JP2013208638A - Ferritic stainless steel having excellent washability and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stainless steel sheet having reduced surface flaws and an excellent washability and suitable as the material for an HDD member such as a cover, a clamp ring, and the hub material of a spindle motor or for a precision instrument member such as a solar battery substrate, and to provide a method for producing the stainless steel sheet.SOLUTION: A ferritic stainless steel sheet having excellent washability includes, by mass, ≤0.1% C, 0.1 to 2.0% Si, 10 to 32% Cr, and the balance Fe with inevitable impurities, and has been subjected to temper rolling, wherein the arithmetic mean roughness Ra in a direction vertical to a rolling direction in the surface of the steel sheet is ≤0.03 μm. In the surface of the steel sheet, the existence density of micropits having a depth of ≥0.5 μm and an opening area of ≥10 μmis ≤10.0 pieces per 0.01 mm, and also, the area ratio of the opening parts of the pits is distributed in ≤1.0%.

Description

  The present invention relates to stainless steel excellent in cleanability suitable for electronic parts such as computer members, digital equipment members, HDD (hard disk) members and solar cell substrates, precision equipment members, and electronic equipment members, and a method for producing the same. .

  In recent years, HDDs are required to have higher speed and higher density, and materials used for interior parts are required to be strictly controlled not only for corrosion resistance but also for fine surface flaws, dirt such as particles and outgas. Yes. Therefore, the manufacturing process of the HDD member is strictly managed. For the HDD member, ordinary steel, Al, stainless steel, etc. are used, but the surface of these materials is often subjected to electroless Ni plating. The electroless Ni plating is applied for the purpose of improving the cleaning property in addition to the purpose of improving the corrosion resistance. Unlike normal electrolytic plating, the electroless Ni plating has the advantage that it can be plated with a uniform film thickness, but the productivity is poor and the process load is large.

  Regarding solar cells, glass plates, stainless steel plates and the like are used as substrates for non-single crystalline semiconductor solar cells. The non-single crystalline semiconductor layer deposited on the substrate is a thin layer having a thickness of 1 to 2 μm or less and needs to be formed uniformly and continuously. That is, the solar cell substrate material is required to be smooth with few surface scratches, and at the same time, no dirt such as particles adheres to the surface before vapor deposition.

  By the way, since stainless steel remains a solid material due to the generation of a passive film and is excellent in corrosion resistance, if a stainless steel plate with less surface scratches and good cleaning properties such as particles can be provided, and its manufacturing method can be provided, electroless Ni plating It is considered possible to provide materials for HDD members that are not necessary or materials for solar cell substrates.

  Examples of application of stainless steel silver plates to HDD and precision equipment interior materials include, for example, Patent Document 1 (resin composite stainless steel damping steel plate for precision equipment covers with excellent contamination resistance), interior BA finish, exterior Stainless steel for precision machine cases has been introduced, which uses a resin composite damping metal plate in which a resin layer is laminated between two metal plates with a dull finish.

  Further, in Patent Document 2 (stainless steel plate material and manufacturing method thereof), it is difficult for minute dust and dust to adhere to the surface by regulating the number of pinholes and surface roughness on the surface of the steel plate after temper rolling. In addition, it introduces a stainless steel plate material for semiconductor manufacturing equipment with excellent cleaning properties and its manufacturing method.

Patent document 1 is only about the force bar of HDD which laminated | stacked the steel plate, and is not knowledge applicable to members, such as another precision instrument. Further, the surface finish of the steel sheet is defined only as the BA finish, but there are a manufacturing method and a steel type in which there are many stains adhering to the surface even in the BA finish. The cause of the adhesion of dirt is due to fine grooves (microgroups) generated along the grain boundaries on the surface of the steel sheet when the grain boundary oxide or Cr-deficient layer formed during annealing is removed by pickling. . For this micro group, the depth is specified to be 0.1 μm or less, but details of the generation status on the steel sheet surface such as area ratio and distribution status are not shown, and the manufacturing that specifies it The details of the method are not described and are insufficient.

