TWI614353B - Cold/hot water supply copper alloy seamless tube - Google Patents

Abstract

The invention relates to a copper alloy seamless pipe for water and hot water supply, which is obtained by processing a copper alloy, and is characterized in that the copper alloy contains 0.45 to 0.90 mass% of Sn, 0.01 to 0.08 mass% of Zr, And 0.004 ~ 0.04 mass% of P, and the balance contains Cu and unavoidable impurities. The conductivity of the copper alloy seamless pipe for water supply and hot water satisfies the following formula (1): (1) ρ2-ρ1 ≧ 0.3 (% IACS) (where ρ1 refers to the conductivity after solution treatment (% IACS), and ρ2 refers to the conductivity after aging treatment (% IACS)).

According to the present invention, a copper alloy seamless pipe for water supply and hot water supply with high strength, less reduction in strength due to welding, high resistance to creep deformation, and high suppression effect of intermediate temperature brittleness can be provided.

Description

Copper alloy seamless pipe for water supply and hot water

The invention relates to a copper alloy seamless pipe, which is a water supply and hot water user who circulates water in the pipe, for example, it can be used for piping heating in a circulating hot water system of a hotel, hospital, apartment, etc. Water flow pipe of heat exchanger for water machine.

Since the previous years, the water flow pipes of heat exchangers for piping water heaters used in circulating hot water supply systems in hotels, hospitals, apartments, etc. have mostly used seamless copper alloy pipes.

In recent years, in order to reduce the weight or reduce the cost of these heat exchangers, it is necessary to reduce the thickness of the seamless tube. However, the strength of the previous phosphorus deoxidized copper tubes is low, so it is difficult to reduce the thickness. Replace it with copper alloy seamless pipe.

Therefore, as a solid solution-strengthened copper alloy, Patent Document 1 proposes a copper alloy to which Sn is added. Moreover, as a solid solution strengthening and precipitation strengthening type copper alloy, in patent document 2 and patent document 3, the copper alloy which added Sn and Zr was proposed.

[Prior technical literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2003-268467 (Scope of patent application)

Patent Document 2: WO2008 / 041777 (Scope of patent application)

Patent Document 3: Japanese Patent Laid-Open No. 2011-94174 (Scope of patent application)

The copper alloy seamless pipe for water supply and hot water circulation in the pipe has the risk of fatigue cracking due to thermal fatigue accompanied by repetition of thermal expansion and thermal contraction. In addition, the seamless pipe is subject to tension due to thermal expansion, and there is a risk of latent deformation due to use temperature.

Therefore, for copper alloy seamless pipes for water supply and hot water circulation in the pipe, in addition to requiring "higher strength" and "less reduction in strength due to welding", it is also required to have the characteristics of heat-resistant fatigue cracking and Resistance to creep deformation.

However, the solid solution-strengthened copper alloy seamless pipe made of Sn added with reference to Document 1 has intermediate temperature brittleness, and thermal fatigue and creep failure are liable to occur in the brittle temperature region. In the manufacture of heat exchangers, intermediate temperature brittleness occurs due to heating such as welding while tension is acting in the seamless pipe, and brittleness and cracking easily occur.

The factors that increase the intermediate temperature brittleness are S and H. By reducing the contents of S and H to the limit, the intermediate temperature brittleness can be suppressed to a certain extent, but it is not sufficient. In addition, in order to reduce the content of S to the limit, it is necessary to use a high-purity base metal, which is not good in terms of cost. In addition, in order to reduce the content of H to the limit, long-term melting treatment is required, and environmentally-controlled melting and casting are not satisfactory in terms of cost.

Therefore, even if the content of S and H is a normal level (a level that has not been reduced to the limit), it is expected to effectively suppress the intermediate temperature brittleness. In addition, the content of S and H in the so-called normal level (the level that has not been reduced to the limit) is that S is about 0.0005 to 0.0008 mass%, and H is about 0.0002 to 0.0010 mass%.

