evfreek Posted February 8, 2007 Share Posted February 8, 2007 Hi. I bought some steel off Ebay which was sold as S-7. I spark tested it, and it looks like it has the molybdenum arrows or bud breaks in the spark pattern. I am attaching two pictures. The first is a base image of A36 mild steel from the steel supply store. The A36 really cuts and forges like mild steel, but I have not tried the S-7 sample yet. Oops, the system will not allow images over 200 odd K to be uploaded. I will try to load to the gallery and insert a link:http://www.iforgeiron.com/gallery/showphoto.php?photo=2983&cat=500http://www.iforgeiron.com/gallery/showphoto.php?photo=2984&cat=500 Does this look right?:confused: Quote Link to comment Share on other sites More sharing options...
Vernon Posted February 10, 2007 Share Posted February 10, 2007 If nobody posts an answer by Monday I'll grind a piece of KNOWN S-7 at work and compare the sparks...not sure if that'll help ya. Quote Link to comment Share on other sites More sharing options...
evfreek Posted February 11, 2007 Author Share Posted February 11, 2007 Hi Vernon. That would be great if you could! Focus on the ends of the sparks. They should disappear, then reappear as little arrows or spears at the ends. I think I see that in the second photo. Unfortunately, I let the opportunity to fire up the forge slip this weekend, so I will not be able to try hitting it hot until next week. There weren't too many replies to my initial question. One person sent me a comment asking if I could post more spark photographs for other known steels to make a blueprint. I would be glad to do this, but these two samples are the only known steels that I have. Of course, I have old files, grade 2 and 5 bolts, railroad steel and HSS drill bits. These are kind of known, and have been "forge tested". Color spark snapshots are not all that popular on the WWW. Tai Goo had a tutorial which featured the difference between sparks from "useful" and "less useful" spikes, but it seems to have disappeared. Quote Link to comment Share on other sites More sharing options...
Woody Posted February 11, 2007 Share Posted February 11, 2007 You can tell the approximate carbon content of steel by spark testing it, but it is impossible to determine the actual alloy type by this method. If you are going to buy "S-7" get it from a reputable dealer with a certificate of analysis or go to the junk yard and buy scrap that is typically made of S-7 like jackhammer bits. Buying on EBay you are lucky you got steel. Woody Quote Link to comment Share on other sites More sharing options...
evfreek Posted February 13, 2007 Author Share Posted February 13, 2007 Hi Woody. If you look at BP0020http://www.iforgeiron.com/index.php?categoryid=13&p2_articleid=350 it has some tips about recognizing molybdenum in the spark pattern. Especially informative are the pictures for 4130 (a standard chrome moly steel used for structural tubing), 4615 and 4640. So it should be possible to see. As for jackhammer bits, there is this phrase on the Internet called YMMV. It means "your mileage may vary". We have a similar expression at the office: "the data has noise". It basically means the same thing. There is a reason for the difference, but nobody knows what it is. And people use this expression with a straight face. I picked up a couple of bits from different sources, and they spark test very differently. The first, from a blacksmith shop which does bit sharpening, tests like 1070 with no distinguishing alloy features. But it is not 1070, and requires the services of my striker. The other one has a strange pattern where the main stream is almost completely suppressed, and all you see are reddish arrow tips. If this is S-5, there is no mistaking it for any carbon steel, no matter what the content. I need to fire up the forge and do a "moving metal" test. Does anybody have a small sample of known S-7 that they can send to me? I would be very grateful and post a picture of the spark test. Thanks, Eric Quote Link to comment Share on other sites More sharing options...
Woody Posted February 13, 2007 Share Posted February 13, 2007 Gee those steel mills have been wasting money on metalurgists and analysis for years when all they had to do was take a hunk of what they produce and spark test it. Why is it that the blacksmith community insists on mistaking Alchemy for Science? A spark test is a SWAG and nothing more. Woody Quote Link to comment Share on other sites More sharing options...