Patent Document 2 defines the size and number of pinholes from the viewpoint that dirt easily adheres to the pinholes. The pinholes are generated in the form of indentation due to the roll deposits in the heat treatment furnace in the continuous annealing pickling line. As the distribution of pinholes, it is prescribed that “the number of pinholes whose size exceeds 0.25 mm ² in area is 10 or less per 10 cm ² ”, but because the size of the target scratch is too large, As a member for precision equipment, dirt is likely to adhere and is inappropriate.
In addition, the evaluation method of the cleaning property is insufficient in the three-throw evaluation of the SEM observation result, is not appropriate as an evaluation method for HDDs and precision instruments, and cannot be used as a material for these fields. Absent.

  As described above, in the conventional invention, there is a problem in using stainless steel as an HDD member. Therefore, the inventors have intensively devised, an austenitic stainless steel plate having excellent cleaning properties, and a manufacturing method thereof (Patent Document 3). Devised. However, Patent Document 3 is an invention limited to austenitic stainless steel and has a problem that it cannot be applied as it is to ferritic stainless steel.

Japanese Patent No. 3956346 Japanese Patent Laid-Open No. 2001-20045 JP 2011-202253 A

  The present invention has been made to solve the above-mentioned problems, and is suitable as a material for HDDs such as covers, clamp rings, spindle motor hubs, and precision instrument members such as solar cell substrates. An object of the present invention is to propose a stainless steel plate having few surface scratches and excellent cleanability and a method for producing the same.

The ferritic stainless steel sheet having excellent detergency of the present invention is C: 0.1 mass% or less, Si: 0.1-2.0 mass%, Cr: 10-32 mass%, with the balance being Fe and A temper-rolled stainless steel plate made of inevitable impurities, the arithmetic average roughness Ra in the direction perpendicular to the rolling direction of the steel plate surface is 0.03 μm or less, and the steel plate surface has a depth of 0.5 μm or more and The density of micropits having an opening area of 10 μm ² or more is 10.0 or less per 0.01 mm ² , and the opening area ratio of the pits is distributed at 1.0% or less.

  Further, the ferritic stainless steel sheet having excellent cleaning properties of the present invention is Nb: 0.005 to 0.8 mass%, Ti: 0.005 to 0.5 mass%, Mo: 0.2 to 5 mass%, Cu : One or more of 0.1 to 3% by mass may be included.

Ferritic stainless steel sheet excellent in cleaning properties of the present invention is a hot rolled pickling material as a starting material, and finally in the manufacturing procedure of performing each step of "finish cold rolling, bright annealing" in the order described above,
(A) The total cold rolling ratio before the bright annealing step is 70% or more,
(B) The cold rolling rate in the finish cold rolling step is 30% or more, and at least in the final rolling pass, a work roll having an arithmetic average roughness Ra of 0.3 μm or less is used, and the rolling rate is 15% or more, Rolling at a rolling speed of 200 m / min or less,
(C) In the finish annealing, performing a bright annealing process,
Manufactured under conditions that satisfy

  The ferritic stainless steel sheet having excellent detergency according to the present invention uses a work roll having an arithmetic average roughness Ra of 0.1 μm or less in a temper rolling process after bright annealing, and a lubricant between the work roll and the steel sheet material. Is produced under the condition of an elongation of 0.1 to 2.0% by a dry skin pass method in which no is inserted.

Specific examples of the production procedure employed in the present invention include the following.
(1) [Hot rolled material] → Annealing → Pickling → Finish cold rolling → Finish bright annealing → (temper rolling)
(2) [Hot rolled material] → Cold rolling → Annealing → Pickling → Finish cold rolling → Finish bright annealing →
(Temper rolling)
(3) [Hot rolled material] → Annealing → Pickling → Cold rolling 1 → Annealing 1 → Pickling 1 → Cold rolling 2
→ Annealing 2 → Pickling 2 → Finish cold rolling → Finish bright annealing → (temper rolling)
(4) [Hot rolled material] → Annealing → Pickling → Cold rolling → Bright annealing → Finish cold rolling →
Finish bright annealing → (temper rolling)

  The “total cold rolling ratio before bright annealing process” in (a) corresponds to the rolling ratio of finish cold rolling in the manufacturing procedure of (1), and cold rolling and finish cold rolling in (2). (3) corresponds to the total rolling rate of cold rolling 1, cold rolling 2 and finish cold rolling, and (4) corresponds to the total rolling rate of cold rolling and finish cold rolling. It corresponds to.

