A magnetic collector for electromagnetic bulging

Abstract

The present invention relates to the field of magnetic collector technology, and specifically to a magnetic collector for electromagnetic expansion, which includes a magnetic collector body and a coil, wherein the magnetic collector body includes an inner sleeve and an outer sleeve connected to the outside of the inner sleeve, the inner sleeve is a hollow structure, the coils are evenly distributed on the inside of the inner sleeve, a groove is provided between the outer cylindrical surface of the outer sleeve and the inner cylindrical surface of the inner sleeve, and multiple annular grooves connected to the outside are provided axially at both the upper and lower ends of the outer sleeve. The present invention analyzes the induced eddy current of a traditional magnetic collector, combines the skin depth of the current, and leaves sufficient thickness after providing annular grooves to ensure the flow of eddy current and the structural strength of the magnetic collector, and provides annular grooves for useless parts on the magnetic collector to reduce its mass, improve material utilization, and reduce excess ohmic loss.

Description

Technical Field

[0001] The present invention relates to the technical field of expansion magnetism collectors, in particular to a magnetism collector for electromagnetic expansion. Background Art

[0002] At present, lightweight alloys are widely used in pipelines, automobiles, aerospace and other fields to meet the demand for lightweight in these industries. Electromagnetic forming (EMF) technology is very suitable for the processing of such alloys due to its unique technical characteristics, and has therefore developed rapidly; as a common auxiliary tool in the electromagnetic forming process, the magnetizer has the function of improving the magnetic field configuration and improving the forming quality. It is also an important auxiliary equipment for realizing EMF flexible processing; the magnetizer used in traditional electromagnetic bulging has a trapezoidal structure in the vertical section. The incompletely closed rotating body formed by rotating the cross-section shape along the vertical center axis at a certain angle is the geometric structure of the magnetizer, such as Figure 1 As shown in the figure, its key structural design features the upper and lower bases and the slits. This is generally achieved by placing a coil inside the rotating body and a pipe outside. The induced current is first generated on the larger inner surface (the trapezoidal lower base), then flows through the opening of the rotating body to the outer surface of the magnet collector. Finally, the current converges on the smaller outer surface, increasing the density of the induced current per unit area and thus achieving the effect of "magnetic collection."

[0003] In electromagnetic forming technology, the existing magnetic collector for bulging is mostly a solid rotating body. The pulsed magnetic field generated by the driving coil will induce a large eddy current in the magnetic collector. Due to the skin effect of the current, the induced eddy current tends to converge and flow on the surface of the magnetic collector; this means that there will only be a small amount of stray current in a large area in the middle of the magnetic collector. This current has no effect on forming and brings about excess ohmic loss. Therefore, this part belongs to the "useless area", resulting in material waste and excessive weight of the magnetic collector; in addition, the large pulsed current flowing through the magnetic collector is bound to bring about rapid heat changes. The solid metal body structure makes the ventilation and heat dissipation performance of the overall forming system poor, which is not conducive to air circulation and subsequent cooling treatment. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a magnetic concentrator for electromagnetic bulging to solve the above problems.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a magnetic collector for electromagnetic bulging, which includes a magnetic collector body and a coil, the magnetic collector body includes an inner sleeve and an outer sleeve connected to the outside of the inner sleeve, the inner sleeve is a hollow structure, the coils are evenly distributed on the inside of the inner sleeve, a groove is provided between the outer cylindrical surface of the outer sleeve and the inner cylindrical surface of the inner sleeve, and multiple annular grooves connected to the outside are provided in the axial direction at the upper and lower ends of the outer sleeve.

[0006] In a preferred solution, the depth of the annular groove is not less than one third of the height of the outer casing.

[0007] In a preferred solution, a cooling water pipe made of non-metallic material is arranged in the annular groove.

[0008] In a preferred solution, a cooling air pipe made of non-metallic material is further provided in each of the annular grooves.

[0009] In a preferred embodiment, a cooling water pipe is arranged in one of the multiple annular grooves of the outer shell, and a cooling air pipe is arranged in the annular groove adjacent to the cooling water pipe, and the cooling water pipe and the cooling air pipe are arranged in sequence and spaced apart.

[0010] In a preferred solution, an insulating coating and a high-temperature resistant coating are coated on the wall surface of the annular groove.

[0011] In a preferred embodiment, the outer surface area of ​​the outer casing is 0.4-0.9 times the inner surface area of ​​the inner casing.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The present invention analyzes the induced eddy current of the traditional magnetic collector and, in combination with the skin depth of the current, leaves sufficient thickness after the annular groove is opened to ensure the flow of eddy current and the structural strength of the magnetic collector. Annular grooves are opened on the useless parts of the magnetic collector to reduce its mass, improve material utilization, and reduce excess ohmic loss.

