JP2003306747A - Steel wire and production method therefor, and spring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel wire which has high strength and high toughness and has a high fatigue limit, and to provide a production method therefor. <P>SOLUTION: The steel wire comprises as chemical components, by mass, 0.4 to 1.0% C, 1.8 to 2.5% Si, 0.4 to 1.3% Mn, 0.7 to 1.2% Cr and 0.05 to 1.00% Co, and the balance Fe with inevitable impurities. The matrix phase obtained by performing quenching and tempering has a tempered martensitic phase and a retained austenitic phase. The retained austenitic phase is present in the martensite in the range of 1 to 10% by a volume ratio. The content of Co in the austenitic phase remaining in the martensitic structure is 0.05 to 2.00 mass%. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire having a tempered martensite structure, a method for manufacturing the steel wire, and a spring using the steel wire. In particular, the present invention relates to a compression / tensile coil spring having excellent fatigue resistance used in home appliances and automobile parts, and a steel wire for spring suitable for a wire spring and a manufacturing method thereof.

[0002]

2. Description of the Related Art High-strength oil-tempered wire mainly composed of Si-Cr steel has been used as a spring component material used in an exhaust system of an automobile engine. 2. Description of the Related Art In recent years, in order to meet the demand for low fuel consumption and high efficiency of engines in response to rising global environmental problems, weight reduction and space saving of valve train mechanisms and suspension spring units have been performed. As a result, there is a tendency for downsizing of springs, that is, higher strength of spring steel wires. Oil tempered wire has high fatigue resistance and is excellent as a steel wire for springs, but lack of toughness occurs due to the progress of higher strength, resulting in breakage during spring forming and deterioration of toughness. The deterioration of fatigue resistance is a problem.

[0003]

With respect to such a problem, in Japanese Patent Publication No. 3-6981, the strength and toughness are improved by specifying the amount of added V and the quenching condition and setting the grain size to 10 or more. It is proposed to secure. However, when the grain size is set to 10 or more, the strength and toughness of the oil tempered wire are actually determined by tempering after quenching, and the toughness is dramatically improved by the improvement in the quenching process that determines the grain size. Is unlikely to improve.

Further, in JP-A-3-162550, a residual austenite phase of 5 to 20 is contained in tempered martensite which is a matrix structure after tempering of an oil tempered wire.
It has been proposed to ensure toughness by making it exist by volume%. However, if a large amount of the retained austenite phase is present, the retained austenite phase is transformed into a martensite phase during use as a spring, which may cause permanent strain due to volume expansion and deteriorate sag resistance.

Regarding such control of the retained austenite phase, JP-A-9-71843 also defines the volume ratio of the retained austenite phase to the parent phase and the size and existence probability of undissolved carbide during quenching. It aims to secure toughness. This method does not mention the chemical composition of the residual austenite phase, and the expected toughness may not always be obtained depending on the toughness of the austenite phase and the nature of the grain boundary between austenite and tempered martensite.

Therefore, a main object of the present invention is to provide a steel wire having a high strength and a high toughness and a high fatigue limit, and a manufacturing method thereof.

Another object of the present invention is to provide a spring using the above steel wire.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to improve the toughness of the oil tempered wire for high strength springs and improve the fatigue limit, and as a result, the austenite phase remaining in the tempered martensite structure has been found. The mass% of Co in it is 0.
The content of 02 to 2.00% improves the toughness and improves the fatigue limit, and the present invention has been completed.

That is, the characteristics of the steel wire of the present invention are as follows: C: 0.4 to 1.0, Si: 1.8 to 2.5, Mn: 0.4 as a chemical composition by mass%.
~ 1.3, Cr: 0.7 ~ 1.2, Co: 0.05 ~ 1.00, the balance is a component consisting of Fe and unavoidable impurities, the mother phase obtained by quenching and tempering is a tempered martensite structure and residual austenite phase. The residual austenite phase is present in the tempered martensite in the range of 1 to 10% by volume, and the content of Co in the austenite phase remaining in the martensite structure is 0.05 to 2.00% by mass.
Is characterized in that.

[0012] Such chemical components are limited, the amount of retained austenite phase is limited, and Co in the retained austenite phase is limited.
By specifying the amount, the toughness can be improved and the fatigue limit can be increased. Particularly, the preferable content of Co in the retained austenite phase is Co: 0.25 to 0.70 mass%.

