JP7709012B2 - Martensitic stainless steel plates and cutlery - Google Patents

Description

The present invention relates to a martensitic stainless steel plate. It also relates to a blade made from the martensitic stainless steel plate.

Until now, metals used for kitchen knives and other items have included ordinary steel and stainless steel, with stainless steel having excellent corrosion resistance and being easy to maintain, and being used primarily for household use. SUS420J2 is the most commonly used. However, in recent years, the demand for hardness and corrosion resistance for metals used for kitchen knives and other items has become more stringent, and the demand for high-C martensitic stainless steels is increasing. A steel type with even greater hardness is SUS440A steel, but it is very difficult to manufacture, so it is expensive and has some problems with corrosion resistance. There is a demand for a material that is both hard and corrosion-resistant.

For example, Patent Document 1 discloses a steel in which N and Cu are added to improve hardness and corrosion resistance. However, it is difficult to add a large amount of nitrogen, and in some cases additional equipment is required, resulting in increased costs.

Furthermore, Patent Document 2 discloses a steel that has excellent hardness and corrosion resistance by using low C, high N, and low Cr. Again, the high nitrogen content leads to increased costs.

In this context, 0.45C-13Cr EN1.4034 steel, as disclosed in Non-Patent Document 1, and EN1.14116 steel, which is a 0.45C-13Cr steel with added Mo and V, are becoming more and more popular because they can be manufactured using general-purpose equipment.

Patent document 3 also discloses a martensitic stainless steel for cutlery that contains a small amount of tin and 0.40 to 0.50% C.

Japanese Patent Application Publication No. 11-61351 International Publication No. 2016/146857 JP 2018-9231 A

Stainless steel European standard EN10088-2

High-C martensitic stainless steels such as the 0.45C-13Cr alloy steel disclosed in Non-Patent Document 1 have a good balance between strength and corrosion resistance, but because of the high C content, there are many issues with manufacturability when produced using general-purpose equipment, especially equipment using continuous casting. In particular, hot ductility tends to be low, which makes them prone to cracking during continuous casting, and in some cases may lead to production being discontinued. Furthermore, products are prone to defects, which reduces product yield. Therefore, they are often produced using ingot casting rather than continuous casting equipment, which leads to increased costs. Thus, the present inventors recognized that there was no high-C martensitic stainless steel with excellent manufacturability. Therefore, the present invention aims to improve the manufacturability of high-C martensitic stainless steels.

In order to solve the above problem, the inventors first investigated the occurrence of defects in steel sheets. The defects in steel sheets are so-called scuff marks, and are thought to occur during hot rolling. However, they discovered that the actual situation is that microcracks caused by insufficient hot ductility during casting are stretched out during hot rolling and appear as defects.

After extensive research into ways to improve this hot ductility, it was discovered that the cause of microcracks is liquid phase embrittlement at grain boundaries. In order to prevent this, it was found that it is effective to reduce P and S, add Ca, and also include an appropriate amount of REM. REM has a particularly large effect, and adding a larger amount of it has a significant effect. It was also found that the effect of adding REM and Ca is small if low P and S are not achieved. It was also found that it is necessary to limit O in order to suppress the formation of REM-based inclusions.

The present invention was developed based on these findings, and its gist is as follows:

(1)
In mass percent,
C: 0.40-0.60%,
Si: 0.05-0.60%,
Mn: 0.10 to 1.50%,
P: 0.020% or less,
S: 0.0050% or less,
Cr: 11.0-15.0%,
Ni: 0.01-2.00%,
Cu: 0.01 to 0.50%,
Al: 0.05% or less,
N: 0.010-0.090%,
O: 0.0050% or less,
Ca: 0.0001 to 0.0010%,
REM: 0.01~0.20%
and the balance being Fe and impurities.
(2)
The martensitic stainless steel sheet according to (1), characterized in that on the surface of the martensitic stainless steel sheet, the presence rate R of surface defects, calculated by dividing the total length of surface defects having a length of 10 mm or more by the total area of the steel sheet, is 0.100/m or less.
(3)
Further, in mass%,
Mo: 1.00% or less,
A martensitic stainless steel sheet according to (1) or (2), characterized in that it contains one or both of V: 0.30% or less.
(4)
Further, in mass%,
Sn: 0.100% or less,
The martensitic stainless steel sheet according to any one of (1) to (3), further comprising one or both of Bi: 0.20% or less.
(5)
A blade made of the martensitic stainless steel according to any one of (1) to (4).

