Bar extrusion method

Abstract

The invention provides a bar extrusion method and relates to the technical field of metal processing.The extrusion method is based on an extrusion device, the extrusion device comprises an extrusion die, an extrusion cylinder, an extrusion shaft and an extrusion gasket, the extrusion shaft and the extrusion gasket are both arranged in the extrusion cylinder, the extrusion gasket is connected to the extrusion end of the extrusion shaft, and the extrusion die is connected with the extrusion cylinder. The extrusion gasket comprises a filling part, the extrusion die is of a cylindrical structure, the inlet end of the extrusion die is correspondingly connected with the outlet end of the extrusion cylinder, an inner cavity of the extrusion die is composed of a deformation cavity and a sizing cavity in the axial direction, the deformation cavity is located at the inlet end of the extrusion die, and the sizing cavity is located at the outlet end of the extrusion cylinder. And the shape of the filling part is matched with that of the deformation cavity, so that the tail pressure residue of the bar can be improved, and the structure uniformity of the bar can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and more particularly, to an extrusion method for bars. Background Art

[0002] Since it is not easy to crack and the production efficiency is relatively high when forging bars by extrusion, currently, for the processing of high-value-added and difficult-to-deform bars such as nickel-based alloys and titanium alloys, the extrusion method is gradually being adopted for production. When using a traditional bar extrusion device to extrude bars, since the extrusion shaft is a regular cylinder, when the extrusion shaft contacts the entrance of the extrusion die, the extrusion ends, but there is still a part of the blank remaining in the deformation zone of the extrusion die. After that, a ejector device is required to push the extruded bar and the redundant material back in the opposite direction to complete the demolding. After extrusion, there is redundant material with no deformation and very little deformation at the tail of the bar. The internal structure of the redundant material part does not meet the requirements and needs to be cut off during subsequent machining. Moreover, after extrusion, a ejector mechanism is required to push the extruded bar back along the original path to complete the demolding, and continuous production cannot be achieved, resulting in a reduction in material utilization rate, production efficiency, and an increase in manufacturing cost. In addition, during the bar extrusion process, since mechanical energy is converted into internal energy, there is a temperature rise in the core area (central axis area) of the bar, which in turn causes grain growth in the core area of the bar. And as the extrusion progresses, the temperature difference between the core area of the head of the bar and the core area of the tail of the bar gradually increases. Therefore, the temperature of the core area of the tail of the bar is relatively high, seriously affecting the uniformity of the structure of the tail of the bar and making the structure uniformity of the bar poor. Summary of the Invention

[0003] The problems solved by the present invention are at least one of the following problems: (1) how to improve the redundant material at the tail of the bar; (2) how to improve the structure uniformity of the bar.

[0004] To solve the above problems, the present invention provides an extrusion method for bars. Based on an extrusion device, the extrusion device includes an extrusion die, an extrusion cylinder, an extrusion shaft, and an extrusion gasket. The extrusion shaft and the extrusion gasket are both disposed in the extrusion cylinder. The extrusion gasket is connected to the extrusion end of the extrusion shaft. The extrusion gasket includes a filling portion. The extrusion die is a cylindrical structure. The inlet end of the extrusion die is correspondingly connected to the outlet end of the extrusion cylinder. The inner cavity of the extrusion die consists of a deformation cavity and a sizing cavity along the axial direction. The deformation cavity is located at the inlet end of the extrusion die. The shape of the filling portion matches the shape of the deformation cavity. The extrusion method of the bar includes: heating the blank to the extrusion temperature and then placing it in the extrusion cylinder of the preheated extrusion device for extrusion to obtain the bar; wherein, the length of the blank is L, the moving speed of the blank at the initial stage of the extrusion process is the first speed, when the remaining length of the blank in the extrusion cylinder is 1 / 3L to 1 / 2L, the moving speed of the blank is decelerated from the first speed to the second speed at a preset deceleration until the blank completely enters the sizing cavity, the first speed is 25mm / s to 35mm / s, and the second speed is 10mm / s to 20mm / s.

[0005] Optionally, the extrusion ratio of the extrusion process is 2 to 9.

[0006] Optionally, the preset deceleration is 3 mm / s 2 to 15mm / s 2 。

[0007] Optionally, the extrusion temperature is 950°C to 1100°C.

[0008] Optionally, the temperature of the preheating treatment is 300°C to 400°C, and the time is 2h to 4h.