On the other hand, as in Patent Documents 2 and 3, Sn is added And Zr solid solution strengthening and precipitation strengthening copper alloy seamless pipes, by adding Zr, in addition to higher strength and less reduction in strength due to welding, can also suppress the performance of intermediate temperature brittleness to a certain extent .

However, it is required to further improve the characteristics of thermal fatigue crack generation and the resistance to creep deformation.

Therefore, the object of the present invention is to provide a copper alloy seamless pipe for water supply and hot water supply, which has higher strength, less reduction in strength due to welding, higher resistance to creep deformation, and higher suppression effect of intermediate temperature brittleness. .

The present inventors have made intensive research in order to solve the problems in the above-mentioned conventional technology. As a result, they have found that the copper alloy contains Sn and Zr at a specific content, and Zr is present in the copper alloy in an appropriate state to obtain strength. A copper alloy seamless pipe for water supply and hot water with high strength, less reduction in strength due to welding, high resistance to creep deformation, and high suppression effect of intermediate temperature brittleness, thereby completing the present invention.

That is, the present invention (1) provides a copper alloy seamless pipe for water and hot water supply, which is obtained by processing a copper alloy, and is characterized in that the copper alloy contains 0.45 to 0.90% by mass of Sn, 0.01 to 0.08 Zr by mass% and P by 0.004 ~ 0.04 mass%, and the balance includes Cu and unavoidable impurities. The conductivity of the copper alloy seamless pipe for water supply and hot water meets the following formula (1): (1) ρ2-ρ1 ≧ 0.3 (% IACS)

(In the formula, ρ1 refers to the conductivity (% IACS) after solution treatment, and ρ2 refers to the conductivity (% IACS) after aging treatment).

In addition, the present invention (2) provides a copper alloy seamless pipe for water supply and hot water, which is obtained by processing a copper alloy, and is characterized by: The copper alloy contains 0.45 to 0.90 mass% of Sn, 0.01 to 0.08 mass% of Zr, and 0.004 to 0.04 mass% of P, and the balance includes Cu and unavoidable impurities. The conductivity of the copper alloy seamless pipe for water supply and hot water satisfies the following formula (2): (2) ρ4-ρ3 ≧ 0.3 (% IACS)

(In the formula, ρ3 refers to the conductivity (% IACS) after heating-water cooling test at 950 ° C for 10 minutes, and ρ4 refers to the conductivity (% IACS) after heating-water cooling test at 550 ° C for 60 minutes).

According to the present invention, a copper alloy seamless pipe for water supply and hot water supply with high strength, less reduction in strength due to welding, high resistance to creep deformation, and high suppression effect of intermediate temperature brittleness can be provided.

The copper alloy seamless pipe for water supply and hot water supply according to the first aspect of the present invention (hereinafter also referred to as the copper alloy seamless pipe for water supply and hot water supply (1)) is obtained by processing a copper alloy, and It is characterized in that the copper alloy contains 0.45 to 0.90% by mass of Sn, 0.01 to 0.08% by mass of Zr, and 0.004 to 0.04% by mass of P, and the balance contains Cu and inevitable impurities. The copper for water supply and hot water supply The conductivity of the alloy seamless pipe satisfies the following formula (1): (1) ρ2-ρ1 ≧ 0.3 (% IACS)

(In the formula, ρ1 refers to the conductivity (% IACS) after solution treatment, and ρ2 refers to the conductivity (% IACS) after aging treatment).

Copper alloy seamless pipe for water supply and hot water according to the second aspect of the present invention The copper alloy seamless pipe (2) for water and hot water supply of the present invention is obtained by processing a copper alloy, and is characterized in that the copper alloy contains 0.45 to 0.90% by mass of Sn, 0.01 to 0.08 Zr by mass, and P by 0.004 to 0.04 mass%, and the balance contains Cu and unavoidable impurities. The conductivity of the copper alloy seamless pipe for water supply and hot water meets the following formula (2): (2) ρ4-ρ3 ≧ 0.3 (% IACS)

(In the formula, ρ3 refers to the conductivity (% IACS) after heating-water cooling test at 950 ° C for 10 minutes, and ρ4 refers to the conductivity (% IACS) after heating-water cooling test at 550 ° C for 60 minutes).

