A comparative analysis of copper and brass surface films in contact with tap water

A study of the surface oxide films naturally grown on copper and brass in contact with drinkable water is presented. The investigation focuses on the influence of Zn as alloying element on the corrosion resistance of brass. Artificial tap water, employed as electrolyte, simulates a practical application of these materials. The surface films were grown at open circuit potential for 2 and 192 hours. Diverse in-situ techniques such as cyclic voltammetry, polarization curves, electrochemical impedance spectroscopy and UV-Vis reflectance spectroscopy were employed. Even when the surface layer is mainly composed of cuprous oxide, Zn(II) species are incorporated in the surface film grown on brass. At longer ageing times, the thickness increases, without affecting the composition of the surface films. The corrosion current was calculated for both materials using various techniques. The corrosion current density and the anodic currents in the polarization curves decreased as the ageing time increased, particularly in the case of brass. This improvement in the performance of the film on brass can be attributed to the incorporation of Zn(II) species into the surface layer, particularly as the film consolidates at longer times.     

低磷共聚物循环冷却水处理剂对黄铜的缓蚀作用研究

采用过氧化氢-次磷酸引发体系引发马来酸酐与对苯乙烯磺酸钠共聚,制备了一种磷含量低于4%的新型循环冷却水处理剂.用试片失重法和电化学方法研究了自制低磷共聚物在配制循环冷却水中对黄铜的缓蚀作用,试片表面元素分析和电化学分析表明,低磷共聚物对黄铜的缓蚀作用是共聚物在黄铜试片表面吸附形成的保护膜抑制了阳极电化学过程的结果.     

Failure analysis of the brass tubes in a lubricating oil cooler

Failure analysis was carried out on leaked brass tubes of a lubricating oil cooler. Direct evidences of dezincification and stress corrosion cracking (SCC) were observed by scanning electron microscope (SEM) and energy dispersive spectroscopic (EDS) analysis. It is found that there are many small pits distributed on the fracture surface and EDS analysis revealed the occurrence of dezincification in the small pits. SCC was observed on the cross-sectional plane of the fracture by SEM. Ammonia test has proved the existence of residual stress in the as-received tubes. It is determined that the brass tubes have been suffered from the co-action between dezincification and SCC.     

Failure Analysis of a Fractured Leaded-Brass (CuZn39Pb3) Extruded Hexagonal Rod

A fractured extruded brass (CuZn39Pb3 alloy) hexagonal rod of 6 mm across flats (AF) was received with the request to perform a failure investigation. Visual inspection, and optical and scanning electron microscopy/local elemental x-ray analysis (SEM/EDS) were used as the principal tools for the investigation. Metallographic and fractographic observations indicated the occurrence of brittle intergranular fracture. The collected evidence suggests that hot shortness is the failure mechanism.     

弹壳开裂失效分析

对某型H68黄铜弹壳进行检查时发现大量弹壳存在裂纹。通过对弹壳进行宏观和微观观察、能谱分析、金相检验和残余应力测定等,分析了弹壳开裂的原因。结果表明:弹壳的开裂性质为应力腐蚀开裂,其原因是由于收口位置存在一定的残余拉应力,且该位置的晶粒尺寸较大,在外界介质的协同作用下产生了应力腐蚀裂纹。     

节温器开裂原因分析

通过断口分析、金相检验、腐蚀性能测定等方法对节温器壳体开裂的原因进行了分析。结果表明:节温器的开裂属于应力腐蚀开裂。引起应力腐蚀开裂的主要原因是节温器中作用于壳体内侧应力较高和含硫橡胶对黄铜壳体产生腐蚀。     

H68黄铜弹壳开裂原因分析

通过化学成分分析、裂纹宏观和微观检验、显微硬度测试与微区成分能谱分析等方法,分析了H68黄铜弹壳开裂失效的原因。结果表明：材料本身存在冶金缺陷β相偏析与零件收口处退火不良是造成弹壳开裂失效的原因。     

水表连接黄铜螺母断裂分析

居民住宅内与水表连接的黄铜螺母发生断裂,造成管路泄漏.采用宏、微观检验方法对失效螺母进行了分析.结果表明,黄铜材料中含有较多的铅,使金属基体脆化并在晶界上存在脆性共晶体网膜,加上金属中还存在孔洞、缩松等铸造缺陷,是造成螺母断裂的主要原因.     