[0009] Optionally, the extrusion device further includes an annular filling pad, the annular filling pad is sleeved on the side wall of the filling part, the annular filling pad, the extrusion gasket and the extrusion shaft together form a columnar extrusion unit, the material of the annular filling pad is glass powder, and the melting point of the glass powder is lower than 900°C.

[0010] Optionally, the inner diameter of the inlet end of the deformation cavity, the inner diameter of the extrusion cylinder and the diameter of the extrusion unit are the same.

[0011] Optionally, an annular lubricating pad is provided on the inner wall of the outlet end of the extrusion cylinder, and the material of the annular lubricating pad is glass powder.

[0012] Optionally, the deformation cavity is frustum-shaped, the inner diameter of the inlet end of the deformation cavity is larger than the inner diameter of the outlet end of the deformation cavity, the vertical cross-section of the deformation cavity is an isosceles trapezoid, and the base angle of the isosceles trapezoid is 30 degrees to 80 degrees.

[0013] Optionally, the extrusion gasket further includes a transition part and a first connecting part, the filling part, the transition part and the first connecting part are connected in sequence, a second connecting part is provided at the extrusion end of the extrusion shaft, and the first connecting part is connected to the second connecting part.

[0014] Compared with the related technologies, the present invention uses a specific extrusion device and a specific process for bar extrusion. Specifically, the blank is heated to the extrusion temperature and then placed in the extrusion cylinder of the pre-heated extrusion device for extrusion. During the extrusion process, under the action of the extrusion force, the blank undergoes extrusion deformation through the deformation cavity and then enters the sizing cavity. Subsequently, the blank is extruded from the sizing cavity to obtain a bar. Since the extrusion end of the extrusion shaft is connected with an extrusion gasket having a filling portion, and the shape of the filling portion matches the shape of the deformation cavity, when the filling portion contacts the entrance of the extrusion die, the extrusion is not completed. The extrusion shaft continues to move upward until the side wall of the filling portion fits with the inner wall of the deformation cavity. At this time, the filling portion just reaches the boundary line between the deformation cavity and the sizing cavity, and the blank is completely pushed into the sizing cavity. After the extrusion is completed, the tail of the blank also undergoes effective extrusion deformation in the deformation cavity. Therefore, there is no residue with no deformation or very small deformation amount at the tail of the obtained bar, which can improve the material utilization rate and production efficiency. In addition, the present invention also controls the movement speed of the blank during the extrusion process. Specifically, in the initial stage of the extrusion process, the movement speed of the blank is relatively large (25 mm / s to 35 mm / s), which can reduce the idle stroke and the contact time between the blank and the extrusion cylinder and the extrusion die during the extrusion process to reduce the temperature drop on the surface of the blank. When the remaining length of the blank in the extrusion cylinder is 1 / 3L to 1 / 2L, the movement speed of the blank is gradually reduced to a lower level (10 mm / s to 20 mm / s), and then the extrusion continues until the blank completely enters the sizing cavity, which can ensure that the temperature rise in the core area of the bar tail is not too high, and thus can improve the tissue uniformity of the bar. In summary, by using the device and method of the present invention, not only can the tail residue of the bar be improved, but also the tissue uniformity of the bar can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of the extrusion device in the embodiment of the present invention; Figure 2 is a schematic structural diagram of the extrusion device before improvement; Figure 3 is a schematic structural diagram of the extrusion gasket in the embodiment of the present invention Figure 4 is a physical picture of the bar obtained in Example 2; Figure 5 is a physical picture of the bar obtained in Comparative Example 1; Figure 6 is a finite element analysis diagram of the temperature field of the vertical section of the bar in Example 3; Figure 7 is a finite element analysis diagram of the temperature field of the vertical section of the bar in Comparative Example 2; Figure 8 is a metallographic structure picture of the core area of the tail of the bar obtained in Example 3; Figure 9 This is a metallographic structure picture of the tail core area of the rod prepared in Example 3.