Here, further in mass%, Mo: 0.05 to 0.5
0, V: 0.05 to 0.50, W: 0.05 to 0.15, Nb: 0.05 to 0.15, T
It is preferable to contain one or more of i: 0.01 to 0.20, Ni: 0.02 to 1.00, and Cu: 0.02 to 1.00.

By containing at least one of these elements, the fatigue limit can be further improved.

The average grain size of austenite (former austenite) during quenching in the cross section of the steel wire is preferably 1.0 to 7.0 μm. By refining the metal structure in this way, it is possible to obtain a steel wire having both high strength and high toughness. More preferable average austenite grain size is
1.0 to 5.0 μm. To set the average grain size of old austenite in the range of 1.0 to 7.0 μm, the quenching heating temperature is set to 980.
It is preferable that the temperature is not higher than ° C.

The tensile strength of the steel wire of the present invention is 1800 N / mm ² or more 230
0N / mm ² or less is desirable. By providing such a tensile strength, it is possible to obtain a spring having excellent working characteristics and fatigue resistance.

The cross-sectional shape of the steel wire of the present invention is most generally circular, but is not limited to this. For example, various shapes such as a rectangle, a trapezoid, and an ellipse may be used.
As described above, the steel wire having a non-circular cross section can be adjusted by the shape of the die used for drawing.

Further, in the method for producing a steel wire according to the present invention, C: 0.4 to 1.0, Si: 1.8 to 2.5, Mn: 0.4 as a chemical component by mass%.
~ 1.3, Cr: 0.7 ~ 1.2, Co: 0.05 ~ 1.00, the rest is a steel material having a component consisting of Fe and unavoidable impurities is a method for producing a steel wire by quenching and tempering, wherein the quenching Heating rate during heating and tempering is 50-2000 ° C /
The holding time is 0.5 to 30 s.

By thus specifying the quenching and tempering conditions, it is possible to obtain a steel wire having high strength and high toughness and a high fatigue limit. More preferable heating conditions at the time of quenching and tempering are a temperature rising rate of 300 to 2000 ° C./s and a holding time of 0.5.
~ 10s.

Here, as the steps leading up to quenching, usually, melting casting of steel material → forging → hot rolling → heat treatment →
Cold drawing is performed. The conditions from melt casting to cold drawing may be known conditions.

In the subsequent quenching, the quenching heating temperature is preferably 850 to 1050 ° C. The cooling rate during quenching may be a rate that can be obtained by quenching with oil or water. When cracking occurs in water quenching, it is preferable to reduce the cooling rate by adding an organic solvent. The heating temperature in tempering is preferably 350 to 600 ° C. The cooling during tempering is preferably water cooling in order to avoid the embrittlement temperature range during cooling.

In this manufacturing method, as a chemical component, Mo: 0.05 to 0.50, V: 0.05 to 0.50, W: 0.
05 ~ 0.15, Nb: 0.05 ~ 0.15, Ti: 0.01 ~ 0.20, Ni: 0.02
It is preferable to use a steel material containing at least one of ˜1.00 and Cu: 0.02 to 1.00.

Further, the spring of the present invention is characterized by being manufactured using the above-mentioned steel wire of the present invention. As described above, the steel wire of the present invention has both high toughness and tensile strength and a high fatigue limit. Therefore, by spring-forming this steel wire, a spring having high fatigue resistance can be obtained.

The reasons for limiting the constituent elements of the present invention will be described below. <C: 0.4 to 1.0% by mass> C is an important element that determines the mechanical properties of steel, but if it is less than 0.4% by mass, sufficient strength cannot be obtained. On the other hand, if it exceeds 1.0% by mass, the toughness is lowered, the flaw sensitivity of the steel wire is further increased, and the reliability is lowered. Therefore, the content of C is set to 0.4 to 1.0% by mass.

<Si: 1.8 to 2.5% by mass> Si is used as a deoxidizing agent during melting and refining. It also has the effect of forming a solid solution in ferrite and strengthening it. However, excessive addition leads to lack of toughness, which tends to cause deterioration of hot workability, promotion of decarburization by heat treatment, and breakage during spring processing. Therefore, in order to have a deoxidizing effect, to maintain the strength after spring processing and to avoid lowering the hardness of the inner surface of the nitride layer during spring hardening (nitriding)
The content is 1.8% by mass or more and 2.5% by mass or less to prevent lack of toughness.

