WO2021044889A1 - Martensitic stainless steel plate and martensitic stainless steel member - Google Patents
Martensitic stainless steel plate and martensitic stainless steel member Download PDFInfo
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- WO2021044889A1 WO2021044889A1 PCT/JP2020/031886 JP2020031886W WO2021044889A1 WO 2021044889 A1 WO2021044889 A1 WO 2021044889A1 JP 2020031886 W JP2020031886 W JP 2020031886W WO 2021044889 A1 WO2021044889 A1 WO 2021044889A1
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- 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
- C21D2211/005—Ferrite
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Definitions
- the present invention relates to a martensitic stainless steel sheet and a martensitic stainless steel member having excellent corrosion resistance after quenching. More specifically, the present invention relates to martensitic stainless steel having excellent corrosion resistance even when air-cooled and hardened, which is used for manufacturing Western tableware knives, looms, tools, disc brakes and the like.
- Martensitic stainless steel sheets such as SUS420J1 and SUS420J2 steel are generally used for tools such as Western tableware knives (table knives), scissors, weaving machines, and calipers. In such applications, it is difficult to use plating, painting, and rust preventive oil, and the material itself is required to have rust resistance. It is also important that it does not wear easily, and high hardness is required.
- the manufacturing process of Western tableware knives, etc. is usually made by die-cutting from a steel plate, heating, quenching, and then polishing to make a knife.
- the quenching process is often performed by air cooling, which also depends on the characteristics of the martensitic stainless steel sheet, which has excellent quenching properties.
- Patent Document 1 discloses a martensitic stainless steel that is air-cooled and has excellent corrosion resistance during quenching.
- N is added up to about 0.06% as an element for improving corrosion resistance.
- Patent Document 2 discloses a steel to which N is further added.
- Patent Document 3 discloses a steel in which N is further increased by using special equipment.
- the present inventors first investigated the rusting condition of the table knife in detail. As a result, it was clarified that the rusting site starts from the end face of the steel sheet, more specifically, the central part of the thickness of the steel sheet. Furthermore, the formation of a ⁇ ferrite phase ( ⁇ Fe phase) due to macrosegregation was confirmed, and the grain boundaries of this ⁇ Fe became the accumulation sites of carbides, and the carbides melted by heating during quenching, and then grain boundaries during cooling. It was found that the mechanism of quenching is that precipitation occurs, resulting in sensitization and intergranular corrosion. It was also found that the rusting depends on the cooling rate during quenching.
- the cooling rate varies greatly depending on the quenching equipment, but when evaluated by the average cooling rate from the quenching temperature to 600 ° C, which is the temperature at which carbide precipitation is almost completed, the cooling rate exceeds 100 ° C / s in water quenching.
- the cooling rate is only about 5 ° C / s, and carbide precipitation cannot be suppressed and quenching is unlikely to occur. It turns out that is likely to occur.
- a martensitic stainless steel sheet having a ⁇ p of 120 or more represented by the following formula (1) When the martensitic stainless steel sheet is held at 1050 ° C. for 30 minutes, then air-cooled and quenched, and tempered at 150 ° C. for 30 minutes, the area of ⁇ ferrite ( ⁇ Fe) present in the center of the plate thickness in the plate thickness cross section.
- ⁇ p 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
- the element symbol in the formula (1) means the content (mass%) of the element.
- the ⁇ p represented by the following formula (1) is 120 or more, and Further, a martensitic stainless steel member characterized in that the area ratio of ⁇ ferrite ( ⁇ Fe) existing in the central portion of the plate thickness in the plate thickness cross section is 0.1 to 1%.
- ⁇ p 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
- the element symbol in the formula (1) means the content (mass%) of the element.
- the martensitic stainless steel sheet of the present invention has excellent corrosion resistance, especially end face corrosion resistance, while maintaining sufficient hardness to withstand use for martensitic stainless steel applications such as table knives and other Western tableware. Therefore, when it is used as a martensitic stainless steel member such as a Western tableware knife, it can be expected to have an effect of improving corrosion resistance and prolonging the product life.
- C is an element that determines the quenching hardness together with N, and is required to be 0.100% or more in order to obtain the hardness required for a Western tableware knife. It is preferably 0.110% or more, and 0.120% or more.
- the quenching hardness becomes larger than necessary, the load during polishing increases, and the toughness also decreases.
- Cr carbides are likely to precipitate during air-cooling quenching and the corrosion resistance is likely to be impaired, so the content is set to 0.170% or less. It is preferably 0.155% or less.
- Si 0.25 to 0.60% Since Si is necessary for deoxidation in steelmaking and is also effective in suppressing the formation of oxide scale after quenching heat treatment, it is contained in an amount of 0.25% or more. If it is less than 0.25%, an oxidation scale is excessively generated, which increases the final polishing load. However, excessive addition suppresses austenite production and impairs hardenability, so the content is set to 0.60% or less.
- Mn 0.10 to 0.60%
- Mn is an austenite-stabilizing element and is necessary for ensuring hardness and the amount of martensite during quenching. Therefore, it is contained in an amount of 0.10% or more. However, in order to promote the formation of oxide scale during quenching and increase the subsequent polishing load, the content is set to 0.60% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
- P 0.035% or less
- P is an element contained as an impurity in alloys such as hot metal and ferrochrome, which are raw materials. Since it is an element harmful to the toughness of the steel sheet after hot spreading annealing and quenching, its content shall be 0.035% or less. Excessive addition reduces hot workability and corrosion resistance.
- S 0.015% or less S has a small solid solubility in the austenite phase and segregates at the grain boundaries to promote a decrease in hot workability. Therefore, the content is set to 0.015% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
- Cr 11.0 to 15.0% Cr is required at least 11.0% or more in order to maintain corrosion resistance as a Western tableware knife. On the other hand, since it also has the effect of narrowing the stable temperature of austenite, it should be 15.0% or less. Preferably, it is 12.0% or more. The upper limit is preferably 14.0% or less. The range is preferably 12.0 to 14.0%.
- Ni 0.05 to 0.60% Like Mn, Ni is an austenite-stable element and is necessary for securing hardness and the amount of martensite during quenching. It also has the effect of improving corrosion resistance. Therefore, it is contained in an amount of 0.05% or more. However, since Ni is more expensive than other elements, it should be 0.60% or less.
- Cu 0.010 to 0.50%
- Cu is an austenite-stable element like Mn and Ni, and is an element that improves corrosion resistance. Although it is an element that cannot be avoided from scrap during steelmaking, it is contained in an amount of 0.010% or more in order to improve corrosion resistance. On the other hand, excessive content reduces hot workability and the like, so the content should be 0.50% or less. Although it is cheaper than Ni, it is relatively expensive, so its addition is an element that we want to keep as low as possible.
- V 0.010 to 0.10%
- V is an element that is often inevitably mixed with ferrochrome or the like, which is an alloy element. The reduction is difficult and contains 0.010% or more. However, since excessive content narrows the austenite formation temperature range, it was set to 0.10% or less. Further, if it is added in an excessive amount, VN is formed and N is immobilized, which causes a decrease in hardness and a decrease in corrosion resistance, which is not preferable.
- Al 0.05% or less Al is an effective element for deoxidation, but its content is 0.05 because excessive content produces CaS, which is a soluble inclusion, during heat spreading and reduces corrosion resistance. % Or less. Al may not be contained.
- N 0.060 to 0.090%
- N is an element that determines quenching hardness together with C, and is an important element in the present invention that improves corrosion resistance. Therefore, in the present invention, the content is 0.060% or more. 0.065% or more is preferable. However, if N is excessively contained, bubble defects are likely to occur in the slab and the production cost is increased in the secondary refining by VOD or the like, so the content is set to 0.090% or less. Preferably, it is 0.085% or less.
- C + 1 / 2N 0.130 to 0.190%
- the elements that determine the hardness of the martensite phase in steel are C and N, the sum of which contributes to the hardness. According to the study of the present inventor, the contribution of N to hardness is half that of C, and it is necessary that C + 1 / 2N is 0.130% or more in order to obtain the hardness required for a Western tableware knife. .. It is preferably 0.150% or more. On the other hand, if C + 1 / 2N is excessive, the quenching hardness is excessively increased, and the toughness of the intermediate material (slab or the like) in the product or manufacturing process is impaired. It is preferably 0.180% or less, and may be 0.175% or less.
- ⁇ p may be adjusted to 130 or more, or 140 or more. In the present invention, it may be 170 or less, and may be 150 or less.
- the steel sheet and steel member of the present invention have a steel composition in which the balance is composed of Fe and impurities.
- elements of Mo, Nb, Ti and Sn, Bi are added in place of a part of Fe in order to improve rust resistance and corrosion resistance. it can.
- Mo 0.01-1.0% Mo is an element that improves corrosion resistance, and its effect is exhibited by adding 0.01% or more. However, Mo is also an expensive element, and even if it is added excessively, the effect is not clear, and the upper limit is 1.0%.
- Ti 0.005 to 0.050%
- Ti is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005% or more. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
- Nb 0.005 to 0.050%
- Nb is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005% or more. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
- Sn 0.01% to 0.10% Sn is an element effective for improving corrosion resistance after quenching, preferably 0.01% or more, and preferably 0.05% or more if necessary. However, excessive addition is preferably 0.10% or less because it promotes ear cracking during hot spreading.
- Bi 0.01% to 0.20% Bi is an element that improves corrosion resistance. Although the mechanism has not been clarified, it is considered that the addition of Bi has the effect of miniaturizing MnS, which tends to be the starting point of rusting, and thus reduces the probability of becoming the starting point of rusting. It is effective when added at 0.01% or more. Even if more than 0.20% is added, the effect is only saturated, so the upper limit is set to 0.20%.
- ⁇ ferrite phase ratio of steel plate and steel member The present inventors have found that ⁇ ferrite ( ⁇ Fe) existing in the central portion of the thickness of the steel sheet has a great influence on the end face corrosion resistance of the steel sheet.
- ⁇ ferrite ⁇ Fe
- the grain boundary between ⁇ Fe and the matrix phase ( ⁇ phase) becomes a precipitation site of Cr carbide during cooling, causing sharpening in the vicinity of the precipitated Cr carbide, and end face corrosion resistance. I think it will reduce.
- N improves the end face corrosion resistance is that it also has an effect of suppressing the precipitation of Cr carbides. Therefore, in the present invention, it is effective to suppress ⁇ Fe in steel as well as N content.
- the steel sheet of the present invention is subjected to quenching / tempering treatment and then ⁇ Fe. Evaluate the quantity.
- the quenching conditions for evaluation are heating to 1050 ° C., holding for 30 minutes, and then air cooling, and the tempering conditions are 150 ° C. and 30 minutes.
- the quenching method is air cooling. After quenching and tempering the steel sheet under the above evaluation conditions, good end face corrosion resistance can be obtained if ⁇ Fe is 1% or less when evaluated by the abundance area ratio in the plate thickness cross section. If it is less than 0.1%, excellent corrosion resistance is exhibited regardless of the present invention, but it is not preferable because long-term heat treatment is required to reduce ⁇ Fe and the cost increases. Further, if it exceeds 1%, the improvement of corrosion resistance is not sufficient even with the present invention, and the hardness is also insufficient, which is not preferable. A more preferable upper limit is 0.5%. The range is preferably 0.1% to 0.5%.
- ⁇ Manufacturing method of steel sheet> As the method for producing the steel sheet of the present invention, a conventional method is used. A slab with adjusted components is obtained by melting and casting, which is hot-rolled, then box-annealed, shot, and pickled to obtain a product.
- the slab is preheated.
