JP5806673B2 - Stainless steel wire for cold heading - Google Patents

Description

  The present invention relates to a metal composition plastic working lubricant composition used for various metal materials for work to be subjected to cold or warm working, a lubricant film formed from the composition, and a film coated with the film. The present invention relates to a coated metal material and a method for producing the coated metal material.

  Traditionally, special metal materials such as stainless steel, titanium, and nickel-based alloys have many excellent properties such as corrosion resistance, heat resistance, and mechanical properties compared to other ordinary metals, and are indispensable for today's technological progress. It is supposed to be. These special metal materials are widely used for machine element products such as screws, bolts, nuts, pins, ropes, bearings or springs, and various machine components.

  By the way, the special metal material is positioned as a difficult-to-process material because it is high in strength, hard and lacks toughness. For example, these difficult-to-work metal materials are prone to processing troubles such as cracking, disconnection, or breakage of the material when processing to obtain the various products described above. Therefore, in order to suppress these troubles and to extend the life of processing tools such as dies, rolls, and punches, an optimal lubrication technique is required.

  For example, when drawing the special metal material to reduce the diameter, or for subjecting the obtained thin wire to header forging or spring forming, conventionally, the surface of the metal material is plated with Cu, Ni or other metal. In addition, various kinds of organic and inorganic lubricating coatings such as resin materials, lime, oxalate, and phosphate are applied. In addition to those that form such coatings, auxiliary lubricants such as metal soap, molybdenum disulfide, graphite, borax, lime, etc., or various additives that are added as necessary, immediately before the processing. There is also known a combined lubrication method in which an auxiliary lubricant containing

  In particular, the above-described lubrication method is effective for severe processing such as strong forging to form screws, bolts, nuts and the like with the difficult-to-work metal material and spring forming using a hard wire. . However, for these lubricating coatings, there is a need to examine the composition in consideration of the global environment in recent years in addition to the processing lubrication performance.

  For example, the following Patent Document 1 discloses a metal material containing a carboxylic acid amide wax obtained by a reaction of a higher aliphatic monocarboxylic acid and a diamine, or a mixture of a higher aliphatic monocarboxylic acid and a polybasic acid and a diamine. Drawing lubricants have been proposed.

  Further, in Patent Document 2 below, a stainless steel wire is subjected to Ni plating with a thickness of 1 μm to 5 μm, and the surface thereof is further coated with a synthetic resin containing halogen to perform a wire drawing process with a cross section reduction rate of 60% or more. In addition, it has been proposed to use a steel wire for automatic coiling with a surface roughness adjusted to 0.8 s to 12 s, thereby improving lubrication performance and improving die life and coiling speed during wire drawing.

  Moreover, in the following patent document 3, as an environment-friendly processed coating, any one of K2SO4 and Na2SO4 or a mixture thereof is 75 to 90% by weight, Na2B4O7 is 3 to 25% by weight, and a nonionic surfactant. A stainless steel wire having a sulfate film made of 2 to 10% by weight is proposed.

  Furthermore, in Patent Document 4, in order to provide a spring stainless steel wire having excellent coiling characteristics, a nitrided layer is provided on the surface of the stainless steel wire by nitriding treatment, and this is drawn, and the nitrided layer due to cracks is formed on the surface. It has been proposed to form the islands of a predetermined size, thereby increasing the containment of the applied auxiliary lubricant.

JP-A-4-202396 JP-A-6-226330 JP-A-10-88179 JP-A-9-85332

  However, lubricant coatings that have been treated with a conversion coating with oxalate or phosphate, or a solid lubricant such as metal soap on top of it, can be pickled to remove the lubricant coating after plastic processing of the metal material. In addition, there is a problem in terms of the environment, such as washing with water.

  Further, the lubricant proposed in Patent Document 1 has a problem that it is inferior in heat resistance.

  Furthermore, in Patent Document 2, the constituent film contains a halogen-containing synthetic resin, and specifically, is a fluorine-based resin such as a tetrafluoroethylene resin or a chlorine-based resin, and therefore, its removal is difficult, or its removal. Requires an organic solvent. For this reason, the technique of Patent Document 2 also has a problem in terms of environment.

  Although Patent Document 3 is compatible with the global environment, sulfates and borates themselves have poor lubricity, and these lubricating coatings cannot solve the problem sufficiently.

  Furthermore, in the stainless steel wire of Patent Document 4, the island of the nitride layer formed on the surface remains as it is, so that there is a problem that the surface state of the metal material is lowered and the product value is reduced.

Therefore, the present invention has been devised to solve the problems of conventional lubricating coatings, and has excellent lubrication performance and enhances the processing performance of the metal material, and can be easily removed without reducing the surface state of the metal material. An object of the present invention is to provide a stainless steel wire for cold heading that can be used in-line and can be inlined.