The high-C martensitic stainless steel of the present invention can be stably cast continuously by improving hot ductility, and by suppressing the formation of minute cracks during casting, it is possible to reduce scuff marks during hot rolling. As a result, it is possible to obtain a martensitic stainless steel sheet for cutlery with excellent manufacturability.

The following describes an example of an embodiment of the present invention. Unless otherwise specified, "%" regarding the content of an element means mass%. In addition, if no lower limit is specified, it may include the case where no element is contained (0%).

<Chemical composition of steel plate>
C: 0.40-0.60%
C is an essential element for obtaining a predetermined hardness after quenching. It is preferable to contain 0.40% or more in order to stably obtain the hardness of 54HRC or more required for high-C martensitic stainless steel. On the other hand, if it is added excessively, it becomes easy to crack during casting or hot rolling, the number of defects increases, and further, sensitization during quenching is promoted, impairing the corrosion resistance, and the toughness after quenching due to undissolved carbonitrides is also reduced. Therefore, it is preferable to contain 0.60% or less. From the viewpoint of ensuring a certain strength and hardness, the lower limit of C is preferably 0.42%, 0.44%, 0.46%, 0.48%, or 0.50%.

Si: 0.05% to 0.60%
Si is necessary for deoxidation during melting and refining, and is also useful for suppressing the formation of oxide scale during quenching heat treatment. In addition, if the Si content is low, deoxidation is likely to be insufficient, and inclusions will increase, which may become the starting point for rusting, resulting in poor corrosion resistance. From these points of view, it is preferable to contain 0.05% or more. From the viewpoint of obtaining a stable deoxidation effect, the lower limit of the Si content is preferable to be 0.08%, 0.10%, 0.13%, 0.15%, 0.17%, or 0.20%. In addition, since Si narrows the austenite single phase temperature range and impairs quenching stability, it is preferable to have 0.60%, preferably 0.58%, 0.55%, 0.52%, 0.50%, 0.45%, or 0.40%.

Mn: 0.10-1.50%
Mn is an element added as a deoxidizer, and expands the austenite single phase region and contributes to improving hardenability. If Mn is not added sufficiently, the two-phase region expands and the α phase increases. As a result, Cr carbonitrides also increase, and a Cr-deficient layer is formed around them, which makes them prone to rusting and reduces corrosion resistance. From these points of view, it is recommended that Mn be contained in an amount of 0.10% or more. In order to ensure stable hardenability, the lower limit of the Mn content should be 0.20%, preferably 0.30%, 0.40%, 0.50%, or 0.60%. However, since Mn more than necessary reduces corrosion resistance, promotes the formation of oxide scale during quenching heating, and increases the subsequent grinding load, the upper limit should be 1.50%. Considering the reduction in corrosion resistance caused by granular substances such as MnS, the upper limit of the Mn content should be 1.45%, 1.40%, 1.35%, or 1.30%.

P: 0.020% or less P is an element contained as an impurity in the main raw materials such as molten iron and ferrochrome. Since P is an element that is the main cause of reducing hot ductility, its content should be reduced as much as possible. From this viewpoint, the P content is preferably 0.020% or less, and more preferably 0.015% or less, 0.013% or less, 0.010% or less, or 0.008% or less. However, since an excessive reduction leads to an extreme increase in cost, the lower limit of the P content is preferably 0.001%, 0.002%, 0.003%, 0.004%, or 0.005%.

S: 0.0010% or less S is an element that forms sulfide-based inclusions and deteriorates the general corrosion resistance (general corrosion and pitting corrosion) of steel materials. It also reduces hot ductility and increases the edge cracking sensitivity of hot-rolled steel sheets, so its content is preferably as low as possible. In addition, it has been found that when S and P coexist, they particularly reduce hot ductility and increase cracking sensitivity, so S is particularly limited, with the upper limit of its content being 0.0010%. From these points of view, it is better to have the S content as low as possible, so its upper limit is preferably 0.0009%, 0.0008%, 0.0007%, 0.0006%, 0.0005%, 0.0004%, 0.0003%, or 0.0002%. On the other hand, the lower the S content, the better the hot workability and corrosion resistance. However, reducing the S content increases the desulfurization load and increases the production costs, so the lower limit of the S content may be 0.0001%.

