One-heating-number die forging forming method of forge piece for rail transit

Abstract

The invention discloses a one-heating-number die forging forming method of a forge piece for rail transit, which is characterized by comprising the following specific steps of: S1, heating a blank to a preset temperature, keeping the temperature for a period of time, putting the blank into a lower bending cavity of a lower die, closing the upper die and the lower die, and bending to manufacture the blank, the center of the blank is bent into an arc with the bending radius of the center line of the target forge piece, and oxide skin is removed; s2, the bent blank is put into a lower pre-forging cavity of a lower die, one hammer is hit, and the shape of a forge piece is pre-adjusted; and S3, the pre-forged blank is put into a lower finish forging cavity of the lower die, beating is conducted for 2-3 hammers, and the forge piece is forged into the final shape. Existing equipment can be fully utilized, a multi-cavity forging die is adopted, and bending and forging are achieved within one heating number.

Description

Technical Field

[0001] The present invention belongs to the field of die forging, and in particular relates to a one-shot die forging method for rail transit forgings. Background Art

[0002] With the rapid development of the rail transit industry, people's daily travel has become more convenient and the efficiency of cargo transportation has been significantly improved. However, the rail transit field cannot do without a large number of parts with complex shapes, such as traction rods and side-bend tracks. These parts not only have a certain bending radius, but also have different cross-sectional areas along the axial direction. At the same time, there are clear requirements for the metal flow direction inside the forging. These factors greatly increase the difficulty of forging design and easily lead to defects such as lack of meat and folding.

[0003] At present, such parts are mainly produced by roll forging. However, there are many problems with roll forging, such as: (1) The roll design is complex, and the number, profile and arrangement of rolls need to be adjusted according to the material properties (such as thickness and plasticity) and the complexity of the product section. Improper design can easily lead to defects; (2) Heating and rolling requires precise temperature control to avoid oxidation or overheating, which not only increases energy consumption but also increases equipment costs. Therefore, it is urgent to achieve technological breakthroughs through innovative processes and structural designs to meet the needs of high-precision and high-reliability parts in fields such as rail transit. Summary of the invention

[0004] Based on the above-mentioned prior art problems, the present invention provides a one-shot die forging method for rail transit forgings, which can make full use of existing equipment (such as a screw press) and adopt a multi-cavity forging die to achieve bending and forging in one shot, thereby greatly saving production costs.

[0005] The main technical solutions adopted in the present invention are: A single-fire die forging method for rail transit forgings, the specific steps are as follows: S1: The blank is heated to a preset temperature, kept warm for a period of time, and then placed into the lower bending cavity of the forging die. The upper and lower dies are closed to bend the blank, and the center of the blank is bent into an arc shape, and the oxide scale is removed; S2: Put the bent blank into the lower pre-forging cavity of the forging die, strike with one hammer, and pre-adjust the shape of the forging; S3: Place the pre-forged billet into the lower final forging cavity of the forging die, strike 2-3 times, and forge the forging to the final shape.

[0006] Preferably, the forging die comprises an upper die and a lower die. An upper bending cavity, an upper pre-forging cavity and an upper finish-forging cavity are designed on the upper die, and a lower bending cavity, a lower pre-forging cavity and a lower finish-forging cavity are designed on the lower die. After the upper die and the lower die are closed, a bending cavity, a pre-forging cavity and a finish-forging cavity are formed.

[0007] Preferably, the bending radius of the center line of the bending cavity is the same as that of the target forging.

[0008] Preferably, the bending cavity is longer than the hot blank before bending. After the upper and lower dies are closed, the bending cavity is higher than the blank after bending.

[0009] Preferably, support steps are designed at both ends of the lower bending cavity of the lower die.

[0010] Preferably, upper die intermediate section flash bridges are designed on both sides of the upper pre-forging intermediate bending section of the upper pre-forging cavity, and upper die end flash bridges are designed around both ends of the upper pre-forging cavity; lower die intermediate section flash bridges are designed on both sides of the lower pre-forging intermediate bending section of the lower pre-forging cavity, and lower die end flash bridges are designed around both ends of the lower pre-forging cavity.

[0011] Preferably, the height of the upper die intermediate section flash bridge is less than the height of the upper die end flash bridges at both ends; the height of the lower die intermediate section flash bridge is less than the height of the lower die end flash bridges at both ends, and a slope transition connection is formed between the upper die intermediate section flash bridge and the upper die end flash bridges; a slope transition connection is formed between the lower die intermediate section flash bridge and the lower die end flash bridges.

