JP2007277639A - Martensitic steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a martensitic steel exhibiting high hardness/high corrosion resistance, hardly causing cracks after quenching/subzero treatment and having excellentmirror finishability. <P>SOLUTION: The martensitic steel has a composition cpntaining, by mass, 0.15 to <0.70% C, 0.05 to 1.00% Si, 0.05 to 1.00% Mn, ≤0.030% P, ≤0.030% S, 0.001 to 0.50% Cu, 0.05 to 0.50% Ni, 11.0 to 18.0% Cr, 0.05 to 2.0% Mo, 0.01 to 0.50% W, 0.01 to 0.50% V, 0.05 to 0.40% N, ≤0.02% O, ≤0.080% Al and 0.0005 to 0.0050% B, and the balance substantially Fe with inevitable impurities, and satisfying 0.4%<C+N<0.7%, and C/N≥0.75. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to martensitic steel, and more particularly to martensitic steel that exhibits high hardness and high corrosion resistance and is suitable as a plastic molding die, cold die, bearing, and the like.

Plastic injection molding is a molding method in which a molten resin is pressed into a mold cavity and solidified in the mold. In addition to the main component resin, a hard material (for example, glass fiber) for improving the strength of the plastic product may be added to the plastic product. Further, the resin may be decomposed during the kneading process to generate corrosive gas. This corrosive gas is compressed when the resin is filled into the mold and becomes a high temperature and a high pressure, corroding the mold and causing the surface of the product to become rough and the generation of burrs. Furthermore, plastic products are used for cases and the like, and good molded skin is required.
Therefore, the material used for the plastic mold is
(1) Excellent hardness and wear resistance,
(2) High corrosion resistance,
(3) High specularity,
Etc. are required.

  Conventionally, SUS440C (17% Cr steel), SUS420J2 (13% Cr steel), or an improved material thereof, which is a kind of martensitic stainless steel, is used for this type of application. However, although SUS440C has the highest hardness among stainless steels, sufficient corrosion resistance cannot be obtained because the amount of solid solution Cr in the parent phase is small. On the other hand, since SUS420J2 has a relatively small amount of carbon, sufficient hardness cannot be obtained.

In order to solve this problem, various proposals have heretofore been made.
For example, in Patent Document 1, C: 0.25 to 1.0, Si: maximum 1.0, Mn: maximum 1.6, N: 0.10 to 0.35, Al: maximum 1. 0, Co: maximum 2.8, Cr: 14.0 to 25.0, Mo: 0.5 to 3.0, Ni: maximum 3.9, V: 0.04 to 0.4, W: maximum 3 0.0, Nb: 0.18 at the maximum, Ti: 0.2 at the maximum, the sum of the concentrations of C and N is 0.5 to 1.2 by weight%, the balance is made of iron and inevitable impurities, Alloys for plastic molds that have a hardness of at least 45 HRC and high corrosion resistance and are heat treated are disclosed. This document describes that the fatigue strength is remarkably increased when the sum of the concentrations of C and N is within the above range.

  Patent Document 2 discloses that C: 0.16 to 0.27, N: 0.06 to 0.13 (provided that the total amount of C + N is 0.3 ≦ C + N ≦ 0.4), Si, : 0.1-1.5, Mn: 0.1-1.2, Cr: 12.5-14.5, Ni: 0.5-1.7, Mo: 0.2-0.8, and V: 0.1 to 0.5, and in order to enhance the machinability, S (maximum 0.15%), Ca (maximum 0.01%), and O (maximum 0.01%) 1 Steel alloys are disclosed that contain one or more elements, the balance being Fe and inevitable impurities. This document describes that the hardenability and toughness are improved by using such a composition.

  Furthermore, in Patent Document 3, by weight, C: 0.35 to 0.65%, Si: 1.0% or less, Mn: 1.0% or less, Cr: 12.0 to 18.0%, Mo: 0.2 to 1.0%, V: 0.05 to 0.50% and Nb: 0.05 to 0.50% of one or two types, the balance being substantially Fe A tool steel having an alloy composition is disclosed. This document describes that by using such a composition, a hardness higher than the quenching and tempering hardness of SUS440C and a corrosion resistance exceeding SUS420J2 can be obtained.

