A first embodiment of the inventive maraging steel which has an essential composition: C: 0.01 % or less, Ni: 8 to 19 %, Co: 8 to 20 %, Mo: 2 to 9 %, Ti: 0.1 to 2 %, Al: 0.15 % or less, N: 0.003 % or less, O: 0.0015 % or less, balance: Fe, and has the component segregation ratios for Ti and Mo in its structure of 1.3 or less each; and another embodiment of the inventive maraging steel which has the above composition and contains a non-metal substance having a size of 30 νm or less. The second embodiment of maraging steal can be easily prepared by subjecting to appropriate plastic working a steel ingot having a taper Tp = (D1 - D2) x 100/H of 5.0 to 25.0 %, a height-diameter ratio Rh = H/D of 1.0 to 3.0, and a flatness ratio B = W1/W2 of 1.5 or less.

Maraging steel excellent in fatigue characteristics and method for producing the same

PURPOSE: A method for manufacturing an ultra high tensile steel having a yield strength level of 220 ksi is provided to simplify manufacturing facilities and remove factors of environmental pollution by solution heat treating the boron (B) composed steel after composing the steel by adding boron (B) to steel, and air cooling not oil cooling the solution heat treated steel. CONSTITUTION: The method comprises the processes of hot rolling the steel slab by heating a steel slab comprising 0.13 to 0.19 wt.% of C, 0.1 wt.% or less of Mn, 0.1 wt.% or less of Si, 9.5 to 10.5 wt.% of Ni, 13.5 to 14.5 wt.% of Co, 1.8 to 2.2 wt.% of Cr, 0.9 to 1.1 wt.% of Mo, 0.008 wt.% or less of P, 0.005 wt.% or less of S, 0.0007 to 0.0020 wt.% of B and a balance of Fe and other inevitable impurities to a temperature of 1150 deg.C or more; solution heat treating the cooled steel slab at a temperature ranging from 800 to 900 deg.C after cooling the hot rolled steel slab to an ordinary temperature; and aging treating the air cooled steel slab at a temperature ranging from 500 to 530 deg.C for more than 5 hours after air cooling the solution heat treated steel slab to an ordinary temperature.

The manufacturing method for yield strength 220ksi super high strength steel

PURPOSE:To produce maraging steel for a die casting die excellent in softening resistance and toughness by preparing maraging steel having a specified componental compsn. in which the content of Ni and Ti is prescribed. CONSTITUTION:Maraging steel contg., by weight, 12 to 14% Ni, 4.5 to 6.0% Mo, 7.5 to 9.5% Co, 0.5 to 1.0% Ti, <=0.03% C, <=0.1% Si, <=0.1% Mn, <=0.01% P, <=0.01% S, <=0.05% Cr, <=0.01% N and 0.02 to 0.20% solAl, and the balance Fe with inevitable impurities is prepd. In this way, the maraging steel for a die casting die high in softening resistance and excellent in toughness can be obtd.

Unno Masahide

Papers

Maraging steel for die casting die