Abstract: The precipitation,microstructure and mechanical properties of low carbon steel at different coiling temperatures were investigated by tensile testing,metallography,quantitative analysis of precipitates,TEM and EDS.The results show that with the coiling temperature increasing,the strength and grain size grade of the steel and the content of nitrogen in solution decrease gradually;at a coiling temperature of 740℃,the content of nitrogen in solution is almost zero.Thermodynamic and kinetic analyses indicate that AlN precipitates in coiling chiefly.The sizes of AlN,with complex chemical composition,are between 10nm and 50nm.