TW202020186A - Stainless steel strip or stainless steel foil and method for manufacturing the same capable of satisfying verticality and surface roughness of the end surface in an etching through process, and being applied to medical device applications - Google Patents

Abstract

To provide steel strips or steel foils having high corrosion resistance and a method for manufacturing the same, wherein these steel strips and steel foils are not added with alloy elements such as Nb, V and N, and suitable for precision pressing and precision processing and have a fine crystal grain structure with an average crystal grain size of 1.0 [mu] or less; more specifically, to provide a metastable solid-state austenite-based stainless steel strips or steel foils with a ultra-fine crystal grain structure and a method for manufacturing these steel strips and steel foils, wherein these steel strips and steel foils can satisfy verticality and surface roughness od the end surface in an etching through process, and can be applied to medical device applications. When being calculated in percentage by mass, C: 0.01-0.20%, Si: 0.1-2.0%, Mn: 0.1-3.0%, P: 0.05% or less, S: 0.03% or less, Cr: 15-21% and Ni: 5-15%, and the remaining portion is Fe and inevitable impurities; in addition, the average crystal grain size dave is 0.05-0.33 [mu]m, the maximum crystal grain size dmax is 2.0 [mu]m, the coefficient a (=[sigma]/dave) obtained by dividing the standard deviation [sigma] of the crystal grain size by the average crystal particle size dave satisfies 0.0 ≤ a ≤ 0.5, and the amount of chromium in the precipitated carbide Crptt satisfies 0.4% ≤ Crptt ≤ 1.0%.

Description

Stainless steel belt or stainless steel foil and manufacturing method thereof

The invention relates to a metastable state of austenitic stainless steel belt or steel foil with ultra-fine grain structure and a method for manufacturing such steel belt and steel foil, in particular to a medical electronic device or a precision small electronic device A steel belt or a steel foil to which the constituent materials of the Micro Electro Mechanical Systems (Micro Electro Mechanical Systems; hereinafter referred to as MEMS) device of the heart part are effectively applied, and a manufacturing method thereof.

Background of the invention In recent years, the miniaturization and high precision of MEMS devices are rapidly developing. Therefore, the metal materials constituting the MEMS device, especially the Vostian iron-based stainless steel, are required to be thinner and more durable. In addition, stainless steel for MEMS devices has gradually begun to require secondary machining accuracy and quality stability after machining. In the MEMS manufacturing process, various ultra-fine processing such as precision pressing and high-precision etching are performed on stainless steel strips or steel foils. Such ultra-fine processing is more likely to be greatly affected by the physical properties of the material than general mechanical processing. Especially in high-definition etching, it will be greatly affected by the surface properties, corrosion resistance and metal structure of the material. So far, by refining the crystal grains of metal materials or alloy materials to improve the mechanical properties such as high yield strength, high spring limit, and high endurance fatigue, such methods are widely known. In addition, it is a well-known system: the refinement of crystal grains not only has great benefits in mechanical properties, but also such as the precision of secondary processing during punching and cutting, and the surface roughness that is not likely to occur during forming, etc. , The benefits in parts quality are also great. Based on the above, stainless steel with a fine-grained structure has attracted attention as a material that can be effectively applied to MEMS applications.

Patent Documents 1 to 4 and Non-Patent Document 1 each describe stainless steel having a fine grain structure.

The stainless steels of Patent Literature 1, Patent Literature 2, and Patent Literature 3 all add special alloy elements such as Nb, V, and N to the chemical components of widely used stainless steel, and precipitate the carbonitrides of these added elements. This suppresses the growth of crystal grains in the final annealing, and the refinement of crystal grains is the result. However, the stainless steels of Patent Documents 1, 2, and 3 all refine the structure by making stainless steel a composition designed to be free from widely used components. Therefore, it is difficult to adopt medical devices from the viewpoint of biological safety risks. In addition, since the average crystal grain size of the stainless steel material is greater than 1 μm, it is difficult to say that it has the electrochemical uniformity required for the above-mentioned applications.

The stainless steel of Patent Document 4 is aimed at improving the strength characteristics (spring limit value), and the grains are refined by repeatedly receiving cold rolling (work-induced transformation) and heat treatment (inversion). In the stainless steel of Patent Document 4, no special alloy elements are added to the stainless steel as in Patent Documents 1, 2 and 3. However, the stainless steel of Patent Document 4 refines the crystal grains by repeating the above-mentioned processing and heat treatment, so the following treatments are repeated: through the non-uniform inversion state (α-phase→γ-phase) and re-dissolution in the heat treatment ( Cr carbide dissolves into the γ phase) and introduces processing strain unevenly in the subsequent cold rolling step. Therefore, not only the final average crystal grain size will exceed 1 μm, but it will also easily become a mixed grain microstructure. In addition, although the final cold rolling is performed in order to make the crystal grains finer, it is not suitable for processing such as precision pressing and high-definition etching due to the development of the rolling assembly structure. As a result, it is difficult to say that it can be effectively applied to the above-mentioned uses.

