CN111589955A - Soft magnetic alloy element hot impact extrusion die and preparation method thereof - Google Patents

Abstract

The invention discloses a soft magnetic alloy element hot impact extrusion die and a preparation method thereof, wherein the die comprises an upper die holder and a lower die holder, wherein a male die and a female die which are matched with each other are arranged on the upper die holder and the lower die holder; the position of the lower die body corresponding to the lower die core and the position of the upper die body opposite to the upper die core are provided with cooling cavities, and the lower die body and the upper die body are provided with inlets and outlets communicated with the corresponding cooling cavities. The preparation method mainly adopts the die, and combines the measures of heat preservation, pressure preservation and the like through the structural cooperation of rapid heating, temperature reduction and the like. The heating speed can be effectively improved, the soft magnetic alloy element can be cooled in time, the stable cooling gradient is ensured, the preparation of elements with complex structures can be met, the continuity of the internal crystal grain structure of the soft magnetic alloy element finished product is ensured, the good magnetic conductivity is kept, and the quality of the finished product is improved.

Description

Soft magnetic alloy element hot impact extrusion die and preparation method thereof

Technical Field

The invention relates to the field of die structures, in particular to a hot impact extrusion die for a soft magnetic alloy element and a preparation method thereof.

Background

The soft magnetic alloy is an alloy with high magnetic conductivity and low coercive force in a weak magnetic field, is widely applied to the radio electronic industry, precise instruments and meters, remote control and automatic control systems, is mainly used for energy conversion and information processing in a comprehensive way, and is an important material in national economy.

Generally, the method needs to be processed into a required element shape by adopting a stamping or extruding mode, and for some miniature special-shaped elements, a stamping and extruding combined mode is adopted, generally comprising the processes of raw material heating, stamping, pressure maintaining, grabbing and cooling and the like, meanwhile, in the processing process, the temperature rising process needs to be rapid and stable, the cooling gradient needs to be uniform or controllable, otherwise, the phenomena of crystal grain structure fracture, poor continuity, corresponding attenuation of magnetism and the like in the element are likely to occur, the quality of a finished product is greatly reduced, in the prior art, the raw material is generally heated externally, then is placed on a die for stamping and extruding, after the pressure maintaining is completed, the raw material is then grabbed to other places for cooling, in the steps, because the heating is outside the die, when the heating is completed and placed on the die, the temperature of the raw material is relatively changed, the processing requirement is probably not met, secondly, in the pressure maintaining process, the finished product is actually in a natural cooling state, and secondary cooling is carried out after the pressure maintaining is completed and removed, so that the crystal grain structure fracture caused by uneven cooling and heating can be caused.

In addition, for the processing of soft magnetic alloy components such as Fe-Ni system and Fe-Co system, powder sintering forming and cold working are generally adopted, wherein if powder sintering forming is adopted, although forming is easy, the internal porosity of the material is large, and the soft magnetic performance of the material is influenced. The integral cold-working forming has the defects of large raw material waste, low production efficiency, cracking of blank, reduction of magnetic conductivity due to processing stress, lower product percent of pass and the like.

Disclosure of Invention

In order to solve the problems, the invention provides a soft magnetic alloy element hot impact extrusion die and a preparation method thereof, which are used for improving the heating speed and the cooling uniformity in the impact extrusion process, ensuring the continuous crystal grain structure in a finished product and improving the quality of the soft magnetic alloy finished product.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the utility model provides a soft magnetic alloy component hot-stamping extrusion mould, includes upper die base, die holder to and set firmly respectively on upper die base and die holder, and the terrace die and the die that match each other, the die includes die body down, and sets firmly the lower mold core in this lower die body, the terrace die includes the die body to and set firmly the last mold core on the last die body, its key lies in: the graphite coating layer with uniform thickness is arranged on the circumferential outer side of the lower die body, and induction coils are uniformly distributed on the outer surface of the graphite coating layer along the height direction of the graphite coating layer;

and cooling cavities are respectively arranged at the positions corresponding to the lower mold core in the lower mold body and the positions facing the upper mold core in the upper mold body, and each cooling cavity is provided with an inlet and an outlet communicated with the cooling cavity.