Contribution of Ti addition to characteristics of extruded Cu40Zn brass alloy prepared by powder metallurgy

The aim of this paper was to investigate the properties of Cu40ZnTi for the purpose of developing a new high-strength, lead-free brass by powder metallurgy. The effect of Ti addition on precipitation hardening behavior of Cu40Zn (denoted as BS40) brass was studied with respect to mechanical properties and microstructures. BS40 and Cu40Zn − 1.0 wt.%Ti (denoted as BS40-A) brass powders were prepared by water atomization process, and β phase was retained in the raw powders predominately. The BS40 powder and Ti powder were elementally mixed to prepare Cu40Zn + 0.5 wt.%Ti (denoted as BS40-B) and Cu40Zn + 1.0 wt.%Ti (denoted as BS40-C) premixed powders. The alloy powders and premixed powders were solidified at 1053 K for 600 s by spark plasma sintering (SPS) and extruded subsequently. It was observed that Cu₂ZnTi intermetallic compound (IMC) and CuZnTi metastable phase resulted from the reaction between Ti and CuZn showed distinct grain refinement effect on extruded Cu40Zn brass. Thus, the excellent strengthening effect processes by precipitation hardening and deform working was obtained, which responding to an yield strength of 345 MPa, and a ultimate tensile strength of 597 MPa, showed 65.9% and 30.4% higher than that of extruded Cu40Zn brass, respectively.     

Mn57-2-2-0 . 5 锰黄铜铸造裂纹成因分析及对策

以Mn57-2-2-0.5锰黄铜半连续铸造生产实践为例,分析了试制过程中产生裂纹的原因,通过结晶器结构优化、冷却水强度分配及浇注速度调整等措施,解决了该类缺陷。此工艺措施对同类合金的同类缺陷非常有效,同时对探索复杂黄铜半连续铸造生产有一定借鉴意义。     

利用废杂铜水平连铸生产黄铜棒材技术研究

介绍了现有黄铜棒材生产技术的现状,阐述了我公司利用废杂铜水平连铸生产黄铜棒材的工艺流程、工艺参数、工艺原理,并对该黄铜棒材组织结构及机械性能进行了分析。结果表明,利用废杂铜水平连铸生产黄铜棒材迎合了国家循环经济发展要求,节约了生产成本,棒材综合性能达到了水暖五金卫浴用黄铜棒材行业标准水平。     

Microstructural analysis of the brass seat of a valve from the 1907 steam tug “Hercules”

The steam tug Hercules was an ocean-going and bay tug for 55 years before being retired. It is now being restored by the National Park Service (as of 1993 printing of this article). A broken steam valve was obtained for microstructural examination. The body was gray cast iron, and the stem and seat were brass. The examination centered on corrosion of the brass components. The seat and shaft were α brass, with a hardness of 64 and 79 DPH, respectively. A nut held the shaft onto the seat and was α-β brass with a hardness of 197 DPH. Welded on the end of the shaft was a ring of hard (DPH 294) α-β brass, which seated against the nut. The brass seat and stem showed little corrosion. However, the α-β brass nut and welded tip show extensive dezincification. This process of removal of Zn and the retention of Cu began in the high Zn β phase, but eventually both phases were attacked. The depth of penetration was consistent with dezincification rates reported in the literature for such brasses in salt water if the valve had been in service about 55 years. Reprinted from Microstructural Science, vol. 20, Metallographic Characterization of Metals after Welding, Processing and Service, Proc. of the Twenty Fifth Annual Tech. Meeting of the International Metallographic Society, W.R. Kanne Jr., G.W.E. Johnson, J.D. Braun, and M.R. Louthan, Jr., ed., The International Metallographic Society, Columbus, Ohio, and ASM International, 1993, pp. 471–484.     

