Abstract: A welded product includes: multiple steel members; and one or two or more welds with which the multiple steel members are welded together, at least one of the welds having a surface containing slag, the slag having a Si content of 14% by mass or less and having a mass ratio of Si to Mn of 0.25 or less.

Abstract: Provided is a welded product including: multiple steel members; and one or two or more welds with which the multiple steel members are welded together, at least one of the welds having a surface containing slag, the slag having a Si content of 14% by mass or less and having a mass ratio of Si to Mn of 0.25 or less.

Abstract: Provided is a method of performing pre-paint treatment of an automobile body including a high-tensile steel sheet, in which desirable corrosion resistance can be obtained after painting. A method of performing pre-paint treatment of an automobile body, the method including performing an alkaline degreasing step, a first water-washing step, a chemical conversion treatment step, a second water-washing step, and a cationic electrodeposition painting step, in this order, wherein the chemical conversion treatment step is performed using an chemical conversion treatment agent including zirconium (A), free fluorine ions (B), an allylamine-diallylamine copolymer (C), aluminum ions (D), nitrate ions (E) each at a predetermined concentration; the allylamine-diallylamine copolymer (C) forms an acid addition salt having an anionic counter ion, and the pKa of an acid thereof falls within the range of ?3.7 to 4.8; and the content percentage of diallylamine is 80 mol % or more and 98 mol % or less.

Abstract: Provided is a method of performing pre-paint treatment of an automobile body including a high-tensile steel sheet, in which desirable corrosion resistance can be obtained after painting. A method of performing pre-paint treatment of an automobile body, the method including performing an alkaline degreasing step, a first water-washing step, a chemical conversion treatment step, a second water-washing step, and a cationic electrodeposition painting step, in this order, wherein the chemical conversion treatment step is performed using an chemical conversion treatment agent including zirconium (A), free fluorine ions (B), an allylamine-diallylamine copolymer (C), aluminum ions (D), nitrate ions (E) each at a predetermined concentration; the allylamine-diallylamine copolymer (C) forms an acid addition salt having an anionic counter ion, and the pKa of an acid thereof falls within the range of ?3.7 to 4.8; and the content percentage of diallylamine is 80 mol % or more and 98 mol % or less.