Push-bending forming device and method for titanium alloy tubes

A push-bending forming method for titanium alloy tubes using a push-bending forming device, the push-bending forming device comprising:

• a die main body;
• a plurality of filling balls;
• a differential temperature assembly;
• and
• a punch;
• the die main body being provided with a forming cavity;
• a tube blank being configured to be driven to move relative to the forming cavity;
• the forming cavity being provided with a bent segment;
• and the forming cavity being configured for push-bending forming of the tube blank to obtain a bent tube;
• the plurality of filling balls being configured to be filled in the tube blank;
• the plurality of filling balls being made of a metal material, and having a heat-resistance temperature over 500° C.;
• and a diameter of each of the plurality of filling balls being less than an inner diameter of the tube blank;
• the differential temperature assembly comprising a first heating device and a second heating device;
• the first heating device being arranged on an inner side of the bent segment, and being configured to heat the inner side of the bent segment to a first preset temperature;
• the second heating device being arranged on an outer side of the bent segment, and being configured to heat the outer side of the bent segment to a second preset temperature;
• and the first preset temperature being lower than the second preset temperature;
• and
• the punch comprising a first pushing part and a second pushing part;
• a diameter of the first pushing part being smaller than an inner diameter of the tube blank;
• the first pushing part being configured to push the plurality of filling balls into the tube blank;
• a diameter of the second pushing part being larger than the inner diameter of the tube blank;
• and the second pushing part being configured to push the tube blank to move along the bent segment;
• and
• the push-bending forming method comprising:
• (S1) starting the first heating device to heat the inner side of the bent segment to the first preset temperature and keeping the inner side of the bent segment at the first preset temperature, and starting the second heating device to heat the outer side of the bent segment to the second preset temperature and keeping the outer side of the bent segment at the second preset temperature, such that a temperature difference is formed between the inner side of the bent segment and the outer side of the bent segment;
• wherein the first preset temperature is 200-300° C.;
• the second preset temperature is 400-500° C.;
• after reaching the first preset temperature, a temperature change of the inner side of the bent segment is less than 2° C.;
• and after reaching the second preset temperature, a temperature change of the outer side of the bent segment is less than 2° C.;
• (S2) when a temperature difference between the first preset temperature and the second preset temperature is 100-300° C., aligning a front end of the tube blank with an inlet of the bent segment;
• opening an accommodating cavity to allow a preset number of filling balls among the plurality of filling balls to move into the forming cavity, wherein the preset number of filling balls constitute a first filling ball group, and a gap between adjacent filling balls among the first filling ball group is less than 1 mm;
• pushing, by the first pushing part, the first filling ball group into the tube blank at a uniform speed until an end of a first filling ball of the first filling ball group away from the punch is flush with the front end of the tube blank, and driving the second pushing part to push the tube blank into the bent segment for bending, wherein after bending the tube blank to an angle of 10°-30°, the first filling ball of the first filling ball group is separated from the tube blank and pushed into the forming cavity;
• (S3) moving the punch in a direction away from the tube blank, so that one of filling balls among the plurality of filling balls in the accommodating cavity moves into the forming cavity;
• driving the first pushing part to push the one filling ball leaving the accommodating cavity into the tube blank, wherein at this time, filling balls in the tube blank constitute a second filling ball group;
• pushing, by the first pushing part, the second filling ball group to drive the tube blank to move relative to the forming cavity, until a first filling ball of the second filling ball group is separated from the tube blank and pushed into the forming cavity;
• and
• (S4) repeating step (S3) until the bent tube is obtained, wherein a motion trajectory of each of the plurality of filling balls in the tube blank is a continuous envelope curve.