JPH10219402A - Rolling supporting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance of a component member of a rolling supporting device and also to improve its hardness by forming any of a rolling element, a track member on a fixed body side, and a track member on a moving body side in a rolling supporting device by the use of an iron and steel material of specific composition and carrying out heat treatment under specific conditions. SOLUTION: A component member, such as rolling element, bearing ring, screw, and rail, is formed of an iron and steel material which has a composition containing, by weight, <=1.0% Si, <=1.5% Mn, 8.0-20.0% Cr, >=0.5% Mo, >=2.0% W, and >=4.0% Co as essential components, also containing <=0.6% C, <=3.0% V, <=4.0% Ni, and <=5.0% Cu as selective components, and satisfying equations (Ni equivalent)=Ni+Co+0.5Mn+30C+0.3Cu and (Cr equivalent)=Cr+2Si+1.5 Mo+5V+0.75W and inequality (Ni equivalent)>=1.14×(Cr equivalent)-14, which is subjected to hardening at >=1050 deg.C and to tempering at >=540 deg.C. By this method, the member having high corrosion resistance and >= about 58 HRC hardness can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling support device such as a rolling bearing, a ball screw, a linear guide and the like, and more particularly, to forming a component of such a device from a specific steel material to improve corrosion resistance and hardness. Related to the technology for improving the quality.

[0002]

2. Description of the Related Art Conventionally, rolling support devices such as rolling bearings are formed of high-carbon chromium bearing steel (SUJ2) in order to use them severely under repeated shearing forces under high surface pressure. After quenching and tempering, the hardness is 58 HRC (Rockwell hardness of scale C).
The required rolling fatigue life is ensured by setting the value to ６４64. In addition, case hardening steel (SCR420, S
CM420, SAE4320H, etc.)
By performing carburizing or carbonitriding treatment, quenching and tempering, the surface hardness is HRC 58 to 64 and the core hardness is HRC 30 to 48,
The required rolling fatigue life is ensured.

However, when these methods are used in a corrosive environment such as in which water is mixed, rust is generated at an early stage and the method cannot be used. Therefore, as a material for the rolling support device used in such a corrosive environment,
Conventionally, martensitic stainless steel (SUS44) which is resistant to rust and can obtain a surface hardness of HRC 58 or more.
0C).

[0004] However, high carbon martensitic stainless steels represented by SUS440C have a large content of Cr and C, so that a large number of coarse carbides having a diameter exceeding 100 µm are present in the matrix. However, there is a problem that the fatigue life characteristics and acoustic characteristics are deteriorated. In addition, martensitic stainless steel has a problem that corrosion resistance is inferior to austenitic stainless steel.

In order to solve such a problem, C is set to N
It has been studied to increase the corrosion resistance of martensitic stainless steel by substituting the same. This means that C, which is a component that improves hardness but lowers corrosion resistance, is reduced, and the decrease in hardness is compensated for by the addition of N, which is the same intrusive element as C, and the addition of N is steelmaking. It is performed by nitriding at the time or after the member is formed, and the hardness of the entire member or only the surface is increased.

[0006]

However, in the method of adding N to martensitic stainless steel as described above, quenching at a high temperature exceeding 1000 ° C. is required to obtain a hardness of HRC 58 or more. When quenching at such a high temperature is performed in a vacuum furnace, denitrification of the surface layer occurs. Unless the denitrification layer is removed by increasing the allowance during finish grinding, sufficient corrosion resistance cannot be obtained. Therefore, this method causes a decrease in productivity and an increase in manufacturing cost.

When quenching is performed in a nitrogen atmosphere to prevent denitrification, high-temperature treatment exceeding 1000 ° C.
Heat is transferred to the furnace wall and details of the furnace, and the equipment is severely damaged, thereby increasing maintenance costs. In addition, dedicated new equipment may be required. Further, if the addition of N is excessively large in order to improve the corrosion resistance, there is a problem that the amount of retained austenite which is not preferable in terms of impact resistance and dimensional stability increases. Although the method using nitrogen is one effective means as described above, there are some points to be noted in practical use.

Ceramics are high corrosion resistant materials other than steel materials having a surface hardness of HRC 58 or more. Ceramics can be used as a rolling element material, but because of their low toughness and reliability issues with large products, they can be applied to bearing races, ball screw screws, and linear guide rails. It is difficult.

The present invention has been made in view of such problems of the prior art. In a rolling support device such as a rolling bearing, a ball screw, a linear guide, etc., the rolling elements as these components are used. Corrosion resistance and hardness of HR, races, screws, rails, etc.
An object of the present invention is to make the material harder than C58 and to reduce the manufacturing cost for that purpose.

