Water-cooled Copper Anode Research Articles

The character of the structure formation of model alloys of the Fe-Cr-(Zr, Zr-B) system synthesized by powder metallurgy

Purpose: The purpose of the work is to synthesize and investigate the character of structure formation, phase composition and properties of model alloys Fe75Cr25, Fe70Cr25Zr5, and Fe69Cr25Zr5B1. Design/methodology/approach: Model alloys are created using traditional powder metallurgy approaches. The sintering process was carried out in an electric arc furnace with a tungsten cathode in a purified argon atmosphere under a pressure of 6·104 Pa on a water cooled copper anode. Annealing of sintered alloys was carried out at a temperature of 800°C for 3 h in an electrocorundum tube. The XRD analysis was performed on diffractometers DRON-3.0M and DRON-4.0M. Microstructure study and phase identification were performed on a REMMA-102-02 scanning electron microscope. The microhardness was measured on a PMT-3M microhardness meter. Findings: When alloying a model alloy of the Fe-Cr system with zirconium in an amount of up to 5%, it is possible to obtain a microstructure of a composite type consisting of a mechanical mixture of a basic Fe2(Cr) solid solution, solid solutions based on Laves phases and dispersive precipitates of these phases of Fe2Zr and FeCrZr compositions. In alloys of such systems or in coatings formed based on such systems, an increase in hardness and wear resistance and creep resistance at a temperature about 800°C will be reached. Research limitations/implications: The obtained results were verified during laser doping with powder mixtures of appropriate composition on stainless steels of ferrite and ferrite-martensitic classes. Practical implications: The character of the structure formation of model alloys and the determined phase transformations in the Fe-Cr, Fe-Cr-Zr, and Fe-Cr-B-Zr systems can be used to improve the chemical composition of alloying plasters during the formation of ferrite and ferrite-martensitic stainless steel coatings. Originality/value: The model alloys were synthesized and their phase composition and microstructure were studied; also, their microhardness was measured. The influence of the chemical composition of the studied materials on the character of structure formation and their properties was analysed.

Decarburization of high-chromium melts by argon–oxygen plasma

The treatment of Fe–Cr and Fe–Cr–Ni alloys by means of oxygen-bearing plasma is investigated in the laboratory, using a plasma furnace with a tungsten cathode and a water-cooled copper anode. That permits modeling of the processes in the contact spot of the plasma arc and the melt surface. The mathematical model developed describes the melt–plasma interaction. The kinetic parameters of the decarburization of high-chromium melt by argon–oxygen plasma are determined from experimental data. The results show that considerable decarburization of high-chromium melt is possible, with little loss of chromium, by treatment with plasma containing no more than 15–17% oxygen. Comparison shows that the model data and experimental results are in good agreement.

STUDY OF THE KINETICS OF CARBON OXIDATION BY ARGON-OXYGEN PLASMA IN CHROMIUM-CONTAINING MELTS

The article describes the investigation of treatment processes of such alloys as Fe – Cr and Fe – Cr – Ni by oxygen-containing plasma. The laboratory unit, which is a plasma furnace with a tungsten cathode and a water-cooled copper anode, can simulate processes that occur in the contact area of plasma arc and melt surface. It was also developed a mathematical model describing the processes occurring in the interaction between plasma torch and surface of the molten metal. According to the results of the experiments the authors have determined the kinetic parameters of decarburization process of high-chromium melts by argon-oxygen plasma. The results allow to conclude that treatment of high-chromium melts by plasma which contents less than 15–17 % of oxygen provides a high degree of decarburization with low chromium haze. The comparison of model calculations and experimental data has shown good reproducibility.

DC Emission Characteristic of Nanosized-Scandia-Doped Impregnated Dispenser Cathodes

To meet the requirements for advanced vacuum electron devices and modern electron beam instruments, dc emission properties of nanosized-scandia-doped impregnated (SDI) cathodes have been investigated in a closely spaced diode configuration system with water-cooled copper anode. The SDI cathodes were made from nanosized-scandia-doped tungsten powder, which was produced by a spray-drying process. A space-charge-limited dc current density of over 60 ${\rm A}/{\rm cm}^{2}$ has been measured at 950 $^{\circ}{\rm C}_{\rm b}$ . An on-going life test with a dc load of 30 ${\rm A}/{\rm cm}^{2}$ at 950 $^{\circ}{\rm C}_{\rm b}$ has completed more than 2000 h of operation to date. The electron cooling for dc beam emission is discussed.

