Factors of TC4 alloy rod die forging and material extrusion

1: Reasons for cracks in titanium rod extrusion

 Titanium rods and titanium alloy rod blanks have low thermal conductivity, which will cause a great temperature difference between the surface layer and the inner layer during hot extrusion. When the temperature of the extrusion cylinder is 400 degrees, the temperature difference can reach 200 to 250 degrees. Under the combined influence of suction strengthening and the large temperature difference of the blank section, the metal on the surface and the center of the blank produces very different strength and plastic properties, which will cause very uneven deformation during the extrusion process. Large additional tensile stress is generated in the extruded product, which becomes the source of cracks and cracks on the surface of the extruded product.

It can be divided into:

1) Extrusion method. Reverse extrusion is more uniform than forward extrusion, cold extrusion is more uniform than hot extrusion, and lubricated extrusion is more uniform than non-lubricated extrusion. The influence of the extrusion method is realized by changing the friction conditions.

2) Extrusion speed. As the extrusion speed increases, the unevenness of metal flow increases.

3) Extrusion temperature. When the extrusion temperature increases and the deformation resistance of the blank decreases, the uneven flow of the metal increases. During the extrusion process, if the heating temperature of the extrusion cylinder and the mold is too low, and the metal temperature difference between the outer layer and the center layer is large, the unevenness of the metal flow will increase. The better the thermal conductivity of the metal, the more uniform the temperature distribution on the end surface of the ingot.

4) Metal strength. When other conditions are the same, the higher the metal strength, the more uniform the metal flow.

5) Die angle. The larger the mold angle (that is, the angle between the end face of the mold and the central axis), the more uneven the metal fluidity. When a porous die is used for extrusion, the die hole arrangement is reasonable, and the metal flow tends to be uniform.

6) Degree of deformation. The degree of deformation is too large or too small, and the metal flows unevenly.

Solution:

1: When forging with a press under the same unit pressure as forging with a forging hammer. The heating temperature of the blank can be reduced by 50100℃. In this way, the interaction between the heated metal and the periodic gas and the temperature difference between the blank and the mold are correspondingly reduced, thereby improving the uniformity of deformation, the uniformity of the structure of the die forging is also greatly improved, and the consistency of mechanical properties is also improved. .

2: Increase the forging angle and fillet radius and use lubricant: The height of the burr bridge on the forging die is larger than that of steel, and the deformation of the titanium rod is characterized by more difficult to flow into the deep and narrow die groove than steel.

3: Reduce the deformation speed, the area shrinkage rate with the most obvious numerical increase, and the area shrinkage rate is the most sensitive to the structural defects caused by overheating.
AMS 4928 Titanium Alloy Bar     titanium straight wire     titanium tig welding wire     titanium pure powder