JP2004211115A - Method for producing copper pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a copper pipe by which a small diameter copper pipe having an outer diameter of ≤ 10 mmϕ produced by applying a cold-working of a large reducing area ratio of ≥ 99% to an extruded blank pipe hardly causes crack when the pipe is further subjected to pipe-expanding work or pipe-shrinking work having a large expanding ratio or shrinking ratio. <P>SOLUTION: When producing the small diameter copper pipe of an outer diameter of ≤ 10 mmϕ which is used after being subjected to the pipe-expanding work or the pipe-shrinking work, on the way of the cold-working, an intermediate annealing of the copper pipe is performed and the copper pipe is tempered with the intermediate annealing, in the range of O to 1/8H in quality symbol of JIS and also, the area reducing ratio of the copper pipe in the cold-working to a finish annealing after the intermediate annealing, is made to be 10-95% to the extruded blank pipe. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００４６】
【発明の効果】
本発明によれば、押出素管に対し99% 以上の大きな減面率の冷間加工を施した、外径がΦ10mm以下の小径銅管であって、拡管率や縮管率が大きい厳しい加工条件の拡管加工あるいは縮管加工などの際に割れが生じにくい、銅管の製造方法を提供することができる。したがって、銅管の前記拡管加工用途あるいは縮管加工用途への拡大を図ることができる点で、多大な工業的な価値を有するものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a copper tube in which a crack is prevented from occurring when the copper tube is further expanded or contracted.
[0002]
[Prior art]
A general method of manufacturing a copper pipe generally used for a refrigerator, an air conditioner, and the like is as follows. In other words, pure copper such as phosphorous deoxidized copper is melted, cast, and then made into a raw tube by hot extrusion, which is cold-rolled by a reducer or the like, drawn (drawn, drawn), finished, annealed, and finished. It is a copper tube. This product copper tube is processed and assembled as piping for the refrigerator, the air conditioner, and the like, including the case where the product copper tube is further drawn and reduced in diameter after the finish annealing.
[0003]
In recent years, with the demand from refrigerators, air conditioners, and the like, these copper tubes have been increasingly reduced in diameter, and small-diameter copper tubes having an outer diameter of Φ10 mm or less have been widely used. In addition, there is an increasing number of cases where these small-diameter copper tubes are further expanded or contracted, and then assembled as piping for the refrigerator, the air conditioner, or the like.
[0004]
However, when these small-diameter copper pipes are subjected to such pipe expansion processing or contraction processing, cracks are likely to occur in the copper pipe processing portion. This crack is particularly likely to occur when processing conditions for pipe expansion or contraction are severe, such as when the pipe expansion or contraction rate is large.
[0005]
In addition, the occurrence of the crack tends to be more remarkable as the copper pipe has a smaller diameter. In recent years, small-diameter copper tubes use large-diameter extruded raw tubes in order to improve the productivity of copper tubes, and have a surface reduction rate (cross-sectional area ratio to extruded raw tubes) of 99% or more compared to extruded raw tubes. It is manufactured with a large degree of cold work. This problem of cracking becomes remarkable in the case of a small-diameter product copper pipe having an outer diameter of not more than Φ10 mm, which has such a large degree of cold work.
[0006]
The problem of the cracks is that, after the finish annealing, regardless of whether or not it is further drawn, the crystal grains of the small-diameter product copper pipe to be expanded or contracted are significantly coarsened or unrecrystallized grains ( (Fibrous processed structure) tends to be significant when remaining in the structure.
[0007]
Conventionally, in order to make the crystal grains of the product copper tube into dense recrystallized grains, including a small-diameter product copper tube having an outer diameter of 10 mm or less, intermediate annealing of the copper tube during the drawing after the cold rolling. (See, for example, Patent Documents 1 and 2).
