Li Xubo, Zhai Chuanmiao, He Wenqi, Lu Ye, Zhang Bodong
College of Mechanical Engineering, Baoji University of Arts and Sciences, Baoji 721016, China.
Shaanxi Key Laboratory of Advanced Manufacturing and Evaluation of Robot Key Components, Baoji 721016, China.
Materials (Basel). 2023 Oct 14;16(20):6686. doi: 10.3390/ma16206686.
Nuclear power tube plates are made from the high-strength, low-carbon alloy steel SA-5083, which has high values of toughness and plasticity, though it is forged with poor consistency and entails serious work hardening. It requires a large number of deep holes with a high machining accuracy and high surface quality to be processed. However, the quality of the processed holes is often not up to the standard of the Boring and Trepanning Association (BTA) for the deep-hole drilling of tube plates; this has led to deep-hole processing becoming a bottleneck in the manufacture of steam generators for the main equipment of nuclear power islands. The variation laws of the diameter, roundness, perpendicularity, roughness, microhardness, and residual stress in relation to the feed, speed, and drilling depth are explored in the macro- and micro-dimensions; also explored is the wear morphology of BTA drills. The internal influence mechanisms between them are revealed in order to provide a scientific basis for the control of surface quality and machining accuracy as well as the optimization of process parameters. Our research results indicate that the guide block wear is mainly concentrated at the top 1-2 mm and that the drilling depth and feed have a great influence on the machining diameter. The hole wall roughness is between 0.3 and 0.6 μm, the maximum microhardness is about 2.15 times the hardness of the matrix material, and the residual stress is compressive stress. With increases in the feed and drilling depth, the hole diameter and the roughness increase. With an increase in the speed, the roughness decreases and the compressive stress of the BTA deep-hole drilling wall increases.
核电管板由高强度、低碳合金钢SA - 5083制成，该材料具有较高的韧性和塑性值，不过其锻造一致性较差且存在严重的加工硬化现象。它需要加工大量具有高加工精度和高表面质量的深孔。然而，加工孔的质量往往达不到管板深孔钻削的镗孔和套料协会（BTA）标准；这导致深孔加工成为核电岛主设备蒸汽发生器制造中的一个瓶颈。从宏观和微观维度探究了直径、圆度、垂直度、粗糙度、显微硬度和残余应力相对于进给量、速度和钻孔深度的变化规律；还探究了BTA钻头的磨损形态。揭示了它们之间的内部影响机制，以便为控制表面质量和加工精度以及优化工艺参数提供科学依据。我们的研究结果表明，导向块磨损主要集中在顶部1 - 2毫米处，钻孔深度和进给量对加工直径有很大影响。孔壁粗糙度在0.3至0.6μm之间，最大显微硬度约为基体材料硬度的2.15倍，残余应力为压应力。随着进给量和钻孔深度的增加，孔径和粗糙度增大。随着速度的增加，粗糙度减小，BTA深孔钻削孔壁的压应力增大。
