In order to ensure that the metal has good malleability in the forging process and good internal structure after forging, forging must be carried out within the specified temperature range. The upper and lower limits of this temperature range are called the start forging temperature (initial forging temperature) and the end forging temperature (final forging temperature).
The principle of determining the forging temperature range is to ensure that the metal has high plasticity, small deformation resistance and high quality and performance forgings. At the same time, the forging temperature range should be as wide as possible, so as to reduce the number of fires, improve the productivity of forgings, and achieve the dialectical unity of technology and economic rationality.
50~100℃。
Heating temperature of (α + β) titanium alloy
It is generally believed that the forging heating temperature of (α + β) titanium alloy (except for ingot opening) should be lower than the α+β/β transition temperature. If the heating temperature is higher than the α + β /β transition temperature, it will cause the sharp growth of β grains and the reduction of plasticity at room temperature, which is called β brittleness. When the heating temperature is in the β phase region, the lattice of titanium is body centered cubic, which has high plasticity and low deformation resistance. But high temperature, serious gas pollution, alloy plasticity decline, structure deterioration make forging quality change.
2. Heating temperature of α - titanium alloy
The effect of forging temperature on the room temperature properties and grain size of α - titanium alloy is similar to that of (α + β) titanium alloy.
3. Heating temperature of β - titanium alloy
(1) For the straightening process, the heating temperature is 700-800℃.
(2) Repeated heating in the middle is allowed. If the deformation of the later process is small, the intermediate heating temperature should be 50~100℃ lower than the initial forging temperature.
Determination of heating time and heating speed
When metal is heated, there must be a certain process of temperature rise. The degree of temperature rise in unit time (℃/ hour) is called heating speed. The heating speed can also be expressed by the metal thickness of heat penetration in unit time, i.e. mm / min.
The thermal conductivity of titanium at room temperature is 0.036 Ka / cm·s·D, which is 3.5 times smaller than that of steel.
According to the heat conduction characteristics of titanium alloy, the sectional heating method should be adopted when the diameter and thickness are more than 300 mm.
