JP3900169B2 - Martensitic stainless steel for disc brakes - Google Patents

Description

  The present invention relates to martensitic stainless steel used in disc brake discs (disks) of motorcycles (motorcycles), automobiles, bicycles, etc., and in particular, even after being kept at a high temperature for a long time by frictional heat during braking. The present invention relates to a martensitic stainless steel for disc brakes that is difficult to soften and is excellent in resistance to tempering softening (also referred to as high-temperature softening resistance) that can maintain an appropriate initial hardness.

  A disc brake used in a motorcycle or the like has a function of suppressing the rotation of a wheel by a frictional force between a disc and a pad, and the temperature of the disc at the time of braking greatly increases due to generated frictional heat. However, in recent years, the thickness of the disk has also been reduced in the trend of reducing the weight of the vehicle for the purpose of improving fuel efficiency, which has been promoted from the viewpoint of protecting the global environment. For this reason, there is a concern that the brake disk having a small plate thickness has a higher heat capacity, resulting in a larger temperature rise due to frictional heat during braking, tempering and softening of the disk, and faster wear.

  That is, conventionally, as a disk brake disk material, 12 mass% Cr low carbon (C: 0.06 mass%) martensitic stainless steel is mainly used from the viewpoint of hardness and corrosion resistance. This stainless steel is usually used as it is after being processed into a predetermined shape, and the hardness is HRC (Rockwell C hardness JIS Z2245), and the components are designed to be in the range of 32-38.

  However, when the temperature of the brake disc using the martensitic stainless steel rises due to frictional heat, particularly when it reaches a high temperature of 550 ° C. or higher, the hardness is rapidly increased due to strain recovery and carbonitride precipitation. The HRC may fall below 32, which is the lower limit of the appropriate range, during use. In particular, due to the above-mentioned thinning of the disk, the disk may reach a temperature exceeding 600 ° C., and the actual situation is that the demand for improving the tempering softening resistance has further increased.

For such a problem, for example, Patent Document 1 discloses a steel sheet in which the problem of warpage due to a temperature rise of the disk is improved. However, the temperature studied in the technology is up to 600 ° C., and no measures for improving the temper softening resistance that suppress the decrease in hardness after the temperature rise has been studied. On the other hand, Patent Document 2 discloses a steel plate having tempering softening resistance that can maintain 30 or more in HRC even after being held at 530 ° C. or higher. However, it has high tempering resistance even at a temperature exceeding 600 ° C. The characteristics were insufficient for the requirement to stably secure the softening property.
JP 2002-146482 A JP 2001-220654 A

  The object of the present invention is that temper softening hardly occurs even after being kept at a temperature exceeding 600 ° C., and the hardness after tempering at a temperature of 650 ° C. is 32 or more in HRC, and further after tempering at a temperature of 670 ° C. However, the object is to provide martensitic stainless steel for disc brakes that has a hardness of 30 or more in HRC and has excellent tempering softening resistance.

  In order to solve the above-mentioned problems of the prior art, the inventors have investigated in detail the influence of the component composition of martensitic stainless steel on temper softening resistance. As a result, if appropriate amounts of Nb and Cu are added and these precipitates are finely precipitated at a temperature of 500 ° C. to 700 ° C. to prevent dislocation movement, softening due to strain recovery can be suppressed. In addition, by adding appropriate amounts of N and Ni, and suppressing the precipitation of carbides at high temperatures to ensure solid solution C, the hardness of the martensite structure is maintained, so that it is maintained at a high temperature exceeding 600 ° C. After that, it was newly found that high hardness can be maintained, and the present invention was completed.

The present invention developed on the basis of the above findings is C: less than 0.050 mass%, Si: 1.0 mass% or less, Mn: 2.0 mass% or less, P: 0.04 mass% or less, S: 0.010 mass% or less, Al: 0.2 Less than mass%, Cr: more than 11.5 to 15.0 mass%, Ni: 0.5 to 2.0 mass%, Cu: more than 0.50 to 4.0 mass%, Nb: more than 0.08 to 0.6 mass%, N: less than 0.09 mass%,
However, the contents (mass%) of C, N, Nb, Cr, Si, Ni, Mn and Cu are the following formulas (1) and (2):
0.03 ≦ [C] + [N] −13 / 93 × [Nb] ≦ 0.09 ・ ・ ・ ・ ・ ・ (1)
5 × [Cr] + 10 × [Si] + 30 × [Nb] −9 × [Ni] −5 × [Mn] −3 × [Cu] −225 × [N] −270 × [C] ≦ 40 ... (2)
However, the element symbols enclosed in [] in the expressions (1) and (2) represent the content of each element (hereinafter the same).
Is a martensitic stainless steel for disc brakes that contains Fe and the inevitable impurities.

