PURPOSE: To produce an extra-thick tempered high tension steel plate having excellent low-temp. toughness by subjecting a steel plate of a specific thickness consisting of a specific compsn. successively to heating, air cooling, force cooling, and tempering under specific conditions.
CONSTITUTION: The steel plate of 75W200mm thickness which contains, by weight %, 0.03W0.20% C, 0.05W0.50% Si, 3.0% Mn, ≤0.010% P, ≤0.010% S, 0.03W0.10% Al, 1.0W10.0% Ni, 0.0005W0.0030% BV, and ≤0.0040% N, contains 1 or ≥2 kinds of 0.01W1.50% Cu, 0.01W1.50% Cr, and 0.01W1.50% Mo, and consists of the balance iron and inevitable impurities and has 26W42 parameter (x) expressed by the formula is prepd. This steel plate is then heated to a 900W1,050°C range and is air-cooled down to 800W850°C, following which the steel plate is forcibly cooled down to ≤500°C at ≥1°C/sec cooling rate and is then tempered at the Ac1 transformation point or below. The extra-thick tempered high tension steel plate having the excellent low-temp. toughness and about ≥80kgf/mm2 tensile strength is obtd.
HAJI TOSHIAKI
AIHARA SHUJI
YAMAMOTO KOICHI
| JPS57126955A | 1982-08-06 | |||
| JPS62177120A | 1987-08-04 | |||
| JPS4963617A | 1974-06-20 |