JP2016166385A - Stainless steel for surface modified spring and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stainless steel for spring excellent in property of adhesion of coating to the stainless steel, used for an automobile related component, a home electric appliance, a casing for an OA device, a building material for use such as roof and external facing, and having inexpensive price and high strength.SOLUTION: The stainless steel sheet for a spring is provided that has a chemical component containing, by mass%, C:0.1 to 0.4%, Si:2.0% or less, Mn:0.1 to 6.0%, Cr:10.0 to 28.0%, N:0.17% or less and the balance Fe with inevitable impurities and that has structure which is a dual phase structure containing, by vol.%, ferrite phase of 30% or less and retained austenite phase of 20% or less and the balance martensite phase or is a martensite single phase and that has Si amount in a sheet surface of 2.0% or less.SELECTED DRAWING: None

Description

  The present invention relates to a stainless steel for springs that is excellent in coating adhesion and has low strength and high strength, which is used for automobile-related parts, home appliances, OA equipment casings, roofing and exterior building materials, and the like.

  In automobiles and related parts applied to them, home appliances and related parts applied to them, OA equipment casings, roofs and exterior applications, etc., many coated stainless steel sheets using stainless steel sheets as the coating raw plates are used. These coatings apply different materials to stainless steel sheets to give new characteristics, and stainless steel is a material with excellent corrosion resistance. However, in order to further improve corrosion resistance, or to provide design properties It is carried out from.

  In Patent Documents 1 to 5, a cylinder head gasket used in an automobile engine is a rubber coated with a heat-resistant rubber layer such as a thin fluorine rubber or NBR rubber for the purpose of improving the sealing performance of engine oil or cooling water. A coated stainless steel sheet is disclosed.

  Patent Document 6 discloses a stainless steel plate on which a coating for the purpose of improving heat dissipation is applied to a home appliance, a related component applied to the home appliance, and a housing of an OA device.

 Patent Document 7 discloses a stainless steel sheet that has been coated for the purpose of improving design properties.

  Patent Document 8 discloses a stainless steel plate on which coating for the purpose of antiglare effect that improves light absorption for high resolution in an optical device is performed.

  Patent Documents 9 to 11 disclose stainless steel sheets that have been coated for the purpose of further improving corrosion resistance and providing design properties in roof and exterior applications.

  Stainless steel has a passive film on its surface and has excellent corrosion resistance. However, since there is a passive film, it is difficult to obtain good paint adhesion as it is. For this reason, a chemical conversion treatment such as a chromate treatment is performed as a pre-coating treatment, and excellent coating adhesion is ensured.

  Recently, in consideration of environmental pollution caused by hexavalent chromium, a unique chromium-free chemical conversion treatment has been applied. Along with this, in order to ensure sufficient adhesion of the coating, the stainless steel plate itself, which is the material, also needs to have a coating of chromium-free chemical conversion treatment (hereinafter referred to as “paint coating”), which is a pre-painting treatment. .

  Patent Document 12 discloses stainless steel with a modified passive film.

  Patent Documents 13 to 15 disclose stainless steel in which the composition and the like of a passive film containing Si, which is considered to be a cause of deteriorating the adhesion of a paint film, are particularly limited.

  Patent Documents 4, 6, and 12 disclose stainless steel in which the adhesion of the coating film is improved by adjusting the plate surface shape.

  Patent Document 16 discloses steel that defines nonmetallic inclusions containing Mg on the plate surface.

  On the other hand, in the case of automobile-related parts, home appliances, OA equipment casings, roofs / exterior applications, it is necessary to increase the strength of the stainless steel plate as a material for the purpose of weight reduction.

  Patent Document 17 discloses a stainless steel mainly composed of a martensite phase in which Ni, which is an expensive alloy element, is reduced, Cr is a main component and is expected to be inexpensive and have high strength. ing.

