JPH0673444A - Aging treatment method of stainless steel foil for spring - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of stainless steel foil which shortens the heating time by quickly heating the stainless steel foil and allows the foil to have high spring limited value and little difference of the residual stress between the front and the back surfaces of the foil. CONSTITUTION:At the time of executing aging treatment of the cold-rolled stainless steel foil coil by a heat roll heating while continuously passing the foil, the foil is manufactured keeping following relation between a D value and the heat roll diameter (H). D value =(T+273){10+log(t/360)} R/100 H>=1000 t0 Wherein, T: heat roll temp. ( deg.C), t: contact time between the heat roll and the foil (sec), R: cold rolling ratio (%), t0: plate thickness (mm), alpha series: 2000<=D value <=6000, and beta series 2600<=D value <=6000. By this method, the aging treatment can be executed in shorter time than the conventional method and the production efficiency is remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aging treatment method for stainless steel foil for springs, which is suitable for automobile parts, electronic device parts, machine structural parts, parts for general household use and the like, which are required to have high spring properties. .

[0002]

2. Description of the Related Art As components requiring high strength as described above, gaskets for automobiles, metal carriers for automobile catalyst carriers, electronic devices such as switches, belts, lifters, suspension springs, mechanical springs, etc. There is.
Since rust resistance is required for these parts, stainless steel is often used as the material.

Further, these parts are required to have a small set during use, and therefore, a spring limit value of 80 kgf / mm ² or more is required as a mechanical property. In addition, etching and pressing are often used as the processing method, and in that case, the difference in residual stress of the material between the front and back of the plate is 2 kgf / mm ²
If it is not below, the shape of the product is deteriorated.

As a method for improving the spring property and reducing the residual stress of a thin leaf spring material, a tension annealing method (Patent Publication No. 46-26219) is used, in which a thin plate spring is passed through a furnace at a recrystallization temperature or lower while a tension below the yield point is applied. ) Is known,
No consideration has been given to the heat treatment method for thin plates.
As a method for heating the spring material foil, a radiant heating furnace or a batch annealing furnace is generally used. In this case, the heating rate is slow and a long heating time is required.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, the foil is rapidly heated to shorten the heating time, and the difference between the high spring limit value of 80 kgf / mm ² or more and the residual stress between the front and back of the plate is 2 kgf / mm ² or less. It is an object of the present invention to provide a method for producing a foil having

[0006]

According to the present invention, the foil is brought into contact with a heated roll for rapid heating, and the residual stress can be made uniform by limiting the diameter of the heating roll. That is, the gist of the present invention is as follows.

(1) When a cold rolled stainless steel foil coil is continuously aged and aged by heat roll heating, a spring limit value (K
From the relationship between b) and the D value, the D value corresponding to the predetermined spring limit value is determined, and the heat roll temperature (T) and the contact time between the heat roll and the foil satisfying the formula (1) according to the D value are determined. Aging treatment is performed at (t). D value = (T + 273) {10 + log (t / 3600)} (R / 100) …………………… (1) Formula T: Heat roll temperature (℃) where T ≦ 650 ℃ t: Heat roll and foil Contact time (sec) R: Cold rolling rate (%) of stainless steel foil before aging treatment

(2) When the coil of cold-worked ferritic stainless steel foil is aged by heat roll heating while continuously passing the coil, the cold working ratio of the ferritic stainless steel foil before aging is Accordingly, the aging treatment is performed at the heat roll temperature (T) and the contact time (t) between the heat roll and the foil, which are determined by the formula (2). 2000 ≦ D value = (T + 273) {10 + log (t / 3600)} (R / 100) ≦ 6000 (2) Formula T: Heat roll temperature (° C) where T ≦ 650 ° C t: Contact between heat roll and foil Time (sec) R: Cold rolling rate (%) of stainless steel foil before aging treatment

(3) When the cold working austenitic stainless steel foil coil is aged by heat roll heating while continuously passing the coil, the cold working ratio of the austenitic stainless steel foil before aging treatment is Depending on,
Aging treatment is performed at the heat roll temperature (T) and the contact time (t) between the heat roll and the foil, which are determined by the formula (3). 2600 ≦ D value = (T + 273) {10 + log (t / 3600)} (R / 100) ≦ 6000 (3) Formula T: Heat roll temperature (° C) where T ≦ 650 ° C t: Contact between heat roll and foil Time (sec) R: Cold rolling rate (%) of stainless steel foil before aging treatment

(4) Aging treatment is performed using a heat roll having a diameter (H) determined by the equation (4) according to the plate thickness of the stainless steel foil. H ≧ 1000 ・ t ₀ ………………………………………… (4) Formula H: Heat roll diameter (mm) t ₀ : Plate thickness (mm)

The reasons for limiting the constitution requirements of the present invention will be described below. The heat transfer coefficient from the heated roll is larger than that of radiant heating or air heat transfer, and rapid heating is possible.
It is possible to downsize equipment and save labor. The heat pattern when heat-treated with a heat roll is shown in FIG.

The heat roll treatment can perform rapid heating as compared with radiant heating and air transfer, and can downsize the equipment and save labor. Also, because it is restrained by the heat roll,
The residual stress of the foil can be reduced. Therefore, the heating method of the foil is the heat roll method.

The spring limit value is improved by fixing the solid solution C and N in the material to dislocations introduced by working.
Appropriate cold work ratio and heat treatment are required to fix C and N on the dislocations introduced by cold work. Therefore, the spring limit value is related to the diffusion of C and N and the cold working rate,
The temperature, time, and cold work rate of heat treatment influence. The D value of the equation (1) is used as an index indicating that.

