Agma 923-B05
Agma 923-B05
Agma 923-B05
ABSTRACT
This document identifies metallurgical quality characteristics which are important to the performance of steel
gearing. The AGMA gear rating standards identify performance levels of gearing by heat treatment method and
grade number. For each heat treatment method and AGMA grade number, acceptance criteria are given for
various metallurgical characteristics identified in this document.
Published by
ii
AGMA 923--B05
Contents
Page
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
1
Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2
Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4
Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5
Metallurgical requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Tables
1
2
3
4
15
17
22
27
Figures
1
2
3
4
5
6
7
8
9
10
11
12
13
14
iii
AGMA 923--B05
Foreword
[The foreword, footnotes and annexes, if any, in this document are provided for
informational purposes only and are not to be construed as a part of AGMA Information
Sheet 923--B05, Metallurgical Specifications for Steel Gearing.]
In November, 1984, an ad hoc Metallurgy and Gear Rating Committee met to define the
factors required to qualify the various metallurgical quality grades that were to be introduced
into the gear rating standard that eventually became ANSI/AGMA 2001-- B88, Fundamental
Rating Factors and Calculation Methods for Involute Spur and Helical Gear Teeth.
In May, 1988, ANSI/AGMA 6033--A88, Standard for Marine Propulsion Gear Units -- Part 1,
Materials, was published using a short list of metallurgical factors in table form.
In September, 1988, ANSI/AGMA 2001--B88 was published using metallurgical factors in
table form.
Starting in July, 1992, AGMA representatives participated in writing ISO 6336--5,
Calculation of Load Capacity of Spur and Helical Gears -- Part 5: Strength and Quality of
Materials, which was a modification of the tables in ANSI/AGMA and DIN Standards.
In February, 1993, AGMA 6002--B93, Design Guide for Vehicle Spur and Helical Gears, was
published using a modified version of the tables used in ANSI/AGMA 2001--B88.
In September, 1993, the AGMA Metallurgy and Materials Committee accepted the task of
consolidating the various tables to avoid redundancies and conflicting requirements, and
started work on AGMA 923--A00, Metallurgical Specifications for Steel Gearing.
In January, 1995, a revised ANSI/AGMA 2001--C95 was published using a version of the
ANSI/AGMA 2001--B88 tables as revised by the AGMA Helical Gear Rating Committee.
In November, 1997, a revised ANSI/AGMA 2003--B97, Rating the Pitting Resistance and
Bending Strength of Generated Straight Bevel, Zerol Bevel and Spiral Bevel Gear Teeth,
was published using a version of the ANSI/AGMA 2001--B88 tables as revised by the AGMA
Bevel Gearing Committee.
The committee reviewed all metallurgical tables of the gear rating standards ANSI/AGMA
2001--B88, ANSI/AGMA 2003--A86, and ISO 6336--5:1996 and their proposed revisions to
develop consolidated tables describing the metallurgical characteristics associated with
each specific type of heat treatment and metallurgical quality grade. Effort was made to
reference ISO specifications where possible. The consolidated tables were submitted to
the gear rating committees for their agreement and are published here for reference by
other standards.
AGMAs goal is to develop a consistent metallurgical specification which reflects the quality
requirements for steel gearing. AGMA 923--A00 was such a document, and was intended to
be consistent with the applicable portions of ISO 6336--5:1996, to the extent possible while
the two standards were in parallel development. The AGMA Technical Division Executive
Committee approved the publication of AGMA 923--A00 in August, 2000.
This edition of the information sheet, AGMA 923--B05, incorporates changes to item 8,
microstructure, of table 1, Metallurgical characteristics for through hardened gearing. The
balance of the document remains unchanged. The AGMA Technical Division Executive
Committee approved the publication of AGMA 923--B05 in May, 2005.
Suggestions for improvement of this information sheet will be welcome. They should be
sent to the American Gear Manufacturers Association, 500 Montgomery Street, Suite 350,
Alexandria, Virginia 22314.
iv
AGMA 923--B05
ACTIVE MEMBERS
C. Berndt . . . . . . . . . . . . . . . . . . . . . . . . . .
I. Botto . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D. Breuer . . . . . . . . . . . . . . . . . . . . . . . . .
R.J. Cunningham . . . . . . . . . . . . . . . . . . .
G. Diehl . . . . . . . . . . . . . . . . . . . . . . . . . . .
D. Herring . . . . . . . . . . . . . . . . . . . . . . . . .
D.R. McVittie . . . . . . . . . . . . . . . . . . . . . .
J. Mertz . . . . . . . . . . . . . . . . . . . . . . . . . . .
R.L. Schwettman . . . . . . . . . . . . . . . . . . .
M. Stein . . . . . . . . . . . . . . . . . . . . . . . . . . .
J.B. Walenta . . . . . . . . . . . . . . . . . . . . . . .
L.L. Witte . . . . . . . . . . . . . . . . . . . . . . . . . .
Caterpillar, Inc.
FFE Minerals
Metal Improvement Company
Consultant
Philadelphia Gear Corporation
The Herring Group, Inc.
Gear Engineers, Inc.
Falk Corporation
Xtek, Inc.
Applied Process Southridge, Inc.
Caterpillar, Inc.
