Carbon-containing Cr-based stainless steel sheet and its manufacturing method

Abstract

To provide a carbon-containing Cr-based stainless steel in which carbide is uniformly and finely dispersed and surface properties are good.SOLUTION: In the present invention, a carbon-containing Cr-based stainless steel is produced by a method including a casting process in which an alloy with a specified component is melted, cast and held at 400°C or higher, a hot working process in which the alloy is subsequently heated as necessary and hot worked at 950°C or higher and 1300°C or lower with a reduction rate in the cross section of the longitudinal vertical section of 10% or higher, and a softening annealing process in which the hot-worked alloy is softened and annealed.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing carbon-containing Cr-based stainless steel. In particular, it discloses a method for producing intermediate materials for ingots and products that are suitable for producing martensitic stainless steel products suitable for cutting tools such as razors and kitchen knives. [Background technology]

[0002] Cr-based stainless steels containing 0.16% or more carbon, such as SUS420J1, SUS420J2, and EN1.4116 (Non-Patent Document 1), are used as materials for cutlery such as razor blades and kitchen knives. These steels are also specified in JIS G43034 and G43035.

[0003] In carbon-containing Cr-based stainless steels, rapid cooling using water or oil from a high-temperature austenite phase, where a relatively high concentration of carbon is solid-solubilized, results in a hard martensite phase with supersaturated carbon solid-solubilized at room temperature.

[0004] The hardness of the martensite phase corresponds to the amount of dissolved carbon in the austenite phase when heated to high temperatures, and generally the more carbon added, the higher the hardness after quenching. SUS420J1 contains 0.16% to 0.25%, SUS420J2 0.26% to 0.40%, and EN1.4116 0.45% to 0.55%.

[0005] While SUS420J1 and SUS420J2 are used for general-purpose blades, EN1.4116, which has a high Cr content and is also added with V and Mo to enhance corrosion resistance, is used for high-end blades that require even higher hardness and corrosion resistance.

[0006] Carbon-containing Cr-based stainless steels, such as SUS420J1, SUS420J2, and EN1.4116, have very coarse carbides crystallizing in the center due to center segregation during casting. It is difficult to eliminate these coarse carbides through heating in typical hot rolling or quenching heat treatments, and the process of eliminating them increases costs.

[0007] Furthermore, undissolved coarse carbides remain before and after quenching to produce the finished product, preventing the desired properties from being achieved. Specifically, this causes deterioration in the workability of the intermediate material between the ingot and the finished product, and the hardness of the finished product after quenching often does not achieve the target value or fluctuates. Furthermore, the coarse carbides often appear as undesirable surface patterns on cutlery products or cause chipping of the cutting edge.

[0008] That is, there has been a demand for a method for inexpensively and stably producing carbon-containing Cr-based stainless steel in which carbides are uniformly and finely distributed and which has good surface properties.

[0009] As a prior art that solves these problems, Patent Document 1 discloses a method for producing high-carbon stainless steel having a uniform and fine carbide structure, which is characterized by casting the stainless steel while controlling the cooling rate in the temperature range from the liquidus to the solidus, and then spheroidizing annealing the steel.

[0010] However, the technology described in Patent Document 1 requires rapid cooling in the temperature range from the liquidus to the solidus, and it is very difficult to adjust the cooling rate to such a level in a thick steel slab.

[0011] Patent Document 2 discloses a method for producing a carbon-containing Cr-based hot-rolled stainless steel sheet in which coarse carbides are refined by subjecting a stainless steel slab cast by a continuous casting method to a homogenizing heat treatment.

[0012] However, to dissolve the coarse carbides, it is necessary to eliminate the surrounding Cr segregation, which requires high-temperature and long-term homogenization heat treatment, which may increase production costs.In addition, it is prone to uneven oxidation, where the thickness of the oxide scale varies from place to place, which may deteriorate the surface quality of the slab cast.

[0013] Furthermore, when the steel sheet is formed, the depressions may appear as streaks, which may mar the appearance of the product. In such cases, the streaks can be removed by grinding, but this may result in a decrease in yield and an increase in labor costs, which may increase the manufacturing cost of the martensitic stainless steel product.

