S705 Tap Heat Treatment Process Details

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Process details of the heat treatment of taps In machining, taps are the most common cutting tool used to process internal thread buckles, which consist of a cutting part and a shank. In addition to being subjected to a variety of stresses, it is also subjected to strong friction during the cutting process. Therefore, the taps are required to have high strength, hardness, wear resistance and less distortion after heat treatment. According to the above requirements, the materials for manufacturing taps are generally S705, T12A, T10A carbon tool steel, CrWMn steel, 9CrSi and W18Cr4V high-speed steel, W6Mo5Cr4V2 steel, etc. Shanghai Gehang Vacuum Technology Co., Ltd. uses 10bar vacuum gas quenching furnace to do heat treatment process .

In the heat treatment production process of taps, because people often ignore some of the details, the heat treatment of taps is distorted, even cracked and scrapped, resulting in a higher rejection rate and greater economic losses. For this reason, the following issues should be paid attention to in production:

1)  Quality inspection of the material used to make the taps should be carried out before machining. The microstructure of the material should be a spheroidized structure, with fine carbides and uniform distribution. If the microstructure of the material is flaky pearlite and the carbide size is too large, the unevenness is too high, or even the presence of network carbides, the plasticity of the tap will decrease, the tendency of quenching distortion and cracking will increase, and the brittleness of the tool tip will increase. Chipping, reducing the service life of the tap.

2)   In order to reduce the tendency of distortion and cracking during quenching before the tap is quenched, especially for taps with higher precision requirements, the machining stress generated in the previous process should be eliminated.

3)  The taps should be preheated before quenching to reduce the temperature difference, reduce the thermal stress, and reduce the distortion tendency of the taps. Especially for W18Cr4V high-speed steel, because the quenching heating temperature is relatively high, if the cold tap is directly heated in a high temperature salt bath furnace up to 1280 ℃, the heating speed will cause a large thermal stress and increase Distortion cracking tendency. Therefore, the taps should be preheated before quenching and heating to reduce the temperature difference and reduce the thermal stress.

4) When the tap is heat-treated, only the blade and shank can be quenched, and the intermediate transition part is not quenched. This can make the transition part tough to facilitate future corrections. The quenching heating temperature should be as low as possible to prevent coarse grains and reduce the strength, plasticity and toughness of the tap. Especially for small diameter taps, it is better to reduce the hardness, but also to maintain a certain degree of toughness, and absolutely avoid high temperature quenching. At the same time, the quenching and heating time should not be too long, otherwise, the excessively high heating temperature and holding time will also cause the tap grains to be coarse, decarburization, overheating and even overburning, affecting its performance and service life, or even scrapping.

5)  The taps after quenching should be tempered immediately to prevent long-term storage. The tempering temperature should be determined according to the hardness requirements of the tap, and the following two points should be noted: ①Adjust the tempering temperature in time according to the quenching situation; ②Avoid the first type of tempering brittle zone of steel, such as the tempering temperature of CrWMn steel It is 250℃～300℃. The tempering and holding time should be as long as possible. The hardness of carbon steel and alloy steel wire cone after heat treatment is preferably 61～63HRC, and the suitable hardness of high-speed steel is 63～66HRC.

Practice has proved that “details determine success or failure”, if you pay attention to the above details in the production process of taps, it will greatly reduce the heat treatment defects, distortion and cracking of the taps, increase the qualification rate and service life of the taps, reduce production costs and increase economic benefits.

Shanghai Geheng Vacuum Technology Co., Ltd. is a vacuum heat treatment furnace manufacturer with many years of experience in design, manufacturing and production. Mainly produce vacuum heat treatment furnace, vacuum sintering furnace, vacuum brazing furnace, New Energy And Environmental Protection Equipment and other vacuum equipments.Provide customized services, equipment work area can be based on customer output.