Method for researching relationship between metal hafnium extrusion ratio and structure and extrusion die

Abstract

The extrusion die comprises a cylindrical die body, the die body comprises a deformation area and a sizing area, the interior of the deformation area is in a horn shape, and the inner diameter of an opening in the end, away from the sizing area, of the deformation area is matched with the diameter of an extrusion ingot; the inner diameter of the connecting part of the deformation area and the sizing area is matched with the diameter of a finished extrusion rod; the sizing area is cylindrical, and the inner diameter of the sizing area is matched with the diameter of a finished extrusion bar. The invention further discloses a method for researching the relationship between the metal hafnium extrusion ratio and the structure by adopting the extrusion die. According to the method, a special extrusion die is adopted, a semi-extrusion blank is prepared, evolution characteristics of tissues under different extrusion ratios can be visually seen, so that a reasonable extrusion ratio range is determined, meanwhile, other characterization means can be adopted to further reduce a parameter range, continuity and visualization of the relationship between the extrusion ratios and the tissues are realized, and the method is suitable for large-scale popularization and application. And the raw material input is reduced, and the test period is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of hafnium material plastic processing, and in particular relates to a method for studying the relationship between the extrusion ratio and structure of metal hafnium and an extrusion die. Background Art

[0002] Hot extrusion is a very important plastic processing method in metal materials, which has many advantages. First, during the extrusion process, the material is subjected to strong three-dimensional compressive stress, which can well achieve microstructure refinement and homogenization, and improve the strength and plasticity of the material. Second, the extrusion process is flexible and easy to operate. Usually, various profiles can be prepared by simply replacing the mold. The extrusion process is constrained by a variety of process parameters, such as extrusion temperature, extrusion speed, extrusion ratio, etc., among which the extrusion ratio is one of the core parameters affecting the extrusion process. At present, the relationship between the extrusion ratio and the grain size is generally satisfied that the grain size will decrease synchronously with the increase of the extrusion ratio, but when the extrusion ratio exceeds a certain threshold, the grain size will no longer change significantly with the increase of the extrusion ratio, and even the extrusion ratio will increase further. Due to factors such as a sharp increase in strain, the extrusion temperature rises, making the subsequent microstructure changes more complicated.

[0003] The formulation of traditional extrusion processes often requires the use of controlled variable methods to find the best extrusion parameters. For example, extrusion temperature, extrusion speed, extrusion die, etc. are used as quantitative factors, and extrusion ratio is used as a variable to conduct multiple rounds of tests to determine the best process parameters. The test cycle is long and the raw material investment is huge. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and an extrusion die for studying the relationship between the extrusion ratio and the organization of metal hafnium in view of the deficiencies of the above-mentioned prior art. The method uses a special extrusion die to prepare a semi-extruded billet, which can intuitively see the evolution characteristics of the organization under different extrusion ratios, thereby determining a reasonable extrusion ratio range, and other characterization methods can be used to further narrow the parameter range. Compared with traditional research methods, this method realizes the continuity and visualization of the relationship between the extrusion ratio and the organization, reduces the input of raw materials, and shortens the test cycle.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: an extrusion die for studying the relationship between the extrusion ratio and the structure of metal hafnium, characterized in that it includes a cylindrical die body, the die body includes a deformation zone and a sizing zone, the interior of the deformation zone is trumpet-shaped, the inner diameter of the opening at one end of the deformation zone away from the sizing zone matches the diameter of the extruded ingot, and the inner diameter of the connecting part of the deformation zone and the sizing zone matches the diameter of the finished extruded rod; the angle between the inner wall of the deformation zone and the end plane of the deformation zone is θ1, the angle between the inner wall and the outer wall of the deformation zone is θ2, θ1+θ2=90°; the sizing zone is cylindrical, and the inner diameter of the sizing zone matches the diameter of the finished extruded rod.