Here, “hot-rolled material” means a hot-rolled steel sheet that has not been cold-rolled yet. “Bright annealing” is annealing performed in a reducing atmosphere, and the conditions of “bright heat treatment” applied to BA finishing (JISGO 203: 2009, number 4225) can be adopted. In the present invention, bright annealing is applied as the final finish annealing.
The “finish cold rolling” in the present invention means a cold rolling process comprising one or more rolling passes performed after the final annealing step and immediately before the bright annealing step. The finish cold rolling process may be carried out using a plurality of different types of rolling mills (for example, a general Sendzimir mill and a thin sheet exclusive mill) one after another. In this case, the total cold rolling rate by a plurality of rolling mills is adopted as the “cold rolling rate in the finish cold rolling process”.

Moreover, as shown in (4), in the process between cold rolling and finish rolling, bright annealing may be performed instead of annealing and pickling processes.
Further, in the manufacturing processes shown in (1) to (4), a polishing process and a degreasing process may be inserted as necessary, and the surface shape is affected after the last temper rolling. In some cases, it may be passed through the finishing process such as degreasing, tension leveler, and slit.

The total cold rolling rate specified in the present invention is the plate thickness after the last rolling pass, h ₀ (mm) before the first rolling pass among a series of rolling passes in all the corresponding cold rolling steps. When the thickness is h _l (mm),
It is represented by (h ₀ −h ₁ ) / h ₀ × 100 (%).
Furthermore, the rolling of the final pass to be defined in the present invention, the plate thickness before the final rolling pass h _{2 (mm),} the plate thickness after the final rolling pass when to _{h 1 (mm), (h} 2 -h ₁₎ / _h is represented by ₂ × 100 (%).

  The ferritic stainless steel sheet having excellent detergency according to the present invention is suitable as an electronic component such as a computer member, a digital device member, an HDD (hard disk) member, a solar cell substrate, a precision device member, and an electronic device member.

  ADVANTAGE OF THE INVENTION According to this invention, the stainless steel plate with the very favorable detergency performed in a clean environment can be provided with the manufacturing process suitable for industrial mass production. Since this stainless steel plate has excellent corrosion resistance and cleanability even if it is not subjected to surface treatment such as electroless Ni plating, it is advantageous in terms of cost and is expected to be used as a material for HDD members.

The inventors have repeatedly made ingenuity with regard to stainless steel having a cleaning property and a method for producing the same, and have arrived at the present invention.
Hereinafter, matters will be described in detail to identify the present invention.

[Surface properties]
The inventors have conducted a detailed investigation on the cleaning performance when the stainless steel plate is subjected to cleaning performed in the clean environment as described above, and the presence of minute pits distributed on the surface of the stainless steel plate. It was found that the cleaning performance is greatly affected. The pit here is a fine depression on the surface of the steel sheet, and is mainly generated in cracks in the hot rolling process, gaps in the grain boundary oxidation part, grain boundary eaten parts, gaps between different kinds of particles such as inclusions and carbides. Dents, dropping marks of those particles, depressions caused by biting of metal particles and other particles in the manufacturing process, dropping marks of oxide scale residue, pits caused by rolling oil rolling during cold rolling, cold This may be due to fine surface defects due to mismatching of rolling conditions or processing cracks due to inclusions during cold working.

Among such pits, in particular, “pits having a depth of 0.5 μm or more and an opening area of 10 μm ² or more” are referred to as “micropits” in the present specification. According to the inventors' investigation, it has been found that such micropits tend to be trapping sites for foreign matters, and are a major factor that impairs cleaning properties. As a result of detailed examination, the surface density of the micro pits is 10.0 or less per 0.01 mm ² and the surface area of the stainless steel plate whose opening area ratio of the pits is 1.0% or less is as described above. It was found that the cleaning performed in a clean environment exhibits good cleaning properties. The micropits mentioned here are caused by the surface defects of the cold-rolled steel sheet described in the previous section, and satisfy the specified size, but the irregularities of the cold-rolled work roll are transferred to the steel sheet surface. The pits are not covered because they are not surface defects.