General Motors Corporation/Allison Transmission Division
AGMA 923--B05
vi
Metallurgical
Specifications for Steel
Gearing
AGMA 923--B05
1 Scope
This information sheet recommends steel material
and metallurgical quality characteristics for use in
conjunction with AGMA gear rating standards. This
information sheet identifies specifications and requirements for various metallurgical quality grades
for through hardened, carburize and hardened,
induction and flame hardened, and nitrided gearing.
Characteristics covered include raw material, heat
treatment and post heat treat processing, and their
associated inspections. Topics related to gear design and rating, such as case depth, stress numbers,
and quality control sampling plans are not included in
this document.
2 Normative references
The following standards contain provisions which,
through reference in this text, constitute provisions of
this document. At the time of initial development, the
editions shown were valid. All standards are subject
to revision, and parties to agreements based on this
document are encouraged to investigate the possibility of applying the most recent editions of the
standards shown below.
AGMA 904--C96, Metric Usage
ANSI/AGMA 1010--E95, Appearance of Gear Teeth
-- Terminology of Wear and Failure
ANSI/AGMA 1012--F90, Gear Nomenclature,
Definitions of Terms with Symbols
Ultrasonic
AGMA 923--B05
for
Preparation
of
Test
Method
for
3 Definitions
The terms used in this document, wherever applicable, conform to AGMA 904--B89, ANSI/AGMA
1012--F90, and ASTM A919, but they have been
modified to cover only those concepts applicable to
this document. For definitions of technical terms not
included in this clause, see ANSI/AGMA 1012--F90,
ANSI/AGMA 2004--B89, ASTM A919, and ASTM
A941. Key terms used in this document are defined
as follows:
NOTE: These definitions may differ from those in other
AGMA publications. The user should not assume that
familiar terms can be used without a careful study of
their definitions.
AGMA 923--B05
AGMA 923--B05
5% nital etch
400 X mag.
5% nital etch
400 X mag.
5% nital etch
400 X mag.
5% nital etch
400 X mag.
AGMA 923--B05
6 in
(150 mm)
8 in
(200 mm)
6 in
(150 mm)
Teeth
Controlling section:
8 in (200 mm) diameter
4 in
(100 mm)
8 in
(200 mm)
12 in
(300 mm)
Controlling section: 2 in
(50 mm) wall thickness
NOTE: If the bore diameter is less than 20 percent of
the length of the bore, then the controlling section is determined by figures 5 or 7.
Teeth
12 in
(300 mm)
1.5 in
(40 mm)
2 in
(50 mm)
Controlling section: 2 in
(50 mm) thickness
AGMA 923--B05
36 in
32 in (900 mm)
(800 mm)
Controlling section: 2 in
(50 mm) rim thickness
8
(200 mm)
converted hardness: The hardness number reported on a scale different from the scale used for
hardness testing. For example an actual microhardness test reading of 542 HK500 has a converted
hardness of 50 HRC and would be properly reported
as 50 HRC (542 HK500) with the hardness number
and scale in parentheses representing the actual
testing result and method.
core hardness: The hardness at the intersection of
the root circle and the centerline of the tooth at
mid--face width that was developed during the
hardening of carburized gearing. An alternative
location is given by ISO 6336--5, table 4, item 8.
The material must have adequate hardenability for
the required hardness and section size combination
for the required core hardness to be achieved. The
quench severity must also be adequate in order to
achieve the required core hardness.
The term core hardness is applicable to carburize
and hardened gearing. Induction, flame, and nitride
hardened gearing may use the term base hardness.
The core hardness of non--tooth portions (such as
journal areas of carburize and hardened gearing), is
AGMA 923--B05
hardness conversion chart: A published document for use in converting from one hardness testing
scale to another.
Unetched
400 X mag.
AGMA 923--B05
non--martensitic structures: Inclusive terminology for ferrite, carbide, retained austenite, pearlite,
and bainite due to incomplete transformation to
martensite or incomplete austenization. Retained
austenite is not included in the quantitative
metallographic measurement of non--martensitic
structures.
non--martensitic transformation products: Inclusive terminology for ferrite, cementite, pearlite, and
upper bainite in the surface microstructure of
carburize hardened gearing due to incomplete
transformation to martensite. See figure 10 for a
photograph of non--martensitic transformation products in martensite.
normalizing: The heating of a ferrous alloy to a
suitable temperature above the transformation
range and then cooling, typically in air, to a
temperature substantially below the transformation
range.
pearlite: A microstructural constituent consisting of
lamellar ferrite and cementite resulting from the
transformation of austenite at temperatures above
the bainite range.
5% nital etch
400 X mag.
(1)
where
RR
is reduction ratio;
C, D, E, F, G and H = 1.
For upset forged gearing blanks as in figures 7 and 8:
B
E, F, G and H = 1.
AGMA 923--B05
is the height of the upset blank after upsetting before piercing, inch (mm);
representative test coupon: A test coupon designed to represent the quenching rate of the
finished gearing tooth. If the coupon is to be used
only to determine the case properties, it can be
smaller than one used to determine the core
properties of the gear tooth. A representative test
coupon sized for determining the core hardness and
microstructure can also be used for determining the
case properties or as a process control test coupon.
