Disclosed is 500-MPa low-yield-ratio weather-resistant bridge steel and a manufacturing method therefor; the weather-resistant bridge steel includes the following components in percentage by mass: C: 0.04%-0.09%, Si: 0.15%-0.30%, Mn: 1.40%-1.50%, P: 0.009%-0.015%, S: ≤0.002%, Nb: 0.020%-0.050%, Ti: 0.010%-0.020%, V: 0.010%-0.030%, Cu: 0.30%-0.40%, Ni: 0.30%-0.45%, Cr: 0.45%-0.60%, Mo: 0.08%-0.15%, Alt: 0.02%-0.04%, and the balance Fe and inevitable impurities; through scientific component designing and a matched manufacturing method combining controlled rolling and cooling and tempering, the weather-resistant bridge steel has a low yield ratio, high low-temperature toughness and high elongation.

Provided is a free-cutting steel that, despites not containing Pb, has machinability by cutting higher than or equal to that of a low carbon sulfur-lead composite free-cutting steel. A free-cutting steel comprises: a chemical composition that contains, in mass %, C: less than 0.09%, Mn: 0.50% to 1.50%, S: 0.250% to 0.600%, O: more than 0.010% and 0.050% or less, and Cr: 0.50% to 1.50%, with a balance consisting of Fe and inevitable impurities, and in which a A value defined by the following formula (1) is 6.0 to 18.0, and a steel microstructure in which at least 500 particles/mm.sup.2 of sulfide of less than 1 μm in equivalent circle diameter and at least 2000 particles/mm.sup.2 of sulfide of 1 μm to 5 μm in equivalent circle diameter are distributed.

A method of manufacturing a hot stamping includes: inserting a blank having a plating layer formed on at least one surface of a base material into a heating furnace having a plurality of sections having different temperature increase rate ranges; and multi-stage heating the blank gradually while passing through the plurality of sections. The plurality of sections include: a first heating section having a first average temperature increase rate change rate; a second heating section having a second average temperature increase rate change rate different from the first average temperature increase rate change rate; and a third heating section having a third average temperature increase rate change rate different from the first average temperature increase rate change rate and the second average temperature increase rate change rate. The third average temperature increase rate change rate includes a section in which a positive value is changed to a negative value.

A die steel which enables manufacturing a hot stamp die that has both high hardness and high thermal conductivity, a hot stamp die, and a manufacturing method thereof are provided. This steel for a hot stamp die has a component composition, in mass% of 0.45-0.65% C, 0.1-0.6% Si, 0.1-0.3% Mn, 2.5-6.0% Cr, 1.2-2.6% Mo, and 0.4-0.8% V, the remainder being Fe and unavoidable impurities. Further, this hot stamp die has the aforementioned component composition, and the manufacturing method is for manufacturing said hot stamp die.

A slab library for separate storage of cold blanks and hot blanks of heavy plates and heating furnace layout, and a furnace loading method are provided. The slab library and heating furnace layout comprises: 1# slab library and 2# slab library span, i.e. feeding span, arranged side by side; continuous casting blank delivery roller way connected to the continuous casting process arranged at the inlet of the 2# slab library span; heating furnace span arranged at the outlet of the 2# slab library span, wherein more than two heating furnaces are arranged in the heating furnace span, and arranged side by side at the outlet of the 2# slab library span; slab preparatory library span, which is across the inlets of the 1# slab library span and the 2# slab library span; span-crossing traverse trolley roller way, which is across the cold blank zones of the 1# slab library span and the 2# slab library span, and the heating furnace span; span-crossing roller way, which is across the slab preparatory library span and the 1# slab library span; and, feeding roller way, arranged between the 2# slab library span and the heating furnace span, and across the hot blank zone and the cold blank zone of the 2# slab library span and the two ends of the heating furnace span, wherein the feeding roller way has a structure for delivery in two directions.