- heating at 1100 to 1150 ° C. is preferably set to a soaking time of 1 hour or more and 50 hours or less.
- the heating temperature exceeds 1150 ° C.
- the two phases ( ⁇ + ⁇ ) become stable and the amount of ⁇ Fe rapidly increases, which is not preferable.
- the rapidly increased ⁇ Fe remains in a large amount even in the subsequent process, which causes a decrease in hardness.
- ⁇ Fe does not decrease even if it is heated for a long time, which is not preferable.
- the amount of ⁇ Fe is smaller than that in the case of exceeding 1150 ° C., the hardness may be maintained depending on the post-process. Further, if it is less than 1 hour, the amount of ⁇ Fe becomes too large, which is not preferable, and if it exceeds 50 hours, the cost becomes high, which is not preferable.
- This preheating is performed as slab heating before hot rolling, and hot rolling may be performed as it is.
- the obtained steel sheet is punched, hardened, tempered, and polished to prepare a member. After punching, forging is performed and the shape is adjusted.
- the following are preferable conditions for quenching and tempering.
- the quenching temperature is preferably 1000 to 1150 ° C. If it is less than 1000 ° C, the austenite phase is small at high temperature and the hardness after quenching becomes low, which is not preferable. If it is more than 1150 ° C, the ⁇ phase and the stable austenite phase increase, and the hardness also increases in this case. It is not preferable because it decreases.
- the holding time during quenching is preferably 1 minute to 1 hour.
- the cooling rate at the time of quenching is an average cooling rate from the quenching temperature to 600 ° C., preferably 1 ° C./sec or more. If it is less than this, the hardness is lowered, which is not preferable. By air-cooling the quenching, the preferable cooling rate can be realized.
- the tempering is preferably 100 ° C to 250 ° C. If the temperature is lower than 100 ° C, the effect of tempering is poor, and if the temperature exceeds 250 ° C, the decrease in hardness becomes too large, which is not preferable.
- the steels having the composition shown in Tables 1 and 2 were melted and cast into a slab having a thickness of 250 mm.
- these slabs were heat-treated at 1150 ° C. for 40 hours as preheating, and the amount of ⁇ Fe was set within a certain range.
- the A2 steel was preheated at 1175 ° C. for 40 hours and at 950 ° C. for 40 hours to obtain A2'steel and A2'steel, respectively.
- the hot-rolled steel sheet was annealed by box annealing.
- the maximum heating temperature was set to a temperature range of 800 ° C. or higher and 900 ° C. or lower.
- the scale on the surface of the steel sheet after annealing was removed by shot blasting and pickled.
- Example 1 In order to evaluate the obtained steel sheet, a sample for evaluation was cut out from the steel sheet, and the sample was heated to 1050 ° C. for 30 minutes as a quenching / tempering process, held for 30 minutes, and then air-cooled at 150 ° C. for 30 minutes. It was tempered. After that, each evaluation of ⁇ Fe amount measurement, hardness measurement, and end face corrosion resistance was performed. The results obtained are shown in Table 3.
- ⁇ Fe The amount of ⁇ Fe was measured by mirror-polishing and etching the end face of the sample to reveal the structure.
- ⁇ Fe can be expressed in aqua regia or the like as the etching solution, but it is preferable to use a reagent called the improved Murakami reagent described in Non-Patent Document 1 because ⁇ Fe is deeply etched in brown, and evaluation is performed using this. did.
- a typical example is shown in FIG.
- the tissue revealed by the improved Murakami reagent is examined under a microscope, a photograph of ⁇ Fe is taken from the total thickness of a certain width (2 mm in this example), the ⁇ Fe area is obtained from the image analysis, and then the area ratio ( ⁇ Fe area ( ⁇ Fe area ( ⁇ Fe area)). mm 2 ) / 2 mm ⁇ total thickness (mm) ⁇ 100 (%)) was calculated.
- its value needs to be 0.1 to 1%. Further, it is preferably 0.1% to 0.5%.
- ⁇ Fe area ratio 0.1 to 1% was regarded as pass (A), and more than that was regarded as fail (X).
- the surface hardness is evaluated by the Rockwell hardness tester C scale in accordance with JIS Z2245, and 50 or more is passed (A), and the others are rejected (Failure). X).
- the end face corrosion resistance After polishing the sample surface and end face with # 600, the end face is used as the evaluation surface and the salt spray test is performed for 24 hours (JIS Z 2371 "salt spray test method") to determine the rusting point. I counted. A score of 2 or less was regarded as a pass (A), and a score exceeding that score was a failure (X). In particular, those with zero rusting points were regarded as passing (S). Even if the salt spray test was carried out for 24 hours or more, rust did not develop further, so the end face corrosion resistance was judged based on the results for 24 hours.
- All of the steel sheets of the present invention are excellent not only in end face corrosion resistance but also in other properties, and are preferable as steel sheets for Western tableware knives.
- the comparative steel has inferior end face corrosion resistance or inferior other characteristics, and it is clear that it is not preferable as a steel plate for Western tableware knives.
- Example 2 Using the member cut out from the obtained steel sheet, quenching and tempering were performed under the conditions shown in Table 4 to obtain a steel member. Quenching was performed by heating at 1050 to 1150 ° C., and then cooling was performed by controlling the cooling rate from the quenching temperature to 600 ° C. to the cooling rate shown in Table 4. Further, a tempering treatment for 1 to 2 hours was carried out at 150 to 250 ° C. to obtain a steel member. Further, A2'steel and A2'steel were also treated in the same manner.
- Table 4 shows the ⁇ Fe amount measurement, hardness measurement, and end face corrosion resistance evaluation of the obtained steel member together with the heat treatment conditions.
- the evaluation method and evaluation criteria were the same as in Example 1.
- All of the steel members of the present invention are excellent not only in end face corrosion resistance but also in other characteristics, and are preferable as steel members for Western tableware knives.
- the comparative steel has inferior end face corrosion resistance or inferior other characteristics, and it is clear that it is not preferable as a steel member for Western tableware knives.
- the present invention it is possible to produce a martensitic stainless steel member having excellent end face corrosion resistance after air-cooling and quenching with high productivity, and the corrosion resistance of a Western tableware knife produced by using the martensitic stainless steel member is improved, and industrially. , Very useful.
Abstract
Provided are a martensitic stainless steel plate and a martensitic stainless steel member, which are used in the manufacture of western tableware knives, looms, tools, disc brakes, etc. and have excellent corrosion resistance even after being air-cooling quenched. The martensitic stainless steel plate contains, in mass%, 0.100-0.170% of C, 0.30-0.60% of Si, 0.10-0.60% of Mn, 11.0-15.0% of Cr, 0.05-0.60% of Ni, 0.010-0.50% of Cu, 0.010-0.10% of V, 0.05% or less of Al, 0.060-0.090% of N, and 0.130-0.190% of C＋1/2N, and has a γp of at least 120 as represented by equation (1), wherein after the martensitic stainless steel plate is quenched and tempered, the areal ratio of δ ferrite (δFe) present in the central portion of the thickness of the steel plate is 0.1-1% in a cross section along the thickness direction of the plate.
Description
本発明は焼き入れ後の耐食性に優れたマルテンサイト系ステンレス鋼板およびマルテンサイト系ステンレス鋼部材に関する。より詳しくは、本発明は洋食器ナイフ、織機、工具、ディスクブレーキ等の製造に用いられる空冷焼き入れを行っても優れた耐食性を有するマルテンサイト系ステンレス鋼に関する。
The present invention relates to a martensitic stainless steel sheet and a martensitic stainless steel member having excellent corrosion resistance after quenching. More specifically, the present invention relates to martensitic stainless steel having excellent corrosion resistance even when air-cooled and hardened, which is used for manufacturing Western tableware knives, looms, tools, disc brakes and the like.
洋食器ナイフ（テーブルナイフ）やはさみ、織機、ノギス等の工具には、ＳＵＳ４２０Ｊ１、ＳＵＳ４２０Ｊ２鋼等のマルテンサイト系ステンレス鋼板が一般に用いられている。このような用途においては、めっきや塗装、防錆油の使用が困難であり、素材そのものに耐銹性が求められる。また、摩耗しくにいことも重要で高い硬度が必要とされているからである。
Martensitic stainless steel sheets such as SUS420J1 and SUS420J2 steel are generally used for tools such as Western tableware knives (table knives), scissors, weaving machines, and calipers. In such applications, it is difficult to use plating, painting, and rust preventive oil, and the material itself is required to have rust resistance. It is also important that it does not wear easily, and high hardness is required.
洋食器ナイフ等の製造工程は、通常、鋼板から型抜きし、加熱、焼き入れ後、研磨工程を経てナイフとなる。焼き入れ工程は空冷程度で行われることが多く、これも焼き入れ性の優れたマルテンサイト系ステンレス鋼板の特性に依存している。
The manufacturing process of Western tableware knives, etc. is usually made by die-cutting from a steel plate, heating, quenching, and then polishing to make a knife. The quenching process is often performed by air cooling, which also depends on the characteristics of the martensitic stainless steel sheet, which has excellent quenching properties.
特許文献１には、空冷で焼き入れ時に耐食性に優れたマルテンサイト系ステンレス鋼が開示されている。ここで、耐食性を向上させる元素としてＮを０．０６％程度まで添加している。
特許文献２には、さらにＮを添加した鋼が開示されている。また、特許文献３には、特殊な設備を用いてさらにＮを高めた鋼が開示されている。 Patent Document 1 discloses a martensitic stainless steel that is air-cooled and has excellent corrosion resistance during quenching. Here, N is added up to about 0.06% as an element for improving corrosion resistance.
Patent Document 2 discloses a steel to which N is further added. Further, Patent Document 3 discloses a steel in which N is further increased by using special equipment.
特許文献２には、さらにＮを添加した鋼が開示されている。また、特許文献３には、特殊な設備を用いてさらにＮを高めた鋼が開示されている。 Patent Document 1 discloses a martensitic stainless steel that is air-cooled and has excellent corrosion resistance during quenching. Here, N is added up to about 0.06% as an element for improving corrosion resistance.
Patent Document 2 discloses a steel to which N is further added. Further, Patent Document 3 discloses a steel in which N is further increased by using special equipment.
近年、欧州を中心に洋食器の耐食性に対する要求が高度化してきている。その結果、耐銹性評価試験において、テーブルナイフの刃の背または刃先、持ち手部の中央部に発銹が見られる場合が散見されており、その改善が求められている。
In recent years, the demand for corrosion resistance of Western tableware has become more sophisticated, especially in Europe. As a result, in the rust resistance evaluation test, rusting may be observed on the back or tip of the blade of the table knife and in the center of the handle, and improvement thereof is required.
近年、欧州を中心に洋食器の耐食性に対する要求の高度化に伴い、厳格な耐食性試験でのテーブルナイフの刃の背または刃先、持ち手部の中央部に発銹に対する改善要求が高まっている。本発明では、テーブルナイフなどの洋食器用等のマルテンサイト系ステンレス鋼の用途に対して使用に耐えうる十分な硬さを保持しつつ、耐食性に優れたマルテンサイト系ステンレス鋼板およびマルテンサイト系ステンレス鋼部材を提供することを目的とした。
In recent years, with the increasing demand for corrosion resistance of Western tableware, mainly in Europe, there is an increasing demand for improvement in rusting on the back or tip of the table knife blade and the central part of the handle in strict corrosion resistance tests. In the present invention, a martensitic stainless steel plate and a martensitic stainless steel having excellent corrosion resistance while maintaining sufficient hardness to withstand use for martensitic stainless steel applications such as table knives and other Western tableware. The purpose was to provide members.
