WO2005061141A1 - Lubricating oil for cold drawing and lubricating coating film, and method for producing cold-drawn steel pipe - Google Patents

Abstract

A first lubricating oil for cold drawing, which has an S content of 3 mass % or less and a viscosity of 5 X 10-4 to 1 X 10-3 m2/s (400 to 1000 cSt); and a second lubricating oil for cold drawing, which has an S content of 10 to 30 mass % and a viscosity of 5 X 10-5 to 2 X 10-4 m2/s (50 to 200 cSt). A lubricating coating film formed by using one of the above lubricating oils can combine the insurance of satisfactory lubricity during drawing and the reduction of the amount of an annealing residue to 3 g/m2 or less, and thus the oil lubricating treatment by using the above lubricating oil in cold drawing allows the production of a cold-drawn steel pipe which can be most suitably used as various machine structural members, for example, for an automobile.

Description

 Specification

Lubricating oil and lubricating coating for cold drawing, and method for manufacturing cold drawn steel pipe

Technical field

 The present invention relates to a lubricating oil and a lubricating coating used for cold drawing of a steel pipe for a machine structure, and a production method using the same. More specifically, the present invention relates to a high-strength, surface- The present invention relates to a lubricating oil and a lubricating film which are optimal for cold drawing of a steel pipe for a machine structure, and a method of manufacturing a cold drawn steel pipe.

Background art

 As cold working methods for steel pipes for machine structures such as carbon steel, alloy steel, and stainless steel, a drawing method using a doro bench and a rolling method using a pilger mill are known. Of these methods, the drawing method using the doro-bench can produce a high-quality cold-finished steel pipe more efficiently than the rolling method using the pilger mill. For this reason, the cold drawing method using this dro-bench (hereinafter, the cold drawing method using this dro-bench is referred to as “cold drawing”) is used to manufacture steel pipes for machine structures such as automobiles. Commonly used.

 In this cold drawing, lubrication is required as a pretreatment. From the viewpoint of workability in the cold drawing process and the quality of the steel pipe, it is important to ensure lubricity by lubrication and to prevent seizure. For this purpose, after removing the scale of the surface of the tube to be subjected to cold drawing by pickling or the like, a conversion coating of zinc phosphate is formed on the surface of the tube in advance, and furthermore, A method of forming a lubricating film such as a metal stone on the film is known.

Various methods have been proposed so that this method can be fully effective. For example, Japanese Patent Application Laid-Open No. H10-2866616 discloses a device for applying lubricating oil to the inner surface of a pipe via a hollow mandrel at the time of drawing, wherein the residual oil in the hollow mandrel is stored in a tank. There has been proposed a pipe inner surface oiling device in which a relief valve is provided in the piping path returning to the pipe.

 Also, in Japanese Patent Application Laid-Open No. 62-368986, when cold-drawing to reduce the cross-sectional area to 30% or more, the base oil is 10 to 60% by weight and the sulfur-based extreme pressure is reduced. A lubricating method using a lubricating oil has been proposed in which an additive of 10 to 60% by weight and a thickener is mixed at 35% by weight, and the viscosity at 40 ° C is 100 to 500 centipoise. I have.

 Similarly, Japanese Patent Publication No. 4-488839 discloses that after pickling a carbon steel, alloy steel wire, rod or tube, the material surface has a viscosity of 100 to 100 ° C at 20 ° C. A lubrication treatment method for applying a lubricating oil having a viscosity of 300 centipoise is disclosed.

 Here, the composition of the proposed lubricating oil is a compound of 5-40% of a dialkyl polysulfide having a sulfur content of 30% or more, and a compound of oil and fat and olefin, and the sulfur content in the compound is 15%. 20 to 70% of a compound selected from the above combined, etc., one or more base oils selected from fats and oils, synthetic oils, mineral oils and higher fatty acids, and a polyisobutylene-based thickener, It is composed of at least one or more thickeners selected from olefin copolymer thickeners and polymethacrylate thickeners.

 In addition, in Japanese Patent Application Laid-Open No. 2002-192022, the base tube is immersed in an aqueous solution containing a metal salt, and the metal salt of boric acid is coated on the inner and outer surfaces of the base tube. Alternatively, there has been proposed a method for producing a cold drawn steel pipe in which a coating of an alkali metal salt of boric acid and a metal salt of a fatty acid is formed, and a liquid lubricant is applied thereon to perform cold drawing. I have.

By the way, in recent years, steel pipes for mechanical structures used as various mechanical structural members such as automobiles have been developed from the viewpoint of weight reduction of structural members. High strength is required.

 In order to respond to such demands, a method is adopted in which annealing is performed at a relatively low temperature after cold drawing, and the work strain generated by cold working remains in the product steel pipe to ensure high strength of the steel pipe. There is.

 In addition, since it is necessary to ensure the smoothness and surface properties of the steel pipe surface after annealing, it is desirable to suppress the scale generated during annealing and reduce the scale thickness formed on the steel pipe surface. For this reason, bright annealing for adjusting the furnace atmosphere to non-oxidizing is often used as annealing of steel pipes for mechanical structures.

 Furthermore, from the viewpoint of cost reduction, the steel pipe is often used as it is as a structural member without grinding the inner and outer surfaces of the steel pipe after cold drawing. In this case, in the method of forming a chemical conversion coating described above, zinc phosphate and a part of metal lithography adhere to the surface of the steel pipe after cold drawing, and the metallic luster of the cold drawn steel pipe is impaired. Become.

 Under such circumstances, it is becoming difficult to perform a process of forming a chemical conversion coating on the surface of the raw tube as a pretreatment for cold drawing.