Cr: 11.0-15.0%
In order to ensure the corrosion resistance required for martensitic stainless steels, the Cr content should be 11.0% or more. On the other hand, in order to prevent the formation of residual austenite after quenching, the Si content should be 15.0% or less. In order to more effectively exert these effects, the lower limit of the Cr content should be 11.3%, 11.5%, or 12.0%, and the upper limit should be 14.7%, 14.5%, or 14.0%.

Ni: 0.01-2.00%
Ni is an austenite stabilizing element like Mn. It also has the effect of improving toughness after quenching and suppressing the progress of pitting corrosion. From this viewpoint, the lower limit of the Mn content is preferably 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.10%. On the other hand, a large amount of Ni added makes the austenite phase too stable and suppresses martensitic transformation, so the Ni content is limited to an upper limit of 2.00%. In hot-rolled annealed steel sheets, Ni may cause a decrease in press formability due to solid solution strengthening, and since Ni is an expensive element, the upper limit of the Ni content is preferably 1.70%, 1.40%, 1.10%, 0.80%, 0.60%, 0.50%, 0.40%, or 0.30%.

Cu: 0.01~0.50%
Cu is effective in improving the corrosion resistance of the martensite structure containing δ-ferrite, and from the viewpoint of obtaining this effect, the lower limit of the Cu content is preferably 0.01%, 0.02%, 0.03%, 0.04%, or 0.05% or more. In addition, Cu may be actively added as an austenite stabilizing element to improve hardenability. However, excessive addition leads to a decrease in hot workability and an increase in raw material costs, so the upper limit of the Cu content is preferably 0.50%, 0.45%, 0.40%, 0.35%, or 0.30%.

Al: 0.05% or less Al is added as a deoxidizing element and also improves oxidation resistance. From the viewpoint of obtaining this effect, the Al content is preferably 0.001% or more. On the other hand, the inclusion of Al makes it easier to form large oxide-based inclusions, and Cr segregates at the interface with the parent phase, deteriorating the rust resistance of the parent phase. For this reason, the upper limit of the Al content is preferably 0.05%. The lower the Al content, the more preferable it is, and the upper limit is preferably 0.04%, 0.03%, 0.02%, or 0.01%. Of course, Al does not have to be contained. Here, the Al content is the T. Al (total Al) content.

N: 0.010-0.090%
When N is dissolved, it has an excellent effect on rust resistance. This effect is clearly expressed. From the viewpoint of reliably obtaining this effect, the lower limit of the N content is preferably 0.010%, 0.015%, 0.020%, 0.025%, or 0.030%. However, when Cr-based nitrides are formed, a Cr-deficient layer may be formed, which reduces rust resistance. In addition, when added in excess, it is difficult to control at the steelmaking stage, and bubble-based defects are likely to be formed. When bubble-based defects are formed, they tend to become the starting point of rusting, which not only reduces rust resistance but also reduces product yield, so the upper limit of the N content is preferably 0.090%, 0.080%, 0.070%, 0.060%, or 0.050%.

O: 0.0050% or less In the present invention, since REM and Ca are added, it is preferable that the O content is small in order to reduce REM-based inclusions that cause nozzle clogging. If the O content exceeds 0.0050%, the number of large REM-based inclusions remaining in the steel increases, adversely affecting manufacturability and rust resistance, so the upper limit of the O content is preferably 0.0050%, 0.0040%, or 0.0030%. It is preferable to reduce it as much as possible, but excessive reduction will increase costs, so the practical lower limit of the O content may be 0.001%. Here, the O content is the TO (total oxygen) content.

Ca: 0.0001% to 0.0010%
Ca is added to adjust the composition at the steelmaking stage, but it is added because it acts as a strong deoxidizer and has the effect of promoting deoxidation. However, since it is a strong deoxidizing element, most of it floats in the molten steel as inclusions and hardly remains in the steel. In addition, it is said that Ca alone has the effect of improving hot ductility, but it has been found that adding it together with REM improves hot workability more significantly. Therefore, the lower limit of the Ca content should be 0.0001%, 0.0002%, 0.0003%, 0.0004%, 0.0005%, or 0.0006%. On the other hand, since there is a concern that Ca may reduce corrosion resistance, the upper limit of its content should be 0.0010%.