The invention according to claim 1 is a soft stainless steel wire having a wire diameter of 0.5 to 10 mm and a tensile strength of 900 MPa or less, and (A) a sulfate, borate or silicate on the surface. At least one inorganic salt selected from the group consisting of: (B) a lubricating material having an average particle size of 20 μm or less, comprising graphite, molybdenum disulfide or boron nitride; and (C) the inorganic salt (A) and the lubricating material (B ) Is fixedly held and comprises a lubricating film made of a solidified material containing an acrylic acid-based, sulfonic acid-based or polyvinyl-based water-soluble resin material having an average molecular weight of 8000 to 50000, and the lubricating film is composed of constituent raw materials (A): ( B): The weight ratio of (C) is 1: 0.5 to 3: 0.5 to 8, and the lubricating film has a crystal part in which at least a part of the inorganic salt (A) is crystallized. In the surface view of the lubricating film, A cold stainless steel wire for forging, wherein the serial crystalline portion area ratio of 40 to 70%.

  Since the resin material (C) used as a solid lubricant dispersing agent is water-soluble, the lubricant composition according to claim 1 of the present application is easy to prepare and has an excellent ability to disperse the solid lubricant. Therefore, it has excellent dispersion stability. Moreover, the film formed in the present invention can be easily removed with water without the need for an organic solvent. Furthermore, the inorganic salt (A) and the lubricant (B) are firmly held on the metal material surface by the water-soluble resin material (C), so that it is necessary to have a surface treatment such as a chemical film treatment with oxalate or phosphate. Instead, the composition can be directly applied to the surface of the metal material and dried to easily provide a lubricating coating having excellent lubricating performance.

  The resin material (C) is more preferably an anionic group-containing alkyl acrylate copolymer having an alkyl acrylate as a main component.

The lubricating coating is composed of an inorganic salt (A), a slipping material (B) having a particle size of 20 μm or less, and a water-soluble resin material (C) that binds and holds these to a metal material, and is environmentally improved. The lubricating film is a crystal in which the inorganic salt (A) and the lubricant (B) are firmly held on the surface of the metal material by the resin material (C), and at least a part of the inorganic salt (A) is crystallized. Since it has a portion, it has a further improved lubricating performance, and is particularly suitable as a lubricating coating for a metal material that is hard or difficult to process.

  Moreover, it is preferable that the said crystal | crystallization part has one or more types of a granular form, a short fiber form, and a vein form, and is formed as an overhang | projection part protrudingly provided on the outer surface of the lubricating film.

The lubricating coating is preferably a coated metal material formed on the surface of the metal material to be processed with an adhesion amount of 0.3 to 12 g / m ² .

  The coated metal material having such a lubricating coating may be used in combination with the auxiliary lubricant such as metal soap, molybdenum disulfide, graphite, borax or lime as the second lubricating substance in the molding process by plastic deformation, In such a case, the second lubricating substance is effectively held between the crystal parts, and the lubricating performance is further improved. In addition, the micro unevenness formed by the protrusion of the crystal part is formed in the lubricating coating, and has an effect of increasing the efficiency of housing the lubricant without providing a different phase like the nitride layer in Patent Document 4. . For this reason, the metal material from which the surface lubricant has been removed contributes to cost reduction, such as a reduction in surface properties and a reduction in the finishing process.

Moreover, it is preferable that the soft stainless steel wire is wire-drawn with a processing rate of 30% or less after a solution heat treatment finish .

It is an expansion perspective view which shows an example of the coating metal material which concerns on this embodiment. It is the microscope picture which expanded the outer surface of the lubricating film, and shows the distribution state of the crystal | crystallization part currently formed as the overhang | projection part in which the crystal | crystallization part mixed with the dot shape and the short fiber shape. It is the microscope picture which expanded the outer surface of the lubricating film, and shows an example of the distribution state by which the crystal part is formed as a leaf-like overhang part. It is process drawing which illustrates the manufacturing process of a covering metal material. It is a relationship figure which shows the relationship between the area ratio of a crystal | crystallization part, and the process life in a forging process. It is an enlarged photograph which shows the surface state of the processed product of a metal material after removing a lubricating film.

1 Coated metal material 2 Metal wire 3 Lubricating film K Crystal part

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the coated metal material 1 has a long metal wire 2 and a lubricating film 3 that covers the entire outer surface almost uniformly. The metal wire 2 and the lubricating film 3 are integrated. The lubricating coating 3 has a crystal part K due to crystallization of a partial composition thereof.

  The metal wire 2 is a metal wire selected according to its purpose and application. As the metal material, those conventionally applied to plastic working can be used. As such a metal material, for example, stainless steel, titanium or a titanium alloy, nickel or a nickel alloy, niobium or a niobium alloy, or the like, is preferably a difficult-to-work metal material, and among them, the stainless steel having a high work hardening property. And titanium alloys are preferred. In addition, the plastic working includes various types such as forging, pressing, bending, rolling, or spring.

  In particular, the forging and pressing processes press the metal material instantaneously and cause a large overhanging deformation, so that the lubricating coating of the present invention is effective in suppressing deformation cracking of the material and loss of tools. The lubricating coating of the present invention is also effective for plastic working using a high-strength fine metal wire having a predetermined spring elasticity in spring forming.

