Material Selection and Heat Treatment Process of Taps and Dies For Tool Heat Treatment

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Taps are tools for processing internal threads, and die are tools for processing external threads. When working, the shank and the core bear greater torsional stress, the tooth edge bears greater friction and wear, and the tooth edge bears a higher working temperature during high-speed cutting. The main failure modes are wear and tear. Therefore, the tooth edge should have high hardness (59～64HRC), high wear resistance, and a certain degree of thermal hardness (depending on the cutting speed); the handle and core should have sufficient strength and toughness, with a hardness of 35～45HRC .

The commonly used materials and heat treatment of taps and dies can be divided into the following two situations:

1. Hand taps and dies have low cutting speed and no requirement for thermal hardness. They can be made of T10A and T12A steels and are quenched and tempered at low temperature.

2. Machine taps and dies have requirements for thermal hardness due to higher cutting speeds. Higher cutting speed (8～10m/min) requires higher thermohardness, so it can be made of 9SiCr, 9Mn2V, CrWMn steel. When the cutting speed reaches 25-55m/min, high thermal hardness is required, and it can be made of W18Cr4V steel and subjected to appropriate heat treatment.

Taking hand taps as an example, according to the above analysis, M12 hand taps are made of T12A steel, and the processing route is:

Cutting → spheroidizing annealing → machining → quenching, low temperature tempering → handle tempering → anti-rust treatment.

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