Here, the depth of the pit is the maximum depth of the pit based on the average height of the edge of the outer periphery of the pit. The opening area of the pit refers to the projected area of the portion surrounded by the edge of the pit in the observation image when the steel plate surface is viewed in the thickness direction.
It is preferable to measure the pit depth and opening area using a laser microscope or white interference microscope that can measure the surface shape. The measurement area is a total area of 0.1 mm ² or more for a plurality of visual fields randomly selected from the steel sheet surface. For example, the micropit existence density and the opening area ratio may be calculated by observing 20 fields of view or more at a magnification of 1000 times. The abundance density counts the number of micropits existing in the measurement area set in each field of view (including the micropits where a part of the pit opening protrudes from the boundary of the measurement area). The total number of counts at is converted to the number per 0.01 mm ² by dividing by the total area of all measurement region areas.
The opening area ratio is the opening area of the coarse micropits existing in the measurement area set in each field of view (the micropit where a part of the pit opening protrudes from the boundary of the measurement area exists in the measurement area) Is calculated), and the sum of the total aperture area in each field of view is divided by the total measurement area area.

  In the stainless steel plate of the present invention, the arithmetic average roughness Ra (JISB0601: 2001) measured in the direction perpendicular to the rolling direction is preferably adjusted to 0.03 μm or less. According to the manufacturing method described later, a material having such a surface roughness can be realized.

[Chemical component value]
In the present invention, if the ferritic stainless steel sheet has the surface properties optimized as described above, good cleaning properties are exhibited in various stainless steel types. Therefore, a stainless steel type having appropriate properties (particularly corrosion resistance level) may be selected depending on the application.

  As a main component, it can select from the range of C: 0.1 mass% or less, Si: 0.1-2.0 mass%, Cr: 10-32 mass%. Moreover, Nb: 0.005-0.5 mass%, Ti: 0.005-0.5 mass%, Mo: 0.2-5 mass%, Cu: 0.1-3.0 mass% are added. I can do it.

  In addition to the above alloy components, the present invention may include other alloy components as necessary. For example, Mn: 2% by mass or less, Zr: 0.01 to 0.5% by mass, Y: 0.05% by mass or less, W: 1% by mass or less, Ag: 0.5% by mass or less, Sn: 0.00%. You may add 1 type, or 2 or more types, such as 5% mass or less and Co: 1 mass% or less. As long as P contained as impurities is regulated to 0.05% by mass or less and S is regulated to 0.01% by mass or less, the characteristics are not adversely affected.

〔Production method〕
The ferritic stainless steel plate having excellent cleaning properties of the present invention can be manufactured using existing stainless steel plate manufacturing equipment. However, it is necessary to devise a manufacturing method.
What is important in the production method of the present invention is to produce a stainless steel base plate having excellent smooth cleanability with few micropits by annealing / pickling, cold rolling, bright annealing process, and temper rolling.
That is, using a hot-rolled sheet manufactured by a conventional method as a starting material, (i) removing coarse deposits such as metal and scale in an annealing / pickling process, etc. (ii) for subsequent cold-rolling finish To secure a sufficient rolling rate and smooth the dents (dropping marks) generated by pickling and the pits caused by grain boundary erosion as much as possible by using a work roll having high smoothness in the final stage (iii) At the same time, by making the total cold rolling ratio sufficiently large, the dents such as dents derived from hot-rolled steel sheets and detachment marks of foreign matters that have fallen off in the annealing l pickling process are smoothed as much as possible. (Iv) Further, finish cooling In the final pass, rolling is performed under conditions of low speed and high pressure using a smooth work roll to prevent entrainment of oil and foreign matter, and finish to a smooth surface. (V) Also, bright annealing is adopted as finish annealing Do And producing less original plate pit eliminate the unnecessary grain boundary erosion subsequent pickling prevents the formation of recess by surface oxidation by. (Vi) Hot-rolled sheet annealing and pickling are performed according to the non-lubricated state.