REM: 0.01~0.20%
It is an important element in the present invention. By containing an appropriate amount of REM, a significant improvement in hot ductility is observed. It has been confirmed that this effect is improved more significantly by reducing the content of P and S and further containing an appropriate amount of Ca and REM. Although the reason for this is unclear, P and S in the molten metal are distributed in the molten metal, so that they are concentrated in the molten metal during solidification, which has the effect of lowering the melting point of the molten metal, forming a so-called low melting point phase. The low melting point phase exists at the grain boundary in the final stage of solidification, lowering the hot ductility. It is believed that the presence of Ca and REM there results in the preferential formation of those sulfides, and as a result, the low melting point phase is no longer formed, and therefore the hot ductility is improved. In order to obtain this effect, the lower limit of the content of REM should be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.06%. On the other hand, excessive addition is undesirable because it tends to form large REM oxides, which can cause nozzle clogging during casting, and the upper limit of the REM content is preferably 0.20%, 0.19%, 0.18%, 0.17%, 0.16%, or 0.15%. REM is usually added in the form of a composite misch metal, but the addition of single elements such as La, Ce, Pr, and Nd also has the same effect. Here, REM (rare earth elements) refers to two elements, scandium (Sc) and yttrium (Y), and 15 elements (lanthanoids) from lanthanum (La) to lutetium (Lu), according to the general definition. These REM elements may be contained alone, or multiple REM elements may be contained. When multiple REM elements are contained, the total amount of the elements should be within the above-mentioned lower and upper limits.

In one embodiment of the present invention, in addition to the above elements, the remainder is Fe and impurities. Here, impurities refer to elements that are unavoidably and unintentionally mixed in raw materials such as ores and scraps during the industrial production of steel, and are acceptable within the scope of not adversely affecting the present invention.

By containing the above elements in the specified amounts, it is possible to obtain a high-C martensitic stainless steel that has a good balance between strength and corrosion resistance, and further has good hot ductility with no microcracks during solidification, resulting in significantly improved manufacturability. Furthermore, in addition to these elements, the stainless steel of this embodiment may contain one or more of Mo, V, Sn, and Bi in place of a portion of the Fe. These elements do not have to be contained, but by containing them, further effects can be obtained. These elements are described below.

Mo: up to 1.00%
Mo is effective in improving the corrosion resistance of the martensite structure containing δ-ferrite, and may be contained since it also has the function of increasing tempering softening resistance. However, Mo is an element that stabilizes the ferrite phase, and excessive addition of Mo narrows the austenite single phase temperature range and impairs the hardening characteristics, so the upper limit is preferably 1.00%, and more preferably 0.90% or 0.80%. The lower limit is not particularly limited, but from the viewpoint of reliably obtaining the effect, it is preferably 0.01%, 0.02%, or 0.03%.

V: 0.30%
V is an element that is mixed as an inevitable impurity in the alloy raw material of ferritic stainless steel and is difficult to remove in the refining process, but it may be contained because it forms fine carbonitrides, improves wear resistance, and is also effective in improving corrosion resistance. On the other hand, excessive content may cause coarsening of precipitates, resulting in a decrease in toughness after quenching, so the upper limit of the V content is 0.30%, preferably 0.20%. The lower limit of the V content is not particularly limited, but considering production costs and manufacturability, it is preferably 0.01%, 0.03%, 0.05%, 0.08%, or 0.10%.

Sn: 0.100% or less Sn is an effective element for improving corrosion resistance after quenching, but excessive addition promotes edge cracking during hot rolling. Therefore, the upper limit of the Sn content is 0.100%, preferably 0.090% or 0.080%. The lower limit of the Sn content is not particularly limited, but from the viewpoint of reliably obtaining the effect, it is 0.002%, preferably 0.005%, 0.010%, 0.015%, or 0.020%.

Bi: 0.20% or less Bi is an element that improves corrosion resistance. Although the mechanism is not clear, it is believed that the addition of Bi has the effect of refining MnS, which is prone to become a rust starting point, and therefore reduces the probability of becoming a rust starting point. On the other hand, even if it is contained excessively, the effect will simply saturate, so the upper limit of the Bi content should be set to 0.20%, preferably 0.15%. There is no particular limit on the lower limit of the Bi content, but from the viewpoint of reliably obtaining the effect, it is preferable to set it to 0.01%, preferably 0.02%, 0.03%, 0.04%, or 0.05%.

