A process for producing low-alloy steel plates of yield strength at 450¯C not less than two-third of that at room temperature, suitable for fabrication of carrier tubes and heat exchanger shells for hot gases, characterised in that the process comprises the following steps in sequence: (a) melting predetermined quantities of pig iron, scrap iron, iron ores, aluminium bars and ferro-alloys such as petroleum coke, Si-Mn and Fe-Mo, in a basic oxygen furnace (BOF), and transferring to ladle as molten iron of chemical composition (by weight %): C-O.15 to 0.20, Mn-0.75 to 1,00, P-0.020 max., S-0.015 max., Si-0.25 to 0.50, Al-0.02 max., Mo-0.35 to 0.50, N-100 ppm max., H-2 ppm max. and Fe-the balance; (b) tapping the molten steel in a preheated ladle at 1630 Ý 20¯C; (c) transferring the molten steel from the ladle to a vacuum arc degassing (VAD) unit; (d) transferring the molten steel from the VAD unit to tundish of a continuous casting (CC) machine; (e) casting the molten steel at tundish temperature 1540-1550¯C into slabs of thickness 200 to 250 mm and of width 1500 mm in the CC machine at a speed 0.6-0.8 m/min and slab unbending temperature 900-920¯C; (f) cooling the slabs to room temperature in natural air; (g) reheating the slabs and soaking the reheated slabs in a furnace at 1240 Ý 20¯C for at least 3 hours; (h) rolling the slabs into plates of thickness 8-32 mm in a plate mill with 10-20% reduction per pass at a finishing temperature of 850-900¯C; (i) normalising the plates of thickness above 10 mm at 910 Ý 20¯C for 30-45 minutes; (j) cooling the plates to room temperature in natural air; and (k) straightening the plates which are found to be bent.

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