LUBRICANT COMPOSITION FOR FORMING HEMIMORPHITE-CONTAINING LUBRICATION COATING, METHOD FOR FORMING SAID LUBRICATION COATING ON SURFACE OF METAL WORKPIECE, AND METAL WORKPIECE COMPRISING SAID LUBRICATION COATING

Abstract

Problems addressed by the present invention are to provide a lubricant composition that is capable of being used as an alternative to chemical conversion treatment by means of phosphate, to provide a lubricant composition having practical stable lubricative performance without the need for additional unwanted operations, and to provide a method for using this to form a lubrication coating, and a metal workpiece at which a lubrication coating is formed on a surface thereof. Provided as a means for solving such problems is a lubricant composition for causing formation of a hemimorphite-containing lubrication coating that contains a silicate compound (e.g., colloidal silica) and water-soluble zinc in solution.

Claims

1. A lubricant composition for causing formation of a hemimorphite-containing lubrication coating that contains a silicate compound and water-soluble zinc in solution.

2. The lubricant composition according to claim 1 wherein the silicate compound is colloidal silica.

3. The lubricant composition according to claim 1 characterized in that a water-soluble polymer is further added thereto.

4. The lubricant composition according to claim 1 characterized: in that at least one of metal soap and/or polyethylene is further added thereto.

5. The lubricant composition according to claim 1 characterized in that at least one of hydrated lime, calcium carbonate, molybdenum disulfide, and/or carbon is further added thereto.

6. The lubricant composition according to claim 1 characterized in that at least one of nitrite and/or metal sulfonate is further added thereto.

7. A lubricant composition for causing formation of a hemimorphite-containing lubrication coating that contains hemimorphite.

8. The lubricant composition according to claim 7 characterized in that the hemimorphite is synthetic hemimorphite.

9. The lubricant composition according to claim 7 characterized in that the hemimorphite consists of particles for which the volume mean diameter thereof is not greater than 10 μm.

10. The lubricant composition according to claim 7 characterized in that it contains gel like synthetic hemimorphite.

11. A method for forming a lubrication coating wherein the lubricant composition according to claim 1 is made to adhere to a surface of a metal material; and by then causing this metal material to undergo plastic working as a metal workpiece, a lubrication coating that contains hemimorphite is formed on a surface of the metal workpiece at a time when there is deformation as a result of the plastic working thereof.

12. A method for forming a lubrication coating wherein a lubrication coating that contains hemimorphite is formed as a result of causing the lubricant composition according to claim 7 to adhere to a surface of a metal workpiece.

13. A metal workpiece at which a lubrication coating that contains hemimorphite is formed at a surface thereof by means of the lubricant composition according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0055] FIG. 1 Drawings showing results of measurement of x-ray diffraction before and after creation of synthetic hemimorphite. (a) is the result of measurement of residue dried during the stage before heating of solution when white gel-like substance had not been created. (b) is the result of measurement of dried white gel-like substance produced following heating for 18 hours. (c) is JCPDS data showing peaks of known hemimorphite.

[0056] FIG. 2 Secondary electron image produced by a scanning electron microscope of the substance used at (b) in FIG. 1.

[0057] FIG. 3 Schematic diagram of apparatus employed during backward extrusion friction testing.

[0058] FIG. 4 Results of Raman spectroscopic analysis of coating surface at Target Material 1 to which the lubricant composition of Working Example 1 was made to adhere.

[0059] FIG. 5 Drawing provided for reference purposes of Raman spectroscopic analysis of natural crystals of hemimorphite.

[0060] FIG. 6 Schematic diagram of reflux apparatus used for heated synthesis of hemimorphite.

[0061] FIG. 7 Bar graph showing results (in units of kN) of backward extrusion testing at TABLE 3.

EMBODIMENTS FOR CARRYING OUT INVENTION

[0062] Compositions of respective substances contained in solutions at lubricant compositions in accordance with the present invention will be described.

[0063] A lubricant composition in accordance with the present invention is a solution that contains (1) water-soluble zinc and (2) a silicate compound, a prime example of which would be colloidal silica. This (1) and this (2) are substances that are necessary for artificial creation of hemimorphite (Zn.sub.4(OH).sub.2Si.sub.2O.sub.7H.sub.2O).

