1、Page 1 of 10RDSO SPECIFICATION. . . NO. MP.0.2800.09 (REV-0. 2)JUNE, 2005Page 2 of 10TECHNICAL SPECIFICATION FOR THE CASE CARBURISED GEARS AND PINIONS FOR ELECTRIC LOCOMOTIVES1.0 FOREWARDTraction gears constitute vital part of the power transmission system of locomotives and call for sophisticated t
2、echniques in manufacture, with special material, equipment and quality control requirements.2.0 SCOPEThis specification is applicable for traction gears and pinions used in electric locomotives listed at Annexure A. It covers technical requirements of manufacture and supply from the raw material to
3、finished stage.2.1 MATERIALGears and pinions shall be manufactured from forging quality steel made by open hearth, electric, duplex, basic oxygen or a combination of these processes. The steel shall be fully killed and homogenous the steel shall also be subjected to secondary refining including vacu
4、um degassing. Sufficient discard shall be made from each ingot to ensure freedom from pipe, harmful segregation and other defects 2.2 Chemical Composition & Mechanical Properties:The pinions and gears shall be manufactured from steel grade 15Ni7Cr4Mo2 TO IS: 4432-1988 (Indian Standard Specification,
5、 First Revision for Case Hardening Steel.)2.3 The inclusion rating of the steel shall not exceed 2.0 A, 2.0 B, 2.0 C, & 2.0 D for both thick and thin series. The field of each type of inclusion shall be determined in accordance with IS: 4163 and shall be taken as the rating.2.4 Chemical composition
6、and mechanical properties of the steel used shall conform to the relevant material specification or as per the given table of 1 and 2.2.4.1 Chemical composition: The chemical composition of gear/pinion steel shall be as given table TABLE : 1 15Ni7Cr4Mo2 To IS: 4432-1988Sr. no. Element Minimum Maximu
7、m1 Carbon 0.12 % 0.18 %2 Manganese 0.60 % 1.00 %3 Phosphorus 0.035 Maximum4 Sulphur 0.035 Maximum5 Silicon 0.15% 0.35%6 Nickel 1.50% 2.00%7 Chromium 0.75% 1.25%8 Molybdenum 0.10% 0.20%Page 3 of 102.4.2 Mechanical Properties : - The mechanical properties of gear / pinion steel shall be as given in ta
8、ble 2TABLE : 2 2.5 case of steel to any other composition, prior approval of RDSO shall be obtained3.0 MANUFACTURING OF FORGED BLANK 3.1 The gear and pinion shall be manufactured by rolling/forging ingots in to the blooms / billets / bars (made from adequately rolled / forged cropped ingots ) to the
9、 blank stage, followed by closed die or upset forging, or peripheral forging. The ratio of reduction at different stages shall be as follows.a) The minimum-reduction ratio from the minimum section of the ingot to maximum section of the round bloom / billet by forging shall be 4:1b) The gear blanks s
10、hall be made by a process of upset forging, followed by peripheral forging under a power hammer or press. The reduction ratio in height by upset forging from round bloom/bar to the gears blank shall be at least 4:1c) The forging and rolling processes shall be performed in such a manner, that central
11、 axis coincides with the axis of the gear wheel.d) The semi-product (bloom) intended for the manufacture of forged blanks of the gears /pinions shall be obtained from cropped ingots, without any pipe.e) In case only forged blanks are purchased, the manufacturer shall ensure free access of the inspec
12、ting authority at his works for the satisfaction of the latter that the material is being supplied in accordance with this specification4.0 FORGED BLANKS FREE FROM DEFECTS :4.1 Billets, blooms, slabs and bars shall be free from cracks, surface flaws, laps, rough, jagged and imperfect edges and all o
13、ther surface defects, which may result in defects in the forging made there from.4.2 The pre machined gears and pinions shall be free from cracks, lap or any otherharmful surface or internal defects. (With 16mm dia Test piece)MATERIAL Tensile strength (Mpa)minimumYield strength(Mpa)minimum %Elongati
14、on (mm)minimumReduction area(mm2)minimum15Ni7Cr4Mo2 1100 to1400750 9 % 40 %Page 4 of 104.3 No welding shall be permitted on the forged blank. The out side surface of the forged blanks shall not show any flaw, cracks, fold or other injurious defects. The forged blanks shall be provided with adequate
15、allowance for machining all over, and shall suitably be annealed to facilitate subsequent machining.4.4 Forging supplier shall furnish test report showing the Mill source, Chemical composition, inclusion rating of material, forging ratio and grain flow pattern of gear and pinion blanks supplied to t
16、he gears manufacturer.4.5 A photograph of grain flow pattern of forging blank of pinion and gear should be submitted prior to prototype inspection by RDSO.5.0 TEST ON ROUGH FORGED GEAR BLANKS .5.1 Macro etch test: The macroetch examination shall be done as per ASTM-E381(method of Macroetch testing a
17、nd inspection of steel forging). The macroetched section shall reveal satisfactory flow line pattern right up to the centerof the forged blank.5.2 Grain size: The grain size of forging when tested in accordance with IS/2853/Latest Version shall be in the range of 5 to 8 inherently fine-grained struc
18、ture This as per IS: 4432-1988.5.3 Ultrasonic Test: All forged blanks, before and after machining is performed on them, shall be tested ultrasonically for the ensuring freedom from casting and forging defects. A tentative standard for Ultrasonic Testing and criteria for acceptance/rejection of the g
19、ear / gear blanks is given at Appendix A.5.4 Hardness Test: The forging when tested in accordance with IS-1500 shallshow a hardness value of 170-220HB.6.0 PRE-MACHINING HEAT TRETMENT OF FROGED BLANK6.1 To relive the residual, forgings stresses, the forging shall be normalized at 840 0 C to 870 0 C.
