Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Masahito Tasaka

Yoshiaki Nakazawa

Yasuaki Tanaka

Kaori Kawano

Toshiro Tomida

Toshiya Suzuki

Masahiro Nakata

Kenji Tamura

Naoaki Shimada

Takuya Nishio

Hiroki Fujimoto

Takeshi Kawachi

Masanori Yasuyama

Yoshihiro Serizawa

Akihiro Sakamoto

Jun Haga

Masayuki Wakita

Hideki Matsuda

Yasuhiro Masaki

Manabu Kanzaki

Norimasa Yamasaki

Hitomi Nishibata

Shoji Kinomura

Akihiro Uehira

Ryuji Hamada

According to the present invention, there is provided a cooling apparatus for a steel material in which one portion in a longitudinal direction of an elongated steel material () is heated while the steel material is fed in the longitudinal direction in a state where one end portion of the steel material is gripped, and the one end portion is moved in a two-dimensional or three-dimensional direction so as to form the steel material into a predetermined shape including a bent portion and thereafter to cool a heated portion including the bent portion. The cooling apparatus includes a first cooling apparatus () that ejects a first cooling medium to the heated portion, and a second cooling apparatus () that is disposed on a downstream side from the first cooling apparatus when viewed along a feeding direction of the steel material, and that ejects a second cooling medium to the heated portion. A plurality of the second cooling apparatuses are disposed along the feeding direction, and flow rates of the second cooling media can be controlled independently of each other. According to the configuration, it is possible to reduce the insufficient quenching of the steel material.

Cooling apparatus and cooling method for steel material

The present invention has as its object the provision of a T-shaped joint structure sufficiently securing a mounting region for another member and securing rigidity of a joint part. A first member and a second member joined with the first member and extending in a direction vertical to the longitudinal direction of the first member are provided. In a side view of first member in the longitudinal direction, the part of the first member joined with the second member, that is, a first member side joining element, is slanted from the first member toward the second member so that the first member becomes tapered. The part of the second member joined with the first member, that is, a second member side joining element, is slanted from the first member toward the second member in the same direction as the first member side joining element. The first member side joining element and second member side joining element are smoothly joined to form a joined part. The joined part is present at least at single side of the first and second member in the lateral direction.

T-shaped joint structure

A steel material comprising, by mass%, C: greater than 0.05% to 0.2%, Mn: 1% to 3%, Si: greater than 0.5% to 1.8%, Al: 0.01% to 0.5%, N: 0.001% to 0.015%, Ti or a sum of V and Ti: greater than 0.1% to 0.25%, Ti: 0.001% or more, Cr: 0% to 0.25%, Mo: 0% to 0.35%, the balance: Fe and impurities, comprising a multi-phase structure having a ferrite main phase and a second phase containing one or more of bainite, martensite and austenite, wherein an average nanohardness of the second phase is less than 6.0 GPa, an average grain diameter of all crystal grains in the main phase and the second phase is 3 &#x3bc;m or less, and a proportion of a length of small-angle grain boundaries where the misorientation is 2&#xb0; to less than 15&#xb0; in a length of all grain boundaries is 15% or more.

Steel material

A formed member is provided which can be manufactured at a low cost, which has excellent dimensional accuracy, which has excellent axial crushing properties and three-point bending properties, which has excellent bending stiffness and torsional stiffness, and which is suitable for use in a component of an automobile. The formed member () has a reinforcing member () which is joined by a weld () provided on a ridge portion (). It is manufactured by joining a flat sheet blank and a flat sheet reinforcing member () by a weld () and performing bending so that the weld () becomes a ridge portion ().

