| The influence of TMCP and heat treatment on microstructure and mechanical properties of coiled tubing steel had been investigated by the modern analytical methods such as SEM, TEM, tensile test and so on, and the best TMCP and heat treatment law had been selected. The following conclusions could be drawn from this investigation:(1) With the finish rolling temperature decreasing, the grain size got smaller, when the finish rolling temperature was too low, the organization of banded appeared clearly. The strength was rising up with the decreasing of finish rolling temperature. The best finish rolling temperature was about850℃. The lower the final cooling temperature was, the smaller the grain sizes were. When the final cooling temperature was between550℃and600℃, the mechanical properties of the CT80steel were good.(2) The grain size was getting bigger when the cooling rate was decreasing. The faster the cooling speed after rolling was, the thinner and closer the microstructure of CT80was. The properties of CT80steel were best when the cooling speed was between16℃/s and18℃/s.(3) With the quenching temperature rising, the values of yield strength and tensile strength were also increased. When the temperature was close to AC3, the properties of experimental steel were good, but when the quenching temperature was up to940℃, the strength value and hardness value were both decreased. When the quenching temperature was850℃, CT80steel had the best mechanical properties.(4) The strength value and hardness value were both decreased with the tempering temperature and tempering time increasing, by contrary elongation decreasing. For CT80steel the best tempering temperature range was550℃～600℃, and the best tempering time was10minutes. |
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