Hydraulic press is a kind of forging equipment which uses liquid pressure to transfer energy, it includes hydraulic press which uses oil as working medium and hydraulic press which uses water as working medium.

Forging hydraulic presses include free forging hydraulic presses, die forging hydraulic presses and edge cutting hydraulic presses. The common die forging hydraulic presses in forging production can be divided into two categories: general-purpose die forging hydraulic presses and special die forging hydraulic presses. The main structural forms of hydraulic presses are pull-down type and push-down type, and various specifications of four-column hydraulic presses are generally selected in the form of push-down design.

The characteristics of hydraulic press die forging are in the direct drive hydraulic press, the movable beam can get the load in any position of the whole stroke.

Both the direct drive hydraulic press and the accumulator drive hydraulic press are structurally easy to get larger total pressure, larger working space and longer stroke, so it is easy to forge longer and higher large forgings, which is often difficult to do with forging hammers and other forging equipment.

In addition to large die pads and positioners, the hydraulic press has a movable beam synchronized balancing system to ensure that the die is not skewed during eccentric forging. Compared with forging hammers, hydraulic presses work smoothly, with little impact and vibration and little noise; they do not require high requirements for plants and foundations and do not damage the surrounding environment. Compared with mechanical press, the structure of hydraulic press body is simpler, and the relief valve can limit the liquid pressure acting on the plunger, so the planting load can be restricted to protect the die and not cause bogging. The speed of the movable beam of the hydraulic press can be controlled, and the speed of the movable beam is about 50mm/s during the working stroke, and the load can be regarded as static load; it is suitable for isothermal die forging and super plastic die forging.

Some hydraulic presses are equipped with side cylinders, so that they can complete the multi-directional die forging process. Hydraulic presses are generally equipped with ejectors and loading and discharging mechanized devices. The disadvantages of hydraulic presses are low productivity and large floor space.

Features of the die forging forming process include low working speed of hydraulic press, uniform metal deformation under hydrostatic conditions, full recrystallization, and uniform forging organization. When die forging, the blank and tool contact time is long, such as poor lubrication die preheating temperature and low, in the deformation of the upper and lower end of the blank, due to temperature drop will cause deformation dead zone. When forging large thin-walled structural parts, the metal flow inertia is much smaller than hammer forging and mechanical press forging, for complex, narrow and deep grooves, the metal is not easy to fill up. Compared with die forging on hammer, it is not easy to have defects such as reflux, folding and piercing ribs.

Heating and holding devices can be installed on the die so that the die can be kept at a higher temperature (depending on the die material), which is beneficial for isothermal (or hot die) forging and forming of aluminum alloys, titanium alloys and high temperature alloys. As in the case of die forging on crank presses, the metal billet is continuously deformed in one press stroke until it fills the groove, so the deformation is deep and uniform. In particular, the multi-directional die forging hydraulic press can forge the blank in several directions at the same time, so that the forging flow line is more reasonably distributed, the mechanical properties of each place is more uniform, and the size of the forging is more accurate. As the hydraulic press is static load, the die can be manufactured by casting plus a small amount of mechanical processing instead, shortening the die making cycle and reducing the production cost.

Because of the ejector mechanism, the hydraulic press can die forging small die forging slope or no die forging slope of the fine forgings. Hydraulic press forging in general in one stroke forming, so can reduce the heating fire times. However, in order to reduce eccentric loading, hydraulic presses mostly use single-step die forging. Hydraulic presses are mainly used for die forging large forgings of non-ferrous alloys that are sensitive to strain rate.