Sensitivity of springback and section deformation to process parameters in rotary draw bending of thin-walled rectangular H96 brass tube

In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis method and the springback/section deformation prediction finite element model, and by using this model the sensitivities of the springback and the section deformation to process parameters were analyzed and compared. The results show that the most sensitive process conditions for springback angle are the boost speed and the pressure of pressure die, and the most sensitive process condition for section deformation is the number of cores. When the clamp force, the boost speed and the pressure of pressure die are utilized to control section deformation, the effect of these process parameters on springback should be considered. When the process parameters are mainly used to control springback, the effect of these process parameters on the section deformation should be always considered.

Preparation of lead-free free-cutting graphite brasses by graphitization of cementite

Graphite brasses were prepared by graphitizing annealing of cast brasses containing cementite particles,which were in-situ formed during the fasting process.The eutectic cast iron as carbon source was added into common brasses by casting.SEM and EDS were used to analyze the microstructure of graphite brasses,and the relationship between the microstructure and machinability was investigated.The results show that graphite particles are formed by the decomposition of cementite particles in cast brasses.The graphite particles are uniformly dispersed in the brass matrix with the average size of 5.0 μm and the volume fraction of ~1.1%.The machinability in the graphite brass is dramatically increased relative to the common brass,because of the lubricating properties of graphite particles and its role in chip breaking.The workpiece surface of the graphite brasses chips is smooth and burr-free,and the chips of graphite brasses are short（C-shape） and discontinuous,which is much better than that of the long spiral chips of common brasses.

Corrosion behavior of brass coinage in synthetic sweat solution

Corrosion behavior of brass coinage was investigated in synthetic sweat solution by electrochemical measurement and surface analysis methods including scanning electron microscope （SEM） and energy dispersive X-ray spectrometer （EDX）. It is indicated that chloride ions in sweat solution accelerate the anodic active dissolution of brass, which is the main reason of pitting corrosion and dezincification corrosion. Meanwhile, lactic acid and ammonia water also promote the anode reaction. The corrosion products on the surface are mainly composed of basic copper chloride, cuprous oxide, the complex consisting of urea in association with copper, and few lactate ion. The kinetics of pitting corrosion development obeys the following equation of J0=0.3735（t＋185.93）^-1/2, and the process is controlled by dissolution of salt deposited on pit surface.

微电热(DZR)新技术在茶叶加工中的应用前景

茶叶加工过程中,需要利用热能的工序有杀青和干燥。目前,茶叶杀青、干燥设备的热能传递方式主要是采用对流式热风和传导式两种。烘干机是采用热风式传递热能,炒干机是采用传导式。辐射传递热能的茶叶干燥设备也有少量生产。杀青、干燥设备的热能产生途径不外乎燃烧燃料和电热式两种。 电热式杀青、干燥设备具有清洁生产、易于控制等优点,近两年在机制名优茶中得到大力发展,随着电热材料的不断更新换代,热效率提高,茶叶电热干燥设备开发将日益受到重视。 近年来,我国在电热材料研究上取得了重要进展,开发出一种新型微电热转换材料,

Influence of composition on friction-wear behavior of composite materi-als reinforced by brass fibers

In the study, for the composite materials reinforced by brass fibers, theinfluence of dominant ingredients, such as organic adhesion agent, cast iron debris, brass fiber,and graphite powder, on the friction-wear characteristics was investigated. The friction-wearexperiment was carried out on the block-on-ring tribometer MM 200. The worn surfaces of the frictionpair consisting of the composite materials and grey cast iron HT 200 under dry sliding frictionwere examined using scanning electron microscope (SEM), energy dispersive analysis (EDX) anddifferential thermal analysis-thermogravimetric analysis (DTA-TAG). The experimental results showedthat the friction coefficient and the wear loss of the composite material increase obviously withthe increase of cast iron debris content, but decrease obviously with the increase of graphitepowder content, and increase a little when the mass fraction of brass fiber was over 19 percent, andthe orientation of brass fiber has obvious influence on friction-wear property. When the massfraction of organic adhesion agent was about 10-11 percent, the composite materials have anexcellent friction-wear performance. The friction heat can pyrolyze organic ingredient in wornsurface layer.

Constitutive modeling for high temperature flow behavior of a high-strength manganese brass

The hot compressive deformation behaviors of ZHMn34-2-2-1 manganese brass are investigated on Thermecmastor-Z thermal simulator over wide processing domain of temperatures （923–1073 K） and strain rates （0.01–10 s^–1）. The true stress–strain curves exhibit a single peak stress, after which the stress monotonously decreases until a steady state stress occurs, indicating a typical dynamic recrystallization. The analysis of deviation between strain-dependent Arrhenius type constitutive and experimental data revealed that the material parameters （n, A, and Q） for the ZHMn34-2-2-1 manganese brass are not constants but varies as functions of the deformation conditions. A revised strain-independent sine hyperbolic constitutive was proposed, which considered the coupled effects of strain rate temperature and strain on material parameters. The correlation coefficient and the average absolute relative error are used to evaluate the accuracy of the established constitutive model. The quantitative results indicate that the proposed constitutive model can precisely characterize the hot deformation behavior of ZHMn34-2-2-1 manganese brass.

