CN105414233A - Backward extrusion die with back pressure and processing technology adopting same - Google Patents

Abstract

The invention discloses a reverse extrusion die, which comprises a top die, a side pressing punch and a bottom die, the top die includes a press table, and a central punch fixed at the lower part of the press table and formed an integral structure with the press table ; The edge pressing punch is set outside the center punch and is set together with the pressure table through a spring; the middle part of the bottom mold is recessed to form a working space for accommodating the center punch, the edge pressing punch and the workpiece.

Description

A reverse extrusion die with back pressure and processing technology using the die

technical field

The invention relates to the technical equipment field of back-extrusion processing of cup/cylindrical parts, in particular to a back-pressure back-extrusion die and a processing technique using the die.

Background technique

As an advanced metal plastic forming process with less cutting and no cutting, reverse extrusion has the advantages of high efficiency, high quality, low consumption, and refined grains. It is widely used in cup/tube shapes of aluminum, magnesium, titanium and other non-ferrous alloys and steel materials. Parts or sleeves are formed. The cup/barrel "hugging" phenomenon and cracks in the wall are caused by the back-extruded material undergoing a large plastic deformation process and friction-induced non-uniform deformation. The phenomenon of "molding" makes the cup/tube parts unable to be demoulded, greatly reducing production efficiency and product quality; the occurrence of wall cracks leads to an increase in the scrap rate, especially for plastic deformation of magnesium alloys, titanium alloys, high-strength aluminum alloys, etc. Metals with low capacity are difficult to back-extrude to obtain high quality and performance cup/barrel parts.

Contents of the invention

Aiming at the disadvantages of cup/cylindrical part back-extrusion process and the disadvantages of low-plastic materials that are difficult to back-extrude, the purpose of the present invention is to provide a simple structure, low manufacturing and maintenance costs, which can well overcome the mold-hugging phenomenon. A reverse extrusion die with back pressure to improve the reverse extrusion forming ability of low-plastic material cup/cylindrical parts and a processing technology using the die.

Its technical solution is, a reverse extrusion die, including a top die, a side pressing punch, and a bottom die, the top die includes a press table, a central convex structure fixed at the lower part of the press table and integrated with the press table die; the edge-holding punch is set outside the center punch and is set together with the pressure table through a spring; the middle part of the bottom mold is recessed to form a working space for the center punch, edge-holding punch and workpiece.

The lower part of the press table and the upper part of the blank-holding punch are respectively provided with grooves matched with the spring, and the two ends of the spring are respectively fixed in the two grooves.

The bottom surface of the blank-holding punch forms an included angle of 2-5° with the horizontal plane.

A kind of technology that adopts above-mentioned anti-extrusion die to make the cup/barrel of alloy/metal, described technology comprises the following steps:

(1) casting billet, casting metal/alloy cylindrical billet;

(2) Cutting the billet, cutting off the skin of the billet and cutting the billet to the size required by the mold;

(3) Preheat billet, put billet into furnace and heat to 0.5-0.7Tm, Tm is the melting point temperature of this billet metal or alloy; In this step, generally according to furnace instrument insulation 1-2 hour;

(4) Lubricate the mold, apply lubricant on the center punch, bottom die and edge punch that participate in the extrusion operation;

(5) Set parameters, set the downward speed, downward displacement and final displacement of the central punch in the hydraulic machine parameter control instrument panel;

(6) Preheat the mold, heat the mold to 150-200°C, install a temperature tester on the mold and connect it to the control panel to realize real-time testing and control of the mold temperature;

(7) Extrusion operation, put the hotter billet into the mold, extrude according to the set parameters, the center punch goes down to squeeze the center of the billet, and the edge punch is produced under the action of the spring to meet the metal flow The force in the opposite direction is the back pressure, which avoids the extrusion of the billet periphery by the metal mold on the wall, and finally processes the billet into a cup/cylindrical piece. The above back pressure is calculated by the following formula;

$\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; S</span>}$

In the formula, F1 is the real-time back pressure during the extrusion process, the unit is N, k is the elastic coefficient of the spring, the unit is N/m, S is the downward displacement of the central punch, the unit is m, and it is fed back by the displacement sensor test, and d is the cup The inner diameter of the cup-shaped part, in m, and D is the outer diameter of the cup-shaped part, in m.

(8) Take out the cup/cylindrical piece and complete a reverse extrusion with back pressure.

The lubricant in the above step (4) is molybdenum disulfide.

The principle of the mold and process provided by the present invention to overcome the phenomenon of "mold holding" is as follows: during the reverse extrusion process, the center punch goes down, and the edge punch goes down at the same time, and the spring compresses, and the edge punch gives the cup/cylindrical part through spring compression. Downward pressure on the wall. Since there is a 2-5° inclination on the contact surface between the blank holder punch and the top of the wall of the cup/cylindrical part, the back pressure F1(N) generated is perpendicular to the surface of the end and is at the same angle as the axis of the center punch. 2-5° included angle, the F1 vector is decomposed into:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}$

is the back pressure vector, is the component force vector perpendicular to the inner surface of the die, is the component force vector perpendicular to the bottom of the die. F1, F2, F3 unit is N. Under the action of the horizontal outward component force F2, the inward flow tendency of the metal on the wall of the cup/cylindrical part will be changed, thereby avoiding the phenomenon that the wall of the cup/cylindrical part embraces the central punch.

