(57) Low alloy steel shape of at least 4.8 mm thickness is produced by providing a steel
consisting essentially of from about 0.02% to 0.07% carbon, 1.2% to 2.0% manganese,
0.020% maximum sulfur, up to 0.5% silicon, 0.1% to 0.4% molybdenum, 0.01% to 0.1%
columbium, about 0.01% to 0.10% acid soluble aluminum, about 0.8% to 2.0% copper,
about 0.4% to 2.0% nickel, residual chromium, and balance iron; hot reducing the steel
to a desired final thickness with a total reduction in thickness of at least 30% while
within the temperature range of about 760° to 927°C whereby to avoid substantial recrystallization
of austenite and to obtain a predominant heavily deformed austenite phase; and cooling
at a rate which transforms the austenite phase to a predominantly fine acicular ferrite
and lower-bainite phase. The steel may also be precipitation hardened, or may be hot
reduced either by the above-described controlled hot reduction or by conventional
hot reduction, austenitized, quenched, and precipitation hardened. The product has
high strength, improved low temperature toughness and excellent weldability.
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