If the actual selection of the tube outer diameter is smaller than the calculated according to the formula Dp value, and fit the mold of good performance, but within easy wrinkling elbow arc. If the actual selection of the tube outer diameter is larger than the calculated according to the formula Dp value, the result is just the opposite. According to these principles, to push the system in this test tube elbow push the system used in Table 1 (A segment is part of the left elbow). Material and shape of (2) to push the mandrel head elbow geometry affect the material and shape of the mandrel head is an important process parameter, directly controlled by the design and manufacturing. Mandrel head material generally ZG1Cr18Ni9Ti, ZG3Cr20Ni14, ZG1Cr25Ni20Si2, ZG0Cr20Ni25 and other high-temperature strength and wear resistance gradually increased, the price is increased accordingly. If it is small batch, you can choose ZG1Cr18Ni9Ti, ZG3Cr20Ni14; if it is mass-produced, should choose ZG3Cr25Ni20 Si2, ZG0Cr20Ni25, but ZG0Cr20Ni25 price is too high, so this test mandrel head material selection ZG1Cr25Ni20 Si2. Divided by the radius of curvature of the mandrel head singles rate, double curvature and three multi-curvature. Single rate, double curvature, the curvature of the mandrel more thrust decreases, production costs increased gradually. The selected test double curvature mandrel. Press the cross-sectional shape and the elliptical cross section is divided into two kinds of circular cross-section, circular cross-section making simple, low cost, but push the elbow ovality and thinning rate is too large; oval cross-section production of complex, high cost, but push the system elbow ovality and thinning rate is small. The selected test mandrel oval cross-section. Plastic sections divided according to whether there have plastic mandrel head first two paragraphs and no shaping mandrel segments. There are shaping mandrel segment production of complex, high-cost, long time; no plastic segment mandrel making simple, low cost, but the front-end wear faster. This experiment has selected shaping mandrel segments.