This invention provides a method and apparatus for casting, hot rolling and annealing of non-heat treatable aluminum alloys which comprises continuously casting, hot rolling and, in-line with the hot rolling line, heating the aluminum sheet using infrared heat. The infrared heating system uses a control to assure that the aluminum alloy is heated to the proper temperature based on one or a number of process variables, such as hot rolling exit temperature, hot rolled product exit rate in terms of speed and product dimensions, and sheet temperature at the exit of the infrared heater. Variations in the infrared heating temperature can be tolerated in the product without deviating from target mechanical properties.