JP2016000445A - Superfinishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superfinishing method using water-soluble grinding oil and a whetstone, capable of achieving stable lubrication performance, being excellent in cleaning effect and finishing performance (grindability, abrasion of the whetstone, and roughness of a surface), and less likely to generate the clogging of the whetstone.SOLUTION: In the superfinishing method, water-soluble grinding oil and a vitrified superfinishing whetstone are used. The water-soluble grinding oil contains polyoxyethylene alkyl ether acetic acid or salt thereof, an amine compound, and a nonionic surface-active agent. The vitrified superfinishing whetstone is a composite abrasive grain vitrified superfinishing whetstone obtained by bonding, with vitrified bond, composite abrasive grains including: 5-80 vol.% soft abrasive grains having chemical reactivity and not having cutting ability, with respect to a material to be processed; and 20-95 vol.% hard abrasive grains having cutting ability with respect to the material to be processed. Surface pressure of the whetstone during the processing is equal to or over 0.3 MPa.

Description

  The present invention relates to a superfinishing method using a water-soluble grinding oil and a vitrified superfinishing grindstone.

  Superfinishing is made of fine abrasive grains and presses a grindstone with a relatively low degree of bonding against the surface of the work piece at a low pressure to give rotation to the work piece. This is a process that gives a reciprocating motion and finishes the surface of the workpiece into a highly accurate mirror surface, etc., by performing fine grinding while pouring a large amount of grinding oil having cleaning and cooling properties.

  Examples of the grinding oil include oil-based grinding oil and water-soluble grinding oil. Conventionally, honing and super-finishing processes provide stable lubrication performance, excellent cleaning effect, and less clogging of the grinding wheel, resulting in excellent finishing performance (grindability, grinding wheel wear, surface roughness). Many oil-based grinding oils are used.

  However, oil-based grinding oil has a flammability and a fire risk in addition to the problem of poor cooling. Therefore, in recent years, in addition to rationalizing, automating and unmanned production lines, the conventional oil-based grinding oil has been converted to water-soluble grinding oil for the purpose of considering the grinding environment and the global environment, and reducing risks such as factory fires. There is a growing demand for this. However, a superfinishing method using a water-soluble grinding oil that can withstand actual use has not been obtained.

  Patent Document 1 discloses a vitrified superfinishing grindstone formed by combining mixed abrasive grains composed of soft abrasive grains and hard abrasive grains and vitrified bonds, but superfinishing using a predetermined water-soluble grinding oil. The method is not disclosed. Patent Document 2 discloses a lubricating oil for metal processing containing a predetermined polyoxyethylene alkyl ether carboxylic acid, but does not disclose a superfinishing method using a predetermined grindstone.

JP 2006-130635 A Japanese Patent Application Laid-Open No. 07-212477

  The present invention is a super finishing method using a water-soluble grinding oil and a grindstone, which provides a stable lubricating performance, is excellent in cleaning effect, hardly clogs the grindstone, and finish performance (grindability, grindstone wear) The object is to provide a superfinishing method having excellent properties and surface roughness.

  The superfinishing method of the present invention is a superfinishing method using a water-soluble grinding oil and a vitrified superfinishing grindstone, and the water-soluble grinding oil comprises polyoxyethylene alkyl ether acetic acid or a salt thereof, an amine compound, and a non-finishing grindstone. A water-soluble grinding oil containing an ionic surfactant, wherein the vitrified superfinishing grindstone has a chemical reactivity to the workpiece and 5 to 80% by volume of soft abrasive grains having no machinability, and the workpiece Is a composite abrasive vitrified superfinished grindstone formed by combining hard abrasive grains having a cutting ability of 20 to 95% by volume with vitrified bonds, and the grinding wheel surface pressure during processing is 0.3 MPa or more. This is a superfinishing method.

  The average particle diameter of the hard abrasive is preferably 2.0 to 20 μm.

  The soft abrasive is preferably cerium oxide having a purity of 99.0% by mass.

  When the soft abrasive grains are cerium oxide having a purity of 99.0% by mass, the surface pressure during processing of the superfinishing grindstone is preferably 0.3 to 1.5 MPa.

  According to the present invention, by using a super-finishing method using a predetermined water-soluble grinding oil and a predetermined vitrified super-finishing grindstone, a stable lubricating performance can be obtained despite using a water-soluble grinding oil. It is possible to provide a superfinishing method that is excellent in cleaning effect, hardly clogs the grindstone, and has excellent finishing performance (grindability, grindstone wear, surface roughness).

