An inline thermal treatment system for thermally treating a continuous product includes a housing comprising a first opening and second opening respectively configured to allow the continuous product to enter and to exit the housing. The system includes at least one laser coupled to a laser power source and configured to output at least one laser beam that impinges upon and heats the portion of the continuous product.

A steel wire for high-strength bolts is used for a non heat-treatment bolt with an excellent cold forgeability for which quenching and tempering steps have been omitted after bolt formation, and which has a tensile strength of 1200 MPa or more and an excellent delayed fracture resistance. The steel wire includes C, Si, Mn, P, S, Cr, Al, N, and B, at least one selected from the group consisting of Ti, V, and Nb with the balance consisting of iron and inevitable impurities. The steel wire has a microstructure wherein ferrite and perlite have a total area rate of 98% or more, perlite lamellar spacing is 250 nm or less, and an area rate of the perlite is more than 40%, and 80% or less. The steel wire has a tensile strength of 1300 MPa or less.

A steel wire for high-strength bolts is used for a non heat-treatment bolt with an excellent cold forgeability for which quenching and tempering steps have been omitted after bolt formation, and which has a tensile strength of 1200 MPa or more and an excellent delayed fracture resistance. The steel wire includes C, Si, Mn, P, S, Cr, Al, N, and B, at least one selected from the group consisting of Ti, V, and Nb with the balance consisting of iron and inevitable impurities. The steel wire has a microstructure wherein ferrite and perlite have a total area rate of 98% or more, perlite lamellar spacing is 250 nm or less, and an area rate of the perlite is more than 40%, and 80% or less. The steel wire has a tensile strength of 1300 MPa or less.

A steel reinforcing bar contains 0.06 wt % to 0.11 wt % carbon, more than 0 and not more than 0.25 wt % silicon, 0.8 wt % or more and less than 2.0 wt % manganese, more than 0 and not more than 0.01 wt % phosphorus, more than 0 and not more than 0.01 wt % sulfur, 0.01 to 0.03 wt % aluminum, 0.50 to 1.00 wt % nickel, 0.027 to 0.125 wt % molybdenum, more than 0 and not more than 0.25 wt % chromium, more than 0 and not more than 0.28 wt % copper, more than 0 and not more than 0.01 wt % nitrogen, and the remainder being iron and unavoidable impurities. The reinforcing bar has a surface layer and a core. The surface layer has a hardened layer of tempered martensite, and the core has a mixed structure of bainite, ferrite and pearlite.

A steel reinforcing bar contains 0.06 wt % to 0.11 wt % carbon, more than 0 and not more than 0.25 wt % silicon, 0.8 wt % or more and less than 2.0 wt % manganese, more than 0 and not more than 0.01 wt % phosphorus, more than 0 and not more than 0.01 wt % sulfur, 0.01 to 0.03 wt % aluminum, 0.50 to 1.00 wt % nickel, 0.027 to 0.125 wt % molybdenum, more than 0 and not more than 0.25 wt % chromium, more than 0 and not more than 0.28 wt % copper, more than 0 and not more than 0.01 wt % nitrogen, and the remainder being iron and unavoidable impurities. The reinforcing bar has a surface layer and a core. The surface layer has a hardened layer of tempered martensite, and the core has a mixed structure of bainite, ferrite and pearlite.

A process for smelting steel for ultrafine carborundum sawing wires, comprising: 1) in a vacuum induction furnace, using pure iron and low-phosphorus pig iron as raw materials to be melted into molten steel under the protection of argon; vacuumizing and smelting, and degassing; using silicon iron as a deoxidizer to adjust components of the molten steel; and casting a circular ingot in vacuum; 2) cleaning the surface of the circular ingot to produce an electrode bar; 3) remelting and smelting the electrode bar as raw material to a cylindrical electroslag ingot in an electroslag furnace, wherein the electroslag protecting slag comprises: CaF.sub.2: 45-55%, Al.sub.2O.sub.3: 15-25%, SiO.sub.2: 20-25%, Na.sub.2O: 2-4%, and K.sub.2O: 1-2%; 4) forging the electroslag ingot to a square billet; and 5) rolling the forged billet to a steel wire rod, and the steel wire rod comprising [C]: 0.92-1.1%, [Si]: 0.3-0.4%, [Mn]: 0.5-0.8%, [Al]<0.0008%, [N]<0.005%, [S]<0.01%, and [P]<0.015%.

A method of manufacturing a steel strip for coiled tubing includes melting molten steel having a composition including, in terms of percent by mass, C: 0.10% or more and 0.16% or less, Si: 0.1% or more and 0.5% or less, Mn: 0.5% or more and 1.5% or less, P: 0.02% or less, S: 0.005% or less, Sol. Al: 0.01% or more and 0.07% or less, Cr: 0.4% or more and 0.8% or less, Cu: 0.1% or more and 0.5% or less, Ni: 0.1% or more and 0.3% or less, Mo: 0.1% or more and 0.2% or less, Nb: 0.01% or more and 0.04% or less, Ti: 0.005% or more and 0.03% or less, N: 0.005% or less, and the balance of Fe and inevitable impurities; casting the molten steel into a steel material; subjecting the steel material to hot rolling; and coiling a resultant steel strip, wherein a finish rolling temperature is 820° C. or more and 920° C. or less, a coiling temperature is 550° C. or more and 620° C. or less, and a time taken from the finish hot rolling to the coiling is 20 seconds or less.

A method of manufacturing a steel strip for coiled tubing includes melting molten steel having a composition including, in terms of percent by mass, C: 0.10% or more and 0.16% or less, Si: 0.1% or more and 0.5% or less, Mn: 0.5% or more and 1.5% or less, P: 0.02% or less, S: 0.005% or less, Sol. Al: 0.01% or more and 0.07% or less, Cr: 0.4% or more and 0.8% or less, Cu: 0.1% or more and 0.5% or less, Ni: 0.1% or more and 0.3% or less, Mo: 0.1% or more and 0.2% or less, Nb: 0.01% or more and 0.04% or less, Ti: 0.005% or more and 0.03% or less, N: 0.005% or less, and the balance of Fe and inevitable impurities; casting the molten steel into a steel material; subjecting the steel material to hot rolling; and coiling a resultant steel strip, wherein a finish rolling temperature is 820° C. or more and 920° C. or less, a coiling temperature is 550° C. or more and 620° C. or less, and a time taken from the finish hot rolling to the coiling is 20 seconds or less.

In a rolled steel bar or rolled wire rod for a cold-forged component having a predetermined chemical composition, Y1 represented by Y1=[Mn]×[Cr] and Y2 represented by Y2=0.134×(D/25.4−(0.50×√[C]))/(0.50×√[C]) satisfy Y1>Y2, the tensile strength is 750 MPa or less, an internal structure is a ferrite-pearlite structure, and the ferrite fraction in the internal structure is 40% or greater.

AMOUNT IS 0.30%

To achieve a substantially uniform microstructure across a continuously cast thin metal strip, it is beneficial to cool a width of the strip to a substantially constant temperature before further cooling the strip to reach any desired phase transformation temperature. Accordingly, methods of continuously casting a thin metal strip may include moving the thin strip to a cooling section, the cooling section having a plurality of coolant discharge ports configured to discharge a flow of coolant along the thin strip; initially sensing the temperature of the thin strip to determine a temperature distribution across the width of the thin strip, and producing a sensor signal corresponding to a sensed temperature at each of the first plurality of locations; and individually controlling the cooling across a width of the thin strip by way of the plurality coolant discharge ports in each zone of a first row using the determined temperature distribution.