JP2009120931A - Metal material to be plastic-worked and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a useful method for manufacturing a metal material to be plastic-worked, which is provided with a film that does not contain a substance such as phosphate, which gives a load to the environment, and that shows the lubricity and seizure resistance of a level equal to or higher than a film made from (phosphate + soap). <P>SOLUTION: The method for manufacturing the metal material to be plastic-worked includes: forming the first layer which is a plated layer, on the surface of a base metal; and subsequently forming the second layer on the plated layer by dipping the base metal having a plated layer formed thereon in a fluidal aliphatic acid. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a metal material for plastic working useful for performing plastic working such as drawing, wire drawing, forging, forging, and the like, and a method useful for producing such a metal material. In particular, the present invention relates to a metal material for plastic working, which is excellent in seizure resistance and lubricity by forming a film having a specific structure, and which can also avoid the phosphorus immersion phenomenon during heat treatment, and a method for producing the same.

  For example, a metal wire obtained by performing cold wire drawing is generally further subjected to cold work such as cold forging according to various applications. Therefore, it is necessary to form a film having both seizure resistance and lubricity on the surface of a metal wire material (hereinafter, sometimes referred to as “metal material”) that is a workpiece.

  By forming the film as described above, direct contact between the plastic working tool and the metal material is avoided, processing heat generation is suppressed, thereby preventing the occurrence of seizure, and further, the surface of the work material is prevented. Since the friction coefficient decreases, the processing load is reduced and the processing energy is reduced.

  By the way, as a treatment agent (lubricant) for forming the film as described above, a powdery lubricant containing a metal soap such as calcium stearate and sodium hydroxide as a carrier agent is generally used. is there. However, when cold wire drawing is performed using such a powdery lubricant, the film becomes inadequate in lubricity due to cold wire drawing, and severe after cold wire drawing. There is a problem that defects such as seizure occur in a processing step (for example, cold forging).

  For this reason, when formation of a film having high lubricity and seizure resistance is required, such as a material for cold forging, for example, a chemical conversion film is previously formed on the surface of the base material by phosphate conversion treatment. Generally, a soap layer made of zinc stearate and sodium stearate is formed thereon to form a (phosphate + soap) film to meet the required characteristics. In particular, when machining under severe conditions such as bolting of steel materials is required, lubrication with lubricating oil alone is insufficient, and chemical conversion treatment such as phosphate treatment is a necessary process. ing. In fact, steel materials in which a (phosphate + soap) film is previously formed are also shipped as products.

  The above (phosphate + soap) film has high lubricity and seizure resistance that can sufficiently follow severe processing such as cold forging and has excellent rust prevention properties. Become. However, when phosphating is performed, a delay due to diffusion of phosphorus in the phosphate film (hereinafter referred to as “immersion phosphorus”) when heat treating the product after cold drawing There is a problem that the breakage is likely to occur in, for example, a high tension bolt.

  In addition, when using phosphates such as zinc phosphate, although it is excellent in lubricity (workability) and corrosion resistance after processing, it also points out the disadvantage of requiring complicated liquid management and many processes. Is done. In addition, there is a problem that a large amount of sludge is generated due to a chemical reaction with a workpiece, and a great amount of labor and cost are required for the treatment.

  Regarding high-tensile bolts, JIS B1051 stipulates that “a threaded part of 12.9 class strength section shall not have a white phosphorus-concentrated layer that can be confirmed with an optical microscope on the surface where tensile stress is applied”. Yes. For these reasons, various techniques have been proposed for surface treatment agents (non-phosphorus lubricants) that exhibit excellent lubricity without using phosphates.

For example, in Patent Document 1, lubricity and seizure resistance of a metal material are formed by forming a first layer containing potassium silicate and a second layer containing various stearates and a fluororesin on a metal wire surface. A technique for improving the performance has been proposed. In Patent Document 2, a metal lubricating film (for example, a plating film) having, as a main phase, one type of Cu, Ni and Zn or an alloy of these metals is formed on the surface of the steel wire. Techniques for preventing wear deterioration of dies are disclosed.
JP 2003-53422 A JP 2003-82437 A

  As described above, various conventional techniques have been proposed for improving the lubricity and seizure resistance of a metal material for plastic working without using a phosphate. However, further improvements in lubricity and seizure resistance are constantly being sought by users of plastic working metal materials. The present invention has been made by paying attention to such a situation, and its purpose is not to include an environmental load substance such as phosphate, and is equivalent to or higher than (phosphate + soap) film. An object of the present invention is to provide a metal material for plastic working provided with a film exhibiting lubricity and seizure resistance, and a useful method for producing a metal material provided with such a film.

