WO2024225118A1 - マルテンサイト系ステンレス鋼材及びその製造方法、並びに刃物の製造方法 - Google Patents

マルテンサイト系ステンレス鋼材及びその製造方法、並びに刃物の製造方法 Download PDF

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WO2024225118A1
WO2024225118A1 PCT/JP2024/015180 JP2024015180W WO2024225118A1 WO 2024225118 A1 WO2024225118 A1 WO 2024225118A1 JP 2024015180 W JP2024015180 W JP 2024015180W WO 2024225118 A1 WO2024225118 A1 WO 2024225118A1
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less
quenching
martensitic stainless
stainless steel
steel material
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French (fr)
Japanese (ja)
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航 西村
詠一朗 石丸
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Nippon Steel Stainless Steel Corp
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Nippon Steel Stainless Steel Corp
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Priority to JP2025516749A priority Critical patent/JPWO2024225118A1/ja
Priority to CN202480013518.0A priority patent/CN120641593A/zh
Priority to EP24796871.2A priority patent/EP4675002A1/en
Priority to KR1020257027403A priority patent/KR20250138756A/ko
Publication of WO2024225118A1 publication Critical patent/WO2024225118A1/ja
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    • C21D1/18—Hardening; Quenching with or without subsequent tempering
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    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
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Definitions

  • the present invention relates to martensitic stainless steel materials and their manufacturing methods, as well as to methods for manufacturing blades.
  • Stainless steel materials used in various blades such as shavers, scissors, and kitchen knives require high hardness, so martensitic stainless steel materials with a high C content are used (for example, Patent Document 1).
  • the C content is high, it will generate carbides with alloy elements such as Cr, and will easily precipitate as coarse eutectic carbides during the manufacturing process.
  • This eutectic carbide is difficult to completely dissolve even by annealing, and the amount of C in solid solution will decrease during quenching or quench-tempering, causing excessive softening.
  • this eutectic carbide will become a corrosion starting point, causing a decrease in corrosion resistance, and will also cause chipping during processing and the occurrence of irregular stripe-like or island-like patterns.
  • C is a strong austenite stabilizing element, if a large amount of residual austenite remains after quenching or quench-tempering due to the segregation of C, it will also lead to a decrease in hardness, deterioration of sharpness, and the occurrence of irregular stripe-like or island-like patterns.
  • Patent Document 2 describes the following composition by mass: C: 0.40 to 0.50%, Si: 0.05 to 0.60%, Mn: 0.5 to 1.5%, P: 0.035% or less, S: 0.010% or less, Cr: 11.0 to 15.5%, Ni: 0.01 to 0.30%, Cu: 0.01 to 0.30%, Mo: 0.01 to 0.30%, V: 0.01 to 0.10%,
  • Patent Document 3 also proposes a method for producing a grain-refined martensitic stainless steel material, which includes the steps of: preparing a base material having a composition consisting of 13.0-14.0% by weight of Cr, 1.15-1.35% by weight of Mo, 0.35-0.55% by weight of C, 0.20-0.50% by weight of Si, 0.20-0.50% by weight of Mn, 0.025% by weight or less of P, 0.020% by weight or less of S, and the balance being Fe and unavoidable impurity elements; subjecting this base material to at least one of a high-density dislocation introduction method and an ultra-rapid solidification method, and then annealing the resultant to obtain a fine-structured ferritic steel; and subjecting the ferritic steel to cold rolling, annealing, and, if necessary, plastic working into a predetermined shape, and then quenching to obtain a grain-refined martensitic stainless steel material.
  • Patent Document 4 proposes a method for producing a martensitic stainless steel material (martensitic stainless steel thin plate) in which the number density of carbides having a circle equivalent diameter of 0.5 ⁇ m or more is controlled to 0 to 50 pieces/1000 ⁇ m 2 by heating a stainless steel thin plate material having a thickness of 0.1 mm or less to a temperature exceeding 1000 ° C for 1 to 10 minutes in a nitrogen atmosphere and then cooling the material, which is made of a component composition of C: 0.25 to 0.45%, Si: 1.0% or less, Mn: 0.1 to 1.5%, Cr : 12.0 to 15.0%, Mo: 0.5 to 3.0%, N: 0.30 to 0.45%, and the balance Fe and impurities, when quenched and tempered, the martensitic stainless steel material produced by this method can obtain high hardness from the surface to the center of the plate thickness, and also has good corrosion resistance.
  • Patent Document 5 describes a method for producing a steel slab having a composition, by mass%, of C: 0.45-0.60%, Si: 0.05-1.00%, Mn: 0.05-1.00%, P: 0.05% or less, S: 0.020% or less, Cr: 13.0% or more but less than 16.0%, Ni: 0.10-1.00%, and N: 0.010-0.200%, with the balance being Fe and unavoidable impurities, comprising a first step of holding the steel slab at 1200-1350°C for 30 minutes or more;
  • a method for producing a martensitic stainless steel material (stainless steel sheet) has been proposed, which includes a second step of coiling the hot-rolled steel sheet and a third step of annealing the hot-rolled steel sheet to produce a hot-rolled annealed steel sheet, in which the hot-rolling in the second step includes three or more rolling passes with an end temperature of 1050°C or higher and a reduction rate of 20% or higher, the coiling temperature of the hot-rolled steel sheet is
  • the martensitic stainless steel material described in Patent Document 2 has an inclusion (particularly, carbide) having an average grain size that is not controlled, and therefore may have insufficient workability or may develop irregular patterns.
