JP2013194292A - Bearing washer, thrust needle roller bearing, and methods of manufacturing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing washer that ensures excellent durability and reduces manufacturing cost, and to provide a thrust needle roller bearing and methods of manufacturing them.SOLUTION: A bearing washer 11 with a thickness of 2 mm or less for a thrust needle roller bearing 1 is made of steel that contains ≥0.60 and ≤0.90 mass% of carbon, ≥0.15 and ≤0.35 mass% of silicon, ≥0.10 and ≤1.10 mass% manganese, and iron and impurities as a remainder and is quenched, and the hardness of a raceway 11A is 700 HV or more and the total warpage is within 120% of the thickness.

Description

  The present invention relates to a washer, a thrust needle roller bearing, and a manufacturing method thereof, and more specifically, a washer, a thrust needle roller bearing, and a method for reducing the manufacturing cost while ensuring excellent durability. It is to provide a manufacturing method.

  In recent years, with the rise of emerging countries, machine products such as automobiles have to be further improved in price competitiveness. For this reason, a reduction in manufacturing cost is required for bearings widely used as mechanical parts. In particular, thrust needle bearings used in automobile ATs (automatic transmissions) have a large number of units used per unit, and there is a strong demand for cost reduction. There is also a demand for a longer bearing life as well as a reduction in manufacturing costs. In order to reduce the cost of the current product, it is conceivable to reduce the material cost by adopting a material such as an inexpensive low alloy steel, or reduce the heat treatment cost by improving the heat treatment method.

  As a material for the washer of the thrust needle bearing, steel plates of mechanical structure alloy steel (JIS standard SCr material, SCM material, SNCM material), which is mainly low carbon steel, are often used. After this steel plate is formed, a shallow carburizing process is performed, the surface hardness is adjusted to 58 HRC or more, and the bearing disc is manufactured. The alloy steel for machine structure contains Cr, Mo, Ni, etc. in the steel, and has higher hardenability than carbon steel for machine structure (JIS standard SC material). If a steel material with high hardenability is used, the cooling rate during quenching can be reduced, so that deformation due to thermal stress can be suppressed. Further, in the microstructure of the low carbon steel, the amount of pearlite structure is small and there is no precipitation of proeutectoid cementite. Therefore, the material hardness can be suppressed by adopting a material made of a low carbon alloy steel for machine structural use. As a result, since the workability when producing a washer from a steel plate by pressing is excellent, the wear of the mold can be reduced.

  On the other hand, due to Cr, Mo, and Ni contained in the steel, the mechanical structural alloy steel has a higher material price than the mechanical structural carbon steel. In particular, since Ni and Mo have high raw material prices, SCM materials and SNCM materials are more expensive materials than bearing steel (JIS standard SUJ material). Furthermore, in recent years, prices and availability of rare metals such as Cr, Ni, and Mo have become unstable due to resource depletion and political export restrictions. For this reason, steel materials that do not contain rare metals are desired. Also, the bearing life tends to be better when the surface hardness is higher. Since the conventional product has a low carbon content of 0.1 to 0.3% by mass, for example, when increasing the carbon concentration of the surface layer to 0.8% by mass for the purpose of ensuring high surface hardness, it is compared with sub-quenching. Processing time is several times longer.

  In order to cope with such a problem, selection of high carbon steel as a raw material can also be considered. For example, carbon tool steel (JIS standard SK material) and carbon steel for machine structure are considered as material candidates from the viewpoint of securing availability in various countries around the world. Since these steel materials are not added with Cr, Mo and Ni, the material price is cheaper than SCM materials and SNCM materials. In addition, if the carbon concentration in the base material is high, the carburization time can be shortened even when the carbon concentration in the surface layer portion is increased, so that the heat treatment cost can be reduced. Furthermore, expectation of sufficient solid solution carbon and precipitation strengthening by carbides, it can be expected to improve the bearing life compared to conventional carburized steel.

  Further, since the washer of the thrust needle bearing is thin, heat treatment deformation such as warpage is likely to occur during quenching. Since warpage causes rotational vibration, it needs to be reduced. In order to cope with this, warping may be performed during tempering. However, the correction process for correcting the warpage takes time and causes an increase in manufacturing cost. Also, when SC material or SK material with high carbon concentration inside is selected as the material, the entire washer transforms into high carbon martensite, so the amount of deformation is large compared to carburized steel such as SCr material and SCM material. Become.

  Under such circumstances, many studies have been made on suppressing heat treatment deformation such as warping, and various countermeasures have been proposed (see, for example, Patent Documents 1 and 2).

JP-A-2-240249 International Publication No. 2003/056054

  However, the techniques disclosed in Patent Documents 1 and 2 are based on the premise that low-carbon steel is adopted, and in order to ensure the surface hardness necessary as a washer, a long-time carburizing process or the like is required. Necessary. As a result, it is difficult to reduce manufacturing costs. As a method for directly suppressing deformation during quenching, there is press quenching. Specifically, for example, a press hardening method in which an object to be processed is immersed in a coolant while being constrained by a mold has been proposed. However, in such a method, since the number of sheets that can be quenched at one time cannot be increased, the productivity is poor and it is difficult to reduce the manufacturing cost.

  The present invention has been made in view of the above-described problems, and its object is to provide a bearing disc, thrust needle roller bearing (JIS standard) capable of reducing the manufacturing cost while ensuring excellent durability. B0104) and their manufacturing methods.

  The washer according to the first aspect of the present invention is a washer of a thrust needle roller bearing having a thickness of 2 mm or less. This washer is composed of 0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.10% by mass or more and 1.10% by mass or less. It consists of quench-hardened steel containing manganese and the balance iron and impurities. And the hardness of a rolling surface is 700HV or more, and total curvature is less than 120% of thickness.