Formed member and manufacturing method thereof

A steel material contains: by mass %, C: greater than 0.05% to 0.18%; Mn: 1% to 3%; Si: greater than 0.5% to 1.8%; Al: 0.01% to 0.5%; N: 0.001% to 0.015%; one or both of V and Ti: 0.01% to 0.3% in total; Cr: 0% to 0.25%; Mo: 0% to 0.35%; a balance: Fe and impurities; and 80% or more of bainite by area %, and 5% or more in total of one or two or more selected from a group consisting of ferrite, martensite and austenite by area %, in which an average block size of the above-described bainite is less than 2.0 &#x3bc;m, an average grain diameter of all of the above-described ferrite, martensite and austenite is less than 1.0 &#x3bc;m, an average nanohardness of the above-described bainite is 4.0 GPa to 5.0 GPa, and MX-type carbides each having a circle-equivalent diameter of 10 nm or more exist with an average grain spacing of 300 nm or less therebetween.

The steel material for an impact absorbing member has a composition containing: by mass %, C: 0.05 to 0.18%, Mn: 1 to 3%, Si+Al: at least 0.5% and less than 2.5%, and N: 0.001 to 0.015%, and in some cases, Cr: at most 0.5%, Mo: at most 0.2%, Ti: at most 0.05%, Nb: at most 0.05%, V: at most 0.2%, and B: at most 0.002%, the remainder being Fe and impurities. The steel material structure contains at least 70% by area of bainite made up of a lath structure having an average interval of at most 1 mm and martensite, 5 to 30%, and satisfies Formulas (1) and (2): (1) 1.2 &#xa3; H/H&#xa3; 1.6, (2) 0.90 &#xa3; {(H/H)/(H/H) &#xa3; 1.3, where Hand Hrepresent average nano hardness in an initial state and after 10% tensile deformation of the martensite, and Hand Hrepresent that of bainite, respectively.

Steel material and impact absorbing member

A steel sheet suitable as a starting material for a vehicle impact absorbing member with high absorption of impact energy and resistance to cracking contains, by mass %, C: 0.08-0.30%, Mn: 1.5-3.5%; Si+Al: 0.50-3.0%, P: 0.10% or less, S: at most 0.010%, and N: at most 0.010%, and optionally, one or more types selected from Cr: at most 0.5%, Mo: at most 0.5% , B: at most 0.010%, Ti: less than 0.04%, Nb: less than 0.030%, V: less than 0.5%, Ca: at most 0.010%, Mg: at most 0.010%, REM: at most 0.050%, and Bi: at most 0.050%. The microstructure contains, by area %, bainite: more than 50%, martensite: 3-30%, and retained austenite: 3-15%, the remainder comprising ferrite having an average grain diameter of less than 5 mm. The product of uniform elongation and hole expansion ratio is at least 300%and 5% effective flow stress is at least 900 MPa.

Steel sheet suitable for impact absorbing member and method for its manufacture

Provided is a crash box having improved robustness, wherein an angle of the pair of corner portions is set to 90&#xb0; or larger and 150&#xb0; or smaller, an angle of the another pair of corner portions is set to 30&#xb0; or larger and 90&#xb0; or smaller, one or more inwardly convex trench portions extending in a longitudinal direction are provided, a cross-sectional peripheral length of the tubular body in the one end side is shorter than a cross-sectional peripheral length of the tubular body in the other end side, an aspect ratio between the longest one and the shortest one of diagonal lines of a polygon changes depending on a position on the axial direction of the tubular body, and overall sides on the cross section in the one end are formed in parallel to the opposite sides on the cross section in the other end.

Crash box and automobile chassis

There is provided a Cr-containing austenitic alloy tube, wherein a chromium oxide film with a thickness of 0.05 to 1.5 &#x3bc;m having the relationship defined by Formula (i) is formed on the inner surface of the tube, wherein the average concentration of C in the depth range of 5 to 10 &#x3bc;m from the inner surface is lower than the concentration of C in a base metal;0.4&#x2266;&#x3b4;1/&#x3b4;2&#x2266;2.5&#x2003;&#x2003;(i)wherein &#x3b4;1 and &#x3b4;2 are thicknesses (&#x3bc;m) of the chromium oxide film at both ends of tube, respectively.

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Tokyo, Japan

Masahito Tasaka