A new method called compression and setting round was proposed to replace the mechanical expanding to reduce the ellipticity and increase the compressive strength of large pipes. The compression and setting round by mold was completed by a upper die and a lower die whose cavities could be closed to a whole round. In order to reduce the springback, the within and outside walls of the pipe must be compressed into the plastic deformation, namely, the compression rate must be sufficient. In this paper, the small curvature plane bending theory of curved beam was used to analyze the compression and setting round of the pipe. The springback equation of the compression and setting round was deduced to express the relationship between the curvature radius of any poin on cross-section center line after springback and the initial geometric parameters, material properties and the compression rate of the pipe. After a compression experiment, the ellipticity is less than 0.12%, which fully meets the technical requirements of line pipes for 0. 5 % to 1 % in practice. Furthermore, the relative ellipticity deviation of theoretical analysis and experimental results is less than 0. 09% and the relative geometric size deviation is less than 0.19%. Experimental results verify that the springback equation ofcompression and the setting round method have important application values.%提出以模压式缩径矫圆的方式代替机械扩径以减小管件椭圆度,提高其承压强度.模压式缩径矫圆采用闭合后模腔为一整圆的上、下模具对椭圆管坯进行矫圆,为减小矫圆后管坯的回弹,须使整个管坯内外壁均进入压缩塑性变形,即有足够的压缩率.本文采用小曲率曲梁平面压弯的分析方法对模压式缩径矫圆工艺进行了理论分析,推导出缩径矫圆弹复方程,该方程表示了管坯截面壁厚中心线上任意一点弹复后的曲率半径与管坯初始几何参数、材料性能、缩径率间的关系.工程中管线钢管的椭圆度技术要求一般为0.5％～1％,采用本文方法缩径矫圆后的管坯椭圆度＜0.12％,完全满足技术要求.理论分析与实验结果的椭圆度相对偏差＜0.09％,几何尺寸相对偏差＜0.19％,表明模压式缩径矫圆在工程实际中具有应用价值.
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