<Mn: 0.4 to 1.3% by mass> Mn is also used as a deoxidizing agent during melting and refining like Si, improves the hardenability of steel and fixes S in steel to prevent its damage. . Also, Mn is N
It is also an austenite forming element that substitutes i and has an effect of improving toughness. However, Mn is also an element that facilitates the center segregation of the wire rod, and causes martensite at the center segregation site during the patenting treatment after hot rolling, which remarkably increases the wire breakage rate during wire drawing. Therefore, the lower limit of the deoxidizing action is 0.4% by mass or more, and the upper limit is 1.3% by mass so as not to cause deterioration of toughness.

<Cr: 0.7 to 1.2% by mass> Cr improves the hardenability of steel similarly to Mn, and imparts toughness by the patenting treatment after hot rolling to improve the softening resistance during tempering and tempering. It is an element that is effective in increasing the strength and increasing the strength. If it is less than 0.7% by mass, its effect is small, and if it exceeds 1.2% by mass, on the other hand, it suppresses the solid solution of carbides, resulting in a decrease in strength and an excessive increase in hardenability, resulting in a decrease in toughness. is there.

<Mo: 0.05 to 0.50 mass%> Mo is an element that forms carbides during tempering and increases the softening resistance. However, if less than 0.05% by mass, the effect is small, and 0.50% by mass.
When the content exceeds Mo, the wire drawability is deteriorated, so the content is Mo:
It was set to 0.05 to 0.50 mass%.

<W: 0.05 to 0.15, Nb: 0.05 to 0.15, V: 0.
05 to 0.50 mass%> W, Nb, and V also have the effect of forming carbides in the steel during tempering and increasing the softening resistance. However, in all cases, if the amount is less than 0.05% by mass, the effect cannot be sufficiently exhibited. On the other hand, when V exceeds 0.50 mass% and W and Nb exceed 0.15 mass%, a large amount of carbide is formed during quenching and heating, resulting in a decrease in toughness. Therefore, V: 0.05 to 0.50 mass%, W: 0.05 to 0.15 mass%, Nb:
It was defined as 0.05 to 0.15 mass%.

<Ti: 0.01 to 0.20 mass%> Ti also has the effect of forming carbides in the steel during tempering and increasing the softening resistance. However, Ti produces TiO which is a non-metallic inclusion having a high melting point. Therefore, it is important to set the conditions for refining. 0.01 mass% or more as an amount that can be expected to improve the softening resistance, 0.20 considering the deterioration of toughness due to excessive increase of carbides and inclusions.
It was set to not more than mass%.

<Ni: 0.02 to 1.00, Co: 0.05 to 1.00, Cu:
0.02 to 1.00 mass%> Ni, Co and Cu are austenite forming elements, and are materials that easily generate retained austenite by adding Ni, Co and Cu. The increase of retained austenite has the effect of lowering the hardness of the steel wire, but on the contrary, it imparts toughness to the solid solution strengthened by Si and the steel wire reinforced by carbide precipitation elements such as Mo, W, Nb, V and Ti. Have an effect. Also,
Ni also has a role of blocking the intrusion of Cl element in a salt water corrosive environment. The minimum toughness improving effect is 0.02% by mass, and the upper limit that does not cause hardness reduction is 1.00% by mass.

<Co content in retained austenite phase: 0.
02 to 2.00% by mass> In order to improve the fatigue limit of the steel wire having the above components, Co must be present in the austenite phase remaining in the tempered martensite phase in an amount of 0.02 to 2.00% by mass. Since Co has the effect of lowering the stacking fault energy, it is easy to introduce dislocations in the retained austenite phase, and as a result, the retained austenite phase flexibly deforms in the extremely hard martensite phase, thereby improving the toughness of the entire steel wire. It has a great effect on improving the fatigue limit. Conversely speaking, in order to improve the fatigue limit of the steel wire in which this soft retained austenite phase exists, the presence of a carbide-forming element such as Cr that promotes hardening by nitriding and the effect of improving the softening resistance by heat treatment are effective. The existence of such elements is essential. Therefore, the mass% of Co in the retained austenite phase was determined for the steel wire having the above chemical composition. If the mass% of Co in the retained austenite phase is small, the toughness improving effect is lost, and if it is too large, the mechanical properties of the entire steel wire deteriorate. The minimum amount in the retained austenite phase to obtain the fatigue limit improvement effect accompanying this toughness improvement is 0.02% by mass, and the maximum amount in the retained austenite phase that does not cause a decrease in the tensile strength of the entire steel wire is 2.00% by mass. did. In particular, the Co content in the retained austenite phase is Co:
It is preferably 0.25 to 0.70 mass%.

