GENERAL
4140 Gnee steel is a steel processing with medium hardening capacity, associated with chromium and molybdenum, which is used in the manufacture of various mechanical components in which you want a good combination of medium strength and fracture resistance. It also has a high resistance to fatigue.
Chemical composition – C (0.38 – 043) of Si (0.10 – 0.35), Mn (0.75-1.00), Cr (0.80-1.10), Mo (0.15 – 0.25)
Supply conditions – Supplied with a maximum hardness of 340 HB. Provided in the temperate state and tempered in the consultation phase.
APPLICATIONS
It is used in components for commonly used mechanical systems, where the use of SAE 1045 steel is not applied as a consequence of its better hardening capacity in the larger cross sections, fatigue and fracture resistance. It is used in bearings, cylinders, gears, hydraulic shafts, drilled wells, rings, nuts and screws, rods, etc.
FORGE
Gnee 4140 steel must be kept at a minimum temperature of 925ºC and a maximum of 1220ºC.
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: Treatment should be carried out at a temperature of 870-900 ° C 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 70 ° C ~ The tempering temperature should be selected according to the hardness specified in the component. To do this use the tempering curve. Maintain the tempering temperature for at least 1 hour for every 25 mm thickness and used for at least two hours. No tempering between 230-370ºC due to the weakness of tempering.
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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