In addition to the elements described above, other elements may be contained within a range that does not impair the effects of the present invention.
In particular, Ti, Nb, and B have the effect of improving tempering characteristics, and one or more of Ti: 0.05% or less, Nb: 0.05% or less, and B: 0.0050% or less may be contained.

It is also preferable to reduce the amount of Zn, Pb, Se, Sb, H, Ga, Ta, Mg, Zr, etc. as much as possible. On the other hand, these elements may contain one or more of the following elements as necessary, within the limits that solve the problems of the present invention: Zn: 100 ppm or less, Pb: 100 ppm or less, Se: 100 ppm or less, Sb: 500 ppm or less, H: 100 ppm or less, Ga: 500 ppm or less, Ta: 500 ppm or less, Mg: 120 ppm or less, Zr: 120 ppm or less.

<Surface defects>
The number, length, and depth of surface defects (scratches) found on steel sheets are important, but the important factor affecting quality is their presence rate. The inventors visually measured the number and length of defects on steel sheet coils, and evaluated the presence rate R (/m) of surface defects, which is the sum (m) of the lengths of defects 10 mm or more divided by the total area (m ² ) of the coil. The lower the presence rate R, the higher the quality pass rate during blade manufacturing. However, defects less than 10 mm in length are shallow and do not affect product quality in most cases, so they were not counted as defects. Usually, it is preferable that the presence rate R of surface defects is 0.010 m/m ² (/m) or less. In addition, the fewer the number of defects, the better, and they are evaluated by the number per unit area (number density), and 0.10 pieces/m ² or less is preferable. The inspection method is not limited to visual inspection, and a method capable of detecting the number and length of defects (for example, an optical defect inspection device) can also be used.

<Manufacturing method>
An embodiment of the method for manufacturing a steel plate according to the present invention will be described.
The steel sheet of this embodiment is a hot-rolled steel sheet or a cold-rolled steel sheet manufactured by a normal manufacturing method for a martensitic stainless steel sheet. That is, the hot-rolled steel sheet is manufactured by a process of melting/casting-hot rolling-annealing and pickling of the hot-rolled steel sheet, and the cold-rolled steel sheet is manufactured by cold rolling-annealing and pickling of the cold-rolled steel sheet following the hot-rolled steel sheet.

It is possible to improve the hot workability during casting and reduce cracks during casting and cracks and defects during hot rolling. That is, the presence of Ca and REM under low P and S contents suppresses the concentration of P and S in the liquid phase, and sulfides of Ca and REM are preferentially formed to suppress the formation of a low melting point phase, thereby improving hot ductility and improving hot workability during casting. However, as a drawback of adding REM, large inclusions (REM oxides) are easily formed, so an appropriate amount of Al is contained to reduce O as much as possible and suppress the presence of large inclusions. Therefore, although not particularly specified, in the melting process, it is preferable to reduce stirring as much as possible, within 1 hour, and then to leave it still for 3 minutes or more to allow the inclusions to float up. The longer the leaving time, the easier it is for the inclusions to float up and be removed, but this is not preferable because the molten steel temperature decreases, and it is preferable that it be within 30 minutes. Furthermore, in the continuous casting process, the time for the inclusions to float up can be secured by casting as slowly as possible. The drawing speed in the continuous casting is preferably 2 m/min or less.
By controlling the operating conditions in this manner, the adverse effects of adding REM can be eliminated, the hot ductility during casting can be improved, and cracks can be reduced.

There are no particular limitations on the hot rolling and hot-rolled sheet annealing processes, and conventional manufacturing methods for martensitic stainless steel can be applied. For example, in the hot rolling process, the slab is heated to 1100-1300°C, and then rough rolling and finish rolling are performed to finish the sheet to a thickness of 2-8 mm. In the hot-rolled sheet annealing process, normal box annealing is used, and annealing is performed at 750-900°C. After that, the surface scale is removed by pickling to obtain a hot-rolled steel sheet. The obtained hot-rolled steel sheet is then cold-rolled, and subjected to final annealing and pickling to obtain a cold-rolled steel sheet.

When the resulting steel plate is to be used for blades, it is usually subjected to quenching and tempering treatment. The heating temperature for quenching is preferably 1000 to 1100°C. This results in a hardness of 56 HRC or more. The tempering condition is preferably a temperature of 150 to 250°C for 5 min to 1 h.

