Design of roll forging die for blank making of cro

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Design of roll forging die for blank making of skew head connecting rod Abstract: blank making roll forging is mainly used to provide reasonable blank shape and size for die forging equipment. For connecting rod forgings, at present, the straight head symmetric connecting rod is mainly formed by billet roll forging press. In this paper, the roll forging die for the blank making of the skew head connecting rod is studied. The four pass volume distribution roll forging die and the one pass bending die are used to obtain the blank shape and size required for the skew head connecting rod. The problems such as the determination of roll forging passes, the selection of groove system, the arrangement of roll forging process and the design of dies have been successfully solved. According to the research results, a new type of connecting rod roll forging production line has been built, which can produce 180 connecting rods per hour. The line uses five roll forging dies installed on the forging rolls of the roll forging machine to provide the press with the blanks required for die forging the skewed head connecting rod

key words: crooked head connecting rod; Blank making roll forging; Die

I. Introduction

roll forging is a rotary plastic processing technology. It has the advantages of small deformation force, high production efficiency, good forging quality, long die life, good working conditions and so on. Roll forging provides appropriate blank for die forging, which is called blank making roll forging; It is used for directly forming some forgings, which is called forming roll forging. In recent 20 years, China has made great progress in roll forging technology. Blank making roll forging is widely used in automobile and tractor manufacturing. For some complex forgings with great forming difficulty, forming roll forging has been successfully developed and applied to production, such as connecting rod, forklift fork, automobile front axle and other parts, and has formed a professional production plant

crooked connecting rod means that the joint surface of connecting rod and connecting rod cap is not perpendicular to the main axis of connecting rod, and is generally inclined at an angle of 45 ° (as shown in Figure 1). If the connecting rod cap has a double rib shape and is concave (as shown in Figure 2), the connecting rod and connecting rod cap cannot be combined for die forging. The existing forging methods for the crooked head connecting rod are tire die forging and die forging on the die forging hammer. Blank roll forging is used to provide blank for straight head connecting rod, which is then formed by die forging on a press. It has not been reported at home and abroad that the blank rolling forging of the crooked head connecting rod. The author has studied the blank rolling forging process and die design method of the skew head connecting rod as shown in Figure 1. The research results have been applied to production, which is the first application of the blank rolling forging of the skew head connecting rod at home and abroad

Figure 1 crooked head connecting rod

Figure 2 double rib connecting rod cap

II. Determination of roll forging passes and selection of groove system for crooked head connecting rod

the function of blank making roll forging is to make the volume distribution law of blank metal meet the requirements of forging forming, and make its shape conform to the shape of forging parting surface. In the die design, 4 pass volume distribution roll forging die, 1 pass bending forming roll forging die, and the blank obtained after 5 passes of roll forging die are used, It can be formed on die forging equipment. Friction press is used as die forging (pre forging and final forging) forming equipment in the development

1. Determination of volume distribution roll forging passes

volume distribution roll forging is mainly used for the extension deformation of billets. According to the forging drawing, the calculation blank section and diameter drawing are made. It can be seen that the maximum section is at the transition between the connecting rod and the big end. After simplifying the calculated blank drawing, the roll forging blank drawing is designed, and its shape is shown in Figure 3

Figure 3 roll forging blank figure

Ⅰ small end Ⅱ rod Ⅲ large end

roll forging passes are determined according to the following formula according to the total elongation coefficient and average elongation coefficient of each section:

where n - roll forging passes

λ—— Total elongation coefficient, i.e. the ratio of the original billet cross-sectional area fo to the billet cross-sectional area FN after roll forging, λ= Fo/Fn

λ C - average elongation coefficient, usually taken as λ C = 1.4 ~ 1.6

select the blank with the original blank diameter of 60mm according to the maximum section of the forging, and calculate the roll forging passes of each section respectively from the above formula. After calculation, it is known that the rod section B needs to adopt 4 passes of roll forging, so there should be 4 roll forging grooves for distributing metal volume, For sections a and C with small extension, in order to meet the requirements of process and section shape, two passes of roll forging are actually adopted (in case of the other two passes of roll forging, the metal in the section with a total output value of 5billion yuan will not be deformed in 2025). The calculation results and the actually adopted roll forging passes are shown in Table 1. Table 1 roll forging pass calculation

project section λλ C the calculated value n is actually na1.541.51.072b5.031.53.984c2.731.52.482

2 The oval square groove system is selected to ensure the quality and forming of forgings. When the blank is deformed in the elliptic square groove system, the four sides of the metal are compressed, so that the corners of the blank often change positions, as shown in Figure 4. When the round blank is rolled in the elliptical groove, the blank a and a contact with the depth of the elliptical groove first and are compressed and deformed, while when the square groove is rolled, the elliptical blank B and B are compressed and deformed first to obtain the square section blank. When the square section blank enters the third elliptical groove, the square edges and corners are flattened to obtain the elliptical blank; When the blank enters the fourth square groove roll forging, the square edges and corners appear in a new position. This can make the metal around the billet get uniform cooling. Because the four sides are repeatedly pressed, it also has a good effect on the microstructure and properties of the deformed metal. In addition, the stability of roll forging with elliptical square groove system is good, which is conducive to blank deformation