<Volume ratio of retained austenite phase: 1.0 to 1
0.0%> The volume ratio of the retained austenite phase in the tempered martensite is preferably large as a means for improving the toughness of the entire steel wire. However, if a large amount of retained austenite phase is present, the retained austenite phase is transformed into a martensite phase during use as a spring, which may cause permanent strain due to volume expansion and deteriorate sag resistance. Therefore, the minimum amount that improves the toughness of the entire steel is 1.0% by volume.
And 10.0% by volume as the maximum amount that does not reduce the sag resistance.

<Old austenite average crystal grain size: 1.0 to
7.0 μm> If the former austenite average crystal grain size is 1.0 to 7.0 μm, the above steel wire is further excellent in fatigue resistance. This is due to the fact that a material having both high strength and high toughness can be obtained by strengthening the crystal grains and refining the metal structure. When the grain size is 7.0 μm or less, the refinement effect appears, but when it is further set to 5.0 μm or less, the effect of strengthening due to the refinement is remarkable. However, crystal grain size 1.0
When it is less than μm, heating becomes insufficient and it becomes very difficult to remove undissolved carbides by heat treatment, so the lower limit was made 1.0 μm.

<Tensile strength: 1800 N / mm ² or more 2300 N / mm ²
Hereinafter> Tensile when strength 1800 N / mm ² or more 2300N / mm ² or less, exhibits particularly excellent performance as a spring steel wire. Since the fatigue limit of a spring is mainly proportional to the tensile strength, the tensile strength that achieves the high fatigue limit required for a spring is 1800 N / mm ² or more, and the toughness that does not break during coiling
It was set to 00 N / mm ² or less.

<Manufacturing Conditions> In order to control the volume ratio of the retained austenite phase to the martensite phase, tempering heating for an extremely short time is required. Prolonged heating causes spheroidization and coarsening of intragranular carbide. Also, 1.0-7.0μ
It is also necessary to achieve the average grain size of old austenite such as m. Therefore, it is possible to manufacture a steel wire having both toughness and tensile strength by setting the heating rate of heating during quenching / tempering to 50 to 2000 ° C./s and holding time to 0.5 to 30 s.

Such high-speed soaking heating also has the effect of suppressing the diffusion of metal elements in the steel wire. For example, when heating is performed for a long time, a carbide forming element such as Cr or Mo may be coarsely coarsened in the form of carbide, and there is also a risk of impairing the uniformity of Co, which is the key to improving the toughness of the present invention. is there. Under these circumstances, the quenching and tempering conditions are: heating rate: 300
More preferably, it is carried out at ˜2000 ° C./s and holding time: 0.5 to 10 s.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. (Example 1) Steels having the compositions shown in Examples A to M of Table 1 and Comparative Examples N and O are melted in a vacuum melting furnace, and hot forged and hot rolled to a diameter of 6.5. mm wire rod was produced.

This wire was heat treated, peeled, and cold drawn to a diameter of 3.2 mm. Furthermore, the obtained wire rod is quenched at a quenching heating temperature of 1000 ° C, a quenching heating rate of 1000 ° C / s, and a holding time of 5s, tempering heating temperature: 450 ° C, a tempering heating rate of 1000 ° C / s, holding After tempering for 10 seconds, an oil tempered wire was obtained.

The chemical composition of the oil tempered wire obtained in Table 1, the mass ratio of Co in the retained austenite phase, the volume ratio of the retained austenite (γ) phase, the average particle size of the former austenite,
And the tensile strength at room temperature. For the measurement of former austenite grains, each sample was annealed at 550 ° C for about 2 hours,
It was carried out by precipitating carbides on the former austenite grain boundaries, etching the steel wire cross section, and calculating the average value of the former austenite crystal grains from the optical micrograph (the same applies to other examples described later).

[0039]

[Table 1]

In the example and the comparative example, the amount of Co in the chemical composition is different, and accordingly, the Co mass ratio in the residual γ phase is different. In the examples, 0.05 to 1.0% by mass, while in the comparative examples
It is set to 0.02 to 1.5% by mass. Since Co becomes a solid solution with Fe in almost all the steps of manufacturing the spring, the content of Co in the steel material and the content of Co in the residual γ phase are almost the same.

