A Metallurgical Evaluation of Iodide Chromium

Abstract

Both the physical condition and the purity of chromium are important factors in its ductility. By proper fabrication techniques, iodide chromium sheet having an average ductile-to-brittle bend-transition temperature below 0~ has been obtained. Small quantities of oxygen, nitrogen, iron, molybdenum, tungsten, and silicon have little effect on the bend ductility of chromium. However, nickel, carbon, or sulfur adversely affect both the hot and cold ductility. ~NTRODUCTIONWhile chromium finds widespread use in electroplated form and as an alloying addition to other metals, the cold brittleness of commercially available grades of the metal has thus far precluded any direct applications of it in massive form. Recent work at various laboratories, however, has furnished strong evidence that pure chromium is actually a ductile metal.The first report of any ductility in chromium was that given by Kro} 1 (1). By utilizing various reduction processes, he obtained chromium granules of "better than 99 per cent purity" which, although brittle when cold, could withstand deformation by forging when red hot. In later work (2), Kroll and his associates prepared chromium powder which analyzed 99.9% pure by the reduction of chromic chloride with magnesium and subsequent deoxidation with pure, dry hydrogen. Sheet prepared from this product by powder metallurgical processes was ductile at temperatures above 500~ but brittle at temperatures below 500~ At about this same time, Greiner (3) showed that chromium could be deformed in compression at room temperature. Additional evidence of the ductility of chromium in cold compression was obtained in exploratory work at Battelle (4).In 1952, Hayes (5) and Gilbert (6) reported that arc melting of hydrogen-treated chromium had been accomplished and that successful forging, rolling, and swaging of this material had been carried out. A representative analysis (7) of the hydrogenreduced arc-melted chromium showed that 0.001% iron, 0.05 % silicon, 0.003 % oxygen, 0.002 % nitrogen, and 0.005 % hydrogen were present. In regard to all other metallic impurities, the metal was described as pure as the best spectrographic standards available. The workability of this chromium was shown by the ability to drill, saw, grind, tap, turn, and file in the Manuscript received September 9, 1954. This p~per w~s prepared for delivery before the Chicago Meeting, May 2 to 6, 1954. 316 cold state, and to spot weld chromium to either chromium or iron. The metal could not be bent cold, but did withstand a free bend at 325~Recently, Sully and coworkers (8), using sintered compacts of hydrogen-reduced electrolytic chromium, showed that chromium undergoes a sharp transition in bend tests from brittleness to appreciable ductility over the range of a few degrees of temperature. The lowest temperature at which he found substantial ductility in bend tests was 50~ In a study of the influence of impurities on this transition temperature, Sully observed that oxygen in the range 0.001-0.9 % has hardly any influence on the transitio...

Chromium and chromium-based alloys: Problems and possibilities for high-temperature service

“…16 A minor increase in transition temperature in bending for recrystallized chromium sheet resulted when the oxygen was raised from 0.05% to 0.18%, though there was no measurable increase for asrolled sheet. 26 Small amounts of sulfur (0.02%) make chromium impossible to warm roll. 26 An alloy containing 4.5% sulfur was brittle at temperatures as high as 500°C, and fracture occurred along sulfide phases at the grain boundaries.…”

“…26 Small amounts of sulfur (0.02%) make chromium impossible to warm roll. 26 An alloy containing 4.5% sulfur was brittle at temperatures as high as 500°C, and fracture occurred along sulfide phases at the grain boundaries. 16 Hydrogen is present in large amounts in as-deposited electrolytic chromium but is evolved on heating above 400°C.…”

“…42 Silicon is a relatively sluggish and probably weak nitrideformer and aluminum results in a small but defi nite improvement of the ductility of chromium. 15,26,43,44 Boron addition can modify the nitride impurity after heat treatment and reduce the DBTT of impure cast chromium. 45 Some researchers attempted to correlate properties of the alloying element with its effect on the DBTT and their work indicated that the effect of alloying on the DBTT of chromium is not directly related to the atomic size of the solute atoms.…”

Ductile–brittle transition behavior of rolled chromium

“…It was reported that some thermomechanical treatments combined with plastic deformation and heat treatment were useful to the decrease of DBTT for some kinds of cast chromium [7,8]. In the present study, a sintered pure chromium was thermomechanically treated, i.e.…”