[0010]

In order to solve the above-mentioned problems, a rolling support device according to the present invention is interposed between a fixed body and a moving body, and has a rolling body and a trajectory of the rolling body. A track member fixed to the body side and the moving body side, and a rolling support device that allows the moving body to move relative to the fixed body by the rolling body rolling on the track, the rolling element, the fixed body side track member, and At least one of the moving body-side track members has Si of 1.0% by weight or less, Mn of 1.5% by weight or less, Cr of 8.0 to 20.0% by weight, and Mo of 0.5% by weight. As described above, W is 2.0% by weight.
In addition, Co is contained as an essential component in each proportion of 4.0% by weight or more, C is 0.6% by weight or less, V is 3.0% by weight or less, Ni is 4.0% by weight or less, and Cu To 5.
0% by weight or less as a selective component, and the relationship between the Ni equivalent represented by the following formula (1) and the Cr equivalent represented by the following formula (2) is expressed by the following formula (3). After being formed of a steel material to be filled and quenched at a temperature of 1050 ° C. or more, 540
It is characterized by being obtained by tempering at a temperature of not less than ° C.

Ni equivalent = Ni + Co + 0.5Mn + 30C + 0.3Cu {(1) Cr equivalent = Cr + 2Si + 1.5Mo + 5V + 0.75W} (2) Ni equivalent ≧ 1.14 × (Cr equivalent) −14 ° (3) In the present invention, the components of the rolling support device (the rolling element, the fixed-body-side track member, and the moving-body-side track member) reduce the content of C to 0.6% by weight or less,
After quenching at a temperature of 1050 ° C. or higher, using a steel material having an o content of 0.5% by weight or more, a W content of 2.0% by weight or more, and a Co content of 4.0% by weight or more. 540
By being obtained by tempering at a temperature of not less than ° C., precipitation hardening is effectively generated, and generation of coarse carbides is suppressed.
Further, since the C content is low, corrosion resistance is improved. further,
When the steel material used satisfies the expression (3),
The formation of δ ferrite is suppressed, and HRC 58 or more is achieved.

The rolling element, the fixed body-side track member, and the moving body-side track member may be formed by powder metallurgy using a steel material satisfying the above conditions, and may be obtained by performing the same heat treatment as described above. preferable. Thereby, especially when the addition amount of C is increased by adding V, the formation of coarse carbides can be prevented and the structure can be refined, so that the toughness is improved. However, when powder metallurgy is employed, it is preferable to further forge after performing a pressure sintering method such as HIP (hot isostatic pressing) in order to minimize voids.

[0013] The rolling support device of the present invention is not limited as long as at least one of the rolling elements, the fixed body-side track member, and the moving body-side track member satisfies the above conditions. Are those in which only the rolling element satisfies the above-mentioned conditions, those in which only the fixed body-side orbital member satisfies the above-mentioned conditions, those in which only the moving-body-side orbital member satisfies the above-mentioned conditions, those in which the rolling element and the fixed-body-side orbital member Satisfies the above conditions, rolling elements and moving body side trajectory members satisfy the above conditions, moving body side trajectory members and fixed body side trajectory members satisfy the above conditions, rolling elements and fixed body side trajectory members And all the moving body side track members satisfy the above conditions.

Hereinafter, the reasons for limiting the numerical values of the respective components will be described. [C ≦ 0.6% by weight] C is an element that forms a carbide and increases the strength by converting the structure into martensite, and has an effect of suppressing the formation of δ ferrite, which lowers the toughness. It also has the effect of lowering it. From this point, the smaller the C content, the better.