The copper alloy seamless pipe (1) for water supply and hot water supply of the present invention and the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention, and the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention ) Satisfies the formula (1), while the copper alloy seamless pipe (2) for water supply and hot water supply according to the present invention satisfies the formula (2).

The copper alloy seamless pipe (1) for water supply and hot water supply of the present invention and the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention are used as circulating hot water supply systems in hotels, hospitals, apartments, etc. The seamless pipes such as the water flow pipe of the heat exchanger for the water heater used in the water supply pipe, and the water flow pipe for water supply and hot water circulation, are copper alloy seamless pipes made of copper alloy. It is a copper alloy seamless pipe for water and hot water supply.

The copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention contains Sn, Zr, and P as essential elements, and the balance is Contains Cu and unavoidable impurities.

In the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention, Sn is improved by solid solution strengthening. The effect of the strength of the copper alloy and the effect of improving the ductility at room temperature. In the case of these elements, alloying can be performed at a relatively low temperature, which is advantageous in terms of manufacturing.

In the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention, Zr has the effect of enhancing the strength of the copper alloy by precipitation strengthening. . In addition, Zr has the effect of reducing the decrease in strength by remaining Zr precipitates and suppressing the coarsening of crystal grains before the welding temperature is not too high.

In the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless copper alloy (2) for water supply and hot water supply of the present invention, the content of Sn is 0.45 to 0.90% by mass. If the content of Sn in the copper alloy is less than 0.45 mass%, even if the solid solution strengthening of Sn and the precipitation strengthening of Zr are combined, the strengthening of the copper alloy is insufficient, and if it exceeds 0.90 mass%, work hardening becomes Significantly, the workability, especially the cold-drawing workability, is deteriorated, and the intermediate temperature brittleness is easily caused.

In the copper alloy seamless pipe (1) for the water supply and hot water supply of the present invention or the copper alloy seamless copper pipe (2) for the water supply and hot water supply of the present invention, the content of Zr is 0.01 to 0.08 mass%. If the content of Zr in the copper alloy is less than 0.01% by mass, the effect of suppressing the coarsening of crystal grains is reduced, the strength reduction due to welding is increased, and even if solid solution strengthening of Sn is combined with precipitation strengthening of Zr, The strengthening of copper alloys is also insufficient. On the other hand, if the content of Zr in the copper alloy exceeds 0.08% by mass, excessive precipitation hardening occurs, and workability is reduced. In particular, the cold rolling workability is deteriorated. As a result, the transfer of the spiral groove shape on the inner surface of the tube becomes insufficient, and it is difficult to obtain the heat transfer performance obtained by C1220.

The copper alloy seamless pipe (1) for the water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for the water supply and hot water supply of the present invention has a content of P of 0.004 to 0.04 mass%, preferably It is 0.015 to 0.030 mass%. Contains 0.004 mass% with copper alloy With the above P element, deoxidation in the display material proceeds sufficiently. In addition, if the content of P in the copper alloy is too large, the thermal conductivity of the copper alloy is reduced, so the content of P in the copper alloy is 0.040% by mass or less.

The electrical conductivity of the copper alloy seamless pipe (1) for water supply and hot water of the present invention satisfies ρ2-ρ1 of 0.3 or more, that is, it satisfies the following formula (1): (1) ρ2-ρ1 ≧ 0.3 (% IACS)

(In the formula, ρ1 refers to the conductivity after solution treatment (% IACS), ρ2 refers to the conductivity after aging treatment (% IACS)), and it is preferred to satisfy ρ2-ρ1 of 0.5 or more and 20 or less, that is, The following formula (1a) is satisfied: (1a) 0.5 ≦ ρ2−ρ1 ≦ 20.

