Method of producing steel having high strength and toughness

Details Method of producing steel having high strength and toughness Method of producing steel having high strength and toughness

1984-09-04

1986-05-27

Stallard, Wayland

Metal treatment

Compositions

Heat treating

C21D 714

Patent

active

045913960

ABSTRACT:
A micro-alloy plate having not only high tensile strength and high toughness both at room temperature and low temperature but which also displays superior weldability and excellent toughness at a heat affected zone (HAZ) of welding.
The steel contains 0.005-0.08 C, not more than 0.6% Si, 1.4-2.4% Mn, 0.01-0.03% Nb, 0.005-0.025% Ti, 0.005-0.08% Al, not more than 0.003% S, 0.0005-0.005% Ca, not more than 0.005% O, not more than 0.005% N, all being represented by weight and the balance being incidental impurities, further the steel must satisfy the following requirements; ##EQU1## The steel thus prepared is heated at a temperature range of 900.degree.-1000.degree. C., hot rolled with a rolling reduction of more than 60% below 900.degree. C. with a rolling finishing temperature within a range from 20.degree. C. above the Ar.sub.3 point down to 10.degree. C. below the Ar.sub.3 point and, immediately after the rolling, the steel stock is cooled down to 300.degree. C. or lower at a cooling rate of 15.degree.-60.degree. C./sec.
The steel may further contain small amounts of at least one alloying element selected from the group of Ni, Cu, Cr, Mo, V and B.
Due to these composition controls together with controlled heating, rolling and cooling, the product steel stock obtains a very fine grained and uniform microstructure and thereby satisfies the required mechanical properties suitable for use in welded constructions in many fields such as buildings, pressure vessels, the ship building industry and pipe lines.

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"Control of Microstructure by the Processing Parameters and Chemistry in the Arctic Line Pipe Steels", by Chiaki Ouchi, Junichi Tanaka, Isao Kosasu, and Koshiro Tsukada, issued in Micon 78: Performance Through Microstructural Control, ASTM STP 672, Halle Abrams, G. N. Maniar, D. A. Nail, and H. D. Solomon (Editors), pp. 105-125, Philadelphia, Pa. 1979, (Thesis of Nippon Kokan K.K., Japan).

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