[0014] On the other hand, Patent Document 3 discloses a method for producing martensitic stainless steel with fine carbides, which is characterized by hot rolling stainless steel containing 0.5 to 1.5% C and 10 to 25% Cr, in which the stainless steel is rolled at a total reduction of at least 10% in a solid-liquid coexistence temperature range of 1250°C to 1450°C, and then rolled at a total reduction of at least 50% in a solid phase range below 1250°C, for the purpose of refining carbides.

[0015] However, controlling the reduction in the presence of both solid and liquid is difficult and requires the introduction of dedicated equipment, which is costly.

[0016] Patent Document 4 also discloses a method for producing martensitic stainless steel billets, which is characterized by continuously casting a stainless steel containing 0.4% or less C, 10-15% Cr, and others, followed by cooling from the austenite temperature range to 300°C at a cooling rate of 20°C / Hr or less, heating to 1200-1250°C and hot rolling, and then cooling at a rate of 10°C / Hr or less, in order to prevent cracking due to transformation during cooling of the ingot.

[0017] Patent Document 4 shows the effect of preventing cracking of slabs, but does not mention the effect of refining carbides. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] Japanese Patent Application Publication No. 5-209252 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-82838 [Patent Document 3] Japanese Patent Application Publication No. 1-230714 [Patent Document 4] Japanese Patent Application Publication No. 4-276014 [Non-patent literature]

[0019] [Non-Patent Document 1] Stainless steel European standard EN10088-2 Summary of the Invention [Problem to be solved by the invention]

[0020] The present invention is intended to solve the problems of the prior art, and aims to provide a carbon-containing Cr-based stainless steel with a high C content, in which carbides are uniformly and finely distributed and the surface properties are good, and a method for producing the same.

[0021] Here, uniform and fine distribution of carbides means a state in which there are no coarse carbides, that is, the maximum value of the diameter of the circle equivalent to the projected area of ​​the carbides at the center of the plate thickness is 5 μm or less. [Means for solving the problem]

[0022] The present inventors have focused on hot working (hereinafter referred to as "breakdown"), which is carried out successively without cooling the cast material to room temperature, and investigated the effect on the metal structure of carbon-containing Cr-based stainless steel.

[0023] As a result, they discovered that when the center of the cast material is cooled to a temperature range where nucleation is dominant, carbide precipitation occurs not only at the grain boundaries of the parent phase but also within the grains, and that when the material passes through a temperature range where nucleation growth is dominant during the subsequent heating process, the carbides precipitated within the grains of the parent phase grow and aggregate with the carbides that crystallized during casting, forming clusters.

[0024] On the other hand, it was also confirmed that when cooling is stopped within the temperature range where nucleation growth is dominant and the temperature is raised again, the clusters are not formed.

[0025] Furthermore, when the inventors investigated the breakdown, they discovered that a temperature distribution was obtained in which the center of the cast material was higher than the surface, and that the strain caused by processing was concentrated in the center, which effectively crushed coarse carbides in the center and compressed the segregated regions of substitutional elements such as Cr, thereby shortening the diffusion distance of the substitutional elements required for eliminating segregation. They also discovered that this promoted the re-dissolution of carbides in the subsequent homogenization heat treatment.

[0026] Furthermore, we discovered that by promoting re-dissolution, high-temperature, long-term homogenization heat treatment is no longer necessary, which prevents the occurrence of streaky patterns caused by non-uniform oxidation and reduces manufacturing costs.

[0027] The present inventors have clarified the conditions for the manufacturing method that can achieve the above-mentioned effects, and have thereby completed the present invention. The gist of the invention is as follows.

[0028] (1) A method for producing a carbon-containing Cr-based stainless steel, comprising: a casting step of melting and casting an alloy having a chemical composition of a carbon-containing Cr-based stainless steel containing, by mass, C: 0.40% to 1.00% and Cr: 10.5% to 18.0%; and maintaining the alloy at 400°C or higher; a hot working step of, following the casting step, heating the alloy as necessary and hot working the alloy at 950°C to 1300°C with a cross-sectional area reduction rate of 10% or more in a vertical cross section in the longitudinal direction; and a softening annealing step of softening the hot-worked alloy.