Next, Table 2 shows the results of applying the above samples to the Nakamura rotary bending fatigue tester. In the test, stress was applied with constant strain, and the amplitude stress without breakage was averaged at the number of repetitions of 1 × 10 ⁷ (n number = 8). This test method is the same as the fatigue strength evaluation method in other examples described later.

[0042]

[Table 2]

In the samples A to F, it was confirmed that the fatigue strength increased by 30 to 85 MPa with respect to N and O having different Co contents. Also, sample D
On the other hand, it was confirmed that in Samples G to M containing at least one of Mo, V, W, Nb, Ti, Ni and Cu, higher fatigue strength could be obtained. From the results of Examples A to F and Comparative Examples N and O, it is found that when the Co content is 0.05 to 1.00 mass% and the retained austenite phase content is 1 to 10 volume%, it is effective for increasing the fatigue strength. In particular, it was confirmed that Co: 0.3 to 0.5 mass% exhibited excellent fatigue strength. In addition, from the results of Comparative Examples P and Q, C in the retained austenite phase
o Even if the amount satisfies the range of 0.05 to 2.00% by mass, the amount of Si deviates from 1.8 to 2.5% by mass and the amount of Cr is 0.7 to 1.2% by mass.
It was confirmed that the fatigue strength could not be improved if the temperature was out of range.

(Example 2) Next, using a steel having the same composition as the sample D, the cooling rate at the time of quenching was changed, and the volume ratio of the retained austenite phase was changed. U was made. In Example R, water was cooled after heating, and then rapidly cooled. In Example S, after being heated, it was cooled in the air relatively slowly as compared with the case where oil was used as the refrigerant. In addition, Comparative Example T
After heating, the heating source of the heating furnace was turned off and the sample was slowly cooled in the furnace as it was, and in Comparative Example U, the sample was immersed in liquid nitrogen immediately after heating and rapidly cooled. Except for the cooling conditions during quenching, the quenching and tempering conditions are the same as in Example 1. Then, the quenching cooling rate of each sample, the Co mass ratio in the retained austenite phase, the volume ratio of the retained austenite (γ) phase, the former austenite average grain size, the tensile strength at room temperature and the fatigue strength were obtained. The results are shown in Table 3. The cooling rate is estimated from the temperature of the furnace and the type and temperature of the refrigerant.

[0045]

[Table 3]

As is clear from Table 3, when the volume ratio of the retained austenite phase is in the range of 1.0 to 10.0%, it is effective for improving the fatigue strength, and particularly about 7% by volume of Example D is excellent. Recognize.

(Example 3) Further, in Examples V, W, in which the heating temperature at the time of quenching was changed by using the steel having the same composition as the samples D and G, the former austenite grain size of the retained austenite was changed.
X and Y were produced. Samples having different heating temperatures from sample D are V and W, and samples having different heating temperatures from sample G are X and Y. These samples are subjected to high frequency heating and heating rate: 1000 ° C / s
Then, the heating temperature was set to 950 ° C. and 980 ° C., and the holding time was set to 3 seconds (set to a holding time that enables uniform heating according to the wire diameter), and quenching was performed. Except for the heating temperature during quenching, the quenching and tempering conditions are the same as in Example 1. Then, the quenching heating temperature of each sample, the Co mass ratio in the retained austenite phase, the volume ratio of the retained austenite (γ) phase, the old austenite average grain size, the tensile strength at room temperature, and the fatigue strength were determined. The results are shown in Table 4.

[0048]

[Table 4]

As is clear from Table 4, further improvement in fatigue limit could be confirmed by setting the former austenite average particle size within the range of 1.0 to 7.0 μm. In particular, by performing heating by high frequency heating, austenitization by uniform heating,
It becomes possible to dissolve the carbide into the parent phase, and the change in the crystal grain size of the austenite phase can be made uniform throughout the material. In addition to the above-mentioned samples, the same uniform austenitization and melting of carbides could be confirmed by using high frequency heating in the example steel wires having carbide forming components such as Mo and Ti.