Non-Patent Document 1 discloses a technique that uses the inversion state to make the average grain size of the Vostian iron ultrafine grains of 0.5 μm or less, as in Patent Document 4. However, this technology is based on the metastable Vostian iron-based stainless steel containing Mo and N, that is, 12.5Cr-9.5Ni-2Mo-0.1N steel, and the above-mentioned special element N is added in a trace amount. 2 and 3 have the same problem.

Prior technical literature Patent Literature Patent Document 1: Japanese Patent No. 5920555 Patent Document 2: Japanese Patent No. 4324509 Patent Document 3: Japanese Patent No. 3562492 Patent Document 4: Japanese Patent No. 6252730

Non-Patent Document 1; Journal of the Japanese Society of Metals, Vol. 55, No. 4 (1991), pages 376-382 ("Tensile deformation behavior of metastable steady-state austenitic stainless steel with ultra-fine grain structure")

Summary of the invention Problems to be solved by invention The object of the present invention is to provide a steel belt or a steel foil and a method for manufacturing the same without adding alloy elements such as Nb, V and N. The steel belt or steel foil is suitable for precision pressing and precision machining, It also has a fine grain structure with an average crystal grain size of 1.0 μm or less and has high corrosion resistance. Specifically, the object of the present invention is to provide a metastable state of Vostian iron-based stainless steel strip or steel foil with ultra-fine grain structure and a method for manufacturing the same. The stainless steel strip or steel foil can satisfy the end face in the etching through process The verticality and surface roughness, and can be used for medical equipment.

Means for Solving the Problems Hereinafter, the present invention will be described in detail. (Gist of the present invention) The most important feature of the present invention is that Cr as a main component is added to widely used stainless steel, and the carbides formed (the carbide is mainly Cr ₂₃ C ₆ , but the Cr carbide of the steel of the present invention) It is not limited to Cr ₂₃ C ₆ ), and it is used to refine the crystal grains. That is, in stainless steel containing 12% by mass or more of Cr, Cr carbide is precipitated at grain boundaries and the like during the heating step. As Cr carbide precipitates, a Cr-depleted layer is formed in the vicinity. This phenomenon is called "sensitization." This sensitization may cause stress corrosion cracking unique to Vostian iron-based stainless steel. In order to avoid the above-mentioned problems, in the conventional technology, the following treatment is performed in the final manufacturing step: the steel plate is heated to 1000° C. or higher to re-dissolve the Cr carbide, and then quenched, that is, so-called solution treatment. The feature of the present invention lies in the active use of Cr carbide and Cr-depleted layers in controlling metal structure and controlling electrochemical characteristics. That is, in the present invention, the Cr carbide precipitated is finely dispersed to uniformly refine the crystal grains, and the Cr-depleted layer is uniformly and finely dispersed by repeatedly performing cold rolling and heat treatment. This improves the uniformity electrochemically or corrosively, and can realize high-definition etching.

In the prior art, Cr carbides have been avoided to prevent sensitization. In contrast to this, the present invention strictly controls the amount of Cr (Cr _ptt ) contained in the precipitated carbide that will induce sensitization, thereby utilizing the content of stainless steel without adding carbide-forming elements such as Nb and V The Cr itself achieves grain refinement. That is, through repeated cold rolling and recrystallization heat treatment, the following were found: Cr depletion layer will be separated and uniformly dispersed; in the heat treatment stage, fine Cr carbides will become obstacles to the movement of grain boundaries and will be mostly grouped Into the recrystallized grains; in this process, the metal structure will become a uniform fine grain structure; and, because the final product thickness is mostly less than 0.1mm, the embrittlement phenomenon due to sensitization will hardly appear come out. The core knowledge of the present invention is among the above points.