[0029] (2) A method for producing a carbon-containing Cr-based stainless steel according to (1), characterized in that after the hot working step and before the softening annealing step, a homogenization heat treatment step is further included in which the alloy is held at 1100°C or higher and 1300°C or lower for 4 hours or higher and 30 hours or lower.

[0030] (3) The method for producing a carbon-containing Cr-based stainless steel according to (1) or (2), characterized in that the carbon-containing Cr-based stainless steel has the shape of a slab, plate, or strip with a thickness of 4.0 mm or more.

[0031] (4) The method for producing a carbon-containing Cr-based stainless steel according to any one of (1) to (3), characterized in that the alloy contains, in mass %, C: 0.40% or more and 1.00% or less, Cr: 10.5% or more and 18.0% or less, Si: 0 to 1.00%, Mn: 0 to 1.00%, Ni: 0 to 1.0%, Mo: 0 to 1.00%, V: 0 to 1.00%, N: 0 to 0.10%, P: 0.040% or less, S: 0.030% or less, and the balance: Fe and impurities.

[0032] (5) A carbon-containing Cr-based stainless steel containing, by mass%, C: 0.40% or more and 1.00% or less, and Cr: 10.5% or more and 18.0% or less, and characterized in that the maximum value of the diameter of the projected area circle equivalent of carbides at the center of the plate thickness is 5 μm or less.

[0033] (6) The carbon-containing Cr-based stainless steel according to (5), characterized in that it contains, by mass%, C: 0.40% or more and 1.00% or less, Cr: 10.5% or more and 18.0% or less, Si: 0 to 1.00%, Mn: 0 to 1.00%, Ni: 0 to 1.0%, Mo: 0 to 1.00%, V: 0 to 1.00%, N: 0 to 0.10%, P: 0.040% or less, S: 0.030% or less, and the balance: Fe and impurities. [Effects of the Invention]

[0034] According to the present invention, it is possible to inexpensively and stably produce carbon-containing Cr-based stainless steel in which carbides are uniformly and finely distributed and which has good surface properties. DETAILED DESCRIPTION OF THE INVENTION

[0035] The method for producing carbon-containing Cr-based stainless steel of the present invention will be described in detail below. Hereinafter, the "%" designation for the content of an element means "% by mass."

[0036] 1. Manufacturing method of carbon-containing Cr-based stainless steel

[0037] A method for producing the carbon-containing Cr-based stainless steel of the present invention will now be described.

[0038] <Casting process>

[0039] First, an alloy having the components of carbon-containing Cr-based stainless steel containing C: 0.40% or more and 1.00% or less and Cr: 10.5% or more and 18.0% or less is melted and cast.

[0040] In the casting of martensitic stainless steel, the slab is slowly cooled to room temperature after casting to prevent cracking. In contrast, in the present invention, when the alloy is cast and cooled, it is important to maintain the temperature at 400°C or higher, which is the temperature range in which nucleation is dominant. If the temperature falls below 400°C, nucleation becomes dominant, resulting in the formation of carbide clusters and coarse carbides. 420°C or higher is preferred, and 450°C or higher is more preferred. The time for maintaining the temperature at 400°C or higher is not particularly limited, as long as the temperature does not fall below 400°C during cooling. Furthermore, as described below, after casting, the temperature may be maintained at 950°C or higher, which is the processing temperature for the next step.

[0041] As described above, the present invention aims to suppress the formation of coarse carbides resulting from centerline segregation during casting, and differs from the method aimed at preventing cracks due to martensitic transformation shown in Patent Document 4. However, this does not exclude the prevention of cracks due to transformation that is thought to start at around 300°C.

[0042] After holding at the aforementioned temperature, the material is heated to a temperature between 950°C and 1300°C. If the heating temperature is below 950°C, deformation resistance is high, increasing the processing load. On the other hand, if the heating temperature exceeds 1300°C, oxidation progresses significantly and uneven oxidation occurs, damaging the surface quality and increasing the possibility of streaking on the surface of the product. Therefore, the heating temperature for breakdown is set to between 950°C and 1300°C. A temperature between 970°C and 1280°C is more preferable, and a temperature between 980°C and 1250°C is most preferable.

