A forged iron is, well, forged – meaning the club is hammered or pounded into shape from one piece of metal, while cast irons are molded from liquid metal in a custom die cast. Forged irons are traditionally made from low carbon steel, which is “softer,” and cast irons are usually made from stainless steel.
It is important to note that forging and casting refer to the way the club is made – a forged iron and a cast iron can be both a muscle back (blade), where the weight on the head is even throughout, and a cavity back, where the weight on the head is shifted away from its center and sometimes results in a more forgiving shot if the ball is hit off-center.
Cast irons are more economical to produce (and cheaper to buy) as casting is a less labour intensive process, and most of the irons on the market are produced this way. Many traditionalists like forged clubs for the way they are designed and find the lofts and lie of a forged iron easier to adjust.
Some golfers say they can “feel” a difference between a forged iron and a cast iron due to the vibrations in the shaft upon impact with the ball–not all air bubbles escape the metal during casting, which results in a “muffled” sound and less vibration (“feel”) upon impact.
So which should you choose? The average player will probably not be able to tell the difference between a forged iron and a cast iron at the molecular level, and most problems for the average golfer are related to swing, not air bubbles. Try out some irons – if you find a set you feel really comfortable with get those, regardless of if they’re cast or forged.