The martensitic stainless steel of the present invention is characterized by further containing any one or more selected from the following groups A to D in addition to the above component composition.
Group A; V: 0.02 to 0.3 mass%
Group B; Mo: 0.02 to 2.0 mass%, Co: 0.02 to 2.0 mass%, or one type C group; Ti: 0.02 to 0.3 mass%, Zr: 0.02 to 0.3 mass%, and Ta: 0.02 to 0.3 1 type or 2 types or more of mass%: Group D: B: 0.0005 to 0.0050 mass%, Ca: 0.0005 to 0.0050 mass%, 1 type or 2 types

  The martensitic stainless steel of the present invention is a hot rolled steel plate or a cold rolled steel plate.

  According to the present invention, it is possible to obtain martensitic stainless steel that is difficult to soften even at temperatures exceeding 600 ° C. by controlling the component composition of the steel within an appropriate range. This disc brake disc made of martensitic stainless steel has a hardness of 32 or more in HRC even after tempering at 650 ° C for 1 hr, and 30 or more in HRC even after tempering at 670 ° C for 1 hr. It has excellent tempering softening resistance.

  The martensitic stainless steel for disc brakes of the present invention having the above-described structure has a hardness after quenching of 32 to 38 in HRC, and 32 or more in HRC even after tempering at a temperature of 650 ° C., and further 670 ° C. Even after tempering at temperature, it has excellent softening resistance against tempering that can maintain a hardness of 30 or more in HRC. Moreover, the martensitic stainless steel for disc brakes of the present invention also has the characteristics of being excellent in toughness and corrosion resistance.

The reason for limiting the component composition of the martensitic stainless steel of the present invention having the above characteristics to the above range will be described.
C: Less than 0.050 mass% C, like N, is an element effective in increasing the hardness of steel after quenching. In order to acquire the effect, it is preferable to contain 0.015 mass% or more. However, when C is kept at a high temperature exceeding 600 ° C. and forms coarse Cr23C6 by combining with Cr, it not only contributes to the improvement of hardness but also becomes a starting point of rusting and decreases the corrosion resistance. Let Furthermore, excessive addition of C reduces toughness. Therefore, it is necessary to limit the addition amount of C to less than 0.050 mass%. In particular, from the viewpoint of improving toughness and corrosion resistance, it is desirable that the content be less than 0.05 mass%, more preferably less than 0.045 mass%.

N: Less than 0.09 mass% N, like C, is an element effective for increasing the hardness of steel after quenching. In particular, fine Cr2N is formed and precipitated in a temperature range of 500 ° C. to 700 ° C., and the tempering softening resistance is improved by the precipitation hardening action. Therefore, in order to improve the temper softening resistance, it is more effective to add N than C. In order to acquire those effects, it is preferable to contain 0.015 mass% or more, and it is preferable to add exceeding 0.03 mass% from a viewpoint of improving tempering softening resistance more. On the other hand, excessive addition of N causes a decrease in toughness, so it is necessary to limit it to less than 0.09 mass%.

Si: 1.0 mass% or less
Since Si will reduce toughness if added excessively, it is limited to 1.0 mass% or less. Preferably it is 0.3 mass% or less.

Mn: 2.0 mass% or less
Since Mn combines with S to form MnS and lowers the corrosion resistance, it is limited to 2.0 mass% or less. Preferably it is less than 1.0 mass%, More preferably, it is less than 0.5 mass%.

P: 0.04 mass% or less P is an element that decreases hot workability, and is preferably reduced as much as possible from the viewpoint of manufacturability. However, if it is reduced too much, steelmaking costs will increase, so 0.04 mass% is made the upper limit. In order to further improve the hot workability, it is desirable that P is 0.02 mass% or less.

S: 0.010 mass% or less S, like P, is preferable as the content is high because the hot workability is lowered. However, it is preferably 0.010 mass% or less in view of the de-S treatment cost in steelmaking. From the viewpoint of improving hot workability, the S content is preferably 0.005 mass% or less.

Al: 0.2 mass% or less
Al is limited to 0.2 mass% or less in order to reduce toughness when added excessively. Preferably it is 0.20 mass% or less, More preferably, it is 0.05 mass% or less.

