Patent Publication Number: US-2023136509-A1

Title: Die block device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent Application No. 2021-178531 filed on Nov. 1, 2021 and Japanese Patent Application No. 2021-114632 filed on Jul. 19, 2022. The content of this application is incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a die block device used in an extrusion press machine. 
     Description of the Related Art 
     An extrusion press machine is a device for manufacturing aluminum products by pressing an easily workable metal material such as aluminum or its alloys (hereinafter referred to as aluminum material) through a die and continuously extruding an aluminum product having a predetermined cross-sectional shape through the die (extrusion). The die has an opening with a cross-sectional shape similar to that of the aluminum product. An extruded long aluminum product is cut into individual aluminum products having a predetermined length. 
     With reference to  FIG.  1   , a conventional extrusion press machine and its extrusion process will be described.  FIG.  1    is a schematic cross-sectional side view of an outline of a configuration of an extrusion press machine  100  without a detailed configuration shown. An aluminum material to be extruded is formed as a cylindrical billet B having a predetermined diameter appropriate for an extruded product W to be manufactured, and inserted into a billet accommodating portion  1 A as a gap in a container  1 . 
     A main cylinder  4  that creates extrusion pressure constitutes a hydraulic cylinder having only an oil chamber for moving a cylinder rod forward, and a main ram  4 A corresponds to the cylinder rod. An extrusion stem  3  is mounted to the main ram  4 A. Hydraulic oil supplied from a main pump unit  5  through a hydraulic circuit to the oil chamber in the main cylinder  4  moves a position of the main ram  4 A (ram position) toward the die  2  (forward/to the right side in  FIG.  1   ), and then the extrusion stem  3  also moves (forward) to press the billet B through the die  2 . By this pressing, the billet B is pressurized in the container  1 , and continuously extruded through an opening of a die  2  having a cross-sectional shape similar to that of an extruded product W. Reference numeral  6  denotes an end platen, and reference numeral  6   a  denotes a pressure ring embedded in the end platen  6  and subjected to a pressing force applied to the die  2 . In  FIG.  1   , the main pump unit  5  is shown as a hydraulic pump for simplicity of drawing. 
     Although not shown in  FIG.  1   , the die  2  includes a plurality of members, is accommodated in a die block (also referred to as a die cassette), and is arranged movably by a die slide mechanism (not shown) between an extrusion operation position during the extrusion process and a die changing position spaced apart from the extrusion press machine. The die  2  includes a small diameter part  2 A and a large diameter part  2 B, and the small diameter part  2 A is provided for extrusion. 
     As disclosed in JP 10-085830 A, a die block may include a plurality of heating means arranged in parallel with an extrusion direction. This is for preventing defective dimension accuracy or shape of an extruded product by heating and keeping a peripheral surface of the die  2  at a desired temperature for a billet preheated to about 400° C. for extrusion. 
     However, continuing the extrusion process causes a rise in temperature of the die due to friction between an inner peripheral surface of the part of the die that has an opening with a cross-sectional shape similar to that of the extruded product and is provided for extrusion, and the extruded product being extruded. The rise in temperature of the die may reduce quality of the extruded product. On the other hand, if a cooling mechanism is to be arranged in the die block to suppress the rise in temperature of the die, the die block is moved by the die slide mechanism between the extrusion operation position (operation position) and the die changing position (changing position), and thus the cooling mechanism also needs to be moved, which complicates piping of the cooling mechanism. 
     The present invention is achieved in view of the above described problems, and has an object to provide a die block device in an extruder including a cooling mechanism of a simple structure reciprocable between the extrusion operation position and the die changing position. 
     SUMMARY OF THE INVENTION 
     The die block device according to the present invention includes: a die block portion configured to reciprocate between an operation position for extrusion and a changing position for die changing; and a gas supply portion configured to supply a cooling gas toward the die block portion. 
     The die block portion includes a block body having a support surface that supports the die, and a gas channel having a supply port for the cooling gas and an exhaust port that extends from the supply port through the block body and opens into the support surface. 
     The gas supply portion includes a supply passage provided to communicate with the gas channel through the supply port when the die block portion is in the operation position. 
     The die block portion in the present invention may include a plurality of gas channels, and the gas supply portion may include the supply passage communicating with each of the plurality of gas channels. 
