JP2001096337A - Method of manufacturing copper tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a copper tube which is inexpensive and stable in quality. SOLUTION: A material tube of copper is cast by a continuous casting process using a heated mold, and the resultant material tube having a directionally solidified structure is processed by applying at least twice of cold drawing and annealing to form the copper tube having a prescribed size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a copper tube, and more particularly to a method for manufacturing a copper tube which is low in cost and stable in quality.

[0002]

2. Description of the Related Art As a conventional method of manufacturing a copper pipe used for a heat exchanger or a hot water supply for construction, an ingot is formed from a molten metal, and after heating the ingot, a copper pipe is formed by hot extrusion. There is known a method of manufacturing a copper tube of a predetermined size by repeatedly performing rolling and drawing with a tube reducer and the like.

As another conventional manufacturing method, a metal plate having a desired thickness is once manufactured by subjecting an ingot to hot working and cold working, and then the metal plate is formed into a copper tube having a predetermined size. There is known a method in which the joint is bent by welding or forging.

[0004]

However, according to these conventional manufacturing methods, in the former case, not only expensive hot extrusion equipment is required, but also the process is complicated, so that there is a problem in cost. In addition, since the capacity of the extruded billet is limited, the length of the raw tube that can be manufactured is limited, which also causes an increase in cost.

On the other hand, in the latter manufacturing method, hot and cold rolling for obtaining a metal plate, bending for forming a tubular body, or subsequent welding and forging are performed in a large number of steps. In addition, the cost becomes higher, and furthermore, this method has a quality problem due to the fact that corrosion tends to occur in the welded portion or the forged portion.

Accordingly, an object of the present invention is to provide a method for manufacturing a copper tube which is low in cost and stable in quality.

[0007]

Means for Solving the Problems To achieve the above object, the present invention provides a method for producing a copper tube of a predetermined size by stretching a copper tube.
The copper tube having a unidirectional solidification structure is cast by continuous casting using a heating mold, and the copper tube is subjected to a cold drawing process and an annealing process two or more times to form a copper tube having a predetermined size. And a method for manufacturing a copper tube.

[0008] Continuous casting using the above-mentioned heating mold is as follows.
Means a casting method that continuously discharges the molten metal from the mold,
A casting method in which the temperature of the inner wall surface at the outlet of the mold is maintained at a temperature equal to or higher than the freezing point of the cast material by using a heating mold as a mold, thereby preventing the formation of a casting shell.

In the present invention, the first stretching and annealing in the cold stretching and annealing performed twice or more times are performed to recrystallize the cast structure, and the second and subsequent times are performed in accordance with the crystal structure according to the application. , Hardness, and mechanical properties.

[0010] Multistage processing in which a cold drawing process of each time or an appropriate time is not performed only once to one size, but is reduced to a predetermined size through several sizes in several times. Is possible.

The working ratio in the cold stretching performed before the first annealing is preferably set to 35 to 80%. If it is less than 35%, the density of strain accumulated in the copper tube due to processing is too low, so that a uniform recrystallized structure cannot be obtained even if annealing treatment is performed. On the other hand, if the working ratio is set to be more than 80%, disconnection occurs during the working, which is not preferable.

[0012] The working ratio of the cold drawing between the first annealing and the second annealing or between the subsequent annealing should be set to 50% or more. Sufficient hardness and mechanical properties cannot be obtained.

[0013] The first annealing treatment is preferably carried out in a temperature range of 650 to 880 ° C, which ensures the formation of a homogeneous and fine recrystallized structure. Processing temperature is 650
When the temperature is lower than ℃, it is difficult to secure a uniform recrystallized structure.

[0014] This is because the copper raw tube manufactured by continuous casting using a heating mold has a unique unidirectional solidification structure.
This is because it is difficult to recrystallize.
If the temperature exceeds 0 ° C., the recrystallized structure is likely to be coarse, and it is difficult to secure a fine crystal structure.

For the second and subsequent annealing treatments,
It is preferable to set the temperature in the range of 300 to 650 ° C. If the set temperature is lower than this range, a recrystallized structure cannot be obtained. Conversely, if the temperature exceeds this range, the crystal structure is enlarged and the tensile strength and elongation are increased. Cannot be obtained.

The processing equipment required in the present invention includes:
For example, a continuous casting apparatus and a heating mold attached to the apparatus, and a drawing apparatus using a simple floating plug for stretching, etc., all of which are widely spread or inexpensive equipment. No special equipment is required, such as the hot extrusion equipment that has been required to produce seed copper tubing.

[0017]

Next, an embodiment of a method for manufacturing a copper tube according to the present invention will be described.

EXAMPLE 1 Using a graphite mold heated to 1050 ° C. and opened vertically, and a vertical continuous casting apparatus with a core positioned at the center of the mold, the casting speed was set to 250 mm / min. In this manner, a copper tube (circular in section; the same applies hereinafter) having an outer diameter of 36 mm and a thickness of 2 mm was continuously cast.

Next, the copper tube was cold-drawn under the condition of a working degree of 60% to form a copper tube having an outer diameter of 21 mm and a wall thickness of 1.4 mm. At the temperature of 1
It is processed to the target size with an outer diameter of 11 mm and a wall thickness of 0.5 mm.
Finally, a predetermined copper tube was manufactured by performing an annealing treatment at 450 ° C. for 20 minutes.