  However, regarding the improvement of the adhesion of the paint film, a study considering the difference in the structure of stainless steel as a material has not been sufficiently performed. Specifically, it is expected to expand in the future, has high strength corresponding to the reduction in size and weight of the product, it is inexpensive by using Cr as the main alloy element without using expensive Ni as much as possible There has been no study on improvement of paint film adhesion for martensitic stainless steel which is substantially finished by quenching heat treatment.

JP 2002-106718 A JP 2002-226978 A JP 2003-342745 A JP 2005-42130 A JP 2006-283182 A JP 2007-144661 A JP 2006-103269 A JP 2011-179097 A JP 2001-342548 A JP 2004-122409 A JP 2009-214383 A JP 2009-256785 A JP 2006-274303 A JP-A-8-225897 JP-A-9-31665 JP 2001-295073 A International Publication No. 2013/080699

  The present invention is excellent in adhesion of a paint film for imparting new characteristics to a material, and is compatible with miniaturization and weight reduction of automobile-related parts, home appliances, OA equipment casings, building materials for roofs and exterior applications, and the like. An object is to stably supply stainless steel for springs mainly composed of an inexpensive martensite phase containing Cr as a main alloy element without using expensive Ni as much as possible.

  In order to improve the adhesion of the coating film, the present inventors have an influence on the structure of the stainless steel, particularly on the martensitic stainless steel, which is expected to expand in the future, as well as the influence of the passive film and the shape considered to be the cause. We examined and clarified their combined effects.

  Specifically, we continue to intensively research and develop stainless steel mainly composed of martensite phase with Cr as the main alloy component, which can be expected to be inexpensive and have high strength, and prototype tests and actual equipment with small ingots with adjusted components Through trial tests, it was clarified that the adhesion of the paint film can be improved by limiting the Si content on the plate surface and the structure mainly composed of the martensite phase.

  The present invention is based on the above findings, and the gist thereof is as follows.

  (1) In mass%, C: 0.1 to 0.4%, Si: 2.0% or less, Mn: 0.1 to 6.0%, Cr: 10.0 to 28.0%, and N: containing 0.17% or less, the balance being a chemical composition of Fe and impurities, the structure containing 30% or less by volume ferrite phase and 20% or less residual austenite phase, and the balance being martensite A stainless steel plate for springs having a multiphase structure composed of phases or a single phase of martensite and having an Si content of 2.0% or less on the plate surface.

  (2) The stainless steel plate for springs according to (1), wherein the steel plate has a surface roughness Rz of 1.0 μm or more and 3.0 μm.

  (3) The chemical composition further includes, in mass%, Ni: 2% or less, Cu: 2% or less, Nb: 0.5% or less, V: 0.5% or less, and Ti: 0.5% The stainless steel plate for springs according to (1) or (2) above, comprising at least one or more of the following.

  (4) In mass%, C: 0.1 to 0.4%, Si: 2.0% or less, Mn: 0.1 to 6.0%, Cr: 10.0 to 28.0%, and N: A slab containing 0.17% or less and having a chemical composition with the balance being Fe and impurities is rolled into a product plate thickness to form a steel plate, and the steel plate is in a non-oxidizing gas atmosphere having a dew point of -40 ° C. or less. A method for producing a stainless steel plate for springs, characterized by holding the steel plate at a temperature of 750 to 1100 ° C for 10 seconds or more, cooling the steel plate to 600 ° C at a rate of 1 ° C / s or more, and subjecting the steel plate to surface treatment.

  (5) The stainless steel for springs according to (4), wherein the surface treatment is immersion in a mixed aqueous solution of 2% or more and 20% or less sulfuric acid and 2% or more and 20% or less nitric acid. A method of manufacturing a steel sheet.

  (6) The chemical composition further includes, in mass%, Ni: 2% or less, Cu: 2% or less, Nb: 0.5% or less, V: 0.5% or less, and Ti: 0.5% The method for producing a stainless steel plate for springs according to (4) or (5) above, comprising at least one or more of the following.

