民用飞机主起落架断离销的300M钢热表处理及力学性能研究

Effect of heat and surface treatment on mechanical properties of 300M steel for civil main landing gear fuse-pin

摘要:

民用飞机主起落架应急断离销准确的破坏载荷控制成为断离销结构设计的关键。为了提出适用于断离销热表处理工艺要求，探讨断离销材料力学性能设计指标，分别研究回火温度（300、350 和 400 ℃）、喷丸、镀铬和超声速火焰喷涂（HVOF）对 300M 钢微观组织和力学性能的影响。结果表明：300 和 350 ℃回火温度下，300M 钢主要由回火马氏体和贝氏体组成，表现出韧性断裂特征，保障了材料综合力学性能，但 350 ℃回火的材料屈强比达 0.87，冲击韧性略有增加，对保障准确的破坏载荷尤为重要；表处理不影响基体材料的组织形貌，但因减小了试样几何尺寸，降低了其承载力；相比于喷丸和镀铬表处理，HVOF 中高温 WC-10Co4Cr 粉末熔融了试样表面基体，进一步减小了局部尺寸，导致试样的承载力最小。

Abstract:

The control of accuracy breakaway load for emergency fuse-pin of civil aircraft main landing gear is crucial for mechanical design of fuse-pin. To propose requirements for heat and surface treatment process of fuse-pin and explore the mechanical property design index of fuse-pin material, a series of experiments were conducted to study the influence of tempering temperature (300°C、350°C和400°C) and surface treatments (shot peening, chromium plating and high-velocity oxygen-fuel) on microstructure and mechanical properties of 300M steel. The results reveal that the microstructure of 300M steel mainly consists of tempered martensite and bainite by tempering treatment of 300°C and 350°C, exhibiting the ductile fracture property, which ensuring the comprehensive mechanical properties. Moreover, due to the higher yield ratio(0.87) and better impact strength by 350°C tempering temperature, the breakaway load can be accurately controlled. All surface treatments are not change the microstructure and reduce the structural size of specimens, resulting in lower tensile force. Compared to shot peening and chromium plating, tensile force of specimen with HVOF treatment is the lowest because higher temperature of WC-10Co4Cr power melt the specimen surface and reduced its local size.