Applied Research and Development in the Steel Industry . . .The successive stages of a development can be illustrated with a recent one of our own.. . . The development concerns cans for beer rtnd beverages, and a. little history will be useful to hring the subject into focus. Everyone has seen and handled a tin can but he may not have redly noticed how it is made. The construction and design The side seam is doubled over and soldered, while the ends are crimped on by a process called go back many years. double seaming, with an organic sealant making the joint leakproof. The container is versatile, safe, and efficient and finds very wide iwe. Actually, of course, it is not a tin can hut a can made of steel coated with tin, the coating accounting for less than 1% of the weight of the can. Althongh tin accounts for very little of the weight of the tin-coated steel, it is an important element of cost. I n the early days of this century, the coating was applied by dipping the sheets of steel into molten tin, and various mechanical develop ments had brought the coating thickness down to about the lower limit for that method by the late 1930's. At about t,hat time, electrolytic tin plating was developed, and this is the met,hod in w e today. Since the late 1930'8 the price of tin has more than tripled, and the average coating thickness har been reduced to about a quarter of what i t was then. At present coating thicknesses, i t would take only a pound of tin to cover the Roars in an average-sized house, that is, one with about
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cans or roughly 1.5 billion dollars a year. About three years sga, we had for some time been doing exploratory work on coatings to substitute for tin, but the soldered side seam had been an insurmountahle obstacle. At that point, two of the major can companies told 11s zhont two independent developments which, by replacing the soldered side seam, eliminated the need for tin as rtn aid to solderability. One of these developments was the cemented side seam, which uses a thermoset.ting plastic, and t,heather was the weldedside seam. Our previous work on other coatings had shown that chromium would he the preferred coating, and a t that stage d l departments concerned were instructed to cooperate in developing a process and equipment for the production of chrominmnlated canstock. looking towards earliest mssible eommercialieabion. This material has become known as TFS-CT, standing for ('tin-freeiteel, cGome type." The first step in the development utilized a laboratory rotating esthode apparatus. In this apparabus, a rotating cathode simnlrttes the movement of a. steel strip through a bath, and a hoist and an overhead trolley arrangement move the cathode from one bath to another through a sequence of cleaning, plating, and post-treating baths. Times, speeds, and corrent densities are controlled according to a predetermined program. The information obtained was used to plan runs on the pilot line. This is a continuous line capable of plating strip up to 12 in. wide. Data from pilot runs were transmitted to the design group without delay, and alternate designs for a full-width development line were promptly evaluated. Considerable time was saved by modifying an idle tinning line a t one of the plants. . . T h e foll-width development line was in operation less than a year &er instructions to go were received. The product for can bodies istypically a steel strip %hoot0.006 in. thick coated with successive layers of approximately 100 A of metallic chromium, 60 A of a. complex oxide treatment film, and 50 A of dioctyl sebscabe. At that thickness of metallic chromium, one poond would cover two football fields.
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. . .Taken from an address "Applied Research and Development in the Steel Industry" by John E. Eberhardt, Assistant 1)irector of Research, Bethlehem Steel Corp., given a t the 1.57th meeting of the American Chemical Society, Minneapolis, April, 1069.
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Journal o f Chemical Education