It is the photograph which image | photographed the action surface of the grindstone for a test after the actual cutting test in Example 15 (A), Example 9 (B), and Comparative Example 4 (C).

  The superfinishing method of the present invention is characterized by using a predetermined water-soluble grinding oil and a predetermined vitrified superfinishing grindstone.

Water-soluble grinding oil The water-soluble grinding oil according to the present invention is an aqueous solution or dispersion in which polyoxyethylene alkyl ether acetic acid or a salt thereof, an amine compound and a nonionic surfactant are dissolved in water.

The polyoxyethylene alkyl ether acetic acid or a salt thereof is a compound represented by the following formula (1) or a salt thereof. By blending polyoxyethylene alkyl ether acetic acid or a salt thereof, the cleaning effect of the water-soluble grinding oil is improved, and clogging (welding) of the grindstone can be suppressed.
Equation ^{(1): R 1 -O- (} CH 2 CH 2 O) n -CH 2 -COOH

R ¹ in Formula (1) is an alkyl group, preferably an alkyl group having 8 to 20 carbon atoms, more preferably an alkyl group having 10 to 18 carbon atoms, and further preferably a lauryl group having 12 carbon atoms. When the number of carbon atoms is less than 8, the odor tends to increase and the lubricity tends to decrease. Moreover, when it exceeds 20, there exists a tendency for it to become difficult to melt | dissolve in water.

  N in Formula (1) is an average addition mole number of an oxyethylene group, 4-20 are preferable, 6-18 are more preferable, 8-12 are more preferable, and 10 is the most preferable. When n is less than 4, it tends to be difficult to dissolve in water. Moreover, when it exceeds 20, the foaming of grinding oil becomes intense and there exists a tendency for work to become difficult.

  Examples of the object in which polyoxyethylene alkyl ether acetic acid forms a salt include alkali metals such as sodium and potassium, ammonium, monoethanolamine, diethanolamine, triethanolamine, and isopropanolamine. Of these, alkali metals are preferable. The salt of polyoxyethylene alkyl ether acetic acid in the present invention can be prepared by adding an alkali component to form a salt to polyoxyethylene alkyl ether acetic acid and allowing it to react.

  The content of the polyoxyethylene alkyl ether acetic acid or a salt thereof in the total amount of the water-soluble grinding oil is preferably 0.5 to 10.0% by mass, and more preferably 1.0 to 6.0% by mass. When the content is less than 0.5% by mass, the detergency tends to decrease. Moreover, when it exceeds 10.0 mass%, foaming of grinding oil becomes intense and there exists a tendency for work to become difficult.

  The amine compound can form a salt with the polyoxyethylene alkyl ether acetic acid or the like in the water-soluble grinding oil, and can improve the rust prevention and rot resistance of the water-soluble grinding oil. Examples of the amine compound include monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, aminomethylpropanolamine, aminoethylpropanolamine, cyclohexylamine, dicyclohexylamine and N, N-bis (2 -Hydroxyethyl) -N-cyclohexylamine and the like. These amine compounds can be used individually by 1 type or in combination of 2 or more types.

  1.0-10.0 mass% is preferable and, as for content in the water-soluble grinding oil whole quantity of an amine compound, 2.0-7.0 mass% is more preferable. When the content is less than 1.0% by mass, the rust prevention property is lowered, and rust tends to be easily generated on the workpiece and the processing machine. Moreover, when it exceeds 10.0 mass%, pH will become high and there exists a tendency for the problem of hand roughness to generate | occur | produce.

  By containing the nonionic surfactant, the cleaning effect of the water-soluble grinding oil is further improved, and clogging (welding) of the grindstone can be suppressed. Nonionic surfactants include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, polyoxyethylene alkyl ethers such as polyoxyethylene oleyl ether and polyoxyethylene lauryl ether, polyoxyethylene oleyl esters, and polyoxyethylene lauryl esters. And polyoxyethylene fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, and polyoxyalkylene alkylamines. Of these, alkyl ether nonionic surfactants are preferred, polyoxyethylene alkyl ethers are more preferred, and polyoxyethylene alkyl ethers having 8 to 20 carbon atoms in the alkyl group are more preferred.

