NAVISTAR MPAPS A-52-2015 Classification of Grinding Microstructural Alterations.pdf

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1、 This document is restricted and may not be sent outside Navistar, Inc. or reproduced without permission from Corporate Technical Standards. Suppliers are required to assume all patent liability. 2015 by Navistar, Inc. DECEMBER 2015 Page 1 of 9 NAVISTAR, INC. Material, Parts, and Process Specificati

2、ons (MPAPS) NUMBER: MPAPS A-52 Former Designation: CEMS A-52 TITLE: Classification of Grinding Microstructural Alterations CURRENT REV No.: 1512 DATE: December 2015 WRITTEN/EDITED BY: J. Goldschmidt APPROVED BY: R. Goluch SUPERSEDES: Rev. August 2006 PRINTED COPIES OF THIS DOCUMENT MUST BE VERIFIED

3、FOR CURRENT REVISION This specification may involve hazardous materials, equipment, and procedures. This specification does not purport to address all of the safety issues associated with its use. The user is responsible to consult appropriate safety and health practices and to determine the applica

4、bility of regulatory limits prior to use. Change Notice: Combined with CEMS A-52 appendix and updated to MPAPS format; editorial changes. 1.0 APPLICATION To satisfy final dimensional requirements after a heat treating process a final grinding operation is often required on components such as gears,

5、bearings, and crankshafts. The grinding process can produce excessive localized surface heating if not done correctly. The excessive localized heating can cause surface tempering, grinding burns, re-hardening and cracking which can be detrimental to the part. The microstructural alterations resultin

6、g from the grinding process have been found to have a significant impact on the durability of the part. 2.0 SCOPE This specification provides a means of specifying the surface metallurgical quality, as related to grinding temper of steel parts, primarily heat treated parts such as gears, bearings an

7、d crankshafts. It is intended to be used at the discretion of the design and materials engineers in applications acknowledged to be sensitive to material alterations resulting from grinding temper and should not be used indiscriminately for all ground parts. Reference section 7.0 (method of test) fo

8、r evaluating this quality. 2.1 RESTRICTED CHEMICAL SUBSTANCES Effective January 1, 2007, all product supplied to the requirements of this specification must comply with the requirements of the MPAPS B-50 specification. 3.0 REFERENCE DOCUMENTS Unless otherwise specified, the latest issue of all refer

9、enced standards shall apply. The following Specifications, Standards, and Regulations are referenced in this specification. Quality System Standard ISO 9001 or TS-16949 NAVISTAR MPAPS B-50 CFR Title 29, Part 1910 ASTM E 709 NAVISTAR Manufacturing Std. MS-D-13 ASTM E 165 NAVISTAR Engineering Design S

10、td A-16 NUMBER: MPAPS A-52 TITLE: Classification of Grinding Microstructural Alterations REVISION: 1512 This document is restricted and may not be sent outside Navistar, Inc. or reproduced without permission from Corporate Technical Standards. Suppliers are required to assume all patent liability. 2

11、015 by Navistar, Inc. DECEMBER 2015 Page 2 of 9 4.0 CLASSIFICATION 4.1 The surface metallurgical quality with respect to grinding temper of ground steel parts may be specified by classes per this standard. Classification of quality is based on the extent to which grinding temper is permitted. 4.2 Ta

12、ble 1 lists several classes of grinding temper for specifying the extent permitted for an application. In specifying a selected class from Table I, the designated area of the part to which this class applies be clearly shown on the part drawing. TABLE I CLASSIFICATION OF METALLURGICAL QUALITY OF GRO

13、UND SURFACES* CLASS REFERENCE QUALITY* Allowable Degree of Grinding Temper A Figure 1 No grinding temper permitted; uniform light gray color after etching. B Figure 2 Randomly distributed lightly tempered areas (slightly darker etching) not exceeding a total of 1% of the designated ground surface ar

14、ea with each indication being no more than 0.5 mm (0.02 inch) square. C Figure 2 Distributed tempered areas (darker gray to black etching), not exceeding a total of 10% of the designated ground surface area with each indication being no more than 3.2 mm (0.12 inch) square. D Figure 2 Tempered areas

15、(dark etching) not exceeding 30% of the designated ground surface area. E Figure 3 Same as “D” except with randomly distributed rehardened areas (white etching) not exceeding a total of 5% of the designated ground surface area. * Classification is based on visual appearance after the surface has bee