Japanese Patent No. 3438121 JP-T-2004-503676 JP 2001-294987 A

In general, the higher the amount of carbon in the steel, the lower the martensitic transformation end temperature (Mf), and in high carbon steel, Mf is below room temperature. When such steel is quenched, it does not become martensite on the entire surface, and retained austenite is generated, and the required hardness cannot be obtained. In addition, when the retained austenite is left at room temperature, the structure gradually changes and the dimensions are distorted. Therefore, in such a case, after quenching, a process (sub-zero process) for quickly cooling to a temperature of 0 ° C. or less is performed.
Since the material used for the plastic mold is generally required to have high hardness, the amount of carbon is relatively large. Therefore, in order to obtain high dimensional accuracy and required hardness, it is preferable to perform sub-zero treatment after quenching.
However, since the martensitic transformation is accompanied by volume expansion, cracking (quenching, setting crack) may occur in the material when quenching and subzero treatment are performed. When a crack occurs in a plastic molding die, the crack is transferred to the surface of the product, or the strength of the die is reduced, causing problems such as chipping. Moreover, if coarse carbides, nitrides, and the like are contained in the steel, it will cause a decrease in specularity.
Furthermore, there has never been proposed an example of a material that exhibits high hardness and high corrosion resistance, is resistant to cracking during quenching and sub-zero treatment, and has excellent specularity.

The problem to be solved by the present invention is to provide martensitic steel exhibiting high hardness and high corrosion resistance.
Another problem to be solved by the present invention is to provide a martensitic steel that is unlikely to crack after quenching and sub-zero treatment.
Furthermore, another problem to be solved by the present invention is to provide martensitic steel excellent in specularity.

In order to solve the above problems, the martensitic steel according to the present invention is
0.15 mass% ≦ C <0.70 mass%,
0.05 mass% ≦ Si ≦ 1.00 mass%,
0.05 mass% ≦ Mn ≦ 1.00 mass%,
P ≦ 0.030 mass%,
S ≦ 0.030 mass%,
0.001 mass% ≦ Cu ≦ 0.50 mass%,
0.05 mass% ≦ Ni ≦ 0.50 mass%,
11.0 mass% ≦ Cr ≦ 18.0 mass%,
0.05 mass% ≦ Mo ≦ 2.0 mass%,
0.01 mass% ≦ W ≦ 0.50 mass%,
0.01 mass% ≦ V ≦ 0.50 mass%,
0.05 mass% ≦ N ≦ 0.40 mass%,
O ≦ 0.02 mass%,
Al ≦ 0.080 mass%, and
0.0005 mass% ≦ B ≦ 0.0050 mass%
And the balance substantially consists of Fe and inevitable impurities,
0.4 mass% <C + N <0.7 mass% and C / N ≧ 0.75
It is a summary.

  Adding N in addition to C as an interstitial atom and optimizing the amount of C + N and the C / N ratio can increase the solid solubility limit of C at the quenching temperature (that is, widen the austenite region). it can. Therefore, high hardness is obtained after martensitic transformation. Moreover, in addition to adding various elements that improve the corrosion resistance, when an appropriate amount of N is dissolved in the matrix, the corrosion resistance is further improved. Furthermore, the grain boundary is strengthened by adding B to the steel, and cracks during quenching and sub-zero treatment can be reduced.

Hereinafter, an embodiment of the present invention will be described in detail.
The martensitic steel according to the present invention contains the following elements, with the balance being substantially composed of Fe and inevitable impurities. The kind of additive element, its component range, and the reason for limitation are as follows.

(1) 0.15 mass% ≦ C <0.70 mass%.
C is an element necessary for ensuring strength and wear resistance, and is an element that forms a carbide by combining with a carbide forming element such as Cr, Mo, W, V, and Nb. Moreover, it is an element which ensures hardness by forming a solid solution in the matrix at the time of quenching and forming a martensite structure in the matrix. In order to obtain such an effect, the amount of C is preferably 0.15 mass% or more.
On the other hand, when the amount of C becomes excessive, C combines with the carbide-forming element to form carbide, and the solid solution amount of Cr, Mo, etc. in the matrix phase decreases. A decrease in the amount of solid solution of Cr, Mo, etc. in the matrix phase causes a decrease in corrosion resistance. Therefore, the amount of C is preferably less than 0.70 mass%.

