Fine-grain spring steel strip for coil spring and preparation method of fine-grain spring steel strip

The invention belongs to the technical field of steel and iron, and particularly relates to a fine grain spring steel strip for a coil spring and a preparation method of the fine grain spring steel strip for the coil spring, and the fine grain spring steel strip comprises the following chemical components in percentage by weight: 0.62%-0.64% of C, 1.90%-2.00% of Si, 0.80%-0.90% of Mn, less than or equal to 0.010% of S, less than or equal to 0.015% of P, 0.12%-0.20% of Cr, 0.010%-0.020% of Nb, less than or equal to 0.008% of Al and the balance of iron and inevitable impurities. The grain size is not less than 10 grades, and the total grade of non-metallic inclusions is not more than 2.5 grades. By adding microalloying elements, strictly controlling the content of Al in the steel, reducing the grade of non-plastic inclusions and adopting a high-reduction-rate hot rolling process and a slow cooling process, the product has the characteristics of high grain size, pure steel, excellent banded structure and the lik