  Further, the washer according to the second aspect of the present invention is a washer of a thrust needle roller bearing having a thickness of 2 mm or less. This washer is composed of 0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.10% by mass or more and 1.10% by mass or less. It consists of quench-hardened steel containing manganese and 0.0010 mass% or more and 0.0100 mass% or less of boron, and the balance iron and impurities. And the hardness of a rolling surface is 700HV or more, and total curvature is less than 120% of thickness.

  Moreover, the washer in the third aspect of the present invention is a washer of a thrust needle roller bearing having a thickness of 2 mm or less. This washer is composed of 0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.10% by mass or more and 1.10% by mass or less. Quenched and hardened steel containing manganese, 0.0010 mass% to 0.0100 mass% boron, and 0.01 mass% to 0.05 mass% titanium, the balance being iron and impurities It is made up of. And the hardness of a rolling surface is 700HV or more, and total curvature is less than 120% of thickness.

  The washer according to the present invention is made of steel that does not contain rare metal elements such as Cr, Mo, and Ni. As a result, the material cost is reduced and the availability of the material is improved. Moreover, since the hardness of a rolling surface is set to 700 HV or more, it is possible to ensure a sufficient rolling fatigue life. Furthermore, since the total warpage is suppressed within 120% of the thickness, the rotational vibration of the bearing is suppressed, and the durability is improved and the noise is reduced.

  Furthermore, in the washer in the second aspect, 0.0010% by mass or more and 0.0100% by mass or less of boron is further added to the steel constituting the washer in the first aspect. Boron is an element that greatly improves the hardenability with a small addition amount. When hardenability becomes inadequate by not containing the said rare metal element, required hardenability can be ensured, suppressing material cost by adding boron.

  Furthermore, in the washer in the third aspect, 0.01 mass% or more and 0.05 mass% or less of titanium is further added to the steel constituting the washer in the second aspect. When boron is added to the steel, the boron combines with nitrogen in the steel to form a nitride. Thus, boron which became nitride does not contribute to improvement of hardenability. On the other hand, nitrogen in the steel is fixed as titanium nitride by adding titanium that is more reactive with nitrogen than boron, and the effect of improving the hardenability by boron can be reliably obtained.

  Thus, according to the washer of the present invention, it is possible to provide a washer capable of reducing the manufacturing cost while ensuring excellent durability. In the manufacture of a thrust needle bearing washer, the processing step is about the press-out of the steel plate and the removal of the black skin after the heat treatment, and the material cost and the heat treatment cost account for about half or more of the production cost. Therefore, reduction of material cost and heat treatment cost greatly contributes to reduction of manufacturing cost.

  The total warpage is the smallest slit width value that can be passed through the washer when the washer is passed through the slit gauge.

  Moreover, the reason which limited the component composition of the steel which comprises the said washer to the said range is as follows.

Carbon: 0.60% by mass or more and 0.90% by mass or less From the viewpoint of securing a sufficient rolling fatigue life, it is preferable to impart a high hardness, for example, a hardness of about 60 HRC or more, to the rolling surface of the washer. The hardness of the quench-hardened steel increases as the carbon content increases, but saturates at 0.60% by mass or more. Therefore, the carbon content is 0.60% by mass or more. Moreover, when carburizing, the carburizing time can be shortened by setting the carbon content to 0.60% by mass or more. On the other hand, if the amount of carbon exceeds 0.9% by mass, the hardness of the material increases, and there is a risk that the processing cost will increase due to the occurrence of cracks at the time of forming the collar portion and wear of the press die. Therefore, the carbon content is set to 0.90% by mass or less.

Silicon: 0.15 mass% or more and 0.35 mass% or less Silicon contributes to the improvement of temper softening resistance. When the silicon content is less than 0.15% by mass, it is difficult to sufficiently secure the function. On the other hand, when silicon is added exceeding 0.35 mass%, workability, such as forgeability, will fall. Therefore, the silicon content is 0.15% by mass or more and 0.35% by mass or less.

Manganese: 0.10 mass% or more and 1.10 mass% or less Manganese contributes to improvement of hardenability. When the manganese content is less than 0.10% by mass, it is difficult to sufficiently secure the function. On the other hand, when manganese is added in excess of 1.10% by mass, a large amount of MnS (manganese sulfide), which is a non-metallic inclusion, is formed in the steel, which may adversely affect the rolling fatigue life. Therefore, manganese content shall be 0.10 mass% or more and 1.10 mass% or less.

Boron: 0.0010% by mass or more and 0.0100% by mass or less Boron clearly contributes to improving hardenability even when added in a small amount of 0.0010% by mass. On the other hand, even if boron is added over 0.0100 mass%, the above effect is saturated. Therefore, boron can be added in the range of 0.0010% by mass or more and 0.0100% by mass or less as necessary. Moreover, by adding 0.0020% by mass or more of boron, hardenability equivalent to or higher than that of SUJ2 which is a high carbon chromium bearing steel can be secured.

Titanium: 0.01% by mass or more and 0.05% by mass or less As described above, the added boron reacts with nitrogen to form BN (boron nitride). If it does so, the solid solution amount of the boron in a base material will reduce, and the improvement effect of the hardenability by boron addition will fall. On the other hand, by adding titanium having a higher reactivity with nitrogen than boron, nitrogen in the steel can be consumed, and the solid solution amount of boron in the base material can be increased. When the addition amount of titanium is less than 0.01% by mass, the above effect is not sufficiently exhibited. On the other hand, it is not necessary to add more than 0.05% by mass of titanium because of the relationship with the amount of nitrogen in general steel. Therefore, titanium can be added in a range of 0.01% by mass to 0.05% by mass as necessary. In addition, TiN (titanium nitride) formed by adding titanium does not dissolve in the base metal even at high temperatures, so it exerts a pinning effect and contributes to the refinement of steel crystal grains, and It can also contribute to the improvement of dynamic fatigue life.

