WO2008013305A1

WO2008013305A1 - Stainless steel sheet for parts and process for manufacturing the same

Info

Publication number: WO2008013305A1
Application number: PCT/JP2007/064910
Authority: WO
Inventors: Kazuhiko Adachi; Masaru Abe; Kazuyoshi Fujisawa
Original assignee: Sumitomo Metal Industries, Ltd.
Priority date: 2006-07-28
Filing date: 2007-07-30
Publication date: 2008-01-31
Also published as: CN101490298B; JPWO2008013305A1; EP2048256B1; EP2048256A4; EP2048256A1; JP4475352B2; CN101490298A

Abstract

The invention provides a stainless steel sheet which has excellent strength and ductility and is improved in workability (formability and etchability) and fatigue characteristics and a process for manufacturing the stainless steel sheet. Further, the invention ensures industrial and stable supply of the stainless steel sheet at a low cost. A stainless steel sheet which contains by mass C: 0.01 to 0.08%, Si: 0.1 to 2.0%, Mn: 3.0% or below, Cr: 10.0 to 20.0%, Ni: 3.0 to 12.0% and N: 0.02 to 0.24% when the whole amount of the stainless steel is taken as 100% by mass and has an Md value of 0 to 80 as defined by the formula: Md=500-458(C+N)-9(Si+Mn)-14Cr-20Ni and in which compounds formed from the above components and having maximum diameters of 20μm or above reside in an amount of at most 30 pieces per 5g by mass of the stainless steel and the metal structure of the whole of the stainless steel is a mixed structure composed of recrystallized grains and unrecrystallized parts.

Description

Specification

Stainless steel sheet for parts and manufacturing method thereof

Technical field

TECHNICAL FIELD [0001] The present invention relates to a stainless steel plate processed as an industrial product and a method for producing the same, and in particular, has high strength, high fatigue characteristics and excellent workability, and further has high flatness and low residual stress. The present invention relates to a stainless steel plate for parts and a manufacturing method thereof. That is, the present invention relates to a stainless steel plate that exhibits excellent performance in many products and parts manufactured from a stainless steel plate or a steel strip (hereinafter sometimes collectively referred to as “stainless steel plate”), and its It relates to a manufacturing method. In particular, the present invention relates to a stainless steel plate suitable for a wide variety of parts used in industrial products, which is highly accurate and complicated as products become smaller, lighter, and more complicated.

Background art

[0002] A wide variety of parts are used inside and outside various industrial products such as automobiles, home appliances, IT equipment, and mobile phones. There are a wide variety of materials for each part, but many metal materials are used, and stainless steel is often used. Many of these parts made of stainless steel are manufactured from stainless steel plates by methods such as pressing and etching.

[0003] For example, in the case of press working, the stainless steel plate is formed into a predetermined shape using a die after being made into a predetermined size by cutting I ", blanking or the like. A typical example is the ability to list panel parts. Panel parts are used in many industrial products and may be used in many parts of a product. In addition, there are many types of panel parts, which are roughly divided into dish panels and plate panels. Specific examples include washers inserted between bolts and nuts, small dish panels used under mobile phone buttons, gaskets used in automobiles and motorcycles, and methanol packing.

On the other hand, in the etching process, a pattern is formed on the surface of the plate by a photoresist method, and a part of the material is corroded and removed (etched) by chemical means such as dipping in acid or spraying to cope with the pattern. It is to obtain a shape. Etching is difficult to press There are many applications to the processing of precision parts that are difficult, for example. This includes, for example, small parts such as the paper used for fixing magnetic heads, printer paper feed gears, shadow masks for conventional TVs that have an extremely large number of small holes, and meshes for printed circuit board printing. The power of S

[0005] In these parts using stainless steel, in recent years, there has been a tendency for the parts to be smaller, lighter, more complex and more accurate, and the following various characteristics have been further required.

• Strength: For panel parts, stress is applied, and there are many other parts that have the side of the structure.

• Formability: Complicating parts · With higher precision, it is necessary to process more complex shapes with high precision, so excellent formability is required. In general, the formability is proportional to the elongation (ductility) of the material, and the strength and elongation are in conflict (incompatible), and both high strength and excellent formability are required.

• Etching performance: Similarly, as parts become more complex and highly accurate, excellent etching performance is required to obtain a smooth machined surface free from defects such as locally generated holes (etching pits).

• Fatigue characteristics: Panel parts are often subjected to repeated fluctuating stress, and the amount of deformation increases with the reduction in size and weight. Moreover, although it is excellent at the material stage, it is required to be excellent as a part that is often greatly deteriorated by molding and to have high reliability.

• Flatness: High accuracy • Stablely acquires the shape of parts that continue to become more complex, and lowers the defect rate (increases the yield) when incorporated in products that are smaller and lighter. Must be stable.

• Residual stress: When taken from a relatively large material (relative to the part), the part is released from surrounding constraints and changes shape due to the release of residual stress. In other words, the parts do not show the prescribed shape, and the defect rate when assembled into a product (which is smaller and lighter) increases (yield decreases). For this reason, the force S is required that the residual stress is low and stable.

[0006] Conventionally, the above-mentioned parts and the like are metastable like SUS301 and SUS304. Stenai Kγ) stainless steel has been used. In the austenitic stainless steel, the transformation from the γ parent phase to the hard martensite phase (processing-induced martensite (α ′) transformation) can be caused by processing at room temperature. As a result, it is possible to obtain a stainless steel plate having high strength while having a certain degree of ductility. This processing is usually performed by cold rolling, and the strength can be adjusted by adjusting the rolling reduction of the cold rolling. High strength is obtained while having ductility because only the part is hardened by the transformation-induced martensite (α ') transformation, and local deformation is suppressed, and deformation into a soft untransformed part (γ part). Is propagated, and the whole is uniformly deformed to show high elongation. This is the TRI Ρ effect. Because of these features, metastable austenitic (γ) stainless steel is also classified as a stainless steel strip for springs in the JIS standard (IIS G 4313).

[0007] Further, regarding the fatigue properties of these stainless steels, Patent Document 1 discloses the fatigue characteristics due to the limitation of the dimensions of the compounds that are the starting points of fracture. Patent Document 2 discloses an improvement in etching properties by limiting the distribution of compounds that serve as starting points of etching pits (holes). Further, Patent Document 3 discloses improvement of formability and fatigue characteristics by refining crystal grains!

[0008] The production process of these metastable austenitic (γ) stainless steels is generally described as having a process as shown in FIG. In other words, the molten ingot is hot-rolled and annealed as necessary, and then cold-rolled and annealed as shown in Fig. 5 to reduce the thickness to a predetermined thickness. Next, temper rolling, shape correction, and strain relief annealing for strain relief are performed. Of these, temper rolling can reduce the thickness to the product sheet thickness, and at the same time adjust the performance by work hardening. When the temper rolling is completed, the thickness is reduced to the specified thickness so that the target performance can be obtained with the product thickness. After that, within the range that does not change the performance significantly, the residual stress is reduced by the flatness improvement by shape correction and the strain relief annealing for strain relief.