 On the other hand, it is clear that the oil lubrication treatment, in which lubricating oil is applied to the tube surface before cold drawing, simplifies the treatment process and can significantly reduce the number of work steps and running costs as compared with the conversion coating treatment. For this reason, oil lubrication is increasingly used as a pretreatment for cold drawing.

 As described above, steel pipes for automobiles and other mechanical structures are required to have high strength and are used without grinding the surface, so they must be annealed in a low-temperature atmosphere conditioning furnace after cold drawing. Is required.

 When performing such annealing, it is a new problem to be solved to promote the thermal decomposition of the remaining lubricating oil and to sufficiently evaporate and remove the lubricating oil to reduce the annealing residue.

By the way, if the apparatus proposed in the above-mentioned Japanese Patent Application Laid-Open No. H10-286666 is used, after the predetermined inner surface oiling, the tip of the hollow mandrel is awaited during drawing. This solves the problem that the lubricating oil leaked from the portion flows from the narrowed portion toward the other end and is carbonized in the subsequent heat treatment process to generate inner surface contamination. However, lubricating oil itself is not being improved, so the new problem of annealing residue cannot be solved.

 Further, Japanese Patent Application Laid-Open Nos. Sho 62-236986 and Japanese Patent Publication No. 4-48839 disclose the use of sulfur (S) type extreme pressure additives to improve lubricity during cold drawing. In order to prevent seizure and galling, Japanese Patent Application Laid-Open No. 2002-192922 discloses that the inner and outer surfaces of the raw tube are made of metal alloy. The purpose of the present invention is to form a salt film and suppress the occurrence of seizure during cold drawing, and at the same time, to prevent phosphorus immersion in heat treatment after cold drawing.

 For this reason, the three patent publications of the above-mentioned Japanese Patent Application Laid-Open Nos. Sho 62-236986, Japanese Patent Publication No. 4-48839 and Japanese Patent Publication No. By adopting the method proposed in the patent document, it is possible to suppress the occurrence of seizure and galling during cold drawing and the occurrence of chatter vibration, but the above-described new problem of annealing residue It is not intended to solve a problem.

 Therefore, when a steel pipe cold drawn by the method proposed in these three patent documents is annealed, for example, when subjected to a bright heat treatment at a temperature of 65 ° C. or less, when a sulfur (S) -based extreme pressure additive is used, Insufficient volatilization of the lubricating oil will result in more annealing residues. Disclosure of the invention

The present invention is intended to secure lubricity when performing cold drawing by oil lubrication processing on the assumption that low-temperature annealing is performed in a low-temperature atmosphere furnace. A method for manufacturing a lubricating oil and a lubricating coating, and a method for manufacturing cold drawn steel pipes using them, while preventing galling and preventing the occurrence of annealing residues such as soot and sticking on the surface of the steel pipe. Offer It is intended to be offered.

 The present inventors have conducted various studies in order to respond to the demand for high strength of steel pipes for mechanical structures and to omit the demand for surface grinding of steel pipes. As a result, the following (a) to (c) are important technical matters. I noticed that.

 (a) In order to obtain excellent surface properties, it is necessary to reduce the scale generated during annealing and reduce the scale thickness on the surface of the steel pipe. Specifically, after cold drawing and annealing, the scale thickness of the steel pipe surface is reduced to 0.5 to 10;

 (b) In order to efficiently secure high strength, low-temperature annealing is used, and the work strain caused by cold drawing remains in the steel pipe. At this time, the heating temperature is set to be equal to or lower than 65 ° C. for the reason described later.

(c) In order to ensure excellent surface properties and surface quality, it is necessary that no annealing residue adheres to and remains on the steel pipe surface. It is a specific measure, the amount of deposition of annealing residues is 3 g Z m ² or less.

 In addition, the present inventors examined the relationship between S-based extreme pressure additives in lubricating oil and annealing residues in order to ensure lubricity, prevent seizure, and reduce annealing residues. Was added.

 In normal lubrication, extreme pressure additives are used to enhance lubricity, and lubricity can be ensured even when oil runs out at the interface between the raw pipe and the tool (plug, die).

 Therefore, when it is desired to enhance the lubricity and perform stable cold drawing, a large amount of the S-based extreme pressure additive is added to the lubricating oil. However, S-based extreme pressure additives tend to remain as annealing residues themselves, further hindering the thermal decomposition of the base lubricating oil and impairing its volatility.

In addition, since high strength is required for steel pipes for machine structures, strength processing is performed in the process of cold drawing, so that oil film breakage occurs and seizure easily occurs. To prevent this, lubricate the surface of the tube prior to cold drawing. It is effective to form a coating of boric acid metal salt of boric acid, which has excellent retention properties, and to perform a base treatment.

 The same effect can be obtained by forming a coating film of an alkali metal salt of phosphoric acid instead of the alkali metal salt of boric acid. Further, a film of an alkali metal salt of boric acid and an alkali metal salt of phosphoric acid may be formed.

 The present inventors have presupposed the above-mentioned examination results, and based on different viewpoints, have different lubricating properties, but all have the best lubricating oil for producing cold drawn steel pipes with excellent surface properties. Development proceeded.

 (1) About the first lubricant

 As mentioned above, in the oil lubrication process, S-based extreme pressure additives added to lubricating oil to enhance lubricity tend to remain as annealing residues themselves, and also cause thermal decomposition of the base lubricating oil. Therefore, we decided to minimize the amount of S-based extreme pressure additives.

 By keeping the sulfur content in the lubricating oil low, the oil film breaks and seizure easily occurs, but to prevent this, before the cold drawing, the lubricating oil A film of boric acid metal salt with excellent retention was formed, and the viscosity of lubricating oil was increased. Similar effects can be obtained by forming a film of an alkali metal salt of phosphoric acid instead of the alkali metal salt of boric acid.