本発明者らは、上記目的を達成するために、まず、テーブルナイフの発銹状況を詳細に調査した。その結果、発銹部位は鋼板端面、詳しくは、鋼板厚み中央部が起点となっていることが明らかになった。さらに、マクロ偏析に起因するδフェライト相（δＦｅ相）の生成が確認され、このδＦｅの粒界が炭化物の集積サイトとなり、その炭化物が焼き入れ時の加熱で溶解し、その後の冷却時に粒界析出し、その結果、鋭敏化が起こり、粒界腐食を引き起こすことが発銹のメカニズムであることが判明した。
また、その発銹は焼き入れ時の冷却速度にも依存することを見出した。冷却速度は、焼き入れ設備に大きく依存し変わるものの、焼き入れ温度から炭化物析出が概ね完了する温度である６００℃までの平均冷却速度で評価すると、水焼き入れでは１００℃／ｓを超える冷却速度が得られるので、炭化物析出が抑制され発銹は起こりにくいが、テーブルナイフの製造工程で多く用いられる空冷では、その冷却速度が５℃/s程度に過ぎず、炭化物析出が抑制できず発銹が起こりやすいことが分かった。 In order to achieve the above object, the present inventors first investigated the rusting condition of the table knife in detail. As a result, it was clarified that the rusting site starts from the end face of the steel sheet, more specifically, the central part of the thickness of the steel sheet. Furthermore, the formation of a δ ferrite phase (δFe phase) due to macrosegregation was confirmed, and the grain boundaries of this δFe became the accumulation sites of carbides, and the carbides melted by heating during quenching, and then grain boundaries during cooling. It was found that the mechanism of quenching is that precipitation occurs, resulting in sensitization and intergranular corrosion.
It was also found that the rusting depends on the cooling rate during quenching. The cooling rate varies greatly depending on the quenching equipment, but when evaluated by the average cooling rate from the quenching temperature to 600 ° C, which is the temperature at which carbide precipitation is almost completed, the cooling rate exceeds 100 ° C / s in water quenching. However, in air cooling, which is often used in the manufacturing process of table knives, the cooling rate is only about 5 ° C / s, and carbide precipitation cannot be suppressed and quenching is unlikely to occur. It turns out that is likely to occur.
また、その発銹は焼き入れ時の冷却速度にも依存することを見出した。冷却速度は、焼き入れ設備に大きく依存し変わるものの、焼き入れ温度から炭化物析出が概ね完了する温度である６００℃までの平均冷却速度で評価すると、水焼き入れでは１００℃／ｓを超える冷却速度が得られるので、炭化物析出が抑制され発銹は起こりにくいが、テーブルナイフの製造工程で多く用いられる空冷では、その冷却速度が５℃/s程度に過ぎず、炭化物析出が抑制できず発銹が起こりやすいことが分かった。 In order to achieve the above object, the present inventors first investigated the rusting condition of the table knife in detail. As a result, it was clarified that the rusting site starts from the end face of the steel sheet, more specifically, the central part of the thickness of the steel sheet. Furthermore, the formation of a δ ferrite phase (δFe phase) due to macrosegregation was confirmed, and the grain boundaries of this δFe became the accumulation sites of carbides, and the carbides melted by heating during quenching, and then grain boundaries during cooling. It was found that the mechanism of quenching is that precipitation occurs, resulting in sensitization and intergranular corrosion.
It was also found that the rusting depends on the cooling rate during quenching. The cooling rate varies greatly depending on the quenching equipment, but when evaluated by the average cooling rate from the quenching temperature to 600 ° C, which is the temperature at which carbide precipitation is almost completed, the cooling rate exceeds 100 ° C / s in water quenching. However, in air cooling, which is often used in the manufacturing process of table knives, the cooling rate is only about 5 ° C / s, and carbide precipitation cannot be suppressed and quenching is unlikely to occur. It turns out that is likely to occur.
本発明者らは、これらの知見に基づき、その改善方法を検討した結果、鋼板成分にＮを添加することにより、成形・熱処理後の洋食器ナイフにおいて、この発銹が抑制できることを見出した。
As a result of examining the improvement method based on these findings, the present inventors have found that by adding N to the steel sheet component, this rusting can be suppressed in the Western tableware knife after molding and heat treatment.
その後、さらに詳細な検討を行い、発明を完成させるに至った。
すなわち、
（１）質量％で、
Ｃ：０．１００～０．１７０％、
Ｓｉ：０．２５～０．６０％、
Ｍｎ：０．１０～０．６０％、
Ｐ：０．０３５％以下、
Ｓ：０．０１５％以下、
Ｃｒ：１１．０～１５．０％、
Ｎｉ：０．０５～０．６０％、
Ｃｕ：０．０１０～０．５０％、
Ｖ：０．０１０～０．１０％、
Ａｌ：０．０５％以下
Ｎ：０．０６０～０．０９０％
Ｃ＋１／２Ｎ：０．１３０～０．１９０％
であり、残部がＦｅおよび不純物からなる鋼組成を有し、
下記式（１）で示されるγｐが１２０以上であるマルテンサイト系ステンレス鋼板において、
前記マルテンサイト系ステンレス鋼板を１０５０℃で３０分保持後空冷焼き入れし、１５０℃、３０分の焼き戻しを行ったとき、板厚中央部に存在するδフェライト（δＦｅ）の板厚断面における面積率が０．１～１％となることを特徴とするマルテンサイト系ステンレス鋼板。
γｐ＝４２０Ｃ＋４７０Ｎ＋３０Ｎｉ＋７Ｍｎ＋９Ｃｕ－１１．５Ｃｒ－１１．５Ｓｉ－１２Ｍｏ－２３Ｖ－４７Ｎｂ－５２Ａｌ＋１８９ ・・・ 式（１）
式（１）中の元素記号は、当該元素の含有量（質量％）を意味する。
（２）さらに、前記Ｆｅの一部に替えて、質量％で、
Ｍｏ：０．０１～１．０％、
Ｔｉ：０．００５～０．０５０％、
Ｎｂ：０．００５～０．０５０％
の１種または２種以上を含有することを特徴とする本発明のマルテンサイト系ステンレス鋼板。
（３）さらに、前記Ｆｅの一部に替えて、質量％で、
Ｓｎ：０．０１～０．１０％、
Ｂｉ：０．０１～０．２０％
の１種または２種を含有することを特徴とする本発明のマルテンサイト系ステンレス鋼板。 After that, a more detailed study was conducted, and the invention was completed.
That is,
(1) By mass%
C: 0.100 to 0.170%,
Si: 0.25 to 0.60%,
Mn: 0.10 to 0.60%,
P: 0.035% or less,
S: 0.015% or less,
Cr: 11.0 to 15.0%,
Ni: 0.05 to 0.60%,
Cu: 0.010 to 0.50%,
V: 0.010 to 0.10%,
Al: 0.05% or less N: 0.060 to 0.090%
C + 1 / 2N: 0.130 to 0.190%
Has a steel composition with the balance consisting of Fe and impurities.
In a martensitic stainless steel sheet having a γp of 120 or more represented by the following formula (1),
When the martensitic stainless steel sheet is held at 1050 ° C. for 30 minutes, then air-cooled and quenched, and tempered at 150 ° C. for 30 minutes, the area of δ ferrite (δFe) present in the center of the plate thickness in the plate thickness cross section. A martensitic stainless steel sheet having a ratio of 0.1 to 1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element.
(2) Further, instead of a part of the Fe, by mass%,
Mo: 0.01-1.0%,
Ti: 0.005 to 0.050%,
Nb: 0.005 to 0.050%
The martensitic stainless steel sheet of the present invention, which comprises one or more of the above.
(3) Further, instead of a part of the Fe, by mass%,
Sn: 0.01 to 0.10%,
Bi: 0.01 to 0.20%
The martensitic stainless steel sheet of the present invention, which comprises one or two of the above.
すなわち、
（１）質量％で、
Ｃ：０．１００～０．１７０％、
Ｓｉ：０．２５～０．６０％、
Ｍｎ：０．１０～０．６０％、
Ｐ：０．０３５％以下、
Ｓ：０．０１５％以下、
Ｃｒ：１１．０～１５．０％、
Ｎｉ：０．０５～０．６０％、
Ｃｕ：０．０１０～０．５０％、
Ｖ：０．０１０～０．１０％、
Ａｌ：０．０５％以下
Ｎ：０．０６０～０．０９０％
Ｃ＋１／２Ｎ：０．１３０～０．１９０％
であり、残部がＦｅおよび不純物からなる鋼組成を有し、
下記式（１）で示されるγｐが１２０以上であるマルテンサイト系ステンレス鋼板において、
前記マルテンサイト系ステンレス鋼板を１０５０℃で３０分保持後空冷焼き入れし、１５０℃、３０分の焼き戻しを行ったとき、板厚中央部に存在するδフェライト（δＦｅ）の板厚断面における面積率が０．１～１％となることを特徴とするマルテンサイト系ステンレス鋼板。
γｐ＝４２０Ｃ＋４７０Ｎ＋３０Ｎｉ＋７Ｍｎ＋９Ｃｕ－１１．５Ｃｒ－１１．５Ｓｉ－１２Ｍｏ－２３Ｖ－４７Ｎｂ－５２Ａｌ＋１８９ ・・・ 式（１）
式（１）中の元素記号は、当該元素の含有量（質量％）を意味する。
（２）さらに、前記Ｆｅの一部に替えて、質量％で、
Ｍｏ：０．０１～１．０％、
Ｔｉ：０．００５～０．０５０％、
Ｎｂ：０．００５～０．０５０％
の１種または２種以上を含有することを特徴とする本発明のマルテンサイト系ステンレス鋼板。
（３）さらに、前記Ｆｅの一部に替えて、質量％で、
Ｓｎ：０．０１～０．１０％、
Ｂｉ：０．０１～０．２０％
の１種または２種を含有することを特徴とする本発明のマルテンサイト系ステンレス鋼板。 After that, a more detailed study was conducted, and the invention was completed.
That is,
(1) By mass%
C: 0.100 to 0.170%,
Si: 0.25 to 0.60%,
Mn: 0.10 to 0.60%,
P: 0.035% or less,
S: 0.015% or less,
Cr: 11.0 to 15.0%,
Ni: 0.05 to 0.60%,
Cu: 0.010 to 0.50%,
V: 0.010 to 0.10%,
Al: 0.05% or less N: 0.060 to 0.090%
C + 1 / 2N: 0.130 to 0.190%
Has a steel composition with the balance consisting of Fe and impurities.
In a martensitic stainless steel sheet having a γp of 120 or more represented by the following formula (1),
When the martensitic stainless steel sheet is held at 1050 ° C. for 30 minutes, then air-cooled and quenched, and tempered at 150 ° C. for 30 minutes, the area of δ ferrite (δFe) present in the center of the plate thickness in the plate thickness cross section. A martensitic stainless steel sheet having a ratio of 0.1 to 1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element.
(2) Further, instead of a part of the Fe, by mass%,
Mo: 0.01-1.0%,
Ti: 0.005 to 0.050%,
Nb: 0.005 to 0.050%
The martensitic stainless steel sheet of the present invention, which comprises one or more of the above.
(3) Further, instead of a part of the Fe, by mass%,
Sn: 0.01 to 0.10%,
Bi: 0.01 to 0.20%
The martensitic stainless steel sheet of the present invention, which comprises one or two of the above.
