WO2020050053A1

WO2020050053A1 - Steel material for sliding members, and method for producing same

Info

Publication number: WO2020050053A1
Application number: PCT/JP2019/032891
Authority: WO
Inventors: 和潔來村; 慎宮島; 松本　圭司
Original assignee: 日本製鉄株式会社
Priority date: 2018-09-07
Filing date: 2019-08-22
Publication date: 2020-03-12

Abstract

Provided is a steel material for sliding members, which has excellent seizure resistance. The steel material for sliding members has a chemical composition containing, in % by mass, 0.05 to 5.0% of In and a texture having, dispersed therein, particles of metal In or particles of an oxide mainly composed of In, wherein the number density of particles each having a diameter of 50 nm to 5 μm among the particles of metal In is 5000 particles/mm2 or more or the number density of particles each having a diameter of 1 μm or more among the particles of the oxide mainly composed of In is 30 particles/mm2 or more.

Description

Steel for sliding parts and method of manufacturing the same

The present invention relates to a steel material for a sliding part and a method for producing the same.

クランク Crankshafts for automobile engines are examples of parts that require sliding characteristics. In recent years, downsizing of engines, low viscosity of lubricating oils, and simplification of lubrication systems have been progressing for the purpose of fuel efficiency, and sliding parts used for crankshafts have been used from the viewpoint of dry start by intermittent operation. Steel materials for use are required to have better seizure resistance.

The seizure phenomenon of steel materials is caused not only by physical factors such as abrasion powder generated at the time of sliding, but also by chemical factors generated at a sliding interface (for example, due to chemical reaction such as transfer and adhesion of a sliding partner material). Generation of dissimilar materials that may be caused by In a dry environment, as a method of suppressing seizure, for example, measures such as DLC (diamond-like carbon) film formation on a steel material surface and coating with a PTFE-based fluororesin are taken.

In the case of a crankshaft, seizure occurs at the contact point between the crankshaft and the bearing. The crankshaft and the bearing are usually in a fluid lubricated state in which they slide through lubricating oil. However, the lubricating oil may be chemically degraded due to an increase in the temperature of the contact interface accompanying high-speed and high-pressure sliding. As a result, it is thought that the lubricating oil stops functioning or the wettability of the lubricating oil is impaired, so that the crankshaft and the bearing come into direct contact, and the structure of the steel material is plastically deformed and seizure occurs. I have.

Therefore, studies are being made to increase the mechanical strength of the steel material to suppress the amount of wear and plastic deformation of the steel material, and to control the surface properties of the steel material in order to improve the wettability with lubricating oil. For example, Japanese Unexamined Patent Publication No. 7-18379 discloses a steel for machine structural use which has a compound layer formed by nitrocarburizing on the surface and has excellent seizure resistance and fatigue strength. Japanese Patent Application Laid-Open No. 2007-238965 discloses a crankshaft having an induction hardening layer on the surface and having excellent seizure resistance.

摺動 As a different approach, sliding parts using solid lubricants have been proposed. For example, Japanese Patent Application Laid-Open No. Sho 60-1424 discloses a sliding member composed of a base having irregularities on the surface and a solid lubricant held in a concave portion of the base.

JP-A-7-18379 JP 2007-238965 A JP-A-60-1424 JP 2001-131684 A

場合 When the above-mentioned DLC film is formed on the surface of a steel component, good surface properties can be obtained. However, in a high-temperature and high-pressure environment during sliding, unexpected thermal shock and stress concentration may occur. At present, DLC film formation cannot be said to be sufficiently resistant to such an environment. In addition, although the above-mentioned fluororesin coating is a highly convenient and low-cost surface treatment method, in addition to early corrosion deterioration considered to be caused by pinholes formed inside the fluororesin, it is toxic in a high-temperature environment. There are environmental concerns such as the generation of certain dangerous gases. As described above, in the above-described method, there is a limit in sufficiently suppressing the seizure phenomenon on the surface of the steel material and maintaining good sliding performance.

技術 The techniques described in Patent Documents 1 to 3 also have the following problems.

The above-mentioned nitrocarburizing or carburizing is a technique for chemically modifying the surface of a steel component into a harder composition and structure. Since gas treatment is performed at a high temperature separately from a normal heat treatment process, the treatment time And the cost of the apparatus increases. In addition, it cannot be ignored that the steel component to be processed is restricted by the inner volume of the furnace of the gas processing apparatus.

特開 The above-mentioned Japanese Patent Application Laid-Open No. 60-1424 describes that irregularities are formed on the surface of a substrate by shot blasting or etching, and a solid lubricant is embedded in the concave portions. In this method, in addition to the complicated manufacturing process, there is a concern that the solid lubricant is consumed on the sliding surface and the lubricating performance is significantly impaired if the supply is interrupted.

目的 An object of the present invention is to provide a steel material for sliding parts having excellent seizure resistance and a method for producing the same.

The steel material for a sliding part according to one embodiment of the present invention has a chemical composition containing mass%, In: 0.05 to 5.0%, and metal In particles or In-based oxide particles dispersed therein. The number density of particles having a diameter of 50 nm to 5 μm among the metal In particles is 5000 particles / mm ² or more, or 1 μm among the oxide-based particles mainly containing In. The number density of the above particles is 30 particles / mm ² or more.

In the sliding part steel material according to one embodiment of the present invention, among the particles of the metal In, the number density of particles having a diameter of 50 nm to 5 μm is 5000 / mm ² or more.

A method for producing a steel material for a sliding component according to an embodiment of the present invention is a method for producing a steel material for a sliding component as described above, wherein the chemical composition contains 0.05 to 5.0% by mass of In. And a step of heating the material at 800 to 1200 ° C. for 5 to 30 minutes, and then subjecting the material to quenching treatment with water or oil cooling.

In the steel material for a sliding part according to one embodiment of the present invention, the chemical composition has an In content of 0.3 to 5.0% by mass%, and of the oxide particles mainly containing In. The number density of particles having a diameter of 1 μm or more is 30 particles / mm ² or more.

A method for manufacturing a steel material for a sliding component according to an embodiment of the present invention is a method for manufacturing a steel material for a sliding component as described above, wherein the chemical composition contains 0.3 to 5.0% by mass of In. Preparing a material having the following characteristics: heating the material at 800 to 1200 ° C. for 5 to 30 minutes, and then subjecting the material to a quenching process to water cooling or oil cooling; Heating for 5 to 60 minutes, and then performing a heat treatment for furnace cooling.

