GENERAL
4340 Gnee steel is a steel processing with high hardening capacity, associated with chromium-nickel-molybdenum, which is used in the manufacture of various mechanical components, including coarse sections, when a combination of medium strength and fracture strength is desired. It also has a high resistance to fatigue.
Chemical composition – C (0.38 – 0.43), Si (0.15 – 0.30), Mn (0.60 to 0.80), Cr (0.80 – 1.10), Ni (1, 65 to 2.00), Mo (0.20-0.30)
Supply conditions – Supplied with a maximum hardness of 260 HB. Provided in the temperate state and tempered in the consultation phase.
APPLICATIONS
It is used in components of mechanical systems, mainly structural, where there is a uniformity hardness along the cross section large or small sections. Its main applications are: shafts, gears, planetary gears, columns, sleeves and cylinders.
FORGE
Gnee 4340 steel must be kept at a minimum temperature of 900 ° C and a maximum of 1220 ° C.
HEAT TREATMENT
Annealing: Treatment should be carried out at a temperature of 850 ° C for at least 1 hour per 25 mm. Cool slowly in the oven.
Normalization: The treatment should be carried out at a temperature of 860 – 880ºC for at least 1 hour per 25 mm. Cold air. In special cases forced air can be used.
Temper: austenize temperature between 840 – 870ºC. Heat for 1 hour for every 25 mm thickness and add an additional 1 hour for every 25 mm. Cool in oil or polymer. Cooling polymer leads to smaller dimensional change and better microstructural homogeneity.
Tempering: It should be done immediately after tempering when the temperature reaches about 70ºC The tempering temperature should be selected according to the hardness specified for the component. To use this tempering curve Arrangement. Maintain the tempering temperature for at least 1 hour for every 25 mm thickness and used for at least two hours. Not tempered in the temperature range between 230-370ºC due to the possibility of inducing the fragility of the tempered information. Temperability curves contained in this catalogue are indicative, depending on the characteristics of the material and test conditions.
Nitriding: Steel can be nitrided to increase the wear resistance of surface hardening. The maximum hardness depends on the heat treatment condition. Performance elements before nitriding have better hardening characteristics leading to the next maximum hardness of 800 HV. Tempering depth between 0.30 and 0.60 mm is recommended.
Surface hardening: can be performed by flame or induction process of hardness greater than 55 HRC.
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