Hot die forging could be divided into two processing
1.Open die forging is also called free forging. In open die forging, the billet is placed between multiple dies that do not enclose the metal entirely. The dimensions will be changed by hammering and stamping the metal through a series of movement until the final dimensions are achieved.

2.Closed die forging process, is also referred to as impression die forging. It utilizes high pressure to compress the metal piece to fill an enclosed die impression for required shapes. A medium frequency induction heating furnace is used to heat the metal for pressing into dies.

The technique of both open die forging and closed die forging is different. In general, for closed die forging, the molding dies are first precision machined and cost is high. The metal bars are then placed on between upper and lower dies and forged to any shapes needed. After closed die forging very less or no machining will be operated due to its high accuracy throughout the process. So closed die forging is also a net shape or near net shape process.

For open die forging, enormous compressive forces are imposed by the continuous strike of a forging hammer to deform the metal billets. Unlike closed die forging, dies of open die forging is very simple. And secondly machining operation is always carried out.

Alloy steel. Alloy steel is a broad term referring to a variety of steels that have had their properties altered or enhanced by alloying the steel with additional metals, such as silicon, manganese, or nickel. These added metals may provide specific characteristics such as corrosion resistance, malleability, or thermal/electrical conductivity. Alloy steel offers exceptional wear
resistance and strength for forging metal parts.
Carbon steel. Carbon steel contains higher levels of carbon to offer more increased strength than regular steel. The metal also performs well in high-temperature and high-pressure applications.
Microalloy steel. Microalloy typically contains additives of vanadium, titanium, or niobium. Microalloy steel develops excellent toughness as it cools, and typically does not require post heat treat to achieve increased mechanical properties
Stainless Steel. Stainless steel has exceptional corrosion resistance, heat resistance, strength, and durability. All of these properties get further enhanced when the metal undergoes a forging process.
Titanium.Titanium is a lightweight metal with exceptional strength. The metal offers superior resistances to corrosion and high temperatures.