A representative test coupon sized for determining
the case properties can also be used as a process
control test coupon but not for determining core
properties unless substantiated by documented test
data. For procedures associated with representative
test coupons, see 4.2.2.
retained austenite: The metastable austenite
retained within a quenched microstructure. The
amount of retained austenite is a function of carbon
content, alloy content (especially nickel and
manganese), quench temperature and subsequent
thermal or mechanical treatments. See figures 11,
12 and 13 for examples of visual estimates of
retained austenite (white constituent) in tempered
martensite. More precise measurements of retained
austenite can be obtained by X--ray diffraction
techniques.
shot peening: A cold working process performed
by bombarding the surface of a part with small
spherical media. This results in a thin layer of high
magnitude residual surface compressive stress and
generally improves the bending strength in the roots
of gear teeth. Shot peening should not be confused
with grit blasting or shot blasting which are cleaning
operations.
AGMA 923--B05
10
surface hardness:
The hardness measured
directly on the functional surface, after appropriate
surface preparation. Surface hardness is not to be
confused with case hardness, which is taken on a
AGMA 923--B05
Case hardness
4 Procedures
4.1 Recommended test methods
The test methods listed in this clause are to be used
when no other method is clearly defined or specified.
These are the methods to be used for evaluations to
the requirements of clause 5.
Testing of the actual part is preferred and should
always be used whenever practical. However,
properly selected test coupons can also be used.
The dimensions in this document are always to be
measured normal (not oblique) to the surface.
11
AGMA 923--B05
--
--
--
--
Nitrided parts
--
--
--
--
Nitrided parts
--
--
--
--
--
Nitrided parts
--
12
AGMA 923--B05
13
AGMA 923--B05
5 Metallurgical requirements
The metallurgical characteristics identified in the
tables of this clause are intended to be used for all
steel gearing. Metallurgical characteristics defined
in the tables of this clause are intended to assure the
quality of the finished gear teeth.
Individual AGMA rating standards may have specific
modifications to the metallurgical characteristics
grading; but the intent is to formalize the assumptions and definitions on which the various AGMA
standards are based. These characteristics should
be compatible, wherever possible, with ISO 6336--5.
Users of this document must be aware that the
Grade 1, Grade 2 and Grade 3 gearing produced by
different heat treatment processes have different
14
ratings.
Refer to the applicable gear rating
standards for specific gear ratings.
Individual customers and manufacturers may have
specific modifications to the metallurgical grade
requirements or special material and processing
conditions that are not covered in these tables.
These modifications and special conditions are
permissible with mutual agreement.
The following tables establish reasonable minimum
limits for each material and metallurgical characteristic that will allow gearing, which meet dimensional
tolerances, to meet the minimum expectations of the
gear rating design standards. As individual gearing
designs increase in size and complexity of features,
they become more difficult to manufacture, heat
treat, and inspect. This document, as a general rule,
does not differentiate based on gearing size.
However, where necessary, specific notation is
made to reflect the special processing methods,
techniques and inspections required for large gear
manufacturing.
All requirements for a metallurgical quality grade
must be met in order to use the stress value, from the
AGMA rating standard, for that grade. This can be
accomplished by specifically certifying each requirement where necessary, or by establishing practices
and procedures to obtain the requirements on a
production basis. It is not the intent of this document
that all requirements for metallurgical quality grade
be certified, but that practices and procedures be
established for their compliance on a production
basis. Intermediate values are not classified since
the effect of deviations from the quality standards
cannot be evaluated easily. Specific sampling plans
and test methods need to be addressed by either the
manufacturer, the customer, or both.
The various characteristics are listed in the order in
which that characteristic is typically evaluated during
the manufacturing sequence. Each individual
characteristic has the same item number in tables 1,
2, 3 and 4 whenever it is used, regardless of which
table it appears. Some characteristics are only
applicable to specific heat treat methods. Therefore,
some item numbers are not used in some tables.
Characteristics that are typically evaluated at the
same time are grouped by having the same number
before the decimal point, and modified with different
numbers after the decimal point for the individual
characteristics evaluated at that time.
5.1 Through hardened gearing
The major metallurgical characteristics that affect
through hardened gearing performance are shown
AGMA 923--B05
Grade 1
Not specified
verified.
Grain size
Verification
required.
Hardenability
Not specified.
Non--metallic
inclusions Not specified.
(cleanliness, steelmaking) 3)
5.1
Material form
5.2
Material
reduction
(wrought only)
Heat treatment
Mechanical properties
heat treatment6)
Microstructure3)
or
Grade 2
Test report only. Medium carbon alloy steel.
0.025% maximum sulfur.
not
after Hardness testing is required. Other mechanical testing is required only if specified.
Not specified.
Sound metallurgical practice dictates that the microstructure requirements in the tooth area should be predominantly tempered martensite
with limited upper transformation products (ferrite, upper bainite and fine
pearlite). The microstructure shall be free of blocky ferrite (due to incomplete austenization) with the following limits for non--martensitic upper
transformation products:
Controlling section size,
Non--martensitic structures,
inch
maximum
at least
less than
---5
5%
5
10
10%
10
15
20%
15
---Hardness must be obtained at
roots with 900F minimum temper
Controlling section size,
mm
at least
less than
---125
125
250
250
375
375
----
Ultrasonic inspection3) 5)
Wrought material.
Either method is acceptable.
-- Flat bottom hole (FBH) Not specified.
technique
Non--martensitic structures,
maximum
5%
10%
20%
Hardness must be obtained at
roots with 480C minimum temper
(continued)
15
AGMA 923--B05
Table 1 (concluded)
Item
Characteristic1) 2)
9
(continued)
-- Back reflection technique
Not specified.
Castings
-- Back reflection technique
Not specified.
-- ASTM A609 Level 1 from outside surface to 1.5 times tooth height below finished tooth tips.