[Total cold rolling ratio]
Total rolling rate: 70% or more As described above, many surface defects are generated during hot rolling, and in order to eliminate micropits as much as possible, the total cold rolling rate before the bright annealing step is increased, It is important to sufficiently stretch the surface defects present in the starting material. In addition, foreign matter buried in the vicinity of the surface may be removed by hot-rolled sheet annealing or pickling before cold rolling, and it is effective to increase the total cold rolling rate in order to extend the removal mark. As a result of various studies, it has been found that it is extremely effective to set the total cold rolling ratio before the bright annealing step to 70% or more, so in the present invention, it is defined within this range.
The rolling rate may be 70% or more in total. For example, rolling may be performed at a rolling rate of 70% or more without performing intermediate annealing from the state of the hot rolled sheet. It is only necessary that the total rolling rate is 70% or more regardless of the rolling rate before and after.
Further, the upper limit of the total cold rolling rate is not particularly required because it is restricted by the material deformation resistance and the capability of the cold rolling mill to be used, but it is usually set within a range of 98% or less.

[Annealing and pickling process]
This is an effective process for removing coarse foreign matters such as metal and scale adhering to the steel plate surface. In the present invention, the annealing / pickling process is not limited. For example, the annealing process may be performed under conditions necessary for producing the material and obtaining characteristics. Although the annealing step depends on the material, either batch annealing or continuous annealing may be used as long as the shape of the surface is not affected. Further, the pickling step is performed with a combination of neutral salt, acid such as sulfuric acid, nitric acid, hydrofluoric acid, and hydrochloric acid, and electrolytic pickling may be performed.

[Finish cold rolling process]
Rolling ratio of finish rolling: 30% or more Surface roughness of work roll in final rolling of final rolling: Ra ≦ 0.3 μm
Finishing rolling final pass rolling rate: 15% or more Finishing rolling final pass rolling speed: 200 m / min or less Finish cold rolling in the present invention is an important process for determining the surface state of a steel sheet. In other words, it is necessary to extend the recess neatly so that the micropits have a predetermined density or less and an opening area ratio. For that purpose, first, it is important to sufficiently extend the drop marks of foreign matters generated in the above-described pickling process and the recesses due to grain boundary erosion. In order to realize this, it is necessary to make the rolling ratio of finish cold rolling 30% or more. It is more preferable to set it as 40% or more, and it is still more preferable to set it as 50% or more. The upper limit of the finish cold rolling rate is not particularly specified because it is restricted by the material deformation resistance and the capacity of the cold rolling mill to be used, but it is usually within a range of 90% or less. Further, in order to obtain a smooth surface as much as possible, it is extremely effective to use a work roll whose arithmetic average roughness Ra of the roll surface is adjusted to 0.3 μm or less in at least the final rolling pass of finish cold rolling. . In particular, it is necessary to secure a rolling rate of 15% or more in the final rolling pass using a work roll with Ra of 0.3 μm or less. In the examples of the present invention in Examples to be described later, finish cold rolling that satisfies this condition is performed. Moreover, in order to prevent generation | occurrence | production of the pit by entrainment of the rolling oil to the work roll and the steel plate surface, the rolling speed | rate in the final rolling pass was prescribed | regulated as 200 m / min or less.

[Bright annealing process]
In the present invention, finish annealing is performed by “bright annealing” in a reducing atmosphere. In order to maintain the surface properties with very few micropits obtained by finish cold rolling, finish annealing needs to prevent surface oxidation and eliminate the need for subsequent oxide scale removal steps (pickling, polishing, etc.). Because. As the bright annealing conditions, the normal conditions for producing a BA-finished stainless steel sheet can be used. The atmospheric gas is preferably, for example, hydrogen gas or a hydrogen-nitrogen mixed gas. The annealing temperature can be appropriately set according to the component, the plate thickness, and the use. However, if it is ferritic stainless steel, it may be set in the range of 800 to 1100 ° C, for example.