  The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, a first layer which is a plating layer is formed on the surface of the base metal, and then a second layer is formed on the plating layer by immersing the base metal on which the plating layer is formed in a liquid fatty acid. The present invention was completed by finding that the multi-layer coating exhibited lubricity and seizure resistance comparable to the (phosphate + soap) coating. That is, in the method for producing a metal material for plastic working according to the present invention, the first layer which is a plating layer is formed on the surface of the base metal, and then the base metal on which the plating layer is formed is immersed in a liquid fatty acid. Thus, the present invention has a gist in that the second layer is formed on the plating layer.

  In the production method of the present invention, it is preferable to form a copper plating layer as the plating layer, and in order to form such a copper plating layer, means for immersing the base metal in an aqueous copper sulfate solution is preferable. The fatty acid used in the production method of the present invention is preferably stearic acid and / or palmitic acid. That is, a preferred embodiment of the production method of the present invention is to immerse the base metal on which the plating layer is formed in molten stearic acid and / or palmitic acid. The metal material for plastic working produced by such a production method of the present invention exhibits excellent lubricity and seizure resistance comparable to a metal material having a (phosphate + soap) film. Can do. Therefore, this invention also provides the metal material for plastic working manufactured with the said manufacturing method.

  First, a plating layer is formed as a first layer on the base metal surface of the metal material for plastic working, and then immersed in a liquid fatty acid to form a second layer, thereby forming the base metal and the first layer (plating). Layer) and the first and second layers were firmly adhered, and good lubricity and seizure resistance were realized.

  Conventional non-phosphorous lubricants are mainly composed of silicate, stearate, etc., but these lubricants ensure sufficient performance (lubricity and seizure resistance). It's hard to say. The present inventors have examined the reason why sufficient performance cannot be ensured with conventional lubricants from various angles.

  As a result, the idea that the non-phosphorous lubricants proposed so far have lower adhesion to the base metal surface than the (phosphate + soap) film was obtained. That is, in the (phosphate + soap) film, the film is firmly attached to the base metal by forming a phosphate (for example, zinc phosphate) by a chemical reaction with the base metal. However, in the conventional non-phosphorous lubricant, the chemical reaction with the base metal hardly proceeds, and the lubricant component is only weakly adhered to the base metal. Therefore, sufficient performance cannot be ensured only with conventional non-phosphorous lubricants.

  In the prior art, in order to improve the lubricity of the metal material for plastic working, a metal lubricating film such as copper plating is formed on the surface of the base metal. The plating layer adheres strongly to the base metal as compared with the conventional non-phosphorous lubricant. However, when plastically processing a metal material on which a plating layer is formed, simply using a solid lubricant (for example, stearate) is sufficient in severe processing steps because the adhesion between the plating layer and the solid lubricant is weak. It is hard to say that it is possible to show the performance.

In contrast to these conventional techniques, the manufacturing method of the present invention forms a plating layer that adheres firmly to the base metal as the first layer, and then from the fatty acid, the plating layer that adheres firmly to the first layer (plating layer). The metal material for plastic working in which two layers are formed can exhibit lubricity and seizure resistance equal to or higher than those of the metal material for plastic working formed with a (phosphate + soap) film. The reason why the second layer formed from a fatty acid (for example, stearic acid) is firmly attached to the first layer (for example, a copper plating layer) that is a plating layer is that a chemical reaction represented by the following formula (1) occurs. (As a basis for this chemical reaction, when a copper plating layer is used as the first layer, the surface film (second layer and intermediate layer) is formed by C-, O, Cu (ion) by X-ray photoelectron spectroscopy (XPS). ))):
2Cu + 4CH ₃ (CH ₂ ) ₁₆ COOH + O ₂
→ 2 (CH ₃ (CH ₂ ) ₁₆ COO) ₂ Cu + 2H ₂ O (1)

  In the metal material for plastic working produced by the production method of the present invention as described above, an intermediate layer (fatty acid salt of the plating metal) is formed between the first layer (plating metal) and the second layer (fatty acid). Is done. By interposing this intermediate layer, the first layer and the second layer adhere firmly. In this technical field, soap or metal soap (for example, zinc stearate) is used as a solid lubricant. However, the solid lubricant is simply brought into physical contact with the base metal or the like, and the solid lubricant is not necessarily reliably present on all surfaces. On the other hand, since the intermediate layer (fatty acid salt of plating metal, such as copper stearate or zinc stearate) in the present invention is formed on the surface of the first layer (plating metal) by reaction, it is surely present on the surface. . As a result, the metal material for plastic working according to the present invention exhibits higher lubricity.

