摘要:

An investigation of arc zone pressures duringCEVAR(consumable-electrode vacuum-arc remelting) experiments has shown that pressure differences and gradients within furnaces are functions of pressure itself, electrode composition, and the degree of arc-zone confinement. There is evidence also that some previously puzzling contrasts in arc-furnace behavior may be explainable on the basis that two pressure dependent forms of electrical discharge operate with distinct potentials. The lower voltage form tends to become unstable at pressures1 Torr. The higher voltage form seems to be most stable at pressures<0.1 Torr. For continuous operation and maximum versatility, aCEVARfurnace should be able to accommodate both discharge forms by providing for variability of vacuum conditions.

ISSN:0022-5355    

DOI:10.1116/1.1315408

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

This report discusses results from melting with water-cooled nonconsumable electrodes since their introduction to the industry at the 1969 Vacuum Metallurgy Conference in Pittsburgh. In production these electrodes have proven to be attractive for the first melting of titanium sponge and scrap directly into remelt electrodes thereby avoiding the electrode fabrication step previously required. They have also been applied to reclamation of small superalloy scrap directly into forgeable ingot avoiding the two-step practices of air induction melting followed by consumable melting and are currently being used to replace the graphite electrode melting and casting of uranium carbide fuel rods. Experiments reported in this paper were conducted to determine the application of the nonconsumable melting technique to some of the many problems in scrap recovery and the casting industry. For example, we have investigated isolation of high density inclusions from titanium scrap, elimination of low density inclusions, effect of superheating on metal fluidity in casting, and the operation of nonconsumable electrodes at low pressure.

ISSN:0022-5355    

DOI:10.1116/1.1315396

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

A production plant containing three vacuum arc remelting (VAR) furnaces and one electroslag remelting (ESR) furnace is described. Production of about ten million pounds of a variety of material grades is analyzed by breakdown of the production program by steel grades and ingot size in order to evaluate the economies of the VAR and ESR processes. A realistic annual remelting capacity of the three VAR furnaces is about 11.5 million pounds for a mixed ingot production program with specific requirements of material quality and processing technology, taking into account the factors influencing the possible annual production. A graph illustrating the scattered values of melt rate and power consumption for steel remelted under varying conditions shows that the complexity of the ESR process can lead to very different statements when comparing the VAR and ESR processes. A correct comparison of the advantages and disadvantages of the two remelting processes and an understanding of the economic factors of each process requires a knowledge of the base on which the figures for comparison are determined.

ISSN:0022-5355    

DOI:10.1116/1.1315397

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

A preliminary survey of beryllium-base alloys was conducted by melting and testing small button-shaped ingots. Hardness and impact resistance were compared with those of pure beryllium. Structures were examined by microprobe analysis and conventional metallographic techniques. Larger homogeneous ingots of alloys showing promise were then consolidated by consumable electrode arc melting of pressed electrodes of beryllium and the intermetallic compound NiAl. The ingots were formed into rods of 1.7-cm(58-in.)diameter at reductions of 9-1 by impact extrusion. Evaluation of the rods was by tensile tests, hardness measurements, and microprobe analysis. Tensile properties at room temperature ranged from about 51 000 to 55 000 psi; tensile modulus was30−50 × 106psi; elongation was about 1% at room temperature and 2–9% at 600 °C.

ISSN:0022-5355    

DOI:10.1116/1.1315398

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

A technique of melting, processing, and testing small (80 g) rods of titanium alloys has been developed. The technique is designed for screening large numbers of alloy formulations to determine those with enough potential for further evaluation. The hearth plate of an arc button-melting furnace was modified to produce rod ingots which are forged to a shape suitable for testing. Strength and toughness measurements are used to compare a series of alloys relatively, and with respect to their bulk properties. It is recognized that a number of factors, such as cooling rates and amount of forging, prevent duplication of production material properties. Nevertheless, the apparent alloying and microstructural effects and the degree of correlation with plate properties are discussed.

ISSN:0022-5355    

DOI:10.1116/1.1315399

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

Sound ingots of titanium and Ti–6Al–4V alloy,110-mm diam×400 mmlong, were cast in a 60-kW HHCD furnace. Oxygen and hydrogen levels were reduced considerably. Triple melting and casting of Nb–56Ti–3.3Zr alloy in an 80-kW HHCD furnace produced a satisfactory superconducting material on which test data is reported. A description of the furnace and the operating procedure is outlined.

