JP2021105210A - Accessory and method for producing accessory - Google Patents

Abstract

To provide an accessory and a method for producing an accessory.SOLUTION: An accessory contains a predetermined chemical component with the balance being Fe and impurities. The structure includes, in area%, austenite of 95% or more. When a diameter of a circle having a minimum area required to contain one intermetallic compound inside is defined as a size of an intermetallic compound, the number of the intermetallic compounds with the size of 150 μm or more is 0, and the number of the intermetallic compounds with the size of 13 μm or more and less than 150 μm is 3 or less. The austenite has an average equivalent circle diameter of 150 μm or less. A PRE defined by the following (1) formula is 40 or more. The accessory has excellent corrosion resistance. PRE=[Cr]+3.3 [Mo]+16[N] (1)SELECTED DRAWING: Figure 1

Description

The present invention relates to accessories and methods for manufacturing accessories.

In recent years, some accessories such as wristwatches, necklaces, brooches, earrings, etc. use stainless steel as in Patent Document 1, for example.

On the other hand, the demand for corrosion resistance for jewelry is increasing more and more.

JP-A-2019-168407

As a method for improving the corrosion resistance of the accessory, there is a method of manufacturing the accessory from a material containing a large amount of Cr and Mo. On the other hand, when an accessory is manufactured from a material containing a large amount of Cr and Mo, a compound having a high Cr and a high Mo remains in the cross section of the material containing a large amount of Cr and Mo. Since the compound having high Cr and high Mo has a phase different from that of the parent phase, there is a problem that the mirror surface property of the accessory is deteriorated. Further, since the compound having high Cr and high Mo reduces the Cr and Mo contents of the parent phase, there is a problem that the corrosion resistance of the accessory is deteriorated.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an accessory and a method for manufacturing the accessory, which are excellent in corrosion resistance and mirror surface property.

(1) The chemical composition is mass%
C: 0.10% or less,
Si: 1.5% or less,
Mn: 1.5% or less,
P: 0.050% or less,
S: 0.050% or less,
O: 0.020% or less,
Ni: 15.0-38.0%,
Cr: 17.0 to 27.0%,
Mo: 4.0-8.0%,
Contains Cu: 3.0% or less and N: 0.55% or less,
The rest contains Fe and impurities
The tissue is area%, austenite is 95% or more,
When the diameter of the circle having the smallest area that can contain one intermetallic compound is defined as the size of the intermetallic compound, the size is 150 μm or more on the exposed surface of the trinket. The number of intermetallic compounds is 0, and the number of the intermetallic compounds having a size of 13 μm or more and less than 150 μm is 3 or less.
The average circle-equivalent diameter of the austenite is 150 μm or less.
An accessory characterized in that the PRE defined by the following equation (1) is 40 or more.
PRE = [Cr] +3.3 [Mo] +16 [N] ... (1)
However, [Cr], [Mo] and [N] in the formula (1) mean the content of Cr, Mo and N in the component composition of the accessory in mass% of Cr, Mo and N, and if not contained, 0 is used. substitute.
(2) The chemical composition is further increased by mass%.
Al: 0.001 to 0.10%,
Co: 0.001 to 3.0%,
W: 0.001 to 8.0%,
Ta: 0.001 to 1.0%,
Sn: 0.001 to 1.0%,
Sb: 0.001 to 1.0%,
Ga: 0.001 to 1.0%,
Ti: 0.001 to 1.0%,
V: 0.001 to 1.0%,
Nb: 0.001 to 1.0%,
Zr: 0.001 to 1.0%,
Te: 0.001 to 1.0%,
Se: 0.001 to 1.0%,
B: 0.0001 to 0.01%,
Ca: 0.0001 to 0.05%,
Mg: 0.0001 to 0.05%, and rare earth elements: 0.001 to 1.0%
The accessory according to (1), which contains one or more selected from the above.
(3) The accessory according to (1) or (2), wherein the accessory is a watch exterior.
(4) The method for manufacturing an accessory according to any one of (1) to (3).
The process of manufacturing plate materials and
A heat treatment step of heat-treating the plate material and
It has a cold rolling process for plastic working the plate material, and has
In the heat treatment step, the heat treatment temperature is 1350 to 1600K, and the heat treatment time satisfies the following formula (2).
A method for manufacturing an accessory, which comprises a rolling reduction of 7 to 50% in the cold rolling step.
t _dif ≧ (6869 / T _dif 4.3326) × λ ² ··· (2)
However, in the formula (2), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (how), and λ represents the plate thickness (mm) of the plate material.
(5) The method for manufacturing an accessory according to any one of (1) to (3).
The process of manufacturing rods and
A heat treatment step of heat-treating the bar and
It has a cold wire drawing process for plastic working the bar.
In the heat treatment step, the heat treatment temperature is 1350 to 1600K, and the heat treatment time satisfies the following formula (3).
A method for manufacturing an accessory, which comprises a surface reduction rate of 7 to 50% in the cold wire drawing step.
t _dif ≧ (6869 / T _dif 4.3326) × d ... (3)
However, in the formula (3), T _dim represents the heat treatment temperature (K), t _def represents the heat treatment time (how), and d represents the circle-equivalent diameter (mm) of the bar.
(6) The method for manufacturing an accessory according to any one of (1) to (3).
The process of manufacturing plate or bar and
A heat treatment step of heat-treating the plate material or the bar material, and
A hot forging step of hot forging the plate material or the bar material, and
It has a cold forging step of cold forging the plate material or the bar material, and the heat treatment temperature is 1350 to 1600 K in the heat treatment step.
A method for manufacturing an accessory, characterized in that, in the case of the plate material, the heat treatment time satisfies the formula (2), and in the case of the bar material, the heat treatment time satisfies the formula (3).
t _dif ≧ (6869 / T _dif 4.3326) × λ ² ··· (2)
t _dif ≧ (6869 / T _dif 4.3326) × d ... (3)
However, in the formula (2), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (how), λ represents the plate thickness (mm) of the plate material, and in the formula (3), T _def is the above-mentioned. The heat treatment temperature (K) and t _dim represent the heat treatment time (how), and d represents the circle-equivalent diameter (mm) of the bar.

According to the present invention, it is possible to provide an accessory and a method for manufacturing the accessory, which are excellent in corrosion resistance and mirror surface property.

It is external drawing of the accessory which concerns on embodiment of this invention.