  The HLB of the nonionic surfactant is preferably 8.0 to 18.0, and more preferably 10.0 to 16.0. When HLB is less than 8.0, the solubility in water tends to be poor and actual use tends to be difficult. Moreover, when it exceeds 18.0, there exists a tendency for foaming to become intense.

  The content of the nonionic surfactant in the total amount of the water-soluble grinding oil is preferably 0.5 to 5.0 mass%, more preferably 1.0 to 3.0 mass%. When the content of the nonionic surfactant is less than 0.5% by mass, the detergency tends to deteriorate. Moreover, when it exceeds 5.0 mass%, there exists a tendency for foaming to become intense.

  The water-soluble grinding oil according to the present invention contains an extreme pressure additive in addition to the polyoxyethylene alkyl ether acetic acid or a salt thereof, an amine compound and a nonionic surfactant, so that the grindability and surface roughness can be further improved. This is preferable because it is an excellent superfinishing method.

  Examples of extreme pressure additives include sulfur-based extreme pressure agents, phosphorus-based extreme pressure agents, and other extreme pressure agents containing metals such as molybdenum. Among these, it is more preferable to contain a sulfur-based extreme pressure agent and / or a phosphorus-based extreme pressure agent because the superfinishing method is more excellent in grindability and surface roughness.

  Examples of the sulfur-based extreme pressure agent include thiadiazole compounds, sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, and dihydrocarbyl polysulfide. These extreme pressure agents can be used alone or in combination of two or more. Among these, a thiadiazole compound is preferable and dimercaptothiadiazole is more preferable because the grindability and surface roughness are particularly improved.

  Examples of the phosphorus extreme pressure agent include phosphoric acid esters, acidic phosphoric acid esters, amine salts of acidic phosphoric acid esters, phosphorous acid esters, and amine salts of phosphorous acid esters. These extreme pressure agents can be used alone or in combination of two or more. Of these, acidic phosphates are particularly preferred because the grindability and surface roughness are improved.

  0.01-5.0 mass% is preferable and, as for content in the water-soluble grinding oil whole quantity in the case of containing an extreme pressure additive, 0.1-2.0 mass% is more preferable. When content of an extreme pressure agent is less than 0.01 mass%, there exists a tendency for the effect by containing an extreme pressure additive to become difficult to be acquired.

  Moreover, the water-soluble grinding oil which concerns on this invention can contain suitably other components normally used for water-soluble grinding oil besides the said component, unless the effect of this invention is impaired. Examples of other components include base oils, polyoxyethylene alkyl ether acetic acid and salts thereof, and surfactants (other surfactants) other than nonionic surfactants, preservatives, metal corrosion inhibitors, and antifoaming agents. And a dispersing agent.

  It does not specifically limit as said base oil, Mineral oil, fats and oils, synthetic oil, etc. are mentioned. Examples of mineral oil include kerosene, light oil, spindle oil, machine oil, and liquid paraffin oil. Examples of the oils and fats include vegetable oils such as rapeseed oil, soybean oil, palm oil, castor oil, nuka oil and coconut oil, and animal oils such as beef tallow and lard oil. Synthetic oils include ether oils, ester oils, polyalkylene glycol oils, polyalphaolefins, and the like. These base oils can be used singly or in combination of two or more.

  When the base oil is contained, the content in the total amount of the water-soluble grinding oil is preferably 0 to 3.0% by mass, and more preferably 0 to 2.0% by mass. When the content of the base oil exceeds 3.0% by mass, the detergency tends to be extremely lowered. In addition, it is preferable not to contain a base oil in water-soluble grinding oil from the reason of not deteriorating detergency.

  Examples of surfactants (other surfactants) other than the polyoxyethylene alkyl ether acetic acid and salts thereof and nonionic surfactants include anionic surfactants and cationic surfactants other than polyoxyethylene alkyl ether acetic acid. , Amphoteric surfactants can be mentioned, and they can be appropriately contained within a range not impairing the effects of the present invention.

  As for content in the water-soluble grinding oil whole quantity in the case of containing other surfactant, 0-5.0 mass% is preferable. When the content of the other surfactant exceeds 5.0% by mass, foaming tends to become intense.

  The water-soluble grinding oil according to the present invention can be produced by stirring until each component is uniformly dissolved or dispersed in water. Specifically, after mixing the surfactant such as polyoxyethylene alkyl ether acetic acid and its salt and the amine compound while heating to 30 to 40 ° C., other components such as base oil are added and stirred uniformly. What was filtered can be manufactured by dissolving or dispersing in water.