（４）本発明の鋼組成を有するマルテンサイト系ステンレス鋼部材において、
下記式（１）で示されるγｐが１２０以上であり、
さらに、板厚中央部に存在するδフェライト（δＦｅ）の板厚断面における面積率が０．１～１％であることを特徴とするマルテンサイト系ステンレス鋼部材。
γｐ＝４２０Ｃ＋４７０Ｎ＋３０Ｎｉ＋７Ｍｎ＋９Ｃｕ－１１．５Ｃｒ－１１．５Ｓｉ－１２Ｍｏ－２３Ｖ－４７Ｎｂ－５２Ａｌ＋１８９ ・・・ 式（１）
式（１）中の元素記号は、当該元素の含有量（質量％）を意味する。 (4) In the martensitic stainless steel member having the steel composition of the present invention.
The γp represented by the following formula (1) is 120 or more, and
Further, a martensitic stainless steel member characterized in that the area ratio of δ ferrite (δFe) existing in the central portion of the plate thickness in the plate thickness cross section is 0.1 to 1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element.
下記式（１）で示されるγｐが１２０以上であり、
さらに、板厚中央部に存在するδフェライト（δＦｅ）の板厚断面における面積率が０．１～１％であることを特徴とするマルテンサイト系ステンレス鋼部材。
γｐ＝４２０Ｃ＋４７０Ｎ＋３０Ｎｉ＋７Ｍｎ＋９Ｃｕ－１１．５Ｃｒ－１１．５Ｓｉ－１２Ｍｏ－２３Ｖ－４７Ｎｂ－５２Ａｌ＋１８９ ・・・ 式（１）
式（１）中の元素記号は、当該元素の含有量（質量％）を意味する。 (4) In the martensitic stainless steel member having the steel composition of the present invention.
The γp represented by the following formula (1) is 120 or more, and
Further, a martensitic stainless steel member characterized in that the area ratio of δ ferrite (δFe) existing in the central portion of the plate thickness in the plate thickness cross section is 0.1 to 1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element.
本発明のマルテンサイト系ステンレス鋼板はテーブルナイフなどの洋食器用等のマルテンサイト系ステンレス鋼の用途に対して使用に耐えうる十分な硬さを保持しつつ、耐食性、特に端面耐食性に優れる。よって洋食器ナイフ等のマルテンサイト系ステンレス鋼部材として使用された場合、耐食性が向上し製品寿命が長くなる効果も期待できる。
The martensitic stainless steel sheet of the present invention has excellent corrosion resistance, especially end face corrosion resistance, while maintaining sufficient hardness to withstand use for martensitic stainless steel applications such as table knives and other Western tableware. Therefore, when it is used as a martensitic stainless steel member such as a Western tableware knife, it can be expected to have an effect of improving corrosion resistance and prolonging the product life.
さらに、詳細に説明する。
＜鋼板および鋼部材の化学成分＞（％は質量％を意味する。）
Ｃ：０．１００～０．１７０％
ＣはＮとともに焼き入れ硬さを決める元素であり、洋食器ナイフに必要な硬さを得るためには０．１００％以上必要である。好ましくは０．１１０％以上であり、０．１２０％以上である。一方、過度に添加すると焼き入れ硬さが必要以上に大きくなり、研磨時の負荷が増えるほか、靱性も低下させる。また、本発明をもってしても空冷焼き入れ時にＣｒ炭化物が析出し耐食性を損なうことも起こりやすくなるため、０．１７０％以下とする。好ましくは０．１５５％以下である。 Further, it will be described in detail.
<Chemical composition of steel sheet and steel member> (% means mass%)
C: 0.100 to 0.170%
C is an element that determines the quenching hardness together with N, and is required to be 0.100% or more in order to obtain the hardness required for a Western tableware knife. It is preferably 0.110% or more, and 0.120% or more. On the other hand, if it is added excessively, the quenching hardness becomes larger than necessary, the load during polishing increases, and the toughness also decreases. Further, even with the present invention, Cr carbides are likely to precipitate during air-cooling quenching and the corrosion resistance is likely to be impaired, so the content is set to 0.170% or less. It is preferably 0.155% or less.
＜鋼板および鋼部材の化学成分＞（％は質量％を意味する。）
Ｃ：０．１００～０．１７０％
ＣはＮとともに焼き入れ硬さを決める元素であり、洋食器ナイフに必要な硬さを得るためには０．１００％以上必要である。好ましくは０．１１０％以上であり、０．１２０％以上である。一方、過度に添加すると焼き入れ硬さが必要以上に大きくなり、研磨時の負荷が増えるほか、靱性も低下させる。また、本発明をもってしても空冷焼き入れ時にＣｒ炭化物が析出し耐食性を損なうことも起こりやすくなるため、０．１７０％以下とする。好ましくは０．１５５％以下である。 Further, it will be described in detail.
<Chemical composition of steel sheet and steel member> (% means mass%)
C: 0.100 to 0.170%
C is an element that determines the quenching hardness together with N, and is required to be 0.100% or more in order to obtain the hardness required for a Western tableware knife. It is preferably 0.110% or more, and 0.120% or more. On the other hand, if it is added excessively, the quenching hardness becomes larger than necessary, the load during polishing increases, and the toughness also decreases. Further, even with the present invention, Cr carbides are likely to precipitate during air-cooling quenching and the corrosion resistance is likely to be impaired, so the content is set to 0.170% or less. It is preferably 0.155% or less.
Ｓｉ：０．２５～０．６０％
Ｓｉは製鋼での脱酸のために必要であるほか、焼き入れ熱処理後の酸化スケールの生成を抑制するにも有効であるため、０．２５％以上含有させる。０．２５％未満であると酸化スケールが過度に生成し、最終の研磨負荷を増大させる。しかし、過剰の添加はオーステナイト生成を抑制し、焼き入れ性を損ねるために、０．６０％以下とする。 Si: 0.25 to 0.60%
Since Si is necessary for deoxidation in steelmaking and is also effective in suppressing the formation of oxide scale after quenching heat treatment, it is contained in an amount of 0.25% or more. If it is less than 0.25%, an oxidation scale is excessively generated, which increases the final polishing load. However, excessive addition suppresses austenite production and impairs hardenability, so the content is set to 0.60% or less.
Ｓｉは製鋼での脱酸のために必要であるほか、焼き入れ熱処理後の酸化スケールの生成を抑制するにも有効であるため、０．２５％以上含有させる。０．２５％未満であると酸化スケールが過度に生成し、最終の研磨負荷を増大させる。しかし、過剰の添加はオーステナイト生成を抑制し、焼き入れ性を損ねるために、０．６０％以下とする。 Si: 0.25 to 0.60%
Since Si is necessary for deoxidation in steelmaking and is also effective in suppressing the formation of oxide scale after quenching heat treatment, it is contained in an amount of 0.25% or more. If it is less than 0.25%, an oxidation scale is excessively generated, which increases the final polishing load. However, excessive addition suppresses austenite production and impairs hardenability, so the content is set to 0.60% or less.
Ｍｎ：０．１０～０．６０％
Ｍｎはオーステナイト安定元素であり、焼き入れ時の硬さとマルテンサイト量確保のために必要である。そのため、０．１０％以上含有させる。しかし、焼き入れ時の酸化スケール生成を促進させ、その後の研磨負荷を増大させるため、０．６０％以下とする。また、過剰に添加するとＭｎＳが多く生成し耐食性も低下させる。 Mn: 0.10 to 0.60%
Mn is an austenite-stabilizing element and is necessary for ensuring hardness and the amount of martensite during quenching. Therefore, it is contained in an amount of 0.10% or more. However, in order to promote the formation of oxide scale during quenching and increase the subsequent polishing load, the content is set to 0.60% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
Ｍｎはオーステナイト安定元素であり、焼き入れ時の硬さとマルテンサイト量確保のために必要である。そのため、０．１０％以上含有させる。しかし、焼き入れ時の酸化スケール生成を促進させ、その後の研磨負荷を増大させるため、０．６０％以下とする。また、過剰に添加するとＭｎＳが多く生成し耐食性も低下させる。 Mn: 0.10 to 0.60%
Mn is an austenite-stabilizing element and is necessary for ensuring hardness and the amount of martensite during quenching. Therefore, it is contained in an amount of 0.10% or more. However, in order to promote the formation of oxide scale during quenching and increase the subsequent polishing load, the content is set to 0.60% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
Ｐ：０．０３５％以下
Ｐは原料である溶銑やフェロクロム等の合金中に不純物として含まれる元素である。熱延焼鈍後や焼き入れ後の鋼板の靱性に対して有害な元素であるため、その含有量は０．０３５％以下とする。過剰に添加すると熱間加工性や耐食性を低下させる。 P: 0.035% or less P is an element contained as an impurity in alloys such as hot metal and ferrochrome, which are raw materials. Since it is an element harmful to the toughness of the steel sheet after hot spreading annealing and quenching, its content shall be 0.035% or less. Excessive addition reduces hot workability and corrosion resistance.
Ｐは原料である溶銑やフェロクロム等の合金中に不純物として含まれる元素である。熱延焼鈍後や焼き入れ後の鋼板の靱性に対して有害な元素であるため、その含有量は０．０３５％以下とする。過剰に添加すると熱間加工性や耐食性を低下させる。 P: 0.035% or less P is an element contained as an impurity in alloys such as hot metal and ferrochrome, which are raw materials. Since it is an element harmful to the toughness of the steel sheet after hot spreading annealing and quenching, its content shall be 0.035% or less. Excessive addition reduces hot workability and corrosion resistance.
Ｓ：０．０１５％以下
Ｓはオーステナイト相に対する固溶度が小さく、粒界に偏析して熱間加工性の低下を促進する。そのため、その含有量を０．０１５％以下とする。また、過剰に添加するとＭｎＳが多く生成し耐食性も低下させる。 S: 0.015% or less S has a small solid solubility in the austenite phase and segregates at the grain boundaries to promote a decrease in hot workability. Therefore, the content is set to 0.015% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
Ｓはオーステナイト相に対する固溶度が小さく、粒界に偏析して熱間加工性の低下を促進する。そのため、その含有量を０．０１５％以下とする。また、過剰に添加するとＭｎＳが多く生成し耐食性も低下させる。 S: 0.015% or less S has a small solid solubility in the austenite phase and segregates at the grain boundaries to promote a decrease in hot workability. Therefore, the content is set to 0.015% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
Ｃｒ：１１．０～１５．０％
Ｃｒは洋食器ナイフとして耐食性を保持するために、少なくとも１１．０％以上必要である。一方、オーステナイト安定温度を狭める効果もあるため、１５．０％以下とする。好ましくは、１２．０％以上である。また上限は１４．０％以下が好ましい。範囲としては１２．０～１４．０％とするのが良い。 Cr: 11.0 to 15.0%
Cr is required at least 11.0% or more in order to maintain corrosion resistance as a Western tableware knife. On the other hand, since it also has the effect of narrowing the stable temperature of austenite, it should be 15.0% or less. Preferably, it is 12.0% or more. The upper limit is preferably 14.0% or less. The range is preferably 12.0 to 14.0%.
Ｃｒは洋食器ナイフとして耐食性を保持するために、少なくとも１１．０％以上必要である。一方、オーステナイト安定温度を狭める効果もあるため、１５．０％以下とする。好ましくは、１２．０％以上である。また上限は１４．０％以下が好ましい。範囲としては１２．０～１４．０％とするのが良い。 Cr: 11.0 to 15.0%
Cr is required at least 11.0% or more in order to maintain corrosion resistance as a Western tableware knife. On the other hand, since it also has the effect of narrowing the stable temperature of austenite, it should be 15.0% or less. Preferably, it is 12.0% or more. The upper limit is preferably 14.0% or less. The range is preferably 12.0 to 14.0%.
