The Locomotive - Lighthouse Survival Blog

18 THE LOCOMOTIVE, [Februaky,
strength from 60° to 400° ; but an increase of heat from that point to a dull red heat
shows a considerable reduction of strength and a great increase of ductility, the plates
being in the ratio of 20.3 to 15.5 tons per square inch, as regards strength, and the rivet
iron as 35 to 16. The iron suffers little or no diminution in its powers of resistance up
to a temperature of 500° Fah."
Next in order, after Fairbairn's experiments, came those made by the British Admiralty
at the Portsmouth (Eng.) dock-yard, in 1877. The specimens to be tested were
heated in an oil bath, and " the dies for gripping them were also so heated. The pro-
cess of fixing and breaking occupied about one minute, during which care was taken to
prevent, as far as possible, loss of heat by radiation and conduction." The temperature
of each test-piece was recorded as equal to the temperature of the bath in which it was
heated. Owing to the cooling of the specimens, and the suddenness with which they
had to be pulled apart in order to compress the whole experiment into one minute, we
cannot consider this series of tests to be very satisfactory, although it made an acceptable
addition to what was then a very meagre knowledge of the effect of temperature on
the strength of iron. The general conclusions that were reached by the committee hav-
ing charge of these tests were as follows: " Wrought-irons, Yorkshire and re-manu-
factured, increase in strength up to 500°, but lose slightly in ductility up to 300°, after
which the ductility increases up to 500°, at which point it is still less than at the ordi-
nary temperature of the air. The strength of Landore steel is not affected by tempera-
ture up to 500°, but its ductility is reduced more than one-half."
In the same year (1877) Dr. Charles Huston of the Lukens Rolling Mills, Cc^tesville,
Pa., made some tests bearing on this question, at which we were present by his invita-
tion. As they have never been published it may be of interest to give a brief account
of them. The test strips were a little less than an inch wide, and about threeeighths
of an inch thick, and through the middle of each piece a quarter-inch hole was
drilled, as shown in the cut. These holes were tilled with fusible alloys, whose melting
points were determined beforehand with considerable accuracy. By reducing the sec-
tional area of the piece, the hole also determined the point of fracture. In making a test
the piece was fixed in the jaws of the testing machine, and warmed along the central portion,
as uniformly as possible, by a Bunsen burner. The piece was gradually put under
tension at the same time, and when the strain upon it had approached its tensile strength
the machine was stopped until the fusible alloy was seen to be fairly melted, and the
piece was then broken by a slight additional pull. It was considered that in this way
a very fair idea might be had of the effect of temperature upon the pieces tested. Six
specimens were fractured in all. Three of them were cut from plates of the best flange
boiler iron, made from cold blast charcoal blooms, and the remaining three were samples
of Otis steel, furnished by the Baldwin Locomotive Works of Philadelphia. The
results are given in the accompanying table.
Material
Tested.
Results of Dr. Huston's Tests in 1877.