Vitrified superfinishing grindstone The vitrified superfinishing grindstone according to the present invention is a composite abrasive vitrified superfinishing grindstone formed by combining composite abrasive grains composed of predetermined soft abrasive grains and hard abrasive grains with vitrified bonds. The composite abrasive vitrified superfinishing grindstone is obtained by vitrifying a composite abrasive compounded with a predetermined amount of soft abrasive grains having chemical reactivity with a work material and having no machinability and hard abrasive grains having machinability. Because it is a super-finished grindstone bonded with a bond, it removes the micro-reaction layer generated by the chemical reaction between the workpiece and soft abrasive grains by contact frictional force, and "clogging" occurs during cutting due to the lubricity of the soft abrasive grains. ”And“ clogging ”are small, scratches are not scratched on the superfinished surface, precise processing is possible with vitrified bond, and each finish performance is excellent.

  The composite abrasive is a composite abrasive obtained by blending a predetermined amount of predetermined soft abrasive and hard abrasive.

Examples of the soft abrasive grains include metal oxides such as cerium oxide (CeO ₂ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), and magnesium oxide (MgO), or nonmetals such as silicon oxide (SiO ₂ ). Examples thereof include inorganic salt abrasive grains such as oxide, barium sulfate (BaSO ₄ ), and calcium carbonate (CaCO ₃ ). Among these, cerium oxide is a soft abrasive grain that is chemically brittle and does not have machinability, such as oxidizing the surface layer of the contact point with the steel material being processed. It is preferable to use one kind selected from barium sulfate, calcium carbonate, silicon oxide and zirconium oxide alone or in combination of two or more kinds. Further, the purity of the component in the soft abrasive is preferably 40% by mass or more. When the purity is less than 40% by mass, the grindstone wear property tends to deteriorate. Further, the purity is more preferably 80% by mass or more, and further preferably 99.0% by mass or more. By using high-purity soft abrasive grains, it is possible to improve the finishing performance, particularly the grindstone wearability.

  The average particle diameter of the soft abrasive grains is not particularly limited as long as the effects of the present invention are not impaired, but is preferably 0.1 to 8.0 μm. However, it may be less than 0.1 μm or more than 8 μm depending on the application.

  As said hard abrasive grain, the abrasive grain generally used as a grindstone for superfinishing can be used. Examples thereof include normal (hard) abrasive grains such as diamond (SD) and cubic boron nitride (CBN), and normal abrasive grains such as aluminum oxide (WA) and silicon carbide (GC) abrasive grains.

  The average particle size of the hard abrasive grains is not particularly limited as long as the effects of the present invention are not impaired, but 20 μm or less (600 mesh: JIS R 6001, Table 8 “Particle size distribution of fine powder for precision polishing (electric resistance test method)”) The same shall apply hereinafter), and more preferably 6.7 μm (2000 mesh) or less. The average particle size is preferably 2.0 μm (6000 mesh) or more. In addition, let an average particle diameter be a particle diameter from which the cumulative value of volume distribution measured by the method prescribed | regulated to JISR6002 "electrical resistance test method" will be 50%.

  The mixing ratio of the soft abrasive grains and the hard abrasive grains in the composite abrasive grains according to the present invention is 20 to 95 volume% hard abrasive grains and 5 to 80 volume% soft abrasive grains. Practically, it is only necessary that the hard abrasive grains are reduced by blending the soft abrasive grains and the grinding wheel cutting performance is not deteriorated.

  In particular, when the superfinishing grindstone according to the present invention is a superabrasive (CBN, SD) grindstone, in order to maintain a grain ratio of 10.0 to 27.0 vol% (concentration 40 to 110) as a guide. As a suitable mixing ratio, it is preferable to set the hard abrasive grains to 40 to 80% by volume and the soft abrasive grains to 20 to 60% by volume. Furthermore, when using a fine-grained grindstone mainly composed of a mirror finish, the tribological (friction, wear, lubrication) effect should be emphasized to make hard abrasive grains 20-40 volume% and soft abrasive grains 60-80 volume%. Is preferred.