[0064] With regard to the blended ratio of these substances, the amounts of the water-soluble zinc and colloidal silica components may be adjusted in advance so as to cause these to be present in amounts such as will cause the molar ratio of Zn and Si to be in the ratio in which they are present in hemimorphite.

[0065] As the water-soluble zinc is the source of the Zn that is supplied for formation of hemimorphite, it is water-soluble. For example, where zinc oxide and the chelating agent EDTA (ethylenediaminetetraacetic acid) are used, because that which results from causing the zinc oxide to be dissolved in advance by the chelating agent is capable of being suitably used, it will also be moreover possible to favorably employ EDTA.Zn.2Na.3H.sub.2O (Chelest Zn manufactured by Chelest Corporation) or the like. Furthermore, as water-soluble zinc, a water-soluble zinc compound or the like resulting from redissolution of zinc oxide by an acidic solution (e.g., nitric acid, sulfuric acid, acetic acid, hydrochloric acid, or an organic acid or the like) may be used.

[0066] Silicate compound refers, for example, to waterglass (sodium silicate) or sodium-silicate-derived wet silica, dry silica, precipitated silica, silica gel, colloidal silica, or the like which is water soluble or is dispersible in solution. As the silicate compound is the source of the Si that is supplied for formation of hemimorphite, it is necessary.

[0067] Colloidal silica is a colloid of SiO.sub.2 or a hydrate thereof, and is also referred to as colloid-like silica. Colloidal silica consists of particles having excellent dispersion characteristics which when in a sol state at room temperature do not readily precipitate. It may be obtained by methods which employ inexpensive waterglass as raw material, liquid-phase synthetic methods of the sort referred to as alkoxide hydrolysis, gas-phase synthetic methods such as aerosil synthesis involving pyrolysis of silicon tetrachloride, and so forth. Because what is referred to as colloidal silica in the context of the present invention is thus colloidal silicon dioxide, it includes fumed silica. It is preferred that it be a colloidal silica permitting use of a water-soluble solvent as dispersion medium. Those in which bonding of hydroxyl ions (OH.sup.−) with silanol groups at the surfaces of silica particles under alkaline conditions causes mutual repulsion of respective silica particles that have acquired a negative charge such that the stability thereof can be maintained as they are dispersed in solution without bonding therebetween may be cited as examples. Moreover, the average particle diameter of primary particles in the colloidal silica might, for example, be 1 nm to 100 nm.

[0068] The description that follows is given in terms of the example of colloidal silica.

[0069] As solution (dispersion medium), this may be water, or methanol, ethanol, isopropanol, n-propanol, isobutanol, n-butanol, or other such alcohol-type solvent, ethylene glycol or other such polyhydric-alcohol-type solvent, or ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, or other such polyhydric alcohol derivative, or the like. Water may be favorably employed.

[0070] In accordance with the present invention, to form a lubrication coating that contains hemimorphite, as viscosity will be low where only water-soluble zinc and colloidal silica are present, it will be necessary to cause this to adhere to the metal material surface. From the standpoints of coating forming characteristics, viscosity, and dispersion characteristics, water-soluble polymer(s) may therefore be added to the lubricant composition. As water-soluble polymer, vinyl acetate resin, carboxymethylcellulose sodium, and so forth may be cited as examples. Because vinyl acetate resin is water-soluble and is effective in terms of retention of coating forming characteristics, it is able to favorably retain hemimorphite, hemimorphite precursor substances, or water-soluble zinc and colloidal silica involved in the creation of hemimorphite at the metal material surface. Furthermore, methyl cellulose and the like are capable of imparting increased viscosity thereto.

[0071] Moreover, to cause emulsification and dispersion of the foregoing lubricant composition, a small amount of emulsifier may be added thereto. As emulsifier, known anionic surfactants, cationic surfactants, nonionic surfactants, zwitterionic surfactants, and/or other such surfactants, water-soluble macromolecules having protective colloid ability, and/or the like may be employed. As anionic surfactant, sodium laurate, sodium stearate, sodium oleate, ammonium lauryl alcohol sulfate ester, sodium lauryl sulfate ester, and so forth may be cited as examples. As cationic surfactant, methylammonium chloride, laurylammonium chloride, stearylammonium chloride, dimethylammonium chloride, trimethylammonium chloride, lauryltrimethylammonium chloride, polyoxyethylene monolauryl amine, and so forth may be cited as examples. As nonionic surfactant, polyethylene glycol lauric acid ester, polyethylene glycol oleic acid diester, glycerin oleic acid monoester, polyoxyethylene lauryl ether, polyethylene glycol distearic acid ester, and so forth may be cited as examples.