[Temper rolling process]
After bright annealing, temper rolling can be performed as necessary. In a normal temper rolling process, a lubricant containing additives may be used for the purpose of improving glossiness or preventing rust. In this case, the lubricant film is between the work roll and the steel sheet surface. It becomes a factor that enters and forms a new pit. Therefore, in this invention, the dry skin pass method which does not insert a lubricant between a work roll and a steel plate material is adopted. Moreover, in order to improve the smoothness of the steel sheet surface, it is important to use a work roll whose roll surface arithmetic average roughness Ra is adjusted to 0.1 μm or less. However, such a smoothing work roll may be used only for the surface on the side that imparts good cleanability. If the temper rolling ratio is excessive, the formation of pits due to the biting of foreign matter may increase and become a problem. As a result of various studies, it is effective to perform temper rolling in the range of an elongation of 0.1 to 2.0%. The elongation rate of temper rolling referred to here means the total elongation rate when temper rolling is performed for one pass or more.

  In temper rolling, a method of wiping with a wiper or the like using a cleaning liquid may be employed to remove foreign matter on the surface of the work roll, but when wiping the cleaning liquid, the present invention may be used unless other lubricants are used. This corresponds to the dry skin pass.

In the present invention, the above-described manufacturing process is adopted, but a process such as a mechanical polishing process or a degreasing process may be passed as long as the shape of the surface is not affected.
Thus, the present invention has been achieved.

The present invention will be described below with reference to examples.
Stainless steel having the chemical composition shown in Table 1 was melted in an electric furnace, converter, and VOD process, and continuously cast to obtain a slab.
Next, the continuous cast slab was aged and rolled by a conventional method to obtain a “hot rolled material”. Using this hot-rolled pickling material as a starting material, a tempered rolled material having a thickness of 0.3 to 1.5 mm was produced by the procedure (2) or (3) described above, and these were used as test materials. For the example using steel type b, the procedure of (3) was adopted, and otherwise, the procedure of (2) was adopted. However, in some comparative examples, there are those in which annealing and pickling are performed instead of bright annealing as finish annealing, or electrolytic pickling is performed after bright annealing.
Bright annealing was performed in an atmosphere of 75-100 volume% hydrogen and the balance nitrogen. The manufacturing conditions and final plate thickness are shown in Table 2. Each specimen is finished on both sides under the same conditions. In addition, a commercially available electroless Ni plating material used for a rotating member of an HDD was obtained as a control material for cleaning performance evaluation, and this was added to one of the test materials.

[Measurement of arithmetic mean roughness of steel sheet surface]
A 50 mm square sample cut out from each test material was subjected to ultrasonic cleaning using acetone, and then JIS.
The arithmetic average roughness (Ra) was measured by a method according to B 0601. At that time, the measurement was performed three times in the direction perpendicular to the rolling direction, and the average value was evaluated. The results are shown in Table 2.

[Quantification of micropits]
A sample of 50 mm square cut out from each test material was subjected to ultrasonic cleaning using acetone, and then the surface was observed with a laser microscope, and “a depth of 0.5 μm or more and an opening area of 10 μm ² or more” The existence density of the micropits and the area ratio of the opening were obtained by the above-described method. At that time, the observation magnification was 1000 times, the number of observation fields was 10, and the total measurement region area was 0.1 mm ² . The results are shown in Table 2.

[Evaluation of cleanability]
About the sample of 50 square mm cut out from each test material, washing | cleaning operation was performed in the following procedures, and the sample for surface cleanliness measurement was obtained. All the steps after the acetone degreasing of the cleaning operation and the measurement of the surface cleanliness were carried out in a class 5 clean environment defined by JISB9920.
(Washing operation)
Degreasing by ultrasonic cleaning using acetone → Ultrasonic cleaning using fluorine-based cleaning liquid → Steam cleaning → Vacuum drying → Ultrasonic cleaning using weak alkaline detergent → Rinsing immersed in ultrapure water → Low speed lifting → Hot air Drying (evaluation of the number of particles)
The surface cleanliness was measured using an LPC (liquid particle counter) apparatus as follows. First, put the ultrapure water for immersing the cleanliness measurement sample in a beaker, set the ultrapure water in this state in the LPC device, measure the number and size distribution of the particles present in the ultrapure water, The number of particles having a particle diameter of 0.3 μm or more was calculated from the data, and this was used as the number of particles before sample immersion (blank measurement value). Next, the sample for cleanliness measurement is immersed in the beaker containing the above-described ultrapure water, subjected to ultrasonic cleaning for a certain time, and the particles adhering to the sample surface are extracted into ultrapure water. The number and size distribution of particles present in ultrapure water were measured with an LPC apparatus, and the number of particles having a particle diameter of 0.3 μm or more was calculated. The difference between this value and the blank measurement value was taken as the number of particles extracted from the sample. At that time, the same liquid was measured three times or more by the LPC apparatus, and the average value was adopted. Using 3 samples of the same type of sample, the above measurement was performed with the number of tests n = 3,
The average value was defined as the number of particles remaining attached to the groove purity measurement sample. From this value, the “number of particles adhering to the cleaning sample” per unit area of the steel sheet surface was calculated. The results are shown in Table 2.

