Analysis of TC4 Titanium Forging Process
The effect of forging temperature on the β grain size and room temperature properties is that β grains become larger with the increase of temperature（ β Above phase transition), However, the elongation and reduction of area decreased, and the plasticity decreased; to ensure TC4 forgings have good comprehensive performance β Forging below the transition temperature.
Titanium alloy has high deformation resistance but poor thermal conductivity. Deformation resulting from severe alloy flow and heavy hammer impact during forging may cause individual parts of the forging to exceed temperature β Transition temperature, excessive deformation and small deformation will cause grain coarsening and performance degradation. Based on the above, the possible causes of TC4 forging nonconformity can be preliminarily determined:
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(1) The temperature of the forging blanks is too high when heated to exceed the β Transition point;
(2) Overweight single hammer strike during forging causes excessive single deformation, which leads to local overheating and aggregation recrystallization, thus degrading performance.
(3) The temperature of heat treatment after forging is too high, which makes the temperature of TC4 forging exceed the β transition point. Widmanstatten structure is formed to reduce the performance of forgings.
TC4 Titanium Forging-Selection of test parameters and results
According to the above analysis, change the forging process parameters of TC4 (Table 1) and pay attention to gentle strikes while forging. (Note: Blanking size 50 × 113, forging size 50 × 65 × 65)
The test results show that all the performance indexes are qualified, and the notch stress fracture index is more than 5 hours.
TC4 Titanium Forging-Analysis of test results
(1) Viewed from the furnace temperature and initial forging temperature, the heating temperature is not too high. qualified parts can be forged even at temperatures exceeding 20 degrees Celsius.
(2) A single hammer tap was used in the test. the test forgings are up to standard. It is proved that tapping is an important factor to improve the properties of forgings.
(3) The temperature of heat treatment after forging is 20 degrees lower than that of the original parameter, which may also be a factor to improve the properties. Because from the point of view of temperature, if the deviation of furnace temperature due to temperature control reaches 795 C, which exceeds 780 degrees Celsius specified in the manufacturer's instructions and results in reduced forging properties.