[0072] Metal soap is for imparting supplemental lubrication capability so as to be suited for more efficient plastic working when a lubricant composition in accordance with the present invention that creates hemimorphite is used. As metal soap, while calcium stearate, barium stearate, aluminum stearate, and so forth may be cited as examples, there is no limitation with respect thereto. Furthermore, because polyethylene has a low melting point, and because by melting on the die surface it will permit sliding thereon, it is effective for supplemental lubrication.

[0073] Moreover, hydrated lime, calcium carbonate, molybdenum disulfide, and/or carbon may be added as appropriate to the lubricant composition of the present invention. Thereamong, hydrated lime and/or calcium carbonate may function as carrier agent. Furthermore, molybdenum disulfide and/or carbon would be added with the goal of reducing friction and reducing seizing.

[0074] Furthermore, to improve rust preventability as a result of the lubrication coating, nitrite and/or metal sulfonate may be added to the lubricant composition. As nitrite, while sodium nitrite may be cited as example, there is no limitation with respect thereto so long as rust preventability is improved thereby. As metal sulfonate, calcium sulfonate, sodium sulfonate, barium sulfonate, and so forth may be cited as examples.

[0075] It is preferred that the lubricant composition be prepared in such fashion that the pH thereof is maintained at a pH of 10 to 12. By maintaining the alkalinity thereof, because there will be production of a passivation coating at the surface layer when a metal material is immersed therein, this will improve rust preventability, and will also suppress occurrence of rust due to exposure in air during long-term storage.

[0076] Furthermore, while a lubricant composition in accordance with the present invention may be such that, after a lubricant composition containing water-soluble zinc and colloidal silica has been made to adhere to metal material, at the time of deformation as a result of plastic working, formation of hemimorphite causes formation thereof as a lubrication coating at the surface of the metal workpiece, it is moreover also possible to cause hemimorphite to be dispersed in advance within the lubricant composition in advance. While the hemimorphite used in such case may be such that natural-mineral-derived or synthetic hemimorphite in the form of fine powder is dispersed therein, this may alternatively be such that gel-like hemimorphite and precursor substances thereof are made to be present within a lubricant composition solution.

[0077] Synthetic hemimorphite in the form of fine powder might for example be created after a lubricant composition containing water-soluble zinc and colloidal silica in accordance with the present invention has been formed into a coating under the pressure such as plastic forming and pulverized of that coating; or alternatively, it may be obtained after a gel-like substance containing hemimorphite is dried and solidified, when this is pulverized.

[0078] The gel-like substance containing hemimorphite might, for example, be obtained by the following procedure. After appropriate addition of H.sub.2O to a solution obtained by mixing water-soluble zinc and colloidal silica in amounts such as will cause the Zn:Si molar ratio to be approximately 4:2, this may be heated to 80° to 90° C. to obtain the gel-like substance as a result of formation thereof in this solution.

[0079] For example, 1814 g of Chelest Zn (Chelest Corporation) and 347 g of colloidal silica (AT-30 manufactured by Adeka Corporation) were diluted in an equal quantity of pure water, and the apparatus shown in FIG. 6 was thereafter used to heat this for 18 hours while refluxing at 85° C., upon which there was creation—in the solution that had initially been colorless and transparent—of a white gel-like substance after 18 hours had elapsed. Thereupon the liquid as it existed prior to heating and the white gel-like substance that was created were respectively dried, and the residues were measured using an x-ray diffraction device. Results are shown in FIG. 1. A MiniFlex 600 (manufactured by Rigaku) x-ray diffraction device was used to carry out measurement, measurement being performed over the range for which 2θ was 5 deg to 90 deg, at 40 kV, 15 mA output, and 0.0200 deg step width. As shown in (a) at FIG. 1, it was more or less amorphous prior to gel formation. On the other hand, following gel formation, as shown in (b) at FIG. 1, in addition to the fact that the Chelest Zn peaks were observed toward a lower angle, hemimorphite peaks were observed.

[0080] The white gel-like substances that had been dried and solidified were observed under SEM. Results are shown at FIG. 2 in the form of a secondary electron image.

