1、I 2000FTM3 O I Comparison of New Gear Metallurgy Documents, IS0 6336-5 and AGMA 923 with Gear Rating Standards AGMA 2001 and 2003 by: A.A. Swiglo, IIT Research Institute American Gear Manufacturers Association TECHNICAL PAPER O Comparison of New Gear Metallurgy Documents, IS0 6336-5 and AGMA 923 wit
2、h Gear Rating Standards AGMA 2001 and 2003 A. Alan Swiglo, IIT Research Institute The statements and opinions contained herein are those of the author and should not be construed as an official action or opinion of the American Gear Manufacturers Association. Abstract This paper will compare and con
3、trast two newly revised documents. IS0 6336-5 and AGUA 923, with two that are familiar to todays gear producers -AGMA 2001 and 2003. These new documents were prepared on a consensus basis for big gears, little gears, high production, one-of-a-kind gears, and everything in between. A short history of
4、 the long evolution and the logic behind the new documents ispresented. This paper discusses whats new, whats different, whats clarified, whats the same, and whats hidden in the footnotes. The observations are presented from the viewpoint of a gear metallurgistbeat treater - one who has a long and a
5、ctive record of participation in the preparation of these documents. Knowing the differences will be important to the users of these new documents. Weil thought out practical consistency was the goal. Was it accomplished? This paper recommends working according to the requirements and recommendation
6、s of the new documents. The ultimate goal of this paper is to get the questions and feedback known to the preparen of the next generation of documents, so that there will be more consistency between the documents the next time. Copyright O 2000 American Gear Manufacturers Association 1500 King Stree
7、t, Suite 201 Alexandria, Virginia, 22314 October, 2000 ISBN: 1-55589-764-9 Contents * Page Scope Introduction 1 2.1 - Basic assumptions . 1 2.2 - Inclusions and exclusions . 2 2.3 - Cautions 2 References . 3 Purpose . 3 Conventions . 4 Metallurgical topic discussed . 5 General changes in AGMA 923 .
8、5 Specific comparisons 6 Conclusions and recommendations 109 Whats next? 109 Acknowledgements . 110 I 2 3 4 5 6 7 8 9 10 11 1 2 3 4 e 5 10 I1 12 13 14 15 16 Chemistry 7 Grain size . 10 Hardenability 12 Non-metallic inclusions 14 Material (no table) 5.1 - Form 22 5.2 - Reduction ratio (wrought only)
9、. 24 Heat treatment (prior to any case or surface hardening) 26 Mechanical properties after heat treatment prior to any case or Surface hardening 28 Microstructure prior to any case or surface hardening . 31 Ultrasonic inspection (no table) 9a -Wrought material - Flat bottom hole (FBH) technique 36
10、9b - Wrought material - Back reflection technique) . 40 9c - Castings - Back reflection technique 44 Overheating, especially at the tooth tips and end faces . 47 Tempering after case or surface hardening . 48 Surface hardness . 49 Case depth - General . 52 13.1 - Effective (on flank) 55 13.2 - Effec
11、tive at root radius 57 13.3 - Total 59 Core (Base) hardness after any case or surface hardening 60 Surface carbon . 62 Surface microstructure - General . 64 16.1 - Intergranular oxidation (IGO) . 66 16.2 - Non-martensitic transformation products 68 16.3 - Decarburization 70 i Con tents (continued) P
12、age 16.4 . Epsilon nitride (white layer) . 75 17 Case microstructure - General 77 17.1 - Carbide precipitation . 79 17.2 - Retained austenite 81 17.3 - Near surface above the root (along flank) . 83 17.4 - Mid case above the root (along flank) . 85 17.5 - Near surface at the root 87 17.6 - Mid case
13、at the root 89 17.7 - Microcracks 91 18 Core microstructure 92 19 Heat affected zone 94 20 Surface temper etch inspection of ground teeth 95 21 Surface cracks 97 22 Magnetic particle inspection of finished gearing 100 23 Shot peening 107 1 Scope This paper compares the requirements and recommendatio
14、ns of four documents (AGMA 923, AGMA 2001, AGMA 2003 and IS0 6336- 5). AGMA 923 and IS0 6336-5 are works-in- progress in the final stages of development but are not yet approved AGMA or IS0 documents. This paper shares some of the history and logic that went into the creation of these documents and
15、highlights the nuances of meaning between the various terminologies that are used. In order to make comparisons easier, this paper rearranged the requirements from the various referenced documents in a manner such that each table covers a single metallurgical topic and includes all of the requiremen
16、ts for that topic regardless of the heat-treat method. The exact wording from each of the referenced documents is copied in that table and is annotated with comments from the author. This paper also highlights the authors opinions as to what are the significant comparisons between the docu- ments, e
17、specially between AGMA 923 and IS0 6336-5. 2 Introduction Once upon a time, AGMA rating standards gave ranges for its ratings with a statement implying that good metallurgy entitled the user to use higher allowable stresses. This begged the question of, “What is good metallurgy?“ After much discussi
