What are the categories of forging?-Goodwill Valve Fittings

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What are the categories of forging?

Release Date：

21 Jun,2023

Forging is mainly classified according to the forming method and deformation temperature.According to the forming method, forging can be divided into two categories: forging and stamping; according to the deformation temperature, forging can be divided into hot forging, cold forging, warm forging and isothermal forging.

Hot forging

It is forging above the metal recrystalline temperature.Increasing the temperature can improve the plasticity of the metal, which is conducive to improving the inherent quality of the workpiece and making it not easy to crack.High temperature can also reduce the deformation resistance of the metal and reduce the tonnage of the required forging machinery.However, there are many hot forging processes, the accuracy of the workpiece is poor, the surface is not clean, and the forgings are prone to oxidation, decarbonization and burning.When the workpiece is processed is large, thick, the material strength is high, and the plasticity is low (such as the rolling of extra-thick plates, the drawing of high-carbon steel rods, etc.), hot forging is used.When the metal (such as lead, tin, zinc, copper, aluminum, etc.) has sufficient plasticity and the amount of deformation is not large (as in most stamping processes), or the total amount of deformation is large and the forging process used (such as extrusion, radial forging, etc.) is conducive to the plastic deformation of the metal, hot forging is often not used, but cold forging is used instead.In order to complete as much forging work as possible with one heating, the temperature interval between the initial forging temperature and the final forging temperature of the hot forging should be as large as possible.However, the initial forging temperature is too high, which will cause excessive metal grain growth and overheating, which will reduce the quality of the forged parts.When the temperature is close to the melting point of the metal, the melting and intergranular oxidation of low-melting substances will occur, forming overburden.Overburned blanks tend to shatter when forged.The generally used hot forging temperature is: carbon steel 800～1250℃; alloy structural steel 850～1150℃; high-speed steel 900～1100℃; commonly used aluminum alloy 380～500℃; titanium alloy 850～1000℃; brass 700～900℃.

Cold forging

It is a forging that is carried out at a temperature lower than the recrystalline temperature of the metal. The cold forging commonly referred to refers to the forging at room temperature, while the forging at a temperature higher than room temperature but not exceeding the recrystalline temperature is called warm forging.The accuracy of temperature forging is high, the surface is smooth and the deformation resistance is not large.

Workpieces formed by cold forging at room temperature have high shape and dimensional accuracy, smooth surface, few processing steps, and easy to automate production.Many cold-forged and cold-stamped parts can be used directly as parts or products without the need for cutting.However, during cold forging, due to the low plasticity of the metal, it is easy to crack when deformed, and the deformation resistance is large, which requires large-tonnage forging machinery.

Warm forging

The forging pressure that is higher than room temperature but does not exceed the recrystalline temperature is called warm forging.The metal is pre-heated, and the heating temperature is much lower than that of hot forging.The accuracy of temperature forging is high, the surface is smooth and the deformation resistance is not large.

Isothermal forging

The blank temperature is maintained at a constant value throughout the forming process.Isothermal forging is to make full use of the high plasticity of certain metals at isothermal temperatures, or to obtain specific tissues and properties.Isothermal forging requires the mold and the blank to be kept at a constant temperature together, which requires a high cost, and is only used for special forging processes, such as superplastic forming.

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