     The support surface in the present invention may have an arcuate surface when viewed from front, and may have the exhaust port of the gas channel, the exhaust port opening within a range of ±30° in a height direction with reference to a center of curvature of the arcuate surface. 
     The block body in the present invention may hold the die including a small diameter part provided for extrusion and a large diameter part continuous with the small diameter part, and the block body may include a small diameter support part that supports the small diameter part of the die, and a large diameter support part that supports the large diameter part of the die. 
     The gas channel is provided in one or both of the small diameter support part and the large diameter support part. 
     The block body in the present invention preferably has a temperature sensor incorporated therein, and when a detected temperature of the block body by the temperature sensor exceeds a previously set temperature, the cooling gas is supplied to the supply passage. 
     The block body in the present invention preferably has a heater incorporated therein, and when the detected temperature exceeds the previously set temperature, a heating set temperature by the heater is reduced, and the detected temperature is further monitored for a previously set time. When the detected temperature exceeds the set temperature, the cooling gas is supplied to the supply passage until the detected temperature falls below the set temperature. 
     In the die block device according to the present invention, the gas channel is provided in the die block portion configured to reciprocate between the operation position and the changing position, and when the die block portion is in the operation position, the supply passage in the gas supply portion communicates with the gas channel. Then, when the die block portion is moved from the operation position to the changing position, the communication between the gas channel and the supply passage is released. As such, the gas supply portion is positionally fixed independently of the position of the die block portion. Thus, even if the gas supply portion includes other components in the supply passage such as an open/close switching valve or a stop valve, such components need not be moved according to the movement of the die block portion. Thus, even if the die block device according to the present invention includes a cooling mechanism configured to cool the die, the cooling mechanism is not complicated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic cross-sectional side view showing an outline of a configuration of an extrusion press machine; 
         FIG.  2    is a view taken along the arrowed line A-A in  FIG.  1    showing a die block device according to a first embodiment; 
         FIG.  3    is a view taken along the arrowed line B-B in  FIG.  2    showing the die block device according to the first embodiment; 
         FIG.  4    is a view taken along the arrowed line C-C in  FIG.  2    showing the die block device according to the first embodiment; 
         FIG.  5    is a view taken along the arrowed line A-A in  FIG.  1    showing the die block device according to the first embodiment and showing a die block having moved to a die changing position; 
         FIG.  6    shows a variant of the die block device according to the first embodiment; 
         FIG.  7    is a flow diagram of a first control mode of a cooling gas CG in the die block device according to the first embodiment; 
         FIG.  8    is a flow diagram of a second control mode of the cooling gas CG in the die block device according to the first embodiment; and 
         FIG.  9    is a view taken along the arrowed line C-C in  FIG.  2    showing a die block device according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are not intended to limit the invention according to claims, and not all of combinations of features described in the embodiments are essential to the solution of the invention. 
     First embodiment: FIGS.  2 ,  3 ,  4 ,  5 ,  6 , and  7   
     With reference to  FIGS.  2  to  7   , a die block device  10  in an extrusion press machine  100  according to a first embodiment will be described.  FIG.  2    is a view taken along the arrowed line A-A in  FIG.  1    showing the die block device  10  according to the first embodiment. Similarly,  FIG.  3    is a view taken along the arrowed line B-B in  FIG.  2    showing the die block device  10  according to the first embodiment, and  FIG.  4    is a view taken along the arrowed line C-C in  FIG.  2    showing the die block device  10  according to the first embodiment. 
     As shown in  FIGS.  2  to  4   , the die block device  10  includes a die block portion  20  including a die block body  21 , and a gas supply portion  40  configured to supply a cooling gas CG to the die block body  21 . The die block portion  20  is reciprocable between an operation position P 1  in  FIG.  2    and a changing position P 2  in  FIG.  5    in a width direction Y. On the other hand, the gas supply portion  40  is positionally fixed. The gas supply portion  40  includes a plurality of components as described later, but has a simple structure because of its fixed position. Now, configurations of the die block portion  20  and the gas supply portion  40  will be sequentially described, and then operation of the die block device  10  will be described. 
     Die block portion  20 : FIGS.  2  to  4   
     As shown in  FIGS.  2  to  4   , the die block portion  20  includes the die block body  21  that accommodates and supports a die  2 , and a heater  22  and a temperature sensor  23  which are incorporated in the die block body  21 . The die block portion  20  includes gas channels  24 A,  24 B configured to supply a cooling gas CG toward the die  2  held by the die block body  21 . 
