
patrick
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Mokume, Tool Making, Industrial Forging
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Beloit, WI
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Bronze age steel chisel found in Iberia.
patrick replied to BillyBones's topic in Historical Ironwork
I have not read the referenced article but based on the assessments you've provided it doesn't sound that good. There is evidence for the use of steel going back to the times referenced though. There is a two volume set by V.F. Buchwald that discusses the ancient use of iron and steel in Europe and traces the historical development of that technology. In those books, he details the use of steel found in fasteners used to too join the stone blocks that were used to build the Parthenon. He also points out that Homer gives a description of quench hardening. Homer's works are not quite as old as 900 BC, but the setting (The Trojan War) is roughly 1250 BC. In the book of Proverbs, Solomon writes that "iron sharpens iron" which I take to mean a file sharpening something else. It could be a different technique, but if he was referring to a file then you have another piece of literary evidence from about 900 BC pointing to a knowledge of quench hardening steel. -
Hi DaniH-You've raised an interesting question and I may be able to help a little bit. In the US, stainless grades, especially those that are austenitic, are mostly made starting with scrap stainless steel that has a composition close to that desired in the final product. Because the starting material is already loaded with chrome and nickel, special techniques are used to remove what little carbon is in the melt charge. It will be MUCH less that what is in your pig iron. The methods used are either Argon Oxygen Decarburization (AOD) or Vacuum Oxygen Decarburization (VOD). Both methods are used because they substantially limit the amount of chrome that is lost to oxidation. If the conventional methods of removing carbon by blowing oxygen into the liquid metal under normal atmospheric conditions are used, a great deal of chromium is lost and that is very expensive. If you are starting with conventional pig iron you will not have much chromium in it, but it will be high in carbon. You could used an oxygen blow to get rid of the carbon, but getting the chromium into that melt gets to be a challenge. Adding pure chromium to liquid pure iron is pretty hard because the melting temp of the chromium is a good bit higher than the iron. In conventional steel making this problem is solved by adding something called ferro chrome to the bath. That is a very high chromium, iron carbon alloy. For steels other than the austenitic stainless grades, this method works well because the carbon in the ferro chrome is not so high as to cause a problem. Lots of steel has carbon over 0.10%, in fact quite a bit more. But to successfully make austenitic stainless (316L) you have to get the carbon down below 0.08%. It is getting that low carbon without loosing a substantial portion of the chromium that is so hard. You can do it, you just loose a lot of chrome and that makes for a very expensive heat of steel. This difficulty in getting rid of carbon is one of the reasons that the martensitic stainless grades, which do have some carbon, were the first to made commercially. It took a bit longer to develop the technology to get rid the carbon. In your original question you asked if you could add something to a 70Kg melt to get rid of the carbon without blowing in oxygen. The answer is YES! Historically, mill scale, forge scale or other sources of iron oxide where added to furnaces for the purpose of reducing carbon. This was done as part of the puddling process used to make wrought iron and was also used in the open hearth steel making process, which has some similarities to the puddling process. this will not help you get the chromium and nickel into the iron, but it will help you get the carbon out. Here in the west we no longer add mill scale to the pig iron as part of steel making because so much of our steel is make by remelting scrap via electric arc melting. In that process it is more cost effective and faster to just blow oxygen into the liquid steel, but for your situation this may be a workable solution to your carbon issue. Good luck.
