Abstract
The work described in this paper is part of a current programme that has two objects: (1) to investigate further the reasons for the different scaling behaviour of steel in steam and carbon dioxide, although these gases have similar oxygen potentials; (2) to provide background information for an investigation into the effect of variations in re‐heating furnace atmospheres upon scaling and scale adhesion.
Abstract
TWO nickel‐bearing commercial steels were oxidised in the range 1100°–1250°C for up to 8 hr. in air and CO2. The increase in thickness of the scale and the inner layer with embedded metal particles was followed in detail. A distinction is made between filaments which retain continuity with the base metal and discrete particles. The continuous filaments may be of practical importance in holding the scale to the metal in hot rolling, leading to surface defects on hot‐rolled products.
J.A. von Fraunhofer and G.A. Pickup
THE oxidation behaviour of low binary iron alloys with aluminium, chromium and silicon in air has been discussed at length. Rather less work has been performed on the ternary…
Abstract
THE oxidation behaviour of low binary iron alloys with aluminium, chromium and silicon in air has been discussed at length. Rather less work has been performed on the ternary systems, Fe‐Cr‐Al and Fe‐Cr‐Si, and very little on Fe‐Al‐Si alloys.
One of the problems in the production of narrow hot‐rolled mild steel strip is the formation, at the edges of the strip, of scale that can be extremely resistant to pickling; This…
Abstract
One of the problems in the production of narrow hot‐rolled mild steel strip is the formation, at the edges of the strip, of scale that can be extremely resistant to pickling; This extreme resistance to pickling of ‘hard edge scale’ sometimes requires repickling of a considerable percentage of coils with consequent loss of production and deterioration of surface finish. The paper considers in detail the correlation between the microstructure of scale on the strip and its pickling behaviour. It is shown that certain characteristics of the microstructure, peculiar to ‘hard edge scale’, i.e. increased thickness, the presence of a primary magnetite layer, greater degree of wüstite transformation and the nature and presence of haematite, can be suppressed to a greater or lesser degree by variations in the cooling cycle. It is considered that no single one of these structural differences between hard edge scale and that which is removed readily from the centre of the strip would, by itself, interfere with pickling, but when these characteristics occur together repickling is made necessary. The above observations and conclusions are supported by results obtained from pickling tests carried out in the laboratory on samples taken from a wide range of coils.
Abstract
The work described in this paper is part of a current programme that has two objects: (1) to investigate further the reasons for the different scaling behaviour of steel in steam and carbon dioxide, although these gases have similar oxygen potentials; (2) to provide background information for an investigation into the effect of variations in re‐heating furnace atmospheres upon scaling and scale adhesion.
J.A. von Fraunhofer and G.A. Pickup
THE variation in weight gains of the binary (and ternary) iron alloys with change in the atmosphere composition clearly demonstrates the sensitivity of oxidation behaviour to…
Abstract
THE variation in weight gains of the binary (and ternary) iron alloys with change in the atmosphere composition clearly demonstrates the sensitivity of oxidation behaviour to conditions. In particular it can be seen from Figs. 3 and 4 that the presence of atmospheric pollutants (sulphur and nitrogen oxides, water vapour) markedly increases the oxidation rate in air. This is supported by the further marked increase in oxidation in flue gases produced by the presence of sulphur oxides. Oxidation in flue gases at 700°C is far greater than in air, Figs. 7 and 10 and Table 3. This is due to the formation of wustite which was not present in air‐formed oxide scales.
Certain previously unobserved features of scale formed in an oil‐fired billet reheating furnace are described. It is shown that sulphur‐rich melts formed at the scale/metal…
Abstract
Certain previously unobserved features of scale formed in an oil‐fired billet reheating furnace are described. It is shown that sulphur‐rich melts formed at the scale/metal interface penetrate the grain boundaries of the overlying scale: subsequently the sulphur is removed by an oxidation reaction in which the surrounding manganese‐containing oxide takes part, to form a complex manganese silicate. The thermodynamics of possible reactions are discussed briefly and hypotheses put forward for the transport mechanisms of sulphur from the furnace atmosphere to the scale/metal interface.
Certain classes of organic chemicals that can behave like carbon black in protecting polythene from thermal degredation have recently been developed at Bell Telephone laboratories…
Abstract
Certain classes of organic chemicals that can behave like carbon black in protecting polythene from thermal degredation have recently been developed at Bell Telephone laboratories in the U.S.A. Mrs. A. Worthington and Dr. W. L. Hawkins described their discovery at a recent meeting of the American Chemical Society in New York. They demonstrated that a number of compounds containing alternating unsaturated bonds provide excellent thermal anti‐oxidant properties in combination with previously reported sulphur‐bearing compounds.
During hot rolling and subsequent cooling, scaling always occurs on the steel strip. It is necessary to be completely removed before further processing (such as cold rolling)…
Abstract
During hot rolling and subsequent cooling, scaling always occurs on the steel strip. It is necessary to be completely removed before further processing (such as cold rolling). Usually continuous pickling is a more economic and convenient process to be used to remove the scale. However, the pickling rate is affected by many variables such as the type of acid, acid solution condition, steel composition, scale structure and different inhibitors at various concentrations as reported in the literature. In the mill, except machine breakdown, the troubles in the pickling line are often caused by the presence of acid‐resisted scale of nonuniform scale structure. Although a lot of information has been accumulated on the relationship between the microstructure of scales on steel strip and their response to pickling, most of them concerned the pickling in sulphuric acid. In the present work, the scale composition and thickness are examined after isothermal oxidation and simulated different mill cooling processes. Furthermore, their effects on pickling rate in hydrochloric acid solution is also studied and discussed.