  • the martensitic stainless steel material described in Patent Document 3 is not suitable for mass production because it requires special processes such as a high density dislocation introduction method and an ultra-rapid solidification method, and also has a high Mo content and is expensive.
  • the martensitic stainless steel material described in Patent Document 4 is expensive because it is heat-treated in a nitrogen atmosphere to increase nitrogen and dissolve coarse carbides.
  • this martensitic stainless steel material is limited to a thin plate having a thickness of 0.1 mm or less, making it difficult to use it for cutting tools such as knives.
  • knives and other blades are mainly manufactured by forging and grinding martensitic stainless steel material to form it into the product shape, then hardening it through quenching and sub-zero treatment, and tempering it to ensure toughness. If the martensitic stainless steel material is overly hardened before quenching, its workability through forging and grinding decreases, making it difficult to form it into the desired product shape.
  • the present invention has been made to solve the above-mentioned problems, and aims to provide a martensitic stainless steel material that has good workability due to its softness before quenching or quenching and tempering, and has high hardness and corrosion resistance after quenching or quenching and tempering, and can suppress the occurrence of irregular patterns, and a manufacturing method thereof.
  • Another object of the present invention is to provide a method for manufacturing a blade that is easy to process, has high hardness and corrosion resistance, has good sharpness, and is capable of suppressing the occurrence of irregular patterns.
  • the inventors then discovered that all of the above problems could be solved by controlling the average grain size of carbides, the number of carbides with a size of 10 ⁇ m or more, the Vickers hardness before quenching or quenching and tempering, the amount of retained austenite after quenching or quenching and tempering, and the amount of dissolved C and N after quenching or quenching and tempering, in addition to the steel composition, and thus completed the present invention.
  • the present invention has a composition, on a mass basis, of C: 0.305 to 0.600%, Si: 0.05 to 1.00%, Mn: 0.05 to 2.50%, P: 0.0085 to 0.0400%, S: 0.0300% or less, Cr: 13.0 to 18.0%, Ni: 0.01 to 1.00%, Mo: 0.01 to 1.00%, Al: 0.100% or less, N: 0.010 to 0.350%, Ca: 0.0001 to 0.0050%, O: 0.001 to 0.010%, with the balance being Fe and impurities;
  • the average grain size of the carbide is 0.50 ⁇ m or less,
  • the number of the carbides having a size of 10 ⁇ m or more is 0.10 pieces/cm2 or less,
  • the Vickers hardness before quenching or quenching and tempering is 320 HV or less;
  • the amount of retained austenite after quenching or quenching and tempering is 10.0 vol.% or less, This is a martensitic stainless steel material in
  • the present invention also provides a steel sheet having, on a mass basis, C: 0.305 to 0.600%, Si: 0.05 to 1.00%, Mn: 0.05 to 2.50%, P: 0.0085 to 0.0400%, S: 0.0300% or less, Cr: 13.0 to 18.0%, Ni: 0.01 to 1.00%, Mo: 0.01 to 1.00%, Al: 0.100% or less, N: 0.010 to 0.350%, Ca: 0.0001 a breakdown rolling step in which a slab having a composition containing 0.0050% or less, 0.001% or less, and the balance being Fe and impurities is heat-treated at a temperature of 1000°C or more and less than 1200°C for 1 to 10 hours, and then roughly rolled under conditions in which a total rolling ratio is 30 to 70% and a rolling ratio per pass is 10% or more, and two or more passes are performed to obtain a breakdown material; a hot rolling step of performing a heat treatment on the breakdown material at a temperature of 1000° C.
  • the hot-rolled material is coiled at a coiling temperature of 800°C to 900°C, and then heated at a temperature of Ac1 point to (Ac1 point - 50°C) for 1 to 5 hours for softening.
  • the present invention relates to a method for manufacturing a blade that includes a hardening process in which the martensitic stainless steel material is processed, then heated at a temperature of 1000°C to 1200°C for 5 to 60 minutes, and cooled at a cooling rate of 3°C/sec or more.
  • a martensitic stainless steel material and a manufacturing method thereof which has good workability due to its softness before quenching or quenching and tempering, and has high hardness and corrosion resistance after quenching or quenching and tempering, and can suppress the occurrence of irregular patterns. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a blade that is easy to process, has high hardness and corrosion resistance, has good sharpness, and is capable of suppressing the occurrence of irregular patterns.
  • the martensitic stainless steel material according to an embodiment of the present invention has a composition containing C: 0.305-0.600%, Si: 0.05-1.00%, Mn: 0.05-2.50%, P: 0.0085-0.0400%, S: 0.0300% or less, Cr: 13.0-18.0%, Ni: 0.01-1.00%, Mo: 0.01-1.00%, Al: 0.100% or less, N: 0.010-0.350%, Ca: 0.0001-0.0050%, O: 0.001-0.010%, with the balance being Fe and impurities.
  • steel material means materials of various material shapes such as steel plate.
  • steel plate is a concept including steel strip.
  • impurities means components that are mixed in due to various factors in raw materials such as ores and scraps and manufacturing processes when industrially manufacturing stainless steel materials, and are allowed within a range that does not adversely affect the present invention. Examples of impurities include Zn, Pb, Se, Sb, H, Ga, Ta, Mg, and Zr.
