JP5256401B2 - Lubricant composition for cold plastic working and manufacturing method of steel pipe joint using the same - Google Patents

Description

  The present invention is a cold plastic working lubricant composition capable of forming a raw steel pipe (element pipe) without subjecting it to chemical conversion lubrication and causing no alteration of the surface of the element pipe due to carburization or the like during heat treatment, and this The present invention relates to a method for manufacturing a steel pipe joint that can efficiently manufacture an excellent quality steel pipe joint using a lubricant.

  Steel pipe joints used in power generation and chemical plants are usually used by welding both ends of the joint to steel pipes, as seen in elbow pipes and the like. As a method for manufacturing a joint, there are a hot working method in which a raw pipe is heated and formed, and a cold working method in which a chemical conversion treatment is performed to form a chemical conversion coating on the surface of the raw pipe.

  In the hot working method, since the processing temperature must be maintained by heating the raw tube as well as the tool, temperature management is not easy, and molding defects are likely to occur due to variations in the heating temperature and the heated part. The loss of heat energy is also great. As the lubricant, solid lubricants such as graphite and boron nitride that can withstand high temperatures must be used, carburization occurs, and the residue of solid lubricant adheres to the inner surface of the pipe, which impedes product quality. Sometimes. Furthermore, the working environment is inevitably deteriorated due to the scattering of solid lubricants such as graphite.

  On the other hand, as a cold working method, a chemical conversion treatment film is formed on the surface of the raw tube, and further, a lubricant containing a chlorine-based extreme pressure agent or a sulfur-based extreme pressure agent or a solid such as graphite or molybdenum disulfide. A method of applying a lubricant and molding has been proposed. In addition, there are a method in which lubricating oil is applied to the surface of the base tube or the tool and molding, and a method in which a polyethylene sheet is placed on the tool for the purpose of lubrication.

  For example, in Patent Document 1, a short element pipe, which is a workpiece, is attached (ringed) to a mandrel whose tip is bent in a celel shape, and then the normal tube is expanded with a mandrel by a pusher. A cold-working method for a steel pipe that forms an elbow by punching, and as a lubricant to be applied to the inner surface of the base pipe, from the base steel side, the base film, metal soap, and hot water-treated soap There is described a lubricant comprising a film and a lubricating powder of metal soap powder, graphite powder or molybdenum disulfide powder applied to the lubricating film. In addition, this cold working method requires a forming process for each workpiece (element pipe) in the bent pipe manufacturing apparatus proposed in Patent Document 2 in which an elbow is formed by a cold bending method by a push-bending method. It is a method that has been developed to solve problems such as improvement in molding efficiency cannot be expected.

  As a lubricant for metal forming in cold, for example, Patent Document 3 contains a resin having a highly polar functional group such as polyethylene glycol resin and polyester resin, and solid lubricant such as metal soap and wax is used. In addition, Patent Document 4 discloses a copolymer containing styrene and a vinyl compound having a carboxyl group copolymerizable therewith and a lubricant (various waxes) in a predetermined ratio. The surface treatment agent contained in is described. However, the treatment with these lubricants does not provide satisfactory moldability in the production of joints, and the lubrication treatment for forming the above-described chemical conversion treatment film is performed.

  However, the chemical lubrication treatment is inefficient because a chemical conversion treatment film must be formed on the inner surface of the raw material tube. Further, in order to prevent carburization that occurs during the heat treatment performed to adjust the mechanical properties of the product after cold working, the soap contained in the chemical conversion coating must be removed by performing a degreasing treatment before the heat treatment. Furthermore, the chemical treatment film and the material surface react during the heat treatment and the surface state deteriorates, and since a lubricant residue remains after the heat treatment, surface treatment such as cleaning and shot blasting may be required. There is also a problem that it is necessary to dispose of the recovered lubricant residue.

JP 2006-247664 A JP-A-6-114453 Japanese Patent Laid-Open No. 5-70787 JP 2001-234349 A

  As described above, when manufacturing a pipe joint by hot working, a heating device is required, which increases the cost required for thermal energy, and there are many product defects associated with molding defects, carburization, and other processing, There is a problem that molding yield and molding efficiency are lowered. On the other hand, in the case of cold working, there are many necessary processes such as formation of a chemical conversion treatment film, degreasing treatment before heat treatment, and, when using a polyethylene sheet, maintenance of the product due to the occurrence of seizure flaws due to film breakage, increasing the manufacturing cost It is a factor of.