[0012] Preferably, stop-off grooves are arranged on both sides of the upper pre-forging intermediate bending section of the upper pre-forging cavity and the lower pre-forging intermediate bending section of the lower pre-forging cavity.

[0013] Preferably, the finish-forging cavity is designed according to the outer contour of the target forging, and the outer contours of the pre-forging cavity and the finish-forging cavity are similar.

[0014] Preferably, upper finish-forging flash bridges and lower finish-forging flash bridges are respectively arranged around the upper finish-forging cavity and the lower finish-forging cavity.

[0015] Beneficial effects: The present invention provides a one-fire die forging forming method for forgings used in rail transit, having the following advantages: (1) The present invention uses a multi-cavity forging die to cooperate with existing equipment (such as a screw press) to realize die forging processing. The bending cavity, the pre-forging cavity and the finish-forging cavity are arranged in the same set of die, reducing the die debugging cycle and the blank transfer time between each working step, enabling one-fire forming, reducing the number of heating times and energy consumption, improving production efficiency, reducing the loss of scale, increasing the material utilization rate, and reducing production costs.

[0016] (2)The present invention uses a pre-forging cavity to pre-adjust the bent blank. By designing the stock stop groove and flash bridge, precise control of the material flow distribution is achieved, improving the dimensional accuracy and surface quality of the forging. At the same time, the wear of the final forging cavity can be reduced, and the die life can be extended.

[0017] (3)The present invention prolongs the die life through the progressive matching of the pre-forging and final-forging cavity shapes, while reducing equipment occupancy and processing loss costs. Description of the Drawings

[0018] Figure 1 is a schematic diagram of the die structure of the upper die of Embodiment 1; Figure 2 is a schematic diagram of the die structure of the lower die of Embodiment 1; Figure 3 is a schematic longitudinal sectional view of the bending cavity of Embodiment 1; Figure 4 is a schematic cross-sectional view of the bending cavity of the lower die of Embodiment 1; Figure 5 is a schematic cross-sectional view of the intermediate bending section of the pre-forging cavity and the final-forging cavity of Embodiment 1; Figure 6 is a schematic diagram of the structure before bending of Embodiment 1; Figure 7 is a schematic diagram of the structure after bending of Embodiment 1; Figure 8 is a schematic diagram of the structure before pre-forging of Embodiment 1; Figure 9 is a schematic diagram of the structure after pre-forging of Embodiment 1; Figure 10 is a schematic diagram of the structure before final forging of Embodiment 1; Figure 11 is a schematic diagram of the structure after final forging of Embodiment 1; In the figure: upper die 1, upper bending cavity 1-1, upper pre-forging cavity 1-2, upper pre-forging intermediate bending section 1-2-1, upper die end flash bridge 1-2-2, upper die middle section flash bridge 1-2-3, upper final-forging cavity 1-3, upper final-forging flash bridge 1-3-1, lower die 2, lower bending cavity 2-1, support step 2-1-1, lower pre-forging cavity 2-2, lower pre-forging intermediate rod section 2-2-1, lower die end flash bridge 2-2-2, lower die middle section flash bridge 2-2-3, lower final-forging cavity 2-3, lower final-forging flash bridge 2-3-1, stock stop groove 3. Detailed Embodiments

[0019] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application. Embodiment 1

[0020] Taking the rod body of a traction rod in the rail transit industry as an example, the material is 42CrMo, the target forging outer dimensions are 720×204×87mm, the thickness of the middle rod part is 60mm, and the bending radius of the center line of the forging is 600mm. A forging die is designed according to the target forging outer dimensions. As Figure 1 and 2 shown, the forging die of this Embodiment 1 includes an upper die 1 and a lower die 2, and the upper die 1 is designed with an upper bending cavity 1-1, an upper pre-forging cavity 1-2 and an upper final-forging cavity 1-3. The lower die 2 is designed with a lower bending cavity 2-1, a lower pre-forging cavity 2-2 and a lower final-forging cavity 2-3. When the upper die 1 and the lower die 2 are closed, a bending cavity, a pre-forging cavity and a final-forging cavity are formed. Among them, as Figure 3 shown, in order to reserve a certain gap between the die cavity and the blank, so that when placing and striking the blank, the blank will not get stuck in the bending cavity, the center of the bending cavity is slightly longer than the hot blank before bending, and the bending cavity is higher than the blank after bending when the upper and lower dies are closed. In addition, the radius of the center line of the bending cavity is the same as that of the target product.