According to the present invention, a steel material for sliding parts having excellent seizure resistance can be obtained.

FIG. 1 is a graph showing a time change of each friction coefficient of a test material having a maximum friction coefficient exceeding 0.5 and a test material having a maximum friction coefficient of 0.5 or less in a friction test in a dry environment. is there. FIG. 2 is a graph showing a time change of each friction coefficient of a test material having a maximum friction coefficient exceeding 0.5 and a test material having a maximum friction coefficient of 0.5 or less in a friction test in a wet environment. is there.

The present inventors have focused on metal elements added to steel materials and studied a method for improving seizure resistance more simply and effectively than in the past. As a result, they found that the addition of indium (In) was effective in improving seizure resistance.

In has a lower melting point (156 ° C.) than other metal elements and is soft (Mohs hardness is 1.2). In is used as a solid lubricant together with lead and graphite having similar properties (for example, see JP-A-2001-131684). However, the solid lubricant is consumed on the sliding surface, and if the supply is interrupted, there is a concern that the lubricating performance is significantly impaired.

The present inventors have clarified that a lubricating film can be formed on a sliding surface for a long time by finely dispersing metal In particles or In-based oxide particles in steel.

ＩｎIn which does not form a solid solution in steel exists as a precipitate. The undissolved In diffuses into the steel surface even under a normal temperature environment to form a concentrated In layer, and the concentrated In layer serves as a lubricating film, thereby contributing to an improvement in sliding characteristics. In addition, when the lubricating film is consumed by sliding, the undissolved In in the steel rapidly diffuses to the steel surface to regenerate the lubricating film.

The precipitation form of In changes due to heat treatment at the time of manufacturing. Specifically, when passing through a temperature range of 650 to 100 ° C. at a cooling rate equal to or higher than air cooling, the number of In (metallic In) deposited as a single substance increases. On the other hand, when the temperature is kept in the same temperature range for a long time, or when the temperature is passed through the same temperature range at a low cooling rate such as furnace cooling, the number of Ins forming oxides increases.

In order to regenerate the lubricating film more quickly and to ensure excellent sliding characteristics over a long period of time, it is necessary to finely disperse the In particles. It depends on the form. Specifically, the number density of metal In particles having a diameter of 50 nm to 5 μm is set to 5000 particles / mm ² or more, or the number density of In-based oxide particles having a diameter of 1 μm or more is set to 30 particles / mm ^2. By doing so, excellent sliding characteristics can be obtained over a long period of time. In addition, when a particle is not spherical, "diameter" means a circle equivalent diameter in an observation cross section.

The present invention has been completed based on the above findings. Hereinafter, a steel material for a sliding part according to an embodiment of the present invention will be described in detail. In the following description, “%” of the content of an element means mass%.

[Steel for sliding parts]
[Chemical composition]
The steel material for a sliding component according to the present embodiment has a chemical composition containing In: 0.05 to 5.0%.

In: 0.05-5.0%
Indium (In) forms a lubricating film on the surface of the steel material and improves the sliding characteristics of the steel material. On the other hand, when the In content is excessive, segregation at the grain boundary becomes remarkable, which may cause brittle fracture or grain boundary corrosion. Therefore, the In content is 0.05 to 5.0%. The lower limit of the In content is preferably 0.1%, more preferably 0.2%, and still more preferably 0.3%. The upper limit of the In content is preferably 4.0%, and more preferably 3.0%.

In the case where In is deposited as metal In, compared with the case where In is deposited as oxide, the desired sliding characteristics can be ensured even if the In content is reduced. From the viewpoint of manufacturing cost, it is preferable to reduce the In content as much as possible. Therefore, when In is deposited as metal In, the In content is more preferably 1.0% or less, further preferably 0.5% or less, and further preferably less than 0.3%.

On the other hand, when In is deposited as an oxide, it is preferable to increase the In content as compared with the case where In is deposited as metal In. When In is deposited as an oxide, the lower limit of the In content is preferably 0.3%, more preferably 0.6%, further preferably 0.8%, and further preferably 1.%. 0%.

の他 The other chemical composition of the steel for sliding parts according to the present embodiment is not particularly limited. Steel materials of various chemical compositions can be used as the steel materials for sliding parts according to the present embodiment, depending on the intended use. The chemical composition of the steel material for a sliding part according to the present embodiment is not limited thereto, but is as follows, for example.

C: 0.05-1.80%
Carbon (C) enhances the hardenability of steel and contributes to improvement in hardness. If the C content is less than 0.05%, the hardenability of steel may be insufficient. On the other hand, if the C content exceeds 1.80%, the rollability and workability of the steel may decrease. Therefore, the C content is preferably 0.05 to 1.80%. The lower limit of the C content is more preferably 0.15%, and still more preferably 0.25%. When importance is placed on the strength of steel, the lower limit of the C content is more preferably 0.30%, more preferably 0.35%, and still more preferably 0.40%. On the other hand, the C content is preferably 1.50% or less when emphasizing the rollability and workability of steel, and is 1.00% or less when emphasizing machinability. Is preferred. When the machinability is emphasized, the upper limit of the C content is more preferably 0.60%, more preferably 0.55%, and further preferably 0.50%.

Si: 1.5% or less Silicon (Si) is an element used as a deoxidizing agent for steel. However, if the Si content exceeds 1.5%, the thermal conductivity of the steel may decrease, and sufficient seizure resistance may not be obtained. Therefore, the Si content is preferably 1.5% or less. The upper limit of the Si content is more preferably 1.0%, more preferably 0.80%, more preferably 0.70%, and still more preferably 0.50%. On the other hand, when Si is positively contained, there is an effect of suppressing generation of coarse cementite. In order to obtain the above effects remarkably, the Si content is preferably set to 0.05% or more, more preferably 0.10% or more.

Mn: 2.0% or less Manganese (Mn) is an element having an effect of improving the hardenability of steel. However, if the Mn content exceeds 2.0%, the thermal conductivity of the steel may decrease, and sufficient seizure resistance may not be obtained. Therefore, the Mn content is preferably 2.0% or less. The upper limit of the Mn content is more preferably 1.8%, more preferably 1.6%, more preferably 1.5%, further preferably 1.0%, and still more preferably 0.5%. On the other hand, when Mn is positively contained, there is an effect of suppressing recovery of dislocations in addition to an effect of improving hardenability. In order to obtain the above effects remarkably, the Mn content is preferably set to 0.05% or more, more preferably 0.10% or more, and further preferably 0.20% or more. .