Cr: Over 11.5 to 15.0 mass%
Cr is an essential component for ensuring the corrosion resistance, which is an excellent feature of stainless steel, and in order to obtain sufficient corrosion resistance, it is necessary to contain more than 11.5 mass%. From the viewpoint of obtaining more corrosion resistance, it is preferable to add 12.0 mass% or more. On the other hand, the workability and toughness decrease as the amount of Cr added increases. In particular, if the content exceeds 15.0 mass%, the toughness decreases significantly, so the upper limit is made 15.0 mass%. From the viewpoint of ensuring excellent toughness, it is preferably less than 14.0 mass%, more preferably less than 13.0 mass%.

Ni: 0.5-2.0mass%
Ni effectively contributes to the improvement of the tempering softening resistance by delaying the precipitation of Cr carbonitride at a high temperature exceeding 600 ° C. and maintaining the hardness of the martensite structure containing solid solution C in supersaturation. Furthermore, the corrosion resistance, which is a characteristic of stainless steel, is improved and the toughness is also improved. In order to obtain these effects, addition of 0.5 mass% or more is necessary. Preferably it exceeds 0.50 mass%, More preferably, it is 0.55 mass% or more. Furthermore, it is preferable to add exceeding 1.0 mass% from a viewpoint of ensuring sufficient tempering softening resistance. On the other hand, even if added over 2.0 mass%, the effect of improving the temper softening resistance is saturated and only the raw material cost is increased, so the amount is limited to 2.0 mass% or less.

Cu: more than 0.50 ~ 4.0mass%
Cu precipitates finely as ε-Cu in the vicinity of a temperature of 600 ° C., and its precipitation hardening action improves the tempering softening resistance. In order to obtain the effect, it is added exceeding 0.50 mass%, preferably exceeding 0.5 mass%. From the viewpoint of securing sufficient tempering softening resistance, it is more preferable to add 1.0 mass% or more, and further preferably 1.5 mass% or more. On the other hand, even if added in excess of 4.0 mass%, the tempering softening resistance is saturated and only the raw material cost is increased, so it is limited to 4.0 mass% or less.

Nb: more than 0.08 ~ 0.6mass%,
Nb has a strong binding force with C and N, and precipitates as NbC and NbN. Although it does not contribute to the improvement of hardness after quenching, it suppresses the recovery of strain introduced into martensite by quenching treatment, thereby improving the temper softening resistance when held at a high temperature around 600 ° C. Improve. In order to acquire the effect, it is necessary to add exceeding 0.08 mass%, and it is preferable to add 0.10 mass% or more. On the other hand, even if added over 0.6 mass%, the tempering softening resistance is saturated and the toughness is lowered, so the amount is limited to 0.6 mass% or less. From the viewpoint of ensuring toughness, it is preferably 0.4 mass% or less, more preferably 0.2 mass% or less.

(1) Formula: 0.03 ≦ [C] + [N] −13 / 93 × [Nb] ≦ 0.09
C and N are effective elements for increasing the hardness of steel after quenching, but NbC and NbN combined with Nb do not contribute to increasing the hardness after quenching. Therefore, when controlling the hardness of the steel after quenching, the effect of C and N is obtained by subtracting the amount consumed by precipitates from C and N in the steel. [C] + [N] -13 / 93 × [Nb]). If the value of this intermediate term is less than 0.03, the hardness after quenching is less than 32 in HRC, while if it exceeds 0.09, the hardness exceeds 38 in HRC. Therefore, in order to set the hardness after quenching to an appropriate HRC of 32 to 38 for disc brake applications, it is necessary to control the value of the intermediate term in the equation (1) to be in the range of 0.03 to 0.09.

(2) Formula: 5 × [Cr] + 10 × [Si] + 30 × [Nb] −9 × [Ni] −5 × [Mn] −3 × [Cu] −225 × [N] −270 × [C] ≦ 40
Equation (2) is an evaluation parameter related to quenching stability. In order to ensure the hardenability of the disk material, it is necessary that 90 vol% or more of the austenite phase is generated when heated to 900 ° C. to 1000 ° C., and that it is martensitic transformed when air cooled. Usually, in martensitic stainless steel, the austenite phase increases most around 1000 ° C., and the amount of austenite phase decreases both above and below 1000 ° C. (2) If the value of the left-hand side of the formula exceeds 40, the temperature range in which the austenite phase is 90 vol% or more is narrowed, and due to fluctuations in the quenching temperature in the manufacturing process, sufficient quenching does not occur. It comes out of the hardness range. Also, from the viewpoint of productivity, if the quenching temperature is high, the heating time becomes long and the manufacturing cost increases. Therefore, it is desirable that the quenching temperature is as low as possible. Even when quenching at 900 ° C., HRC: 32 or more is obtained. It is important to be able to. Therefore, in order to obtain stable hardenability, it is necessary to control the component composition of steel so that the value on the left side of equation (2) is 40 or less.