[0006] The above-mentioned extrusion die for studying the relationship between the extrusion ratio and the structure of metal hafnium is characterized in that the length L1 of the deformation zone along the axial direction is 75 mm, and the length L2 of the sizing zone along the axial direction is 10 mm.

[0007] The above-mentioned extrusion die for studying the relationship between the extrusion ratio and the structure of metal hafnium is characterized in that the conical deformation zone and the sizing zone are an integrated structure.

[0008] Furthermore, the present invention provides a method for studying the relationship between the extrusion ratio and the structure of metal hafnium using the above extrusion die, characterized in that it comprises the following steps:

[0009] Step 1: design the size of the extrusion die and prepare the extrusion die according to the extrusion ratio range and the extrusion ingot size to be studied;

[0010] Step 2, heating an extruded ingot with a diameter of D mm to a temperature to be studied, keeping the temperature for D / 2 min, and then sending the kept extruded ingot into the extrusion die described in step 1 for extrusion. When the extruded ingot is extruded from the end of the sizing zone of the extrusion die away from the deformation zone, stop extruding and retract the extrusion rod to obtain a semi-extruded billet;

[0011] Step 3: split the semi-extruded billet described in step 2 along the extrusion direction, and cut samples along the central axis to obtain continuous high and low magnification metallographic structure evolution photos.

[0012] The above method is characterized in that the extrusion die in step 1 is made of H13 steel.

[0013] The above method is characterized in that the extrusion in step 2 is performed using a forward extruder.

[0014] The above method is characterized in that the sample cutting in step 3 can be carried out in any area of ​​the semi-extruded billet located in the deformation zone of the extrusion die according to research needs.

[0015] The above method is characterized in that it also includes determining a reasonable extrusion ratio range based on the high and low magnification metallographic structure evolution photos obtained in step three.

[0016] The above method is characterized in that the basis for determining the reasonable extrusion ratio range is: observing the grain distribution in the metallographic photograph of the deformation zone, the beginning of the appearance of fine grains with complete grain boundaries in the organization is regarded as the minimum value of the reasonable extrusion ratio range; except for a few flattened and elongated difficult-to-deform grains, a large number of fine grain areas are formed, which is regarded as the maximum value of the reasonable extrusion ratio range.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. Compared with the single extrusion ratio design of the existing extrusion die (that is, the extrusion ratio can only achieve a certain fixed value), the present invention adopts a trumpet-shaped variable diameter zone design, which has a simple structure and can observe the continuous changes of the organization within a certain extrusion ratio range.

[0019] 2. The present invention uses a special extrusion die to prepare a semi-extruded billet, which can intuitively see the evolution characteristics of the organization under different extrusion ratios, thereby determining a reasonable extrusion ratio range, and other characterization methods can be used to further narrow the parameter range. Compared with traditional research methods, this method realizes the continuity and visualization of the relationship between extrusion ratio and organization, reduces raw material input, and shortens the test cycle.

[0020] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the extrusion die of the present invention.

[0022] Figure 2 This is a schematic diagram of the regional distribution of samples cut in the present invention.

[0023] Figure 3 These are the metallographic photographs of the metallographic samples in various regions of Example 2 of the present invention.

[0024] Figure 4 These are metallographic photographs of the head portion of the first deformation zone structure and the tail portion of the first deformation zone structure of Example 2 of the present invention.

[0025] Description of reference numerals:

[0026] 1—deformation zone; 2—sizing zone. DETAILED DESCRIPTION

[0027] like Figure 1 As shown, the extrusion die of the present invention comprises a cylindrical die body, the die body comprises a deformation zone and a sizing zone, the interior of the deformation zone is trumpet-shaped, the inner diameter of the opening at one end of the deformation zone away from the sizing zone matches the diameter of the extruded ingot, and the inner diameter of the connecting part of the deformation zone and the sizing zone matches the diameter of the finished extruded rod; the angle between the inner wall of the deformation zone and the end plane of the deformation zone is θ1, the angle between the inner wall and the outer wall of the deformation zone is θ2, θ1+θ2=90°; the sizing zone is cylindrical, and the inner diameter of the sizing zone matches the diameter of the finished extruded rod.