On the other hand, C is bonded to V selectively added at a weight ratio of V: C ≒ 1: 0.2, and is very fine and has high hardness and high temperature stability. It also has the effect of forming carbides to improve wear resistance. Where V ≦
V: C = 1: 0.2 to C ≦ C
0.6% by weight was set. When V is not contained, C
≦ 0.2% by weight, and for higher corrosion resistance, C
It is preferred to be ≦ 0.1% by weight. [Si ≦ 1.0% by weight] Si is necessary as a deoxidizing agent and is a component usually added to stainless steel. However, if too much is contained, it inhibits forgeability and lowers toughness. % Or less. Usually, the addition of about 0.2% by weight is appropriate. The lower limit of the Si content is, for example, 0.15% by weight. [Mn ≦ 1.5% by weight] Mn is necessary as a deoxidizing agent, and is a component usually added to stainless steel, and improves quenching properties. % By weight or less. Usually, the addition of about 0.2% by weight is appropriate. The lower limit of the Mn content is, for example, 0.1% by weight. [8.0% by weight ≦ Cr ≦ 20.0% by weight] Cr is an element necessary for forming an oxide film on the surface of steel and improving corrosion resistance. When the amount of addition is less than 8% by weight, good corrosion resistance is obtained. Can not be obtained. On the other hand, if the Cr content exceeds 20.0% by weight, δ ferrite is extremely likely to be formed.
% By weight or less. [Mo ≧ 0.5% by weight] Mo has an effect of significantly increasing tempering softening resistance and significantly improving pitting corrosion resistance.
If the amount is less than 0.5% by weight, the effect cannot be sufficiently obtained, so that 0.5% by weight or more is added. Further, if too much is added, decarburization or Mo is likely to occur, and the toughness may be reduced. Therefore, the content of Mo is preferably set to 6.0% by weight or less. [W ≧ 2.0% by weight] W forms a hard carbide, and is partially dissolved in a matrix to increase tempering softening resistance. Therefore, W is an element that increases hardness at high temperature and improves wear resistance. It is. Further, when added simultaneously with Mo and Co, it is an element having a high effect of increasing the hardness of steel by precipitation hardening treatment. In order to obtain these effects sufficiently,
The content is 2.0% by weight or more. The upper limit of the W content is, for example, 19% by weight. [Co ≧ 4.0% by weight] Co is an austenite stabilizing element, suppresses the formation of δ ferrite, dissolves in a matrix to increase the amount of C dissolved, and increases the hardness at high temperatures. Also, if added simultaneously with Mo and W, it contributes to precipitation strengthening and increases its hardening. In order to obtain these effects sufficiently, the content is set to 4.0% by weight or more. Further, if added in an excessively large amount, the toughness may be reduced. Therefore, the Co content is preferably set to 18.0% by weight or less. [V ≦ 3.0% by weight] V increases tempering softening resistance,
In order to generate carbide having high hardness, hardness at high temperatures is increased, and wear resistance is also improved. However, if the added amount is too large, it becomes difficult to grind. Therefore, when added, it is added at a ratio of 3.0% by weight or less. In some cases, it is not added in consideration of other components.

In particular, in the case of an aircraft, since heat resistance and wear resistance are also important, 0.8% by weight or more of V is added, and as described above, the weight ratio of V: C ≒ 1: 0. It is preferable to form a very fine VC carbide having high hardness and high temperature stability by adding C at a ratio of 0.2. [Ni ≦ 4.0 wt%] Like Co, Ni is an austenite stabilizing element and has an effect of suppressing the formation of δ ferrite. However, when a large amount is added, residual austenite is easily generated, and not only a required hardness cannot be obtained, but also dimensional stability is adversely affected. I do. In some cases, it is not added in consideration of other components. [Cu ≦ 5.0% by weight] Cu is an element effective for improving corrosion resistance and contributes to precipitation hardening. However, even if the content exceeds 5.0% by weight, the effect is saturated, so the upper limit is set to 5.0% by weight. In some cases, it is not added in consideration of other components.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to specific examples. A test piece No. 1 for a Rockwell hardness test and a corrosion resistance test was formed by molding a steel material having a composition of symbols A to V shown in Table 1 below and quenching and tempering at the temperature shown in Table 2. To 22 were prepared.

No. 10 using the symbol J as a material has a temperature of 11
H under the conditions of 00 to 1150 ° C and a pressure of 100 to 150 MPa.
The material of the test piece was produced by performing forging after performing IP. Except for No. 10, the material of the test piece was produced by the usual melting method under the same conditions.

Each material is turned on a lathe to a diameter of 20 mm and a thickness of 10 mm
A test piece was formed by cutting into a shape of. Quenching was performed by holding the molded body in a vacuum at the temperature shown in Table 2 for 30 minutes, and then rapidly cooling in oil (vacuum quenching). The tempering was performed by repeating the process of maintaining the temperature shown in Table 2 for 2 hours and then air cooling three times.

In Table 1, Cr equivalents and Ni equivalents were calculated from the above equations (1) and (2) for the material of each symbol, and the values are shown. Further, whether or not these relationships satisfy the above-mentioned expression (3) is indicated by “○” and “×”. Further, FIG. 1 shows that, for the material of each symbol in Table 1, C
It is a graph which shows the relationship between r equivalent and Ni equivalent. In the graph of FIG. 1, a line (*) indicates the following equation (3 ′), and the material above this line satisfies the above equation (3).

Ni equivalent = 1.14 × (Cr equivalent) −14 ‥‥ (3 ′) The results of measuring Rockwell hardness (HRC) using test pieces obtained from each material and Table 2 also shows the results of the corrosion resistance test. [Corrosion Resistance Test] The surface of the test piece was polished with a # 800 water-resistant sandpaper, immersed in a 3.5% by weight aqueous solution of NaCl, and examined for the state of rust formation after 100 hours. The results are shown as "◎" when no rust was generated, "○" when slightly rust was generated, "△" when almost all rust was generated, and "△" when substantially rust was generated over the entire surface. To “×”
It was expressed by.

As a comparative example, test pieces (Nos. 23 and 24) were prepared in the same manner for SUS440C which is a high carbon martensitic stainless steel and SUS304 which is an austenitic stainless steel. Was measured. For SUS304, only the corrosion resistance was measured.

[0023]

[Table 1]

[0024]

[Table 2]

As can be seen from these results, in Nos. 1 to 13 within the scope of the present invention, the hardness was all HRC58.
As described above, the corrosion resistance was also good as “◎” or “○”. In No. 10, since the molding was performed by the HIP method, the structure was refined and the toughness was high. In addition, No. 2, Nos. 5 to 8, and No. 2 having a C content of 0.10% by weight or less or a Cr content of 10% by weight or more.
No. 11 had particularly high corrosion resistance. In contrast, No. 1 has a relatively low Cr content, and No. 3 and
4, 9, 10, 12, and 13 had a relatively high C content, so that the corrosion resistance was slightly inferior to No. 2, No. 5 to 8, and No. 11.

Nos. 14 to 17 in the comparative examples are as follows:
Nos. 14 and 15, which had a hardness of HRC 58 or more but had a small Cr content of 3.2% by weight and 6.7% by weight, had a C content of 0.06% by weight and 0.08% by weight.
Corrosion resistance was poor despite its low weight percentage. No. 16 having a high C content of 0.72% by weight also had poor corrosion resistance. No. 17 had poor corrosion resistance because it did not contain Mo.

No. 18 has a low W content of 1.2% by weight, and No. 19 has a low Co content of 3.2% by weight. No. 20 to 22 have the above formula (3). Were not satisfied, the hardness was less than HRC58.

Therefore, in the same manner as in the test pieces of Nos. 1 to 13, a bearing race, a screw for a ball screw, a rail for a linear guide, and rolling elements such as balls and rollers are manufactured to produce a bearing and a ball screw. In addition, it is possible to increase the corrosion resistance of a rolling support device such as a linear guide, and to secure a necessary rolling fatigue life. In addition, since special treatment such as quenching in a nitrogen atmosphere is not required, manufacturing costs can be reduced.

[0029]

As described above, according to the rolling support device of the present invention, at least one of the rolling element, the fixed-body-side track member and the moving-body-side track member has both high corrosion resistance and hardness HRC58 or more. As a result, the rolling life of the rolling support device can be extended. This makes it possible to lengthen the maintenance cycle of the mechanical device using the rolling support device. According to the present invention, the production cost can be reduced as compared with the method of increasing the corrosion resistance of martensitic stainless steel by replacing C with N.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows a material for each symbol used in the embodiment.
It is a graph which shows the relationship between r equivalent and Ni equivalent.

Claims (1)

[Claims] 1. A rolling element which is interposed between a fixed body and a moving body, includes a rolling element, and respective track members having orbits of the rolling element and fixed to the fixed body side and the moving body side, respectively. In a rolling support device that allows the moving body to move relative to the fixed body by rolling, at least one of the rolling element, the fixed body-side track member, and the moving body-side track member contains 1.0% by weight or less of Si, Mn.
Is 1.5% by weight or less, and Cr is 8.0% by weight or more and 20.0% or less.
% Or less, Mo is 0.5% by weight or more, W is 2.0% by weight or more, and Co is 4.0% by weight or more as an essential component, and C is 0.6% by weight or less. V to 3.0
% Or less, 4.0% by weight or less of Ni, and 5.0% by weight or less of Cu as selective components. The Ni equivalent represented by the following formula (1) and the following (2) After being formed from a steel material that satisfies the following formula (3) in relation to the Cr equivalent represented by the formula, and quenched at a temperature of 1050 ° C. or more, 5
A rolling support device obtained by tempering at a temperature of 40 ° C. or higher. Ni equivalent = Ni + Co + 0.5Mn + 30C + 0.3Cu {(1) Cr equivalent = Cr + 2Si + 1.5Mo + 5V + 0.75W} (2) Ni equivalent ≧ 1.14 × (Cr equivalent) −14 ° (3)