  The washer may have a washer type shape. A washer having a washer-type shape (a flat plate shape having no collar) is particularly susceptible to rotational vibration due to warping. Therefore, it is appropriate to use the washer of the present invention that can reduce rotational vibration for the washer having the washer type shape.

  In the above washer, a carbon-enriched layer having a carbon concentration higher than the inside and having a carbon concentration of 0.8% by mass or more and 1.2% by mass or less may be formed in a region including the rolling surface. .

  By increasing the carbon concentration of the rolling contact surface, carbide (for example, cementite) can be formed on the rolling contact surface. The carbide has an effect of preventing the coarsening of crystal grains, and can also be expected to improve the wear resistance by precipitation strengthening. In order to obtain such an effect by the carbide, it is preferable to form a carbon enriched layer of 0.8% by mass or more. On the other hand, in order to increase the carbon concentration beyond 1.2% by mass, a treatment at a higher concentration than the general carburizing treatment is required, which causes an increase in manufacturing cost.

  In the above washer, a nitrogen-enriched layer having a nitrogen concentration higher than the inside and having a nitrogen concentration of 0.05% by mass or more and 0.5% by mass or less may be formed in a region including the rolling surface. .

  By forming the nitrogen-enriched layer on the rolling surface, the rolling fatigue life of the bearing disc can be extended. When the nitrogen concentration of the nitrogen-enriched layer is less than 0.05% by mass, the effect cannot be obtained sufficiently. On the other hand, if the nitrogen concentration exceeds 0.5 mass%, vacancies are generated in the nitrogen-enriched layer, which may cause a decrease in strength of the base material.

  A thrust needle roller bearing according to the present invention includes a raceway disk and a plurality of needle rollers arranged in contact with a rolling surface of the raceway disk. The washer is the washer of the present invention. By including the raceway of the present invention, according to the thrust needle roller bearing of the present invention, it is possible to provide a thrust needle roller bearing capable of reducing manufacturing costs while ensuring excellent durability. .

A method for manufacturing a washer according to the first aspect of the present invention is a method for producing a washer for a thrust needle roller bearing. The method of manufacturing this washer includes 0.60% by mass to 0.90% by mass of carbon, 0.15% by mass to 0.35% by mass of silicon, and 0.10% by mass to 1.10% by mass. And a step of preparing a molded body that is made of steel containing iron and impurities, and that is formed of the balance iron and impurities, and formed into a shape corresponding to the shape of the washer, and a step of quenching and hardening the molded body ing. Then, in the step of quenching and hardening the formed body, the formed body is quenched and hardened by immersing the formed body heated to a temperature of _one point A or more in a cooling liquid of 200 ° C. or higher and 220 ° C. or lower.

A method for manufacturing a washer according to the second aspect of the present invention is a method for producing a washer for a thrust needle roller bearing. The method of manufacturing this washer includes 0.60% by mass to 0.90% by mass of carbon, 0.15% by mass to 0.35% by mass of silicon, and 0.10% by mass to 1.10% by mass. % Of manganese and 0.0010% by mass or more and 0.0100% by mass or less of boron, made of steel consisting of the remaining iron and impurities, and formed into a shape corresponding to the shape of the washer A step of preparing and a step of quenching and hardening the molded body. Then, in the step of quenching and hardening the formed body, the formed body is quenched and hardened by immersing the formed body heated to a temperature of _one point A or more in a cooling liquid of 200 ° C. or higher and 220 ° C. or lower.

A method for manufacturing a washer according to the third aspect of the present invention is a method for manufacturing a washer for a thrust needle roller bearing. The method of manufacturing this washer includes 0.60% by mass to 0.90% by mass of carbon, 0.15% by mass to 0.35% by mass of silicon, and 0.10% by mass to 1.10% by mass. % Of manganese, 0.0010 mass% or more and 0.0100 mass% or less of boron, and 0.01 mass% or more and 0.05 mass% or less of titanium, and the balance iron and impurities. And a step of preparing a molded body formed into a shape corresponding to the shape of the washer and a step of quenching and hardening the molded body. Then, in the step of quenching and hardening the formed body, the formed body is quenched and hardened by immersing the formed body heated to a temperature of _one point A or more in a cooling liquid of 200 ° C. or higher and 220 ° C. or lower.

  In the above-described method for manufacturing a washer according to the present invention, a molded body made of steel having an appropriate composition described above is immersed in a coolant and quenched and hardened from the viewpoints of material cost reduction and durability. At this time, by setting the temperature of the coolant to 200 ° C. or higher and 220 ° C. or lower, generation of warpage during quenching is suppressed, and rotational vibration is reduced. As described above, according to the method for manufacturing a washer according to the present invention, it is possible to reduce the manufacturing cost while ensuring excellent durability.

A method for manufacturing a washer according to the fourth aspect of the present invention is a method for producing a washer for a thrust needle roller bearing. The method of manufacturing this washer includes 0.60% by mass to 0.90% by mass of carbon, 0.15% by mass to 0.35% by mass of silicon, and 0.10% by mass to 1.10% by mass. And a step of preparing a molded body that is made of steel containing iron and impurities, and that is formed of the balance iron and impurities, and formed into a shape corresponding to the shape of the washer, and a step of quenching and hardening the molded body ing. Then, the step of quench-hardening the molded body, immersing the molded body is heated to a temperature not lower than A ₁ point of the steel, the cooling liquid which is maintained at a temperature of more than Mf point or less Ms point of the steel Then, the step of cooling until the temperature of the molded body and the temperature of the cooling liquid become uniform, and the step of further air-cooling or gas-cooling the molded body cooled to a temperature below the Ms point and above the Mf point to room temperature Including.