(2) 0.05 mass% ≦ Si ≦ 1.00 mass%.
Si is mainly added for deoxidizer or nitrogen addition. For that purpose, the Si amount is preferably 0.05 mass% or more.
On the other hand, when the amount of Si is excessive, hot workability is lowered or toughness is lowered. Therefore, the amount of Si is preferably 1.00 mass% or less.

(3) 0.05 mass% ≦ Mn ≦ 1.00 mass%.
Mn is added as a hardenability improving element. Moreover, S contained unavoidable is also fixed and there exists an effect which prevents the fall of toughness. In order to obtain such an effect, the amount of Mn is preferably 0.05 mass% or more.
On the other hand, when the amount of Mn becomes excessive, hot workability is lowered. Therefore, the amount of Mn is preferably 1.00 mass% or less.

(4) P ≦ 0.030 mass%.
(5) S ≦ 0.030 mass%.
P and S are inevitably contained in the steel. P segregates to the grain boundaries, and S forms sulfides, causing toughness to decrease. Therefore, the amount of P is preferably 0.030 mass% or less. The amount of S is preferably 0.030 mass% or less.

(6) 0.001 mass% ≦ Cu ≦ 0.50 mass%.
Cu is an element that improves the corrosion resistance. In particular, the effect of suppressing erosion by hydrochloric acid is great. In order to obtain such an effect, the amount of Cu is preferably 0.001 mass% or more.
On the other hand, when the amount of Cu becomes excessive, the amount of retained austenite increases and causes aging of the dimensions. In addition, hot workability is reduced. Therefore, the amount of Cu is preferably 0.50 mass% or less.

(7) 0.05 mass% ≦ Ni ≦ 0.50 mass%.
Ni is an element that increases the amount of nitrogen dissolved. In order to obtain such an effect, the Ni amount is preferably 0.05 mass% or more.
On the other hand, when the amount of Ni becomes excessive, the amount of retained austenite increases and causes aging of the dimensions. Therefore, the amount of Ni is preferably 0.50 mass% or less.

(8) 11.0 mass% ≦ Cr ≦ 18.0 mass%.
Cr is an element that improves the corrosion resistance. Cr also increases the amount of nitrogen dissolved. In order to obtain such an effect, the Cr content is preferably 11.0 mass% or more.
On the other hand, when the amount of Cr becomes excessive, the amount of retained austenite increases and the hardness decreases even if the sub-zero treatment is performed. Therefore, the Cr amount is preferably 18.0 mass% or less.

(9) 0.05 mass% ≦ Mo ≦ 2.0 mass%.
Mo is an element that improves the corrosion resistance. In order to obtain such an effect, the Mo amount is preferably 0.05 mass% or more.
On the other hand, when the amount of Mo becomes excessive, coarse carbonitrides are formed and the specularity is lowered. Therefore, the Mo amount is preferably 2.0 mass% or less.

(10) 0.01 mass% ≦ W ≦ 0.50 mass%.
W is an element that improves hardenability. In order to obtain such an effect, the W amount is preferably 0.01 mass% or more.
On the other hand, when the amount of W becomes excessive, coarse carbonitrides are formed, resulting in a decrease in specularity. Therefore, the amount of W is preferably 0.50 mass% or less.

(11) 0.01 mass% ≦ V ≦ 0.50 mass%.
V is an element that increases the amount of nitrogen dissolved. In order to obtain such an effect, the V amount is preferably 0.01 mass% or more.
On the other hand, when the amount of V becomes excessive, coarse carbonitrides are formed, resulting in a decrease in specularity. Therefore, the V amount is preferably 0.50 mass% or less.

(12) 0.05 mass% ≦ N ≦ 0.40 mass%.
N is an interstitial element and contributes to an increase in the hardness of the martensite structure. Further, when N is dissolved in the matrix, the corrosion resistance is improved. In order to obtain such an effect, the N amount is preferably 0.05 mass% or more. In addition, it is possible to add N more than atmospheric dissolution by dissolving under pressure according to Sievert's law.
On the other hand, when the amount of N becomes excessive, the concentration of nitrogen during solidification exceeds the limit of nitrogen gas ejection suppression by pressurization, and nitrogen gas is generated. Therefore, the amount of N is preferably 0.40 mass% or less.