The present inventor has obtained the following findings as a result of conducting various studies in order to improve the corrosion resistance and mirror surface of the accessory.
Many intermetallic compounds are present in the cross section of commercially available materials having a PRE of 40 or more. Here, the intermetallic compound is an intermetallic compound having a Cr and Mo content higher than the Cr and Mo content of the matrix.
When a material having a PRE of 40 or more containing a large amount of intermetallic compounds is polished, the intermetallic compounds appear as different phases, and a mirror surface applicable to accessories cannot be obtained. Further, since the intermetallic compound reduces the Cr and Mo contents of the matrix phase, excellent corrosion resistance cannot be exhibited on the exposed surface of the intermetallic compound.

The present invention has been made as a result of the above studies, and the reasons for limiting the technical requirements and the preferred embodiments of the embodiments according to the present invention will be sequentially described below. First, an accessory according to an embodiment of the present invention will be described.

(Ingredient composition of jewelry)
The chemical components contained in the accessories according to the embodiment of the present invention (hereinafter, may be abbreviated as "accessories") and the reasons for limiting the content of each component will be described. In the following description, "%" means "mass%" unless otherwise specified.

C: 0.10% or less The C content should be 0.10% or less. When the C content is more than 0.10%, Cr carbides are excessively formed and the corrosion resistance of the accessory is deteriorated. The upper limit of the C content is preferably 0.08% or less, and more preferably 0.05% or less. On the other hand, since C is an element that forms austenite, it may be contained. The lower limit of the C content is preferably 0.005% or more, more preferably 0.010% or more.

Si: 1.5% or less The Si content should be 1.5% or less. When the Si content is more than 1.5%, the precipitation of the intermetallic compound is promoted, and the corrosion resistance and the mirror surface property of the accessory are deteriorated. The upper limit of the Si content is preferably 1.0% or less, more preferably 0.6% or less. On the other hand, since Si is an element having a deoxidizing action, it may be contained. The lower limit of the Si content is preferably 0.10% or more, and more preferably 0.30% or more.

Mn: 1.5% or less The Mn content needs to be 1.5% or less. When the Mn content is more than 1.5%, the corrosion resistance of the accessory is deteriorated. The upper limit of the Mn content is preferably 1.0% or less, more preferably 0.8% or less. On the other hand, Mn may be contained because it is an element that forms austenite and an element that has a deoxidizing action. The lower limit of the Mn content is preferably 0.01% or more, more preferably 0.10% or more.

P: 0.050% or less The P content needs to be suppressed to 0.050% or less. If the P content is more than 0.050%, the toughness of the accessory deteriorates. The upper limit of the P content is preferably 0.045% or less, and more preferably 0.035% or less.

S: 0.050% or less The S content needs to be suppressed to 0.050% or less. When the S content is more than 0.050%, the toughness and corrosion resistance of the accessory deteriorate. The upper limit of the S content is preferably 0.040% or less, more preferably 0.015% or less.

O: 0.020% or less The O content should be suppressed to 0.020% or less. If the O content is more than 0.020%, the toughness of the accessory deteriorates. The upper limit of the O content is preferably 0.015% or less, more preferably 0.010% or less.

Ni: 15.0-38.0%
The Ni content should be 15.0 to 38.0%. When the Ni content is less than 15.0%, ferrite is excessively formed, and the toughness and corrosion resistance of the accessory are deteriorated. The lower limit of the Ni content is preferably 17.0% or more, and more preferably 18.0% or more. On the other hand, when the Ni content is more than 38.0%, the effect of improving the corrosion resistance of the accessory is saturated. In addition, the Ni content becomes excessively high, and the jewelry becomes expensive. The upper limit of the Ni content is preferably 30.0% or less, more preferably 20.0% or less.

Cr: 17.0 to 27.0%
The Cr content should be 17.0 to 27.0%. If the Cr content is less than 17.0%, the corrosion resistance of the accessory deteriorates. The lower limit of the Cr content is preferably 18.0% or more, and more preferably 19.0% or more. On the other hand, when the Cr content is more than 27.0%, the ferrite and the intermetallic compound are excessively formed, and the toughness and corrosion resistance of the accessory are deteriorated. The upper limit of the Cr content is preferably 25.0% or less, more preferably 21.0% or less.

Mo: 4.0-8.0%
The Mo content should be 4.0-8.0%. If the Mo content is less than 4.0%, the corrosion resistance of the accessory deteriorates. The lower limit of the Mo content is preferably 5.0% or more, and more preferably 6.0% or more. On the other hand, when the Mo content is more than 8.0%, ferrite and intermetallic compounds are excessively formed, and the toughness and corrosion resistance of the accessory are deteriorated. The upper limit of the Mo content is preferably 7.5% or less, more preferably 7.0% or less.

Cu: 3.0% or less The Cu content should be 3.0% or less. When the Cu content is more than 3.0%, cracks are likely to occur during casting. The upper limit of the Cu content is preferably 1.0% or less, more preferably 0.8% or less. On the other hand, Cu may be contained because it has an effect of suppressing the progress of corrosion when corrosion occurs. The lower limit of the Cu content is preferably 0.01% or more, more preferably 0.10% or more.

N: 0.55% or less The N content should be 0.55% or less. When the N content is more than 0.55%, cracks are likely to occur during casting. The upper limit of the N content is preferably 0.50% or less, more preferably 0.35% or less, and further preferably 0.25% or less. On the other hand, N may be contained because it has an effect of improving corrosion resistance and an effect of forming austenite. The lower limit of the N content is preferably 0.05% or more, more preferably 0.10% or more, and further preferably 0.15% or more.

PRE is 40 or more The PRE defined by the following equation (1) must be 40 or more. If the PRE is less than 40, the corrosion resistance of the accessory deteriorates.
PRE = [Cr] +3.3 [Mo] +16 [N] ... (1)
However, [Cr], [Mo] and [N] in the formula (1) mean the content of Cr, Mo and N in the component composition of the accessory in mass% of Cr, Mo and N, and if not contained, 0 is used. substitute.

In addition to the above-mentioned elements, the fittings according to the present embodiment further include Al, Co, W, Ta, Sn, Sb, Ga, Ti, V, Nb, Zr, Te, Se, B, Ca, Mg, and And one or more selected from rare earth elements may be contained. Since these elements do not have to be contained, the lower limit of the content is 0.

Al: 0.10% or less The jewelry according to this embodiment may contain 0.10% or less of Al. Since Al is an element having a deoxidizing action, it may be contained. In order to obtain this effect, the content when Al is contained is 0.001% or more, more preferably 0.005% or more. On the other hand, when the Al content is more than 0.10%, Al nitrides and Al oxides are excessively formed, and the corrosion resistance and toughness of the accessory are deteriorated. The upper limit of the Al content is preferably 0.05% or less, more preferably 0.02% or less.

