JP2000282185A - Martensitic stainless steel parts excellent in machinability and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce steel parts having corrosion resistance of a certain degree, good in cold workability and warm forgeability, moreover having excellent machinability and whose surface hardness is controlled to >=630 HV by induction hardening and to provide a method for producing the same. SOLUTION: This steel parts are ones having a compsn. contg., by mass, 0.3 to 0.6% C, <=1.0% Si, <=1.0% Mn, <=0.04% P, 0.005 to 0.2% S, 4.0 to 11.0% Cr, 0.001 to 0.1% Al, 0.0005 to 0.02% Ca, 0.0005 to 0.01% O, and the balance substantial Fe, also contg. sulfides of >=5 μm diameter equivalent to a circle contg. 0.1 to 10% Ca by >=5 pieces per 3.3 mm2, and in which the face to be used is subjected to induction hardening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a martensitic system excellent in machinability, which is used by subjecting a surface to be used to induction hardening such as a cylinder and a piston used under high pressure in a fuel pump system for automobiles and the like. The present invention relates to a stainless steel part and a method for manufacturing the same.

[0002]

2. Description of the Related Art Cylinders and pistons of precision machines are required to have a certain level of corrosion resistance and wear resistance. Therefore, SUS440C (C: 0.95 to 1.20%, martensitic stainless steel) is usually used. S
i: 1.00% or less, Mn: 1.00% or less, P: 0.
040% or less, S: 0.030% or less, Cr: 16.0
However, the martensitic stainless steel SUS440C is not good in cold and warm workability. Molding is taking place. Further, since this material has very good hardenability, the entire part is hardened and hardened in the quenching and tempering treatment, and it is difficult to machine after quenching and tempering. Further, distortion due to quenching and tempering is large, and it is difficult to correct the distortion.

[0003] Further, since the martensitic stainless steel has very poor machinability, it is difficult to form a fine hole or the like when manufacturing a precision part. In such a case, corrosion resistance is required. In addition, SUS440C is used only for a portion requiring hardness by quenching, and structural steel (for example, S45C) is used for other structural parts.
It was sometimes used in combination. However, in order to form a composite, steps such as welding and shrink fitting are required after machining.

Therefore, SUS420J2 of martensitic stainless steel (C: 0.26 to 0.40%, Si:
1.00% or less, Mn: 1.00% or less, P: 0.04
0 or less, S: 0.030% or less, Cr: 12.00 to 1
If 4.00% is contained and the balance is substantially Fe), cold workability is good and cold forging and warm forging are possible, but when induction hardening is performed, the quenching hardness is low. HV63
0 (HRC57) or more.

The inventor of the present invention has proposed that a material capable of being cold worked, having a hardness of HRC 57 or more by induction hardening and having good corrosion resistance is provided.
A technique disclosed in Japanese Patent No. 317973 was proposed. According to this, cold workability is good, cold forging and warm forging are possible, and when induction hardening is performed, hardness of HV630 or more can be obtained. However, as in the case of the above-described cylinder, it has been found that for applications in which the requirements for inner surface dimensional accuracy and surface roughness are strict, a large amount of time is required for cutting even after spheroidizing annealing. Became a big problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention has a certain degree of corrosion resistance, good cold workability, and can have a hardness of HV630 (HRC57) or higher when subjected to induction hardening. Can be hardened only to the depth,
The use of steel with excellent machinability, which does not require a long time for cutting even for parts with strict dimensional accuracy, and steel parts with high hardness by induction hardening etc. only on the used surface and its production The aim is to provide a method.

[0007]

SUMMARY OF THE INVENTION According to the present invention, cold workability is close to that of structural steel, and quenching hardness can be increased to HV630 (HRC57) or more when induction hardening is performed. This is based on the following findings obtained as a result of research on hardened steel that can be quenched only to a suitable depth and is suitable for use in pistons and cylinders.