18、on, the proposals included those that observed that good metallurgy was related to the salary of the chief metallurgist and the length of the specifications referenced on the gear drawing. Since those proposals, while somewhat true, were not practical or acceptable as a national standard, a good bra
19、instorming session ultimately resulted in a collection of metallurgical factors that were listed in sequence of percieved decreasing. importance. This col-lection of factors ultimately was included in ANSIIAGMA 6033-A88, Standard for Marine Propulsion Gear Units, Part I, Materials and ANSIIAGMA 2001
20、-888, Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear Teeth. The forewords of the referenced documents contain a more detailed history of the various documents The three /SO 6336-5 material quality grades, ML, MQ and ME, stand in relationship to the diagrams of
21、that document that refer to allowable stress numbers. IS0 6336-5 gives the following meaning for its grade designations. ML stands for modest demands on the material quality and on the material heat treatment process during gear manufacture. MQ stands for requirements that can be met by experienced
22、manufacturers at moderate cost. ME represents requirements that must be realized when a high degree of operating reliability is required. The referenced AGMA documents do not have a parallel explanation for its grade designations Note that for through hardened gearing, IS0 Grade MQ is similar in all
23、owable stress ratings to AGMA Grade 1, and IS0 Grade ME is similar in allowable stress ratings to AGMA Grade 2. 2.1 Basic assumptions This paper does not in any way replace the referenced standards. The knowledge and judgement required to eval- uate the items discussed in this paper and the referenc
24、ed documents comes from years of accumulated experience in gear design, gear manufacturing, and gear metallurgy. These documents are not intended for use by the engineering public at large. Those not meeting the stated requirements should be cautious and seek the advice and counsel of those meeting
25、the requirements. All of the referenced documents require that all criteria in any given grade must be met in order to qualify for use of the stress number allowable for that grade. There is no partial credit in these gear rating standards for meeting or exceeding some, but not all, of the criteria.
26、 The careful user of the referenced standards will find that 1 documented experience and good engineering, whatever that is, permits use of allowable stresses other than those given in the refer- enced standards. All of the referenced documents have provisions such that unless otherwise specified, p
27、roper process control, with periodic verification, is an acceptable method to meet the requirements of that document. It should also be noted that all of the referenced documents are consensus-based documents. As such they rely on the experience and expertise of all those who participate in creating
28、 the documents. Unanimous agreement is not necessary. Only substantial agreement is nec- essary. Individual and special cases are not included. Actual test data in suppo.rt of detailed information is not required for admission into these documents. 2.2 Inclusions and exclusions AGMA 923 and the refe
29、renced documents address only the tooth areas of gearing, but not the other features such as shafts, bearing sur- faces, splines, keyways, hubs, and webs. AGMA 923 unlike /SO 6336-5 does not discuss allowable stress numbers or case depth specifi- cations. These topics are considered by AGMA to be wi
30、thin the domain of the ratings com- mittees. Carbonitriding, nitrocarburizing and cast pinions are not covered by any of the referenced documents. The only exception being that IS0 6336-5 does cover nitrocarburizing. The surface hardened (SH) Grade 3 applies only to induction hardening with Type A (
31、contour) pattem. Note that AGMA 6002 includes allow- able stresses for SH Grade 3 but AGMA 2001 and 2003 do not. 2.3 Cautions Meeting the requirements of one or more of the referenced documents does not imply that the requirements of any of the other referenced documents are met. This is especially
32、true between the AGMA and IS0 documents, including the versions that will soon be published. There are three areas of microstructural concern in AGMA 923 core. surface (the first 0.002 - 0.003 inch), case (which includes the surface),and Note that not all of the referenced documents use the same def
33、initions of these terms. The user of the referenced documents must also clearly understand the definitions and nuances of meaning of related terms, especially: Required, recommended, Capable of, certified, Case hardness, surface hardness, Process control coupon, representative Surface, case, and cor