P: 0.10% or less Phosphorus (P) is contained in steel as an impurity. If the P content exceeds 0.10%, excessive P segregates at the grain boundaries, and the fatigue strength of the steel may be reduced. Therefore, the P content is preferably 0.10% or less. The upper limit of the P content is more preferably 0.08%, further preferably 0.06%, further preferably 0.05%, and still more preferably 0.03%.

S: 0.10% or less Sulfur (S) is contained as an impurity in steel. If the S content exceeds 0.10%, hot workability may be reduced. Therefore, the S content is preferably 0.10% or less. The upper limit of the S content is more preferably 0.080%, more preferably 0.070%, and still more preferably 0.050%. On the other hand, when S is positively contained, sulfide-based inclusions are formed and the machinability of steel is improved. In order to remarkably obtain the above effects, the S content is preferably set to 0.005% or more, and more preferably set to 0.010% or more.

Al: 0.10% or less Aluminum (Al) is contained as a deoxidizing material. If the Al content exceeds 0.10%, the machinability of steel may decrease. Therefore, the Al content is preferably 0.10% or less. On the other hand, when Al is positively contained, it contributes to refinement of austenite grains by a pinning effect of nitride. In order to obtain the above effects remarkably, the Al content is preferably 0.005% or more, more preferably 0.010% or more, and still more preferably 0.020% or more. The upper limit of the Al content is more preferably 0.080%, more preferably 0.060%, more preferably 0.055%, and still more preferably 0.050%.

N: 0.030% or less Nitrogen (N) is contained in steel as an impurity. If the N content exceeds 0.030%, the toughness of the steel may decrease. Therefore, the N content is preferably 0.030% or less. On the other hand, when N is positively contained, it contributes to refinement of austenite grains by a pinning effect of nitride. In order to obtain the above effects remarkably, the N content is preferably 0.001% or more, more preferably 0.0015% or more, and further preferably 0.002% or more. The upper limit of the N content is more preferably 0.020%, and still more preferably 0.015%.

In the chemical composition of steel, one or more elements selected from the following elements may be further contained in addition to the above elements. The reasons for limiting each element will be described below.

Cr: 0 to 15.0%
Chromium (Cr) is an element having an effect of improving strength and wear resistance. In addition, Cr is an element effective in suppressing the austenite structure from coarsening. Therefore, Cr may be contained as necessary. However, if the Cr content exceeds 15.0%, an imbalance between strength and toughness may occur. Therefore, the Cr content is preferably 15.0% or less. The upper limit of the Cr content is more preferably 10.0%, and still more preferably 5.0%. Note that the lower limit of the Cr content is preferably 0.01%, more preferably 0.02%, further preferably 0.05%, and still more preferably 0.10%. When emphasis is placed on machinability, the Cr content is preferably set to 0.30% or less. The Cr content when emphasizing machinability is more preferably 0.25% or less, and further preferably 0.20% or less.

Ni: 0 to 0.50%
Nickel (Ni) is an element having an effect of improving the strength and toughness of steel. Therefore, Ni may be contained as necessary. However, even if the Ni content exceeds 0.50%, the effect is saturated and the alloy cost is increased. Therefore, the Ni content is preferably 0.50% or less. The upper limit of the Ni content is more preferably 0.40%, and still more preferably 0.35%. When Ni is not positively contained, the Ni content is preferably set to 0.10% or less, more preferably 0.05% or less.

Cu: 0 to 0.50%
Copper (Cu) is an element having an effect of improving the strength and toughness of steel. Therefore, Cu may be contained as necessary. However, even if the Cu content exceeds 0.50%, the effect is saturated and the alloy cost is increased. Therefore, the Cu content is preferably 0.50% or less. The upper limit of the Cu content is more preferably 0.40%, and still more preferably 0.35%. When Cu is not positively contained, the Cu content is preferably set to 0.10% or less, more preferably 0.05% or less.

Ti: 0 to 0.050%
Titanium (Ti) forms nitrides and carbonitrides, and contributes to miniaturization of austenite grains by a pinning effect. Therefore, you may contain Ti as needed. However, if the Ti content exceeds 0.050%, the toughness of the steel may decrease. Therefore, the Ti content is preferably 0.050% or less. The upper limit of the Ti content is more preferably 0.040%, and still more preferably 0.030%. Note that the lower limit of the Ti content is preferably 0.005%, more preferably 0.010%.

Nb: 0 to 0.050%
Niobium (Nb) forms nitrides and carbonitrides and contributes to miniaturization of austenite grains by a pinning effect. Therefore, Nb may be contained as needed. However, if the Nb content exceeds 0.050%, the toughness of the steel may decrease. Therefore, the Nb content is preferably 0.050% or less. The upper limit of the Nb content is more preferably 0.040%, and still more preferably 0.030%. The lower limit of the Nb content is preferably 0.005%, and more preferably 0.010%.

V: 0 to 2.5%
Vanadium (V) forms nitrides and carbonitrides, and contributes to miniaturization of austenite grains by a pinning effect. Moreover, the strength of steel is improved by forming carbides. Therefore, V may be contained as needed. However, if the V content exceeds 2.5%, the toughness of the steel may decrease. Therefore, the V content is preferably 2.5% or less. The upper limit of the V content is more preferably 2.0%, further preferably 1.5%, and particularly preferably 1.0%. The lower limit of the V content is preferably 0.005%, and more preferably 0.010%.

Mo: 0 to 3.0%
Molybdenum (Mo) is an element having the effect of improving the hardenability of steel and improving the strength of steel. Therefore, Mo may be contained as needed. However, if the Mo content exceeds 3.0%, the machinability of the steel may decrease. Therefore, the Mo content is preferably 3.0% or less. The upper limit of the Mo content is more preferably 2.5%, further preferably 2.0%, and particularly preferably 1.5%. In addition, when Mo is positively contained, the lower limit of the Mo content is preferably 0.3%, more preferably 0.5%. When Mo is not positively contained, the Mo content is preferably 0.10% or less, more preferably 0.05% or less.