In the present invention, in addition to the above essential elements, the following components may be added as necessary.
V: 0.02 ~ 0.3mass%
V, like Nb, forms fine carbonitrides and precipitates, and is an element effective for improving the tempering softening resistance, and is preferably added 0.02 mass% or more, more preferably 0.10 mass% or more. be able to. However, since addition of more than 0.3 mass% reduces toughness, it is preferable to set 0.3 mass% as the upper limit.

One or two of Mo: 0.02 to 2.0 mass%, Co: 0.02 to 2.0 mass%
Mo and Co are effective elements for improving the corrosion resistance, and can be added in an amount of 0.02 mass% or more if necessary. Mo, like Ni, has the effect of improving the tempering softening resistance by delaying the precipitation of Cr carbonitride and maintaining the hardness of the martensite phase containing C in supersaturation. From the viewpoint of further improving the corrosion resistance, it is preferable to add 0.5 mass% or more, respectively, but if it is 1.5 mass% or less, sufficient corrosion resistance can be obtained. On the other hand, if each element contains more than 2.0 mass%, the effect of improving the corrosion resistance is not only saturated but also the toughness is lowered. Therefore, the upper limit is preferably 2.0 mass%.

One or more of Ti: 0.02-0.3 mass%, Zr: 0.02-0.3 mass% and Ta: 0.02-0.3 mass%
Ti, Zr, and Ta are elements that form fine carbonitrides and precipitate in the same way as Nb and improve tempering softening resistance, and can be added in amounts of 0.02 mass% or more, if necessary. However, if added over 0.3 mass%, the toughness decreases, so it is preferable that the upper limit is 0.3 mass%.

B: One or two of 0.0005 to 0.0050 mass%, Ca: 0.0005 to 0.0050 mass% B and Ca have the effect of increasing the toughness of the steel by adding a small amount, and each 0.0005 mass% or more as necessary. Can be added. However, even if added over 0.0050 mass%, the effect is not only saturated, but also the corrosion resistance is lowered, so 0.0050 mass% is preferable as the upper limit.

  In the martensitic stainless steel of the present invention, components other than the above are composed of Fe and inevitable impurities. The inevitable impurities may contain small amounts (0.01 mass% or less) of alkali metals such as Na, Ba, La, Y, and Hf, alkaline earth metals, rare earth elements, and transition metals. It does not interfere with the effect of.

Next, the steel sheet structure of the martensitic stainless steel of the present invention will be described.
As described above, in the steel of the present invention, 90% by volume or more of the austenite phase is generated when heated to 900 ° C. to 1000 ° C., and it is martensitic transformed when air-cooled in order to ensure sufficient hardenability. is required. Therefore, it is desirable that the steel sheet structure of the martensitic stainless steel of the present invention is composed of a martensite phase of 90 vol% or more and the remaining ferrite phase. This is because if the martensite phase is less than 90 vol%, the soft ferrite phase increases so much that it becomes difficult to obtain the desired hardness.

Next, the manufacturing method of the martensitic stainless steel of this invention is demonstrated.
The method for producing the steel of the present invention is not particularly limited, and generally known methods generally employed in the production of martensitic stainless steel can be applied as they are. For example, in the steelmaking process, steel containing the above essential components and components added as necessary is melted in a converter or an electric furnace or the like, and vacuum degassing method (RH method), VOD (Vacuum Oxygen Decarburization) Alternatively, a method of performing secondary refining by a refining method such as AOD (Argon Oxygen Decarburization) is suitable. The molten steel can be made into a steel material (slab) by a known method such as a continuous casting method or an ingot-bundling rolling method, but in terms of productivity and quality, the continuous casting method is applied. Is preferred. The obtained steel material is heated to 1100-1250 ° C, hot-rolled at a finish rolling temperature of 800-1100 ° C, wound up in a temperature range of 600-900 ° C, and a hot-rolled steel strip having a thickness of 3-8 mm Is preferable. This hot-rolled steel strip is annealed at 650 to 900 ° C. for 4 to 20 hours in a batch furnace such as a box annealing furnace, and then processed into a sheet as necessary to make a material for a brake disk. Moreover, you may perform descaling processes, such as pickling and shot blasting, to the said hot-rolled steel strip as needed.