     Die Block Body  21   
     The die block body  21  includes a small diameter support part  21 A that supports a small diameter part  2 A of the die  2 , and a large diameter support part  21 B that supports a large diameter part  2 B of the die  2 . As shown in  FIG.  1   , the small diameter support part  21 A is arranged closer to a container  1 , and the large diameter support part  21 B is arranged closer to an end platen  6 . Thus, the small diameter support part  21 A holds the small diameter part  2 A on the side of the container  1  (near side in  FIG.  2   ), and the large diameter support part  21 B supports the large diameter part  2 B on the side of the end platen  6 . As shown in  FIG.  1   , a billet B is extruded by the small diameter part  2 A of the die  2  into an extruded product W, and the extruded product W sequentially passes through the large diameter part  2 B and the end platen  6 . 
     The small diameter support part  21 A and the large diameter support part  21 B of the die block body  21  include a small diameter support surface  21 C and a large diameter support surface  21 D that support the small diameter part  2 A and the large diameter part  2 B, respectively, of the die  2 . The small diameter support surface  21 C and the large diameter support surface  21 D are arcuate surfaces when viewed from front. A region surrounded by the arcuate surfaces is an accommodation space  21 S for the die  2 . The small diameter support surface  21 C has a smaller radius of curvature than the large diameter support surface  21 D. When the die block body  21  holds the die  2 , the small diameter part  2 A comes into contact with the small diameter support surface  21 C, and the large diameter part  2 B comes into contact with the large diameter support surface  21 D, with a clearance through which the cooling gas CG flows between the die block body  21  and the die  2 . 
     The small diameter support surface  21 C and the large diameter support surface  21 D each include a lower support surface  21 E and a pair of side support surfaces  21 F,  21 F continuous with the lower support surface  21 E. The side support surfaces  21 F,  21 F are provided opposite each other on opposite sides of the accommodation space  21 S in the width direction Y. As described below in detail, the gas channels  24 A,  24 B are provided correspondingly to the lower support surface  21 E. 
     The die block portion  20  can reciprocate with a slide device (not shown) between an operation position P 1  ( FIG.  2   ) and a changing position P 2  ( FIG.  5   ) in the width direction Y perpendicular to an extrusion direction X. Thus, the die block portion  20  is arranged on a lower gib  33  via a guide member  31  ( FIG.  4   ) extending in the width direction Y. The lower gib  33  is supported by a lower gib support member  35  arranged to protrude from the end platen  6 .  FIG.  2    shows the die block portion  20  in the operation position P 1 , and  FIG.  5    shows the die block portion  20  in the changing position P 2 . Another guide member configured to guide linear reciprocation between the operation position P 1  and the changing position P 2  in the width direction Y perpendicular to the extrusion direction X of the die block body  21  is also provided on an upper side of the die block portion  20 , but is not shown for clarity of the drawing. 
     Heater  22  and Temperature Sensor  23   
     As shown in  FIGS.  2  and  3   , the heater  22  and the temperature sensor  23  are incorporated in the die block body  21  of the die block portion  20 . The heater  22  and the temperature sensor  23  are inserted into insertion holes (far side in  FIG.  2   /upper side in  FIG.  3   ) formed from a rear end to a front end of the large diameter support part  21 B of the die block body  21  and thus incorporated in the die block body  21 . 
     The heater  22  may be various devices capable of heating an object, such as a rod-like ceramic heater or a wire heater. The heater  22  is provided such that its length direction is along the extrusion direction X. In this embodiment, a plurality of heaters  22  are arranged to surround the small diameter support surface  21 C and the large diameter support surface  21 D each having the arcuate shape of the die block body  21 . In this embodiment, no heater  22  is provided between the gas channels  24 A,  24 B. However, a heater  22  may be provided between the gas channels  24 A,  24 B depending on arrangement of the gas channels. 
     The temperature sensor  23  may be various devices capable of measuring a temperature, such as a thermocouple, a thermistor, a platinum resistance temperature detector, or a bimetallic thermometer. A plurality of temperature sensors  23  are also provided as an example, and temperature sensors  23 A,  23 B are provided on opposite sides in the width direction Y near upper ends of the small diameter support surface  21 C and the large diameter support surface  21 D, and a temperature sensor  23 C is provided near lower ends of the small diameter support surface  21 C and the large diameter support surface  21 D. 
