TC4 Titanium Alloy Forging Process And Tooling Design

Titanium alloy has excellent comprehensive properties such as low density, high specific strength, high temperature resistance, corrosion resistance and non-magnetic, etc. Titanium alloy forgings are not only widely used in aviation and aerospace manufacturing industries, but also have a wide range of applications in the marine, chemical, automotive industry and medical devices. Therefore, we choose TC4 titanium alloy as the ideal material for manufacturing this connecting plate. Forging process and tooling design points:

1, the selection of bar material specifications. Through the three-dimensional model to take the cross-section analysis, it can be seen that the forging large cross-section is located at both ends, the equivalent diameter of φ90mm, the rest of the cross-section equivalent diameter of φ68mm, forging in the length direction cross-section size is relatively uniform. The length of the forging is 300mm, according to our experience in developing a variety of similar shapes of forgings, the length of the bar is close to the size of the forging in order to be full of two-end molding, so the preliminary selection of the bar length of 300mm, and then multiply the volume of the forging by 1.25 as the volume of the bar, the bar diameter is calculated to be φ80mm, which initially results in the specification for the material φ80mm × 300mm.

2, titanium alloy bar preparation. Forging (rolled) bar, the surface has a layer of hard and brittle α layer, die forging, need to remove the layer, so as not to cause cracking of the surface of the billet when forging. Diameter greater than 50mm, generally turned to remove 5mm. turning, such as individual parts are still defective, must be polished to eliminate, grinding depth of not more than 0.5mm. bar ends of R5 rounded corners, so as to avoid cracking of blanks when forging.

3, equipment selection. The forging force is calculated as 4000t. Titanium alloy thermal conductivity is low, room temperature is aluminum 1/15, iron 1/5, forging hammer forging titanium alloy speed faster when the central thermal effect is easy to produce overheating phenomenon, the forging performance has a greater impact, and the deformation heat generated by the press is not obvious. According to the forging precision requirements and the actual situation of my plant equipment, choose 5000t high energy screw press as forging equipment.

4, billet lubrication. Billet preheating temperature of 120 ± 30 ℃, preheating in the preheating furnace for 20min, evenly sprayed glass lubricant, billet surface lubricant drying before loading the furnace.

5, heating specifications. According to the standard to determine the TC4 titanium alloy beginning forging temperature of 960 ℃, the final forging temperature of 800 ℃, holding time of 0.8min/mm. Titanium alloy has a low thermal conductivity, in order to prevent overheating oxidation and absorption of hydrogen, the new furnace and a long time not to be used for a long time in the furnace should be empty first burned to remove the moisture and then use the furnace temperature field accuracy ± 10 ℃. The temperature is too high, the organization is coarsened, the grain is coarse; the temperature is too low, the deformation resistance is large, easy to produce cracks and other forging defects.
6, billet making. The purpose is to reasonably distribute the metal, this product needs to gather the metal to the two sides and ends of the forging, the design of the shape of the billet is crucial to the pre-forging and final forging molding effect. In order to avoid excessive deformation caused by cracking of the blank, the deformation of the blank ≤ 60%, the shape of the blank is designed as shown in Figure 2.

7, forging mold cavity design. The first fire to complete the production of blanks and pre-forging, the second fire to complete the final forging and precision forging. After pre-forging, cutting edge, sandblasting, grinding, on the one hand, to remove surface defects of forgings, improve the surface quality of forgings after final forging; on the other hand, cutting edge can reduce the metal forming resistance, which is conducive to the thickness of forgings size to play by. Cavity design for four cavities (Figure 3): billet (upper left) → pre-forging (upper right) → final forging (lower right) → precision forging (lower left). The purpose of the design of precision forging cavity is to improve mold life and forging dimensional accuracy. In order to form full forging, relatively complex and deeper cavities are placed in the upper mold. Deformation control: billet mold plate thickness design for 21.5mm, pre-forging plate thickness design size of 12mm, the final forging plate thickness of 5.2mm, the final forging deformation is greater than 30%, otherwise it is easy to cause the forging grain size, performance decline. Preheating temperature of the mold: 200-300℃.
8, cutting edge mold design. Cutting edge mold design has two cavities (Figure 4), the right side of the pre-forging cutting edge, cutting edge to retain part of the flying edge used as a final forging top material, the left cavity for the final forging after cutting edge cavity. In order to cut the edge precision, cut the edge of the upper and lower die clearance is designed for 0.8mm, the design of the guide pillar guide sleeve structure for cutting edge die assembly and positioning and control of the upper and lower die clearance dimensional accuracy.

9,Forging cooling and heat treatment. After the forging is air-cooled, annealing heat treatment is completed.
10,Pollution and cleaning of titanium alloy in the forging process. The billet should be cleaned up before heating, there shall be no oil, iron filings, chlorinated products, fingerprints are not allowed to remain; the electric furnace shall not be residual oxidized skin, there shall be no steel billet, the bottom of the furnace lining plate to casting stainless steel as well; billet coated with glass lubricant, or heated in a protective atmosphere.