JPH05271878A - Stainless steel for spring excellent in formability and stress corrosion cracking resistance and its manufacture - Google Patents

Abstract

PURPOSE:To improve the formability, stress corrosion cracking resistance and spring properties of stainless steel by specifying components of C, Si, Mn, Ni, Cr, N or the like and subjecting the stainless steel in which these components are regulated to a specified rolling process. CONSTITUTION:Stainless steel constituted of, by weight, 0.03 to 0.15% C, 1.5 to 3% Si, <=3% Mn, 4 to 10% Ni, 12 to 20% Cr, <=0.3% N, <=0.008% S, >=0.1% C+N and >=30 M-value, and the balance Fe is smelted. The M-value is defined by M=330-(480XC%)-(2XSi%)-(10XMn%)-(14XNi%)-(5.7XCr%)-(5XMo%)--(14XCu%)-( 320XM%). Then, the stainless steel is subjected to hot rolling, cold rolling and annealing, then subjected to >=20% temper rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel for springs suitable for spring parts which have high strength and require forming such as bending and which are required to have stress corrosion cracking resistance. INDUSTRIAL APPLICABILITY The stainless steel of the present invention is suitably applied to a metal gasket portion that constitutes an engine of, for example, an automobile or a motorcycle.

[0002]

2. Description of the Related Art Conventionally, work-hardening type metastable austenitic stainless steels, such as SUS301 and 301L, that can easily obtain high strength by cold working have been used as stainless steel materials for spring parts that require corrosion resistance. Has been widely used.

[0003]

[Problems to be Solved by the Invention] With SUS301 and 301L, it is necessary to perform strong cold working in order to obtain high strength.
When this high-strength material is formed and processed, there is a problem that cracks and microcracks occur in the processed R part. When microcracks are generated, fatigue cracks often occur from microcracks to fractures when cyclically varying stress is applied to the machined part. For this reason, it has been unavoidable to deal with it by increasing the molding process R or reducing the fluctuating stress.

From the above, in the spring member which is required to have corrosion resistance, it is not possible to obtain a desired component shape, the component shape becomes large, or the plate thickness is large when trying to obtain high strength. It was accompanied by the problem of becoming.

On the other hand, in a metal gasket around an engine of an automobile or a motorcycle, stress corrosion cracking may occur due to contact with dew condensation water in combustion exhaust gas or Cl ⁻ existing in cooling water. Also, since auto fasteners used in marine register products are used in seawater, stress corrosion cracking becomes a problem in this case as well.

However, SUS301 and 301L had a problem that the stress corrosion cracking resistance was deteriorated when the strength was increased.

Therefore, it has been unavoidable to use a spring component having low strength as a spring component which requires both moldability and stress corrosion cracking resistance.

An object of the present invention is to provide a stainless steel spring component which is used after being subjected to such a molding process, while having excellent fatigue properties and spring properties, while maintaining high strength and moldability. , To obtain a stainless steel spring material with better stress corrosion cracking resistance.

[0009]

According to the present invention, the weight percent is
In, C: 0.03% to 0.15% or less, preferably 0.05% to
0.13%, Si: more than 1.5% to 3.0% or less, Mn: 3.0% or less, preferably less than 0.5%, Ni: 4.0 to 10.0%, Cr: 12.0 to 20.0%, N: 0.30% or less, preferably 0.06 to 0.15 %, S: 0.008% or less, preferably 0.003% or less C + N: 0.10% or more, and 3.0% or less Mo or 0.5 to 3.0 in some cases.
% Cu of 1 or 2 and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14 × Ni%) − (5.7 × Cr% )-(5 * Mo%)-(14 * Cu%)-(320 * N%) so that the M value becomes 30 or more, C, Si, Mn, Ni,
(EN) Provided is a stainless steel for springs, in which the amounts of Cr, Cu, Mo, N are adjusted, and the balance is Fe and impurities inevitably mixed in, which are excellent in formability and stress corrosion cracking characteristics.

Then, as a method for producing a material for achieving the object on an industrial scale, a stainless steel having the above-mentioned components and composition is subjected to a normal hot rolling step and a cold rolling step, and then 20% after annealing. There is provided a method for producing the stainless steel, which comprises temper rolling as described above and aging treatment at a temperature of 100 ° C or higher and lower than 300 ° C.