     Gas Channels  24 A,  24 B: FIGS.  2  and  4   
     As shown in  FIGS.  2  and  4   , the die block portion  20  includes the gas channels  24 A,  24 B configured to discharge the cooling gas CG supplied from the gas supply portion  40  toward the die  2  accommodated in the die block body  21 . The gas channels  24 A,  24 B are gaps formed to extend between an outer peripheral surface of the small diameter support part  21 A and the small diameter support surface  21 C along a height direction Z. The gas channels  24 A,  24 B include supply ports  24 D,  24 D through which the cooling gas CG is supplied from the gas supply portion  40 , and exhaust ports  24 C,  24 C through which the supplied cooling gas CG is discharged toward the small diameter part  2 A of the die  2 . 
     In this embodiment, the pair of gas channels  24 A,  24 B are provided symmetrically with respect to a line segment CL (see  FIG.  6   ) extending in the height direction Z through a center of curvature C of the arcuate small diameter support surface  21 C. The cooling gas CG discharged through the gas channels  24 A,  24 B flows through the clearance between the small diameter support part  21 A of the die block body  21  and the small diameter part  2 A of the die  2 , mainly from the lower support surface  21 E toward the side support surfaces  21 F,  21 F, thereby cooling the small diameter support part  21 A and the die  2 . The main flow of the cooling gas CG corresponds to a region provided with the heaters  22 . Also between the gas channels  24 A,  24 B, the cooling gas CG flows between the small diameter support part  21 A and the small diameter part  2 A. 
     As the die block body  21  reciprocates in the width direction Y, the positions of the gas channels  24  move. The gas channels  24  as the gaps formed by perforating the small diameter support part  21 A has been described herein, but the gas channels  24  may be formed of pipes. 
     In  FIG.  6   , with reference to the center of curvature C on the line segment CL, a range of a center angle of ±30° is referred to as a lower area α, and regions above the lower area a are referred to as side areas β, β. The temperature sensors  23 A,  23 B are provided in the side areas β, β, and the temperature sensor  23 C is provided in the lower area α. The gas channels  24 A,  24 B are also provided in the lower area α. 
     Gas Supply Portion  40 : FIGS.  2  and  5   
     Next, the gas supply portion  40  configured to supply the cooling gas CG toward the die block portion  20  will be described. 
     The gas supply portion  40  includes a supply passage  41  ( 41 A,  41 B) configured to supply the cooling gas CG toward the gas channels  24 , an open/close switching valve  43  and a stop valve  45  arranged in the supply passage  41 , and a gas supply source  47  that stores the cooling gas CG to be supplied to the supply passage  41 . The supply passage  41  is connected to the gas supply source  47  at an upstream end of the flow of the cooling gas CG. The supply passage  41  branches to the supply passage  41 A and the supply passage  41 B downstream of the open/close switching valve  43 . 
     While the die block portion  20  is moving between the operation position P 1  and the changing position P 2 , the gas supply portion  40  remains in a fixed position. The supply passage  41 A corresponds to the gas channel  24 A, and the supply passage  41 B corresponds to the gas channel  24 B. As shown in  FIG.  2   , in the operation position P 1 , the supply passage  41 A communicates with the gas channel  24 A, and the supply passage  41 B communicates with the gas channel  24 B. As shown in  FIG.  5   , when the die block portion  20  is moved by a die slide mechanism (not shown) from the operation position P 1  to the changing position P 2 , the communication between the gas channels  24 A,  24 B and the supply passages  41 A,  41 B is released. Thus, the supply passage  41 , the open/close switching valve  43 , and the stop valve  45  that constitute the gas supply portion  40  need only be arranged on the lower gib support member  35  or the like positionally fixed near the die block portion  20  in the operation position P 1 , and such components need not be moved according to the movement of the die block portion  20 . With such a configuration, even if the cooling mechanism configured to cool the die  2  accommodated in the die block portion  20  is arranged in the die block portion  20 , piping of the cooling mechanism is not complicated. 
     Although not shown, in communicating parts between the gas channels  24 A,  24 B and the supply passage  41 , packing or the like is preferably provided in an opening of each communicating part on the side of the die block portion  20  or the side of the lower gib  33 , thereby suppressing leakage of the cooling gas CG through the communicating parts between the gas channels  24 A,  24 B and the supply passage  41 . 