[0081] Furthermore, upon performing simple identification of the surface of the solid substance by EDX, it was indicated that the compositional ratio of Si and Zn in units of at % was Zn=47.7% and Si=25.6%. Although compositional indications resulting from EDX contain large errors and should thus be considered as being for reference purposes only, Zn:Si was close to the 4:2 molar ratio of Zn and Si in hemimorphite, and the indicated result was not inconsistent with the results obtained by x-ray diffraction.

[0082] Note that while when colloidal silica is present in excess it is sometimes the case that this will facilitate gel formation, adjusting the molar ratio of Zn and Si raw materials in advance to agree with the molar ratio of Zn and Si in hemimorphite so as to cause reaction to proceed smoothly will reduce the tendency for trouble to occur and will make it such that there is no interference with creation of hemimorphite even when hemimorphite precursor substances are present during the course of creating hemimorphite.

[0083] Because it is possible to obtain a substance containing synthetic hemimorphite in accordance with the foregoing procedure, it is possible to employ as lubricant composition raw material the white gel-like substance or the powder obtained by fine pulverization following drying of the white gel-like substance. Moreover, with regard to the particle size distribution of hemimorphite made to be present in advance in solution, the volume mean diameter may be ascertained by for example using a Microtrac (laser diffraction/scattering method) to measure the volume distribution thereof. In this regard, grading may be carried out as appropriate to adjust particle size.

[0084] Below, embodiments of the present invention are described in terms of the working examples that follow. The present invention is of course not limited only to these working examples.

Working Example 1

[0085] As an example of a solution in accordance with the present invention, the following components were mixed to obtain a lubricant composition. [0086] Chelest Zn: 5%; [0087] Adelite AT-30: 1.2%; [0088] Calcium stearate: 3%; [0089] Calcium carbonate: 2.5%; and [0090] Pure water: Remaining portion

[0091] As the foregoing exemplary blending ratios are merely given by way of example, there is no limitation with respect thereto; for example, in addition to Working Example 1, keeping the molar ratio of Zn and Si at 4:2, further adding soluble polymer in the form of acetate emulsion resin, calcium stearate, polyester, molybdenum disulfide, calcium sulfonate, emulsifier, and/or the like, and adjusting pH to on the order of 10 is also a favorable example of the present invention. Added substance(s) may be appropriate combinations chosen from among those presented in the foregoing descriptions.

[0092] Furthermore, the aforementioned white gel-like substance may be created in advance by synthesis of hemimorphite, and this may be combined with acetate emulsion resin, calcium stearate, polyester, molybdenum disulfide, calcium sulfonate, emulsifier, and/or the like to obtain a lubricant composition. When this is applied to a metal material and this is subjected to cold plastic working, the pressure acting thereon will cause stable formation of a hemimorphite coating on the surface of the metal workpiece.

[0093] Alternatively, a small amount of powdered synthetic hemimorphite may be added to water-soluble polymer to obtain a lubricant composition that is capable of forming a coating. In this case as well, calcium stearate, polyester, molybdenum disulfide, calcium sulfonate, emulsifier, and/or the like may be combined therewith as appropriate.

Testing for Evaluation of Lubricity

[0094] To evaluate lubricity, Bowden testing, ring compression testing, and backward extrusion testing were carried out.

Bowden Testing

[0095] Bowden testing refers to testing using a reciprocating-type sliding friction tester which permits measurement of the coefficient of dynamic friction by causing sliding to occur while a point load is applied between a test piece and a spherical contact.

[0096] First, as test pieces, JIS (Japanese Industrial Standards) SCM 435 wire rod (serving as metal material) of diameter 5.5 mm was descaled in hydrochloric acid (18%), and after rinsing with water this was immersed for 1 minute in lubricant composition (1-1 and 1-2) in accordance with the present invention, these were dried for 1 minute and were thereafter again immersed therein for 1 minute, and a dryer was used to dry the lubricant composition adhering to the surface of the wire rod, in which state the test materials (Target Material 1-1 and Target Material 1-2) were prepared.

[0097] Furthermore, for comparative purposes, wire rod that was similar but at which instead of causing lubricant composition in accordance with the present invention to adhere thereto was subjected to phosphate coating treatment and thereafter immersed in Na soap (bonderization/lubricant carrier treatment=Comparative Material 1-1), that was subjected to zinc phosphate treatment and thereafter immersed in lime soap (bonderized/lime=Comparative Material 1-2), and that was akin to that which was subjected to lime soap (Comparative Material 1-3) were prepared.