That is, since the corrosion resistance of pistons and cylinders is not required to be as high as that of SUS440C steel or SUS420J2 steel, the Cr content is set to 4.
When the content is in the range of 0 to 11.0%, both cold workability and corrosion resistance can be achieved. In order to suppress the formation of coarse carbides that impair cold workability and to obtain the desired quench hardness, C
What is necessary is just to make a content rate 0.3-0.6%. In the present system steel, when an appropriate amount of N and Mo is contained in the steel, the corrosion resistance can be improved.

In order to stably improve the machinability of steel without impairing cold and warm forgeability, an appropriate amount of Ca,
It is necessary to contain Al, O, and S, and to control their morphology, particularly the morphology and distribution of sulfide. Further, in order to avoid the occurrence of large distortion due to the entire quenching and to cure only the surface layer of the working surface requiring abrasion resistance, surface hardening by induction hardening is effective.

Therefore, the martensitic stainless steel parts of the present invention having excellent machinability are: (1) by mass% (the same applies hereinafter), C: 0.3 to 0.6%,
Si: 1.0% or less, Mn: 1.0% or less, P: 0.0
4% or less, S: 0.005 to 0.2%, Cr: 4.0 to 4.0
11.0%, Al: 0.001 to 0.1%, Ca: 0.
0005-0.02%, O: 0.0005-0.01%
And the balance substantially consists of Fe, and 0.1%
It is assumed that five or more sulfides having a circle equivalent diameter of 5 μm or more containing 10 to 10% of Ca are contained per 3.3 mm ² , and the surface to be used is induction hardened. (2) Mo: 1.
0% or less and N: 0.02 to 0.2%. (3) C: 0.3 to 0.6%, Si: 1.0% or less, M
n: 1.0% or less, P: 0.04% or less, S: 0.00
5 to 0.2%, Cr: 4.0 to 11.0%, Al: 0.
001-0.1%, Ca: 0.0005-0.02%,
O: 0.0005 to 0.01%, and P
b: 0.4% or less, Bi: 0.4% or less, Se: 0.5
% Or less and Te: 0.1% or less, containing at least one of them, and the balance substantially consisting of Fe;
And a circle equivalent diameter of 5 μm containing 0.1 to 10% of Ca
It is characterized by containing 5 or more of the above sulfides per 3.3 mm ^{2 and} subjecting the surface to be used to induction hardening. (4) C: 0.3 to 0.6%, Si: 1.0% or less, M
n: 1.0% or less, P: 0.04% or less, S: 0.00
5 to 0.2%, Cr: 4.0 to 11.0%, Al: 0.
001-0.1%, Ca: 0.0005-0.02%,
O: 0.0005 to 0.01%.
o: 1.0% or less and N: 0.02 to 0.2%.
4% or less, Bi: 0.4% or less, Se: 0.5% or less, and Te: 0.1% or less. And,
It is characterized by containing at least 5 sulfides having an equivalent circle diameter of 5 μm or more containing 0.1 to 10% of Ca per 3.3 mm ² and induction hardening the used surface. (5) The martensitic stainless steel part according to any one of the above (1) to (4) is a cylinder or a piston.

Further, the method for producing a martensitic stainless steel part excellent in machinability according to the present invention is as follows: (6) The method for producing a martensitic stainless steel part according to any one of the above (1) to (5). After induction hardening on the surface to be used, one or two of high-speed shot injection treatment and nitriding treatment of fine particles are performed thereon. (7) After cold forging or warm forging the martensitic stainless steel according to any one of the above (1) to (5), induction hardening is performed on a working surface, and the surface is subjected to the induction hardening. It is characterized in that any one or two of the high-speed shot injection treatment and the nitridation treatment of the fine particles are performed.

[0012]

The components of the martensitic stainless steel used in the present invention and the reasons for limiting the content will be described. C: 0.3 to 0.6% C is an element contained to increase the hardness of the steel and improve the wear resistance. If the content is less than 0.3%, the effect is small. %, Coarse carbides are formed and the cold workability is reduced, and quenching cracks are likely to occur during induction hardening and hardly form a solid solution. Therefore, the content is set to 0.3 to 0.6%. .