复配气相缓蚀剂对多种金属大气腐蚀的综合保护作用研究

为了应对海洋大气环境中电子设备容易被腐蚀的难题,制备了一种复配气相缓蚀剂。通过半封闭空间挥发减量试验、缓蚀膜疏水性表征、模拟环境和海洋大气环境试验等评价了复配气相缓蚀剂对钢、T2紫铜、黄铜、银、铝等电子设备常用金属的气相缓蚀性能。结果表明:复配气相缓蚀剂对以上金属均具有显著的缓蚀作用,其中对钢的缓蚀率为86.9%,对T2紫铜为58.7%,对黄铜为96.2%,对银和铝在模拟腐蚀环境中具有一级气相缓蚀能力,是一种性能优良的电子设备多金属大气腐蚀综合防护材料。     

Stress corrosion cracking of leaded brass in a sulphuric acid environment

Free-cutting leaded brass is commonly used as sleeve fittings (also termed clamping ferrules) on polytetrafluoroethylene-lined flexible hoses for the filling and distribution of compressed gases, e.g., oxygen, nitrogen and carbon dioxide, for various industrial and medical applications. Some of the gas-filling and gas distribution facilities are located in the proximity of highly industrialized areas for the convenience of transportation, application and customer service. Therefore, the gas-filling and gas distribution gears are frequently exposed to the environment containing various chemical substances, which in the presence of ambient moisture and under the influence of mechanical and residual stresses in the material can effect an undesirable material degradation reaction. Stress corrosion cracking (SCC) has been identified to occur in C36000 Cu–Zn–Pb leaded brass ferrules under the synergistic reactions of a sulphuric acid production environment in a sustained tensile stress environment. The tensile stress was imparted to the material by the mechanical crimping process applied on the ferrules, and superimposed by cyclical high-pressure gas-cylinder-filling operations. The chemical species responsible for the SCC originated from the gaseous vapours and/or ionic derivatives of S-containing substances emitted from a neighbouring sulphuric acid production plant, which reacted with water and moisture condensates on the brass ferrule surfaces and effected the chemical corrosion reaction(s). SCC of the leaded brass ferrules gave rise to predominantly intergranular failures with fracture surfaces heavily decorated by corrosion products of various configurations. Most corrosion products were found to have embedded on the grain-boundary planes of the fracture surfaces, suggesting that grain-boundary short-circuit diffusion may have served as a viable mechanism for the SCC of C36000 leaded brass under the operating conditions of this case study.     

Deformation of duplex crystals and two-phase bicrystals of alpha-beta brass

A two-phase transition zone of alpha-beta brass forms as a result of the melting of beta brass on alpha brass single crystal substrates. Specialized heat-treatments can convert this transition zone into a duplex crystal region of alpha-beta brass, or eliminate this region resulting in a sharp boundary between alpha and beta crystals. Specimens prepared by these treatments were deformed in uniaxial tension to study the initiation of plastic deformation and its propagation across the phase boundary. Although the phase boundary initially poses a resistance to the approaching slip, its effectiveness as a barrier depends on the crystallographic relationships between alpha and beta crystals. No void formation was observed at the boundaries.     