The present invention is based on the above knowledge and knowledge. The metastable steady-state austenitic stainless steel strip or steel foil of the present invention contains C: 0.01~0.20%, Si: 0.1~2.0%, Mn: 0.1~3.0%, P: 0.05% or less, S: 0.03% or less, Cr: 15~21% and Ni: 5~15%, and the rest is Fe and unavoidable impurities; and the average crystal grain size d _ave is 0.05~0.33μm, the maximum crystal grain size d _max is 2.0 μm, the coefficient a (=σ/d _ave ) obtained by dividing the standard deviation σ of the crystal grain size by the average crystal grain size d _ave satisfies 0≦a≦0.5, and the amount of chromium in the precipitated carbide Cr _ptt Satisfy 0.4%≦Cr _ptt ≦1.0%. In addition, the preferred plate thickness of the metastable stainless steel strip or steel foil of the present invention is 0.01 mm or more and 0.20 mm or less. In addition, the manufacturing method of the metastable state of Vostian iron stainless steel strip or steel foil of the present invention is (a) preparing hot-rolled steel, which contains C: 0.01 to 0.20% and Si: 0.1 to 2.0% in mass% , Mn: 0.1~3.0%, P: 0.05% or less, S: 0.03% or less, Cr: 15~21% and Ni: 5~15%, and the remaining part is Fe and unavoidable impurities; (b) After cold-rolling the hot-rolled steel, heat treatment is carried out in the temperature range of 500 ℃ ~ 900 ℃; (c) repeat the above steps (b) more than 3 times to obtain a steel strip or steel foil, the steel strip or steel foil The average crystal grain size d _ave is 0.05~0.33 μm, the maximum crystal grain size d _max is 2.0 μm, the coefficient a (=σ/ is obtained by dividing the standard deviation σ of the crystal grain size by the average crystal grain size d _ave d _ave ) satisfies 0≦a≦0.5, and the amount of chromium in the precipitated carbide Cr _ptt satisfies 0.4%≦Cr _ptt ≦1.0%. In the aforementioned cold rolling step, it is preferable to set the range of the primary cold rolling rate to 50 to 99% and to set the total rolling rate to 90 to 99%.

Here, in this specification, P and S of the components in steel are expressed as "below", and here "below" does not include 0%. In addition, the average crystal grain size and plate thickness of the steel strip or the steel foil are expressed by the description of "below", and "below" here does not include 0%. In addition, the present invention is directed to "steel belt" or "steel foil", and the two are only different in length and width, and there is no essential difference between the two at other points. In addition, the term "steel strip or foil" also includes steel plates (especially thin steel plates). Therefore, unless otherwise specified in the following description, the terms steel strip, steel foil, steel plate, and thin steel plate are used without distinction.

(The composition of the steel belt etc.) In the present invention, the reasons for defining the chemical composition of steel and the reasons for limiting the upper limit and lower limit of their equivalent contents are as follows. (1) C: 0.01~0.20% If C is annealed at a low temperature to refine the crystal grain size, carbides are easily formed, but Cr-depleted layers are formed around Cr carbides, which deteriorates the corrosion resistance. In addition, Cr carbides can cause smuts (oxidized coatings) and roughen the etched surface due to its barrier effect. If it is greater than 0.20%, in addition to the roughening of the etching surface, there may be a sensitization phenomenon (the formation of Cr-depleted layer), so the upper limit of the C content is set to 0.20%. The upper limit of the C content is more preferably set to 0.15%. On the other hand, the present invention also targets extremely low carbon-containing steels such as SUS316L and SUS304L, so the lower limit of the C content is set to 0.01%. Also, the lower limit of the C content is preferably set to 0.02%. (2) Si: 0.1~2.0% Si is used as a deoxidizing material in the stainless steel manufacturing process, and it contains 0.1% or more. If the Si content is increased to more than 2.0%, the etching rate will be reduced, so the Si content is limited to 2.0%. (3) Mn: 0.1~3.0% Mn is an element added to improve hot workability. If the Mn content is greater than 3.0%, the effect will be saturated and the cost will become higher. Therefore, the upper limit of the Mn content is set to 3.0%. In addition, the Mn content is preferably set to 2.0% or less. On the other hand, if the Mn content is less than 0.1%, the hot workability will be impaired. Therefore, the lower limit of the Mn content is set to 0.1%. (4) Cr: 15.0~21.0% Cr is the most important element in improving corrosion resistance. In particular, in the present invention, Cr is an important element used to precipitate Cr carbides in the structure. If the Cr content is less than 15.0%, the corrosion resistance will be deteriorated, and if it is greater than 21.0%, the cost will be increased, so the Cr content is set in the range of 15.0 to 21.0%. In addition, the optimal Cr content is in the range of 16.0 to 20.0%. (5) Ni: 5.0~15.0% Ni is an essential element in improving the corrosion resistance and strength of stainless steel. If the Ni content is less than 5.0%, the corrosion resistance will be deteriorated, and if it is greater than 15.0%, the cost will be increased, so the Ni content is set in the range of 5.0 to 15.0%. The more preferable Ni content is in the range of 6.0 to 15.0%. (6) Mo: 0.1~3.0% Mo is an alloy element that improves the corrosion resistance of SUS316 stainless steel. If the Mo content is greater than 3.0%, not only the addition effect will be saturated, but also the cost will become higher, and if the Mo content is less than 0.1%, the corrosion resistance will be deteriorated. Therefore, let the Mo content be in the range of 0.1 to 3.0%. (7) P: below 0.05% If the P content is increased to more than 0.05%, the hot workability will be deteriorated, so the upper limit is set to 0.05%. It is better to set the upper limit of P content to 0.045%. (8) S: 0.03% or less If the S content becomes more than 0.03%, the hot workability will be deteriorated, so the upper limit is set to 0.03%.

