JP2009191334A - Steel member for plastic working, method for producing the same, and plastic-worked product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a steel for plastic working provided with a lubricating film which exhibits plastic workability and corrosion resistance equal to or above those of a phosphate-soap film as a representative lubricating film even if the film does not comprise a phosphate. <P>SOLUTION: Disclosed is the method for producing the steel for plastic working whose surface is provided with a film, and the method includes: a stage (a) where a steel member is immersed into an aqueous solution containing a halogen, manganese, the oxygen acid of iron, the salt thereof or the complex salt of iron as an oxidizer, and soap; or a stage (b) where a steel member is immersed into an aqueous solution containing the oxidizer, and thereafter, the steel member is contacted with soap. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steel material for plastic working that is useful for performing plastic working such as drawing, wire drawing, forging, forging, and the like, a manufacturing method thereof, and a plastic working product obtained using the steel material for plastic working. . The steel material for plastic working of the present invention includes, for example, machine parts such as bolts, nuts and springs obtained by cold working such as cold forging, cold heading, cold rolling, steel cord, bead wire, PC (prestressed). concrete) It is preferably used for manufacturing plastic processed products such as wire drawn products such as steel wires.

  Steel materials for plastic working are subjected to various plastic processing such as drawing, wire drawing, forging, forging, etc., depending on the application. At that time, high pressure is applied between the processing tool and the work material (steel material). In addition, seizure is likely to occur with sliding between them. Therefore, in order to reduce friction on the surface of the work material and prevent seizure or the like, a lubricating film is usually formed on the surface of the metal material.

  A typical example of the lubricating coating is a composite coating composed of a phosphate coating and a soap layer (hereinafter sometimes referred to as “phosphate / soap coating”). This phosphate / soap film is formed by subjecting a metal material to a phosphate treatment to form a phosphate film, followed by a reactive soap lubrication treatment. And a soap layer composed of zinc stearate (metal soap) and sodium stearate (bath soap) with good adhesion is formed. The film obtained in this way is excellent in lubricity and seizure resistance, and also has good rust resistance. Therefore, the steel material provided with the film is suitable for severe processing such as cold forging. Used for.

  However, when the above steel material is used and heat treatment is performed after cold wire drawing to produce a final product such as a bolt, phosphorus diffuses into the metal material during the heat treatment, causing delayed fracture. There is. In addition, the formation of the phosphate film requires complicated management of the treatment liquid and many processes, and a large amount of sludge is generated by the chemical reaction between the treatment liquid and the material to be treated (steel material). Processing takes a lot of labor and expense.

  Therefore, a method of forming a lubricating film excellent in lubricity and the like without interposing a phosphate film has been proposed (for example, Patent Documents 1 to 5).

Of these, Patent Document 1 includes a lubricant mainly composed of lime soap, Patent Document 2 includes a lubricant film composed mainly of an alkali metal borate, Patent Document 3 includes potassium silicate, Lubricants containing stearates, fluororesins and the like are proposed in Patent Document 4, and lubricants containing carbonates of alkali metals or alkaline earth metals have been proposed. Patent Document 5 was proposed by the applicant of the present application, and here, “an aqueous solution containing one or more of silicates, borates or calcium hydroxide and peroxide” or “boric acid” is proposed. A method of forming a lubricating film using an “aqueous solution containing a salt, calcium hydroxide and a peroxide” is proposed.
JP-A-9-3476 JP 2002-192220 A JP 2003-53422 A JP-A-11-222599 JP 2006-272461 A

  As described above, various steel materials for plastic working that are excellent in lubricity and the like have been proposed, but further improvements are required.

  The object of the present invention is to provide a lubricating film that exhibits plastic workability and corrosion resistance equivalent to or higher than that of a phosphate / soap film, which is a typical lubricating film, even if the film does not contain phosphate. Another object of the present invention is to provide a steel material for plastic working, a manufacturing method thereof, and a plastic processed product obtained from the steel material for plastic working.