[0043] As mentioned above, it is not necessary to cool the material to 400°C or higher but less than 950°C. The processing described below may be carried out when the material has reached 950°C or higher and 1300°C or lower by cooling after casting. In this case, there is no need to heat the material. This is preferable because the temperature at the center is maintained higher than at the surface, which promotes the introduction of strain into the center.

[0044] The heating time is preferably such that the material reaches a uniform temperature and the temperature distribution is such that the center is hotter than the surface where cooling progresses during breakdown, and the temperature is preferably held in the range of 950°C to 1300°C for 0.5 hours or more, and more preferably for 1 hour or more. Note that the present invention aims to crush, in the solid state, coarse carbides resulting from center segregation during solidification and to effectively compress the segregation regions of substitutional elements such as Cr, and it is desirable that the temperature at the center be higher than the surface, facilitating the introduction of strain into the center.

[0045] <Hot processing process>

[0046] After heating, processing is performed. If the processing rate (reduction of area) is less than 10%, the effect of shortening the distance over which substitutional elements must diffuse to eliminate segregation is insufficient, and coarse carbides remain. A processing rate of 12% or more is preferable, and 15% or more is most preferable. On the other hand, the higher the processing rate, the greater the effect of eliminating segregation, and the finer the carbides can be made. The processing rate can be determined based on the capacity of the rolling equipment, and there is no particular upper limit. In laboratory-level equipment, the upper limit was around 40%. The processing end temperature is preferably less than 1100°C (the lower limit of the homogenization heat treatment temperature described below), and more preferably 950°C, at which deformation resistance becomes high. There are no particular restrictions on the subsequent cooling. Cooling to room temperature is also possible.

[0047] <Homogenization heat treatment process>

[0048] After that, it is desirable to reheat the steel slab after the breakdown and perform a homogenization heat treatment. If the heating temperature of the homogenization heat treatment is less than 1100°C, the diffusion rate of the substitutional elements is insufficient, which prevents the elimination of segregation and prevents the effect of refining carbides. On the other hand, if the temperature exceeds 1300°C, non-uniform oxidation occurs, resulting in the appearance of streaks on the surface of the steel sheet, which impairs the appearance. Therefore, the heating temperature of the homogenization heat treatment is set to 1100°C or higher and 1300°C or lower. 1100°C or higher and 1280°C or lower are more preferable, and 1120°C or higher and 1250°C or lower are most preferable.

[0049] The duration of the homogenization heat treatment is preferably 4 hours or more and 40 hours or less, more preferably 5 hours or more and 37 hours or less, and even more preferably 6 hours or more and 30 hours or less, from the viewpoint of facilitating dissolution of carbides by sufficiently diffusing substitutional elements without segregating them, and from the viewpoint of the appearance of the steel sheet surface.

[0050] The cooling rate after the homogenization heat treatment is not particularly limited. For example, it may be a cooling rate of 0.05°C / s or more, or air cooling may be used. After the homogenization heat treatment, hot rolling is performed. The hot rolling may be performed under conditions generally used in the production of carbon-containing Cr-based stainless steels.

[0051] <Softening annealing process>

[0052] After hot rolling, the steel is softened by annealing. The softened annealing may be performed under typical conditions for the production of carbon-containing Cr-based stainless steel. For example, the treatment may be performed at a temperature in the range of 700 to 900°C for 1 to 100 hours.

[0053] After soft annealing, pickling, cold rolling, and final heat treatment can be repeated as necessary to obtain a steel sheet of a desired thickness. Pickling is a process for removing surface oxide scale, cold rolling is a process for obtaining a desired thickness, and final heat treatment is a process for releasing strain introduced by the cold rolling and softening the steel by recrystallization, and conditions generally used in the production of carbon-containing Cr-based stainless steels may be used.

[0054] The carbon-containing Cr-based stainless steel after breakdown is preferably in the form of a slab with a thickness of 100 mm or more, as it is often produced by a general-purpose sheet processing process and is therefore efficient. A thickness of 200 mm or more is more preferable, and 250 mm or more is even more preferable. The thickness after hot rolling is preferably 4.0 mm or more and 6.0 mm or less, and the thickness at the subsequent cold rolling stage is preferably 0.4 mm or more and less than 4.0 mm. These shapes are generally plate or strip.