  According to the present invention, stable stainless steel for springs that is applied to automobile-related parts, home appliances, OA equipment casings, roofing / exterior building materials, etc. that have excellent coating film adhesion and high strength. Can be supplied.

  First, the composition of the material will be described.

“C: 0.1% or more, 0.4% or less”
C is an inexpensive, most powerful and effective interstitial solid solution strengthening element. It is also a powerful austenite stabilizing element. For this reason, it is an additive element indispensable for the present invention, and 0.1% or more is added. Preferably, it is 0.12% or more. However, when it is contained excessively, it forms coarse carbides with Cr, which is the main alloy element, and Nb, V, Ti added for the purpose of suppressing grain growth in the high-temperature austenite region described later in the quenching heat treatment. A large amount of ferrite phase is formed, the adhesion of the coating film is deteriorated, and high strength cannot be obtained. Further, even when the precipitation of coarse carbides is suppressed, a large amount of austenite phase remains up to room temperature, and the adhesion of the coating film is deteriorated as compared with the martensite phase in which fine precipitates are uniformly dispersed. For this reason, it is 0.4% or less. Preferably it is 0.38% or less, More preferably, it is 0.36% or less.

“Si: 2.0% or less”
Si is generally used as a deoxidizer during melting. There is also a side as a solid solution strengthening alloy element. However, as described above, the adhesion of the coating film deteriorates due to the concentration in the surface film accompanying the heat treatment. For this reason, it is made 2.0% or less. Furthermore, it is preferably 1.0% or less.

“Mn: 0.1% or more, 6.0%”
Mn is a relatively inexpensive and effective austenite stabilizing alloy element. An increase in the amount of solid solution strengthening elements such as C and N is also expected. In the quenching heat treatment, the austenite region at a high temperature is expanded to a lower temperature, the precipitated compounds due to C and N are refined, and excellent coating film adhesion can be obtained. Moreover, the fluctuation | variation of the intensity | strength by a cooling rate is also suppressed. For this reason, 0.1% or more is added. Preferably, it is 0.2% or more. However, excessive addition forms a coarse compound, which deteriorates the adhesion of the coating film and may significantly deteriorate the manufacturability of the plate. For this reason, it is made 6.0% or less. Preferably, it is 5.6% or less.

“Cr: 10.0% or more, 28.0% or less”
Cr is a basic element of stainless steel, and in order to obtain effective and necessary corrosion resistance, 10.0% or more is added. However, it is a ferrite stabilizing element, and excessive addition makes the high temperature austenite phase unstable. Furthermore, the possibility of forming a coarse compound with C and N increases. For this reason, it was made 28.0% or less. Furthermore, it is preferably 10.2% or more and 26.0% or less.

“N: 0.17% or less”
N, like C, is the most powerful and effective interstitial solid solution strengthening element. It is also a powerful austenite stabilizing element. However, if it is contained in excess, it forms coarse nitrides with Nb, V, Ti, which are added for the purpose of suppressing grain growth in the high temperature austenite region, which will be described later, in the main alloying element Cr by quenching heat treatment. The ferrite phase is formed, the adhesion of the coating film is deteriorated, and high strength cannot be obtained. In addition, the manufacturability of the plate may be significantly deteriorated. For this reason, it is 0.17% or less. Preferably, it is 0.15% or less.

  The following elements are arbitrary additive elements that can be contained as required.

“Ni: 2% or less, Cu: 2% or less, Nb: 0.5% or less, V: 0.5% or less, Ti: 0.5% or less”
Ni and Cu are austenite stabilizing elements and are added to supplement the effect of Mn. For this reason, you may make it contain in 2.0% or less of those 1 type or 2 types. Preferably, the content of each is 1.8% or less. In addition, in order to acquire the effect as an austenite stabilization element, it is desirable that it is 0.1% or more.