Diffusion mechanism of dezincification in double phase brass exposed to seawater

Zinc diffusion kinetics of double phase brass as they were corroded in seawater was investigated by means of metallography microscope and mathematics regression analysis. The results showed that, the dezincification corrosion of β phase continuous HMn58 2 brass is characterized by β phase volume diffusion, while that of α phase continuous HSn62 1 brass is controlled by α phase grain boundary diffusion. Apparent diffusion coefficients of zinc in both types alloys were calculated out by founding diffusion equation and boundary conditions. It was found that the value of theoretical calculation is close to that of experimentally measured, and it confirmed that Sn element inhibits dezincification of brass. The relativity between the dezincification depth and corrosion rate of different double phase brasses immersed in seawater was revealed. : Zinc diffusion kinetics of double phase brass as they were corroded in seawater was investigated by means of metallography microscope and mathematics regression analysis. The results showed that, the dezincification corrosion of β phase continuous HMn58 2 brass is characterized by β phase volume diffusion, while that of α phase continuous HSn62 1 brass is controlled by α phase grain boundary diffusion. Apparent diffusion coefficients of zinc in both types alloys were calculated out by founding diffusion equation and boundary conditions. It was found that the value of theoretical calculation is close to that of experimentally measured, and it confirmed that Sn element inhibits dezincification of brass. The relativity between the dezincification depth and corrosion rate of different double phase brasses immersed in seawater was revealed.

Heterogeneous structure-induced strength and ductility synergy of α-brass subjected to rapid cooling friction stir welding

The 2 mm-thickα-brass plates were successfully joined using conventional friction stir welding(CFSW)with air cooling and rapid cooling friction stir welding(RCFSW)with liquid CO2 cooling.The microstructure and mechanical properties of the two welds were carefully investigated by electron back-scattered diffraction and transmission electron microscopy.The stir zone of CFSW exhibited homogeneous equiaxed grains,while the stir zone of RCFSW showed a heterogeneous grain structure,i.e.ultrafine grains containing massive dislocations and nano twins.Compared with the CFSW,yield strength and ultimate tensile strength of RCFSW were increased by 31%and 24%,respectively.The enhanced yield strength and improved strain hardening capacity were attributed to grain boundary strengthening and dislocation strengthening.Furthermore,good ductility was achieved due to the released stress concentration of the nano twins caused by the plastic deformation.

The Influence of the Precipitation Heat Treatment Temperature on the Metallurgical, Microstructure, Thermal Properties, and Microhardness of an Alpha Brass

Metals obtain optimum conditions of metallurgical and physical properties through a heat treatment. Brass is one of the copper alloys which has many applications in everyday life and in the industry. Brass is one of the copper alloys which has many applications in everyday life and the industry. In this work, the influence of the precipitation heat treatment temperature on the metallurgical microstructure, structure, thermal properties, and microhardness of an alpha brass is analyzed. Samples were heat treated by precipitation for 2 h at 300°C, 400°C, 500°C, 600°C, and 700°C. The best mechanical properties were found at 500°C of precipitation heat treatment temperature. Specimens were characterized by scanning electron microscopy, X-ray diffraction, Vickers microhardness, photothermal radiometry, and photoacoustic to study the thermal diffusivity and conductivity, as well as the heat capacity. The inverse of the full width at the half maximum analysis showed that the crystallinity decreased as the precipitation heat treatment temperature increased. Metallurgical microstructure and microhardness were correlated to the precipitation heat treatment temperatures to determine the effect on the metallurgical and mechanical properties, as well as the effect on the thermal properties of alpha brass.

Plasma electrolytic oxidation behavior and corrosion resistance of brass in aluminate electrolyte containing NaH2PO4 or Na2SiO3

Plasma electrolytic oxidation(PEO) of brass was carried out in aluminate electrolytes with the addition of NaH2PO4(S1) and Na2SiO3(S2), respectively, with the aim to investigate the effect of additives on the coating formation and corrosion resistance. For the PEO in S1 electrolyte, a mixed layer of AlPO4and Al2O3is formed at the initial stage, which leads to fast plasma discharges and formation of black coatings with the compositions of Al2O3,CuO, Cu2O and ZnO. However, in S2 electrolyte, plasma discharges are delayed and the coatings show a reddish color due to more Cu2O. Mott-Schottky tests show that the S1 coatings are p-type semiconductors;while the S2 coatings can be adjusted between n-type and p-type. Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) tests show that the PEO treatment can significantly improve the corrosion resistance of brass, with protection efficiency up to 91.50% and the largest charge transfer resistance of 59.95 kΩ·cm^(2) for the S1 coating.