[0009] Further, Patent Document 4 and Patent Document 5 disclose a TA (Tension-Annealing) process as an improvement of the series of manufacturing steps. In this method, heating is performed at a relatively low temperature while applying tension within a range in which the performance after temper rolling is not significantly changed, and flatness improvement and residual stress reduction can be performed simultaneously. [0010] Further, as another manufacturing method, Patent Document 6 and Patent Document 7 describe a stainless steel manufacturing method having a temper annealing method and a high-performance metastable γ obtained by the temper annealing method. A stainless steel sheet is disclosed. The outline of the process is shown in Fig. 6. This means that a stainless steel material having a predetermined composition is softened by temper annealing of a material that has been work-hardened by cold rolling to a product sheet thickness, and the performance is adjusted. As a result, the material becomes a mixed structure of the recrystallized grains and the unrecrystallized portion that remains affected by the pre-processing, and it is possible to achieve both high strength and high ductility by optimizing the ratio. Furthermore, during temper annealing, transformation from work-induced martensite ( _α ') phase to austenite (γ) parent phase (this is referred to as "reverse transformation"), recovery and recrystallization occur, resulting in residual stress. Reduced. In addition, since reverse transformation is accompanied by volume change, softening can be adjusted by applying tension, and performance adjustment and shape correction can be performed relatively easily in a short time. That is, it is possible to reasonably and stably manufacture a high-performance material suitable for a material of a part that is incorporated in a product and used.

[0011] In Patent Documents 8 to 10, the rolling conditions and heat treatment conditions of the stainless steel plate as the material are specified, and transition and martensite are introduced into the crystal grains to increase the etching rate in the crystal grains. An increasing stainless steel sheet for photoetching is disclosed. This means that the smoothness of the etched surface is improved by making the etching rate in the crystal grains equal to that of the crystal grain boundaries.

Patent Document 1: Japanese Patent Application Laid-Open No. 2005-290449

Patent Document 2: Japanese Patent Laid-Open No. 2000-273586

Patent Document 3: Japanese Patent Laid-Open No. 5-279802

Patent Document 4: Japanese Patent Laid-Open No. 10-34237

Patent Document 5: JP 2001-226718

Patent Document 6: Japanese Patent No. 3603726

Patent Document 7: Japanese Patent Application Laid-Open No. 2002-194506

Patent Document 8: Japanese Patent Laid-Open No. 2005-314772

Patent Document 9: JP-A-2005-320586

Patent Document 10: Japanese Unexamined Patent Application Publication No. 2005-320587 Disclosure of the invention

Problems to be solved by the invention

[0013] However, a stainless steel plate capable of responding to the recent trend of miniaturization, weight reduction, precision, and accuracy of parts is required, and further improvement of the above-described characteristics has been a problem. Each invention shown in Patent Documents 1 to 3 has a limit and further performance improvement has been demanded. For spring materials in particular, improvement of fatigue characteristics after being processed as a product and improvement of workability (formability and etching property) capable of processing a miniaturized part with high accuracy were problems.

[0014] The manufacturing method has the same problem, and it has been an object to adopt a method for manufacturing a stainless steel plate that can solve the above-described problem. However, the conventional manufacturing method and the manufacturing methods of Patent Document 4 and Patent Document 5 have a limit in achieving both high strength and high ductility of the material. In addition, since the material is thinner and stronger, shape correction becomes difficult and the plate shape tends to deteriorate. In addition, strain relief annealing took a long time and became a factor that hindered productivity. In addition, since many parts are used, the plate thickness and hardness are different, and the amount used may be relatively small, these problems become prominent, resulting in a significant increase in product cost.

[0015] The manufacturing methods described in Patent Document 6 and Patent Document 7 have problems for coping with further improvement in workability by promoting the tendency to reduce the size and weight of products and parts, and expanding the variety of products. It was.

[0016] The stainless steel plates for photoetching described in Patent Documents 8 to 10 have a strength that is not necessarily provided with good strength, ductility, and fatigue properties, although etching smoothness can be obtained. Thus, there is a problem that further performance improvement is necessary.

[0017] Therefore, the present invention provides a stainless steel plate capable of improving workability (formability, etching property) and fatigue characteristics while having good strength and ductility, and a method for producing the stainless steel plate. Let it be an issue. Furthermore, another object is to stably supply the stainless steel plate of the present invention at low cost and industrially by the method for producing the stainless steel plate. Means for solving the problem

[0018] As a result of intensive studies, the present inventors have obtained the following knowledge and the like in order to solve the above problems. The present invention has been completed. That is, a mixed structure for improving the properties of a stainless steel sheet that could not be obtained by a conventional stainless steel sheet and its manufacturing method (a recrystallized structure of high ductility and an unrecrystallized structure in which a high-strength work-induced martensite phase remains) To obtain a tissue that is mixed). To that end, we investigated in detail the effects of the final rolling rate and material composition in a series of rolling processes. As a result, it was found that workability and fatigue characteristics can be improved by a stainless steel plate having a mixed structure as described later and its manufacturing method.

[0019] The details are based on the following knowledge.

The performance is improved by the structure having the ω mixed structure. This is because the recrystallization part in the mixed structure has the effect of strengthening by grain refinement and the suppression of non-uniform deformation at the grain boundary due to the increase in density, while the non-recrystallized part in the mixed structure has work hardening and reverse transformation. There is a TRIP effect due to the processing-induced α 'transformation from the _γ phase. This allows the materials to maintain their combined effect strength and strength. In addition, the deformation progresses uniformly and the formability (ductility) is improved. Similarly, the etching property can be considered, and it is considered that the etched surface becomes uniform due to the refinement of crystal grains and the increase in the single structure of the γ parent phase. As a result, the non-uniform portion that becomes the starting point of fatigue fracture disappears, and the fatigue characteristics after molding and after etching are improved.

[0020] (b) It is possible to improve the workability and fatigue characteristics of the material by optimizing various conditions such as the material composition and adjusting the mixed structure of the stainless steel plate and the distribution of the underlying compound. Specifically, in addition to the mixed structure, by reducing the number of compounds with a maximum diameter of 20 m or more per mass of 5 g to 30 or less, defects that are manifested by processing are not observed, and the surface of the processed part becomes smooth. Become. As a result, the fatigue strength of 90% or more is maintained after machining. Since fatigue failure occurs due to stress concentration on the defect, we believe that the same strength improvement can be achieved by reducing this defect.

[0021] (c) Regarding the production method, the tensile force applied to the stainless steel plate during production is changed, or the ratio of the recrystallized grains composed of the _γ phase in the structure of the stainless steel plate is changed, or the γ phase in the unrecrystallized portion Change the ratio. This is because, when a production method with temper annealing is applied, from the α ′ (work-induced martensite) phase with volume change to the γ matrix. This is because the reverse transformation of is controlled by the tension during temper annealing. Since the softening is moderated by the application of the tension, it is considered that the increase in the tension suppresses the reverse transformation and increases the amount of α ′ (processing induced martensite) remaining. That is, the metal structure of the stainless steel can be controlled by the tension.

