The Locomotive - Lighthouse Survival Blog

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PUBLISHED BY THE HARTFORD STEAM BOILER INSPECTION AND INSURANCE COMPANY,
Nkw Skiuks—Vol. XIV. IIAKTFORD, CONN.. FEliKUAHY. 1893. No. 2.
The Effect of Temperature on the Strength of Iron.
This subject has attracted cunsiderable attention on account of its iinportauce iu
connection with steam boilers and other structures that are exposed, when in use, to a
temperature several hundred degrees higher than the ordinary temperature of the air;
but notwitlistanding tlie interest tiiat engineers have taken in tlie matter there seems to
have been but little done in the way of experimental investigation.
Tlie first experiments bearing upon the influence of temperature on the strength of
iron, so far as we know, were those made by the Franklin Institute, in 1833, and published
in the Journal of that institution in 1837. There is a difference of opinion among
the authorities as to what these experiments really show, but they have usually been
considered to show that iron grows stronger when its temperature is raised from, say, 60**
up to 500° Fall. Chief Engineer Isherwood of the U. S. Navy has criticised the method
FoK.M OF THE Test Pieces Used BY Dk. llusTu^ IN 1877.
in which they were carried out, and has pointed out a source of error to which they are
doubtless liable. (For his remarks see the Journal of the Franklin Institute for July,
1874, page 38.)
Ten years later, in 1843, Baudrimont made a series of experiments with wires of
gold, platinum, copper, silver, palladium, and iron. According to Isherwood, Baudri-
mont's average results for iron were as follows: Strength of iron wire, per square inch
of section, was 295,000 lbs. at 32° Fah., 279,000 lbs. at 212° Fah., and 301,000 lb.s. at
392° Fall. These results are interesting, but they are of no particular importance be-
cause iron wire is a very different thing from boiler plate, or bar iron.
In 1856 Sir "William Fairbairn published the results of his experiments. They indi-
•cated that the strength of common boiler-plate is not materially affected by ordinary
•changes in temperature, but that as a dull red heat is approached the tensile strength
falls rapidly. He says, "I have completed a series of experiments on wrought-iron
plates and rivet-iron at various temperatures, from 30° under the freezing point to red
heat. These experiments are the more satisfactory as they exhibit no diminution of