[0016] Description of reference numerals: 1. Extrusion die; 11. Deformation cavity; 12. Sizing cavity; 2. Extrusion cylinder; 3. Extrusion shaft; 4. Extrusion gasket; 41. Filling part; 42. Transition part; 43. First connecting part; 5. Blank; 6. Annular filling pad; 7. Annular lubricating pad. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0019] The term "including" and its variations used in this article are open inclusions, that is, "including but not limited to"; the term "based on" is "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first" and "second" mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0020] It should be noted that Figure 1 The direction indicated by the arrow X is upward, which is the direction of movement of the billet during extrusion; Figure 1As shown in the figure, during the extrusion process, the blank 5 moves from bottom to top. The lower end of the extrusion die 1 is the inlet end of the extrusion die 1, the upper end of the extrusion die 1 is the outlet end of the extrusion die 1, and the upper end of the extrusion cylinder 2 is the outlet end of the extrusion cylinder 2. In the present invention, the extrusion end of the extrusion shaft 3 is the end of the extrusion shaft 3 that is close to the blank 5 during the extrusion of the blank 5. For example, Figure 1 as shown in the figure, the extrusion end of the extrusion shaft 3 is the upper end of the extrusion shaft 3.

[0021] Aiming at the problems existing in the above related technologies, an embodiment of the present invention provides an extrusion method for bars, based on an extrusion device, such as Figure 1 as shown in the figure, the extrusion device includes an extrusion die 1, an extrusion cylinder 2, an extrusion shaft 3 and an extrusion gasket 4. The extrusion shaft 3 and the extrusion gasket 4 are both arranged in the extrusion cylinder 2. The extrusion gasket 4 is connected to the extrusion end of the extrusion shaft 3. The extrusion gasket 4 includes a filling part 41. The extrusion die 1 is a cylindrical structure. The inlet end of the extrusion die 1 is correspondingly connected to the outlet end of the extrusion cylinder 2. The inner cavity of the extrusion die 1 is composed of a deformation cavity 11 and a sizing cavity 12 along the axis. The deformation cavity 11 is located at the inlet end of the extrusion die 1. The shape of the filling part 41 matches the shape of the deformation cavity 11. During the extrusion process, when the filling part 41 just reaches the boundary line between the deformation cavity 11 and the sizing cavity 12, the side wall of the filling part 41 fits against the inner wall of the deformation cavity 11; The extrusion method for the bars includes: heating the blank 5 to the extrusion temperature and then placing it in the extrusion cylinder 2 of the preheated extrusion device for extrusion treatment to obtain bars; wherein, the length of the blank is L, the movement speed of the blank at the initial stage of the extrusion treatment is the first speed. When the length of the part of the blank remaining in the extrusion cylinder 2 is 1 / 3L to 1 / 2L, the movement speed of the blank 5 is reduced from the first speed to the second speed at a preset deceleration until the blank 5 completely enters the sizing cavity 12. The first speed is 25 mm / s to 35 mm / s, and the second speed is 10 mm / s to 20 mm / s.

[0022] It should be noted that in the present invention, the shape of the filling part 41 matches the shape of the deformation cavity 11, which should be understood as that the shape and size of the filling part 41 are the same as the shape and size of the deformation cavity 11, so that the filling part 41 can just be embedded in the deformation cavity 11.

[0023] Figure 2The extrusion device before improvement is shown. It can be seen that the extrusion end of the extrusion shaft 3 of this extrusion device does not have an extrusion gasket 4. When using this extrusion device to extrude a bar, since the extrusion shaft 3 is a cylinder, when the extrusion shaft 3 touches the entrance of the extrusion die 1, the extrusion ends. However, the tail of the blank 5 is still located in the deformation cavity 11 of the extrusion die 1. That is to say, the tail of the blank 5 does not undergo effective extrusion deformation in the deformation cavity 11. After that, a ejecting device is needed to push the extruded bar back in the reverse direction to complete demolding. After extrusion, there are leftovers with no deformation and very small deformation amount at the tail of the obtained bar. The internal structure of the leftover part does not meet the quality requirements and needs to be cut off during subsequent machining. Moreover, after extrusion, an ejecting mechanism is needed to push the extruded bar back along the original path to complete demolding, and continuous production cannot be carried out, resulting in a reduction in material utilization rate, production efficiency, and an increase in manufacturing cost.