  The present invention has been made to solve such problems, and it is possible to manufacture a pipe joint by cold working without subjecting it to chemical lubrication treatment even for difficult-to-work materials such as stainless steel. , A lubricant composition for cold plastic working that does not cause surface modification due to carburizing or the like during heat treatment after cold working, and a method for efficiently producing an excellent quality steel pipe joint using this lubricant It is intended to provide.

  As a result of repeated researches to solve the above problems, the present inventors have found that a lubricant composition for cold working containing polyethylene powder, a specific vinyl resin and a dispersant is applied to the inner surface of a steel blank. The adhesion of the material is excellent, the lubricity is excellent, and carburization is not observed even if heat treatment is performed after cold working, and this lubricant composition is applied to the inner surface of the raw tube and cold working is performed. It was confirmed that it was possible to manufacture a steel pipe joint of excellent quality.

  The present invention has been made on the basis of such findings and examination results. The gist of the present invention is to use the following lubricant composition for cold plastic working (1) and the lubricant composition (2) to It exists in the manufacturing method of the steel pipe joint in any one of (5).

  (1) 5 to 50% by mass of polyethylene powder having an average particle diameter of 1 to 100 μm and an average molecular weight of 20,000 or more, a water-soluble vinyl resin not containing an alkali metal, or a nonionic surfactant or / and A lubricant composition for cold plastic working, comprising 1 to 20% by mass of a water-dispersible vinyl resin emulsion-polymerized with a protective colloid and 0.1 to 5% by mass of a nonionic dispersant.

  The “average particle size” here refers to the arithmetic average of the particle sizes of all the particles obtained based on the particle size distribution. The “average molecular weight” is a number average molecular weight obtained from a molecular weight distribution curve.

  (2) The lubricant composition according to (1) is applied to the inner surface, and the raw tube, which is a dried workpiece, is wrapped around a bent conical mandrel, and the normal tube is bent by a pusher. A method of manufacturing a steel pipe joint, wherein an elbow is formed by extruding while expanding with a conical mandrel.

  Examples of the material of the raw pipe, which is the workpiece, include stainless steel (SUS304 steel, 316L steel, etc.) in addition to carbon steel and alloy steel (Mn steel, Cr—Mo steel, etc.). This is the same also in the manufacturing method of the steel pipe joint in any one of following (3)-(5).

  (3) The lubricant composition described in (1) above is applied to the outer surface, and hydroforming that applies an internal pressure using a fluid as a medium is applied to a raw tube that is a dried workpiece, and the elbow, T, A method of manufacturing a steel pipe joint, wherein a cap or a reducer is formed.

  (4) Applying the lubricant composition described in (1) above to the outer surface, and applying a diameter reduction process by pressing the raw tube, which is a dried workpiece, into a molding die whose inner surface has a product shape. And a reducer is formed.

  (5) Applying the lubricant composition described in (1) above to the inner surface and applying a tube expansion process by inserting a punch, which is a dried workpiece material, into which the outer surface has the shape of the inner surface of the product. And a reducer is formed.

  In the method for manufacturing a steel pipe joint according to any one of the above (2) to (5), the formed steel pipe joint is subjected to a heat treatment at 900 to 1300 ° C. so as to be subjected to a blank pipe surface (inner surface). Alternatively, it is desirable that the lubricant remaining on the outer surface) can be completely decomposed, evaporated, or burned and removed, and surface alteration due to carburization or the like does not occur.

  The lubricant composition for cold plastic working of the present invention is a water-dispersible composition, has good adhesion to the surface of a steel base tube, and is excellent in lubricity.

  The method for manufacturing a steel pipe joint according to the present invention is a method for manufacturing a steel pipe joint by applying this lubricant composition to the surface (inner surface or outer surface) of a raw pipe and performing cold working. Even difficult-to-work materials such as these can be cold-worked without being subjected to chemical lubrication treatment, and an excellent quality pipe joint can be produced efficiently. Carburization is not observed even when heat treatment is performed to adjust the mechanical properties of the product after cold working.