  The vitrified bond (bonding agent) is combined with composite abrasive grains composed of soft abrasive grains and hard abrasive grains to form a grindstone, and is homogenously mixed with composite abrasive grains and the like and fired at a predetermined temperature. In this way, it is melted once and then becomes a solid phase by cooling, so that it is firmly bonded to composite abrasive grains and the like to constitute a grindstone.

  The firing temperature (whetstone firing temperature) is preferably less than 800 ° C., preferably 650 to 750 ° C., after confirming the sinterability of soft abrasive grains and the degeneration properties (weight change, transition expansion, etc.) due to firing. It is more preferable. By setting the grinding stone firing temperature within the above range, a sufficient bonding force by vitrified bond can be obtained without impairing the original grain function of the soft abrasive grains.

  The vitrified bond is preferably composed of 80 to 95% by mass of low-melting inorganic glass and 5 to 20% by mass of high-melting inorganic mineral.

In order to obtain a stable bonding force even if the soft abrasive grains are not easily affected by heat and have a grinding stone firing temperature of 650 to 750 ° C., the binder needs to be melted at a lower temperature. Therefore, the low-melting inorganic glass is a low-melting inorganic glass having a softening temperature of 750 ° C. or less, and a borosilicate glass (SiO ₂ —B ₂ O ₃ —R ₂₎ by blending several kinds of frit raw materials. O + RO, R ₂ O: alkali metal oxide, RO: alkaline earth metal oxide) is preferable.

The chemical composition of the borosilicate _glass, SiO 2 40-48 mol%, Al ₂ O ₃ 4.5~5.5 mol%, B ₂ O ₃ 25~32 mol% and R ₂ O + RO20~27 mol% Is preferred.

The high-melting inorganic mineral is mainly composed of natural minerals such as feldspar, porcelain stone and clay. Chemical composition of KoTorusei inorganic _minerals, SiO 2 75 to 78 mol%, Al ₂ O ₃ 11~13 mol%, B ₂ O ₃ 0~0.5 mol% and R ₂ O + RO8~10 mol% is preferred.

Low-melting inorganic glass contains a large amount of boric acid (B ₂ O ₃ ) and alkali components (R ₂ O) and melts at low temperatures, but has reactivity with chemically unstable soft abrasive grains, The liquidity at the time is also great. Therefore, a mixed raw material in which 80 to 95% by mass of a low-melting inorganic glass is blended with 5 to 20% by mass of a high-melting inorganic mineral mainly composed of silicic acid (SiO ₂ ) and alumina (Al ₂ O ₃ ) is used. Thus, the reactivity between the soft abrasive grains and the alkali is suppressed, and the fluidity and thermal expansion at high temperatures are reduced. As a result, the thermal expansion difference between the vitrified bond and the abrasive grains is reduced, and the grindstone mechanical strength is also increased. When the content of the highly fusible inorganic mineral is less than 5% by mass, the above-mentioned effect tends not to be obtained. Moreover, when content of a highly fusible inorganic mineral exceeds 20 mass%, there exists a tendency for an abrasive bond force to become weak, without being able to obtain a sufficient molten state.

  The vitrified superfinishing grindstone according to the present invention can appropriately contain chloride, a pore material and other auxiliary agents in addition to the composite abrasive grains and vitrified bond.

By containing the chloride, the vitrified bond softens and melts at a low temperature and exhibits low viscosity despite the increase in SiO ₂ and Al ₂ O ₃ due to the inclusion of the high-melting inorganic mineral. Affects the fusion action (adsorption action, increase of reaction area) and relates to dissolution and diffusion of other components. Finally, even with a small amount of binder, it is possible to stably obtain the target grinding wheel performance and performance. It becomes.

Examples of the chloride include zinc chloride (ZnCl ₂ ), tin chloride (SnCl ₂ ), iron chloride (FeCl ₂ , FeCl ₃ ), and potassium chlorate (KClO ₃ ), one kind alone or two or more kinds. You may mix | blend combining.

The content of chloride is preferably 2 to 2.5 mol% in terms of the binder compounding ratio as the dissolved mass in the solution. That is, the chemical composition of the vitrified bond containing chloride is as follows: SiO ₂ 42-50 mol%, Al ₂ O ₃ 5-7 mol%, B ₂ O ₃ 24-28 mol%, R ₂ O + RO 20-25 mol% and chloride 2 to 2.5 mol% of the product is preferable.

