A steel sheet has a composition comprising 0.060%≤C≤0.085%, 1.8%≤Mn≤2.0%, 0.4%≤Cr≤0.6%, 0.1%≤Si≤0.5%, 0.010%≤Nb≤0.025%, 3.42N≤Ti≤0.035%, 0≤Mo≤0.030%, 0.020%≤Al≤0.060%, 0.0012%≤B≤0.0030%, S≤0.005%, P≤0.050%, 0.002%≤N≤0.007% and optionally 0.0005%≤Ca≤0.005%, the remainder of the composition being iron and unavoidable impurities. The microstructure consists of 34% to 80% bainite, 10% to 16% martensite, and 10% to 50% of ferrite. The surface fraction of unrecrystallized ferrite, with respect to the whole structure, is of less than 30%. The martensite consists of self-tempered martensite and fresh martensite, the surface fraction of self-tempered martensite being comprised between 4% and 10%.

An embodiment of the present invention provides a steel wire rod and a method for producing same, the steel wire rod comprising 0.3-0.5 wt % of C, 0.02-0.4 wt % of Si, 1.0-1.5 wt % of Mn, 0.3-0.7 wt % of Cr, 0.003 wt % or less of B, 0.03 wt % or less of Ti, 0.03 wt % or less of P, 0.01 wt % or less of S, 0.02-0.05 wt % of Al, and 0.001-0.01 wt % of N, with the balance being Fe and inevitable impurities, and having a microstructure in which the main phase thereof is a complex structure of ferrite+pearlite, and contains at most 5 area % (including 0 area %) of at least one of bainite or martensite, wherein the average pearlite colony size in a region extending from the ⅖ point to the ⅗ point of the diameter is at most 7 μm.

A hot-stamping formed body has a predetermined chemical composition and includes microstructure which includes residual austenite of which an area ratio is in a range of 20% to 30%. Among grain boundaries of crystal grains of bainite and tempered martensite in the microstructure, a ratio of a length of a grain boundary having a rotation angle in a range of 55° to 75° to a total length of a grain boundary having a rotation angle in a range of 4° to 12°, a grain boundary having a rotation angle in a range of 49° to 54°, and a grain boundary having a rotation angle in a range of 55° to 75° to the <011> direction as a rotation axis is 30% or more.

This steel sheet for a can is a steel sheet for a can containing, by mass %, C: 0.010% to 0.050%, Si: 0.020% or less, Mn: 0.10% to 0.60%, P: 0.020% or less, S: 0.020% or less, Al: 0.050% or less, N: 0.0100% or less, Nb: 0% to 0.03%, Ti: 0% to 0.03%, B: 0% to 0.0020%, and a remainder including Fe and an impurity, in which, when the number of carbides having an equivalent circle diameter of 2 μm or more and 5 μm or less is indicated by a, and the number of carbides having an equivalent circle diameter of 0.1 μm or more and less than 2 μm is indicated by b, a/b satisfies a range of the following formula (1), a fracture strain is 1.6 or more, and a sheet thickness is 0.10 to 0.30 mm.

a/b<0.12  (1)

A hot-rolled steel sheet has, as a chemical composition, by mass %: C: 0.01% to 0.30%; Si: 0.01% to 3.00%; Mn: 0.20% to 3.00%; P: 0.030% or less; S: 0.030% or less; Al: 0.001% to 2.000%; N: 0.0100% or less; and Ni: 0.02% to 0.50%, in which among measurement points at which elemental analysis is performed at a measurement pitch of 1 μm using an EPMA in a region of 250 μm×250 μm on a surface, the percentage of measurement points having a Ni content of 0.5 mass % or more is 10% to 70%.

A steel sheet includes a predetermined composition, in which a microstructure at a ¼ thickness position from a surface in a sheet thickness direction includes, by vol %, ferrite: 80% or more, martensite: 2% or less, and residual austenite: 2% or less, a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and in the microstructure of the steel sheet stretched by 10% at the ¼ thickness position from the surface in the sheet thickness direction, a number density of voids having a maximum diameter of 1.0 μm or more is 1.0×10.sup.9 pieces/m.sup.2 or less.

The invention provides an endless rolling method based on temperature uniformity control, and belongs to the field of iron and steel metallurgy. By optimizing the process path, a new layout mode is adopted, a double heat storage soaking furnace and a descaling box are additionally arranged, transverse and longitudinal bonding magnetic induction heating device is adopted, transverse and longitudinal temperature uniform of the slab in the rolling process is realized, the cross section temperature difference is reduced, and the product quality is improved. On the basis of five-stand arrangement of a traditional finish rolling mill, a rolling mill is additionally arranged to serve as a standby rolling mill, such that on-line non-shutdown change roller of the finish rolling mill is realized. The method of the invention realizes a full-continuous production of production and meets the high-quality development requirements of iron and steel metallurgy, such that traditional cool rolling can be replaced with hot rolling, traditional thick-specification strip can be replaced with high-added-value thin specification strip. There is important significance in the aspects of productivity optimization layout, green manufacturing, intelligent manufacturing and the like.

Disclosed is, as a high-strength steel plate of API X80 grade or higher with a thickness of 38 mm or more, a thick steel plate for structural pipes or tubes that exhibits high strength in the rolling direction and excellent Charpy properties at its mid-thickness part without addition of large amounts of alloying elements. The thick steel plate for structural pipes or tubes disclosed herein has: a specific chemical composition; a microstructure at its mid-thickness part that is a dual-phase microstructure of ferrite and bainite with an area fraction of the ferrite being less than 50%, and that contains ferrite grains with a grain size of 15 μm or less in an area fraction of 80% or more with respect to the whole area of the ferrite; a tensile strength of 620 MPa or more; and a Charpy absorption energy vE.sub.−20+ C. at −20° C. at the mid-thickness part of 100 J or more.

To provide an austenitic stainless steel material having a high creep strength and a high creep ductility even in a high-temperature environment at 800° C. or more. An austenitic stainless steel material according to the present disclosure has a chemical composition that includes, in mass %: C: 0.060% or less; Si: 1.0% or less; Mn: 2.00% or less; P: 0.0010 to 0.0400%; S: 0.010% or less; Cr: 10 to 25%; Ni: 25 to 45%; Nb: 0.2 to 2.0%; W: 2.5 to 6.0%; B: 0.0010 to 0.0100%: Al: 2.5 to 4.5%; and the balance being Fe and impurities, and satisfies Formulae (1) and (2), and the sum of the content of dissolved Nb and the content of dissolved W is 3.2 mass % or more.
(W/184+Nb/93)/(C/12)≥5.5  (1)
(W/184+Nb/93)/(B/11)≤450  (2) In Formulae (1) and (2), the content in mass % of the corresponding element is substituted for each symbol of element.

A method for manufacturing a rolled product for automobile bodywork or body structure with an alloy containing Si: 0.75-1.10, Fe: max 0.4, Cu: 0.5-0.8, Mn: 0.1-0.4, Mg: 0.75-1, Ti: max 0.15, Cr: max 0.1 and V: max 0.1 is disclosed with several process steps from casting the ingot to forming and painting a car body part. The various possibilities of pre aging of the sheet as well as of the heat treatment of the part offer advantageous material properties in forming, material strength and low sensitivity to the bake hardening process which can vary depending in the part location in the car body.