アルゴンGTAにおける非平衡プラズマ特性の電流値依存性

Gas Tungsten Arc (GTA) is suitable as a heat source device for many applications because it can stabilize high temperature arc plasma easily by employing shielding gas. In many cases, (Magneto Hydro Dynamic) MHD simulation model assuming the local thermodynamic equilibrium (LTE) is utilized for analyzing property of GTA. Although the LTE assumption is effective to evaluate high temperature region in the arc column, it is difficult to apply it to low temperature region such as the fringe of the arc column or the sheath regions closed to the electrodes due to decrease of energy exchange caused by collisions. Especially, in order to consider the influence of chemical reaction between the arc plasma and the material surface such as oxidation, non-equilibrium property of the arc plasma should be considered without the LTE assumption, since it is required to understand precise property of the arc plasma closed to the material surface. We have developed a simulation model of GTA assuming chemical and thermal non-equilibrium. In this paper, as a first step of the study, heat source property of argon GTA employing a water-cooled copper anode was simulated and dependence of non-equilibrium plasma property on argon GTA on arc current was investigated.

Numerical Simulation of Heat Source Property of Tube Cathode Arc and Influence on Weld Penetration Geometry in Anode Material

Tungsten Inert Gas (TIG) arc is the most widely employed type of a plasma torch and enables to produce arc plasma with high energy density. Therefore it is suitable as a heat source device especially for processes to require concentrating the heat input at a point. On the other hand, Tube Cathode Arc (TCA) to be a kind of TIG produces the arc plasma by introducing inner shielding gas through the central hole of the tube cathode. As the basic heat source property of argon (Ar) TCA, the property of the arc plasma and the heat input intensity onto a water-cooled copper anode for various inner shielding gas flow rates were numerically analyzed. Furthermore, by employing stainless steel SUS304 anode, the geometry of its weld penetration was also predicted. The results were compared with those for the conventional TIG. As a result, it was shown that since TCA enables to heat the target material uniformly by controlling the inner shielding gas flow rate and preserve it from damage due to excessive heat input during the process, it is suitable for processes such as brazing, buildup or thermal spraying.

Non-equilibrium plasma modeling of Gas Tungsten Arc in middle current range

Gas Tungsten Arc (GTA) is suitable as a heat source device for many applications because it can stabilize high temperature arc plasma easily by employing shielding gas. In many cases, MHD simulation model assuming the local thermodynamic equilibrium (LTE) is utilized for analyzing property of GTA. Although the L TE assumption is effective to evaluate high temperature region in the arc column, it is difficult to apply it to low temperature region such as the fringe of the arc column or the sheath regions closed to the electrodes due to decrease of energy exchange. In order to consider the effect of chemical reaction between the arc plasma and the material surface, we have developed a simulation model of GTA assuming chemical and thermal non-equilibrium. In this paper, as a first step of the study, heat source property of argon GTA employing a water-cooled copper anode was simulated.

A CO<sub>2</sub> Gas Shielded Gas Tungsten Arc and its Application to Welding of Steel Sheets

In order to develop a novel welding process with low costs and high productivity in comparison with the TIG welding process, the characteristics of a CO 2 gas shielded gas tungsten arc (GTA) are studied. A double gas shielded system which consists of CO 2 gas and inert gas is employed for the GTA welding torch due to avoiding the consumption of tungsten electrode. The arc voltage of the CO 2 gas shielded GTA in the conditions of arc current 150 A and arc gap 3 mm is about 19 V which is much higher than 12 V of TIG arc in the same conditions. The CO 2 gas clearly constricts the arc and the maximum heat intensity at the surface of a water cooled copper anode in the CO 2 gas shielded GTA becomes about 10 times larger than that of TIG arc. Furthermore, the CO 2 gas shielded GTA has very good performance in the traveling speed for welding zinc coated steel sheets in comparison with the TIG welding process.

Effects of Copper Vapor on Heat Transfer from Atmospheric Nitrogen Plasma to a Molten Metal Anode

As an object of nitrogen plasma operated with an arc current to 200 A, an arc length about 35 mm, we evaluated heating efficiency from arc plasma to the molten copper anode and the water-cooled solid copper anode. The heating efficiency to the molten anode is smaller than that to the solid anode by about 20%. We focused on copper vapor concentration in plasma as a possible cause for a decrease in heating efficiency, and estimated it by means of the Cu and the N spectral line measurement. Simple numerical analysis, taking into consideration measured copper vapor concentration, suggested that an increase in electrical conductivity due to copper vapor, made the plasma temperature change and consequently caused a decrease in thermal conductivity. We concluded that one of the reasons for a decrease in heating efficiency would be caused by copper vapor contamination.

