1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEASUREMENT FOR STEEL EDS-T-7108 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06. 19 VERSION: 5 EDS-T-7108METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEASUREMENT FOR STEE
2、L PAGE: 1/7 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology 1. PURPOSE This standard aims at helping test personnel perform the test in an appropriate way by describing the method of measuring case depth by carburizing and carbonitriding heat treatment for
3、 steel. 2. SCOPE This standard specifies the methods of carburizing and carbonitrided depth measurement for steel. 3. DEFINITIONS 3.1. Carburization The work of increasing carbon contents on the surface of steel by heating low carbon steel, low Ni steel or Ni-Cr steel placed in carburizer at a tempe
4、rature of about 850900 for 810 hours. 3.2. Carbonitrition Surface hardening method by penetrating C(about 0.8%) and N(about 0.3%) into the steel at a temperature of about 800900 in a gas state after heating the steel beyond transformation point. Generally, N is not contained in carburized layer and
5、C is not contained in Nitride layer. 3.3. Effective case depth The distance from the surface of a case, as quenched or as quenched-tempered under temperature not exceeding 200, to the position of critical hardness (See Fig 1). The critical hardness varies according to carbon content of the raw mater
6、ial and is as shown in Table 1. When specified in drawings, a separate critical hardness may be used. Fig. 1. Definition of Effective Case Depth EDS-T-7108METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEASUREMENT FOR STEEL PAGE: 2/7 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06. 19 VERSION: 5 GM D
7、AEWOO Auto & Technology Table 1. Critical hardness and internal hardness according to carbon content of the raw material Nominal carbon content of raw material Critical hardness Maximum allowable hardness of core MAX. 0.25% 550 HV 450HV 0.26 0.32% 600 HV 500 HV MIN. 0.33% 650 HV 550 HV 3.4. Total ca
8、se depth The distance from the surface of the hardened case to the point where the difference in chemical or physical properties between the carburized layer and the core material is no longer determinable. Physical properties shall be determined by the hardness and chemical properties by the macro-
9、structure. 4. TEST SPECIMEN 4.1. For the test specimen, the carburized product or carbornitrided product itself shall be used. If not possible, the separate test piece of the same material treated under the same method as applied to the carburized product and the carbonitrided product may be used. 4
10、2. Be careful lest decarburizing should occur on the product when quenching after carburizing and cabornitriding. 4.3. More than three pieces for primary approval and more than one test piece for routine quality control shall be tested. 4.4. Unless specified otherwise, the test sample shall be cut
11、in the following method and its cut surface shall be polished to serve as the inspection surface 4.4.1. Helical and Spur Gear Teeth The hardening depth shall be measured at right angle to the surface along the pitch diameter by vertically cutting the tooth flank face at its mid point of width. In ca
12、ses when the pitch diameter is not clearly defined, as with bevel gears, it shall be measured perpendicular to the surface at the mid point between the gear tooth apex and root. Fig 2. Hardening depth measuring point for gear teeth EDS-T-7108METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEASUREMENT F
13、OR STEEL PAGE: 3/7 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology 4.4.2. Gear End (Thrust) Face It shall be measured perpendicular to the surface at the point of the radial plane width parallel with the gear axis. (See Fig 3) Fig 3. Hardening depth measur
14、ing point for gear end (thrust) face 4.4.3. Shafts, Bearing Journals and Pins It shall be measured perpendicular to the surface at 1/3 point of the shaft or journal length by vertically cutting the shaft. (See Fig 4.) Fig 4. Hardening depth measuring point for shafts, bearing journals, pins 4.4.4. O
15、ther Components It shall be measured perpendicular to the surface at a functionally important point of the part 4.5. In cutting or polishing the sample, special care shall be taken that the hardness and textures of its inspection surface are not affected and the edge of the inspection surface is not
16、 blunted. The inspection surface shall be polished until it is like a mirror surface to suit observation with a microscope. EDS-T-7108METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEASUREMENT FOR STEEL PAGE: 4/7 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technolo
