OCR Text |
Show The views expressed above do not present a very optimistic picture for the future of the steel industry. In p0int of fact, the future is substantially brighter than would he indicated on the surface. Many old, high cost, obsolete mills have been closed. The mills that remain are generally more modern and can more readily be optimized for tonnage and more efficient operation and the capital cost to bring these newer mills into compliance w'ith the now more rigid quality standards for the finished product are usually less costly. Many newer mills have a substantially lower manning requirement per ton of steel produced, which helps to improve their overall competitive position both domestically and internationally. In the case of multi-plant operations it has not been uncommon to see several plants operating at 50 to 60 percent of rated capacity. The closing of margfnal mills and reallocation of production to the more modern facilities has raised their operating rates to a point where these mills can now operate at a profitable level. It must be recognized that at operating levels below 70 to 75 percent on these modern facilities profitability of the plant and equipment cannot be maintained. We note that tonnage rates, fuel consumption and manning costs per ton produced in a number of the mini mills are competitive or better than results being achieved anywhere else in the world. Labor rates as low as 1.4 man hours per ton of steel produced are being achieved in the best of these mills. In sev~ral of the larger mills substantial improvements in operating techniques are being achieved, often at very low capital cost, to realize lower fuel costs and often to improve product quality, equipment life and achieve reduced maintenance cost. The combination of these factors can often turn a questionable operation into a viable entity. Much of the steel industry has suffered very substantial operating losses in recent years which makes it very difficult for the industry to invest in anything but the most highly productive areas. We will attempt to review a few of the areas where meaningful improvement can be achieved either in reduction in fuel usage or improved product quality. LADLE HEATING Ladle Heating would on the surface appear to be an area of little significance. For a great number of years ladles were heated with raw gas torches or at best inspirator burners. This procedure obviously did a poor job of heating the ladle and consumed huge quantities of gas at extremely poor efficiency rates. Ladles are initially dried and subsequently heated to relatively high temperatures to receive hot metal in the form of either iron from the blast furnace or steel from the BOF or electric furnace. 14 Modern ladle heaters are constructed with a cover as illustrated in Figure 1 and 2 to retain the products of combustion within the ladle for an adequate period of time to give up their heat and to attain full penetration of the heat to the bottom of the ladle with the result that fuel consumption to effect heating of these ladles is greatly reduced and much more uniform temperatures of the ceramic lining of the ladle are achieved. Many ladle heating installations are equipped with recuperators or other heat saving devices to further improve overall efficiency. These fuel savings are important, however, further benefits are present since the metal when charged is not chilled as would be the case with a semi-cold ladle used to transfer iron to the oxygen vessel, thus, the enthalpy of the constituents of the molten metal can be more effectively used to convert the iron to steel while at the same time permitting a higher percentage charge weight of scrap in place of hot metal. Scrap cost is frequently lower than the cost of hot metal thus resulting in substantially lower cost per ton produced. The reducti.on in the percentage of hot metal charge can far outweigh the basic savings in fuel consumption that are also realized. THE SOAKING PIT Soaking pits of several design concepts have been a standard fixture in most integrated mills throughout this century. The basic pit designs include circular pits (Figure 3), bottom fired pits (Figure 4), regenerative pits, top two-way fired pits (Figure 5), and top single-way fired pits (Figure 6). Most of these pit types, with the exception of the top single-way fired pit illustrated in Figure 6, have ceased to be used extensively due to their high initial cost and the extensive building requirements to charge an adequate tonnage of steel under the mill crane runways. Several of these pit types were highly effective heating tools but the disadvantages outweighed the merits of the design. The single-way top fired pit, which is by far the most common pit design used in our mills today, has the disadvantage that when not properly designed or operated, substantial temperature variation can occur in the ingots being heated for rolling. We have noted temperature variation top to bottom and end to end of such pits of several hundred degrees. Figure 6 illustrates conditions where the top of the pit over the ingot charge can be hot, where the end of the pit opposite the burner can be fairly hot but the area of the pit below t,he burner and adjacent to the flues is often extremely cold. A new burner deSign has been developed which when operated in conjunction with special control equipment can |