     Variant of Gas Channel  24 : FIG.  6   
     The example of the pair of gas channels  24 A,  24 B being provided has been described. However, as shown in the upper section in  FIG.  6   , one gas channel  24  may be provided along a centerline CL. Alternatively, as shown in the lower section in  FIG.  6   , two gas channels  24 ,  24  may be provided symmetrically with respect to one gas channel  24 . The two gas channels  24 ,  24  in the latter case open into the side support surfaces  21 F,  21 F. 
     Controller  50 : FIG.  2   
     The die block device  10  includes a controller  50  configured to control operation of the die block device  10 . 
     In an extrusion process, the controller  50  performs heating control of the die  2  with the heater  22  and cooling control of the die  2  with the cooling gas CG. The controller  50  can also control the reciprocation of the die block portion  20 . 
     The controller  50  stores previously set heating and heat retaining patterns of the die  2  for the heating control of the die  2 . The controller  50  also stores information on a set temperature Ts relating to an upper limit of detected temperatures and a previously set time Ss used in a second control mode. The controller  50  can store other information required for operation of the die block device  10 . 
     The controller  50  continuously obtains information on detected temperatures Td (TdA, TdB, TdC) by the temperature sensors  23 A,  23 B,  23 C and compares the detected temperatures Td with the set temperature Ts. Based on a result of the comparison of the detected temperatures Td with the set temperature Ts, the controller  50  operates the gas supply portion  40  to supply the cooling gas CG from the supply passage  41  to the gas channel  24 . 
     The controller  50  also compares an elapsed time Sd with the set time Ss for suppressing heating of the heater  22 . Based on a result of the comparison of the elapsed time Sd with the set time Ss, the controller  50  can operate the gas supply portion  40  to supply the cooling gas CG from the supply passage  41  to the gas channel  24 . 
     The controller can include a display device such as an LCD (liquid crystal display) for displaying the above results of comparisons. 
     Cooling Control: FIGS.  7  and  8   
     Next, with reference to  FIG.  7    (first control mode) and  FIG.  8    (second control mode), the cooling control of the die  2  accommodated in the die block body  21  will be described. The cooling control is performed based on instructions from the controller  50  described above. In the first control mode ( FIG.  7   ), the cooling gas CG is immediately discharged toward the die  2  based on the result of comparison of the detected temperatures Td with the set temperature Ts. In the second control mode ( FIG.  8   ), the heating temperature by the heater  22  is reduced before discharge of the cooling gas CG. Now, the first control mode and the second control mode will be sequentially described. 
     First Control Mode: FIG.  7   
     When the extrusion process starts, the controller  50  operates the heater  22  to control temperatures of the lower area α and the side areas β of the die block body  21  based on the previously set heating and heat retaining patterns of the die  2  with reference to the detected temperatures Td by the temperature sensors  23  (S 101  in  FIG.  7   ). In the first embodiment, the temperature sensors  23  ( 23 A,  23 B,  23 C) are arranged in three places ( FIG.  2   ) such that heating control is performed in each of three areas: the lower area and the opposite side areas of the block body  21 . The temperatures detected by the temperature sensors  23 A,  23 B,  23 C are denoted by TdA, TdB, TdC, respectively, but sometimes collectively referred to as the detected temperatures Td. 
     When the extrusion process continues, the billet B is pressed through the die  2 , and an extruded product W is extruded through an opening having a cross-sectional shape similar to that of the extruded product W, and thus the die  2  is heated by friction with the extruded product W and rises in temperature. The temperature sensors  23 A,  23 B,  23 C continuously detect the temperatures since the start of the extrusion process, and the detected temperatures TdA, TdB, TdC (Td) as detection results are transmitted to the controller  50 . The controller  50  compares each of the obtained detected temperatures TdA, TdB, TdC with the previously stored set temperature Ts (S 103 ). 
     When the controller  50  determines that any of the detected temperatures TdA, TdB, TdC (Td) exceeds the set temperature Ts (Yes in S 103 ), the controller  50  operates the gas supply portion  40  and instructs the gas supply portion  40  to supply the cooling gas CG from the supply passages  41 A,  41 B to the gas channels  24 A,  24 B (S 110 ). 