In this manufacturing method, the aging treatment can be applied to the as-tempered steel strip or steel sheet. In this case, the spring component is formed by using the steel strip or steel plate after the aging treatment as a raw material. In some cases, a spring component having a desired shape can be subjected to an aging treatment at a temperature of 100 ° C or higher and lower than 300 ° C after the forming process.

[0012]

The action of each component and the reason for limiting the content range of each component in the stainless steel for springs according to the present invention will be individually described as follows.

C is an austenite-forming element, and it suppresses δ-ferrite produced at high temperature, cold working (temper rolling from an annealing state exhibiting an austenite phase, cold working unless otherwise specified). It acts very effectively on the strengthening of the martensite phase induced by. Therefore, in order to obtain more excellent formability, it is effective to make C as high as possible and obtain higher strength at a low cold workability in order to achieve both excellent formability and high strength. Is. However, if the C content is too high, carbides will be precipitated at the grain boundaries, causing intergranular corrosion resistance and reduced ductility. Therefore, the C content was set to more than 0.03% and 0.15% or less. More preferably, it is more than 0.05% and 0.13% or less.

Si is also effective as a deoxidizing agent, but it acts effectively in inducing and strengthening the martensite phase by cold working, and also effective in hardening by aging treatment at low temperature, and resistance to It is an important element of the steel of the present invention that effectively acts to impart stress corrosion cracking characteristics. At least 1.5% or more is required to exert such effects. However, if it is made too high, the formation of the δ-ferrite phase is promoted, and if it is made too high, the effect becomes small in proportion, so the upper limit was made 3.0%.

Mn works effectively as a deoxidizer, but it is an element that controls the stability of the austenite phase, and its utilization is considered in balance with other elements. In the present invention, the utilization can be achieved with the Mn amount up to 3.0%. However, the Mn content is 0.5 for applications with particularly severe formability.
%, It is preferable to avoid the formation of MnS as much as possible.

Cr is an essential component for ensuring the corrosion resistance of spring parts. At least 12.0% or more of Cr is required to provide the intended corrosion resistance. However,
Since Cr is also a ferrite-producing element, if it is made too high, a large amount of δ-ferrite will be produced at high temperatures. Therefore, in order to suppress the δ-ferrite phase, it is necessary to add austenite-forming elements (C, N, Ni, Mn, Cu, etc.) in an amount commensurate with that. The austenite phase is stable and high strength cannot be obtained even after cold working or aging. Therefore, the upper limit of Cr is set to 20%.

Ni is an essential component for obtaining an austenite phase at high temperature and room temperature. In the case of the steel of the present invention, a metastable austenite phase should be obtained at room temperature, and a martensite phase should be induced by cold working. In the steel of the present invention, when Ni is lower than 4.0%, a δ ferrite phase may be generated in the austenite phase at a high temperature and a hardened martensite phase may be considerably generated at room temperature. Is not preferable because the ratio of the austenite phase is insufficient. On the other hand, when Ni exceeds 10%, it becomes difficult to induce the martensite phase during cold working. Therefore, the amount of Ni is set to 4.0 to 10.0%. It is more preferably 5.0 to 8.0%.

Mo increases the base hardness of the steel and also increases the hardness after aging treatment, and therefore works effectively in obtaining high strength. It is also an effective element for improving corrosion resistance. However, since it is a ferrite former, a large amount of it causes the δ-ferrite phase to crystallize, which rather causes a decrease in strength. Therefore, the upper limit was made 3.0%.

Cu serves to harden the steel by interacting with Si during the aging treatment. If the amount is too small, the effect is small, and if the amount is too large, the hot workability is impaired and cracking occurs. For this reason, it is set to 0.5 to 3.0%.

S produces MnS in the coexistence with Mn,
It causes a decrease in ductility. For this reason, it is set to 0.008% or less. Especially in the case of thin plate products, Mn and S should be low because the inclusions adversely affect ductility and fatigue properties in the high strength region.
Less, S content is preferably 0.003% or less.

N is an austenite-forming element and an extremely effective element for hardening the austenite phase and the martensite phase. It also contributes to lowering the aging temperature. However, a large amount causes blow holes during casting, so the content was made 0.30% or less. More preferably 0.06
Included in the range of ~ 0.15%.

C and N have similar effects and are compatible with each other. Each upper limit is limited as described above,
In order to fully exert these effects, the total amount is 0.10
It must be at least%.

