1. A method of manufacturing a heavy-wall seamless steel pipe comprising subjecting a steel pipe with a wall thickness over 30 mm to a quench-and-tempering treatment process comprising a quenching step (a) and a tempering step (b) as below, in the order as described, the pipe being made through a pipe making step by hot working:
(a) a quenching step that involves heating the steel pipe to a temperature in the range of not less than 900\xb0 C. to not more than 1000\xb0 C. by using, as a heating means, induction heating at a frequency of not more than 200 Hz specifically in a temperature range of at least not less than 750\xb0 C. during the heating stage, and subsequently performing quenching by water cooling; and
(b) a tempering step that involves performing tempering at a temperature in the range of not less than 500\xb0 C. to not more than 750\xb0 C.
2. The method of manufacturing a heavy-wall seamless steel pipe according to claim 1, wherein the quenching step further involves a soaking treatment in a temperature range of not less than 900\xb0 C. to not more than 1000\xb0 C. for 10 minutes or less between the induction heating and the quenching.
3. The method of manufacturing a heavy-wall seamless steel pipe according to claim 1, wherein in performing heating in the quenching step the steel pipe is preliminarily heated from room temperature to a temperature in the range of not less than 600\xb0 C. to not more than 750\xb0 C. by using an atmosphere temperature control type heating furnace.
4. The method of manufacturing a heavy-wall seamless steel pipe according to claim 2, wherein in performing heating in the quenching step the steel pipe is preliminarily heated from room temperature to a temperature in the range of not less than 600\xb0 C. to not more than 750\xb0 C. by using an atmosphere temperature control type heating furnace.
5. The method of manufacturing a heavy-wall seamless steel pipe according to claim 2, wherein the soaking treatment is performed in an atmosphere temperature control type heating furnace.
6. The method of manufacturing a heavy-wall seamless steel pipe according to claim 4, wherein the soaking treatment is performed in an atmosphere temperature control type heating furnace.
7. The method of manufacturing a heavy-wall seamless steel pipe according to claim 1, wherein the seamless steel pipe to be subjected to the quench-and-tempering treatment process is water cooled from a temperature of not less than Ar3 point after pipe making by hot working.
8. The method of manufacturing a heavy-wall seamless steel pipe according to claim 2, wherein the seamless steel pipe to be subjected to the quench-and-tempering treatment process is water cooled from a temperature of not less than Ar3 point after pipe making by hot working.
9. The method of manufacturing a heavy-wall seamless steel pipe according to claim 1, wherein the seamless steel pipe to be subjected to the quench-and-tempering treatment process is soaked at a temperature in the range of not less than 900\xb0 C. to not more than 1000\xb0 C. and is subsequently water cooled after pipe making by hot working.
10. The method of manufacturing a heavy-wall seamless steel pipe according to claim 2, wherein the seamless steel pipe to be subjected to the quench-and-tempering treatment process is soaked at a temperature in the range of not less than 900\xb0 C. to not more than 1000\xb0 C. and is subsequently water cooled after pipe making by hot working.
11. The method of manufacturing a heavy-wall seamless steel pipe according to claim 3, wherein the seamless steel pipe to be subjected to the quench-and-tempering treatment process is soaked at a temperature in the range of not less than 900\xb0 C. to not more than 1000\xb0 C. and is subsequently water cooled after pipe making by hot working.
12. The method of manufacturing a heavy-wall seamless steel pipe according to claim 4, wherein the seamless steel pipe to be subjected to the quench-and-tempering treatment process is soaked at a temperature in the range of not less than 900\xb0 C. to not more than 1000\xb0 C. and is subsequently water cooled after pipe making by hot working.
13. The method of manufacturing a heavy-wall seamless steel pipe according to claim 1, wherein the quench-and-tempering treatment involves an additional quenching step as set forth in claim 1 between the quenching step as set forth in claim 1 and the tempering step.
14. The method of manufacturing a heavy-wall seamless steel pipe according to claim 2, wherein the quench-and-tempering treatment involves the additional quenching step according to step (a) between the quenching step further involving soaking and the tempering step.
15. The method of manufacturing a heavy-wall seamless steel pipe according to claim 2, wherein the quench-and-tempering treatment involves the additional quenching step involving soaking between the quenching step involving soaking and the tempering step.
16. The method of manufacturing a heavy-wall seamless steel pipe according to claim 4, wherein the quench-and-tempering treatment involves an additional quenching step according to step (a) between the quenching step involving preliminary heating and the tempering step.
17. The method of manufacturing a heavy-wall seamless steel pipe according to claim 4, wherein the quench-and-tempering treatment involves the additional quenching involving soaking between the quenching step involving preliminary heating and the tempering step.
18. The method of manufacturing a heavy-wall seamless steel pipe according to claim 5, wherein the quench-and-tempering treatment involves the additional quenching step involving soaking between the quenching step involving soaking in the atmosphere temperature control type heating furnace and the tempering step.