W: 0 to 6.0%
Tungsten (W), like Mo, is an element having the effect of improving the hardenability of steel and improving the strength of steel. Therefore, W may be contained as needed. However, if the W content exceeds 6.0%, the machinability of the steel may decrease. Therefore, the W content is preferably 6.0% or less. The upper limit of the W content is more preferably 4.0%, and still more preferably 2.0%. Note that the lower limit of the W content is preferably 0.01%, more preferably 0.1%, and still more preferably 0.5%.

B: 0 to 0.005%
Boron (B) contributes to improvement in toughness as a grain boundary strengthening element. Therefore, you may contain B as needed. However, if the content of B exceeds 0.005%, the toughness may be rather reduced. Therefore, the B content is preferably 0.005% or less. The upper limit of the B content is more preferably 0.004%, and still more preferably 0.002%. The lower limit of the B content is preferably 0.0003%, and more preferably 0.0005%. In order to effectively use the effect of B, it is preferable that N in steel is fixed by Ti.

In the steel chemical composition, the balance is Fe and impurities. Here, the "impurities" are components that are mixed due to various factors in the ore, scrap and other raw materials, and the manufacturing process when steel is industrially manufactured, and are acceptable as long as they do not adversely affect the present invention. Means something.

元素 Note that elements that can be mixed into steel as impurities include, for example, Pb, Ca, Mg, Sb, Ta and REM. Even when these elements are contained, their contents are respectively Pb: 0.10% or less, Ca: 0.001% or less, Mg: 0.001% or less, Sb: 0.005% or less, If Ta: 0.10% or less and REM: 0.001% or less, the present invention can be practiced without any problem.

組成 Typical compositions of the above steels are the following five types.

(A) C: 0.35 to 0.60%, Si: 0.50% or less, Mn: 0.80% or less, P: 0.10% or less, S: 0.050% or less, Al: 0. 005 to 0.060%, N: 0.001 to 0.020%, In: 0.05 to 5.0%, Cr: 0 to 0.30%, Ni: 0 to 0.20%, Cu: 0 0.10%, Nb: 0 to 0.050%, Mo: 0 to 3.0%, balance: Fe and steel as impurities.

(B) C: 0.35 to 0.40%, Si: 0.80% or less, Mn: 1.00 to 1.80%, P: 0.10% or less, S: 0.070% or less, Al : 0.005 to 0.060%, N: 0.001 to 0.020%, In: 0.05 to 5.0%, Cr: 0 to 0.25%, Ni: 0 to 0.15%, Cu: 0 to 0.25%, Ti: 0 to 0.050%, Nb: 0 to 0.050%, Mo: 0 to 0.10%, balance: Fe and steel as impurities.

(C) C: 0.95 to 1.10%, Si: 0.15 to 0.30%, Mn: less than 0.40%, P: 0.020% or less, S: less than 0.020%, Al : 0.005 to 0.060%, N: 0.001 to 0.020%, In: 0.05 to 5.0%, Cr: 1.30% to 1.60%, Ni: 0 to 0. 15%, Cu: less than 0.20%, Ti: 0 to 0.050%, Nb: 0 to 0.050%, V: 0 to 2.5%, Mo: 0 to 3.0%, B: 0 0.005%, balance: Fe and steel as impurities.

(D) C: 1.40 to 1.60%, Si: less than 0.40%, Mn: less than 0.60%, P: 0.020% or less, S: less than 0.020%, Al: 0. 005 to 0.060%, N: 0.001 to 0.030%, In: 0.05 to 5.0%, Cr: 11.0 to 13.0%, Ni: 0 to 0.50%, Cu : Less than 0.40%, Ti: 0 to 0.050%, Nb: 0 to 0.050%, V: 0.20 to 0.50%, Mo: 0.80 to 1.20%, B: 0 0.005%, balance: Fe and steel as impurities.

(E) C: 0.05 to 0.60%, Si: 1.5% or less, Mn: 2.0% or less, Cr: 0.3% or less, In: 0.05 to 5.0%, P : 0.10% or less, S: 0.10% or less, Al: 0.10% or less, Cu: 0.10% or less, Ni: 0.10% or less, Mo: 0.10% or less, N: 0 0.03% or less, balance: Fe and steel as impurities.

[Organization]
The steel material for a sliding part according to the present embodiment has a structure in which particles of metal In or particles of an oxide mainly containing In are dispersed.

The solid solubility limit of In in the Fe—In binary system is about 0.57%, but since various other elements are dissolved in steel, the solid solubility limit of In in the steel is Fe—. It becomes lower than the solid solubility limit of In. In which does not form a solid solution in steel exists as a precipitate. The undissolved In diffuses into the steel surface even under a normal temperature environment to form a concentrated In layer, and the concentrated In layer serves as a lubricating film, thereby contributing to an improvement in sliding characteristics. In addition, when the lubricating film is consumed by sliding, the undissolved In in the steel rapidly diffuses to the steel surface to regenerate the lubricating film.

In order to ensure that the lubricating coating is regenerated more quickly and to ensure excellent sliding properties over a long period of time, it is necessary to finely disperse the metal In particles or the In-based oxide particles. The number density of the In particles varies depending on the precipitation form of In. Specifically, the number density of metal In particles having a diameter of 50 nm to 5 μm is set to 5000 particles / mm ² or more, or the density of oxide particles mainly composed of In having a diameter of 1 μm or more is set to 30 particles / mm 2. If it is ^two or more, excellent sliding characteristics can be obtained for a long time. In addition, when a particle is not spherical, "diameter" means a circle equivalent diameter in an observation cross section.

The microstructure of the steel material for sliding parts is that the number density of particles having a diameter of 50 nm to 5 μm among the particles of metal In is 5,000 / mm ² or more, and the diameter of oxide particles mainly containing In is 1 μm. It suffices if at least one of the above-mentioned number density of particles of 30 particles / mm ² or more is satisfied. That is, as long as the number density of particles having a diameter of 50 nm to 5 μm among the metal In particles is 5000 / mm ² or more, the number density of the oxide-based particles mainly containing In is arbitrary. The number density of metal In particles is arbitrary as long as the number density of particles having a diameter of 1 μm or more among oxide particles mainly containing In is 30 particles / mm ² or more.

基地 The base (matrix) of the structure of the steel material for sliding parts is not particularly limited. The base of the structure of the steel material for sliding parts is, for example, martensite, tempered martensite, ferrite perlite, perlite, and the like.

