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US 4,051,270 AGranted
Method of measuring vapor deposited coating thickness
AssigneeJones & Laughlin Steel Corporation
InventorJohn F. Butler
Life of this patent
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Abstract
The temperature of a substrate to be vacuum vapor coated is measured immediately before its is passed over a source of coating metal vapor and immediately after the vapor has condensed on it. Costing conditions are controlled to maintain the difference between those temperatures at a value which is related to the thickness of the condensed coating by a heat balance equation.
Claims13
A method of vacuum vapor coating a thin metal substrate in strip form with a metal coating of a desired thickness without heating the substrate over about 1000.degree. F comprising:
- measuring the temperature of the substrate immediately before coating;
- moving the substrate past a source which contains a pool of liquid coating metal which gives off metal vapor at its surface so as to condense coating metal on the substrate, to form a coating of said metal on said substrate, to supply heat to the substrate, and to increase the temperature of the substrate;
- immediately thereafter measuring the increase in temperature of the substrate resulting therefrom under conditions where temperature equilibrium through the substrate thickness is reached in less than 0.1 second and substrate heat loss is negligible;
- adjusting coating conditions to obtain the desired metal coating thickness in accordance with the equation, ##EQU4## t.sub.c is the thickness of the coating in mils, C.sub.st is the average heat capacity of the substrate for temperatures between T.sub.o and T.sub.f in BTU's per pound per degree F.,
- T.sub.f is the final temperature of the substrate immediately after coating in degrees F.,
- T.sub.o is the temperature of the substrate immediately before coating in degrees F.,
- .rho..sub.st is the density of the substrate in pounds per cubic inch,
- t.sub.st is the thickness of the substrate in mils, .rho..sub.c is the density of the coatng metal in pounds per cubic inch,
- C.sub.k is the heat of condensation of the coating metal at T.sub.c in BTU's per pound,
- C.sub.c is the average heat capacity of the solid coating metal for temperatures between T.sub.f and T.sub.o in BTU's per pound per degree F., and
- T.sub.c is the temperature of condensation of the coating metal in degrees F.;
- and
- measuring the increase in temperature of the substrate caused by radiation from the vapor source, subtracting said temperature increase caused by radiation from T.sub.f, as defined above, to obtain a value, and using said value for T.sub.f in the equation.
10 more elements
Dependencies are inferred from the claim text.