In addition, the electrical conductivity of the copper alloy seamless pipe (2) for water and hot water supply of the present invention satisfies ρ4-ρ3 of 0.3 or more, that is, it satisfies the following formula (2): (2) ρ4-ρ3 ≧ 0.3 (% IACS)

(In the formula, ρ3 refers to the electrical conductivity after heating-water cooling test at 950 ° C for 10 minutes (% IACS), and ρ4 refers to the electrical conductivity after heating-water cooling test at 550 ° C for 60 minutes (% IACS). Preferably, ρ4-ρ3 is 0.5 or more and 20 or less, that is, the following formula (2a) is satisfied: (2a) 0.5 ≦ ρ4-ρ3 ≦ 20.

In the present invention, the so-called solution treatment refers to a treatment for sufficiently solid-solving the Zr-based intermetallic compound crystallized out during the cooling of the ingot during the melting and casting steps, and the so-called aging treatment refers to the Zr-based metal Treatment of precipitation of intermediate compounds. The copper alloy seamless pipe system for water supply and hot water supply according to the present invention is sequentially manufactured by "melting and casting steps → hot extrusion steps → cold working steps → intermediate annealing and rolling steps as needed → aging treatment". Moreover, in this manufacturing step, a hot extrusion step The heating in the solution is a solution treatment for sufficiently solid-solving the Zr-based intermetallic compound crystallized out during the cooling of the ingot during the melting and casting steps.

In copper alloy seamless pipes, if the Zr crystallized from the ingot during the melting and casting steps during the cooling process is not sufficiently solid-dissolved in the solution treatment, in order to obtain an aging treatment with a strength corresponding to the Zr content The amount and distribution of the fine precipitates precipitated in the medium become inappropriate. In addition, Zr-based crystals that have not been completely dissolved in the solution treatment not only do not contribute to the improvement of strength, but also hinder the workability in the subsequent cold working step, rolling step, and bending processing step when manufacturing a heat exchanger. Furthermore, Zr in solid solution captures S by forming compounds with S in the solidification process or solution treatment during casting, and captures H that forms grain boundary voids during hot extrusion, thereby improving the creep resistance. Deformation characteristics to suppress brittleness at intermediate temperatures. Therefore, the Zr dissolved in solution after the solution treatment not only contributes to the precipitation strengthening by the aging treatment in the subsequent steps, but also contributes to the improvement of the creep deformation resistance and the suppression of the intermediate temperature brittleness. Moreover, by making the precipitation state of Zr in the aging treatment appropriate, the effect of suppressing the intermediate temperature brittleness is improved.

However, it is difficult to quantify the solid solution state of Zr in solution treatment and the precipitation state of Zr in aging treatment. Therefore, the present inventors repeatedly conducted intensive research, and found that the difference between the electrical conductivity after the solution treatment and the electrical conductivity after the aging treatment (ρ2-ρ1) can be used to grasp the Zr value in the solution treatment. The state of precipitation of Zr in the solid solution state and the aging treatment, and ρ2-ρ1 is specified to a specific range, thereby improving the creep deformation resistance and suppressing intermediate temperature brittleness. That is, the electrical conductivity of the copper alloy seamless pipe (1) for water supply and hot water of the present invention satisfies ρ2-ρ1 of 0.3 or more, that is, the following formula (1) is satisfied: (1) ρ2-ρ1 ≧ 0.3 (% IACS) It is preferable to satisfy ρ2-ρ1 from 0.5 to 20, that is, to satisfy the following formula (1a): (1a) 0.5 ≦ ρ2-ρ1 ≦ 20.

When ρ2-ρ1 is in the above range, the creep deformation resistance can be improved and the intermediate temperature brittleness can be suppressed.

