SAE 4320


The GGD 4320 steel is a steel for processing connected to the chromium, nickel and molybdenum and with a low carbon content to facilitate welding. The low carbon content allows the use of carburizing to increase the wear resistance. It has average hardenability with a combination of medium strength and fracture resistance.

Chemical composition – C (.17-.22), Si (0.15 – 0.35), Mn (0.45 – 0.65), Cr (0.40-0.60), Ni (1 , 65-2.00), Mo (0.20-0.30)
Supply conditions – Supplied with maximum hardness of 260 HB.


It is used in mechanical components where systems require a hardness uniformity throughout the cross section large or small sections. For its lower carbon content hardships are minor when compared to steels with 00:40%. Its main applications are: shafts, gears, bearing caps, planetary gears, sprockets, columns, crowns, sleeves and cylinders.


The GGD 4320 steel should be held at a minimum temperature of 870ºC and a maximum of 1240ºC.


Annealing: The treatment should be done at the temperature of 870ºC for at least 1 hour for every 25 mm. Cool the oven. Usually used in esferoidizado state to reheat it at 680 – 700 ° C, hold for 8 hours, cooling in the furnace to 300 ° C and then in air.

Standardization: The treatment should be done at the temperature of 920 – 930ºC for at least 1 hour for every 25 mm. Cool air. In special cases can use forced air.

Carburizing: the hardening process can be used in cash, gas or salt bath. The temperature should be between 900 – 925ºC. The hardening time should be controlled according to the carbon potential and the hardening depth specified.

Quenching: Quenching can be performed directly after hardening simply by that decrease the temperature to 840 – 850 ° C, maintaining the time necessary to homogenize the temperature in cross section and cooling in oil. The quenching can also be performed after the carburizing components with cooling to room temperature. In this case, using the same procedure described.

Tempering: It must be done immediately after hardening when the temperature reaches about 70 ° C. The tempering is performed at temperatures between 150 – 200 ° C. The tempering there is no significant drop in hardness, but it ensures better resistance to fracture and the formation of surface cracks in retífica.Curva TemperabilidadeAs of information contained in this catalog are indicative, depending on the characteristics of the raw material and test conditions.

Nitriding: The steel can be nitrided to increase the wear resistance of the surface hardening. The maximum hardness depends on the precondition of heat treatment. benefit components before nitriding have better hardening characteristic reaching next maximum hardness of 800 HV. It is recommended hardening depth of between 0.30 and 0.60 mm and Layer White Not less than 10 mm.

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