Hot Forging of Connecting Rod

Posted on Posted in Steel Forging

About Hot Forging

Forging is the metal working manufacturing process in which the useful shape of metal component is obtained in solid state by compressive forces through the use of dies and tools. Traditionally, forging was performed by a smith using hammer and anvil. Using hammer and anvil is a crude form of forging. The smithy or forge has evolved over centuries to become a facility with engineered processes, production equipment, tooling etc. In forging, the required shape is obtained from a simple shape like billet or bar into the desired shape in one or more. It is one of the oldest methods in metalworking operations, dating back at least 4000 B.C. Forging were first used to make jewelry, coins and various implements by hammering metal tools made of stone.

Hot Forging is the most widely used forging process. In hot forging, the process is carried out at a temperature above the recrystallization temperature of the metal. The recrystallization temperature is known as the temperature at which the new grains are formed in the metal. Extreme heat of this kind is very necessary in avoiding strain hardening of the metal during deformation.

Typical hot forging products are: crank hook, connecting rod, gear, pinion, crown wheel, crankshaft etc. In the hot forging process, starting material has comparable simple geometry; then the material is plastically deformed in one or more operation using heat and applying load into a product of relatively complex configuration. In forging product, elongation occurs plastically, and usually exhibits much better ductility in a direction parallel to that of plastic elongation. Grains are oriented parallel to elongation due to plastic deformation. Defects are defined as imperfections that exceed certain limits due to unexpected occurrences. There are many imperfections which are considered as being defect, ranging from those traceable to the starting material to those caused by one of the forging processes or by post forging operations like trimming, coining or cooling.

Manufacturing Connecting Rod in Hot Forging

hot forged connecting rod

A connecting rod is a shaft which connects a piston to a crank or crankshaft in a reciprocating engine. Together with the crank, it forms a simple mechanism that converts reciprocating motion into rotating motion. A connecting rod may also convert rotating motion into reciprocating motion, its original use. Earlier mechanisms, such as the chain, could only impart pulling motion. Being rigid, a connecting rod may transmit either push or pull, allowing the rod to rotate the crank through both halves of a revolution. In a few two-stroke engines the connecting rod is only required to push.

Today, the connecting rod is best known through its use in internal combustion piston engines, such as automobile engines. These are of a distinctly different design from earlier forms of connecting rod used in steam engines and steam locomotives.

Hot forged connecting rods, in particular forged connecting rods for an internal combustion engine, especially when they are made of steel, are manufactured by a process which comprises hot forging of a connecting rod rough forging, a heat treatment and a machining operation.

The hot forging includes several steps:

hot forging of connecting rod

Step 1:- Rods are cut in to proper size from billet and length by using band saw or billet shearing machine.
Step 2:- Heating of billet into oil fire furnace up to 3 forging temperature ranges i.e. from 1240℃-1270℃ and approx. 15 different ranges of temperature.
Step 3:- Placing billet in between upper & lower die using tong and completing forging in two stages i.e. forging rolling and finishing.
Step 4:- Visual Inspection is carried out after completion of forging.

After hot forging, it can produce connecting rod in most net shaped status with less machining operations, which is very well adapted to both small and large batches. The main advantages are:

  • Good ductility
  • Possibility to manufacture customized parts
  • Excellent surface quality
  • High formability ratios
  • Decreased yield strength and thus less energy required
  • Increased diffusion and thus reduced chemical inhomogeneity

The heat treatment, which may be carried out at a later stage or while the rough forging is still hot, depends especially on the grade of steel used and on the desired mechanical properties.

Fly Steel Forging devotes itself in hot forging field for more than 20 years, and is now cooperating with many overseas automotive companies for various automotive forgings. If you have any demand on hot forged connecting rod or other automotive forged components, pls get in touch with us.

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