CN110883122A - Large-size and large-height-diameter ratio magnesium alloy cast rods with short flow and large deformation billet making method - Google Patents

Abstract

The invention discloses a short-process large-deformation blank making method for a large-size large-height-diameter ratio magnesium alloy cast rod, which relates to a short-process large-deformation blank making die for upsetting and extruding the magnesium alloy cast rod, and the method comprises the steps that firstly, an ejecting cylinder ascends, a force is applied to a back pressure plate through an ejecting rod, a first male die descends, and the lower section of a blank gradually enters the lower part of an upper cavity and is deformed by upsetting and extruding; then the lower section of the blank gradually enters the upper part of the lower cavity and further contacts the cambered surface structure, the first male die is continuously pressed downwards, and when the lower section of the blank is completely filled with the upper part of the lower cavity, the back pressure plate descends; and when the first male die touches the bottom in the upper cavity, replacing the first male die with a second male die, downwards extruding the blank at the lower part of the upper cavity by the second male die to enable all the blanks to completely enter the lower female die, and finally reforming the cylindrical blank with the same original size, thereby completing upsetting deformation. The scheme has the advantages of no need of multi-pass upsetting and extruding, short flow, convenience in use, capability of effectively overcoming instability defects and capability of upsetting and extruding large-size blanks with large height-diameter ratio.

Description

Large-size and large-height-diameter ratio magnesium alloy cast rods with short flow and large deformation billet making method

technical field

The invention belongs to the metal extrusion forming technology, and is suitable for one-time large deformation billet making of a magnesium alloy cast rod with a large aspect ratio far greater than 3.

Background technique

The reciprocating upsetting-extrusion process is a large plastic deformation method that combines the two deformations of multi-pass upsetting and extrusion. The schematic diagram is shown in Figure 1. The first step: place the D×h blank in the first group of molds for upsetting; the second step: place the upsetting blank in the second group of molds for extrusion, the size of the extruded part is D ×h. So far, one step of upsetting-extrusion is completed, and the above deformation process is repeated until the required number of passes is reached, resulting in a large cumulative deformation. Although the process is simple in structure and convenient in operation. But there are still the following shortcomings:

In the process of upsetting deformation and extrusion deformation, due to the different sizes of blanks, different molds need to be replaced, and large cumulative strains are obtained through multi-pass reciprocating deformation, resulting in high production costs and long process.

Upsetting deformation is an uneven deformation process. When upsetting a cylindrical blank, the height-diameter ratio (h/D) is generally limited to within 2.5. In particular, when the height-diameter ratio is greater than 3, the cylindrical blank will be unstable, resulting in "double drum" and folding defects, making subsequent deformation impossible.

In view of this, the existing technology needs to be improved. Hence the case.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a large-size and large-height-diameter ratio magnesium alloy cast rod, a short-flow and large-deformation billet making method, which can effectively avoid "double drum shape" and folding defects due to instability, and realize large-size and large-height-diameter ratio cast rods. The short process large plastic deformation, and the steps are simple, easy to use.

In order to achieve the above-mentioned purpose, the solution of the present invention is:

The invention relates to a method for making a magnesium alloy cast rod with a large size and a large height and diameter ratio in a short process and large deformation. A punch, a punch installed on the lower table of the press, a back pressure plate, and an ejector rod connected to an ejection cylinder of the press, the punch includes a replaceable and installed first punch and a second punch; the punch The die includes an upper die and a lower die fixed under the upper die. The upper die is provided with an upper cavity with a wide upper part and a narrow lower part for inserting blanks; A lower cavity with a wide lower part, the lower part of the upper cavity and the upper part of the lower cavity are communicated with the same central axis; the lower diameter of the upper cavity, the upper diameter of the lower cavity and the diameter of the second punch are the same, the first The axial length of the second punch can at least reach into the cavity; the upper diameter of the upper cavity and the lower diameter of the lower cavity are the same as the diameter of the first punch; The rod and the back pressure plate can be moved up and down and enclosed in the lower part of the lower cavity, the upper surface of the back pressure plate is an arc structure with a concave middle part, and the method includes the following steps:

S1: Cylinder magnesium alloy bar blanking;

S2: Homogenize the cylindrical magnesium alloy bar as a cylindrical blank;

S3: heat the cylindrical blank to the forming temperature and keep it warm, and heat the mold to above the temperature of the cylindrical blank and keep it warm;

S4: Install the preheated and heat-preserved mold on the press, and evenly spray the organic graphite lubricant on the first punch, the second punch, the upper punch, and the lower punch; put the homogenized and heat-treated cylindrical blank into the in the upper part of the upper cavity;

S5: In the initial stage of upsetting extrusion, the ejector cylinder moves upward, and the push rod exerts a force on the back pressure plate. The press drives the first punch to move downward, and the lower section of the cylindrical blank gradually enters the lower part of the upper cavity. It is gradually deformed due to the upsetting extrusion; then the lower section of the billet gradually enters the upper part of the lower cavity, and then contacts the arc surface structure, and the first punch continues to press down. When the lower section of the billet completely fills the upper part of the lower cavity, the back pressure plate follows In the later stage of upsetting extrusion, when the first punch bottoms out in the upper cavity, most of the blanks have entered the lower part of the upper cavity and the lower part at the same time. In the cavity, replace the first punch with the second punch, and the second punch goes down to squeeze the lower blank of the upper cavity so that all the blanks can completely enter the lower die, and all the blanks at the back pressure plate can completely enter the lower blank. The position of the die is finally reshaped to form a cylindrical blank with the same size as the original, and the upsetting deformation is completed.

Preferably, the mold further includes a punching plate, and the method further includes step S6: after the punching plate is installed on the upper die, the press drives the second punch upward, and a very small part of the sticking left in the upper die is adhered to. The blank was knocked off by the beater plate.

Preferably, the method further includes step S7: the ejector cylinder drives the ejector rod and the back pressure plate to withdraw downward from the lower part of the lower cavity, so that the upsetting cylindrical blank can be taken out from the lower part of the lower cavity.

Preferably, the punch and the die are each fixedly connected to the upper worktable and the lower workbench by means of fasteners, and the method further includes step S8: after the cylindrical blank is taken out, the second punch goes down to the upper concave die and the lower concave die. Clamp the mold, loosen the fastening bolts connected with the upper worktable and the lower worktable, and unload the mold.

After the above scheme is adopted, the gain effect of the present invention is that in the extrusion forming process, the back pressure plate exerts back pressure on the lower cavity of the billet extrusion, so that the extrusion end of the billet can be corrected, and the upsetting deformation can be performed without instability. In addition, the present invention has simple steps, no need for multiple upsetting and extrusion, short process and convenient use, so that billets with large specifications and a height-diameter ratio far greater than 3 can be quickly upset and extruded, laying a certain foundation for the subsequent deformation process.

Description of drawings

Fig. 1 is the schematic diagram of traditional upsetting and extrusion deformation process;

Fig. 2 is the structural representation of the mould involved in the present invention;

3 is a schematic view of the working state when the cylindrical blank is put into the mold before upsetting and extrusion deformation in an embodiment of the present invention;

Fig. 4 is a schematic diagram of the working state of the mold in the deformation stage of the lower section of the cylindrical blank entering the upper part of the lower cavity during the upsetting and extrusion deformation process in an embodiment of the present invention;

5 is a schematic view of the working state of the mold in the deformation stage of the lower section of the cylinder blank gradually filling the upper part of the lower cavity during the upsetting and extrusion deformation process according to an embodiment of the present invention;

6 is a schematic diagram of the working state of the mold in the deformation stage of the lower section of the cylindrical blank entering the lower part of the lower cavity in the process of upsetting and extrusion deformation in an embodiment of the present invention;

7 is a schematic view of the working state of the mold in the final forming stage of upsetting and extrusion of the cylindrical blank after the first punch is replaced with the second punch according to an embodiment of the present invention.

