The actual production verification of precision forging of driven spiral bevel gear is carried out in Luoyang Guanhua Precision Forging Gear General Factory, and the forging equipment is j53-1000c double disc friction press.
The process flow of precision forging of driven spiral bevel gear can be designed as follows: blanking, turning (deoxidizing and peeling), less oxidation free heating, blank making, precision forging, heat treatment (isothermal normalizing) – rough turning, fine turning – heat treatment (improving the comprehensive mechanical properties of gear) – shot peening (removing oxide scale and improving the fatigue strength of forging surface) – fine machining.
1.Blank size
The blank in production is a semi-finished product after processing, and the shape, volume and mass calculation of the blank is slightly larger than that of the precision forged gear. Figure 1 (a) shows the physical drawing of the processed blank, and Figure 2 (b) shows the double disc friction press.
2.Gear die processing
The purpose of precision forging driven spiral bevel gear is to directly produce products close to the size of the final formed parts, or it can be directly put into production after a little processing. Therefore, when designing the die, we should ensure the machining dimensional accuracy of the male and female die as much as possible. In the process of precision forging, because the temperature of the blank can reach 1000 ℃, in a short time, plus the previous preheating temperature of the die, after the blank is put into the die cavity, the final temperature of the die cavity can reach about 500 ~ 600 ℃, and during each forging, the punch tooth die is squeezed by the back impact of the high-temperature blank, and the tooth die is subjected to a great impact force. Secondly, at the end of forging, spray water agent graphite on the surface of the punch and die for cooling and lubrication. At this time, the surface of the gear die of the punch and die will be subjected to the alternating load of cold and heat. Based on the above factors, especially the punch, has fast failure and short service life. Therefore, the selection of punch and die materials is very important for the whole precision forging process. The die steel H13, i.e. 4Cr5MoSiV1, is specially selected as the die material.
When machining the male and female die of the driven spiral bevel gear, in order to ensure its machining accuracy, high-precision gear milling machine or high-speed machining center is used to process the electrode gear. In the process of EDM, in order to ensure the accuracy of punch tooth profile and cavity dimension, the machining standard is divided into three times: coarse, medium and fine. The discharge intensity is from strong to weak, and the discharge gap is from large to small. The following figure shows the punch and die processed by electrode.
3.Mold debugging
After installing the punch and die, debug the die, set the stroke, start the double disc friction press and see if it runs well. The mold can be used after debugging. Figure 3 (a) shows the worker debugging the mold.
4.Forging process
(1) Before forging, the punch and die shall be preheated for about 20 minutes to 350 ℃, and the blank shall be heated to 1000 ℃ in the heating forging furnace.
(2) Spray water graphite on the surface of punch and die, adjust the stroke of friction press, and start the friction press for preparation before forging.
(3) Clamp the blank with iron pliers and put it into the mold cavity sprayed with water agent graphite lubricant. Start the friction press for one-time forging.
(4) After forging, press the operation button to make the upper die go up, and the ejector rod in the lower die goes up to eject the forging and separate it from the female die. Clamp the forging with iron pliers and remove it into the isothermal normalizing furnace box.
(5) Spray water agent graphite lubricant on the surface of convex concave film again and wait for the next forging. At this point, a forging process is completed.
Blank material | Die material | Blank temperature (℃) | Coefficient of friction |
20CrMnTi | 4Cr5MoSiV1 | 1000 | 0.03 |
The main purpose of putting it into the isothermal normalizing furnace box is to eliminate the residual stress in the forging, refine the internal structure and improve the comprehensive processing performance of the forging. Figure 4 (a) is the physical drawing of the driven spiral bevel gear after forging. Figure 4 (b) shows the finished driven spiral bevel gear.