[0022] However other hand, if the tension is too large, _I phase of non-recrystallized portion is found you to transform to alpha 'phase during cooling. This is thought to be due to work-induced martensitic transformation (α ') occurring below the specified temperature during cooling due to the influence of tension, in addition to the work strain in which the γ phase remains in the unrecrystallized part. Therefore, the tension to be applied must be performed within a predetermined range in consideration of reverse transformation.

[0023] (d) As for the manufacturing method, the final cold rolling can pulverize and refine the compound by increasing the reduction ratio. This is one of the advantages of performance adjustment as a separate process (temper annealing), and temper rolling is inevitably performed at a predetermined processing rate for performance adjustment.

[0024] Hereinafter, the present invention will be described.

[0025] The invention as described in claim 1 is the entire stainless steel is taken as 100 mass%, 0.1 to C 01-0. 08 mass ^_0/0, Si and 0. 1 2. 0 weight ^_0/0, Mn and 3.0 mass ^_0/0 or less, the Cr 10. 0-20. 0 wt ^_0/0, Ni 3. 0-12. 0 wt ^_0/0, N and 0.02 -0. containing each ingredient 24 mass ^_0/0, and the formula wherein is contained the values of the mass% of each component is substituted

Md = 500-458 (C + N) -9 (Si + Mn) -14Cr-20Ni

The compound having a chemical composition in which the Md value represented by the formula 0 to 80 is satisfied, and the balance is an unavoidable impurity, and the maximum amount of the compound formed by each component is 20 m or more. By providing a stainless steel sheet for parts, wherein the number of stainless steel is 30 or less per 5 g of stainless steel, and the metal structure of the entire stainless steel is a mixed structure of recrystallized grains and non-recrystallized parts. The problem is solved.

[0026] The invention described in claim 2 is the whole stainless steel is taken as 100 mass%, 0.1 to C 01-0. 08 mass ^_0/0, Si and 0. 1 2. 0 weight ^_0/0, Mn and 3.0 mass ^_0/0 or less, the Cr 10. 0 to 20. 0 wt ^_0/0, Ni of 3.0 to 12.0 mass ^_0/0, N and 0.02 to 0. 24 wt ^_0/0, and Nb, Ti, and containing each component at least one of 0.5 mass% or less selected from V, and the hydrated Formula that substitutes the mass% value of each component

Md = 500-458 (C + N) -9 (Si + Mn)-14Cr-20Ni- 65Nb- 27Ti- 61V Md value of 0 ~ 80 is satisfied, the balance is unavoidable chemical composition And the internal diameter of the compound having a maximum diameter of 20 m or more among the compounds formed by each component is 30 or less per 5 g of the stainless steel mass, and the metal structure of the entire stainless steel is The problem is solved by providing a stainless steel sheet for parts, which is a mixed structure of recrystallized grains and non-recrystallized parts.

[0027] The invention described in claim 3 is characterized in that the average grain size of recrystallized grains of the stainless steel sheet for parts described in claim 1 or 2 is 10 m or less. To do.

[0028] The invention described in claim 4 is characterized in that the mixed structure of the stainless steel sheet for parts described in claim 3 is an austenitic phase of 70 mass% or more.

[0029] The invention described in claim 5 is the entire stainless steel is taken as 100 mass%, 0.1 to C 01-0. 08 mass ^_0/0, Si and 0. 1 2. 0 weight ^_0/0, Mn and 3.0 mass ^_0/0 or less, the Cr 10. 0-20. 0 wt ^_0/0, Ni 3. 0-12. 0 wt ^_0/0, N and 0.02 -0. containing each ingredient 24 mass ^_0/0, and the formula wherein is contained the values of the mass% of each component is substituted

Md = 500-458 (C + N) -9 (Si + Mn) -14Cr-20Ni

A first cold rolling step (S1) in which a material having a chemical composition with an Md value of 0 to 80 and a balance of inevitable impurities is cold-rolled at least once (S1), The first annealing step (S2) arranged after the first cold rolling step in combination with the hot rolling step, and the final rolling provided on the subsequent step side of the first annealing step, with a reduction rate of 20% The second cold rolling step (S3) in which the total rolling reduction with the first cold rolling is 60% or more, and the material after the second cold rolling step is 650 to 1000 ° C. And a second annealing step (S4) in which the material is held at 300 seconds or less and tempered by applying a tensile strength of 0.2% or less of the material at the held temperature. Solve the problem.

[0030] The invention described in claim 6 is the entire stainless steel is taken as 100 mass%, 0.1 to C 01-0. 08 mass ^_0/0, Si and 0. 1 2. 0 weight ^_0/0, Mn and 3.0 mass ^_0/0 or less, the Cr 10. 0 to 20. 0 wt ^_0/0, Ni of 3.0 to 12.0 mass ^_0/0, N and 0.02 to 0. 24 wt ^_0/0, and Nb, Ti, and containing each component at least one of 0.5 mass% or less selected from V, and the hydrated Formula that substitutes the mass% value of each component

Md = 500-458 (C + N) -9 (Si + Mn)-14Cr-20Ni- 65Nb- 27Ti- 61V Md value of 0 ~ 80 is satisfied, the balance is unavoidable chemical composition A first cold rolling step (S1) for cold rolling a material having at least once, and a first annealing step arranged after the first cold rolling step in combination with the first cold rolling step ( S2) is the final rolling provided on the post-process side of the first annealing process, and the second rolling reduction ratio is 20% or more and the total rolling reduction ratio with the first cold rolling is 60% or more. Holds the material after the cold rolling step (S3) and the second cold rolling process from 650 to; at 300 ° C for 300 seconds or less, and at the same temperature, less than 0.2% resistance to the material. The above-mentioned problems are solved by providing a method for producing a stainless steel sheet for parts, which includes a second annealing step (S4) in which tension is applied to perform tempering.

[0031] The invention described in claim 7 is the material at a temperature where the tension in the second annealing step of the method for manufacturing a stainless steel sheet for parts according to claim 5 or 6 is maintained. 0. 40% or less of 2% yield strength.

[0032] The invention described in claim 8 is further adjusted after the second annealing step (S4) in the method for manufacturing a stainless steel plate for parts according to any one of claims 5 to 7. It is characterized by applying quality rolling.

The invention's effect

[0033] According to the present invention, it is possible to provide a stainless steel plate and a method for manufacturing the same that can manufacture a wide variety of parts with high accuracy and high reliability. In particular, according to the present invention, it is possible to provide a stainless steel plate that is excellent in formability and fatigue characteristics after forming and is highly reliable at low cost and industrially stably. In addition, in response to recent environmental problems, it is possible to further promote the effective use of resources by reducing the size and weight.

Brief Description of Drawings

FIG. 1 is a diagram for explaining one embodiment of the flow of the production method of the present invention.

FIG. 2 is a graph showing an example of the relationship between the temperature of a material and the 0 · 2% proof stress.

[Fig. 3] The hardness and elongation of the stainless steel plate prepared based on the results obtained in this example.

[FIG. 4] The surface of the bent portion in the case of No. 4 and No. 28 of this example is shown enlarged. It is a photograph.

FIG. 5 is a diagram for explaining one example of a conventional method for producing a stainless steel plate.

FIG. 6 is a view for explaining another example of a conventional method for producing a stainless steel plate.

