tag:blogger.com,1999:blog-8515829.post111346557453328004..comments2024-03-29T05:15:40.793-07:00Comments on Irons in the Fire: The problem of sulphur in steelFirehandhttp://www.blogger.com/profile/04562365951182027709noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-8515829.post-23205571709465811612008-11-14T09:56:00.000-08:002008-11-14T09:56:00.000-08:00I know the entry is old, but I was searching Googl...I know the entry is old, but I was searching Google about the topic and this post actually showed on top. So I decided to post what I (think I) know.<BR/><BR/>BTW only to complete (I mean correct really) something I said. To improve machinability the idea is not reducing toughness overall. The key is always the microstructure. Not only the amount but the conditions and treatments must be adequate so that the iron sulphide forms as finely distributed particles. That way the effect on a normal part is minimal; but since chips are very thin and long, each of these particles reduce their cross section and so their resistance much further.<BR/><BR/>Again talking by heart, since my book doesn't include an alphabetical index.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8515829.post-86080663887671549432008-11-14T06:36:00.000-08:002008-11-14T06:36:00.000-08:00JD, that makes sense. Thanks for the info; and ye...JD, that makes sense. Thanks for the info; and yes, I do need to dig out a book and read back up on it.Firehandhttps://www.blogger.com/profile/04562365951182027709noreply@blogger.comtag:blogger.com,1999:blog-8515829.post-57041588127530487722008-11-13T07:43:00.000-08:002008-11-13T07:43:00.000-08:00When hot, iron and sulphur combine to form a third...When hot, iron and sulphur combine to form a third substance called iron sulphide. It's not a metal and it's very brittle like the ceramic (or intermetallic?) it is.<BR/><BR/>The intention when adding to improve machinability is the same, to make the alloy somewhat brittler--when that's no problem for the application at hand--so the chips break earlier and don't turn too long.<BR/><BR/>Also this iron sulphide melts at far lower temperatures than steel. So when a steel with lots of sulphur is cooled from liquid, the iron sulphide solidifies last, and the resulting structure shows iron grains completely surrounded by a brittle cement, so the alloy doesn't benefit from the properties of iron since the material can break apart without the iron itself breaking apart.<BR/><BR/>Don't quote me on all this since I'm trying to recall my college, but I think it's basically like this.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8515829.post-1113670025570648702005-04-16T09:47:00.000-07:002005-04-16T09:47:00.000-07:00The actual chemical wherefores I've never gotten a...The actual chemical wherefores I've never gotten ambitious enough to dig up. <BR/><BR/>One old smith's trick for punching a hole through thick iron was to set the piece level in the fire, and put a lump of sulphur on the spot. By the time the piece was at red heat and kept there a minute, the piece would be much easier to drive the punch through. Whichever it is that causes it, it works.Firehandhttps://www.blogger.com/profile/04562365951182027709noreply@blogger.comtag:blogger.com,1999:blog-8515829.post-1113642432366487622005-04-16T02:07:00.000-07:002005-04-16T02:07:00.000-07:00Is it actually sulpher or is it hydrogen embrittle...Is it actually sulpher or is it hydrogen embrittlement caused by the sulpher?Anonymousnoreply@blogger.com