     Even after the instruction to supply the cooling gas CG, the controller  50  continuously obtains the detected temperatures TdA, TdB, TdC and compares the detected temperatures with the set temperature Ts. If any of the detected temperatures TdA, TdB, TdC exceeds the set temperature Ts, the controller  50  continues the instruction to supply the cooling gas CG (No in S 111 ). If all of the detected temperatures TdA, TdB, TdC become equal to or lower than the set temperature Ts (Yes in S 111 ), the controller  50  stops the instruction to supply the cooling gas CG (S 113 ). 
     The controller  50  continues the above control until the end of the extrusion process. 
     Second Control Mode: FIG.  8   
     Next, with reference to  FIG.  8   , the second control mode will be described. The second control mode partially follows the first control mode, and thus differences from the first control mode will be mainly described below. 
     If the controller  50  determines that any of the detected temperatures TdA, TdB, TdC (Td) exceeds the set temperature Ts (Yes in S 103 ), the controller  50  instructs to suppress heating by the heater  22  incorporated in the die block body  21  in an area where the temperature higher than the set temperature is detected (S 105  in  FIG.  8   ). For example, if the detected temperature TdA by the temperature sensor  23 A exceeds the set temperature Ts, the controller  50  instructs to suppress heating by the heater  22  in the side area β. Suppressing heating herein means both stopping heating by the heater  22  and reducing the heating temperature. 
     The controller  50  suppresses heating, and also monitors the detected temperature Td by the temperature sensor  23  in that area. Then, if the elapsed time Sd from the start of suppression of heating exceeds the previously set time Ss (Yes in S 107 ), but the detected temperature Td by the temperature sensor  23  in that area does not fall below the set temperature Ts (No in S 109 ), the controller  50  opens the open/close switching valve  43  in the supply passage  41  to eject the cooling gas CG toward the small diameter part  2 A of the die  2  through the supply passage  41  and the gas channels  24 A,  24 B, thereby starting cooling of the die  2  (S 110 ). The cooling is continued until all of the detected temperatures by the temperature sensors  23 A to  23 C fall below the set temperature (S 111 ). Hereinafter, control is performed through the same steps as in the first control mode. 
     The two cooling control modes have been described above. However, the detected temperatures TdA, TdB, TdC (Td) by the temperature sensors  23  may be displayed on a display device of the controller  50 , and an operator may check the display device. When any of the detected temperatures exceeds the set temperature, the operator may manually operate the gas supply portion  40  to supply the cooling gas CG from the supply passage  41  to the gas channel  24 . 
     Effect of First Embodiment 
     As described above, the gas channels  24 A,  24 B arranged in the die block body  21  communicate with the supply passage  41  of the gas supply portion  40  when the die block body  21  is in the operation position. Thus, even if the cooling mechanism configured to cool the die  2  accommodated in the die block body  21  is arranged in the die block body  21 , piping of the cooling mechanism is not complicated. 
     Also, both the heating and heat retaining control and the cooling control of the die  2  accommodated in the block body  21  can be performed. This can prevent defective dimension accuracy or shape of an extruded product by heating and keeping a peripheral surface of the die  2  at a desired temperature. 
     In the first embodiment, assuming that an area near the small diameter part  2 A of the die  2  is heated by friction with the extruded product W and most rises in temperature, the area can be cooled by ejecting the cooling gas CG. According to the first embodiment, an increase in cooling efficiency of the die  2  can be expected. A flow control valve may be provided in the supply passage  41  such that a supply amount of the cooling gas CG to be ejected is adjustable. 
     Second Embodiment: FIG.  9   
     In the first embodiment, in the extrusion process, the small diameter part  2 A of the die  2  is heated by friction with the extruded product W and most rises in temperature. However, depending on extrusion conditions or extruded products, areas other than the small diameter part  2 A of the die  2 , for example, a predetermined area of the large diameter part  2 B of the die  2  may most rise in temperature. A second embodiment accommodates such a case. 
     As shown in  FIG.  9   , in the second embodiment, gas channels  24 A′,  24 B′ of the die block body  21  are provided in the large diameter support part  21 B that supports the large diameter part  2 B of the die  2 . 
     The first embodiment and the second embodiment have been described above. However, the present invention is not limited to the above embodiments, but may be embodied in various ways without departing from the contents of claims.