  The lubricant composition for cold plastic working of the present invention is a water-soluble vinyl resin not containing an alkali metal, 5 to 50% by mass of polyethylene powder having an average particle size of 1 to 100 μm and an average molecular weight of 20,000 or more, Or 1 to 20% by mass of a water-dispersible vinyl resin emulsion-polymerized with a nonionic surfactant or / and a protective colloid, and 0.1 to 5% by mass of a nonionic dispersant. It is a water-dispersible lubricant composition.

Polyethylene is an ethylene polymer (—C ₂ H ₄ —) _n that is self-lubricating, has a low coefficient of friction, and is a major constituent of the lubricant composition of the present invention. The lower limit of the average particle diameter of the polyethylene powder is defined as 1 μm. If the average particle diameter is less than 1 μm, a large amount of dispersant is required. As a result, the blending ratio of the polyethylene powder decreases and the lubricity of the dry film deteriorates. Because it does. The upper limit of the average particle diameter is 100 μm because if it exceeds 100 μm, the polyethylene powder is not dense in the dry film and the lubricity is lowered.

  The reason why the average molecular weight of the polyethylene powder is 20,000 or more is that when it is less than 20,000, the lubricity during molding is poor and seizure occurs over a wide range. Low density polyethylene or high density polyethylene powder having an average molecular weight of 20,000 or more, or ultrahigh molecular weight polyethylene powder having an average molecular weight of 1,000,000 to 6,000,000 can be used.

  Further, the content (blending ratio) of the polyethylene powder is set to 5 to 50 mass% when the blending ratio is less than 5 mass%, a film thickness sufficient to maintain lubricity cannot be obtained, and 50 mass%. This is because the viscosity increases and the applicability of the lubricant deteriorates.

  The vinyl resin used in the lubricant composition of the present invention has the effect of improving the adhesion of the lubricant to the surface of the base tube. Also functions as a binder for polyethylene powder.

  The vinyl resin is a water-soluble vinyl resin obtained by polymerizing one or more of monomers such as vinyl acetate, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, and ethylene. A water-dispersible vinyl resin obtained by emulsion polymerization using a non-ionic surfactant or a non-ionic protective colloid may be used. The nonionic surfactant and the nonionic protective colloid may be used simultaneously.

  The water-soluble vinyl resin does not contain an alkali metal because, for example, when the water-soluble vinyl resin contains sodium (sodium salt), sodium is not formed during heat treatment after molding by applying this lubricant. It is because it remains as a residue and alkali corrosion may occur.

  In obtaining the water-dispersible vinyl resin, the emulsion polymerization is performed by emulsifying, dispersing, and polymerizing a poorly water-soluble monomer in water using an emulsifier (that is, a surfactant or a protective colloid). is there. In addition, nonionic surfactants and / or protective colloids are used in emulsion polymerization because the molecules that make up these nonionic surfactants and protective colloids are composed of carbon, hydrogen, and oxygen. This is because, for example, an alkali metal contained in an anionic surfactant is not contained, and therefore, when heat-treated, it is gasified and no residue remains. Further, alkaline corrosion at high temperatures does not occur.

  As the nonionic surfactant, for example, polyoxyethylene alkyl ether such as polyoxyethylene lauryl ether can be used, and as the nonionic protective colloid, for example, polyvinyl alcohol can be used.

  The compounding ratio of the vinyl resin is 1 to 20% by mass. When the blending ratio is less than 1% by mass, it is insufficient to adhere the polyethylene powder to the surface of the material, resulting in poor lubrication due to peeling or the like, and when it exceeds 20% by mass, the vinyl resin inhibits the lubricating action of polyethylene. Because it does.

  The nonionic dispersant is blended in the lubricant composition of the present invention in order to uniformly disperse the polyethylene powder in the lubricant, and the blending ratio is 0.1 to 5% by mass. If the blending ratio is less than 0.1% by mass, it is insufficient for uniform dispersion of the polyethylene powder, and if it exceeds 5% by mass, the lubricity of polyethylene is hindered and the cost increases.