The inventors have found that the difference (ρ4-ρ3) between the electrical conductivity after a heating-water cooling test at 950 ° C for 10 minutes and the electrical conductivity after a heating-water cooling test at 550 ° C for 60 minutes can be grasped. The solid solution state of Zr in the solution treatment and the precipitation state of Zr in the aging treatment, and ρ4-ρ3 are specified in a specific range, thereby improving the creep deformation resistance and suppressing intermediate temperature brittleness. That is, the electrical conductivity of the copper alloy seamless pipe (2) for water supply and hot water of the present invention satisfies ρ4-ρ3 of 0.3 or more, that is, the following formula (2) is satisfied: (2) ρ4-ρ3 ≧ 0.3 (% IACS) It is preferable that ρ4-ρ3 is 0.5 or more and 20 or less, that is, the following formula (2a) is satisfied: (2a) 0.5 ≦ ρ4-ρ3 ≦ 20.

When ρ4-ρ3 is in the above range, the creep deformation resistance can be improved and the intermediate temperature brittleness can be suppressed.

Furthermore, in the present invention, the so-called heating-water cooling test at 950 ° C for 10 minutes is a test of water-cooling a copper alloy seamless pipe to be tested after heating at 950 ° C ± 25 ° C for 10 minutes. Proceed as follows: First, place the test object in an electric furnace set to a nitrogen environment at 950 ± 25 ° C. After the temperature in the furnace has returned to 950 ° C, hold it at 950 ° C ± 25 ° C for 10 minutes. Direct water cooling. Then, the conductivity (% IACS) of the test object after the heating-water cooling test at 950 ° C for 10 minutes was measured, and ρ3 was determined.

In the present invention, the so-called heating-water cooling test at 550 ° C for 60 minutes is a copper alloy seamless tube to be tested, which is heated and water-cooled at 950 ° C for 10 minutes, and then at 550 ° C ± 10 ° C. Water cooling test after heating for 60 minutes The test was carried out as follows: First, in the same manner as the heating-water cooling test at 950 ° C for 10 minutes, the test object was directly water-cooled from 950 ° C after heating at 950 ° C ± 25 ° C for 10 minutes. The test object heated and water-cooled at 950 ° C for 10 minutes was put into a salt bath furnace, and kept at 550 ° C ± 10 ° C for 60 minutes, and then directly water-cooled. Then, the electrical conductivity (% IACS) of the test object after the heating-water cooling test at 550 ° C ± 10 ° C for 60 minutes was measured, and ρ4 was determined.

The copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for copper water supply and hot water supply of the present invention may further contain S atoms. When the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention further contains S, the S in the copper alloy The content is 0.0005 to 0.0010 mass%. The copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention may further contain H. When the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention further contains H, the H content in the copper alloy The content is 0.0002 to 0.0020% by mass. If the content of S or H in the copper alloy exceeds the above range, S or H cannot be captured sufficiently by the solid solution of Zr, and the effects of improving creep deformation resistance and suppressing intermediate temperature brittleness cannot be obtained. On the other hand, when the content of S or H in the copper alloy is less than the above range, although the effects of improving the creep deformation resistance and suppressing the intermediate temperature brittleness can be obtained, it is easy to increase the cost.

The copper alloy seamless pipe system for water supply and hot water supply according to the present invention is sequentially manufactured by melting, casting and cooling → hot extrusion and cooling → cold working → intermediate annealing and rolling as required → aging treatment.

First, melting, casting and cooling are performed. During melting and casting Melting and casting are usually performed to obtain a blank with a specific content and a specific element. For example, in a manner that the content of the copper alloy seamless pipe for water supply and hot water supply of the present invention reaches a specific content, the copper base metal and the base metal containing element of the copper alloy seamless pipe for water supply and hot water supply of the present invention or The alloy containing the element and copper is adjusted in composition, and a casting material such as a high-frequency melting furnace is used. The billet is then cooled after casting.

