Forging technology and die manufacturing of the ho

2022-09-21
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Due to the limitation of equipment conditions, the production line is composed of 750KG air hammer free forging precision blank making, 1000t friction press die forging, 300t friction press hot edge cutting, 100t oil press hot punching, cold correction, etc; In terms of die design and blank making and forging, some skills are used to develop and produce the forging production process of large and complex die forgings of heavy-duty truck brake plates at low cost

automobile brake plates are the key parts of heavy-duty vehicle axles. An automobile axle manufacturer in Guangdong needs a large number of automobile brake plates because its axle products are exported to the Middle East. In order to meet the low-cost supporting requirements of the food industry, we have tapped the potential of the existing forging equipment, formed a production line, and produced die forgings of car brake plates at low cost, alleviating the urgent needs of manufacturers

the material of automobile brake plate is 20Mn, with complex shape. The design requires mass die forging production, with small machining allowance and high strength. The shape and size of forgings are shown in Figure 1. Divide 2 in Figure 1 Φ 60mm、 Φ 144mm、 Φ The 70mm inner hole and plane need to be cut, and the others are black leather surface forgings, so they are no longer cut

1. Structural characteristics of automobile brake plate die forgings

its structural characteristics are: ① the shape of the part is complex, there are three parting plane slopes, and the size of the part is large. ② The projection area of forgings on the parting surface is large (about 650cm). ③ The forgings are thin (the thickness of forgings is 9 ~ 56.5mm). ④ Large inner hole of forgings (inner hole Φ 144mm)。 ⑤ There are many depressions and many rib plates of the boss (the width of the rib plate is 8mm). ⑥ The forging allowance is small, and the unilateral machining allowance is 2 ~ 2.5mm

2. Process analysis of automobile brake plate die forgings

(1) determine the projected area and perimeter of automobile brake plate die forgings on the horizontal plane, and calculate according to its geometric shape

f=40 403mm

the peripheral length of forgings can be obtained by directly measuring the perimeter of the plane projection of Forgings: x=1193mm

(2) the theoretical calculation of equipment tonnage is calculated according to the empirical formula:

p= (17.5 ~ 28) KF total

where p - nominal pressure of friction press, kn

k - steel grade coefficient, for 20Mn material, k=l.1

f total - total deformation area of forgings (about 650cm)

therefore, p=20 × one point one × 650kN=14 300kN。

die forging equipment usually adopts forging equipment that is close to the calculated value but slightly larger. It can be seen that if a 10000 kn friction press is used for the brake plate of heavy-duty vehicles, the tonnage of the equipment is relatively small, so countermeasures need to be taken to do big work with a small hammer and produce brake plate die forgings

(3) determine the size of burr groove of automobile brake plate die forgings. The shape and size of burr groove have a great influence on the forming of forgings. When forging with hammer, the metal flow process can be divided into four stages. In the first stage, the blank height decreases and the radial size gradually increases, which has the characteristics of upsetting deformation and local pressing deformation. In the second stage, the metal flow is blocked by the mold wall, which helps the metal flow to the height direction of the groove. At the same time, it begins to flow into the burr groove, and a little burr appears. At this time, the deformation force increases significantly. The third stage is the process of filling the groove, in which a stronger three-dimensional compressive stress is formed in the deformed metal. The groove is gradually filled everywhere, the thickness of the burr is thinner and thinner, the width is increased, the temperature is reduced, and the deformation resistance is significantly increased. In the fourth stage, the last stage of forging feet, the strike energy will reach the hardness and rigidity of the whole forging metal? 30% - 50% of the energy consumed in the whole forming process; Cause enough resistance in the horizontal direction, make the groove full, accommodate excess metal, and buffer the hammering

the width of the burr groove is selected according to the forgings with high complexity. The bridge height of the burr groove decreases. The service life of the equipment is

the bridge of the burr groove b=14mm, the width of the burr groove b1=38mm, the cross-sectional area of the burr groove sk=278mm, the height of the burr groove h1=5mm, and the radius of the entrance r=2mm. See Figure 2 for the shape and size of the burr groove

figure 2

delivered offline to customers in Chinalco Luoyang Copper Co., Ltd.

(4) draw the cross-sectional drawing and diameter drawing of the calculation blank. Select 18 typical cross-sections from the brake plate forgings, and obtain the cross-sectional data as shown in the attached table after calculation and mapping. In order to draw the section diagram of the blank, the total area of each section of the forging is converted into height, and then the section diameter is calculated

the sectional view and diameter diagram of brake plate forgings are shown in Figure 3

figure 3

according to the attached table, the average sectional area of brake plate forgings is 3170mm, the average diameter is 64mm, and the maximum calculated diameter is 85mm

