Titanium alloy die forging process Titanium alloy, as a lightweight, high-strength and excellent corrosion-resistant material, is widely used in aviation, medical, chemical and other fields. Die forging process is the key link in titanium alloy processing, and its quality directly affects the performance of the final product.
This article will discuss in detail the seven elements of titanium alloy die forging process: billet preparation, heating, lubrication, forging, cleaning, die design and forging of two-phase titanium alloy.
1. Billet preparation Titanium alloy billets must be carefully prepared before die forging. The billet surface should be rough-machined or rough-ground to ensure that the surface is flat and free of obvious defects and impurities. Bars are usually processed by turning or centerless grinding. When cutting the billet, it is recommended to use a band saw to avoid heat-affected zones and oxidation that may be caused by gas cutting.
2. Heating During the heating process, the slag and scale at the bottom of the furnace must be removed first to ensure a clean environment in the furnace. When heating titanium alloys, an oxidizing atmosphere should be used to slow down the saturation process of hydrogen and reduce the oxidation and gas pollution of titanium alloys. At the same time, the heating temperature and time should be strictly controlled to minimize the growth of grains. The mold should also be preheated to 250-350℃ in advance and kept warm for more than 12 hours to reduce the temperature difference between the mold and the titanium alloy.
3. Lubrication Titanium alloy has poor fluidity during forging, so the mold should be lubricated before forging. Lubrication can improve the fluidity of titanium alloy and prevent forgings from sticking to the mold. Commonly used lubricants include a mixture of colloidal graphite and water or a mixture of graphite and oil-based or water-based.
4. The die forging deformation of forged titanium alloy is generally controlled between 40% and 80%. After the last heating, the entire metal should have uniform deformation, and the temperature distribution during the deformation process should be uniform to prevent deformation at too low a temperature from causing cracking. For two-phase titanium alloys, sufficient deformation is particularly important because its grain refinement cannot be achieved by heat treatment methods, but only by deformation.
5. Cleaning A brittle oxide layer will form on the surface of the titanium alloy after forging, which may cause cracking of the metal under the surface during the next forging. Therefore, after each fire die forging, the oxide layer should be removed by methods such as sand blowing.
Sixth, mold design The design of titanium alloy forging molds is different from that of steel forging molds. The shrinkage rate of titanium alloy forging molds is small, usually 1:1.87 compared with the shrinkage rate of steel forging molds. When using the same deep and complex die bore, the mold for forging titanium alloy is 50% thicker than the mold for forging steel. In addition, the fillet radius of the mold should be larger, and the surface finish of the die bore should be higher.
Seventh, forging of two-phase titanium alloys When forging two-phase titanium alloys in the full-phase region, the forging performance of titanium alloys at high temperatures can be improved or the notch toughness of forgings can be improved. In order to obtain forgings with higher comprehensive performance, the microstructure of the alloy after forging should be controlled within a certain range. The content of equiaxed phase should be controlled between 15% and 30%. Too much will lead to reduced notch toughness, and too little will reduce elongation. If the forging contains too much phase, its performance can be restored by heat treatment.
In summary, the titanium alloy die forging process is a complex and delicate process involving multiple key elements. By carefully controlling each link, the quality and performance of titanium alloy forgings can be ensured to be optimal.
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