Because the reactor in Iron Man's chest was designed to suck up shrapnel close to his heart, after surgery at the end of Iron Man 3, the shrapnel in Tony's heart was removed and the chest reactor was no longer needed.
The battle armor that appears in the movie Iron Man 3 is Mark 8. Mark 8 is the eighth suit of armor created by Tony Stark.
The main feature is the transformation process, Tony can use the infrared sensor bracelet, at any time and place to let the steel armor to cover his body, while the shoulder shrapnel weapon was changed to a dispersal of small missiles, which is not bad, the laser weapon also increased the performance of prolonged use, and the back of the pusher has been modified to fly out of the atmosphere.
Expanded Information: Iron Man: Iron Man is a character who is a member of the Iron Man family. p>Iron Man: is an armor designed by Tony Stark, this armor gives Stark superhuman strength, superhuman endurance, the ability to fly and multiple weapons. The armor was designed by him and worn by him most of the time. Iron Man's appearance and abilities continue to change as Stark continues to modify and update his equipment, especially his power armor. In addition to the general-purpose functional armor he wore during the general period, Stark developed several sets of special functional armor that allowed him to adapt to states such as space travel, deep-sea diving, and stowaway sneaking. Stark also used add-on components he called modular armor to create heavy armor such as the Hulkbuster, which was designed to increase the armor's strength and endurance to allow him to take on Hulk Hulk alone. There was also a suit of armor designed to fight Thor, based on Thor's arch-enemy, the Destroyer, and using a secret energy source. Stark developed a cybernetic box during the Armor Wars that, when placed on an armor using Stark technology, could burn out the mechanism and cripple the armor. However, the E-Box is not effective against later developed models.