30CrMnSiA钢沉头螺栓断裂失效分析

某飞机用30CrMnSiA钢沉头螺栓在拆卸过程中发生断裂,同炉批未曾使用的螺栓经磁粉检测也存在裂纹。为查找失效分析原因,通过对断裂件和同炉批开裂的螺栓外观检查、断口宏微观分析、能谱分析、硬度检测、金相分析等方法对断裂和开裂的螺栓进行了分析。结果表明:断裂螺栓和开裂螺栓断裂类型为氢脆,螺栓氢脆断裂主要与抗拉强度和热处理工艺有关,通过改善热处理工艺参数,适当降低螺栓的强度,增加酸洗后的除氢时间降低氢含量,从而避免氢脆发生的可能性。     

30CrMnSiA螺栓断裂原因分析

30CrMnSiA螺栓在安装一段时间后断裂.通过断口宏微观观察、金相组织检查、硬度和化学成分检测、破坏拉力试验、氢含量测定以及模拟试验等,确定了螺栓断裂性质和原因.结果表明,螺栓在其材质氢含量仅1ppm条件下发生断裂的性质为氢脆断裂,断裂原因并非由于氢含量过高,而主要是由于该批次螺栓存在一定程度的回火脆化,加之螺栓材质C元素含量偏高和马氏体组织较粗大,提高了螺栓材料的抗拉强度,增加了材料的氢脆敏感性,最终导致螺栓的氢脆断裂.     

30CrMnSiA钢螺栓的断裂失效分析

通过显微组织分析、硬度测试、断口形貌及能谱分析、氢含量测试等手段对发动机固定螺栓的断裂失效原因进行了分析。结果表明,当氢含量偏高、硬度偏高、承受较大载荷这三个条件同时具备才导致螺栓发生氢脆断裂。     

某型高强度螺栓断裂失效分析

为了能确定某海上设备使用的35CrMnSiA高强度螺栓的断裂原因,对断裂的螺栓进行外观检查,断口宏观、微观分析,氢含量检测,金相组织检查及硬度检测等试验.在理化试验的基础上,运用微观断裂机理对螺栓的断裂原因进行分析,得出结论:其断裂失效性质为由应力,氢和腐蚀共同作用引起的氢致开裂型应力腐蚀断裂.其中,引起螺栓断裂的氢来自外界腐蚀环境.提出改善螺栓的加工工艺和使用无氢脆的涂覆层来提高螺栓的抗腐蚀断裂能力.     

汽车下摆臂球销座连接螺栓断裂失效分析

汽车下摆臂球销座连接螺栓在使用时发生早期断裂。采用金相分析、硬度测试及氢含量测定等方法对其断裂原因进行了分析。结果表明,螺栓在电镀过程引入氢而后续处理时间过短除氢不完全,加上R转角处容易造成应力集中,因此在使用后不久便发生螺栓断裂失效。同时提出了相应的改进措施。     

35CrMo高强螺栓脆性断裂原因分析

35CrMo钢高强螺栓在使用中发生脆性断裂。为了揭示螺栓断裂的原因,对断裂的螺栓进行了化学成分分析、硬度、显微组织、断口分析、氢含量等方面检测。结果表明,螺栓的化学成分、硬度指标、抗拉强度、夹杂物含量以及氢含量均符合要求。由断裂螺栓的断口分析发现,保留马氏体位相的回火索氏体易在心部形成应力集中,导致在该位置形成细微的应力裂纹,装配过程中受到外部的拉应力下,逐步向周围扩展,最终在多因素叠加下而产生脆性断裂。     

45钢螺栓断裂失效分析

对45钢连接螺栓断裂件的显微组织、断口形貌、硬度和抗拉强度进行了观察分析和测试.结果表明,螺栓头部圆周外缘部分组织为正常回火索氏体,但其心部和螺杆部分出现非正常的网状铁素体和珠光体组织,降低了零件的硬度和强韧性,是导致螺栓断裂的主要原因.另外,螺栓加工头部支承面到螺杆颈部的肩胛根部没有过渡圆弧,也是螺栓断裂失效的一个原因.     

飞机盖板螺栓断裂失效分析

某飞机服役一段时间后，机翼盖板1根螺栓发生断裂。通过外观痕迹和断口形貌观察、显微组织检查、硬度测试、能谱成分分析、氢含量测试以及氢脆试验，对螺栓的断裂性质和原因进行了分析。结果表明，螺栓断裂性质为氢致延迟脆性断裂。材料强度偏高，氢脆敏感性较大是螺栓发生氢脆断裂的内因，表面局部腐蚀吸氢是导致螺栓氢脆断裂的直接原因。调整热处理工艺，在满足设计要求的前提下适当降低螺栓的强度，同时加强螺栓的腐蚀防护，可以有效预防氢脆断裂的发生。     

某600MW亚临界机组2Cr13钢螺栓的断裂失效分析

通过对一起2Cr13钢循环水泵地脚螺栓失效断裂事件进行失效分析,开展了包括化学成分、力学性能、微观组织等方面的系统分析,对螺栓断裂原因进行了研究。结果表明:该批次螺栓C含量较低,室温抗拉强度、规定塑性延伸强度、硬度、冲击性能均低于标准要求,结合断口分析表明材料脆性较大。同时,显微组织分析表明该2Cr13耐热钢热处理工艺为退火处理,退火处理状态的2Cr13耐热钢综合性能均明显低于调质处理后材料综合性能,故该批次螺栓热处理工艺不当导致螺栓微观组织和性能不符合相关要求是引起螺栓运行时疲劳断裂的主要原因。     

重整氢压缩机连杆螺栓断裂失效分析

某60万吨/年重整氢压缩机的两根35CrMoA钢连杆螺栓在运行过程中发生断裂失效,对断裂连杆螺栓的断口形貌进行了分析,同时对其化学成分、金相组织和硬度等进行了理化分析。结果表明,断裂连杆螺栓的组织分布不均匀、硬度偏差较大,扫描电镜观察断口发现存在有多个疲劳源。对相同材料的35CrMoA钢棒料进行与失效螺栓相同的热处理,分析其金相组织和硬度,并与失效螺栓进行对比,表明断裂连杆螺栓的调质热处理不善,导致组织分布不均匀、夹杂物较多,螺栓的力学性能下降,在交变载荷的作用下,最终发生早期疲劳失效。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.