M value: C, Si, Mn, Ni, C for 30 or more
Although r, Mo, Cu and N are contained in the above ranges respectively, the respective components are adjusted so that the M value according to the following formula (1) becomes 30 or more. M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14 × Ni%) − − (5.7 × Cr%) − (5 × Mo%) − (14 × Cu%) − (320 × N%) ··· (1) The constants of each component in the equation (1) were determined in the laboratory during the development of the steel of the present invention. This M value is an index of austenite stability, and if it is lower than 30, it is necessary to apply a strong rolling reduction of 60% or more at room temperature to obtain high strength after temper rolling or aging treatment. In this case, the ductility decreases. Therefore, it is necessary to set the M value to 30 or more to secure the moldability.

The chemical composition of the steel of the present invention is adjusted within the above range. However, in addition to these components, Al added as a deoxidizing agent, Ca and REM added as a desulfurizing agent, B (0.01% or less) with an effect of improving hot workability, and inevitably mixed. It can contain impurities. However, Al is not used when high strength and high fatigue strength is required, or it is desirable to use an amount that does not form nonmetallic inclusions in steel. If the strength and fatigue strength are similar to those of conventional steel, a larger amount of Al can be contained.

The steel according to the present invention adjusted to the range of the content of each component described above exhibits substantially austenite structure in the solution treatment state. By temper-rolling in this state, it is possible to obtain a suitable material as a spring component that has higher strength and excellent target formability and stress corrosion cracking resistance.

Temper rolling requires a rolling ratio of at least 20% or more to obtain a target strength level. Although the upper limit of the rolling ratio is not particularly limited, in the case of the steel of the present invention, the target strength can be achieved even at a lower rolling ratio than that of the conventional steel, and in the sense that the forming workability as good as possible is secured. The upper limit of the rate is appropriately around 60%.

The temper-rolled steel strip is subjected to an aging treatment as it is or after being formed into a desired spring component in order to further develop strength characteristics as a spring component. The aging temperature in the present invention is 100 ° C or higher and lower than 300 ° C.

The range of the aging treatment temperature is set to 100 ° C. or more and less than 300 ° C. The steel of the present invention has an aging temperature lower than that of the conventional steel due to the addition of Si and N and, in some cases, addition of Mo and Cu. However, low temperature aging is preferable in order to have excellent age hardening ability and therefore higher strength, and to obtain better stress corrosion cracking resistance. If the aging temperature is 300 ° C or higher, excellent stress corrosion cracking resistance cannot be obtained. However, the desired high strength cannot be obtained at an aging temperature lower than 100 ° C.

Aging treatment in this temperature range is performed for 10 minutes or more.
If the time is shorter than this, the effect of the aging treatment cannot be sufficiently obtained. The upper limit of the aging treatment time is not particularly limited, but it is preferably about 1 hour from the viewpoint of manufacturing cost.

As described above, according to the present invention, in particular, Si is added so that the total amount of C and N is 0.1% or more, and the proper component balance is adjusted. Moreover, it was found that the α'phase (work-induced martensite phase) can be densely distributed, and that the addition of Si and N produces sufficient age hardening ability even at low temperature aging treatment. It is characterized in that it imparts high formability and high strength at the rolling ratio and imparts excellent stress corrosion cracking resistance characteristics to low temperature aging.

The steel thus obtained has high ductility in the temper-rolled state, excellent fatigue properties of the worked part, and excellent stress corrosion cracking resistance properties. And fatigue resistance and stress corrosion cracking resistance are required, for example, when used for auto fasteners used in seawater, metal gaskets around engines such as automobiles and motorcycles, cracks in the processed part are prevented and Destruction,
Since stress corrosion cracking is prevented, it can withstand long-term use.

As described above, the present invention is characterized in that high strength, forming workability, and stress corrosion cracking resistance are imparted at an appropriate temper rolling rate. In particular, in the present invention, the following operational effects are obtained. Play.

(A) Si that contributes to the refinement and strengthening of the martensite phase induced by cold working (temper rolling) is more than 1.5% and 3.0% or less, which is larger than that of the conventional steel, and the martensite phase is increased. The total of C and N which are strengthening elements of
If the induced martensite phase is Si, C,
Since it is hardened by N, it is a material with high strength and ductility in the temper-rolled state.