Co: 3.0% or less The jewelry according to this embodiment may contain 3.0% or less of Co. Co may be contained because it has the effect of forming austenite and suppressing the formation of intermetallic compounds. In order to obtain this effect, the content when Co is contained is 0.001% or more, more preferably 0.1% or more. On the other hand, when the Co content is more than 3.0%, the workability deteriorates. The upper limit of the Co content is preferably 2.0% or less, more preferably 1.5% or less.

W: 8.0% or less The jewelry according to this embodiment may contain 8.0% or less W. W may be contained because it has an effect of improving corrosion resistance. In order to obtain this effect, the content when W is contained is 0.001% or more, more preferably 0.1% or more. On the other hand, when the W content is more than 8.0%, the workability deteriorates. The upper limit of the W content is preferably 5.0% or less, more preferably 1.0% or less.

Ta: 1.0% or less The accessory according to this embodiment may contain 1.0% or less of Ta. Ta may be contained because it has an effect of making crystal grains finer and an effect of improving corrosion resistance. In order to obtain these effects, the content when Ta is contained is 0.001% or more, more preferably 0.005% or more. On the other hand, when the Ta content is more than 1.0%, the workability deteriorates. The upper limit of the Ta content is preferably 0.5% or less, more preferably 0.1% or less.

Sn: 1.0% or less The accessory according to the present embodiment may contain 1.0% or less of Sn. Sn may be contained because it has an effect of improving corrosion resistance. In order to obtain this effect, the content when Sn is contained is 0.001% or more, more preferably 0.005% or more. On the other hand, when the Sn content is more than 1.0%, the workability deteriorates. The upper limit of the Sn content is preferably 0.5% or less, and more preferably 0.3% or less.

Sb: 1.0% or less The accessory according to this embodiment may contain 1.0% or less of Sb. Sb may be contained because it has an effect of improving corrosion resistance. In order to obtain this effect, the content when Sb is contained is 0.001% or more, more preferably 0.005% or more. On the other hand, when the Sb content is more than 1.0%, the workability deteriorates. The upper limit of the Sb content is preferably 0.5% or less, more preferably 0.3% or less.

Ga: 1.0% or less The jewelry according to this embodiment may contain 1.0% or less of Ga. Ga may be contained because it has an effect of improving corrosion resistance and an effect of improving processability. In order to obtain this effect, the content when Ga is contained is 0.001% or more, more preferably 0.015% or more. On the other hand, when the Ga content is more than 1.0%, the effect of improving the corrosion resistance and the effect of improving the workability are saturated. The upper limit of the Ga content is preferably 0.5% or less, more preferably 0.3% or less.

Ti: 1.0% or less The jewelry according to this embodiment may contain 1.0% or less of Ti. Ti may be contained because it has the effect of fixing C and N as carbonitride to improve the corrosion resistance and the effect of refining the crystal grains. In order to obtain this effect, the content when Ti is contained is 0.001% or more, more preferably 0.01% or more. On the other hand, when the Ti content is more than 1.0%, an excessive amount of oxides and nitrides are formed, and the workability is deteriorated. The upper limit of the Ti content is preferably 0.5% or less, more preferably 0.3% or less.

V: 1.0% or less The jewelry according to this embodiment may contain V of 1.0% or less. V may be contained because it has the effect of fixing C and N as carbonitride to improve the corrosion resistance and the effect of refining the crystal grains. In order to obtain these effects, the content when V is contained is 0.001% or more, more preferably 0.02% or more. On the other hand, when the V content is more than 1.0%, an excessive amount of oxides and nitrides are formed, and the workability is deteriorated. The upper limit of the V content is preferably 0.9% or less, more preferably 0.5% or less.

Nb: 1.0% or less The jewelry according to this embodiment may contain Nb of 1.0% or less. Nb may be contained because it has the effect of fixing C and N as carbonitride to improve the corrosion resistance and the effect of refining the crystal grains. In order to obtain these effects, the content when Nb is contained is 0.001% or more, more preferably 0.02% or more. On the other hand, when the Nb content is more than 1.0%, an excessive amount of oxides and nitrides are formed, and the workability is deteriorated. The upper limit of the Nb content is preferably 0.5% or less, more preferably 0.2% or less.

Zr: 1.0% or less The accessory according to this embodiment may contain 1.0% or less of Zr. Zr may be contained because it has the effect of improving the strength and the effect of refining the crystal grains. In order to obtain these effects, the content when Zr is contained is 0.001% or more, more preferably 0.02% or more. On the other hand, when the Zr content is more than 1.0%, the workability deteriorates. The upper limit of the Zr content is preferably 0.5% or less, more preferably 0.2% or less.

Te: 1.0% or less The jewelry according to this embodiment may contain 1.0% or less of Te. Te may be contained because it has an effect of improving machinability. In order to obtain this effect, the content when Te is contained is 0.001% or more, more preferably 0.01% or more. On the other hand, when the Te content is more than 1.0%, the corrosion resistance deteriorates. The upper limit of the Te content is preferably 0.05% or less, more preferably 0.02% or less.

Se: 1.0% or less The jewelry according to this embodiment may contain 1.0% or less of Se. Since Se has an effect of improving machinability, it may be contained. In order to obtain this effect, the content when Se is contained is 0.001% or more, more preferably 0.01% or more. On the other hand, when the Se content is more than 1.0%, the corrosion resistance deteriorates. The upper limit of the Se content is preferably 0.2% or less, and more preferably 0.1% or less.

B: 0.01% or less The jewelry according to this embodiment may contain 0.01% or less of B. B may be contained because it has an effect of improving hot workability. In order to obtain this effect, the content when B is contained is 0.0001% or more, more preferably 0.0005% or more. On the other hand, when the B content exceeds 0.01%, the corrosion resistance deteriorates. The upper limit of the B content is preferably 0.005% or less, and more preferably 0.003% or less.

Ca: 0.05% or less The jewelry according to this embodiment may contain 0.05% or less of Ca. Ca may be contained because it has an effect of improving hot workability. In order to obtain this effect, the content when Ca is contained is 0.0001% or more, more preferably 0.0005% or more. On the other hand, when the Ca content is more than 0.05%, the hot workability is rather deteriorated. The upper limit of the Ca content is preferably 0.005% or less, and more preferably 0.003% or less.

