Cooling system and cooling method for hot isostatic pressurizing equipment

Abstract: A cooling system for the hot isostatic pressurizing equipment is composed of valves (22) and actuators (28) disposed at the lower part of the equipment so that they are not subject to thermal deformation. The valves (22) and actuators (28) are installed independently from each other so as to eliminate a need for increasing the size of the equipment. Each valve (22) opens and closes a lower vent hole (24) formed in the radial direction in a supporting cylinder (20) installed on the inner bottom closure (3B) of a high-pressure vessel (11). Each valve (22) is closed by a spring (26) and is operated by the associated actuator (28) installed on the outer bottom closure (3B) detachable from the inner bottom closure (3A).

Description: The present invention relates to a cooling system and cooling method for hot isostatic pressurizing (HIP) equipment. One of the disadvantages of HIP processing is the lengthy cycle time. One way to reduce the cycle time is to shorten the cooling time after heating as far as possible. This is usually accomplished by rapidly cooling the hot gas used for heating. The conventional cooling method involves releasing the hot gas from the heat-insulated furnace through a vent hole formed in the top of a heat insulator, introducing the released hot gas into a high-pressure chamber, and causing the hot gas to circulate therein by forced or natural convection so that the hot gas undergoes heat exchange with the high-pressure vessel and top closure. A cooling system for this method is disclosed in Japanese Utility Model Laid-open No. 123999/1988. This system comprises a stirring fan for uniform cooling in the furnace and an inner bottom closure which can be removed downward together with a processed workpiece placed thereon, with the heater remaining in the vessel. This arrangement facilitates the handling of the workpiece. A disadvantage of this prior art technology is that the valve to release hot gas is subject to damage due to thermal deformation because it is attached to the top of the heat insulator and hence is exposed to hot gas. Another disadvantage is that the heat insulator is deformed by the axial force which is applied as the valve is actuated, because the axial force of the actuator is imparted to the heat insulator. A device to overcome these disadvantages is disclosed in Japanese Patent Laid-open No. 87032/1984. This device comprises a damper ring which is attached to the lower part of the furnace to avoid the effect of hot gas. A disadvantage of this device is that the damper (including the actuator) takes up a large space which makes it necessary to increase the diameter of the vessel. This advantage is economically serious in the case of HIP equipment designed for high pressure is excess of 100 MPa. It is an object of the present invention to provide a cooling system for the HIP equipment which is designed such that the valve and its actuator are protected from deformation by hot gas and accommodated without any adverse effect on the mechanism of discharging the workpiece through the bottom and without a need for increasing the diameter of the vessel. A cooling system according to the present invention is intended for HIP equipment. The HIP equipment has a high-pressure chamber formed by a high-pressure vessel, a top closure, and a bottom closure (which is composed of an inner bottom closure and an outer bottom closure). The high-pressure chamber accommodates an insulation mantle provided with a heater on the inside thereof. The insulation mantle accommodates a furnace in which a workpiece undergoes HIP processing by a gaseous pressure medium. After the completion of HIP processing, the hot gas is released through a vent hole formed in the upper part of the furnace. The released hot gas is introduced into the passage outside the furnace and then returned to the furnace through a vent hole formed in the lower part of the furnace. At the same time, the hot gas is preferably stirred in the furnace. Thus, the hot gas is cooled while it is circulated and stirred as mentioned above. The cooling system of the present invention is characterized in that the above-mentioned lower vent hole is formed in the radial direction in a