16、n etched (see “Methods of Test” in MPAPS AT_4). In case of disagreement on classification of grinding temper between user and supplier, the plant metallurgist of the using International plant and/or the controlling design engineering department will have the final decision. * Definitions of degree o

17、f temper are shown below in Figures 1 through 4. The figures are not intended to depict any one class, but to illustrate the visual appearance of grinding temper. Examples of Grinding Temper Figure 1 No Grinding Temper (Uniform Light Gray Color after Etching) Figure 2 Randomly Distributed Tempering

18、(Darker Etching Areas) Figure 3 Tempering longer times may be required to obtain accurate results. 7.2.2.8 Examine the sample for tempering and rehardening under adequate light. Low power magnification (up to 10X) may be used to aid the examination. 7.2.2.9 Compare part with class specified in Table

19、 I to determine acceptability exercising care so as not to misinterpret false indications from staining, spotting fingerprints, etc. 7.2.2.10 If the part is to be used, it should be coated with a rust preventive oil. 7.3 REPORT The acceptance or rejection of the part based on the comparison of part

20、classes in table I. 8.0 QUALIFICATION The first piece from a new set-up or after any significant set-up change will be checked. Plant Quality control departments will establish the level of inspection to be used during production. This inspection must be conducted prior to subsequent finishing opera

21、tions which may interfere with satisfactory evaluation of the ground surface. 8.1 QUALITY CONTROL PLAN A Quality Control Plan for products supplied to the requirements of this specification will be established by mutual agreement between NAVISTAR and the supplier. Unless specific exception is noted,

22、 the following characteristics, where applicable*, shall be included in the plan as features for management by statistical process control.* * Other characteristics for inclusion in the control plan may be specified on the engineering drawing and/or purchase order. * See NAVISTAR Engineering Design

23、Standard A-16 9.0 SOURCE APPROVAL AND QUALITY CONTROL 9.1 SUPPLIER REQUIREMENTS All suppliers to NAVISTAR are required to be registered to ISO 9001 Quality System Requirements. NAVISTAR will also accept TS-16949 registration as long as the supplier can also fulfill all AIAG PPAP (Production Part App

24、roval Process) documentation and approval requirements. Suppliers must NUMBER: MPAPS A-52 TITLE: Classification of Grinding Microstructural Alterations REVISION: 1512 This document is restricted and may not be sent outside Navistar, Inc. or reproduced without permission from Corporate Technical Stan

25、dards. Suppliers are required to assume all patent liability. 2015 by Navistar, Inc. DECEMBER 2015 Page 5 of 9 maintain their certification with an accredited registrar and must furnish copies of registration certificates to their Corporate Buyer upon request. 9.2 APPROVAL Parts supplied against con

26、tracts or purchase orders citing this specification shall be equivalent in all respects to those samples which were approved by the purchaser. No changes in formulation or processing practices are permitted without approval. In the event that changes in material, properties, processing practices, co

27、nstruction, color, or labeling of the product are required, the supplier shall notify NAVISTAR Materials Engineering and Purchasing and Supplier Development of the proposed change(s). Test data indicating conformance to all requirements of this specification, test samples, and new or amended or upda

28、ted Material Safety Data Sheet(s) (MSDS), in accordance with CFR Title 29, Part 1910 shall be submitted with the request for change. 9.3 PROCESS CONTROL The supplier shall either perform and report results of tests on specific lots of parts produced using ISO 9001 or TS-16949 guidelines, or provide

29、statistical evidence of the lot having been produced in a state of statistical control and with a process capable of providing all required properties. The part supplier and the quality control manager of the using NAVISTAR plant may determine testing and reporting requirements on specific products.

30、 10.0 SHIPPING AND HANDLING Shipping and identification shall be in accordance with NAVISTAR Manufacturing Standard MS-D-13. Parts shall be packaged so as to avoid any damage in shipment detrimental to the appearance of the part. 11.0 DESIGNATION ON DRAWINGS The level of grinding quality required fo

31、r satisfactory part performance will be indicated on design drawings and purchase orders by specification of an International grinding temper class. The area of the part to which the class applies will also be indicated. Examples: Grind designated fillets, Class B, MPAPS A-52 Grind 76 mm OD, Class C

32、, MPAPS A-52 12.0 TECHNICAL INFORMATION For further information related to the technical content of this specification, contact: Suppliers may purchase controlled copies of this specification by contacting: Materials Engineering and Technology Dept. 10400 W. North Avenue Melrose Park, IL 60160 E-mai

