JPH07316662A - Production of stainless steel strip having high strength and high toughness - Google Patents

Abstract

PURPOSE:To produce a stainless steel strip combining higher strength with higher toughness by specifying manufacturing conditions at the time of producing an austenitic stainless steel strip having specific composition. CONSTITUTION:An austenitic stainless steel strip, consisting of, by weight, <=0.10% C, >1.0-3.0% Si, <=2.5% Mn, 4.0-8.0% Ni, 12.0-18.0% Cr, 1.0-3.5% Cu, <=0.15% N, <=0.008% S, and the balance Fe and satisfying C+N>=0.10, is produced. This steel strip shows austenite phases in a solution-heat-treated state. At this time, final solution heat treatment is done by means of bright annealing under the conditions of <=1150 deg.C annealing temp. and <=60sec soaking time. By this method, an austenitic stainless steel strip of >=7.0 grain size number by JIS G 0551 can be produced. Further, temper rolling is done without performing acid pickling, by which the stainless steel material combining high strength with high toughness, having <0.47mum surface roughness (maximum height Rmax) by JIS B 0601 in an age-treated state, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ID blade for accurately and thinly slicing silicon single crystal, ferrite, ceramics, etc., which are semiconductor materials, a floppy disk head drive belt, a continuously variable transmission (C) for automobiles and the like. .V.
The present invention relates to a method for producing a stainless steel strip having high strength and high toughness, which is preferably used for a transmission belt for T).

[0002]

2. Description of the Related Art For example, an ID blade will be described. The ID blade is an abbreviation for Inner diameter blade, and the thickness formed on a donut-shaped thin plate is 0.05 to 5.
It has a structure in which diamond abrasive grains are adhered to the tip of the inner circumference of a high strength stainless steel substrate of 0.3 mm by a special electrodeposition method, and silicon single crystal, ferrite, ceramics, etc. are sliced to high precision thinness. It is an inner circumference blade.

As shown in FIG. 1, an ID blade 2 having a diamond abrasive grain 1 adhered to the tip of the inner circumference is used as a slicing device 3
At the time of setting, the peripheral edge of the ID blade 2 is clamped between the chuck body 4 and the top ring 5 placed on the spindle, and fixed by the mounting bolt 6. Then, by applying tension with the tension bolt 7, the ID blade 2 is pressed against the recess 9 via the tension ring 8 and the ID blade 2 is pulled up like the skin of the drum. The stainless steel strip used for the ID blade 2 is required to have higher strength and toughness because it is thinned to increase the yield of the material to be cut.

Here, the applicant of the present invention has previously disclosed Japanese Patent Laid-Open No. 63-31.
7628, C: 0.10% in weight%
Below, Si: more than 1.0% and less than 3.0%, Mn: 2.5%
Below, Ni: 4.0 to 8.0%, Cr: 12.0 to 18.0
%, Cu: 1.0% to 3.5%, N: 0.15% or less, S:
0.008% or less, the total of C and N is 0.10% or more, and the balance is Fe and the stainless steel strip having an austenite phase composed of impurities that are inevitably mixed. Disclosed is a method of producing a stainless steel excellent in high overhang strength and toughness by performing surface aging, and then cold rolling to generate a work-induced martensite phase, followed by aging treatment.

[0005]

However, even when the ID blade is manufactured by using the stainless steel disclosed in Japanese Patent Laid-Open No. 63-317628, when the tension is applied by the tension bolt when setting it in the slicer, ，
The ID blade often breaks when cutting a silicon single crystal. Stainless steel used for ID blades and the like is required to have high strength, and it is extremely difficult to have excellent toughness that does not cause cracks when the ID blade is set in a slicer and stretched.

Therefore, it is an object of the present invention to provide a method for producing a stainless steel strip having higher strength and toughness in the steel having the above-described composition.

