HOT-FORGING MICRO-ALLOYED STEEL AND HOT-ROLLED STEEL EXCELLENT IN FRACTURE-SPLITABILITY AND MACHINABILITY, AND COMPONENT MADE OF HOT-FORGED MICROALLOYED STEEL

摘要

The invention provides a hot-forging micro-alloyed steel and a hot-rolled steel which achieve excellent fracture-splitability and machinability, without impairing productivity or mechanical properties and without addition of Pb or the like. It also provides a component made of hot-forged micro-alloyed steel.;The hot-forging micro-alloyed steel comprises, in mass %, C: greater than 0.35 to 0.60%, Si: 0.50 to 2.50%, Mn: 0.20 to 2.00%, P: 0.010 to 0.150%, S: 0.040 to 0.150%, V: 0.10 to 0.50%, Zr: 0.0005 to 0.0050%, Ca: 0.0005 to 0.0050% and N: 0.0020 to 0.0200%, Al being limited to less than 0.010%, and a balance substantially of Fe and unavoidable impurities.

主权项

1. A hot-forging micro-alloyed steel excellent in fracture-splitability and machinability comprising, in mass %, C: from 0.35 to 0.60%, Si: 0.50 to 2.50%, Mn: 0.20 to 2.00%, P: 0.010 to 0.150%, S: 0.040 to 0.150%, V: 0.10 to 0.50%, Zr: over 0.0023 to 0.0050%, Ca: 0.0005 to 0.0050% and N: 0.0069 to 0.0200%, Al being limited to less than 0.010%, and a balance substantially of Fe and unavoidable impurities, further including MnS inclusions having an average aspect ratio of 10 or less and wherein greater than 90% of a total number of MnS inclusions present in ¼ diameter of the hot-forging micro-alloyed steel have a width of 1 μm or less.