Then, hot extrusion and cooling are performed. In hot extrusion, a billet obtained by casting is heated at a specific temperature and hot extrusion is performed. Hot extrusion is performed by mandrel extrusion. That is, hot extrusion is performed while inserting a mandrel into a blank that has been cold perforated before heating or a blank that is hot perforated before extrusion. Then, after performing hot extrusion, it was rapidly cooled to obtain a hot-extruded rough processed tube.

Then, cold working is performed. In cold working, cold-rolled or cold-drawn cold-worked hot-extruded rough-drawn tubes obtained by hot extrusion are used to reduce the outer diameter and wall thickness of the tube to obtain seamless rough-drawn tubes.

When an inner smooth pipe (bare pipe) without an inner groove is obtained, after cold working, the seamless rough-processed pipe obtained by cold working is heated at 400 to 600 ° C, and then subjected to cooling aging treatment . Then, the aging treatment is performed to obtain the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention.

When a tube with an inner surface groove is obtained, after cold working, the intermediate rough annealing of the seamless rough-processed tube obtained by cold working at 400 to 600 ° C is followed by rolling, followed by rolling. . Rolling is performed by placing a rolling insert with spiral groove processing on the outer surface of the seamless rough-machined tube, and pressing a plurality of rolling balls rotating at high speed from the outside of the tube to make rolling The slot of the insert is transferred to the inner surface of the tube. Then, the aging process is performed on the rolled seamless tube. Time The effect treatment is performed by heating and cooling the rolled seamless tube at 400 to 600 ° C. Then, the aging treatment is performed to obtain the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention.

In addition, in the copper alloy seamless pipe (1) for water and hot water supply of the present invention, the conductivity is set to formula (1): ρ2-ρ1 ≧ 0.3 (% IACS), preferably formula (1a): 0.5 ≦ The method of ρ2-ρ1 ≦ 20, and in the copper alloy seamless pipe (2) for water supply and hot water supply of the present invention, the conductivity is set to formula (2): ρ4-ρ3 ≧ 0.3 (% IACS), preferably This is a method of formula (2a): 0.5 ≦ ρ4-ρ3 ≦ 20, and examples thereof include a method of adjusting the cooling rate of the billet during melting and cooling after casting. The inventors have found that due to the different cooling rates of the billet during melting and cooling after casting, the existence state of Zr in copper alloys is different, and the existence state of Zr after melting and casting is different. For "ρ2-ρ1" and The value of "ρ4-ρ3" affects. Furthermore, according to the diameter of the billet, the cooling method after casting, the cooling conditions after casting, the solution treatment conditions, and the aging treatment conditions, etc., it is suitable to adjust the conductivity to the formula (1), preferably the formula (1a) Cooling speed; or suitable for adjusting to different cooling speeds of formula (2), preferably formula (2a), so the cooling speed of the billet during melting and cooling after casting can be based on the billet diameter, cooling method, and cooling conditions after casting , Solution treatment conditions, aging treatment conditions, etc., are appropriately selected. Furthermore, by appropriately adjusting the billet diameter, cooling conditions after casting, solution treatment conditions, aging treatment conditions, etc., the conductivity of the copper alloy seamless pipe (1) for water supply and hot water supply of the present invention satisfies formula (1) ), It is preferably adjusted in the manner of formula (1a), and the conductivity of the copper alloy seamless pipe (2) for water supply and hot water of the present invention satisfies the formula (2), preferably in the formula (2a) Way to adjust.

The copper alloy seamless pipe for water supply and hot water of the present invention is wound into a coil shape as a heat transfer pipe for a heat exchanger, and is used for manufacturing a heat exchanger (cross-finned tube heat exchanger). The cross-fin tube type heat exchanger combines the aluminum fins on the air side with the The heat transfer tube on the refrigerant side is assembled as a single body.