Reference number:

The first punch 1, the upper concave die 2, the upper cavity 21, the upper part 211 of the upper cavity, the lower part 212 of the upper cavity, the first corner joint 22, the second corner joint 23, the lower cavity 3, the lower Cavity 31, upper part 311 of lower cavity, lower part 312 of lower cavity, third corner connection 32, fourth corner connection 33, back pressure plate 4, arc structure 41, ejector 5, second punch 6 , blank 7, beater plate 8.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in Figure 2-7, the magnesium alloy cast rod upsetting and extrusion composite short-flow large-deformation billet-making mold includes a punch installed on the upper table (not shown in the figure) of the press, and is installed on the lower part of the press. The concave die of the table (not shown in the figure), the back pressure plate 4, the ejector rod 5 and the punching plate 8 connected to the ejection cylinder (not shown in the figure) of the press, wherein the punch includes a replaceable and installed The first punch 1 and the second punch 6, that is to say, the first punch 1 and the second punch 6 are replaceably installed on the upper table of the press, and the installation methods and positions of the two are the same , easy to replace. The male mold and the female mold are each fixedly connected to the upper worktable and the lower worktable by fasteners (not shown in the figure), and the fasteners can be fastening bolts.

The die includes an upper die 2 and a lower die 3 fixed below the upper die 2. The lower die 3 is installed on the lower table of the press. The upper die 2 is provided with a wide upper part and a narrow lower part. The upper cavity 21, that is, the diameter of the upper part 211 is larger than the diameter of the lower part 212, and the lower die 3 is provided with a lower cavity 31 with a narrow upper part and a wider lower part, that is, the diameter of the upper part 311 is smaller than the diameter of the lower part 312, and the lower part of the upper cavity 212 communicates with the upper part 311 of the lower cavity through the same central axis;

The diameter of the lower part 212 of the upper cavity and the diameter of the upper part 311 of the lower cavity are the same as the diameter d of the second punch 6, and the axial length of the second punch 6 can at least reach into the cavity;

The diameter of the upper part 211 of the upper cavity and the diameter of the lower part 312 of the lower cavity are the same as the diameter D of the first punch 1;

The back pressure plate 4 is lifted above the top rod 5 so that the top rod 5 and the back pressure plate 4 can be moved up and down and enclosed in the lower part 312 of the lower cavity. The upper surface of the back pressure plate 4 is an arc structure with a concave middle.

The upper cavity 21 is used for placing the cylindrical blank 7, and the axial length of the second punch 6 is designed to be longer than the axial length of the first punch 1 to ensure that the second punch 6 has sufficient axial length to extend into the concave. mode 3.

The punching plate 8 is cylindrical, and a through hole with the same diameter as the second punch 6 is formed in the middle of the punching plate 8 for the second punch 6 to shuttle. The punching plate 8 is detachably installed on the upper die 2 .

The method for making a large-size large-height-diameter ratio magnesium alloy cast rod with a short flow and large deformation includes the following steps:

S1: Cylinder magnesium alloy bar D×h blanking;

S2: Homogenize the cylindrical magnesium alloy bar as the cylindrical blank 7;

S3: heating the cylindrical blank 7 to the forming temperature and maintaining the temperature, and heating the mold to a temperature above the cylindrical blank 7 and maintaining the temperature;

S4: Install the preheated and heat-preserved mold on the press, and evenly spray the organic graphite lubricant on the first punch 1, the second punch 6, the upper punch 2, and the lower punch 3; The body blank 7 is placed in the upper part 211 of the upper cavity, as shown in Figure 3;