[0028] The axial length L1 of the deformation zone is 75 mm, and the axial length L2 of the sizing zone is 10 mm.

[0029] The conical deformation zone and the sizing zone are an integrated structure.

[0030] Example 1

[0031] A method for studying the relationship between the extrusion ratio and the structure of metal hafnium in this embodiment includes the following steps:

[0032] Step 1: The diameter of the extrusion ingot is 40 mm, and the extrusion ratio range is 1 to 40. The specific parameters of the extrusion die design are: inlet diameter D1 = 40 mm, outlet diameter D2 = 7.12 mm, θ1 = 77.5°, θ2 = 12.5°, deformation zone length L1 = 75 mm, and sizing zone length L2 = 10 mm.

[0033] Step 2: After heating an extrusion ingot with a diameter of 40 mm to 750° C. and keeping it warm for 20 minutes, the extrusion ingot is quickly placed into the extruder and semi-extruded, that is, when the material is extruded from the outlet of the die sizing zone, the extrusion rod is stopped from advancing and retracted, and the semi-extruded billet is taken out from the die after cooling;

[0034] Step 3: Split the semi-extruded billet along the extrusion direction and cut the sample along the central axis. Figure 2 The material was divided into four equal parts along the extrusion direction and metallographic samples were made to obtain continuous high and low magnification metallographic structure evolution photos, based on which the reasonable extrusion ratio range was determined.

[0035] Example 2

[0036] A method for studying the relationship between the extrusion ratio and the structure of metal hafnium in this embodiment includes the following steps:

[0037] Step 1: The diameter of the extrusion ingot is 60 mm, and the extrusion ratio range is 1 to 40. The specific parameters of the extrusion die design are: inlet diameter D1 = 60 mm, outlet diameter D2 = 10.27 mm, θ1 = 72°, θ2 = 18°, deformation zone length L1 = 75 mm, and sizing zone length L2 = 10 mm;

[0038] Step 2: After heating an extrusion ingot with a diameter of 60 mm to 850° C. and keeping it warm for 30 minutes, the extrusion ingot is quickly placed into the extruder and semi-extruded, that is, when the material is extruded from the outlet of the die sizing zone, the extrusion rod is stopped from advancing and retracted, and the semi-extruded billet is taken out from the die after cooling;

[0039] Step 3: Split the semi-extruded billet along the extrusion direction and cut the sample along the central axis. Figure 2 The sample was divided into four equal parts along the extrusion direction to obtain metallographic samples. Continuous high- and low-magnification metallographic structure evolution photos were obtained, and characteristic areas were selected to make XRD samples.

[0040] Example 3

[0041] A method for studying the relationship between the extrusion ratio and the structure of metal hafnium in this embodiment includes the following steps:

[0042] Step 1: The diameter of the extrusion ingot is 80 mm, and the extrusion ratio range is 1 to 40. The specific parameters of the extrusion die design are: inlet diameter D1 = 80 mm, outlet diameter D2 = 13.44 mm, θ1 = 66.5°, θ2 = 23.5°, deformation zone length L1 = 75 mm, and sizing zone length L2 = 10 mm.

[0043] Step 2: After heating an extrusion ingot with a diameter of 80 mm to 950° C. and keeping it warm for 40 minutes, the extrusion ingot is quickly placed into the extruder and semi-extruded, that is, when the material is extruded from the outlet of the die sizing zone, the extrusion rod is stopped from advancing and retracted, and the semi-extruded billet is taken out from the die after cooling;

[0044] Step 3: Split the semi-extruded billet along the extrusion direction and cut the sample along the central axis. Figure 2 The sample was divided into four equal parts along the extrusion direction to obtain metallographic samples. Continuous high- and low-magnification metallographic structure evolution photos were obtained, and characteristic areas were selected to make SEM samples.