The production method of the present invention capable of achieving the above-mentioned object is a method for producing a steel material for plastic working provided with a film on the surface of the steel material, and as an oxidizing agent, halogen, manganese or iron oxygen acid or a salt thereof, or Using a complex salt of iron, the gist of the invention includes the following step (a) or (b).
(A) The process of immersing steel materials in the aqueous solution containing the said oxidizing agent and soap (b) The process of making the said steel materials contact with soap, after immersing steel materials in the aqueous solution containing the said oxidizing agent.

  As the halogen, manganese or iron oxyacid salt or iron complex salt, an alkali metal salt or an alkaline earth metal salt is preferably used. The aqueous solution concentration of the halogen, manganese or iron oxygen acid or salt thereof, or iron complex salt is preferably 0.01 to 10 mol / L.

  The present invention also includes a steel for plastic working produced by the above production method.

  The steel for plastic working of the present invention is a steel for plastic working provided with a coating on the surface of the steel, and the coating is, in order from the steel, the first layer containing an oxide of the steel component, soap, and halogen. And a second layer containing manganese or iron oxyacid salt or iron complex salt.

  The first layer preferably further contains an alkali metal salt or an alkaline earth metal salt. Moreover, it is preferable that the steel material component contained in the first layer has a concentration distribution that decreases from the steel material side toward the second layer side.

  The thickness of the first layer is preferably 10 nm to 10 μm.

  The present invention also includes a plastic processed product obtained by plastic processing the above-described steel for plastic processing.

  According to the production method of the present invention, a steel material for plastic working having a film that exhibits plastic workability equivalent to or higher than that of a phosphate / soap film even when the film does not contain a phosphate is obtained. It is done. Moreover, since the film formed by the production method of the present invention does not contain phosphorus, it does not generate immersion phosphorus during heat treatment. Since the steel for plastic working obtained in this way can perform plastic working satisfactorily, a plastic working product (for example, a bolt or the like) having extremely excellent corrosion resistance can be obtained.

  The present inventors have conducted research in order to provide a steel material for plastic working having a lubricating film excellent in plastic workability such as lubricity and corrosion resistance. As a result, oxidizing agents such as halogen, manganese or iron oxyacids (oxo acids) or salts thereof, or iron complex salts are extremely useful as film adhesion improvers. With these film adhesion improvers and film forming agents, The present inventors have found that a film obtained using a certain soap can exhibit plastic workability and corrosion resistance that are equal to or superior to those of conventional phosphate / soap films, thereby completing the present invention.

  When a conventional non-phosphorous lubricant is used, the chemical reaction with the steel material component that is the base material hardly proceeds, so the resulting film is extremely weak in adhesion only by physically contacting the steel surface. . On the other hand, according to the present invention, the film adhesion improver halogen, manganese or iron oxygen acid or salt thereof, or iron complex salt reacts with the steel material component (especially iron) and adheres to the steel material. Therefore, a very excellent reaction layer (an oxidation reaction film including an oxide layer of steel material) is formed on the steel material surface. This reaction layer has irregularities, and the adhesiveness is further improved by the soap component entering the irregularities. In addition, when an iron complex salt is used as the film adhesion improver, the adhesion is further improved by bonding with iron constituting the steel material. As a result, according to the present invention, an extremely strong lubricating film comparable to the conventional phosphate / soap film is formed.

  Hereinafter, the film adhesion improver (oxidant) and the soap component used in the present invention will be described.

(Film adhesion improver)
The present invention is characterized in that halogen, manganese, or iron oxyacid (oxo acid) or a salt thereof, or a complex salt of iron is used as a film adhesion improver. Since these function as an oxidant, if the steel material is immersed in a treatment solution containing the film adhesion improver and soap, the steel material component and the film adhesion improver, and further the soap component, on the surface of the steel material. A strong oxidation reaction product (mainly containing an oxide of a steel material component) is formed (details will be described later).

  Of the film adhesion improvers, halogen, manganese or iron oxyacid salts or iron complex salts are preferable, and iron oxyacid salts or iron complex salts are more preferable. If iron oxyacid salt or iron complex salt is used, iron reduced in the film production process will be included in the oxide formed on the steel surface, so the oxide layer may be made thicker. And the adhesion of the film is further enhanced (see the examples described later).

