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Open Die Forging

Open die forging is a processing method in which the metal is freely deformed in all directions between the upper and lower anvil surfaces by impact force or pressure, and the required shape and size and certain mechanical properties are obtained without any restriction, which is referred to as free forging.Open die forgings are offered here at Pintejin Forging Company.Our unique forging equipment is capable of forging close tolerances to minimise the amount of machining required on a finished part.

Open die forging is characterized by simple tools and equipment, good versatility and low cost. Compared with casting blanks, Open die forging eliminates shrinkage holes, shrinkage porosity, pores and other defects, so that the blanks have higher mechanical properties. Open Die Forgings are simple in shape and flexible in operation. Therefore, it has special significance in the manufacture of heavy machinery and important parts.

What Is Open Die Forging

Open die forging is another drop forging process that metal is getting deformed for desire shapes without any limitation between the top and bottom anvils in all directions utilizing power or pressure.The term open die comes from the workpiece not being enclosed. With each continuous strike of the metal, it is gradually shaped to the required dimensions increasing the strength and grain structure.

The Application Fields Of Open Die Forging

Open Die Forging relies on manual operation to control the shape and size of forgings, so forgings have low precision, large machining allowance, high labor intensity and low productivity, so it is mainly used in single-piece and small batch production.

The Classification Of Open Die Forging

Open Die Forging is divided into manual open die forging and open die forging via machine. Manual open die forging has low production efficiency and high labor intensity, and is only used for repairing or the production of simple, small and small batches of forgings. In modern industrial production, machinery open die forging has become the main method of forging production, and it plays a particularly important role in heavy machinery manufacturing. The shape and size of the forgings produced are mainly determined by the technical level of the operator.

The Major Equipment Of Open Die Forging

The equipment of Open Die Forging is divided into two categories: forging hammers and hydraulic presses. The forging hammers used in production include air hammers and steam-air hammers. Some factories also use spring hammers, plywood hammers, lever hammers and wire hammers with simple structure and low investment. The hydraulic press deforms the blank by the static pressure generated by the liquid. , is the only way to produce large forgings.

The Defect Of Open Die Forging

  • Cracks: may be caused by poor billet quality, insufficient heating, too low forging temperature, improper cooling of forgings and wrong forging methods.
  • End depression and axial crack: It may be caused by the fact that the inside of the billet is not heated during forging or the entire section of the billet is not forged through, and the deformation only occurs on the surface of the billet.
  • Folding: It may be caused by the feeding amount of the blank during forging is less than the single-sided pressing amount.
What Is Open Die Forging

The Process Of Open Die Forging

The basic processes of Open Die Forging include upsetting, drawing, punching, bending, torsion, offset, cutting and forging.

Pull Out

[Pull Out] is also called elongation, which is a forging process that reduces the cross-sectional area of the blank and increases the length. Pull out length is often used for forging rods and shaft parts. There are two main methods of pulling out:

  1. Pull out on the flat anvil.
  2. Pull out on the mandrel. During forging, the mandrel is first inserted into the punched billet, and then drawn as a solid billet. When drawing long, it is generally not drawn at one time. First, the blank is drawn into a hexagonal shape, and after forging to the required length, the chamfer is rounded and the mandrel is taken out. In order to facilitate the removal of the mandrel, the working part of the mandrel should have a slope of about 1:100. This drawing method can increase the length of the hollow blank, reduce the wall thickness, and keep the inner diameter unchanged. It is often used for forging long hollow forgings such as sleeves.

[Upsetting] is a forging process that reduces the height of the blank and increases the cross-sectional area. The upsetting process is mainly used for forging gear blanks and round cake forgings. The upsetting process can effectively improve the blank structure and reduce the anisotropy of mechanical properties. Repeated upsetting and drawing can improve the morphology and distribution of carbides in high-alloy tool steels. Upsetting mainly has the following three forms:

  1. Complete upsetting. Complete upsetting is to place the blank vertically on the anvil surface, and under the hammering of the upper anvil, the blank will be plastically deformed with a height reduction and an increase in the cross-sectional area.
  2. The end upsetting. After the billet is heated, one end is placed in a drain or mold to limit the plastic deformation of this part, and then the other end of the billet is hammered to make it upsetting. The upsetting method of the leaking disc is mostly used for small batch production; the method of upsetting the tire mold is mostly used for mass production. Under the condition of single-piece production, the part that needs upsetting can be heated locally, or after all heating, the part that does not need upsetting can be chilled in water, and then upsetting is performed.
  3. Upsetting in the middle. This method is used for forging forgings with large middle section and small sections at both ends. For example, gear blanks with bosses on both sides are forged by this method. Before the upsetting of the billet, both ends of the billet should be thinned first, and then the billet should be upright in the middle of the two leakage pans for hammering to make the middle part of the billet upsetting. In order to prevent the billet from bending during upsetting, the ratio of the billet height h to the diameter d h/d ≤ 2.5.
Upsetting In Metal Forging
Open Die Forging Process


[Punching] is a forging process in which a through hole or an impermeable hole is punched out of the blank. There are two main methods of punching:

  1. Double-sided punching method. When the punch is punched to the depth of 2/3 to 3/4 on the blank, take out the punch, turn the blank, and then use the punch to align the position from the reverse side to punch out the hole.
  2. Single-sided punching method. For blanks with small thickness, single-sided punching method can be used. When punching, the blank is placed on the backing ring, the big end of a slightly tapered punch is aligned with the punching position, and the blank is hammered into the blank until the hole penetrates.


[Bending] A forging process in which a blank is bent into a specified shape using a certain tool and die is called bending.
There are two commonly used bending methods:

  1. Forging hammer compression bending method. One end of the blank is pressed by the upper and lower anvils, and the other end is struck with a sledgehammer or pulled by a crane to bend it into shape.
  2. Die bending method. Bending in the pad die can obtain small forgings with more accurate shape and size.


[Cutting] refers to the forging process in which the blank is divided into several parts or partially cut, or a part is cut from the outside of the blank, or a part is cut from the inside.

Staggered Shift

[Staggered shift] refers to the forging process in which one part of the blank is staggered in parallel with another part by a distance, but the axis is still kept parallel. It is often used for forging crankshaft parts. When staggered, the blank is first cut locally, and then impact force or pressure of equal size, opposite method and perpendicular to the axis is applied on both sides of the incision, so that the blank can be offset.

Forging Connect

[Forging Connect] is a forging process in which the billet is heated to a high temperature in a furnace, and then struck with a hammer to combine the two in a solid state. Forging methods include lap joint, butt joint, snap joint and so on. The strength of the seam after forging can reach 70% to 80% of the strength of the connected material.


[Twisting] is a forging process in which a part of the wool is rotated around its axis by a certain angle relative to another part. This process is mostly used for forging multi-turn crankshafts and correcting some forgings. When the torsion angle of the small billet is not large, the hammering method can be used.

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