[0098] Next, a wiredrawing die was used to draw the test materials until the diameters thereof went from 5.5 mm to 5.25 mm to obtain test pieces. A Bowden-type tester was used to carry out sliding testing in which these test pieces were made to engage in reciprocating motion under testing conditions which were such that sliding speed was 20 mm/min and stroke was 10 mm with a load of 5 Kgf being imparted thereto by a stationary pin (made of SUJ-2) that was 5 mm in diameter. Sliding was carried out repeatedly, and the number of times that sliding had to be carried out to cause the coefficient of friction to rise until 0.25 was reached was recorded.

[0099] Results (number of times sliding had to be carried out) of such Bowden testing are shown in TABLE 1.

Target Material 1-1: This had the lubricant composition of Working Example 1 adhering thereto.
Target Material 1-2: This had a lubricant composition adhering thereto which was such that the water-soluble zinc of Working Example 1 was changed from Zn chelating agent to Zn alkoxide.
Comparative Material 1-1: This was immersed in Na soap following phosphate coating treatment (bonderization/lubricant carrier treatment)
Comparative Material 1-2: This was immersed in lime soap following zinc phosphate treatment (bonderized/lime)
Comparative Material 1-3: This was immersed in lime soap
Comparative Material 1-4: That which adhered thereto was the lubricant composition of Working Example 1 without the colloidal silica
Comparative Material 1-5: That which adhered thereto was the lubricant composition of Working Example 1 without the water-soluble zinc chelating agent

TABLE-US-00001 TABLE 1 Number of Times Sliding Had To Be Carried Out for Coefficient of Friction to Reach 0.25 Target Material 1-1: 6200 times Target Material 1-2: 6695 times Comparative Material 1-1: 5004 times Comparative Material 1-2: 1393 times Comparative Material 1-3:  843 times Comparative Material 1-4: 1846 times Comparative Material 1-5:  890 times

[0100] In accordance with this testing, a lubricant for which the number of times that sliding has to be carried out for the coefficient of friction to reach 0.25 is 3000 or more can be evaluated as excellent in terms of the practical lubricity thereof.

[0101] From the results of testing shown in TABLE 1, it was confirmed that those at which a lubricant composition in accordance with the present invention had been made to adhere were as good as or better than those at which there was bonderized/lime or bonderization/lubricant carrier treatment involving phosphate coating treatment. And based on the fact that this was strong with respect to repeated sliding, this may be taken as indication that the properties thereof would be capable of being maintained and that lubrication would not easily be exhausted during deformation in the context of plastic working.

[0102] Where as indicated at Comparative Material 1-4 and Comparative Material 1-5 either water-soluble zinc or colloidal silica is missing from what would otherwise be the lubricant of the present invention, ability to perform as lubricant composition was such that there was dramatic decrease in the number of times that sliding had to be carried out.

Ring Compression Testing

[0103] A press was used to compress ring-shaped test pieces of outside diameter 15 mm, inside diameter 7.5 mm, and height 5 mm, and the coefficient of friction of the rings as they existed following working was determined. Because the phenomenon by which use of planar pressure plates to compress a ring-shaped test piece causes there to be a change in the inside diameter thereof following compression depending on the interfacial lubricative state that existed thereat is known, this may be adopted to determine coefficient of friction. Using test pieces respectively including Target Material 2 that was a ring at which a lubricant composition in accordance with Working Example 1 of the present invention had been made to adhere, Comparative Material 2-1 that was a ring which was subjected to phosphate coating treatment and thereafter immersed in Na soap, and Comparative Material 2-2 that was a ring which was immersed in lime soap, the coefficients of friction thereof were measured when height following compression by the press was 50 mm, and when this was 60 mm. Results are shown in TABLE 2.

TABLE-US-00002 TABLE 2 Target Material 2: 50 mm: 0.108 60 mm: 0.097 Comparative Material 2-1: 50 mm: 0.100 60 mm: 0.090 Comparative Material 2-2: 50 mm: 0.130 60 mm: 0.117

[0104] At ring compression testing as well, it was indicated that lubricity of the Target Material at which a lubricant composition in accordance with the present invention had been made to adhere was vastly superior to that of lime soap, and that the lubricative performance thereof was close to that of that which was subjected to phosphate coating treatment and thereafter immersed in Na soap.