  • xx% or less means including an amount of xx% or less, but greater than 0% (particularly, greater than the impurity level).
  • the martensitic stainless steel material according to an embodiment of the present invention may further contain one or more selected from V: 0.50% or less, Nb: 0.50% or less, Ti: 0.30% or less, Cu: 4.0% or less, Sn: 0.10% or less, B: 0.005% or less, and Co: 0.30% or less.
  • V 0.50% or less
  • Nb 0.50% or less
  • Ti 0.30% or less
  • Cu 4.0% or less
  • Sn 0.10% or less
  • B 0.005% or less
  • Co 0.30% or less
  • C is an essential element for obtaining a predetermined hardness (Vickers hardness) after quenching or quenching and tempering.
  • the C content is set to 0.305% or more.
  • the lower limit of the C content is preferably 0.320%, and the upper limit is preferably 0.600%. is preferably 0.580%.
  • Si 0.05-1.00%> Silicon is necessary for deoxidation during melting and refining, and is also a useful element for suppressing the formation of oxide scale during quenching. If the silicon content is low, deoxidation tends to be insufficient. However, the amount of carbides increases, which may cause rusting and reduce corrosion resistance. Therefore, the Si content must be 0.05% or more. On the other hand, Si has a high austenite single phase temperature. In order to stably obtain the above-mentioned effects of Si, the lower limit of the Si content is set to 1.00%. The content is preferably 0.07%, and the upper limit is preferably 0.98%.
  • Mn is an element added as a deoxidizer, and also expands the austenite single phase temperature range and contributes to improving hardenability. If not enough Mn is added, the two-phase region expands and the ⁇ phase increases. As a result, the amount of Cr carbonitrides also increases, and a Cr-deficient layer forms around them, which can easily become the starting point for rusting and reduce corrosion resistance. Therefore, the Mn content must be 0.05% or more. From the viewpoint of stably obtaining the above-mentioned effects of Mn, the lower limit of the Mn content is preferably 0.10%. On the other hand, Mn in an amount greater than necessary decreases the corrosion resistance and increases the formation of oxide scale during quenching.
  • the Mn content must be 2.50% or less. Taking into consideration the decrease in corrosion resistance caused by granulated matter, the content is preferably 1.50% or less.
  • P is an element contained as an impurity in main raw materials such as molten iron and ferrochrome.
  • P is also a harmful element to the toughness and corrosion resistance of materials after quenching or quenching and tempering. Therefore, the P content
  • excessive reduction in P content causes problems such as the necessity to use high-purity raw materials, which leads to increased costs.
  • the lower limit of the P content is 0.0085%.
  • S forms sulfide-based inclusions, which deteriorate the general corrosion resistance (general corrosion and pitting corrosion) of steel materials. S also reduces hot workability and increases the edge cracking susceptibility of hot-rolled sheets. Therefore, the S content must be 0.0300% or less, preferably 0.0200% or less.
  • the lower limit of the S content is not particularly limited, but The lower the S content, the better the corrosion resistance, but the greater the desulfurization load and the higher the production cost. Therefore, the lower limit of the S content is preferably 0.0001%.
  • Cr is an element that maintains the corrosion resistance required for the main applications of martensitic stainless steel materials. Therefore, the Cr content must be 13.0% or more. On the other hand, Cr forms carbides. The addition of a large amount of Cr not only causes the formation of coarse carbides, but also increases the amount of retained austenite after quenching or quench-tempering. From the viewpoint of stably obtaining the above-mentioned effects due to Cr, the lower limit of the Cr content is preferably 13.1% and the upper limit is preferably 17.8%. be.
  • Ni like Mn
  • Ni is an austenite stabilizing element and has the effect of improving the toughness after quenching or quenching and tempering.
  • the press formability is deteriorated due to solid solution strengthening in the hot rolled annealed material.
  • the amount of retained austenite may increase after quenching or quenching and tempering, and the manufacturing cost increases because Ni is an expensive element.
  • the Ni content since Ni is an element effective in suppressing the progress of pitting corrosion, the Ni content must be 0.01% or more. Therefore, the lower limit of the Ni content is preferably 0.02%, and the upper limit is preferably 0.80%, more preferably 0.50%.
  • Mo is an element that is effective in improving the corrosion resistance of the martensite structure containing ⁇ -ferrite. To obtain this effect, the Mo content must be 0.01% or more. On the other hand, Mo is an element that effectively improves the corrosion resistance of the martensite structure containing ⁇ -ferrite. Mo is a stabilizing element, and excessive addition of Mo narrows the austenite single phase temperature range, impairing hardenability. Therefore, the Mo content must be 1.00% or less. From the viewpoint of stably obtaining this, the lower limit of the Mo content is preferably 0.02%, and the upper limit is preferably 0.80%, more preferably 0.60%.
  • Al is added as a deoxidizing element and also as an element that improves oxidation resistance.
  • carbides tend to become large.
  • Al is a ferrite stabilizing element, It prevents austenite transformation and raises the Ac1 line. Therefore, the content of Al must be 0.100% or less, preferably 0.050% or less, and more preferably 0.030% or less.
  • the lower limit of the content is not particularly limited, but from the viewpoint of obtaining the above-mentioned effects due to Al, the lower limit of Al is preferably 0.001%.
  • Al is T.Al.
