HEAT TREATMENT OF HARDENABLE CARBON STEEL PIPES

Abstract: An apparatus for heat treating hardenable steel pipes (10) comprises a production line (11), along which a pipe is moveable in a first direction, an input station (12), an induction heater (13) and an outlet station (14). The process of hardening the pipe involves advancing the pipe into an induction heater (13). After the pipe has been moved through the induction heater it is quenched. Adjustment means comprising a lance mechanism enables a quench head and lance to be moved axially in a direction away from the heater (13) until the quench head is clear of the pipe.

Description: HEAT TREATMENT OF HARDENABLE CARBON STEEL PIPES This invention relates to an apparatus and process for hardening a steel pipe by heating and then quenching the pipe. A known method of heat treating eutectoid steel is to first convert the ferrite phase to austenite by heating the steel to temperatures of the order of 1000°C. The steel is then cooled sufficiently rapidly for the austenite phase to convert to martensite rather than to ferrite and carbide. A known apparatus for carrying out the above described method is described in European patent application no 0151838 in the name of the present Applicant, to which reference is herein directed. The apparatus described therein comprises an annular induction heater for enclosing and heating an annular zone of a pipe. A quench head serves to quench the internal surface of the pipe in the heated zone. The quench head is axially aligned with the pipe axis and is supported by an elongate lance which also provides cooled water to the quench head. The lance is supported at one end by a support tower mechanism. A problem with this known method and apparatus for heat treating a eutectoid steel pipe is that after the pipe has been moved through the induction heater and quenched it is positioned over the lance and must therefore be reversed back to its initial position, and taken off rollers which support it, before a new section of pipe can be delivered onto the rollers and the process may be repeated. This means that the time taken to heat treat one length of pipe is relatively long. A second problem with the known method and apparatus f.or heat treating a hardenable carbon steel pipe is that it is not suitable for slender pipes having a narrow diameter of for example less than 100mm, nor is it suitable for thin wall pipes having thinner walls, for example 8mm or less thick. This is because deformity occurs during the heat treatment and also it is difficult to control the hardening of sections of the pipe wall in such pipes. A third problem with the known apparatus and process, is that as the pipe is moved through the induction heater, it is often inadequately supported, which results in deformed pipes after processing. According to the first aspect of the invention, there is provided apparatus for heat treating a hardenable carbon steel pipe having a predetermined length comprising: a heater for enclosing and heating a zone of the pipe; a quench head for emitting a cooling fluid onto the interior surface of the pipe, proximate said zone; a lance having a first end and an opposite end, the quench head being supportable by the lance and attachable to the first end; supply means for supplying fluid to the lance head, which supply means is attachable to the second end of the lance, characterised in that the apparatus further comprises adjustment means for enabling the lance to move axially such that the quench head moves between a first position and a second position, the distance between the first and second positions being at least equal to the length of the pipe. In order to heat treat a pipe by means of the apparatus according to the invention, a pipe to be treated is caused to move axially in a first direction, such that it passes through the heater. As the pipe moves in the first direction through the heater it moves into a position over the lance. Because the quench head is moveable axially through a distance greater than the length of the pipe being quenched, once the pipe has been heat treated, it is possible to retract the quench head such that it is no longer positioned within the pipe, which pipe may then be removed without having to move the pipe in an opposite direction to the first direction. This means that the total time taken to heat treat a pipe is considerably reduced. Preferably, the opposite end of the lance is connected to the supply means by means of a high pressure hose mounted on a hose drum. Thus, as the distance between the opposite end of the lance and the supply means increases, the hose is unwound from the drum to accommodate the increased distance. Similarly, when the lance moves in a direction towards the supply means, the hose may be rewound onto the drum. Advantageously, the movement of the lance is controlled by a conveyor belt driven by a drive sprocket. The lance is supportable on the conveyor chain, and rotation of the sprocket causes the lance to move in a particular direction. Rotation of the sprocket in an opposite sense causes the lance to move in an opposite direction. Preferably, the pipe is supported by rollers which rollers are driveable in order to cause the pipe to move through the induction heater in a first direction. Advantageously, the rollers are positioned such that their axis of rotation is perpendicular to the axis of the pipe, and the surface of each roller is formed into a groove which is shaped to fit the pipe being treated. Known rollers typically comprise a V-shaped groove, in which a pipe