摘要迅速发展的海洋工程对高性能紧固件用钢的需求不断增加。常用不锈钢和高强螺栓钢均难以满足海洋工程领域对高强度紧固件用钢的需求，基于这一现状，本文提出将新型高氮奥氏体不锈钢用于加工海工紧固件，系统研究了高氮钢的静拉伸、缺口拉伸、缺口偏斜拉伸、冲击、疲劳和耐腐蚀性能，观察了高氮钢的微观组织与断口形貌，分析了高氮奥氏体不锈钢的强韧化机理。研究结果表明：高氮钢的屈服强度为640MPa；断面收缩率为67。5%，断后伸长率为52。2%；缺口敏感度为1。22；室温时冲击韧性为311J；疲劳强度为330MPa，耐腐蚀性优于316L不锈钢。通过热力学计算发现，高氮钢的层错能为14。73mJ/m2，层错能很低，提高了层错宽度，促进了位错的平面滑移和孪晶的形成，提高高氮钢的屈服强度、冲击韧性和塑性。87731

毕业论文关键词：高氮钢、紧固件、海洋工程、力学性能、层错能

毕业设计说明书外文摘要

Title study on microstructure, properties and mechanism of strengthening and toughening of high nitrogen austenite stainless steel for marine engineering fasteners                                     

Abstract   Rapidly developed marine engineering needs numerous high performances steel for fasteners。 Common used stainless steel and high strength steel can’t fully satisfy the need of marine engineering fasteners for high strength。 Based on the situation, this article proposed that use new type high nitrogen austenite stainless steel to fabricate marine engineering fasteners, systematically studied high nitrogen steel’s properties of static tensile, notch tensile, deflect tensile, impact, fatigue and corrosion, observed microstructure and fracture of high nitrogen steel, analyzed high nitrogen steel’s mechanic of strengthening and toughening。 Study results indicates that yield strength is 640MPa; reduction in area is 67。5%; elongation of fracture is 52。2%; notch sensitivity is 1。22; impact toughness is 311J; fatigue strength is 330MPa; corrosion resistance is higher than 316L stainless steel。 Stacking fault energy of high nitrogen steel is 14。73mJ/m2 computed according to thermodynamic theory, lower stacking fault energy increases width of stacking fault energy, promotes planer shift of dislocation and formation of twins, and thus, improves yield strength, toughness and ductility of high nitrogen steel。

Keywords：high nitrogen steel, marine engineering， fastener, mechanical property, mechanism of strengthening and toughening

目   次 

1  绪论 1

1。1  高氮钢的发展 1

1。2  常用螺栓钢介绍 4

1。3  海洋工程对紧固件的需求 6

1。4  本文的工作 7

2  实验 9

2。1  高氮钢的成分 9

2。2  高氮钢的熔炼与加工 9

2。3  相与组织分析 10

2。4  拉伸性能实验 10

2。5  冲击实验 11

2。6  疲劳试验 11

2。7  耐腐蚀性能实验 12

3  高氮钢的组织和性能 13

3。1  高氮钢的相与组织