(13) O ≦ 0.02 mass%.
O is an element inevitably contained in the molten steel. When the amount of O is excessive, coarse oxides are formed with Al and Si to become inclusions, and toughness and specularity are lowered. Therefore, the amount of O is preferably 0.02 mass% or less.
(14) Al ≦ 0.080 mass%.
Al is an element added as a deoxidizer. When the amount of Al becomes excessive, coarse nitrides are formed and the specularity is lowered. Therefore, the Al content is preferably 0.080 mass% or less.

(15) 0.0005 mass% ≦ B ≦ 0.0050 mass%.
B is an element that strengthens the grain boundaries and reduces cracks during quenching and sub-zero treatment. In order to obtain such an effect, the amount of B is preferably 0.0005 mass% or more.
On the other hand, when the amount of B becomes excessive, nitride is formed and corrosion resistance is lowered. Therefore, the amount of B is preferably 0.0050 mass% or less.

The martensitic steel according to the present invention is characterized by having the following relationship between the C content and the N content in addition to the additive element being in the above-described range.
(A) 0.4 mass% <C + N <0.7 mass%.
(B) C / N ≧ 0.75.
N is an element that improves both corrosion resistance and hardness. However, sufficient hardness cannot be obtained with N alone. On the other hand, when N is further added to steel containing C, the solid solubility limit of C at the quenching temperature is increased, and high hardness is obtained after martensitic transformation. In order to obtain such an effect, the C + N amount is preferably larger than 0.4 mass%.
On the other hand, when the amount of C + N becomes excessive, coarse carbonitrides are formed and the specularity is lowered. Therefore, the amount of C + N is preferably less than 0.7 mass%.
On the other hand, if C is relatively small with respect to N, the hardness during quenching cannot be ensured. Therefore, C / N is preferably 0.75 or more.

The martensitic steel according to the present invention may contain the following first additive element in addition to the various elements described above.
(16) 0.001 mass% ≦ Co ≦ 0.50 mass%.
Co can be added to improve hardenability. In order to obtain such an effect, the amount of Co is preferably 0.001 mass% or more.
On the other hand, even if Co is added excessively, the effect is saturated and there is no actual benefit. Therefore, the amount of Co is preferably 0.50 mass% or less.

The martensitic steel according to the present invention may further include any one or more of the following second additive elements in addition to or instead of the first additive element described above.
(17) 0.001 mass% ≦ Se ≦ 0.3 mass%.
(18) 0.001 mass% ≦ Te ≦ 0.3 mass%.
(19) 0.0002 mass% ≦ Ca ≦ 0.10 mass%.
(20) 0.001 mass% ≦ Pb ≦ 0.20 mass%.
Se, Te, Ca, Pb and Bi can all be added to improve machinability. In order to obtain such an effect, the amount of each element added is preferably equal to or greater than the lower limit value described above.
On the other hand, when these elements are added excessively, the toughness is reduced. Therefore, the addition amount of each element is preferably equal to or less than the upper limit value described above.

The martensitic steel according to the present invention may further include any one or more of the following third additive elements in addition to, or instead of, the first additive element and / or the second additive element described above. good.
(21) 0.001 mass% ≦ Nb ≦ 0.30 mass%.
(22) 0.001 mass% ≦ Ta ≦ 0.30 mass%.
(23) Ti ≦ 0.20 mass%.
(24) 0.001 mass% ≦ Zr ≦ 0.30 mass%.
Ti, Nb, Ta, and Zr all combine with C and N to form carbonitrides, and are effective in suppressing coarsening of crystal grains. In order to obtain such an effect, the addition amount of these elements is preferably equal to or greater than the lower limit value described above.
On the other hand, if these elements are added excessively, the machinability is deteriorated. Therefore, the addition amount of these elements is preferably equal to or less than the upper limit value described above.

The martensitic steel according to the present invention is usually used after melting and casting, followed by quenching, sub-zero treatment, and tempering (or aging treatment).
The quenching treatment is generally performed by heating a steel material to a quenching temperature or a solution temperature (1020 to 1150 ° C.) and then rapidly cooling it at a predetermined cooling rate using a method such as oil quenching or gas cooling.
In addition, the subzero treatment is performed after quenching, and a cryogen of 0 ° C. or less (for example, dry ice, dry ice + alcohol (−80 ° C.), carbon dioxide (−130 ° C.), liquid nitrogen (−196 ° C.), etc.) It is performed by re-quenching again using
Furthermore, a tempering process (or aging process) is performed by heating the steel material by which the subzero process was performed to 200 to 450 degreeC as needed.
By performing such a treatment, the hardness after quenching / sub-zero treatment-tempering (HRC) is 55 or more, 58 or more, or 59 or more (that is, has a hardness equal to or more than SUS440C), And the martensitic steel which has corrosion resistance exceeding SUS420J2 is obtained. In addition, martensitic steel with high specularity can be obtained without cracking during quenching and sub-zero treatment.