  Nonionic dispersants include polyoxyalkylene (C2 or / and C3) alkyl ether, polyoxyalkylene (C2 or / and C3) alkylphenyl ether, 2,4,7,9 tetramethyl-5-decyne 4, Nonionic compounds such as 7-diol [polyoxyethylene] ether are desirable. In addition, in “polyoxyalkylene (C2 or / and C3)” which is a part of the name of the dispersant, C2 means ethylene, C3 means propylene, and alkylene is ethylene or / and propylene. Represent.

  In the lubricant composition of this invention, you may add a viscosity modifier, an antifoamer, a rust preventive agent, etc. as needed.

  The viscosity modifier is added in order to secure a good coating property of the lubricant and to obtain a viscosity sufficient to obtain a film thickness sufficient to maintain the lubricity. When blending the viscosity modifier in an amount of 0.1% by mass or more, nonionic compounds such as methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, polyethylene glycol, and polyvinyl alcohol are desirable, but a trace amount of less than 0.1% by mass is preferable. In this case, an anionic one such as sodium carboxymethyl cellulose can also be used.

  The antifoaming agent is added to prevent the generation of innumerable small bubbles generated when the lubricant is stirred, and an alcohol-based or ester-based one in which no residue remains after annealing is desirable. A silicon-based antifoaming agent or the like can be used as long as it does not affect the quality of the material.

  As the rust preventive agent, an amine-based one such as alkanolamine such as triethanolamine and organic acid salts thereof which does not contain an alkali metal salt is particularly desirable.

  The lubricant composition for cold plastic working of the present invention has good adhesion to the surface (inner surface or outer surface) of a steel base tube, and is excellent in lubricity. If this lubricant is used, chemical lubrication Pipe joints can be manufactured by cold working without any treatment. Carburization is not observed even if heat treatment is performed after cold working. Since this lubricant has good adhesiveness and excellent lubricity, it can be used satisfactorily as a lubricant for cold plastic working other than for the production of pipe joints.

  One of the manufacturing methods of the steel pipe joint of the present invention is the manufacturing method according to the above (2), wherein the lubricant composition of the present invention is applied to the inner surface, and the raw pipe which is a dried workpiece is used. In this method, an elbow is formed by attaching a bent conical mandrel to the mandrel, and pushing out the raw tube at room temperature with a pusher while expanding the tube with the bent conical mandrel.

  This pipe joint manufacturing method is a method for cold bending a steel pipe (hereinafter, also referred to as “punch expansion elbow processing method using a mandrel”). This is a method of applying a polyethylene resin-based lubricant containing the above-described polyethylene of the present invention as a main constituent.

  FIG. 1 is a diagram showing a schematic manufacturing process of a steel pipe joint (elbow). (A) shows a case where chemical lubrication treatment is applied to the inner surface of a raw pipe, and (b) shows that the lubricant of the present invention is applied. Is the case. (A) is the manufacturing process by the punching pipe expansion elbow processing method using the mandrel described in patent document 1. FIG.

  In FIG. 1A, in the “chemical conversion treatment” step, a base coating (such as ferrous oxalate), metal soap (for example, iron stearate), and hot water-dissolved soap (stearic acid) from the base steel side of the tube. A three-layer chemical conversion film made of sodium) is formed and dried, and then a metal soap powder, graphite powder or molybdenum disulfide powder is applied onto the film.

  In the subsequent “cold working” step, the base pipe is formed into an elbow by punching and expanding elbow processing using a mandrel. Subsequently, in the “degreasing treatment” step, the soap is removed to prevent carburization, and in the “pickling with nitric hydrofluoric acid”, the undercoat is similarly removed to prevent carburization, followed by heat treatment.

  On the other hand, in the method for manufacturing a steel pipe joint of the present invention, as shown in FIG. 1 (b), a lubricant is applied to the inner surface of the raw pipe and dried, and then the same as in FIG. 1 (a). Apply cold working. After that, it is immediately sent to a heat treatment process for annealing or the like to become a product.

The lubricant applied to the inner surface of the raw tube in the “lubricant application” step is the above-described lubricant composition of the present invention. As a coating method, brush coating, spray coating or the like can be applied. The lubricant film after drying is preferably 10 to ²⁰⁰ g / m ² . If the lubricant film is less than 10 g / m ² , the film is too thin and the lubricating action is not sufficient, and if it exceeds 200 g / m ² , not only does the lubrication effect saturate, but also the efficiency of coating and drying decreases, economically. Is also disadvantageous. A more desirable lubricant film thickness is 50 to 150 g / m ² .

