LEDs get very hot if not properly heatsinked.
The electric energy is converted basically into light energy and heat which should be dissipated. Conventional light bulbs are less efficient but dissipate most of its energy as radiated energy (infrared light) and therefere heatsinking is not necessary. Maybe you need a heatsink with lower thermal resistance. Check if the thermal contact between LED and aluminum plate is correct (you can use thermally conductive paste, adhesives or films). Improving the heat dissipation will also increase LED efficiency (the lower the temperature, the higher the lumen/W!)
In additon LEDs should be powered with constant current sources rather than constant voltage power sources. Check the LED manufacturer datasheet, 1 W leds have a maximum of 350 mA (typical) constant current, you may have burnt the chip with 440 mA current.
Ernest