[0007]

Means for Solving the Problems As a means for achieving the above object, the present invention provides C: 0.
10% or less, Si: more than 1.0% and 3.0% or less, Mn:
2.5% or less, Ni: 4.0 to 8.0%, Cr: 12.0 to 1
8.0%, Cu: 1.0% to 3.5%, N: 0.15% or less, S: 0.008% or less, the sum of C and N is 0.10% or more, and the balance is Fe and unavoidable. When producing an austenitic stainless steel strip that consists of impurities that are mixed in as a mixture and exhibits an austenitic phase in the solution heat treated state, the final solution heat treatment is performed at an annealing temperature of 1150 ° C or less and a soaking time of 60 ° C.
JIS G 055 by performing bright annealing under the condition of sec or less
Austenitic stainless steel strips with a grain size number of 7.0 or more according to 1 are manufactured, then temper-rolled without pickling and then subjected to aging treatment to obtain surface roughness according to JIS B 0601 (max. Provided is a method for producing a high strength and high toughness stainless steel strip having a height Rmax) of less than 0.47 μm. In addition,
In this manufacturing method, the range of the reduction ratio of the temper rolling is preferably 30 to 60%.

[0008]

[Action]

As described with reference to FIG. 1, when the ID blade is set in the slicing device, the ID blade is pressed into the recess by the tension ring, and tension is applied to the entire ID blade. The ID blade is required to have high toughness so that cracks do not occur even when the ID blade is pressed against the concave portion and deformed. On the other hand, the Erichsen test B method of JIS Z 2247 (hereinafter referred to as "Erichsen test"), which is usually performed to check the formability of a metal plate, sandwiches the periphery of the plate material by applying a load with a die and a wrinkle retainer. , It is done so as to cause a crack by pressing the punch in the center. Therefore, the Erichsen test is considered to be the most suitable method for evaluating the toughness of an ID blade or the like that is pressed by a tension ring and deformed. That is, a steel material used for an ID blade or the like is required to have high Erichsen value and Erichsen rupture strength measured by the Erichsen test.

Therefore, the inventors of the present invention produced steel strips having the above-described component compositions by setting various annealing conditions before temper rolling, temper rolling conditions, aging treatment conditions, etc. After conducting an Erichsen test on each of the steel strips and investigating how the annealing conditions and the like affect the toughness of the steel strip, the manufacturing method of the present invention as described above was constructed. Hereinafter, the limiting requirements of the present invention will be described in detail.

(Composition) C is an austenite-forming element, which suppresses the formation of δ-ferrite at high temperatures and is extremely effective in strengthening the martensite phase induced by cold rolling, but the steel used in the present invention. Since the Si content is high, the solid solubility limit of C is lowered. Therefore, if C is increased, Cr
Carbide precipitates and causes intergranular corrosion resistance and a decrease in toughness. Therefore, the C component range was set to 0.10% or less.

Si is an important element for inducing and strengthening the martensite phase by cold working, and is important together with Cu for hardening by aging treatment. In order to exert its effect, at least 1.0% or more is required. However, if it is made too high, the formation of the δ ferrite phase is promoted and the effect is small for the added amount, so the upper limit was made 3.0%.

Mn is an element that controls the stability of the austenite phase, and the content of Mn is determined by the balance with other elements. In the present invention, the utilization can be achieved with an Mn amount of up to 2.5%.

Ni is an element contained to obtain an austenite phase at high temperature and room temperature. In the steel of the present invention, it is a metastable austenite phase at room temperature, and a martensite phase is induced during cold rolling. It is desirable to be prepared. When the Ni content is lower than 4.0%, a large amount of δ ferrite phase is formed at high temperature, and a martensite phase is formed during the cooling process up to room temperature so that it cannot exist as a single austenite phase. The amount is 8.0
%, The martensite phase is less likely to be induced during cold rolling, so the Ni component range is 4.0 to 8.0.
%.

