Hot rolled steel sheet, steel forged part and production method therefor

A hot rolled steel sheet having a chemical composition consisting of, in mass %,

• C:
• 0.020 to 0.070%,
• Si:
• 0.05 to 1.70%,
• Mn:
• 0.60 to 2.50%,
• Al:
• 0.005 to 0.020%,
• N:
• more than 0.0030% to 0.0060% or less,
• P:
• 0.050% or less,
• S:
• 0.005% or less,
• Ti:
• 0.015 to 0.170%,
• O:
• 0.0010 to 0.0100%,
• Nb:
• 0 to 0.100%,
• V:
• 0 to 0.300%,
• Cu:
• 0 to 2.00%,
• Ni:
• 0 to 2.00%,
• Cr:
• 0 to 2.00%,
• Mo:
• 0 to 1.00%,
• B:
• 0 to 0.0100%,
• Ca:
• 0 to 0.0100%,
• Mg:
• 0 to 0.0100%,
• REM:
• 0 to 0.1000%,
• Zr:
• 0 to 1.000%,
• Co:
• 0 to 1.000%,
• Zn:
• 0 to 1.000%,
• W:
• 0 to 1.000%,
• Sn:
• 0 to 0.050%, and,
• the balance:
• Fe and impurities, wherein
• the chemical composition satisfies a formula (i) below, and
• when a width and a thickness of the steel sheet in a cross section perpendicular to a rolling direction of the steel sheet are defined as W and t, respectively, a metal microstructure includes, in area %, at a position ¼ W or ¾ W from an end face of the steel sheet and ¼ t or ¾ t from a surface of the steel sheet,
• ferrite:
• 5 to 70%,
• bainite:
• 30 to 95%,
• retained austenite:
• 2% or less,
• martensite:
• 2% or less, and,
• pearlite:
• 1% or less, and
• a total of ferrite and bainite:
• 95% or more, and wherein
• the ferrite contains precipitates including Ti in grains of the ferrite,
• a number density of the precipitates including Ti is 1.0×1016 to 50.0×1016/cm3,
• the steel sheet includes TiN precipitates,
• an average circle-equivalent diameter of the TiN precipitates is 1.0 to 10.0 μm,
• an average of minimum distances between adjacent TiN precipitates is 10.0 μm or more, and
• a standard deviation of nano hardness is 1.00 GPa or less:
• Ca+Mg+REM≥0.0005 (i)
• where a symbol of an element in the above formula represents a content (in mass %) of the element in the hot rolled steel sheet and is substituted by zero when the element is not contained.