is positionable. This means that they are able to be used with pipes having a range of diameters. However, it also means that they are not able to properly support the pipe, since a proportion of the surface of the pipe will not be in contact with the roller. By means of the roller of the present invention, although a particular roller may only be used with a pipe having a given diameter, the shape of the roller is chosen to fit as exactly as possible with the diameter of the pipe, and therefore the pipe is more adequately supported. The groove is thus curved. Preferably, the pipe is supported by a plurality of spaced apart rollers positioned both above and below the axis of the pipe. This further improves the support for the pipe. Preferably, the apparatus comprises: an input station comprising a magazine, and a rack for supplying pipes from the magazine onto a production line the production line comprising: a set of input rollers, an induction heater and a series of output rollers; and an output station comprising a rack by which rollers may be kicked off the production line and onto an output line. The lance and quench head are positioned between the heater and the output station and are moveable axially towards the induction heater. Once the pipe has emerged onto the series of output rollers, the adjustment means is operable to retract the lance in a direction away from the induction heater. This allows the heat treated pipe to be kicked off the production line and onto the rollers at the output line. Advantageously, the apparatus includes sensors to determine when the pipe has completely emerged from the induction heater and positioned on the series of output rollers. When the position of the pipe has been so determined, the adjustment means is activated to retract the lance, and the pipe is kicked off the production line and onto the output line. Advantageously the heater is an induction heater which heats an annular zone of the pipe. Preferably the cooling fluid is water soluble oils, a mix of air or water, or proprietary coolants. According to a second aspect of the invention there is provided apparatus for heat treating a hardenable carbon steel pipe comprising: a heater for enclosing and heating a zone of the pipe; a quench head for emitting a cooling fluid onto an interior surface of the pipe, proximate said zone; support means for supporting and moving the pipe through the induction heater and over the quench head, characterised in that the support means comprises a plurality of rollers, the surface of each of which rollers is shaped into a groove having a dimension to fit the diameter of the particular pipe being treated. According to a third aspect of the invention there is provided a method of heat treating a hardenable steel pipe comprising the steps of: moving a pipe along a production line in a first direction, through heating means thereby to heat a zone of a pipe to austenising temperature; simultaneously quenching the heated pipe proximate to the heat zone by means of a quenching head supported by a lance, characterised in that the pipe is removed from the production line by causing the quench head to move axially in an direction opposite to the first direction. By means of the method according to the third aspect of the invention, it is possible to heat treat a pipe and then to remove the pipe from the production line without having to cause the pipe to move in a reverse direction in order to disengage it from the lance and quench head. This significantly improves the efficiency of the process. The invention will now be further described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of an apparatus according to the first aspect of the invention; Figure 2 is a more detailed representation of the lance mechanism of the apparatus of Figure 1; Figure 3 is a schematic representation of the apparatus of Figure 1 showing the lance mechanism of Figure 2; Figure 4 is a detailed representation of the rollers used for supporting a pipe in the apparatus of Figure 1; Figure 5 is a schematic diagram of the drive arrangement for driving the rollers of Figure 4; Figure 6 is a schematic representation of the apparatus of Figure 1 showing the rollers of Figure 4; Figures 7 to 12 are schematic representations of the quench head of the apparatus of Figure 1. Referring to Figure 1, apparatus for heat treating hardenable steel pipes is designated generally by the reference numeral 10. The apparatus 10 comprises a production line 11 along which a pipe is moveable in a first direction, an input station 12, an induction heater 13, and an outlet station 14. The input station 12 comprises a magazine 15 and a rack 16. Pipes from the magazine 15 are rolled down the rack 16 onto an series of output rollers 17. A pipe thus positioned will travel along the production line through the induction heater 13. While the pipe is moving through the induction heater 13, it will also pass over a quench head (not shown) which is supported by and attached to a lance 18 which also provides cooling water to the quench head. The lance 18 is supported at one end by a geared chain (Figure 2) . The process of hardening a pipe involves advancing the pipe from the series of input rollers into the induction heater 13 which heats a small annular zone of the pipe as it is moves through the heater 13, and over the quench head. The pipe is advanced by driving the rollers 17. After the pipe has been moved through the induction heater and quenched, adjustment means comprising a lance mechanism (Figure 2) enables the quench head and lance to be moved