Cr is a component contained for obtaining corrosion resistance. At least 1 to impart the intended corrosion resistance
It requires 2.0% Cr. However, since Cr is a ferrite forming element, if the content is made too high, a large amount of δ ferrite phase will be generated when the steel is heated to a high temperature.
Further, in order to suppress the formation of the δ ferrite phase, C, N, N
It becomes necessary to add austenite forming elements such as i, Mn and Cu. However, C, N, Ni, Mn, Cu
Addition of elements such as these excessively stabilizes the austenite phase at room temperature, prevents the formation of work-induced martensite phase during cold rolling, and makes it impossible to obtain high strength even after aging treatment. . Therefore, the Cr component range is set to 12.0 to 18.0%.

Cu has a function of hardening the steel by the interaction with Si as described above when the steel is aged.
The excessive addition deteriorates the hot workability and causes the occurrence of cracks, so the content range of Cu is set to 3.5% or less. However, if it is too small, the effect is small, so 1.0% was made the lower limit.

N is an element which forms austenite and is an element which is extremely effective in hardening the austenite phase and the martensite phase. However, since a large amount of addition causes blowholes during casting, 0.15% Below.

S produces MnS under the coexistence of Mn,
Since it causes a decrease in ductility, it was set to 0.008% or less.

C and N have similar hardening effects. In order to fully exert such curing action, C + N is a total of 0.
It must be 10% or more.

In addition to the above components, the steel used in the production of the present invention contains Al and Ti added as a deoxidizing agent, Ca and REM added as a desulfurizing agent, and an improvement in strength when aged. In addition to Mo that is effective for the above, impurities that are inevitably mixed can be contained.

In the production method of the present invention, an austenitic stainless steel strip exhibiting an austenite phase in the solution treated state having the above composition is temper-rolled and then subjected to an aging treatment.

(Brightness Annealing) As shown in the manufacturing method of Japanese Patent Application Laid-Open No. 63-317628 as the prior art of the present application, in the conventional manufacturing process of stainless steel strip, pickling is performed immediately before temper rolling. It is generally done. However, this pickling inevitably causes digging at the grain boundaries on the surface of the steel strip, and I produced by using such steel.
When the D blade is set on the slicer and pulled up,
There is a problem that the dug portion becomes a starting point and cracks are likely to occur at the time of stretching. In view of this, in the present invention, the final solution treatment is performed by bright annealing at the time of manufacturing, thereby omitting the pickling step that has been performed immediately before the conventional temper rolling. Thus, if solution annealing is performed immediately before temper rolling by bright annealing, oxide scale is not generated by bright annealing, so pickling is not necessary and the grain boundaries on the steel surface by pickling are eliminated. Problems such as digging can be avoided, and the surface roughness can be further reduced in the steel strip that is finally produced by temper rolling that is subsequently carried out.

Next, the present inventors investigated the relationship between the grain size number, the Erichsen value and the Erichsen rupture strength of the stainless steel having the above-described composition. as a result,
The relationship shown in FIG. 2 was obtained. That is, it was confirmed that both the Erichsen value and the Erichsen rupture strength increased as the grain size number increased and the crystal grains became finer. Especially JIS
In the range where the grain size number specified by G 0551 is 7.0 or higher,
It was found that the Erichsen value of 5.0 mm or more was certainly satisfied, the Erichsen rupture strength was increased, and a stainless steel strip having high strength and toughness required for an ID blade was obtained. It is considered that as the grain size becomes smaller, the triple points where stress concentrates at the grain boundaries increase and the stress disperses.

In the solution treatment of the above-mentioned steel components, the change in grain size was examined under the conditions of annealing temperature of 950 ° C. to 1200 ° C. and soaking time of 60 seconds or less, and the results shown in FIG. 3 were obtained. It was From this result, the grain size number is 7.
It was found that the solution treatment conditions of 0 or more were an annealing temperature of 1150 ° C. or less and a soaking time of 60 seconds or less. Therefore, also in the manufacturing method of the present invention, the final solution treatment is performed by bright annealing under the conditions of an annealing temperature of 1150 ° C. or less and a soaking time of 60 seconds or less, so that the grain size number becomes 7.0 or more, The grain size was reduced.