  As the metal wire 2 for cold heading, for example, a metal wire material having a wire diameter of about 0.01 to 20 mm, preferably 0.5 to 10 mm, and a soft finish so that its tensile strength is 900 MPa or less. Is preferred. On the other hand, the metal wire 2 for the spring is, for example, a cold drawn metal wire material having a high strength characteristic of a wire diameter of about 0.01 to 10 mm and a tensile strength of about 1600 to 2600 MPa. Preferably used. When the metal material is stainless steel, in order to obtain the above-described strength characteristics, the former metal wire for forging processing is, for example, a solution heat-treated finish, or a processing rate of 30% or less (preferably 3 (~ 20%) is preferably subjected to skin pass finishing by mild wire drawing or rolling. In the latter metal wire for springs, it is preferable that the final finish is work hardened by cold wire drawing with a work rate of 60% or more.

  The cross-sectional shape of the metal wire 2 may be either circular or non-circular. Further, the surface roughness and shape of the metal wire 2 in the longitudinal direction are arbitrarily set. For example, the metal wire 2 may have a corrugated shape in which the outer diameter is periodically changed along the longitudinal direction. Furthermore, the metal material covered with the lubricating film can be widely used for various shaped products such as rods, strips, sheets or lumps in addition to long wires, and the present invention includes those having these shapes.

  In the present invention, the lubricant film 3 covering such a metal material (in this embodiment, the metal wire 2) is formed from a lubricant composition for metal material plastic working containing the following three types of constituent materials. As the first constituent material, at least one inorganic salt (A) selected from the group consisting of sulfate, borate, silicate, phosphate, molybdate and tungstate is used. As the second constituent material, a particulate lubricant (B) having an average particle size of 20 μm or less is used. Furthermore, a water-soluble resin material (C) is used as the third constituent material, which has a function of fixing and holding the inorganic salt (A) and the slipping substance (B). The lubricating coating 3 is obtained by applying an aqueous lubricant composition in which these constituent materials (A) to (C) are blended at a predetermined ratio to the metal material and drying and solidifying it. The present invention is characterized in that the lubricating film 2 made of these constituent materials has a crystal part K in which at least a part of the inorganic salt (A) is crystallized.

  The inorganic salt (A) of the first constituent material improves the carrier property and pressure resistance of the lubricating coating, is water-soluble, and is heated to a predetermined temperature together with the resin material (C) used in combination therewith. Easily soluble in water. As the inorganic salt (A), those capable of crystallizing at least a part thereof with drying of the coating film are suitable.

  Examples of the inorganic salt (A) include sulfates such as sodium sulfate and potassium sulfate, borates such as sodium borate, potassium borate and ammonium borate, silicates such as sodium silicate and potassium silicate, and zinc phosphate. And phosphates such as calcium phosphate, molybdates such as ammonium molybdate and sodium molybdate, and tungstates such as sodium tungstate. These may be used alone or in combination of two or more. In particular, potassium sulfate and sodium borate are suitable in the present invention because they provide an excellent carrier effect in wire drawing, and are water-soluble and crystals have excellent pressure resistance.

  The second constituent material is a lubricating material (B) that constitutes the lubricating coating 3 together with the inorganic salt (A), and exhibits a function of reducing frictional resistance in the lubricating coating. As the slipping material (B), for example, graphite, molybdenum disulfide, boron nitride, tungsten disulfide, fluorinated graphite, PTFE, or the like is preferably used. Any of these lubricants can be used alone or in combination of two or more. The average particle size of the lubricant (B) is 20 μm or less, but the lower limit is preferably 1 μm or more. The shape of the lubricant (B) is not particularly limited, but for example, a fine particle is preferable.

  It is presumed that the slipping material (B) changes its shape with the coating process and subsequent processing. However, when the average particle size is larger than 20 μm, when it is mixed in the liquid as a lubricant, it is easy to deposit on the bottom and it is difficult to obtain a uniform coating state. Moreover, with coarse particles, the coating surface properties are lowered. From this viewpoint, the more preferable average particle diameter of the lubricant (B) is 15 μm or less. In addition, the said average particle diameter shall mean the average of the largest dimension of each particle | grain which measured several particle | grains arbitrarily extracted from the group.

  Graphite is particularly excellent in slipperiness and provides good lubrication performance, and can be easily fine-grained with a slight impact, and also has excellent heat resistance and electrical conductivity. For this reason, graphite is particularly suitable as the lubricating material (B) of the present invention. Therefore, when the lubricating film including this is used for processing that momentarily receives a large pressure, such as forging, for example, the load pressure is absorbed to prevent seizure due to generated heat. In addition, the lubricating film containing graphite facilitates heating during warm working performed directly by energization, and contributes to an increase in tool life and troubles such as machining cracks.