[0008]
[Patent Document 1]
JP-A-2001-96337 (pages 1 to 5)
[Patent Document 2]
JP 2001-96338 A (Pages 1 to 5)
[0009]
Also, intermediate annealing conditions at a temperature of 400 to 600 ° C., which is lower than the intermediate annealing conditions of Patent Documents 1 and 2, are known (for example, see Patent Document 3).
[0010]
[Patent Document 3]
JP-A-11-92898 (pages 1 to 6)
[0011]
[Problems to be solved by the invention]
However, the methods described in Patent Documents 1 and 2 are not the production methods presupposed in the present invention in which pure copper such as phosphorous deoxidized copper is melted, cast, and then extruded into a raw tube by hot extrusion. These production methods, after dissolving the phosphorus deoxidized copper, by continuous casting, omitting hot extrusion, directly into a relatively small diameter tube with an outer diameter of about Φ36mm, then drawing, the outer diameter of Φ10mm The following small-diameter product copper tubes shall be used.
[0012]
For this reason, in the methods of Patent Documents 1 and 2, etc., the reduction in area of the small-diameter product copper tube in cold working does not exceed 90% with respect to the continuous casting tube. Accordingly, the present invention provides a large-diameter extruded raw tube having an outer diameter of Φ90 mm or more, which is subjected to a large cold reduction process with a reduction in area of 99% or more to obtain a small-diameter product copper tube having an outer diameter of Φ10 mm or less. As compared with the manufacturing method presupposed in the above, the working ratio in the cold working is remarkably low.
[0013]
As a result, the copper tube is relatively easily and finely recrystallized by the intermediate annealing when the cold working degree of the small-diameter product copper tube is low as in Patent Documents 1 and 2 and the like.
[0014]
However, in a manufacturing method such as a manufacturing method presupposed by the present invention, in which the degree of cold working is increased to obtain a small-diameter product copper tube having an outer diameter of Φ10 mm or less, the above Patent Documents 1 and 2 are preferred. When the intermediate annealing at 650-880 ° C. is performed, the recrystallized grains are rather coarsened. As a result, cracks are likely to occur on the contrary in the case of the above-mentioned pipe expansion or contraction under severe processing conditions where the pipe expansion or contraction rate is large.
[0015]
Furthermore, the intermediate annealing conditions at lower temperatures known in Patent Document 3 and the like are used for the purpose of removing the processing strain accumulated in the previous process, reducing the oxidation discoloration portion, and processing remaining on the inner and outer surfaces of the copper tube. It did not leave the area such as oil removal. That is, the relationship between the intermediate annealing conditions and the cracks generated by the pipe expansion or contraction processing, which is the subject of the present invention, in other words, the solutions for the cracks generated by the pipe expansion or contraction processing have been described so far. The fact was unknown.
[0016]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an extruded raw tube that has been subjected to cold working with a large area reduction of 99% or more and has a small diameter of 10 mm or less in outer diameter. An object of the present invention is to provide a method for producing a copper tube, which is a copper tube and is less likely to be cracked even during the tube expansion or the tube reduction having a large tube expansion ratio or a tube reduction ratio.
[0017]
[Means for Solving the Problems]
In order to achieve this object, the gist of the method for producing a copper tube of the present invention is that a pure copper extruded raw tube is subjected to cold working with a reduction of area of 99% or more and finish-annealed to a small diameter of Φ10 mm or less. In producing a copper tube which is a copper tube, which is further subjected to a tube expansion process or a contraction tube process, an intermediate annealing of the copper tube is performed in the middle of the cold working, and the copper tube is subjected to JIS according to the intermediate annealing. With a temper symbol of O and temper in the range of 1 / 8H, the area reduction rate of the copper tube in the cold working until the finish annealing after this intermediate annealing is 10-95% with respect to the extruded raw tube. It is to be.