(Temperature Rolling) After bright annealing, temper rolling is performed without pickling. This is because the pickling inevitably causes digging at the crystal grain boundaries on the surface of the steel strip, and tends to cause defects that are the starting points of cracks that occur when the ID blade is pulled up. The reduction ratio of temper rolling is preferably 30 to 60%. If the rolling reduction is less than 30%, the high strength required for an ID blade or the like cannot be secured. On the other hand, the higher the rolling reduction, the higher the strength obtained. However, since the ductility may be impaired as the rolling reduction increases, the upper limit was set to 60%, and the strength was further increased by the aging treatment performed later. .

(Aging treatment) After temper rolling, an aging treatment is performed. The conditions for the aging treatment are not particularly limited, and can be performed, for example, by heat treatment at a target material temperature of 400 to 500 ° C. However, with this aging treatment, JIS B 06
It is important that the surface roughness (maximum height Rmax) of 01 is less than 0.47 μm. This is because in high-strength and high-toughness stainless steels such as steel strips used for ID blades, the greater the surface roughness, the higher the susceptibility to cracking, and the lower the Erichsen value and Erichsen rupture strength.

Here, in the solution treatment of the component steel used in the present invention, when atmospheric annealing is performed using a normal catenary annealing furnace, the surface of the steel strip is oxidized and oxidized. Since scale is generated, it is necessary to remove the oxide scale by performing pickling or the like after that. When pickling is performed in this way, as described above, digging is inevitably generated in the grain boundaries on the surface of the steel strip, and the surface is inevitably roughened to increase the surface roughness. However, when the final solution treatment is performed in a bright annealing furnace as a feature of the method of the present invention, the bright annealing is higher than the atmospheric pressure of an atmosphere containing hydrogen gas as a furnace gas, which is normally shielded from the atmosphere. Since the annealing is carried out in the furnace kept in this state, the surface of the steel strip is not oxidized and it is possible to prevent the formation of oxide scale, and the surface roughness before the bright annealing is very small and beautiful. The surface roughness of the steel strip formed by the cold rolling process using the work roll is small, and the beautiful surface texture having metallic luster can be maintained as it is. According to the method of the present invention, the steel strip which retains the glossy and beautiful surface skin formed by the cold rolling in the previous step after the bright annealing as described above is not subjected to pickling, The surface roughness is much smaller than that of cold rolling, and by performing temper rolling using a work roll such as a normal mirror, the surface roughness becomes extremely small and the maximum height Rma
x is less than 0.47 μm. Therefore, it is considered that the stainless steel strip manufactured by the method of the present invention has such a small surface roughness that the crack susceptibility is suppressed to be low and the Erichsen value and the Erichsen rupture strength are increased. Although the aging treatment performed after temper rolling is significantly lower than the solution treatment temperature such as bright annealing, the target material temperature 400
Since it is performed under low temperature heat treatment conditions of up to 500 ° C, it is considered that oxide scale having a relatively thin uniform thickness is formed on the surface of the aged stainless steel strip. Usually, the product is not directly used as it is. In such a case, it is preferable to remove the oxide scale by a nitric acid electrolytic treatment or the like, which is lighter than the general pickling with boiling nitric acid. However, the surface roughness (maximum height Rmax) is 0.47 μm even under such a mild nitric acid electrolysis treatment.
It is important to keep it below.

