Forming Parameter Design and Thickness Uniformity Control of Short Radius Elbow Made by Expanding Diameter and Pushing Bend

The forming theory of elbow made by expanding diameter and pushing bend is introduced in this paper. The tube blank of elbow takes place combined deformation with compression deformation in the axial direction and in the circumferential direction. The compression deformation in the axial direction makes tube bending deformation under the restricted condition of ram-shape die, then the belly metal of elbow thicken after compression deformation, while the back metal of elbow don’t take part in deformation. The eccentric expanding diameter in the circumference direction ensures the thickened wall thickness flowing favorably from elbow belly to elbow back and supplying the reduced wall thickness of back elbow. Comparatively, the compression deformation and expanding diameter deformation of short radius elbow is larger than that of long radius elbow. According to metal flowing law, proper ram-shape die design and pushing rate, increasing heating temperature, improving temperature field distribution and lubrication condition can assure uniformity wall thickness.