  • N is an essential element for obtaining a predetermined hardness (Vickers hardness) after quenching or quenching and tempering.
  • N since the C content is reduced, Instead, N must be contained.
  • N has the effect of improving corrosion resistance when in solid solution. From the viewpoint of obtaining these effects, the N content is set to 0.010% or more.
  • N may form Cr-based nitrides and cause a Cr-deficient layer, which reduces corrosion resistance.
  • adding excessive N makes it difficult to control at the steelmaking stage. It is difficult to remove the defects, and air bubble defects are likely to form.
  • the N content must be 0.350% or less. From the viewpoint of stably obtaining the above-mentioned effects of N, the lower limit of the N content is preferably 0.015%, more preferably 0. The upper limit is preferably 0.300%, and more preferably 0.290%.
  • Ca is added to adjust the composition during steelmaking.
  • Ca acts as a strong deoxidizer and has the effect of promoting deoxidation.
  • the Ca content must be 0.0050% or less, preferably 0.0045% or less, and more preferably 0.0040% or less. Since it is impossible to achieve this, it is difficult in the manufacturing process to make the Ca content less than 0.0001%, so the Ca content is set to 0.0001% or more.
  • O In order to reduce inclusions, O, along with Al and Ca, is an important element. If a large amount of O is added, the number of large inclusions (especially carbides) remaining in the steel increases, which has a negative effect on corrosion resistance. Therefore, the content of O must be 0.010% or less. It is preferable to reduce the content of O as much as possible, but excessive reduction increases the cost. Therefore, the content of O is From the viewpoint of the balance between cost and corrosion resistance, the lower limit of the O content is preferably 0.002% and the upper limit is preferably 0.009%.
  • C and N are essential elements for obtaining a predetermined hardness (Vickers hardness) after quenching or quenching and tempering.
  • N is added.
  • C contributes to the hardness 2.5 times as much as N. Therefore, from the viewpoint of obtaining a predetermined hardness, 2.5C+N is 0.80% or more, preferably 0.85% or more.
  • the upper limit of 2.5C+N is preferably set to 1. It is preferably less than 20%, more preferably less than 1.10%.
  • V is an element that forms fine carbonitrides and contributes to improving corrosion resistance, and is added as necessary.
  • V is an element that forms fine carbonitrides and contributes to improving corrosion resistance, and is added as necessary.
  • excessive addition of V may cause coarsening of precipitates, As a result, the toughness after quenching or quenching and tempering is reduced. Therefore, the V content is 0.50% or less, preferably 0.30% or less, and more preferably 0.20% or less.
  • the lower limit of the V content is not particularly limited, but V is mixed into the alloy raw material as an inevitable impurity, and it may be difficult to remove it in the refining process.
  • the lower limit of the V content is preferably 0.01%, more preferably 0.02%, and further preferably 0.03%.
  • Nb is an element that forms carbonitrides and suppresses sensitization and a decrease in corrosion resistance due to the precipitation of chromium carbonitrides, and is added as necessary.
  • the Nb content is set to 0.50% or less, preferably 0.35% or less, more preferably 0.30% or less, and further preferably 0.25% or less.
  • the lower limit of the Nb content is not particularly limited, but from the viewpoint of obtaining the above-mentioned effects, it is preferably 0.01%, and more preferably 0.05%.
  • Ti is an element that forms carbonitrides and suppresses sensitization and a decrease in corrosion resistance caused by the precipitation of chromium carbonitrides, and is added as necessary. However, if Ti is added in excess, coarse TiN particles are formed. This leads to the occurrence of hot rolling defects and a decrease in toughness. Therefore, the Ti content is set to 0.30% or less, and preferably 0.25% or less.
  • the lower limit of the Ti content is Although not particularly limited, from the viewpoint of obtaining the above-mentioned effects, the content is preferably 0.01%, more preferably 0.06%, and further preferably 0.10%.
  • Cu is an element that is effective in improving the corrosion resistance of the martensite structure containing ⁇ -ferrite, and also contributes to improving hardenability as an austenite stabilizing element, and is added as necessary.
  • the Cu content is set to 4.0% or less, preferably 3.8% or less, and more preferably 3.5% or less.
  • the lower limit of the Cu content is not particularly limited, but from the viewpoint of obtaining the above-mentioned effects, it is preferably 1.0%, more preferably 1.3%, and further preferably 1.5%. .
  • Sn is an element effective in improving corrosion resistance after quenching or quenching and tempering, and is added as necessary. However, excessive addition of Sn promotes edge cracking during hot rolling. Therefore, the content of Sn is The amount of Sn is 0.10% or less, preferably 0.09% or less.
  • the lower limit of the Sn content is not particularly limited, but from the viewpoint of obtaining the above-mentioned effects, it is preferably 0.002% or less. More preferably, it is 0.05%.
  • B is an element effective in improving hot workability and is added as necessary.
  • the content of B is set to 0.005% or less, preferably 0.0045% or less.
  • the lower limit of the content of B is not particularly limited, but from the viewpoint of obtaining the above-mentioned effects, it is preferably set to 0.005% or less. It is 0.0002%.
  • Co is an element that improves heat resistance and is added as necessary. However, since Co is an expensive element, if the Co content is too high, it leads to an increase in manufacturing costs.
  • the content of Co is 0.30% or less, preferably 0.10% or less, and more preferably 0.05% or less.