[0028]

EXAMPLES Stainless steels having the compositions shown in Table 1 (test numbers A1 to A6) were melted and stainless steel strips were manufactured by the method of the present invention and the conventional method. In the production of the stainless steel strip by the method of the present invention, the molten stainless steel piece is hot-rolled, and then the steps of annealing, pickling and cold rolling are repeated,
Bright annealing was performed to carry out the final solution treatment, followed by temper rolling and aging treatment to manufacture a thin steel strip having a thickness of 0.147 mm. In the conventional method, after the molten stainless steel piece is hot-rolled, the steps of annealing, pickling, and cold rolling are repeatedly performed, followed by atmospheric annealing and pickling, followed by temper rolling and aging treatment. A thin steel strip having a plate thickness of 0.147 mm was manufactured. The annealing conditions in both the method of the present invention and the conventional method are continuous threading at an annealing temperature of 1000 ° C. to 1150 ° C. for a soaking time of 60 seconds or less, and the same solution treatment conditions were used during bright annealing. . The temper rolling condition is that the plate thickness is 0.28.
It was temper-rolled with a reduction rate of 48% from 3 mm to 0.147 mm. In addition, the aging treatment has a target material temperature of 400 to 500 ° C.
The heat treatment is as follows.

[0029]

[Table 1]

With respect to each of the stainless steel strips manufactured as described above, an Erichsen test was carried out using the sample to measure the Erichsen value and the Erichsen breaking strength. Also, the surface roughness is measured according to JIS B 0601,
The maximum height R _max was measured. The results are shown in Table 2. Table 2 also shows the grain size numbers of the steel strips measured before temper rolling.

[0031]

[Table 2]

As shown in FIG. 4, even if the grain size numbers measured before temper rolling were in the same range of 7.0 or more, the present invention was compared with those produced by the conventional method. The surface roughness (maximum height Rma
x) is less than 0.47 μm, which indicates that the steel strip produced by the method of the present invention has higher Erichsen value and Erichsen rupture strength as a whole. In the method of the present invention, it is considered that there is no digging of the surface grain boundaries because the annealing / pickling process immediately before temper rolling is changed to bright annealing. When the surface of the steel strip manufactured by the conventional method was observed with an optical microscope, the grain boundaries were remarkably observed even without etching, but the steel manufactured by the method of the present invention was etched by boiling nitric acid. However, no grain boundaries appeared on the surface.

[0033]

According to the present invention, Japanese Patent Laid-Open No. 63-3176.
In the steel having the known components already disclosed in No. 28, it becomes possible to manufacture a stainless steel strip having higher strength and toughness.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an ID blade

FIG. 2 is a graph showing the relationship between grain size number, Erichsen value, and Erichsen rupture strength.

FIG. 3 is a graph showing the relationship between solution treatment conditions and particle size numbers.

FIG. 4 is a graph showing a comparison of Erichsen value and Erichsen rupture strength between the method of the present invention and the conventional method.

FIG. 5 is a graph showing a comparison of surface roughness between the method of the present invention and the conventional method.

[Explanation of symbols]

 1 Diamond Abrasive Grains 2 ID Blade 3 Slicing Device 4 Chuck Body 5 Top Ring 6 Mounting Bolt 7 Tension Bolt 8 Tension Ring 9 Recess

Claims (2)

[Claims] 1. In weight%, C: 0.10% or less,
Si: more than 1.0% and less than 3.0%, Mn: less than 2.5%,
Ni: 4.0 to 8.0%, Cr: 12.0 to 18.0%, C
u: 1.0% to 3.5%, N: 0.15% or less, S: 0.0
08% or less, the sum of C and N is 0.10% or more, and the balance is Fe
In addition, when manufacturing an austenitic stainless steel strip that is inevitably mixed with impurities and exhibits an austenitic phase in the solution heat treated state, the final solution heat treatment is performed at an annealing temperature of 1150 ° C or less and a soaking time of 60 seconds or less. Austenitic stainless steel strip with a grain size number of 7.0 or more according to JIS G 0551 was manufactured by performing bright annealing, and then subjected to temper rolling without pickling and then subjected to aging treatment. The method for producing a high strength and high toughness stainless steel strip according to JIS B 0601 having a surface roughness (maximum height Rmax) of less than 0.47 μm. 2. The method for producing a high-strength and high-toughness stainless steel strip according to claim 1, wherein the rolling reduction in the temper rolling is 30 to 60%.