axially in the direction away from the heater 13, until the quench head is clear of the pipe. The pipe may then be caused to roll off the output rollers 19 down the rack 14 and to output station 20. Sensors are positioned along the production line to detect when a pipe has completely passed through the heater 13, and is thus positioned on the series of output rollers. When this has been detected, the lance mechanism will be activated to retract fully the quench head and lance, and the pipe will be kicked off the production line. Referring to Figure 2, the lance mechanism is shown in more detail. The lance 18 is connected to a high pressure water supply, by means of a high pressure hose 22 which in turn is connected to a hose drum 23. A sprocket 24 serves to drive the conveyor belt 25, which in turn causes the lance 18 to move either towards the induction heater 13 or away from the induction heater 13, depending on the direction of rotation of the sprocket. A guide wheel 26 guides the lance 18 as it moves. As the lance 18 moves in a direction away from the drum 23, the hose is caused to unwind from the drum thus increasing the distance between the lance 18 and the drum 23. When the lance 18 is caused to move in an opposite direction, the hose 22 will rewind onto the drum 23. The drive sprocket is responsive to the sensors 26, (Figure 1) which sense when a pipe is positioned on the output series of rollers. At the beginning of the heat treatment process, the lance 18 will be positioned such that the quench head 27 is positioned within the induction process 13 proximate to the annular zone heated by the induction heater 13. When the pipe is positioned clear of the heater 13 on the series of output rollers, the drive sprocket will be caused to rotate such that the lance 18 retracts away from the induction heater 13 and completely clear of the pipe. Once this has occurred, the pipe may be kicked off such that it rolls down the rack 14 and to the output station. By means of this mechanism therefore it is not necessary for the pipe to be reversed back into its initial position in order to take it off the rollers. Referring to Figure 3, the apparatus in Figure 4 is shown in cross section showing the lance mechanism 30 and the series of output rollers. Referring to Figure 4, the rollers used in the apparatus of Figure 1 are shown in more detail. As can be seen from Figure 4, each roller 40 is shaped to fit the circumference of the pipe being heat treated. This means that a particular roller can only be used with a pipe of a given circumference. However, the advantage of such a roller is that it more fully supports the pipe and thus reduces the possibility that the pipe will bend or be subject to stresses during the heat treatment. Figure 4 is a view looking down on the apparatus, and shows a first series of rollers. The pipe will be supported underneath by a similar series of rollers. The apparatus also includes a quench head support 41 which ensures that the quench head 41 when moving towards the induction heater 13 is aligned correctly with the pipe, and therefore is correctly positioned within the pipe. Referring to Figure 5, the drive arrangement for the rollers is shown. Referring to Figures 7 to 12, the quench head is shown in more detail. The quench head 70 comprises a front nozzle 71 mounted on a body 72. The body 72 is threaded internally as shown in Figure 9 in order that it may be attached to an end of the lance 18. Water is directed from the lance out of the nozzle 71 under pressure to produce an even conical sheet spray towards the interior surface of the pipe at an angle thereto of less than 25°C. The shape of the body of the quench head is shown in Figures 8 to 12. The quench head is designed to control the quench water at high pressure (typically 1500 psi) to produce a smooth conical spray in the opposite direction of water flowing up the pipe. The conical spray must have an angle such that the contact angle between the spray and the pipe wall is less than 30 degrees (typically 22 degrees) which controls the water to maintain contact with the pipe wall as well as creating a vacuum in the pipe which draws any extraneous or mis-diverted water down the pipe into the general body of the spray, therefore controlling the cooled area. It is most important that: 1. The angle of the conical spray maintains the contact with the pipe wall after contact. 2. The velocity of the water will penetrate any steam barrier formed ahead of it. 3. All the water including back spray is removed away from the impact zone. The quench comprises three parts, namely the body 72, a stem and a cone. The body 72 houses the stem which is a loose fit inside and provides a fine threaded stem to attach the cone which is adjustable so that the volume and the velocity of the water can be controlled by varying the orifice the volume of water, and the pressure of the water. A particular feature of the cone is that internal angle of the cone is less than 25 degrees and that the maximum diameter of the cone is larger than the mating surface of the body. This maximum diameter is also sharp edged which prevents flow over the end, and produces a smooth equi-cone. By making the stem of the head slightly loose inside the body the water pressure centralizes the stem and the cone. It is to be understood that the rollers used in the apparatus illustrated in the above description may also be incorporated into a conventional heat treatment apparatus for example one of the type described in European patent application no 0151838, to which reference is herein directed.