  Examples of the “salt” include alkali metal salts (Li salt, Na salt, K salt, etc.), alkaline earth metal salts (Mg salt, Ca salt, Sr salt, Ba salt, etc.) and the like. In particular, when using an alkali metal salt of fatty acid (generally referred to as “soap”) or an alkaline earth metal salt (generally referred to as “metal soap”) as a soap, a film adhesion improver is also used. As described above, it is preferable to use an alkali metal salt or an alkaline earth metal salt. This is to prevent adverse effects such as generation of reaction floating substances and change in the composition of the reaction liquid due to the oxidation-reduction reaction between the soap and the film adhesion improver.

  Specifically, as the oxygen acid of halogen or a salt thereof, for example, hypochlorous acid or a salt thereof (sodium salt, potassium salt, magnesium salt, calcium salt, barium salt, etc.), hypobromous acid or a salt thereof (sodium) Salt, potassium salt, magnesium salt, calcium salt, barium salt, etc.), hypoiodic acid or salt thereof (sodium salt, potassium salt, magnesium salt, calcium salt, barium salt etc.); chloric acid or salt thereof (sodium salt, Potassium salt, magnesium salt, calcium salt, barium salt, etc.), bromic acid or salt thereof (sodium salt, potassium salt, magnesium salt, calcium salt, barium salt etc.), iodic acid or salt thereof (sodium salt, potassium salt, magnesium) Salt, calcium salt, barium salt, etc.); perchloric acid or its salt (Natri) Arm salts, potassium salts, magnesium salts, calcium salts, barium salts), periodic acid or a salt thereof (sodium salt, potassium salt, magnesium salt, calcium salt, barium salt) and the like. Examples of the oxygen acid of manganese or a salt thereof include permanganic acid or a salt thereof (sodium salt, potassium salt, magnesium salt, calcium salt, barium salt, etc.). Examples of the iron oxygen acid or a salt thereof include iron acid or a salt thereof (sodium salt, potassium salt, magnesium salt, calcium salt, barium salt, and the like). Examples of iron complex salts include potassium ferricyanide.

(Soap ingredient)
In the present invention, “soap” means a soap in a broad sense including soap in a narrow sense (generally referred to as “soap” and means an alkali metal salt of a fatty acid), as well as metal soap and lime soap. ing. The soap used for this invention will not be specifically limited if it is normally used for formation of a lubricating film. For example, representative examples of the alkali metal salt of fatty acid include sodium stearate. The “metal soap” generally means a metal salt of a fatty acid other than an alkali metal salt, and examples thereof include calcium stearate and aluminum stearate. In addition, “lime soap” generally means a product obtained by adding excess quick lime (calcium oxide) to soap (alkali metal salt of fatty acid) and reacting in water. Usually, lime soap contains calcium hydroxide, sodium stearate, water and the like. In addition to the above, lime soap may further contain calcium carbonate by absorbing carbon dioxide in the atmosphere.

  Next, the steel material for plastic working according to the present invention will be described.

  The steel for plastic working according to the present invention has a coating on the surface of the steel, and the coating is, in order from the steel, the first layer containing the oxide of the steel component, soap, oxygen of halogen, manganese or iron. And a second layer containing an acid salt or a complex salt of iron. According to the present invention, an oxide having excellent adhesion to the steel material is formed on the surface of the steel material, so that the lubricity and corrosion resistance are almost the same as or higher than those of conventional soap / phosphate films. An excellent lubricating film can be obtained.

  As described above, the coating includes a first layer containing an oxide of a steel material component and a second layer containing a soap or the like. The first layer formed on the surface of the steel material greatly contributes to improving the adhesion of the film.

  The first layer is composed of an oxide generated by a reaction between a steel material component and components (soap component and film adhesion improver) used in the production of the film, and one or more of these oxides are formed. included.

  Specifically, the oxide contains at least a steel material component. By forming the oxide of the steel material component on the surface of the steel material, a strong adhesive film can be obtained.