  Usually, a porous (body) grindstone in which artificial pores larger than intrinsic pores are formed by using a pore material is typically selected as the superfinished fine grindstone. The artificial pores on the grinding wheel working surface activate the function of discharging chips generated around the cutting abrasive grains, and at the same time, it facilitates the formation of a lubricant layer on the gas phase of the grinding wheel, and lifts the grinding stone with an effective dynamic pressure effect. Due to the phenomenon, grinding wheel wear is suppressed. As a result, the grinding wheel finishing performance (cutting amount / whetstone wear amount) is improved, and the economy is improved.

  Examples of the porous (body) grindstone include a porous grindstone using one kind of pore material and a composite porous grindstone using two kinds of pore material. Among these, a composite porous grindstone using two kinds of pore materials is preferable because it provides better grinding wheel finishing performance, and two kinds of pores having a particle diameter equal to or larger than the average particle diameter of the hard abrasive grains used. A composite porous grindstone using a material, for example, two types of pore materials having a small particle diameter of 1 to 15 times the average particle diameter and a large particle diameter of 20 to 60 times the average particle diameter is more preferable.

  The vitrified superfinishing grindstone according to the present invention can be manufactured by the following method. For example, after the vitrified bond is homogeneously mixed with the composite abrasive, the pore material is added and further mixed homogeneously. After that, the powder can be adjusted, molded, dried and fired. Further, if necessary, the grindstone pores may be filled with an organic processing agent.

  As for the melting temperature of the vitrified superfinishing grindstone concerning the present invention, 650-750 ° C is preferred. When the melting temperature is lower than 650 ° C., the binder is not sufficiently softened and the abrasive grain holding force tends to be weakened. On the other hand, when the temperature exceeds 750 ° C., as the softening proceeds, the natural porosity is reduced, and the chip cannot function as a discharge hole and tends to cause chipping. The melting temperature is the melting temperature at which the tip of the test cone comes into contact with the cradle under the condition of a heating rate of 125 ° C./hour according to JIS R 2204.

  The RL hardness of the vitrified superfinishing grindstone according to the present invention is preferably minus 30 to 50 when, for example, CBN having an average particle diameter of 4.8 μm is used as the hard abrasive grains. When the RL hardness is less than minus 30, the wear amount of the grindstone tends to increase, and when it exceeds 50, chipping tends to occur and the cutting amount tends to decrease. Moreover, when using CBN whose average particle diameter is 2.8 micrometers as a hard abrasive grain, minus 80-0 are preferable. When the RL hardness is less than minus 80, the wear amount of the grindstone tends to increase. When the RL hardness exceeds 0, chipping occurs, and the cutting amount tends to decrease. The RL hardness is a value measured using a Rockwell superficial hardness tester with a steel ball indenter of 3.175 mm, a standard load of 29.4 N, and a test load of 196 N.

Superfinishing method The superfinishing method of the present invention uses the above-mentioned water-soluble grinding oil and vitrified superfinishing grindstone, except that the pressing pressure of the grindstone against the workpiece (grinding wheel pressure) is within a predetermined range. There is no particular limitation, and a conventional superfinishing method such as a superfinishing method including roughing and finishing may be used.

  The pressing pressure (grinding wheel surface pressure) of the grindstone against the workpiece is 0.3 MPa or more, preferably 0.5 MPa or more. When the grinding wheel surface pressure is less than 0.3 MPa, the cutting amount tends to decrease and the finishing performance tends to decrease. On the other hand, the upper limit of the grindstone surface pressure is preferably 1.5 MPa or less when a vitrified superfinished grindstone having a purity of cerium oxide of 99.0% by mass or more as soft abrasive grains is used. Moreover, when using the vitrified superfinishing grindstone whose purity of a cerium oxide is 40 mass% or more and less than 80 mass%, it is preferable to set it as 1.0 Mpa or less. When the upper limit of the grinding wheel surface pressure is exceeded, the grinding wheel wear amount and the welding amount increase, and there is a tendency that appropriate superfinishing processing becomes difficult.

  Other various conditions in the superfinishing method of the present invention can be adjusted as appropriate according to the workpiece and the apparatus to be used.

  The surface peripheral speed of the workpiece can be appropriately adjusted within a range of 100 to 500 m / min.

  The rocking rocking number can be appropriately adjusted within a range of 6.7 to 20 Hz for roughing and 1.0 to 3.3 Hz for finishing.