Backward Extrusion Testing

[0105] The backward extrusion friction testing procedure was such that sample (1) was placed within the internal space of cylindrical die (4) shown in FIG. 3, the front thereof was closed off by knockout punch (3), and punch (2) was pressed thereagainst from a central location behind sample (1) so as to be directed toward the front, causing the outside circumference of sample (1) to be extruded backward in cylindrical fashion. The backward extrusion load at that time was measured using strain gauge (6) provided at punch holder (5).

[0106] Using a H1F200S-11 (manufactured by Komatsu) as tester, backward extrusion testing was carried out on Samples 3a to 3l, below, at which the various lubricants were made to adhere, and the lubricities thereof were evaluated.

[0107] Sample 3a: Comparative Example 3-1: Bonderization/lubricant carrier treatment. Sample was subjected to bonderization (zinc phosphate coating) and was thereafter rinsed with water and immersed in lubricant carrier solution having sodium soap as primary component. Sodium soap reacted with the bonderized coating, created zinc soap at the surface layer, and exhibited satisfactory lubricity.

[0108] Sample 3b: Comparative Example 3-2: Bonderized/lime. Zinc phosphate coating was created on sample, and this was thereafter rinsed with water, immersed in lime soap solution, and dried.

[0109] Sample 3c: Comparative Example 3-3: Lime soap. Mixture was created on sample by metathetical reaction between hydrated lime (or quicklime) and sodium stearate. Primary component of created components that adhered thereto was a mixture of calcium stearate and hydrated lime.

[0110] Sample 3d: Inventive Example 3-1: Lubricant composition comprising water-soluble zinc (Chelest Zn) and colloidal silica (Adelite AT-30), with the remaining portion being pure water, was made to adhere to sample.

[0111] Sample 3e: Inventive Example 3-2: Lubricant composition having components as at Sample 3d was applied thereto and this was thereafter heated for 2 hours at 105° C.

[0112] Sample 3f: Inventive Example 3-3: Lubricant composition comprising water-soluble zinc (Chelest Zn) and colloidal silica (Adelite AT-30) and molybdenum disulfide, with the remaining portion being pure water, was made to adhere to sample.

[0113] Sample 3g: Inventive Example 3-4: Lubricant composition comprising water-soluble zinc (Chelest Zn) and colloidal silica (Adelite AT-30) and barium stearate, with the remaining portion being pure water, was made to adhere to sample.

[0114] Sample 3h: Inventive Example 3-5: Lubricant composition comprising water-soluble zinc (Chelest Zn) and colloidal silica (Adelite AT-30) and water-soluble polymer, with the remaining portion being pure water, was made to adhere to sample.

[0115] Sample 3i: Inventive Example 3-6: Lubricant composition comprising water-soluble zinc (Chelest Zn) and colloidal silica (Adelite AT-30) and powdered carbon, with the remaining portion being pure water, was made to adhere to sample.

[0116] Sample 3j: Inventive Example 3-7: Lubricant composition comprising water-soluble zinc (Chelest Zn) and colloidal silica (Adelite AT-30) and barium stearate and water-soluble polymer, with the remaining portion being pure water, was made to adhere to sample.

[0117] Sample 3k: Inventive Example 3-8: Lubricant composition comprising water-soluble zinc (Chelest Zn) and colloidal silica (Adelite AT-30) and barium stearate and molybdenum disulfide, with the remaining portion being pure water, was made to adhere to sample.

[0118] Sample 3l: Inventive Example 3-9: Lubricant composition comprising water-soluble zinc (Chelest Zu) and colloidal silica (Adelite AT-30) and barium stearate and molybdenum disulfide and water-soluble polymer and powdered carbon, with the remaining portion being pure water, was made to adhere to sample.