Si: 1.0% or less Si is added as a deoxidizing agent during the production of steel. However, in steel, the ferrite phase, which is a matrix in a spheroidized structure, is solid-solution strengthened and cold workability is improved. , And
If it exceeds 0%, fine cracks tend to occur during processing, so the content is set to 1.0% or less. When the processing in the product forming process is cold forging or warm forging, the Si content needs to be 0.25% or less.

Mn: 1.0% or less Mn is added as a deoxidizing agent at the time of steel production like Si, but it is also an element that enhances hardenability. Therefore, it is preferable to contain an appropriate amount of Mn. However, if the content exceeds 1.0%, work hardening is promoted and cold workability is impaired, so the content is set to 1.0% or less. When the processing in the product forming process is cold forging or warm forging, the Mn content is preferably set to 0.4% or less.

P: not more than 0.04% P is an element which lowers the toughness of steel, so it is preferable to make it as thin as possible. However, if it is not more than 0.04%, there is no problem. 0.04%. When cold or warm forging is performed in the forming process, P
The content is preferably set to 0.015% or less.

S: 0.005 to 0.2% S is an element contained for improving the machinability of steel. If the content is less than 0.005%, the machinability is not improved.
If it exceeds 0.2%, the toughness is significantly reduced, so the content is made 0.005 to 0.2%.

Cr: 4.0-11.0% Cr is an element contained in order to increase corrosion resistance and induction hardening hardness. In order to obtain corrosion resistance to a degree that does not rust in a relatively mild environment, it is necessary to contain 4.0% or more. When a large amount of Cr is contained, the corrosion resistance increases, but the amount of carbides increases, and when it exceeds 11.0%,
It forms coarse carbides, which reduce the cold workability of the steel. Further, since the solid solution of the carbide during the induction hardening becomes insufficient and it becomes difficult to secure the quenching hardness, the content is set to 4.0 to 11.0%. Even in this range C
As the amount of r increases, the solid solution of the carbide during induction quenching becomes more difficult. Therefore, in the case where induction hardening is more important than corrosion resistance, it is better to suppress the Cr amount lower.

Al: 0.001 to 0.1% Al is an element added for deoxidizing steel.
If it is less than 01%, the effect cannot be obtained, and if it exceeds 0.1%, hard alumina clusters are formed and the machinability of the steel is reduced. I do.

Ca: 0.0005-0.02% Ca is contained in the sulfide to form a protective film on the surface of the cutting tool during steel cutting and to extend the life of the tool. If the effect is less than 0.0005%, the effect cannot be obtained, and if it exceeds 0.02%, excessive Ca forms CaS having a high melting point and causes obstacles such as clogging of a nozzle in a casting process of molten steel. Therefore, the content of Ca is set to 0.0005 to 0.02%. Preferably, 0.
0015 to 0.010%.

O: 0.0005 to 0.01% O is an oxide (CaO, Al ₂ ) serving as a nucleus for crystallization of sulfide.
O _3, etc.).
If it is less than 0005%, a large amount of Ca sulfide having a high melting point is generated to lower the pouring property, and if it exceeds 0.01%, a large amount of hard oxide is generated to lower the machinability of the steel. At the same time, all of the Ca forms oxides and no longer produces sulfides, so the content is 0.0005.
To 0.01%. Preferably 0.001 to 0.00
4%.

Mo: 1.0% or less Mo is contained in order to improve the corrosion resistance of steel. However, when the content exceeds 1.0%, the cold workability of the steel is lowered and the cost is increased. Therefore, the upper limit of the Mo content is set to 1.0%.

N: 0.02 to 0.2% N is contained in order to improve the corrosion resistance of steel, like Mo. If the N content is less than 0.02%, the effect cannot be obtained, and if it exceeds 0.2%, the workability of the steel is reduced, so the content is made 0.02 to 0.2%. In addition,
The N content can be controlled by selecting a scouring atmosphere, bubbling N ₂ gas, or introducing a nitride alloy.