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Hey Guys- I know I'm a bit late to this conversation but I thought I'd add a little bit. The spark test actually was used for differentiation of more than just carbon until fairly recent times. I have a copy of the spark testing training manual that was used at Inland steel and it very clearly shows and discusses how to distinguish the spark characteristics of elements like molybdenum and chromium. The training required to get that good was extensive. The manual was given to me by a former salesman who represented the successor to Inland Steel. I asked why that technique was still in use since laboratory methods that are much better have been in place for a long time. He said the method was used with a hand grinder by inspectors checking bundles of bars as the left the mill. The goal was to quickly hit the ends of the bars in the bundle and confirm different steel grades had not been mixed in the bundle. Up until fairly recent times there was no other method fast enough to keep up with production in a steel mill setting. Within the last 10 years or so portable X-ray analysis tools have replaced the spark testing method for this application. Interestingly, the most common laboratory method, optical emission spectroscopy, is really just an advanced version of the spark test. In this method an electric arc is struck between a steel sample and a tungsten electrode in an environment flooded with argon. Special optics and software analysis the colors in the light and determine the percentages of each of the elements present in the steel. The use of the traditional spark testing technique to sort steel by carbon content is one of the earliest tests. By 1916 this was a well established test and is discussed, with illustrations, in the book Heat Treatment of Tool Steel by Harry Brearly. The image shared by the original poster does not have a lot of spark features shown. I agree that pictures zoomed out with more of the spark showing, especially the burst if there is one, would be helpful. Assuming there actually are no bursts then I'd guess this to be something like a high speed steel rather than 01, but I don't think there is enough info to say for sure.
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I'm an active member of ASTM and user of their specificaitons. Not only do they have specifications by application, such as the music wire , bearings and rail road applications but within a given standard their are often several, sometimes many, different grades. For example, Specification A350 has several different grades with substantially different compositions. We work with A350 LF2 and LF6. Those names have no connection to the composition, they are just generic labels so you have to look up the spec to see what the compositions are for each of those materials.
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All- i have an anvil in need of repair. Before people jump on me about need for the repair or my abilities to execute this kind of welding, please know I've done this on numerous occasions in the past and I'm well aware of when and when not to do this kind of work. In this case, the anvil in question is definitely in need of repair. My go-to rod for hard facing has been a Hobart product-Hardalloy 58, which was recommended by them years ago specifically for this application. However, I can no longer find this rod. It is a self hardening rod that does not crack or cross check provided the layers thickness is limited to 2 passes. It appears to be similar to tool steel grade H-12. I have found similar products by Weld Mold and Core-Met. I have also seen many people refer to Robb Gunther's method using Stoody 2110/1105. The 2110 product is described as work hardening grade that, after work hardening, will have the hardness i'm looking for. However, my experience with other work hardening alloys has been that they really need a lot of pounding to bring the hardness up. I'd rather not have to do a bunch of cold work to the weld deposit to get it to harden. I'm curious what experience this group has had with the Gunther method or even using 2110 by itself. Thanks in advance.
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I'm not of the rules regarding public posting of specific vendors. If you send me a PM I can put you in touch with sources for mokume blocks, bars etc.
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Your questions about hardness and heat treatment of these dies are addressed in some other threads. But seeing the pics you've shared I have real concerns about cracking in the corner of the dovetail during quenching. I had that happen to similar dies I made from 4340. I suggest you use a ball end mill of at least 1/2 diameter to create a bigger radius in that corner. If you can go bigger, like 5/8 or 3/4, I'd do that. these dies are designed for load bearing on the bottom of the die, not the shoulders, so if you have to take a little off that shoulder to improve the corner radius it will not hurt die performance.
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15N20 etc are not specific designations by one company but are the designations used in many of the European countries. 17CrNiMo6 is another example, but there are hundreds, just like in the SAE system. Many times there are equivalents from one system to another and sometimes not. Each system make sense in its own way, but they are all different. Japan has a different system as does China. There is also something called the Unified Number System. In that system, most of the familar SAE designations are prefixed by the letter G and given a couple of extra digits at the end. For example, 1095 is G1095x. In this system Tool steels all start with T, stainless with S, copper with C, titanium and other refractory metals with R. Each system has strengths and weaknesses. I like the SAE system because that is what I learned first and am most familiar with, but I"m sure someone from Europe would say the same about their system.