  • the lower limit of the Co content is not particularly limited, but if the above effect is not obtained, the lower limit of the Co content is 0.30% or less, more preferably 0.10% or less, and even more preferably 0.05% or less. From the viewpoint of obtaining the desired result, the content is preferably 0.01%.
  • the average grain size of the carbides is 0.50 ⁇ m or less, preferably 0.48 ⁇ m or less.
  • the lower limit of the average grain size of the carbides is not particularly limited, but is preferably 0.01 ⁇ m, more preferably 0.05 ⁇ m, and even more preferably 0.10 ⁇ m.
  • the carbides for which the average grain size is specified include both eutectic carbides formed during casting and precipitated carbides formed during the rolling process.
  • the average grain size of the carbides can be calculated by observing the cross section of the martensitic stainless steel material with a SEM, measuring the circle equivalent diameter of each carbide in the observed field of view, and finding the average value.
  • the number of carbides having a size of 10 ⁇ m or more is 0.10 pieces/cm2 or less, preferably 0.05 pieces/cm2 or less. Since carbides having a size of 10 ⁇ m or more tend to be the starting point of rusting, by controlling the number of carbides having a size of 10 ⁇ m or more within such a range, rusting can be suppressed and corrosion resistance can be improved. In addition, since carbides having a size of 10 ⁇ m or more can also cause irregular patterns, the occurrence of irregular patterns can also be suppressed by controlling the number of these carbides.
  • the number of carbides having a size of 10 ⁇ m or more is mainly intended to refer to eutectic carbides formed during casting.
  • the size of the carbide is defined as (major axis + minor axis)/2 of the carbide.
  • the number of carbides having a size of 10 ⁇ m or more can be calculated by observing the cross section of the martensitic stainless steel material with an optical microscope to determine the number of carbides having a size of 10 ⁇ m or more, and dividing that number by the area of the measurement region.
  • the martensitic stainless steel material according to the embodiment of the present invention has a Vickers hardness of 320 HV or less, preferably 300 HV or less, and more preferably 290 HV or less before quenching or quenching and tempering. Since the material has a Vickers hardness in this range, it is soft and can improve the workability by forging, polishing, etc.
  • the lower limit of the Vickers hardness is not particularly limited, but is preferably 150 HV, and more preferably 200 HV. In this specification, the Vickers hardness means a value measured at room temperature (25° C.) using a Vickers hardness tester.
  • the martensitic stainless steel material according to an embodiment of the present invention has a residual austenite amount after quenching or quenching and tempering of 10.0% by volume or less, preferably 8.0% by volume or less, and more preferably 5.0% by volume or less.
  • Retained austenite occurs when austenite formed during quenching remains without transforming into martensite during subsequent treatments (e.g., sub-zero treatment, tempering treatment). Retained austenite is particularly likely to occur in areas where carbon, a strong austenite stabilizing element, is segregated. Retained austenite is softer than martensite, so if a large amount is present, the desired hardness cannot be obtained.
  • the amount of retained austenite can be calculated as follows. First, a cross section of a martensitic stainless steel material is observed using EBSD to distinguish between the BCC and FCC crystal structure phases and determine their respective areas. Next, based on these areas, the ratio of the area of the FCC crystal structure phase to the total area of the BCC and FCC crystal structure phases (i.e., the area ratio of the FCC crystal structure phase) is calculated. The area ratio of the FCC crystal structure phase calculated in this way is regarded as the amount of retained austenite (volume %).
  • [C] + 0.3 [N] when the amount of dissolved C after quenching or quenching and tempering is [C] and the amount of dissolved N is [N], [C] + 0.3 [N] is 0.15% or more.
  • [C] + 0.3 [N] when the martensitic stainless steel material is used for blades, it is preferable that [C] + 0.3 [N] is 0.20% or more. With [C] + 0.3 [N] in this range, strength for blades can be ensured.
  • the upper limit of [C] + 0.3 [N] is not particularly limited, but is preferably 1.00%, and more preferably 0.80%.
  • the amounts of C and N dissolved in solid solution can be measured by the following electrolytic extraction residue method.
  • a test piece of about 20 mm square is cut out from the width center of the martensitic stainless steel material, and the entire surface of the test piece corresponding to the surface of the martensitic stainless steel material is wet-polished with water-resistant abrasive paper of number #600. After polishing, the test piece base material (stainless steel base material) is dissolved by electrolysis at a constant potential of -100 mV in a methanol solution containing 10% maleic anhydride and 2% tetramethylammonium chloride.
  • the residue (precipitate) remaining in the solution without dissolving is captured using a 200 nm mesh filter.
  • the captured precipitate is washed with pure water and dried.
  • the precipitate is dissolved with aqua regia and perchloric acid, and then elemental analysis is performed using ICP atomic emission spectroscopy in accordance with JIS G1258:2014 to determine the mass of C in the precipitate.
  • the obtained mass is divided by the mass change of the test piece due to electrolysis ("mass of the test piece before electrolysis" - "mass of the test piece after electrolysis") and expressed as a percentage to obtain the "amount of precipitation Cp " (%).
  • the amount of solid solution [N] can also be determined in a similar manner.
  • the martensitic stainless steel material according to the embodiment of the present invention preferably has a Vickers hardness of 500 HV or more after quenching or quenching and tempering.
  • the Vickers hardness is 550 HV or more. If the Vickers hardness is in this range, the strength required for a blade can be ensured.