3. automobile brake plate die forging process

(1) the cutting weight is determined to be 12kg after the above mapping and calculation. Combined with the actual situation of the material market, 120mm square steel is used for forging, and the cutting size is 120mm × 106mm。 Use a 100t oil press to cold cut the blank, adjust the gap between the upper and lower scissors to make the shear fracture neat and normal, conduct weighing and spot check to ensure that the weight of the blank is not less than the required weight, and grind some defective blanks with fracture to ensure the cutting quality

(2) the oil heating furnace is used for heating to 1200 ~ 1250 ℃. Heating in sections, control the heating speed and ensure the heating quality. Two fire forging, the first fire heating raw materials, billet forging; The second fire heats the blank, soaking, heat preservation and penetration, and forging into the die. Because the forging is large, the hammering force is slightly obvious, and the feeding effect and negative shrinkage will increase enough. Visually control the upper limit of heating temperature, maximize the plasticity and reduce the deformation resistance

(3) blank making blank making free forging on 750KG air hammer. The work step is complex, and this process is extremely critical. It requires accurate material distribution and accurate design of the blank making mold, so it can't stick to the rules. After repeated exploration, two sets of forming die and one set of punching die are determined for forging and punching. The shapes of the two sets of forming die are shown in Figure 4 and figure 5

(4) die forging on a 1000t friction press

the screw friction press is forged with a single-mode cavity closed force system, with good guiding performance and slow striking speed. The forged blank is directly taken out from the heating furnace. After the oxide skin is simply removed, the human die is forged and the brake plate is forged for three times; Fully preheat the forging die and female die with red iron to 200 ℃. In the forging process, heavy oil graphite lubrication is used to reduce friction, reduce deformation resistance, and help metal flow forming, facilitate forging out of the die, and cool the forming forging die, so that the surface temperature of the groove is ≤ 450 ℃

(5) cut edges and punch holes on 300t friction press, hot edge and 100t oil press. After forming and die forging on a 1000t friction press, hot edge cutting shall be carried out on a 300t friction press immediately, and the limit shall be made to make the punch enter the female die by 10 ~ 20mm. After trimming, the forging blank is immediately sent to the next station for simple punching and inner hole peeling

(6) normalize, cold calibrate on a 100t oil press, blast clean the oxide skin, and grind and deburr. Apply primer

in order to eliminate the residual stress of brake plate forgings and improve their microstructure, mechanics and machinability, forgings need to be normalized. Because the brake plate forgings have the characteristics of complexity, thin and large drop, bending, torsion and other deformation occur in the subsequent process, so the forgings must be cold corrected to make the forgings meet the requirements of the drawing, and the burrs of some forgings must be removed to eliminate surface defects. The roller shot blasting can remove the oxide skin, improve the surface quality, and apply anti rust primer so that the brake plate forgings can be directly installed on the axle after processing

4. Structural design of die forging die for automobile brake plate

(1) forming die forging die transmits power, forces metal blank to form, and bears repeated instantaneous impact load and alternating cold and heat. The working conditions are heavy and the stress is large. Brake plate forgings have three parting planes and inclined planes, and it is easy to produce horizontal components during die forging, which will cause the dislocation of the forging die. Diagonal lock catch is used to balance the horizontal displacement force. Design the mold according to the cold shrinkage rate of 1%, and fasten it with bolts and pressing plates. The mold is made of 5CrMnMo material, and the quenching hardness of the mold after heat treatment is 42 ~ 46hrc. In view of the low price strategy of brake plate parts, during mold manufacturing, low-cost ordinary machining methods such as turning, milling, drilling, planing and grinding and fitter grinding methods are used to the greatest extent, and EDM is used for a few parts. Two sets of moulds are manufactured at the same time, which is convenient for maintenance and replacement and does not affect production. The method of argon arc filling welding is also adopted for mold maintenance to do a good job in details and reduce costs. See Fig. 6 and Fig. 7 for the shape and size of the forming die

(2) the punching die uses a punch to punch the inner skin of the forging hole. The punching die plays the role of supporting forgings, and the size of the cutting edge of the punch is determined according to the punching size

(3) the edge size of the edge cutting die of the edge cutting die is designed according to the size of the forming model, and the unilateral clearance is 1mm, and the clearance of the convex and concave dies is 2.5mm; The side mold is flat and the spoon forming is consistent with the lower mold, and the bolt pressing plate is used to tighten the circumference; The trimming die and concave die are made of Cr12MoV material, and the quenching hardness of the hot part of the die is 42 ~ 46hrc; The trimming punch plays the role of transmitting pressure. It adopts 5CrMnMo material, and the quenching hardness of the hot part of the die is 42 ~ 46hrc

5. Conclusion

although the forging of heavy-duty vehicle brake plates is complicated and involves many steps, through brainstorming, we have made full use of the existing production conditions to forge and produce heavy-duty vehicle brake plates in large quantities, which meets the requirements of low-cost matching sets in the market for the export of heavy-duty vehicle axle parts, improves the die forging competitiveness of the enterprise, expands the business market, and wins reputation and economic benefits for the enterprise

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