The “steel material component” includes not only iron which is the main component of the steel material but also alloy components (for example, Si, Cr, Mo, etc.) that can be contained in the steel material. The “oxide of steel material component” means an oxide of iron (for example, FeO, Fe ₂ O ₃ , Fe ₃ O _4, etc.) or an oxide such as Si, Cr, or Mo that is an alloy component. The above “oxide” does not necessarily satisfy the stoichiometric relationship, and includes those whose component ratio is out of stoichiometric composition, for example, those lacking oxygen. In the examples to be described later, when elemental analysis in the film depth direction was performed by Auger electron spectroscopy, observation was made as “steel component oxide” when both the steel component and oxygen were detected at 1% by mass or more. I did it.

The oxide may further contain a film adhesion improver. Specifically, the oxide may further contain an alkali metal salt, an alkaline earth metal salt, or the like constituting the film adhesion improver. In the present invention, soap is used in the production process of the film, but the oxide may further contain an alkali metal, an alkaline earth metal, aluminum or the like constituting the soap component. These existing forms are not limited, and may exist as single oxides such as alkali metals (for example, MgO, K ₂ O, CaO, etc.), or exist in the form of oxides with steel components (particularly iron). May be. In addition, as in the case of the steel component oxide described above, the above oxide does not necessarily satisfy the stoichiometric relationship, and the component ratio deviates from the stoichiometric composition, for example, lacks oxygen. Also included.

  The steel material component contained in the first layer preferably has a “gradient composition” that decreases from the steel material side toward the second layer side. For example, when the oxide of the steel material constituting the first layer includes an alkali metal or an alkaline earth metal, the mass ratio of the steel material component to the total of the alkali metal and the alkaline earth metal in the first layer is the steel material. The closer to the surface, the larger. The one having such a concentration gradient is excellent in adhesiveness with the steel material, so that it is difficult to peel at the time of plastic processing and can withstand severe plastic processing. Whether or not it has a gradient composition can be determined by Auger electron spectroscopy, which will be described later.

  The thickness of the first layer is preferably 10 nm or more (more preferably 100 nm or more), preferably 10 μm or less (more preferably 7 μm or less). If the thickness of the first layer is too thin, contact between the plastic working tool and the steel material cannot be sufficiently prevented, and seizure or the like is likely to occur during plastic working. On the other hand, if the first layer is too thick, the coating tends to crack. The thickness of the first layer can be measured by Auger electron spectroscopy described later.

  The second layer contains soap and a halogen, manganese or iron oxyacid salt or iron complex salt. The second layer is distinguished from the first layer in that it does not contain an oxide obtained by a reaction with a steel material component. Even when a halogen, manganese or iron oxygen acid is used as the film adhesion improver, these oxygen acids are not included in the second layer as they are, but exist as oxygen acid salts. This is because these oxyacids are converted into oxyacid salts during the production of the film.

  The above film may further contain an additive usually contained in the lubricating film. As an additive used for this invention, a rust preventive agent, a solid lubricant, etc. are illustrated typically, for example. Examples of the rust inhibitor include molybdate, vanadate, polyacrylic acid, silica, and benzotriazole. The solid lubricant is effective in reducing the friction coefficient, and examples thereof include molybdenum disulfide, graphite, boron nitride, mica, graphite fluoride, polytetrafluoroethylene, and paraffin.

  In the present invention, the type of steel material is not particularly limited, and various steel materials such as carbon steel, low alloy steel, and stainless steel can be used. In addition, the form of the steel material is not particularly limited as long as it is plastically processed, for example, plastic parts such as machine parts such as bolts, nuts, and springs, steel cords, bead wires, and drawn products such as PC steel wires. Examples thereof include wires and rods used for manufacturing products.

  The composition, thickness, and adhesion amount of the first layer and the second layer constituting the film can be measured, for example, by the following method.

[Measurement method of the composition and thickness of the first layer and the second layer]
The composition of the first layer and the second layer, and the thickness of the first layer and the second layer can be measured, for example, by Auger electron spectroscopy. Detailed measurement conditions are as follows. This measurement method can also determine whether the first layer and the second layer have a single composition or a gradient composition.
・ Device: “PHI650 Scanning Auger Electron Spectrometer” manufactured by Perkin Elmer
Primary electron energy, current: 10 keV, 300 nA
・ The incident angle: 30 degrees with respect to the sample normal ・ The beam diameter: <5 μmφ
・ Analysis area: Same as above (point analysis)
・ Ion sputtering energy, current: 3 keV, 25 mA
-Incident angle: about 58 degrees with respect to the sample normal-Sputtering speed: about 31 nm / min