[0019]

Example 2 In Example 1, the heating temperature of the graphite mold was set at 1070 ° C., the casting speed was set at 200 mm / min, and a copper material containing 0.023% by weight of P was used as the copper material. In this way, a copper phosphate tube having an outer diameter of 51 mm and a wall thickness of 2.6 mm was manufactured, and then this tube was subjected to cold stretching with a working ratio of 52.5% to an outer diameter of 35 mm and a wall thickness of After processing into a 1.8 mm copper tube, and further performing an annealing process at 800 ° C. for 30 minutes, cold drawing was performed again to obtain an outer diameter of 12.5 mm and a wall thickness of 0.6 mm.
And finally annealed at 450 ° C. for 30 minutes to produce a predetermined copper tube.

[0020]

Example 3 In Example 1, the heating temperature of the graphite mold was set at 1010 ° C., the casting speed was set at 200 mm / min, and a copper material containing 15% by weight of Ni was used as the copper material. , Outer diameter 42mm, wall thickness 2.2
mm cupronickel tube was manufactured, and then the tube was subjected to cold drawing at a working ratio of 55.4% to an outer diameter of 26 m.
m, processed into a 1.6 mm thick copper tube.
After performing an annealing treatment at 80 ° C. for 1 hour, cold drawing is performed again, the tube is reduced to an outer diameter of 13 mm and a wall thickness of 0.6 mm, and finally, an annealing treatment is performed at 500 ° C. for 10 minutes. Was manufactured.

[0021]

Reference Example 1 In Example 1, the working ratio in the cold stretching after casting was set to 25%, and the other conditions before the first annealing were set to the same as those in Example 1; Was carried out at 780 ° C. for 1 hour, and a disconnection occurred in the second cold stretching. As a result of confirming the crystal structure, a mixed particle state was exhibited.

[0022]

Reference Example 2 All the conditions before the first annealing were set to the same conditions as in Example 1, and the first annealing was performed at 640 ° C. for 1 hour. A tube has developed. As a result of confirming the crystal structure, a mixed particle state was exhibited.

[0023]

[Reference Example 3] All conditions before the first annealing were set to the same conditions as in Example 1, and the first annealing was performed at 900 ° C for 1 hour. Occurred. As a result of confirming the crystal structure, enlargement of the crystal was observed.

Table 1 shows the main points in the above Examples and Reference Examples, the results of observation of the crystal grain size of the copper tubes obtained in these Examples, and the elongation characteristics.

[0025]

[Table 1]

According to Table 1, it was recognized that all of the copper tubes manufactured in the examples had a fine crystal structure of 50 μm or less and a high hardness, and were found to be piping materials for heat exchangers or hot and cold water for construction. It has been confirmed that the material has sufficient properties as a piping material for use.

The reason why the reference example did not reach the stage of property evaluation is that reference example 1 had a low workability in cold stretching before the first annealing treatment, and reference example 2 had a temperature reduction in the first annealing treatment. Insufficiency is caused by the fact that the first annealing treatment is too high in Reference Example 3. In carrying out the present invention, it is necessary to consider the degree of cold stretching before the first annealing and the temperature of the first annealing.

[0028]

As described above, according to the method for manufacturing a copper tube according to the present invention, a copper tube is cast by continuous casting using a heating mold, and the copper tube obtained by this method is used. In consideration of the directionally solidified structure, cold drawing and annealing are performed twice or more to produce a copper tube having predetermined characteristics. Therefore, the production process from casting to obtaining a finished copper tube Does not require any special equipment such as a hot extrusion apparatus, and therefore has a small economic burden on equipment investment.

Further, since the process is simple and the copper raw tube is manufactured by casting, the length of the copper raw tube due to the limitation of the billet capacity as in the conventional hot extrusion system is reduced. There are no restrictions, so low-cost manufacturing is possible from this point as well. Of course, there is no quality problem as in the conventional method of bending and welding or forging a metal plate.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B22D 11/059 120 B22D 11/059 120A 120B C22F 1/08 C22F 1/08 A // C22C 9/00 C22C 9/00 C22F 1/00 626 C22F 1/00 626 686 686 686B 691 691B 694 694A (72) Inventor ▲ Winter ▼ Keihei 3550 Kida Yomachi, Tsuchiura-shi, Ibaraki Pref. Person Kiyoshi Oizumi 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Within the Tsuchiura Plant of Hitachi Cable Co., Ltd. (72) Inventor Gen Hajime 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture F-term within the Hitachi Cable, Ltd. System Materials Research Laboratory 4E004 CA00 MD05 NC07 4E096 EA04 EA16 HA22 KA02 KA04

Claims (4)

[Claims] 1. A method for producing a copper tube having a predetermined size by stretching a copper tube, wherein said copper tube having a directionally solidified structure is continuously cast using a heating mold. Cold drawing and annealing are performed on the cast copper base tube in two steps.
A method for producing a copper tube, wherein the copper tube is formed into a copper tube of a predetermined size by performing the process more than once. 2. The method according to claim 1, wherein the cold drawing performed before the first annealing is performed by processing the copper tube at a working ratio of 35 to 80%. Manufacturing method of copper tube. 3. The method according to claim 1, wherein the cold drawing performed before the second annealing is performed by processing the copper tube at a working ratio of 50% or more. The method for producing a copper tube according to the above item. 4. The annealing process is characterized in that the annealing temperature in the first annealing process is set to 650 to 880 ° C., and the annealing temperature in the second and subsequent annealing processes is set to 300 to 650 ° C. The method for producing a copper pipe according to any one of claims 1 to 3.