[0024] As Figure 1 shown, the embodiment of the present invention uses a specific extrusion device and a specific process for bar extrusion. Specifically, after heating the blank 5 to the extrusion temperature, it is placed in the extrusion cylinder 2 of the pre-heat-treated extrusion device for extrusion treatment. During the extrusion process, under the action of the extrusion force, the blank 5 undergoes extrusion deformation through the deformation cavity 11 and then enters the sizing cavity 12. Subsequently, the blank is extruded from the sizing cavity 12 to obtain a bar. Since the extrusion end of the extrusion shaft 3 is connected with an extrusion gasket 4 having a filling part 41, and the shape of the filling part 41 matches the shape of the deformation cavity 11. When the filling part 41 touches the entrance of the extrusion die, the extrusion does not end. The extrusion shaft 3 continues to move upward until the side wall of the filling part 41 fits with the inner wall of the deformation cavity 11. At this time, the filling part 41 just reaches the boundary line between the deformation cavity 11 and the sizing cavity 12, and the blank 5 is completely pushed into the sizing cavity 12. After extrusion, the tail of the blank 5 also undergoes effective extrusion deformation in the deformation cavity 11. Therefore, there are no leftovers with no deformation and very small deformation amount at the tail of the obtained bar, which can improve the material utilization rate and production efficiency. In addition, the embodiment of the present invention also controls the movement speed of the blank during the extrusion process. Specifically, at the initial stage of the extrusion process, the movement speed of the blank is relatively large (25 mm / s to 35 mm / s), which can reduce the idle stroke and the contact time between the blank 5 and the extrusion cylinder 2 and the extrusion die 1 during extrusion to reduce the surface temperature drop of the blank 5. When the remaining length of the blank 5 in the extrusion cylinder 2 is 1 / 3L to 1 / 2L, the movement speed of the blank is gradually reduced to a lower level (10 mm / s to 20 mm / s), and then extrusion continues until the blank 5 completely enters the sizing cavity, which can ensure that the temperature rise in the core area of the bar tail is not too high, and thus can improve the tissue uniformity of the bar. In summary, by using the device and method of the embodiment of the present invention, not only can the tail leftovers of the bar be improved, but also the tissue uniformity of the bar can be improved.

[0025] As Figure 1As shown, since the shape of the deformation cavity 11 is frustum-shaped, the matching filling part 41 is also frustum-shaped. During the extrusion process, the working surface of the filling part 41 cannot completely cover the extruded surface (the tail of the blank 5) of the blank 5, and there is a gap between the blank 5 and the filling part 41. During the extrusion process, the force on the extruded surface of the blank 5 is mainly concentrated in the middle area, resulting in severe tail shrinkage in the produced bar, and the inner concave of the bar tail forms a flared shape.

[0026] In some embodiments of the present invention, in order to further avoid severe tail shrinkage of the bar, the extrusion device further includes an annular filling pad 6. The annular filling pad 6 is sleeved on the side wall of the filling part 41. The annular filling pad 6, the extrusion gasket 4 and the extrusion shaft 3 together form a columnar extrusion unit. The material of the annular filling pad 6 is glass powder. Thus, before the filling part 41 enters the extrusion die 1, the upper end surface of the columnar extrusion unit completely covers the extruded surface of the blank 5, and there is no gap between the blank 5 and the filling part 41, making the force on the tail of the blank 5 more uniform and avoiding severe tail shrinkage of the blank 5. As the extrusion continues, the filling part 41 enters the extrusion die 1. Under the combined action of high temperature (the temperature of the blank 5 is relatively high during extrusion) and extrusion force, the annular filling pad 6 made of glass powder will partially melt, and the non-melting part of the annular filling pad 6 will also be extruded from the extrusion die 1. Finally, the side wall of the filling part 41 fits with the inner wall of the deformation cavity 11. After the extrusion ends, the tail of the blank 5 also undergoes effective extrusion deformation in the deformation cavity 11. Therefore, there is no non-deformed or very small deformation residue at the tail of the obtained bar. Since the time from when the filling part 41 enters the extrusion die 1 to the end of extrusion is relatively short, during this process, the time for the tail of the blank 5 to experience uneven force is short, and severe tail shrinkage will not occur. It can be seen that using the extrusion device in this embodiment can not only avoid the tail residue of the bar, but also avoid severe tail shrinkage of the bar.

[0027] For the case where the material of the bar is nickel-based alloy, titanium alloy, aluminum alloy, or magnesium alloy, in some embodiments of the present invention, the melting point of the glass powder is lower than 900°C. Exemplarily, the manufacturer of the glass powder is Beijing Tianli Chuang Glass Technology Development Co., Ltd., and the product model is MF-TE4 or MF-TD4.