Ｎｉ：０．０５～０．６０％
Ｎｉは、Ｍｎと同様にオーステナイト安定元素であり、焼き入れ時の硬さとマルテンサイト量確保のために必要である。また、耐食性を向上させる効果もある。そのため、０．０５％以上含有させる。しかし、Ｎｉは他の元素と比較して高価であるため、０．６０％以下とする。 Ni: 0.05 to 0.60%
Like Mn, Ni is an austenite-stable element and is necessary for securing hardness and the amount of martensite during quenching. It also has the effect of improving corrosion resistance. Therefore, it is contained in an amount of 0.05% or more. However, since Ni is more expensive than other elements, it should be 0.60% or less.
Ｎｉは、Ｍｎと同様にオーステナイト安定元素であり、焼き入れ時の硬さとマルテンサイト量確保のために必要である。また、耐食性を向上させる効果もある。そのため、０．０５％以上含有させる。しかし、Ｎｉは他の元素と比較して高価であるため、０．６０％以下とする。 Ni: 0.05 to 0.60%
Like Mn, Ni is an austenite-stable element and is necessary for securing hardness and the amount of martensite during quenching. It also has the effect of improving corrosion resistance. Therefore, it is contained in an amount of 0.05% or more. However, since Ni is more expensive than other elements, it should be 0.60% or less.
Ｃｕ：０．０１０～０．５０％
Ｃｕは、Ｍｎ、Ｎｉと同様にオーステナイト安定元素であり、また、耐食性を向上させる元素である。製鋼時のスクラップからの混入が避けられない元素でもあるが、耐食性向上のために、０．０１０％以上含有させる。一方、過度の含有は熱間加工性等を低下させるので、０．５０％以下とする。Ｎｉよりは安価であるが比較的高価であるため、その添加はできるだけ低くしたい元素である。 Cu: 0.010 to 0.50%
Cu is an austenite-stable element like Mn and Ni, and is an element that improves corrosion resistance. Although it is an element that cannot be avoided from scrap during steelmaking, it is contained in an amount of 0.010% or more in order to improve corrosion resistance. On the other hand, excessive content reduces hot workability and the like, so the content should be 0.50% or less. Although it is cheaper than Ni, it is relatively expensive, so its addition is an element that we want to keep as low as possible.
Ｃｕは、Ｍｎ、Ｎｉと同様にオーステナイト安定元素であり、また、耐食性を向上させる元素である。製鋼時のスクラップからの混入が避けられない元素でもあるが、耐食性向上のために、０．０１０％以上含有させる。一方、過度の含有は熱間加工性等を低下させるので、０．５０％以下とする。Ｎｉよりは安価であるが比較的高価であるため、その添加はできるだけ低くしたい元素である。 Cu: 0.010 to 0.50%
Cu is an austenite-stable element like Mn and Ni, and is an element that improves corrosion resistance. Although it is an element that cannot be avoided from scrap during steelmaking, it is contained in an amount of 0.010% or more in order to improve corrosion resistance. On the other hand, excessive content reduces hot workability and the like, so the content should be 0.50% or less. Although it is cheaper than Ni, it is relatively expensive, so its addition is an element that we want to keep as low as possible.
Ｖ：０．０１０～０．１０％
Ｖは合金元素であるフェロクロム等から不可避的に混入する場合が多い元素である。その削減は困難であり、０．０１０％以上を含有させる。しかし、過度の含有はオーステナイト形成温度域を狭めるので、０．１０％以下とした。また、過剰に添加するとＶＮを形成し、Ｎを固定化するため、硬さ低下や耐食性低下を引き起こすため好ましくない。 V: 0.010 to 0.10%
V is an element that is often inevitably mixed with ferrochrome or the like, which is an alloy element. The reduction is difficult and contains 0.010% or more. However, since excessive content narrows the austenite formation temperature range, it was set to 0.10% or less. Further, if it is added in an excessive amount, VN is formed and N is immobilized, which causes a decrease in hardness and a decrease in corrosion resistance, which is not preferable.
Ｖは合金元素であるフェロクロム等から不可避的に混入する場合が多い元素である。その削減は困難であり、０．０１０％以上を含有させる。しかし、過度の含有はオーステナイト形成温度域を狭めるので、０．１０％以下とした。また、過剰に添加するとＶＮを形成し、Ｎを固定化するため、硬さ低下や耐食性低下を引き起こすため好ましくない。 V: 0.010 to 0.10%
V is an element that is often inevitably mixed with ferrochrome or the like, which is an alloy element. The reduction is difficult and contains 0.010% or more. However, since excessive content narrows the austenite formation temperature range, it was set to 0.10% or less. Further, if it is added in an excessive amount, VN is formed and N is immobilized, which causes a decrease in hardness and a decrease in corrosion resistance, which is not preferable.
Ａｌ：０．０５％以下
Ａｌは脱酸のために有効な元素であるが、過度の含有は熱延時に可溶性介在物であるＣａＳを生成させ、耐食性を低下させるので、その含有は０．０５％以下とする。Ａｌは含有しなくても良い。 Al: 0.05% or less Al is an effective element for deoxidation, but its content is 0.05 because excessive content produces CaS, which is a soluble inclusion, during heat spreading and reduces corrosion resistance. % Or less. Al may not be contained.
Ａｌは脱酸のために有効な元素であるが、過度の含有は熱延時に可溶性介在物であるＣａＳを生成させ、耐食性を低下させるので、その含有は０．０５％以下とする。Ａｌは含有しなくても良い。 Al: 0.05% or less Al is an effective element for deoxidation, but its content is 0.05 because excessive content produces CaS, which is a soluble inclusion, during heat spreading and reduces corrosion resistance. % Or less. Al may not be contained.
Ｎ：０．０６０～０．０９０％
ＮはＣとともに焼き入れ硬さを決める元素であるとともに、耐食性を向上させる本発明では重要な元素である。そのため、本発明では、０．０６０％以上含有させる。０．０６５％以上が好ましい。しかし、Ｎを過剰に含有させると、スラブ中に気泡欠陥ができやすくなるとともにＶＯＤ等による二次精錬では製造コストを増加させるため、その含有量は、０．０９０％以下とする。好ましくは、０．０８５％以下である。 N: 0.060 to 0.090%
N is an element that determines quenching hardness together with C, and is an important element in the present invention that improves corrosion resistance. Therefore, in the present invention, the content is 0.060% or more. 0.065% or more is preferable. However, if N is excessively contained, bubble defects are likely to occur in the slab and the production cost is increased in the secondary refining by VOD or the like, so the content is set to 0.090% or less. Preferably, it is 0.085% or less.
ＮはＣとともに焼き入れ硬さを決める元素であるとともに、耐食性を向上させる本発明では重要な元素である。そのため、本発明では、０．０６０％以上含有させる。０．０６５％以上が好ましい。しかし、Ｎを過剰に含有させると、スラブ中に気泡欠陥ができやすくなるとともにＶＯＤ等による二次精錬では製造コストを増加させるため、その含有量は、０．０９０％以下とする。好ましくは、０．０８５％以下である。 N: 0.060 to 0.090%
N is an element that determines quenching hardness together with C, and is an important element in the present invention that improves corrosion resistance. Therefore, in the present invention, the content is 0.060% or more. 0.065% or more is preferable. However, if N is excessively contained, bubble defects are likely to occur in the slab and the production cost is increased in the secondary refining by VOD or the like, so the content is set to 0.090% or less. Preferably, it is 0.085% or less.
Ｃ＋１／２Ｎ：０．１３０～０．１９０％
鋼中のマルテンサイト相の硬さを決める元素はＣとＮであり、その合計が硬さに寄与する。本発明者の検討によれば、硬さに対するＮの寄与はＣの半分であり、洋食器ナイフとして必要な硬さを得るにはＣ＋１／２Ｎが０．１３０％以上であることが必要である。好ましくは０．１５０％以上である。一方、Ｃ＋１／２Ｎが過剰になると、焼き入れ硬さが上がりすぎて、製品や製造工程における中間材（鋳片等）の靱性を損ねるために、０．１９０％以下とする。好ましくは０．１８０％以下であり、０．１７５％以下としても良い。 C + 1 / 2N: 0.130 to 0.190%
The elements that determine the hardness of the martensite phase in steel are C and N, the sum of which contributes to the hardness. According to the study of the present inventor, the contribution of N to hardness is half that of C, and it is necessary that C + 1 / 2N is 0.130% or more in order to obtain the hardness required for a Western tableware knife. .. It is preferably 0.150% or more. On the other hand, if C + 1 / 2N is excessive, the quenching hardness is excessively increased, and the toughness of the intermediate material (slab or the like) in the product or manufacturing process is impaired. It is preferably 0.180% or less, and may be 0.175% or less.
鋼中のマルテンサイト相の硬さを決める元素はＣとＮであり、その合計が硬さに寄与する。本発明者の検討によれば、硬さに対するＮの寄与はＣの半分であり、洋食器ナイフとして必要な硬さを得るにはＣ＋１／２Ｎが０．１３０％以上であることが必要である。好ましくは０．１５０％以上である。一方、Ｃ＋１／２Ｎが過剰になると、焼き入れ硬さが上がりすぎて、製品や製造工程における中間材（鋳片等）の靱性を損ねるために、０．１９０％以下とする。好ましくは０．１８０％以下であり、０．１７５％以下としても良い。 C + 1 / 2N: 0.130 to 0.190%
The elements that determine the hardness of the martensite phase in steel are C and N, the sum of which contributes to the hardness. According to the study of the present inventor, the contribution of N to hardness is half that of C, and it is necessary that C + 1 / 2N is 0.130% or more in order to obtain the hardness required for a Western tableware knife. .. It is preferably 0.150% or more. On the other hand, if C + 1 / 2N is excessive, the quenching hardness is excessively increased, and the toughness of the intermediate material (slab or the like) in the product or manufacturing process is impaired. It is preferably 0.180% or less, and may be 0.175% or less.
さらに、焼き入れた時に硬さが安定して発現するように、前記（１）式で記載されたγｐが１２０以上となるように相互調整を行う必要がある。γｐが１２０未満であると焼き入れ条件によっては硬さのばらつきが大きくなる。また、鋼中のδＦｅも多くなる。本発明においては、γｐを１３０以上に調整しても良いし、１４０以上であっても良い。本発明においては１７０以下で良く、１５０以下であっても良い。
Further, it is necessary to perform mutual adjustment so that the γp described in the above formula (1) is 120 or more so that the hardness is stably developed when quenching. If γp is less than 120, the hardness varies greatly depending on the quenching conditions. In addition, δFe in steel also increases. In the present invention, γp may be adjusted to 130 or more, or 140 or more. In the present invention, it may be 170 or less, and may be 150 or less.
本発明の鋼板および鋼部材は、残部がＦｅおよび不純物からなる鋼組成を有する。加えて、本発明では、上記に説明してきた元素に加えて、耐銹性、耐食性を向上させるために、前記Ｆｅの一部に替えて、Ｍｏ、Ｎｂ、ＴｉおよびＳｎ、Ｂｉの元素を添加できる。
The steel sheet and steel member of the present invention have a steel composition in which the balance is composed of Fe and impurities. In addition, in the present invention, in addition to the elements described above, elements of Mo, Nb, Ti and Sn, Bi are added in place of a part of Fe in order to improve rust resistance and corrosion resistance. it can.
Ｍｏ：０．０１～１．０％
Ｍｏは耐食性を向上させる元素であり、０．０１％以上の添加でその効果を発現する。しかし、Ｍｏは高価な元素でもあり、過度に添加しても効果が明確でなく、１．０％を上限とする。 Mo: 0.01-1.0%
Mo is an element that improves corrosion resistance, and its effect is exhibited by adding 0.01% or more. However, Mo is also an expensive element, and even if it is added excessively, the effect is not clear, and the upper limit is 1.0%.