Mg: 0.05% or less The accessory according to this embodiment may contain 0.05% or less of Mg. Mg may be contained because it has an effect of improving hot workability. In order to obtain this effect, the content when Mg is contained is 0.0001% or more, more preferably 0.0005% or more. On the other hand, when the Mg content is more than 0.05%, the hot workability is rather deteriorated. The upper limit of the Mg content is preferably 0.005% or less, more preferably 0.003% or less.

Rare earth element: 1.0% or less The accessory according to this embodiment may contain 1.0% or less of rare earth element. Rare earth elements may be contained because they have the effect of improving hot workability. In order to obtain this effect, the content when the rare earth element is contained is 0.001% or more, more preferably 0.005% or more. On the other hand, when the rare earth element content is more than 1.0%, the hot workability is rather deteriorated. The upper limit of the rare earth element content is preferably 0.1% or less, more preferably 0.03% or less.

The balance contains Fe and impurities The balance other than the above-mentioned elements contains Fe and impurities. In addition to the elements described above, they can be contained within a range that does not impair the effects of the present embodiment. The balance other than the above-mentioned elements is preferably composed of Fe and impurities.

The method for measuring the component composition of jewelry is as follows. For elements other than O and N, first, a sample is taken from the plate material having a plate thickness of 1/4. For the bar, a sample is taken from the length of 1/2 of the line segment connecting the surface and the center. Then, in 2013, the component composition is measured according to JIS G 1256 (iron and steel fluorescent X-ray analysis method).
Further, O is measured with respect to the above sample by using JIS G 1239 (inert gas melting-infrared absorption method) in 2014. N is measured for the above sample using JIS G 1228 (iron and steel-nitrogen quantification method) in 2006.
The shape of the plate material conforms to the regulations of JIS G 4304 (hot-rolled stainless steel plate and steel strip) in 2012 or JIS G 4305 (cold-rolled stainless steel plate and steel strip) in 2012.
In addition, the shape of the bar material conforms to the provisions stipulated in JIS G 4303 (stainless steel bar) in 2012.

(Organization of jewelry)
The reason for limiting the structure of the accessory according to the embodiment of the present invention will be described. In the following description, "%" means "area%" unless otherwise specified.

Austenite must be 95% or higher Austenite must be 95% or higher. If the austenite is less than 95%, the amount of intermetallic compound will be excessively large. The mirror surface and corrosion resistance of jewelry deteriorate. The austenite is preferably 97% or more, more preferably 98% or more, and even more preferably 99% or more.
When the heat treatment of the present invention is carried out, a characteristic structure other than the recovery of crystal defects and the formation of annealed twins observed by ordinary annealing (annealing) is generated. For example, primary recrystallized austenite grains that erode old austenite grains containing twins are observed. Further, depending on the heat treatment conditions, secondary recrystallized coarse austenite crystal grains may be observed. Such a structure can be confirmed by using an electron backscatter diffraction (EBSD) apparatus attached to an electron microscope.

The method for measuring the area% of austenite is as follows. First, the reflected electron image (SEM-BSE) of a scanning electron microscope is used. The measurement magnification is the same as the standard drawing described in the microscopic test method (2003) for non-metal inclusions of JIS G0555 steel, and the measurement is performed at a magnification in which a square having a side of about 710 μm is included in the observation field of view.
In the case of a plate material, the measurement location is such that the center of the plate thickness is parallel to one side (about 710 μm) of the square field of view and passes through the center of the square. In the case of a bar, observe at a position where the center of the cross section perpendicular to the longitudinal direction becomes the center of the square field of view. In the plate material and the bar material, the most abundant intermetallic compounds having high Cr and high Mo are present at the above-mentioned observation place. On the exposed surface of the jewelery, the area fraction of austenite is higher and the area fraction of the intermetallic compound is lower than in the above-mentioned observation place.
In the backscattered electron image, the contrast of the matrix phase, which is austenite, appears bright (white) when there is an intermetallic compound having high Cr and high Mo, and dark (black) when there are non-metal inclusions. If there is a captured image display, adjust so that the dense portion of the compound other than austenite is at the center of the square.
Next, the photographed reflected electron image is image-analyzed and classified into three levels of luminance pixels: an intermetallic compound (high-luminance pixel), an austenite (intermediate-luminance pixel), and a non-intermetallic compound (low-luminance pixel). Let the percentage of the number of pixels of austenite to the total number of pixels be the area% of austenite.

On the exposed surface of the accessory, the number of intermetallic compounds having a size of 150 μm or more is 0, and the number of intermetallic compounds having a size of 13 μm or more and less than 150 μm is 3 or less.
In the accessory according to the present embodiment, the number of intermetallic compounds having a size of 150 μm or more needs to be 0 on the exposed surface of the accessory. If the number of intermetallic compounds having a size of 150 μm or more is more than 0, the mirror surface property and corrosion resistance of the accessory are deteriorated. The size of the intermetallic compound is the diameter of a circle having the smallest area that can contain one intermetallic compound inside. The exposed surface of the accessory is the surface of the accessory whose appearance can be observed.
Further, in the accessory according to the present embodiment, the number of intermetallic compounds having a size of 13 μm or more and less than 150 μm must be 3 or less on the exposed surface of the accessory. If the number of intermetallic compounds having a size of 13 μm or more and less than 150 μm is more than 3, the mirror surface property and corrosion resistance of the accessory are deteriorated.

Since the intermetallic compound has a different phase from the parent phase, austenite, the appearance of the intermetallic compound and the parent phase is different. Therefore, when the number of intermetallic compounds is excessive, sufficient mirror surface properties applicable to accessories cannot be obtained.
Further, a region having an excessively low Cr and Mo content is formed on the matrix side of the interface between the intermetallic compound and austenite which is the matrix. Therefore, if the number of intermetallic compounds is excessive, the corrosion resistance of the accessory is deteriorated.

The method for measuring the number of intermetallic compounds having a size of 150 μm or more and intermetallic compounds having a size of 13 μm or more and less than 150 μm is as follows. First, using an optical microscope, a photograph of the structure of the exposed surface of the accessory is taken at a magnification of 10 times. Measure the size of the intermetallic compound in the photograph taken. The size of the intermetallic compound is the diameter of a circle having the smallest area that can contain one intermetallic compound inside. Then, the number of intermetallic compounds having a size of 150 μm or more and intermetallic compounds having a size of 13 μm or more and less than 150 μm is counted.

The average circle-equivalent diameter of austenite must be 150 μm or less. The average circle-equivalent diameter of austenite must be 150 μm or less. If the average equivalent circle diameter of austenite is more than 150 μm, the mirror surface of the accessory deteriorates. The average equivalent circle diameter of austenite is preferably 70 μm or less.

