Quenching heat treatment process of high-speed steel pharmaceutical channel groove milling cutter

To process the medicine channel groove in the medicine tray on the 13-A fuze (the material is duralumin 2A11 type), the medicine channel groove milling cutter used has an outer dimension of 5mm x 40mm and a structure similar to a double-head center drill. The hardness requirement is 60-66HRC. The main failure mode of middle milling cutters is breakage. According to conventional heat treatment, although the hardness and metallography meet the requirements, the toughness is not high. For processing aluminum parts, toughness should be the first, and hot hardness and wear resistance are the second. The heat treatment process was adjusted for this purpose.

Since the medicine channel groove itself is a 41mm arc, narrow and deep, the groove width is 3.Smm and the depth is 4.2mm. During the milling process, the milling cutter is easy to break at the beginning and end of milling, so the toughness requirements are particularly high. Since duralumin itself has low hardness, the requirements for the tool's thermal hardness and wear resistance are not high, so the tool hardness does not need to be too high. , is planned to be changed to 60 -63HRC, low temperature quenching, high temperature tempering, the effect is very good.

1) Heat treatment process. If M2 or 9341, two general-purpose high-speed steels, are selected, the heat treatment process is: 840 - 860℃ , use 58WC x lh for the first tempering, and 560gC x lh for the second tempering. Processed according to the above process, the metallographic grade is 11-12 and the hardness is 60. 5-63HRC. Regarding the issue of whether low-temperature quenching should require high-temperature tempering (tempering higher than the conventional tempering temperature), colleagues have great differences. The author's experience is that high-temperature tempering will increase the life of the milling cutter. If you choose W18 high-speed steel to make a milling cutter, you only need to adjust the quenching heating temperature, and the other steps are similar.

2) Theoretical analysis. Low-temperature heating and quenching is used because the heating temperature decreases. After quenching, the austenite grains of the steel are refined, the number of remaining carbides in the steel increases, and the content of carbon and alloying elements in the matrix decreases, which is conducive to the formation of lath martensite, so the toughness of the steel after quenching increases. The wear resistance is not reduced. In order to simplify the process and save energy, it is feasible to use twice tempering. Increasing the tempering temperature can accelerate the transformation of retained austenite; the second tempering at conventional temperature can also achieve a greater secondary hardening effect and ensure sufficient tempering. At the same time, compared with conventional triple tempering, the strength and toughness are improved.

3) Effect. Milling cutters treated with conventional heat treatment processes can only process 10-20 pieces, and sometimes break after processing 1-2 pieces. However, milling cutters using low-temperature quenching can process 180-200 pieces after reasonable grinding, and have a longer service life. improve. If the surface strengthening treatment process is added, the service life will be further improved.