[0018]
According to the knowledge of the present inventors, when producing a small-diameter product copper tube having an outer diameter of Φ10 mm or less, which has been subjected to cold working with a large area reduction rate of 99% or more with respect to an extruded raw tube, intermediate annealing is performed. If the copper pipe is subjected to intermediate annealing to reduce the surface reduction rate (working rate) of the copper pipe until it is processed and further temper the copper pipe in the range from O to 1 / 8H with the JIS temper symbol, a small diameter of Φ10mm or less can be obtained. It has been found that the problem of cracking can be solved regardless of the average crystal grain size of the copper tube even if the average crystal grain size of the copper tube is large or the average crystal grain size of the small-diameter copper tube.
[0019]
Intermediate annealing under the conditions of the present invention is particularly effective in preventing cracking of small-diameter product copper pipes during expansion or contraction, which is a severe processing condition such as a large expansion or contraction rate.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The copper pipe to which the present invention is applied is mainly a direct pipe, an inner grooved pipe, an outer grooved pipe, an inner and outer grooved pipe, etc., which are generally used for refrigerators and air conditioner pipes. For this reason, in the manufacturing method of the present invention, the manufacturing process itself is the same as the ordinary manufacturing method of these copper tubes. That is, first, pure copper such as phosphorous deoxidized copper is melted and cast, and then a raw tube is formed by hot extrusion. This extruded raw tube, including the intermediate annealing, cold rolling of a reducer or the like, drawing, drawing, stretching, etc., are subjected to cold working appropriately combined, etc., to form a copper tube, finish annealing and product copper tube. I do. In the case of a copper tube with a groove on the inner or outer surface, after the above-mentioned cold working or during the cold working, intermediate annealing (including partial annealing) is performed again if necessary, and then the inner or outer surface is processed. A groove is machined, and then finish annealing is performed to obtain a product copper tube. The form of the product copper tube may be a coil shape or a tubular shape.
[0021]
First, pure copper used in the present invention is exemplified by oxygen-free copper, tough pitch copper, deoxidized copper and the like. However, among them, phosphorus deoxidized copper, which is widely used for piping of refrigerators and air conditioners, is preferable as a copper tube material. Phosphorus-deoxidized copper, whose chemical components are specified in the JIS standard for copper products, C1201 phosphorous deoxidized copper 1A class (P: 0.004 to 0.015% by mass, Cu: 99.90% by mass or more), Copper oxide 1B type (P: 0.015 to 0.040% by mass, Cu: 99.90% by mass or more), 1221 phosphorous deoxidized copper 2 type (P: 0.004 to 0.040% by mass, Cu: 99.75% by mass or more) . These phosphorus deoxidized copper are appropriately selected and used in accordance with the grade of the small-diameter product copper tube.
[0022]
When P is contained in the above content range, it has the effect of preventing the development of the texture of the copper pipe, and has the effect of suppressing cracking in the pipe expansion or contraction processing under the strict processing conditions. Further, in a copper alloy or the like, since the alloy element develops a texture, the crack is easily generated. Therefore, from this point, it is preferable to use phosphorus deoxidized copper.
[0023]
The copper slab of the round bar obtained by melting and casting these pure coppers is heated and subjected to a homogenizing heat treatment, and then turned into a raw tube by hot extrusion. This extruded raw tube is preferably a large-diameter extruded raw tube having an outer diameter of 90 mm or more in order to increase the productivity of the copper tube manufacturing process.
[0024]
Next, the extruded tube is subjected to cold working including the intermediate annealing. At this time, the intermediate annealing of the copper tube during the cold working limits the degree of work of the copper tube until this intermediate annealing is performed, and the intermediate annealing causes the copper tube to be changed from O with a JIS classification symbol of O. Temper up to 1 / 8H. Incidentally, in the present invention, the working degree of the copper tube until the above-mentioned intermediate annealing is performed is defined by the area reduction rate of the copper tube in the cold working after the intermediate annealing until the finish annealing, and the extruded raw tube is On the other hand, the area reduction rate is 10 to 95%.