  Further, the water-soluble resin material (C) which is the third constituent material has an adhesive property for firmly fixing the inorganic salt (A) and the lubricant (B) to the metal material 2 in a state where it is solidified as a lubricating film. Demonstrate. The resin material (C) can generate repulsive force on the slipping substance (B) in a solution state, or can prevent sedimentation of the slipping substance (B) by increasing the viscosity of the aqueous solution, or can be used as a surfactant. The property of stabilizing the dispersion by making (B) hydrophilic is required. Also, the lubricating coating is often removed after its processing. In that case, the resin material (C) is made of a resin material having an electrical property with an average molecular weight of 5000 to 100000 that brings about water solubility so that it can be easily dissolved in water or hot water without using a special solvent or the like. Yes.

  That is, when the average molecular weight is less than 5,000, the viscosity of the lubricant composition decreases, the adhesion amount decreases, the fixing strength decreases, and it is difficult to obtain a good coating, that is, an appropriate lubrication state. On the contrary, a polymer having an average molecular weight exceeding 100,000 is not suitable for the present invention because it exceeds the water-soluble region. Moreover, it cannot be said that it is structurally preferable that the viscosity is increased to reduce the wettability of the sliding material (B), or that fine pores are provided inside. More preferably, the resin material (C) has an average molecular weight of 8000 to 50000, more preferably 10,000 to 35,000.

  More preferable examples of the water-soluble resin material (C) include acrylic resins such as acrylamide resins and acrylate resins and other carboxylic acid group-containing resins, sulfonic acid resins, and polyvinyl resins such as polyvinyl alcohol. And those having a hydrophilic functional group. These resin materials preferably have the electrical properties described below, and more preferably have a non-dielectric constant of 2 to 12, more desirably 2.0 to 8.0. This is preferable because properties can be promoted. Some of the acrylic acid resins form a strong film by thermosetting. For example, when it is not necessary to remove the film after plastic working, it is also possible to form a film in which the inorganic salt (A) and / or the lubricant (B) is not easily removed by heat drying or heat treatment. Particularly preferable resin material (C) includes an anionic group-containing alkyl acrylate copolymer having an alkyl acrylate as a main component.

  The resin material (C) having electrical properties means a resin material having electric charge and / or polarity, and its verification is a structural formula required by, for example, chromatograph or FT-IR. Can be done from. Such characteristics can be achieved particularly with a hydrophilic functional group containing O and H in its molecular structure, which can be a water-soluble resin material. Similarly, the non-dielectric constant is also shown in JIS-K6911. For example, various methods such as a parallel plate method using a capacitor formed by forming a capacitor and a free space method of measuring reflection by applying radio waves are proposed. Such a resin material (C) is entangled with the particulate lubricant (B) and generates an attractive force to be aggregated and a repulsive force due to an electric charge to be released, thereby causing an increase in water-soluble viscosity and causing the lubricant. It is also possible to prevent the sedimentation of (B), or to make the lubricant (B) hydrophilic as a surfactant to stabilize the dispersion, thereby providing a stable and uniform lubricant composition.

  The resin material (C) used in the present invention is water-soluble and easily dissolves in water or warm water. For this reason, in order to remove the film at the coating treatment stage or after the final processing, there is a merit that the use of a harmful chemical solution such as an organic solvent can be suppressed, which is preferable from the environmental viewpoint.

The lubricant composition for metal material plastic working according to the present invention is prepared by dissolving or dispersing the constituent materials (A) to (C) in water, and the water is finally removed by a drying means after coating. By doing so, a lubricating coating made of the constituent materials (A) to (C) is formed. The blending ratio of each constituent material (A) to (C) is 1: 0.01 to 20: 0.01 to 20 (solid content weight ratio), preferably 1: 0.1 to 20 in terms of weight in the solidified state. 12: 0.1-10. More preferably, for example, it is 1: 0.5 to 3: 0.5 to 8 for cold heading, and 1: 1 to 6: 1 to 10 for springs. For example, the concentration and viscosity of the lubricant composition are adjusted so that the solid content is about 0.3 to 12 g / m ² . Usually, the lubricant composition is prepared so that the solid content concentration is 3 to 30% by weight.

When the adhesion amount is less than 0.3 g / m ² , the lubrication performance is not sufficiently exerted, and even if an amount exceeding 12 g / m ² is applied, the corresponding lubrication performance cannot be obtained, and clogging at the time of processing is on the contrary. It will cause harmful effects such as. Further, when the solid content concentration is less than 3% by weight, it is difficult to obtain a sufficient amount of adhesion by one coating operation, and when it exceeds 30% by weight, problems in coating operation such as excessively high solution viscosity arise. .

  The coated metal material of the present invention is obtained by applying the lubricant composition to the metal wire 2 and drying the coating film. The lubricant composition can be applied by any method such as dip coating or spray coating. In the drying step, the inorganic salt (A) is crystallized and the water-soluble resin material (C) is formed, and a lubricant film that adheres to the surface of the metal material is formed by the completion of water evaporation. The lubricant composition is preliminarily heated to, for example, 40 to 100 ° C., preferably 60 to 100 ° C., so that the lubricant composition (B) is provided and the crystallization of the inorganic salt (A) can be promoted. preferable.