The method for measuring the average circle-equivalent diameter of austenite is as follows. The orientation of individual crystal grains is determined by a backscattered electron diffractometer (EBSD device) attached to a field emission SEM. A place where the orientation difference between adjacent pixels is 5 ° or more is defined as a grain boundary. Furthermore, the actual area of the crystal grains is measured, and the average circle-equivalent diameter of austenite is calculated from the formula for obtaining the area of a circle. The annealed twins existing in the crystal grains are subjected to a treatment that is not determined to be a grain boundary.

Residues other than intermetallic compounds and austenite The remnants other than intermetallic compounds and austenite may contain non-metallic phases such as inclusions, oxides, nitrides and carbides.

The accessories according to the present embodiment are not particularly limited, and examples thereof include a watch exterior, a necklace, and eyeglasses. Here, the exterior of the watch is not particularly limited, and examples thereof include a case and a belt of a watch, a case and a belt of a wearable device having a watch function, and the like.

Subsequently, a method of manufacturing an accessory according to an embodiment of the present invention will be described. Since the manufacturing method differs depending on whether the plate material is used or the bar material is used, the case where the plate material is used and the case where the bar material is used will be described separately.

The method for manufacturing a fitting according to an embodiment of the present invention includes a step of manufacturing a plate material having the above-mentioned chemical components, a heat treatment step of heat-treating the plate material, and a cold rolling step of plastically processing the plate material.

(Process for manufacturing plate materials)
A known method can be used in the step of manufacturing the plate material. The process of manufacturing the plate material is not particularly limited, but for example, the following method can be adopted. In a melting furnace such as a pressurable electric furnace or a pressurable high frequency induction furnace, the alloy having the above-mentioned chemical composition is melted and cast into a steel ingot. Next, the obtained ingot is hot-worked to obtain a plate material having a desired shape. Then, after hot working, solution heat treatment is performed.

(Heat treatment process)
In the heat treatment step, the heat treatment temperature needs to be 1350 to 1600K. If the heat treatment temperature is less than 1350 K, the corrosion resistance and mirror surface property of the accessory deteriorate. The heat treatment temperature is preferably 1473 K or higher. On the other hand, when the heat treatment temperature exceeds 1600 K, high temperature deformation or partial melting occurs due to the weight of the material itself. The heat treatment temperature is preferably 1548 K or less.

In the heat treatment step, the heat treatment time needs to satisfy the following equation (2).
t _dif ≧ (6869 / T _dif 4.3326) × λ ² ... (2). However, in the formula (2), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (how), and λ represents the plate thickness (mm) of the plate material. If the heat treatment time does not satisfy the equation (2), the amount of the intermetallic compound becomes excessively large, and the corrosion resistance and the mirror surface property of the accessory are deteriorated.

The heat treatment method may be partial heating of the inert gas. By partially heating the inert gas, sublimation of Cr during the heat treatment is suppressed, and the corrosion resistance of the accessory is further improved.
After the heat treatment step, cooling may be performed at 60 ° C./min or higher. By cooling at 60 ° C./min or higher, the reprecipitation and increase in the content of the intermetallic compound are further suppressed, and the corrosion resistance and mirror surface property of the accessory are further improved.

(Cold rolling process)
In the cold rolling process, the rolling reduction ratio needs to be 7 to 50%. When the reduction rate is less than 7%, the average circle-equivalent diameter of austenite becomes excessively large, and the mirror surface property of the accessory deteriorates. The reduction rate is preferably 13% or more. On the other hand, when the reduction rate is more than 50%, the hardness of the material becomes excessively large. As a result, the machinability and pressability of the material deteriorate.

(Hot forging process and cold forging process)
The method for manufacturing the fittings according to the embodiment of the present invention is a hot forging step and a cold forging step in which the above-mentioned cold rolling step is omitted and the plate material is heated to a temperature in the austenite stable region to perform hot plastic deformation. It may have a cold forging step of performing plastic deformation in. The amount of plastic deformation in the hot forging step and the cold forging step is not particularly limited as long as the average circle equivalent diameter of austenite on the exposed surface of the fitting is 150 μm or less. The amount of plastic deformation in the hot forging step and the cold forging step is preferably selected so that the average circle equivalent diameter of austenite on the exposed surface of the fitting is 70 μm or less. The hot forging step and the cold forging step tend to have a higher material yield than the cold rolling step. Therefore, it is preferable to omit the cold rolling step and perform the hot forging step and the cold forging step.

Subsequently, a method of manufacturing an accessory according to another embodiment of the present invention will be described.

The method for manufacturing a fitting according to another embodiment of the present invention includes a step of manufacturing a bar having the chemical composition described in the above-described embodiment, a heat treatment step of heat-treating the bar, and a cold process of plastic working the bar. It has an inter-drawing process.

(Process for manufacturing rods)
A known method can be used in the step of producing the bar material.

(Heat treatment process)
In the heat treatment step, the heat treatment temperature needs to be 1350 to 1600K. When the heat treatment temperature is less than 1350 K, the amount of the intermetallic compound becomes excessively large, and the corrosion resistance and the mirror surface property of the accessory are deteriorated. The heat treatment temperature is preferably 1473 K or higher. On the other hand, when the heat treatment temperature exceeds 1600 K, high temperature deformation or partial melting occurs due to the weight of the material itself. The heat treatment temperature is preferably 1548 K or less.

In the heat treatment step, the heat treatment time needs to satisfy the following equation (3).
t _dif ≧ (6869 / T _dif 4.3326) × d ... (3). However, in the formula (3), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (how), and d represents the circle-equivalent diameter (mm) of the bar. If the heat treatment time does not satisfy the equation (3), the amount of the intermetallic compound becomes excessively large, and the corrosion resistance and the mirror surface property of the accessory are deteriorated.

The concentration diffusion of Cr and Mo during heat treatment of high Cr and high Mo intermetallic compounds progresses one-dimensionally from the central surface in the thickness direction to both sides of rolling in the plate material, and the circumference from the central axis in the wire drawing direction in the rod material. It travels two-dimensionally in the lateral direction.
In equation (2) regarding the heat treatment time of the plate material, it is assumed that the amount of diffusion from the high Cr and high Mo intermetallic compound into the surrounding austenite becomes equivalent between the plate material and the bar material. Then, in the bar used for the jewelry, the equation (3) is derived by replacing the ^{plate thickness λ 2 with the diameter d.}

As for the conditions other than the heat treatment temperature and the heat treatment time, the conditions described in the method for manufacturing accessories according to the previous embodiment can be adopted.

