Proven Engineering Material: T1 Steel (1950s)

[Music] this is t1 steel the most important development in alloy steels in the past 40 years it is more than just another steel it has proved itself in many ways and one of the most effective demonstrations took place in Birmingham Alabama the project was operation t1 the time was June 1954 on this day some of the nation's top ranking authorities on steel applications saw dramatic proof that t1 was a new advanced in alloy steels the project was built around a series of pressure vessels each made of 1/2 inch T 1 plates half of the vessels were stress relieved after welding and half were not each of the vessels was to be subjected to the same destructive tests and the results were almost identical a first test was the first part of operation t1 the vessel was cooled down to minus 45 degrees Fahrenheit if t1 had any tendency to brittleness it would certainly become evident at this extremely low temperature with a panel set to measure every phase of temperature and pressure the signal was given to activate the pressure pump the test was on when pressure reached 1875 psi t1 already showed three times the yield strength of ordinary steel but how extraordinary was it it held at two thousand pounds it passed twenty five hundred finally at two thousand eight hundred fifty psi the vessel burst at a pressure seven and a half times the maximum now required for equipment of this kind after such a burst even at this frigid temperature t1 showed no evidence of brittleness or shattering note the simple tear incredible ductility for an alloy steel having such a high strength level other vessel subjected to similar burst tests ruptured at about the same pressure demonstrating the same remarkable degree of toughness all this with a half-inch plate of t1 and carbon steel been used the plates would have had to be three times as thick to withstand that much pressure the impact test was even more brutal and dynamic the vessels temperature was dropped to minus 38 degrees Fahrenheit and its internal pressure raised to 1875 psi the nominal limit 41 here certainly were adverse conditions for meeting the colossal hammer blows in store suspended in the 150-foot tower was a massive wait ready to hurtle down with devastating impact this tough weighing over 13 tons was raised to a height of 52 feet for the first drop a force of almost 1 and 1/2 million foot pounds yet below the saddle there was no more than a slight dent for its second drop the top rose to 73 a shattering impact of almost 2 million foot-pounds and there wasn't even a leaf the distortion increased but t-one still held for the third drop the tuff was raised to over 100 feet above the vessel t1 had already proved its superiority this was to be the crusher it took almost 3 million foot-pounds to rupture the vessel there was no question that t1 had remarkable mechanical properties and again the experts were surprised by the kind of rupture an absolutely clean tear despite the terrific impact here was conclusive evidence of T ones unique properties a combination of ductility and toughness not usually expected in the same steel a second series of tests confirmed the dramatic performance of t1 steel the results were almost identical again and again the unique combination of toughness and strength was conclusively demonstrated [Applause] [Music] when operation t1 ended the engineering and technical authorities present were truly amazed at what they'd seen while to us steel this was just another step in the research and development of t1 prior to this demonstration we spent years testing this material in many other applications behind its unique qualities are many things first a judicious combination of elements chosen with specific properties and the price book in mind Carbon held to approximately point 15% for improved weld ability for harden ability and toughness we found that manganese and nickel could be held to 1% maximum and chromium to about 0.5 percent molybdenum of a round point 45% was used for depth of hardening and high-temperature strength copper of about point 30% was used to improve atmospheric corrosion resistance small amounts of vanadium made possible high tempering temperatures and improved welding we found a little boron to be the least expensive way to further increase harden ability and here is a typical heat analysis with all elements falling within a fixed range to create a highly versatile steel but to produce a steel which can take the punishment of operation t1 two basic steps are necessary it must be quenched and tempered the as rolled plate is charged into a furnace and heated to 1650 degrees Fahrenheit it has not yet been trimmed to size since from the side and an crop we will later obtain enough test material to be sure the high quality standards of t1 are met after a thorough heating at this temperature the plate is water quench to room temperature to do this low carbon is a must or only with low carbon can we quench from so high o temperature with no danger of cracking the tempering which follows is done at 1200 degrees when necessary the plate is flattened in the roller leveler both water quenching and tempering are carried out under precise time and heat controls for it is these two phases which give t1 the structure aimed for low-carbon tempered martensite the toughest microstructure in steel note that there is a distinct difference in the microstructure of t1 as compared with a 7 carbon steel but asks a practical engineer what about fabrication for example how sensitive is t1 to cold forming the effect of cold forming and the toughness of t1 has been carefully measured and actual applications have confirmed the fact that t1 is less sensitive to such treatment than most deals doesn't flame cutting affect the edge toughness of t1 naturally the plane cut edge will be considerably harder than the rest of the plate but still so tough it will show no cracks at all