  Although the temperature and time in the drying step are not particularly limited, heating is usually performed at room temperature to 150 ° C., for example, for about 1 to 1000 seconds. For drying, hot air drying at, for example, 80 ° C. or higher, preferably 100 ° C. or higher is suitably performed so that the time can be shortened. The lubricating film thus obtained contains the inorganic salt (A), the lubricant (B), and the water-soluble resin material (C) in the above blending ratio. When the compounding ratio of the lubricant (B) and the resin material (C) is less than 0.01 respectively, the area ratio of the crystal part K becomes too large, or a strong coating is difficult to be obtained. On the other hand, when these compounding ratios exceed 20, the area ratio of the crystal part K becomes small and the ratio of the resin material (C) is too large, so that sufficient lubrication performance is not exhibited.

FIG. 3 is an example of a manufacturing process of the coated metal wire (coated metal material 1). The process
(1) A preparation stage for preparing the material metal wire (material metal material 11) for processing and the lubricant composition 12, and (2) the material metal wire 11 added to the lubricant composition 12 heated to a predetermined temperature. A step of heating the surface of the material metal wire 11 and applying the lubricant composition 12;
(3) A film-forming stage in which the constituent materials (A) to (C) are crystallized or filmed on the material metal wire 11, and (4) a lubricant film having a crystal part is dried and solidified to form the crystal part. It comprises a drying step for fixing.

  In this embodiment, the material metal wire 11 is prepared by winding a long material having dimensions, shapes, and characteristics adjusted according to its purpose and application, for example, on a reel or a carrier 10, and this is a guide roll. The aqueous lubricant composition 12 is introduced into a tank 13 in which the aqueous lubricant composition 12 is stored in a heated state while being continuously fed through R1, R2, and R3. Thereby, the predetermined amount of the lubricant composition 12 is applied to the surface of the material metal wire 11.

  The lubricant composition 12 is an aqueous dispersion in which the lubricant (B) is dispersed in the aqueous solutions of the constituent materials (A) and (C), and is preferably heated to a predetermined temperature by an appropriate heating means (not shown). . The heating temperature is appropriately set according to the type and crystal content of the resin material (C). For example, in the case of the one containing the alkyl acrylate copolymer, the film is solidified by setting to 60 to 100 ° C. Crystals of the inorganic salt (A) can be effectively precipitated on the subsequent lubricating coating.

  For example, in the case where the constituent material (C) includes a sulfonic acid resin or an acrylic acid resin having an amide group, the set temperature in the drying or the subsequent heat treatment is set to, for example, the glass transition temperature TG of the resin material. By using the above heating temperature, thermosetting property can be increased and the firmness as a lubricating coating can be enhanced.

  The storage tank 13 has a sufficient volume with a strand length adjusted with the feeding speed of the metal wire 11 so that the long metal wire 11 has a predetermined temperature. Then, the crystal and film are formed on the outer surface of the metal wire 11 that has come out of the liquid surface of the storage 13 by the heat of the lubricant composition 12, and is dried by the dryer 15. Thereafter, the metal wire 11 is wound around the take-up reel 14. In this embodiment, the hot air dryer 15 is disposed at a preset position so that the amount of lubricant adhering to the predetermined range is fixed, and lubrication is performed by supplying hot air at a temperature of 100 ° C. or higher, for example. Fix the agent.

  In this process, the immersion / heating step is performed in the storage tank 13, and the film formation step of crystallization of the inorganic salt (A) and film formation of the resin material (C) is performed from the liquid level of the storage tank 13 to the dryer 15. Done in the area up to. Therefore, continuous processing can be achieved by a series of steps, and in-line processing becomes possible. Needless to say, the feeding speed of the metal wire 11 can be appropriately adjusted according to the composition of the lubricant composition 12 and the drying conditions thereof.

  When intermediate processing is further performed after the formation of the lubricating coating 3, a different type of lubricating material from the lubricating material (B) contained in the formed lubricating coating 3 may be applied to the coated metal material as the second lubricating material. . Examples of the second lubricant include metal soap, molybdenum disulfide, graphite, boron nitride, tungsten disulfide, graphite fluoride, borax, lime, or PTFE powder. Examples of the intermediate processing include mild wire drawing or rolling with a processing rate of 30% or less, and wire drawing or rolling with strength of a processing rate of 60% or more. Since the coated metal material of the present invention has fine irregularities on the surface of the lubricating coating as described above, the applied second lubricating substance is highly retained and exhibits excellent lubricating performance.

  2A and 2B show an example of the distribution state of the crystal part K formed on the lubricating coating 3, and these are micrographs magnified 35 to 80 times. The crystal part K has a different crystal state depending on the type and quantity ratio of the constituent material of the lubricating coating, and the one shown in FIG. 2A is a point-like or short fiber-like overhang part by using a sulfate or the like as an inorganic salt. Is formed. Further, in the case of FIG. 2B, a vein-shaped overhanging portion is formed by using borate or the like.

  As seen in each of the above figures, on the outer surface of the lubricating coating, each crystal part K is uniformly distributed in a protruding state protruding from the surface, and is flat between the crystal parts K. A recess is provided. For this reason, the outer surface of the coated metal material is formed as a micro uneven surface having a convex portion by the crystal portion K and the concave portion, and contributes to improvement of lubricity.