Next, the operation of the martensitic steel according to the present invention will be described.
Adding N in addition to C as an interstitial atom and optimizing the amount of C + N and the C / N ratio can increase the solid solubility limit of C at the quenching temperature (that is, widen the austenite region). it can. Therefore, high hardness is obtained after martensitic transformation. Moreover, in addition to adding various elements that improve the corrosion resistance, when an appropriate amount of N is dissolved in the matrix, the corrosion resistance is further improved. Furthermore, the grain boundary is strengthened by adding B to the steel, and cracks during quenching and sub-zero treatment can be reduced.

(Examples 1-16 and Comparative Examples 1-5, AI)
[1. Preparation of sample]
Steel having the chemical composition shown in Table 1 was melted in a pressure melting furnace, cast to 50 kg, and a 60 mm square bar was manufactured by hot forging. Thereafter, annealing was performed. Test pieces for use in various tests were cut out from the obtained bar material, and were subjected to quenching, sub-zero treatment (excluding some samples), and tempering under the conditions shown in Table 2.
In addition, quenching was performed by oil cooling or gas spray cooling after holding at each temperature.
Further, the sub-zero treatment was performed by immersing in liquid nitrogen or dry ice + alcohol.
Furthermore, tempering was performed by repeating air cooling twice after holding at each temperature for 1 hour.

[2. Test method (1)]
[2.1. Hardness]
A cubic block having a side of 10 mm was cut out from the bar and heat-treated under the conditions shown in Table 2. Next, the measurement surface and the ground contact surface were polished to # 400, and the hardness was measured by Rockwell C scale.
[2.2. Abrasion resistance]
Two pins with a diameter of 8 mm were cut out from the bar and heat-treated under the conditions shown in Table 2. Wear resistance was evaluated by a pin-on-disk friction and wear tester using the pins after heat treatment. S45C was used for the disk. The test conditions were: sliding speed: 1.6 m / s, sliding distance: 5000 m, pressing load: 10.5 kgf, no lubricant.
The weight of the pin was measured before and after the test, and the wear weight was measured. Further, the wear amount of each sample was expressed as a relative value with the wear amount of Comparative Steel 3 (equivalent to SUS440C) being 100.
[2.3. Specularity]
A 50 × 45 × 12 plate was cut out from the bar and heat treated under the conditions shown in Table 2. Next, the mirror surface of the test piece was polished to # 14000 by mechanical polishing. According to JIS B 0633, the surface roughness of the test piece was measured to evaluate the specularity.
[2.4. Salt spray]
A round bar of φ15 × 60 was cut out from the bar and heat-treated under the conditions shown in Table 2. Next, the surface was made equivalent to # 400 by finishing, and a salt spray test was performed according to JIS Z 2371. Rusting was evaluated by A (no rusting), B (slightly occurring), C (considerably occurring), and D (entire corrosion).
[2.5. Pitting potential]
A 12 × 12 × 3 mm plate was cut out from the bar and heat treated under the conditions shown in Table 2. Subsequently, the pitting corrosion potential Vc100 was measured according to JIS G 0577 “Measurement of pitting corrosion potential of stainless steel” using the obtained test piece.
[2.6. Sinterability]
Ten cubic blocks each having a side of 15 mm were cut out from the bar and heat-treated under the conditions shown in Table 2. Then, it polished to the mirror surface and the presence or absence of the crack was confirmed by the color check.

[3. Result (1)]
Table 3 shows the test results. In Comparative Example 1, since C + N is less than 0.4%, the hardness is low. In Comparative Example 2, since C + N exceeded 0.7 and B was not added, the hardness and corrosion resistance were sufficient, but there were fire cracks. Comparative Example 3 (equivalent to SUS440C) does not contain N, and the amount of C is excessive, so that the corrosion resistance is low. Since Comparative Example 4 (equivalent to SUS420J2) has C + N of less than 0.4 and does not contain N, hardness and corrosion resistance are low. Furthermore, since Comparative Example 5 (equivalent to SUS630 (precipitation hardening type stainless steel)) is a precipitation hardening type by precipitation of Cu, the hardness is low.
On the other hand, all of Examples 1 to 16 showed the hardness equal to or higher than SUS440C and the corrosion resistance exceeding SUS420J2 because the C amount and the N amount were optimized and contained an appropriate amount of B. . In addition, the wear resistance and specularity were equal to or higher than those of conventional steel, and no burning cracks were observed.