Specifically, based on the elemental analysis results in the depth direction by Auger electron spectroscopy, the first layer (including steel oxides) and the second layer (including steel oxides) formed on the steel material according to the following criteria: The thickness of the oxide was measured. According to the profile in the depth direction by the above method, the first layer and the second layer can be distinguished mainly by Fe and O (oxygen), and the first layer detects a large amount of Fe and O. On the other hand, the amount of O detected in steel is small. On the other hand, the second layer has a small amount of detected Fe. Therefore, each layer was defined as follows.
Steel: Fe as the main component, average concentration of O <1 atomic%
1st layer: range from the depth above the steel material (average concentration of O ≧ 1%) to the depth inside the second layer (average concentration of Fe ≧ 1 atomic%) 2nd layer: formed on the outermost surface side Fe average concentration <1 atomic%

[Measurement method of film composition]
A steel material for plastic working provided with a film is prepared, and the composition of the film is measured by X-ray diffraction (XRD) using the steel material as it is or a film obtained by scraping the steel material with a metal piece as a film measurement sample. According to X-ray diffraction, for example, oxides such as soap-derived alkali metals or alkaline earth metals, complex oxides of alkaline earth metals and the like with silicon or boron can be identified. Alternatively, the composition of the film may be measured with an infrared spectrophotometer (IR) or a gas chromatograph mass spectrometer (GC-MS) using the film shaved off as described above as a film measurement sample. According to these methods, soap-derived organic components, halogen, manganese or iron oxyacid salts, iron complex salts, and the like can be identified.

[Measurement method of coating amount]
A sample having a diameter of about 10 mm and a length of about 50 mm is prepared as a sample for measuring the coating amount. After scraping the film over the entire circumference using metal pieces, etc., dipping until 50% hydrogen bubbles are generated in 1N sulfuric acid, washing with water and drying. Measure.

  Next, the manufacturing method of the steel material for plastic working provided with said film | membrane is demonstrated.

The production method of the present invention is characterized in that the above film is formed using the above-mentioned film adhesion improver (halogen, manganese or iron oxygen acid or salt thereof, or iron complex salt) and a film forming agent (soap). There is. Specifically, the production method of the present invention includes the following step (a) or (b) using the halogen, manganese or iron oxygen acid or a salt thereof, or an iron complex salt as an oxidizing agent. .
(A) Step of immersing steel in an aqueous solution (treatment liquid) containing the above oxidizing agent and soap (b) After immersing the steel material in an aqueous solution (treatment liquid) containing the above oxidizing agent, the steel material is soaped Process

  Which of the above (a) and (b) is used is mainly determined by the type of the film adhesion improver that functions as an oxidizing agent. For example, when using a film adhesion improver having low reactivity with soap (for example, sodium hypochlorite having a liquid property of neutral to alkaline and having an oxidizing action at a temperature at which soap is treated) It is preferable to use the step (a). On the other hand, when using a film adhesion improver having high reactivity with soap (for example, one having liquid acidity), the step (b) is used. preferable.

  In the above (b), the means for bringing the steel material into contact with the soap is not particularly limited. For example, the steel material may be immersed in an aqueous soap solution, or the steel material and the solid metal soap are in physical contact (for example, , Rub).

  The temperature (treatment temperature) of the “aqueous solution containing the film adhesion improver and soap” in (a) and the “aqueous solution containing the film adhesion improver” in (b) is preferably 30 ° C. or more (more preferably Is 40 ° C. or higher), preferably 80 ° C. or lower (more preferably 70 ° C. or lower). When the temperature is lower than 30 ° C., it takes time to dry the treatment liquid adhering to the steel material. On the other hand, when the temperature exceeds 80 ° C., the evaporation of moisture is intense, and the film adhesion improver may be decomposed during film formation.

  In the above (a) and (b), the immersion time of the steel material in the aqueous solution (treatment liquid) is appropriately set according to, for example, the desired amount of coating, the degree of plastic working, and the process after plastic working. Generally, it is preferably 1 minute or longer (more preferably 2 minutes or longer), preferably 20 minutes or shorter (5 minutes or shorter).