  In the above-described method for manufacturing a washer according to the present invention, a molded body made of steel having an appropriate composition described above is immersed in a coolant and quenched and hardened from the viewpoints of material cost reduction and durability. At this time, the molded body is first immersed in a cooling liquid maintained at a temperature equal to or lower than the Ms point and equal to or higher than the Mf point, and cooled until the temperature of the molded body and the temperature of the cooling liquid become uniform. Thereby, the steel which comprises a molded object will be in the state which started the martensitic transformation and the martensitic transformation stopped, and the martensitic transformation will advance further irrespective of a cooling rate by further cooling. Thereafter, the molded body is further air-cooled or gas-cooled to room temperature, whereby martensitic transformation proceeds. Here, by advancing martensite transformation by air cooling or gas cooling with a slow cooling rate, the cooling rate distribution in the molded body becomes uniform, the occurrence of warp accompanying quench hardening is suppressed, and rotational vibration is reduced. As described above, according to the method for manufacturing a washer according to the present invention, it is possible to reduce the manufacturing cost while ensuring excellent durability. From the viewpoint of further reducing the warpage of the washer, it is preferable that the ratio of martensitic transformation by air cooling or gas cooling is large in the martensitic transformation in quench hardening. Therefore, the holding temperature of the coolant is preferably close to the Ms point of the steel, and specifically, the difference from the Ms point is preferably 30 ° C. or less.

A method for manufacturing a washer according to the fifth aspect of the present invention is a method for producing a washer for a thrust needle roller bearing. The method of manufacturing this washer includes 0.60% by mass to 0.90% by mass of carbon, 0.15% by mass to 0.35% by mass of silicon, and 0.10% by mass to 1.10% by mass. % Of manganese and 0.0010% by mass or more and 0.0100% by mass or less of boron, made of steel consisting of the remaining iron and impurities, and formed into a shape corresponding to the shape of the washer A step of preparing and a step of quenching and hardening the molded body. In the step of quenching and hardening the formed body, the formed body heated to a temperature of _one point A or more of steel is brought into contact with a cooling gas of 0.5 MPa or more and less than 1.0 MPa to quench and harden the formed body. To do.

A method for manufacturing a washer according to the sixth aspect of the present invention is a method for producing a washer for a thrust needle roller bearing. The method of manufacturing this washer includes 0.60% by mass to 0.90% by mass of carbon, 0.15% by mass to 0.35% by mass of silicon, and 0.10% by mass to 1.10% by mass. % Of manganese, 0.0010 mass% or more and 0.0100 mass% or less of boron, and 0.01 mass% or more and 0.05 mass% or less of titanium, and the balance iron and impurities. And a step of preparing a molded body formed into a shape corresponding to the shape of the washer and a step of quenching and hardening the molded body. In the step of quenching and hardening the formed body, the formed body heated to a temperature of _one point A or more of steel is brought into contact with a cooling gas of 0.5 MPa or more and less than 1.0 MPa to quench and harden the formed body. To do.

In the above-described method for manufacturing a washer according to the present invention, a molded body made of steel having the above-mentioned component composition appropriate from the viewpoint of material cost reduction and durability is cooled from a temperature of _one point A or more and hardened by hardening. At this time, hardenability is improved by adding an appropriate amount of boron to the steel constituting the compact. Therefore, quenching by high-pressure gas cooling, which has a cooling capacity smaller than that of a coolant such as oil, is possible. And by implementing the high pressure gas cooling by the cooling gas of the said suitable pressure range, quench hardening can be achieved, suppressing the cooling rate distribution in a molded object. As a result, the occurrence of warpage during quenching is suppressed, and rotational vibration is reduced. In addition, high-pressure gas cooling does not require the use of quenching oil, so that the oil washing process can be omitted and the work environment can be improved. As described above, according to the method for manufacturing a washer according to the present invention, it is possible to reduce the manufacturing cost while ensuring excellent durability. In addition, as cooling gas, gas, such as nitrogen and helium, is employable, for example.

  In the method of manufacturing the bearing disc, the warping of the molded body may not be corrected in a process after the process of quenching and curing the molded body. As described above, according to the method for manufacturing a washer according to the present invention, occurrence of warpage is suppressed. Therefore, the manufacturing cost can be reduced by not performing the warp correction step.

  A method of manufacturing a thrust needle roller bearing according to the present invention includes a step of preparing a washer, a step of preparing a plurality of needle rollers, and a plurality of needle rollers so as to come into contact with the washer. And assembling the roller bearing. And the process of preparing a washer is implemented using the manufacturing method of the washer of the said invention.

  By producing a washer using the method for producing a washer according to the present invention, the thrust needle roller bearing according to the present invention can be manufactured with reduced durability while ensuring excellent durability. Is possible.

Incidentally, the present specification, claims, abstract, in the drawings, the _point A is the temperature at which the steel corresponding to the temperature for starting the austenite transformation at the time of raising the temperature of the steel. The Ms point is a temperature corresponding to a temperature at which the steel starts martensitic transformation when the steel is cooled. The Mf point is a temperature corresponding to the temperature at which the martensitic transformation of the steel is completed when the steel is cooled. Further, as the steel satisfying the above component range, for example, a JIS standard SC material or SK material, or a material obtained by adding boron or boron and titanium to these can be employed.