(Cold wire drawing process)
In the cold wire drawing process, the surface reduction rate needs to be 7 to 50%. When the surface reduction rate is less than 7%, the average circle-equivalent diameter of austenite becomes excessively large, and the mirror surface property of the accessory deteriorates. The reduction rate is preferably 13% or more. On the other hand, when the surface reduction rate is more than 50%, the hardness of the material becomes excessively large. As a result, the machinability and pressability of the material deteriorate.

As for the conditions other than the surface reduction rate, the conditions described in the method for manufacturing accessories according to the previous embodiment can be adopted.

(Hot forging process and cold forging process)
The method for manufacturing a fitting according to another embodiment of the present invention is a hot forging step in which the above-mentioned cold wire drawing step is omitted and the bar is heated to a temperature in the austenite stable region to perform hot plastic deformation. And may have a cold forging step of performing plastic deformation in the cold. The amount of plastic deformation in the hot forging step and the cold forging step is not particularly limited as long as the average circle equivalent diameter of austenite on the exposed surface of the fitting is 150 μm or less. The amount of plastic deformation in the hot forging step and the cold forging step is preferably selected so that the average circle equivalent diameter of austenite on the exposed surface of the fitting is 70 μm or less. The hot forging step and the cold forging step have a higher material yield than the cold wire drawing step. Therefore, it is preferable to omit the cold wire drawing step and perform the hot forging step and the cold forging step.

The above-mentioned method for manufacturing an accessory according to an embodiment of the present invention may include a manufacturing process for forming the accessory into a predetermined shape and appearance. A known manufacturing method can be used in the manufacturing process for obtaining the accessory into a predetermined shape and appearance.

Although not particularly limited, a method for manufacturing a watch exterior will be shown as an example. First, the manufacturing method of the watch case inside the watch exterior will be described.

(Manufacturing method of watch case)
A blank is punched from a plate or bar (hereinafter sometimes referred to as "material") that has undergone the above-mentioned heat treatment step, cold rolling step, or cold wire drawing step using a crank press machine and a punching die. .. The punched blank is molded into a near-net shape using a plurality of molding dies. If the material is work-hardened on the way, an annealing step is appropriately carried out in which the material is heated to a temperature equal to or higher than the solution temperature and rapidly cooled in a bright annealing furnace.

Separately from the above, a method for manufacturing a blank that employs a hot forging step and a cold forging step will be described. First, the plate material or bar material that has undergone the above-mentioned heat treatment step is heated by high-frequency induction heating or a heating furnace, and is formed by hot forging into a shape close to the above-mentioned punching blank using a plurality of press machines and heat-resistant dies. .. After removing the oxide film on the surface by pickling or sandblasting, a near-net-shaped blank is prepared coldly using a press and a molding die. Intermediate annealing may be carried out as appropriate during the hot forging step and the cold forging step.
It is preferable to reduce the number of dies in the hot forging process and increase the number of dies in the cold forging process. As a result, the average circle-equivalent diameter of austenite can be further reduced.

The press-up blank can be used for multiple cutting such as inner diameter grinding, which is the standard for machining with a numerical control (NC) lathe, surface cutting of the press surface, drilling of can holes and winding holes for attaching bands, screwing for back cover attachment, etc. After undergoing a drilling process, it becomes an unpolished watch case.

The unpolished watch case is roughly polished with a Zaratsu polishing machine equipped with # 360, # 800, # 1200 and # 2000 water resistant abrasive papers. Subsequently, the water-resistant polishing paper is replaced with a polishing cloth, and finish polishing is performed using alumina polishing agents having particle sizes of 3 μm, 1 μm, 0.3 μm, and 0.05 μm.

After finish polishing, polish puff polishing is performed. Depending on the design of the exterior of the watch, a mask may be applied and decoration such as streaking with a rotating wire brush or honing (sandplast) processing may be performed. The case is completed by brazing and gluing the winding pipe to which the crown is attached. The back cover and glass rim are also made by the same process.

Next, a method of manufacturing a metal band inside the watch exterior will be described.
(Manufacturing method of metal band)
From the material subjected to the above-mentioned heat treatment step, cold rolling step or cold wire drawing step, the pieces are punched out by a press in the same manner as the watch case, and the pieces are molded into a shape close to the finished product by a molding press. Furthermore, the surface is cut and pin holes for connecting the pieces are drilled for polishing. Finally, the predetermined arrangement pieces are connected by a C ring pin or the like, and a clasp used for attachment / detachment is attached.

The method for manufacturing the watch exterior is not limited to the method described above, and any of the known manufacturing methods used in the manufacture of the watch exterior may be used.

Next, examples of the present invention will be described. The conditions shown in the examples are examples adopted for confirming the feasibility and effect of the present invention. Therefore, the present invention is not limited to this example. In the present invention, various conditions can be adopted as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Heat treatment conditions)
Steel types A to D having the component compositions shown in Table 1 were prepared. Steel type A having a plate thickness of 6 mm to 22 mm was heat-treated under the conditions shown in Table 2, and the material was rapidly cooled after the heat treatment. The number of intermetallic compounds having a size of 150 μm or more and a size of 13 μm or more and less than 150 μm was measured with respect to the material after the heat treatment.

The method for measuring the component composition of the material was as follows. For elements other than N, first, a sample was taken from a 1/4 thick part of the plate material. Then, in 2013, the component composition was measured according to JIS G 1256 (iron and steel fluorescent X-ray analysis method).
N was measured on the above sample using JIS G 1228 (iron and steel-nitrogen quantification method) in 2006.

The method for measuring the number of intermetallic compounds having a size of 150 μm or more and intermetallic compounds having a size of 13 μm or more and less than 150 μm was as follows. First, using an optical microscope, a photograph of the structure at the center of the plate thickness was taken at a magnification of 10 times. The size of the intermetallic compound was measured in the photograph taken. The size of the intermetallic compound is the diameter of a circle having the smallest area that can contain one intermetallic compound inside. Then, the number of intermetallic compounds having a size of 150 μm or more and intermetallic compounds having a size of 13 μm or more and less than 150 μm was counted. In the plate material, the most abundant intermetallic compounds having high Cr and high Mo at the center of the plate thickness. Therefore, the number of intermetallic compounds measured by the above method was assumed to be the number of intermetallic compounds having a size of 150 μm or more and a size of 13 μm or more and less than 150 μm. Moreover, since the cold rolling step is carried out at room temperature, the number of intermetallic compounds in the material does not change substantially.
The measurement was completed when the number of intermetallic compounds having a size of 150 μm or more became one. The measurement was completed when the number of intermetallic compounds having a size of 13 μm or more and less than 150 μm reached four. Table 2 shows the measurement results of the number of intermetallic compounds having a size of 13 μm or more and less than 150 μm. In Table 2, the number of intermetallic compounds having a size of 13 μm or more and less than 150 μm was 0, and the number of intermetallic compounds having a size of 150 μm or more was also 0.