Sliding wear behavior of magnetorheological fluid for brass with and without magnetic field

A pin-on-disc wear apparatus was used to carry out the tribological experiment of brass to investigate the effect of a magnetorheological （MR） fluid on the interfacial surface with and without magnetic field. A series of tests were performed at the loads of 20-100 N and rotating speeds of 127-425 r/min for 2 h. The friction coefficient and wear rate were monitored by the wear apparatus, while the microstructures of the worn surfaces were observed by scanning electron microscope （SEM）. In addition, the chemical composition of worn surfaces was analyzed by energy dispersive X-ray spectroscopy （EDS）. Test results show different friction and wear performance of the MR fluid with and without magnetic field. At the same time, the effects of various normal loads and rotating speeds on the tribological behavior were investigated. Through the investigation of the morphologies of the wom surfaces under the magnetic field, it is found that the MR particles are clearly evident on the wom surface and the plastic flow of ridges causes the lateral extrusion. This directly indicates that abrasive wear is the predominant wear mechanism observed with MR fluid.

Relativity between corrosion-induced stress and stress corrosion cracking of brass in an ammonia solution

The susceptibility to stress corrosion cracking (SCC) of brass in an ammoniasolution with various pH values or under various applied potentials was measured at slow strain ratetests. The additive stress in the same solution was measured using two methods. The resultsindicate that the variation of the susceptibility to SCC with pH value or with potential is in anexcellent agreement with the corrosion (passive film or dezincification layer)-induced stress. WhenpH >= 7, the corrosion-induced tensile stress and the susceptibility to SCC have maximum values andhardly change with increasing the pH value. However, when pH <7, both the corrosion-induced tensilestress and the susceptibility to SCC reduce rapidly with decreasing the pH value. Both thecorrosion-induced tensile stress and the susceptibility to SCC have maximum values at theopen-circuit potential, decrease slightly under the anodic polarization, and reduce gradually tozero under the cathodic polarization.

Corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding in alkaline solution

This study was done to evaluate the nugget zone(NZ)corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding(FSLW)in a solution of 0.015 mol/L borax(pH 9.3).To this end,dissimilar copper/brass plates were welded with two dissimilar heat inputs(low and high)during the welding procedure.The high and low heat inputs were conducted with 710 r/min,16 mm/min and 450 r/min,25 mm/min,respectively.Using open circuit potential(OCP)measurements,electrochemical impedance spectroscopy(EIS)and Tafel polarization tests,the electrochemical behavior of the specimens in borate buffer solution was assessed.With the help of scanning electron microscope(SEM),the morphology of welded specimen surfaces was examined after immersion in the test solution.According to the results,the NZ grain size and resistance improvement reduced due to the nugget zone corrosion with a decreased heat input.The results obtained from Tafel polarization and EIS indicated the improved corrosion behavior of the welded specimen NZ with a decrease in the heat input during the welding process unlike the copper and brass metals.Furthermore,an increased heat input during the welding process shows a reduction in the conditions for forming the passive films with higher protection behavior.

Study on high frequency brazing of brass-red copper

Two kinds of silver based medium temperature brazing filler metals(45AgCuZnSn and 60AgCuSn) were selected to braze and seal brass flange pipe and copper pipe by high frequency heating brazing. In this paper, the quality of the braze was evaluated by immersion ultrasound, and the microstructure of the brazed joint was observed by SEM and EDS. The experimental results show that the high frequency heating brazing can quickly achieve the device sealing;through the ultrasonic flaw detection image calculation, the brazed bonding rate obtained by 60AgCuSn brazing is 87%, and by 45AgCuZnSn brazing is 71%;the cross-sectional area of the brazed joint obtained by two kinds of silver based medium temperature brazing filler metals is observed, the brazed joint obtained by 45AgCuZnSn brazing has defects visual, and a large amount of Zn element gathered in the defects, there is no obvious porosity in the brazed joint by 60AgCuSn brazing,and the bonding layer is dense and coherent. Through the contrast test, the choice of 60AgCuSn alloy brazing can meet the needs of high frequency brazing of brass flange pipe and copper pipe.