TABLE-US-00003 TABLE 3 Comparative Example 3-1: 849 kN Comparative Example 3-2: 862 kN Comparative Example 3-3: 858 kN Inventive Example 3-1: 849 kN Inventive Example 3-2: 844 kN Inventive Example 3-3: 840 kN Inventive Example 3-4: 842 kN Inventive Example 3-5: 840 kN Inventive Example 3-6: 844 kN Inventive Example 3-7: 836 kN Inventive Example 3-8: 840 kN Inventive Example 3-9: 825 kN

[0119] Because an extremely large force is applied to the test piece surface during backward extrusion testing, it constitutes testing in which lubricative performance is ascertained under extremely severe conditions; the lower the load required when carrying out working to achieve a prescribed shape the higher the lubricity of the evaluation it will be capable of receiving.

[0120] The results of the backward extrusion testing at TABLE 3 are shown in the form of a bar graph at FIG. 7. As Comparative Example 3-1 is the result of testing for bonderization/lubricant carrier treatment which was best in terms of phosphate coating treatment, using Comparative Example 3-1 as reference, the lubricant composition consisting of water-soluble zinc and colloidal silica in accordance with the present invention at Inventive Example 3-1 exhibited lubricity equivalent to that of bonderization/lubricant carrier treatment.

[0121] Moreover, when barium stearate, molybdenum disulfide, water-soluble polymer, powdered carbon, and/or the like were further added in the lubricant composition of the present invention as at Inventive Example 3-3 to Inventive Example 3-9, it was confirmed that lubricity was further improved as compared with Inventive Example 3-1.

[0122] At Inventive Example 3-2, because, prior to backward extrusion testing, as a result of causing lubricant composition to adhere thereto, in which state it was dried through application of heat, it was in a state in which hemimorphite had formed on the surface, lubricity was improved.

[0123] As described above, a lubricant composition employing Working Example 1 in accordance with the present invention was such that the lubricity thereof was higher than that with treatment involving lime soap, the properties thereof being adequate in tenors of lubricative performance during plastic working of a metal workpiece, and exhibited a practical lubricity equivalent to, being not worse than, that with bonderization/lubricant carrier treatment. Because it is able to ensure practical lubricity while also achieving a phosphorous-free constitution, it is therefore able to provide practical lubricative performance while also avoiding a causal factor of delayed fracture, and because it is moreover able to impart lubricity without requiring that unwanted additional procedures be introduced into existing operations, it imposes few constraints on manufacturing operations in situations where lubricant compositions are employed.

Hemimorphite within Lubrication Coating

[0124] Next, Raman spectroscopic analysis was used to observe hemimorphite within the lubrication coating at the surface of Target Materials 1 after this had been used at Bowden testing. Results of Raman spectroscopic analysis are shown in FIG. 4. FIG. 5 shows the results of observation of the surface of natural hemimorphite by means of Raman spectroscopic analysis for comparative purposes.

[0125] As the Raman spectral peak at the lubrication coating of FIG. 4 matched the location of the peak seen at the natural hemimorphite of FIG. 5, it was identified as hemimorphite. It was thus confirmed that when the lubricant composition of Working Example 1 is applied to a metal material and the metal workpiece is made to undergo plastic deformation, the mere fact that working involving plastic deformation causes pressure to be applied to the coating surface is enough to cause creation of hemimorphite crystals in the lubrication coating even when at room temperature or under other such low-temperature ambient conditions.

Employment of Lubricant Composition of Present Invention at Metal Material Surface

[0126] While the lubricant composition of the present invention is used by causing it to adhere to the surface of a metal material, in causing it to adhere to the metal material surface, the metal material might be immersed in a solution of the lubricant composition, or a solution of the lubricant composition might be applied to or sprayed on the metal material, it being possible to employ any of various means such as causing the lubricant composition to adhere to the surface of the metal material and so forth. Regardless of what means is employed to cause it to adhere thereto, because the metal material at which the lubricant composition adheres to the surface will be such that this will be capable of undergoing plastic working as a metal workpiece, and such that when some stress acts thereon at room temperature or under such other low-temperature condition during such plastic working thereof, the pressure therefrom will cause creation of hemimorphite, it will be possible to form a lubrication coating at which hemimorphite is present at the surface of the metal workpiece. Because the surface of this metal workpiece will be imparted with lubricity by the lubrication coating, it will be possible for it to subsequently undergo forging or other such working. And because this lubrication coating will tend not to change due to absorption of moisture or the like, it will be capable of retaining its properties in stable fashion for a long period of time.

[0127] Furthermore, causing a lubricant composition which contains natural or synthetic hemimorphite to be applied to a metal material surface will make it possible to impart lubricity thereto.