  The disc material obtained as described above is then punched into a disc mold, heated to a temperature of 900 ° C. to 1000 ° C., and then subjected to a quenching treatment of cooling at an air cooling rate or higher, and further required. In accordance with the above, descaling and painting are performed, and then the sliding surface with the brake pad is mechanically polished to increase the aesthetics and thickness accuracy to obtain a disc product.

  The martensitic stainless steel of the present invention obtained as described above can be used for brake discs for bicycles, automobiles, snowmobiles, etc., as well as brake discs for motorcycles. Since the thickness of the bicycle disc brake is about 2 mm, the hot-rolled steel strip after annealing and pickling obtained as described above is further used as a reverse rolling mill such as Sendzimir or a tandem rolling mill. After performing cold rolling, annealing at a temperature of 600 to 900 ° C. is performed as necessary, and pickling is performed as necessary to obtain a disk material. Thereafter, the disk material is hot-rolled steel sheet. The product can be made through the same process as the product.

  Various steels (No. 1 to 67) having the composition shown in Tables 1 to 4 were melted in a small vacuum melting furnace, cast into a steel ingot with a weight of 50 kgf, and then hot rolled at a finish rolling temperature of 900 ° C. Rolled to obtain a hot-rolled sheet having a thickness of 5 mm. This hot-rolled sheet is annealed at 700 ° C for 8 hours in an argon gas atmosphere, then slowly cooled, and then pickled by immersing it in a 60 ° C mixed acid (aqueous solution of 10 mass% nitric acid + 3 mass% hydrofluoric acid). After removing the surface scale, it was used as a specimen for the following investigation.

(Hardening hardness)
Cut out 30mm x 30mm x plate thickness specimens from the above specimens, heat and hold for 10 minutes each at 900 ° C and the other 1000 ° C, and then air-cooled and quenched After removing the scale by pickling, the surface hardness HRC (JIS Z2245) was measured at five points for each test piece to determine the average hardness. In addition, as steel for disks, the hardness when quenched from both the above-mentioned temperatures of 900 ° C. and 1000 ° C. needs to be in the range of 32 to 38 in HRC at any temperature. If it is out of the above range, it can be evaluated that the quenching stability is poor and a hardness failure may occur due to variations in the heat treatment temperature.

(Tempering resistance softening)
Cut out two 30mm x 30mm x plate thickness specimens from the above specimens, heat and hold them for 10 minutes at a temperature of 1000 ° C, then air-cool and quench, and then one piece at 650 ° C. Each sheet was tempered by heating and holding at a temperature of 670 ° C. for 1 hour, and then the surface scale was pickled and removed. Then, the surface hardness (HRC) was measured at five points for each test piece, and the average was obtained. The tempering softening resistance at 650 ° C. and 670 ° C. was evaluated by determining the value. In addition, if the hardness after tempering is HRC32 or more at 650 ° C. and HRC30 or more at 670 ° C., it can be evaluated that it has sufficient tempering softening resistance.

(Corrosion resistance)
In the corrosion resistance test, the above specimens were heated and held at 1000 ° C. for 10 minutes, then air-cooled and then tempered at 650 ° C. for 1 hour, and then 70 mm × 150 mm × Cut out each test piece of sheet thickness, and after wet-polishing the test surface (test piece one side) with # 800 emery polishing paper, this test piece was subjected to salt spray test for 8 hours according to JIS Z2371 The measurement was performed by measuring the number of rusting points on the test surface. The corrosion resistance was evaluated as ◯ when there was no rust point, Δ when rust points were 1 to 4, and x when rust points were 5 or more. In addition, it can be evaluated that there is a problem in corrosion resistance practically when the rusting point is 5 or more.

(Toughness)
The toughness is determined according to JIS Z2202 from each of the test materials that were heated and held at 1000 ° C for 10 minutes and then subjected to quenching treatment that was air-cooled and then tempered that was heated and held at 650 ° C for 1 hour. Three compliant sub-size Charpy impact test pieces (thickness: 10 mm, width: 5 mm (thickness of hot-rolled sheet), length: 55 mm) were sampled, and Charpy impact at 25 ° C according to JIS Z 2242 The test was performed, the Charpy impact value was measured, and the average value of the three test pieces was obtained and evaluated. If the Charpy impact value is 50 J / cm 2 or more, it can be evaluated that there is no practical problem.

