When removing a seized pin, weather its on a track chain assembly or when removing a hyrdaulic cylinder. Apply direct heat to the pin bosses, not the pin itself. You want the bosses to expand with heat, not the pin. Heating the pin will only cause it to expand in the bosses, making it tighter, defeating the initial purpose. Using a rosebud attachment on your torches works much better than heating with a cutting tip.
Quenching the heated area with water will help break the bond as well. But as always, be sure to wear proper safety gear when heating and quenching. Steam BURNS!