Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Munenobu Sato

Hidenori Nako

Wataru Urushihara

Takuya Kochi

Yoshihiko Kitagawa

Yoshitomi Okazaki

Masafumi Yamakami

The present invention is a weld metal formed by gas shielded arc welding using a flux cored wire, the welded metal having a predetermined chemical composition, residual austenite particles being present in an amount of at least 2500 particles/mm, and the volume fraction of residual austenite particles being at least 4.0%.

Weld metal having excellent resistance to hydrogen embrittlement

Disclosed is a weld metal which is formed by gas-shielded arc welding using a flux-cored wire, and which has a specific chemical composition, in which retained austenite particles are present in a number density of 2500 per square millimeter or more and in a total volume fraction of 4.0% or more based on the total volume of entire structures of the weld metal. The weld metal has excellent hydrogen embrittlement resistance and is resistant to cracking at low temperatures even when the weld metal has a high strength.

Weld metal excellent in hydrogen embrittlement resistance

The weld metal of the present invention is formed by gas shield arc welding using a flux-cored wire, has a predetermined chemical component composition, and contains 20% or more of Ti. The amount of Ti-containing oxide particles having a circle-equivalent diameter of 0.15-1.0 &#x3bc;m is at least 5000 per square mm, the amount of V per total mass of weld metal present as a compound within the weld metal is 0.002% or more, and the average circle equivalent diameter of V-containing carbide present in the weld metal is 15 nm or less.

Weld metal having excellent resistance to hydrogen embrittlement susceptibility

The objective of the present invention is to provide a similar-metal-composition welding solid wire, and weld metals therefor, with which both excellent bead shape and high ultralow-temperature toughness for the weld joints can be achieved when welding 9% Ni steels together by means of a high-efficiency MIG welding method. A fixed ratio of a REM and O are included in a similar-metal-composition welding solid wire of a 9% NI steel base material, and oxygen is supplied in a trace amount in a range that does not hinder the ultralow-temperature toughness of the weld joint () but that is capable of forming fine REM oxides in the weld metal () and of controlling the weld metal to produce an excellent bead shape. In addition, both Al and Ti are regulated and an argon gas that contains little or no carbon dioxide gas is used as the shield gas in the MIG welding method. Thus, both an excellent bead shape and high ultralow-temperature toughness for the weld joint () can be achieved.

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Fujisawa, Japan

Munenobu Sato