Talk:Tempering (metallurgy)

message: 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)
replies: text: 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)
thread_title: Untitled comment

message: 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)
replies: text: 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)
replies: text: Hmm, I don't know how I missed that. Thanks, Kjkolb 16:07, 19 December 2005 (UTC)
thread_title:  Tempered glass 

message: 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)
thread_title:  This article is in need of some work. 

message: --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)
thread_title: Contradiction?