Pb: 0.4% or less Pb is a well-known element for improving the machinability of steel, and exists alone or in a form adhering to the periphery of sulfide in steel. Has the effect of improving machinability. However, when the content exceeds 0.4%, the solubility in steel is exceeded, and because of its large specific gravity, the excess is aggregated and precipitated as a single substance and becomes a defect in the steel.
The content is set to 0.4% or less.

Bi: 0.4% or less Bi has similar properties to Pb and is a well-known machinability improving element. However, when the content exceeds 0.4%, the solubility in steel is reduced. Excess and exceeding due to its large specific gravity agglomerate and precipitate as a single substance and become defects in the steel, so the content is made 0.4% or less.

Se: 0.5% or less Se is a well-known machinability improving element.
%, The hot workability of the steel deteriorates and cracks occur frequently. Therefore, the upper limit of the content is set to 0.5%. Te: 0.1% or less Te is a well-known machinability improving element.
%, The hot workability of the steel deteriorates and cracks occur frequently. Therefore, the upper limit of the content is set to 0.1%.

Next, the form of the sulfide of the martensitic stainless steel used in the present invention will be described. Generally, the main component of the sulfide contained in the steel is MnS, but in the steel for the present invention to which Ca is added, a part of Mn in the MnS is replaced by Ca. The properties of MnS vary depending on the degree to which a part of Mn is substituted by Ca. Ca content in sulfide is 0.1 ~
The sulfide in the range of 10% forms a film for protecting the tool at the time of cutting, but if the Ca in the sulfide is less than 0.1% of the entire sulfide, the above-mentioned tool protective film is not formed. In addition, the effect of improving the tool life cannot be obtained, and if it exceeds 10%, CaS having a high melting point is excessively generated, so that a tool protective film is not formed and the productivity of steel is deteriorated.

In addition, a sulfide having an equivalent circle diameter of 5 μm or more is used.
If not more than 5 per 3 mm ^{2, the} amount of the formed tool protective film is small, so that the front surface of the tool is not completely covered and the effect of improving the tool life is small. The “equivalent circle diameter” in the present invention is the diameter of a circle assuming a circle having the same area as the cross-sectional area.

During the smelting of high alloy steel, Ni is often mixed in from the raw material scrap. In the martensitic stainless steel parts excellent in machinability of the present invention, there is an effect of slightly improving the ductility of the martensite phase, but if excessively contained, it becomes difficult to soften and anneal. Preferably, the Ni content is 0.6% or less.

The martensitic stainless steel part having excellent machinability according to the present invention is a steel part having a chemical composition as described above, a steel having a sulfide form adjusted, and requiring high hardness and wear resistance. Manufactured by induction hardening the surface. As a result, the martensitic stainless steel part having excellent machinability according to the present invention can be formed by cold forging and
The plastic working such as warm forging is easy, and the cutting work can be performed efficiently because of excellent machinability. When parts are used, no rust is generated in a relatively mild environment, and only the required depth is hardened to the required hardness HV630 (HRC57) or more by induction hardening, so that excellent strength is obtained. Demonstrates wear resistance.

Further, the martensitic stainless steel part having excellent machinability according to the present invention is obtained by subjecting the above-mentioned surface to use induction hardening, and further subjecting any of the high-speed shot injection treatment and the nitridation treatment to fine particles. Since one or two kinds of surface treatments are performed, the surface hardness is further increased and the wear resistance is improved, and when high-speed shot injection treatment of fine particles is performed, the retained austenite becomes martensite, A structure with high hardness and high toughness can be obtained. Furthermore, fatigue strength and seizure resistance are improved, and since a large number of minute concave portions are formed by using a spherical shot, an oil reservoir is formed, and the seizure resistance of the sliding portion is further improved.

[0031]

Next, an embodiment of the present invention will be described. The steel used for the martensitic stainless steel part having excellent machinability according to the present invention is melted by a method of melting ordinary alloy steel such as an arc furnace or an induction furnace, and cast into an ingot, followed by hot rolling and hot rolling. It can be manufactured by a usual method of manufacturing a steel material having a required size by hot forging and then sizing by hot forging.