 In other words, as a first point of view, assuming that the surface of the raw pipe is subjected to a base treatment of applying a high-viscosity lubricating oil to a film having excellent lubricating oil retention properties, the annealing residue on the surface of the steel pipe is reduced. We chose to minimize the amount of S-based extreme pressure additives to eliminate them.

The first lubricating oil of the present invention has been completed based on the first paying attention above, S content is 3 mass% or less, a viscosity of 5 X 1 0- ⁴ ~ 1 X

1 0 - ³ m ² s: are characterized by a (4 0 0~ LOOO c S t ). (2) About the second lubricant

In order to ensure lubricity, the S-based extreme pressure additive added to the lubricating oil forms a low-shear F e S, F e ₂ S, etc. on the surface of the tube where cold drawing is performed, and seizure occurs. The occurrence of is suppressed. As described above, S in the lubricating oil itself becomes an annealing residue and hinders the volatility of the lubricating oil.

We found that S, which formed Fe ₂ S, etc., did not hinder the thermal decomposition and volatilization of lubricating oil.

Therefore, as the second paying attention to ensure lubricity, low F e S of pruning shear force on the blank tube surface, it was decided to positively contain S to form a F e ₂ S or the like.

Fig. 1 is a graph showing the relationship between the amount of residual oil on the steel pipe surface after cold drawing and the S detection intensity. Since the oil amount and oil film thickness in cold drawing are proportional to the viscosity of the lubricating oil, the viscosity of the lubricating oil is adjusted to change the amount of residual oil (g Zm ² ) after cold drawing. The amount of sulfur (Kcps) on the surface of the steel pipe was detected by X-ray fluorescence analysis. The S content in the lubricating oil used was three types: 5% by mass, 20% by mass and 30% by mass.

The formation of F e S, F e ₂ S, etc. is a reaction that occurs at the interface of the tube surface, and is therefore limited to a partial reaction of S contained in the lubricating oil. Therefore, urchin by are shown in FIG. 1, increasing the amount of oil adhering to the blank tube surface, F e S being formed, F e ₂ S or the like is not much change. On the other hand, the S detection intensity greatly depends on the S content in the lubricating oil.

That, F e S, forming amount of such F e ₂ S of blank tube surface will depend on the S-containing organic content in the lubricating oil, the influence of the oil quantity and oil film thickness is small. Therefore, F e S to blank tube surface to ensure lubrication and to effectively form a F e ₂ S, etc., it is necessary to use a lubricant having a predetermined S content.

Then, F e S, after the formation of such F e ₂ S, in order to reduce the amount of S remaining in the lubricating oil (absolute amount), less amount of oil adhering to the blank pipe, or oil film The thickness may be reduced.

Since the oil amount and oil film thickness in cold drawing are proportional to the viscosity of the lubricating oil, by appropriately selecting the S content of the lubricating oil according to the lubricity, by selecting the appropriate viscosity, F e S of blank tube surface, to ensure formation of such F e ₂ S, can be reduced amount of S remaining in the lubricating oil.

As described above, by positively containing S in the lubricating oil, lubricity can be ensured and the annealing residue can be reduced to 3 g / m ² or less. The second lubricating oil of the present invention is the well has been completed based on the second paying attention above, S content is 1 0-3 0% by weight, a viscosity of 5 X 1 0 _ ⁵ ~ 2 is characterized in that it is ^{4 m 2 / s (5 0~} 2 0 0 c S t) - X 1 0. (3) Methods for manufacturing lubricating coatings using the first and second lubricating oils and cold drawn steel pipes

 As described above, when performing cold drawing with oil lubrication, in order to prevent the occurrence of oil film breakage and seizure, it is necessary to have excellent lubricating oil retention on the surface of the pipe prior to cold drawing. It is effective to form a coating of boric acid metal salt and apply a base treatment.

 As the base treatment, a film of an alkali metal salt of phosphoric acid may be formed instead of the alkali metal salt of boric acid, or a film of an alkali metal salt of boric acid or a film of an alkali metal salt of phosphoric acid. And a similar effect can be exerted.

 Accordingly, the lubricating coating of the present invention comprises an alkali metal borate coating formed on the inner and outer surfaces of the immersed pipe and the first lubricating oil or the second lubricating oil applied to the coating surface. It is characterized by being composed of oil.

 Further, the lubricating coating of the present invention may be formed by forming an alkali metal salt coating of phosphoric acid on the inner and outer surfaces of the raw tube, and the alkali metal borate and the phosphoric acid on the inner and outer surfaces of the raw tube. A metal salt coating may be formed.

Further, the method for producing a cold drawn steel pipe according to the present invention includes the steps of: Dipping in an aqueous solution containing a metal salt to form a boric acid alkali metal film on the inner and outer surfaces of the tube, and applying the first lubricating oil or the second lubricating oil on the surface of the film After cold-drawing, the furnace is annealed at 65 ° C or lower while supplying a CO-containing gas to the furnace atmosphere.

 Further, in the method for producing a cold drawn steel pipe according to the present invention, an aqueous solution containing an alkaline metal salt of phosphoric acid is used instead of the aqueous solution containing the alkali metal salt of boric acid, and the inner and outer surfaces of the raw tube are used. A metal coating of phosphoric acid can be formed on the surface. Furthermore, instead of the aqueous solution containing the boric acid alkali metal salt, an aqueous solution containing the boric acid alkali metal salt and the phosphoric acid alkali metal salt is used, and boric acid is coated on the inner and outer surfaces of the raw tube. An alkali metal salt and an alkali metal salt film of phosphoric acid can be formed.