[0128] Metal materials and metal workpieces that have undergone coating treatment in such fashion will be excellent in terms of their lubricative performance and rust preventability. As an example of a metal workpiece, steel wire on which a hemimorphite-containing lubrication coating is formed will therefore be such that the steel wire will be capable of being adequately drawn into fine wire by means of a die without the need to further impart supplemental lubricant thereto.

Rust Preventability

[0129] Humidity testing was carried out in which respective steel rods of Target Material 4 at which the lubricant composition of Working Example 1 was made to adhere, Comparative Material 4-1 which was immersed in Na soap following phosphate coating treatment, and Comparative Material 4-2 which was immersed in lime soap were left undisturbed for 24 hours in humid ambient conditions of saturated humidity. Furthermore, indoor exposure testing was carried out for 1 week.

[0130] As a result, with the lime soap at 4-2, much rust was observed to have occurred as a result of humidity testing for 24 hours, and the entire surface thereof was severely corroded as a result of exposure testing for 1 week. With the bonderization at 4-1, locations at which there was sporadic formation of rust were observed as a result of humidity testing for 24 hours. Furthermore, with exposure testing for 1 week, progress of rust was observed not over the entire surface but at portions thereof. In contradistinction thereto, Target Material 4 exhibited high rust preventability, occurrence of rust not being observed as a result of humidity testing for 24 hours. With exposure testing for 1 week, while progress of rust was observed at portions thereof, the degree to which progress of rust formation had occurred was on a level that was equivalent to or better than with bonderization, and higher rust preventability than with lime soap was exhibited thereby.

[0131] As described above, use of a lubricant composition in accordance with the present invention makes it possible to obtain a lubrication coating that as compared with a conventional lubrication coating has the following characteristics.

[0132] (1) Because a lubricant composition in accordance with the present invention does not contain phosphorous, when a metal workpiece at which a lubrication coating has made to adhere or a metal workpiece which is such that a product further subjected to secondary working is made to undergo quenching, there will be no concern that this could lead to occurrence of delayed fracture due to the phosphorization phenomenon which is a concern with zinc phosphate and other such chemical conversion treatments.

[0133] (2) Because lubricative performance is dramatically better than that with widely known existing lubrication by means of lime soap, and the lubricity exhibited thereby is excellent, being equivalent to or better than that with zinc phosphate treatment coating, it is a lubrication coating which is capable of being employed even in the context of cold forging or other such plastic working at which there had conventionally been no choice but to rely on zinc phosphate treatment.

[0134] (3) Because the degree of alkalinity thereof is less than with silicate-type lubricants, it permits suppression of occurrence of scum at the time of immersion.

[0135] (4) Because there is no employment of boron among the lubrication components thereof, a lubricant composition in accordance with the present invention has little enviromnental impact when discarded as waste liquid, and is gentler on the environment than would be the case with a lubricant in which B was present among the components thereof.

[0136] (5) Because where a lubricant composition in accordance with the present invention is employed there will tend not to be occurrence of sludge of the type that occurs during phosphate treatment, it is better from the standpoint of the environment.

[0137] (6) Whereas bonderization and other such chemical conversion treatment requires that rinsing with water be carried out following chemical conversion treatment, because a lubricant composition in accordance with the present invention is of the adhesion type by which a lubrication coating is made to adhere thereto and is formed thereon, there is no production of waste liquid such as would accompany rinsing with water, and so from this standpoint as well the environmental impact thereof is small.

[0138] (7) A lubricant composition in accordance with the present invention will make it possible to obtain a coating that not only has excellent lubricity but that also is extremely superior with respect to rust preventability.

[0139] (8) Because a lubricant composition in accordance with the present invention is of the adhesion type, not only does it permit reduction in treatment time, but because it also does not increase the number of operations that must be carried out, it has a wide scope of application, inasmuch as it facilitates employment in an existing production line, is capable of accommodating inline treatment, and so forth.

[0140] (9) A lubricant composition in accordance with the present invention will not lead to occurrence of bad plating such as is the case with waterglass-type lubricants.

EXPLANATION OF REFERENCE NUMERALS

[0141] 1 Sample [0142] 2 Punch [0143] 3 Knockout punch [0144] 4 Die [0145] 5 Punch holder [0146] 6 Strain gauge [0147] 7 Load cell