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Generally speaking it is going to be tough to get 4340 up to HRC 60. The maximum as-quenched hardness of any steel is a function of the carbon content (barring the very highly allowed cutlery and high speed steel types). It typically takes about 0.57% carbon to hit HRC 60. More carbon above that value will not give you higher hardness, but it does give increased wear resistance which is why cutlery grades have carbon close too or sometimes exceeding 1% carbon. For steels in the 0.405 carbon ranges, max hardness is going to be in the mid 50s HRC. Usually, the parts will be tempered, so working hardness will be somewhat, or maybe a lot, less than this. Flame hardening is a technique using a torch to locally heat the surface. Typically a quench nozzle or spray follows close behind the torch tip. The goal is to create a hardened surface layer while keeping the interior of the part at a lower hardness for better toughness. For the power hammer dies that were discussed in another thread, I would suggest a through hardened part rather than a surface hardened one. With the use of special coatings or other treatments such as carburizing and nitriding, it is possible to achieve surface hardness of HRC 60 or above, but I can't think of an application in the blacksmith shop that would benefit from this. This type of hardness is used for gears and bearings in high wear applications or shafting subjected to a lot of sliding wear. In the blacksmith shop, the hardest tools usually will be power hammer dies, anvil faces and hand hammer faces. These should all be made with hardness closer to the low 50 HRC range to reduce the chances of brittle failure.
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Heat Treating 4340 Power Hammer Dies
patrick replied to acein's topic in Heat Treating, general discussion
45-50 HRC is a good hardness for a power hammer die and 4340 is fine material for that application. Your original post in this thread does have some errors though. Normalizing is done at temperatures in the 1600-1700 f range. Those you gave were for high temperature tempering. they will not have the same effect as the higher temperature range. When it comes to heat treatment, especially of critical tools like power hammer dies, control of the heat treat process really is extremely important to getting the outcome you need. Uniformity of temperature during heating, sufficient volume of quench fluid etc all must be considered. Here are the recommended temperatures for your project: 1. Normalize at 1600 F. Air Cool. 2. Austenitize at 1550 F. Oil Quench. 3. Temper in the range of 600-700 F for a final hardness of 45-50 HRC You will want a minimum of 10 gallons of oil. you will need to agitate the part vigorously during the quench. Paying a commercial heat treater to process these dies to your specification will be much cheaper than buying a furnace with the proper controller needed to properly heat treat these dies. of course, if you have other projects planned for that kind of furnace, you could justify the cost that way. -
I'll give you the metallurgy perspective: All the grades will perform equally well. They will all get hard enough for a hand hammer. The choice really comes down to what you can get and what resources you have for heat treatment. If you are buying new steel, 4330 will be the most expensive. 1045 will probably be the cheapest. 1045 is probably the lest likely to crack in hammer-section sizes and should be water quenched. They will all respond about the same to tempering. I'd suggest 450-475 F for 30 minutes per inch of maximum thickness. For a typical 2-3 pound hammer 1-2 hours should be fine. I would be sure to temper as soon as you are done with the quench. I would avoid stamping a makers mark in if you are going to heat the entire hammer to the critical temperature and quench. If you are able to heat just the faces (both at the same time) and quench then you could stamp in a region that will not be above critical. I have seen cracks originate in these kinds of stamps after quenching on numerous occasions.
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Many grades are sold "hot rolled" which may or may not be fully soft. 4340 is not really a tool steel by industrial standards, but it is quite hardenable. Most likely that grade would be sold either in the fully annealed condition or the pre-hardened condition. In this condition the material has been quenched and tempered, but the tempering temperature used is high enough to get something like 30 HRc. 4140 can also be found in this condition. These two grades are most often NOT used at very high hardness. Rather a lower hardness/higher toughness is desired. At HRc 30, the material is hard enough for many applications but can still be machined. Other tool steels like 01, A2, D2, M2 etc are normally sold in the fully annealed condition because they are used at much high hardness and machining them at such a high hardness is very difficult and time consuming.
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Steel faced wrought iron tools were the norm until large scale steel production made steel cheap enough to use for the entire tool. This did not happen until Bessemer steel making (initially 1856 but it really took off a few years later) followed shortly thereafter by the Open Hearth steel making process. The high carbon steels made by the blister/shear and crucible process persisted in industry until the early 1900s because crucible steel making was capable of delivering a higher quality product than the other two method and because high carbon steels (which was what crucible methods were used to make) was not used in such high volumes as the non-tooling grades. When electric arc steel making was introduced in 1906 (US) that began to take the place of the crucible process. From an anvil making perspective we see Hay Budden switching from wrought iron with a steel face to full steel anvils in the early 1900s (I think around 1910 but I'd have to verify that). If I recall correctly , Trenton never made that switch and continued to make anvils into the middle part of the 1900s. You definitely start to see descriptions of the type of steel to use for hand tools in the old blacksmithing reference books in the early 1900s, but when companies like Heller or Champion started using all steel tools, I don't know. I don't know if they ever made wrought iron/steel composite tools. I do have a couple of hammers that were made that way, but there are no makers marks. Where you find this method of construction most prominently is actually in wood working tools such as axes, planes and chisels. Once steel became cheap enough to use for the entire tool, those tool makes made the same kind of switch that the other tool makers did. Interestingly, composite tool construction is still common in high end wood working tools made in Japan and by some other custom tool producers.