[0045] Example 4

[0046] A method for studying the relationship between the extrusion ratio and the structure of metal hafnium in this embodiment includes the following steps:

[0047] Step 1: The diameter of the extrusion ingot is 100 mm, and the extrusion ratio range is 1 to 40. The specific parameters of the extrusion die design are: inlet diameter D1 = 100 mm, outlet diameter D2 = 16.60 mm, θ1 = 61°, θ2 = 29°, deformation zone length L1 = 75 mm, and sizing zone length L2 = 10 mm.

[0048] Step 2: After heating an extrusion ingot with a diameter of 100 mm to 1050° C. and keeping the temperature for 50 minutes, the extrusion ingot is quickly placed into the extruder and semi-extruded, that is, when the material is extruded from the outlet of the die sizing zone, the extrusion rod is stopped from advancing and retracted, and the semi-extruded billet is taken out from the die after cooling;

[0049] Step 3: Split the semi-extruded billet along the extrusion direction and cut the sample along the central axis. Figure 2 The sample was divided into four equal parts along the extrusion direction to obtain continuous high- and low-magnification metallographic structure evolution photos, and characteristic areas were selected to make EBSD samples.

[0050] Example 5

[0051] A method for studying the relationship between the extrusion ratio and the structure of metal hafnium in this embodiment includes the following steps:

[0052] Step 1: The diameter of the extrusion ingot is 120 mm, and the extrusion ratio range is 1 to 40. The specific parameters of the extrusion die design are: inlet diameter D1 = 120 mm, outlet diameter D2 = 19.76 mm, θ1 = 56.5°, θ2 = 33.5°, deformation zone length L1 = 75 mm, and sizing zone length L2 = 10 mm.

[0053] Step 2: After heating an extrusion ingot with a diameter of 120 mm to 1150° C. and keeping the temperature for 60 minutes, the extrusion ingot is quickly placed into the extruder and semi-extruded, that is, when the material is extruded from the outlet of the die sizing zone, the extrusion rod is stopped from advancing and retracted, and the semi-extruded billet is taken out from the die after cooling;

[0054] Step 3: Split the semi-extruded billet along the extrusion direction and cut the sample along the central axis. Figure 2 The sample was divided into four equal parts along the extrusion direction to obtain metallographic samples. Continuous high- and low-magnification metallographic structure evolution photos were obtained, and characteristic areas were selected to make TEM samples.

[0055] The semi-extruded billet of Example 2 was cut open along the extrusion direction, and samples were cut along the central axis. The test was carried out according to GB / T6349 "Method for Determination of Average Grain Size of Metals". The results are shown in Figure 3 . Figure 3 The five metallographic photographs are respectively the initial structure, the IV deformation zone, the III deformation zone, the II deformation zone, the I deformation zone (the specific location is as follows Figure 2 As shown). In the low-magnification metallographic photograph, it can be seen that the initial grains are coarse. With the increase of the extrusion ratio, the grains are gradually flattened and elongated, and finally a mixed structure with obvious streamline (hard-to-deform grains and re-dynamically recrystallized grains) is formed. By observing the head and tail positions of region I at high magnification, it can be seen that when the material flows into region I, except for the hard-to-deform grains being flattened and elongated, most of the grains have completed dynamic recrystallization. With the further increase of the extrusion ratio, the structure does not change much, so the threshold of the extrusion ratio occurs in the first deformation zone.