(B) An appropriate γ-stability is adjusted by the M value and a proper amount of Si is added to produce a more dense martensite phase in the light rolling, and further N is added to effect the low temperature aging treatment by the action of Si and N. However, the strength increases due to aging. Furthermore, the addition of Cu increases the strength increase due to the aging treatment. As a result, it is possible to keep the temper rolling rate low, improve the formability, and improve the fatigue properties of the formed part.

(C) For the stress corrosion cracking resistance property, S
The amount of i and the aging temperature affect. By adding an appropriate amount of Si and setting the aging temperature to less than 300 ° C, excellent stress corrosion cracking resistance is imparted. Furthermore, by adding Mo and Cu, the stress corrosion cracking resistance can be further improved.

The effects of the present invention will be specifically described below with reference to examples.

[0037]

EXAMPLES Steels of the present invention (H1 to 8), conventional steels (A and B) and comparative steels (a to d) having the components shown in Table 1 were melted by a conventional method, hot-rolled, and then cooled. It was rolled, annealed, pickled or bright annealed, and finally temper-rolled at each rolling rate shown in Table 2 so that the final strip thickness was 0.25 mm, and a sample with a strip thickness of 0.25 mmt was taken.

The yield strength, elongation and bendability of the obtained cold rolled steel sheet sample were investigated and the results are shown in Table 2. In addition, the proof stress, elongation, and ΔYS of each steel sheet after aging treatment at 250 ° C for 30 minutes were examined, and for one part, the fatigue properties after bending were examined. The stress corrosion cracking resistance was also investigated. The results are also shown in Table 2.

ΔYS in Table 2 is the difference in proof stress before and after the aging treatment. The bendability was measured by observing the outer R part (tip R = 0.2 mm) when the test piece 3 was inserted between the die 1 and the punch 2 as shown in Fig. 1 and 90-degree butt bending was applied. No cracks (○), fine cracks (△), cracks in this part
It was evaluated by (X mark).

The fatigue test is a one-sided tensile fatigue test in which a stress amplitude of 350 N / mm ² is applied at a maximum stress of 1000 N / mm ² to a test piece molded into a W bead shape having the dimensions shown in FIG. ， Evaluated by the number of repetitions until breakage.

The resistance to stress corrosion cracking was measured by cutting a 0.25 mm thick × 10 mm wide × 80 mm long strip, and applying 100 ppm Cl of 200 ° C with surface stress of 1400 N / mm ² bending stress applied.
^- it was immersed in the solution, was evaluated by the time until cracking.

[0042]

[Table 1]

[0043]

[Table 2]

From the results shown in Table 2, the following is clear.
It is desirable for the spring material to have high strength, and the target strength is at least 1500 N / mm ^{2 in} terms of proof stress after aging treatment.

In Examples H1 to H8 according to the present invention, after annealing, a material having the indicated temper rolling rate was given (as-rolled material).
As for the bending workability, which is the basis of the forming workability, it can be seen that there is no crack in the 90 ° butt bend evaluated at the tip R = 0.2 mm, and it has sufficient strength.

On the other hand, conventional steels A (SUS301) and B (S
In US301L), cracking occurred and sufficient moldability was not obtained. This is because in conventional steels A and B, the age-hardening degree (here, ΔY
Because S) is small, it is necessary to increase the temper rolling ratio before aging treatment.

In Comparative Steel a, since the M value specified in the present invention is 30 or less, it is necessary to have a high temper rolling rate to obtain strength, and good bending workability is not obtained.

The amount of increase in proof stress due to aging treatment is shown in Table 2 as ΔYS. In the steels of the present invention, both are 200 N / mm ²
The above shows a high ΔYS. This was brought about by moderate γ stability and addition of Si, N. That is, since the M value specified by the present invention is 30 or more and Si and N are within the range specified by the present invention, good age hardening ability can be obtained even at a low aging treatment temperature.

From the above, in the steel of the present invention, even if the strength before aging treatment is lower than that of the conventional steel, the same or higher strength is obtained after aging. Therefore, the temper rolling ratio before aging treatment can be kept low, and the desired formability can be obtained.

FIG. 2 shows the relationship between the aging temperature and the proof stress for H2 of the present invention steel, conventional steel A, and comparative steel b. It can be seen that the steel of the present invention has a high rate of increase in yield strength from a low temperature.

FIG. 3 shows the investigation of the influence of the formability on the fatigue characteristics. That is, W of the dimension shown in FIG.
A test piece with a bead formed thereon was subjected to a unilateral tensile fatigue test (as shown in Fig. 5, the amplitude stress was variously changed under the condition that a maximum stress of 1000 N / mm ² was applied to the test piece with W bead processing). The effect of forming workability on the fatigue properties was investigated.