  Nb, V, and Ti form a compound with C and N in the quenching heat treatment, and suppress grain growth by their pinning effect. Accordingly, the unevenness on the surface of the plate becomes fine and uniform, and better adhesion of the coating film is obtained. For this reason, you may contain those 1 type, or 2 or more types at 0.5% or less. Preferably, the content of each is 0.4% or less. In addition, in order to acquire those effects, it is desirable that it is 0.01% or more.

  The balance other than the above is Fe and impurities. Impurities are components that are contained in raw materials or mixed in during the manufacturing process and are not intentionally contained in steel. Specific examples include P, S, O, Al, Ca, Sb, Sn, W, Co, As, Mg, Pb, Bi, B, H, and REM, and the content is less than 0.1%. is there.

  Next, the composition distribution near the plate surface will be described.

“Si content on plate surface: 2.0% or less”
Stainless steel has a passive film on its surface and has excellent corrosion resistance. However, it may be difficult to obtain good paint film adhesion as it is. The cause of deterioration in the adhesion of the paint film is Si concentration. For this reason, the amount of Si on the plate surface is set to 2.0% or less, which is the upper limit of the addition amount. Preferably, it is less than or equal to the amount added in the material. The surface film of stainless steel is sufficiently thin, and the Si amount on the plate surface is the average value of the distribution in the thickness direction from the plate surface to 0.03 μm.

  The surface film of martensitic stainless steel, which is substantially finished by quenching heat treatment, is generally formed during holding at a high temperature and may be achieved after the heat treatment by adjusting the heat treatment conditions. The heat treatment is generally performed in a non-oxidizing gas, for example, a mixed gas atmosphere of nitrogen and hydrogen, and oxygen concentration and moisture in the atmosphere are reduced, and the concentration of Si is suppressed by adjusting the heating temperature. Be expected. The moisture in the atmosphere is controlled by the dew point.

When the amount of Si on the plate surface does not become 2.0% or less, pickling, for example, in an aqueous solution containing about several percent hydrofluoric acid that dissolves SiO ₂ , in a mixed aqueous solution of several percent sulfuric acid and nitric acid, etc. It is achieved by chemical surface treatment such as electrolytic treatment or physical surface treatment such as sputtering. Furthermore, when there is a Si-reduced layer directly under the concentration of Si on the surface film, Si can be reduced by surface treatment.

  Furthermore, the organization of the material is described.

“A multiphase structure containing a ferrite phase of 30% or less by volume and a residual austenite phase of 20% or less, with the balance being a martensite phase, or a single martensite phase”
The stainless steel of the present invention transforms from an austenite phase at a high temperature to a martensite phase at room temperature during quenching heat treatment. At this time, the target high strength can be obtained by dissolving more interstitial solid solution strengthening elements such as C and N. On the other hand, by forming appropriate irregularities on the surface of the plate by the volume change and precipitation of the compound in the same transformation, excellent adhesion of the coating film can be obtained without adjusting the surface shape (roughness). That is, it is most desirable to use a martensite phase as a main component and a single phase. Furthermore, excellent adhesion of the coating film can be obtained by finely depositing carbides, nitrides and their composite compounds that inevitably precipitate during cooling. When these carbides and nitrides become coarse, the adhesion deteriorates.

  In the case of a multiphase structure, the structure other than the martensite phase is a ferrite phase of 30% or less by volume% and a residual austenite phase of 20% or less. If the ferrite phase exceeds 30% by volume, irregularities due to martensite transformation are not formed on the plate surface, and there is a high possibility that coarse C and N compounds will precipitate, resulting in poor adhesion of the coating film. It is to do. In addition, since the martensite phase is reduced, the required strength may not be obtained. The ferrite phase is preferably 25% or less by volume. If the residual austenite phase exceeds 20% by volume, unevenness due to martensite transformation is not formed on the plate surface, and fine C and N compounds do not precipitate, so the adhesion of the coating film deteriorates. It is. Preferably, it is 15% or less by volume%.