The martensitic stainless steel parts having excellent machinability according to the present invention include hollow parts such as cylinders, pistons, shaft parts and the like, which are manufactured by, for example, spheroidizing annealing. After that, cut, form by cold forging, warm forging, etc., make parts of predetermined shape and dimensions by machining such as cutting and grinding, and then induction harden at least on the used surface, if necessary Then, one or two kinds of surface treatments of high-speed shot injection treatment and nitridation of fine particles are performed.

Induction quenching according to the present invention is conventionally performed in the case of a shaft-like product such as a piston by cooling it by dropping it into a cooling liquid or jetting the cooling liquid after heating it in a heating coil. It can be performed by a known induction hardening method.

When quenching the inner surface of a hollow part such as a cylinder, particularly a part having a hole with an inner diameter of 10 mm or less, as shown in FIG. 5, the lower component-holding / coil component 4 is placed with the insulating plate 6 interposed therebetween, and the hollow upper component-holding / coil component 3 is further placed on the component 1 to be cooled. Tubular coil component 2 through which water passes
And a high-frequency current is passed through the lower component-holding / coil component 4, the tubular coil component 2, the component 1, and the lower component-holding / coil component 4 to flow the component 1 After heating to a predetermined quenching temperature, a quenching liquid is introduced from the upper component-to-be-processed / coiled component 3 to cool the inner surface of the component-to-be-processed 1 and passes through the lower component-to-be-processed / coiled component 4. It can be quenched as it is discharged. The reference numerals 7 and 8 are seals.

The high-speed shot injection treatment of the fine particles used in the present invention is 10 to 200 μm, preferably 5 to 100 μm.
80 μm on a surface where a number of μm hard particles are induction hardened
It can be performed by projecting at a collision speed of m / sec or more.

The nitriding treatment used in the present invention may be a commonly performed nitriding treatment, for example, a treatment in an atmosphere of NH ₃ gas heated to 450 to 600 ° C. for 2 to 6 hours, followed by rapid cooling. And so on.

[0037]

EXAMPLES The steels shown in Table 1 were melted and cast into steel ingots using a high-frequency induction furnace, and then the steel ingots were divided by hot forging. This was made into a bar having a diameter of 35 mm by hot rolling. The bar was heated to 850 ° C. for 3 hours, cooled to 600 ° C. at a cooling rate of 15 ° C./hour, and then subjected to air-cooled spheroidizing annealing to obtain a test material, which was subjected to the following tests.

[0038]

[Table 1]

Sulfide measurement: The number of sulfides having a circle-equivalent diameter of 5 μm or more in 3.3 mm ² (corresponding to about 30 visual fields at a microscope magnification of 100) on a longitudinal section including the central axis of the test material was determined. Measured. Table 1 shows the results as the number of sulfides.
Shown in The components were analyzed for sulfides arbitrarily selected from the measured sulfides, and Ca was 0.1 to 10%.
It was confirmed that it was in the range.

Machinability test: The test material was cut into a length of 12 mm, and a machinability test was performed using this as a test piece. Using a high-speed steel drill with a nominal diameter of 4 mm, drill a large number of holes with a depth of 10 mm perpendicular to the cross section of the test piece without cutting oil,
The total length of the hole drilled until it became impossible to drill was measured. Assuming that the total drilling length obtained for the test piece of Comparative Example 1 was 1, the ratio of the total drilling length of each test piece was determined, and the tool life ratio was used as an index of machinability.

Cold forgeability test: A cylindrical test piece having a diameter of 6 mm and a height of 12 mm was prepared from the test material by machining, and a load was applied in the axial direction of the test piece. Was determined as a critical upsetting ratio and used as an index of cold forgeability.

