Improving the efficiency of metal-bonded diamond abrasive end tools by improving manufacturing technology

OBRABOTKAMETALLOV Vol. 20 No. 3 2018 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 3 2 21 steel 45 weld joint microhardness with an intermediate case in the form of a screw stud show (Fig. 4) that the screw stud material has a microhardness of 200 HV 0.05, and the case (shank) of a tool made of steel 45 after quenching and tempering has 500 HV 0.05. The weld joint region thickness, including the heat- affected zone, where the tool case hardness decreases (Fig. 4), is 0.3...0.4 mm. Fig. 4. Change in microhardness in the area of the welded joint of the body with the transition body of the diamond grinding head The efficiency of the investigated grinding heads with a shank made of thermally strengthened steel 45 was checked by comparative tests when processing plates made of hard alloy T15K6 on a milling and en- graving machine of “CARVER Mini-0609” model. Tests were carried out under the following conditions: • head rotation speed of 24,000 rpm; • cutting depth of 0.04 mm per double stroke; • longitudinal feed speed of 0.5 m/min; • head stroke length of 15 mm; • test duration of 60 min; • without the use of coolant. All the investigated samples of grinding heads in the amount of 3 pcs. with a shank made of heat-treated medium-carbon steel 45, were manufactured according to the above technology using condenser welding and one grinding head with a shank made of steel R6M5, was manufactured according to the standard technology, passed these tests, retaining further operability. Conclusions Thus, the results of comparative studies allow arguing that the joint efficiency between the shank and the working diamond part according to the proposed technology is superior to similar characteristics of the joint efficiency between the shank and the diamond layer of grinding heads obtained using the standard bonding technology. The proposed technology of diamond heads manufacture increases the joint efficiency between the case and the diamond working part, reduces the cost of manufacturing grinding heads due to the use of quenched medium-carbon steel as the tool case material instead of high-speed steel grades, the technology is simplified and a possibility of automating the manufacture of tools appears. Comparative operational tests of the grinding heads show a comparable service life with traditional tools. It is not possible to completely avoid the formation of voids in the weld area during condenser reflow