The cross-finned tube-type heat exchanger is produced by firstly forming an aluminum plate fin in which a plurality of specific assembly holes are formed by pressing and the like, and then laminating the obtained aluminum plate fins. The copper alloy seamless pipe (1) for water supply and hot water supply of the present invention or the copper alloy for water supply and hot water supply of the present invention is inserted through the assembly hole and cut to a specific size and shape (hairpin). The seam pipe (2) is then expanded with a seamless pipe and fixed to an aluminum plate fin, and a U-shaped pipe is welded to the end of the seamless pipe opposite to the side where the bending process has been performed.

[Example]

Next, the present invention will be further described in detail by enumerating examples, but this is merely an example and does not limit the present invention.

(Examples and Comparative Examples) <Copper alloy seamless pipe for water and hot water supply> (Melting, casting and cooling)

By semi-continuous casting, a billet having an outer diameter of 254 mm containing the chemical composition shown in Table 1 was cast, followed by cooling. The amount of cooling water in the billet at this time is set as follows. In Table 1, the balance is Cu and inevitable impurities.

Cooling condition A: 1,000L / min cooling water

Cooling condition B: 600L / min cooling water

(Hot extrusion and cooling)

The billet obtained in the above manner was heated by holding it in a continuous heating furnace at 950 ° C (± 25 ° C) for more than 10 minutes, and then extruded at an extrusion temperature of 950 ° C with an outer diameter of 81 mm × wall thickness of 8 mm. Tube, directly put into water for cooling after extrusion, obtain Hot extrusion of roughed tubes. At this time, the solution treatment is performed simultaneously.

A sample for measuring the electrical conductivity was sampled from the head and tail of the obtained hot-extruded rough-drawn tube (sample 1).

(Cold processing)

The hot-extruded rough-processed tube obtained in the above manner was subjected to cold rolling and cold-drawing to obtain a seamless rough-processed tube having an outer diameter of 9.52 mm and a wall thickness of 0.8 mm.

(Aging treatment)

In a batch furnace, the seamless rough-processed tube obtained in the above manner was heated at 550 ° C. for 60 minutes in a non-oxidizing environment to obtain a copper alloy seamless tube for water supply and hot water supply.

A sample 2 of the obtained copper alloy seamless pipe for water supply and hot water was used for conductivity measurement. Samples 3 and 4 were used for the heating-water cooling test.

<Heating-Water Cooling Test>

The so-called heating-water-cooling test at 950 ° C for 10 minutes is a copper-alloy seamless pipe to be tested, which is heated at 950 ° C ± 25 ° C for 10 minutes and then water-cooled. The test is performed as follows: First, test The object was placed in an electric furnace set to a nitrogen environment at 950 ± 25 ° C. After the temperature in the furnace was restored to 950 ° C, it was maintained at 950 ° C ± 25 ° C for 10 minutes, and then water-cooled directly from 950 ° C. Then, the conductivity (% IACS) of the test object after the heating-water cooling test at 950 ° C for 10 minutes was measured, and ρ3 was determined.

In addition, the so-called heating-water cooling test at 550 ° C for 60 minutes refers to a copper alloy seamless tube to be tested, which is heated and water-cooled at 950 ° C for 10 minutes, and then heated at 550 ° C ± 10 ° C for 60 minutes. The water cooling test was performed as follows: First, in the same manner as the heating-water cooling test at 950 ° C for 10 minutes, the test object was heated at 950 ° C ± 25 ° C for 10 minutes, and then water-cooled directly from 950 ° C. , Then, the test object heated and water-cooled at 950 ° C for 10 minutes was put into a salt bath furnace, and kept at 550 ° C ± 10 ° C for 60 minutes, and then directly water-cooled. Then, the electrical conductivity (% IACS) of the test object after the heating-water cooling test at 550 ° C ± 10 ° C for 60 minutes was measured, and ρ4 was determined.

