There is a discussion of the advantages and disadvantages of copper and steel fireboxes at pp. 103-105 of John H. White, A History of the American Locomotive: Its Development, 1830-1880 (Dover Publications, 1980). Extensive excerpts from this book, including these pages, are available on Google Book Search. Here is a link to the main page for the book:

http://books.google.ca/books?id=1A4iiGAz628C

By 1900 steel fireboxes were in general use in North America, but as I understand railways in many other parts of the world continued to regard copper fireboxes as preferable because they were more resistant to the stresses caused by thermal expansion and contraction. In some countries the transition to steel only came with the need to conserve strategic materials during the 1939-1945 war. For example, these are the comments of the eminent Richard Maunsell (Chief Mechanical Engineer of the Southern Railway in England) as reported in R.P. Wagner, "Some New Developments of the Stephenson Boiler," 20 Journal of the Institution of Locomotive Engineers (1930), at p. 22:

Hi all,
Red dot= rebuilt boilers.

Dr D

Here's a bit more information specific to the German context, mostly gleaned from Dampflokomotivkunde. Leitfaden zum Lehrfach m 3 II, Dampflokomotiven - Lokomotivkunde für Dienstanfängerlehrgänge. Eisenbahn-Lehrbücherei der Deutschen Bundesbahn Band 134 (Josef Keller Verlag, 1959), at pp. 291-298.

Steel fireboxes were adopted in Germany in 1914-1918 in order to conserve copper, but they were not very durable because suitable specialty steels had not been developed. Copper and copper alloys such as "Kuprodur" (98.8% copper, 0.7% nickel, 0.4% silicon, 0.1% iron) were used again after 1918.

The BR 59 (Württemberg Class K) locomotives are one example:

K 1801 - 1803 / 59 001 - 59 003 (built 1917-1918): copper
K 1804 - 1815 / 59 004 - 59 015 (built 1918): steel
K 1816 - 1844 / 59 016 - 59 044 (built 1922-1923): copper

The copper fireboxes in these locomotives gave so much trouble that they were replaced in the 1920s: Rudolf Röder, Die Baureihe 59.0 (EK-Verlag, 2007), pp. 66-68.

The introduction of special grades of steel such as Krupp IZ II in the 1930s allowed the DR to adopt the steel firebox from about 1935 on, e.g. 03 294 (September 1935) as illustrated in the documentation reproduced here:

http://drehscheibe-online.ist-i...orum/read.php?17,3741601

As René noted, steel does not conduct heat as well as copper. Because of this, steel fireboxes reach a higher temperature than copper ones. At full load the walls of a copper firebox will only be 10-30º C hotter than the boiler water. The walls of a steel firebox will be 100-160º hotter than the water. So the steel firebox is subjected to significantly greater thermal stress. The higher temperature also results in increased deposition of ash particles which interfere with efficient heat transfer, and thus the steel firebox requires more frequent cleaning.

It seems that the DRG (and later the DB) issued a special instruction card (Merkblatt) for locomotives with steel fireboxes, admonishing the fireman to ensure gradual and even heating and cooling, to maintain an even fire and to avoid rapid reductions in steam pressure or water temperature. Good advice in every circumstance, I'm sure, but apparently especially important with a steel firebox.

What I don't know seems to be a lot. Copper for the firebox? How can copper be forged thick enough to withstand all the heat, and not warp, or crack? Copper is a non-ferrous metal that is soft. I always thought fireboxes were thick cast iron. Books that I have include: Locomotive stokers by J.W. Harding, Scranton Pa. USA 1922 and Catechism of the Locomotive (USA) 1887.

Boiling water at about 12 bar has a temperature of approx. 190 degrees celcius. So the temperature of the copper wil become about 210-240 C. An iron firebox will become about 290-350 C. Quite a difference!

René

Thank's for explaining that. I wondered why the copper would not warp, or melt.