1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards TEST METHOD OF MAGNETIC PARTICLE PENETRANT EDS-T-7128 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 EDS-T-7128TEST METHOD OF MAGNETIC PARTICLE PENETRANT PAGE: 1/11 ISSUED DATE: 1990. 03. 27 REVISED D
2、ATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 1. PURPOSE This standard aims at specifying the magnetic particle test method, thus helping the test engineer perform tests in an appropriate manner. 2. SCOPE This standard specifies the method for magnetic particle penetrant test (hereinafter
3、 referred to as test) of ferrous materials and the products made from them (forged products, cast products, welded products, etc., hereinafter referred to as the test specimens.) 3. DEFINITIONS 3.1. Wet method: A method of applying magnetic particles suspended in a appropriate liquid. 3.2. Dry metho
4、d: A method of applying magnetic particles dried. 3.3. Solution of magnetic particles: Solution that suspends magnetic particles used for wet method. 3.4. Application of magnetic particles: The operation for making magnetic particles in inspection liquid or for dry method easily reach the defects, e
5、tc. in the test specimen. 3.5. Magnetic particles pattern: The pattern produced by the adhesion of magnetic particles at the discontinuous part occurring due to the defects, etc. of the test specimen. 3.6. Continuous method: The method of completing the application of magnetic particles while flowin
6、g a magnetizing current or attaching a permanent magnet. 3.7. Residual method: A method wherein magnetic particles are applied after the magnetizing current has been turned off. 3.8. Magnetizing current: The electric current used to induce magnetic flux in the test specimen. 3.9. Demagnetizing field
7、: The magnetic field which is produced by the magnetic poles appearing in the test specimen to reduce the magnetic field applied, when the test specimen is magnetized. 3.10. Effective magnetic field: The magnetic field actually working on the part under test. The residue of applied magnetic field su
8、btracted by demagnetizing field. 3.11. Magnetic particles: Fine particles of ferromagnetic material used for the test. 3.12. Visible magnetic particles: Magnetic particles whose pattern shall be observed under the visible light. 3.13. Fluorescent magnetic particles: Magnetic particles processed to f
9、luorescence when irradiated by ultraviolet rays. EDS-T-7128TEST METHOD OF MAGNETIC PARTICLE PENETRANT PAGE: 2/11 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 3.14. False indication: The magnetic particles pattern produced by other reasons than defects.
10、3.15. Skin effect: The phenomenon of electric current and alternating magnetic flux applied to the test specimen accumulating in the part near the surface. 4. TESTING ENGINEER The personnel in charge of the tests shall have the qualification necessary for the task or shall have enough knowledge, tec
11、hnique and experience equivalent thereto. 5. APPARATUS 5.1. The test apparatus shall, as a rule, be capable of performing the four operations on the test specimen, i.e., magnetization, application of magnetic articles, observation and demagnetization. 5.2. The magnetizing equipment shall be of eithe
12、r electric current using system of permanent magnet using system. 5.3. For the test fluorescent magnetic particles, an ultraviolet-ray irradiator shall be used. 6. TEST MATERIALS 6.1. Magnetic particles shall be classified into the ones for dry method used and the ones for wet method use by the qual
13、ity of dispersible agent used in their application, and further classified into the fluorescent ones and visible ones by the method of observation. 6.2. The magnetic particles shall have suitable magnetism, particle size(usually, 1-4 micron), dispersing characteristics, suspending characteristics an
14、d colour tone depending on the quality of material surface condition and nature of defects of the test specimen. 6.3. For the wet method, the liquid composed of kerosene specified in KS M 2613 or water, etc. as the dispersible agent, added with suitable rust-preventive and surface active agent as ne
15、cessary, shall be used. 6.4. For fluorescent magnetic particles, the concentration of magnetic particles dispersing in the suspension shall be determined taking consideration of the applying period, applying method of magnetic particles, but it shall be usually 0.2 ml - 0.5 ml for fluorescent ones a
16、nd 1.5 ml - 3.4 ml for visible ones when the test is performed according to 14.1.1. However, the suspension composed of both fluorescent and nonfluorescent magnetic particles may not be used. 6.5. The performance of suspension and magnetic particles shall be confirmed, by using a suitable standard t
