Systems and methods for low-manganese welding alloys are disclosed. An example arc welding consumable may comprise: less than 0.4 wt % manganese; strengthening agents selected from the group consisting of nickel, cobalt, copper, carbon, molybdenum, chromium, vanadium, silicon, and boron; and grain control agents selected from the group consisting of niobium, tantalum, titanium, zirconium, and boron. The grain control agents may comprise greater than 0.06 wt % and less than 0.6 wt % of the welding consumable. The resulting weld deposit may comprise a tensile strength greater than or equal to 70 ksi, a yield strength greater than or equal to 58 ksi, a ductility (as measured by percent elongation) of at least 22%, and a Charpy V-notch toughness greater than or equal to 20 ft-lbs at −20° F. The welding consumable may provide a manganese fume generation rate less than 0.01 grams per minute during the arc welding operation.

Systems and methods for low-manganese welding alloys are disclosed. An example arc welding consumable may comprise: less than 0.4 wt % manganese; strengthening agents selected from the group consisting of nickel, cobalt, copper, carbon, molybdenum, chromium, vanadium, silicon, and boron; and grain control agents selected from the group consisting of niobium, tantalum, titanium, zirconium, and boron. The grain control agents may comprise greater than 0.06 wt % and less than 0.6 wt % of the welding consumable. The resulting weld deposit may comprise a tensile strength greater than or equal to 70 ksi, a yield strength greater than or equal to 58 ksi, a ductility (as measured by percent elongation) of at least 22%, and a Charpy V-notch toughness greater than or equal to 20 ft-lbs at −20° F. The welding consumable may provide a manganese fume generation rate less than 0.01 grams per minute during the arc welding operation.

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%.

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%.

Disclosed is a stainless steel having excellent surface electrical conductivity for a fuel cell separator. According to an embodiment of the disclosed stainless steel having excellent surface electrical conductivity for a fuel cell separator, a value of the following surface oxide atomic ratio (1) may be 0.5 or less, as measured on the surface of a stainless steel containing 15 wt % or more of Cr by X-ray angle-resolved photoemission spectroscopy using an Al-Kα X-ray source under the condition where a take-off angle of photoelectrons is from 12° to 85°.

[00001]$\begin{array}{cc}\frac{\begin{array}{c}\mathrm{sum}\mathrm{of}\mathrm{atomic}\mathrm{concentrations}\left(\mathrm{at}\%\right)\\ \mathrm{of}\mathrm{metal}\mathrm{elements}\mathrm{in}\mathrm{metal}\mathrm{oxide}\left(\mathrm{MO}\right)\end{array}}{\begin{array}{c}\mathrm{sum}\mathrm{of}\mathrm{atomic}\mathrm{concentrations}\left(\mathrm{at}\%\right)\\ \mathrm{of}\mathrm{metal}\mathrm{elements}\mathrm{in}\mathrm{total}\mathrm{oxides}\mathrm{and}\mathrm{hydroxides}\end{array}}& \left(1\right)\end{array}$

The metal oxide (MO) includes a mixed oxide: M represents an alloying element other than Cr and Fe or a combination thereof in the matrix; and O represents oxygen. The total oxides and hydroxides include a Cr oxide, a Cr hydroxide, an Fe oxide, an Fe hydroxide, and the metal oxide (MO).

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.

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.

The invention relates a duplex ferritic austenitic stainless steel having high formability utilizing the TRIP effect and high corrosion resistance with the balanced pitting resistance equivalent. The duplex stainless steel contains less than 0.04 weight % carbon, less than 0.7 weight % silicon, less than 2.5 weight % manganese, 18.5-22.5 weight % chromium, 0.8-4.5 weight % nickel, 0.6-1.4 weight % molybdenum, less than 1 weight % copper, 0.10-0.24 weight % nitrogen, the rest being iron and inevitable impurities occurring in stainless steels.

A method of manufacturing steel strip including the steps of: casting molten steel into slabs; reheating the slabs at 1150° C. or more for 1 hour or more; hot rolling the steel into a strip, preferably with an average F1 slab entry temperature above 1000° C.; coiling the hot rolled steel strip; batch annealing the steel strip: at an intercritical temperature (i.e. between Ac1 and Ac3), preferably below 700° C.; in non-oxidising and non-nitrogenated atmosphere; total annealing time at least 5 hours, preferably at least 10 hours to get Mn enrichment in austenite such that Mn content is at least 1.25 times bulk Mn content of the steel and C enrichment such that C content is at least 1.2 times bulk C content of the steel; cooling the steel after batch annealing in air, forced air or water quench.

A method of manufacturing steel strip including the steps of: casting molten steel into slabs; reheating the slabs at 1150° C. or more for 1 hour or more; hot rolling the steel into a strip, preferably with an average F1 slab entry temperature above 1000° C.; coiling the hot rolled steel strip; batch annealing the steel strip: at an intercritical temperature (i.e. between Ac1 and Ac3), preferably below 700° C.; in non-oxidising and non-nitrogenated atmosphere; total annealing time at least 5 hours, preferably at least 10 hours to get Mn enrichment in austenite such that Mn content is at least 1.25 times bulk Mn content of the steel and C enrichment such that C content is at least 1.2 times bulk C content of the steel; cooling the steel after batch annealing in air, forced air or water quench.