[0055] In the method for producing carbon-containing Cr-based stainless steel of the present invention, it is efficient and rational to also perform hot rolling, and the thickness of the intermediate material between the ingot and the product is preferably in the range of 4.0 mm or more. The thickness of the product is preferably in the range of 0.4 mm to 6.0 mm. However, this assumes a general-purpose plate process and does not exclude shapes such as bars, pipes, section steel, or billets made from intermediate materials thereof.

[0056] 2. Chemical composition of carbon-containing Cr-based stainless steel

[0057] The manufacturing method of the present invention is a manufacturing method for preventing the formation of coarse carbides in high-C martensitic stainless steel containing a large amount of C. It can be applied to the manufacturing of carbon-containing Cr-based stainless steel containing 0.40% to 1.00% C and 10.5% to 18.0% Cr, and can achieve the effect of uniformly and finely distributing carbides and improving surface properties. Therefore, other components are not particularly important. Below, an example of the components of carbon-containing Cr-based stainless steel to which the manufacturing method of the present invention can be applied will be described.

[0058] C is an important element for ensuring the hardness and wear resistance of martensite. If the C content is less than 0.40%, the hardened hardness and wear resistance required for blade applications cannot be obtained. A preferable lower limit of the C content is 0.45%. Taking into consideration the amount of retained austenite after quenching, corrosion resistance, and toughness, the upper limit of the C content is preferably set to 1.00%, and more preferably to 0.60%.

[0059] Cr is an element that improves corrosion resistance. Taking into consideration the corrosion resistance and the amount of retained austenite after quenching, the lower limit of the Cr content is preferably 10.5%, more preferably 13.0%. The upper limit of the Cr content is preferably 18.0%, more preferably 16.0%.

[0060] The balance other than C and Cr can be Fe. Other elements may be contained depending on the properties required for the carbon-containing Cr-based stainless steel. Impurities may also be contained within a range that does not adversely affect the properties required for the carbon-containing Cr-based stainless steel.

[0061] Below, examples of elements other than C, Cr, and Fe that can be added depending on the application will be described.

[0062] Si is an element that improves oxidation resistance and may be added as needed. Taking into consideration the occurrence of cracks during manufacturing, the Si content is preferably 1.00% or less.

[0063] Mn is used as a deoxidizing element and may be added as needed. Taking into consideration the reduction in corrosion resistance due to the formation of compounds such as sulfides, the Mn content is preferably 1.0% or less.

[0064] Ni is an element that improves toughness when the martensite phase is formed, and may be added as needed. Taking into consideration the decrease in hardness due to an increase in the amount of retained austenite, the increase in alloy cost, and the impediment to manufacturability, the Ni content is preferably 1.0% or less.

[0065] Mo is an element that improves corrosion resistance and may be added as needed. In consideration of the effect that justifies the cost of adding Mo, the Mo content is preferably 1.00% or less.

[0066] V is an element that improves corrosion resistance and may be added as needed. In consideration of the effect that justifies the cost of adding it, the V content is preferably 1.00% or less.

[0067] N is an element for ensuring the hardness and corrosion resistance of martensite and may be added as needed. Taking into consideration the decrease in hardness due to an increase in the amount of retained austenite, the N content is preferably 0.10% or less.

[0068] P is an unavoidably contained impurity element that reduces formability and corrosion resistance. The lower the P content, the better. Therefore, the P content is preferably 0.040% or less.

[0069] S is an unavoidably contained impurity element that promotes cracking during manufacturing, so the S content is preferably 0.030% or less.

[0070] In addition, other elements may be contained depending on the properties required of the carbon-containing Cr-based stainless steel. [Example]

[0071] Examples of the present invention are given below.

[0072] The alloys shown in Table 1 were melted and then cast into slabs of 200 mm in thickness by continuous casting, and then held at the holding temperature after casting shown in Table 2. After this holding, the temperature was raised again and heated at the breakdown heating temperature shown in Table 2 for 2 hours, and then the total reduction shown in Table 2 was applied, followed by cooling to room temperature.