The present invention improves the plastic forming limit of reverse extrusion and the principle of the depth dimension of the cup/cylindrical part: under the action of the pressure F3 perpendicular to the bottom of the die, the stress state of the deformation zone of the cup/cylindrical part is:

σ ₃ <σ ₂ <σ ₁ <0

The average stress value is:

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}$

Among them, σ ₁ (MPa) is the first principal stress, σ ₂ (MPa) is the second principal stress, σ ₃ (MPa) is the third principal stress, and σ ₀ (MPa) is the average stress.

Since compressive stress is generated in all three directions, strong three-dimensional compressive stress is generated inside the material during the reverse extrusion process under back pressure conditions. Extrusion forming limit and forming depth of cup/tube part, and three-dimensional compressive stress state are conducive to crack healing, thus avoiding cracks caused by uneven deformation of cup/tube part during reverse extrusion process.

The above technical scheme has the following advantages: the present invention designs different mold sizes according to the size and material of the cup/cylindrical part, and the three-dimensional compressive stress generated under the back pressure condition improves the forming limit of the cup/cylindrical part, and the back pressure contact of a certain slope The horizontally outward component force generated by the surface can overcome the inward flow of metal materials, thereby avoiding the phenomenon of "molding" and improving material utilization and product quality. Compared with prior art, the advantages of the present invention are:

1. The use of a certain slope of the blank-holding punch can not only effectively avoid the difficult problem of demoulding caused by the "mold-holding" phenomenon, but also play a role in positioning to a certain extent;

2. The use of the back pressure device is to produce a strong three-dimensional compressive stress state inside the material during the reverse extrusion process, and this three-dimensional compressive stress state greatly improves the forming limit of the reverse extrusion and the forming depth of the cup/cylindrical part. It is very beneficial to the reverse extrusion forming of cup/tube parts of advanced non-ferrous metals such as magnesium alloy, titanium alloy and high-strength aluminum alloy.

3. The reverse extrusion die with back pressure is simple in structure, easy to disassemble, and the back pressure does not need to be too large, so the cost is low and easy to maintain.

4. Through different mold materials and size designs, this method can be used for back-extrusion forming of cups/tubes of any shape and metal material, and the function is broadened

Description of drawings

Fig. 1 is a structural representation of an embodiment of the present invention;

detailed description

The present invention will be further described below in conjunction with specific embodiments.

In conjunction with Fig. 1, a kind of reverse extrusion mold comprises a top die 1, a side pressing punch 2, a bottom die 3, it is characterized in that, the top die comprises a press table 11, is fixed on the bottom of the press table and is connected with the press table The table is a central punch 12 with an integrated structure; the edge-holding punch is set outside the center punch and is set together with the pressure table through a spring 4; space. In this embodiment, the lower part of the press table and the upper part of the blank-holding punch are respectively provided with grooves 21 that cooperate with the springs, and the two ends of the springs are respectively fixed in the two grooves. The bottom surface of the blank-holding punch forms an included angle of 2-5° with the horizontal plane.

A kind of technology that adopts above-mentioned reverse extrusion die to make alloy/metal cup/bobbin, described technology comprises the following steps:

(1) casting billet, casting metal/alloy cylindrical billet;

(2) Cutting the billet, cutting off the skin of the billet and cutting the billet to the size required by the mold;

(3) Preheating the billet, heating the billet to 0.5-0.7Tm, where Tm is the melting point temperature of the billet metal or alloy;

(4) Lubricate the mold, apply lubricant on the center punch, bottom die and edge punch that participate in the extrusion operation;

(5) Set parameters, set the downward speed, downward displacement and final displacement of the central punch;

(6) Preheat the mold and heat the mold to 150-200°C;

(7) Extrusion operation, put the hotter billet into the mold, and extrude according to the set parameters, the center punch goes down to squeeze the center of the billet, and the edge punch squeezes the billet under the drive of the spring The periphery will finally process the ingot into a hollow cup/bobbin;

(8) Take out the cup/tube and complete a squeeze.

The lubricant in the above step (4) is molybdenum disulfide.