[0056] The basis for determining the reasonable extrusion ratio range is: observe the grain distribution in the metallographic photograph of the deformation zone, find the area where fine grains with complete grain boundaries begin to appear in the organization, and it can be found that when the grains enter the second deformation zone, fine recrystallized grains appear in the organization ( Figure 4 a white arrow), then this position is regarded as the minimum value of the reasonable extrusion ratio range. When the extrusion enters the first deformation zone, it can be found that except for a few flattened and elongated difficult-to-deform grains (such as Figure 4 b), the other regions are all small recrystallized grains, which is regarded as the maximum value of the reasonable extrusion ratio range (such as Figure 4 c). Therefore, the II deformation zone is within the reasonable extrusion ratio range.

[0057] The present invention adopts a special mold design, which can intuitively see the process of continuous change of organization under different extrusion ratios, so as to determine the reasonable extrusion ratio range, and other characterization methods can be used to further narrow the parameter range. Compared with traditional research methods, this method realizes the continuity and visualization of the relationship between extrusion ratio and organization, reduces raw material input, and shortens the test cycle.

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. An extrusion die for studying the relationship between the extrusion ratio and structure of metal hafnium, characterized in that: The invention comprises a cylindrical die body, wherein the die body comprises a deformation zone (1) and a sizing zone (2); the interior of the deformation zone (1) is trumpet-shaped; the inner diameter of the opening of the end of the deformation zone (1) away from the sizing zone (2) matches the diameter of the extruded ingot; the inner diameter of the connecting portion between the deformation zone (1) and the sizing zone (2) matches the diameter of the finished extruded rod; the angle between the inner wall of the deformation zone (1) and the plane at the end of the deformation zone (1) is θ1; the angle between the inner wall and the outer wall of the deformation zone (1) is θ2, θ1+θ2=90°; the sizing zone (2) is cylindrical, and the inner diameter of the sizing zone (2) matches the diameter of the finished extruded rod.

2. The extrusion die for studying the relationship between the extrusion ratio and the structure of metal hafnium according to claim 1, characterized in that: The axial length L1 of the deformation zone (1) is 75 mm, and the axial length L2 of the sizing zone (2) is 10 mm.

3. The extrusion die for studying the relationship between the extrusion ratio and the structure of metal hafnium according to claim 1, characterized in that: The conical deformation zone (1) and the sizing zone (2) are an integrated structure.

4. A method for studying the relationship between the extrusion ratio and the structure of metal hafnium using the extrusion die as described in claim 1, 2 or 3, characterized in that: The following steps are involved: Step 1: design the size of the extrusion die and prepare the extrusion die according to the extrusion ratio range and the extrusion ingot size to be studied; Step 2, heating an extruded ingot with a diameter of D mm to a temperature to be studied, keeping the temperature for D / 2 min, and then sending the kept extruded ingot into the extrusion die described in step 1 for extrusion. When the extruded ingot is extruded from the end of the sizing zone (2) of the extrusion die away from the deformation zone (1), stop extruding and retract the extrusion rod to obtain a semi-extruded billet; Step 3: split the semi-extruded billet described in step 2 along the extrusion direction, and cut samples along the central axis to obtain continuous high and low magnification metallographic structure evolution photos.

5. The method according to claim 4, characterized in that The extrusion die described in step 1 is made of H13 steel.

6. The method according to claim 4, characterized in that The extrusion in step 2 is performed using a forward extruder.

7. The method according to claim 4, characterized in that Step 3: Cutting samples can be carried out in any area of ​​the semi-extruded billet within the deformation zone of the extrusion die according to research needs.

8. The method according to claim 4, characterized in that It also includes determining a reasonable extrusion ratio range based on the high and low magnification metallographic structure evolution photos obtained in step three.

9. The method according to claim 8, characterized in that The basis for determining the reasonable extrusion ratio range is as follows: observing the grain distribution in the metallographic photograph of the deformation zone, the appearance of fine grains with complete grain boundaries in the organization is regarded as the minimum value of the reasonable extrusion ratio range; except for a few flattened and elongated difficult-to-deform grains, a large number of fine grain areas are formed, which is regarded as the maximum value of the reasonable extrusion ratio range.

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