  The crystal part K is not limited to a single layer formed in the lubricating coating 3 but may be formed in a plurality of stacked distribution states in the thickness direction. Furthermore, the directionality of the crystal part K does not require that all crystal parts are in parallel with the planar direction of the lubricating coating, and includes, for example, a case where the crystal part K intersects in an oblique direction.

  In addition, the fact that the crystal part K is due to the inorganic salt (A) as a constituent element indicates that the constituent pattern for each element and the crystal part are obtained by image diffraction using a scanning electron microscope or X-ray analysis. It is confirmed by the sign K. By the image analysis of such a pattern, the area ratio of the crystal part K can be easily obtained. The area ratio of the crystal part K is defined as a ratio of the total area of the crystal part K per unit area of the lubricating coating in plan view, and is preferably 20 to 80%. In this case, the area ratio is represented by an average value of the results of several arbitrarily selected measurement visual fields.

  According to the observation by the image diffraction, it is recognized that the slip material (B) is substantially detected in the part other than the crystal part K, and that the part is a concave part. Therefore, such a micro uneven surface can efficiently contain the auxiliary lubricant applied at the time of subsequent processing, for example, and can improve lubricity. That is, by optimizing the area ratio of the crystal part K, it is possible to give excellent lubricity to harsh processing such as forging of difficult-to-work materials and spring forming, and between the area ratio and the lubricity. It has also been confirmed that

  FIG. 4 shows an example of the result, in which the horizontal axis indicates the area ratio (%) of the crystal part K, and the vertical axis indicates the relationship between the processing life (number of processing) in the forging process. In this embodiment, the area ratio is preferably set to 20 to 80%. As is apparent from FIG. 4, when the area ratio is less than 20%, the holding and holding force of the auxiliary lubricant applied to the coated metal material in the intermediate processing appropriately performed is lowered, and the tool life is shortened. On the contrary, when the area ratio exceeds 80%, a sufficient storage space for the auxiliary lubricant cannot be obtained, and the crystal part K is very hard. The surface property of the metal material for processing is deteriorated, and the life of the processing tool is reduced. Therefore, the area ratio of the crystal part K is more preferably set to 30 to 80%, further preferably 40 to 70%, and particularly preferably 40 to 60%.

  Note that the size and form of the crystal part K appropriately change depending on the processing conditions, the types of constituent materials, and the like. The shape of the crystal part K is not particularly limited, but it is preferable to have at least one of a powder form, a short fiber form, or a vein form as shown in FIGS. 2A and 2B, and its size (constituent dimension). Is preferably as fine as 0.5 mm or less. Here, the constituent dimensions of the crystal part K are indicated by the average value of the maximum diameter in the case of powdery crystals, and the maximum thickness of the single element (each single line) constituting this in the case of a fibrous or leaf-like one. It is shown as an average value.

  If the size of the crystal part K exceeds 0.5 mm, the surface will be roughened in the subsequent molding process, and in the case of the short fiber shape or the vein shape, the space between the crystal parts is reduced, thereby assisting. Lubricant storage efficiency decreases. The dimension of the crystal part K is more preferably 0.1 mm or less.

  When the crystal part K has a short fiber shape or a vein shape, a single element of the crystal part has a predetermined length (L) (for example, 0.01 to 1 mm), and its length (L) and thickness (D) The aspect ratio (L / D) is preferably in the range of 1.5 to 50 on average. In particular, when the crystal part K is longer than necessary, the network determined by the random distribution becomes large, which is not preferable. A more preferable aspect ratio for the crystal part K is 2 to 20. Such adjustment of the aspect ratio can be performed, for example, by setting the drying conditions.

  In the present embodiment, the case where the metal material to be processed is a lubricating coated wire used for cold head forming or spring forming is described. Further, the description has been made mainly on the case where the lubricant composition is uniformly applied to the entire surface of the metal material and subjected to a coating formation treatment. However, the present invention is not limited to these, for example, selection of various shaped products such as bars, strips, sheets, and lump materials as metal materials, and application of the types and sizes of the materials, It can be easily made by those skilled in the art and should be included as one embodiment of the present invention.

  The following examples further illustrate the present invention.

[Production of test materials]
In this embodiment, steel materials SUS304 and 316 and XM7 type austenitic stainless steels 3 for cold heading are selected as the materials to be treated, and each material is cold drawn to a wire diameter of 3.65 mm. It was. These were subjected to a solution heat treatment at a temperature of 1000 to 1100 ° C. with a strand type heat treatment apparatus and coated with the following lubricant composition to obtain a coated stainless steel wire. In this processing step, the heat treatment apparatus is configured as a series of in-line apparatuses so that the coating apparatus having the structure shown in FIG. 3 is connected to the outlet side so that the solution heat treatment and the coating process can be performed simultaneously. A lubricant composition having the following composition was used.