By adopting the scheme, the heating and cooling can be completed on the die in the whole processing process, the rapid heating of the lower die body is realized by utilizing the characteristic of rapid heating and heat conduction of the graphite, namely, the raw material in the lower die body is heated, and because the graphite is completely coated on the circumferential outer side of the lower die body, the raw material is subjected to heat transfer through the side wall of the lower die body, so that the outer edge of the raw material is heated relatively quickly, the flow property of the extrusion die can meet the extrusion requirement relatively quickly, and then the back surfaces of the lower die core and the upper die core are subjected to surface cooling by adopting a cooling medium through arranging a cooling cavity, when impact extrusion is finished, in the pressure maintaining process, the front surfaces of the upper and lower mold cores are contacted with the upper and lower surfaces of the raw material, the upper mold core and the lower mold core are cooled, so that the finished product is synchronously cooled, and the consistency of the overall cooling speed can be basically ensured, thereby effectively improving the quality of the finished product.

Preferably, the method comprises the following steps: the inlet and the outlet are respectively positioned at two ends of the cooling cavity, and one end, close to the inlet, in the cooling cavity is provided with a flow dividing structure. By adopting the scheme, the flow of the cooling medium in the cooling cavity is favorably enhanced through the flow dividing structure, the heat accumulation at the position is avoided due to the flowing dead circulation point, and the condition that the corresponding mold core position is cooled asynchronously is avoided.

From the viewpoint of reducing the cost of the mold and replaceability, the flow dividing structure preferably comprises flow dividing pipes which are positioned in the end parts of the corresponding mold bodies and arranged along the width direction of the corresponding mold bodies, the outer sides of the flow dividing pipes are communicated with the inlets, the inner sides of the flow dividing pipes are provided with nozzles distributed along the length direction of the flow dividing pipes, and the nozzles extend into the cooling cavity.

Preferably, the method comprises the following steps: and the lower die body is provided with a jack penetrating through the graphite coating layer. By adopting the scheme, the jacks can be used for mounting the thermocouples so as to better monitor the temperature of the lower die body.

Preferably, the method comprises the following steps: the lower die body is provided with a uniform wall thickness, and uniform distances are reserved between the lower die core and the corresponding cooling chamber and between the upper die core and the corresponding cooling chamber. By adopting the scheme, the phenomenon that the heating or cooling speed is inconsistent due to the thickness of the die body can be avoided.

Preferably, the method comprises the following steps: the two ends of the lower mold core are provided with extrusion grooves, the middle part of the lower mold core is provided with a main punching hole, and the lower mold body is provided with symmetrically arranged demolding ejector rods. By adopting the scheme, the extrusion grooves on the two sides are used for forming the convex shoulders at the two ends of the product, and the demoulding ejector rod arranged in the middle is used for assisting demoulding after pressure maintaining and cooling to eject the finished product element out of the female die.

Preferably, the method comprises the following steps: and a positioning guide structure is arranged between the upper die base and the lower die base and comprises guide cylinders which are symmetrically distributed on the lower die base and guide rods which are positioned on the upper die base and matched with the guide cylinders. By adopting the scheme, the positioning guide structure can ensure that the female die and the male die can be just engaged, and the quality consistency of the formed product is improved.

On the basis, the application provides a preparation method of a soft magnetic alloy element, so as to improve the quality of a finished product of the soft magnetic alloy and improve the yield, and the technical scheme is as follows:

the key point of the preparation method of the soft magnetic alloy element is that: firstly, processing a plate into a proper sample blank by wire cutting, installing a die on a hot stamping machine, starting a power supply of the hot stamping machine, then placing the processed sample blank into a female die, electrifying and heating the sample blank through an induction coil, keeping the temperature until the temperature of the blank is consistent with that of the die after the die is heated to a proper temperature, and then driving an upper die holder to perform punch forming through the punch;

secondly, after the punching is finished, heat preservation and pressure maintaining are carried out according to the material properties, then the pressure is relieved, the induction coil heating power supply and the punching machine heating power supply are closed, and cold water is pumped into the cooling cavity through the inlet;

and thirdly, demolding and taking out the element.

