Effect of pearlite morphology on microstructure and hardness after spheroidizing annealing of SK85 steel

doi:10.13251/j.issn.0254-6051.2023.11.033

Abstract

Abstract: Simulation of spheroidizing annealing process of the SK85 steel cold rolled sheet was carried on by simultaneous thermal analyzer. The effect of morphology of deformed pearlite and granular pearlite on the spheroidized structure and properties was studied by means of optical microscope, scanning electron microscope and hardness tester. The results show that as the annealing temperature increases, the spheroidizing hardness of two morphic pearlites specimens first decreases and then increases, and reaches the minimum values when the annealing temperature is 740-750 ℃. When the annealing temperature is lower than 740 ℃, the spheroidized microstructure is granular pearlite, the spheroidizing speed of deformed pearlite is greater than that of granular pearlite, and the annealing hardness is greater than that of granular pearlite specimen. When the annealing temperature is higher than 750 ℃, the spheroidized microstructure is lamellar pearlite and granular pearlite, and both hardness changes tend to be consistent. The carbide particle size obtained after granular pearlite spheroidizing is larger than that of deformed pearlite, which is the reason why the spheroidization hardness of granular pearlite is lower than that of deformed pearlite. Adjusting the carbide dispersion through softening annealing process design can further reduce the hardness of SK85 steel cold rolled sheet and meet the industry requirements of cold stamping.

Key words: pearlite morphology, SK85 steel, spheroidizing annealing, carbide

CLC Number:

TG162.86

Deng Suhuai, Liang Jiangtao, Liu Kun, Li Yue, Xu Haiwei. Effect of pearlite morphology on microstructure and hardness after spheroidizing annealing of SK85 steel[J]. Heat Treatment of Metals, 2023, 48(11): 210-215.

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