Warm forgeability test: Diameter 30 from the test material
A cylindrical test piece having a height of 30 mm and a height of 30 mm was cut out, the test piece was heated to 300 ° C., a load was applied in the axial direction by a 400-ton press, and a hole having a diameter of 10 mm was punched out in the forging step shown in FIG. Whether or not punching is possible at the time of punching is divided into those without cracks (○), those with cracks in some parts (△), and those without punching (x). The index was used.

Hardness test: A cylindrical test piece having an outer diameter of 30 mm, an inner diameter of 10 mm and a height of 30 mm was prepared from the test material by machining, and the frequency was set to 80 K using the apparatus shown in FIG.
The inner surface of the hole was subjected to induction hardening under the conditions of Hz, output of 100 KW, and time of 10 sec. The center of the height of the induction hardened test piece was cut, and the hardness at a position of 0.5 mm from the inner surface was measured in four directions on the diameter, and the average value was obtained. did. The hardness was measured at a load of 300 g using a micro Vickers hardness meter.

A high-speed shot-treated test piece was prepared by injecting hard beads having an average particle size of 50 μm at a speed of 100 m / sec onto the test piece subjected to the induction hardening. The center of the height of the test piece was cut, and the cross section was 5 μm from the inner surface.
The hardness at the position of m is measured in four directions on the diameter, and the average value is obtained, and induction hardening + shot material (IH + S
P) Hardness. The hardness was measured with a load of 5 g using a micro-Vickers hardness meter.

The above-mentioned induction hardened test piece was further
The nitriding treatment was performed at a treatment temperature of 520 ° C., an NH ₃ gas atmosphere, and a treatment time of 3 hours. The central part of the height of the test piece was cut, and the hardness at a position of 50 μm from the inner surface was measured in four directions on the diameter, and the average value was obtained, which was defined as induction hardened + nitrided material (IH + nitrided) hardness. The hardness was measured at a load of 300 g using a micro Vickers hardness meter.

Hard beads having an average particle size of 50 μm were added to the test piece subjected to the induction hardening and nitriding treatment at a speed of 100 m / m.
Injected in sec. The center of the height of the test piece was cut, and the hardness of the cross section at a position of 5 μm from the inner surface was measured in four directions on the diameter, and the average value was determined. Induction hardening + nitriding + shot material (IH + (Nitridation + SP) hardness. The hardness was measured with a load of 5 g using a micro-Vickers hardness meter. Table 2 shows the results of the above tests.

[0047]

[Table 2]

As is clear from Table 2, the examples of the present invention show a remarkably large tool life ratio as compared with the comparative examples, indicating that the examples of the present invention are excellent in machinability. In addition, the examples of the present invention exhibited good cold forgeability with an upsetting ratio of 65% or more, and good hole drilling in a warm forgeability test of Δ or more. Further, in Examples of the present invention, the quenching hardness of the used surface is HV630 (HRC57) or more, and the induction hardening property is excellent.

Fine particles were subjected to high-speed shot injection treatment after induction quenching (IH + SP), those subjected to nitridation treatment after induction quenching (IH + nitridation), and subjected to nitridation treatment after induction quenching and further subjected to high-speed shot injection treatment. The specimen (IH + nitriding + SP) showed a hardness higher by 40% or more than that of the specimen subjected to induction hardening (IH).

[0050]

As described above, according to the martensitic stainless steel part excellent in machinability and the method of manufacturing the same according to the present invention, working such as cold forging and warm forging is easy. Even parts with strict dimensional accuracy can be cut with high accuracy without requiring a long time for cutting, and high surface hardness HV630 (H
RC57) A steel part having the above is obtained. This steel part contains an appropriate amount of Cr and, if necessary, contains Mo, N, etc., and is also excellent in corrosion resistance. Therefore, in particular, cylinders and pistons used under high pressure such as fuel pump systems for automobiles are used. For example, it is suitable as a component requiring high hardness and corrosion resistance, and it can be said that the economic effect of the present invention is extremely large.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an apparatus for induction hardening the inner surface of a hole of a martensitic stainless steel part having excellent machinability according to the present invention.

