

[Table 5]

[Table 6]

All of the steel wires of the examples of the present invention shown in Test Nos. 45 to 53 had a processing-induced α' fraction of 20 to 90 vol.%, and the fraction of austenite helical dislocations at a position 200 μm from the surface layer of the steel wire was 0.9 or less, and the tensile strength was 1600 MPa or more, and the shear strain rate at which delamination occurred was 3.0 × 10 ^-4 /s or more. On the other hand, in the steel wires of Comparative Examples 54 to 58 in which wire drawing was not performed under appropriate conditions, either the tensile strength or the delamination resistance properties were deteriorated.

ADVANTAGE OF THE INVENTION According to this invention, since the high strength stainless steel wire excellent in delamination resistance can be provided, it is extremely useful in industry. By applying this stainless steel wire to a spring part, etc., the spring part etc. excellent in the delamination resistance property can be provided. In addition, the spring component means a spring for automobiles, a spring for industrial machines, a spring for home appliances, and the like.

Claims (10)

in mass %,
C: 0.005 to 0.15%;
Si: 0.1~4.0%,
Mn: 0.1~8.0%,
Ni: 1.0 to 10.0%,
Cr: 13.0~20.0%,
Mo: 0.01~3.00%,
Cu: more than 0.80%~4.00%,
N:0.005~0.20%,
V: 0~2.5%,
B: 0~0.012%,
Al: 0~2.0%,
W: 0-2.5%,
Ga: 0~0.0500%,
Co: 0~2.5%,
Sn: 0~2.5%,
Ti: 0~1.0%,
Nb: 0~2.5%,
Ta: 0~2.5%,
Ca: 0~0.012%,
Mg: 0~0.012%,
Zr: 0~0.012%,
REM: 0~0.05%,
the balance consists of Fe and unavoidable impurities,
Md30 represented by the following formula (a) is -20 to 40,
The processed organic martensite phase has a metal structure of 20 to 95 vol.%,
The stainless steel wire whose helix dislocation fraction of the austenite phase in the position of 200 micrometers from the surface layer of a steel wire is 0.9 or less.
Md30=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo... (a)
However, the element symbol in Formula (a) means content (mass %) in steel of the said element. In addition, when content of the element in Formula (a) is 0 %, "0" is substituted for the said symbol location, and it calculates. The method according to claim 1,
Also in mass %,
V: 0.001 to 2.5%,
B: 0.001 to 0.012%,
Al: 0.001~2.0%,
W: 0.05-2.5%,
Ga:0.0004~0.0500%,
Co:0.05-2.5%,
Sn: 0.01~2.5%,
Ti: 0.01~1.0%,
Nb: 0.01~2.5%,
Ta: 0.01~2.5%,
Ca: 0.0002~0.012%,
Mg: 0.0002~0.012%,
Zr:0.0002~0.012% and
REM: A stainless steel wire containing at least one selected from 0.0002 to 0.05%. The method according to claim 1,
The said metal structure comprises an austenite phase, stainless steel wire. 3. The method according to claim 2,
The said metal structure comprises an austenite phase, stainless steel wire. The method according to claim 1,
A stainless steel wire having a tensile strength of 1600 MPa or more and a shear strain rate causing delamination of 3.0 × 10 ^-4 /s or more. 3. The method according to claim 2,
A stainless steel wire having a tensile strength of 1600 MPa or more and a shear strain rate causing delamination of 3.0 × 10 ^-4 /s or more. 4. The method according to claim 3,
A stainless steel wire having a tensile strength of 1600 MPa or more and a shear strain rate causing delamination of 3.0 × 10 ^-4 /s or more. 5. The method according to claim 4,
A stainless steel wire having a tensile strength of 1600 MPa or more and a shear strain rate causing delamination of 3.0 × 10 ^-4 /s or more. in mass %,
C: 0.005 to 0.15%;
Si: 0.1~4.0%,
Mn: 0.1~8.0%,
Ni: 1.0 to 10.0%,
Cr: 13.0~20.0%,
Mo: 0.01~3.00%,
Cu: more than 0.80%~4.00%,
N:0.005~0.20%,
V: 0~2.5%,
B: 0~0.012%,
Al: 0~2.0%,
W: 0-2.5%,
Ga: 0~0.0500%,
Co: 0~2.5%,
Sn: 0~2.5%,
Ti: 0~1.0%,
Nb: 0~2.5%,
Ta: 0~2.5%,
Ca: 0~0.012%,
Mg: 0~0.012%,
Zr: 0~0.012%,
REM: 0~0.05%,
the balance consists of Fe and unavoidable impurities,
A method for producing the stainless steel wire according to any one of claims 1 to 8 by wire drawing a wire having an Md30 of -20 to 40 represented by the following formula (a), comprising:
The method for producing a stainless steel wire, wherein the wire drawing is performed under the conditions of a total reduction in area: 40 to 90%, the number of passes: 7 or more, and a reduction in area in the final pass: 0.5 to 25%.
Md30=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo... (a)
However, the element symbol in Formula (a) means content (mass %) in steel of the said element. In addition, when content of the element in Formula (a) is 0 %, "0" is substituted for the said symbol location, and it calculates. A spring component using the stainless steel wire according to any one of claims 1 to 8.