20、The soaking time shall be given according to ruling thickness forged blanks.7.0 MACHINING: as per clause 9.08.0 HEAT TREATMENT8.1 Case Hardening :The active tooth surface of the gear/pinion shall be suitably case carburised, hardened and tempered to obtain specified case depth, case hardness and phy
21、sical properties of core.Page 5 of 108.2 Effective Case Depth:8.2.1 Definition and Measurement:The effective case depth is defined as that at which a hardness of 500 HV 30 (50RC) is obtained . The depth is measured perpendicularly inwards from the surface. The available case depth after finish grind
22、ing shall be 1.8 mm minimum or as mentioned in relevant drawing.8.21.1 Case Depth of Carburised and Hardened Gears:For checking the case depth, one spy-piece shall be provided per container when box carburising and, at least, one but preferably two (towards top and bottom of furnace) when gas carbur
23、ising. The spy-piece shall be of a section. Which adequately simulates that of the teeth, which is represent and shall be placed near. to but not on the gear teeth. The spy-piece shall be of the same material from which the gears are made.After carburizing, the spy-piece shall be hardened and temper
24、ed along with the gear it represents, and then broken. Hardness survey of the case shall be careered out after grinding and polishing as per IS: 6416 (method of measuring case depth of steel). The results shall be as specified in clause 8.2.1Alternatively, the end of the teeth remote from the tracti
25、on motor side may be ground back at an angle to reveal the case of visual examination or hardness testing.8.2.2 Hardness of Case-hardened Layer: Surface hardness of the gear after grinding measured at tip, flank or root shall not be less than 650 HV 30 or 58 RC (620 HB). For the position where the e
26、ffective case depth is measured on either spy-piece or gear the hardness shall not be less than 500 HV 30 (50 RC).8.2.3 Micro Examination: At least one spy-piece per carburising batch shall be microscopically examined for establishing absence of cementite network and free cementite. Retained austeni
27、tecontent of 15% - 30% may be permitted in carburised zone. This is as per IS 4432-1988 9.0 GENRAL GUIDE LINE FOR MACHINING OF ALL TYPES OF GEARS AND PINIONS 9.1 Bore of the pinions / gears is referred to as the fitting surface. 9.2 Fitting surfaces of the gear and pinion shall be ground finished be
28、fore finish grinding the teeth.Page 6 of 109.3 The surface texture of the fitting surfaces of gear and pinion shall no be coarser than the value specified in the relevant drawings.9.4 The gear teeth shall be involute profile, cut and ground on gear generating machines. Protuberance cutter shall be u
29、sed for generating the teeth for automatically producing the most suitable stock allowance for grinding and generating simultaneously the largest possible tooth fillet of semi-circular shape with absolute uniform transition for the involute tooth flank to the tooth root after grinding. No discontinu
30、ity / Step formation from the ground tooth flank and the machined root fillet shall be permitted.9.5 The tooth profile shall be given the tip and root relief in accordance with the specification mentioned in the relevant drawings The longitudinal crowning shall be provided as specified in the releva
31、nt drawings.9.6 The dimensions, tolerances and surface finish specified in the relevant drawings shall strictly adhered to. The followings errors / deviations shall be measured as per gear/pinion relevant drawings. a) Over all dimensions.b) Individual error of pitch Consecutive error of pitch .c) Cu
32、mulative error of pitch .d) Profile error.e) Alignment error.f) Radial run out.9.7 The gear / pinion should be free from sharp edges.9.8 The working face of the teeth shall be free from defects such as heterogeneity inmetal and forging /cutting / grinding imperfections. Any repair of these surface d
33、efects shall be prohibited.9.9 The end faces of the teeth shall also not show defects similar to clause 9.8 particularlynear the root circle.10.0 SHOT PEENING:Shot peening should be done on fillet radius and root of gears before grindingto impart compressive stress. All tooth surfaces should be prot
34、ected against peeningor should be as per relevant drawings requirements. Use S330 hard shot to obtain 200% minimum coverage in root area. Peening intensity should be between 0.007 to 0.010 C or shall conform to the relevant drawings.11.0 TESTS11.1 Physical Testing on Material11.1.1 The followings te