By adopting the scheme, the soft magnetic alloy element is manufactured by adopting the hot impact extrusion die, the problems of complex special-shaped elements in the traditional manufacturing process can be effectively solved, the internal structure of the soft magnetic alloy can be kept complete and higher magnetic permeability, and the soft magnetic alloy element can play a role in inhibiting ordered transformation in the alloy through quick cooling of the lower die, inhibiting the generation of harmful phases, improving the qualification rate of finished products, and enabling the element and the lower die which are subjected to quick cooling to be more easily subjected to cold contraction separation and demoulding.

Preferably, the method comprises the following steps: and before the sample blank is placed into the female die, uniformly spraying boron nitride on the surface of the die, which is in contact with the sample blank. By adopting the scheme, the later-stage quick demoulding is facilitated, and adhesion is reduced.

Preferably, the method comprises the following steps: in the first step, the plate is Fe-50% Ni with the thickness less than or equal to 4mm, and when the mould is heated to 800-850 ℃, the heat is preserved for 10-15 s until the blank temperature is consistent with the mould;

and in the second step, after the stamping is finished, the temperature is kept for 30-35 s, and after the element is taken out in the third step, the element is subjected to stress relief annealing at 200 ℃, and then surface polishing treatment is carried out. The Fe-Ni soft magnetic alloy prepared by the scheme has better continuity of internal crystal grains, and is beneficial to further improving the magnetic conductivity of elements through annealing treatment.

Compared with the prior art, the invention has the beneficial effects that:

the hot impact extrusion die for the soft magnetic alloy element and the preparation method thereof can meet the requirement of preparing the soft magnetic alloy element with the special-shaped complex structure, can effectively improve the heating speed in the impact extrusion process, timely cool and ensure stable cooling gradient, are favorable for ensuring the continuity of the internal crystal grain structure of a finished product of the soft magnetic alloy element, keep good magnetic conductivity and improve the quality of the finished product.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a cross-sectional view of FIG. 1;

FIG. 3 is a schematic cross-sectional view of a flow-splitting structure;

FIG. 4 is a schematic view of a male die mounting structure;

FIG. 5 is a schematic view of a female die mounting structure;

fig. 6 is a schematic structural diagram of a finished soft magnetic alloy element.

Detailed Description

The present invention will be further described with reference to the following examples and the accompanying drawings.

Referring to fig. 1 to 5, the soft magnetic alloy element hot impact extrusion mold and the manufacturing method thereof are shown, wherein the mold mainly includes an upper mold base 1 and a lower mold base 2, a male mold and a female mold are respectively and fixedly arranged on the upper mold base 1 and the lower mold base 2, and the male mold and the female mold are matched with each other, wherein the male mold mainly includes an upper mold body 10 and an upper mold core 11 fixedly arranged on the upper mold body 10, the upper mold core 11 is vertically arranged downward, the female mold mainly includes a lower mold body 20 and a lower mold core 21 fixedly arranged in the lower mold body 20, as shown in the figure, the lower mold body 20 mainly includes an annular portion enclosing a space corresponding to the lower mold core 21, the annular portion is vertically arranged, and a supporting portion located at the bottom of the annular portion.

For avoiding raw and other materials heating to transport the influence to the temperature of mould process in this application, ensure simultaneously and carry out rapid heating up to raw and other materials, so the annular part circumference outside of die body 20 down is provided with graphite coating 3 rather than the surperficial hugging closely, the even unanimity of thickness of graphite coating 3, and highly equal with the annular part, the wall thickness of each part of annular part keeps unanimous simultaneously, guarantee like this that 3 surfaces of graphite coating and the raw and other materials that are in the die are outer along each distance equals, the same heat radiation volume of accessible heats, adopt the electric heating mode in this embodiment, as shown in figure 1, have along its direction of height evenly distributed's induction coil 4 at the surface of graphite coating 3.

On this basis, still through set up from taking cooling structure on the mould in this embodiment, it is longer to also avoid pressurize process and later stage cooling process interval time, it is unsatisfactory to lead to the cooling result, the condition that influences finished product quality takes place, the cooling result mainly includes cooling chamber 5, as shown in the figure, go up the position that corresponds the back of mold core 11 in the mold body 10, and the position that corresponds the back of lower mold core 21 in the lower mold body 20 all is equipped with cooling chamber 5, simultaneously, the both ends of going up mold body 10 and lower mold body 20 are equallyd divide and are equipped with respectively with import 50 and export 51 that correspond cooling chamber 5 intercommunication, can introduce the cooling chamber 5 with outside cooling medium through import 50, then export 51 is derived, and introduce and derive through the circulation, realize the refrigeration that flows of cooling medium.