[0028] As Figure 1 shown, in some embodiments of the present invention, the inner diameter of the inlet end of the deformation cavity 11, the inner diameter of the extrusion cylinder 2, and the diameter of the extrusion unit are all the same. During the extrusion process, the extrusion die 1, the extrusion cylinder 2, the blank 5, and the extrusion unit are in a coaxial state.

[0029] In some embodiments of the present invention, an annular lubricating pad 7 is provided on the inner wall of the outlet end of the extrusion cylinder 2, and the annular lubricating pad 7 is made of glass powder. During the extrusion process, the annular lubricating pad 7 plays a role of continuous lubrication. Under the combined action of high temperature (the temperature of the blank 5 is relatively high during extrusion) and extrusion pressure, the annular lubricating pad 7 made of glass powder will melt or be extruded from the device. In this embodiment, the melting point of the glass powder is lower than 900 °C. Exemplarily, the manufacturer of the glass powder is Beijing Tianli Chuang Glass Technology Development Co., Ltd., and the product model is MF-TE4 or MF-TD4.

[0030] In some embodiments of the present invention, specifically, the deformation cavity 11 is frustum-shaped, and the inner diameter of the inlet end of the deformation cavity 11 is larger than the inner diameter of the outlet end of the deformation cavity 11.

[0031] In some embodiments of the present invention, the vertical cross-section of the deformation cavity 11 is an isosceles trapezoid, and the base angle of the isosceles trapezoid is 30 degrees to 80 degrees.

[0032] In some embodiments of the present invention, as Figure 1 and Figure 3 shown, the extrusion gasket 4 further includes a transition portion 42 and a first connection portion 43. The filling portion 41, the transition portion 42, and the first connection portion 43 are connected in sequence. A second connection portion is provided at the extrusion end of the extrusion shaft 3, and the first connection portion 43 is connected to the second connection portion. Exemplarily, the first connection portion 43 is a bolt, and the second connection portion is a threaded hole corresponding to the bolt.

[0033] In some embodiments of the present invention, the extrusion gasket 4 is made of die steel.

[0034] If the extrusion ratio is too small, it cannot play the role of extrusion deformation, and the grains in the core cannot be refined. If the extrusion ratio is too large, the temperature rise of the bar will be too large, resulting in the growth of recrystallized grains, and the required extrusion pressure will increase, possibly exceeding the maximum tonnage of the equipment. Therefore, in some embodiments of the present invention, the extrusion ratio of the extrusion treatment is 2 to 9.

[0035] In some embodiments of the present invention, the preset deceleration is 3 mm / s 2 to 15 mm / s 2 .

[0036] In some embodiments of the present invention, the extrusion temperature is 950 °C to 1100 °C.

[0037] In some embodiments of the present invention, the temperature of the preheating treatment is 300 °C to 400 °C, and the time is 2 h to 4 h.

[0038] The present invention will be further described below with specific embodiments.

[0039] Example 1: The blank is extruded using the extrusion device as shown in Figure 1 . The extrusion device includes an extrusion die 1, an extrusion cylinder 2, an extrusion shaft 3, an extrusion gasket 4, and an annular filling pad 6. The extrusion shaft 3 and the extrusion gasket 4 are both arranged inside the extrusion cylinder 2. The extrusion gasket 4 is connected to the extrusion end of the extrusion shaft 3. The extrusion gasket 4 includes a filling portion 41. The extrusion die 1 is of a cylindrical structure. The inlet end of the extrusion die 1 is correspondingly connected to the outlet end of the extrusion cylinder 2. The inner cavity of the extrusion die 1 consists of a deformation cavity 11 and a sizing cavity 12 along the axial direction. The deformation cavity 11 is located at the inlet end of the extrusion die 1. The shape of the filling portion 41 matches the shape of the deformation cavity 11. The annular filling pad 6 is sleeved on the side wall of the filling portion 41. The annular filling pad 6, the extrusion gasket 4, and the extrusion shaft 3 together form a columnar extrusion unit. The material of the annular filling pad 6 is glass powder. The inner diameter of the inlet end of the deformation cavity 11, the inner diameter of the extrusion cylinder 2, and the diameter of the extrusion unit are all 900 mm. An annular lubricating pad 7 is provided on the inner wall of the outlet end of the extrusion cylinder 2. The material of the annular lubricating pad 7 is glass powder. The deformation cavity 11 is frustum-shaped, and the inner diameter of the inlet end of the deformation cavity 11 is larger than the inner diameter of the outlet end of the deformation cavity 11. The vertical cross-section of the deformation cavity 11 is an isosceles trapezoid, and the base angle of the isosceles trapezoid is 30 degrees.