  As is clear from the above description, according to the raceway disk, thrust needle roller bearing and the manufacturing method thereof according to the present invention, the raceway disk and thrust needle capable of reducing the manufacturing cost while ensuring excellent durability. A roller bearing and a manufacturing method thereof can be provided.

It is a schematic sectional drawing which shows the structure of a thrust needle roller bearing. It is the general | schematic fragmentary sectional view which expanded and showed the washer of FIG. It is a flowchart which shows the outline of the manufacturing method of a thrust needle roller bearing. It is a flowchart which shows another example of the manufacturing method of a thrust needle roller bearing. It is a figure which shows the relationship between quenching oil temperature and total curvature. It is a figure which shows the result of a life test.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
Hereinafter, Embodiment 1 which is one embodiment of the present invention will be described. Referring to FIG. 1, a thrust needle roller bearing 1 has a disk-like shape, a pair of washer-type bearings 11 arranged so that one main surface faces each other, and a plurality of rolling elements as rolling elements. Needle roller 13 and annular retainer 14 are provided. The plurality of needle rollers 13 are in contact with and held on a rolling surface 11A formed on one main surface of the pair of raceways 11 facing each other on a roller rolling contact surface 13A that is an outer peripheral surface of the needle roller 13. By being arranged at a predetermined pitch in the circumferential direction by the vessel 14, it is held so as to be able to roll on an annular track. With the above configuration, the pair of washer disks 11 of the thrust needle roller bearing 1 can be rotated relative to each other.

  Referring to FIG. 2, the washer 11 has a carbon of 0.60 mass% or more and 0.90 mass% or less, silicon of 0.15 mass% or more and 0.35 mass% or less, and 0.10 mass% or more. 1. It is made of a hardened and hardened steel containing not more than 10% by mass of manganese and comprising the balance iron and impurities. And the hardness of 11 A of rolling surfaces is 700 HV or more, and total curvature is less than 120% of thickness.

  The washer 11 in the present embodiment is made of steel that does not contain rare metal elements such as Cr, Mo, and Ni. Therefore, the material cost is reduced, and the stable acquisition of the material is easy. Moreover, since the hardness of 11 A of rolling surfaces is 700 HV or more, it is possible to ensure sufficient rolling fatigue life. Furthermore, since the total warpage is suppressed within 120% of the thickness, the rotational vibration of the thrust needle roller bearing 1 is suppressed, and the durability is improved and the noise is reduced. Thus, according to the washer disk 11 and the thrust needle roller bearing 1 in the present embodiment, the manufacturing cost can be reduced while ensuring excellent durability.

  Here, 0.0010% by mass or more and 0.0100% by mass or less of boron may be added to the steel constituting the washer 11. Thereby, it becomes easy to ensure the necessary hardenability while suppressing the material cost. Moreover, when boron is added to the steel constituting the bearing disc 11, 0.01 mass% or more and 0.05 mass% or less of titanium may be further added to the steel. Thereby, nitrogen in steel can be fixed as titanium nitride, and the effect of improving the hardenability by boron can be reliably obtained.

  Furthermore, the washer disk 11 in the present embodiment has a carbon concentration higher in the region including the rolling surface 11A than in the interior 11C and having a carbon concentration of 0.8 mass% or more and 1.2 mass% or less. It has the strengthening process layer 11B which is a formation layer. The formation of this strengthening treatment layer 11B is not essential in the present invention, but by forming this, it is possible to expect the effect of preventing coarsening of crystal grains, the effect of improving wear resistance by precipitation strengthening, and the like. Further, the strengthened layer 11B may be a nitrogen-enriched layer having a nitrogen concentration higher than that inside and having a nitrogen concentration of 0.05% by mass or more and 0.5% by mass or less. Thereby, the durability of the washer 11 can be further improved. Note that the strengthening treatment layer 11B may be a layer having only one of the carbon concentration and the nitrogen concentration higher than the inner 11C, or may be a layer having both a carbon concentration and a nitrogen concentration higher.

  Next, a method for manufacturing the washer and the thrust needle roller bearing in the present embodiment will be described. With reference to FIG. 3, a steel material preparation process is first implemented as process (S10). In this step (S10), 0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.10% by mass or more and 1.10% by mass or less. A steel material containing the following manganese and comprising the remaining iron and impurities, for example, a SK material that is a JIS standard carbon tool steel (JIS G4401) or a steel material made of carbon steel for mechanical structure (JIS G4051) is prepared. Specifically, for example, a steel plate having the above component composition is prepared. Moreover, 0.0010 mass% or more and 0.0100 mass% or less of boron may be added to the said steel material. Furthermore, when boron is added, 0.01 mass% or more and 0.05 mass% or less of titanium may be added to the said steel material.

  Next, a forming step is performed as a step (S20). In this step (S20), for example, by performing press punching on the steel plate prepared in step (S10), a formed body formed into the shape of the washer 11 shown in FIGS. Produced.

  Next, a strengthening process layer formation process is implemented as process (S30). In this step (S30), carburizing treatment or carbonitriding treatment is performed on the molded body produced in step (S20).

Next, a quench hardening process is implemented as process (S40). In this step (S40), the molded body on which the strengthened layer is formed in step (S30) is cooled to a cooling liquid (for example, a firing temperature of 200 ° C. or higher and 220 ° C. or lower from a predetermined quenching temperature (A temperature of _one point or higher). It is quenched and hardened by being immersed in the oil). In addition, quenching temperature can be 800 degreeC or more and 850 degrees C or less, for example. Moreover, the temperature of the quenching oil used when quenching and hardening a bearing component made of JIS standard SUJ2 used as a material in a general rolling bearing is usually about 90 to 100 ° C. That is, in the present embodiment, a coolant having a temperature considerably higher than usual is used.