The method for measuring the area% of austenite was as follows. First, it was performed with a reflected electron image (SEM-BSE) of a scanning electron microscope. The measurement magnification was the same as the standard drawing described in the microscopic test method (2003) for non-metal inclusions of JIS G0555 steel, and the measurement was performed at a magnification in which a square having a side of about 710 μm was included in the observation field of view.
The measurement location was a position where the center of the plate thickness was parallel to one side (about 710 μm) of the square field of view and passed through the center of the square.
Next, the photographed reflected electron image is image-analyzed and classified into three levels of luminance pixels: an intermetallic compound (high-luminance pixel), an austenite (intermediate-luminance pixel), and a non-intermetallic compound (low-luminance pixel). The percentage of the number of pixels of austenite to the total number of pixels was defined as the area% of austenite. Moreover, since the cold rolling step is carried out at room temperature, the area% of austenite in the material does not change substantially. Therefore, the area% of the austenite of the material after the heat treatment step is assumed to be the area% of the austenite of the accessory. The measurement results of the area% of austenite are shown in Table 3.

As shown in Tables 2 and 3, when the heat treatment conditions in the heat treatment step satisfy the following formula (2), the area% of austenite, the intermetallic compound having a size of 150 μm or more, and the size of 13 μm or more and less than 150 μm The number of certain intermetallic compounds is within the scope of the present invention. Area% of austenite was 95% or more under all conditions. Also, the rest of the structure was a non-metallic phase.
t _dif ≧ (6869 / T _dif 4.3326) × λ ² ... (2). However, in the formula (2), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (how), and λ represents the plate thickness (mm) of the plate material.

(Cold rolling conditions)
A plate material having a thickness of 6 mm of steel type A was heat-treated at 1473 K for 12 hours. After the heat treatment, cold rolling was carried out with a two-stage rolling mill to a predetermined thickness. The rolling reduction amount for one pass was 0.10 mm, and rolling was completed when the thickness reached a predetermined value. The rolling reduction of cold rolling is shown in Table 4.

The rolled material was cut out in a plane perpendicular to the rolling direction. A blank was punched out from the cut out material using a crank press machine and a punching die. The punched blank was molded into a near-net shape using a plurality of molding dies.
Pressed-up blanks are processed with a numerical control (NC) lathe to grind the inner diameter, cut the surface of the press surface, drill sharp holes and can holes for attaching bands, screw processing for attaching the back cover, and multiple cutting and drilling processes. To obtain an unpolished watch case.

The unpolished watch case was rough-polished with a Zaratsu grinding machine equipped with # 360, # 800, # 1200 and # 2000 water-resistant abrasive papers. Subsequently, the water-resistant polishing paper was replaced with a polishing cloth, and finish polishing was performed using alumina polishing agents having particle sizes of 3 μm, 1 μm, 0.3 μm, and 0.05 μm. After finish polishing, polish puff polishing was performed.

As a result, the watch cases of Examples 1 to 6 and Comparative Examples 1 to 4 were obtained. The hardness of the material immediately after cold rolling was measured. A Vickers hardness tester was used to measure the hardness. The load at the time of hardness measurement was 0.3 kgf, and the holding time was 15 seconds. The measurement results of the Vickers hardness tester are shown in Table 4.

The average circle-equivalent diameter of the austenite crystal grains was determined as follows. The orientation of each grain was determined by a backscattered electron diffractometer (EBSD device) attached to the field emission SEM. A place where the orientation difference between adjacent pixels is 5 degrees or more is defined as a grain boundary. Furthermore, the actual area of the crystal grains was measured, and the average circle-equivalent diameter of austenite was calculated from the formula for calculating the area of the circle. The annealed twins present in the crystal grains were treated so as not to be determined to be grain boundaries. Table 4 shows the measurement results of the average circle equivalent diameter of austenite.

The mirror surface of the watch case was measured by judging the appearance. Mirrorness was evaluated on a three-point scale: inferior, normal and good. Table 4 shows the measurement results of the mirror surface property.

In Examples 1 to 6, the heat treatment conditions of the heat treatment step and the reduction rate of cold rolling were within the range of the present invention, so that the material did not become excessively hard. Therefore, the material has sufficient workability even after the cold rolling process. Moreover, since the average circle-equivalent diameter of austenite did not become excessively large, the mirror surface of the watch case was sufficient.

On the other hand, in Comparative Examples 1 to 3, the reduction rate of cold rolling was insufficient, so that the mirror surface of the watch case was insufficient. Further, in Comparative Example 4, the rolling reduction of the cold rolling was excessive, so that the workability of the material after the cold rolling step was insufficient.

(Corrosion resistance)
In Example 7, a test piece for a corrosion resistance test was prepared as follows. A plate material having a thickness of steel type B having a thickness of 2 mm was heat-treated at 1473 K for 1.5 hours. The plate material was rapidly cooled after the heat treatment. Then, the plate material was cold-rolled at a rolling reduction of 25%. The thickness of the plate material after cold rolling was 1.5 mm. The plate material after cold rolling was cut into a rectangle having a height of 20 mm and a width of 40 mm. After chamfering the corners, the rolled surface (2 surfaces) and the cut side surface (4 surfaces) were subjected to the same polishing process as the manufacturing method of the watch case of Example 1 to be finished as a mirror surface.
Comparative Examples 5 to 7 were not subjected to heat treatment or cold rolling. A test piece for a corrosion resistance test was prepared in the same manner as in Example 7 except for the above.

The corrosion resistance test was as follows. A semi-immersion test was performed on 10 mirror-finished rectangular test pieces in a saturated saline solution at 60 ° C. Specifically, a saturated saline solution coexisting with solid saline was placed in a container, and the test piece was set in a rack made of polytetrafluoroethylene leaning at an inclination of 30 degrees from the vertical direction and submerged in the container. Then, the amount of the liquid was adjusted so that the height of the test piece up to 10 mm was immersed in the saline solution. The container was allowed to stand in a constant temperature bath at 60 ° C. The test pieces were taken out periodically, and after cleaning, pitting corrosion and intergranular corrosion were confirmed with a stereomicroscope. The semi-immersion test was carried out for a maximum of 1000 hours. The average time until corrosion of 10 test pieces was taken as the corrosion time. The corrosion time of the test piece that did not corrode in 1000 hours was 1000 hours. The corrosion resistance test results are shown in Table 5.