ADVANTAGE OF THE INVENTION According to the lubricating oil and lubricating film for cold drawing of this invention, lubricating property can be ensured at the time of cold drawing, and an annealing residue can be reduced to 3 gZm < ² > or less. Therefore, if these are subjected to an oil lubrication treatment to produce a cold drawn steel pipe, it is possible to provide an optimum steel pipe as various mechanical structural members including those for automobiles.

 In the present invention, "cold drawn steel pipe" is a steel pipe obtained by cold drawing a carbon steel, alloy steel such as chrome steel or chrome molybdenum steel, or stainless steel pipe, and is used for automobiles and other industries. A steel pipe used as a structural member in the field.

Incidentally, "CO-containing gas" defined by the manufacturing method of the cold drawn steel pipe of the present invention is a gas that is supplied in order to prompt the circulation of the atmosphere, ventilation, for example, volume ⁰ /. In, CO: 0:.!. ~ 3 0%, CO 2:.. 1 0 0~ 1 4 0%, H 2:.. 0 1 ~ 1 5%, referred to the gas and the balance N _2. Brief Description of Drawings

Figure 1 shows the relationship between the amount of residual oil on the steel pipe surface after cold drawing and the S detection intensity. FIG. BEST MODE FOR CARRYING OUT THE INVENTION

 In the production method of the present invention, the base tube is immersed in an aqueous solution in advance during cold drawing, and the inner and outer surfaces of the base tube are coated with an alkali metal salt of boric acid or an alkali metal salt of Z and phosphoric acid. After applying a lubricating oil on the film, forming a two-layer lubricating film and performing cold drawing, annealing at a low temperature while supplying a CO-containing gas to the furnace atmosphere It is characterized by

 Hereinafter, the contents of the present invention will be described by dividing into the formation of an alkali metal salt film (undercoat treatment), lubricating oil and low-temperature annealing.

 1. Film formation of alkali metal salts

 As a base treatment for the lubricating oil, the base tube is immersed in an aqueous solution containing an alkali metal salt of boric acid to form a coating film of an alkali metal salt of boric acid on the inner and outer surfaces of the base tube.

 The coating of an alkali metal salt of boric acid has good adhesion to the base tube, and also has excellent retention when lubricating oil is applied on the coating. Therefore, by forming a coating of boric acid alkali metal salt on the surface of the base tube and applying lubricating oil on the surface, the base tube and the drawing tools (dies and plugs) can be connected during cold drawing. The frictional force between them can be reduced, and seizure between the raw tube and the drawing tool can be prevented.

 The coating thickness of the alkali metal borate is preferably set to 0.4 to 20 / im. If the coating thickness exceeds 20 μm, it will be easy to peel off. In some cases, the lubricating oil remains on the surface of the steel pipe and remains as an annealing residue after annealing. On the other hand, if the coating thickness is less than 0.1, direct contact between the surface of the raw tube and the drawing tool occurs, and the holding power of the lubricating oil is reduced, so that the lubricity may be reduced.

Examples of alkali metal salts of boric acid include lithium borate, potassium borate, And sodium borate. Of these, potassium borate is desirable.

 In order to form a coating film of an alkali metal borate on the inner and outer surfaces of the tube, the tube is immersed in an aqueous solution containing the alkali metal borate. The thickness of the coating is adjusted by adjusting the immersion time or the temperature of the aqueous solution, so that the thickness of the coating after the treatment is desirably 0.4 to 20 / im.

 The concentration of the boric acid alkali metal salt in the aqueous solution may be determined in consideration of the thickness of the coating, the immersion time, and the like. For example, the concentration is preferably in the range of 2 to 10% by mass. It is. The temperature of the aqueous solution is preferably in the range of 70 to 100 ° C.

 Next, the tube after immersion is dried. As a result, a coating of an alkali metal borate is formed on the inner and outer surfaces of the tube. Drying of the immersed tube may be performed by a usual method in which the tube is placed in a drying room at about 150 ° C. As another base treatment applicable to the present invention, an aqueous solution containing an alkali metal salt of boric acid is used instead of the aqueous solution containing an alkali metal salt of boric acid, and the inner and outer surfaces of the raw tube are used. A similar effect can be obtained by forming a film of a metal salt of phosphoric acid on the surface. In other words, this coating also has good adhesion to the raw pipe, excellent retention of lubricating oil, and can suppress seizure between the raw pipe and the drawing tool during cold drawing.

 In this case, the effects of the alkali metal salt of boric acid and the alkali metal salt of phosphoric acid are slightly different. The former has the effect of increasing the adhesion between the raw tube and the coating, and further improving the retention of the lubricating oil applied on the coating to prevent seizure between the raw tube and the drawing tool.

 On the other hand, the latter not only enhances the retention of lubricating oil applied to the surface of the coating, but also has the effect of preventing direct contact between the raw tube and the drawing tool and preventing seizure.

When using an aqueous solution containing an alkali metal salt of phosphoric acid, The film thickness is 0.4 to 20 / zm as in the case of the alkali metal borate.

 Examples of the alkali metal salts of phosphoric acid include sodium diphosphate, sodium tertiary phosphate, sodium pyrophosphate and the like. Of these, sodium diphosphate is preferred.

 The coating of the phosphoric acid metal salt on the inner and outer surfaces of the raw tube may be formed by an immersion method as in the case of the boric acid alkali metal salt. The concentration of the alkali metal salt of phosphoric acid in the aqueous solution is suitably, for example, in the range of 0.1 to 0.5% by mass, and the temperature of the aqueous solution is 60 to 100 ° C. It should be a range. The drying of the tube after immersion may be performed in the same manner as in the case of the alkali metal salt of boric acid.