35、sts shall be conducted at the works of the gear manufacturer or in an approved test house at the cost of manufacturer on the test samples selected as per clause 11.1.2. At least, one sample per cast shall be subjected to following tests .Page 7 of 10i) Ultimate tensile strength.ii) Yield stress.iii)
36、 Elongation Percentage .11.1.2 Test Sample:The test sample shall be made in the form of a bar from a bloom of relevant cast selected at random, shall be first forged down to of the original section and then a test bar of diameter as per relevant material specification shall be turned from the forgin
37、g. This test bar shall then be heat treated (blank carburising, hardening and tempering) along with the gear /pinions of the same cast of as indicated in clause 11.1.1 and then the test piece machined. It shall carry the following markings for identifications.a) Steel used b) The cast number / Heat
38、no.Note: i) Blank carburising means the thermal treatment associated with carburising as applied to a test piece without using any carburising,medium.ii) Tests on bar stock:- one bar stock shall be cut in the presence of the inspecting authority and macro test shall be carried out to determinedif su
39、fficient working as defined in this specification has been done asthe ingot to obtain the bar stock.iii) Test sample shall be repeated at an interval of every three years and also whenever the failures of gears and pinions takes place.11.1.3 Chemical composition & Physical properties: One test sampl
40、e per cast shall be chosen for chemical composition. The analysis of steel shall be carried out either by method specified in IS:228 “Method of chemical analysis of steel and its relevant parts of any other established instrumental method (Spectrometer )”. The chemical composition and physical test
41、results shall confirm to the relevant material specification.The chemical composition and physical test result shall conform to the relevant material specification, If any one of the test sample fail to meet the requirement as mentioned in the relevant material specification, the entire lot shall be
42、 rejected.In the events of rejection of entire lot, the lot offered shall be made unusable in presence of purchasing / inspecting authority. However approving /purchasing authority reserves the right to repeat the tests at their discretion at certain time interval. Page 8 of 1011.2 TESTS ON FINISHED
43、 GEARS : (a) Type Tests:- These will be conduced by RDSO on prototype gears. Whenever a new source is to be approved . The lot offered for prototype tests should not have less than 6 gears. These shall also be conducted once in every three years after approval of prototype at any instance and deemed
44、 necessary byRDSO. The following tests shall be conducted in addition to acceptance testmentioned at Para 11.2(b) and other tests laid down in relevant specifications .i)Material Tests: Confirmation of the properties of material as mentioned in material relevant specification are mandatory for produ
45、ct approval or approval of manufacturer. It will be carried out in presence of RDSO representative.ii)Hardness Check: The hardened teeth of all gears, after appropriate heat treatment, shall be tested for surface hardness. The hardness shall be measured at four equidistant points in the proximity of
46、 the root circle of the teeth. The average value of four readings shall conform to the value specified in clause 8.2.2. The variation between the maximum and minimum values shall not exceed 20 points HV.iii)Crack Detection check: All the finished gears/pinions should be subjected to crack detection
47、by suitable method such as magnetic particle test, die-penetrate test or fluorescent test. On the discretion of inspection authority. Ultrasonic testing on rim & hub portion can also be employed to check any internal cracks in the forged and finished gears / pinions.iv)Dimensional & Tolerance checks
48、: The finish gears shall be checked for dimensional accuracies, tolerance, surface finish and tooth errors / deviations as per clause 9.6.If any one of the gears fails to meet to requirement as mentioned in relevant material specification and dimension of drawing, the entire lot shall be rejected.(b
49、) Acceptance Tests (During Routine inspection): These are the tests to be conducted, during routine inspection by purchaser / RITES against individual orders:(a) Overall dimensions check.(b) Hardness check.(c) Crack detection tests(d) Tooth error/deviations as per gear / pinion relevant drags.During