  • the upper limit of the hardness is not particularly limited, but is preferably 900 HV, more preferably 800 HV.
  • quenching is performed at 1000 to 1200° C.
  • tempering is performed at 100 to 400° C. After quenching, it is desirable to perform sub-zero treatment at ⁇ 200 to ⁇ 50° C.
  • the martensitic stainless steel material according to the embodiment of the present invention is not particularly limited, but is preferably a hot-rolled sheet, a hot-rolled annealed sheet, a cold-rolled sheet, or a cold-rolled annealed sheet.
  • the martensitic stainless steel material according to an embodiment of the present invention can be manufactured by using a slab having the same composition as the martensitic stainless steel material described above, and by a method including a breakdown rolling process, a hot rolling process, and a softening process.
  • the breakdown rolling process is a process in which the slab is subjected to a heat treatment at a temperature of 1000° C. or more and less than 1200° C. for 1 to 10 hours, and then roughly rolled under conditions in which the total rolling ratio is 30 to 70% and includes two or more passes with a rolling ratio of 10% or more per pass, to obtain a breakdown material.
  • the upper limit of the heat treatment temperature is preferably 1180° C. or less, more preferably 1160° C. or less, and even more preferably 1150° C. or less.
  • the width of macrosegregation is reduced by rough rolling, and carbon diffusion is promoted by the introduction of dislocations extending to the center of the breakdown material, so that the segregation of carbon generated during casting is eliminated. Furthermore, it is possible to suppress the generation of retained austenite caused by the decrease in Ms point due to carbon segregation. As a result, it is possible to control the average grain size of carbides, the number of carbides with a size of 10 ⁇ m or more, and the amount of retained austenite after quenching or quenching and tempering within the above ranges. These effects can be effectively obtained by combining with the next hot rolling process and the soaking treatment process performed as necessary.
  • the heat treatment time in the breakdown rolling step is less than 1 hour or the heat treatment temperature is less than 1000° C., the effect of solution of eutectic carbides and reduction of carbon segregation cannot be sufficiently obtained. Also, if the heat treatment time in the breakdown rolling step exceeds 10 hours or the heat treatment temperature is 1200° C. or higher, sagging deformation occurs due to the weight of the slab, making it difficult to carry out the subsequent steps. In addition, if the total rolling ratio of the breakdown rolling process is less than 30%, the introduction of dislocations is insufficient and the width of macrosegregation is difficult to reduce, so that the effect of solution of eutectic carbides and reduction of carbon segregation cannot be sufficiently obtained.
  • the rolling ratio of the subsequent hot rolling is insufficient.
  • the rolling reduction ratio of each pass during breakdown is low, the strain does not reach the center of the plate, and the effect of eliminating macrosegregation is weakened, so it is necessary to perform two passes with a rolling ratio of 10% or more.
  • the number of passes in the breakdown rolling step is not particularly limited as long as it is 2 or more, but is preferably 2 to 9, and more preferably 2 to 6.
  • the position of the pass with a rolling ratio of 10% or more is also not particularly limited, but it is preferable that the rolling ratio of the final pass and the pass before that is 10% or more.
  • the hot rolling step is a step in which the breakdown material is heat treated at a temperature of 1000° C. or higher and lower than 1200° C. for 1 to 5 hours, and then hot rolled to obtain a hot-rolled material.
  • the eutectic carbides formed during casting can be completely brought into solution, making it possible to control, within the above-mentioned ranges, the average grain size of the carbides, the number of carbides having a size of 10 ⁇ m or more, and the amount of retained austenite after quenching or quenching and tempering.
  • the hot rolling conditions are not particularly limited, but it is preferable to finish the plate to a thickness of 2 to 8 mm.
  • the heat treatment time in the hot rolling process is less than 1 hour or the heat treatment temperature is less than 1000°C, the effect of solution of eutectic carbides and reduction of carbon segregation will not be fully achieved. Furthermore, if the heat treatment time in the hot rolling process exceeds 5 hours or the heat treatment temperature is 1200°C or higher, sagging deformation will occur due to the weight of the breakdown material, making it difficult to carry out subsequent processes. From the viewpoint of stably ensuring the above effects, it is preferable that the heat treatment time in the hot rolling process is 1.5 to 3 hours.
  • the softening process is a process in which the hot-rolled material is coiled at a coiling temperature of 800° C. to 900° C., and then heated at a temperature of Ac1 point to (Ac1 point ⁇ 50° C.) for 1 to 5 hours.
  • a softened material (martensitic stainless steel material) having a Vickers hardness of 320 HV or less and high workability can be obtained before quenching or quenching and tempering.
  • the heating is performed by holding the coiled hot-rolled sheet in a heated state at a temperature of Ac1 point to (Ac1 point - 50°C). Therefore, it should be noted that the heating is not performed by once cooling the coiled hot-rolled sheet and then reheating it to the same temperature. The heating is performed in a batch annealing furnace.
  • the Ac1 point is calculated by the following formula (1).
  • each element symbol indicates the mass percentage of each element.
  • the softened material obtained in the softening step may be pickled as necessary.
  • a soaking step may be carried out, if necessary, between the breakdown rolling step and the hot rolling step.
  • the soaking treatment step is a step in which the breakdown material is held at a temperature of 1000° C. or higher and lower than 1200° C. for 1 to 24 hours. By carrying out the soaking treatment step under such conditions, it is possible to enhance the effect of bringing eutectic carbides into solution and reducing carbon segregation.