A slab library for separate storage of cold blanks and hot blanks of heavy plates and heating furnace layout, and a furnace loading method are provided. The slab library and heating furnace layout comprises: 1# slab library and 2# slab library span, i.e. feeding span, arranged side by side; continuous casting blank delivery roller way connected to the continuous casting process arranged at the inlet of the 2# slab library span; heating furnace span arranged at the outlet of the 2# slab library span, wherein more than two heating furnaces are arranged in the heating furnace span, and arranged side by side at the outlet of the 2# slab library span; slab preparatory library span, which is across the inlets of the 1# slab library span and the 2# slab library span; span-crossing traverse trolley roller way, which is across the cold blank zones of the 1# slab library span and the 2# slab library span, and the heating furnace span; span-crossing roller way, which is across the slab preparatory library span and the 1# slab library span; and, feeding roller way, arranged between the 2# slab library span and the heating furnace span, and across the hot blank zone and the cold blank zone of the 2# slab library span and the two ends of the heating furnace span, wherein the feeding roller way has a structure for delivery in two directions.

An example bushing has three portions along its radial direction including an inner portion most proximal to a central hole of the bushing, an outer portion most distal from the center hole, and a core portion between the inner portion and the outer portion. The core portion has a hardness that is less than the hardness of the inner portion or the outer portion of the bushing. The bushing may be formed using high carbon steel, which in some cases may be spheroidal cementite crystal structure. A rough bushing may be formed using the high carbon steel, followed by a direct hardening process, and an induction hardening process on the inner surface most proximal to the central hole of the bushing. The induction hardening on the inner surface may harden the outer portion while tempering the core portion of the bushing.

A continuous hot-dip galvanizing apparatus has a vertical annealing furnace, one or more hearth rolls, a hot-dip galvanizing apparatus, an alloying line, and humidified gas supply ports. When the steel sheet having a Si content of 0.2 mass % or more is conveyed inside the annealing furnace, the humidified gas supply ports positioned in a latter part of the soaking zone supply the humidified gas to the soaking zone and the at least one dry gas supply port supplies the dry gas to the soaking zone. When the steel sheet having a Si content of less than 0.2 mass % is conveyed inside the annealing furnace, the plurality of the humidified gas supply ports do not supply the humidified gas to the soaking zone and the at least one dry gas supply port supplies the dry gas to the soaking zone.

Method of producing cast-steel molded parts especially suited to low-temperature applications, particularly, handling liquid hydrogen. Conventional high-nickel alloy austenitic stainless steels must be used as forged, not cast, products with high wall thicknesses to lend them the mechanical properties sufficient for handling liquid hydrogen and preventing hydrogen embrittlement. According to the method, an alloy consisting essentially of 2.5-4.5% Si, 10.5-19.0% Cr, 13.5-20.0% Ni, 0.5-1.5% Mn, 1.0-2.0% Co, and 0.5-1.5% Mo is melted; the melt is poured into a mold; and the molded part is solution heat-treated at a temperature of from 950° C. to 1150° C. The cast steel parts have a high content of hydrogen-embrittlement curtailing silicon, and nickel, chromium and other components lending them properties not essentially due to the conventional-steel presence of carbon. The molded parts thus produced have sufficient fracture toughness even at liquid-hydrogen temperatures.

A controlled thermal coefficient product manufacturing system and method is disclosed. The disclosed product relates to the manufacture of metallic material product (MMP) having a thermal expansion coefficient (TEC) in a predetermined range. The disclosed system and method provides for a first material deformation (FMD) of the MMP that comprises at least some of a first material phase (FMP) wherein the FMP comprises martensite randomly oriented and a first thermal expansion coefficient (FTC). In response to the FMD at least some of the FMP is oriented in at least one predetermined orientation. Subsequent to deformation, the MMP comprises a second thermal expansion coefficient (STC) that is within a predetermined range and wherein the thermal expansion of the MMP is in at least one predetermined direction. The MMP may be comprised of a second material phase (SMP) that may or may not transform to the FMP in response to the FMD.