[Metal In]
When the sliding characteristics are ensured by the metal In, the number density of the metal In particles having a diameter of 50 nm to 5 μm is set to 5000 / mm ² or more. The number density of metal In particles having a diameter of 50 nm to 5 μm is preferably 10,000 particles / mm ² or more, more preferably 15,000 particles / mm ² or more, and further preferably 20,000 particles / mm ² or more.

Here, “metal In” means In which is not forming a compound such as an oxide and is precipitated as a single substance.

数 The number density of the metal In particles is measured as follows. From the vicinity of the surface of the steel material, a test piece is collected with a cross section perpendicular to the surface as an observation surface. After the observation surface is mirror-polished, it is magnified 5000 times using an electron beam microanalyzer (EPMA) to observe a composition image by a reflected electron image, and further from a mapping image of In by a wavelength dispersive spectrometer (WDS). Specifically, the metal In is specified, and the number of particles having a diameter of 50 nm to 5 μm is counted. The number of particles is divided by the area of the visual field to obtain a number density.

The reason why the diameter of the metal In to be counted is limited to 50 nm to 5 μm is for convenience of measurement. That is, it is difficult to discriminate noise having a diameter of less than 50 nm from the observation visual field if it has a diameter of more than 5 μm. The structure of the steel material for a sliding part may be such that the number density of metal In particles having a diameter of 50 nm to 5 μm is at least 5000 / mm ² , and in addition, metal In particles having a diameter of less than 50 nm or more than 5 μm are present. You may.

数 The number density of the metal In particles can be adjusted by the In content of the steel material and the conditions of the quenching treatment. Specifically, the higher the In content of the steel material, the higher the number density of metal In particles tends to be. On the other hand, as the holding temperature of the quenching process is increased or the holding time of the quenching process is increased, the number density of the metal In particles tends to decrease.

摺動 It is preferable that the steel material for a sliding component according to the present embodiment has a concentrated In layer on the surface. The concentrated In layer is a layer in which the concentration of In obtained by Auger electron spectroscopy is 10 at% or more. In the steel material for sliding parts according to the present embodiment, the concentrated layer of In functions as a lubricating film, and excellent sliding characteristics are obtained. The In-concentrated layer preferably has a thickness of 3 nm or more, more preferably 5 nm or more.

The presence or absence and thickness of the In-concentrated layer can be measured by Auger electron spectroscopy. Specifically, by repeating elemental analysis while performing Ar sputtering from the surface of the steel material, the presence or absence and thickness of the In-enriched layer can be measured. The analysis depth is calculated based on the case where SiO ₂ is used as a standard sample.

[Oxide mainly composed of In]
When the sliding characteristics are secured by an oxide mainly composed of In, if the number density of particles of the oxide mainly composed of In having a diameter of 1 μm or more is set to 30 particles / mm ² or more, excellent sliding properties can be obtained for a long time. Characteristics are obtained. The number density of the oxide-based particles having a diameter of 1 μm or more is preferably 50 particles / mm ² or more, and more preferably 100 particles / mm ² or more.

Here, “an oxide mainly composed of In” means an oxide whose In content in cations is 50% or more in atomic%.

The number density of oxide particles mainly composed of In is measured as follows. After placing the mirror-polished sample in an Auger electron spectrometer (AES), Ar ion sputtering is performed on the sample surface. Then, the surface immediately after the sputtering is analyzed by a SEM-EDS apparatus. In-kα rays and O-kα rays are detected, and particles containing both In and oxygen are extracted by mapping image processing, and are defined as oxides mainly containing In. The above-described SEM-EDS analysis is performed at an observation magnification of 100 times, particles of oxides mainly composed of In having a circle equivalent diameter of 1 μm or more are counted, and the total number of the particles is defined as the number. The number of particles is divided by the area of the visual field to obtain a number density.

If a large amount of In is contained in steel, brittle fracture and intergranular corrosion may be caused. Therefore, it is desirable to increase the number density of the oxide particles while keeping the In content in the steel low. Specifically, it is preferable that the number density of the oxide satisfy the following expression (i) in relation to the In content. By performing the special heat treatment described below, the precipitation of the oxide is promoted, and the following formula (i) can be satisfied.
M> 80 × In (i)
Here, M in the above formula is the number density (particles / mm ² ) of oxide particles mainly containing In contained in the steel, and In is the content (% by mass) of In contained in the steel. is there.

[Method of manufacturing steel for sliding parts]
Hereinafter, an example of the method for manufacturing a steel material for a sliding component according to the present embodiment will be described. The manufacturing method described below is merely an example, and the manufacturing method of the steel material for a sliding component according to the present embodiment is not limited thereto.

In: After melting steel containing 0.05 to 5.0%, a material is manufactured by hot forging. The material may be subjected to hot working or cold working as necessary. When an oxide mainly containing In is dispersed, the In content of the material is preferably set to 0.3 to 5.0%.

Hereinafter, the case where the metal In particles are dispersed and the case where the oxide mainly containing In is dispersed will be described separately.

When dispersing the metal In particles, the material is subjected to a quenching treatment. As the quenching treatment, for example, heating at 800 to 1200 ° C. for 5 to 30 minutes, followed by water cooling or oil cooling.

数 The number density of the metal In particles tends to decrease as the holding temperature in the quenching process is increased or as the holding time is increased. Therefore, the holding temperature of the quenching treatment is preferably 1100 ° C. or lower, more preferably 1050 ° C. or lower. The holding time of the quenching treatment is preferably 20 minutes or less, and more preferably 15 minutes or less.

(4) After the quenching treatment, if necessary, a tempering treatment of heating at 150 to 650 ° C. for 5 to 60 minutes and then air cooling or water cooling may be performed. In the case of tempering, if the holding temperature of the tempering is too high, the holding time of the tempering is too long, or the temperature is gradually cooled (for example, furnace cooling) after the holding, the oxide In is formed by the supply of oxygen from the surface layer. The number density of metal In particles may decrease. The cooling rate at this time is preferably 1 ° C./sec or more. The holding temperature for tempering is preferably 500 ° C. or lower, more preferably 450 ° C. or lower. The holding time for tempering is preferably 30 minutes or less, and more preferably 20 minutes or less.

Also in the case of dispersing an oxide mainly composed of In, the material is first subjected to a quenching treatment. As the quenching treatment, for example, heating at 800 to 1200 ° C. for 5 to 30 minutes, followed by water cooling or oil cooling. The holding temperature of the quenching treatment is preferably 850 to 1050 ° C. The holding time of the quenching treatment is preferably 20 minutes or less, and more preferably 15 minutes or less.

