Using TZM Alloy to Produce Titanium Isothermal Forging Material

Titanium alloy has some special requirements on isothermal forging, for example, there are some special requirements on mold temperature, pressure and dwell time. During isothermal forging the mold temperature should be at 850~950 ℃ and pressure should be control at 100~120 MPa. Besides, the dwell time should be at 5~15 minutes, and based on the above requirements, commonly used nickel-base superalloy, insoluble metals and their alloys (TZM alloy), ceramic material, such as silicon nitride, silicon carbide and so on as titanium isothermal forging material. The experiment found that compared to the performance of other material TZM alloy has more favorable advantages. TZM alloy not only has good temperature resistance and high strength property, but the die service life also has a strong advantage.

Using TZM alloy as sophisticated forgings materials during isothermal forging, there may be has some crack happening in forging die to cause damage, and forging die damage may be caused by the following reasons:
1. The forging die happen some local plastic deformation and dimensional change;
2. Effected by the lubricant and protective gas, the embedding of material cause wearing;
3. The cracks concentrated on the place where the local stress is highly.

In order to prevent forging die early damage, understanding the carrying capacity before the crack spread of TZM alloy forging die, understanding of the conditions of forging die appeared, have important significance for judging the operation reliability and evaluation the forging die service life.

The cracks in the forging die are often unavoidable, so to slow the pace of cracks expansion has a certain influence on the service life of the mold. It was found that if the dwell time is too long, there will have a certain impact on crack formation and expansion. So isothermal forging pressing time should be as short.On the other hand, forging die at preheating and cooling will produce high thermal stress, causing cracks. In order to avoid large thermal stress, people should pay special attention to preheat uniformity.

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