US 6,187,117 B1Granted

Method of making an as-rolled multi-purpose weathering steel plate and product therefrom

AssigneesBethlehem Steel Corporation, Pohang Iron & Steel Co., Ltd.

InventorsYulin Shen, Richard L. Bodnar, Jang-Yong Yoo, Wung-Yong Choo

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Abstract

A method of making a weathering grade steel plate includes the steps of establishing a minimum yield strength:plate thickness target from one of 50 KSI:up to 4″, 65 KSI:up to 1.5″, and 70 KSI:up to 1.25″. A modified weathering grade alloy composition is cast into a slab employing effective levels of manganese, carbon, niobium, vanadium, nitrogen, and titanium. The cast slab is heated and rough rolled to an intermediate gauge plate. The intermediate gauge plate is controlled rolled and subjected to one of air cooling or accelerated cooling depending on the minimum yield strength and thickness target. With the controlled alloy chemistry, rolling and cooling, the final gauge plate exhibits discontinuous yielding and can be used for applications requiring a 70 KSI minimum yield strength in plate thicknesses up to 1.25″, a 65 KSI minimum yield strength in plate thickness up to 1.50″ and a 50 KSI minimum yield strength for plates as thick as 4″.

Claims26

Dependent claims

A method of making an as-rolled and cooled weathering grade steel plate comprising:

a) selecting a minimum yield strength:plate thickness target from one of 50 KSI:up to 4 inches, 65 KSI:up to 1.5 inches, and 70 KSI:up to 1.25 inches;
b) providing a heated shape consisting essentially of, in weight percent:
from about 0.05% to about 0.12% carbon;
from about 0.50% to about 1.35% manganese;
up to about 0.04% phosphorous;
up to about 0.05% sulfur;
from about 0.15% to about 0.65% silicon;
from about 0.20% to about 0.40% copper;
from greater than zero to up to about 0.50% nickel;
from about 0.40% to about 0.70% chromium;
from about 0.01% to about 0. 10% vanadium;
from about 0.01% to about 0.05% niobium;
from about 0.005% to about 0.02% titanium;
an amount of aluminum up to about 0.1%;
from about 0.001% to about 0.015% nitrogen;
with the balance iron and incidental impurities;
c) rough rolling the heated shape above the recrystallization stop temperature to an intermediate gauge plate;
d) finish rolling the intermediate gauge plate from an intermediate temperature below the recrystallization stop temperature to a finish rolling temperature above the Ar3 temperature to produce a final gauge plate;
e) subjecting the final gauge plate to one of air or accelerated cooling when the minimum yield strength plate thickness target is 50 KSI:up to 4 inches, and liquid media accelerated cooling when the yield strength:plate thickness target is one of 65 KSI:up to 1.5 inches and 70 KSI:up to 1.25 inches, the air cooling having a start cooling temperature above the Ar3 temperature, and the accelerated cooling having a start cooling temperature above the Ar3 temperature, and finishing cooling temperature below the Ar3 temperature.

16 more elements

Dependencies are inferred from the claim text.