-- ASTM A609 Level 2 greater than 1.5 times tooth height below finished
tooth tips.
16
Surface microstructure
considering subsequent stock
removal
16.3
Grade 1
Not applicable.
Maximum 2 HRC points or equivalent by conversion.
-- Method 3.
evaluation.
21
Surface cracks7) 8)
22
23
Grade 2
Shot peening10)
Cracks, bursts, seams and laps are not permissible in functional areas of finished gearing.
Not specified.
Indication, maximum
inch
mm
1/8
3.2
3/32
2.4
1/16
1.6
Shot peening per SAE/AMS--S--13165 may be used to increase surface residual compressive
stress.
NOTES:
1) See clause 3 for definitions and clause 4 for test methods.
2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steels.
This microsegregation can produce variations in microstructure and properties that need to be assessed.
3) The grade requirements for non--metallic inclusion, ultrasonic and microstructure characteristics apply only to those portions of the
gearing material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.
4) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesser
reduction ratios may be used down to a minimum of 3 to 1.
5) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detect flaws
before incurring the expense of further machining.
6) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.
7) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.
8) Cracks in non--functional areas require engineering disposition.
9) Limits: maximum of one indication per inch (25 mm) of face width with a maximum of five such indications on any one tooth flank.
Indications less than 1/32 inch (0.8 mm) are not considered.
10) It is recommended that ANSI/AGMA 2004--B89 be reviewed to determine if the benefits of surface residual compressive stress
achieved by shot peening may be beneficial to the particular application. Shot peening of the flanks of gear teeth should be reviewed to
ensure that no detrimental effects are caused to the gear set.
16
AGMA 923--B05
Grain size
Hardenability
Non--metallic inclusions
(cleanliness, steelmaking)3) 4)
5.1
Material form
5.2
Grade 1
Specified, but not
verified.
Verification
not required.
Not specified.
p
Grade 2
Test report only. Alloy steel.
0.025% maximum sulfur.3)
Grade 3
Test report only. Alloy steel.
0.015% maximum sulfur.3)
Wrought gearing
Alternative A:
-- Certified ASTM A534
Alternative B, all of the following:
-- The steel must be certified:
-- electric furnace practice
-- ladle refined
-- deoxidized
-- vacuum degassed
-- bottom poured ingot
-- protected from reoxidation
during teeming or casting
-- oxygen content of 20 ppm
maximum
-- certified cleanliness by either
ASTM E45 or ISO 4967 Method B
Plate II with 0.3 inch2 (200 mm2) inspection area. Acceptable if does
not exceed:
Type
Fine Thick
A (sulfide)
2.5
1.5
B (alumina)
2.0
1.0
C (silicate)
0.5
0.5
D (globular oxide) 1.0
1.0
Alternative C:
Certified SAE/AMS 2300 or
SAE/AMS 2304.
Cast gears
Not permitted.
Forgings per ASTM A837 and either ASTM A290 or ASTM A291
Bar stock per ASTM A29, ASTM A304 or ISO 683--11
Tubing per ASTM A519
Not specified.
(continued)
17
AGMA 923--B05
Table 2 (continued)
Characteristic1) 2)
Item
9
Grade 1
Grade 2
Grade 3
inspection4) 7)
Ultrasonic
Wrought material.
Either method is acceptable.
Not specified.
Not specified.
Recommended.
Required.
Castings
-- Back reflection technique
11
12
55--64 HRC
equivalent
or
-- Normal diametral
finer than 3 (module 8)
-- Tooth root
13
Case
depth
considering
subsequent stock removal
13.1
Effective case depth in finished Minimum and maximum effective case depth requirements for the tooth should be specified in
condition 10) 11)
accordance with the appropriate rating standard.
13.2
21 HRC minimum
25 HRC minimum
12)
14
21 HRC minimum
30 HRC minimum14)
(continued)
18
AGMA 923--B05
Table 2 (continued)
Item
Characteristic1) 2)
15 Surface carbon (typical)15)
Grade 1
16.1
16.2
Grade 2
Grade 3
0.60 -- 1.10%C
0.60 -- 1.00%C
0.60 -- 1.00%C
0.60 -- 1.00%C
0.65 -- 0.95%C
0.65 -- 0.95%C
Surface microstructure consid- The first 0.002 -- 0.003 inch (0.05 -- 0.08 mm) of case microstructure in the tooth area should
ering subsequent stock remov- meet the surface hardness requirement of the specific grade and also meet the following sural 12) 16)
face related characteristics and the requirements of Item 17:
Intergranular oxidation (IGO) Not specified.
(see figure 9)
Minimum specified effective
case depth
inch
(mm)
at
less
at
less
least
than
least
than
---0.030
---(0.75)
0.030 0.060 (0.75) (1.50)
0.060 0.090 (1.50) (2.25)
0.090 0.120 (2.25) (3.00)
0.120
---(3.00)
----
16.3
(mm)
at
less
least
than
---(0.75)
(0.75) (1.50)
(1.50) (2.25)
(2.25) (3.00)
(3.00)
----
Not specified.
-- Method 3.
evaluation.
No partial decarburization apparent on active tooth profile. No ferrite (total decarburization) is permissible in the case microstructure
of the gear tooth.
No partial decarburization apparent on the gear tooth. No ferrite (total decarburization) is permissible
in the case microstructure of the
gear tooth.
Gear tooth surfaces must be file hard to the minimum surface hardness.