17、est piece. 7. LIGHTING EQUIPMENT EDS-T-7128TEST METHOD OF MAGNETIC PARTICLE PENETRANT PAGE: 3/11 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 7.1. Visible magnetic particles The illumination for the test shall be white light or visible light and 1100 lu
18、x or more. 7.2. Fluorescent magnetic particles The test shall be performed in a darkroom of 10 lux or less in illumination and the illumination of suitably filtered ultraviolet-ray shall be 800 1000 uw/cm2. 8. DEMAGNETIZING EQUIPMENT The demagnetizing equipment shall be capable of demagnetizing the
19、test specimen fully and the accuracy of demagnetizing shall be measured using a magnetometer having scaling division of 1.5 oersted. 9. TIME FOR TESTING AND PRETREATMENT 9.1. The test specimen shall as a rule be tested in the condition where all the working and treating process have finished. Howeve
20、r, where surface treatment can interfere with the detection of defects, the test specimen shall be tested before the treatment. 9.2. In case of assemblies, the test shall be performed on the components before assembly, as a rule. 9.3. If the grease adhering to the test specimen and coating of paint
21、and plating, etc. are likely to affect the accuracy of test or to contaminate the suspension, they shall be removed to make the test specimen clean. For that, shot blasting, detergent, organic solvent, oxide film remover, paint remover and ultrasonic cleaner may be used. 9.4. However, for dry method
22、, the surface may not be wet. 10. TEST METHODS 10.1. Classification of test methods Test methods are classified by the time for magnetization in relation to application of magnetic particles, kind of magnetic particles, magnetic particle dispersible agent, type of magnetizing current and magnetizing
23、 method as shown in Table 1. Table 1. Classification of Test Methods Classifying factor Classification Time for magnetization in relation to application of magnetic particle Continuous magnetization method, residual method Kind of magnetic particles Fluorescent magnetic particles, visible magnetic p
24、articles Magnetic particle dispersible agent Dry method, wet method Type of magnetizing current D.C., A.C., pulsating current, impulse current Magnetizing method Axial current method, cross current method, through conductor method, coil method, yoke method, through flux method, prod method EDS-T-712
25、8TEST METHOD OF MAGNETIC PARTICLE PENETRANT PAGE: 4/11 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 10.2. Test procedure The test shall include such operations as the pretreatment, magnetization, application of magnetic particles, observation of magneti
26、c particle pattern and demagnetization, and these operations shall be suitably combined according to the purpose of individual testing. 10.3. Magnetization 10.3.1. Application (1) The method of magnetization shall be determined in consideration of the characteristics of apparatus, magnetic character
27、istics, shape, dimensions, nature of suspected defects (kind, location, direction) of the test specimens. (2) For magnetization, the most suitable method shall be chosen from Table 2 in consideration of the following items in particular. 1) The magnetic field shall be directed at right angles to the
28、 suspected direction of flaw and in parallel to the test surface as far as practicable. 2) Demagnetizing field shall be made little. 3) Where the test piece is not permitted to burn, a magnetizing method that does not require direct flaw of current through the test specimen shall be taken. 4) The te
29、st is shall be overlapped sufficiently so that 100% of the test piece shall be tested 100%. 10.3.2. Magnetizing method (1) Axial current method 1) Let the current flow from one end to the other end of the portion to be tested so that circular magnetization is formed at right angles to the direction
30、of the current flow. Then detect defects in the same direction with the current flow. 2) The test shall be performed at least twice in the same portion. In the second test, the magnetic flux shall be in a perpendicular direction to that in the first test. (2) Coil method 1) Wind coils several turns
31、around the portion to be tested and let the current flow to magnetize the test piece. Then, longitudinal magnetization is formed along the coil axis. 2) As the magnetic filed reaches 150 230mm (6 9 inch) from both ends of the coil, the longer test piece shall be magnetized on several portions. (3) P
32、rod method 1) Perform the test with an interval between prods 150 200mm (6 8 inch) in general. The internal may be shortened in consideration of the size of portions to be tested. However, it shall not be shorter than 75mm as magnetic particles are likely to form near the prod in a band shape. 2) Th
33、e end of prods shall be clean and the contacting portion shall be free from dusts, scale, oil and others. 3) The test shall be performed twice in the same portion. In the second test, the magnetic flux shall be in a perpendicular direction to that in the first test. 4) The test shall be performed wi
