Method and apparatus for manufacturing tubes by rolling
A method for manufacturing a tube made of a non-ferrous material, particularly a tube made of mainly copper, by rolling, in which method, in the first working step the tube billet is worked by rolling with conical rolls, so that mainly owing to the deformation resistance, the temperature of the billet under operation rises up to the recrystallization range, at least on the spot that is being worked. Essentially immediately after the first working step, the tube billet is subjected to at least one second working step with a second set of conical rolls, in which case the tube billet is maintained, at least during the first working step and at least a second working step in non-oxidizing conditions. The invention also relates to an apparatus.
1. A method for manufacturing a tube made of a non-ferrous material, comprising:
feeding a tube billet in predetermined feeding direction through a first rolling station and a second rolling station, wherein the second rolling station downstream of the first rolling station with respect to the feeding direction of the tube and the second rolling station is so located relative to the first rolling station that simultaneously a first length segment of the tube billet is located in the first rolling station and a second length segment of the tube billet is located in the second rolling station and a length segment of the tube billet that leaves the first rolling station substantially immediately enters the second rolling station,
working the tube billet in the first rolling station by rolling with conical rolls, so that mainly owing to deformation resistance, the temperature of the billet under operation rises up to the recrystallization range, at least on the working spot,
working the tube billet at the second rolling station by rolling with a second set of conical rolls, and
keeping at least the first and second length segments of the tube billet in non-oxidizing conditions.
2. A method according to claim 1 , wherein the second length segment of the tube billet is separated from the first length segment of the tube billet by a third length segment that is between the first and second rolling stations, and the method comprises keeping the third length segment of the tube billet in non-oxidizing conditions.
3. A method according to claim 1 , comprising providing the non-oxidizing conditions by means of a protective gas chamber which contains protective gas.
4. A method according to claim 1 , comprising cold working the tube billet in the first rolling station.
5. A method according to claim 1 , comprising reducing the wall thickness of the tube billet in the second rolling station.
6. A method according to claim 1 , comprising reducing the wall thickness of the tube billet about 50-70% in the second rolling station.
7. A method according to claim 1 , wherein the diameter of the tube billet remains essentially constant in the second rolling station.
8. A method according to claim 1 , comprising reducing the diameter of the tube billet in the second rolling station.
9. A method according to claim 1 , comprising increasing the diameter of the tube billet in the second rolling Station.
10. A method according to claim 1 , comprising carrying out several successive rolling operations at the second rolling station.
11. A method according to claim 1 , comprising working the tube billet by planetary rolling at the second rolling station.
12. A method according to claim 1 , comprising working the tube billet by planetary rolling at the second rolling station.
13. A method according to claim 1 , wherein the tube billet is a continuously cast billet.
14. A method according to claim 1 , comprising adjusting the temperature of the tube billet when necessary.
15. An apparatus for working a tube billet by rolling, said apparatus comprising:
first and second rolling arrangements, wherein the second rolling arrangement is downstream of the first rolling arrangement with respect to a feeding direction of the tube and the second rolling arrangement is so located relative to the first rolling arrangement that simultaneously a first length segment of the tube billet is located in the first rolling arrangement and a second length segment of the tube billet is located in the second rolling arrangement and a length segment of the tube billet that leaves the first rolling arrangement substantially immediately enters the second rolling arrangement, wherein the first rolling arrangement comprises a planetary rolling arrangement including at least one conical roll element for performing a first working step and the second rolling arrangement performs at least one second working step, and
means for creating non-oxidizing conditions at least at the first and second rolling arrangements.
16. An apparatus according to claim 15 , wherein the means for creating non-oxidizing condition comprise a protective gas chamber for protecting the tube billet.
17. An apparatus according to claim 16 , wherein the protective gas chamber surrounds the first and second rolling arrangements and the space provided therebetween at least in the vicinity of the tube billet.
18. An apparatus according to claim 15 , wherein the conical roll element of the first rolling arrangement of greater diameter on the input side than on the output side.
19. An apparatus according to claim 15 , wherein the conical roll element of the first rolling arrangement of greater diameter on the output side than on the tube billet input side.
20. An apparatus according to claim 15 , wherein the first rolling arrangement is a planetary including at least three conical roll elements.
21. An apparatus according to claim 15 , comprising at least one other planetary mill.
22. An apparatus according to claim 15 , wherein at least one roll of the second rolling arrangement has an axis of rotation that is inclined to with the longitudinal axis of the tube billet.
23. An apparatus according to claim 15 , wherein at least one roll of the second rolling arrangement has an axis of rotation that is parallel with the longitudinal axis of the tube billet.
24. An apparatus according to claim 15 , comprising at least one mandrel element.