[0040] Step A1: After heating the blank to the extrusion temperature, place it in the extrusion cylinder of the pre-heated extrusion device and perform extrusion treatment to obtain a bar. Among them, the material of the blank is IN617 nickel-based alloy. The blank is cylindrical. The length L of the blank is 1200 mm, the diameter of the blank is 860 mm, the extrusion temperature is 1100 °C, the temperature of the pre-heat treatment is 400 °C, the time is 4 h, the extrusion ratio of the extrusion treatment is 9. In the initial stage of the extrusion treatment, the moving speed of the blank is the first speed. When the remaining length of the blank in the extrusion cylinder is 1 / 3L, the moving speed of the blank is decelerated from the first speed to the second speed at a preset deceleration until the blank completely enters the sizing cavity. The first speed is 25 mm / s, the second speed is 10 mm / s, and the preset deceleration is 15 mm / s 2 .

[0041] Example 2 The difference from Example 1 is that the inner diameter of the inlet end of the deformation cavity 11, the inner diameter of the extrusion cylinder 2, and the diameter of the extrusion unit are all 400 mm.

[0042] Step A1 is as follows: Heat the blank to the extrusion temperature and then place it in the extrusion cylinder of the pre-heat-treated extrusion device for extrusion to obtain a bar. Among them, the material of the blank is GH4169 nickel-based alloy, the blank is cylindrical, the length L of the blank is 1000 mm, the diameter of the blank is 380 mm, the extrusion temperature is 950 °C, the temperature of the pre-heat treatment is 300 °C, the time is 2 h, the extrusion ratio of the extrusion treatment is 2, the moving speed of the blank at the initial stage of the extrusion treatment is the first speed. When the remaining length of the blank in the extrusion cylinder is 1 / 2L, the moving speed of the blank is decelerated from the first speed to the second speed at a preset deceleration until the blank completely enters the sizing cavity. The first speed is 35 mm / s, the second speed is 20 mm / s, and the preset deceleration is 5 mm / s 2 。

[0043] Example 3 The difference from Example 1 is that the inner diameter of the inlet end of the deformation cavity 11, the inner diameter of the extrusion cylinder 2, and the diameter of the extrusion unit are all 600 mm.

[0044] Step A1 is as follows: Heat the blank to the extrusion temperature and then place it in the extrusion cylinder of the pre-heat-treated extrusion device for extrusion to obtain a bar. Among them, the material of the blank is GH4738 nickel-based alloy, the blank is cylindrical, the length L of the blank is 1500 mm, the diameter of the blank is 570 mm, the extrusion temperature is 1040 °C, the temperature of the pre-heat treatment is 350 °C, the time is 3 h, the extrusion ratio of the extrusion treatment is 5, the moving speed of the blank at the initial stage of the extrusion treatment is the first speed. When the remaining length of the blank in the extrusion cylinder is 1 / 2L, the moving speed of the blank is decelerated from the first speed to the second speed at a preset deceleration until the blank completely enters the sizing cavity. The first speed is 30 mm / s, the second speed is 15 mm / s, and the preset deceleration is 3 mm / s 2 。

[0045] Comparative Example 1 The difference from Example 2 is that the used extrusion device is the extrusion device obtained by removing the annular packing pad 6 in the extrusion device of Example 2.

[0046] Comparative Example 2 The difference from Example 3 is that during the whole process of the extrusion treatment, the moving speed of the blank is 30 mm / s.

[0047] Experimental Example Observe the bars prepared in Example 2 and Comparative Example 1, and the results are shown inFigure 4 and Figure 5 , it can be seen from Figure 4 that the rod produced in Example 2 has a smaller tailing; it can be seen from Figure 5 that the rod produced in Comparative Example 1 has serious tailing.

