Talk:Tempering (metallurgy)

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i don't understand the reference to music.

is there such a thing as cryogenic tempering? - Omegatron 17:23, May 26, 2005 (UTC)

Traditional blacksmiths sometimes use music to time their processes; waiting too long leaves a soft product, too little time means brittleness, so a repeatable process was necessary, and a song is easy to teach and to reproduce, without requiring any equipment or even the use of one's hands.

In the strict sense of the word, there is no such thing. Cryogenic treatments can have a profound effect on the "temper" (loosely speaking) of certain steels if their composition and prior heat treatment are such that they retain some austenite at room temperature, but that process is not time-sensitive at all. The transformation from austenite to martensite (mostly accomplished through quenching) is driven farther and farther as temperature decreases, which leads to more of the harder component; in higher-alloy steels such as austenitic stainless steel, this can require very low temperatures indeed. However, (1) the transformation between these phases is instantaneous and not driven by diffusion at all, and (2) this treatment causes more complete hardening rather than moderating extreme hardness, both of which make the word "tempering" technically incorrect. Perhaps I should make this more clear in the article on martensite. I wanted to make a more complete heat treatment article, but time constraints and the opinions of prior contributors have prevented me from doing so.--Joel 21:24, 26 May 2005 (UTC)

Come to think, I should just make up an article on cryogenic hardening, and put in a link from the second paragraph.--Joel 21:32, 26 May 2005 (UTC)

Tempered glass

This article doesn't cover tempered glass. Does an article already exist, should it be added here, or should another article be started? -- Kjkolb 05:08, 19 December 2005 (UTC)

There's a section on tempered glass referenced on the disambiguation page for temper. Is that adequete? Tom Harrison ^(talk) 13:58, 19 December 2005 (UTC)

Hmm, I don't know how I missed that. Thanks, Kjkolb 16:07, 19 December 2005 (UTC)

This article is in need of some work.

It looks like I added the first in-line references, but that's just for the picture caption. I'll come back and try work on this article soon. There are many problems with the steel tempering sections. Tempering steel is most often done in the range of 400 to 725 degrees F. Very hard steel, like hammers and cold chisels, are usually tempered between 400 and 440. Steel with a a lot of flex, like springs, are tempered from around 600 to 650 degrees F. Much above this temperature and steel loses its elasticity, and below 400 has very little effect.

Blacksmiths use a variety of techniques to judge temperature, but time is not a very reliable one, especially with old-time techniques. It's very hard to guarantee an even temperature with coal, and less so with charcoal. Tempering was most often done by judging the color of the steel, as described in the photo. The Farmer's Almanac lists how the various colors would have been applied to produce different products. I'll gather some refs and get back to this article soon. Zaereth (talk) 02:31, 4 November 2011 (UTC)

Precipitation hardening

As mentioned in the above section, I plan to begin doing some work on this article soon. One of the first things that should be addressed is the precipitation hardening section. As the name suggests, precipitation hardening is not tempering. Tempering refers to an increase in toughness caused by a decrease in both hardness and brittleness. Precipitation hardening (also called aging) is just the opposite. This produces a decrease in toughness by increasing hardness and brittleness. Most precipitation hardening alloys will age at room temperature, but are sometimes "artificially aged," which means heating to a temperature that is below the A₁ transformation temperature, to speed up the aging process. This is different from tempering also, in that time is the dominant factor, whereas in tempering, temperature is the dominant factor. Tempered steel must be heated to a precise temperature, but only needs to be heated long enough for the temperature to reach an equilibrium throughout the alloy. In precipitation hardening alloys, the temperature does not always need to be as precise, but must be aged for the proper amount of time at that temperature.

I think this entire section should be removed, because it is irrelevant to the article. Does anybody have any comments or suggestions? Zaereth (talk) 20:34, 13 February 2012 (UTC)

It's an archaic use, but historically "tempering" was also used to refer to hardening. Andy Dingley (talk) 21:46, 13 February 2012 (UTC)

While I agree that a section on history would be useful, I've never read that in any of my sources. Tempering is an old process; one that has been used for steel for thousands of years. This has always referred to the process used after quenching (hardening) to relieve some of the excess hardness and, along with it, some of the brittleness. (These are usually treated as separate processes, because quenched steel is not always tempered. Files, for example, are untempered.) The only other ancient process of hardening I know of is cold hammering, which was used for non heat-treatable metals like bronze, copper, and brass. Precipitation hardening alloys, as far as I know, didn't come into use until the early 1900s. The phenomenon was discovered in 1906, by A. Wilm, when after quenching an aluminum-copper-magnesium alloy, he dicovered that the hardness increased after a period of time at room temperature. Artificial aging was discovered some time after that. Zaereth (talk) 23:03, 13 February 2012 (UTC)

I first came across the use of tempering to indicate hardening (although as you note, precipitation hardening dates from duralumin) when reading that dreadful Alex Weygers "Modern Blacksmith" book. However after claiming this as a mistake on Weygers' part, I was then pointed at a whole load of medieval and rather later ferrous metallurgical texts, mostly about armouring and cutlery, where "tempering" is simply used for the whole process of both hardening (by quenching) and tempering.

Although we shouldn't encourage this now-confusing use, we ought to note that it has been used both ways. Andy Dingley (talk) 00:02, 14 February 2012 (UTC)

That sounds reasonable. How about if we add a brief history section, which could cover this confusing usage. Then we could either eliminate the precipitation hardening section, or, perhaps, reduce it to a few lines to explain that, although the method is similar, the physical process involved and desired results are very different. (I pretty sure the book Practical heat treating describes this in similar terms.) That way we could dispel any confusion and keep the "main article" link. How does that sound? Zaereth (talk) 00:45, 14 February 2012 (UTC)

Fine by me. Andy Dingley (talk) 00:51, 14 February 2012 (UTC)

Ok, then I'll review my sources and work on this over the next couple of weeks. (I tend to work rather slowly because, like swordsmithing, Wikipedia is just a hobby for me.) I will also be adding a lot of info, and correcting many mistakes. (The description of austempering, for example, is all wrong. Austempering consists of quenching in a bath of molten lead, to well above the martensite start temperature, then holding it there until pure bainite forms, without any pearlite or martensite.) Thanks for your assistance, Andy. Zaereth (talk) 01:22, 14 February 2012 (UTC)

OK, I think I'm about finished with this article. It could probably use a section on the physics of tempering, but I'll have to read up and refresh my memory on that. I know it's a three-step process in which unstable carbides precipitate and form into stable carbides, involving terms like "lath martensite" and "plate martensite," but I'll have to read-up and ponder it some more. I'll probably keep working on this article sporadically.

I'll try getting a few more photos, or maybe a diagram or two. The interrupted quenching section could probably use a TTT diagram, similar to the one in the heat treating article, but which shows the cooling used in ausempering and martempering. If anyone here is good with graphics, any help would be appreciated. Zaereth (talk) 01:16, 23 February 2012 (UTC)

Contradiction?

--Doesn't the article contradict itself at the start in terms of its definitions of hardness, toughness and brittle towards the end of the first paragraph as it mixes hardness and brittleness. If brittle is the opposite of tough it should say that heat tempering (e.g. in a furnace), to increase hardness, leaves the material overly brittle which then needs to be resolved by slow tempering (e.g. in an oven at 400 degrees Celsius) which reduces the hardness and hence brittleness of the material slightly to make the material more tough. (Bed633) 16:04 08 Febuary 2015 (GMT)

I'm not really seeing what you're talking about. Perhaps if you copy/paste the problem sentence(s) here it would make it easier to understand what you mean.

Slow tempering or fast tempering can produce the same result, depending on temperature. Hardening is actually an entirely different process, called quenching. The reduction in brittleness is a side-effect of reducing the hardness, but brittleness is not quite the opposite of toughness. Brittleness is the result of internal stresses created from uneven cooling, causing a material to respond to stress in the same way that glass does. By the time an item is tempered to a spring-hardness, most of these internal stresses are relieved and the steel is no longer brittle, meaning that it can bend before breaking, but eventually it will reach a breaking point. The hardness can still be reduced and the toughness increased, despite the fact that most of the brittleness is already gone.

As another analogy, take tempered glass. This method of heat-treatment causes no change in the hardness of the material. Its hardness stays the same regardless of tempering. However, the internal stresses created work against each other in such a way that both toughness and brittleness are increased. The tempered glass will be much more difficult to break, but when it does, it will shatter into a thousand pieces. Zaereth (talk) 21:20, 8 February 2015 (UTC)

I believe Spanish translation-link is wrong

After reading the articles in English and Spanish I believe they are linked wrong. This article, tempering, links to es:Templado_del_acero, probably because the words share the same root but I believe Quenching should correctly be linked to es:Templado_del_acero and this article should be linked to es:Revenido. Maybe someone can have a look at this. GS3 (talk) 23:25, 3 January 2016 (UTC)

You may be right, but I don't speak Spanish (even though I watch Bajo el Mismo Cielo quite often). Google translates revenido as "tempering" and templado del acero as "mild steel." Unfortunately, google is a bit too literal at times, for instance, translating por favor as "for favor" when it really means "please." Therefore, someone who actually speaks Spanish should correct the links, if necessary. Zaereth (talk) 22:46, 7 January 2016 (UTC)

Well, Spanish is my native language but I am not an expert in this field. Google translates revenido as "tempering", which I believe is correct, and templado del acero as "mild steel" which is only kind of wrong in that templado del acero is the quenching process and not the resultant steel. From the descriptions in each Wikipedia page I am pretty sure tempering is "revenido" and quenching is "templado" but I do not know how to correct the links to the Spanish Wikipedia so I will let someone else do it. GS3 (talk) 16:17, 17 February 2016 (UTC)

I do have some expertise in this, plus a fascination with linguistics. Being curious, I did a little digging to see how the terms are used in context. From looking at a few sites like this one and comparing the usage in context, it appears that both may be correct. In English, the word "tempering" is often used to describe both hardening (quenching) and softening (tempering) of steel. Today this is more of a layman's mistake, but not so long ago only blacksmiths really understood the difference. It was really William Austen (the man that austenite was named after) that worked to sort out the difference in a scientific sense, but to this day people often use the word "tempering" to describe both techniques. (See the history section of this article.)

It appears that the same confusion exists in Spanish, and that the phrase templado del acero refers to the finished product rather than the process used to make it. It appears to mean both hardened steel and tempered steel, as well as mild steel, depending on the context in which it's used. (Mild steel simply has a low carbon content, and does not refer to any heat-treating technique.) It appears that the Spanish word for the tempering process is technically revenido and the word for the quenching process is temple. However, that is only based upon a little bit of research, so hopefully a Spanish-speaking expert will come along to assist. Zaereth (talk) 01:28, 18 February 2016 (UTC)

Let's do the easy part first which is the language. I am a well-educated native speaker of Spanish and I can assure you "templado del acero" in not a type of steel but a process done to steel.

If we translate "temper" as "templar" then "templado del acero" means, literally, "tempering of steel" and not "tempered steel" which would be "acero templado". That is simple grammar and does not need any further research.

I have consulted in a metal-working Spanish language forum (metalaficion) and, as can be expected, there was a lot of the discussion which went over my head but there was a simple post with which many people said they agreed and it says "... the English word 'tempering' and the Spanish word 'temple' lead to confusion because they are similar but they are not the same thing: 'tempering' would be 'revenido' and 'quenching' would be equivalent to 'temple'. 'Quenching' is only the cooling but is often used to describe the complete process of heating and cooling that we call 'temple' in Spanish."

So I guess this, even if not perfect, is closer to being correct than the earlier cross-links. GS3 (talk) 10:48, 18 February 2016 (UTC)