1、 FORD LABORATORY TEST METHOD AA 101-04 Date Action Revisions 2000 08 07 Editorial no technical change A. Cockman 2000 03 09 Editorial no technical change A. Cockman 1996 05 03 Printed copies are uncontrolled Page 1 of 8 Copyright 2000, Ford Global Technologies, Inc. DETERMINATION OF CARBON GRADIENT
2、USING TEST BARS Application This test method describes a procedure for determining the surface carbon content and the carbon gradient resulting from exposure of a test bar to the furnace atmosphere during a carburizing o r carbonitriding cycle. Generally this test method is used for processes produc
3、ing total case depths in excess of 0.l4 mm. Apparatus Required Carbon Analyzer Leco Combustion Carbon Determinator. Source: Leco Corporation 3000 Lakeview Avenue St. Joseph , MI 49085 Telephone: (616) 983 - 5531 (or from local Leco agents) Lathe Must be capable of machining the test bar to the dimen
4、sions shown in Figure 1 and 2. Drill Must be capable of drilling test bar to the dimensions shown in Figure 2 (Option “B“ test ba r). Analytical Balance Precision 0.1 mg. Oven (furnace) Muffle - type capable of maintaining 540 +/ - 10 C. Cut-Off Machine Leco CM 20 or equivalent. Brinell Glass The ab
5、ove apparatus is available from any reputable laboratory equipment supply house. FORD LABORATORY TEST METHOD AA 101-04 Page 2 of 8 Copyright 2000, Ford Global Techno logies, Inc. Materials Required Emery Paper 1, 2, or 3 grit. Solvent 1,1,1, trichloroethane or equivalent. Alcohol Nital Acid Solution
6、 3 % solution of nitric acid and alcohol. Hydrochloric Acid 1:1 solution of HCl and water. Conditioning and Test Conditions All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/ - 2 C and 50 +/ - 5 % relative humidity for not less than 24 h prior to t
7、esting and tested under the same conditions unless otherwise specified. Procedure Test Bar Preparation There are two different configurations of test bars specified by this test method (option “A“ and option “B“ (Figure 1 and 2 respectively). The option “A“ test bar has a small step to facilitate wi
8、ring the test bar to a heat treat fi xture. The option “B“ test bar has a hole instead of a step to allow attachment to the fixture. Either configuration may be employed at the discretion of the user. 1. The material used for the carbon concentration bars should be of the same alloy compos ition as
9、the parts being processed. In the instance of carbon and low alloy steel parts, SAE 8620 or DIN 001654 may be used. 2. To assure consistency, a sufficiently large number of specimens should be prepared from the same mill heat to minimize the eff ect of heat chemistry on the test results. 3. The bar
10、stock shall be of an adequate diameter (dim “K“ or greater) to assure removal of decarburization, scale and other surface defects when machined to the dimensions in Figure 1 (Option “A“) or Figure 2 (O ption “B“). 4. Cut bar stock to length (“A“) in Figure 1 or Figure 2. 5. Drill center hole in one
11、end of the bar. 6. Drill transverse hole (“L“) (Figure 2) if Option “B“ test bar is to be used. FORD LABORATORY TEST METHOD AA 101-04 Page 3 of 8 Copyright 2000, Ford Global Techno logies, Inc. 7. Grind to 25.40 +/ - 0.05 mm (dia “H“); 0.013 mm max tap er. Note: The ground surface must be protected
12、from corrosion if the test bars are to be stored before use. (Any corrosion - inhibiting agent must be removed immediately prior to carburization of the test bar). 8. Stamp each end with identification code (E.G., the code could designate grade, mill heat, consecutive test bar number or other pertin
13、ent information). 9. The surface of the test bar must be free from oil, grease, and rust prior to heat treat. (a) Use alcohol to remove light oil films/surface s oils. (b) Use 1.1.1 trichloroethane or equivalent to remove grease or heavy oil and wipe dry. (c) To remove rust, dip in a solution of HCl
14、 (1:1). Thoroughly rinse with water. Immediately wash with alcohol and wipe dry. (d) If the rust is excessive, the b ar should be reground (if dimensionally feasible). If regrinding is not feasible, the bar should be scrapped. 10. Attach or suspend the carbon concentration bar with a load of parts i
15、n such a manner as to assure uniform contact with the furnace atmospher e. 11. Heat treat the test bar through the entire cycle. 12. Remove test bar from the load if the production temper cycle exceeds 550 C. Temper 13. Wash test bar with alcohol to remove any oil prior to tempering. 14. Temper at 5