In the process, through changing the type of the cooling medium, such as water, cold air or liquid nitrogen, or changing the circulation speed, the heat exchange speed between the cooling medium and the corresponding die body can be changed, namely, the cooling speed is reduced, and because in the pressure maintaining process, the front surfaces of the upper die core and the lower die core are tightly attached to the upper surface and the lower surface of the element, when the temperature of the die body is reduced, the heat exchange between the upper die core and the lower die core is carried out, thereby realizing the heat exchange cooling of the element, and because the upper surface and the lower surface are simultaneously cooled, under the condition of smaller thickness, the uniformity of the internal cooling gradient of the element is better.

In this application, for can be better control intensification and cooling process through outside automatic control, so be equipped with the jack 30 that runs through graphite coating 3 on die body 20 down, jack 30 is used for installing the thermocouple, during the use, the inductive head of thermocouple is hugged closely with the annular part of die body 20 down, is favorable to knowing its temperature fast, according to its material property again, can obtain its inside temperature fast to support for temperature control provides more data.

Referring to fig. 2 and 3, considering that in the case of only one inlet 50 and outlet 51, a dead point of fluid flowing in the cooling chamber 5 may exist, or insufficient heat exchange of the fluid occurs, a flow dividing structure 6 is provided at an end of the corresponding die body near the inlet 50, as shown in the figure, the flow dividing structure in this embodiment mainly includes a flow dividing pipe 60 disposed along the width direction of the die body, the outer side of the flow dividing pipe 60 is communicated with the corresponding inlet 50, the inner side thereof has a nozzle 61 communicated therewith, the nozzles 61 are uniformly distributed along the width direction of the cooling chamber 5, and the end of the nozzle 61 extends into the cooling chamber 5, the cross-sectional area of the outlet of all the nozzles 61 is smaller than or equal to the flow area of the inlet 50, so that the nozzles 61 spray, thereby achieving a complete coverage of the width direction of the cooling chamber 5, and achieving the purpose of.

In this embodiment, in order to facilitate the molding of the cooling chamber 5 and the installation of the flow dividing structure 6, it is considered that the mold body is made into a split structure during the development of the mold, i.e. a single mold body is formed by fixedly connecting an upper half structure and a lower half structure, the cooling chamber 5 is formed by two halves surrounding each other, and a sealing structure is provided at the contact position to prevent the fluid from overflowing.

Referring to fig. 1 to 6, a soft magnetic alloy element hot stamping and extruding die is used for preparing a soft magnetic alloy element, and a preparation method thereof mainly includes the following steps of firstly, preparing the size of the element according to needs, preliminarily processing a plate into a proper sample blank in a wire cutting mode so as to be placed into the die for stamping and extruding and molding, then installing the die on a hot stamping machine, namely, respectively fixing an upper die base 1 and a lower die base 2, starting a power supply of the hot stamping machine to preheat the die, then placing the processed sample blank into a concave die on the lower die base 2, electrifying and heating an induction coil 4 to accelerate a temperature rise process, after the die is heated to a proper temperature, preserving the temperature of the die until the temperature of the sample blank is consistent with that of the die, and then driving the upper die base 1 by the stamping machine to complete stamping action.

And secondly, after the punching is finished, carrying out heat preservation and pressure maintaining operation according to the physical properties of the blank, then unloading the pressure, closing a heating power supply of the punching machine and the die, pumping cold water into the cooling cavity 5 through the inlet 50, and discharging the heat-exchanged water from the outlet 51, wherein the water flow speed can be controlled and changed according to the temperature reduction gradient of the die and the physical properties of the blank, so that the influence on the physical properties of the finished product caused by too fast or too slow temperature reduction is prevented.

In the last step, the demoulding process is carried out, the upper die and the lower die are separated, and the element is taken out from the female die.

Specifically, taking the case of preparing the shaped Fe — Ni soft magnetic alloy element shown in fig. 6, it has shoulder protrusions 90 at both ends and a central hole 91 in the middle, and accordingly, the lower core 21 has extrusion grooves 210 adapted to the shoulder protrusions 90 at both ends and a main punched hole 212 adapted to the central hole 91 in the middle.