  The result of the said test is written together in Tables 1-4. The steels (Nos. 1 to 49) shown in Tables 1, 2 and 3 that satisfy the criteria of the present invention have hardness after quenching at 900 ° C. and 1000 ° C. within the appropriate range of 32 to 38 in HRC. And after quenching from 1000 ° C, the hardness when tempered at 650 ° C is 32 or more in HRC, the hardness when tempering at 670 ° C is 30 or more in HRC, and Charpy impact value is also 50 J / cm2 The above is obtained. Moreover, the corrosion resistance in salt spray is also good. On the other hand, the steels (No. 50 to 67) shown in Table 4 that do not satisfy the criteria of the present invention have hardness after quenching from 900 ° C. or 1000 ° C., hardness after tempering at 650 ° C. or 670 ° C., Charpy One or more characteristics of impact value and corrosion resistance are inferior. From the above results, it can be seen that the martensitic stainless steel hot-rolled steel sheet of the present invention has excellent characteristics as a material for a disc brake.

  The steel No. 1 hot-rolled annealed plate (thickness 5 mm) shown in Table 1 of Example 1 was cold-rolled to a thickness of 1.5 mm, annealed at 750 ° C. × 1 minute, air-cooled, It was immersed in a mixed acid of 60 ° C. (nitric acid 10 mass% + hydrofluoric acid 3 mass%) and descaled to obtain a cold-rolled annealed sheet. Using this cold-rolled annealed plate, the same items as in Example 1 were tested. However, the width of the sub-size Charpy impact test piece was 1.5 mm (thickness of cold-rolled sheet).

  As a result of the test on the cold-rolled sheet, the hardness after quenching was 37 for HRC at a quenching temperature of 900 ° C. and 37 for HRC at 1000 ° C. The hardness after quenching from 1000 ° C. and tempering at 650 ° C. was 34 in HRC, and the hardness after tempering at 670 ° C. was 32 in HRC. Furthermore, a Charpy impact value of 85 J / cm 2 was obtained, no rust was generated after the corrosion resistance test by salt spray, and the corrosion resistance was also good. From these results, it was confirmed that the cold-rolled steel sheet of the martensitic stainless steel according to the present invention had excellent characteristics as a disk material for a disk brake, like the hot-rolled steel sheet.

Claims (7)

C: Less than 0.050 mass%, Si: 1.0 mass% or less, Mn: 2.0 mass% or less, P: 0.04 mass% or less, S: 0.010 mass% or less, Al: 0.2 mass% or less, Cr: more than 11.5 to 15.0 mass% , Ni: 0.5 to 2.0 mass%, Cu: more than 0.50 to 4.0 mass%, Nb: more than 0.08 to 0.6 mass%, N: less than 0.09 mass%,
However, the contents (mass%) of C, N, Nb, Cr, Si, Ni, Mn and Cu are the following formulas (1) and (2):
0.03 ≦ [C] + [N] −13 / 93 × [Nb] ≦ 0.09 ・ ・ ・ ・ ・ ・ (1)
5 × [Cr] + 10 × [Si] + 30 × [Nb] −9 × [Ni] −5 × [Mn] −3 × [Cu] −225 × [N] −270 × [C] ≦ 40 ... (2)
And martensitic stainless steel for disc brakes, the balance being Fe and inevitable impurities. In addition to the said component composition, V: 0.02-0.3mass% is contained further, The martensitic stainless steel of Claim 1 characterized by the above-mentioned. The martensitic system according to claim 1 or 2, further comprising one or two of Mo: 0.02 to 2.0 mass% and Co: 0.02 to 2.0 mass% in addition to the component composition. Stainless steel. In addition to the above component composition, Ti: 0.02 to 0.3 mass%, Zr: 0.02 to 0.3 mass%, and Ta: 0.02 to 0.3 mass% are further included. The martensitic stainless steel according to any one of 1 to 3. In addition to the said component composition, B: 0.0005-0.0050 mass%, Ca: 0.0005-0.0050 mass% 1 type or 2 types are contained, The any one of Claims 1-4 characterized by the above-mentioned. Martensitic stainless steel. The martensitic stainless steel according to any one of claims 1 to 5, wherein the steel is a hot-rolled steel sheet. The martensitic stainless steel according to any one of claims 1 to 5, wherein the steel is a cold-rolled steel sheet.