移行形アークプラズマから水冷銅陽極への伝熱量に関する数値解析

移行形アークプラズマから水冷銅陽極への伝熱量に関する数値解析

移行形アークプラズマ加熱における水冷銅陽極への伝熱機構に関する実験的検討

移行形アークプラズマ加熱における水冷銅陽極への伝熱機構に関する実験的検討

Anode-boundary-layer behaviour in a transferred, high-intensity arc

The effects of the plasma's gas-flow rate on phenomena such as the negative anode fall and the heat flux to the anode in high-intensity arcs are discussed on the basis of a numerical model of the anode's boundary layer. The modelling system consists of a rotationally symmetrical argon plasma formed between the outlet of a constrictor tube and a water-cooled flat copper anode perpendicular to the axis of the plasma flow which is directed towards the anode. The arc is operated at atmospheric pressure and at a current level of 200 A. The boundary conditions for the electron temperature and the electron number density at the anode's surface are obtained by solving the electron-energy equation and the diffusion equation at the anode's surface simultaneously with all conservation equations for the calculation domain. A diffuse anode attachment is obtained for a mass flow rate exceeding 0.2 g and a constricted anode attachment is found for rates below 0.02 g . There is a (probably unstable) transition region between these flow rates. The anode boundary layer of the diffuse attachment is strongly affected by the mass-flow rate. Increasing the mass-flow rate shifts the location of the peak of the electrical potential towards the anode while its magnitude decreases and the total heat flux to the anode increases. This is a consequence of the effects of the mass-flow rate on the axial profiles of electron and heavy-particle temperatures and of the electron number density. In contrast, the anode boundary layer of the constricted attachment seems not to be affected by the mass-flow rate.

Experimental investigation of the anode region of a free-burning atmospheric-pressure inert-gas arc I. General characteristics of the discharge. Low-current regime

This paper reports the experimental investigation of the anode region of a free-burning inert-gas arc at atmospheric pressure in the current range from a few amperes to hundreds of amperes. The tungsten thermionic-emission cathode and the large-diameter water-cooled copper anode that were used permitted the anode arc root to assume its natural form. The general characteristics of the discharge are given and results are presented from investigations of the anode region at low currents, where the anode arc root is single and constricted, but erosion-free. Measurements of the plasma parameters as well as the current density in the arc root are reported, and a comparison is made between the values obtained and those characteristic of the region of the cathode arc root.

Prediction of anode temperatures of free burning arcs

Predictions of the temperatures of the anode of free burning arcs are made using a theory that treats an arc and its electrodes as a unified system. The theory predicts the temperature distributions of the arc column, the cathode and the anode as a function of the arc operating conditions. Temperature profiles on the surface of copper anodes for arcs in argon are calculated for various arc operating conditions. Theoretical predictions of the threshold current for melting a water-cooled copper anode range from 1260 to 480 A for anode thicknesses ranging from 2 to 10 mm and are in good agreement with experimental results.

混合ガスシールドＴＩＧアークにおける母板表面上のプラズマガスの組成割合 混合ガス雰囲気下におけるＴＩＧアーク特性に関する研究 第１報

The demixing in gas tungsten arc plasma was investigated by measuring of the helium concentra-tion at a water-cooled copper anode using a mass spectrometer in argon-helium mixed gas shielding arc. It was expected from a study on arc pressure that helium gas, which is lighter than argon gas, is efficiently absorbed near the electrode tip by the plasma stream.In this measurement, a small amount of plasma gas was sampled through a hole (ID: 0.5 mm) in the anode plate by using a setup similar to that of a leak test for a vacuum chamber using mass spectrometer. The helium concentration of the gas was determined from a ratio of the helium spectrum peak value to that of argon in argon-helium arc.From measured concentration distribution of helium at the anode, it was found that helium concentrated in the arc center at the anode surface and it was suggested that argon concentrated at the arc periphery in argon-helium arc.Furthermore, it was shown that blow holes were formed in argon-helium arcs upon introduction of nitrogen. Blow hole formation occurred at lower nitrogen content when argon content in the shielding gas was high. These results could be understood from mass spectroscopic measurements which showed that helium gas concentrated at the core in helium-nitrogen arcs as well as in argon-helium arcs, but both nitrogen and argon distributed uniformly throughout the arc in argon-nitrogen arcs.

Molten Streams of Ti Alloys by a Single-Melt System

The U.S. Bureau of Mines has developed a single-melt system to purify pressedralloy-sponge electrodes and produce molten titanium alloy streams. Melting was done in a vacuum arc furnace under an inert gas atmosphere using a single, funnel-shaped, water-cooled copper anode. Melt parameters were varied to increase the superheat and produce a stream of molten titanium alloy metal that could ultimately be fed to rotary atomizing equipment. Increasing the power to the arc from 36 to 150 kW produced a molten stream of titanium alloy metal, while a constant flow of helium gas removed volatile impurities. Both the chlorine and magnesium concentrations in the product were below 25 ppm, and aluminum and vanadium homogeneity matched that of commercial titanium alloy powder.