  • the heat treatment time in the soaking process is less than 1 hour or the heat treatment temperature is less than 1000°C, the effect of solution of eutectic carbides and reduction of carbon segregation will not be fully achieved. Furthermore, if the heat treatment time in the soaking process exceeds 24 hours or the heat treatment temperature is 1200°C or higher, sagging deformation will occur due to the weight of the breakdown material, making it difficult to carry out subsequent processes. From the viewpoint of stably ensuring the above effects, the heat treatment time in the soaking process is preferably 3 to 20 hours, and more preferably 3 to 15 hours.
  • the cold rolling step is a step in which the softened material obtained in the softening step is cold rolled to obtain a cold rolled material.
  • the cold rolling conditions are not particularly limited and may be appropriately adjusted depending on the required cold rolled material.
  • the annealing step is a step of heating the cold-rolled material from 100° C. to a temperature of Ac1 point to (Ac1 point-50° C.) at a temperature increase rate of 50° C./sec or more.
  • the temperature increase rate is preferably 100° C./sec or more.
  • the temperatures from Ac1 point to (Ac1 point-50° C.) are the annealing temperatures in the annealing process, and the heating rate can be calculated by dividing the value obtained by subtracting 100 from the annealing temperature (annealing temperature-100 [° C.]) by the time [s] required to reach the annealing temperature from 100° C.
  • the martensitic stainless steel material according to the embodiment of the present invention manufactured as described above has, in addition to the steel composition, the average grain size of the carbides, the number of carbides with a size of 10 ⁇ m or more, the Vickers hardness before quenching or quenching and tempering, the amount of retained austenite after quenching or quenching and tempering, and the amount of dissolved C and N after quenching or quenching and tempering, so that it is soft and has good workability before quenching or quenching and tempering, and has high hardness and corrosion resistance after quenching or quenching and tempering, and is able to suppress the occurrence of irregular patterns.
  • the method for manufacturing a blade according to an embodiment of the present invention includes a quenching step in which the above martensitic stainless steel material is processed, then heated at a temperature of 1000° C. to 1200° C. for 5 to 60 minutes, and cooled at a cooling rate of 3° C./sec or more.
  • the cooling rate is preferably 10° C./sec or more, and more preferably 20° C./sec or more.
  • the method for processing the martensitic stainless steel material is not particularly limited, and known methods such as forging and polishing can be used.
  • a tempering step or a sub-zero treatment step can be performed as necessary.
  • the conditions for the tempering step and the sub-zero treatment step are not particularly limited, but it is preferable to perform the tempering step at a temperature of 100 to 400°C and the sub-zero treatment step at a temperature of -200 to -50°C.
  • Knives manufactured using the above manufacturing method are easy to process, have high hardness and corrosion resistance, and have good sharpness, while also preventing the occurrence of irregular patterns.
  • the hot-rolled sheet obtained in the hot rolling process was wound into a coil at a coiling temperature of 850°C, and then the coiled hot-rolled sheet was transferred to a batch annealing furnace, where the softening process was carried out under the conditions shown in Tables 2 and 3.
  • the softened plate obtained in the softening step was cold rolled to a thickness of 2.0 mm.
  • pickling was performed.
  • the cold-rolled annealed sheets (martensitic stainless steel materials) obtained as described above were subjected to the following evaluations.
  • the Vickers hardness (Vickers hardness before quenching or quenching and tempering) of the obtained cold-rolled annealed sheet was measured with a Vickers hardness tester. The measurement temperature was room temperature (25° C.). A Vickers hardness of 320 HV or less was considered to be acceptable.
  • the cold-rolled annealed sheets were quenched under the conditions shown in Tables 2 and 3, subzero-treated at -70°C, and tempered at 200°C. The surfaces were then polished with #80 and the JIS surface hardness (Vickers hardness after quenching or quenching and tempering) was measured with a Vickers hardness tester. The measurement temperature was room temperature (25°C). A Vickers hardness of 500HV or more was considered to pass.
  • the cross section of the obtained cold-rolled annealed sheet parallel to the rolling direction and the sheet thickness direction was observed by SEM, and all carbide particles observed in the observation field were measured for their equivalent circle diameter ( ⁇ m), except for carbide particles with a circle equivalent diameter of less than 0.10 ⁇ m and carbide particles with a part of the particle protruding from the observation field, and the sum of the circle equivalent diameters of the carbide particles to be measured divided by the total number of the carbide particles to be measured was defined as the average particle size ( ⁇ m) of the carbide.
  • the total number of the carbide particles to be measured was set to 100 or more by randomly selected multiple non-overlapping observation fields.
  • the equivalent circle diameter of the carbide particles was calculated from the area of the carbide particles obtained by image processing the SEM images using image processing software.
  • the obtained cold-rolled annealed sheet was quenched under the conditions shown in Tables 2 and 3, subzero-treated at -70 ° C, and tempered at 200 ° C.
  • the cross section parallel to the rolling direction and the sheet thickness direction of the tempered sample thus obtained was measured using EBSD, and then the BCC and FCC crystal structure phases were distinguished and their areas were determined. Next, based on these areas, the ratio of the area of the FCC crystal structure phase to the total area of the BCC and FCC crystal structure phases (i.e., the area ratio (%) of the FCC crystal structure phase) was calculated, and the calculated area ratio of the FCC crystal structure phase was regarded as the amount of retained austenite (volume %).