  In the “drying” step, moisture is evaporated from the applied lubricant to form a dry film. The drying temperature may be in the range of 10 to 150 ° C., but 50 to 100 ° C. is desirable from the viewpoint of securing an appropriate drying rate and obtaining a dense lubricant film.

  In the “cold working” process, a punched tube expansion elbow processing method using a bent conical mandrel is applied. That is, after a raw material pipe, which is a material to be processed, is mounted on a mandrel whose tip is bent like a celel, the normal tube is pushed out by a pusher while being expanded with a mandrel to form an elbow. As a result, the raw tube is expanded by the mandrel, and at the same time, the elbow having less uneven thickness and excellent dimensional accuracy can be formed by distributing the distortion in the punching direction of the raw tube in the circumferential direction of the raw tube. .

  Since the elbow is continuously molded by performing the ringing on the mandrel, the molding efficiency can be improved.

  The molded elbow is shaped using a mold so that the elbow cross section is maintained in a perfect circle, and then subjected to a predetermined heat treatment in the "heat treatment" process, and the end face shape is finished by beveling. It becomes.

The heat treatment is desirably performed in the air or in an atmosphere containing oxygen. Polyethylene is the main component of the lubricant is represented by the formula (-C ₂ H ₄ -) is _n, C is its constituent elements, H is, by heating in an atmosphere of oxygen are present, reaction: It is decomposed by C ₂ H ₄ + 3O ₂ → 2CO ₂ + 2H ₂ O and disappears. Therefore, carburization does not occur by heat treatment due to the polyethylene remaining on the inner surface of the raw tube after cold working. Since the decomposition temperature of polyethylene is about 600 ° C. or higher, it is desirable to consider that the heat treatment temperature falls within this temperature range.

  Another method for producing the steel pipe joint of the present invention is the production method according to (3) above, wherein the lubricant composition of the present invention is applied to the outer surface and is a dried workpiece material. The elbow, T, cap, or reducer is formed by applying an internal pressure using a fluid as a medium. As the fluid, a liquid such as oil or water is used, which is called a hydroforming method.

  This pipe joint manufacturing method uses the polyethylene of the present invention as a main component in place of chemical lubrication treatment on the outer surface of the base pipe when forming various pipe joints, that is, elbows, Ts, caps or reducers by hydroforming. This is a method of applying a polyethylene resin-based lubricant contained as a component. As for the elbow, any of 45 ° elbow, 90 ° elbow and 180 ° elbow can be manufactured. As for T and reducer, any of the same diameter T, different diameter T, concentric reducer, eccentric reducer, etc. can be supported.

  Hydroforming itself may be performed in accordance with a conventionally practiced method. After the molding process, a predetermined heat treatment is performed, and the end face shape is finished by beveling to obtain a product.

  Still another method for producing a steel pipe joint according to the present invention is the production method according to (4) above, wherein the lubricant composition of the present invention is applied to the outer surface and dried. In this method, a reducer is formed by applying a diameter reduction process by pushing a tube into a forming die whose inner surface has a product shape.

  Further, another one of the methods for producing a steel pipe joint of the present invention is the production method as described in (5) above, wherein the lubricant composition of the present invention is applied to the inner surface and dried. In this method, a reducer is formed by applying a tube expansion process by inserting a punch having a certain outer tube into the shape of the inner surface of the product.

  In these methods, when forming a reducer by reducing the diameter or expanding the raw pipe, which is a workpiece, using a forming die or punch, the lubricant composition of the present invention is formed on the outer surface or the inner face of the raw pipe. It is the method of apply | coating. Since this lubricant composition has good adhesion to the surface of a steel tube and is excellent in lubricity, reducers of various shapes such as concentric reducers and eccentric reducers can be used with appropriate dies or punches. Can be produced relatively easily.

  In the method for manufacturing a steel pipe joint according to the present invention (the manufacturing method according to any one of (2) to (5)), the formed steel pipe joint is heat-treated at 900 to 1300 ° C. It is desirable that the lubricant remaining on the surface (inner surface or outer surface) of the tube after cold working can be completely decomposed, evaporated or burned and removed.