 Further, in the different undercoating treatment of the present invention, instead of the aqueous solution containing the alkali metal borate, an aqueous solution containing the alkali metal borate and the alkaline metal salt of phosphoric acid is used. Similar effects can be obtained by forming a coating of boric acid metal salt and phosphoric acid metal salt on the inner and outer surfaces of the raw tube.

 The operation and effect in this case are intermediate between the case where an alkali metal salt of boric acid is used and the case where an alkali metal salt of phosphoric acid is used.

 When using an aqueous solution containing an alkali metal salt of boric acid and an alkali metal salt of phosphoric acid, the desired coating thickness, film formation, and subsequent drying are also performed using the alkali metal salt of boric acid. You can do it in the same way. The concentration of both alkali metal salts in the aqueous solution is suitably adjusted so that the total concentration thereof is in the range of, for example, 0.1 to 3.0% by mass.

As described above, the lubricating coating of the present invention forms a coating of an alkali metal salt of boric acid or an alkali metal salt of phosphoric acid on the inner and outer surfaces of the pipe as a base treatment. Apply a lubricating oil described later to form a two-layer structure. By doing so, excellent lubricity can be exhibited even in cold drawing of carbon steel, alloy steel, or stainless steel.

 2. Lubricating oil

The first lubricating oil of the present invention, S content is 3 mass% or less, a viscosity of ^{5 X 1 0 - 4 ~:} LX 1 0- 3 m 2 / s (4 0 0~ 1 0 0 0 c S t).

 The reason why the S content of the first lubricating oil is set to 3% by mass or less is that, for example, when the S content exceeds 3% by mass by adding an S-based extreme pressure additive to the lubricating oil, This is because the amount of annealing residue increases and thermal decomposition of lubricating oil is hindered.

 Therefore, the S content of the first lubricating oil is desirably as small as possible from the viewpoint of suppressing the generation of annealing residues, and S may not be contained. However, the presence of even a small amount of S has the effect of preventing seizure from occurring. Therefore, in practice, the S content is desirably 1.5 to 3% by mass.

The viscosity (kinematic viscosity) of the first lubricating oil is 4 X 10 _ ⁴ to 1 X 10-3 m ² // s (4

0 0~ 1 0 0 0 c S t) and for, when the viscosity is less than 4 X 1 0 one ⁴ m ² / s, the lubricating oil to between the base pipe and the extraction tool during cold drawing insufficient retraction of, contacts the base pipe and pulling tool directly may crack occurs in base tube, whereas, if so exceeds ^{1 X 1 0 _ 3 m 2} Z s, the lubricating oil This is because it is economically disadvantageous because the amount of adhering to the raw pipe increases.

Next, the second lubricating oil to which the present invention is employed, a 1 0-3 0% by weight the S content, the viscosity ^{5 X 1 0- 5 ~ 2 X} 1 0- 4 m 2 Zs (5 0 ~ 200 cSt).

When S content of the second lubricating oil is less than 1 0% by weight, it is impossible to F e S of blank tube surface, is formed of such F e ₂ S to ensure less lubricity. On the other hand, when the S content is in excess of 3 0 wt%, F e S, can ensure formation of such F e ₂ S, S content in the lubricating oil annealing residue increases increases In addition, thermal decomposition of lubricating oil is hindered. Therefore, the S content of the lubricating oil should be 10 to 30% by mass.

To the viscosity of the second lubricating oil (kinematic ^{viscosity) 5 X 1 0- 5 ~ 2} X 1 0 4 m 2 Roh s (5 0~ 2 0 0 c S t) is, S contained in the lubricating oil The amount of oil adhering to the surface of the pipe and the oil film thickness are adjusted, and the F e S,

This is because by ensuring the amount of FeS and the like formed and reducing the amount of S remaining in the lubricating oil, lubricity is ensured and annealing residues are reduced.

That is, the viscosity is ^{5 X 1 0- 5 m 2 /} s by Ri low, the less amount of oil adhering to the blank tube surface during the cold drawing mother tube and the lubricating oil to between drawing tool Insufficient amount of drawing may cause direct contact between the tube and the drawing tool, causing seizure on the tube.

On the other hand, if the viscosity of the second lubricating oil is increased beyond the ^{2 X 1 0- 4 m 2 /} s, oil quantity and oil film thickness to adhere to the base pipe of the lubricating oil increases, remaining in the lubricant S The amount increases, and the annealing residue cannot be reduced to 3 gZm ² or less.

 The lubricating oil used in the present invention does not limit the base oil to a specific one.In addition to animal and vegetable oils such as lard, tallow, whale oil, palm oil, coconut oil, rapeseed oil, synthetic oils, Mineral oil can be used.

 As a method of applying the lubricating oil of the present invention to the surface of the metallic salt coating, a conventional method may be used. For example, a method of supplying lubricating oil to the outer surface of a raw pipe from a nozzle arranged around the outer circumference of the raw pipe, and a method of supplying lubricating oil to a raw pipe from a hole provided in a hollow mandrel bar inserted inside the raw pipe. The method of supplying to the inner surface can be applied.

 In the production method of the present invention, after a two-layer lubricating film is formed on the surface of the raw tube, cold drawing is performed. The cold drawing of the present invention may be performed by a commonly used method, and it is not necessary to use only a particularly limited method.

 3. Annealing

The annealing in the present invention aims at securing the strength of the cold drawn steel pipe. Then, the processing strain generated by the cold drawing is left. If the annealing temperature is too high, the work strain will recover and the effect of work hardening cannot be obtained. The effect of work hardening can be obtained by annealing the cold drawn steel pipe at a temperature of 65 ° C. or lower.