As can be seen from Table 2, in accordance with the manufacturing conditions specified in the present invention, stainless steel having a micropit existence density of 10.0 or less per 0.01 m ² and an opening area ratio of the pits of 1.0% or less. A steel plate was obtained. Since the number of particles attached to the cleaning sample in these steel plates is in the same order as the electroless Ni finish, it has excellent cleaning properties that can be applied to precision parts such as HDD members while maintaining the surface of a solid stainless steel plate. It is evaluated that
As for Comparative Examples aB, aC, GD, and cocoons, the rolling rate of the cold rolling was insufficient and the micropits could not be sufficiently dipped, resulting in poor cleanability. In Comparative Examples bC and dB, the speed of the final cold rolling pass was too high, resulting in a large number of pits due to rolling oil entrainment and poor cleanability. In Comparative Examples bB and eB, the work roll or the temper rolling roll was too rough, and the pits could not be sufficiently crushed, resulting in poor cleanability. As for Comparative Examples cE and dC, pickling with a mixed acid was performed in finish annealing, so that pickling pits were generated, resulting in poor cleanability. In Comparative Example eC, temper rolling was performed by a wet method, so that there were many pits due to rolling oil entrainment, resulting in poor cleanability.

As is clear from the above, according to the present invention, a stainless steel plate with excellent cleaning properties can be provided by defining the distribution state of micropits on the surface of the steel plate, and electroless Ni plating has been necessary so far. A solid stainless steel material can be used for the HDD member.

Claims (5)

C: 0.1% by mass or less, Si: 0.1-2.0% by mass, Cr: 10-32% by mass, and the balance is a temper-rolled stainless steel plate made of Fe and inevitable impurities. Thus, the arithmetic average roughness Ra in the direction perpendicular to the rolling direction of the steel sheet surface is 0.03 μm or less, and the micropit existence density having a depth of 0.5 μm or more and an opening area of 10 μm ² or more is 0. A ferritic stainless steel sheet excellent in detergency, characterized in that the number is 10.0 or less per 01 mm ² and the opening area ratio of the pits is 1.0% or less.   Nb: 0.005 to 0.8% by mass, Ti: 0.005 to 0.5% by mass, Mo: 0.2 to 5% by mass, Cu: 0.1 to 3% by mass or more, The ferritic stainless steel sheet excellent in cleaning properties according to claim 1. In the manufacturing procedure in which the hot-rolled pickling material is used as a starting material, and finally the steps of “finish cold rolling and bright annealing” are performed in the order described above.
(A) The total cold rolling ratio before the bright annealing step is 70% or more,
(B) The cold rolling rate in the finish cold rolling step is 30% or more, and at least in the final rolling pass, a work roll having an arithmetic average roughness Ra of 0.3 μm or less is used, and the rolling rate is 15% or more, Rolling at a rolling speed of 200 m / min or less,
(G) In the finish annealing, performing a bright annealing process;
The manufacturing method of the stainless steel plate excellent in the washability of Claim 1 or 2 which employ | adopts the conditions which satisfy | fill.   In the temper rolling process after bright annealing, a work roll having an arithmetic average roughness Ra of 0.1 μm or less is used, and an elongation of 0.1 to 0.1 is achieved by a dry skin pass method in which no lubricant is inserted between the work roll and the steel plate material. The method for producing a stainless steel plate with excellent detergency according to claim 3, wherein the rolling is performed at 2.0%. The stainless steel sheet is used for electronic parts such as computer members, digital equipment members, HDD (hard disk) members and solar cell substrates, precision equipment members, and electronic equipment members. Excellent ferritic stainless steel sheet.