supporting cylinder attached to the inner bottom closure, and is provided with a valve which is biased to close the vent hole and is opened by an actuator mounted on the outer bottom closure detachable from the inner bottom closure. The cooling system of the present invention functions as follows after the HIP processing which involves pressurizing the gaseous pressure medium and heating a workpiece by the heater in the furnace. With the heater turned off, the actuator works to open the valve, so that the gas circulates through an upper vent hole in the upper part of the furnace, a passage between the high pressure chamber and the insulation mantle and the lower vent hole. During circulation, the gas cools down rapidly by heat exchange. If uniform cooling in the furnace is necessary, a stirring fan is used to bring about a forced flow of the gas in the furnace. During HIP processing and gas cooling, the lower part of the high-pressure vessel is kept at a comparatively low temperature, so that the actuator is hardly liable to deformation. In addition, during HIP processing, the actuator does not exert any axial force on the insulation mantle to deform it. Besides, the actuator is separate from the valve but is attached to the outer bottom closure. This permits the high-power actuator to be installed without a need for increasing the diameter of the vessel (high-pressure vessel) and also for abandoning the bottom-discharging structure. The invention may be understood more readily and various other aspects and features of the invention may become apparent, from consideration of the following description. Embodiments of the invention will now be described by way of examples only, with reference to the accompanying drawings; wherein Figure 1 is a vertical sectional view of HIP equipment provided with a cooling system constructed in accordance with the present invention; Figure 2 is an enlarged sectional view of part of the equipment shown in Figure 1; and Figure 3 is a vertical sectional view of HIP equipment provided with an alternative comparative form of cooling system in accordance with the invention. As shown in Figures 1 and 3 an entire structure of HIP equipment includes a high-pressure vessel 1 with a top closure 2 and bottom closure 3 which are hermetically fitted into the top and bottom openings of the high-pressure vessel 1, respectively. The high-pressure vessel 1 and the top and bottom closures 2, 3 provide a high-pressure chamber 4. The bottom closure 3 is made up of a circular inner bottom closure 3A fixed to the lower end of the high-pressure vessel 1 and an outer bottom closure 3B detachably fitted into the opening of the inner bottom closure 3A. The high-pressure chamber 4 accommodates a heat sink 6 and an insulation mantle 8. The heat sink 6 is attached to the top closure 2, with a passage 5 interposed between them. The insulation mantle 8 takes on a shape of an inverted glass beaker and has a heater 7 on its inside and a vent hole 9 in its upper part. The insulation mantle 8 defines a furnace 10 in which are placed a pedestal 13 and a holder 16 for a workpiece 15. The pedestal 13 is supported by an under frame 11 standing on the outer bottom closure 3B. The pedestal 13 also has an opening in which a stirring motor 12 is positioned. The holder 16 is supported by a cylinder 14 and an underframe 14A standing on the pedestal 13. On the holder 16 stands a guide cylinder 17 which surrounds the workpiece 15. The pedestal 13 is provided with a lower heat insulator 18 through which passes a motor shaft for a stirring fan 19. The insulation mantle 8 is supported by a supporting cylinder 20 standing on the inner bottom closure 3. The above-mentioned construction permits the workpiece 15 to be charged to and discharged from the furnace 10 in the vertical direction as the outer bottom closure 3B is attached to and detached from the HIP equipment. The outer bottom closure 3B moves together with the guide cylinder 17, stirring motor 12, etc. with the heater 7 and insulation mantle 8 remaining in place. During HIP processing, the top closure 2 and bottom closure 3 are acted on by an axial force, which is supported by a detachable press frame (not shown). In accordance with the invention a cooling system is provided as represented in