不同退火温度对纯铜三通管胀形性能影响

Effect of annealing temperature on bulging property of copper tubes

将轧制态纯铜原始管材经400、500、600、700℃退火处理,对4种退火温度下的原始管材进行显微组织分析、拉伸试验,然后进行三通管胀形破裂试验,并通过扫描电镜观察了不同温度退火后纯铜管胀裂后的断口形貌。结果显示:随着退火温度升高,材料的抗拉强度、屈服强度下降,晶粒显著长大。不同温度退火后纯铜管的破裂形貌均为韧性断裂形貌,其中700℃退火管的韧窝深度相对变深,但韧窝数量急剧下降,并且出现比较平坦的断口。随着退火温度(400、500、600℃)升高,最大破裂内压下降,胀形支管高度升高,最大壁厚升高,最小壁厚降低。500、600℃退火由于其微观组织孪晶出现改善塑性,提高了胀形高度;700℃退火晶粒十分粗大,抗拉强度最低,塑性最差,支管高度最低。

The as-rolled pure copper pipe was annealed at 400,500,600 and 700℃,respectively,and the microstructure was analyzed,the tensile test and the expansion fracture test of the three-way tube were carried out.Fracture morphology of the pure copper tubes annealed at different temperatures was observed by means of scanning electron microscopy(SEM).The results show that with the increase of annealing temperature,the tensile strength and yield strength of the materials decrease,and the grains grow up significantly.The fracture morphology of pure copper tubes annealed at different temperatures is ductile fracture morphology,in which the dimple depth of that annealed at 700℃is relatively deep,but the number of dimples decreases sharply,and the fracture surface is relatively flat.With the increase of annealing temperature(400-600℃),the maximum fracture internal pressure decreases,the height of bulging branch height increases,the maximum wall thickness increases,and the minimum wall thickness decreases.When annealed at 500℃and 600℃,the plasticity is improved due to the appearance of twins,and the bulging height is increased.When annealed at 700℃,the grain size becomes very large,the tensile strength is the lowest,the plasticity is the worst,and the branch height is the lowest.