Figure 4 elliptic square groove system

3 Bending forming roll forging (the fifth roll forging)

the purpose of bending forming roll forging is to use the forging roll to bend the billet into a straight shape, so as to meet the requirements of die forging the shape of the crooked connecting rod on the die forging equipment (as shown in Figure 5). Direct roll forging and bending forming on the roll forging machine can reduce the number of blows and operation time of the later die forging forming equipment, coordinate the production rhythm of the whole line, and have high productivity

Figure 5 blank shape after bending

4 The feeding direction and process arrangement of roll forging blank

in order to facilitate the operation, the blank adopts the reverse feeding method, that is, the blank feeding direction and roll out can ensure the opposite direction of the equipment measurement data, as shown in Figure 6

Figure 6 reverse roll forging

the process sequence is as follows: first, clamp one end of the blank (corresponding to the big end of the connecting rod) with pliers, roll forge the rod and small end in the first and second groove, and the small end (section a) can obtain the required shape and size after two passes of roll forging. Then turn round the blank, clamp the small end with pliers, and then roll forge the 3rd and 4th passes. The blank rod continues to extend and deform, and the head (Section C) extends at the same time. After 4 passes of roll forging, the straight roll forging blank was obtained. The fifth roll forging is to bend the shape of the big end, the pliers still hold the small end, and feed the big end of the blank into the groove for bending to obtain the required blank shape. Each pass of roll forging adopts the form of biting in the middle of the blank to ensure the normal operation of roll forging. The roll forging process and the blank shape of each pass are shown in Figure 7

Figure 7 roll forging process flow

III. groove design

1.1 ~ 4 pass volume distribution roll forging groove design

design and calculate the blank section size and groove size of each pass, which should be calculated one by one. Its main task is to calculate the reduction and widening deformation in each pass, so as to calculate the blank section size after each pass of roll forging

The deformation of the blank in the roll forging groove is complex. In order to simplify the deformation calculation, the method of rolling the rectangular blank on the flat roll is often used to calculate the deformation in the groove, which is called the corresponding rectangular method. When the groove is calculated one by one, the deformation of the corresponding rectangle is calculated according to the corresponding rectangle method, and the corresponding rectangle size after each pass of roll forging is calculated, and finally converted to the cross-section size of each groove

The longitudinal dimension design of the

groove is mainly based on the roll forging blank drawing. Due to the existence of forward sliding, the length of each section of the groove is shorter than that of the corresponding section of the blank. In the following formula, L - Calculation of the section groove length

ls - Calculation of the section roll forging blank length

s - forward sliding value

the forward sliding value can be preliminarily determined in the design according to the tested value. For the rod, it should be considered that during the mold debugging, the mold grinding is easier than repair welding, so the forward sliding can be estimated to be smaller, In this way, if it is found that the rod is long when the mold is to be debugged, the method of grinding the mold with a grinding wheel can be used to shorten it

the forward slip value can be selected as 4% ~ 6% of the empirical value in the equal section of the blank, and can also be calculated by using the relevant forward slip formula. The forward slip value in the transitional wedge section is related to the feeding direction during roll forging. When the thin end of the blank is in the front, the forward slip is small due to the restriction of the front wall of the die on the forward slip of the metal, which is generally 2% ~ 4%; When the thick end of the blank is in the front and there is no forward sliding Constraint Zone, the forward sliding is large, generally 6% ~ 12%

2. Design of the 5th bending forming groove

the 5th bending forming groove shall make the blank conform to the shape of the forging parting surface, so the design of the groove shall be based on the contour shape of the connecting rod on the parting surface. The fan-shaped die installed on the forging roll is used to bend the straight and long billet forged by the roll. The following technical problems must be solved in the design:

(1) the bending forming groove deforms the billet with the help of the reverse rotation of the fan-shaped die on the two forging rolls. Therefore, attention should be paid to and the meshing motion law between the rigid body (fan-shaped die) and the plastic body (blank) so that the product you test has a small capacity should be solved

(2) in the process of bending forming and blank discharge, it is inevitable that the blank will swing up and down. In order to facilitate the operation, the blank deflection should be minimized

(3) when the blank is bent in the die, it should be reliably positioned, otherwise the longitudinal movement will occur when the blank is bent, and the required bending shape cannot be guaranteed

these problems have been well solved in the development. The designed bending forming die has successfully rolled the blank shape required by the skew head connecting rod, which is the key to the blank making of the skew head connecting rod on the roll forging machine

IV. the roll forging die for the crooked connecting rod shown in Figure 1 has been successfully developed on the d roll forging machine (Figure 8). The die is shown in Figure 9. From left to right, there are the first, second, third, fourth and fifth roll forging dies respectively

figure 8d43-630 roll forging machine Figure 9 roll forging die

according to the research results, a new connecting rod roll forging production line was built in 1996. Its main process flow is: blanking → medium frequency induction heating → 5 passes of roll forging → friction press die forging → trimming → correction → residual heat quenching. The average production beat of the line is 20s/piece, and 180 pieces can be produced per hour. The successful development of the roll forging blank die for the crooked head connecting rod has opened up a new way for the die forging production of the crooked head connecting rod


[1] edited by Zhang Chengjian Roll forging technology Beijing: China Machine Press, 1986

[2] edited by Fu Peifu Roll forging theory and technology Changchun: Jilin People's publishing house, 1983

[3] edited by wangzhongren Forging manual (Volume 1) forging Beijing: China Machine Press, 1993 (end)


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