Some points for attention when producing forgings with free forgings

The tools and equipment used for free forgings are simple, universal and low in cost. Compared with the casting blank, free forging eliminates the defects such as shrinkage cavity, porosity and air hole, and makes the blank have higher mechanical properties. The forging is simple in shape and flexible in operation. Therefore, it is of great significance in the manufacture of heavy machinery and important parts.

application area

The shape and size of free forgings are controlled by manual operation, so the precision of forgings is low, the machining allowance is large, the labor intensity is high, and the productivity is not high, so it is mainly used in single piece and small batch production.

1) The blank size and intermediate size must conform to the operation points of each process, such as the height-diameter ratio (H/D) of the material before upsetting is 2-2.5, and the empirical data of cross-section transformation during drawing.

2) It is necessary to estimate the change of blank size in each process of forging, for example, the height of blank is somewhat reduced when punching, generally 1.1 times the height of forging, etc. The height of mandrel increases a little when reaming.

3) When indenting by sections, it is necessary to ensure that all parts of the forging have enough volume, such as when discharging the stepped shaft, crankshaft or gear boss, the volume distribution of all parts should be done well.

4) When forging with multiple heats, attention must be paid to the possibility of heating each heat in the middle. For example, if the forgings are drawn too long at the beginning, the furnace size is not enough for secondary heating, and long forgings cannot be put in. Special attention should be paid to the deformation of the first fire after Z and the control of the initial forging and final forging temperature after Z to ensure the size and quality of forgings.

5) It must be ensured that there is enough finishing allowance after finishing light in Z, and attention should be paid to:

(1) Because the blank is stretched and shrunk in the processes of shoulder pressing, dislocation and punching, it is necessary to leave trimming allowance in the middle process;

(2) Forging long shaft forgings (such as crankshafts) and forgings with recesses cannot be upset again because of their out-of-tolerance in length dimensions. It must be estimated that the dimension in the length direction will extend slightly during trimming, which will lead to out-of-tolerance.

Forging process

6) When selecting tools, children should use general tools. When the production batch is large, tools or tire molds can be made to improve the quality and output of forgings.

7) According to the size and quality of the blank, choose the existing equipment in the workshop.