Explanation of symbols

[0035] S1 First cold rolling process

S2 First annealing process

S3 Second cold rolling process

S4 Second annealing process

BEST MODE FOR CARRYING OUT THE INVENTION

[0036] The above-described operation and gain of the present invention will become apparent from the best mode for carrying out the invention described below.

[0037] The best mode of the present invention and preferred ranges thereof will be described below.

(1) Stainless steel plate

First, the stainless steel plate of the present invention will be described. As described above, the stainless steel sheet of the present invention is characterized by its composition and structure, Md value, and the mode of the underlying compound. Each will be described below.

[0038] (1 1) component

The component contained in this invention and its content are demonstrated. The main component of the stainless steel plate of the present invention is Fe, and the contents shown below show the ratio when the entire stainless steel plate is 100 mass%.

[0039]-C: The content of C is set to 0.01 to 0.08 mass%. C is one of the cheap and effective interstitial solid solution strengthening elements. The effect of strengthening the solid solution by adding 0.1% by mass or more is exhibited. On the other hand, the upper limit is 0.08% by mass. This is because C is a strong γ-stabilizing element, and excessive addition suppresses the processing-induced martensite (α ') transformation that is necessary. In addition, in the case of a manufacturing method including temper annealing, a Cr C compound is substituted during temper annealing.

23 6

This is because coarse carbides are precipitated at the grain boundaries represented, and the workability and corrosion resistance are deteriorated. A more preferable range of the C content is 0.02-0.07% by mass.

[0040]-Si: Si content should be 0 .;!-2.0 mass%. Si is an effective solid solution strengthening element. The reason why the lower limit is set to 0.1% by mass or more is that this increases the high-temperature strength and facilitates acquisition of the above-mentioned mixed structure, which is a feature of the present invention. The upper limit was set to 2.0% by mass because Si is also a ferri (α) stabilizing element, and excessive addition increases the α and phase remaining during temper annealing. A more preferable range of the Si content is 0.2 to 1.8% by mass.

[0041] .Mn: The Mn content is 3.0 mass% or less. Mn is a γ-stabilizing element and is added in consideration of the balance with other elements. The reason why the content is 3.0% by mass or less is that when it is added excessively, α and compatibility S cannot be obtained. In addition, inclusions and the like may be formed, which may deteriorate workability and corrosion resistance. A more preferable range of the Mn content is 2.6% by mass or less.

[0042]-Cr: The content of Cr is 10.0 to 20.0 mass%. Cr is one of the basic alloy elements of stainless steel. The reason why the content is 10.0% by mass or more is to obtain the necessary corrosion resistance. The upper limit was set to 20.0% by mass because Cr is an α-stabilizing element, and excessive addition increases the α ′ phase remaining after temper annealing. A more preferred range of Cr content is 13. 0-19. 0 wt ^_0/0.

[0043] Ni: The Ni content is 3.0 to 12.0% by mass. Ni is one of the basic alloy elements of stainless steel and is the most effective _gamma stabilizing element. The reason why the lower limit is set to 3.0% by mass is that it is indispensable for obtaining a stable γ phase at room temperature. The upper limit is set to 12.0% by mass because it is necessary to cause the α ′ transformation within a predetermined range. A more preferable range of the Ni content is 3.5-11. 5% by mass.

[0044] The content of N: N is 0.02 to 0.25% by mass. N is one of the effective interstitial solid-solution strengthening elements like C, and it has the ability to form a solid solution without forming a compound up to a higher temperature than C. That is, it is the main reinforcing element of the present invention. From this point of view, the lower limit was set to 0.02 mass%. The upper limit is set to 0.25% by mass because when it is added excessively, the hot workability is deteriorated and the production of the plate may be hindered. N, like C, is one of the powerful γ-stabilizing elements, and it also depends on suppressing α ′ transformation. A more preferable range of the content is 0.04-0.20%, a more preferable range is 0.08-0.02%, and a most preferable range is 0.10-0.20% by mass. [0045] Nb: The content of Nb is 0.50 mass% or less. Nb precipitates Nb compounds that are relatively stable and finely dispersed even at high temperatures, making it easy to obtain a mixed structure, and recrystallized grains can be refined by suppressing grain growth. The upper limit is set to 0.50% by mass because excessive addition forms a coarse compound and lowers the ductility of the material. Moreover, since it is an expensive substance, an upper limit is set from the viewpoint of cost. A more preferable range of Nb is 0.45% by mass or less.

[0046] -Ti: The Ti content is 0.50 mass% or less. Ti is considered to have the same effect as Nb. In other words, the precipitation of Ti compound facilitates the acquisition of the mixed structure, and the recrystallized grains can be refined. In addition, it is thought to form compounds more easily than Nb. The upper limit is set to 0.50% by mass because excessive addition forms a coarse compound and lowers the ductility of the material. The Ti content is more preferably 0.45% by mass or less

Yes

[0047] -V: The content of V is 0.50 mass% or less. V has the same effect as Nb and Ti.

That is, the precipitation of the V compound facilitates the acquisition of the mixed structure and refines the recrystallized grains. The upper limit is set to 0.50% by mass because excessive addition forms a coarse compound and lowers the ductility of the material. A more preferable range of the V content is 0.001% by mass or more and 0.45% by mass or less.

[0048] In addition to the above components, elements added from an industrial aspect, such as Ca, A1 or REM (rare earth metal) used as a deoxidizer during melting, and B, which is expected to improve hot workability, are required. Depending on the content, the total amount may be 0.3% by mass or less. In addition, when scrap is used as a raw material, each of Cu and Mo, which are inevitable, may be contained in an amount of 0.4% by mass or less. Cu and Mo act as elements for adjusting the γ stability in the present invention. In addition, inevitable impurities in a normal composition may be included.

[0049] (1 2) Nao Tsuji

The Md value is calculated according to the formula (1) or formula (2) in the present invention, and the value is 0 to 80 ° C. Here, if at least one of the Nb, Ti, and V forces, which are not unavoidable impurities, is selected, formula (2) is used. If neither is added, it is calculated using equation (1). Also, the symbols C, N, Si, M in the formula For n, Cr, Ni, Nb, Ti, and V, the content (% by mass) of the corresponding component is substituted.

Md = 500-458 (C + N) — 9 (Si + Mn) — 14Cr— 20Ni · · · (1)

Md = 500-458 (C + N) — 9 (Si + Mn) — 14Cr— 20Ni

-65Nb- 27Ti- 61V (2)

Md value. It is expressed in units of C and indicates the ease with which processing-induced martensite (α ') transformation occurs. Based on the results of a series of experiments in the present invention, the temperature (30 ° C) at which 50% of the whole transforms into the α 'phase when 30% tensile deformation is applied to the γ single phase material. It is a formulation. As described above, the present invention targets metastable γ stainless steel and utilizes the α ′ transformation, so it is necessary to control the α ′ transformation. Therefore, the optimum Md value for this purpose was set to 0 to 80 ° C. More preferably, it is 10-70 degreeC.