[0021] In this Embodiment 1, as Figure 3 shown, support steps 2-1-1 are designed at both ends of the lower bending cavity 2-1 of the lower die 2. On the one hand, the support steps can be used as physical limits to ensure that the forging is accurately fixed before bending, avoiding the bending position deviation caused by material sliding. On the other hand, it can prevent stress concentration and avoid the wear of the edge of the lower die caused by the stress on both ends of the blank during bending. In this Embodiment 1, as Figure 4 shown, the bottom surface of the support step is an arc-shaped bottom surface, the radius of the arc-shaped bottom surface is r, the depth is a, and the width is b. In this Embodiment 1, r = 45, a = 45, b = 90.

[0022] In this Embodiment 1, as Figure 1 and 2 shown, upper die intermediate-section flash bridges 1-2-3 are designed on both sides of the upper pre-forging intermediate bending section 1-2-1 of the upper pre-forging cavity 1-2, and upper die end-section flash bridges 1-2-2 are designed around both ends of the upper pre-forging cavity 1-2; lower die intermediate-section flash bridges 2-2-3 are designed on both sides of the lower pre-forging intermediate bending section 2-2-1 of the lower pre-forging cavity 2-2, and lower die end-section flash bridges 2-2-2 are designed around both ends of the lower pre-forging cavity 2-2.

[0023] In Embodiment 1, the height of the flash bridge 1-2-3 in the middle section of the upper die is less than the height of the flash bridges 1-2-2 at the two ends of the upper die; the height of the flash bridge 2-2-3 in the middle section of the lower die is less than the height of the flash bridges 2-2-2 at the two ends of the lower die, and there is a sloped transition connection between the flash bridge 1-2-3 in the middle section of the upper die and the flash bridges 1-2-2 at the two ends of the upper die; there is a sloped transition connection between the flash bridge 2-2-3 in the middle section of the lower die and the flash bridges 2-2-2 at the two ends of the lower die.

[0024] In Embodiment 1, as Figure 1 , 2 and 5 show, stop-off grooves 3 are provided on both sides of the upper pre-forging intermediate bending section 1-2-1 of the upper pre-forging cavity 1-2 and the lower pre-forging intermediate bending section 2-2-1 of the lower pre-forging cavity 2-2. And the depth, length and radius of curvature of the stop-off grooves are set according to the target forging parameters. Under the closing die pressure, the stop-off grooves can accommodate a small amount of excess material as a "buffer zone", avoiding its overflow from the parting surface to form flash, and at the same time reducing the wear of the die parting surface.

[0025] In Embodiment 1, the finish-forging cavity is designed according to the outer contour of the target forging, and the outer contours of the pre-forging cavity and the finish-forging cavity are similar. And as Figure 1 and 2 show, upper finish-forging flash bridges 1-3-1 and lower finish-forging flash bridges 2-3-1 are respectively provided around the upper finish-forging cavity 1-3 and the lower finish-forging cavity 2-3. In Embodiment 1, the flash heights of the upper finish-forging flash bridges 1-3-1 and the lower finish-forging flash bridges 2-3-1 are of uniform height.

[0026] The specific preparation method of Embodiment 1 is as follows (the equipment used is a 40MN electric screw press, and the rated impact energy of the equipment is 714000000 N·mm): Step 1: Cut the material according to the required target blank size, and the cutting size is Φ85×750 mm; Step 2: Heat the blank to the preset temperature of 1140-1160 °C, keep it warm for 40-100 min, and then put the blank into the lower bending cavity 2-1 of the lower die 2. As Figure 6 shows, after closing the upper and lower dies, bend the center of the blank into an arc with a radius of 600 mm. As Figure 7 shows, and remove the oxide skin; the single impact energy is 5%-15% of the rated impact energy of the screw press.

[0027] Step 3: Put the bent blank into the lower pre-forging cavity 2-2 of the lower die 2. As Figure 8 shows, strike 1 hammer, and the single impact energy is 70%-90% of the rated impact energy of the screw press to pre-adjust the shape of the forging. As Figure 9 shows; Step 4: Place the pre-forged blank into the lower final forging cavity 2-3 of the lower die 2, as Figure 10 shown. Strike 2-3 times, with the single-strike energy being 60%-80% of the rated strike energy of the screw press, and forge the forging into the target forging, as Figure 11 shown. The flash of the forging is uniform, and no defects such as folding or lack of material occur.