[Lubricant composition]
(A) Sodium sulfate 10% by weight
(B) Sodium borate 2% by weight
(C) Boron nitride (average particle size 5 μm) 10% by weight
(D) Acrylic acid resin 10% by weight
(Anionic acrylic acid alkyl ester copolymer / dielectric constant 3.8 with charge and polarity)
(E) Water 68% by weight
(A) :( B) :( C) :( D) = 5: 1: 5: 5 (solid content weight ratio)
Solid content concentration 32% by weight

  The lubricant composition in which these (A) to (E) are mixed is introduced into a storage tank having a width of 200 × depth of 600 × height of 300 mm, and stirred well while being heated to a temperature range of 80 to 95 ° C. with an external heater. An aqueous dispersion was obtained. In this state, the inorganic salt and the water-soluble resin material were dissolved in the solvent water, and boron nitride was uniformly dispersed in the aqueous solution.

[Film formation / crystallization treatment]
The coating formation treatment is performed so that the coating amount is within a predetermined range by adjusting the feeding speed of the wire to be treated (stainless steel wire) based on the composition of the lubricant composition, the heating temperature and the storage tank volume. Done. In this example, the average adhesion amount was adjusted to be in the range of 6 to 12 g / m ² by setting the wire supply speed to 3 to 7 m / min. The replenishment of the evaporating water was carried out by automatic adjustment as appropriate. For this reason, the coating state of the lubricant was good, and variation in the amount of adhesion could be suppressed.

  The wire to be treated thus applied by dip coating is sent out from the liquid level, and the coated lubricant composition is applied by a cylindrical hot air dryer placed at a position of about 0.8 m from the liquid level. It was completely dried at 100 ° C., and the lubricating coating was fixed on the wire. Moreover, since the said storage tank was heated at 80-95 degreeC, it was observed that a water | moisture content evaporates and the crystal | crystallization of an inorganic salt precipitates between a wire from a liquid level to a warm air dryer.

  By performing such a series of heat treatment and film formation treatment of the metal wire at the above-mentioned speed, each stainless steel wire is coated on its surface with a lubricating film having an adhesion amount of 6 to 12 g / m @ 2, as shown in FIG. 2A. A soft stainless steel wire having a lubricating coating with fibrous crystal parts was obtained. The crystal part obtained by image analysis using an X-ray diffraction apparatus (manufactured by Horiba Seisakusho) is a random distribution of short fibers having a width of 10-50 μm and an average aspect ratio of 2-15. It was 49.6 to 52.1%.

Further, the crystal part has been confirmed to have a protruding state by magnifying microscope observation, and further from the following measurement result of the surface roughness (Rz) depending on the presence or absence of a lubricant at a predetermined position of the coated steel wire. But that was backed up.
・ Surface roughness on the lubricating coating surface 9.6 to 10.4 μm
・ Surface roughness of lubricant removal surface 7.6μm

[Comparative lubricant]
As a comparative lubricating film (comparative example), an oxalate film was formed on each of the three types of stainless steel wires with an adhesion amount of 6 to 12 g / m ² and used as a comparative wire. The oxalate coating has been widely used in the past for cold working of stainless steel, but in the treatment process, harmful heavy metals such as generation of hexavalent Cr and mist containing harmful substances are generated. There is a problem of sludge and waste acid containing, and in recent years it has been on a shrinking trend.

[Intermediate processing]
The coated soft stainless steel wire of this example was further subjected to skin pass drawing at a processing rate of 4% to obtain stainless steel wires for cold heading shown in Table 1. In this skin pass processing, a combination of a metal soap and an auxiliary lubricant was used, and it was confirmed that the auxiliary lubricant was held in the recesses on the surface of the steel wire.

[Lubricity test]
Next, the forging test which evaluates the workability was performed using each stainless steel wire of Table 1 of the said Example. The test was performed by cold forming of the countersunk head screw while dripping the spindle oil. The processing conditions were a total of 25,000 headers formed at a feed rate of 150 pieces per minute using a tool steel header punch. Then, the number of tool surfaces and occurrence of defects such as cracks were observed.

  The test results were good, and the lubricating coating of the present example had a tool life of 15000 tools exceeding the oxalate coating of the comparative example. Moreover, there was no problem of cracking or seizure, and header processing was possible. This number of processing points is an evaluation of the processing life of the forging workability, and it was confirmed that the coating film of this example had a lubricity equivalent to or higher than that of the oxalate film as a comparative lubricant. An example of the surface state of the obtained forged product (sample No. A-2) is shown in FIG. 5, but no trace of seizure is observed.

  Regarding the solution heat treatment material of the XM7 stainless steel wire (wire diameter: 3.65 mm), the following workability is obtained by changing the level of the constituent material (A) inorganic salt, (B) lubricant, and (C) water-soluble resin. The evaluation was performed together. The evaluation was confirmed by the tool life by header processing as described above, and the results are shown in Table 2.

  From these Examples, it was confirmed that the lubricating coating according to the present invention can be used as a stainless steel header forging as in the case of conventional lubricants, in particular, as a highly processing coating for difficult-to-work materials.