As plating for forming the first layer, plating of zinc, nickel, tin, copper, or the like can be used. Among these, nickel, tin, and copper plating, which have a smaller ionization tendency than iron and are capable of displacement plating (immersion plating) on iron, are preferable, and copper plating is more preferable. This is because displacement plating is simple. Here, displacement plating means an ionization tendency as shown by the following formula (2) only by immersing a material to be plated (for example, a steel material) in a plating solution (for example, a copper sulfate aqueous solution) without adding a reducing agent separately. In this method, a metal film (for example, copper plating) is formed by a substitution reaction based on the difference between the two.
Fe + Cu ²⁺ → Fe ²⁺ + Cu (2)

  As the plating method, any one of hot dip plating, electroplating and electroless plating can be used, but electroless plating with a simple apparatus is preferable, and simple substitution plating is preferable among electroless plating. In particular, when forming copper plating, substitution plating that forms copper plating by immersing the base metal in an aqueous copper sulfate solution is preferable. When using an aqueous copper sulfate solution, the concentration of copper sulfate is preferably 10 g / L or more (more preferably 20 g / L or more), and preferably 120 g / L or less (more preferably 110 g / L or less).

  In order to form the first layer, hot dip plating, electroplating or electroless plating (including displacement plating) may be performed under normal conditions. For example, when displacement plating is performed, the treatment temperature when the base metal is immersed in the plating solution (temperature of the plating solution) is preferably 30 ° C. or higher, preferably 70 ° C. or lower (more preferably 60 ° C. or lower). is there. If the temperature is too low, it is difficult to control the temperature, and if the temperature is too high, it is difficult to control the amount of plating. The immersion time of the base metal in the plating solution is preferably 1 minute or more (more preferably 2 minutes or more), preferably 10 minutes or less (more preferably 5 minutes or less). This is because if the immersion time is too short, the amount of plating adhered is small, and if the time is too long, peeling of the plating is observed.

  As the fatty acid for forming the second layer, industrially available normal fatty acids can be used, and only one type of fatty acid may be used, or two or more types of fatty acid may be used in combination. . As the fatty acid, stearic acid, palmitic acid, linoleic acid, linolenic acid and the like are preferable, and stearic acid and palmitic acid are more preferable because they are solid at room temperature. As a method for forming the second layer, the base metal on which the plating layer is formed may be immersed in a liquid or molten fatty acid. When a fatty acid having a melting point exceeding room temperature is used, the fatty acid needs to be heated to the melting point or higher in order to immerse the base metal. The upper limit of the immersion temperature in the liquid or molten fatty acid is generally 100 ° C., although it is influenced by the melting point of the fatty acid. The immersion time of the base metal in the liquid or molten fatty acid is preferably 1 minute or more (more preferably 2 minutes or more), preferably 25 minutes or less (more preferably 20 minutes or less). This is because if the immersion time is too short, the amount of adhesion of the second layer is small, and if the time is too long, the amount of adhesion is saturated and does not increase beyond a certain level.

  The second layer formed from a fatty acid can appropriately contain molybdate, vanadate, polyacrylic acid, silica, benzotriazole, or the like as a rust inhibitor. Further, a solid lubricant, for example, a fatty acid salt such as soap may be supplementarily used on the second layer.

  The base material of the metal material used in the present invention is not particularly limited, and various metal materials such as steel materials (charcoal steel, low alloy steel, stainless steel) and aluminum can be used. Of these, steel is preferred. The form used as the metal material is not particularly limited as long as it is plastically processed. For example, bolts, nuts, springs, PC (pressed concrete) steel wires, steel cords, bead wires, etc. are manufactured. Wires and rods for doing this.

