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orange peel


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hey guys so what I have figured out about this orange peel texture that shows up sometimes is I think it comes from heat and its only on the surface (or at least not all the way through) I had originally noticed this when I would temper a blade low on purpose then grind it do a brass rod test and re temper until its good I have done this on new steels or when I change something in the heat treat. I have recently noticed it showing up on a couple blades when I am grinding them. these blades were not re tempered they were profiled hardened liquid nitrogen and temper. so maybe one of you guys can educate me on this a lil as far as where it comes from and if there is a way to get rid of it without grinding deeper into the blade??? I dip my blades in water on every pass of the grinder so I know I didn't overheat them there so I am stumped on where its coming from 

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I'm not sure if you're talking about the same thing I've seen or not, but where I've seen this is steel that was hotter than it should be when quenched.  I believe there is decarburization that takes place on the outer surface of the steel which can create that effect.  How deep that goes probably depends on the specific alloy and the temperature.  Again, not sure if we're talking about the same thing, but that's where I've seen an effect I would describe as orange peel texture.

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jhcc... ill get a pic up if I can I tried to take a pic of this before and Its very hard to get it to show up in a pic even in person you gota be in the right light,,,however I have heard of people talk about this before but no one has ever pegged all the reasons it might show up. I don't think its the steel being too hot at quench cause I have a even heat oven so my quench is always the same and it doesn't show up in every knife.  how ever decarb may play a part in the past if I heat treat a knife and temper when its only profiled and no bevels it wont show up (or Iactually I think it would if I didn't grind it away)  if I grind the bevels and once I re temper it again boom it shows up at that point you cant grind enough steel away  to get rid of it that is why I think it is a "shallow" effect. but recently I have had 2 blades show up with this when they shouldn't  Steve I have never heard it called alloy bonding maybe if I look that up ill find some answers. and I guess your right the steel itself could be off  I am using 440c have you heard of this more on one steel than another?

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Sent you a PM with this, but here's a snippet from Jay Fisher's site regarding the topic.  If it's inappropriate to quote another site I apologize and please remove it.

 

High chromium martensitic stainless steels like 440C or ATS-34 are processed with conventional heat treat (CHT) or with sub-zero heat treating (SZT), and the steels are then tempered and finished by grinding and then polishing. These steels are beautiful in their own right, with mirror polishes showing some grain texture. These textures appear like a much diminished and less noticeable version of D2 steel's "orange peel" granularity pattern, seen when held in just the right angle of incident light. While D2 has a much bolder and profound pattern, this same type of effect is seen in ATS-34 and 440C, with curves in the pattern following grind terminations, trailing points, and other geometric features of the blade. If the blades are cryogenically treated, these patterns will not appear! The cryogenic treatment makes the finish of these two steels much more like the finish of powder metal technology tool steel, namely CPM154CM. The surface is extremely clean and uniform, and no grain can be seen at all. This makes sense, considering the greater conversion of austenite, but perhaps more so the precipitation of fine carbides throughout the structure. Simply put, cryogenic treatment produces a more even, uniform, smooth, and beautiful finish than conventional heat treating.

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