  The remaining lubricant is a composition containing polyethylene as a main component and additionally containing a vinyl resin, a dispersant and the like. Polyethylene decomposes at about 600 ° C, but vinyl resins, dispersants, etc. may adhere to the tube surface as a residue without being decomposed at 600 ° C depending on the chemicals used, which may hinder product quality. . In addition, carburization occurs when heated to a higher temperature. In such a case, the formed steel pipe joint is heat-treated at 900 to 1300 ° C. to decompose and evaporate the remaining lubricant, and if it is in an atmosphere where oxygen is present, it is burned and completely removed. can do.

  Thus, according to the steel pipe joint manufacturing method of the present invention, it is possible to manufacture pipe joints by cold working without performing chemical lubrication treatment, even for difficult-to-work materials such as stainless steel, An excellent quality pipe joint without carburizing can be efficiently manufactured with a simple manufacturing process.

  The effects of the lubricant composition of the present invention and the method for manufacturing a steel pipe joint of the present invention using this lubricant (punch tube expansion elbow processing method using a mandrel) will be described based on Examples 1 and 2.

Example 1
Using the lubricant composition of the present invention shown in Table 1 (Invention Examples 1 and 2), the adhesion to the surface of the material, the press speed and the lubricant remaining after the press, and the presence or absence of carburization during heat treatment investigated.

(A) Adhesion to material surface The lubricant was thinly applied to a thin plate of stainless steel (SUS304), and the peeling state of the film dried at room temperature or 80 ° C. was investigated. For comparison, the same investigation was performed on a lubricant composition containing no vinyl-based resin (Comparative Example 1).

  The survey results are shown in Table 2. In the same table, the evaluation criteria are as follows, and it was evaluated as good if it was marked with ◯ or △.

○ mark: Hard to peel even when rubbed strongly with finger flat △: Peeled when rubbed strongly with finger flat × mark: Peeled only by rubbing lightly with finger flat

  As shown in Table 2, the lubricant of Comparative Example 1 that does not contain a vinyl-based resin that improves the adhesion to the material surface was peeled off by lightly rubbing with the flat of the finger. The lubricant of No. 2 had good adhesion to the material. If it is dried at 80 ° C., it is desirable that it is difficult to peel off even if rubbed strongly.

(B) Press speed and remaining condition of lubricant after pressing Stainless steel (SUS304; heat treatment condition 1060 ° C. × 20) with dimensions of outer diameter 105.0 mm × thickness 7.5 mm × length 350 mm as a test tube Min → water cooling), and the lubricant shown in Table 1 of the present invention was applied to the inner surface to perform cold mandrel bending to produce a stainless steel elbow, and the press speed and press at that time The state of remaining lubricant was investigated. For comparison, the same applies to the case where the lubricant shown in Comparative Example 1 in Table 1 is applied and the case where the chemical lubrication treatment (treatment described in Patent Document 1) shown in Comparative Example 2 is performed. Was conducted. At that time, in the application of the lubricant of Comparative Example 1, pretreatment of lubrication (grid blasting) was performed on the inner surface of the raw tube in order to improve adhesion.

  The survey results are shown in Table 3. For any lubricant or chemical lubrication treatment, the pressing is performed 8 times and the average value is shown. In the “evaluation” column, “A” means extremely good, “O” means good, and “Δ” means that the product is generally good.

  As is apparent from Table 3, in Examples 1 and 2 of the present invention, the press speed was close to 1.7 times or 3 times that of Comparative Example 2 subjected to chemical lubrication treatment. Judging from the state of lubricant remaining after pressing (results of visual observation), the adhesiveness of the lubricant was good in both inventive examples 1 and 2. Note that the lubricant of Comparative Example 1 (lubricant that does not contain a vinyl resin), which was evaluated as having poor adhesion in the investigation of (a), was generally good in lubricity here (lubricity). :), the press speed comparable to that of Comparative Example 2 subjected to chemical lubrication treatment was due to the inner surface treatment of the tube by grid blasting.