FIG. 3 shows the data for the steel of the present invention (H2), the conventional steel (A), and the comparative steels (a, d).
Magnitude of stress amplitude applied to vertical axis (repeating bending stress)
The horizontal axis shows the number of repetitions until fracture. From the results of FIG. 3, it is clear that the steel of the present invention having excellent bending workability has high fatigue strength and fatigue limit, and it is recognized that the formability has a great influence on the fatigue life.

This is also clear from the fatigue test results shown in Table 2. The fracture life when an amplitude stress of 350 N / mm ² is applied shows that the one with excellent bending workability has a long life. That is, it can be seen that the formability affects the fatigue life.

FIG. 6 shows the relationship between stress corrosion cracking resistance and the amount of Si in steel. That is, as described above, it shows the relationship between the time until crack initiation under stress application in 100 ppm Cl ⁻ at 200 ° C. and the Si content of each steel in Table 1. As is clear from FIG. 6, S defined in the present invention
The material with i exceeding 1.5% has a significantly longer fracture life.

Among them, the comparative steel (d) is a low C alloy to which Si is added, and has a longer life than the steel of the present invention. However, as shown in Table 2, in order to obtain the same level of strength as the steel of the present invention, it is necessary to increase the temper rolling ratio, which is inferior to the steel of the present invention in formability and fatigue after forming. The characteristics are also inferior.

From these facts, when forming workability is not particularly required, low steel such as comparative steel d having Si added thereto is rather excellent in stress corrosion cracking resistance. These results are brought about by carrying out the aging temperature below 300 ° C.

FIG. 7 shows the relationship between the aging temperature of the steel H4 of the present invention and the conventional steels A and B and the time until crack initiation in the stress corrosion cracking test. According to this, when the proof stress after aging treatment is 1500 N / mm ² or more, conventional steel A cracks within 24 hours at any aging treatment temperature. In Comparative Steel B, the time until crack initiation tends to slightly increase at 200 ° C, but in any case, cracking occurs around 24 to 36 hours.

On the other hand, in the case of the steel H4 of the present invention, cracks tend to occur in a shorter time than the conventional steel B at a temperature of 350 ° C. or higher, but at an aging temperature of less than 300 ° C., the time until crack initiation occurs. It is extremely long. That is, by the aging treatment at a low temperature, the steel of the present invention exhibits excellent stress corrosion cracking resistance.

From the viewpoint of improving strength and spring characteristics, a spring material that has been conventionally temper-rolled before aging treatment has a temperature of 400 ° C.
Before and after aging treatment was performed, it was not possible to obtain a material that had high strength and formability and was excellent in stress corrosion cracking resistance. The cracking characteristics could not be improved, and the strength and spring characteristics were not good either. In this respect, the present invention exerts a remarkable effect in the field of stainless steel for springs.

[0060]

As shown in the above embodiments, according to the present invention, there is provided a stainless steel which is excellent in strength, formability, stress corrosion cracking resistance and spring characteristics at the same time.

In particular, the steel of the present invention has a greater strength increase due to aging than conventional stainless steels for springs, such as SUS301 and SUS301L, so that temper rolling before aging treatment can be performed at a low rolling rate. Also, aging treatment at a low temperature can provide stress corrosion cracking resistance superior to that of conventional steel.

From the above, for example, when it is used for auto fasteners used in seawater, metal gaskets around engines of automobiles, motorcycles, etc., stress corrosion cracking is prevented and the service life of conventional materials is reduced. Is significantly improved compared to.

In addition, since the steel of the present invention can be manufactured by a manufacturing method which does not differ from the conventional method in terms of cost, it is advantageous in terms of manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a butt-bending test method for evaluating moldability.

FIG. 2 is an example steel of the present invention, H2, conventional steel A, comparative steel b.
It is a figure which shows the relationship between the aging treatment temperature and yield strength of.

[FIG. 3] Example steel H2 of the present invention, conventional steel A, comparative steel a,
It is a figure which shows the one sided swing fatigue test result of the W bead processed product of d.

[Fig. 4] W for evaluating the influence of fatigue characteristics and workability
It is a schematic sectional drawing which shows a bead shape and dimensions.