In addition, the steel strip and the steel foil of the present invention contain C, Si, Mn, P, S, Cr, Ni, and Mo, and the so-called "contains" here excludes the following components: components other than the above-mentioned components described in the claims It is a component that can be deliberately contained in addition to the components that cannot be avoided, such as Nb, V, or N, etc. that are at risk for biological safety.

(Metal Organization) The metastable steady-state Vostian iron-based stainless steels of the present invention are, for example, SUS304, SUS316L, etc., the metal structure of which is essentially the monolayer of Vostian iron, or the Vostian iron structure and the Matian scattered iron structure. Mixed structure, and the steel of the present invention includes these metal structures.

(Measurement criteria for crystal grain size and Cr content in precipitated carbide) In the present invention, the crystal grain size and its dispersed state, and the amount of Cr contained in the precipitated carbide are specified. The data of these numerical benchmarks is the observation of the structure of the target metastable iron field stainless steel strip and steel foil in the plane orthogonal to the rolling direction, and the numerical values obtained here are used as benchmarks and calculated separately The average crystal grain size, the standard deviation, the maximum value of the crystal grain size, and the amount of Cr in the precipitated carbide.

(Value of average crystal particle size) In the present invention, the value of the average crystal grain size is obtained by calculating the crystal grain size according to the area fraction (Area Fraction) method performed by electron backscatter diffraction (EBSD) for crystal grains to be observed The average area is calculated assuming a true circle and the diameter is converted from the average area value of the obtained crystal grain size. Specifically, in the area fraction method, the total value of (area of arbitrary crystal grains×(area of arbitrary crystal grains/total area)) is the average area of crystal grains. In the present invention, the value converted from the average area value is assumed to be a true circle as the average crystal grain value. (Maximum crystal size) The maximum crystal grain diameter in the crystal group obtained by EBSD analysis is taken as the maximum crystal grain size. (Standard deviation of crystal particle size) The standard deviation σ (= a･dave; however, a≦0.5) of the crystal particle size of the present invention refers to crystal grains having the following characteristics: the variation of each crystal particle size is small and the uniformity is high.

(Measured value of Cr amount in precipitated carbide) The amount of Cr contained in the precipitated carbide is measured by a non-aqueous solvent system constant potential electrolysis (SPEED) method. Specifically, after extracting the sample with 10% AA-based electrolytic extraction, the extracted carbide is captured with a 0.2 μm mesh filter and the mixed acid is decomposed, and then subjected to high frequency inductively coupled plasma (IPC) Mass analysis determined the measured value of Cr.

(The reason for specifying the average crystal grain size of the crystal grains, the maximum value of the crystal grain size, and the standard deviation of the crystal grain size) In the present invention, the average crystal grain size is 1.0 μm or less and the maximum value is 2.0 μm, whereby the chemically active points are uniformly and finely distributed through the microscopic periodic variation of the Cr concentration. Therefore, high-definition etching can be performed. In addition, by setting the range of the standard deviation σ (=a･dave; however, 0≦a≦0.5), it is possible to achieve uniform and fine refinement of the corrosion reaction. In addition, in the specification of this case, "high-definition etching" refers to performing etching at a size less than the thickness of the plate. For example, it refers to etching at a size of 0.20 mm or less for a steel plate having a thickness of 0.20 mm or less.

(Reasons for specifying the amount of Cr in the precipitated carbide) In the present invention, it is assumed that the amount of Cr contained in the precipitated carbide, that is, Cr _ptt is 0.4% or more and 1.0% or less. If Cr _{ptt is} less than 0.4%, the precipitation of Cr carbides is insufficient, and the grain refinement intended by the invention cannot be achieved. In addition, if Cr _{ptt is} greater than 1.0%, there is a possibility of sensitization (formation of Cr depletion layer) due to Cr carbides, so 0.4%≦Cr _ptt ≦1.0%.

