Copper alloy tube for heat exchangers
A copper alloy tube according to the present invention includes Sn 0.1 to 2.0 mass %, P 0.005 to 0.1 mass %, S 0.005 mass % or less, O 0.005 mass % or less, and H 0.0002 mass % or less, and the remainder has a composition consisting of Cu and unavoidable impurities. And, as is annealed, the copper alloy tube has the following characteristics: a tensile strength in the longitudinal direction of the copper alloy tube is 250 N/mm 2 or more; an average grain diameter is 30 μm or less when measured in the direction perpendicular to the thickness direction of the tube, in the cross section perpendicular to the tube axis; and assuming that a tensile strength in the longitudinal direction of the copper alloy tube is σL, and a tensile strength in the circumferential direction of the same is σT, σT/σL>0.93 holds. [With such structure, the copper alloy tube can have a sufficiently high pressure-resistant breaking strength (breaking pressure) without deteriorating its bending workability due to an unnecessarily enhanced tensile strength, and further is excellent in its bending workability and heat resistance.]
1. A copper alloy tube for a heat exchanger, comprising:
Sn 0.1 to 2.0 mass %, P 0.005 to 0.1 mass %, S 0.005 mass % or less, O 0.005 mass % or less, and H 0.0002 mass % or less; and
the remainder has a composition consisting essentially of Cu and unavoidable impurities,
wherein the copper alloy tube has, as is annealed, the following characteristics:
a tensile strength in the longitudinal direction of the copper alloy tube is 250 N/mm 2 or more;
an average grain diameter is 30 μm or less when measured in the direction perpendicular to the thickness direction of the tube, in the cross section perpendicular to the tube axis; and
σT/σL>0.93, where σL is the tensile strength in the longitudinal direction of the copper alloy tube and σT is the tensile strength in the circumferential direction of the same copper alloy tube.
2. The copper alloy tube for a heat exchanger according to claim 1 , wherein the tube further comprises Zn 0.01 to 1.0 mass %.
3. The copper alloy tube for a heat exchanger according to claim 1 , wherein the tube further comprises a total amount of 0.005 to 0.07 mass % of Fe, Ni, Mn, Mg, Cr, Ti, and Ag.
4. The copper alloy tube for a heat exchanger according to claim 1 , wherein the tube has, as is subjected to drawing processing, the following characteristics:
the tensile strength in the longitudinal direction of the copper alloy tube is 280 N/mm 2 or more; and
an average grain diameter is 30 μm or less when measured in the direction perpendicular to the thickness direction of the tube, in the cross section perpendicular to the tube axis.
5. The copper alloy tube for a heat exchanger according to claim 1 , wherein the copper alloy tube for a heat exchanger has, as is heated at 800° C. for 15 seconds, an average grain diameter of 100 μm or less when measured in the direction perpendicular to the thickness direction of the tube in the cross section perpendicular to the tube axis.
6. The copper alloy tube for a heat exchanger according to claim 1 , wherein the copper alloy tube is an inner grooved tube.
7. The copper alloy tube for a heat exchanger according to claim 1 , wherein σT/σL>0.95.
8. The copper alloy tube for a heat exchanger according to claim 1 , wherein the S content is 0.003 mass % or less.
9. The copper alloy tube for a heat exchanger according to claim 1 , wherein the S content is 0.0015 mass % or less.
10. The copper alloy tube for a heat exchanger according to claim 1 , wherein the H content is 0.0001 mass % or less.
11. The copper alloy tube for a heat exchanger according to claim 1 , wherein the average grain diameter is 20 μm or less when measured in the direction perpendicular to the thickness direction of the tube, in the cross section perpendicular to the tube axis.
12. The copper alloy tube for a heat exchanger according to claim 1 , wherein the average grain diameter is 15 μm or less when measured in the direction perpendicular to the thickness direction of the tube, in the cross section perpendicular to the tube axis.
13. The copper alloy tube for a heat exchanger according to claim 3 , wherein the tube further comprises a total amount of 0.005 to 0.05 mass % of Fe, Ni, Mn, Mg, Cr, Ti, and Ag.
14. The copper alloy tube for a heat exchanger according to claim 3 , wherein the tube further comprises a total amount of 0.005 to 0.03 mass % of Fe, Ni, Mn, Mg, Cr, Ti, and Ag.
15. An copper alloy tube for a heat exchanger, comprising:
Sn 0.1 to 2.0 mass %, P 0.005 to 0.1 mass %, S 0.005 mass % or less, O 0.005 mass % or less, and H 0.0002 mass % or less; and
the remainder has a composition consisting essentially of Cu and unavoidable impurities,
wherein the copper alloy tube has, as annealed, the following characteristics:
a tensile strength in the longitudinal direction of the copper alloy tube is 250 N/mm 2 or more;
an average grain diameter is 30 μm or less when measured in the direction perpendicular to the thickness direction of the tube, in the cross section perpendicular to the tube axis; and
σT/σL≧0.95, where σL is the tensile strength in the longitudinal direction of the copper alloy tube and σT is the tensile strength in the circumferential direction of the same copper alloy tube.
16. The copper alloy tube for a heat exchanger according to claim 15 , wherein the tube further comprises Zn 0.01 to 1.0 mass %.
17. The copper alloy tube for a heat exchanger according to claim 15 , wherein the tube further comprises a total amount of 0.005 to 0.07 mass % of Fe, Ni, Mn, Mg, Cr, Ti, and Ag.
18. The copper alloy tube for a heat exchanger according to claim 15 , wherein the tube has, as is subjected to drawing processing, the following characteristics:
the tensile strength in the longitudinal direction of the copper alloy tube is 280 N/mm 2 or more; and
an average grain diameter is 30 μm or less when measured in the direction perpendicular to the thickness direction of the tube, in the cross section perpendicular to the tube axis.
19. The copper alloy tube for a heat exchanger according to claim 15 , wherein the copper alloy tube for a heat exchanger has, as is heated at 800° C. for 15 seconds, an average grain diameter of 100 μm or less when measured in the direction perpendicular to the thickness direction of the tube in the cross section perpendicular to the tube axis.
20. The copper alloy tube for a heat exchanger according to claim 15 , wherein the copper alloy tube is an inner grooved tube.