  In any of the above (a) and (b), the aqueous solution concentration of the film adhesion improver is preferably 0.01 mol / L or more (more preferably 0.5 mol / L or more), preferably 10 mol / L or less ( More preferably, it is 5 mol / L or less. When the concentration of the film adhesion improver is too low, the oxidation reaction with the steel material component does not proceed sufficiently, and the formation of the oxide layer (first layer) of the steel material component contributing to the adhesion improvement becomes insufficient. If the concentration of the film adhesion improving agent is increased, the film adhesion improving action tends to be improved, but if it exceeds about 10 mol / L, the above action is saturated, which is economically useless.

  The present invention also includes a plastic processed product obtained using the steel for plastic processing. The method for producing the plastic processed product is not particularly limited, and a method known in the technical field may be adopted as appropriate. The plastic processed product of the present invention may have the above-described film as it is, or the film may be removed using an acid or an alkaline aqueous solution. Alternatively, the film may be altered by applying a heat treatment after plastic working. For example, when using steel for bolts, quenching and tempering are often performed after plastic working, which causes water and organic components in the second layer (soap layer) constituting the film to evaporate. Are also included within the scope of the present invention.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can meet the above and the following purposes. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
In this example, as shown in Table 1, as a film adhesion improver, calcium hypochlorite (halogen oxyacid salt), potassium permanganate (manganese oxyacid salt), potassium ferrate (iron A film was formed using oxyacid salt) and potassium ferricyanide (iron complex salt), and experiments were conducted.
(Production of test materials)
A hot-rolled wire (wire diameter 10 mm) obtained by hot rolling steel type SCM435 was quenched and tempered so that the strength was about 1200 MPa, and then processed into a size of 10 mm in diameter and 50 mm in length. The processed wire was pickled and descaled, washed with water, and then treated under the immersion conditions shown in Table 1 below to form films (first layer and second layer) on the surface of the wire. In Table 1, the column “type of treatment agent” in step (a) describes the type and concentration of the film adhesion improver and soap constituting the treatment agent. In the “type of treatment agent” column of the step (b), the type of the film adhesion improver constituting the treatment agent is described, and in the “soap type” column, the soap to be contacted with the steel material is described. The type is described.

  In Table 1, No. In No. 6, the wire was immersed in an aqueous potassium ferricyanide solution and then contacted by rubbing powdered Ca stearate.

  For comparison, a wire rod (No. 18 in Table 1) provided with a conventional phosphate / soap film was prepared. Detailed treatment conditions (zinc phosphate treatment) are as follows.

[Zinc phosphate treatment method]
The wire was immersed in a 15% hydrochloric acid solution (50 ° C.) for 10 minutes, washed with water, and treated with 90 g / L zinc phosphate treatment agent (“Palbond 181X” manufactured by Nihon Parkerizing Co., Ltd.) at 80 ° C. Chemical conversion treatment was performed for a minute. Next, a soap treatment was performed at 80 ° C. for 5 minutes using a 70 g / L soap lubricant (“Parube 235” manufactured by Nihon Parkerizing Co., Ltd.).

  In this example, ten samples were produced for each experimental example.

  For each sample thus obtained, the thickness of the first layer and the presence or absence of a gradient composition were measured as follows, and the plastic workability and the corrosion resistance were evaluated.

(Thickness of the first layer)
The thickness of the first layer was measured by Auger electron spectroscopy. Specifically, three samples are prepared for each experimental example, and based on the profile obtained by each Auger electron spectroscopy, from the depth at which the Fe amount becomes 5 atomic% or more, alkali metal or alkaline earth metal is present. The depth up to 5 atomic% or less was calculated as the thickness of the first layer (steel component oxide layer), and the average of these was taken as the thickness of the first layer of each experimental example.

(Presence or absence of gradient composition of the first layer)
Further, as described above, it was examined whether or not the first layer had a gradient composition by performing Auger electron spectroscopy. Specifically, three samples are prepared for each experimental example, and alkali metals or alkalis at positions D / 4, D / 2, and 3D / 4 (D = thickness of the first layer) from the surface of the first layer. The contents of earth metals and iron were determined. When the mass ratio of iron to the alkali metal or alkaline earth metal in the first layer is closer to the surface of the steel material (that is, the deeper the depth), “the first layer has a gradient composition” Judged.

