Atlantic 33 Steel
There are a few places to purchase this Atlantic 33 “non-tempering” steel so I have been getting questions about it over the past couple years. The information is pretty scant and the descriptions are mysterious and confusing to anyone who knows steel [1]. In the advertising it says things like: “Drawing of temper to suit different requirements is unnecessary and completely eliminated.” Also there is no composition listed and the heat treating instructions are very barebones. “Suitable hardness is obtained by merely heating the tool and quenching it in water.” And, “May be heated to almost a melting heat without danger of distortion.” It basically just says to heat treat it however you feel like and skip the tempering. If it’s true that it doesn’t matter how you heat treat that is great, but otherwise it would be nice to know how to best heat treat the steel.
What is a Non-Tempering Steel?
While the advertising online calls Atlantic 33 “a new departure alloy steel” it is in fact not new, it has been around since the mid 1930s [2]. Here is an ad for the steel from 1937:
1937 ad for Atlantic 33
However, “non-tempering” steels actually go back even further than Atlantic 33. The earliest I found was the steel “ABC” made by Darwin and Milner starting in 1909 [3][4]. This steel company was run by Paul Kuehnrich who developed several tool steels including D3 and D5 (later slightly modified to be the common D2 in 1928). He was an early pioneer in tool steel who I wrote about in my book The Story of Knife Steel.
Another early non-tempering steel I found was called Simplex which in 1915 had some advertising which uses a lot of language similar to what we still see for Atlantic 33:
Composition of Atlantic 33 and Other Non-Tempering Steels
There were several other non-tempering steels that would be released over the following years though they never gained much prominence. Here are several that were available in 1954 [5]:
You can see that all are medium carbon, roughly 0.3-0.4%. Each has a chromium addition and either W or Mo (including the original ABC). There is also a Cu addition in some of them. The reason for the copper addition is somewhat of a mystery. Copper additions are not unheard of but are relatively uncommon in low alloy steels, especially back in the 1930s. Copper can help with grain size control from copper precipitates but I have no insight into the 1930s thought process by Atlantic Steel. In any case there were several non-tempering steels without any copper so it does not seem to have been necessary.
What Makes Them “Non Tempering”?
Even in the 1915 ad for Simplex they do not claim that nothing happens during tempering of these steels. It says that “No tempering is necessary except in the case of very small tools, such as punches, when it may be drawn to a straw color with advantage.” In other words, the steels benefit from tempering just like any other steel. However, they selected the carbon content to be in the range of 0.3-0.4% so that they would obtain sufficient hardness for the intended tools while not being brittle. Lower carbon steel is tougher and more ductile than high carbon steel, so you can achieve similar toughness by tempering less with a lower carbon steel. It is kind of an odd idea to recommend skipping tempering altogether. Heating to 300-500°F degrees doesn’t seem all that onerous even in these supposed simple shops they are talking about. So it seems to be a case of marketing more than anything else. Other 0.3-0.4% carbon steels could be used in a similar way. The Ryerson Non Tempering steel could even fit within the 4135 steel specification though the chromium content is borderline for 4135 (0.8-1.1% Cr).
What Happened to Non Tempering Steels?
So Non-Tempering steels saw some use in the industry, though were never particularly popular. Seemingly they were the most useful in shops that have very simple (in other words, bad) heat treating facilities. Those shops that wanted to make quick blacksmith tools, punches, shear blades, and other tools that are subjected to impact at room temperature. The steels fell out of favor by the 1960s and were largely replaced by silicon (S2, S4, S5, S6) or tungsten shock-resisting steels (S1) [6].
What is a Flutagon?
Initially the Atlantic 33 steel was advertised on its own. However, now you often see the steel called “Flutagon Atlantic 33” or “Atlantic 33 Flutagon” and even some people calling it only “Flutagon.” Flutagon was a trademark term by Atlantic steel in 1940 [7] for a new shape of the steel bars they were using that they claimed was more convenient, etc. Because the new shape was advertised for Atlantic 33 the two names became somewhat conflated. However, I think it is better to call the steel “Atlantic 33” and use Flutagon to refer to the shape of the bars instead. After all, the steel is also available in hex bars. Here is a 1941 ad for the new Flutagon shape for Atlantic 33:
1941 ad for flutagon shape
Datasheet for Similar Steel
I did not find a datasheet for Atlantic 33 but I did find heat treating information for Bethlehem’s similar “Non-Tempering” steel from 1958 [8].
Forging and Annealing
The forging temperature range recommendation is pretty standard, 2100-2150°F (1150-1175°C) and finish at 1700°F (925°C).
The datasheet says annealing is recommended if machining will be performed after forging. It says to start at 1400°F (760°C) and cool at a very slow rate of 20°F/hr (11°C/hr) to 900°F (480°C). It is pretty standard for datasheets to recommend such low cooling rates.