[0050] (1 3) Compound Embodiment

In the stainless steel plate of the present invention, in the compounds contained in the stainless steel plate, those having a maximum diameter of 20 m or more are inherent in 30 or less per 5 g of the mass of the stainless steel plate. As a result, the occurrence of defects due to the compound can be reduced. That is, it is considered that the material has excellent moldability, and the probability that a coarse compound exists in the vicinity of the surface becomes extremely small. In the case of pressing, unevenness and minute cracks due to a large difference in deformability between the two (material and coarse compound) are improved. In the case of the etching process, the occurrence of local defects such as compound exposure due to the difference in corrosion resistance, and further, holes (etch pits) due to dropping off is eradicated. As a result, the surface of the machined part becomes smooth and the fatigue characteristics are improved. This local defect is considered to be detected by measuring the maximum roughness of the surface of the processed part.

[0051] (1 4) Aspect of organization

The material structure of the stainless steel sheet of the present invention is a “mixed structure” defined by a mixed structure of recrystallized grains and unrecrystallized parts that remain affected by pre-processing. As a result, it is possible to achieve both high strength and high ductility, as well as high flatness and low residual stress. The mixed structure may have a γ phase force of 70 area% or more. By forming the γ phase as the main structure, formability and fatigue characteristics are further improved. More preferably, it is 80 area% or more.

[0052] By using the stainless steel plate as described above, the various properties are excellent. Further, it is possible to provide a stainless steel sheet that can improve workability (formability, etching property) and fatigue characteristics. In addition, the grain size of recrystallization may be 10 m or less. This further improves the formability and fatigue characteristics resulting from the refinement of crystal grains. More preferably, it is 6 m or less.

[0053] (2) Manufacturing method of stainless steel sheet

Next, one embodiment of the method for producing a stainless steel plate of the present invention will be described. As shown in FIG. 1, the method for producing a stainless steel plate of the present invention comprises a first cold rolling step (S 1) that is at least one cold rolling step, and a first cold rolling step (S1 ) And at least one first annealing step (S2), a second cold rolling step (S3), and a second annealing step (S4) that is annealing for tempering. is there. Each is described below

[0054] (2-1) First cold rolling process (S1)

In the first cold rolling step (S1), a material that has been hot-worked by adding the above-described components is supplied. This process is performed mainly for the purpose of bringing the dimensions of the material closer to the steel sheet that is finally obtained. Therefore, the rolling may be performed several times, not necessarily once. Specifically, if the total rolling reduction with the second cold rolling performed later is 60% or more, preferably 70% or more, more preferably 80% or more, most preferably 90%. That's it.

[0055] (2-2) First annealing step (S2)

This is a process that is combined with the first cold rolling process (S1), and is a process mainly intended to impart softening and ductility of the material. Therefore, the conditions are not particularly limited as long as the annealing process is performed normally. The conditions are determined by the material to be supplied and the form of the steel sheet finally obtained.

[0056] (2-3) Second cold rolling process (S3)

The second cold rolling step (S3) is a step that is arranged after the first cold rolling step (S1) and the first annealing step (S2) and performs the final cold rolling. In the second cold rolling step (S3), the thickness is reduced to the final thickness of the stainless steel plate. At this time, the thickness reduction is 20% or more in terms of rolling reduction, and the total rolling reduction with the first cold rolling is 60% or more. This reduces the rolling reduction by 20 This is because a sufficient work-induced martensite (α ′) phase can be obtained by setting the content to at least%. Furthermore, this makes it possible to refine crystal grains. Preferably it is 30% or more. In addition, the total reduction ratio of the first cold rolling and the second cold rolling was set to 60% or more. By increasing the reduction ratio, the compound was finely pulverized to obtain a coarse compound of 20 inches or more. The number of can be reduced. This makes it possible to reduce the maximum diameter of the compound and reduce the number of coarse compounds of 20 m or more. At this time, cold rolling using a small-diameter work roll is preferable because the effect of crushing coarse compounds is high.

[0057] (2-4) Second annealing step (S4)

The second annealing step (S4) is the final annealing step, and this determines the material aspect of the stainless steel plate that can be finally obtained. Specifically, in this step, the annealing temperature was set to 650 to 1000 ° C, and the holding time was set to 300 seconds or less. This is specified from the viewpoints of adjusting the mechanical properties of the material and also affecting the metal structure of the material, such as crystal grain growth, and the production efficiency. This makes it possible to obtain a stainless steel plate that is efficient and has high flatness and low residual stress.

[0058] Further, in the second annealing step (S4), the annealing temperature is set and tension is applied to the material. The magnitude of the tension is less than 0.2% resistance of the material at the annealing temperature. More preferably, it is 40% or less of the 0.2% proof stress. The reverse transformation is adjusted by applying tension to the material at such a size. Accordingly, fine recrystallized grains are included in the material, and the material can have a mixed structure with a high proportion of γ phase. As a result, the obtained stainless steel sheet is given a well-balanced strength and ductility, and both high flatness and low residual stress can be achieved. Figure 2 shows a graph showing an example of the relationship between the temperature of the material and the 0.2% proof stress value of the material. For example, the tension is determined and applied according to FIG.

[0059] As a method for refining inclusions, it is preferable to take measures for enhancing floating separation of coarse inclusions during melting. This includes a method in which coarse inclusions are floated and separated by extending the heating and holding time of the molten metal. In addition, there can be mentioned a method of finely crushing coarse inclusions by performing the first cold rolling step (S 1) and the second cold rolling step (S 2) with a small-diameter roll. In addition, the above two methods are combined. A compound strength with a maximum diameter of 20 or more contained in a stainless steel plate that can be added is acceptable as long as it can be reduced to 30 or less per 5 g of the mass of the stainless steel plate.

Furthermore, temper rolling can be performed after the second annealing for the purpose of increasing the strength, etc., as long as the effect of the inclusion distribution and the mixed structure exhibiting high performance can be maintained. It is.

[0060] With such a method for producing a stainless steel plate for parts, the stainless steel plate for parts of the present invention can be produced. That is, it is possible to produce and provide a stainless steel plate that can improve the caloric properties (formability, etching property) and fatigue properties while making the above various properties excellent. According to the production method, the stainless steel sheet of the present invention can be supplied inexpensively and industrially stably.

Example

[0061] Next, the embodiment will be described in more detail. However, the present invention is not limited to the examples. In the examples, a stainless steel plate corresponding to the present invention and a stainless steel plate not corresponding to the present invention were manufactured and subjected to various evaluations.

[0062] (i) Manufacture of test materials

Table 1 shows the composition of the specimens. Among each component, those outside the scope of the present invention are marked with “*” for the content number.

