1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE EDS-T-7133 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE:
2、1/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 1. PURPOSE This standard aims at lessoning the differences which could result from differences of equipment and individual skill by standardizing method of the preparation for test piece for metallic mac
3、ro-structure test. 2. SCOPE This standard specifies to the preparation work from sampling of the test to polishing in preparing optic microscopic macro-structure test piece of metals and its alloys and hardness test piece for infinitesimal hardness tester. 3. DEFINITION 3.1. Sampling of test piece:
4、The work of selecting and saparating necessary part for test from the product and sample. 3.2. Mounting: The method of fixing it with simple jig or into the substances like plastic to facilitate grinding and polishing in case sampled test piece is too small or its corners are sharp. 3.3. Grinding: T
5、he work of making the surface plane using abrasive compound having random direction, grinding stone, sand paper and grinding wheel. 3.4. Polishing: The work of making plane inclined surface suitable for observing microstructure with mechanical, chemical, electro chemical method and the combination o
6、f these methods. 4. TYPE AND ITEM 4.1. Sampling of test piece 4.1.1. Destruction (1) Method: Take the test piece by fracturing the sample with impact load and static load applied to sample. (2) Object of application: This standard applies to brittle material with high hardness and in case of materia
7、l with no hardness, sample the test piece by cooling the material with liquid nitrogen. (3) Others: It is not advisable method because with this method, intended portion(direction) can not be taken correctly. 4.1.2. Shearing (1) Method: Take the test sample by cutting sample with shearing machine or
8、 scissors for metal cutting. (2) Object of application: This method applies to thin material(ex: low carbon steel plate) or properly soft material. (3) Others: Deformed portion of the test piece sampled by shearing shall be removed by grinding. 4.1.3. Torch (1) Method: The work of cutting sample or
9、product with the heat generated by oxygen and acetylene torch. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 2/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology (2) Object of application: It is generally used to cut variou
10、s kinds of large test pieces. (3) Others: Cutting method with flame. Enough attention shall be paid lest macro-structure observation portion should be heated and other portions receiving heat shall be removed with other method. 4.1.4. Sawing (1) Method: The most traditional method. The work of cutti
11、ng test pieces with saw blade. (2) Object of application: It may generally apply to various kinds of metals under HRC 35. (3) Others: In case of power hacksaw, it damages test piece, therefore, it is not well used in metal test and used well in cutting large test piece. 4.1.5. Abrasive cutting (1) M
12、ethod: The most widely used method for metallic structure test sampling method with disk fixed with abrasive particle ex) SIC, AL2O3). (2) Object of application: It may be applicable to every metallic structure but cooling water is necessary because heat occurs from friction. (3) Selection of wheel:
13、 Wheel shall be selected according to the characteristics of adhesives, porosity of wheel and kinds of cut product, generally, in case of steel alloy wheels made of AL2O3and in case of non-steel alloy, wheels made of SIC are commonly used. (4) Cautions in use (a) Wheel shall be exchanged according t
14、o characteristics of sample to be cut. (b) Sample shall be cooled with coolant because a lot of heat occurs at the time of cutting. Add water soluble oil to coolant lest rust should occur on the test piece. (c) Pay full attention to safety because it is feared that fractured pieces may be dispersed
15、hard by centrifugal force at the time of fracture due to the high speed rotation of wheel, damaging test personnel. (5) Main causes of problem and measure (See the table1) Table 1. Solutions for problems encountered in abrasive cutoff sectioning 4.2. Cleaning 4.2.1. Rinsing This method is most widel
16、y used in immersing in running water and wiping off the surface with soft brush and absorbetent cotton. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 3/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 4.2.2. Ultrasonic cl
17、eaning The most powerful cleaning method. Polluted substances on the surface and foreign substances in crack and pore by cavitating may be removed with this. 4.2.3. After cleaning, dry the surface rapidly with the liquid of high volatilization and vaporize the remaining liquid inside crack and pore
18、with dryer. 4.3. Mounting 4.3.1. Mechanical mounting device (1) Method: There is the method as shown in Table 1 which facilities such work as grinding and polishing by fixing the test piece with clamp. (2) Surface structure and hardened case depth may be measured by mounting with soft plate such as
19、Cu put to the product whose surface is likely to come off like the soft-nitrided product. (3) Cautions: Grinding and polishing grain shall be removed with ultrasonic cleaning whenever the beginning stage of grinding and polishing is finished, care shall be taken not to damage paper and polishing clo
20、thes. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 4/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 5/18 ISSUED DATE: 1993. 07. 13 REVISED
21、DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 4.3.2. Cold mounting (1) Method: The method of solidifying the uniform mixture of resin and hardening agent at normal temperature by placing it into reusable mould or mould for one time. (2) Usable materials for mounting are Acryl, Polyester,
22、 and Epoxies etc. and problems occurring at the time of mounting and measures against them are shown in Table 2. (3) This test method has the merit of helping resin penetrate into the inside of products(powder metal, ceramic and porous test piece), having blowholes and cracks if vacuum chamber is us
23、ed at the time of mounting. (4) To measure the case depth of surface hardened test piece, mount the test piece in a tilted position as shown in Fig. 2 so that it may be conveniently used at the time of measuring hardened case depth with infinitesimal hardness tester and the relation between tilted a
24、ngle and increased depth at this time shall be as shown in Table 3. 4.3.3. Heat pressure mounting (1) Method: Method of mounting by pressure moulding in the condition heated at about 150 with thermosetting resin plastic and thermoplastic resin (2) Usable mounting materials and its typical characteri
25、stics are shown in Table 4 and 5. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 6/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology (3) Various kinds of problems occurring at the time of hot pressure mounting and measures
26、against them are shown in Table 6. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 7/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology (4) Generally, hardness of mounting material is lower than that of the test piece and so
27、corner rounding as shown in Fig. 3 comes to emerge. Incorrect measurement due to corner rounding can be repressed by mounting filler material(ground glass, cast iron sfiot and pelletized alumina etc.) along with the test piece at the time of mounting. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCO
28、PIC STRUCTURE TEST PIECE PAGE: 8/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 4.4. Marking 4.4.1. Never fail to mark the test piece which has been mounted with adequate tool(marking pen, vibrating engraver etc.) to distinguish it from other test piec
29、e. 4.4.2. The following items shall be recorded in indication contents. (1) Vehicle type (2) Part name (3) Sample number (4) Test date 4.5. Grinding and polishing 4.5.1. Mechanical grinding and polishing (1) Method: The work of flattening test pieces with sand paper, wheel and belt grinder, the most
30、 widely used method in manufacturing metallic structure test piece. (2) Deformation of the surface of test piece: The deformation of the surface of test piece occurs mainly at the time of grinding and plasticity deformation at the time of polishing as shown in Fig. 4. EDS-T-7133METHOD OF THE PREPARA
31、TION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 9/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology (3) Grinding and polishing compound: Polishing compounds used in metal structure test are non-organic powders. Kinds of powders due to moss hardness are sh
32、own in Table 7. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 10/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 11/18 ISSUED DATE: 1993. 07.