Distribution of the heat and current fluxes in gas tungsten arcs

The distribution of heat flux on a water-cooled copper anode as a function of welding process parameters has been determined experimentally following an experimental technique developed previously. The results indicate that arc length is the primary variable governing heat distribution and that the distribution is closely approximated by a gaussian function. The half width of the heat flux is defined by a distribution parameter, σ, which was determined from the experimental data and is expressed as a function of arc length, current, and electrode tip angle. The distribution parameter, σ, increases from 1.5 mm to 3.6 mm as the arc length increases from 2 mm to 9 mm for a 100 A arc. The experimental data also show that arc energy transfer efficiency is greater than 80 pct on the water-cooled anode which is much higher than has been measured in the presence of a molten metal pool. For this reason, it is believed that the distribution of the heat flux and not the magnitude is the most useful information obtained in this study. The effect of helium additions to the argon on the heat distribution is also reported.

A Source for Multiply-Charged Ions and Acceleration of C, N and O Ions by IPCR Cyclotron

The design and performance of the ion source which is now used in the IPCR variable energy cyclotron are described. The source is of the electron-bombarded hot cathode type having two cylindrical cathodes of tungsten and a water-cooled copper anode containing a replaceable molybdenum slit plate. The arc discharge is established continuously but not pulsed. The source is usually operated very stably under an arc power of 1.5 to 3kW with a gas flow rate of 1 to 2 cc/min. The lifetime of the source is mainly limited by the erosion of the upper tungsten cathode at about 24 hours. At present, C4+, N4+, O4+, N5+ and O5+ ions are accelerated up to 48~100, 56~1100, 70~95, 56~125 and 70~125 MeV respectively, and a few micro-amperes of these ions are extracted from the cyclotron. The vacuum obtainable in the accelerating chamber is usually 2 ~ 4 × 10-6 mHg, and the loss of ion beam by the charge exchange effect is comparatively small. Extracted ion beams are used in several experiments for about 1900 hours in a year.

低圧雰囲気におけるアーク現象(第3報)

In the previous works, the authors pointed out that the change of cathode mode of a graphite electrode could be explained rationally by considering the energy balance and ionization process in the cathode fall region. There are still left, however, some difficulties, in a carbon arc, to clarify the cathode mechanism, since there is evaporation of carbon out of electrodes and, consequently, the composition of a plasma at each condition is not consistent. Therefore, systematic researches on low pressure arcs were made with nonconsumable electrodes, such as a thoriated tungsten cathode.and a water-cooled copper anode, to eliminate the influence of vapours from electrodes. Experimental conditions were: the current range of 20-100 A, and the pressure of 20-100 Torr in a pure hydrogen atmosphere.A tungsten cathode did not show the cold cathode mode which was recognized with a graphite cathode, but it took the modes of the plasma cathode and the hot one under this experimental conditions. In an arc with a tungsten cathode, however, the plasma cathode mode clearly appeared in wide ranges of arc currents and pressures, and the mode transition was more exactly observed than in a carbon arc.The anode mode, which was not described in the previous papers, was systematically studied. Under the conditions of low pressure and small current, a glow-like discharge with light violet colour emerged on a water cooled copper anode, and this anode glow gave eminent effects on electrical and thermal characteristics of an arc. Thus, two kinds of anode modes, i.e. the normal and the glow modes, were recognized in low pressure arcs with a copper anode.The anode drop VA in the range of normal anode mode gradually increased, particularly it showed remarkable increase when the current or the pressure came near to the critical conditions of the mode transition. When the glow anode mode emerged, anode energy VA*, as well as arc voltage VA, increased abruptly by 10 volts or so, and this change in VA* and VA was due to the increase of the anode fall VA.Governing factors of the anode modes and their correlations were clarified. They are (a) arc current I, (b) ambient gas pressure p, (3) kinds of atmosphere and (d) anode material. These facts were very similar to the governing factors of the cathode modes and the correlations among factors.

A plasma jet as cathode for an argon laser

The construction and some operational characteristics of an argon laser in which the discharge operates between a water-cooled copper anode and a plasma jet which acts as a cathode is described. With 50 A and 550 G extra cavity powers of 4½ W (6 lines, multimode) are obtained in a tube 80 cm × 5 mm with an unoptimal cavity.