Firstly, selecting Fe-50% Ni plate with thickness not more than 4mm, carrying out linear cutting on the plate to the size with the shape suitable for the section of a concave die, then putting the processed blank into a die (spraying boron nitride on the surface of the die which is possibly contacted with a product before putting the blank into the die), heating the die to 850 ℃, keeping the temperature for about 10s until the temperature of the blank is consistent with that of the die, then punching the blank by a hot punch, the blank raw material is punched by the punch protruding from the upper die core 11, and at the same time, because the soft magnetic alloy has good fluidity at elevated temperature, by pressing it into the pressing groove 210, the corresponding shoulder protrusion 90 is formed, that is, in the process of preparing the soft magnetic alloy, the mold can adapt to the preparation of more soft magnetic alloys with complex structures only by replacing the proper lower mold core 21 according to the required shape.

After the stamping action is finished, the pressure and the temperature of the stamping machine are kept unchanged, namely the temperature and the pressure are kept for about 30s, the bending position is ensured to form a good texture structure above the crystallization temperature, so that the continuity of a crystal grain structure is kept, the magnetic conductivity of a finished product is improved, and after the temperature and the pressure are kept, the heating power supplies of the stamping machine and the die are closed, and the cold is conductedCold water is injected into the cooling cavity 5, so that the upper die and the lower die are rapidly cooled, and the elements are rapidly and uniformly cooled under the action of heat conduction, thereby inhibiting ordered transformation in the alloy and reducing FeNi₃And the formation of harmful phases, namely, the elements and the lower die are easy to demould under the action of cold water due to quick temperature reduction.

In the process, in order to fully ensure that the upper mold core and the lower mold core can be just opposite to impact extrusion, a positioning guide structure is arranged between the upper mold base 1 and the lower mold base 2, the positioning guide structure mainly comprises guide rods 12 symmetrically arranged on the upper mold base 1, as shown in the figure, the guide rods 12 are vertically and downwards arranged, the end parts of the guide rods are provided with ball tops, guide cylinders 22 arranged in one-to-one correspondence with the guide rods 12 are arranged on the lower mold base 2, the guide cylinders 22 are of a hollow structure and penetrate through the lower surface of the lower mold base 2, in order to ensure that the upper mold base 1 is in the whole moving stroke, parts of the guide rods 12 are always positioned in the guide cylinders 22, and therefore the mold is also provided with a support base 8, the lower mold base 2 is fixedly supported on the support base 8 through height-adjustable support legs 80, and the space between the support base.

In addition, because the shoulder protrusion 90 is formed by extrusion, after the pressure maintaining is completed, the component is usually tightly clamped on the lower mold core 21, so in this embodiment, the lower mold body 20 is further provided with the demolding mandril 7, as shown in fig. 1 and fig. 2, the demolding mandril 7 adopts a spring mandril structure and is symmetrically arranged at two sides of the main punched hole 212, and the position of the lower mold core 21 corresponding to the demolding mandril 7 is provided with a through hole, under normal conditions, the demolding mandril 7 protrudes out of the upper surface of the lower mold core 21 under the support of a spring, during the process of putting in the raw material blank and impact extrusion, the demolding mandril 7 is in a compression recovery state, when the temperature maintaining and pressure maintaining are finished and after the cooling is finished, the upper mold base 1 is reset, the finished component 9 can be jacked up under the effect of the demolding mandril 7, and the component demolding efficiency is greatly.

After the element is taken out of the die, the element is subjected to stress relief degradation at 200 ℃ to further improve the magnetic conductivity of the element, and finally polishing treatment is carried out, so that the special-shaped soft magnetic alloy element shown in figure 6 is formed, the magnetic conductivity of the special-shaped soft magnetic alloy element is not less than 30mH/m, the coercive force of the special-shaped soft magnetic alloy element is not more than 10A/m, and the product yield is high.

Finally, it should be noted that the above-mentioned description is only a preferred embodiment of the present invention, and those skilled in the art can make various similar representations without departing from the spirit and scope of the present invention.

