【作者】 刘长勇；

【导师】 张人佶；

【作者基本信息】 清华大学 ， 材料科学与工程， 2011， 博士

【摘要】 大口径厚壁无缝钢管是极为重要的基础工业产品，而垂直挤压工艺是生产该类产品的最佳工艺，对其进行研究具有重要的意义。360MN/150MN垂直挤压机组的投产使我国打破了国外对该类产品的垄断，本课题为此项目的组成部分。首先研究了重型钢丝缠绕黑色金属挤压筒，分析了钢丝缠绕挤压筒设计中存在的问题，包括预热、隔热与冷却和热应力等，提出了高温坯料内置挤压筒预热和电加热预热两种可行的方案。针对两种方案，分别研究了其设计中存在的问题和相应的解决方案，研究表明高温坯料内置预热挤压筒是一种简单易实现的方案，而电加热预热挤压筒则具备更好的性能和使用效果。提出了采用高温内衬和中衬预热膨胀后紧压在外衬上以产生预应力的方法，并基于此方法，完成了挤压筒的设计。针对黑色金属热挤压工艺中玻璃润滑研究的不足，对玻璃润滑行为进行了理论分析，提出了采用理论计算和数值模拟相结合预测挤压钢管表面玻璃润滑膜厚度的方法，通过小直径棒材挤压实验和TP347H不锈钢钢管的挤压生产验证，表明本论文提出的预测方法所计算的结果能够反映玻璃润滑膜厚度的变化趋势，并具有足够的精度，为润滑和挤压工艺提供了指导。通过计算，得出了大口径厚壁无缝钢管表面的玻璃润滑膜厚度以50μm～100μm为宜，与目前360MN压机生产的钢管进行了对比，分析了润滑工艺的不足并提出改进建议。建立了玻璃润滑热挤压工艺的数值模拟模型，并针对传热边界条件研究的不足，设计了测试坯料与模具之间以玻璃润滑剂隔开工况下的界面传热系数的实验装置，为挤压工艺的数值模拟提供了依据。通过数值模拟分析360MN压机挤压工艺，并与实测挤压力数据对比，得到了目前360MN压机生产工况下的摩擦和传热边界条件，分析了目前360MN压机挤压工艺存在的问题，并提出改进建议。依据本论文提出的挤压筒预应力产生方法，设计了内径φ170mm电加热预热钢丝缠绕挤压筒，测试了预紧状态下的应力场以及预热状态下的温度场和热应力。测试结果表明，预热后挤压筒具有合理的预应力分布，通过反挤压实验，证明了所设计的挤压筒效果更佳，为重型钢丝缠绕挤压筒的工程应用提供了重要的依据。更多还原

【Abstract】 Large diameter and thick-walled seamless steel pipes are very importantbasic industrial products. The best way to fabricate such pipes is verticalextrusion process. The success of36,000tons vertical extrusion press broke themonopolization of such products by foreign companies. Supported by thisproject, the large wire winded steel extrusion container was investigated. Thebasic issues, including preheating, thermal insulation, cooling and thermal stress,were analyzed. Two preheating methods, the heated billet inside preheating andelectrical preheating, were proposed. As for each one, the design problems wereanalyzed and solutions were proposed. It was found that the heated billet insidepreheating was an easy way to design extrusion container which was applied by36,000tons extrusion press. But the electrical preheating extrusion containercan perform and function better. A new way to generate pre-stress field wasproposed. Since the inner and middle cylinder expand larger under hightemperature (350℃～400℃) than the outer cylinder and steel wire of which thetemperature is much lower, that would lead to high pressure between them. Thispressure could produce pre-stress on the inner cylinder. Based on this idea, thewhole design was proposed.Since it was still inadequate for the research on glass lubrication behaviorduring the extrusion process, theoretical analysis was conducted. By combiningthe theoretical model and numerical simulation results, the thickness of glassfilm on the surface of the extruded pipes can be calculated. To verify theeffectiveness of this method, bar extrusion experiment and TP347H pipesextrusion process was investigated. Results showed that the model proposed canpredict the variation trend of the glass film and can be used to predict thethickness. The glass film thickness for large diameter and thick-walled steelpipes was calculated. The reasonable glass film thickness is between50μm and100μm. By contrast with pipes extruded by36,000tons extrusion press, theproblems were analyzed and the suggestions for improvement were proposed. The devices to measure the thermal transfer coefficient between the heatedbillet and hot working die steel was set up due to the lack of experimental dataof this coefficient. The coefficient was measured and can be used for numericalsimulations. Numerical simulation models were set up and the calculated resultswere compared with36,000tons press experimental data. The boundaryconditions for36,000tons press were determined and by contrast with the idealboundary conditions, the problems were analyzed and the suggestions forimprovement were proposed.Based on the design methods proposed in this dissertation, the innerdiameter φ170mm electrical preheating extrusion container was designed andmanufactured. The pre-stress field after wire winding, the temperature andthermal stress field after preheating were measured. Results showed that afterpreheating the pre-stress field can meet the requirement. Backward extrusionexperiment showed that the designed extrusion container can function well forextrusion process, thus provide important foundation for its practicalapplication.更多还原