Non-quenched and tempered round steel with high strength, high toughness and easy cutting and manufacturing method therefor

A non-quenched and tempered round steel, comprising the following chemical elements in percentage by mass:

• C:
• 0.36-0.45%;
• Si:
• 0.20-0.70%;
• Mn:
• 1.25-1.85%;
• Cr:
• 0.15-0.53%;
• Ni:
• 0.10-0.25%;
• Mo:
• 0.10-0.25%;
• Al:
• 0.02-0.05%;
• Nb:
• 0.001-0.040%;
• V:
• 0.10-0.25%;
• S:
• 0.02-0.06%;
• and the balance being Fe and inevitable impurities;
• wherein the steel further comprises Cu, and the content of Cu is 0<Cu<0.25% in percentage by mass;
• wherein the non-quenched and tempered round steel has a microstructure comprising bainite, and on any cross-section of the non-quenched and tempered round steel, the area of the bainite accounts for 85% or more of the area of the cross-section;
• wherein the microstructure of the non-quenched and tempered round steel further comprises residual austenite and at least one of ferrite or pearlite;
• wherein the non-quenched and tempered round steel has a tensile strength Rm of greater than or equal to 1000 MPa, an elongation A of greater than or equal to 12%, a cross-sectional shrinkage Z of greater than or equal to 35%, and a Charpy impact energy Aku of greater than or equal to 27 J.