(C) Presence / absence of carburization during heat treatment Stainless steel (SUS304L) having an outer diameter of 66.0 mm and a thickness of 6.4 mm was prepared as a test sample tube. The lubricant was applied to the inner surface, and a heat treatment of 1060 ° C. × 15 minutes → water cooling was performed in an air atmosphere. A sample was taken from the test material after the heat treatment, the carbon content of the inner surface layer was determined, and the microstructure was observed to confirm the presence or absence of carburization. The carbon content was analyzed by a high-frequency induction furnace combustion-infrared absorption method defined in JIS G 1211. The microstructure was subjected to oxalic acid electrolytic etching after polishing the sample and observed at 400 times.

  The survey results are shown in Table 4. In Table 4, Comparative Example 3 is a case where heat treatment was performed without applying the lubricant, and Comparative Example 4 was a case where neither application of the lubricant nor heat treatment was performed.

  As is apparent from Table 4, carburization was not observed even when the heat treatment was performed with the lubricant of the present invention remaining, and no carbide precipitation was observed in the microstructure.

  As a result of the above investigations (a) to (c), the lubricant of the present invention has good adhesion to the material surface, and has a higher press speed and superior lubricity than the case of chemical conversion lubrication treatment. It was confirmed that there was no problem of carburization due to heat treatment after molding.

(Example 2)
Using the lubricant composition shown in Table 5 and Table 6, a manufacturing test of a stainless steel elbow that is cold mandrel bent by an actual machine was performed, and after lubrication, seizure and heat treatment (heating at 900 ° C.) The surface condition was evaluated and the appropriate range of each component contained in the lubricant was confirmed. Table 5 shows the cases where the lubricants satisfying the conditions stipulated in the present invention are used (Invention Examples 1 to 14), and Table 6 shows the cases where the lubricants used for comparison are used (Comparative Examples 1 to 12). Show.

  Stainless steel (SUS304; heat treatment condition 1060 ° C. × 20 minutes → water cooling) having an outer diameter of 105.0 mm, a thickness of 7.0 mm, and a length of 350 mm was prepared as a test tube, and the nominal dimensions were obtained using a horizontal press. Was formed into an elbow having an outer diameter of 114.3 mm × an inner diameter of 101.3 mm and a bending radius of 152.4 mm.

  The details of each component contained in the used lubricant are as follows.

Polyethylene powder (A): average particle size 20 μm, average molecular weight: 130,000
Polyethylene powder (B): average particle size 20 μm, average molecular weight: 60,000
Polyethylene powder (C): average particle size 100 μm, average molecular weight: 5,000
Polyethylene powder (D): average particle size 3.5 μm, average molecular weight: 1,500
Vinyl resin (A): Ethylene / vinyl acetate copolymer Vinyl resin (B): Neutralized amine of acrylic acid / methacrylic acid copolymer Vinyl resin (C): Vinyl acetate polymer Vinyl resin (D ): Amine neutralized product of acrylic acid polymer Vinyl resin (E): Methacrylic acid / ethyl acrylate / methyl methacrylate copolymer Vinyl resin (F): Sodium neutralized product of acrylic acid polymer Vinyl Resin (G): Sodium neutralized product of isobutylene / maleic acid copolymer Vinyl resin (H): Sodium neutralized product of acrylic acid / maleic acid copolymer Dispersant (A): 2, 4, 7, 9 Tetramethyl-5-decyne 4,7-diol [polyoxyethylene] ether Dispersant (B): polyoxyethylene alkylphenyl ether.

  Tables 5 and 6 show the lubricity, seizure evaluation, and the evaluation results of the surface condition after heat treatment and the overall evaluation in the production test of the stainless steel elbow.

  The lubricity was evaluated in four stages, ◎ (very good), ○ (good), △ (bad), and X (very bad).

  The standards for seizure evaluation are as follows. If the mark ◎ or mark ○, the seizure resistance was considered good.

◎ mark: Almost no seizure ○ mark: Slightly seized △ mark: About half of seizure x mark: Almost entire surface seizure Also, the evaluation criteria of the surface condition after heat treatment are as follows, ◎ mark or ○ mark If so, the surface condition after heat treatment was evaluated as good.

◎: Almost no discoloration ○: Little discoloration △: Overall discoloration × ×: Vigorous discoloration
The comprehensive evaluation is based on the evaluation results of the above-described lubricity, seizure evaluation, and surface condition after heat treatment, and the evaluation result of the lowest evaluation item among these evaluation target items was used as the comprehensive evaluation result.