Case microstructure consider- The microstructure of the first 20% of the minimum specified effective case depth should be preing subsequent stock removal, dominantly tempered martensite. Additional requirements for the case microstructure are given
disregarding corner effects 12) in Item 16 and the following case related characteristics:
(continued)
19
AGMA 923--B05
Table 2 (continued)
Characteristic1) 2)
Item
Grade 1
Grade 2
Grade 3
Discontinuous carbides per figure
3 are not acceptable, but dispersed
carbides per figure 4 are acceptable.
17.1
17.2
Retained
case.9)
17.3
17.4
Microstructure of the case from Untempered mara depth of 0.010 inch (0.25 mm) tensite is acceptor the first 20% of the minimum able.
specified effective case depth,
whichever is smaller, to a depth
equal to 40% of the minimum
specified effective case depth
along the flank (for pitting
resistance rating). 18)
austenite
in
Not specified.
Not specified.
5% maximum
structures.
17.5
Microstructure of the case to a Not specified. Undepth of 0.010 inch (0.25 mm) tempered martenor the first 20% of the minimum site is acceptable.
specified effective case depth,
whichever is smaller, at the root
fillet (for bending strength
rating). 18)
17.6
Microstructure of the case from Untempered mara depth of 0.010 inch (0.25 mm) tensite is acceptor the first 20% of the minimum able.
specified effective case depth,
whichever is smaller, to a depth
equal to 40% of the minimum
specified effective case depth
at the root fillet (for bending
strength rating). 18)
-- Normal diametral pitch 3 Not specified.
(module 8) and coarser.
Not specified.
Not specified.
17.7
Not specified.
Untempered martensite is acceptable.
non--martensitic Only
trace
structures.
non--martensitic
non--martensitic
(continued)
20
AGMA 923--B05
Table 2 (continued)
Item
Characteristic1) 2)
18 Core microstructure4) 12)
20
21
22
23
Grade 2
Grade 3
Sound metallurgical practice dictates that the core microstructure requirements are maintained in the tooth area to a depth of twice the minimum specified effective case depth or 0.100 inch (2.5 mm), whichever
is less, below the minimum specified effective case depth. The microstructure in this zone should be predominantly tempered martensite.
This microstructure zone should be free of blocky ferrite, pearlite, and
measurable bainite. Below this zone the core microstructure should be
free of blocky ferrite and be primarily tempered martensite with some
acicular ferrite and bainite permissible.
Surface temper etch inspection Not specified.
FB2, which allows light tempering FB1, which allows light tempering
of ground teeth
on 25% of functional area.
on 10% of functional area.
Surface cracks20)
Cracks, bursts, seams and laps are not permissible in Cracks, bursts, seams and laps are
functional areas of finished gearing.21)
not permissible in any area of finished gearing.
Magnetic particle inspection of
Inspection recommended to the Inspection required to the following
finished gearing 7) 20) 21) 22)
following limits:
limits:
-- Below the pitch line
Not specified.
No indications.
No indications.
-- Above the pitch line
Normal
diametral pitch
Module
Indication, maximum
Indication, maximum
at
less
more
at
inch
mm
inch
mm
least
than
than
most
1/8
3.2
3/32
2.4
---3
8
-- -Not specified.
3/32
2.4
1/16
1.6
3
10
2.5
8
1/16
1.6
1/32
0.8
10
----- -2.5
Shot peening 23)
Grade 1
Not specified.
Shot peening per SAE/AMS--S--13165 may be used to increase surface residual compressive
stress.
NOTES:
1) See clause 3 for definitions and clause 4 for test methods.
2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steels.
This microsegregation can produce variations in microstructure and properties that need to be assessed.
3) Intentional additions of calcium or calcium alloys for deoxidation or inclusion and shape control are not permitted unless specifically
approved by the purchaser. The use of lime or fluorspar, or both, in the steelmaking slag is acceptable.
4) The grade requirements for non--metallic inclusion, ultrasonic, and microstructure characteristics apply only to those portions of the
gear material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.
5) Care should be exercised when using Alternative D because of the risk of rejection after the expense of further manufacturing processes.
6) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesser
reduction ratios may be used down to a minimum of 3 to 1.
7) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detect flaws
before incurring the expense of further machining.
8) Root hardness may be less than flank hardness, depending on the size of the gear and the quench process.
9) If cold treatment is performed, it is recommended that it be preceded by tempering at 300F (150C) minimum in order to minimize
formation of microcracks. Retempering is required after cold treatment. Cold treatment should not be used to transform large amounts of
retained austenite (e.g., 50%) to gain excessive improvements in hardness, even with prior tempering.
10) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.
11) When specifying minimum case depth, note that the optimum values for pitting resistance and bending strength capacity are not the
same. A maximum case depth is prescribed in order to minimize the risk of embrittlement in the tooth area, including the tips.
12) See clauses 3 and 4 for a discussion of test coupons.
13) Core hardness requirements for pitting resistance and bending strength are considered independently. The gear rating may be limited by either pitting resistance or bending strength for the selected metallurgical quality grade and its core hardness requirement.
14) Minimum hardness of 30 HRC for Grade 3 may be difficult to achieve on coarse pitch gearing. Due to the tooth section size of 3 normal
diametral pitch (8 module) gearing and coarser, the alternate (ISO) core hardness test location may be used provided documented testing or experience is available.