FIG. 5 is a diagram for explaining the outline of a unilateral tensile fatigue test using a W bead processing test piece.

[Fig. 6] Inventive Example Steels H1 to H6 (○), Comparative Material b,
c, d (● mark), conventional steel A (□ mark) and conventional steel B (△
It is a figure which shows the relationship between Si amount and stress corrosion cracking generation time in the aging treated material (marked) (250 ° C. × 30 minutes).

FIG. 7 is a diagram showing the relationship between the aging temperature and the time of occurrence of stress corrosion cracking for steel H4 of the present invention and conventional steels (A, B).

[Explanation of symbols]

 1 Soybean 2 Punch 3 Test piece

Claims (6)

[Claims] 1. In% by weight, C: 0.03% to 0.15% or less, Si: 1.5% to 3.0% or less, Mn: 3.0% or less, Ni: 4.0 to 10.0%, Cr: 12.0 to 20.0%, N : 0.30% or less, S: 0.008% or less, C + N: 0.10% or more, and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14 × Ni% ) − (5.7 × Cr%) − (320 × N%) C, Si, Mn, Ni, so that the M value becomes 30 or more.
Stainless steel for springs with excellent Cr formability and stress corrosion cracking characteristics, with the balance of Cr and N adjusted and the balance of Fe and impurities inevitably mixed in. 2. In% by weight, C: more than 0.03% to less than 0.15%, Si: more than 1.5% to less than 3.0%, Mn: less than 3.0%, Ni: 4.0 to 10.0%, Cr: 12.0 to 20.0%, N : 0.30% or less, S: 0.008% or less, C + N: 0.10% or more, 3.0% or less of Mo or 0.5 to 3.0% Cu of 1 or 2 types, and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14 × Ni%) − (5.7 × Cr%) − (5 × Mo%) − (14 × Cu%) − (320 × N%) C, Si, Mn, Ni, so that the M value according to
Cr, Cu, Mo, N content is adjusted, and the balance is Fe and the unavoidably mixed impurities, and it has excellent formability and stress corrosion cracking characteristics. 3. The spring stainless steel according to claim 1, wherein C: more than 0.05% to 0.13%, Mn: less than 0.5%, S: 0.003% or less, and N: 0.06 to 0.15%. 4. In% by weight, C: 0.03% to 0.15% or less, Si: 1.5% to 3.0% or less, Mn: 3.0% or less, Ni: 4.0 to 10.0%, Cr: 12.0 to 20.0%, N : 0.30% or less, S: 0.008% or less, C + N: 0.10% or more, depending on the case, further 3.0% or less Mo or 0.5 to 3.0
% Cu of 1 or 2 and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14 × Ni%) − (5.7 × Cr% )-(5 * Mo%)-(14 * Cu%)-(320 * N%) so that the M value becomes 30 or more, C, Si, Mn, Ni,
The amounts of Cr, Cu, Mo and N are adjusted, and the balance is made of stainless steel consisting of Fe and impurities that are inevitably mixed in. After passing through normal hot rolling process and cold rolling process, 20 % Tempering rolling is performed, and a method for producing spring stainless steel excellent in formability and stress corrosion cracking characteristics. 5. In% by weight, C: more than 0.03% to less than 0.15%, Si: more than 1.5% to less than 3.0%, Mn: less than 3.0%, Ni: 4.0 to 10.0%, Cr: 12.0 to 20.0%, N : 0.30% or less, S: 0.008% or less, C + N: 0.10% or more, depending on the case, further 3.0% or less Mo or 0.5 to 3.0
% Cu of 1 or 2 and M = 330− (480 × C%) − (2 × Si%) − (10 × Mn%) − (14 × Ni%) − (5.7 × Cr% )-(5 * Mo%)-(14 * Cu%)-(320 * N%) so that the M value becomes 30 or more, C, Si, Mn, Ni,
The amounts of Cr, Cu, Mo and N are adjusted, and the balance is made of stainless steel consisting of Fe and impurities that are inevitably mixed in. After passing through normal hot rolling process and cold rolling process, 20 % Tempered rolling, 100 ℃ or more 300
A method for producing a stainless steel for spring, which is excellent in forming workability and stress corrosion cracking property, which comprises performing an aging treatment for 10 minutes or more in a temperature range of less than ℃. 6. The method for producing stainless steel according to claim 5, wherein the aging treatment is performed after the temper-rolled steel sheet is formed into a desired shape.