[0073] [Table 1]

[0074] [Table 2]

[0075] After breakdown, some of the examples were subjected to homogenization heat treatment under the conditions shown in Table 2, and the slabs were air-cooled. The slabs that had been subjected to breakdown or homogenization heat treatment were hot-rolled to form steel plates with a thickness of 5.0 mm. The rolled steel plates were further subjected to softening heat treatment at 800°C for 48 hours to obtain hot-rolled steel plates.

[0076] Thereafter, Nos. 2 to 11, 16 to 26, and 30 to 38 were subjected to sulfuric acid pickling, cold rolling at a total reduction of 60%, and heat treatment at 700 to 800°C for 2 minutes to obtain cold-rolled and annealed steel sheets with a thickness of 2.0 mm.

[0077] Furthermore, for Nos. 3 to 11, 17 to 26, and 30 to 38, the obtained cold-rolled and annealed steel sheets were subjected to cold rolling, cold-rolled sheet annealing, and pickling again to produce cold-rolled and annealed steel sheets with a sheet thickness of 0.8 mm.

[0078] As comparative examples, cold-rolled annealed steel sheets having a thickness of 0.8 mm were also produced without carrying out either or both of the steps of holding at 400°C or higher and breakdown after casting (Nos. 12 to 14, 27 to 29, 39 to 41).

[0079] (Temperature measurement method) The surface temperature of the object was measured using a radiation thermometer.

[0080] (Method for measuring particle size of carbides and determining whether or not coarse carbides are present) The particle size of the carbides was determined using the following method. After mirror polishing the L-section of the hot-rolled steel sheet or cold-rolled annealed steel sheet, it was etched with aqua regia to reveal the carbides, and 200 carbides present at a position half the thickness of the sheet were photographed using an SEM at 5000x magnification. The area of ​​each carbide was calculated from the photographed structure, converted into an equivalent circle, and its diameter was defined as the particle size.

[0081] The carbides observed in the carbon-containing Cr-based stainless steel produced by the present invention are (Cr,Fe) 23 C6 or (Cr,Fe)7C3. The composition of the carbide can be confirmed by EDX.

[0082] The presence or absence of coarse carbides was judged based on the maximum particle size of the carbides observed. If the particle size was larger than 5 μm, it was judged that coarse carbides remained and was rated as unacceptable (×). On the other hand, if the particle size was 5 μm or less, it was judged that no coarse carbides were present and was rated as acceptable (◯). Of the samples judged to be acceptable, those with a particle size of less than 2 μm were rated as even better (◎).

[0083] (Method for determining the presence or absence of streaks on the surface of steel sheets) To evaluate the surface properties, the presence or absence of streaks was investigated for pickled hot-rolled steel sheets with a thickness of 5.0 mm, and cold-rolled annealed steel sheets with thicknesses of 2.0 and 0.8 mm. The presence or absence of streaks was determined by the following method.

[0084] The presence or absence of streaks was visually confirmed along the entire length of one side of the steel sheet. If streaks were found in areas (hereinafter referred to as "segments") that were divided into 1m sections along the entire length of the coil in the longitudinal direction, the area was recognized as a "segment with streaks." The percentage of "segments with streaks" out of the total number of segments along the entire length of the steel sheet (hereinafter referred to as the "defect rate") was calculated, and a defect rate of more than 5% was evaluated as failing (×), and a defect rate of 5% or less was evaluated as passing (◯). The evaluation results are shown in Table 2.

[0085] In Examples 1 to 8, 15 to 23, and 30 to 35, in which the holding temperature after casting and the breakdown conditions were both within the specified ranges, no coarse carbides or streaky patterns were observed. Among the above Examples, in Examples 4 to 8, 19 to 23, and 31 to 35, in which homogenization heat treatment was performed, the particle size of the carbides was particularly small and refined.

[0086] In contrast to the above, coarse carbides remained in Nos. 12, 27, and 39, which were held at temperatures lower than the specified range after casting, and Nos. 13, 28, and 40, which were not subjected to breakdown.