  Next, a tempering step is performed as a step (S50). In this step (S50), the molded body that has been quenched in the step (S40) is tempered. Specifically, for example, the tempering treatment is performed by holding the molded body for 2 hours or more and 4 hours or less in an atmosphere heated to a temperature range of 160 ° C. or more and 200 ° C. or less.

  Next, a finishing process is performed as a process (S60). In this step (S60), the molded body that has been tempered and heat-treated in step (S50) is processed. Specifically, the bearing disc 11 is completed by removing the black skin from the molded body that has been heat-treated.

  Furthermore, an assembly process is performed as a process (S70). In this step (S70), the bearing disc 11 produced in the steps (S10) to (S60), the separately prepared needle roller 13, the cage 14 and the like are combined, and the thrust needle roller in the above embodiment is combined. The bearing 1 is assembled. Thereby, the manufacturing method of the thrust needle roller bearing in the present embodiment is completed.

Here, in a process (S30), the molded object heated by the quenching temperature which is the temperature of ₁ point or more of steel A which comprises a molded object is immersed in the cooling fluid of 200 to 220 degreeC. Quench hardening. Thereby, generation | occurrence | production of the curvature at the time of hardening is suppressed and the rotational vibration of the thrust needle roller bearing 1 finally obtained is reduced.

  Further, in the method for manufacturing a washer according to the present embodiment, since the occurrence of warpage during quenching in step (S30) is suppressed as described above, the warpage of the molded body is not corrected in the subsequent steps. . Further, in the method for manufacturing a washer according to the present embodiment, it is not necessary to adopt a measure for physically reducing the warpage during quenching, such as restraint quenching, even in the step (S30).

  Moreover, when the steel material to which 0.0010 mass% or more and 0.0100 mass% or less boron was added in a process (S10) is prepared, it is based on the cooling liquid in a process (S40) using the high hardenability. Instead of cooling, the molded body may be quenched and hardened by contacting the molded body with a cooling gas (for example, high-pressure nitrogen gas) of 0.5 MPa or more and less than 1.0 MPa.

(Embodiment 2)
Next, as a second embodiment which is another embodiment of the present invention, another manufacturing method of a bearing disc and a thrust needle roller bearing will be described. Referring to FIGS. 4 and 3, the method of manufacturing the washer and the thrust needle roller bearing in the second embodiment is basically performed in the same manner as in the first embodiment. However, in the quench hardening process, the manufacturing method of the second embodiment is different from the case of the first embodiment.

  Referring to FIG. 4, in the method of manufacturing the washer and the thrust needle roller bearing in the second embodiment, first, steps (S10) to (S30) are performed in the same manner as in the first embodiment.

Next, a 1st hardening hardening process is implemented as process (S41). In this step (S41), the molded body heated to a temperature of ₁ point or more of steel A is immersed in a coolant that is below the Ms point of steel and maintained at a temperature of the Mf point or more. And the cooling liquid is cooled until the temperature becomes uniform. More specifically, for example, the molded body is immersed in a salt held at a temperature just below the Ms point of steel, and cooled until the temperature of the molded body is lowered to the holding temperature of the salt. Thereby, the martensitic transformation of the steel constituting the formed body is started and stopped immediately after the start. As the martensitic transformation starts in this way, the pearlite transformation is no longer initiated, and the martensitic transformation is advanced only by lowering the temperature of the compact regardless of the cooling rate.

  Next, a 2nd hardening hardening process is implemented as process (S42). In this step (S42), the molded body cooled to the temperature of the cooling liquid in step (S41) is further air-cooled or gas-cooled to room temperature. Specifically, for example, the molded body cooled to the salt holding temperature is taken out from the salt bath, allowed to cool in air, and cooled to room temperature. Thereby, martensitic transformation advances and the hardening hardening process of a molded object is completed.

  Thereafter, steps (S50) to (S70) are carried out in the same manner as in the first embodiment, thereby completing the washer 11 and the thrust needle roller bearing 1, and the washer and the thrust needle roller bearing in the second embodiment. The manufacturing method is completed.

  In the method of manufacturing the washer according to the second embodiment, the martensitic transformation can be advanced by air cooling or gas cooling with a slow cooling rate in the step (S42). Therefore, the cooling rate distribution in the molded body becomes uniform, and the occurrence of warpage due to quench hardening is suppressed.

  An experiment was conducted to investigate the temperature range of the coolant necessary to reduce the total warpage of the washer to an appropriate range. The experimental procedure is as follows.

  First, the steel grade No. corresponding to the Example of this invention which has a component composition shown in Table 1. 1-3 steel plates were prepared. No. For 1 and 2, rare metals such as Cr, Ni, and Mo are not intentionally added. No. As for No. 3, Cr, Ni, and Mo are not added, but boron is added. Moreover, the steel plate which has the component composition conventionally used as a raw material of a washer as a comparative example was also prepared.

  Of these steel plates, No. The steel plates 1 and 2 (thickness 1 mm) were punched out with a press die to produce a compact having a shape corresponding to a washer-type washer. The shape of the molded body (test piece) is an inner diameter of 55 mm, an outer diameter of 79 mm, and a thickness of 1 mm.