S5: As shown in Figure 4, in the initial stage of upsetting extrusion, the ejector cylinder moves upward, and a force (referred to as back pressure) is applied to the back pressure plate 4 through the cylindrical ejector rod 5, and the press drives the first punch. 1 Move downward, the lower section of the dimension D×h cylindrical blank 7 gradually enters the lower part 212 of the upper cavity, and is gradually deformed due to the upsetting extrusion, and the size is d×H (H=D*h/d, not shown in the figure. As shown in Figure 4 and Figure 5, then the lower section of the d × H blank 7 gradually enters the upper part 311 of the lower cavity, and then contacts the arc structure 41, and the first punch 1 continues to press down, When the lower section of the blank 7 completely fills the upper part 311 of the lower cavity, the back pressure plate 4 moves downwards simultaneously with the gradual return of the ejector rod 5, as shown in FIG. In the later stage of upsetting extrusion, when the first punch 1 bottoms out in the upper cavity 21, at this time, most of the Part of the blank 7 has entered the lower part 212 of the upper cavity and the lower cavity 31, the first punch 1 is replaced with the second punch 6, and the second punch 6 presses down the lower part 212 of the upper cavity to make all the blanks. The blank 7 can completely enter the lower die 3, which is also the design reason why the axial length of the second punch 6 can at least reach into the die; the back pressure plate 4 is at the position where all the blanks 7 can completely enter the lower die 3 , and finally reshape a cylindrical blank 7 with a size of D×h, as shown in Figure 7, the upsetting deformation is completed;

S6: After the punching plate 8 is installed on the upper die 2, the press drives the second punch 6 upward, and a very small part of the adhering blank left in the upper die 2 is knocked off by the punching plate 8;

S7: After the punching is completed, the ejector cylinder drives the ejector rod 5 and the back pressure plate 4 to exit the lower part 312 of the lower cavity downward, so that the upsetting cylinder blank can be taken out from the lower part 312 of the lower cavity;

S8: Finally, the second punch 6 goes down to clamp the upper die 2 and the lower die 3, loosen the fastening bolts connected with the upper worktable and the lower worktable, unload the die, and take out the parts.

The principle of the present invention is: the blank 7 is placed in the upper part 211 (diameter D) of the upper cavity, the press applies a downward force F to the blank 7 through the punch, as shown in FIG. 5. Apply an upward back pressure F0 to the back pressure plate 4; due to the action of the downward pressure F, the blank 7 flows to the lower part 212 (diameter d) of the upper cavity, and gradually flows downward to the upper part 311 (diameter d) of the cavity, when the blank 7. When the lower section is completely filled with the upper part 311 of the lower cavity, the back pressure plate 4 moves downward. At this time, the back pressure plate 4 bears a larger back pressure F0, and the blank 7 continues to flow downward to the lower part 312 (diameter D) of the cavity until it is deformed Finish. During the deformation process, upsetting deformation—extrusion deformation—upsetting deformation was completed, and large-scale large-height-diameter ratio magnesium alloy cast rods with short flow and large deformation were completed. The invention effectively overcomes the long process flow of the existing upsetting and extrusion and the instability defects in the upsetting deformation, so that the blanks with a height-diameter ratio far greater than 3 can be upsetting and extruded, and a certain foundation is laid for the subsequent deformation process. Moreover, multi-pass upsetting is not required, and it has the characteristics of short process and is more convenient to use.

Because the right-angle part often causes the blank to be unfilled, the transition fillet is designed at the position where the blank metal flows slowly, especially at the corner to make the blank metal flow more smoothly and fill more complete. In one embodiment, there are two corner joints between the upper part 211 of the upper cavity and the lower part 212 of the upper cavity, which are the first corner joint 22 and the second corner joint 23 respectively. The first corner joint The part 22 is close to the upper part 211 of the upper cavity and has a first transition fillet, and the second corner connection 23 is close to the lower part 212 of the upper cavity and has a second transition fillet. There are two corner joints between the upper part 311 of the lower cavity and the lower part 312 of the lower cavity, which are the third corner joint 32 and the fourth corner joint 33 respectively, and the third corner joint 32 is close to the lower cavity. The upper part 311 of the upper part 311 is provided with a third transition fillet. The fourth corner connection 33 is close to the lower part 312 of the lower cavity. Since the metal flow at the fourth corner connection 33 has little effect on the forming, there is no need to design the transition fillet.

