SAE 8640

The GGD 8640 steel is a medium carbon steel and low alloy most frequently used. It is a steel processing with medium hardenability. It is used in manufacturing various mechanical components combining high mechanical strength combined with resistance to fracture. It can be nitrided to increase the wear resistance.

Chemical composition – C (0.38 – 0.43), Si (0.15-0.30), Mn (0.75-1.00), Cr (0.40-0.60), Ni (0 , 40-.70), Mo (0.15-0.25)
Supply conditions – Supplied with maximum hardness of 340 HB.

APPLICATIONS

It is used in components for mechanical systems commonly used where the SAE 1045 steel use does not apply as a consequence of a better setting ability in cross-section, resistance to fatigue and fracture. For the manufacture of bearings, bushings, rollers, gears, hydraulic axes, drilled shafts, etc.
FORGING

The GGD 8640 steel should be held at a minimum temperature of 900 ° C and a maximum of 1220ºC.

HEAT TREATMENT

Annealing: The treatment should be done at the temperature of 830ºC for at least 1 hour for every 25 mm. Cool slowly in the oven to 300 ° C and then in still air.

Standardization: The treatment should be done at the temperature of 860 – 880ºC for at least 1 hour for every 25 mm. Cool air. In special cases can use forced air.

Temper: austenize in temperature between 840 – 860ºC. Heat for 1 hour for each 25 mm of thickness. Cooling or oil quenching the polymer. Cooling polymer leads to smaller dimensional change and improved microstructural homogeneity.

Tempering: It must be done immediately after hardening when the temperature reaches about 70 ° C. The tempering temperature must be selected according to the hardness specified for the component. For this use the tempering curve for guidance below. Keeping the tempering temperature for at least 1 hour for each 25 mm thick and used for at least two hours. No tempering in the temperature range between 230-370ºC because of the possibility of inducing the fragility to tempering. Curve TemperabilidadeAs 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.

Surface Hardening: Can be performed by flame or induction process to hardness greater than 50 HRC.