  Thereafter, 30 test pieces were heat-treated simultaneously with 40 dummy test pieces (inner diameter φ55 mm, outer diameter φ77 mm, thickness 1 mm). The heat treatment was held for 35 minutes in an atmosphere of 820 ° C. maintained at a carbon potential (CP) value of 1.0 to 1.1 with the test pieces arranged on the hooks, and then quenched oil (stirring) And so on) and immersed for 5 minutes. The temperature of the quenching oil was set to seven levels of 60 ° C., 90 ° C., 120 ° C., 150 ° C., 180 ° C., 200 ° C., and 230 ° C. And the total curvature of the test piece which completed heat processing was measured by letting a slit gauge pass. The test results are shown in FIG. In FIG. 5, the horizontal axis indicates the temperature of the quenching oil, and the vertical axis indicates the average value of the total warpage amount of 30 test pieces.

  Referring to FIG. 5, it can be seen that there is a clear correlation between the temperature of the quenching oil and the total warpage amount, and the total warpage amount decreases as the temperature of the quenching oil increases. And by setting the temperature of quenching oil to 200 degreeC or more, while the difference between steel types regarding a total curvature becomes small, the value is also small. Further, the total warpage amount of all the test pieces was within a general standard (20% or less of the thickness of the washer), and it was in a state where correction of warpage after quenching was unnecessary. On the other hand, even when the condition of the quenching oil temperature exceeding 220 ° C. was adopted, no further reduction in warpage was achieved. Therefore, it can be said that the temperature of the quenching oil is preferably 220 ° C. or less.

  An experiment was conducted to investigate the effect of coolant temperature on the hardened condition of the washer. First, the specimen was quenched and hardened using quenching oil at 90, 150, 200, and 230 ° C. under the same conditions as in Example 1, and then tempered at 120 ° C. for 120 minutes. Was made. Then, the surface hardness of each test piece was measured and the microstructure was observed. Table 2 shows the measurement results of the surface hardness.

  As shown in Table 2, the steel type No. corresponding to the washer of the present invention. The test specimens 1 and 2 have a surface hardness of 700 HV or higher under the condition of a quenching oil temperature of 200 ° C. or lower, and a higher surface hardness than the test specimen of the comparative example that was quenched and tempered under the conventional conditions. Is obtained. In addition, in the microstructure of these test pieces, incompletely quenched structures such as troost tie and bainite were not observed. On the other hand, when the temperature of the coolant was set to 230 ° C. exceeding 220 ° C., the surface hardness decreased to less than 650 HV, and an incompletely hardened structure was found in the microstructure. From this, it is confirmed that the temperature of the coolant is preferably 220 ° C. or lower.

  Steel type No. The specimens 1 to 3 were subjected to quench hardening using cooling with high-pressure nitrogen gas at a pressure of 9.8 Bar (0.98 MPa) instead of the quenching oil under the same conditions as the quench hardening and tempering. The surface hardness was measured and the microstructure was observed. Table 3 shows the measurement results of the surface hardness.

  Referring to Table 3, the steel type No. to which boron was added. With respect to the test piece 3, sufficient hardness is obtained. In addition, an incompletely hardened structure was not observed in the microstructure. On the other hand, steel type No. to which boron is not added. About the test piece of 1 and 2, the surface hardness was less than 600HV and sufficient hardness as a washer was not obtained. Steel type No. For the test pieces 1 and 2, an incompletely hardened structure was observed in the microstructure, and hardness unevenness was also confirmed. Considering that there is a report (Ishikawajima-Harima Technical Report, Vol. 45, No. 1, 2005) that high-pressure gas cooling can ensure the same cooling performance as oil cooling under the condition of gas pressure of 30 Bar, pressure 9 Under the above conditions using .8 Bar high-pressure nitrogen gas, it can be said that it is necessary to add boron to the material in order to ensure sufficient hardenability.

  In order to investigate the rolling fatigue life of the washer of the present invention, the above steel type No. 1 to 3 (Examples) and Comparative Example steels were produced, and thrust needle roller bearings using the washer were assembled and subjected to a life test.

First, the above steel type No. About 1 and 2, after hardening on the conditions similar to the said Example 1, quenching hardening was implemented by being immersed in 90 degreeC or 230 degreeC hardening oil. On the other hand, steel type No. For No. 3, after heating under the same conditions as in Example 1 above, quenching was performed by cooling with high-pressure nitrogen gas at a pressure of 9.8 Bar. Moreover, about the comparative example, quenching oil temperature was 90 degreeC. And the thrust needle roller bearing of the same model number was produced using the washer disk of the obtained Example and a comparative example. This bearing was subjected to an endurance test under conditions of a surface pressure (Pmax) of 1.2 GPa, a rotation speed of 5000 rpm, and a lubricating oil of a circulating oil supply of spindle oil VG2, and the life until the point of failure was investigated. The test was carried out for 6 test pieces of the same steel type and the same heat treatment, and the L ₅₀ life (life with a cumulative failure probability of 50%) was calculated and evaluated. Steel type No. Of the test specimens 1 and 2, the quenching oil temperature was 90 ° C. and the test specimen of the comparative example had a large total warpage after quenching and hardening treatment, so that the warping was performed during the tempering treatment. The total warpage was made to be within 1.1 mm. The test results are shown in FIG. In FIG. 6, the life is shown as a relative value with the L ₅₀ life of the comparative example as 1.

  Referring to FIG. 6, the steel type No. The bearings 1 and 2 have a longer life than the comparative example. On the other hand, the steel grade no. The bearings 1 and 2 have a shorter life than the comparative example. This is considered to be the effect of hardness reduction and hardness unevenness due to the incompletely hardened structure generated in the washer. Considering this test result together with the test results of Examples 1 and 2 above, it is considered that the temperature of the coolant is preferably 200 to 220 ° C. from the viewpoint of reducing the manufacturing cost by reducing the warpage and ensuring the long life. It is done. On the other hand, the steel type No. added with boron. For 3, a long life is achieved. This is because hardenability is improved by the addition of boron, and the titanium compound added along with the addition of boron exhibits a pinning effect and the refinement of crystal grains is achieved. It is done.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The raceway disk, the thrust needle roller bearing and the manufacturing method thereof according to the present invention are particularly advantageously applied to the thrust needle roller bearing and the manufacturing method thereof that are required to reduce the manufacturing cost while ensuring excellent durability. obtain.