[0063] [Table 1]

Composition (Quality ¾) d Remark Steel c Si Mn Cr Ni N Nb Ti V (¾) a 0.021 0.23 0.25 18.46 4.62 0.203 0.001 <0.001 0.001 42.2-b 0.025 0.48 1.28 17.08 6.83 0.118 <0.001 0.001 0.001 42.9- c 0.054 0.52 1.21 13.03 10.60 0.116 0.001 0.001 <0.001 12.2-d 0.027 0.49 1.27 17.09 6.87 0.110 0.295 0.001 0.001 25.6-e 0.026 0.50 1.25 17.14 6.88 0.119 0.001 0.282 0.001 32.7-f 0.024 0.52 1.29 17.02 6.94 0.121 0.001 <0.001 0.276 23.4-g 0.127 * 0.53 1.12 25.01 * 2.0 0.042 * 0.001 0.001 0.001 17.4 *-

0.124 * 3.29 * 1.16 17.41 6.99 0.289 * 0.001 <0.001 -112.7 *-i 0.024 0.52 1.19 17.11 7.01 0.124 0.694 * 0.001 0.001 -8.0 *-j 0.021 0.49 1.31 17.14 6.91 0.127 0.001 0.596 * 0.001 21.8 *-k 0.118 * 0.61 1.12 17.09 7.04 0.060 0.002 0.001 0.001 22.6 SUS301 steel

I 0.060 0.58 0.83 18.36 8.24 0.050 0.003 0.001 0.001 1.8 Stainless steel 304

Md = 500-458 (C + N) -9 (Si + n) -14Cr-20Ni

Or

Md = 500-458 (C + N) -9 (Si + Mn) -14Cr-20Ni-65Nb-27Ti ~ 61V

[0064] A stainless steel plate was manufactured according to each manufacturing condition for each of the materials having the compositions shown in Tables 1 to 1. Table 2 shows the main conditions in the manufacturing process.

[0065] [Table 2]

Test steel Manufacturing process Inclusion miniaturization measures 1st and 2nd cold 2nd cold rolling 2nd annealing process

No.

Steel Heating time Small diameter Low Rolling ratio ： Dish degree Tension meter rolling ratio Time

(%) (*) (° C) (seconds) (%)

1 a Implementation-95 50 800 30 30

2 b Implementation-95 50 S00 30 30

3 b Implementation-95 30 800 30 30

4 b Implementation-95 50 800 30 30

5 b Implementation-95 70 800 30 30

6 b Implementation 95 50 800 180 30

7 b Implementation 95 50 800 30 50

8 b Implementation-95 50 800 30 70

9 b Implementation-95 60 700 30 30

10 b Implemented Implemented 95 70 800 30 30

1 1 c Implementation-95 30 900 30 30

12 c Implementation-95 50 900 30 30

13 c Implementation-95 50 800 30 30

14 d Implementation-80 50 900 30 30

1 5 d Implementation-80 50 800 30 30

16 e Implementation-80 50 900 30 30

17 f-Implementation 80 50 900 30 30

18 b Implementation-55 * 10 * 700 30 30

19 b--50 * 10 * 800 30 30

20 b Implementation-95 50 1100 * 30 30

21 b Implementation-95 50 800 * 30 30

*

22 g implemented-80 50 900 30 30

23--80 50 800 30 30

*

24 1--80 50 800 30 30

*

25 J--80 50 800 30 30

26 k * out 80 50 S00 30 30

27 k * Implementation-temper rolling, forced shape, straightening annealing 500¾, 300 seconds

28 k * Implementation--Temper rolling, forced shape, straightening annealing 500¾, 300 seconds

29 k * Implementation--Temper rolling, forced shape, straightening annealing 500 ° C, 300 seconds

30 1 * Implementation--Temper rolling, forced shape deformation annealing 500 ° C, 300 seconds

31 r Perform Temper rolling, forced shape, Straightening annealing 500 ° C, 300 seconds

32 r Execution-Temper rolling, shape forced strain relief annealing 500 ° C, 300 seconds With reference to Table 2, the production method will be described in detail. In Table 2, “*” is given to those outside the scope of the present invention. The process up to cold rolling is common to all manufacturing conditions. Specifically, small ingots are melted and cut, hot rolled, and annealed. , If descaling (pickling). In addition, the examples shown in Table 2 (No. l to No. 16, No. 18, No. 20 to No. 22, and No. 26 to No. 32) are coarse at the time of melting as countermeasures for the refinement of inclusions. The heating and holding time of the melt was extended to enhance the floating separation of inclusions.

[0067] For the steel materials indicated as No. 1 to No. 26 for the materials obtained in this way, a part of the steel materials was adjusted by cutting and pickling, and then the first cold rolling and annealing, Second cold rolling and second annealing were performed under the conditions shown in Table 2. The plate thickness was finally 0.2 mm. Here, in the examples shown in No. 10 and No. 17, the roll diameter used for cold rolling as a countermeasure for inclusion miniaturization is 60 mm in diameter compared to the 200 mm diameter work roll used elsewhere. A small diameter work roll was used.

On the other hand, in the examples of No. 27 to No. 32, as shown in Table 2, temper rolling was performed to a thickness of 0.2 mm, and each hardness specification defined in JI S G 4313 was used. Then, straightening with a tension leveler, 500 ° C heating, and strain relief annealing for 300 seconds were performed. The work rolls used in the cold rolling were those with a diameter of 200 mm.

[0069] Test pieces were collected from the 0.2 mm-thick thin plate obtained as described above, and various characteristics were investigated and compared.

[0070] (ii) Evaluation item and evaluation method

Evaluation items and evaluation methods will be described below.

Compound distribution: First, a 5 g sample was taken, and the base metal part was removed by corrosion with a 10% bromine methanol solution. Thereafter, the residue was extracted through a filter having a predetermined size, and the residue was observed using a scanning electron microscope (SEM) to obtain a total number of compounds having a maximum diameter of 20 am or more. .

[0071] Crystal grain size: Regarding the cross section of the sample parallel to the rolling direction (R. D.), the structure after embedding, polishing and etching was observed using an optical microscope and SEM. In addition, a thin film was formed and the structure was observed using a transmission electron microscope (TEM). Then, a photograph of an average structure was taken in each, and the crystal grain size was measured from the photograph. This also determined whether the tissue was a mixed tissue.

[0072] The crystal grain size is No .;! To No. 26 is the value of recrystallized grains after temper annealing,

27 to No. 32 indicate the straightness after the second annealing step. Here, No. 27 to No. 32 In Table 3, since it is deformed by temper rolling and becomes expanded, it is shown in parentheses in Table 3. Also

It was assumed that there was no change in particle size due to strain relief annealing.

[0073] γ phase ratio: A diffraction pattern was measured on the surface of the plate using an X-ray diffractometer, and the ratio of the _negative phase and the α 'phase was calculated from the integrated intensity ratio of each phase peak.

[0074] Hardness: The surface of the plate was measured at a load of 9.8 mm using a Micro'Vickers hardness tester.

[0075] Elongation: Samples taken in parallel with the rolling direction (R. D.) and measured for an IS-3Β test piece were measured using an Instron type tester.

[0076] Surface roughness: The maximum height (Ry) of the surface roughness was measured using a laser microscope on the surface of the outer periphery of the strip-shaped specimen taken perpendicular to the RD before and after the square bending at a bending radius of 2 mm. And

Rate of increase (%) = 100 X (Ry after bending, Ry before processing) / (Ry before processing).

[0077] Fatigue properties: Using a swing-type plane bending tester, the fatigue limit (the upper limit of the stress that can withstand 107 repeated bendings) in a material that has not been bent was clarified. Next, the test specimens whose surface roughness was used for the measurement bending were repeatedly bent at a stress of 90% of the fatigue limit of the material, and the presence or absence of cracks after 107 repeated bendings was investigated. The case of cracking was evaluated as X, and the case of cracking force was evaluated as ○.

