| 摘要 |
<p>Heat treatment of low-carbon, unalloyed or low-alloyed steels includes one or more cycles, in which the steel is heated (S1) to a temperature (Tp) above the Ac3 temperature and is cooled back to a temperature (Te1, Te3) below the Ac1 temperature or a higher temperature, at which not more than one half of the structure of the steel consists of austenite, so that the holding time (td) above the Ac3 temperature is typically of the order of a few seconds or a few tens of seconds, and not more than 5 minutes. Heat treatment is carried out as the last stage in which the temperature is elevated to the Ac3 temperature. Preferably, the heating is started from a temperature (Ts1) in the range 500 to 720 DEG C, and the temperature (Tp) above the Ac3 temperature is 850 to 1050 DEG C. By the heat treatment of the invention strength and impact thoughness of steel is improved. A preferred application of the invention is heat treatment of a weld joint or a welded structure.</p> |