(The reasons for the better thickness of steel strip and steel foil are specified) The final product mainly intended by the present invention has a thickness of mostly 0.01 to 0.20 mm, and if it is this thickness, the embrittlement phenomenon due to sensitization hardly appears. Therefore, it is defined as the thickness in the range of 0.01 to 0.20 mm.

(Manufacturing method of steel belt etc.) The manufacturing method of the steel strip etc. of this invention is a cold rolling process which superimposes a raw material (hot rolled steel material) 3 times or more, and heat-processing 3 times or more. The cold rolling is used to introduce the processing strain and the heat treatment is used to precipitate Cr carbides starting from the processing strain and grain boundaries, and the above three or more times are repeated, thereby uniformly and finely dispersing the Cr carbides throughout the base material. In addition, each cold rolling elongation ratio should be in the range of 50 to 99%, and the total rolling shrinkage ratio should be in the range of 90 to 99%. In order to recover the strain introduced through cold rolling, the intermediate heat treatment temperature (TA) is set to 500° C. or higher, and preferably set to the recrystallization temperature or higher. In the present invention, the upper limit temperature of the heat treatment is important. Cr carbides will be rapidly re-dissolved in the Vostian iron phase, so the complete inversion state will not only make the effect of subsequent cold-rolling delayed Cr carbides disappear, but also due to the uneven re-dissolution of Cr carbides in the subsequent steps Organizations in China tend to become non-uniform. Therefore, it is effective to limit the inversion rate of the iron phase in the Wustfield to 20% or less. To achieve this structure, in the present invention, the upper limit of the intermediate heat treatment temperature is limited to 900°C. By setting the intermediate heat treatment temperature to 900°C or less, the inversion state of the iron phase to the Vostian can be suppressed, and the inversion state rate can be controlled to 2% or more and 20% or less. In addition, in the present invention, when manufacturing the steel strip and steel foil as described above, "the cold rolling step and the heat treatment step are performed three or more times", which refers to the base materials (hot rolled steel materials) after hot rolling treatment. The cold rolling and heat treatment are performed more than three times, and the order of the processing steps of the cold rolling and heat treatment steps is not particularly inconsequential. For example, it may include a process step of performing a combination of cold rolling and heat treatment three times or more, or a step of performing heat treatment three or more times after cold rolling more than three times. In short, as long as it can be obtained by performing the cold rolling step and the heat treatment step three times or more, the metastable state of the austenitic stainless steel strip or steel foil of the present invention can be obtained.

Effect of invention According to the present invention, no special elements can be added to the metastable iron field stainless steel, and the problems unique to the iron field stainless steel, such as sensitization, can be avoided, and the crystal structure can be uniformly refined to submicron level. In this way, higher precision processing can be provided, which could not be achieved by the micronized microstructure in the past. Therefore, when used as a part of a micromachine such as a MEMS device, the dimensional accuracy during processing can be improved. In addition, the present invention disperses the Cr-depleted layer uniformly and finely, so it is suitable for high-precision etching processing and suitable for applications requiring microscopic chemical activity such as biochemistry.

Forms for carrying out the invention In the following, examples and comparative examples of the present invention are presented for explanation to confirm the effects of the present invention. Example samples 1-1, 1-2, 1-3, 1-4, 2-1, 2-2, 2-3 prepared by the manufacturing method of the present invention were prepared, respectively, and manufactured by conventional manufacturing methods The obtained comparative samples 1-1, 1-2, 1-3, 2-1, 2-2, 2-3 and 3. In addition, the conventional manufacturing method is a method for miniaturizing a metal structure by using process-induced metamorphosis and inversion. Table 1 shows the composition of various samples. Table 2 shows the manufacturing process of various samples.

With respect to the various samples obtained (thickness 0.2 mm), the structure was observed on a plane perpendicular to the rolling direction, and the average crystal grain size, standard deviation, maximum value of the crystal grain size, and the amount of Cr precipitated as carbides were measured. , The coefficient a (=σ/dave), the ferrosity rate of the field and the loose rate of the field. The results are shown in Table 3. Each measurement method is as described above. The obtained characteristics of each test material (through-etched end face roughness Ra, through-etched end face angle θ, corrosion resistance, and corrosion resistance) are shown in Table 4. Their observations are shown in Figures 1-7. The relationship between the average crystal grain size and the amount of Cr in the precipitated carbide is shown in Fig. 8. The relationship between the maximum value of the crystal grain size and the amount of Cr precipitated as carbides is shown in FIG. 9. The relationship between the average crystal grain size and the standard deviation is shown in Fig. 10.