[0014] 2. The magnetic collector of the present invention is simple to process, especially the annular groove is simple to process, and is easy to implement in actual engineering applications.

[0015] 3. The use of the present invention can effectively improve the forming efficiency of the workpiece and the ventilation and heat dissipation capacity of the magnetic collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the main structure of the present invention.

[0017] Figure 2 It is a schematic diagram of the three-dimensional structure of the present invention.

[0018] Figure 3 It is a schematic diagram of the top structure of the present invention.

[0019] Figure 4 for Figure 3 Schematic diagram of the cross-sectional structure along the AA axis.

[0020] Figure 5 It is a schematic diagram of the bulging state in the present invention.

[0021] Figure 6 It is a schematic cross-sectional view of a preferred embodiment of the present invention.

[0022] Figure 7 It is a schematic cross-sectional view of another preferred embodiment of the present invention.

[0023] Figure 8 This is a current density cloud diagram of a preferred embodiment of the present invention.

[0024] In the above drawings: 10, magnetic collector body; 11, inner sleeve; 12, outer sleeve; 13, slot; 14, annular groove; 15, cooling water pipe; 16, cooling air pipe; 20, coil; 30, pipe fitting; 40, fixed mold. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0026] Example 1

[0027] See attached Figure 1 -Attached Figure 4 As an embodiment of the present invention, a magnetic collector for electromagnetic bulging is proposed, which includes a magnetic collector body 10 and a coil 20. The magnetic collector body 10 includes an inner sleeve 11 and an outer sleeve 12 connected to the outside of the inner sleeve 11. The inner sleeve 11 is a hollow circular tube structure. The coils 20 are evenly distributed on the inner side of the inner sleeve 11. A groove 13 is provided between the outer cylindrical surface of the outer sleeve 12 and the inner cylindrical surface of the inner sleeve 11. Multiple annular grooves 14 are provided axially at the upper and lower ends of the outer sleeve 12. The annular grooves 14 are connected to the outside. The depth of the annular grooves 14 is one-third of the height of the outer sleeve 12; the wall surface of the annular groove 14 is coated with an insulating coating and a high-temperature resistant coating. The outer surface area of ​​the outer sleeve 12 is 0.8 times the inner surface area of ​​the inner sleeve 11.

[0028] Please refer to the attached Figure 5 The arrow in the figure represents the direction of the electromagnetic force. During the bulging process, the magnetic collector of the present invention is placed in the area to be bulged in the pipe, and a pulse current is passed through the coil. The magnetic collector applies a force to the pipe wall of the pipe 30 in the direction of the arrow. The pipe 30 is locally bulged under the dual action of the fixed mold 40 and the electromagnetic force.

[0029] The current has a skin effect. By analyzing the location where the current is concentrated in the magnetic collector, it can be known that the flow path of the pulse current in the magnetic collector is:

[0030] 1) The pulse capacitor discharges, generating a pulse current flowing through the coil. The pulsed strong magnetic field brought by the pulse current passes through the inner wall of the magnetic collector. According to Lenz's law, induced eddy currents are generated on the inner wall. Due to the influence of the skin effect, the eddy currents converge on the surface of the inner wall of the magnetic collector.

[0031] 2) The eddy current on the inner wall surface of the magnetic collector flows to the outer wall surface through the middle "beam";

[0032] 3) The induced eddy currents on the outer wall of the magnetic collector will in turn induce eddy currents in the pipe, generating Lorentz forces under the action of the magnetic field, thereby causing deformation. In the present invention, since the outer surface area of ​​the outer sleeve 12 is 0.8 times the inner surface area of ​​the inner sleeve 11, the current density gathered on the outer surface of the outer sleeve 12 is greater, which plays a role in regulating the magnetic field.

[0033] 4) When viewed from the ring upward, the current on the magnetic collector flows from the inner wall of the inner sleeve through the slit, converges on the outer wall of the outer sleeve and flows back through the slit, forming a closed loop.

[0034] The present invention is analyzed and calculated according to the following current analysis calculation formula:

[0035]

[0036] ω=2πf (2)

[0037]

[0038] Wherein, δ is the skin depth of the current, μ and σ refer to the relative magnetic permeability and electrical conductivity of the magnetic collector material, ω represents the angular frequency of the current, and f is the frequency of the current, which is related to the overall circuit parameters and is determined by the capacitance and inductance in the circuit. The circuit topology of electromagnetic forming can be simply equivalent to a second-order circuit, in which the discharge capacitor and the circuit equivalent inductance are generally small, so the frequency is large, and the skin depth is shallow, concentrated on the surface of the material. This means that in a large part of the center of the outer shell, there will only be a small amount of stray current. This part of the current has no effect on forming and brings about excess ohmic loss. Therefore, this part belongs to the "useless area", resulting in material waste and excessive weight of the magnetic collector.