[0087] Streaky patterns were observed in Nos. 9, 24, and 36, where the breakdown heating temperature was higher than the specified range. Coarse carbides remained in Nos. 10, 25, and 37, where the breakdown heating temperature and total reduction were lower than the specified range. Coarse carbides remained in Nos. 11, 26, and 38, where the breakdown total reduction was lower than the specified range. Streaky patterns were also observed in Nos. 14, 29, and 41, where the homogenization time of the homogenization heat treatment was longer than the specified range. [Industrial Applicability]

[0088] The manufacturing method of the present disclosure enables stable production of carbon-containing Cr-based stainless steel sheets with uniform and fine carbide distribution and good surface appearance, which in turn allows efficient production of, for example, high-quality cutlery products that require hardness and corrosion resistance.

Claims

1. A method for producing a carbon-containing Cr-based stainless steel sheet, comprising: a casting step of melting and casting an alloy having a chemical composition of a carbon-containing Cr-based stainless steel containing, by mass%, C: 0.40% to 1.00% and Cr: 10.5% to 18.0%, and maintaining the alloy at 400°C or higher; a hot working step of, if necessary, heating the alloy following the casting step and hot working the alloy at a temperature of 950°C to 1300°C with a cross-sectional area reduction rate of 10% or more in a vertical cross section in the longitudinal direction; A softening annealing step in which the alloy that has been hot worked is softened. Equipped with The maximum value of the projected area circle equivalent diameter of carbides at the center of the thickness of the carbon-containing Cr-based stainless steel plate is 5 μm or less, and when the entire length of the coil of the carbon-containing Cr-based stainless steel plate is divided into regions every 1 m in the longitudinal direction, each region is defined as a "segment," and a segment in which a streak pattern is visually recognized within the region is defined as a "segment with a streak pattern," the proportion of the segments with a streak pattern to the total number of segments over the entire length of the carbon-containing Cr-based stainless steel plate is 5% or less. A method for producing a carbon-containing Cr-based stainless steel sheet.

2. After the hot working step and before the soft annealing step, a homogenization heat treatment step is further included in which the alloy is held at 1100°C or higher and 1300°C or lower for 4 hours or higher and 30 hours or lower. The method for producing a carbon-containing Cr-based stainless steel sheet according to claim 1 .

3. 3. The method for producing a carbon-containing Cr-based stainless steel plate according to claim 1, wherein the carbon-containing Cr-based stainless steel plate has a thickness of 4.0 mm or more.

4. The alloy comprises, in mass %: C: 0.40% or more and 1.00% or less, Cr: 10.5% or more and 18.0% or less, Si: 0 to 1.00%, Mn: 0 to 1.00%, Ni: 0-1.0%, Mo: 0-1.00%, V: 0-1.00%, N: 0-0.10%, P: 0.040% or less, S: 0.030% or less Contains The balance is Fe and impurities The method for producing a carbon-containing Cr-based stainless steel sheet according to any one of claims 1 to 3, characterized in that

5. A carbon-containing Cr-based stainless steel plate, The carbon-containing Cr-based stainless steel plate contains, in mass%, C: 0.40% or more and 1.00% or less, and Cr: 10.5% or more and 18.0% or less, The maximum value of the projected area circle equivalent diameter of carbides at the center of the plate thickness of the carbon-containing Cr-based stainless steel plate is 5 μm or less. and When the entire length of the coil of the carbon-containing Cr-based stainless steel plate is divided into regions every 1 m in the longitudinal direction and each region is defined as a "segment," and a segment in which a streak pattern is visually recognized within the region is defined as a "segment with a streak pattern," the proportion of the segments with a streak pattern to the total number of segments over the entire length of the carbon-containing Cr-based stainless steel plate is 5% or less. A carbon-containing Cr-based stainless steel plate characterized by:

6. In mass%, C: 0.40% or more and 1.00% or less, Cr: 10.5% or more and 18.0% or less, Si: 0 to 1.00%, Mn: 0 to 1.00%, Ni: 0-1.0%, Mo: 0-1.00%, V: 0-1.00%, N: 0-0.10%, P: 0.040% or less, S: 0.030% or less Contains The balance is Fe and impurities is The carbon-containing Cr-based stainless steel sheet according to claim 5 .

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