[0025]
The area reduction after the intermediate annealing is less than 10%, and the area reduction (working degree) of the copper tube in the cold working until the intermediate annealing is performed is 90% of the extruded raw tube. If it exceeds, even if it is subjected to intermediate annealing under the above conditions, cracks are liable to occur in pipe expansion or contraction. That is, under the intermediate annealing condition at a relatively low processing temperature of 650 ° C. or less, fine recrystallization of the copper tube structure does not proceed, and many unrecrystallized grains (fibrous processed structure) remain in the structure. Therefore, when the workability of the copper tube before the intermediate annealing is high, it is necessary to perform the intermediate annealing at a high temperature exceeding 650 ° C. However, when the intermediate annealing is performed at such a high processing temperature, the recrystallized grains are remarkably coarsened, and the average crystal grain size of the small-diameter product copper tube is significantly larger than 200 μm. In the case of coarsening exceeding 200 μm as described above, cracks are liable to occur in the present invention in the case of pipe expansion or contraction in which the pipe expansion or contraction rate is large.
[0026]
When tempering a copper tube by this intermediate annealing during cold working, the copper tube after annealing shall be in the range of O to 1 / 8H in JIS temper symbol. This temper symbol indicates the degree of fine recrystallization of the copper tube structure that does not cause cracking during pipe expansion or contraction with a large pipe expansion or contraction rate.
[0027]
It is very difficult to directly quantify the degree of recrystallization in which the crack does not occur, including the measurement method and accuracy. In addition, it is difficult to say that the quantified recrystallization of the copper tube structure uniquely corresponds to the cracks at the time of the tube expansion or the tube reduction, and other influence factors such as the surface condition of the copper tube are involved. There are aspects to come. On the other hand, the above-mentioned gender symbol corresponds well to the tendency of the crack, probably because it includes the influence of these other factors. For this reason, in the present invention, the degree of recrystallization in which the crack does not occur is indicated by the temper symbol. If the copper pipe after annealing has a hardness of more than 1 / 8H, 1 / 4H, 1 / 2H or the like as indicated by the JIS quality symbol, the cracks are likely to occur.
[0028]
In order for the annealed copper pipe to be in the range of O to 1 / 8H in the JIS quality symbol, as described above, the average of small diameter Intermediate annealing is preferably performed at a relatively low temperature of 500 to 650 ° C. so that the crystal grain size does not increase beyond 200 μm. When the intermediate annealing is performed at a low temperature of less than 500 ° C, fine recrystallization of the copper tube structure does not proceed, assuming that the copper tube has the above-mentioned workability, and many unrecrystallized grains are present in the structure. There is a high possibility that the cracks cannot be prevented from remaining.
[0029]
The intermediate annealing time is appropriately selected depending on the selection of the JIS quality symbol and the temperature selected from this temperature range. This intermediate annealing is preferably performed in a non-oxidizing atmosphere such as an inert gas atmosphere.
[0030]
The copper tube intermediately annealed under these conditions is further cold-worked, and by the end of the final annealing, the total area reduction is more than 99% of that of the extruded raw pipe. A small-diameter copper tube with an outer diameter of 10 mm or less that has been processed. This small-diameter copper tube is made into a small-diameter product copper tube after finish annealing, including a case where it is cold-worked for further improving strength as necessary. For the finish annealing itself, conditions according to a conventional method such as bright annealing in a bright atmosphere are selected. When the small-diameter product copper tube of the present invention is processed and assembled as piping for the refrigerator, the air conditioner, or the like, it is further expanded or contracted.
[0031]
The expansion or contraction of copper pipes with a large outside diameter exceeding Φ10 mm or copper pipes with cold reduction of less than 99% of the extruded raw pipe are compared. It is easy to achieve, cracking hardly occurs, and is not targeted in the present invention.