In the above embodiment, when preheating the billet, put the billet into the furnace and heat it to 0.5-0.7Tm, where Tm is the melting point temperature of the metal or alloy of the billet, and keep it warm for 1-2 hours according to the furnace instrument;

Set the descending speed, descending displacement and final displacement of the central punch in the hydraulic machine parameter control panel. The down speed is controlled by feeding back the actual down speed to the instrument panel according to the speed sensor. The downward displacement and final displacement are controlled and fed back according to the displacement sensor;

When preheating the mold, the mold is heated to 150-200°C, and a temperature tester is installed on the mold and connected to the control panel to realize real-time testing and control of the mold temperature;

In the extrusion operation, put the hotter ingot into the mold, and extrude according to the set parameters. The center punch moves down to squeeze the center of the ingot, and the edge punch is produced under the action of a spring, which is opposite to the direction of metal flow. The active force is the back pressure, which avoids the wall metal holding mold to extrude the periphery of the billet and finally processes the billet into cup/cylindrical parts. The back pressure is calculated by the following formula;

$\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; S</span>}$

In the formula, F1 is the real-time back pressure during the extrusion process, the unit is N, k is the elastic coefficient of the spring, the unit is N/m, S is the downward displacement of the central punch, the unit is m, and it is fed back by the displacement sensor test, and d is the cup The inner diameter of the cup-shaped part, in m, and D is the outer diameter of the cup-shaped part, in m.

Example 2, this example uses 7075 high-strength aluminum alloy as the experimental material to further describe the specific implementation of the present invention in detail. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

The first step: smelting 7075 aluminum alloy round bars, and then performing homogenization treatment;

The second step: peeling, and using wire cutting to obtain a round bar blank with a length of 25mm and a diameter of 80mm;

The third step: put it in the heating furnace, the heating temperature is 450°C (the melting point of the alloy is about 700°C), and heat for 2 hours;

Step 4: Set the downward working speed of the central punch to 2.5mm/s, the initial displacement of the working downward is 25mm, and the final downward displacement is 20mm;

Step 5: Apply molybdenum disulfide lubricant to the convex and concave dies;

Step 6: The mold is heated to 120°C with a heating jacket;

Step 7: Put the blank into the concave die, the punch starts to work downward, the working displacement is 25mm, the center material is pressed down, and the edge metal flows upward to contact the blank-press punch; when the punch works downward, the blank-press The punch follows down and gradually comes into contact with the end face of the wall of the cup/barrel, generating a reaction force, the so-called back pressure.

Step 8: The punch continues to descend, the spring is compressed, the back pressure gradually increases, and finally increases to 300N;

Step 9: The downward working displacement of the reverse extrusion punch reaches 5mm, and the punch moves upward;

Step 10: The blank-holding punch returns to its original position under the action of the spring, and the ejector rod pushes out the back-extrusion piece, and the back-extrusion ends.

After back extrusion, the obtained 7075 aluminum alloy cup/barrel.

The depth, verticality and damage of the cup/cylindrical part were measured. The depth-to-diameter ratio was greater than 1.5, the forming limit was significantly improved, the verticality error level between the wall and the bottom was high, and no cracks were found on the wall, and the quality was good.

To sum up, it is not the whole connotation of the present invention: thereafter, any modification, replacement, improvement and upgrading made within the spirit of the subject of the invention shall be included in the scope of protection of the present invention.

Claims (5)

1. an indirect-extrusion mould, comprise a top pressing mold (1), a flanging punch (2), a bed die (3), it is characterized in that, top pressing mold comprise present a theatrical performance as the last item on a programme (11), be fixed on present a theatrical performance as the last item on a programme bottom and with the central punch of presenting a theatrical performance as the last item on a programme in integrative-structure (12); Flanging punch to be located at outside central punch and by spring (4) together with presenting a theatrical performance as the last item on a programme and being set to; Bed die medial recess forms the working space holding central punch, flanging punch and workpiece (5).

2. indirect-extrusion mould according to claim 1, is characterized in that, described in present a theatrical performance as the last item on a programme bottom and flanging punch top be respectively equipped with the groove (21) coordinated with spring, both ends of the spring is separately fixed in two grooves.

3. indirect-extrusion mould according to claim 1, is characterized in that, described flanging punch bottom surface is horizontal by 2-5 ° of angle.

4. adopt indirect-extrusion mould described in claim 3 to make a technique for the cup/cylinder of alloy/metal, it is characterized in that, described technique comprises the following steps:

(1) billet is cast, cast metal/alloy cylinder billet;

(2) cut billet, base is machined away ingot epidermis and billet is cut to and meet mould requirement size;

(3) preheating billet, is heated to 0.5-0.7Tm by billet, and Tm is the melting temperature of this billet metal or alloy;

(4) lubricated dies, is participating in smearing lubricant on the central punch of squeeze job, bed die and flanging punch;

(5) setup parameter, sets the downstream rate of central punch, descending displacement and final mean annual increment movement;

(6) preheated mold, is electrically heated to 150-200 DEG C by mould;

(7) squeeze job, puts into mould by hotter complete billet, according to setting parameter extrude, central punch descending extruding billet center, flanging punch spring drive under extrude billet periphery the most at last billet be processed into hollow cup/cylinder;

(8) take out cup/bobbin, complete and once extrude.

5. method according to claim 4, is characterized in that, in above-mentioned steps (4), lubricant is molybdenum bisuphide.