(continued)
21
AGMA 923--B05
Table 2 (concluded)
NOTES:
15) Optimum pitting resistance is best achieved at surface carbon levels above the eutectoid carbon for a given alloy chemistry.
16) If excessive, salvage may be possible by processes such as shot peening per Item 23 or by grinding provided the integrity of the
gearing is not compromised.
17) At maximum allowable depths the surface may not be file hard and may not have the expected residual stress profile.
18) Bainite, observable at 200X, that extends from the core microstructure into the case area is considered a ratable characteristic.
This bainite is the result of slower heat extraction rates due to part section size, mass of furnace load, marginal agitation, elevated
quenchant temperatures, and generally follows alloy segregation and material flow lines. The bainite that results in a fine pepper
structure at 400 -- 600X, but is still not resolvable at 800X, is considered nonratable (trace).
19) Maximum limit of microcracks (Item 17.5) for Grade 3 gearing may be difficult to achieve if cold treatment is used to transform the
retained austenite level to 30% maximum.
20) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.
21) Cracks in nonfunctional areas require engineering disposition.
22) Limits: maximum of one indication per inch (25 mm) of face width with a maximum of five such indications on any one tooth flank.
Indications less than 1/32 inch (0.8 mm) are not considered.
23) It is recommended that ANSI/AGMA 2004--B89 be reviewed to determine if the benefits of surface residual compressive stress
achieved by shot peening may be beneficial to the particular application. Shot peening of the flanks of gear teeth should be reviewed to
ensure that no detrimental effects are caused to the gear set.
3
4
Characteristic1) 2)
Grade 1
Grade 2
Grade 3
Spin induction Type A
(Contour) only
Material chemistry
Not specified or Test report only.
Test report only.
verified.
0.025% maximum sulfur for 0.015% maximum sulfur for
wrought.
wrought.
Grain size
Predominantly 5
Predominantly 5 or finer. Test report only.
or finer. Verification not required.
Hardenability
Not specified.
A minimum hardenability which is appropriate for part size and quench
severity should be specified.
Non--metallic
inclusions Not specified.
Wrought gearing
Wrought gearing
(cleanliness, steelmaking) 3)
Capable of meeting (certification Capable of meeting (certification
not required) SAE/AMS 2301, not required) SAE/AMS 2301,
ASTM A866 or SAE J422 S2--O2 ASTM A866 or SAE J422 S2--O2
Cast gears
Cast gears
Only permissible if primarily Not permitted
5.2
6
Material form
(continued)
22
AGMA 923--B05
Table 3 (continued)
Item
Characteristic1) 2)
Grade 1
Grade 2
Grade 3
Spin induction Type A
(Contour) only
28 HRC minimum. Other mechani- 30 HRC minimum. Other mechanical testing is required only if speci- cal testing is required only if specified.
fied.
Sound metallurgical practice dictates that the core microstructure requirements are maintained in the tooth area to a depth twice the minimum
specified effective case depth or 0.100 inch (2.5 mm), whichever is less,
below the minimum specified effective case depth. The microstructure
in this zone should be predominantly tempered martensite that is free of
blocky ferrite, pearlite, and measurable bainite observable at 400--600X.
Below this zone the core microstructure should be primarily tempered
martensite and free of blocky ferrite with the following limits:
Controlling section size,
inch
at least
less than
---5
5
10
10
15
15
---Controlling section size,
mm
at least
less than
---125
125
250
250
375
375
----
Non--martensitic structures,
maximum
5%
10%
20%
Hardness must be obtained at
roots with 900F minimum temper
Non--martensitic structures,
maximum
5%
10%
20%
Hardness must be obtained at
roots with 480C minimum temper
Ultrasonic inspection3) 5)
Wrought material.
Either method is acceptable.
Not specified.
Castings
-- Back reflection technique
Not specified.
(continued)
23
AGMA 923--B05
Table 3 (continued)
Item
10
11
12
13
13.1
13.2
14
17
17.3
17.5
19
20
21
22
Characteristic1) 2)
Grade 1
Grade 2
Grade 3
Spin induction Type A
(Contour) only
Overheating, especially at the Avoid surface temperatures that result in grain growth, incipient melting or unfavorable
tooth tips and end faces 8)
residual stresses. Larger chamfers minimize this problem.
Tempering
after
surface
1 hour minimum at temperature furnace temper is required.9)
hardening
Surface hardness on a repre- 50 HRC minimum or 54 HRC minimum as required by 58--64 HRC or equivalent
sentative surface. Alternative rating standard.
method of inspection is case
hardness. 7) 8)
Case depth considering subseShould meet the following characteristics:
quent stock removal. Also see
Item 19. 7) 8) 10)
Effective case depth in finished Minimum and maximum effective case depth should be Minimum and maximum effective
condition
specified in accordance with the rating standard. A case depth should be specified in
hardening pattern per figure 14 shall be specified.
accordance with the rating standard. Figure 14 Type A contour
pattern only shall be specified.
Effective case depth minimum Not specified.
50% of minimum specified effective 100% of minimum specified effecat root radius, or on representacase at 1/4 tooth height above the tive case at 1/4 tooth height above
tive
sample
with
same
root recommended.
the root recommended, and 66% of
geometry and material as work
minimum specified effective case
piece, as determined by
at the root.
bending strength rating.
Base hardness after surface Not specified.
28 HRC minimum
30 HRC minimum
hardening.