  DESCRIPTION OF SYMBOLS 1 Thrust needle roller bearing, 11 Way washer, 11A Rolling surface, 11B Reinforcement process layer, 11C inside, 13 Needle roller, 13A Roller rolling contact surface, 14 Cage.

Claims (11)

A thrust disc of a thrust needle roller bearing having a thickness of 2 mm or less,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.10% by mass or more and 1.10% by mass or less of manganese. Consisting of quench hardened steel consisting of the balance iron and impurities,
The rolling surface has a hardness of 700 HV or more,
A washer with total warpage within 120% of thickness. A thrust disc of a thrust needle roller bearing having a thickness of 2 mm or less,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, Containing 0010 mass% or more and 0.0100 mass% or less of boron, comprising a hardened and hardened steel consisting of the balance iron and impurities,
The rolling surface has a hardness of 700 HV or more,
A washer with total warpage within 120% of thickness. A thrust disc of a thrust needle roller bearing having a thickness of 2 mm or less,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, Containing 0010% by mass to 0.0100% by mass of boron and 0.01% by mass to 0.05% by mass of titanium, comprising a hardened and hardened steel consisting of the remaining iron and impurities,
The rolling surface has a hardness of 700 HV or more,
A washer with total warpage within 120% of thickness. With a washer,
A plurality of needle rollers arranged in contact with the rolling surface of the bearing disc,
The said washer is a thrust needle roller bearing which is a washer of any one of Claims 1-3. A method of manufacturing a washer for a thrust needle roller bearing,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.10% by mass or more and 1.10% by mass or less of manganese. A step of preparing a molded body made of steel consisting of the remaining iron and impurities, and formed into a shape corresponding to the shape of the washer;
A step of quench hardening the molded body,
In the step of quenching and hardening the molded body, the molded body is quenched and hardened by immersing the molded body heated to a temperature of _one point A or more of the steel in a cooling liquid of 200 ° C. or higher and 220 ° C. or lower. A method of manufacturing a washer. A method of manufacturing a washer for a thrust needle roller bearing,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, Containing 0010 mass% or more and 0.0100 mass% or less of boron, comprising a steel composed of the remaining iron and impurities, and preparing a molded body formed into a shape corresponding to the shape of the washer;
A step of quench hardening the molded body,
In the step of quenching and hardening the molded body, the molded body is quenched and hardened by immersing the molded body heated to a temperature of _one point A or more of the steel in a cooling liquid of 200 ° C. or higher and 220 ° C. or lower. A method of manufacturing a washer. A method of manufacturing a washer for a thrust needle roller bearing,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, Containing boron from 0010% by mass to 0.0100% by mass and titanium from 0.01% by mass to 0.05% by mass with the balance being iron and impurities, corresponding to the shape of the washer Preparing a molded body molded into a shape to be
A step of quench hardening the molded body,
In the step of quenching and hardening the molded body, the molded body is quenched and hardened by immersing the molded body heated to a temperature of _one point A or more of the steel in a cooling liquid of 200 ° C. or higher and 220 ° C. or lower. A method of manufacturing a washer. A method of manufacturing a washer for a thrust needle roller bearing,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.10% by mass or more and 1.10% by mass or less of manganese. A step of preparing a molded body made of steel consisting of the remaining iron and impurities, and formed into a shape corresponding to the shape of the washer;
A step of quench hardening the molded body,
The step of quench-hardening the molded body includes
The molded body is heated to a temperature not lower than A ₁ point of the steel is immersed in the cooling liquid which was which was maintained at a temperature of more than Mf point than Ms point of the steel, and the temperature of the green body Cooling until the temperature of the coolant is uniform;
And a step of further cooling the molded body cooled to a temperature not higher than the Ms point and not lower than the Mf point to room temperature by air or gas cooling. A method of manufacturing a washer for a thrust needle roller bearing,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, Containing 0010 mass% or more and 0.0100 mass% or less of boron, comprising a steel composed of the remaining iron and impurities, and preparing a molded body formed into a shape corresponding to the shape of the washer;
A step of quench hardening the molded body,
In the step of quenching and hardening the formed body, the formed body is heated by contacting the formed body heated to a temperature of _one point A or more of the steel with a cooling gas of 0.5 MPa or more and less than 1.0 MPa. A method of manufacturing a washer that hardens. A method of manufacturing a washer for a thrust needle roller bearing,
0.60% by mass or more and 0.90% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, Containing boron from 0010% by mass to 0.0100% by mass and titanium from 0.01% by mass to 0.05% by mass with the balance being iron and impurities, corresponding to the shape of the washer Preparing a molded body molded into a shape to be
A step of quench hardening the molded body,
In the step of quenching and hardening the formed body, the formed body is heated by contacting the formed body heated to a temperature of _one point A or more of the steel with a cooling gas of 0.5 MPa or more and less than 1.0 MPa. A method of manufacturing a washer that hardens. Preparing the washer; and
Preparing a plurality of needle rollers;
A step of assembling a thrust needle roller bearing by combining a plurality of the needle rollers so as to contact the raceway,
The process for preparing the washer is a method for producing a thrust needle roller bearing, which is performed using the method for producing a washer according to any one of claims 5 to 10.

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