Claims (10)

1. The utility model provides a soft magnetic alloy component hot-stamping extrusion mould, includes upper die base (1), die holder (2) to and set firmly respectively on upper die base (1) and die holder (2), and the terrace die and the die that match each other, the die includes die body (20) down to and set firmly lower mold core (21) in this die body (20) down, the terrace die includes die body (10) to and set firmly last mold core (11) on last die body (10), its characterized in that: the graphite coating layer (3) with uniform thickness is arranged on the circumferential outer side of the lower die body (20), and the induction coils (4) are uniformly distributed on the outer surface of the graphite coating layer (3) along the height direction of the graphite coating layer;

and cooling cavities (5) are respectively arranged in the lower die body (20) corresponding to the position of the lower die core (21) and the position of the upper die body (10) opposite to the upper die core (11), and each cooling cavity (5) is provided with an inlet (50) and an outlet (51) which are communicated with the cooling cavity.

2. A softmagnetic alloy component hot-extrusion die as claimed in claim 1, characterized in that: the inlet (50) and the outlet (51) are respectively positioned at two ends of the cooling chamber (5), and one end, close to the inlet (50), in the cooling chamber (5) is provided with a flow dividing structure (6).

3. A softmagnetic alloy component hot-extrusion die as claimed in claim 2, characterized in that: the flow dividing structure comprises flow dividing pipes (60) which are arranged in the end parts of the corresponding die bodies and arranged along the width direction of the flow dividing pipes, the outer sides of the flow dividing pipes (60) are communicated with the inlet (50), the inner sides of the flow dividing pipes are provided with nozzles (61) distributed along the length direction of the flow dividing pipes, and the nozzles (61) stretch into the cooling cavity (5).

4. A softmagnetic alloy component hot-extrusion die according to any of claims 1 to 3, characterized in that: and the lower die body (20) is provided with an insertion hole (30) penetrating through the graphite coating layer (3).

5. A softmagnetic alloy component hot-extrusion die according to any of claims 1 to 3, characterized in that: the lower die body (20) is provided with a uniform wall thickness, and uniform distances are reserved between the lower die core (21) and the corresponding cooling cavity (5) and between the upper die core (11) and the corresponding cooling cavity (5).

6. A softmagnetic alloy component hot-extrusion die as claimed in claim 1, characterized in that: the two ends of the lower mold core (21) are provided with extrusion grooves (210), the middle part of the lower mold core is provided with a main punching hole (212), and the lower mold body (20) is provided with symmetrically arranged demolding mandrils (7).

7. A softmagnetic alloy component hot-extrusion die as claimed in claim 1, characterized in that: a positioning guide structure is arranged between the upper die holder (1) and the lower die holder (2), and comprises guide cylinders (22) which are symmetrically distributed on the lower die holder (2) and guide rods (12) which are positioned on the upper die holder (1) and matched with the guide cylinders (22).

8. A method of making a soft magnetic alloy component, comprising: firstly, processing a plate into a proper sample blank by wire cutting, installing a die on a hot stamping machine, starting a power supply of the hot stamping machine, then placing the processed sample blank into a female die, carrying out power-on heating through an induction coil (4), carrying out heat preservation until the temperature of the blank is consistent with that of the die after the die is heated to a proper temperature, and then driving an upper die holder (1) to carry out punch forming through the punch;

secondly, after the punching is finished, heat preservation and pressure maintaining are carried out according to the material property, then the pressure is relieved, the heating power supply of the induction coil (4) and the heating power supply of the punching machine are closed, and cold water is pumped into the cooling cavity (5) through the inlet (50);

and thirdly, demolding and taking out the element.

9. A method for producing a soft magnetic alloy element according to claim 8, characterized in that: and before the sample blank is placed into the female die, uniformly spraying boron nitride on the surface of the die, which is in contact with the sample blank.

10. A method for producing a soft magnetic alloy element according to claim 8 or 9, characterized in that: in the first step, the plate is Fe-50% Ni with the thickness less than or equal to 4mm, and when the mould is heated to 800-850 ℃, the heat is preserved for 10-15 s until the blank temperature is consistent with the mould;

and in the second step, after the stamping is finished, the temperature is kept for 30-35 s, and after the element is taken out in the third step, the element is subjected to stress relief annealing at 200 ℃, and then surface polishing treatment is carried out.

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