CNC Lathe Precision Forging Parts 20CrMnMo 34CrNi3Mo Material For Mining Machinery

Production of Open Die Forging Auto Parts Forging Parts Used in Mining and Construction Machinery

Defect analysis of Open Die Forging Auto Parts Forging Parts Used in Mining and Construction Machinery
(1) Oxidation
The phenomenon in which the metal billet reacts with the oxidizing gas in the furnace to form oxides when heated is called oxidation. The production of oxide scale not only causes metal burning loss, but also reduces the surface quality and dimensional accuracy of forgings. When the oxide scale is pressed into the forging to a depth exceeding the machining allowance, the forging can be scrapped.
(2) Decarbonization
The phenomenon that the carbon on the surface of the metal billet reacts with oxygen and other media during heating, resulting in the reduction of carbon elements on the surface is called decarburization. Decarburization will reduce the hardness of the surface layer and reduce the wear resistance. If the thickness of the decarburized layer is less than the machining allowance, it will not cause harm to the forging; otherwise, it will affect the quality of the forging. Decarburization can be slowed down by rapid heating, applying protective paint on the surface of the billet, and heating in a neutral or reducing medium.
(3) Overheating
The phenomenon of coarse grains of metal billets caused by too high heating temperature or too long holding time at high temperature is called overheating. Overheating will reduce the plasticity of the blank and the mechanical properties of the forging. To this end, the heating temperature should be strictly controlled, and the holding time in the high temperature stage should be shortened as much as possible to prevent overheating.
(4) Overburning
The heating temperature of the metal billet exceeds the initial forging temperature too much, and the phenomenon of oxidation and melting of the grain boundary is called overburning. After over-burning, the strength of the material is seriously reduced, and the plasticity is very poor. Once forged, it will be broken into waste and cannot be saved. Therefore, it is necessary to strictly implement the correct operating practices.
(5) Crack
When heating large forgings, if the charging temperature is too high or the heating speed is too fast, the temperature difference between the core and the surface of the forging will be too large, resulting in excessive internal stress and cracks. Therefore, when heating large forgings, to prevent the furnace temperature from being too high and the heating speed being too fast, heat protection measures should generally be adopted.

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