[Example of application to titanium-nickel alloy strips]
A lubricant composition having the following composition was prepared.
(A) Sodium silicate (B) Molybdenum disulfide (average particle size 2 μm)
(D) Acrylic acid resin 10% by weight
(Anionic acrylic acid alkyl ester copolymer / dielectric constant 2.7 with charge and polarity)
Solid content weight ratio (A) :( B) :( C) = 5: 4: 2
Solid content 22% by weight

  Ni—Ti alloy is an intermetallic compound and is known as a difficult-to-process material, and it is considered that wrinkles and wire breakage are easily caused by wire drawing dies. As a countermeasure, for example, scaling with an oxide film is performed. However, scaling is not likely to cause wrinkles or disconnection, but it must be descaled with the final product. , There is a drawback of deteriorating product quality.

Therefore, in order to evaluate the adaptability of this lubricating coating to the Ni—Ti alloy wire, ² to 6 g / m ^{2 of the} lubricant composition was applied to 100 kg of the alloy annealed material having a wire diameter of 1.8 mm, and the wire diameter was Drawing was performed to 1.6 mm. There was no wrinkling or disconnection in the wire drawing, and good workability was obtained. In the final product, all of the lubricating coating could be removed by only alkali washing and hot water washing required for removing the upper layer metal soap. As a result, the pickling step can be omitted, the environmental load is reduced, the workability is improved, and the range of the wire diameter tolerance has been successfully reduced in terms of quality.

[Drawing of stainless steel wire for springs]
A lubricant composition having the following composition was prepared.
(A) Potassium sulfate (B) Graphite (average particle size 3 μm)
(C) Carboxylate water-soluble resin (ammonium salt / charged / polar)

Solid content weight ratio (A) :( B) :( C) = 1: 15: 2
Solid content 18% by weight
The lubricant composition was applied in an amount of 0.3-2 g / m ² to 200 kg of an annealed SUS304N1 stainless steel wire having a wire diameter of 1.5 mm, and the wire was drawn to a wire diameter of 0.7 mm. The material after drawing was checked for flaws, but the surface condition was good and no surface defects such as film peeling or wrinkles were found. Subsequently, the coiling property of the spring was confirmed. Conventionally, since nickel plating materials have been the mainstream for coiling of spring materials, comparative tests were conducted using nickel plating materials as comparative materials.

  In the test, compression springs according to the following specifications were evaluated with a spring free length variation 3σ in the coiling molding, and the results were almost the same as the comparative example material 0.24 against the 0.25 of the example material. In addition, in the case of nickel plating materials, for example, in addition to the health effects of biological allergies, there were problems that it was unavoidable to remove the environmental load such as waste liquid treatment and the reduction of the surface condition after removal when removing this. In contrast, the product of the present invention can improve such problems.

Spring origin Push spring D / d = 20.0
Free length 15.5mm
Free length tolerance ± 0.3mm
Total number of turns 10
50 pieces / minute

  As described above, the lubricating coating according to the present invention can be used for various applications that require lubricity. In particular, severe plastic processing such as forging, pressing, bending, rolling, spring processing of difficult-to-work metal materials such as stainless steel, titanium or titanium alloy, nickel or nickel alloy, niobium or niobium alloy, etc. It provides a technology that can be used as a lubrication means and that can be inlined with excellent lubricity and global environmental problems.

Claims (5)

A soft stainless steel wire having a wire diameter of 0.5 to 10 mm and a tensile strength of 900 MPa or less,
(A) at least one inorganic salt selected from the group consisting of sulfate, borate or silicate,
(B) A slipping material having an average particle diameter of 20 μm or less made of graphite, molybdenum disulfide, or boron nitride, and (C) an acrylic acid having an average molecular weight of 8000 to 50000 for fixing and holding the inorganic salt (A) and the slipping material (B). A lubricant film comprising a solidified material containing a water-soluble resin material of a sulfonic acid type or a polyvinyl type,
The lubricating coating has a weight ratio of constituent raw materials (A) :( B) :( C) of 1: 0.5 to 3: 0.5 to 8,
The lubricating film has a crystal part in which at least a part of the inorganic salt (A) is crystallized,
A stainless steel wire for cold heading, wherein an area ratio of the crystal part is 40 to 70% in a surface view of the lubricating film.
The crystal part has one or more shapes of granular, short fiber shape and vein shape,
The stainless steel wire for cold heading according to claim 1, wherein the stainless steel wire is formed as an overhang protruding on the outer surface of the solidified product. Wherein on the surface of the metallic material, wherein the solidified product is formed at a coverage of 0.3~12g / m ² according to claim 1 or 2 cold stainless steel wire for heading according. The said crystal | crystallization part contains the linear single element in which the aspect-ratio (L / D) of the length (L) and thickness (D) exists in the range of 1.5-50. A stainless steel wire for cold heading according to any one of the above . The stainless steel wire for cold heading according to any one of claims 1 to 4, wherein the soft stainless steel wire is drawn after a solution heat treatment finish at a processing rate of 30% or less .

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