It is possible to provide an iron-based sintered sliding material excellent in the sliding performance. Provided is an iron-based sintered sliding material including, a base containing, by mass, 3 to 15% of S, 0.2 to 6% in a total amount of at least one selected from the group consisting of Cr, Ca, V, Ti, and Mg, and a remainder of Fe and inevitable impurities, sulfide particles containing at least one selected from the group consisting of Cr, Ca, V, Ti, and Mg being dispersed in the base, and pores.

There is provided a hot rolled steel according to one aspect of the invention including, as a predetermined chemical composition: Bi: 0.0001 mass % to 0.0050 mass %, in which 90 area % or more of a metallographic structure is configured with a ferrite and a pearlite, and an average number density of Mn sulfides measured on a cross section parallel to a rolling direction having an aspect ratio of more than 10 and 30 or less which is extended along the rolling direction, is 50 pieces/mm.sup.2 to 200 pieces/mm.sup.2.

A steel alloy is disclosed that provides a unique combination of strength, toughness, and fatigue life. The steel alloy has the following composition in weight percent:

TABLE-US-00001 C about 0.15 to about 0.30 Mn about 1.7 to about 2.3 Si about 0.7 to about 1.1 Cr about 1.85 to about 2.35 Ni about 0.5 to about 0.9 Mo + ½W about 0.1 to about 0.3 Cu about 0.3 to about 0.7 V + 5/9 × Nb about 0.2 to about 0.5
The balance of the alloy is iron, usual impurities, and residual amounts of other elements added during melting for deoxidizing and/or desulfurizing the alloy. A hardened and tempered steel article made from the alloy is also disclosed.

A sliding member incudes a back-metal layer and a sliding layer made of a copper alloy. The back-metal layer is made of a hypoeutectoid steel including 0.07 to 0.35 mass % of carbon, and has a structure including a ferrite phase and pearlite. The back-metal layer includes a pore existing region including a plurality of closed pores having an average size of 1 to 10 μm. The pore existing region extends from the bonding surface toward an inner portion of the back-metal layer and having a thickness of 2 to 20 μm. At least a part of the plurality of closed pores has contour that is partially formed by the bonding surface in a cross-sectional view. A ratio V2/V1 of a total volume V2 of the closed pores to a volume V1 of the pore existing region is 0.02 to 0.08.

A sliding member includes a back-metal layer and a sliding layer made of a copper alloy. The back-metal layer is made of a hypoeutectoid steel including 0.07 to 0.35 mass % of carbon, and has a structure including a ferrite phase and pearlite. The back-metal layer includes a pore existing region including a plurality of closed pores that are not open to a bonding surface when viewing a cross-section perpendicular to a sliding surface. The closed pores have an average size of 5 to 15 μm. The pore existing region extends from the bonding surface toward an inner portion of the back-metal layer, and has a thickness of 10 to 60 μm. A ratio V2/V1 of a total volume V2 of the closed pores to a volume V1 of the pore existing region is 0.05 to 0.1.

A sliding member incudes a back-metal layer and a sliding layer made of a copper alloy. The back-metal layer is made of a hypoeutectoid steel including 0.07 to 0.35 mass % of carbon, and has a structure including a ferrite phase and pearlite. The back-metal layer includes a pore existing region including a plurality of closed pores having an average size of 1 to 10 μm. The pore existing region extends from the bonding surface toward an inner portion of the back-metal layer and having a thickness of 2 to 20 μm. At least a part of the plurality of closed pores has contour that is partially formed by the bonding surface in a cross-sectional view. A ratio V2/V1 of a total volume V2 of the closed pores to a volume V1 of the pore existing region is 0.02 to 0.08.

An induction-hardened crankshaft is provided that offers an excellent balance of fatigue strength, machinability and quench-cracking resistance. An induction-hardened crankshaft has a chemical composition of, in mass %: 0.30 to 0.60% C; 0.01 to 1.50% Si; 0.4 to 2.0% Mn; 0.01 to 0.50% Cr; 0.001 to 0.06% Al; 0.001 to 0.02% N; up to 0.03% P; 0.005 to 0.20% S; 0.005 to 0.060% Nb; and balance Fe and impurities, the non-induction-hardened portion having a microstructure mainly composed of ferrite-pearlite and having a fraction of ferrite Fα satisfying the expression (1) provided below, the induction-hardened portion having a microstructure mainly composed of martensite or tempered martensite, and having a prior austenite grain diameter not larger than 30 μm,

Fα≥150×[C %]+84   (1), where the C content in mass % in the induction-hardened crankshaft is substituted for [C %].

A method for manufacturing a crankshaft for an internal combustion engine with a plurality of journals having a hardened case with a first microstructure. The crankshaft is comprised of a steel comprising between about 0.3 wt % and 0.77 wt % Carbon. The first microstructure of the hardened case of the journals comprises between about 15% and 30% ferrite and a balance of martensite and the resultant subsurface residual stress between 310 MPa and 620 MPa.

Provided is a sliding member including: a back-metal layer and a sliding layer including a copper alloy. The back-metal layer includes a hypoeutectoid steel including 0.07 to 0.35 mass % of carbon and has a structure including a ferrite phase and pearlite. The back-metal layer has a high ferrite phase portion at a bonding surface between the back-metal layer and the sliding layer. A volume ratio Pc and a volume ratio Ps satisfy Ps/Pc0.4, where the volume ratio Pc is a volume ratio of pearlite in the structure at a center portion in a thickness direction of the back-metal layer, and the volume ratio Ps is a volume ratio of pearlite in the high ferrite phase portion.

A steel according to one aspect of the present invention has a chemical composition containing, by unit mass %, C: 0.25 to 0.55%, Si: 0.20 to 1.30%, Mn: 0.50 to 1.50%, P: 0.010 to 0.200%, S: 0.010 to 0.100%, Cr: 0 to 1.20%, V: 0.25 to 0.40%, Ti: 0.010 to 0.070%, Mo: 0 to 0.15%, N: 0.0010 to 0.0060%, Al: 0 to 0.200%, Ca: 0 to 0.005%, Zr: 0 to 0.005%, Mg: 0 to 0.005%, Bi: 0 to 0.0050%, Pb: 0 to 0.50%, Nb: 0 to 0.05%, Cu: 0 to 0.05%, and Ni: 0 to 0.05%, with the balance being Fe and impurities, wherein 0.002<Ti3.4N<0.050 is satisfied.