[0028] Compared with the existing roll forging process, the present invention realizes overall forging forming through the closing of the forging die, can complete complex curvatures, variable cross-sections and local fine features (such as bosses and grooves) in one step, avoids the cumulative errors caused by multiple passes of roll forging, and the bending angle accuracy can reach ±0.5°, which is significantly better than roll forging (usually requiring subsequent straightening). And in this Embodiment 1, through the design of the flash bridge and the stock stop groove, combined with the die cavity design, the metal can be forced to flow in a predetermined direction, ensuring that the fiber streamline is continuously distributed along the part contour (such as the bending streamline of the drawbar), reducing the risk of shear fracture, while restricting the lateral overflow of the metal, precisely controlling the material filling, and improving the yield. Moreover, the forging die of the present invention has an integrated design of three stations: bending, pre-forging and final forging, only requiring the cooperation of the upper and lower dies, without the need for the multi-pass roll group design of roll forging. The die debugging cycle is shortened by 50%-70%, and the existing equipment can be fully utilized to reduce the production cost.

[0029] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A single-fire die forging method for rail transit forgings, characterized in that: The specific steps are as follows: S1: The blank is heated to a preset temperature, kept warm for a period of time, and then placed into the lower bending cavity of the forging die. The upper and lower dies are closed to bend the blank, and the center of the blank is bent into an arc shape, and the oxide scale is removed; S2: Put the bent blank into the lower pre-forging cavity of the forging die, strike with one hammer, and pre-adjust the shape of the forging; S3: Place the pre-forged billet into the lower final forging cavity of the forging die, strike 2-3 times, and forge the forging to the final shape.

2. The single-shot die forging method for rail transit forgings according to claim 1, characterized in that: The forging die comprises an upper die and a lower die, wherein the upper die is designed with an upper bending cavity, an upper pre-forging cavity and an upper final forging cavity, and the lower die is designed with a lower bending cavity, a lower pre-forging cavity and a lower final forging cavity, and the upper die and the lower die are combined to form a bending cavity, a pre-forging cavity and a final forging cavity.

3. The single-shot die forging method for rail transit forgings according to claim 2, characterized in that: The bending radius of the center line of the bending cavity is consistent with that of the target forging.

4. The single-shot die forging method for rail transit forgings according to claim 2, characterized in that: The bending cavity is longer than the hot blank before bending, and the bending cavity is higher than the blank after bending after the upper and lower molds are closed.

5. The single-shot die forging method for rail transit forgings according to claim 1, characterized in that: Support steps are designed at both ends of the lower bending cavity of the lower mold.

6. The single-shot die forging method for rail transit forgings according to claim 2, characterized in that: The upper pre-forging middle curved section of the upper pre-forging cavity is designed with upper die middle section burr bridges on both sides, and the upper die end burr bridges are designed around the two ends of the upper pre-forging cavity; the lower pre-forging middle curved section of the lower pre-forging cavity is designed with lower die middle section burr bridges on both sides, and the lower die end burr bridges are designed around the two ends of the lower pre-forging cavity.

7. The single-shot die forging method for rail transit forgings according to claim 6, characterized in that: The height of the burr bridge in the middle section of the upper mold is smaller than the height of the burr bridge at the ends of the upper mold; the height of the burr bridge in the middle section of the lower mold is smaller than the height of the burr bridge at the ends of the lower mold, and the burr bridge in the middle section of the upper mold and the burr bridge at the ends of the upper mold are connected with a slope transition; the burr bridge in the middle section of the lower mold and the burr bridge at the ends of the lower mold are connected with a slope transition.

8. The single-shot die forging method for rail transit forgings according to claim 2, characterized in that: Material blocking grooves are arranged on both sides of the upper pre-forging middle curved section of the upper pre-forging cavity and the lower pre-forging middle curved section of the lower pre-forging cavity.

9. The single-shot die forging method for rail transit forgings according to claim 1, characterized in that: The final forging cavity is designed according to the outer contour of the target forging, and the outer contours of the pre-forging cavity and the final forging cavity are similar.

10. The single-shot die forging method for rail transit forgings according to claim 2, characterized in that: An upper final forging burr bridge and a lower final forging burr bridge are respectively arranged around the upper final forging cavity and the lower final forging cavity.

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