  As is apparent from Table 5, when lubricants satisfying the conditions specified in the present invention are used (Invention Examples 1 to 14), all have good lubricity and little seizure. As a result, the discoloration of the surface after the heat treatment was slight, and the stainless steel elbow could be manufactured smoothly.

  On the other hand, among Comparative Examples 1 to 12 shown in Table 6, Comparative Example 1 deviates from the conditions defined in the present invention in that a lubricant containing no vinyl-based resin and a dispersant is used. The lubricity was very poor and the elbow could not be manufactured.

  In the lubricants used in Comparative Examples 2 to 4, the vinyl-based resin is a sodium salt and is outside the conditions specified in the present invention (in Comparative Example 4, the average molecular weight of the polyethylene powder is also outside the specified range of the present invention. However, the lubricity was very poor, seizure occurred, and the surface discoloration after the heat treatment was severe.

  In the lubricants used in Comparative Examples 4 to 8 and Comparative Examples 11 and 12, the average molecular weight of the polyethylene powder is outside the specified range of the present invention. Further, in Comparative Examples 4 and 7, the vinyl resin is a sodium salt that deviates from the definition of the present invention. In Comparative Example 8, the dispersant exceeds the specified amount, and in Comparative Example 11, the vinyl resin amount is the specified amount. Is over. Therefore, in Comparative Examples 4-8 and Comparative Examples 11 and 12, the lubricity was poor and seizure occurred. In addition, there was almost no discoloration of the surface after heat processing except the lubricant whose vinyl resin is a sodium salt.

  In Comparative Examples 9 and 10, a lubricant having a polyethylene powder content outside the specified range of the present invention was used. In Comparative Example 9, an elbow could not be produced, and in Comparative Example 10, a prototype could be produced. However, the lubricity was poor and seizure occurred almost over the entire surface.

  The lubricant composition for cold plastic working of the present invention has good adhesion to the surface of a steel base tube and is excellent in lubricity. The method for manufacturing a steel pipe joint according to the present invention is a method for manufacturing a steel pipe joint by applying this lubricant composition to the surface (inner surface or outer surface) of a raw pipe and performing cold working. Even difficult-to-work materials such as these can be cold worked without subjecting them to chemical lubrication. Even if heat treatment is performed after cold working, carburization does not occur, and an excellent quality pipe joint can be efficiently manufactured.

  Therefore, the lubricant composition and the method for producing a steel pipe joint of the present invention can be effectively used for the production of a pipe joint.

It is a figure which shows the outline manufacturing process of a steel pipe joint (elbow), (a) is a case where a chemical conversion lubrication process is performed to the raw pipe inner surface, (b) is a case where the lubricant of this invention is apply | coated.

Claims (6)

  5 to 50% by mass of polyethylene powder having an average particle diameter of 1 to 100 μm and an average molecular weight of 20,000 or more, a water-soluble vinyl resin not containing an alkali metal, or a nonionic surfactant or / and a protective colloid A lubricant composition for cold plastic working, comprising 1 to 20% by mass of an emulsion-polymerized water-dispersible vinyl resin and 0.1 to 5% by mass of a nonionic dispersant. Applying the lubricant composition according to claim 1 to an inner surface,
A method of manufacturing a steel pipe joint, wherein an elbow is formed by attaching a bent conical mandrel to a mandrel, and forming the elbow by pushing out the raw tube at room temperature with a pusher while expanding the tube with the bent conical mandrel. The lubricant composition according to claim 1 is applied to an outer surface, and a raw pipe which is a dried workpiece is applied.
A method of manufacturing a steel pipe joint, wherein an elbow, T, cap, or reducer is formed by applying hydroforming that applies an internal pressure using a fluid as a medium. Applying the lubricant composition according to claim 1 to an outer surface, and drying a raw tube which is a workpiece,
A method for manufacturing a steel pipe joint, wherein a reducer is formed by applying a diameter reducing process by pressing into a forming die having an inner surface shaped into a product. Applying the lubricant composition according to claim 1 to an inner surface,
A reducer is formed by applying a pipe expansion process by inserting a punch having an outer surface shaped like an inner surface of a product.   The method for manufacturing a steel pipe joint according to any one of claims 2 to 5, wherein the formed steel pipe joint is heat-treated at 900 to 1300 ° C.

Images