FIG. 2 is a process diagram of warm forging according to an embodiment of the present invention.

[Description of Signs] 1 Component to be processed 2 Tubular coil constituent member 3 Upper component to be pressed and coil component 4 Lower component to be pressed and coil component 5 Support and coil component 6 Insulating plate 7, 8 Seal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C23C 8/26 C23C 8/26

Claims (7)

[Claims] 1. A mass% of C: 0.3 to 0.6%, S
i: 1.0% or less, Mn: 1.0% or less, P: 0.04
%, S: 0.005 to 0.2%, Cr: 4.0 to 1
1.0%, Al: 0.001 to 0.1%, Ca: 0.0
005-0.02%, O: 0.0005-0.01%, the balance substantially consisting of Fe, and 0.1-0.02%.
A martensitic stainless steel excellent in machinability, characterized in that it contains 5 or more sulfides having a circle equivalent diameter of 5 μm or more containing 10% of Ca per 3.3 mm ² , and is induction hardened on the working surface. parts. 2. In mass%, C: 0.3-0.6%, S
i: 1.0% or less, Mn: 1.0% or less, P: 0.04
%, S: 0.005 to 0.2%, Cr: 4.0 to 1
1.0%, Al: 0.001 to 0.1%, Ca: 0.0
005-0.02%, O: 0.0005-0.01%, Mo: 1.0% or less and N: 0.0
Containing any one or two of 2 to 0.2%,
3.3 m of sulfide having a circle-equivalent diameter of 5 μm or more containing 0.1 to 10% of Ca and having a balance of substantially Fe
A martensitic stainless steel part with excellent machinability characterized by containing at least 5 parts per m ² and using induction hardening on the working surface. 3. In mass%, C: 0.3-0.6%, S
i: 1.0% or less, Mn: 1.0% or less, P: 0.04
%, S: 0.005 to 0.2%, Cr: 4.0 to 1
1.0%, Al: 0.001 to 0.1%, Ca: 0.0
005-0.02%, O: 0.0005-0.01%, Pb: 0.4% or less, Bi: 0.4%
Hereinafter, any one or more of Se: 0.5% or less and Te: 0.1% or less are contained, and the balance is substantially composed of Fe, and 0.1 to 10% of Ca A martensitic stainless steel part excellent in machinability, characterized by containing five or more sulfides having an equivalent circle diameter of 5 μm or more per 3.3 mm ² containing indium and hardening the surface to be used. 4. C: 0.3 to 0.6% by mass%, S:
i: 1.0% or less, Mn: 1.0% or less, P: 0.04
%, S: 0.005 to 0.2%, Cr: 4.0 to 1
1.0%, Al: 0.001 to 0.1%, Ca: 0.0
005-0.02%, O: 0.0005-0.01%, Mo: 1.0% or less and N: 0.0
Containing any one or two of 2 to 0.2%,
Also, Pb: 0.4% or less, Bi: 0.4% or less, S
e: one or more of 0.5% or less and Te: 0.1% or less, and the balance is substantially Fe
A sulphide having a circle equivalent diameter of 5 μm or more containing 0.1 to 10% of Ca and having a diameter of 5 μm or more per 3.3 mm ² , wherein the surface to be used is induction hardened. Martensitic stainless steel parts with excellent properties. 5. The martensitic stainless steel part with excellent machinability according to claim 1, wherein the martensitic stainless steel part is a cylinder or a piston. 6. A high-speed shot spraying process of fine particles and a nitriding process after induction hardening the working surface of the martensitic stainless steel part according to any one of claims 1 to 5 above. A method for producing a martensitic stainless steel part excellent in machinability, characterized by performing one or two types of surface treatment. 7. A cold forging or a warm forging of the martensitic stainless steel part according to any one of claims 1 to 5, followed by induction hardening on a surface to be used, and on the surface subjected to the induction hardening. A method for producing a martensitic stainless steel part having excellent machinability, characterized in that one or two types of surface treatment of high-speed shot injection treatment and nitridation treatment of fine particles are performed.