[0032]
【Example】
Next, examples of the present invention will be described. Phosphorus deoxidized copper 1A species of C1201 (P: 0.015%, Fe: 0.002%, Pb: 0.001%, Ni: <0.001%, Co: <0.001%, Sn: <0.001%, As: <0.001%, Sb: <0.001%, Zn: <0.001%, Cr: <0.001%, Mn: <0.001%, S: <0.001%, Ag: <0.001%, Si: <0.001%, Mg: <0.001%, Other impurities: 0.004 %, O: 24 ppm, the balance Cu: 99.90 mass% or more) was melted and cast, and the obtained copper slab of the round bar (outer diameter Φ300 mm) was heated to a hot extrusion temperature, and then hot-extruded. An extruded raw tube having an outer diameter of 94 mm and a wall thickness of 10 mm was obtained. The extruded tube was cold-rolled by a reducer, drawn by a drawing machine, and then subjected to intermediate annealing of the copper tube. After intermediate annealing, after drawing with a drawing machine, bright finish annealing is performed at 450 ° C for 2 hours, and cold work (drawing) with a reduction of 99% or more of the area of the extruded raw tube until the finish annealing is performed. A small-diameter product copper tube having an outer diameter of 6.4 mm and a wall thickness of 0.8 mm was manufactured.
[0033]
Then, the small-diameter product copper tube was subjected to a drawing process for obtaining further strength, thereby obtaining a small-diameter product copper tube having an outer diameter of 6.35 mm and a wall thickness of 0.8 mm for test evaluation. In addition, when drawing was performed after the finish annealing, the final area reduction rate was about 99.5% and the tensile strength was about 340 MPa in each case. In addition, the tensile test was performed according to JIS Z 2201, and the test piece shape was performed using a JIS No. 5 test piece, and the test piece was manufactured such that the longitudinal direction of the test piece coincided with the drawing direction. Therefore, the tensile strength (σ _B ) of each copper tube was measured in the L direction parallel to the drawing direction. The crosshead speed was 5 mm / min, and the test was performed at a constant speed until the test piece broke.
[0034]
Here, a comparative example copper tube not subjected to intermediate annealing was also manufactured (Comparative Example 5 in Table 1), but this comparative example copper tube was also formed into an extruded raw tube in the stage until finish annealing, as in the other examples. On the other hand, a 99.5% reduction in area was drawn.
[0035]
At this time, the area reduction ratio (cross-sectional area ratio to the extruded raw tube,%) of the copper tube until the intermediate annealing was performed, the intermediate annealing temperature, and the tempering degree of the copper tube after the intermediate annealing were changed. Table 1 shows these conditions. However, the area reduction rate of the copper tube before the intermediate annealing is given is the area reduction rate from the intermediate annealing to the finish annealing. In each example, in order to make the total area reduction rate up to the stage of the final annealing substantially the same, the area reduction rate in the drawing after the intermediate annealing is changed.
[0036]
The degree of cracking when the obtained small-diameter product copper tube having an outer diameter of 6.35 mm and a wall thickness of 0.8 mm for test evaluation was further expanded was determined. In addition, the average crystal grain size of these small-diameter product copper tubes was 200 μm or less in each case. The average crystal grain size was the average diameter of crystal grains in the drawing (L) direction of the copper tube. More specifically, the surface of the copper tube that has been mechanically polished by 0.05 to 0.1 mm and then electrolytically etched is observed for the average crystal grain size using an optical microscope, and is measured in the L direction by a line intercept method. 1 The length of the measurement line was 0.95 mm, and the total length of the measurement line was 0.95 x 15 mm by observing a total of 5 visual fields with 3 lines per visual field.
[0037]
In each case, the degree of cracking when the copper tube was expanded was determined by inserting a mandrel into each tube end of 10 test copper tubes randomly sampled in the longitudinal direction, and expanding each tube at an expansion ratio of 200%. Evaluation was made based on the state of occurrence of cracks at the ends of each pipe when the ends were expanded. In each case, x indicates that at least one of the test copper tubes had cracks at the pipe end, and at least one of the test copper pipes had rough skin as a stage prior to cracking at the pipe end. (There is a possibility of occurrence of cracking). The case was evaluated as △, and the case where no crack or rough surface occurred at the pipe end was evaluated as ○. Table 1 also shows these results.