33、 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology (4) Various kinds of compounds used in grinding and polishing test piece of metal structure, which are classified by each stage, are shown in Fig. 5. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 1
34、2/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology (5) Grinding and polishing liquid: Coolant is usually used at the time of grinding and polishing almost all the metallic structure test piece and its merits are as follows. 1) Control of heat occurring b
35、etween test piece and polishing compound. 2) Control of harmful foreign substances 3) Extension of life of sand paper by removing leftovers occurring at the time of work. (6) Pressure, time, speed: If pressure, time and speed are increased, wear of test pieces becomes rapid and the following phenome
36、na occur. 1) Excessive pressure and heat cause the deformation of the surface, resulting in change in microstructure. Be careful not to have excessive pressure applied(especially at the time of polishing). 2) It would be better to make the time of grinding as short as possible and the time of polish
37、ing as long as possible. However, in case of polishing with polishing compound other than diamond, relief effects according to structure occur and so it would be better to make the time of polishing short. 3) As hardness of test piece gets higher, the speed shall be lessened. In case of very hard ma
38、terial(ex: ceramics metallic compound, cemented carbide), polishing speed shall be increased. 4) If the speed is increased, heat occurs on the surface of the test piece so materials sensitive to heat shall be polished at low speed. (7) Grinding and polishing direction 1) Corner rounding gets severe
39、according to grinding and polishing direction. 2) Perform grinding and polishing at each stage in the direction of 90to remove already existing flaws. (8) Grinding and polishing substrate 1) Coated paper disc or coated cloth belts are generally used for coarse grinding and coated paper belts are EDS
40、-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 13/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology widely used for fine grinding. 2) For polishing, wool, silk, cotton cloth and various kinds of synthetic fiber are widely used
41、 and low-nap cloths for coarse polishing and medium-nap cloths for final polishing. 4.5.2. Electrolytic polishing (1) Method: If conducting electric current by making the test piece to be polished plus pole and stainless steel or copper minus pole in an electrolyte, the surface of plus pole gets pol
42、ished. (2) Device 1) Smoothing: If placing the test piece having scratch on the surface in an appropriate electrolyte, liquid polishing film of high viscosity forms due to interaction between the metal and the electrolyte(See Fig. 6). Therefore resistance at peak A(in proportion to distance between
43、A and B) is lower that of peak C. Peak A is selectively dissolued to be polished on the surface prior to C part. 2) Brightening action: This action geherally has to do with the formation of thin static film, concerning removal of roughness of about 0.01W and etching of metal surface. 3) Current volt
44、age relation: Current voltage relation varies at the time of electrolytic polishing according to kinds of electrolytes and test piece. The relation occurring when Aluminum is electrolytic-polished in the solution of HC104is shown in Fig. 4. Current hardly flows at low voltage because of existence of
45、 film on the surface of test piece. Therefore etching is possible at low voltage, but not polishing and when voltage gets higher, polishing is possible. EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 14/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION:
46、2 GM DAEWOO Auto & Technology (3) Device 1) Power source: Generally, direct current(battery, direct-current generator and rectifier etc.) are used. Battery is used in case of polishing with low voltage. 2) Electric circuit: Outline of circuits which are typically used are shown in Fig. 7 on the othe
47、r hand, in case of electrolytic polishing of platinum group(platinum, Iridium, palladium, rhodium etc., alternating circuits similar to (b) of Fig. 7 are used. (4) Electrolyte: Polishing conditions for electrolyte, metal and alloy metal are shown in Table 8. Kinds of applicable metals according to e
48、ach electrolyte are shown in Table 9. Generally, electrolytes have adequate viscosity and high solubility against test piece metal at the time of electrolytic polishing. When polishing is not conducted, plus pole shall not be dissolved into electrolyte. EDS-T-7133METHOD OF THE PREPARATION FOR MICROS
49、COPIC STRUCTURE TEST PIECE PAGE: 15/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 16/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 17/18 ISSUED DATE: 1993. 07. 13 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology EDS-T-7133METHOD OF THE PREPARATION FOR MICROSCOPIC STRUCTURE TEST PIECE PAGE: 18/18 ISSUED DATE: 1993. 07. 13