 Furthermore, in order to maintain stable combustion in the furnace, it is desirable to set the lower limit of the annealing temperature to 350 ° C. In addition, in order to eliminate the variation in strength of the cold drawn steel pipe, it is desirable that the holding time of the cold drawn steel pipe in the furnace be 5 minutes or more.

 Furthermore, in order to control the scale generated during annealing and to control the scale thickness of the cold drawn steel pipe surface to 0.5 to 10 m, it is necessary to use a non-oxidizing atmosphere in the annealing furnace. .

 The furnace used for annealing may be a batch-type closed furnace or a roller hearth-type furnace, and may be a continuous furnace in which the loading and unloading sections for the material to be treated are opened. In the present invention, it is desirable to use a continuous bright annealing furnace.

 In the annealing of the present invention, since the atmosphere is non-oxidizing, the carbon in the lubricating oil is not oxidized, and since the processing temperature is as low as 65 ° C. or less, the lubricating oil adhering to the surface of the cold drawn steel pipe Oil tends to remain as annealing residue such as soot dirt (sticking). Therefore, a sufficient amount of CO-containing gas is supplied to prevent soot contamination from remaining while maintaining sufficient ventilation.

 It is desirable that the supply amount of CO-containing gas to the furnace be 0.5 times or more the furnace volume per hour. If the furnace volume is less than 0.5 times, the thermally decomposed lubricating oil becomes soot and easily adheres to the surface of the cold drawn steel pipe.

 On the other hand, if the supply amount of the gas is too large, the cost is too high for the effect and it is economically disadvantageous. Therefore, it is preferable that the supply amount be four times or less the furnace volume.

Here, "supply of gas four times the furnace volume per hour" While supplying the gas little by little into the furnace, it means discharging the same amount of gas from the furnace and supplying gas four times the furnace volume in one hour.

 Hereinafter, effects of the present invention will be described based on examples. (Example 1) and (Example 2) explain the effect when the first lubricating oil of the present invention is used, and (Example 3) describes the effect when the second lubricating oil of the present invention is used. The effect of is explained.

 (Example 1)

 Using the first lubricating oil of the present invention and the comparative lubricating oil, cold drawing using STKM13A specified in JISG3445 (carbon steel pipe for machine structure) as a test material Was done.

 As a specific example, using a base tube with an outer diameter of 70. O mm X wall thickness of 4. O mm, perform cold drawing to an outer diameter of 60. O mm X wall thickness of 3.4 mm to obtain a non-oxidizing atmosphere. In an atmosphere furnace, a gas containing 2.1% by volume of CO was supplied for 20 minutes at 560 ° C or 700 ° C while supplying an amount equivalent to twice the furnace volume per hour. Annealing was performed to obtain a cold drawn steel pipe.

 At this time, the presence or absence of seizure during annealing and the amount of annealing residue were adjusted, and the tensile strength of the obtained cold drawn steel pipe was measured. Table 1 shows the conditions for oil lubrication, including the S content and viscosity of the lubricating oil used, and the type and presence or absence of the metal salt used in the base treatment before applying the lubricating oil.

 For example, “4 no 5” in the “Seizure” column in Table 1 indicates that seizure occurred in four of the five cold drawn steel pipes obtained under the same conditions. In the evaluation, if “0 5”, “1/5” or “2/5”, it was considered good.

Similarly, in the column of "annealing residue", .smallcircle the annealing residual amount is 3 g Zm ² or less, △ mark also 3 g Zm ² beyond 5 g / m ² or less, X mark also 5 g / m ² greater It means that, and the mark 〇 indicates that it was good. Further, the “tensile strength” was evaluated to be good if the tensile strength was at least 50 MPa. In the column of “Comprehensive evaluation”, the mark ◎ is extremely good, the mark 〇 is good, and the mark お よ び and X indicate that, although varying in degree, both are bad. ◎ or 〇 indicates that it was good.

table 1

 (Note) Book: Example of the present invention

In "primary treatment", borate: potassium borate, phosphate: dibasic sodium phosphate *: out of the range specified in the present invention

As is clear from the results in Table 1, the S content of the lubricating oil is within the range of the "first lubricating oil" defined in the present invention, and the film of boric acid or the alkali metal salt of phosphoric acid is formed. When it was formed (Examples 1 to 3 of the present invention), good results were obtained.

 On the other hand, when the S content of the lubricating oil is out of the range of the “first lubricating oil” specified in the present invention, even though the alkali metal salt film is formed, seizure is not recognized but annealing is performed. If the amount of the residue was large (Comparative Examples 1 to 3), and if a film of the aluminum metal salt was not formed, further seizure might occur (Comparative Examples 6 and 7).

 In Comparative Example 2 in which the annealing temperature was higher than the temperature specified in the present invention, the tensile strength was low.

 In addition, even if the S content of the lubricating oil is within the range of the “first lubricating oil” specified in the present invention, the amount of the annealing residue is small, but seizure occurs, if there is no alkali metal salt film. (Comparative Examples 4 and 5).

 In Comparative Example 5, where the annealing temperature was higher than the specified value, the tensile strength was low. (Example 2).

 Using the first lubricating oil of the present invention and a comparative lubricating oil, C: 0.19%, Si: 0.20%, Mn: 0.71%, Cr: Cold drawing was performed using a carbon steel pipe containing 0.06% (the balance being Fe and impurities) as the test material.

 In the same manner as in Example 1, the outer diameter of the tube was reduced to 70.O mmX and the outer diameter was reduced to 6.0.O mmX and the thickness was 3.4 mm by cold drawing. Annealing was performed in an atmosphere furnace under the same conditions to obtain a cold drawn steel pipe.

