| 摘要 |
<p>A steel body containing 0-02 to 0-50% Te and/or Se to improve machinability is heated prior to hot working in a furnace, the total water vapour content within the furnace interior being limited to no more than 18% by volume to maintain its oxygen content not more than that in air. The heating may be effected by the combustion of fuel including CO and/or CO2 and/or hydrocarbons, such as natural gas or oil, coke oven gas or blast furnace gas, while avoiding the supply of air or oxygen in excess of that required for complete combustion, and limiting the water vapour content within the furnace interior to up to 15% by volume arising from combustion and at most 3% extraneous volume, e.g. by removing any water which has accumulated in a gas line, seeped into preheating checkerwork flues or condensed within the furnace, or by dehumidifying blast furnace gas; or a furnace atmosphere consisting of inert e.g. N2 or A and/or endothermic gases e.g. CO or H2 may be provided and heating performed with radiant electric coils. Ingots may be heated at 1290-1320 DEG C. in a soaking pit prior to hot working into blooms, or blooms already hot rolled into billets may be reheated at 1040-1200 DEG C. prior to hot rolling into bars. The steel body may be plain carbon steel containing 0.08 to 1.0%C, 0.25 to 1.65% Mn, up to 0.30% Si, up to 0.09% P, up to 0.05% S (or 0.25 to 0.35% S for sulphurized steel), 0.02 to 0.05% Te and/or Se and optionally 0.03 to 0.50% Pb to improve machinability, the balance being Fe and impurities; or low alloy steel containing 0.06 to 1.10% C, 0.04 to 1.00% Mn, 0.20 to 2.20% Si, P and S and Te and/or Se with or without Pb in amounts above specified, and one or more of the following alloying elements: 0.20 to 5.25% Ni, 0.20 to 1.75% Cr, 0.08 to 0.30% Mo, 0.10 to 0.15% V (when Ni and Mo absent).</p> |
