Complete annealing process of steel tube

    Process: Heat steel to 20 ~ 30 ℃ above Ac3, cool slowly after heating for a period of time (with furnace) to obtain a heat treatment process (complete austenitization) close to the equilibrium structure.

    Full annealing is mainly used for hypoeutectoid steel (wc = 0.3 ~ 0.6%), generally medium carbon steel and low and medium carbon alloy steel castings, forgings and hot-rolled profiles, and sometimes also used for their weldments. Low carbon steel has a low hardness after full annealing, which is not conducive to cutting. When the hypereutectoid steel is heated to above Accm and slowly cooled and annealed, Fe3CⅡ will precipitate along the grain boundaries in a network shape, making the steel strong, hard, and plastic. And toughness are significantly reduced, leaving hidden dangers to the final heat treatment.

    Purpose: To refine grains, uniform structure, eliminate internal stress, reduce hardness and improve the machinability of steel. The microstructure of the hypoeutectoid steel after complete annealing is F + P.

    In actual production, in order to improve productivity, annealing cooling to about 500 ° C is air cooling.

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