Plate warpage: In this example, flatness was evaluated by plate warpage. The method is to measure the height of the rising warp by hanging the test piece of 500mm in length taken parallel to R.D. before and after temper annealing or shape correction + strain relief annealing.

Decrease rate (%) = 100 X (warp after treatment warp before treatment) / warp before treatment

It was evaluated by.

[0079] Residual stress: For specimens collected before and after temper annealing or shape correction + strain relief annealing, the residual stress at RD on the plate surface was measured using an X-ray stress measurement device, and decreased. Rate (%) = 100 X (post-treatment stress pre-treatment stress) / pre-treatment stress

It was evaluated by.

[0080] (iii) Results Next, the results will be described. First, the structure and structure of the obtained stainless steel sheet will be explained. Table 3 shows the results.

[Table 3]

Compound Organization / Structure

Steel Maximum monster 20 m or more Recrystallized grain size r Phase ratio Remarks

Total number of compounds (pieces)

(%)

a 8 Mix 2 98 Invention Example b 6 Mix 1 1 99 Invention Example b 10 Mix 4 95 Invention Example b 6 Mix 3 95 Invention Example b 8 Mixer 2 99 Invention Example b 6 Mix 5 96 Invention Example b 6 Mixing 2 66 Invention Example b 6 2 57 Invention Example b 6 m ≤2 84 Invention Example b 0 Mixing 2 98 Invention Example

c 13 KON CI 14 100 Invention example

c 4 12 96 Invention Example c 4 4 93 Invention Example d 1 1 4 94 Invention Example d 1 1 itXi 2 92 Invention Example

e 9 3 94 Invention Example f 24 3 96 Invention Example b 26 Non-recrystallized * (None) 99 Comparative Example b 42 * Mixed 16 91 Comparative Example b 6 Recrystallized 22 100 Comparative Example b 6 Uncrystallized-(None) 7 Comparison example

*

g 18 (None) 0 Comparative example h * 32 * Mixed 14 100 Comparative example

*

1 50 * Mix ≤2 96 Comparative Example

*

J 34 * Mix <2 97 Comparative Example k * 12 Obtained 16 100 Comparative Example k * 13 Soil B *

Kiso g (24) 30 Comparative example

8 Not connected (24) 10 Comparative example

10 Not re-read (24) 3 Comparative example

8 Not recrystallized * (26) 60 Comparative example

16 Not regenerated ¾¾3 days (26} 42 Comparative Example

20 Sat

Wood yield fi ± 曰 * (26) 30 Comparative example As can be seen from Table 3, No. satisfying the conditions of the production method of the present invention; With respect to 17, all compounds having a maximum diameter of 20 m or more were 30 or less, and a mixed tissue could be obtained. On the other hand, in each of No. 18 to No. 32, there was a problem that the number of compounds having a maximum diameter of ¾0 m or more was 30 or more, or the structure was not a mixed structure. It appears prominently.

Next, various characteristics of the obtained stainless steel plate will be described. Table 4 shows the results.

[0084] [Table 4]

Increased surface roughness

Hardness Elongation Increase in sheet warpage Residual stress Tempering symbol

Rate (%) Bending fatigue

Addition rate Increase rate (JIS G Remarks Labor characteristics

(%) (%) 4313)

(Hv) (%) Etching

370 43.6 -83 47 o-84 -82-Example of the present invention

31 1 46.6 -48 54 o -92 -94-Example of the present invention

382 42.4 -76 44 o -83 -81-Example of the present invention

396 42.9 -78 40 o -82 -82-Example of the present invention

404 38.2 -81 36 o -79 -81-Example of the present invention

361 46.8 -77 48 o -86 -88-Example of the present invention

399 33.9 -81 52 o -89 -86-Example of the present invention

402 32.9 -81 53 o -92 -84-Example of the present invention

443 31.9 -86 52 o -81 -82-Example of the present invention

398 46.3 -90 30 o -82 -84-Example of the present invention

297 48.6 -41 59 o -92 -93-Example of the present invention

302 43.7 -54 55 ○-90 -94-Example of the present invention

339 49.8 -80 41 o -87 -84-Example of the present invention

329 52.8 -54 42 o -87 -92-Example of the present invention

401 39.5 -88 33 0 -84 -86-Example of the present invention

376 45.3 -89 38 0 -85 -89 ― Example of the present invention

382 41.7 -84 36 o -88 -84-Example of the present invention

21 1 48.2 148 392 X -82 -83-Comparative example

283 39.5 169 319 X -85 -84-Comparative example

192 51.8 81 218 X -96 -98

461 1 5.8 75 462 X -36 -39-Comparative example

328 1 6.4 -48 296 X 13 -46-Comparative example

520 4.1 189 892 {X) X -46 -54-Comparative Example

472 13.6 198 394 X -92 -91-Comparative Example

468 12.8 207 491 (x) X -90 -93-Comparative example

246 32.5 169 277 X -96 -94-Comparative Example

340 34.2 79 221 X -40 -38 301 -1 / 2H Comparative example

389 24.5 24 24S X -36 -34 301 -3 / 4H Comparative example

473 8.9 64 324 X -31 -18 301-H Comparative example

295 30.8 48 205 X -42 -42 304-1 / 2H Comparative example

354 18.4 36 274 X -38 -45 304-3 / 4H Comparative example

394 7.2 50 358 X -42 -40 304-H Comparative Example FIG. 3 shows the relationship between hardness and elongation based on the results of the examples. Table 4 and Figure 3 As can be seen, No. 1 to No. 17 which is an example of the present invention has higher strength and higher ductility than any of No. 18 to No. 32 which are comparative examples.

[0086] Further, in the examples of the present invention, the increase rate of the maximum value of the surface roughness after bending is all 60% or less, and the improvement of formability is exhibited by the progress of uniform deformation. Figure 4 shows a photograph of the surface before and after bending and the surface roughness (Ry) at that time. Specifically, the invention example (No. 4) and the comparative example (No. 28) are shown for a flat plate, a bending radius of 2 mm, and a bending radius of 0.5 mm. These photos and the value of Ry can also see the effect of the present invention. In particular, in the case of flat plates, when stainless steel plates are subjected to force bending, which has almost the same surface roughness, a large difference appears in the surface roughness.

[0087] Further, in Table 4, the bending fatigue characteristics of the present invention are also good. As a result, excellent fatigue characteristics can be maintained even after bending. In other words, by optimizing the distribution of the compound in addition to the mixed structure, uniform deformation progresses and defects that occur during bending are reduced. As a result, it is considered that the excellent formability and high fatigue strength were maintained.

On the other hand, with respect to the etching property, the processed surface has a tendency that the maximum value of the surface roughness is reduced and defects such as etching pits are reduced, and the processed surface is smoothed compared to before processing. That is, according to the present invention, the workability including the etching property can be improved, and the high V and fatigue strength can be maintained even in the processed parts.

[0089] Furthermore, the plate warpage and the residual stress also decreased by 70% or more with respect to the residual stress whose increase rate was small. Therefore, the present invention has a significant effect on such characteristics!

