Electrolyte solutions for electrodeposition of zinc alloys and methods of electrodepositing zinc-iron alloys. An electrolyte solution for electroplating can include an alkali metal hydroxide, a zinc salt, a condensation polymer of epichlorohydrin, a quaternary amine, an aliphatic amine, a polyhydroxy alcohol, an aromatic organic acid and/or salts thereof, an amino alcohol, a bisphosphonic acid and/or salts thereof, an iron salt, an alkali metal gluconate, and an amine-based chelating agent. Electrodepositing zinc alloys on a substrate can include introducing a cathode and an anode into an electrolyte solution comprising an alkali metal hydroxide, a zinc salt, a condensation polymer of epichlorohydrin, a quaternary amine, an aliphatic amine, a polyhydroxy alcohol, an aromatic organic acid and/or salts thereof, an amino alcohol, a bisphosphonic acid and/or salts thereof, an iron salt, an alkali metal gluconate, and an amine-based chelating agent.

Provided are a high-strength galvanized steel sheet having excellent delayed fracture resistance by reducing the diffusible hydrogen content in the steel and a method for producing the same. The high-strength galvanized steel sheet includes a steel sheet having a prescribed composition and a microstructure including martensite and tempered martensite, the total area fraction of the martensite and the tempered martensite being 30% or more, and a galvanizing layer formed on the surface of the steel sheet. The diffusible hydrogen content in the high-strength galvanized steel sheet is 0.50 wt. ppm or less. The half-width of the hydrogen release peak of the high-strength galvanized steel sheet is 70° C. or less. The diffusible hydrogen content and the half-width of the hydrogen release peak are determined by a prescribed analysis method.

The present invention is related to an acidic zinc or zinc-nickel alloy electroplating bath for depositing a zinc or zinc-nickel alloy layer and a method for zinc or zinc-nickel alloy electroplating making use of such an electroplating bath.

The present disclosure provides electrolyte solutions for electrodeposition of zinc-manganese alloys, methods of forming electrolyte solutions, methods of electrodepositing zinc-manganese alloys, and multilayered zinc-manganese alloys. An electrolyte solution for electroplating can include a metal salt, boric acid, an alkali metal chloride, polyethylene glycol, and a hydroxy benzaldehyde. An electrolyte solution can be formed by dissolving a metal salt, boric acid, an alkali metal chloride, polyethylene glycol, and a hydroxy benzaldehyde in water or an aqueous solution. Electrodepositing zinc-manganese alloys on a substrate can include introducing a cathode and an anode into an electrolyte solution comprising a metal salt, boric acid, an alkali metal chloride, polyethylene glycol, and a hydroxy benzaldehyde. Electrodepositing can further include passing a current between the cathode and the anode through the electrolyte solution to deposit zinc and manganese onto the cathode.

An electroplating method and a system for electrolytically coating a steel strip, in particular for the automotive sector, with a coating based on zinc and/or a zinc alloy utilizes pulse technology.

Provided is a method for suppressing an increase in the zinc concentration of a plating solution when a zinc alloy plating member using nickel as an alloy element is manufactured using a zinc alloy plating apparatus. The plating apparatus includes: a plating tank; a first diaphragm tank having a first diaphragm; a cathode holding member; a first anode holding member; a soluble zinc-containing member held by the first anode holding member; a soluble metal-containing member containing the nickel which is the alloy element; and a second anode holding member for anode-electrolyzing the soluble metal-containing member. The first diaphragm tank is arranged in a manner that the first electrolytic solution is in contact with one surface of the first diaphragm and the plating solution is in contact with the other surface of the first diaphragm during use.

Disclosed is a method for manufacturing a corrosion-resistant hot-stamping part and a device thereof. The method includes the following steps: blanking a bare steel plate into a required blank shape; heating the blank to above AC3 in an oxygen-free heating furnace to austenite the blank; putting the austenitized blank into a mold to mold a part; and conducting a surface treatment of the part to form a corrosion-resistant coating layer on a surface of the part. The hot-stamping part manufactured using the described method has good surface quality and great corrosion-resistant performance

A steel sheet has a chemical composition with a steel structure containing, by volume fraction, soft ferrite: 0-30%, retained austenite: 3-40%, fresh martensite: 0-30%, pearlite and cementite: 0-10%, and a remainder including hard ferrite. In the steel sheet, a number proportion of retained austenite having an aspect ratio of 2.0 or more in the total retained austenite is 50% or more, and a soft layer having a thickness of 1-100 μm is present. In the soft layer, a volume fraction of ferrite grains having an aspect ratio of less than 3.0 is 50% or more, and a volume fraction of retained austenite is 50% or more of the volume fraction of the retained austenite of the inside of the steel sheet. A peak of an emission intensity at a wavelength indicating Si appears in a range of more than 0.2 μm to 5 μm or less from the surface.

This invention provides a threaded connection for oil country tubular goods that exhibits excellent corrosion resistance and galling resistance, and a method for producing the threaded connection for oil country tubular goods. The method includes a Zn—Ni alloy plating layer formation step of forming a Zn—Ni alloy plating layer, and a chromate coating formation step of forming a chromate coating after the Zn—Ni alloy plating layer formation step. The chromate coating formation step includes a chromate treatment step and a drying step. The chromate coating formation step satisfy one or more conditions selected from the following conditions 1 to 3. Condition 1: stirring speed of the chromating solution in the chromate treatment step: a linear speed of 0.5 m/s or more; Condition 2: chromate treatment time in the chromate treatment step: less than 50 seconds; and Condition 3: drying temperature in the drying step: 60° C. or less.

Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing, excellent delayed fracture resistance, and high tensile shear stress after resistance spot welding by properly adjusting its chemical composition and its microstructure such that at least 20 Nb-based precipitates having a grain size of less than 0.10 μm are present on average per 100 μm.sup.2 of a cross section parallel to a thickness direction of the member, a prior austenite average grain size is 8 μm or less, an average aspect ratio of prior austenite grains is 2.5 or less, and a volume fraction of martensite is 90% or more, and such that a standard deviation of Vickers hardness measured every 200 μm on a surface of the member is 40 or less.