Hitachi Metals, Ltd.

Setsuo Mishima

Etsuo Fujita

Tatsuya Shouji

Katsufumi Kuroda

Hidemi Takao

Ken-ichiro Hara

Yoshio Bizen

Takashi Meguro

Yukio Shinji

Kenichiro Hara

Toru Taniguchi

Yasushi Ishimoto

Takanori Aikawa

Ken-Ichiro Hara

Provided are a cold working tool material with which high hardness can be obtained in a broad range of tempering temperatures, and a cold working tool manufacturing method using same. The present invention is a cold working tool material comprising a steel component composition that contains, in mass %, C: 0.65-2.40%, Cr: 5.0-15.0%, Mo and W alone or combined (Mo+&#xbd;W): 0.50-4.00%, V: 0.10-1.50%, and N: greater than 0.0300% to 0.0800%, in which martensitic structure can be adjusted by quenching, and in which, in a 90 &#x3bc;m long 90 &#x3bc;m wide region of a cross-sectional structure that does not contain carbides with equivalent circle diameters exceeding 5.0 &#x3bc;m, the number density of carbides A with equivalent circle diameters greater than 0.1 &#x3bc;m to 2.0 &#x3bc;m is at least 9.0&#xd7;105/mm2 and the number density of carbides B with equivalent circle diameters greater than 0.1 &#x3bc;m to 0.4 &#x3bc;m is at least 7.5&#xd7;105/mm2. The present invention is also a cold working tool manufacturing method in which quenching and tempering are performed on said cold working tool material.

Cold working tool material and cold working tool manufacturing method

A cold work tool material has an annealed structure including carbides, and a composition including, in mass %, C: 0.80% to 2.40%, Cr: 5.0% to 15.0%, Mo and W contained alone or in combination in an amount of (Mo+&#xbd;W): 0.50% to 3.00%, and V: 0.10 to 1.50%, and adjusted such that the material has a martensitic structure by quenching. The material includes a cross sectional region of an annealed structure and a length of 90 &#x3bc;m and a width of 90 &#x3bc;m and including no carbides having a circle equivalent diameter exceeding 5.0 &#x3bc;m. In the cross sectional region, a proportion of a number of carbides B having a circle equivalent diameter of more than 0.1 &#x3bc;m and not more than 0.4 &#x3bc;m to a number of carbides A having a circle equivalent diameter of exceeds 0.1 &#x3bc;m and not more than 2.0 &#x3bc;m is greater than 80.0%.

Cold work tool material and method of manufacturing cold work tool

A method for producing a steel ingot, which comprises an Mg oxide forming step of preparing a molten steel containing Mg in an amount sufficient for the molten steel to have an oxide composition having MgO as a primary component and a dissociation step of keeping the pressure of the atmosphere around the molten steel to be lower than that in the Mg oxide forming step, to thereby dissociate MgO to Mg and oxygen and reduce the content of Mg in the steel to 50% or less of that in the Mg oxide forming step through the diffusion thereof into a gas phase. A preferred method further involves a solidifying step.

Method for producing steel ingot

Disclosed is a method of producing maraging steel, which includes producing a consumable electrode for vacuum remelting; and subjecting the consumable electrode to the vacuum remelting. The consumable electrode contains not less 5 ppm Mg. Disclosed is also a maraging steel containing, by mass %, at least, from more than zero to less than 10 ppm Mg, less than 10 ppm oxygen, and less than 15 ppm nitrogen. The steel contains also nitride inclusions having a maximum length of not more than 15 &#x3bc;m and oxide inclusions having a maximum length of not more than 20 &#x3bc;m. Regarding the oxide inclusions, a content rate of spinel form inclusions having a length of not less than 10 &#x3bc;m to a total content of the spinel form inclusions having a length of not less than 10 &#x3bc;m and alumina inclusions having a length of not less than 10 &#x3bc;m exceeds 0.33 (i.e. 33%).

Maraging steel and method of producing the same

The method for producing a mother alloy for an iron-based amorphous alloy has the steps of (a) melting raw materials for elements constituting the amorphous alloy together with at least one oxide of an element constituting the amorphous alloy, the raw materials containing aluminum as an inevitable impurity, and the oxide having a smaller standard free energy of formation than that of Al O in an absolute value; and (b) removing the resultant Al O from the melt, thereby reducing the content of aluminum to 50 ppm or less in the melt.

Method for producing mother alloys for iron-based amorphous alloys

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Yasugi, Japan

Setsuo Mishima