Effect of mandrel diameter on the wall thickness uniformity of the hollow valve of 5Cr21Mn9Ni4 by cross-wedge rolling
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摘要: 楔橫軋空心軸類件存在壁厚分布不均問題，特別是在小直徑大長徑比空心件楔橫軋成形中更為突出.本文在Gleeble-1500D熱模擬實驗機上進行了5Cr21Mn9Ni4N耐熱鋼的熱壓縮實驗，得到了5Cr21Mn9Ni4N的熱變形本構方程.通過改變芯棒直徑，采用有限元仿真和實驗相結合的方法，研究了楔橫軋軋制空心氣門過程中的壁厚變化規律.研究結果表明，帶芯棒軋制時，芯棒直徑存在臨界值，在該值下進行軋制，空心氣門預制坯壁厚均勻性最優；楔橫軋空心件時，金屬軸向均勻流動是壁厚均勻的必要條件；軋件軸向拉應變減小，徑向壓應變變大，周向應變在0附近且為拉應變時，壁厚較為均勻.Abstract: Wall thickness asymmetry is a common problem for cross wedge rolling (CWR) hollow shafts, which is especially usual in the CWR process of hollow shafts of small diameter and large height-diameter ratio. In this paper, the constitutive equation of hot deformation of 5Cr21Mn9Ni4N heat resistant steel was investigated by the thermocompression experiment on the Gleeble-1500D thermo-simulation machine. The law for the variation of wall thickness during forming 5Cr21Mn9Ni4 hollow valve with CWR was presented, which is obtained via changing mandrel diameter and by means of finite element method (FEM) and experiment. The results confirm that when hollow valve with mandrel is formed with the CWR process, there is a critical diameter of mandrel. It makes wall thickness of hollow valve optimal. On the basis of FEM, it is stated that uniform flow of material along the axial direction is necessary for wall thickness uniformity of hollow valve, and circumferential stretching strain near zero, increase of radial compression strain with decrease of axial tension strain permit to improve wall thickness uniformity of hollow valve.
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Key words:
- cross wedge rolling /
- heat-resistant steel /
- constitutive equations /
- hollow valves /
- critical diameter /
- metal flow
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參考文獻
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