表2

Table 1

Table 2

table 3

Table 4

The measurement methods of the through-etched end face roughness Ra, the through-etched end face angle θ, the corrosion resistance, and the corrosion resistance shown in Table 4 are described below. [Through-etching end surface roughness Ra] A method of measuring the through-etching end surface roughness Ra will be described with reference to FIGS. 11 and 12. The etching groove (or hole) shown in FIG. 11 is formed by causing the etching solution 3 to act only on the reference surface 21 side of the stainless steel plate 2. The etching speed is affected by various parameters (etching conditions), so it is not fixed. The above parameters can be exemplified by the concentration and temperature of the etching liquid on the solid-liquid interface, the removal rate of by-products on the solid-liquid interface, and the metal structure at the passing position of the solid-liquid interface. For example, when the solid-liquid interface passes through the grains and when passing through the crystal grain boundaries, the etching rate is different. Therefore, the unit of progress of the etching on the end surface changes, and as shown in FIG. 12, the etching end surface 23 becomes a concave-convex state. This uneven state corresponds to the roughness of the etched end surface 23, and the degree of fineness of the metal structure can be evaluated by measuring the roughness Ra of the through-etched end surface. For the measurement of the roughness Ra of the through-etched end face, a laser microscope can be used. The formation method of the etching groove (or hole) and the measurement method of the roughness Ra of the through-etched end surface will be described in further detail. As the etching solution, a mixed solution of saturated second iron chloride (FeCl ₃ )+hydrochloric acid (HCl)+nitric acid (HNO ₃ )+phosphoric acid (H ₃ PO ₄ ) was used. The etching temperature is controlled in the range of 30~65℃. In order to supply fresh etching liquid to the solid-liquid interface, the etching liquid is circulated until the stainless steel plate 2 having a plate thickness t penetrates. The etching groove (or hole) is cut transversely to cut the sample into two, and the laser light 4 for roughness measurement is irradiated from the front direction of the etching end face 23 as shown in FIG. 12 to measure the surface roughness through the etching end face 23 Degree Ra. In the measurement of the surface roughness Ra, a laser microscope was used to observe the through-etched end surface 23 in a range of 250 μm from the front. The laser microscope uses Lasertec Corporation's hybrid laser microscope "OPTELICS (registered trademark) HYBRID". The measurement results of the roughness Ra of the through-etching end surface are shown in Table 4. [Through-etching end face angle θ] A method of measuring the through-etching end face angle θ will be described with reference to FIGS. 11 and 13. In the single-sided etching as shown in FIG. 11, there is a side erosion problem where the etching end surface 23 is not perpendicular to the reference surface 21 and the back surface 22. Since the final product requires that the etched end face 23 be as close to vertical as possible, the verticality of the etched trench (or hole) end face must be evaluated. In order to evaluate the perpendicularity of the end face of the etching groove (or hole), the angle θ of the through-etching end face of various samples was measured using the above-mentioned laser microscope. As shown in FIG. 13, the through-etched end surface 23 is observed in the range of 250 μm from the front, first the first opening peripheral portion 26 is irradiated with the first laser light 41, and then the second opening peripheral portion 27 is irradiated with the second laser light 42 to calculate After the phase difference W3 between the first part 26 and the second part 27 and the inclination (tan θ) of the end face 23 from the plate thickness t, the etching end face angle θ is calculated from the calculated inclination. The measurement results of the through-etching end face angle θ are shown in Table 4. [Anti-corrosion adhesion] The test method for evaluating the corrosion adhesion is implemented by observing the perforated end surface of the etched sample using a field emission scanning electron microscope (FE-SEM) and comparing the observations. The post-etching morphology and the sample surface morphology before etching are implemented by this. The results are shown in Table 4. In Table 4, whether the perforated end surface is corroded is judged based on the comparison of the sample surface morphology before and after etching. Those who are judged to be corroded by the perforated end surface are indicated by 0, and those judged to be not corroded by the perforated end surface are indicated by ×. [Corrosion resistance] The evaluation test method for corrosion resistance is implemented in accordance with the "Measurement Method for Porosity Potential of Stainless Steel" specified in JIS G0577 (2014 edition). The results are shown in Table 4. In Table 4, the measurement result of the pitting potential is the same as that of the standard SUS304 pitting potential, which is indicated by 0, and the difference is indicated by ×. It can be seen from Table 4 that the thickness of the through-etched end face Ra, the angle θ of the through-etched end face, the corrosion resistance, and the corrosion resistance of the examples are better than those of the comparative examples.

