patrick

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Some of those old references show bottom tools strapped down to flat anvils. In those cases there was no shank on the tool or square hole in the anvil. Instead little horns or hooks were forged on the side of the tool. Iron straps fit the hooks and those passed under the heel/horn of the anvil and were held in place with wedges. I dont know when this technique was first used but you can find very old examples of collard work where the collar stock could have been made using a bottom swage held this way.

George-Depth of work hardening is directly related to how far into the item deformation has penetrated. I did an experiment a year ago where I annealed 3/4 square bars of different steel grades, then forged them at room temp under one of my big power hammers. In the case of a pure iron specimen, I was able to forge it cold into a thin sheet, so in that example the work hardening effect penetrates the full thickness of the final part. But in general, the effect is limited to surfaces unless you have a way to induce deformation through the whole cross section. That usually requires massive rolling mills or other very large metal working equipment. Interestingly, if you are considering something like a knife blade, that could be work hardened through the full cross section along the edge and could be made quite hard without heat treatment. this is true of more than just iron. In fact there is a high likelihood this technique was used to improve the strength and hardness of bronze age weapons and tools. Latticino-you are absolutely right that DI and steel are two very different classes of material. Both are iron based, but DI and some of the other forms of cast iron have so much carbon that some of it exists as graphite. This is not true of any but a very few steels. Ductile iron, especially when properly heat treated, will have properties comparable to many steels, so in that sense it could be a good substitute, but definitely not the same material and is should not be called steel. Cast Steel is in fact just steel that has been cast to shape instead of being forged. Most of the anvils made today are genuine cast steel. There are some ductile iron anvils on the market. A foundry local to me made one as a trial that I got to use. It was not heat treated and was definitely softer than a properly heat treated steel anvil, but it was a perfectly serviceable tool. Had the alloy been adjusted a bit and it been heat treated I think it would have made a very good anvil. As for the work hardening in old anvils, yes I'm sure that there is some, especially when you see evidence of mushrooming or sway back, but generally I'd say that unless you use the anvil primarily for cold work, such as in the case of a sawyers anvil, the amount of cold work is really pretty minimal. the hot steel is doing the plastic deformation, not the anvil or hammer. Remember, the anvil face has to be soft enough to yield plastically. Even in the sawyers anvil example, if the face is hard enough, the hammer/work piece will just bounce off without inducing plastic deformation. If that is not happening, you are not really getting the cold work I'm describing. I've looked at lots of metal under the microscope and you can see deformation and its effects on individual grains. dislocations are not seen without the aid of exceptionally high magnification, much higher than you can get with a conventional microscope. Something like a tunneling electron microscope is needed. An excellent example of work hardening on a common item is rail road rails. Those are soft enough that they do plasticly deform on the surface. Over time, that hardened layer will spall off, leaving a pitted or flaked surface. Eventually such rails have to be replaced.

I should probably start a separate thread just on work hardening as that is a topic that does not seem to be well understood. There are at least two kinds of work hardening. The first is based on the idea that a crystal of metal can be deformed resulting in "misalignments" of the atoms within the crystal. These are called "dislocations" by metallurgists because the structure of the crystal has been dislocated relative to its most stable arrangement. Note that this is not the same as the change in structure we get via the transformation from austenite to martensite. This is simply taking the crystals we have at room temp and deforming them. The dislocations are happening at the atomic scale so it is possible to get a very large number of them into one crystal, but the more we have, the harder it is to get more created. This results in an increase in the actual metal hardness and is what we see as "work hardening". The second method also involves plastic deformation, but some metals will transform to martensite with sufficient plastic deformation. This is what we usually think of when dealing with very high manganese (10% or more) steels. These steels are often used in cast components for railroad and mining applications and especially for hard surfacing welding overlays. It is these alloys that are often recommended for anvil repair. The questions of work hardening a ductile iron anvil falls into the first category. for that method of work hardening to be effective you have to be able to plastically deform the anvil face. With out that, there really won't be much in the way of increased hardness. However, ductile iron can be heat treated to fairly high harnesses. if that is done, then not only do you not have to rely on work hardening, but you really can't get much work hardening anyway. for example, if you start with a heat treated hardness of HRc 50, you are unlikely to be able to deform the anvil face sufficiently to get any increase in hardness, especially if you are mostly hitting hot metal. When we see tools like hammers and anvils fail by spalling or chipping, that is not usually evidence of work hardening but failure by some other mechanism. Personally, I don't like to rely on work hardening as a method of hoping my anvil face will get harder over time. The only way that is really going to be effective is if you take a big sledge and intentionally beat on the anvil face. that will work, but it is very hard to get a smooth uniform finish and that increased hardness region is not very thick so you run the risk of grinding it off. My preference is to heat treat tools to the desired working hardness. You might be wondering why we don't get work hardening when we are forging. We are in fact getting the same crystal misalignments forming, but the high temperatures used in forging provide enough thermal energy to that those misalignments are "reset" automatically, usually by brand new grains of austenite be nucleated. We don't see that happening during forging because it is very fast. It can happen during forging or during re-heating so we don't really experience the "work hardening" effect during hot forging.

