Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)

Hiroshi Irie

Masafumi Shimizu

Takatoshi Yoshida

Minoru Chida

Masaaki Miura

Yuichi Futamura

Michitaka Tsunezawa

Hiroo Shige

Ryota Nakanishi

Takeshi Kojima

Takeshi Minowa

Masaya Nakamura

Kohei Okamoto

Akira Kawakami

Takayuki Maeda

Hang Yu

A steel sheet may be used for hot-dip galvanizing capable of manufacturing hot-dip galvannealed steel sheet(s) with a high Si content and in which alloying unevenness is suppressed. Such a steel sheet for hot-dip galvanizing may include an internal oxide layer containing an oxide of Si between a surface layer of the steel sheet and a steel sheet base portion. The Si content in a chemical composition of the steel sheet may be 1.0 mass % or more. A solid solution Si amount from a surface of the steel sheet to a depth of 1 μm measured at all four positions including positions of 10 mm, 30 mm, and 50 mm from an edge in a coil width direction and a position of a center in the coil width direction at a rear end in a rolling direction of the steel sheet for hot-dip galvanizing may be 1.4 wt. % or less.

Steel sheet for hot-dip galvanizing, hot-dip galvanized steel sheet, and alloyed hot-dip galvannealed steel sheet

Provided is a technique in which a reduction annealing method is used to efficiently produce a high-strength hot-dip galvanizing substrate or high-strength hot-dip galvannealing substrate, which is useful as a raw material for producing a high-strength plated steel sheet suppressed in the occurrence of bare spot. The substrate for hot-dip galvanizing or hot-dip galvannealing of the present invention satisfies the following condition: when the mapping intensity of Fe, which is obtained by using an electron probe microanalyser in a measurement field of view of 33.6 &#x3bc;m&#xd7;41.4 &#x3bc;m on the surface after reduction annealing, of 0 to 240 is divided into 16 parts at an interval of 15, the area occupied by a mapping intensity of 195 or more has 70% or more.

Substrate for hot-dip galvanizing or hot-dip galvannealing, production method therefor, and hot-dip galvanized steel sheet or hot-dip galvannealed steel sheet

Provided is a hot-dip galvannealed steel sheet for hot stamping use, in which a base steel sheet contains Si in an amount of 0.7% or more, and which has excellent joint strength at a spot-welded part and can exhibit excellent adhesion to a coating film after hot stamping and coating with requiring little restriction of a hot stamp step. In the hot-dip galvannealed steel sheet, a base steel sheet contains, in mass %, 0.10 to 0.5% of C, 0.7 to 2.5% of Si, 1.5 to 3% of Mn and 0.01 to 0.5% of Al. The hot-dip galvannealed steel sheet is characterized in that the Mn concentration in a plating layer is 0.20% or more, the plated amount is 75 g/mor less, and the oxygen concentration at the interface between the plating layer and the base steel sheet is 0.50% or less.

Hot-dip galvannealed steel sheet for hot stamping and method for manufacturing steel part

A high tensile strength hot-dip galvannealed steel sheet having excellent coated-layer adhesiveness in which the hot-dip galvannealed layer does not peel off from a base steel sheet even in being subjected to working accompanied by sliding and a method for producing the same are provided. In the high tensile strength hot-dip galvannealed steel sheet, a hot-dip galvannealed layer is formed on the surface of the base steel sheet, the base steel sheet contains Si by 0.04-2.5%, and, when the surface roughness of the base steel sheet after the hot-dip galvannealed layer is removed by dissolution with an acid is measured for a plurality of locations by a laser microscope, the arithmetic mean inclination angle (R&#x394;a) is 23.0&#xb0; or more and the root mean square inclination angle (R&#x394;q) is 29.0&#xb0; or more in 60% or more of all of the locations measured.

High tensile strength hot-dip galvannealed steel sheet having excellent coated-layer adhesiveness and method for producing same

Disclosed is a hot-dip galvannealed steel sheet that stably exhibits satisfactory phosphatability. It is a high-strength hot-dip galvannealed steel sheet which includes a base steel sheet and, arranged on at least one side thereof, an Fe&#x2014;Zn alloyed galvanized layer. The base steel sheet contains 0.03% to 0.3% of carbon, 0.5% to 3.0% of silicon, and 0.5% to 3.5% of manganese, with the remainder including iron and inevitable impurities. The Fe&#x2014;Zn alloyed galvanized layer has a concentration of silicon present as an oxide of [Si] (percent by mass) and a concentration of manganese present as an oxide of [Mn] (percent by mass), and these parameters satisfy the following conditions (1) and (2):[Si]&#x2266;0.25&#x2003;&#x2003;(1)[Mn]/[Si]&#x2266;3.0&#x2003;&#x2003;(2).

High-strength hot-dip galvannealed steel sheet with superior phosphatability

According to a process for hot-dip galvanization of the present invention, a steel sheet is treated by the oxidization/reduction method for better quality of galvanization and then hot-dip galvanized. An annealing line of equipment for hot-dip galvanization is composed of a non-oxidizing zone, an oxidizing zone, and a reducing zone, in his order. A steel sheet containing elements liable to oxidize more easily than iron is oxidized by blowing flames onto it in the oxidizing zone according to the oxidization/reduction method. Further, the steel sheet is reduced and annealed in the reducing zone.

Method and facility for hot dip zinc plating

Disclosed is a high-strength hot dip galvannealed steel sheet having high powdering resistance produced by employing such a constitution that a Fe&#x2014;Zn alloy plated layer is provided on at least one side of a basis steel sheet and a region in which Al (atomic %)/Zn (atomic %)&#x2267;0.10 is present in a thickness of 300 &#x212b; or more from the surface of the plated layer along the depth direction of the plated layer. Also disclosed is a hot dip galvannealed steel sheet whose formability is greatly improved by optionally specifying chemical composition and structure of the basis steel sheet.

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Kakogawa, Japan

Hiroshi Irie