[0048] Perform finite element analysis on the temperature field of the vertical cross-section of the rods in Example 3 and Comparative Example 2. The results are shown in Figure 6 and Figure 7 . It can be seen from Figure 6 and Figure 7 that the temperatures of the core regions of the rod heads in Example 3 and Comparative Example 2 are close. The temperature of the core region at the tail of the rod in Example 3 is lower, about 1050 °C, and the temperature of the core region at the tail of the rod in Comparative Example 2 is higher, about 1070 °C. Perform metallographic structure characterization on the core regions at the tails of the rods produced in Example 3 and Comparative Example 2. The results are shown in Figure 8 and Figure 9 . It can be seen from Figure 8 and Figure 9 that compared with Example 3, due to the higher temperature of the core region at the tail of the rod in Comparative Example 2, the grains at the tail of the rod produced in Comparative Example 2 are larger and the uniformity is poorer, and the tissue uniformity of the rod in Comparative Example 2 is poorer.

[0049] It should be noted that Figure 6 and Figure 7 , on the left side of the rod corresponds to the tail of the rod, and on the right side of the rod corresponds to the head of the rod.

[0050] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. An extrusion method for bars, characterized in that, Based on an extrusion device, the extrusion device includes an extrusion die (1), an extrusion cylinder (2), an extrusion shaft (3) and an extrusion gasket (4). The extrusion shaft (3) and the extrusion gasket (4) are both arranged inside the extrusion cylinder (2). The extrusion gasket (4) is connected to the extrusion end of the extrusion shaft (3). The extrusion gasket (4) includes a filling part (41). The inlet end of the extrusion die (1) is correspondingly connected to the outlet end of the extrusion cylinder (2). The inner cavity of the extrusion die (1) consists of a deformation cavity (11) and a sizing cavity (12) along the axis. The deformation cavity (11) is located at the inlet end of the extrusion die (1). The shape of the filling part (41) matches the shape of the deformation cavity (11). The extrusion method of the bar includes: heating the blank (5) to the extrusion temperature and then placing it inside the extrusion cylinder (2) of the preheated extrusion device for extrusion treatment to obtain a bar. Wherein, the length of the blank (5) is L. In the initial stage of the extrusion treatment, the moving speed of the blank is the first speed. When the remaining length of the blank (5) in the extrusion cylinder (2) is 1 / 3L to 1 / 2L, the moving speed of the blank (5) is reduced from the first speed to the second speed at a preset deceleration until the blank (5) completely enters the sizing cavity. The first speed is 25 mm / s to 35 mm / s, and the second speed is 10 mm / s to 20 mm / s.

2. The extrusion method of the bar according to claim 1, characterized in that, The extrusion ratio of the extrusion treatment is 2 to 9.

3. The extrusion method of the bar according to claim 1, characterized in that The preset deceleration is 3 mm / s 2 to 15 mm / s 2 .

4. The extrusion method of the bar according to claim 1, characterized in that, The extrusion temperature is 950 °C to 1100 °C.

5. The extrusion method of the bar according to claim 1, characterized in that, The temperature of the preheating treatment is 300 °C to 400 °C, and the time is 2 h to 4 h.

6. The extrusion method of the bar according to claim 1, characterized in that, The extrusion device further includes an annular filling pad (6). The annular filling pad (6) is sleeved on the side wall of the filling part (41). The annular filling pad (6), the extrusion gasket (4) and the extrusion shaft (3) together form a columnar extrusion unit. The material of the annular filling pad (6) is glass powder, and the melting point of the glass powder is lower than 900 °C.

7. The extrusion method of the bar according to claim 6, characterized in that, The inner diameter of the inlet end of the deformation cavity (11), the inner diameter of the extrusion cylinder (2) and the diameter of the extrusion unit are all the same.

8. The extrusion method of the bar according to claim 1, characterized in that, An annular lubricating pad (7) is provided on the inner wall of the outlet end of the extrusion cylinder (2). The material of the annular lubricating pad (7) is glass powder.

9. The extrusion method of the bar according to claim 1, characterized in that, The deformation cavity (11) is frustum-shaped. The inner diameter of the inlet end of the deformation cavity (11) is larger than the inner diameter of the outlet end of the deformation cavity (11). The vertical section of the deformation cavity (11) is an isosceles trapezoid, and the base angle of the isosceles trapezoid is 30 degrees to 80 degrees.

10. The extrusion method of the bar according to any one of claims 1-9, characterized in that, The extrusion gasket (4) further includes a transition part (42) and a first connecting part (43). The filling part (41), the transition part (42) and the first connecting part (43) are connected in sequence. A second connecting part is provided at the extrusion end of the extrusion shaft (3), and the first connecting part (43) is connected to the second connecting part.

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