The relationship between the D value and the spring limit value is shown in FIG. The value is 2000-600 for ferritic stainless steel
0, 2600-in case of austenitic stainless steel
It is possible to satisfy the spring limit value of 80 kgf / mm ² or more between 6000. Therefore, the D value was set to 2000 to 6000 in the case of ferritic stainless steel and 2600 to 6000 in the case of austenitic stainless steel. The difference between ferritic stainless steel and austenitic stainless steel is
This is the difference in the diffusion rates of C and N.

D value = (T + 273) {10 + log (t / 3600)} (R / 100) …………………… (1) Formula T: Heat roll temperature (° C) t: Contact between heat roll and foil Time (s) R: Cold rolling rate of stainless steel foil before aging treatment (%) When the temperature of the heating roll exceeds 650 ° C, the foil recrystallizes, so the spring limit value decreases regardless of the D value. . Therefore, the temperature of the heating roll is set to 650 ° C. or lower.

If the diameter of the heating roll is too small, the difference between the front and back of the residual stress becomes large. FIG. 3 shows the relationship between the heat roll diameter and the plate thickness, which affects the difference in residual stress between the front and back. In order to reduce the difference in residual stress between the front and back sides to 2 kgf / mm ² or less, the diameter of the heat roll must be at least (4).

H ≧ 1000 · t ₀ ………………………………………… (4) Formula H: Heat roll diameter (mm) t ₀ : Plate thickness (mm)

[0018]

EXAMPLES Stainless steels shown in Table 1 were melted by a normal converter-VOD method, electric furnace-AOD method or vacuum melting method, and after casting, hot rolling, annealing and cold rolling were performed, A foil with a cold rolled finish was produced.

Final cold rolling rate, heat roll temperature (T), contact time between foil and heat roll (t), D value, roll diameter, spring limit value (Kb), difference in residual stress between front and back of foil (Δσ _r ). Is shown in Table 2.

The spring limit value (Kb) was measured by using a moment tester of JIS H 3130, which was prepared by cutting a plate in a direction parallel to the rolling direction. Residual stress on the front and back of the foil (Δσ _r )
Was determined from the direction parallel to the rolling direction by the stress measurement by X-ray.

The steel of the present invention has a spring limit value of 80 kgf /
mm ² or more and the difference in residual stress between the front and back is 2 kgf / mm ²
It can be seen that

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

According to the method of the present invention, a stainless steel having a high spring property can be provided, which can greatly contribute to the development of the field utilizing high strength.

[Brief description of drawings]

FIG. 1 is a heat pattern of heat roll heating and radiation heat treatment.

FIG. 2 is a chart showing a relationship between a spring limit value and a D value.

FIG. 3 is a table showing the relationship between the roll diameter and the plate thickness, which affects the difference in the residual stress between the front and back sides.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Wataru Mitsumitsu 3434 Shimada, Shinjuku Nippon Steel Co., Ltd. Inside the Hikari Works (72) Inventor Chiaki Furugi 3434 Shimada, Shinjuku Nippon Steel Co., Ltd. Inside the Shoko Works (72) Inventor Masayuki Kasuya 5-3 Tokai-cho, Tokai City Nippon Steel Corporation Nagoya Works

Claims (4)

[Claims] 1. A spring limit value (Kb) obtained by an experiment in advance when a cold rolled stainless steel foil coil is aged by heating with a heat roll while continuously passing the coil.
And the D value, the D value corresponding to the predetermined spring limit value is determined, and the heat roll temperature (T) and the contact time (t) between the heat roll and the foil satisfying the equation (1) are determined according to the D value. ) Aging treatment method for spring stainless steel foil. D value = (T + 273) {10 + log (t / 3600)} (R / 100) …………………… (1) Formula T: Heat roll temperature (℃) where T ≦ 650 ℃ t: Heat roll and foil Contact time (sec) R: Cold rolling rate (%) of stainless steel foil before aging treatment 2. When a coil of a cold-worked ferritic stainless steel foil is aged by heat roll heating while continuously passing the coil, it depends on the cold working rate of the ferritic stainless steel foil before aging. And aging treatment at the heat roll temperature (T) and the contact time (t) between the heat roll and the foil, which are determined by the formula (2). 2000 ≦ D value = (T + 273) {10 + log (t / 3600)} (R / 100) ≦ 6000 (2) Formula T: Heat roll temperature (° C) where T ≦ 650 ° C t: Contact between heat roll and foil Time (sec) R: Cold rolling rate (%) of stainless steel foil before aging treatment 3. A cold-worked austenitic stainless steel foil coil is subjected to aging treatment by heat roll heating while continuously passing through the coil, depending on the cold working ratio of the austenitic stainless steel foil before aging treatment. (3)
An aging treatment method for a ferritic stainless steel foil for spring, which comprises aging treatment at a heat roll temperature (T) and a contact time (t) between the heat roll and the foil determined by the formula. 2600 ≦ D value = (T + 273) {10 + log (t / 3600)} (R / 100) ≦ 6000 (3) Formula T: Heat roll temperature (° C) where T ≦ 650 ° C t: Contact between heat roll and foil Time (sec) R: Cold rolling rate (%) of stainless steel foil before aging treatment 4. Depending on the plate thickness of the stainless steel foil,
The aging treatment method for a stainless steel foil for a spring according to claim 1, claim 2 or claim 3, wherein the aging treatment is performed using a heat roll having a diameter (H) determined by the formula (4). H ≧ 1000 ・ t ₀ …………………………………………… (4) Formula H: Heat roll diameter (mm) t ₀ : Plate thickness (mm)