[0039] Based on the above analysis and calculation, the structure of the outer shell is improved in this embodiment. The inner diameter of the inner shell is set to 62mm, the height is 90mm, and the wall thickness of the inner shell is 3mm. The thickness of the outer shell is 15mm and the height is 36mm. Three annular grooves 14 are provided on the outer shell. The width of the annular grooves 14 is 2mm and the depth is 13mm. In this case, after the coil is energized, the current in the magnetic collector body 10 flows as follows: Figure 4 As shown, the current density cloud diagram in the magnetic collector body 10 is as follows Figure 8 As shown in the figure, the current distribution in the magnetizer body 10 under this structure shows that the current density gathered on the outer surface of the outer shell 12 is larger, the expansion response is rapid, and good performance requirements are achieved. The annular groove 14 has the effect of reducing weight, and more importantly, it has the effect of reducing the stray current in the center of the magnetizer body 10 and reducing the ohmic loss.

[0040] Example 2

[0041] In another preferred embodiment, based on the above embodiment, see the attached Figure 6 The coil is omitted in the figure. A cooling water pipe 15 made of non-metallic material is set in each annular groove 14, and a cooling air pipe 16 made of non-metallic material is set outside the cooling water pipe 15 in each annular groove 14. The outer surface area of ​​the outer sleeve 12 is 0.4 times the inner surface area of ​​the inner sleeve 11.

[0042] In this embodiment, a cooling water pipe 15 and a cooling air pipe are provided in each annular groove 14. During expansion, cooling water and air are respectively introduced into the cooling water pipe 15 and the cooling air pipe 16 to cool the magnetic collector body 10, so that the magnetic collector body 10 maintains a temperature state that can operate sustainably and prevents the magnetic collector from being damaged by high temperature.

[0043] Example 3

[0044] In another preferred embodiment, see the attached Figure 7 In the multiple annular grooves 14 of the outer shell 12, a cooling water pipe 15 is set in one of the annular grooves 14, and a cooling air pipe 16 is set in the annular groove 14 adjacent to the cooling water pipe 15, that is, the cooling water pipe 15 and the cooling air pipe 16 are arranged in sequence in different annular grooves 14, and the outer surface area of ​​the outer shell 12 is 0.9 times the inner surface area of ​​the inner shell 11.

[0045] In this embodiment, cooling water pipes 15 and cooling air pipes 16 are arranged in different annular grooves 14, and water cooling and air cooling are arranged separately, which facilitates the layout of the water cooling system and the air cooling system and avoids interference between different cooling systems. Since the magnetic collector is small in size, separate arrangement can simplify the structure and also simplify the bulging operation.

[0046] Finally, it should be noted that the specific dimensions of the experimental device should not be limited to the dimensional ratios of the accompanying drawings, especially the depth of the experimental tank should be more than one meter, and the distance between the wave plate and the slope simulator should be more than two meters. The above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Although the present invention is described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be covered by the scope of the claims of the present invention.

Claims

1. A magnetic flux collector for electromagnetic bulging, comprising a magnetic flux collector body and a coil, characterized in that: The magnetic collector body includes an inner sleeve and an outer sleeve connected to the outside of the inner sleeve. The inner sleeve is a hollow structure. The coils are evenly distributed on the inside of the inner sleeve. A groove is provided between the outer cylindrical surface of the outer sleeve and the inner cylindrical surface of the inner sleeve. The upper and lower ends of the outer sleeve are provided with multiple annular grooves connected to the outside along the axial direction; the depth of the annular groove is not less than one third of the height of the outer sleeve.

2. The magnetic flux collector for electromagnetic bulging according to claim 1, characterized in that: A cooling water pipe made of non-metallic material is arranged in the annular groove.

3. The magnetic flux collector for electromagnetic bulging according to claim 2, characterized in that: A cooling air pipe made of non-metallic material is also arranged in each annular groove.

4. The magnetic flux collector for electromagnetic bulging according to claim 1, characterized in that: A cooling water pipe is arranged in one of the multiple annular grooves of the outer shell, and a cooling air pipe is arranged in the annular groove adjacent to the cooling water pipe. The cooling water pipe and the cooling air pipe are arranged in sequence and spaced apart.

5. The magnetic flux collector for electromagnetic bulging according to claim 1, characterized in that: The wall surface of the annular groove is coated with an insulating coating and a high-temperature resistant coating.

6. The magnetic flux collector for electromagnetic bulging according to claim 1, characterized in that: The outer surface area of ​​the outer sleeve is 0.4-0.9 times the inner surface area of ​​the inner sleeve.

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