Ｍｏは耐食性を向上させる元素であり、０．０１％以上の添加でその効果を発現する。しかし、Ｍｏは高価な元素でもあり、過度に添加しても効果が明確でなく、１．０％を上限とする。 Mo: 0.01-1.0%
Mo is an element that improves corrosion resistance, and its effect is exhibited by adding 0.01% or more. However, Mo is also an expensive element, and even if it is added excessively, the effect is not clear, and the upper limit is 1.0%.
Ｔｉ：０．００５～０．０５０％
Ｔｉは、炭窒化物を形成することでステンレス鋼におけるクロム炭窒化物の析出による鋭敏化や耐食性の低下を抑制する元素である。その効果は０．００５％以上で発現する。しかし、過度に添加すると、マルテンサイト相を不安定にし、硬さが低下するため、０．０５０％を上限とする。 Ti: 0.005 to 0.050%
Ti is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005% or more. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
Ｔｉは、炭窒化物を形成することでステンレス鋼におけるクロム炭窒化物の析出による鋭敏化や耐食性の低下を抑制する元素である。その効果は０．００５％以上で発現する。しかし、過度に添加すると、マルテンサイト相を不安定にし、硬さが低下するため、０．０５０％を上限とする。 Ti: 0.005 to 0.050%
Ti is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005% or more. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
Ｎｂ：０．００５～０．０５０％
Ｎｂは、炭窒化物を形成することでステンレス鋼におけるクロム炭窒化物の析出による鋭敏化や耐食性の低下を抑制する元素である。その効果は０．００５％以上で発現する。しかし、過度に添加すると、マルテンサイト相を不安定にし、硬さが低下するため、０．０５０％を上限とする。 Nb: 0.005 to 0.050%
Nb is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005% or more. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
Ｎｂは、炭窒化物を形成することでステンレス鋼におけるクロム炭窒化物の析出による鋭敏化や耐食性の低下を抑制する元素である。その効果は０．００５％以上で発現する。しかし、過度に添加すると、マルテンサイト相を不安定にし、硬さが低下するため、０．０５０％を上限とする。 Nb: 0.005 to 0.050%
Nb is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005% or more. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
Ｓｎ：０．０１％～０．１０％
Ｓｎは焼入れ後の耐食性向上に有効な元素であり、０．０１％以上が好ましく、必要に応じて０．０５％以上添加することが好ましい。但し、過度な添加は熱延時の耳割れを促進するため０．１０％以下にすることが好ましい。 Sn: 0.01% to 0.10%
Sn is an element effective for improving corrosion resistance after quenching, preferably 0.01% or more, and preferably 0.05% or more if necessary. However, excessive addition is preferably 0.10% or less because it promotes ear cracking during hot spreading.
Ｓｎは焼入れ後の耐食性向上に有効な元素であり、０．０１％以上が好ましく、必要に応じて０．０５％以上添加することが好ましい。但し、過度な添加は熱延時の耳割れを促進するため０．１０％以下にすることが好ましい。 Sn: 0.01% to 0.10%
Sn is an element effective for improving corrosion resistance after quenching, preferably 0.01% or more, and preferably 0.05% or more if necessary. However, excessive addition is preferably 0.10% or less because it promotes ear cracking during hot spreading.
Ｂｉ：０．０１％～０．２０％
Ｂｉは、耐食性を向上させる元素である。その機構については明確になっていないが、発銹起点となり易いＭｎＳをＢｉ添加により微細化する効果あるため、発銹起点となる確率を低下させると考えている。０．０１％以上の添加で効果を発揮する。０．２０％超添加しても効果は飽和するだけなので、上限を０．２０％とする。 Bi: 0.01% to 0.20%
Bi is an element that improves corrosion resistance. Although the mechanism has not been clarified, it is considered that the addition of Bi has the effect of miniaturizing MnS, which tends to be the starting point of rusting, and thus reduces the probability of becoming the starting point of rusting. It is effective when added at 0.01% or more. Even if more than 0.20% is added, the effect is only saturated, so the upper limit is set to 0.20%.
Ｂｉは、耐食性を向上させる元素である。その機構については明確になっていないが、発銹起点となり易いＭｎＳをＢｉ添加により微細化する効果あるため、発銹起点となる確率を低下させると考えている。０．０１％以上の添加で効果を発揮する。０．２０％超添加しても効果は飽和するだけなので、上限を０．２０％とする。 Bi: 0.01% to 0.20%
Bi is an element that improves corrosion resistance. Although the mechanism has not been clarified, it is considered that the addition of Bi has the effect of miniaturizing MnS, which tends to be the starting point of rusting, and thus reduces the probability of becoming the starting point of rusting. It is effective when added at 0.01% or more. Even if more than 0.20% is added, the effect is only saturated, so the upper limit is set to 0.20%.
＜鋼板および鋼部材のδフェライト相比率＞
本発明者らは鋼板の板厚中央部に存在するδフェライト（δＦｅ）が鋼板の端面耐食性に大きく影響することを見出した。鋼板を冷却速度の遅い空冷程度で焼き入れた場合、δＦｅと母相（γ相）との粒界が冷却中のＣｒ炭化物の析出サイトとなり、析出したＣｒ炭化物近傍の鋭敏化を引き起こし、端面耐食性を低下させると考えている。また、Ｎが端面耐食性を向上させる理由として、Ｃｒ炭化物の析出を抑制する効果もあると推定している。
したがって、本発明ではＮ含有とともに、鋼中のδＦｅの抑制が有効である。 <δ ferrite phase ratio of steel plate and steel member>
The present inventors have found that δ ferrite (δFe) existing in the central portion of the thickness of the steel sheet has a great influence on the end face corrosion resistance of the steel sheet. When the steel plate is hardened by air cooling with a slow cooling rate, the grain boundary between δFe and the matrix phase (γ phase) becomes a precipitation site of Cr carbide during cooling, causing sharpening in the vicinity of the precipitated Cr carbide, and end face corrosion resistance. I think it will reduce. It is also presumed that the reason why N improves the end face corrosion resistance is that it also has an effect of suppressing the precipitation of Cr carbides.
Therefore, in the present invention, it is effective to suppress δFe in steel as well as N content.
本発明者らは鋼板の板厚中央部に存在するδフェライト（δＦｅ）が鋼板の端面耐食性に大きく影響することを見出した。鋼板を冷却速度の遅い空冷程度で焼き入れた場合、δＦｅと母相（γ相）との粒界が冷却中のＣｒ炭化物の析出サイトとなり、析出したＣｒ炭化物近傍の鋭敏化を引き起こし、端面耐食性を低下させると考えている。また、Ｎが端面耐食性を向上させる理由として、Ｃｒ炭化物の析出を抑制する効果もあると推定している。
したがって、本発明ではＮ含有とともに、鋼中のδＦｅの抑制が有効である。 <δ ferrite phase ratio of steel plate and steel member>
The present inventors have found that δ ferrite (δFe) existing in the central portion of the thickness of the steel sheet has a great influence on the end face corrosion resistance of the steel sheet. When the steel plate is hardened by air cooling with a slow cooling rate, the grain boundary between δFe and the matrix phase (γ phase) becomes a precipitation site of Cr carbide during cooling, causing sharpening in the vicinity of the precipitated Cr carbide, and end face corrosion resistance. I think it will reduce. It is also presumed that the reason why N improves the end face corrosion resistance is that it also has an effect of suppressing the precipitation of Cr carbides.
Therefore, in the present invention, it is effective to suppress δFe in steel as well as N content.
焼き入れ前の鋼板に存在するδＦｅを測定できれば良いが、周辺もすべてフェライト相であり、測定は困難である。その代わりに焼き入れ・焼き戻し後の鋼板に存在するδＦｅは周辺がマルテンサイト相であるため、比較的測定しやすいため、本発明の鋼板について、焼き入れ・焼き戻し処理を行った上でδＦｅ量を評価する。評価のための焼き入れ条件は１０５０℃に加熱して３０分保持した後、空冷する条件とし、焼き戻し条件は１５０℃、３０分とする。焼き入れ温度が低すぎ、時間が短すぎるとフェライト相が残りδＦｅ相と区別できないため好ましくなく、焼き入れ温度が高すぎ、時間が長すぎるとδＦｅ相が変化して初期状態と異なるため好ましくない。焼き入れ方法は空冷とする。鋼板について、上記評価条件で焼き入れ・焼き戻しを行った上で、板厚断面での存在面積率で評価してδＦｅが１％以下であれば良好な端面耐食性が得られる。０．１％未満であると、本発明によらずとも優れた耐食性を示すが、δＦｅを減少させるために長時間の熱処理が必要であり、コストも増大するため好ましくない。また、１％を超えると本発明をもってしても耐食性の改善が十分でないととともに、硬さも不十分となるため、好ましくない。さらに好ましい上限は０．５％である。範囲として０．１％～０．５％であると好ましい。
It would be good if δFe existing in the steel sheet before quenching could be measured, but it is difficult to measure because all the periphery is a ferrite phase. Instead, δFe present in the steel sheet after quenching / tempering is relatively easy to measure because the periphery is a martensite phase. Therefore, the steel sheet of the present invention is subjected to quenching / tempering treatment and then δFe. Evaluate the quantity. The quenching conditions for evaluation are heating to 1050 ° C., holding for 30 minutes, and then air cooling, and the tempering conditions are 150 ° C. and 30 minutes. If the quenching temperature is too low and the time is too short, the ferrite phase remains and cannot be distinguished from the δFe phase, which is not preferable. If the quenching temperature is too high and the time is too long, the δFe phase changes and differs from the initial state, which is not preferable. .. The quenching method is air cooling. After quenching and tempering the steel sheet under the above evaluation conditions, good end face corrosion resistance can be obtained if δFe is 1% or less when evaluated by the abundance area ratio in the plate thickness cross section. If it is less than 0.1%, excellent corrosion resistance is exhibited regardless of the present invention, but it is not preferable because long-term heat treatment is required to reduce δFe and the cost increases. Further, if it exceeds 1%, the improvement of corrosion resistance is not sufficient even with the present invention, and the hardness is also insufficient, which is not preferable. A more preferable upper limit is 0.5%. The range is preferably 0.1% to 0.5%.
＜鋼板の製造方法＞
本発明の鋼板の製造方法は、常法が使用される。溶解・鋳造により、成分が調整されたスラブを得、それを熱間圧延したのち、箱焼鈍を行い、ショット、酸洗して製品とする。 <Manufacturing method of steel sheet>
As the method for producing the steel sheet of the present invention, a conventional method is used. A slab with adjusted components is obtained by melting and casting, which is hot-rolled, then box-annealed, shot, and pickled to obtain a product.
本発明の鋼板の製造方法は、常法が使用される。溶解・鋳造により、成分が調整されたスラブを得、それを熱間圧延したのち、箱焼鈍を行い、ショット、酸洗して製品とする。 <Manufacturing method of steel sheet>
As the method for producing the steel sheet of the present invention, a conventional method is used. A slab with adjusted components is obtained by melting and casting, which is hot-rolled, then box-annealed, shot, and pickled to obtain a product.
