STEEL WIRE FOR BOLT, BOLT, AND PRODUCTION METHOD THEREFOR

Provided are a high-strength bolt having a tensile strength of 1,000 to 1,400 MPa and exhibits the same level of the delayed fracture resistance as that of the standard alloy steel even when omitting or reducing Mo and Cr from the SCM steel and the SCr steel, a steel wire for bolts used to manufactu...

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Bibliographische Detailangaben
Hauptverfasser:	MATSUMOTO, Yosuke, CHIBA, Masamichi
Format:	Patent
Sprache:	eng ; fre ; ger
Schlagworte:	ALLOYS BLASTING CHEMISTRY DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS ORMACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS,CLIPS, WEDGES, JOINTS OR JOINTING ENGINEERING ELEMENTS AND UNITS FERROUS OR NON-FERROUS ALLOYS GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVEFUNCTIONING OF MACHINES OR INSTALLATIONS HEATING LIGHTING MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS MECHANICAL ENGINEERING METALLURGY METALLURGY OF IRON MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS THERMAL INSULATION IN GENERAL TREATMENT OF ALLOYS OR NON-FERROUS METALS WEAPONS
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Beschreibung
Zusammenfassung:	Provided are a high-strength bolt having a tensile strength of 1,000 to 1,400 MPa and exhibits the same level of the delayed fracture resistance as that of the standard alloy steel even when omitting or reducing Mo and Cr from the SCM steel and the SCr steel, a steel wire for bolts used to manufacture such a high-strength bolt, and useful methods for manufacturing them. The steel wire for bolts in the present invention satisfies the predetermined chemical composition. When a rate of a B content at D 0 /4 part in the steel wire for bolts is 100% where D 0 is a diameter of the steel wire for bolts, a ratio of a B content at a surface of the steel wire for bolts is 75% or less on average, and a difference between a maximum value and a minimum value of the ratio is 25% or less. A prior austenite crystal grain size number in a region from the surface to a depth of 100 µm of the steel wire for bolts is No. 8 or more.