Also see Item 7. 6) 7) 8) 10)
Case microstructure consider- The first 20% of the case microstructure should be predominantly tempered martensite. The
ing subsequent stock removal, microstructure should be free of undissolved pearlite observable at 100X and measurable
disregarding corner
bainite observable at 400 -- 600X.
effects8) 10) 11)
The following case microstructure characteristics for each grade must be met:
Microstructure of case along Primarily
fine Primarily fine acicular tempered Primarily fine acicular tempered
flank (for pitting resistance acicular marten- martensite. Non--martensitic struc- martensite with no non--martensitic
rating).
site.
tures anywhere in the case should structures.
not exceed 5%.
Microstructure at root (for Primarily
fine Primarily fine acicular tempered Primarily fine acicular tempered
bending strength rating).
acicular marten- martensite. Non--martensitic struc- martensite. Non--martensitic strucsite.
tures anywhere in the case should tures anywhere in the case should
not exceed 10%.
not exceed 5%.
Heat affected zone. Also see Induction and flame hardening heat treatments have a characteristic heat affected zone that
Item 13. 8) 10)
is caused by the surface heating process. This zone can have lower hardness and different
microstructure than the base material. The case depth specification should be established
to avoid gear failure which might initiate in this zone.
Surface temper etch inspection Not specified.
FB2, which allows light tempering FB1, which allows light tempering
of ground teeth
on 25% of functional area.
on 10% of functional area.
Surface cracks 12) 13)
Cracks, bursts, seams and laps are not permissible in functional areas of finished gearing.
Magnetic particle inspection of
Inspection to the following limits:
finished gearing5) 12) 13) 14)
-- Below the pitch line
Not specified.
No indications.
No indications.
-- Above the pitch line
Normal
diametral pitch
Module
Indication, maximum
Indication, maximum
at
less
more
at
inch
mm
inch
mm
least
than
than
most
1/8
3.2
3/32
2.4
---3
8
-- -Not specified.
3/32
2.4
1/16
1.6
3
10
2.5
8
1/16
1.6
1/32
0.8
10
----- -2.5
(continued)
24
AGMA 923--B05
Table 3 (concluded)
Item
23
Characteristic1) 2)
Shot peening 15)
Grade 1
Grade 2
Grade 3
Spin induction Type A
(Contour) only
Shot peening per SAE/AMS--S--13165 may be used to increase surface residual
compressive stress.
NOTES:
1) See clause 3 for definitions and clause 4 for test methods.
2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steels.
This microsegregation can produce variations in microstructure and properties that need to be assessed.
3) The grade requirements for non--metallic inclusion, ultrasonic, and microstructure characteristics apply only to those portions of the
gear material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.
4) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesser
reduction ratios may be used down to a minimum of 3 to 1.
5) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detect
flaws before incurring the expense of further machining.
6) Mechanical properties, including core hardness, may not be the same after induction or flame hardening as they were before induction or flame hardening.
7) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.
8) See clauses 3 and 4 for a discussion on test coupons.
9) Induction tempering is recommended for Grade 3 as a crack preventing stress relief heat treatment prior to furnace tempering.
10) The hardness pattern, depth, facilities and process method must be established, documented and verified to be repeatable. The
process equipment and methods must be sufficiently accurate to reproduce the specified results. Excessive case depth can generate
unfavorable residual stress conditions.
11) Microstructure analysis of induction hardened test specimens have shown indications of undissolved pearlite or ghost pearlite.
This is especially true with rapid (short) heating cycles. This ghost pearlite should not be present.
12) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.
13) Cracks in non--functional areas require engineering disposition.
14) Limits: maximum of one indication per inch of face width with a maximum of five such indications on any one tooth flank. Indications
less than 1/32 inch (0.8 mm) are not considered.
15) It is recommended that ANSI/AGMA 2004--B89 be reviewed to determine if the benefits of surface residual compressive stress
achieved by shot peening may be beneficial to the particular application. Shot peening of the flanks of gear teeth should be reviewed to
ensure that no detrimental effects are caused to the gear set.
25
AGMA 923--B05
Inductor coil
Spin hardening
Induction coil
or flame head
Type A
(Contour)
Grades 1, 2 and 3
Type A
(Non--contour)
Grades 1 and 2 only
Induction coil
or flame head
Type B
Grades 1 and 2 only
Type B
Grades 1 and 2 only
Type B
Grades 1 and 2 only
Type A
Grades 1 and 2 only
NOTE:
-- Type A indicates that flanks and roots are hardened for contour or non--contour patterns.
-- Only spin hardening Type A (Contour) is applicable to Grade 3.
-- Type B indicates that the flanks are hardened only to the form diameter.
-- For Type B the full active profile must be hardened with the transition zone not in the root fillet area.
Figure 14 -- Variations in hardening pattern obtainable on gear teeth with flame or induction
hardening
5.4 Nitrided gearing
The major metallurgical characteristics that affect
nitrided gearing performance are shown in table 4.
These characteristics are not necessarily applicable
to carbonitrided or nitrocarburized gearing, neither
26
AGMA 923--B05
Characteristic1) 2)
chemistry3)
Grade 1
Grade 2
Grade 3
Not specified or
verified.
Material
Grain size
Hardenability
Non--metallic
inclusions Not specified.
(cleanliness, steelmaking) 4)
5.1
Material form
5.2
Material
reduction
(wrought only)
Wrought gearing
Wrought gearing
Capable of meeting (certification Certified to SAE/AMS 2304,
not required) SAE/AMS 2301, ASTM A866 or SAE J422 S2--O2
ASTM A866 or SAE J422 S2--O2
Cast gears
Cast gears
Not permitted.
