Effect of 0.78~0.92% Mn on structure and mechanical properties of ϕ20 mm hot-rolled coil of 0.20% carbon cold-heading steel has been analyzed and studied. End-rolling temperature of hot-rolling coil is 880 ℃

slow-cooling. Results show that with increasing Mn in steel from 0.78% to 0.92%

the tensile strength of coil increases from 485 MPa to 508 MPa

i. e. that increases by 23 MPa；the elongation decreases from 31% to 28%

i. e. decreases by 3 point of percentage

and the reduction of area decreases from 58% to 52%

i. e. decreases by 6 point of percentage； the HRB hardness value increases by 4.5. The size of ferrite groups in structure of test steel reduces from 28μm to 18μm，the pearlite content in structure increases form 23% to 26% and the pearlite lamellar spacing decreases slightly;the hardenability of steel improves.