In the case of dispersing an oxide mainly composed of 後 In, after quenching treatment, after heating at 150 to 650 ° C. for 5 to 60 minutes, heat treatment for furnace cooling is performed. Thereby, an oxide mainly composed of In is formed during cooling. The cooling rate at this time is preferably 2 ° C./min or less.

特殊 Further, in order to increase the number density of the precipitates, it is preferable to further perform a special heat treatment. In the special heat treatment, for example, a heat treatment of heating at 1000 to 1200 ° C. for 5 to 30 minutes and then slowly cooling at an average cooling rate of 300 ° C./h or less can be performed.

As described above, an example of the steel material for a sliding part and the method of manufacturing the same according to the embodiment of the present invention has been described. According to the present embodiment, a steel material for a sliding component having excellent seizure resistance can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to these examples.

[Example 1]
Steel having the chemical composition shown in Table 1 was melted. Steel types A to I in Table 1 are based on JIS G 4051 carbon steel S45C for machine structural use, with the addition amount of In and the like changed. The steel types J to S in Table 1 are obtained by changing the amount of In and the like based on the steel of the alloy steel for machine structure SMn438 according to JIS G 4052. In Table 1, "-" in the chemical composition indicates that the corresponding element is at an impurity level.

After heating each steel at 1200 ° C for 1 hour, hot forging was performed to produce a raw material. This material was heated at 1200 ° C. for 1 hour, and then hot-rolled at 950 ° C. to 1000 ° C. to be formed into a predetermined size. Thereafter, quenching and tempering were performed under the conditions shown in Table 2. Specifically, after performing a quenching treatment of holding at 1000 ° C. for 10 minutes and then cooling with water, a tempering treatment of heating at 400 ° C. for 15 minutes and air cooling was further performed to make the hardness about HV450. In addition, No. In Nos. 8 and 18, quenching was performed at 1200 ° C. for 20 minutes instead of 1000 ° C. for 10 minutes. In addition, No. Nos. 9 and 19 were held at 850 ° C. for 10 minutes instead of holding at 1000 ° C. for 10 minutes as a quenching treatment. Each of the obtained test materials had a martensite structure.

[Number density of metal In]
A test piece for observing a precipitate was collected from each test material, and the number density of metal In particles having a diameter of 50 nm to 5 μm was measured according to the method described in the embodiment.

[Hardness measurement]
From each test material, a test piece for hardness measurement having a surface perpendicular to the rolling direction as a measurement surface was collected. The Vickers hardness at four points was measured at 1 mm intervals along the thickness direction. Vickers hardness was measured according to JIS Z 2244 (2009). The test force was 300 gf (2.942 N). The average of the four points was taken as the hardness of the test material.

[Measurement of In concentrated layer]
A test piece for measuring the In-enriched layer was collected from each test material, and the thickness of the In-enriched layer was measured according to the method described in the embodiment. The Auger electron spectrometer used was SAM670 manufactured by ULVAC-PHI.

[Friction test]
A disc-shaped test piece having a diameter of 20 mm and a thickness of 3 mm was collected from each test material, and a ball-on-disk friction test was performed using this test piece. The tester used was a Tribometer manufactured by CSM Instruments.

(4) The surface of the test piece was roughly polished using # 800 abrasive grains, and was finally mirror-finished using 0.3 μm diamond slurry. The ball was made of alumina having a diameter of 6 mm, and the friction test was performed under the following conditions: load: 10 N, test temperature: room temperature, rotational diameter: 6 mm, friction speed: 10 mm / sec, friction time: 200 seconds, lubricant: none. Carried out. As the coefficient of friction, a value provided from software of the testing machine was used.

焼 Seizure resistance was evaluated from the “maximum coefficient of friction” obtained in the above test. “Maximum friction coefficient” means the maximum value of the friction coefficient from the start to the end of the friction (the sliding distance is 2.0 m). When the maximum coefficient of friction exceeded 0.5, seizure was observed in the observation of sliding traces after the test. On the other hand, when the maximum coefficient of friction was 0.5 or less, no seizure was observed in the observation of sliding traces after the test. Therefore, when the maximum friction coefficient was 0.5 or less, it was determined that the seizure resistance was excellent. FIG. 1 shows a test material having a maximum friction coefficient of more than 0.5 (No. 10 in Table 2) and a test material having a maximum friction coefficient of 0.5 or less (No. 15 in Table 2). 5 shows the change over time of the coefficient of friction.

時間 The time until the coefficient of friction exceeded 0.4 was evaluated as “duration”, and when the duration was 100 seconds or more, it was evaluated as having excellent durability.

Table 2 shows the heat treatment conditions and evaluation results for each test material. The numerical value in the column of “the number of metal In” is the number density of metal In particles having a diameter of 50 nm to 5 μm. The numerical value in the column of “In layer thickness” is the thickness of the In concentrated layer.

No. The test materials 3 to 7 and 12 to 17 have a chemical composition containing 0.05 to 5.0% In, a structure in which particles of metal In are dispersed, and have a diameter of 50 nm to 5 μm. The number density of the particles was 5000 / mm ² or more. These test materials had a maximum coefficient of friction of 0.5 or less and a duration of 100 seconds or more.

No. In the test materials of 1, 2, 8 to 11, 18 and 19, seizure was observed after the test. No. It is considered that the reason why seizure occurred in the test materials 1, 2, 10 and 11 was that the In content was small and the number density of the metal In particles was low. No. It is considered that the seizure occurred in the test materials Nos. 8 and 18 because the number density of the metal In particles was low. No. It is considered that seizure occurred in the test materials 9 and 19 because the In content was small.

[Example 2]
Next, the same evaluation was performed on the test material in which tempering after quenching was omitted.

The test material was produced in the same manner as in Example 1 except that tempering was omitted. As in Example 1, the number density, hardness, and In layer thickness of the metal In particles were measured. Each of the obtained test materials had a martensite structure.

[Friction test]
As a friction test, a friction test in a wet environment was performed instead of the friction test in the dry environment of Example 1. As in Example 1, a disc-shaped test piece having a diameter of 20 mm and a thickness of 3 mm was collected from each test material, and a ball-on-disk friction test was performed using the test piece. The tester used was a Tribometer manufactured by CSM Instruments.

