1、 Titanium ingot casting

When the initial forging temperature is β When the transition point is above 150 ° C to 250 ° C, the plasticity performance of the casting structure is the best. Steel ingots should be deformed by tapping or rapid tapping at the beginning until the original coarse grain structure is destroyed. The degree of deformation must be maintained within the range of 15% to 25%. The titanium ingot should be forged into the required cross-section and then cut into size blanks.

After forging damages the structure, plasticity increases, and with the increase of temperature, prolongation of holding time, and refinement of grains, the aggregation of recrystallization intensifies. In order to prevent the aggregation of recrystallization, the forging temperature must gradually decrease with grain refinement, and the heating and insulation time must be strictly controlled.

2、 Repeated upsetting and drawing of raw materials

In the β Within the temperature range of 90 ° C to 130 ° C at the transition point, alternating upsetting and stretching 2 to 3 times, and alternating transformation of the axis edges can obtain a material with β Recrystallization of fine grain structure with deformation characteristics, such as the absence of multi-directional upsetting on rolling mills.

3、 Rough multi-directional repeated upsetting and drawing

Like the first multi-directional repeated forging and drawing method, the initial forging temperature of titanium alloy bars depends on whether the forged semi-finished product is the next process blank or the delivered product. If the blank is made into the next process, the starting forging temperature can be compared β The transition temperature is 20-60 ℃ higher. If the product is delivered, the starting forging temperature ratio β The transition temperature is 25~45 ℃ lower. Due to the low thermal conductivity of titanium, when upsetting or drawing blanks on free forging equipment, if the preheating temperature of the tool is too low, the impact speed of the equipment is low, and the degree of deformation is large, X-shaped shear bands often form on the longitudinal or transverse section, especially in non isothermal upsetting on hydraulic presses. This is because the tool temperature is low, and the contact between the billet and the tool causes the surface layer of the metal billet to cool and deform. The deformation heat generated by metals does not have time to conduct heat everywhere, forming a large temperature gradient from the surface to the center. As a result, the metal forms a strong flow strain band. The greater the degree of deformation, the more obvious the shear band. Finally, cracks form under tensile stress with opposite signs. Therefore, when forging titanium alloys freely, the striking speed should be fast, the contact time between the billet and the tool should be shortened as much as possible, the tool should be preheated to a higher temperature as much as possible, and the degree of deformation within one stroke should be appropriately controlled.