ISSN:0022-5355    

DOI:10.1116/1.1315400

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

The ability to produce a east titanium configuration has a history of approximately 10 years. It is presently being done in the United States by six companies. Casting of titanium is no simple task when one considers the thousands of foundries in existence producing cast parts from other metals. The difficulties are that titanium must be handled more carefully because molten titanium is very reactive to liquids, gases, and solids. At present, consumable vacuum arc melting offers the only suitable commercial method of producing titanium castings. The rapid contamination of titanium at elevated temperature by oxygen and nitrogen and the severe damage to ductility by small percentages of such contaminants requires that melting of titanium be done in the absence of air. Because liquid titanium is an extremely effective solvent, problems of containing the molten metal within a crucible during the melting operation are encountered. A water-cooled copper crucible is used to extract heat so rapidly from the liquid metal that it solidifies before its solvent reaction can take effect. This provides a thin film of solid titanium between the molten titanium and the copper crucible. This is referred to as skull melting. The liquidus to solidus range of titanium is quite narrow and problems of fluidity exist. When enough molten titanium is accumulated in the crucible, the power is cut, the electrode is rapidly withdrawn, and the pot is tilted, all within a few seconds or the pool will solidify. A centrifuge is used within the furnace vacuum chamber during the pouring of the melt. The highgforces during the casting operation help overcome the lack of fluidity. The centrifuge action assists in filling mold cavities with metal densities vastly superior to those from conventional sand foundry static casting. Conventional materials such as sand, shell, or ceramic molds are unsatisfactory for titanium since titanium above or near its melting point will violently react with these materials. A water soluble, expendable graphite mold system is a relatively new development in titanium casting and configurations with close tolerances and excellent surface finish are obtainable. New information related to the production of titanium castings with the latest applied technology was presented.

ISSN:0022-5355    

DOI:10.1116/1.1315401

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

In the past two decades, remarkable progress has been made in investment casting of airfoil components for gas turbine engines. Cast turbine blades, operating at high stresses and high temperatures, have been widely accepted. Improved production techniques, notably vacuum melting and casting, have stimulated development of greatly improved nickel and cobalt based superalloys. Although individual turbine blades and vanes have been produced in large quantities since 1950, a more recent development is high-volume production of integrally cast turbine wheels and nozzles for small gas turbine engines. This paper is a review of the state of the art in integrally cast airfoil components. The Monoshell process, as applied to integral castings is reviewed and representative illustrations of a wide range of engine castings are presented.

ISSN:0022-5355    

DOI:10.1116/1.1315402

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

Vacuum degassing techniques have been successfully applied to aluminum alloys for the production of sound, high strength, shaped castings. However, the use of a low-pressure environment during the melting process has not been utilized to the authors' knowledge. This experimental study has been an attempt to combine the desirable features of induction melting, such as uniform mixing and good temperature control of the melt, with an environment of low pressure for degassing of the melt and restricting the supply of reactive gases. The study has been limited to a single high strength wrought alloy: 7075-T6 aluminum. The short transverse ductility of this material is a sensitive indicator of deficiencies in materials and processing. Therefore, emphasis has been placed on the material properties in this direction as a means of evaluating melting variables. An attempt was made to correlate melt variables, such as starting material purity, gaseous environment and oxide removal methods, with tensile properties, stress corrosion properties and endurance limit in the short transverse direction of forged material in the solution treated and aged (T6) condition. Preliminary data was presented.

ISSN:0022-5355    

DOI:10.1116/1.1315404

出版商:American Vacuum Society    

年代:1971

数据来源: AIP

摘要:

The reactivity of pure vanadium (<350 ppm total impurity content) and the alloys vanadium–10.5-wt% chromium, vanadium–9.5-wt% molybdenum, andVANSTAR-7 (V–9 wt% Cr–3 wt% Fe–l.3 wt% Zr–0.05-wt%) with oxygen and nitrogen at low partial pressures in the temperature range of 600–800 °C was determined utilizing a hot-wall ultrahigh vacuum microbalance system. The rate of reactivity was determined from continuous weight-gain measurements as a function of both temperature and pressure, for oxygen partial pressures of10−5to10−7Torr and nitrogen partial pressures of10−4to10−6Torr. Linear kinetics were observed, indicative of a process controlled by gas transport to the metal surface. The sticking probability for oxygen of0.185±0.040was found to be independent of temperature, pressure, and alloying additions. The rate of reaction with nitrogen was a function of alloying additions, withVANSTAR-7 andV-10.5Cr exhibiting the lowest reactivity. The sticking probabilities were compared with those reported in the literature. These results indicate that the sticking probabilities of low-pressure gases on refractory metals are not well defined and seem to be a function of the particular experimental apparatus utilized.

ISSN:0022-5355    

DOI:10.1116/1.1315405

出版商:American Vacuum Society    

年代:1971

数据来源: AIP