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The hy alloys (hy stands for high yield strength) are readily forged. We forge them all the time, usually for ship building as noted above. To hit yield strengths of 80 or 100 ksi, tempering temps in the 1100 to 1200 or so range are used. You can get them harder if you use a lower temp, but they are never going to get hard enough for good edge retention, the carbon is to low. Nickel is about 3.5 % and chrome is a bit over 1% so they would be a bright element in damascus. The hy grades are used in very thick plate sections, sometimes 9 inches or more so it is possible to get big chunks if you need that. A203E is used as pipeline steel. I have only ever seen it in thin plate sections like 3/8 inch. It too has enough nickel to make a bright layer in billets. I dont think it has much else in it and it is also a low carbon grade so not good for edges.
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Why is anvil rebound important?
patrick replied to rdennett's topic in Anvils, Swage Blocks, and Mandrels
This is an interesting discussion. From an engineering point of view, the ball bearing rebound test as done by blacksmiths is really a hardness test. it is a variation on the old Shore Scleroscope hardness test that was essentially the same thing but with a graduated column to contain the ball and allow for quantification of the rebound height. A more modern version of this kind of test is a Leeb hardness test which measures the return height of a spring loaded pin that is "shot" against the test item. There are ASTM standards for both of these tests, though I am not aware of the Sclerosocpe test being used much anymore. I first encountered the ball bearing test on anvils probably 20+ years ago when I read about it on another forum hosted by Jock Dempsey. Assuming blocks of equal mass and different hardness, the rebound of any of these test methods will be higher for the higher hardness block. When you use the ball bearing test at a blacksmithing event to "test" an anvil, you are really just getting a feel for the hardness of the anvil surface. This does not account for variations in geometry (heel vs center of mass for example), the fact that a blacksmiths hammer is much heavier than the ball bearing used in the test or that the hammer is accelerated by the smith and has a much greater velocity and momentum than the ball bearing. Plus, each smith will have a somewhat different swing, hammer grip, hammer weight, shape etc. In addition to these variables, there are variables associated with the workpiece itself (material, temperature, yield strength at that temperature, thickness/height, etc.) that will also influence the user experience. The ball bearing test was proposed as away to eliminate these sources of variation when comparing anvils to each other, but it does not really give you a good idea about the user experience. If the question is narrowed from "does rebound of an anvil matter" to "does hardness of an anvil matter" then you can begin to factor in some of the experiential observations that have already been shared. Clearly, excellent work can be done on both hard and soft anvils. Anvil mass and distribution of that mass can matter, assuming the anvil is not anchored to some larger mass. Chambersburg Engineering published data on a study of the effect of anvil mass for closed die forging hammers and concluded that an anvil to ram weight of 20:1 gave the best performance, meaning that ratio transferred the most energy from the ram into the workpiece. larger anvil to ram ratios did not result in increased efficiency. This was for steam hammers with the steam used to accelerate the ram against the anvil. Of course, a hard anvil will last longer than an soft one, but assuming you only pound on hot steel, the anvil hardness is unlikely to make much difference to the deformation experienced by the workpiece. The one benefit I can see besides longevity to a hard anvil, and where rebound could matter, is if you are a blacksmith that likes to keep a hammering rhythm by tapping the anvil when you are not striking the workpiece. In that specific case, the anvil rebound (hardness plus geometry effects) will tend to throw the hammer back up, minimizing the effort required to lift the hammer for another blow. All of the above assume hot working. If you are doing cold work, things may be different. The article linked by wirerabbit is quite good, though pretty math intensive.