Steel Pipes: It's Not as Difficult as You Think



It has long been known that the properties of some metals could be altered by heat treating. Grains in metals tend to grow larger as the metal is warmed. A grain can grow larger by atoms moving from another grain that may ultimately disappear. Dislocations can not cross grain borders easily, so the size of grains determines how quickly the dislocations can move. As expected, metals with little grains are more powerful however they are less ductile. Figure 5 reveals an example of the grain structure of metals. Satiating and Solidifying: There are numerous ways in which metals can be heat dealt with. Annealing is a softening process in which metals are heated and after that enabled to cool slowly. A lot of steels may be solidified by heating and quenching (cooling rapidly). This procedure was used quite early in the history of processing steel. In fact, it was thought that biological fluids made the best quenching liquids and urine was often used. In some ancient civilizations, the red hot sword blades were often plunged into the bodies of hapless detainees! Today metals are quenched in water or oil. In fact, satiating in salt water services is faster, so the ancients were not totally wrong.Quenching results in a metal that is really hard however also breakable. Gently warming a hardened metal and permitting it to cool slowly will produce a metal that is still hard however also less fragile. This process is referred to as tempering. (See Processing Metals Activity). It results in numerous small Fe3C speeds up in the steel, which block dislocation movement which thereby offer the strengthening.Cold Working: Because plastic contortion results from the motion of dislocations, metals can be strengthened by avoiding this motion. When a metal is bent or shaped, dislocations are produced and move. As the number of dislocations in the crystal increases, they will get twisted or pinned and will not be able to move. This will enhance the metal, making it harder to deform. This procedure is referred to as cold working. At greater temperatures the dislocations can reorganize, so little strengthening occurs.You can attempt this with a paper clip. Unbend the paper clip and bend among the straight sections backward and forward several times. Picture what is occurring on the atomic level. Notice that it is harder to bend the metal at the very same place. Dislocations have actually formed and become twisted, increasing the strength. The paper clip will eventually break at the bend. Cold working certainly just works to a specific level! Too much contortion results in a tangle of dislocations that are not able to move, so the metal breaks instead.Heating removes the impacts of cold-working. When cold worked metals are warmed, recrystallization occurs. New grains form and grow to take in the cold worked portion. The brand-new grains have less dislocations welded steel pipe and the original homes are restored.

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