34、th designated test strength so that test area is sufficiently overlapped. (4) Yoke method EDS-T-7128TEST METHOD OF MAGNETIC PARTICLE PENETRANT PAGE: 5/11 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 1) The AC electric yoke shall be able to lift 13.5kg o
35、r more of move at a polar interval of 75 150mm. The DC electric yoke shall be able to lift 13.5kg or move at a polar interval of 50 100mm or 22.5kg or more at a polar interval of 100 150mm. 2) The test shall be performed at least twice in the same portion. Table 2. Magnetizing Methods Magnetizing me
36、thod Symbol Description Fig. Axial current method EA Flow current directly along the longitudinal axis of test specimen. Fig. 1 Cross current method ER Flow current across the longitudinal axis of test specimen. Fig. 2 Prod method P Conduct current to the test specimen by attaching two prods to the
37、appropriate points on it. Fig. 3 Through conductor Method B Flow current through a conductor laid in a hole or the like in the test specimen. Fig. 4 Coil method C Flow current in a coil placed around the test specimen. Fig. 5 Yoke method M Place the test specimen or the part under test between the o
38、pposite poles of an electromagnet or permanent magnet. Fig. 6 Through flux Method I Flow induction current in the test specimen by applying alternating flux to the ferromagnetic material laid in a hole or the like in the test specimen. Fig. 7 Fig. 1 Axial current method Fig. 2 Cross current method t
39、est specimen Fig. 3 Prod method Fig. 4 Through conductor method EDS-T-7128TEST METHOD OF MAGNETIC PARTICLE PENETRANT PAGE: 6/11 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology Fig. 5 Coil method Fig. 6 Yoke method Fig. 7 Through flux method 10.3.3. Type of
40、 magnetizing current For the type of magnetizing current, the most suitable one shall be taken from Table 1 in consideration of the following items in particular. (1) The magnetization using A.C. is, as a rule, applicable to the detection of surface defects and continuous method only. (2) The magnet
41、ization using D.C. is applicable to the detection of surface defects and internal defects near the surface and to the continuous method and residual method. (3) A.C. has less demagnetizing field than D.C. because of skin effect. 10.3.4. Setting of magnetizing current Except for cases where current i
42、s specified in the standard or where it is specified that type A test piece in KS D 0123 shall be used, the following shall be applied. (1) Circular magnetization The magnetizing current shall be 1000A for low stress portion and 1500A for high stress portion for 1 inch(25mm) of outer diameter of the
43、 test piece. The test piece with irregular section shall be divided into several portions and appropriate current shall be applied to each portion. EDS-T-7128TEST METHOD OF MAGNETIC PARTICLE PENETRANT PAGE: 7/11 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technol
44、ogy Table 3 Actual products Tubular products Maximum diameter Magnetizing current Maximum diameter Magnetizing current 1/2 inch 500A 1/2 inch 500A 3/4 750 3/4 750 1 1,000 1 1,000 1 1/2 1,500 1 1/2 1,500 2 2,000 2 2,000 2 1/2 2,500 2 1/2 2,500 3 3,000 3 3,000 3 1/2 3,500 3 1/2 3,500 4 4,000 4 4,000 *
45、 Note: For products with a diameter 4 inches or more, the following shall be applied. a) 5 - 10 inches : 500 700 A/inch b) 10 -15 inches : 300 500 c) 15 inches or more : 100 330 (2) Longitudinal magnetization Magnetization force necessary for the magnetization of test piece shall be calculated by th
46、e following formula. K Ampere turn = - Length/Dia. *K = Constant (low pressure portion: 45,000A high pressure portion: 60,000A) Table 4 Current intensity X No. of turns Current intensity Parts length Parts diameter L/D Low stress portion High stress portion Low stress portion High stress portion 8 i
47、nch 4 inch 2 22,500 A 30,000 A 4,500 A 6,000 A 12 3 4 11,250 15,000 2,250 3,000 12 2 6 7,500 10,000 1,500 2,000 16 2 8 5,625 7,500 1,250 1,500 10 1 10 4,500 6,000 900 1,200 18 1 1/2 12 3,750 5,000 750 1,000 14 1 14 3,214 4,285 643 857 * Note) 1) The above current intensity (A) is when the number of
48、turns coil is 5. 2) In case L/D is less than 2, another magnetization method shall be used. 10.3.5. Application of magnetic particles (1) Wet method Apply the magnetic particles by pouring the suspension on the test specimen or by immersing the test specimen EDS-T-7128TEST METHOD OF MAGNETIC PARTICL
49、E PENETRANT PAGE: 8/11 ISSUED DATE: 1990. 03. 27 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology in the suspension. In the case of immersion by residual method, care shall be paid not to erase magnetic particle pattern when the test piece is taking out of the suspension. 1) Continuous method: Magnetize the test specimen just prior to taking it out of the suspension. The ap