ただし、δＦｅを制御するために、スラブの予備加熱を行う。その時の加熱条件としては、１１００～１１５０℃の加熱を、均熱時間１時間以上５０時間以下とすることが良い。加熱温度が１１５０℃超であると、二相（γ＋δ）が安定となり、δＦｅ量が急増し好ましくない。また、急増したδＦｅはこの後工程でも多量に残存するため硬さも低下させる要因となる。一方、１１００℃未満であると、長時間加熱してもδＦｅが減少せず、好ましくない。δＦｅ量は１１５０℃超の場合よりも少ないため、後工程次第で硬さを維持できる場合もある。また、１時間未満ではδＦｅが多くなりすぎて好ましくなく、５０時間超では高コストなり好ましくない。
However, in order to control δFe, the slab is preheated. As the heating conditions at that time, heating at 1100 to 1150 ° C. is preferably set to a soaking time of 1 hour or more and 50 hours or less. When the heating temperature exceeds 1150 ° C., the two phases (γ + δ) become stable and the amount of δFe rapidly increases, which is not preferable. In addition, the rapidly increased δFe remains in a large amount even in the subsequent process, which causes a decrease in hardness. On the other hand, if it is less than 1100 ° C., δFe does not decrease even if it is heated for a long time, which is not preferable. Since the amount of δFe is smaller than that in the case of exceeding 1150 ° C., the hardness may be maintained depending on the post-process. Further, if it is less than 1 hour, the amount of δFe becomes too large, which is not preferable, and if it exceeds 50 hours, the cost becomes high, which is not preferable.
この予備加熱は熱間圧延前のスラブ加熱として行い、そのまま熱間圧延しても良い。
This preheating is performed as slab heating before hot rolling, and hot rolling may be performed as it is.
＜鋼部材の製造方法＞
本発明では、得られた鋼板を打ち抜き、焼き入れ、焼き戻しを行い、研磨して部材を作成する。打ち抜き後、鍛造を行い、形を整えることを行う。なお、焼き入れ、焼き戻しの条件として以下が好ましい。焼き入れ温度は１０００～１１５０℃が好ましい。１０００℃未満であると、高温時にオーステナイト相が少なく、焼き入れ後の硬さが低くなるため好ましくなく、１１５０℃超であると、δ相や安定オーステナイト相が増加し、この場合も硬さが低下するため好ましくない。また、焼き入れ時の保持時間は、１分～１時間が好ましい。１分未満であると、高温時にオーステナイト相が少なく、焼き入れ後の硬さが低くなるため好ましくなく、１時間超であると、安定オーステナイト相が増加し、この場合も硬さが低下するため好ましくない。焼き入れ時の冷却速度は、焼き入れ温度から６００℃までの平均冷却速度で、１℃／ｓｅｃ以上が好ましい。これ未満であると、硬さが低下するため好ましくない。焼き入れを空冷とすることにより、前記好ましい冷却速度を実現することができる。焼き戻しは、１００℃～２５０℃が好ましい。１００℃未満では焼き戻しの効果が乏しく、２５０℃を超えると、硬さ低下が大きくなりすぎるため、好ましくない。 <Manufacturing method of steel parts>
In the present invention, the obtained steel sheet is punched, hardened, tempered, and polished to prepare a member. After punching, forging is performed and the shape is adjusted. The following are preferable conditions for quenching and tempering. The quenching temperature is preferably 1000 to 1150 ° C. If it is less than 1000 ° C, the austenite phase is small at high temperature and the hardness after quenching becomes low, which is not preferable. If it is more than 1150 ° C, the δ phase and the stable austenite phase increase, and the hardness also increases in this case. It is not preferable because it decreases. The holding time during quenching is preferably 1 minute to 1 hour. If it is less than 1 minute, the austenite phase is small at high temperature and the hardness after quenching becomes low, which is not preferable. If it is more than 1 hour, the stable austenite phase increases and the hardness also decreases in this case. Not preferred. The cooling rate at the time of quenching is an average cooling rate from the quenching temperature to 600 ° C., preferably 1 ° C./sec or more. If it is less than this, the hardness is lowered, which is not preferable. By air-cooling the quenching, the preferable cooling rate can be realized. The tempering is preferably 100 ° C to 250 ° C. If the temperature is lower than 100 ° C, the effect of tempering is poor, and if the temperature exceeds 250 ° C, the decrease in hardness becomes too large, which is not preferable.
本発明では、得られた鋼板を打ち抜き、焼き入れ、焼き戻しを行い、研磨して部材を作成する。打ち抜き後、鍛造を行い、形を整えることを行う。なお、焼き入れ、焼き戻しの条件として以下が好ましい。焼き入れ温度は１０００～１１５０℃が好ましい。１０００℃未満であると、高温時にオーステナイト相が少なく、焼き入れ後の硬さが低くなるため好ましくなく、１１５０℃超であると、δ相や安定オーステナイト相が増加し、この場合も硬さが低下するため好ましくない。また、焼き入れ時の保持時間は、１分～１時間が好ましい。１分未満であると、高温時にオーステナイト相が少なく、焼き入れ後の硬さが低くなるため好ましくなく、１時間超であると、安定オーステナイト相が増加し、この場合も硬さが低下するため好ましくない。焼き入れ時の冷却速度は、焼き入れ温度から６００℃までの平均冷却速度で、１℃／ｓｅｃ以上が好ましい。これ未満であると、硬さが低下するため好ましくない。焼き入れを空冷とすることにより、前記好ましい冷却速度を実現することができる。焼き戻しは、１００℃～２５０℃が好ましい。１００℃未満では焼き戻しの効果が乏しく、２５０℃を超えると、硬さ低下が大きくなりすぎるため、好ましくない。 <Manufacturing method of steel parts>
In the present invention, the obtained steel sheet is punched, hardened, tempered, and polished to prepare a member. After punching, forging is performed and the shape is adjusted. The following are preferable conditions for quenching and tempering. The quenching temperature is preferably 1000 to 1150 ° C. If it is less than 1000 ° C, the austenite phase is small at high temperature and the hardness after quenching becomes low, which is not preferable. If it is more than 1150 ° C, the δ phase and the stable austenite phase increase, and the hardness also increases in this case. It is not preferable because it decreases. The holding time during quenching is preferably 1 minute to 1 hour. If it is less than 1 minute, the austenite phase is small at high temperature and the hardness after quenching becomes low, which is not preferable. If it is more than 1 hour, the stable austenite phase increases and the hardness also decreases in this case. Not preferred. The cooling rate at the time of quenching is an average cooling rate from the quenching temperature to 600 ° C., preferably 1 ° C./sec or more. If it is less than this, the hardness is lowered, which is not preferable. By air-cooling the quenching, the preferable cooling rate can be realized. The tempering is preferably 100 ° C to 250 ° C. If the temperature is lower than 100 ° C, the effect of tempering is poor, and if the temperature exceeds 250 ° C, the decrease in hardness becomes too large, which is not preferable.
以下、実施例により本発明の効果を説明するが、本発明は、以下の実施例で用いた条件に限定されるものではない。
Hereinafter, the effects of the present invention will be described with reference to Examples, but the present invention is not limited to the conditions used in the following Examples.
本実施例では、まず、表１、表２に示す成分組成の鋼を溶製して２５０ｍｍ厚のスラブに鋳造した。次に、これらのスラブを予備加熱として１１５０℃、４０時間の熱処理を行い、δＦｅ量を一定範囲とした。ただし、Ａ２鋼に対しては、１１７５℃、４０時間および９５０℃、４０時間の予備加熱を行い、それぞれＡ２’鋼、Ａ２”鋼とした。
その後、１１５０℃に加熱して、熱間圧延を経て板厚３～８ｍｍの熱延鋼板とした。引き続き熱延鋼板の焼鈍を箱焼鈍で行った。最高加熱温度を８００℃以上、９００℃以下の温度域とした。焼鈍後の鋼板表面のスケールをショットブラストで除去し、酸洗した。 In this example, first, the steels having the composition shown in Tables 1 and 2 were melted and cast into a slab having a thickness of 250 mm. Next, these slabs were heat-treated at 1150 ° C. for 40 hours as preheating, and the amount of δFe was set within a certain range. However, the A2 steel was preheated at 1175 ° C. for 40 hours and at 950 ° C. for 40 hours to obtain A2'steel and A2'steel, respectively.
Then, it was heated to 1150 ° C. and hot-rolled to obtain a hot-rolled steel sheet having a plate thickness of 3 to 8 mm. Subsequently, the hot-rolled steel sheet was annealed by box annealing. The maximum heating temperature was set to a temperature range of 800 ° C. or higher and 900 ° C. or lower. The scale on the surface of the steel sheet after annealing was removed by shot blasting and pickled.
その後、１１５０℃に加熱して、熱間圧延を経て板厚３～８ｍｍの熱延鋼板とした。引き続き熱延鋼板の焼鈍を箱焼鈍で行った。最高加熱温度を８００℃以上、９００℃以下の温度域とした。焼鈍後の鋼板表面のスケールをショットブラストで除去し、酸洗した。 In this example, first, the steels having the composition shown in Tables 1 and 2 were melted and cast into a slab having a thickness of 250 mm. Next, these slabs were heat-treated at 1150 ° C. for 40 hours as preheating, and the amount of δFe was set within a certain range. However, the A2 steel was preheated at 1175 ° C. for 40 hours and at 950 ° C. for 40 hours to obtain A2'steel and A2'steel, respectively.
Then, it was heated to 1150 ° C. and hot-rolled to obtain a hot-rolled steel sheet having a plate thickness of 3 to 8 mm. Subsequently, the hot-rolled steel sheet was annealed by box annealing. The maximum heating temperature was set to a temperature range of 800 ° C. or higher and 900 ° C. or lower. The scale on the surface of the steel sheet after annealing was removed by shot blasting and pickled.
＜実施例１＞
得られた鋼板を評価するため、鋼板から評価用の試料を切り出し、当該試料について、焼き入れ・焼き戻し処理として１０５０℃に加熱して３０分保持した後、空冷し、１５０℃、３０分の焼き戻しを行った。その後、δＦｅ量測定、硬さ測定、端面耐食性の各評価を行った。得られた結果を表３に示す。 <Example 1>
In order to evaluate the obtained steel sheet, a sample for evaluation was cut out from the steel sheet, and the sample was heated to 1050 ° C. for 30 minutes as a quenching / tempering process, held for 30 minutes, and then air-cooled at 150 ° C. for 30 minutes. It was tempered. After that, each evaluation of δFe amount measurement, hardness measurement, and end face corrosion resistance was performed. The results obtained are shown in Table 3.
得られた鋼板を評価するため、鋼板から評価用の試料を切り出し、当該試料について、焼き入れ・焼き戻し処理として１０５０℃に加熱して３０分保持した後、空冷し、１５０℃、３０分の焼き戻しを行った。その後、δＦｅ量測定、硬さ測定、端面耐食性の各評価を行った。得られた結果を表３に示す。 <Example 1>
In order to evaluate the obtained steel sheet, a sample for evaluation was cut out from the steel sheet, and the sample was heated to 1050 ° C. for 30 minutes as a quenching / tempering process, held for 30 minutes, and then air-cooled at 150 ° C. for 30 minutes. It was tempered. After that, each evaluation of δFe amount measurement, hardness measurement, and end face corrosion resistance was performed. The results obtained are shown in Table 3.
δＦｅ量は、試料端面を鏡面研磨、エッチングを行い、組織を現出させて、測定した。エッチング液は、王水等でもδＦｅ現出可能であるが、非特許文献１に記載されている改良村上試薬と呼ばれる試薬を用いるとδＦｅが茶色に濃くエッチングされるので好ましく、これを用いて評価した。図１に代表例を示す。
The amount of δFe was measured by mirror-polishing and etching the end face of the sample to reveal the structure. ΔFe can be expressed in aqua regia or the like as the etching solution, but it is preferable to use a reagent called the improved Murakami reagent described in Non-Patent Document 1 because δFe is deeply etched in brown, and evaluation is performed using this. did. A typical example is shown in FIG.
