采用极值原理的功能平衡法，确定三辊Y型轧机轧制变形区金属的三维位移增量和应变增量函数，并依照求解出的位移增量函数建立轧件的宽展数学模型．经冷轧钢丝实验证明，用本轧件宽展模型计算所得值与实测值较接近． The function balance method based on the extremum principle was used to determine the three-dimensional displacement increment and strain increment function of the metal in the rolling deformation zone of the three-roller Y-type rolling mill and to establish a mathematic model of the rolling element in terms of the displacement increment function. The cold-rolled steel wire experiments show that the calculated value of this rolling material widened model is close to the measured value.