16、40 +/ - 10 C for 2 h . Note: Higher temperatures may result in excessive surface decarburization. Prepare Samples for Carbon Analysis 15. Lightly sand bars to remove any oxide or soot. 16. Wash with alcohol and wipe dry. 17. Straighten bar, if necessary 0.03 mm max T.I.R . FORD LABORATORY TEST METHO
17、D AA 101-04 Page 4 of 8 Copyright 2000, Ford Global Techno logies, Inc. 18. Option “A“; take step cut using lathe as shown in Figure 1 (b) to remove any edge carburizing effect. 19. Using lathe, collect turnings from dia “H“: (Option “A“ and Option “B“). (a) The first 0.10 mm from the diameter repre
18、sents material down to 0.05 mm from the surface. (b) 0.10 - 0.25 mm (c) 0.25 - 0.50 mm Note: Additional turnings of 0.25 mm may be taken at the option of the operator. 20. Wash samples with alcohol, drain off alcohol, and allow samples to dry. 21. Determine carbon content of each collection of turni
19、ngs using the Leco Combustion Carbon Determinator or equivalent. 22. Record carbon content for each sample. Data may be plotted using the chart shown on Figure 4. When plotting, use one half of the midpoint of the distance of the cut from the diameter of the test bar. This value represents the avera
20、ge depth of the sample from the test bar surface (e.g., 0.025 mm for the 0 - 0.10 mm sample). Figure 3 contains a chart for converting to the midpoint of the depth below the test bar surface for a given sample cut. 23. Record such pertinent information as date, sample bar number, process number, fur
21、nace number. Determine Total Case Depth (optional) 24. Section 13 mm from either end of the test bar (on dia “K“). 25. Etch with nital acid solution to reveal carburized case. 26. Measure case depth using Brinell glass and record case depth. Chemicals, materials, parts, and equipment referenced in t
22、his document must be used and handled properly. Each party is responsible for determin ing proper use and handling in its facilities. FORD LABORATORY TEST METHOD AA 101-04 Page 5 of 8 Copyright 2000, Ford Global Techno logies, Inc. DETERMINATION OF CARBON GRADIENT USING TEST BAR Test Bar Option A (a
23、) As machined bar prior to heat , refer to Step 7 Figure 1 A = 152.4 +/ 0.8 mm H = 25.4 +/ - 0.05 mm B = 127 +/ - 0.8 mm I = 123.8 +/ - 0.8 mm C = 25.4 +/ - 0.25 mm J = 6.35 +/ - 0.25 mm D = 3.18 +/ - 0.25 mm K = 30.5 +/ - 0.05 mm E = 15.2 +/ - 0.8 mm L = 6.35 +/ - 0.05 mm F = 12.7 +/ - 0.8 mm M = 1
24、30.18 +/ - 0.8 mm G = 19 +/ - 0.8 mm N = 12.7 +/ - 0.8 mm (b) As tempered bar prior to collecting turnings FORD LABORATORY TEST METHOD AA 101-04 Page 6 of 8 Copyright 2000, Ford Global Techno logies, Inc. DETERMINATION OF CARBON GRADIENT USING TEST BARS Test Bar Option B Figure 2 A = 152.4 +/ 0.8 mm
25、 H = 25.4 +/ - 0.05 mm B = 127 +/ - 0.8 mm I = 123.8 +/ - 0.8 mm C = 25.4 +/ - 0.25 mm J = 6.35 +/ - 0.25 mm D = 3.18 +/ - 0.25 mm K = 30.5 +/ - 0.05 mm E = 15.2 +/ - 0.8 mm L = 6.35 +/ - 0.05 mm F = 12.7 +/ - 0.8 mm M = 130.18 +/ - 0.8 mm G = 19 +/ - 0.8 mm N = 12.7 +/ - 0.8 mm FORD LABORATORY TEST
26、 METHOD AA 101-04 Page 7 of 8 Copyright 2000, Ford Global Techno logies, Inc. DETERMINATION OF CARBON GRADIENT USING TEST BARS Conversion Chart for Determination of Average Depth of Sample from Surface of the Test Bar Range of distance of cut Range of Depth from Midpoint of depth of from diameter of
27、 test ba r surface of the test bar sample from surface of for a given sample for a given sample the test bar 1. 0.10 mm 0 - 0.05 mm 0.025 mm 2. 0.10 - 0.25 mm 0.05 - 0.13 mm 0.064 mm 3. 0.25 - 0.51 mm 0.13 - 0.25 mm 0.191 mm 4. 0.51 - 0.76 mm 0.25 - 0.38 mm 0.318 mm 5. 0.76 - 1.02 mm 0.38 - 0.51 mm
28、0.445 mm 6. 1.02 - 1.27 mm 0.51 - 0.64 mm 0.572 mm 7. 1.27 - 1.52 mm 0.64 - 0.76 mm 0.699 mm 8. 1.52 - 1.78 mm 0.76 - 0.89 mm 0.826 mm 9. 1.78 - 2.03 mm 0.89 - 1.02 mm 0.953 mm 10. 2.03 - 2.29 mm 1.02 - 1.14 mm 1.080 mm 11. 2.29 - 2.54 mm 1.14 - 1.27 mm 1.207 mm 12. 2.54 - 2.79 mm 1.27 - 1.40 mm 1.3
29、34 mm 13. 2.79 - 3.05 mm 1.40 - 1.52 mm 1.461 mm 14. 3.05 - 3.30 mm 1.52 - 1.68 mm 1.588 mm 15. 3.30 - 3.56 mm 1.68 - 1.78 mm 1.715 mm Figure 3 FORD LABORATORY TEST METHOD AA 101-04 Page 8 of 8 Copyright 2000, Ford Global Techno logies, Inc. DETERMINATION OF CARBON GRADIENT USING TEST BARS PLOT OF CARBON GRADIENT DEPTH BELOW SURFACE-mm Figure 4