改良村上試薬で現出させた組織を検鏡し、一定幅（本実施例では２ｍｍ）の全厚からδＦｅの写真を撮影し、その画像解析からδＦｅ面積を求め、それから面積率（δＦｅ面積（ｍｍ2）／２ｍｍ×全厚（ｍｍ）×１００（％））を算出した。本発明の成分の鋼部材が優れた耐食性を示すには、その値が、０．１～１％であることが必要である。さらに、好ましくは、０．１％～０．５％である。δＦｅ面積率：０．１～１％を合格（Ａ）とし、それ以上を不合格（Ｘ）とした。
The tissue revealed by the improved Murakami reagent is examined under a microscope, a photograph of δFe is taken from the total thickness of a certain width (2 mm in this example), the δFe area is obtained from the image analysis, and then the area ratio (δFe area (δFe area (δFe area)). mm 2 ) / 2 mm × total thickness (mm) × 100 (%)) was calculated. In order for the steel member of the component of the present invention to exhibit excellent corrosion resistance, its value needs to be 0.1 to 1%. Further, it is preferably 0.1% to 0.5%. δFe area ratio: 0.1 to 1% was regarded as pass (A), and more than that was regarded as fail (X).
硬度は、試料表面を＃８０研磨仕上げした後、表面硬度（焼入れ硬度）をＪＩＳ Ｚ ２２４５に準拠してロックウエル硬度計Ｃスケールで評価し、５０以上を合格（Ａ）、それ以外を不合格（Ｘ）とした。
As for the hardness, after the sample surface is polished to # 80, the surface hardness (quenching hardness) is evaluated by the Rockwell hardness tester C scale in accordance with JIS Z2245, and 50 or more is passed (A), and the others are rejected (Failure). X).
端面耐食性の評価は、試料表面および端面を＃６００研磨仕上げした後、端面を評価面として上面にして、塩水噴霧試験を２４時間（ＪＩＳ Ｚ ２３７１「塩水噴霧試験方法」）行い、発銹点を数えた。２点以下を合格（Ａ）とし、それを超えた場合を不合格（Ｘ）とした。特に発銹点がゼロであったものは、合格（Ｓ）とした。なお、２４時間以上塩水噴霧試験を行っても、それ以上錆が進展することは少ないため、２４時間の結果をもって、端面耐食性を判断した。
To evaluate the end face corrosion resistance, after polishing the sample surface and end face with # 600, the end face is used as the evaluation surface and the salt spray test is performed for 24 hours (JIS Z 2371 "salt spray test method") to determine the rusting point. I counted. A score of 2 or less was regarded as a pass (A), and a score exceeding that score was a failure (X). In particular, those with zero rusting points were regarded as passing (S). Even if the salt spray test was carried out for 24 hours or more, rust did not develop further, so the end face corrosion resistance was judged based on the results for 24 hours.
本発明の鋼板はいずれも端面耐食性に優れているだけでなく、他の特性も優れており、洋食器ナイフ用鋼板として好ましい。これに対し、比較鋼では、端面耐食性が劣位か、その他の特性が劣位であり、洋食器ナイフ用鋼板として好ましくないことが明らかである。
All of the steel sheets of the present invention are excellent not only in end face corrosion resistance but also in other properties, and are preferable as steel sheets for Western tableware knives. On the other hand, the comparative steel has inferior end face corrosion resistance or inferior other characteristics, and it is clear that it is not preferable as a steel plate for Western tableware knives.
＜実施例２＞
得られた鋼板から切り出した部材を用いて、表４に示す条件で焼き入れ焼き戻しを行い、鋼部材とした。焼き入れは１０５０～１１５０℃で加熱し、その後焼き入れ温度から６００℃までの冷却速度を表４に記載した冷却速度に制御して冷却した。さらに、１５０～２５０℃で１～２ｈの焼き戻し処理を実施して、鋼部材とした。また、Ａ２’鋼、Ａ２”鋼も同様に処理した。 <Example 2>
Using the member cut out from the obtained steel sheet, quenching and tempering were performed under the conditions shown in Table 4 to obtain a steel member. Quenching was performed by heating at 1050 to 1150 ° C., and then cooling was performed by controlling the cooling rate from the quenching temperature to 600 ° C. to the cooling rate shown in Table 4. Further, a tempering treatment for 1 to 2 hours was carried out at 150 to 250 ° C. to obtain a steel member. Further, A2'steel and A2'steel were also treated in the same manner.
得られた鋼板から切り出した部材を用いて、表４に示す条件で焼き入れ焼き戻しを行い、鋼部材とした。焼き入れは１０５０～１１５０℃で加熱し、その後焼き入れ温度から６００℃までの冷却速度を表４に記載した冷却速度に制御して冷却した。さらに、１５０～２５０℃で１～２ｈの焼き戻し処理を実施して、鋼部材とした。また、Ａ２’鋼、Ａ２”鋼も同様に処理した。 <Example 2>
Using the member cut out from the obtained steel sheet, quenching and tempering were performed under the conditions shown in Table 4 to obtain a steel member. Quenching was performed by heating at 1050 to 1150 ° C., and then cooling was performed by controlling the cooling rate from the quenching temperature to 600 ° C. to the cooling rate shown in Table 4. Further, a tempering treatment for 1 to 2 hours was carried out at 150 to 250 ° C. to obtain a steel member. Further, A2'steel and A2'steel were also treated in the same manner.
得られた鋼部材のδＦｅ量測定、硬さ測定、端面耐食性評価を熱処理条件とともに表４に示す。尚、評価方法および評価基準は実施例１と同一とした。
Table 4 shows the δFe amount measurement, hardness measurement, and end face corrosion resistance evaluation of the obtained steel member together with the heat treatment conditions. The evaluation method and evaluation criteria were the same as in Example 1.
本発明の鋼部材はいずれも端面耐食性に優れているだけでなく、他の特性も優れており、洋食器ナイフ用鋼部材として好ましい。これに対し、比較鋼では、端面耐食性が劣位か、その他の特性が劣位であり、洋食器ナイフ用鋼部材として好ましくないことが明らかである。
All of the steel members of the present invention are excellent not only in end face corrosion resistance but also in other characteristics, and are preferable as steel members for Western tableware knives. On the other hand, the comparative steel has inferior end face corrosion resistance or inferior other characteristics, and it is clear that it is not preferable as a steel member for Western tableware knives.
本発明によれば、空冷焼き入れ後の端面耐食性に優れたマルテンサイト系ステンレス鋼部材を生産性良く製造することが可能となり、それを用いて製造した洋食器ナイフの耐食性が向上し、産業上、非常に有用である。
According to the present invention, it is possible to produce a martensitic stainless steel member having excellent end face corrosion resistance after air-cooling and quenching with high productivity, and the corrosion resistance of a Western tableware knife produced by using the martensitic stainless steel member is improved, and industrially. , Very useful.
Claims (4)
- 質量％で、
Ｃ：０．１００～０．１７０％、
Ｓｉ：０．２５～０．６０％、
Ｍｎ：０．１０～０．６０％、
Ｐ：０．０３５％以下、
Ｓ：０．０１５％以下、
Ｃｒ：１１．０～１５．０％、
Ｎｉ：０．０５～０．６０％、
Ｃｕ：０．０１０～０．５０％、
Ｖ：０．０１０～０．１０％、
Ａｌ：０．０５％以下
Ｎ：０．０６０～０．０９０％
Ｃ＋１／２Ｎ：０．１３０～０．１９０％
であり、残部がＦｅおよび不純物からなる鋼組成を有し、
下記式（１）で示されるγｐが１２０以上であるマルテンサイト系ステンレス鋼板において、
前記マルテンサイト系ステンレス鋼板を１０５０℃で３０分保持後空冷焼き入れし、１５０℃、３０分の焼き戻しを行ったとき、板厚中央部に存在するδフェライト（δＦｅ）の板厚断面における面積率が０．１～１％となることを特徴とするマルテンサイト系ステンレス鋼板。
γｐ＝４２０Ｃ＋４７０Ｎ＋３０Ｎｉ＋７Ｍｎ＋９Ｃｕ－１１．５Ｃｒ－１１．５Ｓｉ－１２Ｍｏ－２３Ｖ－４７Ｎｂ－５２Ａｌ＋１８９ ・・・ 式（１）
式（１）中の元素記号は、当該元素の含有量（質量％）を意味する。 By mass%
C: 0.100 to 0.170%,
Si: 0.25 to 0.60%,
Mn: 0.10 to 0.60%,
P: 0.035% or less,
S: 0.015% or less,
Cr: 11.0 to 15.0%,
Ni: 0.05 to 0.60%,
Cu: 0.010 to 0.50%,
V: 0.010 to 0.10%,
Al: 0.05% or less N: 0.060 to 0.090%
C + 1 / 2N: 0.130 to 0.190%
Has a steel composition with the balance consisting of Fe and impurities.
In a martensitic stainless steel sheet having a γp of 120 or more represented by the following formula (1),
When the martensitic stainless steel sheet is held at 1050 ° C. for 30 minutes, then air-cooled and quenched, and tempered at 150 ° C. for 30 minutes, the area of δ ferrite (δFe) present in the center of the plate thickness in the plate thickness cross section. A martensitic stainless steel sheet having a ratio of 0.1 to 1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element. - さらに、前記Ｆｅの一部に替えて、質量％で、
Ｍｏ：０．０１～１．０％、
Ｔｉ：０．００５～０．０５０％、
Ｎｂ：０．００５～０．０５０％
の１種または２種以上を含有することを特徴とする請求項１に記載のマルテンサイト系ステンレス鋼板。 Further, instead of a part of the Fe, by mass%,
Mo: 0.01-1.0%,
Ti: 0.005 to 0.050%,
Nb: 0.005 to 0.050%
The martensitic stainless steel sheet according to claim 1, wherein the martensitic stainless steel sheet contains one or more of the above. - さらに、前記Ｆｅの一部に替えて、質量％で、
Ｓｎ：０．０１～０．１０％、
Ｂｉ：０．０１～０．２０％
の１種または２種を含有することを特徴とする請求項１または請求項２に記載のマルテンサイト系ステンレス鋼板。 Further, instead of a part of the Fe, by mass%,
Sn: 0.01 to 0.10%,
Bi: 0.01 to 0.20%
The martensitic stainless steel sheet according to claim 1 or 2, wherein the martensitic stainless steel sheet contains one or two of the above. - 請求項１～請求項３の何れか１項に記載の鋼組成を有するマルテンサイト系ステンレス鋼部材において、
下記式（１）で示されるγｐが１２０以上であり、
さらに、板厚中央部に存在するδフェライト（δＦｅ）の板厚断面における面積率が０．１～１％であることを特徴とするマルテンサイト系ステンレス鋼部材。
γｐ＝４２０Ｃ＋４７０Ｎ＋３０Ｎｉ＋７Ｍｎ＋９Ｃｕ－１１．５Ｃｒ－１１．５Ｓｉ－１２Ｍｏ－２３Ｖ－４７Ｎｂ－５２Ａｌ＋１８９ ・・・ 式（１）
式（１）中の元素記号は、当該元素の含有量（質量％）を意味する。 In the martensitic stainless steel member having the steel composition according to any one of claims 1 to 3.
The γp represented by the following formula (1) is 120 or more, and
Further, a martensitic stainless steel member characterized in that the area ratio of δ ferrite (δFe) existing in the central portion of the plate thickness in the plate thickness cross section is 0.1 to 1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element.
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