(Plastic workability)
Three samples were prepared for each experimental example, and the plastic workability was examined as follows. Using a surface property measuring machine manufactured by Toh Chemical Co., Ltd., a load of 1000 kgf was applied to a 10 mmφ sphere of SUJ2 as a counterpart material, and 30 mm in length was continuously reciprocated in the length direction of the sample under normal temperature and no lubrication conditions I let you. The friction coefficient was continuously measured, and the number of reciprocating cycles at which the friction coefficient was 0.2 or more was measured. Of the three samples measured, the plastic workability was evaluated based on the smallest number of reciprocating cycles. According to this evaluation method, the temperature rise due to frictional heat did not exceed 40 ° C., and the plastic workability could be evaluated under almost the same conditions.

  It is known that the above evaluation method has a high correlation with the drawability and the forging workability. That is, in the case of a film having inferior lubricity, the friction coefficient increases early and the number of reciprocating cycles decreases. Further, in the case of a film with low adhesion and poor wire drawing and forging workability, the film peels and wears out early and the friction coefficient increases, so the number of reciprocating cycles is also reduced.

(Corrosion resistance)
Four samples were prepared for each experimental example, and the corrosion resistance was examined as follows. The sample was allowed to stand for 2 weeks in a constant temperature and humidity chamber at a temperature of 40 ° C. and a humidity of 90%, and then the area ratio of rust generated on the sample surface was measured visually. Of the four samples tested, the corrosion resistance was evaluated based on the largest rust area ratio.

  These results are summarized in Table 2.

  From Table 2, Experiment No. obtained using the film adhesion improver specified in the present invention and soap. Nos. 1 to 15 were used in Experiment No. 1 treated with only lime soap or Na stearate without using the above-mentioned film adhesion improver. Compared with 16 and 17, it was excellent in plastic workability and corrosion resistance, and showed good characteristics comparable to the conventional example (experiment No. 18) having a phosphate / soap film.

  Among the above, Experiment No. using iron oxyacid salt or iron complex salt. In 3, 5, 7, 10, 12, 14, and 15, iron reduced by the immersion treatment is also included in the first layer (the oxide layer of the steel material component), so that the thickness of the first layer is increased and plasticity is increased. There was a tendency for processability to be higher.

Claims (9)

A method for producing a steel material for plastic working provided with a coating on the steel surface,
A production method comprising the following step (a) or (b) using an oxygen acid of halogen, manganese or iron or a salt thereof, or a complex salt of iron as an oxidizing agent.
(A) A step of immersing a steel material in an aqueous solution containing the oxidizing agent and soap (b) A step of contacting the steel material with soap after immersing the steel material in an aqueous solution containing the oxidizing agent   2. The production according to claim 1, wherein the oxygen acid salt is an alkali metal salt or alkaline earth metal salt of the oxygen acid, and the iron complex salt is the iron alkali metal salt or alkaline earth metal salt. Method.   3. The production method according to claim 1, wherein an aqueous solution concentration of the halogen, manganese, or iron oxygen acid or a salt thereof, or an iron complex salt is 0.01 to 10 mol / L.   The steel material for plastic working manufactured by the manufacturing method in any one of Claims 1-3. A steel material for plastic working with a coating on the steel surface,
In order from the steel material side,
A first layer containing an oxide of a steel component;
A second layer containing soap and a halogen, manganese or iron oxyacid salt or iron complex salt;
A steel material for plastic working, characterized by comprising:   The steel material for plastic working according to claim 5, wherein the first layer further contains an alkali metal salt or an alkaline earth metal salt.   The steel material for plastic working according to claim 5 or 6, wherein a steel material component contained in the first layer decreases from the steel material side toward the second layer side.   The steel material for plastic working according to any one of claims 5 to 7, wherein the thickness of the first layer is 10 nm to 10 µm.   A plastic working product obtained by plastic working the steel for plastic working according to any one of claims 4 to 8.