Figures 1 and 2. Referring to Figure 2, there is shown a valve 22 which connects and disconnects a passage 21 outside the furnace to the lower part of the furnace 10. The passage 21 is formed between the high-pressure vessel 1 and the insulation mantle 8 and supporting cylinder 20. In practice, it is preferred that there are a plurality of such valves 22 which are arranged radially in the supporting cylinder 20 (as viewed from the top). Each valve 22 is a poppet valve with a head which engages or disengages a valve seating 24A to close or open a lower vent hole 24 formed in a valve casing 23 fixed to the supporting cylinder 20. The stem of the valve 22 is provided at the end opposite the head with a guide flange slidably located by the casing 23 and having a number of through-holes 25. A spring 26 is wound around the stem of the valve 22 to urge the valve head against the seating 24A. Each valve 22 is associated with an actuator 28, which confronts the guide flange and is positioned in the radial direction on a support 27 attached to the underframe 11. Each actuator 28 opens the associated valve 22 by means of a motor-driven cylinder 29, in opposition to the force of the spring 26. The above-mentioned opening and closing means (consisting of the valve 22 and its actuator 28) may be replaced by a rotary solenoid-operated means 30 attached to the supporting cylinder 20 as shown in Figure 3. However, this arrangement has a disadvantage in that the closing force is inevitably small and this is not the case with the embodiment of Figures 1 and 2 in which each valve 22 is attached to the supporting cylinder 20 and its actuator 28 is attached to the outer bottom closure 3B, so that the valve 22 and the actuator 28 are separate from each other. This arrangement permits the actuator 28 to be removed downward and also permits the mounting of a large actuator which produces larger acting force. HIP processing is performed on the workpiece 15 placed in the furnace 10, with gaseous pressure medium pressurized in the furnace 10 and the heater 7 energized. During HIP processing, the valves 22 are kept closed by the springs 26. After the completion of HIP processing, the cooling cycle starts in the following manner. First, the motor-driven cylinders 29 are operated to move the actuators 28 forward. Each actuator 28 then pushes the associated valve 22 in opposition to the force of the spring 26, so that the valve head separates from the seating 24A of the valve casing 23. Thus the lower vent holes 24 are opened. The valve openings brings about a circulating flow A (indicated by solid line arrows in Figure 1) through the vent hole 9, the passage 5, the passage 21, and the lower vent holes 24. The circulating flow causes the hot gas to contact the heat sink 6 and the inner wall of the high-pressure vessel 1 and the hot gas is cooled by heat exchange. At the same time, the stirring motor 12 is turned on, so that the stirring fan 19 brings about a forced flow of the hot gas (indicated by dashed line arrows in Figure 1) to keep the temperature uniform in the furnace. In this way, rapid uniform cooling proceeds. After the cooling cycle is complete, the actuators 28 are retracted and then removed downward as the outer bottom closure 3B is detached downward to discharge the HIP-processed workpiece 15, with the valves 22 the heater 7, and the insulation mantle 8 remaining in place. As mentioned above, the cooling system of the present invention permits, after HIP processing, the rapid cooling of the hot gas by circulating and stirring the hot gas. During the cooling cycle the valves 22 and the actuators 28 are protected from high temperature because they are installed at the lower part of the HIP equipment. In addition, the actuators 28 are installed such that they do not exert their working force on the insulation mantle 8 in the axial direction and this protects the insulation mantle 8 from deformation. The valves 22 are installed on the supporting cylinder 20 standing on the inner bottom closure 3A, whereas the actuators 28 are installed on the detachable outer bottom closure 3B, so that they are separate from each other. This construction permits the actuators 28 to be removed downwards together with the outer bottom closure 3B and leads to ease of handling.