At this time, the presence or absence of seizure during annealing and the amount of annealing residue were investigated, and the tensile strength of the obtained cold drawn steel pipe was measured. Table 2 on the next page shows the survey results.

In "primary treatment", borate: potassium borate, phosphate: dibasic sodium phosphate *: out of the range specified in the present invention

The display method of the results in the columns of “burn-in” and “annealing residue” in Table 2 is the same as that in Example 1. The “tensile strength” was evaluated as good if it was 5 10 MP & more.

 Furthermore, the meanings of the symbols in the column of “Comprehensive evaluation” were the same as in Example 1, and a mark ◎ or △ was evaluated as good.

 As is clear from the results in Table 2, the S content and the viscosity of the lubricating oil are within the range of the “first lubricating oil” specified in the present invention, and the heat treatment temperature is within the range specified in the present invention. In the case where a film of a boric acid or / and a phosphoric acid metal salt was formed (Examples 4 to 12 of the present invention), good results were obtained.

 On the other hand, when the S content of the lubricating oil is out of the range of the “first lubricating oil” specified in the present invention, the amount of the annealing residue is large even if the alkali metal salt film is formed (Comparative Example 8, 10, 13, 14, and 18), when the annealing temperature was higher than the temperature specified in the present invention, the amount of the annealing residue was small but the tensile strength was low (Comparative Examples 9 and 15). .

 Further, even if the S content of the lubricating oil is within the range of the “first lubricating oil” defined in the present invention and the alkali metal salt film is formed, the annealing temperature is lower than the temperature specified in the present invention. The higher the tensile strength, the lower the tensile strength (Comparative Example 11), and if the viscosity was lower than the range specified in the present invention, seizure occurred (Comparative Examples 12, 16, and 17).

 (Example 3)

 Using the second lubricating oil of the present invention and a comparative lubricating oil, cold drawing using STKM13A specified in JISG3445 (carbon steel pipe for machine structure) as a test material Was done.

As a pre-treatment for cold drawing, an undercoat treatment (including no treatment) by forming a coating of anorecali metal salt and a two-layer oil lubrication treatment by applying lubricating oil were performed. Specifically, as in Example 1, the outer diameter was 70 mm and the wall thickness was 4.0 mm. The outer diameter of the steel pipe was reduced to 60 mm x wall thickness by 3.4 mm by cold drawing.

 After cold drawing, the gas containing 2.1% by volume of CO was supplied in a non-oxidizing atmosphere furnace at a temperature of 560 ° C or Annealing was performed at 700 ° C. for 20 minutes to obtain a cold drawn steel pipe.

 In the obtained cold drawn steel pipe, the presence or absence of seizure and the amount of annealing residue were investigated, and a test piece was sampled to measure the tensile strength. Table 3 shows the conditions of the oil lubrication treatment, the annealing conditions, and the evaluation results of the cold drawn steel pipe.

 The conditions for oil lubrication are shown as the S content and viscosity of the lubricating oil used, and the type and presence or absence of Al-metallic metal salt used in the base treatment before applying the lubricating oil. .

 The display method of the results in the columns of “burn-in” and “annealing residue” in Table 3 is the same as that in Example 1. Further, the “tensile strength” was evaluated as good if it was 51 OMPa or more.

Furthermore, the meanings of the symbols in the column of “Comprehensive evaluation” were the same as those in Example 1, and a mark ◎ or Δ was evaluated as good.

Table 3

 (Note) In the “base treatment”, borate: potassium borate, phosphate: dibasic sodium phosphate

“In the annealing residue j, 〇: 3 g / m ² or less, Δ: more than 3 to 5 g / m X: more than 5 g / m ² * mark: out of the range specified in the present invention

As is evident from the results in Table 3, in all of Examples 21 to 34 of the present invention, the underlying treatment was formed with a film of boric acid or an alkaline metal salt of phosphoric acid, and the S content of the lubricating oil was reduced. Since the viscosity and the viscosity are within the range of the “second lubricating oil” defined in the present invention, the occurrence of seizure and the amount of annealing residue are reduced, and the tensile strength is 51 OMPa or more, which is a good evaluation result. Was.

 Furthermore, it was confirmed that the scale thickness of the inner and outer surfaces of the cold drawn steel pipe obtained in the present invention example was 10 / Xm or less in each case.

 On the other hand, in Comparative Examples 35 and 36, since the undercoating treatment was not performed, the occurrence of image sticking was remarkable. In Comparative Examples 37 to 42, since the S content of the lubricating oil or the viscosity of the lubricating oil was out of the range of the “second lubricating oil” defined in the present invention, the alkali metal salt film was formed. However, there were many seizures and large amounts of annealing residues.

 In Comparative Example 43, since the annealing temperature was as high as 700 ° C., the tensile strength could not be secured. Industrial potential

"First lubricating oil" of the present invention is in the S content is 3 wt% or less, a viscosity of ^{5 X 1 0 _4 ~: LX} 1 0- 3 m 2 Zs (4 0 0~: LOOO c S t) Power The “second lubricating oil” has an S content of 10 to 30% by mass and a viscosity of 5 × 10 to 2 × 10 to m ² / s (50 to 200 c S t) forces, which can secure lubricity and reduce annealing residue to 3 g Zm ² or less during cold drawing of steel pipes using these. Therefore, it is possible to provide an optimal cold drawn steel pipe as various mechanical structural members including those for automobiles. More specifically, if the manufacturing method of the present invention is adopted, a cold drawn steel pipe that sufficiently reduces the annealing residue and the seizure portion without further grinding the surface after cold drawing and further ensures high strength. Can be provided.

