GB2128207A

GB2128207A - Heat treatment of pipes

Info

Publication number: GB2128207A
Application number: GB08326629A
Authority: GB
Inventors: Klaus Keutmann; Wolfgang Sabatschus; Heinz Bartkowski
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1982-10-05
Filing date: 1983-10-05
Publication date: 1984-04-26
Also published as: DE3237193A1; SE8305449L; IT8322552A0; NL8302697A; FR2533942B1; FR2533942A1; SE8305449D0; IT1169544B; DE3237193C2; JPS5970727A; GB2128207B; GB8326629D0

Abstract

In the heat treatment of pipes they are continuously passed through an annealing chamber (2) and then through cooling chambers (3 and 4) and a faster cooling of the continuously heated pipes is made possible by evacuating the annealing chamber and the cooling chambers of gas, prior to the introduction of the pipes, preferably through the application of an under pressure of at least 10<-1> mbar at 80 DEG C. Multiple stage vacuum locks (9) ensure the maintenance of the vacuum. Alternatively or additionally, during the passing of the pipes through the chambers an atmosphere poor in oxygen may be maintained. A protective gas may also be applied. <IMAGE>

Description

SPECIFICATION Heat treatment of pipes The invention relates to the heat treatment of pipes, and has particular application to pipes of high-grade steel,titanium or non-ferrous metals oralloysthereof.

The invention is especially suited to the treatment of seam welded pipes formed from sheets. It is known to heat such pipes to high temperatures, for example 110000, and then to cool them.

The heating is commonly accomplished inductively, the pipes running continuously firstly through an annealing chamberwith an induction coil and then through a typicallywater-cooled cooling chamber. To increase the cooling effect in the cooling chamber, carbon jaws surrounding the pipe surface can be provided, so that cooling of the pipe also takes place through heat conduction.

The rate of cooling in known methods is relatively low, and the pipes must be passed through the chambers slowly in order to achieve a sufficient cooling.

The present invention is directed at a means by which a quicker cooling of continuously heated pipes is made possible. According to the invention the annealing and cooling chambers are evacuated while the pipes pass therethrough. Alternatively or additionally, the atmosphere in the chambers is maintained poor in oxygen. A protective gas; e.g. argon, may be introduced into either or both chambers.

The under pressure in the chambers is normally maintained at at least 10-1 mbar, usually applied at 8000. The cooling is normally water cooling, with the cooling watertemperature set at at least 4000. The introduction of a protective gas is usually at a rate of at least 40 m/sec, and preferably directed pastthe outer surface ofthe pipes in a direction opposite to that of passage of the pipes through the chamber.

In apparatus according to the invention the respective chambers are normally intercommunicating and sealed externally by vacuum locks. Preferably, the locks are multiple stage vacuum locks atthe pipe entry to the annealing chamber and the pipe exitfrom the cooling chamber, the locks being adapted to seal around the circumference of pipes and to return any leaked protective gas to the introducing means.

Two embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. It will be appreciated that features of one embodiment may be adopted in the other, and vice versa. In the drawings: Figure 1 shows a longitudinal section through a first embodiment (pure gas cooling, gas as heat carrier); Figure 2 shows a longitudinal section through a second form of embodiment (solid matter-surface contact-- cooling); Figure 3 shows in cross-section the arrangement of the carbon jaws in the cooling chamber; and Figure 4 shows vacuum lock chambers at the entry side of the pipes into the apparatus.

Figure 1 shows a first cooling chamber joined on to an annealing chamber 2, which is surrounded by an induction coil 5, the first cooling chamber3 being constructed with double walls, whereby the intermediate space between the walls has cooling water 6 flowing through it. In communication with this cooling chamber 3 is a second cooling chamber 4. In this cooling chamber, carbon jaws 7 are arranged at intervals one behind the other, which embrace the pipes 1 in the manner of a shell. These carbon jaws are water-cooled, indicated by the ducts 8. The arrangement of the cooling jaws 7 in the cooling chamber4 can also be seen from Figure 3.At the entry of the pipes into the device and also atthe exit, facilities are provided which simply enable the through passage of the pipes, but in addition permit a vacuum to be applied to the intercommunicating chambers 2,3 and 4, in order to remove the gas from these chambers.

Figure 4 illustrates as such as such a facility, a multiple stage vacuum lock 9. in a corresponding manner such a lock can also be provided on the pipe outlet side of the apparatus.

In the embodiment represented in Figure 2 there are no carbon jaws in the cooling chamber 4, but rather the pipe is surrounded, at a distance, by a cooling coil.

Here, too, as in the example embodiment previously described, the heat emission from the pipes; i.e., the cooling, takes place through thermal radiation. In this embodiment ducts 10 open into the cooling chamber 4,throughwhich a protective gas is able to be introduced, and the cooling effecttherebyisfurther increased in thatthe inlets of protective gas are arranged such that the protective gas is introduced in counter current in relation to the direction of move mentofthe pipes.

CLAIMS:

1. A method of heat treating pipes comprising annealing and cooling the pipes in passage through respective chambers after welding, wherein the cham bers are substantially evacuated as the pipes pass through the chambers.

2. A method according to Claim 1 wherein the under pressure in the chambers is maintained at at Isast 10-1 mbar.

3. A method according to Claim 2 wherein the under pressure is applied at at least 800C.

4. A method according to any preceding Claim wherein the cooling step is carried out using water cooling, with the water temperature set at at least 40 C.

5. A method according to any preceding Claim including the step of introducing a protective gas into the cooling chamber after it has been evacuated.

