Method for manufacturing a ball bearing, notably for a butterfly valve in an aeronautical environment

A method for manufacturing a butterfly valve for an aeronautical application, comprising

• manufacturing a ball bearing, comprising:
• sintering a steel powder, the chemical composition of which includes in mass percent, 2.3%/of carbon, 4.2%/of chromium, 7%/of molybdenum, 6.5%/of tungsten, 10.5%/of cobalt and 6.5%/of vanadium, so as to obtain a sintered steel;
• shaping of the sintered steel, for forming a bearing ring of the butterfly valve of an aeronautical application, comprising:
• rolling the sintered steel to form a steel bar;
• cutting the steel bar to form a steel washer;
• and machining the steel washer to form the bearing ring, so as to give it an annular general shape having an inner surface and an outer surface;
• and assembling the ball bearing in the butterfly valve, the ball bearing comprising the bearing ring and a plurality of balls.

A method for manufacturing a ball bearing of a butterfly valve for an aeronautical application, comprising:

• sintering a steel powder, the chemical composition of which includes in mass percent, 2.3% of carbon, 4.2% of chromium, 7% of molybdenum, 6.5% of tungsten, 10.5% of cobalt and 6.5% of vanadium, so as to obtain a sintered steel;
• shaping the sintered steel, to form a bearing ring of the butterfly valve of an aeronautical application having satisfactory hardness and corrosion resistance at temperatures on the order of 500 degrees C., comprising:
• rolling the sintered steel, to form a steel bar;
• cutting the steel bar, to form a steel washer;
• machining the steel washer, to form the bearing ring, so as to give it an annular general shape having an inner surface and an outer surface;
• and heat treatment of the bearing ring, comprising:
• mild annealing for approximately three hours in a protected atmosphere at a temperature between 850 degrees C. and 900 degrees C.;
• slow cooling of approximately 10 degrees C. per hour in open air, to a temperature of approximately 700 degrees C.;
• detensioning annealing for approximately two hours at a temperature between 600 degrees C. and 700 degrees C.;
• slow cooling down to a temperature of approximately 500 degrees C.;
• quenching in a protected atmosphere with pre-heating in two stages, namely, a first stage at a temperature between 450 degrees C. and 500 degrees C., and a second stage at a temperature between 850 degrees C. and 900 degrees C.;
• austenization at a temperature based on a desired hardness;
• cooling down to a temperature between 40 degrees C. and 50 degrees C.;
• annealing of at least one hour at a temperature of approximately 560 degrees C.;
• and cooling down to room temperature;
• and assembling the ball bearing, the ball bearing comprising said bearing ring and a plurality of balls.