(Embodiment 4) The above-mentioned evaluation was carried out also on the samples of 1800 and 2200 MPa class in tensile strength of steel wire.
The tensile strength was adjusted by adjusting the temperature during tempering. 1800
The heating temperature for tempering of MPa class samples is 400 ℃, 2200
The heating temperature for tempering of MPa class samples is 550 ° C. The other conditions are the same as in Example 1. As a result of the Nakamura-type rotary bending fatigue test on the obtained samples, the invention materials all exhibited high fatigue strength of about tensile strength × 0.43 (MPa). Then, when these were spring-processed, the springs could be processed without any problems.

[0051]

As described above, the steel wire of the present invention mainly controls the chemical composition of the retained austenite phase and the volume ratio of the retained austenite layer in the steel wire having the tempered martensite structure as the matrix phase. As a result, high fatigue characteristics can be obtained.

Further, by adding carbide-forming elements such as Mo, V, W, Nb, and Ti to enhance precipitation strengthening, and by adding austenite-forming elements such as Ni and Cu to improve toughness, conventional steel wires can be obtained. It is possible to obtain high toughness and fatigue resistance. Fatigue resistance associated with high toughness is also effective for corrosion stress fracture in which a corrosion pit serves as a fracture starting point. By using the steel wire of the present invention, it is possible to obtain a steel wire for a high fatigue strength spring required for a valve spring, a suspension spring or the like, or a corrosion resistant fatigue spring.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16F 1/02 F16F 1/02 B (72) Inventor Kento Yamao 1-1 1-1 Kunyokita, Itami City, Hyogo Prefecture Issue Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Teruyuki Murai 1-1 Kunyo Kita 1-1, Itami City, Hyogo Prefecture Sumitomo Electric Industries Itami Works F-term (reference) 3J059 AB06 AD11 BA31 BC02 EA09 GA01 GA21 4K043 AA02 AB04 AB05 AB08 AB10 AB11 AB13 AB15 AB18 AB21 AB22 AB28 AB29 AB30 AB31 BB02 BB03 DA01 DA04

Claims (8)

[Claims] 1. As a chemical component, C: 0.4 to 1.% by mass%.
0, Si: 1.8 to 2.5, Mn: 0.4 to 1.3, Cr: 0.7 to 1.2, Co:
The matrix containing 0.05 to 1.00 and the balance consisting of Fe and unavoidable impurities, the mother phase obtained by quenching and tempering has a tempered martensite structure and a retained austenite phase, and this retained austenite phase is a tempered martensite. A steel wire having a volume ratio of 1 to 10% and a Co content of 0.05 to 2.00% by mass in the austenite phase remaining in the martensitic structure. 2. Further, as a chemical component, Mo: 0 by mass%.
05 ~ 0.50, V: 0.05 ~ 0.50, W: 0.05 ~ 0.15, Nb: 0.05 ~
0.15, Ti: 0.01 to 0.20, Ni: 0.02 to 1.00, Cu: 0.02 to 1.
2. One or more of 00 are contained, The claim 1 characterized by the above-mentioned.
Steel wire described in. 3. The steel wire according to claim 1, wherein the average crystal grain size of the prior austenite in the cross section of the steel wire is 1.0 to 7.0 μm. 4. A steel wire according to claim 1, the tensile strength is equal to or is 1800 N / mm ² or more 2300N / mm ² or less. 5. The steel wire according to any one of claims 1 to 4, wherein the steel wire has a non-circular cross section. 6. As a chemical component, C: 0.4-1.% By mass%.
0, Si: 1.8 to 2.5, Mn: 0.4 to 1.3, Cr: 0.7 to 1.2, Co:
A method of manufacturing a steel wire containing 0.05 to 1.00, the balance being a steel material having a component consisting of Fe and unavoidable impurities to obtain a steel wire by quenching and tempering, heating during the quenching and tempering, a heating rate 50-20
A method of manufacturing a steel wire, which is performed at 00 ° C / s and a holding time of 0.5 to 30 s. 7. Further, as a chemical component, Mo: 0 by mass%.
05 ~ 0.50, V: 0.05 ~ 0.50, W: 0.05 ~ 0.15, Nb: 0.05 ~
0.15, Ti: 0.01 to 0.20, Ni: 0.02 to 1.00, Cu: 0.02 to 1.
7. One or more kinds of 00 are contained, The claim 6 characterized by the above-mentioned.
The method for manufacturing a steel wire according to. 8. A spring manufactured by using the steel wire according to claim 1.