(Heating-water cooling test 1) 950 ℃ ± 25 ℃ × 10 minutes

First, sample 3 was placed in an electric furnace set to a nitrogen environment at 950 ± 25 ° C. After the temperature in the furnace was restored to 950 ° C, it was maintained at 950 ± 25 ° C for 10 minutes. Then, water cooling was performed directly from 950 ° C. Heating-water cooling test 1.

(Heating-water cooling test 2) 550 ℃ ± 10 ℃ × 60 minutes

First, in the same manner as the heating-water cooling test 1, the sample 4 was heated and water-cooled at 950 ± 25 ° C for 10 minutes. Then, the sample 4 having the same heating and water-cooling as the heating-water cooling test 1 was loaded. Put it into a salt bath furnace and hold it at 550 ° C ± 10 ° C for 60 minutes. Then, directly perform water cooling and perform a heating-water cooling test 2.

<Evaluation> (Mechanical properties)

Using a solder (JIS Z3264 BCuP-2) and an oxygen-propane mixed gas, the torch was brazed to produce a sample for measuring the compressive strength after welding. At this time, soldering is performed until the solder flows into the joint portion. The cooling system was air cooling. After cooling, a rupture test using water pressure was performed. The tensile strength was estimated by the following formula * 1 based on the breaking strength, and the mechanical properties (tensile strength and elongation) before and after welding were evaluated.

The mechanical properties before welding were evaluated by a tensile test, and the tensile strength was measured in accordance with JIS Z2241. Tensile strength and elongation. The results are shown in Table 3.

<Formula * 1> KHK formula: Bursting pressure = 2 × tensile strength × wall thickness / (outer diameter-0.8 × wall thickness)

(Conductivity)

The electrical conductivity is measured by a method based on JIS H0505, that is, a four-terminal method, and the value obtained by dividing by 0.15328 is expressed as a percentage.

(Intermediate temperature brittleness test)

A tensile test was performed on a copper alloy seamless pipe at a tensile speed of 10 ^-4 at a strain rate of 350 ° C. The elongation (δ) was 30% or more.

(Thermal fatigue test)

In a constant temperature bath at 100 ° C, a copper alloy seamless pipe was loaded with a repeated internal pressure of 0 to 15 MPa for 100,000 times to perform a thermal fatigue test. Those who did not produce cracks in the test were regarded as qualified.

Claims (3)

A copper alloy seamless pipe for water and hot water supply is obtained by processing a copper alloy, and is characterized in that the copper alloy contains 0.45 to 0.90 mass% of Sn, 0.01 to 0.08 mass% of Zr, and 0.004 to 0.04 mass% of P, and the balance contains Cu and unavoidable impurities. The conductivity of the copper alloy seamless pipe for water supply and hot water meets the following formula (1): (1) ρ2-ρ1 ≧ 0.3 (% IACS ) (Where ρ1 refers to the conductivity (% IACS) after solution treatment, and ρ2 refers to the conductivity (% IACS) after aging treatment). A copper alloy seamless pipe for water and hot water supply is obtained by processing a copper alloy, and is characterized in that the copper alloy contains 0.45 to 0.90 mass% of Sn, 0.01 to 0.08 mass% of Zr, and 0.004 to 0.04 mass% of P, and the balance contains Cu and inevitable impurities. The conductivity of the copper alloy seamless pipe for water supply and hot water meets the following formula (2): (2) ρ4-ρ3 ≧ 0.3 (% IACS ) (Where ρ3 means the conductivity after heating-water cooling test at 950 ° C for 10 minutes (% IACS), and ρ4 means the conductivity after heating-water cooling test at 550 ° C for 60 minutes (% IACS)). For example, the copper alloy seamless pipe for water supply and hot water supply according to item 1 or 2 of the patent application scope, wherein the copper alloy further contains 0.0005 to 0.0010 mass% of S and 0.0002 to 0.0020 mass% of H.