Method and apparatus for manufacturing tubes

1. A method for manufacturing a tube made of a non-ferrous material, comprising:

feeding a tube billet in a predetermined feeding direction through a first working station and a second working station, wherein the second working station is downstream of the first working station with respect to the feeding direction of the tube billet and the second working station is so located relative to the first working station that simultaneously a first length segment of the tube billet is located in first working station and a second length segment of the tube billet is located in the second working station and a length segment of the tube billet that leaves the first working station substantially immediately enters the second working station,

working the tube billet in the first working station so that mainly owing to deformation resistance, the temperature of the tube billet under operation rises up to the recrystallization range, at least on the working spot,

working the tube billet in the second working station, 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 working 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 working station.

5. A method according to claim 1 , comprising reducing the wall thickness of the tube billet in the second working station.

6. A method according to claim 1 , comprising reducing the wall thickness of the tube billet by about 50-70% in the second working.

7. A method according to claim 1 , comprising keeping the diameter of the tube billet essentially constant in the second working station.

8. A method according to claim 1 , comprising reducing the diameter of the tube billet in the second working station.

9. A method according to claim 1 , comprising increasing the diameter of the tube billet in the second working station.

10. A method according to claim 1 , comprising rolling the tube billet with at least one roll in the second working station.

11. A method according to claim 1 , comprising rolling the tube billet in the first working station.

12. A method according to claim 1 , comprising rolling the tube billet in at least one of the working stations.

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, 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 billet 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 arrangement including at least one roll element for performing a first working step and the second rolling arrangement performs at least a second working step, and

means for creating non-oxidizing conditions, so that at least during the first and second working steps the tube billet is kept in non-oxidizing conditions.

16. An apparatus according to claim 15 , wherein the means for creating non-oxidizing conditions comprise at least one protective gas chamber.

17. An apparatus according to claim 15 , 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 roll element of the first rolling arrangement is a conical roll element and the conical roll element of the first rolling arrangement decreases in diameter in the feeding direction of the tube billet.

19. An apparatus according to claim 15 , wherein the roll element of the first rolling arrangement is a conical roll element and the conical roll element of the first rolling arrangement increases in diameter in the feeding direction of the tube billet.

20. An apparatus according to claim 15 , wherein the first rolling arrangement is a planetary mill comprising at least three conical roll elements.

21. An apparatus according to claim 20 , comprising at least one other rolling arrangement that is a planetary mill.

22. An apparatus according to claim 15 , wherein the second rolling arrangement includes at least one roll having a rotary axis that is inclined to the longitudinal axis of the tube billet.

23. An apparatus according to claim 15 , wherein the second rolling arrangement includes at least one roll having a rotary axis that parallel to the longitudinal axis of the tube billet.

24. An apparatus according to claim 15 , wherein the second rolling arrangement includes at least one roll having a rotary axis that is essentially perpendicular to a plane that is tangential to the longitudinal axis of the tube billet.

25. An apparatus according to claim 15 , comprising at least one mandrel element.