Not permitted.
Forgings per either ASTM A290 or ASTM A291
Bar stock per ASTM A29, ASTM A304 or ISO 683--1
Tubing per ASTM A519
Castings not permitted.
Heat treatment prior to case Quench and temper with tempering temperature 900F (480C) minimum and 50F (28C)
hardening
minimum above the nitriding temperature.
Sound metallurgical practice dictates that the core microstructure requirements are maintained in the tooth area to a depth twice the minimum
specified effective case depth or 0.100 inch (2.5 mm), whichever is less,
below the minimum specified effective case depth. The microstructure
in this zone should be predominantly tempered martensite. This microstructure should be free of blocky ferrite, pearlite, and measurable bainite
observable at 400--600X. Below this zone the core microstructure
should be free of blocky ferrite and be primarily tempered martensite with
the following limits:
Controlling section size,
inch
at least
less than
---5
5
10
10
15
15
---Controlling section size,
mm
at least
less than
---125
125
250
250
375
375
----
Non--martensitic structures,
maximum
5%
10%
20%
Hardness must be obtained at
roots with 900F minimum temper
Non--martensitic structures,
maximum
5%
10%
20%
Hardness must be obtained at
roots with 480C minimum temper
(continued)
27
AGMA 923--B05
Table 4 (continued)
Characteristic1) 2)
Item
9
Grade 1
Grade 2
Grade 3
inspection4) 6)
Ultrasonic
Wrought material.
Either method is acceptable.
-- No indications giving a signal re- -- No indications giving a signal response greater than an 8/64 inch sponse greater than a 5/64 inch
(3.18 mm) reference standard.
(1.98 mm) reference standard.
-- No indications giving a signal
-- No indications giving a signal
response greater than 50% of the response greater than 50% of the
reference standard if accompanied reference standard if accompanied
by a 50% loss of back reflection.
by a 50% loss of back reflection.
12
Not specified.
13
13.1
Effective case depth in finished Minimum effective case depth requirements for the tooth should be specified in accordance
condition
with the appropriate rating standard.
13.3
Total case depth in finished Minimum total case depth requirements for the tooth should be specified in accordance with
condition
the appropriate rating standard.
14
16
Surface
microstructure The first 0.002 -- 0.003 inch (0.05 -- 0.08 mm) of case microstructure in the tooth area should
considering subsequent stock meet the surface hardness requirement of the specific grade and also meet the following surremoval 10)
face related characteristics and the requirements of Item 17:
16.3
28 HRC minimum
Decarburization.
32 HRC minimum
16.4
-- Method 3.
evaluation.
decarburization
(mm)
at
less
least
than
---(0.37)
(0.37)
----
M i
Maximum
allowable depth
inch
(mm)
0.0010 (0.025)
0.0010 (0.025)
(continued)
28
AGMA 923--B05
Table 4 (concluded)
Characteristic1) 2)
Item
17 Case microstructure considering subsequent stock removal,
disregarding corner effects
20 Surface temper inspection
21
22
Grade 1
Grade 2
Grade 3
The first 20% of the case microstructure should be predominantly tempered martensite with
interspersed nitride. The microstructure should be free of blocky ferrite, pearlite, and measurable bainite.
The normal inspection methods, as defined in ANSI/AGMA 2007--B92 or ISO 14104, are not
applicable to nitrided gearing. Care must be taken when grinding nitrided surfaces to ensure
that no harmful surface conditions are produced in the grinding process.
11)
12)
Surface cracks
Cracks, bursts, seams and laps are not permitted in Cracks, bursts, seams and laps are
functional areas of finished gearing.
not permitted in any area of finished
gearing.
Magnetic particle inspection of
Inspection recommended to the Inspection required to the
finished gearing 6) 11) 12) 13)
following limits:
following limits:
-- Below the pitch line
-- Above the pitch line
Normal
diametral pitch
Module
at
less
more
at
least
than
than
most
-- -3
8
-- -3
10
2.5
8
10
-- --- -2.5
Not specified.
Not specified.
No indications.
Indication, maximum
inch
mm
1/8
3.2
3/32
2.4
1/16
1.6
Not recommended.
No indications.
Indication, maximum
inch
mm
3/32
2.4
1/16
1.6
1/32
0.8
23 Shot peening
NOTES:
1) See clause 3 for definitions and clause 4 for test methods.
2) The metallurgical requirements assume homogeneous composition. In practice, microsegregation and banding occurs in steels.
This microsegregation can produce variations in microstructure and properties that need to be assessed.
3) Chemistry must include adequate nitridable alloying elements such as chromium, aluminum, vanadium or molybdenum.
4) The grade requirements for nonmetallic inclusion, ultrasonic and microstructure characteristics apply only to those portions of the
gear material where the teeth will be located to a depth below the finished tooth tip of at least 1.5 times the tooth height.
5) A 7 to 1 minimum reduction ratio is recommended. For large gearing where this reduction ratio is not physically obtainable, lesser
reduction ratios may be used down to a minimum of 3 to 1.
6) In--process ultrasonic and/or magnetic particle inspection of gearing blanks is recommended for large diameter parts to detect
flaws before incurring the expense of further machining.
7) See ASTM A370, ASTM E140 or ISO 6336--5, annex C for hardness conversion tables.
8) