From: Wags1975 ® 06/04/2001 17:36:53 Subject: Embrittlement post id: 273613 Does anyone know the term for the embrittlement caused by freezing a metal pipe. I ask because at work we use nitrogen and the lines are made of copper because it is less susceptible to ???????? embrittlement? What is this type of embrittlement called? Wags From: fish slapping maniac 07/04/2001 2:41:13 Subject: re: Embrittlement post id: 273871 the titanic was made of the cheapest type of iron plate you can get. it was made from cast iron dude. Cast Iron!!! Pooh... A metallurgical analysis of steel taken from the hull of the Titanic's wreckage reveals that it had a high ductile-brittle transition temperature, making it unsuitable for service at low temperatures; at the time of the collision, the temperature of the sea water was -2°C. The analysis also shows, however, that the steel used was probably the best plain carbon ship plate available at the time of the ship's construction. From http://www.tms.org/pubs/journals/JOM/9801/Felkins-9801.html From: Alan™ ® 07/05/2001 7:28:10 Subject: re: Embrittlement post id: 294619 FSM, possibly came the closest to providing the correct answer. 00000 Does anyone know the term for the embrittlement caused by freezing a metal pipe. I ask because at work we use nitrogen and the lines are made of copper because it is less susceptible to ???????? embrittlement? What is this type of embrittlement called? The term your looking for is most likely ductile-brittle transition temperature. However it is possible stress corrosion cracking may occur, when liquid nitrogen is passed through metal pipes, resulting in a fracture that looks to be brittle. Stress corrosion cracking is specific to the alloy, so by choosing a different alloy, the problem will be avoided. Unfortunately, I don't have the information at hand that covers liquid nitrogen and the stress corrosion cracking effected alloys. The term embrittlement AFAIK, is used exclusively for a where chemicals, usually hydrogen are absorbed into the metal and then migrate to the grain boundaries. This results in a weakness across the grain boundaries that may lead to failure of the metal. The failure showing a structure looks very granular and very different to ductile, brittle or fatigue failures. Temper brittleness or more correctly temperature embrittlement occurs for two different reasons. The low temperature form occurs when certain steel alloys are tempered (stress relieved) after quenching (formation of martensite - see here. What occurs during tempering, is that brittle carbides precipitate at the former austenite the grain boundaries. The addition of silicon reduces this effect, which only occurs in when P, Sb, Sn, Al and N are present within the alloy. This form of temper embrittlement effects the toughness or impact resistance of alloy steels but not carbon steels, but not the hardness or strength. The higher temperature form involves the segregation of Sb, P, Sn and As to the grain boundaries of the ferrite, prior to being heat treated to form austenite and then quenched to form martensite. Additions of Ni, Mn, Cr and Si enhance the effect. Subsequent heat treatment, ageing additions of Mo, Ti and Zr Both forms form of temper embrittlement reduce the toughness or impact resistance of the steel, but not the hardness or strength. The term glass transition temperature Tg is usually used only in the plastics industry, although it may be applicable with some amorphous metal alloys (not sure on this). Glass transition occurs with amorphous polymers and not crystalline polymers. Changes in temperature result in a change in the mechanical properties of the polymer, at low temperatures the polymer is hard and brittle, at higher temperatures, the polymers are soft and ductile. 000000 This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.