Shane Stegmeier Posted February 14, 2007 Share Posted February 14, 2007 Actaully steel mills used to employed trained spark testers, I have a client who spent 6 months apprenticing as a spark tester in the late 60s early 70s. You can only tell a few components in the steel, carbon, silicon are the only ones that I remember for sure;-) But he was trained to recognise the alloys that his company made, and he and the guys that he worked with felt pretty cure about wheither the steel was what it was supposed to be. Quote Link to comment Share on other sites More sharing options...
Woody Posted February 14, 2007 Share Posted February 14, 2007 when you buy steel from them do you request a certificate or analysis or a certificate of spark test ? Quote Link to comment Share on other sites More sharing options...
evfreek Posted March 4, 2007 Author Share Posted March 4, 2007 Hi. I have more information on this question. The short answer: it probably is S-7. I bought a bunch of drops from another company on Ebay. It was a pretty good assortment of various steels: S-7, P-20, 4140, 440 and D-2. Note that the martensitic stainless is impossible to tell by surface appearance or magnet test. Since there is no austenitic phase transition, the magnetic force is within 5% of any other steel. Unfortunately, they failed to mark the last three, but the chunk of S-7 spark tested exactly like the original sample I photographed above. Two different uncorrlated companies. That should be enough. This casts a lot of doubt on the old Blueprint (0020), since the molybdenum arrows are not nearly as obvious, as is the trend with composition. I sent back the other three to be marked, and the 4140 will really highlight the composition effect. Either the Blueprint has some "creative editing", or it uses a faster wheel speed, which accentuates the differences. For due diligence, I will redo the experiments with a faster wheel. One smith asked me why I didn't do a forge test. I couldn't get to the forge. Just yesterday, I did a forge test on the first sample. It shows all the correct signs. Start at low yellow, barely moves at orange, clanks like steel at red (hit carefully ). And, my striker suggested that I stick with simple carbon steels and buy S-7 tools pre-made. Cooled slowly in air, it skated an old file. We estimated it was about 3X tougher than 1060 using a striker. Quote Link to comment Share on other sites More sharing options...
Ron Hicks Posted March 4, 2007 Share Posted March 4, 2007 Yellow heat S7 cracks when struck I have some and will get you a pic of the sparks. All I have is a angle grinder. Ron Got you a pic. The S7 doesnt spark that much like other steels Ive tried. I tried to get the end of the spaks. Tell me what you think this is stuff is.I was gave this a few years ago it was a shaft out of a machine and when I got it it had Tungsten Bar printed on it. It really throws the sparks compared to S7 Quote Link to comment Share on other sites More sharing options...
evfreek Posted March 8, 2007 Author Share Posted March 8, 2007 Hi Ron. Thanks for the pictures. The photo you marked as S-7 definitely looks like mine. I am pretty sure now. I need to retry the moly steels with an angle grinder. It has a faster surface speed and throws sparks further. In the old days, spark testers used a handheld cylindrical stone grinder, kind of like an ol' fashion' angle grinder. As for the second sample, I am not sure. It looks higher carbon. The only tungsten alloy steel I am familiar with is M-2, and it has 85 points. But it does not spark like that. It has short, thin reddish sparks near the wheel, with small bursts near the end. I wonder if this is a higher tungsten alloy like the T series. I do not have any of those samples to compare with, though. That S-7 was so hard to work that I don't think that I would make knives out of any hot work steel. I did make a HSS knife, and I have a big dead power hacksaw blade that I could try. The knife is OK, but it dulls rapidly, especially when cutting leather or durock concrete board . The older blades say "tungsten steel". I guess I should try sparking one of those to see what happens. I will take a piece of the S-7 to a blacksmith's shop tomorrow to play around with, and maybe make some tools. Quote Link to comment Share on other sites More sharing options...
Ron Hicks Posted March 8, 2007 Share Posted March 8, 2007 Ive been making a few punches and chisels from the S7 I have , it makes good chisels. Hard to forge very much stayin between Orange & Red kind a slow goin. Quote Link to comment Share on other sites More sharing options...
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