When the workpiece is heat treated with a high-frequency heating power source, a reasonable process flow can reduce the heat treatment distortion of the machine tool parts, prevent cracking, and avoid the generation of waste. Some problems that are difficult to solve by one side of the hot and cold processing technology can be solved smoothly after the adjustment of the two aspects of the cold and hot processing technology.
1) Gears with mass-reduced annular grooves and holes tend to be distorted during induction hardening. If such gears are not ground, these annular grooves and holes should be machined after induction hardening of the teeth to reduce the number of teeth. distortion.
For example, a 45 steel gear has 6 φ35mm holes close to the tooth root. If these holes are machined first and then high-frequency induction hardening is performed, the pitch circle diameter of the tooth portion near the φ35mm hole will become smaller, so these 6 holes can only be drilled after high-frequency induction hardening.
2) For thin-walled gears with a keyway in the inner hole, in order to reduce the quenching distortion, the keyway should be cut after induction hardening of the tooth.
3) For large-sized round nut, if the inner hole thread distortion is too large after induction heating quenching notch (or round wrench hole), the inner hole thread should be processed after induction quenching of the notch.
For example, a 45 steel lock nut requires a hardness of 35-40HRC for the four notched parts. When the notch, internal thread, etc. are all processed, and then quenched and tempered as a whole, although the hardness of the notch can meet the requirements, the internal thread distortion (expansion) is large, and the accuracy requirements cannot be guaranteed; Due to the high hardness, cutting is difficult. In this regard, these contradictions are solved by adjusting the heat treatment method and process flow. The improved technological process is: cutting material, quenching and tempering (hardness: 25-30HRC), processing notch, high-frequency induction hardening (hardness: 35-40HRC), processing internal thread.
4) For parts with regular distortion after heat treatment but inconvenient to correct after quenching, the distortion amount can be reserved during machining, so that the distortion amount after heat treatment is within the tolerance range. For example, the distortion law of the machine tool guide rail after high-frequency induction quenching is concave, then it is processed to be convex before quenching, so that the distortion amount after quenching is within the tolerance range. For parts with low precision requirements, the distortion problem can be solved by improving the precision machining method according to the distortion law after heat treatment.
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