34、e, Non-martensitic structures, non-marten- sitic transformation products, Case hardening, surface hardening, and Methods, alternatives When interpreting specifications, especially IS0 6336-5, and test results, it is extremely important to understand and agree upon the use of certain terminology such
35、 as: case and surface hardness, effective and total case depth, and which hardness criteria is used for defining effective case depth. Some of the requirements and recommend- ations of the referenced documents apply only to the pitting (contact) resistance rating while others apply only to the bendi
36、ng strength rating. The flank area of a gear tooth and the root area of the gear tooth can have different metallurgical requirements and recommendations. The notes shown on each table of this document are important to the understanding of that table. Pay particular attention to notes in the mini-tab
37、le of characteristics (factors) and in the table column headers. Also, pay attention to the location in a table of the reference to a note. It tells whether that specific note applies to all characteristics, all grades for that characteristic, only that grade, or perhaps only a portion of the requir
38、ement or recommendation for that grade. Effective case depth, total case depth, coupon, 2 Pay attention to the borders of the individual cells within the various tables. They indicate grou pings of requirements. WARNING - A little bit of knowledge is a dangerous thing. Errors have intentionally been
39、 introduced and/or left in this document to demonstrate the authors fallibility and to force the reader to think critically, becoming intimately familiar with the reference documents. Please report the errors you find to the author so that he can correct them and possibly insert replacements. 3 Refe
40、rences AGMA 923-AXX (6/00 Committee Comment Draft after Comment Resolution Meeting 8/9- 1 O/OO), Metallurgical Specifications for Steel Gearing. This is a work-in-progress and is not yet an approved AGMA Information Sheet. ANSIIAGMA 2001-888, Fundamental Rating Factors and Calculation Methods for In
41、volute Spur and Helical Gear Teeth. ANSIIAGMA 2003-897 Rating the Pitting Resistance and Bending Strength of Generated Straight Bevel, Zero1 Bevel and Spiral Bevel Gear Teeth. ANWAGMA 6002-B93, Design Guide for Vehicle Spur and Helical Gears. ANSIIAGMA 6033-A88, Standard for Marine Propulsion Gear U
42、nits, Pari I, Materials. ASTM E140-97, Hardness conversion tables for Metals (Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Knoop Hardness and Scleroscope Hardness. IS0 6336-51996, Calculation of load capacity of spur and helical gears - Pari 5: Strength and quality of ma
43、terials. IS0 6336-5 (committee Draft after 11/99 Resolution Meeting), Calculation of load capacity of spur and helical gears - Part 5: Strength and quality of materials. This also is a work-in-progress and is not yet an approved IS0 document. 4 Purpose During the creation of AGMA 923 the author and
44、those others involved in its creation have attempted to accomplish the worthy goals that follow. 0 Consolidate in one place a standardized set of metallurgical requirements applicable for all types of gearing. Minimize the games of “Can you find the differences in the referenced documents?“ and “Can
45、 you de- termine which rules apply to which situa- t ions?“ Standardize definitions, test methods, and test locations, offering alternatives when appropriate Fill in the omissions and correct the errors in the referenced documents, and to clarify those areas subject to misunderstanding. 0 Introduce
46、or modib requirements and recommendations in order to improve the document by minimizing non-value-added costs and reducing the chances of unplea- sant results. 0 Recognize that those inexperienced in the field of gear metallurgy and design may use the referenced documents in legal disputes. The cre
47、ators and modifiers of documents such as AGMA 923 must deal with this issue, since it is well known that whenever bad things happen to good people, a portion of society will try to find the cause, assign blame, and extract compensation. Provide a mechanism for the gear rating cornmittees to modify t
48、he standardized gear metallurgy requirements to address their special situations and concerns. Recognize that the ultimate goal is to get better quality gears for the metallurgical dollar, allow contracting parties to commun- icate in a technically accurate way and to minimize the time and money was
49、ted in disputes between contractual parties. Reach a consensus within the gear design, manufacturing and user communities as to how to achieve the above goals. 3 0 This activity also includes a large educat- Reaching consensus in creating AGMA 923 was extremely difficult. This was particularly true among those involved with small, medium, large, and jumbo size gearing in view of the potential legal implications involved in the use of a document such as AGMA 923. The differences in gear size particularly affect hardenability, material form, forging reduction, microstructure constit
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