In Example 7, since the heat treatment conditions and PRE were within the range of the present invention, good corrosion resistance was exhibited.
In Comparative Example 5, the heat treatment conditions were outside the scope of the present invention, so that the corrosion resistance was inferior to that of Example 7. Comparative Example 6 and Comparative Example 7 had insufficient corrosion resistance because the heat treatment conditions and PRE were outside the scope of the present invention.

(When performing cold forging process and hot forging process)
The test was also conducted in the case where the cold rolling step and the cold wire drawing step were omitted and the hot forging step and the cold forging step were performed.

In Example 8, a round bar having an average circular diameter of 25 mm of steel type A was used. The round bar was heat treated at 1523 K for 8 hours in an argon atmosphere. After the heat treatment, the round bar was rapidly cooled with pressurized nitrogen gas. The heat-treated round bar was cut to a length of about 40 mm to obtain a billet. The billet was heated to 1473K using a high-frequency induction heating method, and the billet was pulled out using a plurality of heat-resistant forging dies and hot forged into a shape close to a blank. After hot forging, the oxide film on the surface was removed by sandblasting or acid cleaning, and then cold forging was performed. Then, a watch case was obtained by the same process as in Examples 1 to 7.

In Example 9, a plate material of steel type A having a plate thickness of 14 mm and a width of 40 mm was used. The heat treatment conditions of Example 9 were 1523 K and 36 hours of heat treatment. The heat-treated plate was cut to a length of about 35 mm. Then, a watch case was obtained under the same conditions as in Example 8.

The average circle equivalent diameter and mirror surface properties of the austenites of Examples 8 and 9 were measured by the same method as in Examples 1 to 7. As a result, the average circle equivalent diameters of the austenites of Examples 8 and 9 were both 150 μm or less, and the mirror surface property was also sufficient.

From the above, according to the present invention, it is possible to provide an accessory having excellent corrosion resistance and mirror surface properties and a method for producing the same, which has high industrial utility value.

Claims (6)

The chemical composition is mass%,
C: 0.10% or less,
Si: 1.5% or less,
Mn: 1.5% or less,
P: 0.050% or less,
S: 0.050% or less,
O: 0.020% or less,
Ni: 15.0-38.0%,
Cr: 17.0 to 27.0%,
Mo: 4.0-8.0%,
Contains Cu: 3.0% or less and N: 0.55% or less,
The rest contains Fe and impurities
The tissue is area%, austenite is 95% or more,
When the diameter of the circle having the smallest area that can contain one intermetallic compound is defined as the size of the intermetallic compound, the metal having the size of 150 μm or more on the exposed surface of the accessory. The number of intermetallic compounds is 0, and the number of intermetallic compounds having a size of 13 μm or more and less than 150 μm is 3 or less.
The average circle-equivalent diameter of the austenite is 150 μm or less.
An accessory characterized in that the PRE defined by the following equation (1) is 40 or more.
PRE = [Cr] +3.3 [Mo] +16 [N] ... (1)
However, [Cr], [Mo] and [N] in the formula (1) mean the content of Cr, Mo and N in the component composition of the accessory in mass% of Cr, Mo and N, and if not contained, 0 is used. substitute. The chemical composition is further increased by mass%.
Al: 0.001 to 0.10%,
Co: 0.001 to 3.0%,
W: 0.001 to 8.0%,
Ta: 0.001 to 1.0%,
Sn: 0.001 to 1.0%,
Sb: 0.001 to 1.0%,
Ga: 0.001 to 1.0%,
Ti: 0.001 to 1.0%,
V: 0.001 to 1.0%,
Nb: 0.001 to 1.0%,
Zr: 0.001 to 1.0%,
Te: 0.001 to 1.0%,
Se: 0.001 to 1.0%,
B: 0.0001 to 0.01%,
Ca: 0.0001 to 0.05%,
Mg: 0.0001 to 0.05%, and rare earth elements: 0.001 to 1.0%
The accessory according to claim 1, wherein the accessory is one or more selected from the above. The accessory according to claim 1 or 2, wherein the accessory is a watch exterior. The method for manufacturing an accessory according to any one of claims 1 to 3.
The process of manufacturing plate materials and
A heat treatment step of heat-treating the plate material and
It has a cold rolling process for plastic working the plate material, and has
In the heat treatment step, the heat treatment temperature is 1350 to 1600K, and the heat treatment time satisfies the following formula (2).
A method for manufacturing an accessory, which comprises a rolling reduction of 7 to 50% in the cold rolling step.
t _dif ≧ (6869 / T _dif 4.3326) × λ ² ··· (2)
However, in the formula (2), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (how), and λ represents the plate thickness (mm) of the plate material. The method for manufacturing an accessory according to any one of claims 1 to 3.
The process of manufacturing rods and
A heat treatment step of heat-treating the bar and
It has a cold wire drawing process for plastic working the bar.
In the heat treatment step, the heat treatment temperature is 1350 to 1600K, and the heat treatment time satisfies the following formula (3).
A method for manufacturing an accessory, which comprises a surface reduction rate of 7 to 50% in the cold wire drawing step.
t _dif ≧ (6869 / T _dif 4.3326) × d ... (3)
However, in the formula (3), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (hour), and d represents the circle-equivalent diameter (mm) of the bar. The method for manufacturing an accessory according to any one of claims 1 to 3.
The process of manufacturing plate or bar and
A heat treatment step of heat-treating the plate material or the bar material, and
A hot forging step of hot forging the plate material or the bar material, and
It has a cold forging step of cold forging the plate material or the bar material, and the heat treatment temperature is 1350 to 1600 K in the heat treatment step.
A method for manufacturing an accessory, characterized in that, in the case of the plate material, the heat treatment time satisfies the formula (2), and in the case of the bar material, the heat treatment time satisfies the formula (3).
t _dif ≧ (6869 / T _dif 4.3326) × λ ² ··· (2)
t _dif ≧ (6869 / T _dif 4.3326) × d ... (3)
However, in the formula (2), T _div represents the heat treatment temperature (K), t _def represents the heat treatment time (how), λ represents the plate thickness (mm) of the plate material, and in the formula (3), T _def is the above-mentioned. The heat treatment temperature (K) and t _dim represent the heat treatment time (how), and d represents the circle-equivalent diameter (mm) of the bar.

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