Corrosion inhibiting performance and mechanism of protic ionic liquids as green brass inhibitors in nitric acid

Four protic ionic liquids(ILs)were synthesized via a one-step method by using benzotriazole(BTA)and benzimidazole as cations,and benzenesulfonic acid and 2-naphthalenesulfonic acid(NSA)as anions.These ILs were used as green corrosion inhibitors for brass specimens in a nitric acid solution.The structure of the protic ILs was characterized by 1H-NMR,13C-NMR,and FT-IR spectroscopy.The effects of the IL structure,IL concentration,acid concentration,and corrosion time on the surface morphology of brass specimens and the inhibition efficiency(η%)of ILs were investigated by the weight loss method combined with SEM and EDS spectroscopy.Polarization curves and impedance spectroscopy were used to analyze the electrochemical corrosion inhibition mechanism of ILs.Results showed that IL synthesis was a proton transfer process,and the proton of the–SO3H group on NSA was deprived by BTA.IL[BTA][NSA],which had a high charge density and large conjugateπband,was the most effective inhibitor for brass corrosion.Theη%of[BTA][NSA]decreased with the increase in acid concentration and corrosion time,which showed an increment with the increase in[BTA][NSA]concentration.The higher theη%of[BTA][NSA]is,the smoother the surface of the brass specimens is,and the smaller the undistributed area of Cu element will be.Corrosion inhibiting mechanism from electrochemical analysis indicated that the addition of[BTA][NSA]increased the polarization resistance of the brass electrode significantly and suppressed both anodic and cathodic reactions.

一种基于DZR的Ad hoc网络路由协议

本文通过对MIMO复用技术和分集技术的研究,提出一种DZR(Double Zone Routing)双区域路由协议,有效的将路由技术和MIMO传输技术相结合,提升了网络吞吐性能。最后在OPNET仿真软件中,从业务负载、节点场景密度以及移动性方面对其进行了网络仿真,在结果分析中验证了DZR协议的综合性能优势,并在测试平台下验证了DZR协议的可实用行。

Microstructure and properties of cutting magnesium-brass containing no lead

A new environmental friend cutting brass containing magnesium instead of lead was produced by casting, extruding and drawing. Its microstructure was observed and its mechanical, chemical and cutting properties were stutied. The results show that the global secondary particles which are brittle and soft intermetallics, distribute in grains and on grain boundries, which is helpful for improvement of cutting ability of the brass. The tensile strength, yield strength, elongation and area reduction of halfhard magnesium-brass are (550MPa,) (280MPa,) (16.30%,) (32.4%,) respectively. The cutting ability of magnesium-brass corresponds to that of lead-brass C3604 judged by the size and appearance of chips of alloy and by the cutting force. The magnesium-brass has excellent corrosion resistance.

Electrolytic Sampling from Pure Copper and Common Brasses Ⅰ: Calculation of the Mass Dissolved from the Samples according to Faraday's Law

In a procedure for electrolytic dissolving pure copper and common brasses, the approximate electrochemical mole mass(k) of the sample was determined in accordance with the brand of the sample, a stitable electrolyte was selected to make the current efficiency equal to 100%, and then the dissolved mass of samples was calculated according to Faraday's law(m=klt).Three representative samples were sampled by the electrolytic dissolution method and the calculated dissolved amounts were equal to the values by weighing the anode.The cxperimental results of zinc and copper in the anode liquor are in agreement with certified values.

Corrosion electrochemical behavior of brass tubes in circulating cooling seawater

Electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) were used to study the corrosion electrochemical behavior of brass tubes in circulating cooling seawater using the developed sensor. EIS study shows that the inhibitor can lead to the formation of corrosion products on metal surface, which will then inhibit the corrosion process. When the flow rate of the seawater increases, the diffusion of oxygen speeds up and the action of filming on HAl77-2 tube accelerates, resulting in decrease of corrosion rate. EN analysis shows that the flow rate of the seawater has little effect on pitting susceptivity of HSn70-1 tube; however the pitting susceptivity of HAl77-2 tube increases with increasing flow rate. Good agreement is observed between the spectral noise resistance Rsn (f) calculated from EN data and the modulus of impedance. It is shown that the electrochemical noise technique can be used in corrosion monitoring.

Growth of brass nanofilms sputtered on organic substrate

The growth of brass nanofilms sputtered on acrylics substrate was studied through experimental investigation of the effect of sputtering voltage, target-to-substrate distance, chamber pressure and sputtering time on the content, growth rate and surface morphology of brass nanofilms. The results show that compared with original brass target, Cu content in brass nanofilms changes by no more than 6.23%(mass fraction). High sputtering voltage and short target-to-substrate distance help to improve brass nanofilm deposition rate. There exists an optimal chamber pressure where deposition rate of nanofilm reaches the maximum. The key factor affecting surface morphology is the kinetic energy of sputtering particles. Low sputtering voltage, large target-to-substrate distance and low chamber pressure are very important for the formation of the high-quality brass nanofilms. The brass films prepared under the conditions of sputtering voltage 1.6kV, target-to-substrate distance 2.5cm, chamber pressure 10Pa and sputtering time 20min, possess following characteristics: smooth and uniform surface, thickness of 41nm and Cu content of 71.0%(mass fraction).