  By adjusting the structure as described above, necessary adhesion and strength of the coating film are achieved. Specifically, the adhesion of the coating film becomes 15 MPa or more in coating peel strength after use for a predetermined time in each product environment. Preferably, it is 17 MPa or more. In addition, when the rubber is further coated after the base treatment by the chromium-free chemical conversion treatment, the peel strength depends on the rubber. With NBR rubber, it is considered difficult to make it 25 MPa or more. The strength of the material is 300 HV or higher in terms of Vickers hardness, which is considered difficult to obtain with an annealed material. Preferably, it is 320HV or more.

  As for the unevenness | corrugation in the board surface achieved by said structure | tissue adjustment, 1.0 micrometer or more is desirable by surface roughness Rz. More preferably, it is 1.1 μm or more. Thereby, it is considered that the concentrated film of Si is divided by the martensitic transformation in the quenching heat treatment, and the adhesion of the coating film is improved by the shape effect. However, when the surface roughness is excessive, it becomes a starting point of fracture, and workability and fatigue characteristics deteriorate. For this reason, the surface roughness Rz is desirably 3.0 μm or less. More preferably, it is 2.0 μm or less. In addition, the maximum diameter corresponding to a sphere of a compound containing carbon and nitrogen is desirably 10 μm or less. Preferably, it is 8 μm or less. These can be adjusted without adding a new process by a composite adjustment such as a structure depending on the quenching heat treatment temperature and a precipitate due to a subsequent cooling rate, by a manufacturing method described later.

  Finally, the manufacturing method, specifically the final heat treatment conditions and surface treatment will be described.

“In a non-oxidizing gas atmosphere with a dew point of −40 ° C. or lower”
As described above, the adhesion of the paint film is deteriorated by the film enriched with Si formed by the final heat treatment. Formation of a Si-enriched surface film is facilitated by an increase in moisture accompanying an increase in dew point. For this reason, the conditions for the final heat treatment were a non-oxidizing gas atmosphere and a dew point of −40 ° C. or lower. Preferably, it is -50 degrees C or less. In an oxidizing atmosphere, since the surface film containing Si is formed to be strong and thick, it is difficult to remove it by subsequent surface treatment.

“Hold at 750-1100 ° C for more than 10 seconds”
The final heat treatment is carried out in order to adjust the steel sheet to a predetermined structure and to obtain the strength required for the stainless steel for springs together with excellent adhesion of the coating film. When the temperature of the heat treatment is less than 750 ° C., a structure mainly composed of a soft ferrite phase is formed with the precipitation of a coarse compound containing carbon and nitrogen. Preferably, the temperature is 800 ° C. or higher at which it is possible to obtain a strength that is difficult to obtain with an annealing material required for a spring application. When the temperature exceeds 1100 ° C., a large amount of δ ferrite phase is generated and remains up to room temperature, and a predetermined structure cannot be obtained. Preferably, it is 1050 degrees C or less. The holding time is set to 10 seconds or more because it is the minimum time necessary for maintaining a uniform temperature of the material. Preferably, it is 30 seconds or more. In this step, a Si-enriched film is uniformly formed on the plate surface.

“Cooling to 600 ° C at a rate of 1 ° C / s or more”
As for the cooling rate, in order to transform the austenite phase during heating into a martensite phase and prevent precipitation of coarse compounds, cooling up to 600 ° C. is performed at a rate of 1 ° C./s or more. Preferably, the cooling rate is 3 ° C./s or more. If the cooling rate to 600 ° C. is 1 ° C./s or more, the cooling rate below 600 ° C. is not particularly limited. In the cooling step, unevenness of RZ 1.0 μm to 3.0 μm is desirably formed on the plate surface, so that the Si concentrated film formed on the plate surface is divided.