Claims: A cooling system for the hot isostatic pressurizing equipment of the type having a high-pressure vessel (1), a top closure (2) fitted into an upper opening of the high-pressure vessel (1), a bottom closure (3) fitted into a lower opening of the high-pressure vessel (1), the bottom closure (3) consisting of an inner bottom closure (3A) and an outer bottom closure (3B) which are detachable from one other and an insulation mantle (8) installed above the inner bottom closure (3A) with a heater (7) on the inside thereof forming a furnace (10) in which a workpiece (15) undergoes hot isostatic pressurizing by gas pressure, the insulation mantle (8) being placed in a high-pressure chamber (4) formed by the high-pressure vessel (1) and the top and bottom closures (2, 3), said cooling system comprising an upper vent hole (9) formed in the upper part of the furnace (10), a passage (21) formed between the high-pressure chamber (4) and the insulation mantle (8), a lower vent hole (24) formed in the lower part of the furnace (10), a valve 22 for opening and closing the lower vent hole (24) and an actuator (28) for operating the valve installed on the outer bottom closure (3B), whereby circulation of gas through the upper vent hole (9), the passage (21) the lower vent hole (24) and the furnace (10) effects cooling of the workpiece after hot isostatic pressurizing. A cooling system for the hot isostatic pressurizing equipment according to Claim 1, wherein there are a plurality of lower vent holes (24) with a plurality of the valves (22) and actuators (28). A cooling system for the hot isostatic pressurizing equipment according to Claim 1 or 2, wherein the or each actuator (28) is of the motor-driven cylinder type. A cooling system for the hot isostatic pressurizing equipment according to Claim 1, 2 or 3 wherein the or each valve (22) is installed in a supporting cylinder (20) held between the insulation mantle (8) and the inner bottom closure (3A). A cooling system for the hot isostatic pressurizing equipment according to Claim 4, wherein the or each valve (22) is biased to close the associated lower vent hole (24). A cooling system for the hot isostatic pressurizing equipment according to Claim 5, wherein the or each valve (22) is composed of a valve casing (23) attached to the supporting cylinder (20), a seating surface (24A) leading to the vent hole (24) formed in the casing (23), a valve head engageable and disengageable with the seating (24A), a valve stem fixed to the valve head, a guide flange with through holes (25) attached to the end of the valve stem and a spring (26) to urge the valve head against the seating (24A). A cooling system for the hot isostatic pressurizing equipment according to any one of Claims 1 to 6 and further comprising a stirring fan (19) installed in the lower part of the furnace (10). A cooling system for the hot isostatic pressurizing equipment according to Claims 1 to 7 and further comprising a guide cylinder (17) which surrounds the workpiece. A cooling system for the hot isostatic pressurizing equipment according to any one of Claims 1 to 8 and further comprising a heat sink (6) installed between the top closure (2) and the insulation mantle (8), with a passage (5) formed between them. A method of cooling a workpiece (15) placed in a furnace (10) of the hot isostatic pressurizing equipment having a high-pressure vessel (1), a top closure (2) fitted into an upper opening of the high-pressure vessel (1) a bottom closure (3) fitted into a lower opening of the high-pressure vessel (1), the bottom closure consisting of an inner bottom closure (3A) and an outer bottom closure (3B), an insulation mantle (8) installed above the inner bottom closure and provided with a heater (7) on the inside thereof, the insulation mantle (8) forming a furnace (10), an upper vent hole (9) formed in the upper part of the furnace (10), a passage (21) formed between the high-pressure vessel (1) and the insulation mantle (8), a lower vent hole (24) formed in the lower part of the furnace (10), a valve (22) for opening and closing the lower vent hole (24), and an actuator (28) for operating the valve installed on the outer bottom closure (3B); said method comprising the steps of placing a workpiece (15) in the furnace (10) supported by the outer bottom closure (3B), introducing a high pressure gas into the furnace (10) and energizing the heater (7) with the valve (22) closed, thereby performing hot isostatic pressurizing of the workpiece (15) and opening the valve (22) by means of the actuator (28), to cause the gas to circulate through the upper vent hole (9), the passage (21), the lower vent hole (24), and the furnace (10) to cool the workpiece (15) closing the valve (22) with the actuator (28) and discharging the processed workpiece (15), from the furnace (10) together with the outer bottom closure (3B). A cooling method according to Claim 10, wherein forced circulation of the gas takes place with the aid of a stirring fan (19) installed at the lower part of the furnace (10).

Inventors: ISHII TAKAHIKO C O KOBE STEEL, NAKAI TOMOMITSU C O KOBE STEEL, ISHII, TAKAHIKO, C/O KOBE STEEL, LTD., NAKAI, TOMOMITSU, C/O KOBE STEEL, LTD.
Applicants: KOBE STEEL LTD, KABUSHIKI KAISHA KOBE SEIKO SHO ALSO KNOWN AS KOBE STEEL LTD.
Application year: 1992
Main classification: B30B11
IPC codes: H01L31, H01L27, B30B11, C12P19, C07H17, A01N43, B22F3, C04B35, F27B17