新型半连续铸造复杂铜合金用结晶器

针对传统半连续铸造结晶器在 HMn57-2-2-0 . 5 锰黄铜生产过程中出现的问题,分析了制约产品浇铸质量的关键因素。 采用一、二次冷却水独立供给系统,通过对喷射水流孔径、喷射角大小及独立的“ 水-气冶 混合冷却系统进行改进,设计出一种适合复杂铜合金半连续铸造用新型结晶器。 实践证明,该新型结晶器对解决复杂铜合金中心裂纹、内部缩孔、分散疏松等问题非常有效,能提高铸造成品率,降低生产成本。     

Ultrasonic characterization of the effect of cold work and grain size in copper and 68:32 brass sheets

The effectiveness of ultrasonic velocity measurements was evaluated as a means for nondestructive characterization of cold-rolled copper and 68:32 brass sheets. An apparatus was designed to generate and receive the zeroth symmetrical mode of ultrasonic Lamb waves in thin copper and brass sheets. The effect of angular variations in propagation direction with respect to the rolling direction on the measured Lamb wave velocities is shown. Interpretation of the variations of ultrasonic Lamb wave velocity were related to deformation mechanisms and texture development in copper and 68:32 brass sheets. Results show that the grain size and cold work influence the velocity as well as the texture of copper and 68:32 brass sheets. Results indicate the possibility of using ultrasonic Lamb wave velocity as a tool to monitor elastic anisotropy.     

Galvanic corrosion of an implant consisting of iron and brass

Corrosion of an implant consisting of almost equal parts of iron and brass proceeded due to the cathodic protection of the brass, which was attacked only after the iron portion had dissolved. The corrosion of the brass proceeded as dezincification, during which dissolved copper was redeposited on the brass where it acted as a cathode that accelerated the corrosion process. Especially noteworthy was the precipitation of secondary corrosion products from ions originating in the acidified area of the anode during the primary stage of corrosion by neutralization with body fluids. These secondary corrosion products were identical with chemical compounds occurring in nature as minerals. The processes of corrosion, as well as the conversion of the primary to secondary corrosion products, are in accordance with thermodynamics, which states that all metals created from minerals through the expenditure of chemical energy have a tendency to revert to their original state.     

黄铜表面复合纳米硅烷膜的制备及其耐蚀性能

目前对黄铜表面处理时采用复合纳米硅烷膜技术的研究报道不多。在黄铜表面采用浸涂技术制备γ-巯丙基三甲氧基硅烷膜,运用电化学方法研究复合纳米硅烷膜在3.50%氯化钠溶液中的耐蚀性,并用SEM表征复合纳米硅烷膜黄铜腐蚀前后的形貌。结果表明:添加纳米材料复合纳米硅烷膜的黄铜在3.50%的氯化钠溶液中具有很强的耐蚀性,其自腐蚀电流密度下降至3.576×10~(-9)A/cm~2,自腐蚀电位正移。添加纳米材料的复合纳米硅烷膜在腐蚀前后的形貌基本不变,耐蚀性明显优于未添加纳米材料的纯硅烷膜。     

The thermal stability of nanocrystalline cartridge brass and the effect of zirconium additions

The thermal stability of nanocrystalline cartridge brass (Cu–30 at.% Zn) and brass–Zr alloys were investigated. The alloys were produced by cryogenic ball milling and subsequently heat treated to a maximum temperature of 800 °C. The grain size of pure brass was found to be relatively stable in comparison to pure copper, and a high hardness was retained up to 600 °C. When 1 at.% zirconium was alloyed with the brass, the grain size was stabilized near 100 nm even at 800 °C. At the highest temperature, hardness was retained above 2.5 GPa for 1 and 5 at.% zirconium alloys, but the pure brass softened significantly. The stabilization is believed to be dominated by Zn–Zr interactions as a second phase of these two was observed in X-ray diffraction and transmission electron microscopy. Thermodynamic modeling indicates a zero grain boundary energy may be achieved depending on the mixing enthalpy value used (i.e., calculated vs. experimental) under ideal conditions, but microstructural features such as twinning and second phase particles are thought to be the dominant stabilization mechanism. Zr worked well in stabilizing the brass in the nanocrystalline state to nearly 90 % of its melting temperature.