Furnace Material Research Articles

A Process for Delubrication, Presintering, Sintering, and Rapid Cooling in a Vacuum Induction Furnace

Delubrication, presintering, and sintering are major steps in the manufacture of many products in the powder metallurgy field. The quality of the final product, to a great extent, depends on the quality, accuracy, and reliability of the sintering equipment used. The vacuum induction furnace for delubrication, presintering, sintering, and rapid cooling described below offers the possibility of delubricating the charge under vacuum and protective or reactive gas atmospheres at reduced pressures and to sinter the material in the same furnace, eliminating charge handling and transfer between the delubrication and sintering processes. All components of the furnace chamber and manifolds which come in contact with lubricant vapors are heated during the delubrication cycle and thus it is impossible to accumulate any traces of condensed wax in critical areas of the furnace. This eliminates the possibility that during sintering the charge is contaminated by lubricant decomposition products. The performance of the total cycle from delubrication to cooling in one furnace and the application of forced gas cooling improve the economic picture of the sintering process. Elaborate controls and programmers provide precise process control and generation of valuable records. The design of the furnace results in reduced maintenance and service costs.

Comparison sensitivity of distributed parameter systems

System parameter values can vary from their assumed nominal values. These perturbations may alter the performance of a distributed parameter system from the desired nominal performance to an unacceptable degree. To overcome these undesirable effects it may be possible to utilize feedback control in the system to insure that parameter variations alter the system performance with feedback to a lesser degree than an equivalent open-loop system subject to the same perturbations. New results are developed in the form of sufficient conditions to insure that feedback compensation decreases the effects of parameter variations upon the system dynamics for distributed parameter systems described by linear constant-coefficient partial differential equations which may be nonseparable. The theory is applied to two examples, the most significant of which is that of heat exchange between a moving and a stationary medium such as heating material in a through-passage furnace.

An analysis of the useful life of refractory materials in tank furnaces for sheet glass

An analysis of the useful life of refractory materials in tank furnaces for sheet glass

Drive Systems for Float Glass Installations

Implementation of the float glass process requires continuous control of the glass ribbon from the molten state through the solid state. The areas which present the greatest challenge to the drive manufacturer are the tin bath and the annealing lehr. Here the glass is changing state continuously, requiring the drive systems to provide precise speed, speed ratio, and position control. To provide this control, while maintaining flexibility and versatility for future process changes, solid-state powered dc drives with digital speed control were chosen. The remainder of the process, including the furnace material input, cutting section, and capping conveyor sections, was automated using more conventional drive systems.

Heat exchange in a furnace with a thin boiling bed

An empirical dependence has been found for determining the effective heat-exchange coefficients, and dependences have been suggested for calculating the incomplete heat-exchange due to temperature gradients in the granules during the heating of granulated material in furnaces with a thin boiling-bed.

Untersuchungen an Niob-Tantal-Legierungen

Sintered and subsequently rolled niobium — tantalum alloys are examined over the whole range of composition. Their hardness, strength and elongation at room temperature, their specific electrical conductivity, electrochemical behaviour and corrosion resistance are reported. The mechanical properties show no maximum. The specific electrical conductivity has a minimum and the leakage current of anodically anodised samples exhibits a maximum at an alloy concentration of 50Nb 50Ta . Such alloys which might be fabricated from inexpensive unseparated niobium — tantalum powder represent advantageous heating element material for vacuum furnaces. Their application as electrodes for electrolytic capacitors and in the chemical industry requires low niobium contents of the alloys.

Heat Insulation in High-Temperature Vacuum Furnaces

In recent years, the high-temperature vacuum furnaces have been widely used in melting metals and alloys, sintering refractory hard metals or heat-treating various materials. One of the most critical factors in such furnaces is the properties of refractory materials used.This report describes the properties of zirconia grain and graphite powder which are used as heat insulating material in the high temperature vacuum sintering furnace. Graphite powder (150 mesh under) shows more excellent features compared with zirconia grain in heat insulation as well as in gas evolution. Thus the temperature above 2500°C was obtained easily by using graphite powder under a vacuum of 2μHg or better. The thermal conductivty and gas evolution rate of such insulating materials are also estimated and discussed.

Design of a High‐Temperature Resistance Furnace

An electric resistance furnace is described that is capable of operating at temperatures up to 3770 °F. (2075°C.) in vucuo or in hydrogen or noble‐gas atmospheres. Problems of outgassing and atmosphere contamination by furnace materials are largely circumvented by eliminating insulation.

A High Temperature Precision X-Ray Camera: Some Measurements of the Thermal Coefficients of Expansion of Beryllium

A high temperature precision x-ray camera has been designed and constructed by modification of the familiar back-reflection symmetrical focusing type of camera. The camera, specimen, and furnace are used within a vacuum chamber to avoid oxidation. The apparatus in its present form has been employed at temperatures up to 1000°C, but higher temperatures could be easily attained by making a few minor changes in the furnace materials. The lattice parameters of beryllium have been measured up to 1000°C. The derived coefficients of thermal expansion, both linear and bulk, are presented as a function of temperature. In addition, the data present strong evidence that the hexagonal close packed form of beryllium which exists at room temperature is stable up to at least 1000°C, contrary to several reports in the literature.