17、gy 5. KIND OF MEASURING METHOD 5.1. Measuring method by hardness test 5.1.1. The case depth shall be measured by means of Vickers hardness test to the test surface. In this case, Vickers hardness test load shall be 0.3 kgf or 1 kgf but if necessary, it shall be selected as 0.1 kgf to 1 kgf. 5.1.2. T
18、he initial measuring point of hardness shall be at least 0.1mm apart from the surface. 5.1.3. 10. Hardness difference between the surface and core shall be at least 100 HV. 5.1.4. Hardness transition curve shall be made according to the following 2 methods. (1) Method A 1) The hardness transition cu
19、rve shall be made by measuring the hardness along the straight line at right angle to the test plane. If necessary, after selecting 2 to 5 points within a 1.5 mm span on the plane, one hardness transition curve shall be made by measuring the hardness on each point along the straight line at right an
20、gle to the plane(See Fig. 5). 2) In the case of marking the hardness transition curve by Vickers hardness test, the space between the measuring points shall be, in principle, not more than 0.1 mm. 3) For the Vickers hardness test, the space between the center of the adjacent indentation shall be not
21、 less than 2.5 times the diagonal length of the indentation. 4) To plot the hardness change curve, at least 5 points with different depth shall be measured. Fig. 5 Arrangement of Hardness Measuring Points (2) Method B(Only for effective case depth) 1) Only in case effective case depth is 0.3 max. th
22、is method may be used for measuring(See Fig. 6). 2) Effective case depth shall exist between t1 and t2 on the surface and distance between t1 and t2 shall be 0.3 max. Effective case depth shall be obtained by means of the following formula. EDS-T-7108METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEAS
23、UREMENT FOR STEEL PAGE: 5/7 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology (t2 - t1)(HL - H2) Eht = t1 = - (H1 - H2) Fig. 6 Definition of Hardness Measuring Location(a) and Effective Case Depth on Hardness Transition Curve 5.2. Measuring method by macro-s
24、tructure test The test surface shall be etched for several seconds in a 5% nitric acid alcoholic solution(Nital 95 ml ethyl alcohol + 5 ml nitric alcohol). After washing the surface in alcohol or water, the distance to the point different from the internal structure shall be measured by examining th
25、e colored condition according to the etching, under a magnifying glass of a proper magnification. 6. INDICATION 6.1. Method A 6.1.1. The meaning of the indication symbol shall be as follows. CD(CASE DEPTH) : Carburized case depth CDN : Carbonitrided case depth H(HARDENESS) : Measurement by hardness
26、test M(MICROSTRUCTURE) : Measurement by structure test E(EFFECTIVE) : Effective case depth T(TOTAL) : Total case depth 6.1.2. The case depth shall be given in mm. EDS-T-7108METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEASUREMENT FOR STEEL PAGE: 6/7 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06.
27、19 VERSION: 5 GM DAEWOO Auto & Technology 6.1.3. The measured result of case depth shall be recorded up to second decimal place below point. Table 2. Classification of Indication Method Measuring method Case depthMeasuring method by hardness test Measuring method by structure test Effective case dep
28、th CD(CDN)-H-E() = - Total case depth CD(CDN)-H-T = CD(CDN)-M-T = Remark) 1. In , test load shall be indicated with the unit of kgf(N) 2. When test load is 1 kgf(9.8N) record of may be omitted 3. indicates critical hardness value. 4. In , record case depth. 6.1.4. Examples (1) CD(CDN)-H1-E(600)= 2.5
29、0 : In case effective case depth which is measured by hardness test method under a test load of 1 kgf(9.8N) is 2.50 mm to the critical hardness of HV 600. (2) CD(CDN)-H0.3-T = 1.50 : In case total case depth which is measured by hardness test method under a test load of 0.3 kgf(2.9N) is 1.50 mm. (3)
30、 CD(CDN)-M-T=2.00 : In case total case depth which is measured by microstructure test method is 2.00 mm. 6.2. Method B 6.2.1. Effective case depth (1) Indication Eht HV = Effective case depth Critical hardness Load(kgf or N) Case depth (2) Examples Eht 600 HV1= 0.50 : In case effective case depth, w
31、hich is measured by hardness test method under a test load of 1 kgf(9.8N), is 0.50 mm to the critical hardness of HV 600. 6.2.2. Total hardening depth (1) Indication TCD = Total hardening depth Hardening depth (2) Examples TCD = 0.20 : In case total case depth by microstructure test is 0.20 mm. EDS-
32、T-7108METHOD OF CARBURIZED AND CARBONITRIDED DEPTH MEASUREMENT FOR STEEL PAGE: 7/7 ISSUED DATE: 1992. 12. 29 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology 7. RELATED SPECS KS D 0215 Methods of measuring case depth for steel JIS G 0557 Methods of measuring case depth for steel DIN 50190 Hardening depth of heat treated pieces.
