High-frequency induction quenching heat treatment technology for spline shafts of precision machine tools

1. Technical conditions for high-frequency induction quenching heat treatment. The hardness of the spline shaft after quenching and tempering is 250HBW, and the hardness of the outer edge of the 30mm diameter spline teeth is 480HRC.

2. Heat treatment process flow. Blank - quenching and tempering treatment - cold press straightening - stress relief annealing - rough machining - stress relief annealing - fine machining - high frequency induction heating surface quenching between flowers - overall low temperature tempering of the workpiece - inspection and toeing - low temperature again Tempering - cleaning and sandblasting.

3. Specification of heat treatment process. a. Quenching and tempering treatment: Heating and quenching temperature (840-860) degrees Celsius ±10℃, holding time 2h, oil cooling; high temperature tempering temperature 600℃±10℃, holding time 2h, air cooling. b. Stress relief annealing in the kitchen. The heating temperature is 580°C, the holding time is 2 hours, and the furnace is cold or the outlet is cold. c. Stress relief annealing treatment d. Spline high-frequency induction heating quenching Heating temperature 860-900℃, water spray cooling. e. Low-temperature tempering: Heating temperature is 280-300℃, holding time is one hour, and then it is air-cooled out of the furnace. F. Low-temperature tempering again. The heating temperature is 160°C, the holding time is 4 hours, and then it is air-cooled out of the oven.

Heat treatment process analysis

a. Quenching and tempering treatment to improve the strength, hardness, toughness, plasticity and other comprehensive mechanical properties of the end face of the spline shaft integral part.

b. Stress relief annealing. Its purpose is mainly to eliminate the residual internal stress caused by cold press straightening, prevent the workpiece from bending and deforming during subsequent high-frequency induction heating quenching, and stabilize the dimensional accuracy of the workpiece.

c. Spline high-frequency induction heating quenching. Its purpose is to ensure the high hardness and high wear resistance of the spline tooth circumferential surface. Since all spline teeth are stressed at the same time, unlike gears that mesh with each other, it is actually only the two sides of the spline teeth that are hardened without having to have too much hardened layer depth, so high-frequency induction heating equipment is used Perform surface quenching heat treatment.

d. Low temperature tempering. In order to eliminate the internal stress of the spline teeth and other parts, stabilize the size and shape of the workpiece, ensure the high hardness and high wear resistance of the spline teeth and reduce their brittleness.

Several key points in the implementation of heat treatment (high-frequency induction heating quenching):

a. The blanks are generally heated to the quenching and tempering temperature in a box-type electric furnace, and batches of blanks should be stacked in parallel and neatly; after heat preservation, the workpieces should be quenched in oil one by one, and cooled to low temperatures to produce oil.

b. After the blank is quenched and tempered, it is cold-pressed and straightened for stress relief annealing at 580°C and held for 2 hours; if it is unqualified after straightening, stress relief annealing needs to be repeated until it is qualified; it should be noted that two straightening After the straightening stress is eliminated, the temperature should be lowered by another 10-20℃.

c. During stress relief annealing, the workpieces should be hung vertically in the loading frame, preferably in a close row and upright.

d. Try high-frequency induction heating surface quenching of spline teeth on a high-frequency quenching machine. For spline teeth that are high and wide, the workpiece must be rotated slowly to ensure uniform heating around the workpiece. If the heating is uneven, it is easy to cause The hardness of the hardened layer of the spline shaft teeth is uneven, that is, the hardness is insufficient on one side and on the other side.