This is a attempt to clarify some of the steel making terms that are often encountered when researching early tool making firms, many firms were involved in steel manufacture, at various stages. Early Steel Making 101 (the short version) Starting from the beginning... iron oxide (iron ore) mixed with clay heated in a blast furnace with coke and limestone Carbon absorbs the oxygen from the iron oxide and leaves iron the furnace is tapped and molten iron is cast into moulds This is "pig iron" Contains 5% carbon and lot's of other inpurities ,is very brittle and no real engineering use. Refining by a second melting reducing carbon to about 4% and fluxing off more of the silicon This is "cast iron" Easily machined, but brittle By reheating and further refining, carbon level can be reduced further by exposure to air as the melting point increases a slag forms which can be removed this pasty material can be forged into strips and rods which is easily welded but contains insufficicient carbon to be hardened This is "wrought iron" Reheating wrought iron bars for a week packed in clay with layers of charcoal at 1000C, the process call cementation produced what is called "Blister Steel" so called due to the appearance of the surface. The steel was brittle and readily fractured into small pieces. By reheating blister steel it could be forged and rolled into various forms, however considerable variation in carbon content from surface to the center was a problem. The problem was difficult to solve, since remelting to distribute the carbon more evenly didn't work, the oxygen in the air combined with the carbon, and you were back to wrought iron! An improvement was to forge together several layers of blister steel and thus produce layers of high/low carbon content, this became known as "Shear Steel" By repeating the process, it was possible to produce "double shear steel" The real breakthrough came with a method to remelt blister steel, and keep the oxygen out.. this enabled the production of steel with carbon distributed more evenly throughout. By melting fractured pieces of blister steel in a crucible covered with a glass flux (thus keeping oxygen out) then casting an ingot and forging this into a rod a greater uniformity could be achieved. This was called "crucible steel" or "cast steel" German Steel, was produced directly from molten pig iron, quenched pellets were drawn out on a forge and welded into faggots. To forge steel several type of hammers were used tilt hammer head helve, belly helve, Bessemer Steel was introduced in the late 1850's (another topic).. I'm still looking for a more definitive definition of "German Steel" there are numerous differing versions. Regards Ray
Hello all, With Ray mentioning Cast Steel ( with or without the dot) in the Timeline thread it encouraged me to come back to this one to re-read it. It is extremely concise and lays out the basic processes/terms. Prior to this I had already looked up steel making on Wikipedia with a view to try to sort out the mechanics of the processes involved because I thought that all steels/irons had been originally melted and cast. That was when I first came across Sponge iron and the Finery process (let alone Puddling and Shingling), and I went on from there. I am sure that you are all capable of looking these things up, but I have provioded three links on Wikipedia below that I think are particularly interesting. http://en.wikipedia.org/wiki/Wrought_iron http://en.wikipedia.org/wiki/Crucible_steel http://en.wikipedia.org/wiki/Bessemer_process It is fascinating to read the economics alone and the rise in steel production from 1740 to 1860, let alone the processes involved. There is also a note on crucible steel production in the Abbeydale Hamlet, the home of so many saws. They still do exhibitions here of forging made with steel from their own furnace. Another place that may well be worth a visit. (How about an organised world tour of Sheffield)?? Fred If you don't want to plough through wrought iron and Bessemer, go to crucible steel first as the section on European steel gives a good overview.
Hi Fred, The story of early steel making (at it's most basic level) is really all about controlling the amount and uniformity of carbon. Thanks for linking to those Wikipedia articles, very interesting stuff. From what little I've been able to glean, cast steel was used in sawmaking from at least somewhere around 1760ish, but may or may not have been stamped as such. As far as I can tell the 1780ish Birminham saws of Dallaway and Barnard, aren't stamped cast steel, just makers mark directly onto the saw plate, but the 1790's Kenyon that Bobbldr posted does have the "CAST.STEEL" So, I've put 1790 as tentatively the first usage of the mark, but could easily be 10 years earlier than that.. Regards Ray