Warren Nakkela Posted April 1, 2009 Author Share Posted April 1, 2009 What does that mean?--macroscopic grain flow lines. Doesn't all that go away when the carbon goes into solution at forging temperatures? Grain flow lines have been depicted as though steel is like wrought iron with grain like wood. Now this is confusing. Warren Quote Link to comment Share on other sites More sharing options...
Dodge Posted April 1, 2009 Share Posted April 1, 2009 If I understand your question, Warren, it is, basically. Sheet or plate steel is just much finer and stronger grain than wrought. However, once you apply heat and reshape the steel through forging, regardless of the method, all bets are off, because you are now changing the grain structure. If you cut an s-hook from plate the grain runs straight through the plane of the face of the "S" from top to bottom or side to side depending on the axial lay out of the cut. If you forge an s-hook from steel, the grain runs in the direction of the "S". Think about bending a round bar into an "S". The grain ran the length of the bar. When you bend the bar, you bend the grain too. Hope I didn't muddy the waters :) Quote Link to comment Share on other sites More sharing options...
Quenchcrack Posted April 1, 2009 Share Posted April 1, 2009 Iron forms "grains" as it solidifies in the ingot or slab. The grains are very long and grow in toward the center of the ingot. The further into the ingot, the smaller the grains are. By hot working (forging or rolling) the grains are distorted and broken up and by re-heating, they re-form into mostly uniform size. By heating again in the forge, the grains begin to grow larger. Large grains are weaker and more easily fractured. Normalizing to a temperature below the forging temperature will re-form smaller grains. Grain flow refers to the re-orienting of the grains to follow the movement of the metal, usually this grain flow is parallel to the surface. The grains in steel have nothing to do with the "grain" seen in wrought iron which is the combination of pure iron (which does have grains) and the silica inclusions (which doesn't have grains). Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted April 1, 2009 Author Share Posted April 1, 2009 (edited) Does this mean that steel is stronger when the load is applied parallel to the direction of grain flow rather than perpendicular? And Does grain always exist in steel when in the solid state (not molten)? Or is it the other way around? If one forges a hook eg. does one wand the deformed grain to follow the bends of the hook? Warren Edited April 1, 2009 by Warren Nakkela Maybe I have got it backward? Quote Link to comment Share on other sites More sharing options...
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