[0038]
As shown in Table 1, the invention examples 1 to 4 perform the intermediate annealing of the copper tube during the drawing after the cold rolling, and the copper tube is reduced from O to 1 / 8H by the JIS quality symbol by the intermediate annealing. After the tempering to the range, the area reduction rate of the copper tube from this intermediate annealing to the finish annealing is set to 10 to 95% of the extruded raw tube, so that the copper tube until the intermediate annealing is performed Is controlled. On this basis, a small-diameter product copper tube with an outer diameter of Φ10 mm or less, which has been subjected to cold working with a surface reduction rate of 99% or more on the extruded raw tube, is manufactured.
[0039]
As is apparent from Table 1, such invention examples 1 to 4 do not crack in the copper pipe even in the pipe expansion test, and are excellent in pipe expandability. From this result, it can be expected that no crack is generated even in the tube shrinking with the same area reduction rate, and it can be said that the tube is excellent in tube shrinkability.
[0040]
On the other hand, in Comparative Example 5, which was not subjected to the above-described intermediate annealing, that is, a conventional example, cracks occurred in the pipe expansion test.
[0041]
The area reduction rate of the copper pipe from the intermediate annealing to the finish annealing was set to 93% of the area of the extruded raw pipe, and the area reduction rate of the copper pipe until the intermediate annealing was applied was the same as in the invention. In Comparative Example 6, the intermediate annealing temperature was too low, 400 ° C., and the temper symbol of the copper tube by the intermediate annealing was / 4, and cracks occurred in the pipe expansion test.
[0042]
Furthermore, the reduction rate of the copper pipe from the intermediate annealing to the finish annealing was too high at 99.0%, and the reduction rate of the copper pipe before the intermediate annealing was applied was too low. As a condition, even if the temper symbol of the copper tube obtained by the intermediate annealing is O 2, a crack occurs in the pipe expansion test.
[0043]
In addition, the reduction rate of the copper pipe from the intermediate annealing to the finish annealing was too low at 5.0%, and the reduction rate of the copper pipe before the intermediate annealing was performed was too high. As a condition, even if the temper symbol of the copper tube obtained by the intermediate annealing is O 2, a crack occurs in the pipe expansion test.
[0044]
Therefore, these examples show the critical significance of each requirement of the present invention, such as intermediate annealing, the symbol of the temper of the copper tube by the intermediate annealing, and the area reduction rate of the copper tube after the intermediate annealing.
[0045]
[Table 1]

[0046]
【The invention's effect】
According to the present invention, an extruded raw tube is a small-diameter copper tube having an outer diameter of 10 mm or less subjected to cold working with a large area reduction rate of 99% or more, and has a severe expansion rate and a large contraction rate. It is possible to provide a method for manufacturing a copper pipe, in which cracks are less likely to occur during expansion or contraction of the pipe under conditions. Therefore, the copper pipe has a great industrial value in that it can be expanded to the above-mentioned pipe expanding and contracting applications.

Claims (3)

This is a small-diameter copper tube with an outer diameter of Φ10 mm or less that has been subjected to cold working with a surface reduction rate of 99% or more on a pure copper extruded raw tube and finish annealed, and is used after further expanding or contracting. In producing a copper tube, an intermediate annealing of the copper tube is performed in the middle of the cold working, and the copper tube is tempered by the intermediate annealing to a range of O to 1 / 8H by a JIS temper symbol, A method for producing a copper pipe, wherein a reduction in area of the copper pipe in the cold working from the intermediate annealing to the finish annealing is 10 to 95% of the extruded raw pipe. The method according to claim 1, wherein the intermediate annealing is performed at a temperature of 450 to 650 ° C. The method for producing a copper tube according to claim 1, wherein the pure copper is phosphorus deoxidized copper.