I really love how this thread had changed subjects several time. Kind of amazing how we went from low cost quenching to microstructures and now to word origins.

Frosty-I don't actually know the answer to your question about the pyrites. That's getting more in the field of mineralogy and geology that metallurgy. That would have been an excellent question for Thomas, who most likely would have know the answer to that one off the top of his head.

George- the earliest folks to look at metals under a microscope (Harold Sorby in July 1863) started by initially looking at rock and minerals, the metorites and finally metals. You might recognize that when I talk about the structures in steel I use terms like "pearlite" "ferrite" "austenite" etc. Those "ite" endings were chosen by the early metallurgists because the structures they were seeing did in fact resemble those of rocks and minerals and the "ite" nomeclature was already well established in that part of the scientific community so they just adopted it for metals. Several of the structure names we use in metallurgy "Martensite", "Austenite" and some others are named after specific people, just as is done in other branches of science.

George- You are exactly correct that etching is used to reveal structures before doing that micro hardness test sometimes. A single grain is often too small to measure its hardness and often there are other features located at grain boundaries. For example, in high carbon steels, (those with over about 0.8%) you sometimes find carbide coating the grain. In this case you basically have an M&M structure-Hard on the outside and soft on the inside. Iron carbide is about 70 HRc. Usually carbides are super small, so when we measure hardness with bulk methods like a conventional HRc tester, we are not measuring the hardness of the carbide itself, but the effect that those little carbides have on preventing plastic deformation of the iron next to the carbides. In the case of some very high carbon steels like Wootz (1.5% carbon) or D2 Tool steel (similar or slightly more carbon than wootz) you do see large carbides in addition to the little ones. (I spent several hours today looking at carbides in wootz in preparation for a lecture I am giving next week). If we ignore the high carbon steels and look at the simplest case-pure iron or any other pure metal, we do know that the grain size will affect the strength, completely independent of heat treatment. If I process pure iron such that it ends up with small grains and compare the yield strength to a larger grained specimen, the smaller grain specimen will be stronger. In pure iron, we do not and cannot have martensite, just ferrite or austenite, depending on the temperature. the smaller grained specimen will have a higher strength (not by a whole lot in pure iron, but still a measurable difference) because the grain boundaries act as barriers to plastic deformation in a way that is a little bit similar to the way carbides do in the high carbon example above. The more boundaries there are, the more force is required to make the metal plastically deform. Likewise, in high carbon steels, we can get to fairly high bulk hardness (HRC 40,) without making martensite if we control the size, shape and distribution of the carbides in a softer matrix like pearlite. This technique is used in some things like rail road rails where martensite is too brittle to give a long lasting part.

Just to add a little bit to the discussion of the chart and how those values were measured: A common tool in a metallurgical lab is a micro hardness tester. This instrument allows you to test the hardness of all sorts of very small features within the microstructure of materials by first locating the feature using a microscope then, without moving the specimen, an indenter is positioned over the area of interest and a hardness meusurement is made. One of the advantages of this type of instrument is that the platform that holds that specimen can be positioned using a micrometer type adjustment. This lets you precisely move the specimen a desired distance in fractions of an inch or fractions of a millimeter from some reference location and then make another measurement. In the case of 1/4 thick steel bar, the way I would have tested this would have been to conduct the quench, then cut a small bit using a water cooled abrasive saw. This could be mounted in epoxy to create a round disc about 1.25" in diameter with the steel in the center. The steel is position so that the thickness (1/4") dimension is visible when looking at the face of the disc. This is then ground and polished to a very fine finish, usually 1/2 micron grit size. Basically it is a super mirror finish. This is then placed under the microscope and the edge of the steel is located in the view finder. The edge becomes your zero position. The specimen can be moved precisely a few thousandths a time. A hardness measurement can be made at regular intervals. This allows for an assessment of change in hardness through the thickness of the specimen without having to grind a little, check, grind a little check etc. I dont' know if this is the method that Dr. Thomas used but I'm sure he is aware of the technique and if you have access this equipment it is probably the best way to asses change in hardness versus location from the as quenched surface. What Dr. Thomas is showing in his graph is that a 1/4 inch thick piece of 1084 heated to 1475 and quenched in canola oil will not get as hard as when it is quenched in the other fluids shown. If the conditions are changed, such as if the section size is thinner (as in the case of most blades at the time of quench), the choice of austenitizing temperature, which might be differenet depending on your preferred temperature, the grain size and the level of agitation in the bath, the as-quenched hardness of a 1084 blade quenched in canola oil likely will be different, and possible quite a bit harder, than shown in his experiment. In fact, by looking at the graph, we can see that when quenched in water, the hardness is in the upper 60s HRc. Water has a faster cooling rate than the various oils shown. If we increase the cooling rate by reducing thickness, as in the case of a knife forged or ground to shape before quench, rather than by swithing away from canola oil, we will in fact get higher hardnesses than shown on the graph. Will they be as high as those obtained with water? I don't know. Possibly. Once you have cooled the steel fast enough for it to reach its maximum hardness, further increases in the cooling rate will note result in any further increases in hardness. There is no doubt that all sorts of fluids have been used to quench for thousands of years. Keep in mind, though that up until the mid 1850s the only alloys available were iron/carbon combinations. These alloys can only harden to extremely shallow depths, so water quenching was common and necessary. Various oils were used for parts with small thicknesses. After about 1882, alloy development really took off. New alloys would harden to much greater depths and maximum hardness could be achieved with slower cooling rates. At about the same time E. F. Houghton developed the first synthetic oil quench. This had the distinct advantages of giving manufacturers a quench fluid that was consistent from batch to batch and maintained a level of consistency of performance that was unparrelled at the time. Oils like canola and other animal or vegiitable based products degrade over time, especially when regularly heating and cooling large masses of steel. In industrial practice, various synthetic oils are still widely used, but now water soluable polymers have replaced them in many applications becuase of the reduced risk of fire, smoke and in some cases, cracking.

Bill-if you pm me or email me I can help get you in touch with folks who can set you up with replacement cushions. I'm in Janesville, WI. I'm pretty sure we met years ago. that shop fire looks horrible. Very sorry to see that. Patrick

Blast Furnaces-These are in fact still the predominate way of converting iron ore into pig iron. There are less that 10 still operating in the US but they are widely used outside of the US. The pig iron that is produced by a blast furnace is then further processed in a basic oxygen furnance (BOF). A BOF is NOT used when make steel directly from scrap metal. In that case and electrical arc furnace is used to melt the scrap metal which then has the chemsitry adjusted to make the desired grade. Since both the blast furnace and the electric arc furnace input heat into the process, I'm sure you could get the gold to melt. Dropping cold solid metal into a bath of liquid steel without adding additional heat to the system is not likely going to result in complete melting of the object dropped into the liquid metal. For a steel works in 1944 you most likely would have been dealing with an open heath style system couple with a blast furnace. The blast furnace would have made pig iron that would have then been converted to steel. Open hearth is no longer used anywhere in the world, but was common back then. If you setting is more of a foundry than a steel mill, melding could be done via electric arc furnace or induction melting. The difference between the foundry and the steel being that the foundry just melts steel and pours that into finished shapes while the steel mill is converting iron ore into steel or scrap steel into new steel raw forms like bars and plates. For the scenario originally described, a 90% gold with 10% of iron would like not have much color change from gold. It might have some, but you would not be able to "hide" the gold in the iron.

Frosty- It's not the presence of the graphite but its shape that makes the difference with respect to properties. By making the graphite round balls as in Ductile iron, you get a material that has good toughness, in some cases on par with steels, but it still has the casting advantages of a very high carbon material (lower melting temp that steel and good flow characteristics in molds). Ductile iron was developed in the 1950s and is arrived at by adding Magnesium to the liquid metal just before it is poured in the mold. This is what make the graphite take on the ball shape. Prior to this, a similar structure could be achieved by heating grey iron for several days or more to high temperatures. This process also resulted in spherical graphite an iron processed in this way was called Malleable Iron. It is no longer made as far as I know since ductile iron is so much cheaper and faster to make.

Cast iron, and specifically grey cast iron which is what Fisher, Star and Vulcan anvils used for the body, has so much carbon in it that much of that carbon exists in the form of graphite. In the case of grey cast iron, this graphite is in the shape of interlocking flakes. It is this shape of graphite that is changing the resonance characteristics of the metal. If you compared this to ductile cast iron in which the graphite is in the shape of little balls, you'd find that the ductile iron rings much like steel. This is also why grey cast iron is so brittle. The graphite flakes act like cracks or even voids. Since there are so many of them, the distance an actual crack has to travel through the metal between the flakes is pretty short. I usually describe grey iron as "pre cracked" metal. It has it's uses, but it is not my favorite material. Frosty's question was about the difference in resonance based on hardness. There is some measurable difference in this quality, but this not usually the dominate factor in anvil ring. That has more to do with the shape of the anvil and how it is mounted. If the mounting method limits the vibration of the entire tool, then you wont get much ring. There is a method of evaluating hardness based on ultrasound. I don't recall the ASTM spec that gives the method for the test because it is not one that we use, but it is used when you need to evaluate hardness without leaving any marks on the part. A simple way to test the resonance question is to take a round bar of hardenable steel. Drill a hole in hole through one end so you can hang it on a string. Anneal the bar, string it up and strike it. then quench the bar and repeat the experiment. If you are really curious, temper the quenched bar at increasing tempering temperatures and repeat the ring test. By using rounds of the same steel grade, diameter and length, you remove the geometry/size variable and can isolate only the microstructure variable. A further test that could be intersting would be to compare the resonance properties of anneal, worked hardened and quenched and tempered specimens since, in some cases, you can achieve the same hardness via cold work that you can via a quench and temper, but the microstructures are different.

Heat treating large pieces is a topic on which I am a bit of an expert (professional metallurgist in an open die forge shop for 20 years) so I thought I'd chime in on this discussion. The quench tank shown in that video is pretty standard for any company that is heat treating large steel parts. In the shop where I work we have two-both containing 50,000 gallons and both capable of handling 50,000# of steel at a time. These are not the largest we have in the company, just in the shop where I spend most of my time. In modern industrial practice, full heat treatment, that is fully austenitizing the entire cross section and quenching it, is common even when some later heat treatment will be done to obtain different properties on the surface. Some folks already mentioned gears, and this is a good example. A surface hardened gear, especially one that is used in a large mining vehicle like a dragline, (these gears are roughly 15 feet in diameter or bigger) are often made from grades like 4340. the gear is quenched and tempered in a bulk manner to achieve a hardness/property combination that gives the necessary core toughness. This might be a rockwell hardness of 30-35 HRc. Later, after the teeth have been machined, the surfaces are re-heated using inducting heating or an oxyfuel torch and quenched. Tempering is done at a low temperature to preserve most of the hardness in the surface. The depth of this surface hardening can be adjusted a bit, but is usually well under one inch. This approach results in a good combination of toughness in the core and wear resistance on the surface. An alternative method to this is to use a steel grade with lower alloy content, for example 8620, then instead of performing a bulk heat treatment as described above, the entire part is austentized in a high carbon atmosphere. The carbon will diffuse into the surface of the steel increasing the hardening potential at the surface. The effect is essential the same as if you forge welded a high carbon piece of steel to a low carbon block. When the entire thing is heated and quenched, only the high carbon portion gets hard. This brings me to the properties needed for anvils. As Joe noted in his post, an anvil does not need to be hard all the way through. Historically, they were not hard all the way through because the desired properties could be most cost effectively acheived by forge welding a higher carbon plate to a low carbon body. Prior to about 1860, the cost of steel was so high that it was used extremely sparingly. Since only the high carbon plate has the potential to get hard, there is no benefit to heating the rest of the anvil for heat treatment and if you did, you might struggle to cool the plate fast enough to get the desired hardness. In modern manufacturing, casting is the preferred method (that is most cost effective) of making anvils. Steel is one of the cheapest materials available on the planet, so there is little reason today to make an anvil of composite construction. It would actually be more expensive to do that since labor is so much more costly than material. Today, there are a wide variety of alloys available. Some are through hardening in large sections, others are not. For a period of time, new anvils were being imported from the Czech republic and being sold by Old World Anvils. These were made from grade 1532 which is a medium carbon steel containing only manganese and carbon as alloying elements. This grade is NOT a through hardening grade in anvil sizes so even with a quench as shown in the video, only the surfaces would be hard. A very effective anvil with a hard face could be made from this grade by induction hardening just the face, but hardening all the surfaces would not detract from the anvils performance. The Nimba anvils were made from 8640 and I've head of others being made from 4340 and H13. All three of these have the potential to harden uniformly in typical anvil sized sections. Doing so is not necessarily going to result in an anvil that is more likely to break. Some modern steels can be both hard and tough at the same time, and though toughness does decrease with increasing hardness, as long as the toughness is high enough, there will be no issues with performance. An anvil with only the face hardened is not necessarily going to be a better performer than one that is fully hardened or surface hardened all the way around. Performing surface hardening on an anvil is a fairly unique process and few heat treat shops are equipped for that type of work, so what you see in the video is actually typical, not an indication of ignorance on the part of the heat treat shop. AND.... When it comes to this type of thing, the responsibility for defining the products properties lies with the purchaser, not the foundary/forge shop/heat treater. If the person who had the anvil made didn't want a through hardened part that should have been specified on the purchase order. Most likely doing so would actually raise the cost of the part since unique heat treatment facilities are required for that.

I just saw the news. Like Terry, i had a chance to spend some time with Thomas last September. Im very glad i did. It is exceptionally difficult to express just how big an influence Thomas has had on me and the entire blacksmith community. He will be missed, but his influence will last for generations.