The coating amount as a whole is preferably 2 g / m ² or more (more preferably 4 g / m ² or more), preferably 40 g / m ² or less (more preferably 20 g / m ² or less). Regarding the amount of coating, after scraping the coating with a piece of metal over the entire circumference of a sample having a diameter of 10 mm and a length of about 50 mm, the sample is colored with 1N sulfuric acid at 50 ° C. and the color of the base metal is It is immersed until it appears, washed with water and dried, and the amount of coating can be measured from the change in mass after removing the coating.

The adhesion amount of the plating metal (especially copper) is preferably 0.01 g / m ² or more and 1 g / m ² or less. The adhesion amount of the plating metal can be calculated by quantifying the plating metal ion (for example, copper ion) in nitric acid in which the film is dissolved by inductively coupled plasma-mass spectrometry (ICP-MS).

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

A hot-rolled wire rod (diameter: 10 mm) made of steel type SCM435 was spheroidized and annealed at 760 ° C., the heat-treated wire rod was pickled and descaled, then washed with water, and then the conditions shown in Table 1 below (No. 1) The first layer and the second layer were sequentially formed by immersing under the conditions of one layer and the second layer. At this time, experiment no. The second layer 11 was formed by rubbing a powder of calcium stearate (Ca stearate) as an auxiliary lubricant on the first layer. The coating amount (measurement method is as described above) is about 8 g / m ² as a whole.

For comparison, Experiment No. In No. 13, the wire was treated with zinc phosphate and soap under the following conditions: The wire was immersed in a 15% hydrochloric acid solution (50 ° C.) for 10 minutes, washed with water, and the zinc phosphate treating agent [“ Using Palbond 181X "(trade name: manufactured by Nihon Parkerizing Co., Ltd.), chemical conversion treatment was performed under the conditions of 90 g / L, 80 ° C, 10 minutes, and washed with water. Next, soap treatment was performed under the conditions of 70 g / L, 80 ° C. for 5 minutes using a soap lubricant [“PAROUB 235” (trade name): manufactured by Nihon Parkerizing Co., Ltd.]. The amount of coating is about 8 g / m ² as a whole.

  Experiment No. No. 11 was used with an auxiliary lubricant (calcium stearate), and other than that, without using the auxiliary lubricant, the diameter of the wire subjected to the above-mentioned various treatments: 10 mm (10 mmφ) was 9.5 mmφ, 8.3 mmφ. 7.45 mmφ, 6.3 mmφ, 5.6 mmφ, 4.9 mmφ, 4.2 mmφ, 3.6 mmφ, wire drawing in stages, and measuring the load at the final wire drawing stage (3.6 mmφ), The surface state (surface skin) after wire drawing was observed. These results are shown in Table 2 below.

  From the above results, in Experiment No. 1 in which the first layer was formed by copper plating and the second layer was formed from fatty acid (stearic acid or palmitic acid). In the cases of Nos. 1 to 8, the experiment No. 1 provided with the (phosphate + soap) film. It can be seen that the wire drawing load is lower than that of No. 13, and the lubricity is excellent. In addition, Experiment No. Although the seizure occurred in the sample No. 13, the experiment No. 1 to 8 have no seizure, and it can be seen that the metal material for plastic working of the present invention is also excellent in seizure resistance. Furthermore, the experiment No. 1 satisfying the requirements of the present invention was performed. 1 to 8 do not contain phosphorus and therefore do not cause the immersion phosphorus phenomenon.

  On the other hand, Experiment No. having only copper plating. 9, Experiment No. having copper plating and stearate film Nos. 10 and 11 and Experiment No. having only a lime soap film. No. 12 is Experiment No. The wire drawing load is higher than those of 1 to 8, and seizure occurs on the surface. In particular, experiment no. The reason why the performances of 10 and 11 are inferior to those of the present invention is considered to be that stearate does not react with copper plating and is inferior in adhesion.

Claims (5)

  Forming a first layer as a plating layer on the surface of the base metal, and then immersing the base metal on which the plating layer is formed in a liquid fatty acid to form a second layer on the plating layer. A method for producing a metal material for plastic working.   The method for producing a metal material for plastic working according to claim 1, wherein a copper plating layer is formed as the plating layer.   The method for producing a metal material for plastic working according to claim 2, wherein the copper plating layer is formed by immersing a base metal in an aqueous copper sulfate solution.   The metal material for plastic working according to any one of claims 1 to 3, wherein the second layer is formed by immersing the base metal on which the plating layer is formed in molten stearic acid and / or palmitic acid. Manufacturing method.   A metal material for plastic working, which is produced by the production method according to claim 1.