1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards METHOD OF TEST PIECE PREPARATION FOR SINTERED MATERIALS EDS-T-7121 ISSUED DATE: 1988. 07. 15 REVISED DATE: 2006. 06. 19 VERSION: 2 EDS-T-7121METHOD OF TEST PIECE PREPARATION FOR SINTERED MATERIALS PAGE: 1/3 ISSUED DAT
2、E: 1988. 07. 15 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 1. PURPOSE The inspection of internal structure of sintered materials aims at finding out types and dimensions of the used powder, distribution of blowholes by portion, shapes of blowholes, microcracks, etc. as well as
3、 microstructure. As the preparation of test piece for this test varies considerably according to appliances used or each persons skill, technical details cannot be standardized. But general method of test piece preparation shall be specified so that an exact inspection of internal structure is perfo
4、rmed. 2. SCOPE This standard specifies the method of test piece preparation for sintered materials and applies mainly to sintered ferrous materials. 3. TEST METHOD 3.1. Sampling of test piece 3.1.1. When general inspections of internal structure are performed, the test piece shall be cut along the s
5、ection parallel to the rolling direction. In case of measuring surface hardening depth of gears, however, it may be cut in transverse direction. 3.1.2. In case of fractured sample, it shall observed in the vicinity of the fractured surface or fracture origin if possible. 3.1.3. In case of newly-deve
6、loped products, it is desirable to examine every part equally. 3.2. Sectioning 3.2.1. The test piece shall be cut by means of a soft abrasive wheel or low-speed diamond wheel. 3.2.2. The appropriate dimensions of test piece is 12 12 mm. 3.2.3. The cut section shall be cooled by cooling water contain
7、ing rust preventive as it is likely to be overheated when sectioned. 3.3. Washing 3.3.1. In the machining of the sectioned test piece, cooling water is contaminated during sectioning, oil during machining or heating, lubricant during sizing, and rust preventive during barreling, therefore the contam
8、inants shall be removed. 3.3.2. In case the quantity of contamination is small and heating is allowed, the contaminants shall be evaporated by heating test sample on a heating plate for one minute or more until its color changes to light blue. It shall be performed in hood. 3.3.3. When heating is no
9、t allowed, the contaminants shall be removed by the soxhlet extractor (Refer to ASTM B EDS-T-7121METHOD OF TEST PIECE PREPARATION FOR SINTERED MATERIALS PAGE: 2/3 ISSUED DATE: 1988. 07. 15 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 328). 3.3.4. It may be washed in heated 1-1-1
10、 trichloroethane solution by an ultrasonic washer for one hour. 3.4. Impregnating 3.4.1. The blowholes shall preferably be filled in wax or epoxy resin to prevent contamination by abrasives, water or corrosives. 3.4.2. When the test piece is dipped in epoxy resin or synthetic wax melted at 175 for 2
11、 4 hours, the blowholes are filled in by capillary action. 3.4.3. This process can be accelerated by dipping the test piece in wax under vacuum using a vacuum chamber, and then releasing the vacuum state. 3.5. Mounting 3.5.1. The test piece impregnated with wax shall be mounted with bakelite or epox
12、y resin. 3.5.2. Thermosetting bakelite resin shall be press-formed at about 160 with a mounting press. 3.5.3. Another method is to put the test piece in a 2-piece cup(about 3225mm) made of steel or plastics, mix it with epoxy resin and hardener and solidify it at the normal temperature. 3.5.4. To pr
13、event edge rounding during polishing, the resin may be mixed with A12O3powder. 3.6. Grinding 3.6.1. The test piece shall be ground rough with a wheel to which 200-mesh diamond particles adhere. 3.6.2. The test piece shall be wet-ground on the 400 and 600-mesh silicon carbide paper for final grinding
14、. Here, it shall be ground so that scratches are formed in one direction and then in the perpendicular direction by rotating it 90. 3.6.3. When using an 8 inch grinding wheel, it shall be ground at 125250 rpm for about 30 seconds. 3.7. Polishing 3.7.1. After grinding, abrasives and polished metal ch
15、ips shall be removed during polishing so that they do not fill in blowholes, and special attention shall be paid to prevent the rounding of the edge. 3.7.2. Before polishing, blowholes shall be opened by dipping the test piece in 2% nital or appropriate etching reagent for 2 minutes. 3.7.3. Rough po
16、lishing shall be performed on the long-fluffed cloth for 2 minutes with 1W A12O3as the abrasive. Here, the pressure applied to the test piece shall be moderated and the number of revolution of the wheel shall be about 250 rpm for 8 in wheels. The test piece shall be rotated slowly in the direction o
17、pposite to that of wheel rotation to prevent the presence of meteor-shape marks. EDS-T-7121METHOD OF TEST PIECE PREPARATION FOR SINTERED MATERIALS PAGE: 3/3 ISSUED DATE: 1988. 07. 15 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 3.7.4. The procedure of 3.7.2 3.7.3 shall be repeat
18、ed 2 3 times to remove foreign matters in blowholes so that the surface of the test piece is uneven like the orange skin when observed visually. 3.7.5. Then, polishing shall be performed on the short-fluffed cloth at 250 rpm for 2 minutes with 1W diamond paste as the abrasive. Here, alcohol-base solvent or thinner shall be used as a coolant. 3.7.6. Final polishing shall be performed on the long-fluffed cloth at 125 rpm for 30 seconds with 0.05W A1203as the abrasive.