(4) The surface of the test piece was roughly polished using # 800 abrasive grains, and was finally mirror-finished using 0.3 μm diamond slurry. The ball used was made of SUJ2 having a diameter of 6 mm, load: 10 N, test temperature: 140 ° C., rotational diameter: 6 mm, friction speed: 0.5 m / sec, friction time: 60 minutes, lubricant: 2 ml of engine oil A friction test was performed under the conditions. The engine oil used had a viscosity equivalent to 0 W-8 and contained an organic molybdenum complex, zinc dialkyldithiophosphate, and calcium sulfonate as additives. As the coefficient of friction, a value provided from software of the testing machine was used.

焼 Similar to Example 1, the seizure resistance was evaluated from the obtained “maximum coefficient of friction”. The “maximum friction coefficient” means the maximum value of the friction coefficient from the start to the end of the friction (sliding distance 1800 m). When the maximum coefficient of friction exceeded 0.5, seizure was observed in the observation of sliding traces after the test. On the other hand, when the maximum friction coefficient was 0.5 or less, no seizure was observed in the observation of the sliding traces after the test. Therefore, when the maximum friction coefficient was 0.5 or less, it was determined that the seizure resistance was excellent. FIG. 2 shows a test material having a maximum friction coefficient of more than 0.5 (No. 30 in Table 3) and a test material having a maximum friction coefficient of 0.5 or less (No. 35 in Table 3). 5 shows the change over time of the coefficient of friction.

時間 The time until the coefficient of friction exceeded 0.4 was evaluated as “duration”, and when the duration was 60 minutes or more, it was evaluated as having excellent durability.

Table 3 shows the processing conditions and evaluation results for each test material. The numerical value in the column of “the number of metal In” is the number density of metal In particles having a diameter of 50 nm to 5 μm. The numerical value in the column of “In layer thickness” is the thickness of the In concentrated layer.

No. The test materials 23 to 27 and 32 to 37 have a chemical composition containing 0.05 to 5.0% of In, a structure in which particles of metal In are dispersed, and have a diameter of 50 nm to 5 μm. The number density of the particles was 5000 / mm ² or more. These test materials had a maximum coefficient of friction of 0.5 or less and a duration of 60 minutes or more.

No. In the test materials 21, 22, 28 to 31, 38 and 39, seizure was observed after the test. No. It is considered that seizure occurred in the test materials 21, 22, 30, and 31 because the In content was small and the number density of the metal In particles was low. No. It is considered that seizure occurred in the test materials Nos. 28 and 38 because the number density of the metal In particles was low. No. It is considered that seizure occurred in the test materials Nos. 29 and 39 because the In content was small.

[Example 3]
Molten steel having the chemical composition shown in Table 4 was smelted by adding In to S45C steel, a carbon steel material for machine structure of JIS G 4051: 2016 standard (Test Nos. 1-1 to 1-7).

(5) Thereafter, hot forging was performed, followed by heating at 900 ° C. for 15 minutes, followed by quenching under the condition of water cooling. Further, after heating at 600 ° C. for 30 minutes, heat treatment was performed under the condition of furnace cooling to obtain test materials (Test Nos. 1-1, 1-3, 1-5 to 1-7). Test No. Samples 1-2 and 1-4 were further heated at 1100 ° C. for 10 minutes, and then subjected to a special heat treatment of slow cooling at an average cooling rate of 100 ° C./h to obtain test materials. According to observation with an optical microscope, the test material without special heat treatment had a martensite structure, and the test material after special heat treatment had a ferrite-pearlite structure.

Thereafter, a test piece for measuring precipitates was cut out from each test material, the surface was mirror-polished, and then placed in AES (SAM670 manufactured by ULVAC-PHI). Then, Ar ion sputtering was performed on the mirror-polished surface. Then, by analyzing the surface immediately after sputtering, an oxide mainly composed of In was specified, and its number density was determined.

Subsequently, an evaluation test for seizure resistance and abrasion resistance was performed using each test material. Specifically, the friction characteristics were evaluated by a ball-on-disk type friction test (CSM Instruments Tribometer). The test piece used for the abrasion test was a disk having a diameter of 15 mm and a thickness of 4 mm, and the evaluation surface was mirror-finished.

ボール Further, a friction test was performed using a ball made of alumina having a diameter of 6 mm, a load of 10 N, a test temperature of room temperature, a rotation diameter of 7 mm, a friction speed of 10 mm / sec, a friction time of 60 minutes, and no lubricant. As the coefficient of friction, a value provided from software of the testing machine was used.

In this example, the seizure resistance is evaluated based on the “maximum initial friction coefficient” obtained by the above test. In the present embodiment, the “maximum initial friction coefficient” means the maximum value of the friction coefficient from the start of friction until the sliding distance becomes 1.5 m.

焼 When the maximum initial coefficient of friction exceeds 0.5, seizure was observed in the observation of sliding traces after the test. On the other hand, when the maximum initial coefficient of friction was 0.5 or less, seizure was not observed in the observation of sliding traces after the test. Therefore, in this example, it was determined that the seizure resistance was excellent when the maximum initial friction coefficient was 0.5 or less.

Also, the width of the wear mark after the test was measured, and when it was 400 μm or less, it was judged that the wear resistance was excellent.

The results are summarized in Table 5.

から From Table 5, Test No. satisfying the requirements of the present invention. In the case of 1-1 to 1-4, the result was excellent in seizure resistance and wear resistance. On the other hand, Test Nos. In the cases of 1-5 to 1-7, both seizure resistance and abrasion resistance were inferior. In particular, the test No. In the cases of 1-2 and 1-4, the number density of the oxide particles mainly composed of In was high, and the above expression (i) was satisfied. And as a result, the test No. 2 having the same In content As a result, the sliding characteristics were extremely excellent as compared with 1-3 and 1-5, respectively.

[Example 4]
Molten steel having the chemical composition shown in Table 6 was smelted by adding In to a steel material with reference to the JIS G 4053: 2016 standard steel alloy material for machine structure, SMn438 steel (Test No. 2-1 to Test No. 2-1). 2-5).

(5) Thereafter, hot forging was performed, followed by heating at 900 ° C. for 15 minutes, followed by quenching under the condition of water cooling. Further, after heating at 600 ° C. for 30 minutes, heat treatment was performed under the condition of furnace cooling to obtain test materials (Test Nos. 2-1 and 2-4). Test No. 2-2, 2-3 and 2-5 were further heated at 1100 ° C. for 10 minutes, and then subjected to a special heat treatment of slow cooling at an average cooling rate of 100 ° C./h to obtain test materials. According to observation with an optical microscope, the test material without special heat treatment had a martensite structure, and the test material after special heat treatment had a ferrite-pearlite structure.