  • the results of the above evaluations are shown in Table 4.
  • the cold-rolled annealed sheets (martensitic stainless steel materials) of Examples 1 to 22 were able to control [C] + 0.3 [N] to 0.15% or more, the Vickers hardness before quenching or quenching and tempering to 320 HV or less, the average grain size of carbides to 0.50 ⁇ m or less, the number of carbides with a size of 10 ⁇ m or more to 0.10 pieces / cm 2 or less, and the amount of retained austenite after quenching and tempering to 10.0 volume % or less.
  • Examples 21 and 22 are examples in which a soaking treatment step was performed, and the corrosion resistance was improved by controlling the heating temperature in the soaking treatment to 1000 ° C. or more and less than 1200 ° C. and the heating time to 1 to 24 hours.
  • the cold-rolled annealed sheets of Comparative Examples 1 to 17 were outside the specified ranges in any of the composition, [C]+0.3 [N], Vickers hardness before quenching or quenching and tempering, average grain size of carbides, number of carbides with a size of 10 ⁇ m or more, and amount of retained austenite after quenching and tempering. Therefore, the cold-rolled annealed sheets of Comparative Examples 1 to 17 did not have the desired characteristics.
  • Figure 1 shows a graph showing the relationship between [C] + 0.3 [N] (the amount of dissolved C (mass%) after quenching or quenching and tempering is [C], and the amount of dissolved N (mass%) is [N]) and Vickers hardness in some examples and comparative examples.
  • there is a proportional relationship between [C] + 0.3 [N] and Vickers hardness and it was found that as [C] + 0.3 [N] increases, the Vickers hardness also tends to increase.
  • a blade was produced from the obtained cold-rolled annealed sheet as follows. First, the obtained cold-rolled annealed sheet was punched out and then polished to form a blade shape, which was then quenched under the conditions shown in Tables 2 and 3, subzero-treated at -70°C, and tempered at 200°C. The surface was then polished, and the portion that would become the cutting edge was then roughly polished and finish-polished to form the cutting edge, thereby obtaining a blade. The blades thus obtained were evaluated as follows.
  • the sharpness of the blades was evaluated using a Hyundai sharpness tester. The sharpness test was performed by fixing the blade, stacking 7.5 mm wide sheets of paper equivalent to newspaper (thickness about 70 ⁇ m), and applying a load of about 750 g while performing a reciprocating motion of 20 mm. One reciprocating motion was counted as one cycle, and 100 cycles were performed, and the number of sheets of paper that were completely cut was counted. The sharpness can be evaluated as good when the number of sheets of paper that were cut was 50 or more.
  • Examples 21 and 22 are examples in which a soaking treatment step was carried out, and by controlling the heating temperature in the soaking treatment to 1000°C or more and less than 1200°C, and the heating time to 1 to 24 hours, the sharpness was improved and the effect of suppressing the occurrence of irregular patterns was also high.
  • Comparative Examples 11 and 12 have insufficient corrosion resistance from the above results.
  • the blades made from the cold-rolled annealed sheets of Comparative Examples 1, 15, and 16 had insufficient workability.
  • the blades made from the cold-rolled annealed sheets of Comparative Examples 1 to 10, 13, and 14 did not have sufficient sharpness and could not suppress the occurrence of irregular patterns. Furthermore, the blade made from the cold-rolled annealed sheet of Comparative Example 17 did not have sufficient sharpness.
  • the present invention can provide a martensitic stainless steel material that is soft before quenching or quenching and tempering and therefore has good workability, and that has high hardness and corrosion resistance after quenching or quenching and tempering and can suppress the occurrence of irregular patterns, as well as a manufacturing method thereof.
  • the present invention can also provide a manufacturing method for a blade that is easy to process, has high hardness and corrosion resistance, has good sharpness, and can suppress the occurrence of irregular patterns.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)
PCT/JP2024/015180 2023-04-26 2024-04-16 マルテンサイト系ステンレス鋼材及びその製造方法、並びに刃物の製造方法 Ceased WO2024225118A1 (ja)

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CN202480013518.0A CN120641593A (zh) 2023-04-26 2024-04-16 马氏体系不锈钢材及其制造方法以及刀具的制造方法
EP24796871.2A EP4675002A1 (en) 2023-04-26 2024-04-16 Martensitic stainless-steel material, method for producing same, and method for producing cutting article
KR1020257027403A KR20250138756A (ko) 2023-04-26 2024-04-16 마텐자이트계 스테인리스 강재 및 그 제조 방법, 그리고 날붙이의 제조 방법

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WO2025197859A1 (ja) * 2024-03-19 2025-09-25 日本製鉄株式会社 マルテンサイト系快削ステンレス棒状鋼材及びその製造方法
WO2025215886A1 (ja) * 2024-04-08 2025-10-16 日本製鉄株式会社 マルテンサイト系ステンレス鋼材及びその製造方法、並びにマルテンサイト系ステンレス鋼の焼入れ又は焼入れ焼戻し材

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WO2025215886A1 (ja) * 2024-04-08 2025-10-16 日本製鉄株式会社 マルテンサイト系ステンレス鋼材及びその製造方法、並びにマルテンサイト系ステンレス鋼の焼入れ又は焼入れ焼戻し材

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