The present invention will be described in more detail with reference to examples, but it should be noted that the present invention is not limited to the conditions used in the following examples.
Steel having the composition shown in Table 1 is melted and cast into a 200 mm thick slab by a continuous casting machine. After heating this slab to 1150 to 1250 ° C, it is subjected to rough hot rolling and finish hot rolling to obtain a hot rolled steel sheet having a thickness of 5 mm. The hot rolled steel sheet is then annealed in a box annealing furnace. The maximum heating temperature is in the range of 800 ° C or more and 900 ° C or less. After that, it is pickled to remove scale, and then cold rolled to obtain a steel sheet having a thickness of 2 mm. Final annealing and pickling are performed to obtain a cold rolled steel sheet as a product sheet. Some of the steel sheets are left as hot rolled steel sheets without undergoing the processes after cold rolling.

<Evaluation of hot ductility>
Greeble test pieces (10φ×120mm) were taken from the slabs and subjected to a molten Greeble test to evaluate hot ductility. In the molten Greeble test, the center of the test piece is heated to just above the melting point to make it semi-molten, and then the temperature is lowered to the tensile temperature and a tensile test is performed. From the results, as an index of hot ductility, in the region of 850 to 1150°C, which corresponds to the surface temperature region of continuous casting, reduction of area of 70% or more was rated as A, 60% to less than 70% was rated as B, 50% to less than 60% was rated as C, and less than 50% was rated as D. A, B, and C are pass marks.

<Evaluation of surface defects>
The surface defects of the hot-rolled steel sheets were also investigated. The entire length and width of the coils were visually inspected. For those with a length of 10 mm or more, the presence rate R (/m) and the number density (pieces/m2) were obtained as described above. The presence rate R of surface defects of 0.010/m or less was rated as pass (○), and those exceeding this were rated as fail (×). Furthermore, those with an presence rate R of 0.0050/m or less were rated as excellent (◎). Furthermore, the number density of 0.10 pieces/m2 or less was rated as excellent (○), and those exceeding this were rated as poor (×).

<Characteristics of steel sheets after heat treatment>
In order to investigate the properties after heat treatment, both the hot-rolled steel sheets and the cold-rolled steel sheets were quenched at 1000 to 1100°C, and then tempered at 150 to 250°C, and the hardness and corrosion resistance were evaluated as shown below. The results are shown in Table 2.

[Hardness evaluation]
After the surface was polished to a #80 finish, the hardness was measured on the Rockwell C scale in accordance with JIS Z 2245. A hardness of 54 HRC or more was rated as pass (◯), and anything less than that was rated as fail (×). Of the pass marks, a hardness of 58 HRC or more was rated as excellent (◎).

[Evaluation of corrosion resistance]
The corrosion resistance was evaluated by polishing the specimens with #600 polishing, conducting a salt spray test for 24 or 96 hours in accordance with JIS Z 2371, and then measuring the rust area ratio. A rust area ratio of less than 10% was rated as pass (◯), and anything above that was rated as fail (×). Furthermore, among the specimens that passed the test, those that did not rust were rated as excellent (◎).

This martensitic stainless steel can be used in industry in general, and in particular for cutlery.

Claims (5)

In mass percent,
C: 0.40-0.60%,
Si: 0.05-0.60%,
Mn: 0.10 to 1.50%,
P: 0.020% or less,
S: 0.0050% or less,
Cr: 11.0-15.0%,
Ni: 0.01 to 1.70 %,
Cu: 0.01 to 0.50%,
Al: 0.05% or less,
N: 0.010-0.090%,
O: 0.0050% or less,
Ca: 0.0001 to 0.0010%,
REM: 0.01~0.20%
and the balance being Fe and impurities. The martensitic stainless steel sheet according to claim 1, characterized in that the surface defect occurrence rate R, calculated by dividing the total length of surface defects having a length of 10 mm or more by the total area of the steel sheet, is 0.100/m or less on the surface of the martensitic stainless steel sheet. Further, in mass%,
Mo: 1.00% or less,
3. The martensitic stainless steel sheet according to claim 1, further comprising one or both of V: 0.30% or less. Further, in mass%,
Sn: 0.100% or less,
The martensitic stainless steel sheet according to any one of claims 1 to 3, further comprising one or both of Bi: 0.20% or less. A blade made of the martensitic stainless steel plate according to any one of claims 1 to 4.