Claims

The scope of the claims 1. is the S content is 3 wt% or less, a viscosity of 5 X 1 0- ⁴ ~: characterized in that the LX 1 0 one ^{3 m 2 / s (4 0} 0~ 1 0 0 0 c S t) Lubricating oil for cold drawing. 2. Metallic salt coating of boric acid formed on the inner and outer surfaces of the immersed tube and S content of 3% by mass or less and viscosity of 5 × 10 — ⁴ to: 1 X 1 0—

s (400 to 100 cSt) Force, a lubricating film for cold drawing, comprising lubricating oil.  3. The lubricating coating for cold drawing according to claim 2, wherein an alkali metal salt coating of phosphoric acid is formed on the inner and outer surfaces of the tube.  4. The lubricating film for cold drawing according to claim 2, wherein an alkali metal salt of boric acid and an alkali metal salt of phosphoric acid are formed on the outer surface of the base tube. 5. The tube is immersed in an aqueous solution containing an alkali metal salt of boric acid to form a boric acid metal salt film on the outer surface of the tube, and the S content is 3 mass on the surface of the film. % or less, a viscosity of 5 X 1 0- ⁴ ~: was ^{1 X 1 0- 3 m 2 /} s (4 0 0~ 1 0 0 0 c S t) lubricating oil is applied by cold drawing a A method for producing a cold drawn steel pipe, wherein annealing is performed at 65 ° C. or less while supplying a CO-containing gas to a furnace atmosphere. 6. The tube is immersed in an aqueous solution containing an alkali metal salt of phosphoric acid to form a phosphoric acid metal salt film on the outer surface of the tube, and the S content is formed on the surface of the film. There 3 wt% or less, a viscosity of 5 X 1 0- ⁴ ~: the ^{LX 1 0 _ 3 m 2 Z} s (4 0 0~ 1 0 0 0 c S t) lubricating oil is applied by cold drawing a A method for producing a cold drawn steel pipe, comprising performing annealing at a temperature of 65 ° C. or less while supplying a CO-containing gas to a furnace atmosphere after performing the step. 7. The tube is immersed in an aqueous solution containing an alkali metal salt of boric acid and an alkali metal salt of phosphoric acid. And forming Al force Li metal salt coating-phosphate, the S content in the coating surface 3 mass% or less, a viscosity of ^{5 X 1 0- 4 ~: LX} 1 0- 3 m 2 s (4 0 0 ~: After applying the lubricating oil LO 0 c St) and performing cold drawing, annealing is performed at 65 0 C or less while supplying a CO-containing gas to the furnace atmosphere. Of manufacturing cold drawn steel pipe. 8. S content is 1 0-3 0% by weight, the viscosity of ^{5 X 1 0- 5 ~2 X 1} 0 ~ 4 m 2 / s (5 0~ 2 0 0 c S t) A characteristic lubricating oil for cold drawing. 9. A boric acid metal salt coating formed on the inner and outer surfaces of the crushed tube, and an S content of 10 to 30% by mass and a viscosity of 5% applied to the coating surface. ^{X 1 0- 5 ~ 2 X 1} 0 _4 m 2 Z s (5 0~ 2 0 0 c S t) consisting Jun Namerayu a lubricating coating for cold drawing, characterized in that it is composed of.  10. The lubricating coating for cold drawing according to claim 9, wherein an alkali metal salt coating of phosphoric acid is formed on the inner and outer surfaces of the raw tube.  11. The lubricating film for cold drawing according to claim 9, wherein an alkali metal salt of boric acid and an alkali metal salt of phosphoric acid are formed on the inner and outer surfaces of the raw tube. 1 2. Immerse the tube in an aqueous solution containing an alkali metal borate to form a boric acid metal salt film on the inner and outer surfaces of the tube, and add S content to the surface of the film. There 1 0-3 0 weight _^0/0, and a viscosity of 5 X 1 0 one ⁵ ~ 2 X 1 0 one ^{4 m 2 / s (5 0~} 2 0 0 c S t) in which by applying a lubricant A method for producing a cold drawn steel pipe, comprising performing cold drawing and then annealing at a temperature of not more than 65 ° C. while supplying a CO-containing gas to a furnace atmosphere. 1 3. Dip the tube into an aqueous solution containing an alkali metal salt of phosphoric acid to form an alkali metal salt coating of phosphoric acid on the inner and outer surfaces of the tube, and add S-containing coating on the surface of the coating. the amount of 1 0 to 3 0% by weight and a viscosity of ^{5 X 1 0- 5 ~ 2 X} 1 0- 4 m 2 / s (5 0~ 2 0 0 c S t) in which by applying a lubricating oil cooling Perform thinning And then performing annealing at a temperature of not more than 65 ° C. while supplying a CO-containing gas to a furnace atmosphere. 1 4. Immerse the tube in an aqueous solution containing an alkali metal salt of boric acid and an alkali metal salt of phosphoric acid, and coat the metal tube and aluminum salt of boric acid on the inner and outer surfaces of the tube. forming Al force Li metal salt coating of phosphate, S content in the coating surface 1 ◦~ 3 0 wt%, and a viscosity of ^{5 X 1 0- 5 ~ 2 X} 1 0 ~ 4 m 2 / s After applying a lubricating oil of (50 to 200 cSt) and performing cold drawing, annealing is performed at 65 ° C or lower while supplying CO-containing gas to the furnace atmosphere. A method for producing a cold drawn steel pipe. 1 5. Claim for 5-7 or claim 1 2-1 4 cold drawn any crab described, wherein the residue in cold drawn steel pipe surface after the heat treatment is 3 g Zm ² below Manufacturing method of steel pipe.