The invention belongs to the technical field of the
metallurgy and
processing of iron and steel and provides a method for improving the thickness of a decarburized layer of a small square billet of tire cord steel. The tire cord steel is produced by adopting the technological processes of heating, rough rolling, intermediate rolling, pre-finishing, finishing and
air cooling. The method for improving the thickness of the decarburized layer of the small square billet of the tire cord steel comprises the following steps that: prior to the technological process of heating, corner
grinding or whole-stripping treatment is carried out on the square billet; the total detention time for the square billet in a
heating furnace is less than 150 min, and the detention time in a soaking section is lessthan 45 min;
fuel gas is fully combusted in the soaking section, wherein the air-fuel ratio in a heating I section is set to be 1.1, the air-fuel ratio in a heating II section is set to be 0.9, and the air-fuel ratio in the soaking section is set to be 0.7; the temperature of the heating I section is 600-700 DEG C, the temperature of the heating II section is 950-1,050 DEG C, the temperature of the soaking section is 1,150-1,180 DEG C; the temperature for starting rolling is controlled at 1,100-1,150 DEG C; and the
temperature difference between coil rod overlapping points and a center duringthe whole process of rolling is no more than 50 DEG C. With the adoption of the method, the thickness of the decarburized layer of the small square billet of the tire cord steel is greatly improved, and the thickness of a total decarburized layer (ferrite and
transition layer) of a hot-rolled coil rod of a tire cord steel finished product can be less than 0.06 mm, so that the requirements of tirecord steel users on the control of the thickness of the decarburized layer are met.