The above descriptions are only the preferred embodiments of the present invention, and are not intended to limit the design of this case. Any equivalent changes made according to the design key of this case fall into the protection scope of this case.

Claims (4)

1. The method relates to a magnesium alloy cast rod upsetting-extruding composite short-flow large-deformation blank making die, which comprises a male die arranged on an upper workbench of a press, a female die arranged on a lower workbench of the press, a back pressing plate and a mandril connected with an ejection cylinder of the press, wherein the male die comprises a first male die and a second male die which can be arranged in a replaceable manner; the female die comprises an upper female die and a lower female die fixed below the upper female die, an upper cavity with a wide upper part and a narrow lower part is arranged in the upper female die and used for placing a blank, a lower cavity with a narrow upper part and a wide lower part is arranged in the lower female die, and the lower part of the upper cavity is communicated with the upper part of the lower cavity by a same central shaft; the diameter of the lower part of the upper cavity, the diameter of the upper part of the lower cavity and the diameter of the second male die are the same, and the axial length of the second male die at least can reach the inside of the female die; the diameter of the upper part of the upper cavity and the diameter of the lower part of the lower cavity are the same as the diameter of the first male die; the method comprises the following steps of:

s1: blanking a cylindrical magnesium alloy bar;

s2: homogenizing the cylindrical magnesium alloy bar to obtain a cylindrical blank;

s3: heating the cylindrical blank to a forming temperature and preserving heat, and heating the die to a temperature higher than the temperature of the cylindrical blank and preserving heat;

s4: mounting the preheated and heat-insulated die on a press machine, and uniformly spraying an organic graphite lubricant on the first male die, the second male die, the upper female die and the lower female die; placing the cylinder blank subjected to the homogenization heat treatment into the upper part of the upper cavity;

s5: in the initial stage of upsetting-extruding forming, the ejecting cylinder moves upwards, acting force is applied to the back pressure plate through the ejecting rod, the press machine drives the first male die to move downwards, the lower section of the cylindrical blank gradually enters the lower part of the upper cavity and is gradually deformed due to upsetting-extruding; then the lower section of the blank gradually enters the upper part of the lower cavity and further contacts the cambered surface structure, the first male die is continuously pressed downwards, and when the lower section of the blank is completely filled with the upper part of the lower cavity, the back pressure plate moves downwards along with the gradual return stroke of the ejector rod; and in the later stage of upsetting-extruding forming, when the first male die touches the bottom in the upper die cavity, most of blanks enter the lower part of the upper die cavity and the lower die cavity, the first male die is replaced by the second male die, the second male die downward extrudes the blanks at the lower part of the upper die cavity to enable all the blanks to completely enter the lower female die, the back pressure plate is positioned at the position where all the blanks can completely enter the lower female die, finally, the cylindrical blank with the same size as the original size is formed again, and upsetting deformation is completed.

2. The method for producing a large-size large-height-diameter-ratio magnesium alloy cast rod with short process and large deformation according to claim 1, which is characterized by comprising the following steps of: the mold further comprises a knockout plate, and the method further comprises the step S6: after the upper female die is provided with the knockout plate, the press machine drives the second male die to move upwards, and the tiny part of the blank left in the upper female die before adhesion is knocked down by the knockout plate.

3. The method for producing a large-size large-height-diameter-ratio magnesium alloy cast rod with short process and large deformation according to claim 1, which is characterized by comprising the following steps of: the method further includes step S7: the ejection cylinder drives the ejector rod and the back pressure plate to downwards exit from the lower part of the lower cavity, and then the upset cylindrical blank can be taken out from the lower part of the lower cavity.

4. The method for producing a large-size large-height-diameter-ratio magnesium alloy cast rod with short process and large deformation according to claim 3, which is characterized by comprising the following steps of: the male mold and the female mold are fixedly connected to the upper working table and the lower working table by fasteners, and the method further comprises the step S8: after the cylindrical blank is taken out, the second male die moves downwards to be matched with the upper female die and the lower female die, fastening bolts connected with the upper workbench and the lower workbench are unscrewed, and the die is unloaded.

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