FIGS. 1 to 3 also show the etching samples of stainless steel thin plates (Examples) and the conventional stainless steel thin plates (Comparative Examples) in which the metal structure is controlled in the above manner. FIG. 1 is a photograph showing the effect of grain refinement on the width of a slit formed by etching. As can be seen from FIG. 1(a), in Comparative Example 1-1, since the verticality of the etching end surface cannot be ensured, the plate does not penetrate through the center of the slit. On the other hand, it can be seen from FIG. 1(b) that in Example 1-1, the minimum width of the slit through which the plate penetrates is reduced due to the refinement of crystal grains. In this way, the problem of "side erosion" where the end face of the etching process is not vertical is solved at a practical level.

FIG. 2 is a scanning electron microscope image showing the state of the end surface after etching. Compared with Comparative Example 1-1, the unit of etching of the end face in Example 1-1 is relatively small, and it can be seen that in the example of the present invention, the corrosion reaction of the material proceeded uniformly and finely.

Fig. 3 is a photograph of the adhesion of the resist film. In Comparative Example 1-1, corrosion marks can be confirmed on the surface of the material near the etching, but in Example 1-1, the grain size is improved due to the penetration. The adhesion of the resist film to the surface of the workpiece is not corroded by the interface from the perforated end surface. This can be explained by the fact that the chemical active points of the material are evenly and finely dispersed, thereby improving the adhesion of the resist film.

4 and 5 are histograms of the EBSD image and crystal grain size of Example 1-1 in which the metal structure has been controlled into a uniform and fine material. FIGS. 6 and 7 are histograms of EBSD images and crystal grain sizes of the material of which the metal structure has been refined in Comparative Example 1-1. Comparing the embodiments of FIGS. 4 and 5 with the comparative examples of FIGS. 6 and 7, it can be seen that if the manufacturing method of the comparative example becomes sub-micron-level micronization, it will become a mixed-grain structure, resulting in etching etc. The precision of machining decreases in precision machining. In addition, it can be seen that, compared with the above, in the example of the present invention, uniform micronization at the sub-micron level has been achieved, and by providing it for micromachining, it can contribute to improving the processing accuracy.

FIG. 8 is a characteristic diagram showing the relationship between the average crystal grain size and the amount of Cr (Cr _ptt ) in the precipitated carbide. From this figure, it can be seen that when Cr _{ptt is} less than 0.4%, the maximum value of the crystal grain size is large and it becomes a mixed grain structure. In addition to this, the corrosion resistance is also deteriorated. On the other hand, if Cr _{ptt is} greater than 1.0%, the corrosion resistance will deteriorate. Therefore, Cr _ptt is most suitable in the range of 0.4~1.0%.

9 is a characteristic diagram showing the relationship between the maximum value of the crystal grain size and the amount of Cr (Cr _ptt ) in the precipitated carbide. According to the results of this figure, when the amount of Cr in the precipitated carbide is less than 0.4%, the maximum value of the crystal grain size is large and the high-fine etching property is deteriorated. On the other hand, if the amount of Cr in the precipitated carbide exceeds 1.0%, the maximum value of the crystal grain size becomes small and the corrosion resistance becomes poor. Therefore, the amount of Cr in the precipitated carbide is set in the range of 0.4 to 1.0%.

Fig. 10 is a graph showing the relationship between the average crystal grain size and the standard deviation. Its linear proportional relationship shows from this result that it can be successfully controlled into a uniform and fine structure according to the present invention.

It can be confirmed from the above examples that, according to the present invention, without the addition of special elements to the metastable Vostian iron-based stainless steel, the problems unique to the Vostian iron-based stainless steel such as sensitization can be avoided and the crystal structure can be made uniform Refine to submicron level.

Industrial availability According to the present invention, the stainless steel band or the steel foil can be provided for higher precision processing which cannot be achieved in the past micron-level micronization. Therefore, in the micromachining of stainless steel for MEMS devices, the dimensional accuracy can be further improved. In the field of medical equipment, for example, it can be expected to be used as a part of a micro pump for anesthesia surgery equipment. In addition, according to the present invention, the Cr-depleted layer is uniformly and finely dispersed, and can be effectively used for applications requiring microscopic chemical activity, that is, high-definition etching processing applications, biochemical applications, and the like.