6. A method according to Claim 5 wherein the protective gas is argon.

7. A method according to Claim or Claim 6 wherein the protective gas is introduced at a rate of at least 40 m/sec.

8. A method according to any of Claims 5 to 7 wherein the protective gas is directed past the outer surface ofthe pipes in a direction opposite to that of passage of the pipes through the chamber.

9. A method of heat treating pipes comprising annealing and cooling the pipes in passage through respective chambers, wherein the atmosphere in the chamber is maintained poor in oxygen as the pipes pass through the chambers.

10. A method according to Claim 9 and to any of Claims 1 to 8.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Heat treatment of pipes The invention relates to the heat treatment of pipes, and has particular application to pipes of high-grade steel,titanium or non-ferrous metals oralloysthereof. The invention is especially suited to the treatment of seam welded pipes formed from sheets. It is known to heat such pipes to high temperatures, for example 110000, and then to cool them. The heating is commonly accomplished inductively, the pipes running continuously firstly through an annealing chamberwith an induction coil and then through a typicallywater-cooled cooling chamber. To increase the cooling effect in the cooling chamber, carbon jaws surrounding the pipe surface can be provided, so that cooling of the pipe also takes place through heat conduction. The rate of cooling in known methods is relatively low, and the pipes must be passed through the chambers slowly in order to achieve a sufficient cooling. The present invention is directed at a means by which a quicker cooling of continuously heated pipes is made possible. According to the invention the annealing and cooling chambers are evacuated while the pipes pass therethrough. Alternatively or additionally, the atmosphere in the chambers is maintained poor in oxygen. A protective gas; e.g. argon, may be introduced into either or both chambers. The under pressure in the chambers is normally maintained at at least 10-1 mbar, usually applied at 8000. The cooling is normally water cooling, with the cooling watertemperature set at at least 4000. The introduction of a protective gas is usually at a rate of at least 40 m/sec, and preferably directed pastthe outer surface ofthe pipes in a direction opposite to that of passage of the pipes through the chamber. In apparatus according to the invention the respective chambers are normally intercommunicating and sealed externally by vacuum locks. Preferably, the locks are multiple stage vacuum locks atthe pipe entry to the annealing chamber and the pipe exitfrom the cooling chamber, the locks being adapted to seal around the circumference of pipes and to return any leaked protective gas to the introducing means. Two embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. It will be appreciated that features of one embodiment may be adopted in the other, and vice versa. In the drawings: Figure 1 shows a longitudinal section through a first embodiment (pure gas cooling, gas as heat carrier); Figure 2 shows a longitudinal section through a second form of embodiment (solid matter-surface contact-- cooling); Figure 3 shows in cross-section the arrangement of the carbon jaws in the cooling chamber; and Figure 4 shows vacuum lock chambers at the entry side of the pipes into the apparatus. Figure 1 shows a first cooling chamber joined on to an annealing chamber 2, which is surrounded by an induction coil 5, the first cooling chamber3 being constructed with double walls, whereby the intermediate space between the walls has cooling water 6 flowing through it. In communication with this cooling chamber 3 is a second cooling chamber 4. In this cooling chamber, carbon jaws 7 are arranged at intervals one behind the other, which embrace the pipes 1 in the manner of a shell. These carbon jaws are water-cooled, indicated by the ducts 8. The arrangement of the cooling jaws 7 in the cooling chamber4 can also be seen from Figure 3.At the entry of the pipes into the device and also atthe exit, facilities are provided which simply enable the through passage of the pipes, but in addition permit a vacuum to be applied to the intercommunicating chambers 2,3 and 4, in order to remove the gas from these chambers. Figure 4 illustrates as such as such a facility, a multiple stage vacuum lock 9. in a corresponding manner such a lock can also be provided on the pipe outlet side of the apparatus. In the embodiment represented in Figure 2 there are no carbon jaws in the cooling chamber 4, but rather the pipe is surrounded, at a distance, by a cooling coil. Here, too, as in the example embodiment previously described, the heat emission from the pipes; i.e., the cooling, takes place through thermal radiation. In this embodiment ducts 10 open into the cooling chamber 4,throughwhich a protective gas is able to be introduced, and the cooling effecttherebyisfurther increased in thatthe inlets of protective gas are arranged such that the protective gas is introduced in counter current in relation to the direction of move mentofthe pipes. CLAIMS:

6. A method according to Claim 5 wherein the protective gas is argon.

10. A method according to Claim 9 and to any of Claims 1 to 8.

11. A method of heattreating seam welded pipes substantially as described herein with reference to Figure 1 or Figure 2 ofthe accompanying drawings.

12. Apparatus for heat treating pipes comprising annealing and cooling chambers; means for passing pipes through the chambers; and meansforsubstan tiallyevacuating the chambers as pipes pass therethrough.

13. Apparatus according to Claim 12 havingtwo cooling chambers, and wherein the chambers are intercommunicating and sealed externally by vacuum locks.

14. Apparatus for heat treating pipes comprising annealing and cooling chambers; means for passing pipes through the chambers; and means for introduc inS a protective gas to at least the cooling chamber as pipes passtherethrough.

15. Apparatus according to Claim 14 and to Claim 12 or Claim 13.

16. Apparatus according to Claim 15 including multiple stage vacuum locks atthe pipe entryto the annealing chamber and the pipe exit from the cooiin, chamber, the locks being adapted to seal around the circumference of pipes and to return any leaked protective gas to the introducing means.

17. Apparatus according to any of Claims 12 to if including groups of at least two carbon jaws spaced along the path of pipesthrough the cooling charnbes thejaws each having a cooling block and being formed with a concave surfacefor engaging pipes in the chambers.

18. Apparatus for heat treating pipes substant as described herein with reference to Figure 1 or Figure 2 of the accompanying drawings.