Titanium and titanium alloys have the advantages of low density, high specific strength, and good corrosion resistance, and are widely used in various fields. To better apply these materials, researchers have done a lot of research on their titanium alloy forging process.
Free forging is generally carried out between two flat dies or molds without a die cavity. The tools used for free forging are simple in shape, flexible, short in manufacturing cycle, and low in cost. However, the labor intensity is high, the operation is difficult, the productivity is low, the quality of the forgings is not high, and the processing allowance is large. Therefore, it is only suitable for use when there are no special requirements for the performance of the parts and the number of pieces is small.
2. Open die forging (forging with burrs)
The blank is deformed between two modules with cavities engraved on them. The forging is confined inside the cavity. The excess metal flows out from the narrow gap between the two dies, forming burrs around the titanium alloy forging. Under the resistance of the die and the burrs around, the metal is forced to be pressed into the shape of the cavity.
3. Closed die forging (forging without burrs)
During the closed die forging process, no transverse burrs perpendicular to the direction of die movement are formed. The cavity of the closed forging die has two functions: one is to shape the blank, and the other is to guide.
4. Extrusion die forging
There are two types of die forging using the extrusion method: positive extrusion die forging and reverse extrusion die forging. Extrusion die forging can manufacture various hollow and solid parts, and can obtain forgings with high geometric dimensional accuracy and denser internal structure.
5. Multi-directional die forging
It is carried out on a multi-directional die-forging machine. In addition to the vertical punching plunger, the multi-directional die forging machine also has two horizontal plungers. Its ejector can also be used for punching. The pressure of the ejector is greater than that of the ejector of the ordinary hydraulic press. During multi-directional die forging, the slider acts on the workpiece alternately from the vertical and horizontal directions, and one or more perforating punches are used to make the metal flow outward from the center of the die cavity to achieve the purpose of filling the die cavity. There is no burr of special forgings on the parting line of the barrel-shaped part.
6. Partial die forging
To forge large integral forgings on the existing hydraulic pressure, partial die forging methods such as segmented die forging and pad die forging can be used. The characteristic of the partial die forging method is to process the forgings section by section, one part at a time, so the required equipment tonnage can be very small. Generally speaking, this method can be used to process extra-large forgings on medium-sized hydraulic presses.
7. Isothermal die forging
Before forging the titanium alloy, the die is heated to the forging temperature of the blank, and the temperature of the die and the blank are kept consistent during the entire die forging process so that a large deformation can be obtained under the action of a small deformation force. Isothermal die forging and isothermal superplastic die forging are very similar, the difference is that in the latter, the blank needs to be superplasticized before die forging[i] to make it have equiaxed grains[ii].
The forging process of titanium alloys is widely used in the aviation and aerospace manufacturing industries (the isothermal die forging process has been used to produce engine parts and aircraft structural parts) and is also becoming more and more popular in industrial sectors such as automobiles, electricity, and ships.
Summary
At present, the cost of using titanium materials is relatively high, and many civilian fields have not fully realized the charm of titanium alloy forging. With the continuous advancement of science, the preparation technology of titanium and titanium alloy products will become simpler and the processing cost will be lower and lower. The charm of titanium and titanium alloy products will be highlighted in a wider range of fields.