  The processing time, the amount of water-soluble cutting oil used, and the size of the vitrified superfinishing grindstone can be appropriately selected according to the part to be processed and the apparatus to be used, as in the conventional superfinishing method.

  The workpiece to which the superfinishing method of the present invention is applied is not particularly limited, and examples thereof include metal members that need to be processed into mirror surfaces such as various bearings.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these.

Preparation of water-soluble grinding oil A water-soluble grinding oil for test was prepared according to the formulation (mass%) shown in Table 1. First, after mixing polyoxyethylene alkyl ether acetic acid, an amine compound, and a nonionic surfactant while heating to 30 to 40 ° C., other components were added and stirred uniformly. The obtained mixture was filtered and dissolved in water to obtain a water-soluble grinding oil for each test.

Each chemical used for preparation of water-soluble grinding oil is shown.
Oleic acid: Nippon Seika Co., Ltd. oleic acid DD
Oleyl sarcosine: Arkomon SO manufactured by Hoechst Industry Co., Ltd.
Polyoxyethylene (10 mol) lauryl ether acetic acid: Taipol Soft ECA-1090 manufactured by Taiko Yushi Chemical Co., Ltd.
Polyoxyethylene (10 mol) lauryl ether acetate potassium salt: Prepared by adding potassium hydroxide at an equimolar ratio to polyoxyethylene (10 mol) lauryl ether acetic acid and allowing them to react.
Monoisopropanolamine: MIPA (monoisopropanolamine) manufactured by Dow Chemical Japan
Triethanolamine: TEA-99 (triethanolamine) manufactured by Japan Chemtech Co., Ltd.
Nonionic surfactant 1: Pelletex 2022 (polyoxyethylene alkyl ether, HLB: 13.2) manufactured by Miyoshi Oil & Fat Co., Ltd.
Nonionic surfactant 2: Pelletex 2822 (polyoxyethylene alkyl ether, HLB: 10.3) manufactured by Miyoshi Oil & Fat Co., Ltd.
Nonionic surfactant 3: Pelletex 2937J (polyoxyethylene alkyl ether, HLB: 15.3) manufactured by Miyoshi Oil & Fat Co., Ltd.
Dimercaptothiadiazole: Addintin RC5201 from Rhein Chemie
Octylphosphonic acid: RHODAFAC ASI-80 manufactured by Rhodia Nikka Co., Ltd.

Vitrified Superfinishing Wheel Table 2 shows soft abrasive grains, hard abrasive grains, and vitrified bonds used in the production of the test vitrified superfinishing grindstone.

  A vitrified bond superfinishing wheel for each test was produced. First, abrasive grains, vitrified bond, pore material (mixture of pore materials 1 and 2) and other auxiliaries (including zinc chloride) are homogeneously mixed, then powdered, molded and dried, and the maximum temperature of 750 ° C. for 3 hours. It was held and fired. Cooling the raw stone after firing, cutting it into a square shape with a width of 5.5 mm, a thickness of 5.0 mm, and a length of 35 mm, and then finishing to a predetermined dimensional accuracy and filling the grindstone pores with an organic treatment agent The vitrified superfinishing grindstone for each test was obtained.

  Table 3 shows the structure and RL hardness of each test vitrified bond superfinished grinding wheel. The RL hardness was measured using a Rockwell superficial hardness tester (3NR-S manufactured by Nakai Seiki Seisakusho Co., Ltd.) with a steel ball indenter of 3.175 mm, a standard load of 29.4 N, and a test load of 196 N.

Each chemical used is shown.
Zinc chloride: ZnCl ₂ manufactured by Nacalai Tesque
Pore material 1: Acrylic resin (average particle size 30 μm)
Pore material 2: Acrylic resin (average particle size 80 μm)

Cutting test examples 1 to 32 and comparative examples 1 to 14
Test water-soluble grinding oils A to J (see Table 1) and test vitrified superfinishing wheels a to j (grinding wheel dimensions: 5.5 × 5 × 35) (see Table 3) Tables 4-10 show the super finishing of 100 ball bearing inner ring raceway surfaces (model number: # 6203, material: SUJ-2) using super finishing machine (KN-533 manufactured by Izumi Metal Co., Ltd.). It carried out according to each processing condition shown. The evaluation was performed on the cutting amount, the grinding wheel wear amount, the finished surface roughness, and the welding to the grinding wheel working surface. Further, as Reference Examples 1 to 11, superfinishing and evaluation using oil-based grinding oil (SF-36 manufactured by Yushiro Chemical Industry Co., Ltd., indicated as “oil” in the table) were similarly performed. The evaluation results are shown in Tables 4 to 10 and FIG.