Yes

[0090] Among the examples of the present invention, No. 2, No. 11, and No. 12 have a relatively high temper annealing temperature, so that the recrystallized grain size exceeds 10 μm. For No. 7 and No. 8, the applied tension exceeds 40% of the 0.2% proof stress, so the ratio of the γ phase of the mixed structure is less than 70%. As a result, although a stainless steel plate superior to the comparative example can be obtained, the balance between strength and ductility tends to be inferior in the present invention. For these, compared to No. 2, No. 11, and No. 12 (as in No. 14, No. 16, and No. 17, the grain growth is suppressed by adding Nb, Ti, and V. Can be further improved, and No. 7, For No. 8, it can be improved by reducing the applied tension as in No. 10.

Yes

[0091] No. l to No. 18, No. 20 to No. 22, and No. 26 to No. 32, in which the measures for inclusion miniaturization were implemented, included in the present invention the number of inclusions having a maximum diameter of 20 or more In particular, No. 10 using the floating of inclusions and a small-diameter work roll shows the best balance between strength and ductility and workability among the examples of the present invention.

On the other hand, the comparative example is inferior in balance between strength and ductility as compared with the inventive example as described above. Specifically, No. 18 to No. 21 fall within the scope of the present invention in terms of component content and Md value, but No. 18 and No. 19 have a maximum diameter of 20 due to insufficient rolling reduction. More than 30 compounds over m were generated. As a result, good characteristics cannot be obtained due to the absence of a mixed structure. In No. 20 and No. 21, the temper annealing temperature was outside the range of the production method of the present invention, so a mixed structure was not formed, and the workability and fatigue characteristics were both equal to or lower than those of conventional materials. In other comparative examples, the material does not satisfy the required composition, and the performance is not improved.

[0093] Further, Table 5 shows the characteristic adjustment results of the material obtained by subjecting the No. 2 material to temper rolling at a reduction rate of 10% and 20%. In Table 5, No. 2-a is when the temper rolling is applied to the No. 2 material at a reduction rate of 10%, and No. 2-b is the same when the reduction rate is 20%. As a result, it is confirmed that the same material retains excellent properties even after temper rolling.

[0094] [Table 5]

[0095] While the present invention has been described with reference to the most practical and preferred embodiments at the present time, the present invention is limited to the embodiments disclosed herein. However, the present invention can be changed as appropriate without departing from the spirit or concept of the invention which can be read from the claims and the entire specification. It is to be understood that the stainless steel plate and the manufacturing method thereof are included in the technical scope of the present invention.

Claims

The scope of the claims

[1] The entire stainless steel is taken as 100 mass%, a C 0-01-0. 08 wt%, 0 · 1 2. 0 mass ^_0/0, Mn and Si 3. 0 mass ⁰ / ₀ or less, the Cr 10. 0-20. 0 mass ^_0/0, Ni 3. 0-1 2. 0 wt%, and containing each component N in 0.02 to 0.24 wt%, and, Formula in which the value of mass% of each contained component is substituted

Md = 500-458 (C + N) -9 (Si + Mn) -14Cr-20Ni

A compound having a chemical composition in which the Md value represented by 0 to 80 is satisfied, and the balance is an inevitable impurity, and the maximum amount of the compound formed by the components is 20 am or more. 30 or less per 5 g of the mass of the stainless steel, and the metal structure of the stainless steel as a whole is a mixed structure of recrystallized grains and non-recrystallized parts.

[2] The entire stainless steel is taken as 100 mass%, a C 0-01-0. 08 wt%, 0 · 1 2. 0 mass ^_0/0, Mn and Si 3. 0 mass ⁰ / ₀ or less, selected the Cr 10. 0-20. 0 mass ^_0/0, Ni 3. 0-1 2. 0 wt%, the N 0. 02-0. 24 wt%, and Nb, Ti, from the V A formula in which each component is contained in an amount of 0.5% by mass or less, and the mass% value of each component contained is substituted.

Md = 500-458 (C + N) -9 (Si + Mn)-14Cr-20Ni- 65Nb- 27Ti- 61V The compound having the maximum diameter of 20 am or more among the compounds formed by the respective components is 30 or less per 5 g of the mass of the stainless steel, and the metal structure of the entire stainless steel is Stainless steel plate for parts, characterized by a mixed structure of recrystallized grains and non-recrystallized parts.

[3] The stainless steel sheet for parts according to claim 1 or 2, wherein the recrystallized grains have an average grain size of 10 m or less.

[4] The stainless steel sheet for parts according to claim 3, wherein the mixed structure is an austenite phase of 70% by mass or more.

[5] the whole stainless steel is taken as 100 mass%, a C 0-01-0. 08 wt%, 0 · 1 2. 0 mass ^_0/0, Mn and Si 3. 0 mass ⁰ / ₀ or less, the Cr 10. 0-20. 0 mass ^_0/0, Ni 3. 0-1 2. 0 wt%, and containing each component N in 0.02 to 0.24 wt%, and, Formula in which the value of mass% of each contained component is substituted

Md = 500-458 (C + N) -9 (Si + Mn) -14Cr-20Ni

A first cold rolling step in which a material having a chemical composition in which the Md value represented by the formula is 0 to 80 and the balance is an inevitable impurity is cold-rolled at least once, and the first cold rolling A first annealing step disposed after the first cold rolling step in combination with a step, and a final rolling provided on the subsequent step side of the first annealing step, and a reduction rate of 20% or more and Holds the material after the second cold rolling process in which the total rolling reduction with the first cold rolling is 60% or more and the second cold rolling process from 650 to 1000 ° C for 300 seconds or less And a second annealing step in which the material is tempered by applying a tension at 0.2% resistance or less of the material at the held temperature.

[6] the whole stainless steel is taken as 100 mass ^_0/0, the C 0-01-0. 08 mass ^_0/0, Si 0 - 1 2.0 mass ^_0/0, Mn 3. 0 weight ^_0/0 or less, the Cr 10. 0-20. 0 wt ^_0/0, Ni 3. 0-1 2.0 mass%, a N 0. 02-0. 24 wt%, and Nb, Ti A formula in which each component is contained at 0.5% by mass or less of one or more selected from V, and the value of mass% of each of the contained components is substituted

Md = 500-458 (C + N) -9 (Si + Mn)-14Cr-20Ni- 65Nb- 27Ti- 61V A first cold rolling step of cold rolling a material having at least one time, a first annealing step arranged after the first cold rolling step in combination with the first cold rolling step, and The second cold rolling process, which is the last rolling provided on the post-process side of the first annealing process, in which the rolling reduction is 20% or more and the total rolling reduction with the first cold rolling is 60% or more. And holding the material after the second cold rolling process at 650 to; 300 ° C. or less at 1000 ° C. and maintaining a tension of 0.2% or less of the material at the held temperature. A method for producing a stainless steel sheet for parts, comprising: a second annealing step for imparting and tempering.

[7] The tension in the second annealing step is 0.2 of the material at the held temperature. The method for producing a stainless steel sheet for parts according to claim 5 or 6, wherein the% proof stress is 40% or less.

The method for producing a stainless steel sheet for parts according to any one of claims 5 to 7, further comprising temper rolling after the second annealing step.