钛合金薄壁筒形件热旋成形技术研究

Study on hot spinning technology of tubular workpieces for TA15 titanium alloy

采用TA15钛合金开展钛合金薄壁筒形件热旋成形技术研究，针对钛合金热旋过程中出现的典型缺陷进行形成机理和控制方法研究，成功地旋制出了质量良好的BT20钛合金大型薄壁筒形件。研究表明，钛合金薄壁筒形件热旋成形的关键是保证金属旋压时变形流动的均匀性，其直接受到热旋加热方式、旋压工艺参数和成形模具等因素的影响。BT20钛合金合适的旋压温度范围为600-700℃，当坯料较厚时温度可稍高以防止裂纹，而坯料较薄时旋压温度可适当降低以防止坯料隆起；钛合金筒形件壁厚越薄，越容易产生鼓包和褶皱等成形缺陷，尤其是当厚径比（t／D）小于1％时，应采用较小的道次减薄率以防止局部失稳；采用较小的工作角和较大的旋轮圆角半径有利于促进旋压变形的均匀性。

To develop hot spinning technology of thin-walled tubular workpieces of titanium alloy, formation mechanism of spinning defects, such as crack, pileup, bulge, wrinkle and diameter error, and corresponding control methods were studied, based on which large thin-walled tubular workpieces of TA15 alloy were well formed. The results show that it is crucial to ensure uniform plastic flow during hot spinning of thin-walled workpieces of titanium alloy, which is directly influenced by heating modes, spinning process parameters and die parameters. The optimum temperature of hot spinning of TA15 alloy is in the range of 600 - 700 ℃. The spinning temperature should keep higher relatively to avoid crack when tube wall is still thick, and the temperature should decrease to control pileup of metal before the rollers when tube wall becomes thinner. With decreasing wall thickness of tubular workpiece of titanium alloy, bulge and wrinkle tend to take place more easily and should be restrained by proper process measures. Especially when the ratio of wall thickness to diameter （t/D） is smaller than 1%, small reduction rates should be adopted to eliminate local buckling. In addition, small working angle and big round radius of rollers could improve the uniformity of spinning deformation of titanium alloy to ensure forming quality of spun workpieces.