Cutting amount The difference between the R-bottom dimension of the 100 ball bearing inner ring raceway groove surfaces subjected to the actual cutting test before and after processing was measured with a dial gauge, and the average value was taken as the cutting amount. When a test grindstone having an average particle diameter of 4.8 μm is used, the performance target value of the cutting amount is Φ7.0 μm or more, and preferably Φ8.0 μm or more. When a test grindstone having an average particle diameter of 2.8 μm is used, the performance target value of the cutting amount is Φ5.0 μm or more, and preferably Φ6.0 μm or more.

Grinding wheel wear amount The grinding wheel wear amount was measured by comparing the length of the test grindstone after the actual cutting test with the length before the test. When a test grindstone having an average particle diameter of 4.8 μm is used, the wear amount of the grindstone can withstand actual use if it is 5.0 μm or less, preferably 2.6 μm or less, more preferably 1.5 μm or less. 1.0 μm or less is more preferable. In addition, when a test grindstone having an average particle diameter of 2.8 μm is used, the wear amount of the grindstone can withstand actual use if it is 5.0 μm or less, preferably 2.6 μm or less, and preferably 1.8 μm or less. More preferably, it is 1.3 μm or less.

Finished surface roughness The surface roughness of three ball bearing inner ring raceways randomly selected from 100 subjected to the actual cutting test was measured with a surface roughness measuring machine (SURFCOM 480A manufactured by Tokyo Seimitsu Co., Ltd.) The average value was the finished surface roughness. When a test grindstone having an average particle diameter of 4.8 μm is used, the performance target value of the finished surface roughness is 0.045 μm Ra or less, and more preferably 0.042 μm Ra or less. When a test grindstone having an average particle size of 2.8 μm is used, the performance target value of the finished surface roughness is 0.030 μm Ra or less, and more preferably 0.025 μm Ra or less.

Welding on the working surface of the test grindstone after the actual cutting test was confirmed 10 to 20 times with a microscope (VH5500 manufactured by Keyence Corporation) and evaluated according to the following criteria.
○: Welding was hardly seen.
(Triangle | delta): Although welding was able to be confirmed, the malfunction (decrease in cutting amount, a remainder) resulting from welding could not be confirmed.
X: Welding could be confirmed, and defects caused by welding (decrease in cutting amount, residual amount) were confirmed.

  Photos A to C shown in FIG. 1 are photographs of the working surfaces of some test wheels after the actual cutting test. The white part of the working surface is where the welding has occurred. A is the working surface of the test grindstone of Example 15 (evaluation result “◯”), B is Example 9 (evaluation result “Δ”), and C is Comparative Example 4 (evaluation result “×”).

  From the results in Tables 4 to 10, the superfinishing method using a predetermined water-soluble grinding oil and a predetermined vitrified superfinishing grindstone uses a water-soluble grinding oil, and stable lubrication performance is obtained. It can be seen that this super-finishing method is excellent in cleaning effect, hardly clogs the grindstone, and has excellent finishing performance (grindability, grindstone wear, surface roughness).

Claims (4)

A super-finishing method that uses water-soluble grinding oil and vitrified super-finishing wheel.
The water-soluble grinding oil is
A water-soluble grinding oil containing polyoxyethylene alkyl ether acetic acid or a salt thereof, an amine compound, and a nonionic surfactant;
The vitrified superfinishing wheel is
Composite abrasive grains comprising 5 to 80% by volume of soft abrasive grains having chemical reactivity with a workpiece and no cutting ability, and 20 to 95% by volume of hard abrasive grains having a cutting ability with respect to the workpiece. Is a composite abrasive vitrified superfinished whetstone formed by bonding with vitrified bond,
Superfinishing method in which the grinding wheel surface pressure during processing is 0.3 MPa or more. The superfinishing method according to claim 1, wherein the hard abrasive has an average particle size of 2.0 to 20 μm. The superfinishing method according to claim 1 or 2, wherein the soft abrasive grains are cerium oxide having a purity of 99.0% by mass or more. The superfinishing method according to claim 3, wherein the surface pressure during processing of the superfinishing grindstone is 0.3 to 1.5 MPa.