PRODUCT CATEGORIES

Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Vacuum sintering of helical milling insert blank

Welded helical milling cutters are used to process deep holes or special workpieces. The manufacturing method is to weld the thread milling cutter head to another tool.

The transverse area of the helical milling insert blank is small, the longitudinal length is long, and there are edge relief angles and welding angles in the longitudinal direction. This shape feature puts forward higher requirements for the forming process and vacuum sintering process in the production process. Commonly used production methods are: extrusion molding, injection molding and compression molding. The products produced by cold shaping after extrusion molding and then hydrogen sintering process have many cracks, and the pass rate is very low, resulting in very high cost. Due to the limitations of equipment and production conditions, injection molding is rarely used. At present, compression molding is the most used. Its production process is to form a blank by vacuum sintering after molding, and then heat shaping. This process basically solves the problem of a large number of scraps due to cracks.

Vacuum heat treatment process

The process flow of producing YS25 spiral milling inserts is: YS25 mixture→mixed with forming agent→drying→sieving→flat steel mold cold pressing forming→ semi-inspection→furnace loading→H2 pre-burning and dewaxing→vacuum sintering→blank inspection→heating Shaping→inspection→qualified products.

Vacuum sintering process of helical milling cutter

Vacuum sintering is the last process in the production process of the helical milling blade blank, and it is also a key process that determines the performance of the helical milling blade blank. One of the technical indicators of the helical milling blade blank is side bending ≤ 0. 3mm, flat bending ≤ 0.15mm. The most common and most difficult problem of this kind of sintered blank is bending deformation. This kind of sintered waste is not only related to the uneven distribution of compact density, but also related to the atmosphere in the furnace during vacuum sintering, heating rate, holding time, furnace loading method, etc. related.

H2 sintering and vacuum sintering

Hydrogen sintering and vacuum sintering have different effects on the bending deformation of the helical milling cutter blank. Due to the following disadvantages in hydrogen sintering: ① The atmosphere in the furnace is unstable, and the product is easy to seep and decarburize. ②The pores inside the product cannot be fully eliminated, leaving residual pores. ③ Some oxide impurities cannot be volatilized and eliminated in time. As a result, the sintered helical milling insert blank is severely bent and deformed, the quality cannot be guaranteed, and the qualified rate is very low.

Compared with hydrogen sintering, vacuum sintering has the following advantages: ① Negative pressure improves the wettability of bonding metal to hard phase. ② The gas impurities in the alloy are easy to get rid of, and there are few residual pores. ③Trace oxide impurities in the briquette are easily volatilized and removed in time during the sintering process, which reduces the amount of impurity segregation between the blank phase interfaces. ④ The atmosphere in the furnace is stable. During vacuum sintering, the change of carbon content in the blank can be predicted, and the carbon content of the blank can be ensured to be in the optimal range through process adjustment, thereby effectively reducing the bending deformation of the sintered blank. Therefore, the quality of the blank produced by vacuum sintering is better, the bending deformation is reduced, and there is almost no cracked waste product, and the qualified rate of the product after thermal shaping is improved.

Formulate a reasonable vacuum sintering curve

Different heating rates and holding times have different effects on the bending deformation of sintered blanks. The main features are as follows: ①The vacuum sintering time of the helical milling insert blank is longer than that of conventional products. ②The heating rate of the spiral milling cutter blank during vacuum sintering is slower than that of conventional products. ③The vacuum sintering of conventional products is only held at 1150°C and the final sintering temperature. The vacuum sintering of the spiral milling blade blank starts from 350°C for the first heat preservation, and 950°C for the second heat preservation. Proper insulation up to final sintering temperature. If the vacuum sintering curve of the conventional product is used to sinter the blank of the spiral milling blade, the sintered blank will have more bending deformation.

Use a reasonable way to load the furnace

The bending deformation of the blank is also related to the placement position of the briquetting block in the heating chamber. Different furnace charging methods will produce different bending deformation waste products. For the same furnace product after pre-burning and dewaxing, decarburization often occurs in the center and peripheral positions of the furnace. When loading the furnace, try to make the uneven distribution of carbon caused by pre-burning and dewaxing only occur at both ends of the compact. If the vacuum sintered blank has a flat bend, it can still be straightened by backfiring. Once the blank is bent sideways, it will become a final waste product.

Vacuum sintering equipment selection: The RVS vacuum sintering furnace provided by SIMUWU is an excellent product for processing this kind of process, which has the characteristics of good temperature uniformity and high temperature control accuracy. SIMUWU provides a professional team of engineers who can solve various problems encountered in the production process and is committed to giving customers the most convenient and efficient experience.