From: MojoBoy 21/06/2001 15:32:22 Subject: Knifes post id: 329284 I just bought a knife that has been Ice tempered and hardended to Rockwell 56c - 58c. What is the ice tempered process? and what is Rockwell? Thanks From: Zardoz ® 21/06/2001 15:42:30 Subject: re: Knifes post id: 329297 WHAT DOES ICE TEMPERED MEAN? The word ICE is so popular that a lot of regular carbon steel shears proclaim to be ice tempered, which does not make any sense technically and is a lot of hot air. Some people even think ICE is a brand name. The important thing to remember is that ice tempering is only beneficial on stainless steel. In a simplified form, stainless steel is regular steel with chromium added to make the steel more rust resistant, thus stainless steel. The disadvantage of the high content of chromium in stainless steel is that the cutting edges dull quicker. To overcome this, the steel is subjected to very low temperatures (frozen or "ice tempered"), to optimize the steel structure for hardness. This is how it works: To make a steel hard, it has to be heat treated. With Stainless steel that means heating the steel above 2000 degrees farenheit. At that temperature the structure of the material is at its optimum. To preserve this structure, the steel is cooled rapidly (quenched) and tempered at about 450 degrees Fahrenheit. Now you have a pretty good hardness and flexibility on your shear except that the chromium in the steel will not permit a long lasting cutting edge. To make the cutting edge last longer, the steel is subjected to about 120 degrees below zero; in other words, Ice tempered. The shear is not much harder, but the steel structure is at its optimum. It is virtually impossible to prove or disprove if Ice tempering was done, without a steel analysis. The only proof is how many cuts one can get with a shear before it dulls. Eickert Stainless shears are all Ice tempered. We have letters from professional stylists who have cut 10 heads or more a day for over 10 years without sharpening. We put on our Eickert shears the word INOX. INOX is the abbreviated French word "Inoxidable" meaning Stainless. YES THIS IS FOR PLASTICS BUT THE TEST FOR METALS IS SIMILAR. The hardness testing of plastics is most commonly measured by the Rockwell hardness test or Shore (Durometer) hardness test. Both methods measure the resistance of the plastic toward indentation. Both scales provide an empirical hardness value that doesn't correlate to other properties or fundamental characteristics. Rockwell hardness is generally chosen for 'harder' plastics such as nylon, polycarbonate, polystyrene, and acetal where the resiliency or creep of the polymer is less likely to affect the results. http://www.matweb.com/measurements/rockwell-hardness.htm Rockwell Hardness Testing of Plastics http://www.arius-eickert.com/articles/ice.htm From: Pete ® 21/06/2001 15:43:17 Subject: re: Knifes post id: 329299 http://www.mee-inc.com/rockhar.html Rockwell Hardness Testing: Rockwell hardness testing is an indentation testing method. An indenter is impressed into the test sample at a prescribed load to measure the material's resistance to deformation. A Rockwell hardness number is calculated from the depth of permanent deformation of the sample after application and removal of the test load. Various indenter shapes and sizes combined with a range of test loads form a matrix of Rockwell hardness scales that are applicable to a wide variety of materials. http://www.arius-eickert.com/articles/ice.asp WHAT DOES ICE TEMPERED MEAN?: To make a steel hard, it has to be heat treated. With Stainless steel that means heating the steel above 2000 degrees Fahrenheit. At that temperature the structure of the material is at its optimum. To preserve this structure, the steel is cooled rapidly (quenched) and tempered at about 450 degrees Fahrenheit. Now you have a pretty good hardness and flexibility on your shear except that the chromium in the steel will not permit a long lasting cutting edge. To make the cutting edge last longer, the steel is subjected to about 120 degrees below zero; in other words, Ice tempered. The shear is not much harder, but the steel structure is at its optimum. It is virtually impossible to prove or disprove if Ice tempering was done, without a steel analysis. The only proof is how many cuts one can get with a shear before it dulls. From: rotorman 21/06/2001 15:46:55 Subject: re: Knifes post id: 329303 Mojoboy . Ice ( or sub zero ) tempering is a very effective process that ( without getting into the metallurgy ) makes the crystalline grain structure of the steel finer and there-fore more resistant to shearing (breaking) and also gives a stronger and better edge .Rockwell is a hardness scale . 56 - 58 is the best range for a "using " knife , it imparts good edge taking and holding capabilities . From: Alan™ ® 21/06/2001 21:35:29 Subject: re: Knifes post id: 329724 Well I was going to dismiss this totally as a gimmick. But after a which discussion with the International Technical Manager one of the world biggest manufactures of stainless steels, after making several educated guesses, we think we know what they are doing and really it's a pretty standard process and just a variation on Austempering, with the formation of martensite rather than bainite and this is achieved by quenching the austenite before it can begin to transform into bainite. So correct me if I'm wrong Rotorman. They anneal the material at 1100°C (1200°F), quench done to 230°C (450°F) where they austemper the material, which is still the austenite phase. Austempering will stress relieve the austenite and if you have the correct alloying eliments, cause the formation of a fine precipitate. The material is then quenched down to -80°C (-120°F), passing through both the Ms and Mf temperatures. Cooling to such low temperatures results in the complete martensitic transformation of the material, without any retained austenite. Because the transformation is so sluggish (even at room temperature) when the material is permitted to return to room temperature, the martensite does not transform back to austenite. My initial thinking was that they were quenching to room temperature to form the martensite. Then reheating to 230°C for the temper, which would probably be better termed precipitation ageing rather than a stress relief temper. Followed by subsequent cooling to -80°C. Personally I found it difficult to see what this subsequent cooling would archieve, as you already had a martensite structure and any atom movement at these low temperauture would both be sluggish and reversed by warming the material back up to room temperature. I suspect it's the terminology used, that through me. Rockwell is a hardness scale . 56 - 58 is the best range for a "using " knife , it imparts good edge taking and holding capabilities . Not necessarily, all it means is that this company believes that firstly they make the best knives in the world (this is probably hard to believe), secondly this is the hardness which they believe gives their knives the optimum hardness. However the guys in the factory down the road maybe producing better knives with a hardness of 62-64Rc. IMHO this is just marketing. 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.