[4. Test method (2)]
In Examples 2, 4, and 10, in order to clarify the effect of B addition, the other components are almost the same, and B <0.0001 mass%, 0.0001 mass% ≦ B <0.0005 mass. %, 0.0005 mass% ≦ B ≦ 0.0050, 0.0050 mass% <B, and the crack resistance and pitting potential were measured.
The method for measuring the cracking resistance and pitting potential has been described above [2. ]. The heat treatment conditions of Comparative Examples A to C, Comparative Examples D to F, and Comparative Examples G to I were the same as those of Examples 2, 4, and 10, respectively.

[5. Result (2)]
Table 4 shows component compositions of Examples 2, 4, 10 and Comparative Examples A to I. Table 5 shows the test results. In Table 5, “not measurable” means that pitting corrosion did not occur and the entire surface was corroded. From Table 5, it can be seen that as the amount of B increases, the anti-cracking resistance improves, but when the amount of B becomes excessive, the corrosion resistance decreases.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

The martensitic steel according to the present invention is
(1) Molds for plastic molding (Sunday miscellaneous goods, home appliance exterior / interior, OA equipment exterior / interior / part, mobile phone exterior, interior / exterior parts such as automobiles and motorcycles, and structural members thereof), light Reflector molds, optical lens molds, food container molds, medical device molds, chemical container molds, precision molded product molds (receiving plates, plastic bottle molds, rubber molds) ), Resin molds, light guide plate molds, film molds,
(2) Tools, jigs in plastic molding machines, dies, chemical fiber molding nozzles,
(3) Cold molds and structural members that are processed by cold forging and progressive die press (cold molds include bending dies, punching dies, cutting blades, rolling dies, punch members, drawing dies, forgings. Corresponding to molds, gear punch members / dies, swaging dies, etc. Structural members include plastic working tools, screw members, cam parts, shafts, bearings, gears, pins, bolts, screws, rolls, turbine blades, seal plates , Gauge, etc.)
Can be used for etc.

Claims (4)

0.15 mass% ≦ C <0.70 mass%,
0.05 mass% ≦ Si ≦ 1.00 mass%,
0.05 mass% ≦ Mn ≦ 1.00 mass%,
P ≦ 0.030 mass%,
S ≦ 0.030 mass%,
0.001 mass% ≦ Cu ≦ 0.50 mass%,
0.05 mass% ≦ Ni ≦ 0.50 mass%,
11.0 mass% ≦ Cr ≦ 18.0 mass%,
0.05 mass% ≦ Mo ≦ 2.0 mass%,
0.01 mass% ≦ W ≦ 0.50 mass%,
0.01 mass% ≦ V ≦ 0.50 mass%,
0.05 mass% ≦ N ≦ 0.40 mass%,
O ≦ 0.02 mass%,
Al ≦ 0.080 mass%, and
0.0005 mass% ≦ B ≦ 0.0050 mass%
And the balance substantially consists of Fe and inevitable impurities,
0.4 mass% <C + N <0.7 mass% and C / N ≧ 0.75
Is martensitic steel. 0.001 mass% ≦ Co ≦ 0.50 mass%
The martensitic steel according to claim 1, further comprising: 0.001 mass% ≦ Se ≦ 0.3 mass%,
0.001 mass% ≦ Te ≦ 0.3 mass%,
0.0002 mass% ≦ Ca ≦ 0.10 mass%, and
0.001 mass% ≦ Pb ≦ 0.20 mass%
The martensitic steel according to claim 1 or 2, further comprising at least one selected from the group consisting of: 0.001 mass% ≦ Nb ≦ 0.30 mass%,
0.001 mass% ≦ Ta ≦ 0.30 mass%,
Ti ≦ 0.20 mass%, and
0.001 mass% ≦ Zr ≦ 0.30 mass%
The martensitic steel according to any one of claims 1 to 3, further comprising any one or more selected from the group consisting of: