JPH0637897B2 - Rolling bearing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rolling bearing used in a fiber dyeing machine, a plating tank, or the like and used in a corrosive atmosphere or an environment where a lubricant cannot be used.

(Prior Art) As shown in FIG. 3, a rolling bearing is generally composed of a bearing ring (inner ring a and outer ring b), a rolling element c and a cage d. Various designs are made according to the purpose of use.

As rolling bearings used in textile dyeing machines or plating tanks, ball bearings using steel balls as rolling elements c are mainly used as shown in FIG. In such a case, since a solution containing hydrogen peroxide solution, sodium hydroxide or other acid, alkali, surfactant, etc. is used as the working liquid, the solution or steam is in a corrosive atmosphere, and If grease or oil adheres to the product, it will cause product failure. As a countermeasure, use JIS: SUS440C, which is martensitic stainless steel, as the material for the bearing rings a, b and steel balls c, and use it without a lubricant. ing.

Further, as a rolling bearing used in a non-lubricated state, for example, as described in Japanese Patent Publication No. 37255/37, the inner ring a,
The outer ring b and the rolling element c are made of a polymer compound such as Teflon, nylon, and tetron, and the metal reinforcing pieces are completely embedded in the inside of the outer ring b and the rolling element c. Some have improved the difficulty of maintaining dimensional accuracy due to their low strength.

Furthermore, as described in JP-A-58-42829,
A solid lubricant such as soft metal or molybdenum disulfide is used for the bearing ring a,
Rolling bearings coated on the rolling surface of b, such as JP-A-58-58
Rolling bearings utilizing the wear resistance and corrosion resistance of hard ceramics as described in Japanese Patent No. 113628 or rolling bearings coated with titanium nitride, and JP-A-58-17.
As described in Japanese Patent No. 4718, there is known a rolling bearing in which the contact surfaces of the bearing rings a and b and the rolling elements c are coated with titanium nitride or a material mainly containing titanium nitride by ion plating. .

(Problems to be Solved by the Invention) However, such conventional techniques have the following problems, respectively.

(1) In the case of bearings using SUS440C SUS400C is stainless steel, but it has high carbon and does not have sufficient corrosion resistance, and since there is no oil due to the lubricant, it will be corroded and worn early and will not be used. Disappear.

By the way, the corrosion is severe in areas other than the rolling area, and the corrosion is relatively small on the rolling surface, but the wear is large, and the surface is roughened in the corrosive atmosphere, which accelerates the wear. Objects penetrate the rolling surface and accelerate the wear of the rolling surface.

Therefore, when it is used in a dyeing machine or a plating tank, the rolling surface is worn and galling occurs at an early stage, and wear powder and corrosion products are caught in the rolling surface, which makes it unusable.

(2) In the case of a bearing using a polymer compound The strength of a polymer compound is weaker than that of steel such as SUS440C, which is about 1/10, and even if the metal reinforcing piece described above is used, the overall deformation does not occur. Although it can be reduced to some extent, since the rolling surface itself is a high molecular compound, its strength is low, and the restrictions on the load conditions that can be used are large. The example is denied.

(3) Bearings coated with a solid lubricant Solid lubricants have a low coefficient of friction even when oil or grease is not used, and have the effect of reducing friction. Due to being sheared by, the hardness is low, and as a result it becomes powdery due to wear,
At the same time that the coating effect disappears, the powder adheres to the processed product, causing product defects.

In JP-A-58-174718, an example of coating with gold or silver is denied in this respect.

(4) Bearings made of hard ceramics or bearings coated with titanium nitride Ceramics generally have high hardness and corrosion resistance, and are very effective in preventing wear in a corrosive atmosphere.

However, ceramics operate by sintering high-hardness powder, and are generally weak to thermal or mechanical impact and poor in toughness. This strength can be improved by the so-called fine ceramics technique, but in this case, the price is very high compared to the case where SUS440C is used due to high hardness and poor workability, This point is one of the important research subjects.

On the other hand, when titanium nitride is coated with ion plating or the like, the titanium nitride itself has high hardness and a low friction coefficient, and therefore has good wear resistance.

However, the coating layer is simply ionized titanium nitride deposited on the surface of the base material, and the thermal effect is small.Therefore, the coating layer does not melt and diffuse sufficiently. It has a weak bond with the material and has voids in a part, and in a corrosive atmosphere, internal corrosion progresses and the coating layer falls off.

Therefore, even if titanium nitride itself has corrosion resistance, the surface coated with titanium nitride does not have sufficient corrosion resistance. In titanium nitride ion plating, in addition to the positional relationship between the evaporation source and the target product (cathode), shape effects such as the position within the product, the evaporation rate of titanium, the partial pressure of nitrogen gas, the degree of element excitation, and the product temperature. The composition, components, density, hardness, defects such as pinholes, etc. of the coating layer and the adhesion to the base material are greatly affected by the above, and these variations are a problem for stabilizing the product quality.

(Means for Solving the Problem) The present invention solves these contradictions and does not provide a rolling bearing having excellent corrosion resistance, wear resistance, and sufficient mechanical strength and fatigue life at a relatively low cost. The rolling bearing according to the present invention comprises a bearing ring, a rolling element and a cage, in which a chromium carbide layer is formed on the surface portion of the bearing ring, and the surface portion is made of a polymer compound. It is characterized in that an impregnated coating layer is formed.

(Operation) Of the rolling bearing components, a steel material is used for the bearing ring, which is particularly prone to corrosion and wear, and a chromium carbide layer is formed on the surface by the diffusion infiltration method. By forming the impregnated coating layer made of a compound, the corrosion resistance and the wear resistance can be improved.

(Example) Hereinafter, the Example of this invention is described based on drawing.

Example 1 A rolling bearing according to the present invention is shown in FIG. 1, and the rolling bearing is specifically a ball bearing and is composed of an inner ring 1, an outer ring 2, rolling elements (steel balls) 3 and a cage 4. ing.

The inner ring 1, the outer ring 2 and the rolling elements 3 are made of martensitic stainless steel SUS440C, and a chromium carbide layer 5 is formed on the surface portion thereof, and a polymer compound impregnated coating layer 6 is formed on the surface portion. ing.

In these manufacturing methods, first, the chromium carbide layer 5 is formed by the diffusion infiltration method. That is, the inner ring 1, the outer ring 2, and the rolling elements 3 made of SUS440C are immersed in a borax bath containing a chromium carbide forming element and heat-treated at 1000 ° C. for 4 hours. Thereby, a chromium carbide layer 5 having a thickness of about 8 μm is obtained on the surface portion. After that, quenching and tempering are performed, and the hardness of the SUS440C portion is HRC58 to
Then, heat treatment is performed so as to obtain 62, followed by vacuum impregnation in a molten bath of fine particles of polytetrafluoroethylene (PTFE) resin and baking, and an impregnated coating layer 6 of about 2 μm is formed on the surface of the vapor chromium carbide layer 5. Form.

The cage 4 is made of PTF which is a self-lubricating polymer material.
The bearing is made of E resin, and smooth rotation and wear reduction of the bearing are achieved even under the condition that the lubricant cannot be used.

In the illustrated example, the chromium carbide layer 5 and the impregnated coating layer 6 are formed on all of the inner ring 1, the outer ring 2, and the rolling elements 3, but the invention is not limited to this, and the purpose of use, conditions of use, etc. The design will be changed as appropriate. That is, there are various levels of requirements for corrosion resistance and wear resistance. Generally, the rolling element 3 is less corroded by rolling, and is actually less corroded and worn than the bearing rings (inner ring 1, outer ring 2). In some cases, it is possible to deal with only 1 and 2 by subjecting the surface treatment to the generation of chromium carbide.

Example 2 This example uses trifluoroethylene chloride (PCTFE) as the impregnated coating layer 6 in Example 1, and its manufacturing method is the same as that of Example 1 except that PCTFE is used as the impregnating agent. . Therefore, other configurations are similar to those of the first embodiment.

Example 3 In this example, an inner ring 1, an outer ring 2, and a rolling element 3 made of SUS440C similar to those in Example 1 were embedded in a coating material mixed with powder of metal chromium, alumina powder, and ammonium chloride, and 1000 ° C. And heat treatment for 4 hours to form a chromium carbide layer 5. After that, quench and temper the SU
The hardness of the S440C portion was set to HRC58 to 62. After that, the surface of the chromium carbide layer 5 was impregnated and coated by immersing it in a melted polypropylene resin in a vacuum container.

Next, the test results of rolling fatigue life, wear resistance and corrosion resistance, which were conducted to investigate the effect of the bearing of the present invention, will be described below.

(1) Rolling fatigue life Using a Mori type thrust type durability life tester, outer diameter 65 mm x
The hardness of the sample with an inner diameter of 18 mm and a thickness of 10 mm, one of which is HRC by quenching and tempering the currently used corrosion-resistant material SUS440C
The sample is about 60, the other is SUS44 according to the present invention.
After forming a chromium carbide layer on the surface of 0C, quenching and tempering are performed and the hardness of the SUS440C part is set to HRC about 5
The rolling fatigue life of the sample No. 8 and the case where the surface thereof was impregnated with PTFE resin were compared.

As a reference, a comparison was also made between the case where the titanium nitride coating by ion plating and the titanium carbide coating by the CVD method were applied to the surface of SUS440C.

(2) Wear resistance In the same test as the rolling fatigue life test, after rotating the above two types of samples for the same time, measure the wear shape of the rolling part with a shape measuring machine and compare the wear resistance of both. did.

(3) Corrosion resistance SUS440C steel balls with a diameter of 3/8 inch and SUS4
40C steel spheres with chromium carbide formed on the surface, then quenched and tempered, and PT on the surface.
Using a sample impregnated with FE resin, the sample was dipped in an aqueous solution of hydrochloric acid and sulfuric acid, the amount of decrease in weight was measured, and the corrosion resistance was compared. As comparative materials, comparisons were made by using titanium nitride coating by ion plating, titanium carbide coating by CVD method and untreated various austenitic corrosion-resistant stainless steels as well as the rolling fatigue life comparative samples described above. .

The above test results are shown in Table 1 in comparison with SUS440C, which is set to 100.

From Table 1, the rolling bearing of the present invention has rolling fatigue life equivalent to that of the current SUS440C and wear resistance of about 4
And the corrosion resistance is about 25 times more than SUS304, SU
It was found that an excellent corrosion and wear resistant bearing equivalent to or better than S316 can be obtained.

From Table 1, among the carbide or nitride coating materials,
It can be seen that the chromium carbide coating material is particularly excellent in rolling fatigue resistance, wear resistance and corrosion resistance. The reason for this will be described below.

(1) Rolling-fatigue resistance, wear resistance, and adhesion resistance As shown in the cross-sectional microstructure photograph of the chromium carbide layer, the chromium carbide layer has a two or three-layered appearance structure, and the outermost surface is (Cr, Fe ) ₂₃ C ₆ and (Cr, F
e) ₇ C ₃ is present, and depending on the base material and the processing conditions, a solid solution phase of Fe—Cr is further present inside thereof.

Further, the chromium carbide is a composite carbide layer in which a part of chromium is replaced with iron as shown by (Cr, Fe) ₂₃ C ₆ and (Cr, Fe) ₇ C ₃ , and as the inside of the base metal gets closer, The amount is increasing. Therefore, there is a metal bond between the layer and the base material, and the bond is strong. In addition, since the physical properties of the layer (hardness, expansion coefficient, etc.) change relatively continuously, peeling of the layer is unlikely to occur due to various external stresses and temperature changes.

Hardness wear resistance of about H _V 1500 is inferior to titanium carbide, since the layer is hardly peeled, resistance to rolling contact fatigue resistance is excellent.

On the other hand, in the titanium nitride coating by ion plating, since the base material temperature is several hundreds of degrees Celsius or less, strain due to the treatment does not occur, but since there is no diffusion between the layer and the base material, there is a metal bond. No, and the adhesion is poor because it is mainly an intermolecular bond.

Furthermore, the base material iron is not contained in this titanium nitride,
Since it is a layer consisting essentially of titanium and nitrogen, the difference in the physical properties at the interface is large, and peeling easily occurs due to external stress.

In this sample, the rolling fatigue limit is reached due to delamination before layer wear occurs.

On the other hand, the titanium carbide coating by the CVD method is treated at the same temperature as the above-mentioned chromium carbide coating, so that titanium and carbon are diffused between the layer and the base material and a metallic bond exists. However, since the layer is made of 100% titanium carbide, the hardness is about H _V 3000, and the abrasion resistance and seizure resistance are excellent, but the physical properties differ greatly at the interface between the layer and the base material. The strength against external stress is smaller than that of chromium carbide, and as in the case of titanium carbide, the rolling fatigue limit is reached due to delamination of layers.

(2) Corrosion resistance As described above, in the chromium carbide, chromium diffuses and permeates from the outside to the sample surface, and at the same time, iron and carbon in the base material diffuse into the layer to form a 2-3 phase layer. . Therefore, there are no voids or voids between the layer and the base material, and it is difficult for the corrosive solution or gas to enter from the outside.

Titanium nitride, titanium carbide, and chromium carbide themselves are not corroded by hydrochloric acid and sulfuric acid shown in Table 1, but the adhered sample is corroded by the fact that the solution penetrates into the micropores of the layer and the interface peeling portion. This is to corrode the base material.

Titanium nitride formed by ion plating has many defects at the interface, and also has many non-uniform portions and voids in the crystal, and therefore has poor corrosion resistance.

Titanium carbide obtained by the CVD method has a better crystal uniformity and less interfacial defects than the above titanium nitride, and therefore exhibits relatively good corrosion resistance, but is inferior to chromium carbide.

Here, after forming chromium carbide on the surface, PT
The FE resin impregnation greatly improves the corrosion resistance even if chromium carbide is formed on the surface, but when a sample in which chromium carbide is formed is observed after immersion, corrosion occurs in the form of pitting and pit-like points are observed. Since it was found that the pit was eroded as a starting point, this was done to seal the pit shape.

In order to seal the pits, it is also possible to thicken the chromium carbide layer by increasing the processing temperature or increasing the time, and repeat the coating process multiple times to make the chromium carbide layer a multilayer. However, this requires a long-time treatment, and there is also a problem that productivity and economic efficiency are reduced, and impregnation with a polymer material is appropriate. It should be noted that the thickness of this polymer material should be 2 μm from the test results,
Moreover, at such a thickness, the function of the rolling bearing is not impaired at all, and it is rather effective in improving lubricity.

The characteristics of the impregnating resin are that it is superior to various corrosive solutions, that it has a viscosity that allows it to penetrate even into minute voids (heating and depressurization conditions may be used), Good adhesion is required.

As a polymer material having these characteristics, PTFE
(Example 1), fluorinated resin such as PCTFE (Example 2), polyethylene, polypropylene (Example 3)
Olefin resins such as are suitable. By the way, P
Even when CTFE is used, it shows rolling fatigue resistance, abrasion resistance and corrosion resistance exactly the same as those of PTFE, and when polypropylene is used, the corrosion weight loss ratio is 1.5 for hydrochloric acid, and for sulfuric acid, It is known that the value is 0.01 or less as a result of the same test as described above.

The present invention can be applied not only to the ball bearings as in the above-mentioned embodiments but also to roller bearings, and further to all rolling bearings such as single-row type, double-row type, radial load, and thrust load. Is.

(Effects of the Invention) As described in detail above, according to the present invention, among the constituent members of the rolling bearing, the chromium carbide layer is formed on the surface portion of the bearing ring which is particularly susceptible to corrosion and wear, and further on the surface portion thereof. An impregnated coating layer made of a high molecular compound is formed, and the rolling elements are also subjected to the same surface treatment as necessary, providing excellent corrosion resistance and wear resistance as well as mechanical strength and rolling fatigue life. It is possible to provide a sufficient rolling bearing.

Moreover, it is relatively inexpensive.

Also, since the cage is made of a self-lubricating polymer material,
It can also be used in environments where lubricants cannot be used.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a rolling bearing according to the present invention, and FIG. 2 is a microscopic structure photograph of a SUS440C material having a chromium carbide layer formed on its surface, magnified 400 times the section, and FIG. It is a longitudinal cross-sectional view showing a conventional rolling bearing. 1 ... Inner ring, 2 ... Outer ring, 3 ... Rolling element (steel ball), 4 ...
... Cage, 5 ... Chromium carbide layer, 6 ... Impregnated coating layer made of polymer compound

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toru Arai, Toru Arai, Nagakute-cho, Aichi-gun, Aichi Prefecture 1 No. 41 Yokomichi, Toyota Central Research Institute Co., Ltd. (72) Inventor Hiroki Fujita, Aichi-gun, Nagakute-machi 1 of 41 Jyokomichi, Toyota Central Research Institute Co., Ltd. (56) Reference JP 54-108150 (JP, A) JP 53-47860 (JP, B1) US Patent 3001837 (US, A)

Claims (3)

[Claims] 1. A bearing ring, a rolling element, and a cage, wherein a chromium carbide layer is formed on the surface portion of the bearing ring, and an impregnated coating layer made of a polymer compound is formed on the surface portion. Characteristic rolling bearing. 2. A rolling member according to claim 1, wherein a chromium carbide layer is formed on the surface of the rolling element, and an impregnated film layer made of a polymer compound is formed on the surface of the chromium carbide layer. bearing. 3. The rolling bearing according to claim 1, wherein the cage is made of a self-lubricating polymer compound.