Claims: CLAIMS 1. Apparatus for heat treating a hardenable carbon steel pipe having a predetermined length comprising: a heater for enclosing and heating a zone of the pipe; a quench head for emitting a cooling fluid onto the interior surface of the pipe, approximate said zone; a lance having a first end and an opposite end, the quench head being supportable by the lance and attachable to the first end; supply means for supplying fluid to the lance head, which supply means is attachable to the second end of the lance, characterised in that the apparatus further comprises adjustment means for enabling the lance to move axially, such that the quench head moves between a first position and a second position, the distance between the first and second positions being at least equal to the length of the pipe. 2. Apparatus as claimed in claim 1 wherein the opposite end of the lance is connected to the supply means by means of a high pressure hose mounted on a hose drum. 3. Apparatus according to claim l or claim 2 wherein the movement of the lance is controlled by a conveyor belt driven by a drive sprocket. 4. Apparatus according to any one of the preceding claims wherein the pipe is supported by rollers, which rollers are driveable in order to cause the pipe to move through the induction heater in a first direction. 5. Apparatus according to any one of the preceding claims wherein the rollers are positioned such that each axis of rotation is perpendicular to the axis of the respective pipe, and the surface of each roller is formed into a groove which is shaped to fit the pipe being treated. 6. Apparatus according to any one of the preceding claims, wherein the pipe is supported by a plurality of spaced apart rollers positioned both above and below the axis of the pipe. 7. Apparatus according to any one of the preceding claims, wherein the apparatus comprises: an input station comprising a magazine, and a rack for supplying pipes from the magazine onto a production line, the production line comprising: a set of input rollers, an induction heater and a series of output rollers; and an output station comprising a rack by which rollers may be kicked off the production line and onto an output line. 8. Apparatus according to any one of the preceding claims, further comprising sensors to determine when the pipe has completely emerged from the induction heater and positioned on the series of output rollers. 9. Apparatus according to any one of the preceding claims, wherein the heater is an induction heater which heats an annular zone of the pipe. 10. Apparatus for heat treating a hardenable carbon steel pipe comprising: a heater for enclosing and heating a zone of the pipe; a quench head for emitting a cooling fluid onto an interior surface of the pipe approximate said zone; support means for supporting and moving the pipe through the induction heater and over the quench head, characterised in that the support means comprises a plurality of rollers, the surface of each of which rollers is shaped into a groove, having a dimensioned diameter of the particular pipe being treated. 11. A method of heat treating a hardenable steel pipe comprising the steps of: moving a pipe along a production line in a first direction, through heating means thereby to heat a zone of the pipe to austenising temperature; simultaneously quenching the heating pipe approximate to the heating zone by means of the quenching head supported by a lance, characterised in that the pipe is removed from the production line by causing the quench head to move axially in a direction opposite to the first direction.

Inventors: BALL DANIEL GRAHAM, BALL, DANIEL, GRAHAM
Applicants: BALL DANIEL GRAHAM, BALL, DANIEL, GRAHAM
Application year: 1992
Main classification: C21D9
IPC codes: C21D9