"surface treatment"
The surface treatment is carried out following the heat treatment in order to quickly and efficiently remove the Si-enriched surface film divided by the martensitic transformation. The surface treatment is intended to remove the Si-concentrated film, and is a chemical treatment such as electrolytic treatment in an aqueous solution containing hydrofluoric acid in which SiO ₂ dissolves, a mixed aqueous solution of sulfuric acid and nitric acid, or a physical treatment such as sputtering. Achieved. A chemical surface treatment in an aqueous solution containing an acid is preferred. Thereby, at the same time as the removal of the Si-enriched film quickly and efficiently, the fluctuation of the characteristics due to the site of the material is suppressed, and a stable strength can be obtained. More preferably, by using a mixed aqueous solution of 2% or more and 20% or less sulfuric acid and 2% or more and 20% or less nitric acid, which does not use hydrofluoric acid or the like which is prescribed as a specific chemical substance and is considered to have a large environmental load. is there. Furthermore, in order to utilize them effectively and stably, it is desirable to use electrolytic treatment. However, in the present invention, since moderate irregularities are formed on the surface of the plate at the time of martensitic transformation, it is possible to obtain excellent coating film adhesion without newly adjusting the surface shape and the like.

  Table 1 shows the composition of the test steel. The underline indicates that it is outside the scope of the present invention. The material test steel is a small ingot or a real machine ingot at the laboratory level. The thickness is reduced to about 3mm by hot rolling, and after solution heat treatment, the thickness is reduced to 1mm by cold rolling. After heat treatment (annealing), descaling, the thickness was reduced to 0.3 mm by cold rolling, and final heat treatment (quenching) was performed. Next, after subjecting some materials to electrolytic treatment in a mixed aqueous solution of 5% nitric acid and 5% sulfuric acid within a range that does not greatly change the surface shape, the Si amount, structure, Now, the peel strength was investigated.

  The hot rolling was performed by passing a plurality of times in the range of 1200 to 900 ° C., and the plate thickness was about 3 mm. The solution heat treatment was heated to 1050 ° C. for 3 minutes, cooled to room temperature, then heated to 750 ° C. for 3 minutes, allowed to cool, and descaled by shot blasting and pickling. Subsequently, cold rolling was performed to make the plate thickness 1 mm. Thereafter, an intermediate heat treatment (annealing) for cooling after holding at 750 ° C. for 3 minutes in the atmosphere was performed, and descaling was performed in the same manner as after the solution heat treatment. Furthermore, the steel sheet is cold-rolled to a thickness of 0.3 mm, and the final heat treatment (quenching) is a mixed gas composed of 25% nitrogen and 75% hydrogen in a non-oxidizing atmosphere having a dew point of −30 to −50 ° C. After holding at 700 ° C. for 30 seconds, it was cooled at 5 ° C./s.

  For the amount of Si on the plate surface, a distribution in the plate thickness direction was measured by sputtering from the surface to 3 μm using a GDS surface analyzer, and an average value up to 0.03 μm was calculated. The structure was cut in a cross-section parallel to the rolling direction, and the metal structure after embedding, polishing, and etching was observed using an optical microscope and SEM. The plate surface was measured using a ferrite meter and an X-ray diffractometer, and the ratio of each phase was calculated together with the observation results. From these, the proportions of martensite phase, ferrite phase, and austenite phase were determined.

  The hardness was measured at a load of 100 g on the plate surface using a micro Vickers hardness meter. Peel strength is assumed to be a cylinder head gasket, chrome-free chemical conversion base treatment, NBR rubber with a thickness of 25 μm is coated on it, and 200 ° C in a commercially available LLC (long life coolant) aqueous solution for automobile engines. After dipping for 200 hours holding, the peel strength of the rubber was measured.