(4) Thereafter, in the same manner as in Example 3, the number density of oxide-based particles was measured, and an evaluation test for seizure resistance and abrasion resistance was performed.

７The results are summarized in Table 7.

から From Table 7, Test No. satisfying the requirements of the present invention. In the cases of 2-1 to 2-3, the results were excellent in seizure resistance and wear resistance. On the other hand, Test Nos. In Nos. 2-4 and 2-5, at least one of seizure resistance and abrasion resistance was inferior. In particular, the test No. In 2-2 and 2-3, the number density of the oxide-based oxide particles was increased, thereby satisfying the expression (i). And as a result, the test No. 2 having the same In content 2-1 and Test No. 2-2, the test No. satisfying the expression (i). 2-2 resulted in more excellent sliding characteristics.

[Example 5]
By adding In to SUJ2 steel, a high carbon chromium bearing steel of JIS G 4805: 2008 standard, molten steel having the chemical composition shown in Table 8 was produced (Test Nos. 3-1 to 3-4).

(5) Thereafter, hot forging was performed, followed by heating at 900 ° C. for 15 minutes, followed by quenching under oil cooling conditions. Further, after heating at 150 ° C. for 30 minutes, heat treatment was performed under conditions of furnace cooling to obtain test materials (Test Nos. 3-1 and 3-4). Test No. 3-2 and 3-3 were further heated at 1100 ° C. for 10 minutes, and then subjected to a special heat treatment of slow cooling at an average cooling rate of 100 ° C./h to obtain test materials.

９The results are summarized in Table 9.

から From Table 9, test Nos. In the cases of 3-1 to 3-3, the results were excellent in seizure resistance and wear resistance. On the other hand, Test Nos. In No. 3-4, both seizure resistance and abrasion resistance were inferior. In particular, the test No. In the cases of 3-2 and 3-3, the number density of the oxide mainly containing In was increased, and the above-mentioned formula (i) was satisfied. And as a result, the test No. 2 having the same In content 3-1 and Test No. 3-2, test No. 3 satisfying the expression (i). 3-2 resulted in more excellent sliding characteristics.

Although one embodiment of the present invention has been described above, the above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

According to the present invention, it is possible to obtain a steel material for sliding parts having excellent seizure resistance and sliding characteristics. Therefore, the steel material for sliding parts according to the present invention can be suitably used as a steel material for sliding parts used in transportation machines such as automobiles and ships, general industrial machines and the like.

Claims

A chemical composition containing, by mass%, In: 0.05-5.0%;
Having a structure in which metal In particles or In-based oxide particles are dispersed,
The number density of the particles having a diameter of 50 nm to 5 μm among the particles of the metal In is 5000 / mm 2 or more, or the number density of the particles having a diameter of 1 μm or more among the particles of the oxide mainly containing In is A steel material for a sliding part having 30 pieces / mm 2 or more.
It is a sliding part molten steel material of Claim 1, Comprising:
The chemical composition is in mass%,
C: 0.05 to 1.80%,
Si: 1.5% or less,
Mn: 2.0% or less,
P: 0.10% or less,
S: 0.10% or less,
Al: 0.10% or less,
N: 0.030% or less,
In: 0.05-5.0%,
Cr: 0 to 15.0%,
Ni: 0 to 0.50%,
Cu: 0 to 0.50%,
Ti: 0 to 0.050%,
Nb: 0 to 0.050%,
V: 0 to 2.5%,
Mo: 0 to 3.0%,
W: 0 to 6.0%,
B: 0 to 0.005%,
The balance: Fe and impurities, steel materials for sliding parts.
It is a steel material for sliding parts according to claim 1 or 2,
A steel material for sliding parts, wherein the number density of particles having a diameter of 50 nm to 5 μm among the particles of the metal In is 5000 / mm 2 or more.
It is a steel material for sliding parts according to claim 3,
A steel material for a sliding component having a concentrated In layer on the surface.
It is a manufacturing method of the steel material for sliding parts of Claim 3 or 4, Comprising:
Preparing a material having a chemical composition containing 0.05 to 5.0% by mass of In:
A step of heating the material at 800 to 1200 ° C. for 5 to 30 minutes, and then subjecting the material to quenching treatment with water cooling or oil cooling.
It is a manufacturing method of the steel material for sliding parts of Claim 5, Comprising:
A method for producing a steel material for a sliding part, further comprising a step of subjecting the quenched material to a tempering treatment of heating at 150 to 650 ° C. for 5 to 60 minutes and then air cooling or water cooling.
It is a manufacturing method of the steel material for sliding parts of Claim 5, Comprising:
A method for producing a steel material for a sliding part, wherein a tempering treatment is not performed after the quenching treatment.
It is a steel material for sliding parts according to claim 1 or 2,
The chemical composition has an In content of 0.3 to 5.0% by mass,
A steel material for sliding parts, wherein the number density of particles having a diameter of 1 μm or more among the oxide particles mainly containing In is 30 particles / mm 2 or more.
It is a steel material for sliding parts according to claim 8,
A steel material for a sliding part, wherein the number density of particles having a diameter of 1 μm or more among the particles of the oxide mainly containing In satisfies the following expression (i).
M> 80 × In (i)
Here, M in the above formula is the number density (particles / mm 2 ) of particles having a diameter of 1 μm or more among the oxide particles mainly containing In, and In is the content (mass) of In contained in the steel. %).
It is a manufacturing method of the steel material for sliding parts of Claim 8 or 9, Comprising:
Preparing a material having a chemical composition containing 0.3 to 5.0% by mass of In:
Heating the material at 800 to 1200 ° C. for 5 to 30 minutes, and then subjecting the material to a quenching treatment with water cooling or oil cooling;
Heating the quenched material at 150 to 650 ° C. for 5 to 60 minutes, and then subjecting the material to furnace cooling.
It is a manufacturing method of the steel material for sliding parts of Claim 10, Comprising:
A method for producing a steel material for a sliding part, further comprising a step of heating the tempered material at 1000 to 1200 ° C. for 5 to 30 minutes and then cooling it at an average cooling rate of 300 ° C./h or less.