19. The method of manufacturing a heavy-wall seamless steel pipe according to claim 6, wherein the quench-and-tempering treatment involves the additional quenching step involving soaking between the quenching step involving soaking in the atmosphere temperature control type heating furnace and the tempering step.
20. The method of manufacturing a heavy-wall seamless steel pipe according to claim 7, wherein the quench-and-tempering treatment involves an additional quenching step according to step (a) between the quenching step involving water cooling and the tempering step.
21. The method of manufacturing a heavy-wall seamless steel pipe according to claim 8, wherein the quench-and-tempering treatment involves an additional quenching step according to step (a) between the quenching step involving water cooling and the tempering step.
22. The method of manufacturing a heavy-wall seamless steel pipe according to claim 9, wherein the quench-and-tempering treatment involves an additional quenching step according to step (a) between the quenching step involving water cooling and the tempering step.
23. The method of manufacturing a heavy-wall seamless steel pipe according to claim 9, wherein the quench-and-tempering treatment involves the additional quenching step involving soaking between the quenching step involving water cooling and the tempering step.
24. The method of manufacturing a heavy-wall seamless steel pipe according to claim 1, wherein in performing the induction heating, the seamless steel pipe is induction heated without being transferred in a longitudinal direction during heating by using an induction heating device having a coil length longer than the length of the steel pipe to be induction heated.
25. The method of manufacturing a heavy-wall seamless steel pipe according to claim 2, wherein in performing the induction heating, the seamless steel pipe is induction heated without being transferred in a longitudinal direction during heating by using an induction heating device having a coil length longer than the length of the steel pipe to be induction heated.
26. The method of manufacturing a heavy-wall seamless steel pipe according to claim 3, wherein in performing the induction heating, the seamless steel pipe is induction heated without being transferred in a longitudinal direction during heating by using an induction heating device having a coil length longer than the length of the steel pipe to be induction heated.
27. The method of manufacturing a heavy-wall seamless steel pipe according to claim 4, wherein in performing the induction heating, the seamless steel pipe is induction heated without being transferred in a longitudinal direction during heating by using an induction heating device having a coil length longer than the length of the steel pipe to be induction heated.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An exercise device comprising:
a foot strap adjustable to secure the device to a user’s foot;
a pull strap having a first end attached to the foot strap and a second end;
a handle disposed on a second end of the pull strap, the handle configured to allow the user to apply tension to the pull strap; and
a resistance band disposed on the pull strap between the first end and the second end of the pull strap;
the resistance band having two ends;
the resistance band attached in parallel to the pull strap; and
a connector between the pull strap and the resistance band located at each of the two ends of the resistance band, the connectors providing a maximum extension length for the resistance band;
wherein the maximum extension length for the resistance band is generally equivalent to the length of the pull strap disposed between the two ends of the resistance band;
wherein the resistance band includes a length of tube; and
wherein each connector includes:
a ball disposed with the length of tube; and
two sides fixed together to compress the resistance band around the ball disposed within the length of tube;
wherein the force exerted by the two sides against the resistance band and the ball resists any axial force exerted by the extension of the resistance band when the exercise device is used.
2. An exercise device according to claim 1, further comprising an ankle safety strap.
3. An exercise device according to claim 1, further comprising one or more comfort handles having a conical shape.
4. An exercise device according to claim 1, wherein the length of the pull strap disposed between the two ends of the resistance band is adjustable.
5. An exercise device according to claim 1, wherein the pull strap is substantially inelastic.
6. An exercise device comprising:
a pull strap having a first end and a second end;
a handle disposed on the first end of the pull strap, the handle configured to allow a user to apply tension to the pull strap;
an elastic resistance band disposed on the pull strap between the first end and the second end of the pull strap;
a foot strap configured to secure the device to a user’s foot;
the foot strap connected to the second end of the pull strap by a connector configured to provide full freedom of rotation between the pull strap and the foot strap;
the elastic resistance band having two ends and a generally tubular shape;
the elastic resistance band attached in parallel to the pull strap; and
a connection between the pull strap and the elastic resistance band located at each of the two ends of the resistance band, the connection providing a maximum extension length for the resistance band;
wherein the maximum extension length for the elastic resistance band is generally equivalent to the length of the pull strap disposed between the two ends of the elastic resistance band;
wherein each connection includes:
a ball disposed within the elastic resistance band; and
two sides fixed together to compress the elastic resistance band around the ball disposed therein;
wherein the force exerted by the two sides against the elastic resistance band and the ball resists any axial force exerted by the extension of the elastic resistance band when the exercise device is used.
7. An exercise device according to claim 6, further comprising an ankle safety strap.
8. An exercise device according to claim 6, further comprising one or more comfort handles having a conical shape.
9. An exercise device according to claim 6, wherein the length of the pull strap disposed between the two ends of the resistance band is adjustable.
10. An exercise device according to claim 6, further comprising:
the foot strap directly connected to the second end of the pull strap by a connector configured to provided full freedom of rotation between the pull strap and the foot strap; and
wherein the pull strap is substantially inelastic.