2: stainless steel plate 21: Reference surface (etching liquid action surface) 22: back 23: Etching the end face 24: the first opening 25: 2nd opening 26: Peripheral part of the first opening on the reference plane side 27: Peripheral part of the second opening on the back side 28: grain 3: etching solution 4: Laser light for roughness measurement 41: First laser beam for angle measurement 42: Second laser beam for angle measurement d: etching depth t: plate thickness W1: opening width on the reference plane side W2: opening width on the back side W3: The phase difference between the 1st and 2nd opening periphery θ: angle

FIG. 1 is an enlarged photograph comparing the effect of the finer crystal grains on the slit width etched by the same slit shape for the sample of the example and the sample of the comparative example. FIG. 2 is a photograph of a scanning electron microscope image showing the state of the end surface of the comparative example sample and the comparative example sample after etching processing. 3 is an enlarged photograph of the adhesion performance of the resist film of the comparative example sample and the comparative example sample. 4 is a photograph showing the EBSD image of the steel foil of the sample of the example. Fig. 5 is a histogram of the crystal grain size of the steel foil of the sample of the embodiment. Fig. 6 is a photograph showing the EBSD image of the steel foil of the comparative sample. Fig. 7 is a histogram of the crystal particle size of the comparative sample. FIG. 8 is a graph showing the relationship between the average crystal grain size and the amount of Cr precipitated as carbides for the example sample and the comparative sample. 9 is a graph showing the relationship between the maximum value of the crystal grain size and the amount of Cr precipitated as carbides for the sample of the example and the sample of the comparative example. FIG. 10 is a graph showing the relationship between the average crystal grain size and the standard deviation for the sample of the example and the sample of the comparative example. Fig. 11 is a cross-sectional view schematically showing a through-etched hole formed in a stainless steel plate. FIG. 12 is a schematic partial cross-sectional view of a through-etched hole for explaining a method for measuring the thickness Ra of a through-etched end surface. 13 is a schematic partial cross-sectional view of a through-etched hole for explaining a method of measuring the angle θ of the through-etched end face.

Claims (10)

A metastable Vostian iron stainless steel strip or steel foil, characterized in that it contains C: 0.01~0.20%, Si: 0.1~2.0%, Mn: 0.1~3.0%, P: 0.05% or less in mass% , S: 0.03% or less, Cr: 15-21% and Ni: 5-15%, and the remaining part is Fe and unavoidable impurities; and, the average crystal particle size d _ave is 0.05~0.33μm, the crystal particle size The maximum value d _max is 2.0 μm, the coefficient a (=σ/d _ave ) obtained by dividing the standard deviation σ of the crystal grain size by the average crystal grain size d _ave satisfies 0≦a≦0.5, and chromium in the carbide is precipitated The amount Cr _ptt satisfies 0.4%≦Cr _ptt ≦1.0%. If the steel belt or steel foil of claim 1, its plate thickness is 0.01mm or more and 0.20mm or less. For example, the steel belt or steel foil of claim 1 contains 16-20% by mass of Cr. If the steel belt or steel foil of claim 1, it contains 6 to 15% by mass of Ni. The steel belt or steel foil according to any one of claims 1 to 4 further contains 0.1 to 3.0% by mass of Mo. A manufacturing method of metastable Vostian iron stainless steel strip or steel foil, which is characterized by comprising the following (a) to (c): (a) Preparation of hot-rolled steel material, the hot-rolled steel material contains C: 0.01 in mass% ~0.20%, Si: 0.1~2.0%, Mn: 0.1~3.0%, P: 0.05% or less, S: 0.03% or less, Cr: 15~21% and Ni: 5~15%, and the rest is Fe and Impurities that cannot be avoided; (b) After cold rolling the aforementioned hot-rolled steel, heat treatment is performed in the temperature range of 500°C to 900°C; (c) Repeat the above steps (b) three or more times to produce steel Strip or steel foil, the average crystal grain size d _ave of the steel strip or steel foil is 0.05 to 0.33 μm, the maximum crystal grain size d _max is 2.0 μm, and the standard deviation σ of the crystal grain size is divided by the average crystal grain size d _ave obtained by the coefficient a (= σ / d _ave) satisfies 0 ≦ a ≦ 0.5, and the amount of precipitation of chromium carbide Cr _ptt satisfies _{0.4% ≦ Cr ptt ≦ 1.0%} . The manufacturing method according to claim 6, wherein in the aforementioned step (b), the cold rolling reduction rate of each time is set in the range of 50 to 99% and the total rolling reduction rate is set in the range of 90 to 99%. The manufacturing method according to claim 6, wherein in the step (b), the hot-rolled steel material is heat-treated at a temperature equal to or higher than the recrystallization temperature of the hot-rolled steel material. The manufacturing method according to claim 6, wherein in the aforementioned step (b), the inversion ratio of dissolving Cr carbide into the Vostian iron phase is controlled to 20% or less. The manufacturing method according to claim 6, wherein the aforementioned hot rolled steel further contains 0.1 to 3.0% by mass of Mo.

Images