It is somewhat strange they recommend such a specific procedure for annealing given the intention of the steel is simple heat treating setups. The steel could be annealed by heating to nonmagnetic and putting in slow cool media like vermiculite.
Normalizing?
There is no mention of normalizing in the Bethlehem datasheet. Perhaps with the low carbon content they were less concerned about it. If you do normalize, the similar 4135 steel has a pretty typical 1600°F (870°C) normalizing temperature.
Austenitizing Temperature
One of the selling points for the steel being viable for simple heat treating setups is that it can be quenched from a range of austenitizing temperatures and still have decent properties. The extra alloy added to the steel helps it resist grain growth, thus having decent toughness even with relatively high austenitizing temperatures. However, perhaps we shouldn’t over-exaggerate this point too much. There is a small drop in toughness and ductility, and a small increase in grain size by austenitizing hotter than the optimal range, which appears to be about 1500-1600°F (815-870°C), see page 170 above. 4135 is typically austenitized at 1600°F (870°C) which is consistent with those results. The steel is relatively insensitive to overheating but if using a furnace I would stick with that range.
Quenching
This is typically an oil hardening steel. Tool Steels by Roberts [6] recommends using water if the cross-section is larger than 2-1/2 inches in diameter.
Tempering Temperature
While the steel is advertised as “non-tempering,” you can see on the page 170 chart the effects of tempering. Comparing “As-quenched” (not tempered) to 300°F (150°C) you can see that the low temper leads to the same hardness (555 Brinell or about 54 Rc), but an increase in yield strength, as well as elongation and reduction in area (measures of ductility). Increasing the tempering temperature to 400°F provides a further increase in yield strength, elongation, and reduction in area at the cost of a little hardness (~1 Rc). So unless I was in a big hurry I would probably still temper these “non-tempering” steels in the range of 300-400°F.
Summary
“Non-Tempering” steels have been around since at least 1909, while Atlantic 33 came out in the 1930s. The steel became connected to their trademark “Flutagon” shape in 1940. The main advantages of non-tempering steels are simple heat treatment where a wide range of austenitizing temperature is acceptable for good properties. While they are advertised as not requiring tempering, the properties actually are improved by tempering. However, the relatively low carbon content is what gives the steels decent properties even when skipping tempering. Other steels with 0.3-0.4% carbon would also behave similarly if tempering was skipped and there isn’t anything particularly special about non-tempering steels apart from the marketing. Austenitizing is best in the 1500-1600°F (815-870°C) range and I would temper Atlantic 33 at least at 300°F/150°C for the small improvement in properties.
[1] https://www.canonballforge.com/about-a33
[2] https://archive.org/details/sim_industry-week_1936-04-06_98_14/page/66/mode/2up?q=%22non+tempering%22+
[3] https://books.google.com/books?id=WH8zAAAAIAAJ&pg=PR57&dq=%22non+tempering+steel%22
[4] https://babel.hathitrust.org/cgi/pt?id=wu.89074782335&seq=282&q1=3332
[5] https://archive.org/details/sim_american-machinist_mid-november-1954_98_24/page/149/mode/1up?q=%22atlantic+33%22
[6] https://babel.hathitrust.org/cgi/pt?id=uc1.b4418480&seq=426
[7] https://books.google.com/books?id=logbAQAAMAAJ&pg=PA823&dq=%22flutagon%22
[8] https://babel.hathitrust.org/cgi/pt?id=uiug.30112008811041&seq=172
Great write up on this steel. Thanks for taking the time to research it and educate us on this and other steels. You’re doing great work Larrin.
Thanks again
No tempering seems like an odd idea. Tempering is much simpler than correct heat treating. It does take an hour or two though ,so maybe that’s the idea.I’d guess you’d get better proprieties from 5160 or a shock steel, hardened and tempered to 400 degrees or whatever. For that matter, shock steels might work w/o tempering if you were not going to use them for breaking concrete or something.
I find A33 useful for hammer punches and drifts that while using tend to get red hot, I see the main benefit of the “non-tempering” aspect being that these tools can be quenched and immediately used without becoming brittle. I have used more modern tool steels (H13 and S7) for punches and drifts and have suffered from chipping and breakage in addition to slower work waiting for the tools to cool to the point where it is safe cool further in water. My personal experience is the cooler I can keep punches and drifts the less deformation I see on them as collateral damage while forging hammers. Another benefit is I can quench in salt based forging lubricants like Fuchs Forge Ease without fear of brittleness. There has been almost no scientific rigor to my experience, just on person’s opinion. Thank you for this article, I have had good experiences with A33 and always wanted to see more technical info on it.
H13 is intended to mantain harness above 50 RC at 1000 degrees.But of course you can’t harden and temper it properly in a forge.