33、l: MaterialsEngineeringN IHS Global Inc. 15 Inverness Way East Englewood CO 80112-5776 Phone: 1-800-854-7179 E-mail: AutomotiveIHS.com Website: http:/ NUMBER: MPAPS A-52 TITLE: Classification of Grinding Microstructural Alterations REVISION: 1512 This document is restricted and may not be sent outsi

34、de Navistar, Inc. or reproduced without permission from Corporate Technical Standards. Suppliers are required to assume all patent liability. 2015 by Navistar, Inc. DECEMBER 2015 Page 6 of 9 A.0 GENERAL INFORMATION A.1 INTRODUCTION A.1.1 In order to satisfy dimensional requirements, hardened steel p

35、arts frequently have to be ground. In grinding heat-treated parts, excessive heat can be generated if grinding conditions are not right. This can result in surface tempering, re-hardening or cracking. In many instances, this can reduce the service life of the ground part significantly. A.1.2 The gen

36、eration of excess heat in grinding is related to several factors. Among these are: condition and type of grinding wheel; amount and type of coolant; feed and speed of grinding wheel; uniformity of grinding stock; surface condition of work piece; composition, structure and properties of the work piec

37、e. Whatever the cause of any excessive heat, changes in the ground surface take place. Residual stresses can be changed and hardness and strength affected. A.1.3 A visible “burning” of the ground surface may occur when high heat is generated in grinding. This is essentially a discoloration of the su

38、rface resulting from its oxidation during momentary exposure to high temperatures. Lack of visible “burn,” however, is no indication that excessive temperatures were not reached, as discoloration developed during severe grinding may be removed during the final passes. Also, the temperature reached m

39、omentarily may be high enough to cause some tempering but not high enough to discolor the surface. A.1.4 Tempering associated with this momentary exposure to a high temperature is often referred to as “metallurgical burn.” This results in a localized softening of the hardened steel at the ground sur

40、face. The degree of softening varies with the amount of heat generated and reduces the hardness and strength of the part in the area affected. If the amount of heat from grinding is sufficient, the transformation temperature of the steel work piece may be exceeded causing a layer of austenite to be

41、formed. The cold metal beneath this layer and the grinding fluid act as a quenchant to quickly transform the austenite to martensite. This resultant martensite is very hard and brittle and generally circumscribed by an area of soft tempered steel. This condition is very susceptible to premature crac

42、king and/or spalling in service. A.1.5 Under the most severe conditions, shallow cracks may develop during or after grinding. As the surface being ground is heated, the area in contact with the wheel tries to expand. This hot region is restrained, however, by the cold rigid surrounding metal and can

43、not expand parallel to the ground surface. The hot region is therefore forced to flow plastically perpendicular to the surface, resulting in a case of hot upsetting on a microscopic scale. Almost immediately, the hot spot cools down and tries to shrink back to its original size but because it is now

44、 cold, and since some of it may have been ground away, it is unable to do so. As a result, the area develops tensile stresses. When these stresses are high enough to exceed the rupture strength of the material, cracks form. The presence of grinding cracks can significantly reduce the service life of

45、 the finished part and as such are unacceptable. A.2 EFFECTS OF MICROSTRUCTURAL ALTERATIONS A.2.1 When excessive heat is generated in grinding, the residual stress distribution within the ground piece is affected. In many cases, tensile residual stresses are developed at the grinding surface. These

46、NUMBER: MPAPS A-52 TITLE: Classification of Grinding Microstructural Alterations REVISION: 1512 This document is restricted and may not be sent outside Navistar, Inc. or reproduced without permission from Corporate Technical Standards. Suppliers are required to assume all patent liability. 2015 by N

47、avistar, Inc. DECEMBER 2015 Page 7 of 9 stresses can reduce the effective strength of the part and especially its fatigue life. These stresses may cause distortion in thinner sections as well. A.2.2 Hardness patterns of heat treated parts can also be affected by excessive heat from grinding. Temperi

48、ng, with a reduction in hardness, initiates at the ground surface and with increasing heat penetrates down into the part. Heavy tempering can extend as deep as 0.040 inch (1.0 mm) below the ground surface. The soft skin thus developed is susceptible to scuffing and galling and can lead to early fail

49、ures in wear applications. Less extensive grinding temper may also be significant in affecting properties of ground parts. In grinding roller bearings, if the surface hardness is tempered back to less than RC 58, the L10 life of the bearing may be reduced. Tempering in the root fillets or on the end faces of highly loaded gear teeth can lead to early fatigue failures. It should be noted, however, that because of