  Table 2 shows the surface Si amount, structure, hardness, and peel strength of the test material. Invention Example No. A1 to K2 satisfy the provisions of the present invention in terms of both the surface Si amount and the structure, and achieve a target surface hardness of 300 HV 0.1 or higher and a target peel strength of 15 MP or higher. In particular, A3 and B5 subjected to high-temperature quenching satisfied the provisions of the present invention in terms of surface Si amount and structure even without surface treatment, and achieved the target performance. That is, in the steel having the chemical composition defined in the present invention, by satisfying the prescribed surface Si amount and structure, the stainless steel for springs having excellent coating film adhesion and high strength at low cost is manufactured.

  On the other hand, B6, 7 using steel that satisfies the chemical composition of the present invention has a surface treatment that does not satisfy the predetermined structure because B6 has a low final heat treatment temperature and B7 has a high final heat treatment temperature. Even when the specified amount of Si was satisfied, the peel strength was not achieved. In B8, the cooling rate was slow, and similarly, the peel strength did not reach the target. In B8, precipitation of a compound having a diameter of 10.6 μm was confirmed.

  Further, even with B9 and C3 satisfying the chemical components of the present invention, the surface treatment after the final heat treatment was not performed, and when the surface Si amount exceeded the specified amount, the peel strength was not achieved as a target. From these, it was confirmed that an inappropriate structure and Si concentration on the surface of the plate deteriorate the adhesion of the paint film.

  Similarly, in M1, which is outside the definition of the chemical component of the present invention, even when the surface treatment is performed, the specified surface Si amount is not satisfied and the peel strength remains low. L1, N1, O1, and P1 do not satisfy the specified structure, and the peel strength remains low. From these, by specifying an appropriate structure and surface Si amount, it is possible to achieve the targeted high peel strength and hardness, and to produce high-strength and inexpensive stainless steel for springs with excellent paint film adhesion. Was confirmed.

  As described above, the present invention stabilizes inexpensive stainless steel for springs that is applied to automobile-related parts, home appliances, OA equipment casings, roofing / exterior building materials, etc. that have excellent paint film adhesion and high strength. Can be supplied.

Claims (6)

% By mass
C: 0.1 to 0.4%
Si: 2.0% or less,
Mn: 0.1 to 6.0%,
Cr: 10.0-28.0%, and
N: including 0.17% or less,
Having the chemical composition with the balance being Fe and impurities,
The structure includes a ferrite phase of 30% or less by volume and a residual austenite phase of 20% or less, and the remaining phase is a multiphase structure consisting of a martensite phase or a martensite single phase,
A stainless steel plate for springs, wherein the Si amount on the plate surface is 2.0% or less.   The stainless steel plate for springs according to claim 1, wherein the steel plate has a surface roughness Rz of 1.0 µm or more and 3.0 µm. The chemical composition is further mass%,
Ni: 2% or less,
Cu: 2% or less,
Nb: 0.5% or less,
V: 0.5% or less, and
The stainless steel plate for springs according to claim 1 or 2, comprising at least one or more of Ti: 0.5% or less. % By mass
C: 0.1 to 0.4%
Si: 2.0% or less,
Mn: 0.1 to 6.0%,
Cr: 10.0-28.0%, and
N: including 0.17% or less,
A slab having a chemical composition with the balance being Fe and impurities is rolled into a product plate thickness to obtain a steel plate,
Holding the steel sheet at a temperature of 750 to 1100 ° C. for 10 seconds or more in a non-oxidizing gas atmosphere having a dew point of −40 ° C. or less,
The steel sheet is cooled to 600 ° C. at a rate of 1 ° C./s or more,
A method for producing a stainless steel plate for springs, wherein the steel plate is subjected to a surface treatment.   5. The method for producing a stainless steel plate for a spring according to claim 4, wherein the surface treatment is immersion in a mixed aqueous solution of 2% to 20% sulfuric acid and 2% to 20% nitric acid. The chemical composition is further mass%,
Ni: 2% or less,
Cu: 2% or less,
Nb: 0.5% or less,
V: 0.5% or less, and
The method for producing a stainless steel plate for a spring according to claim 4 or 5, comprising at least one or more of Ti: 0.5% or less.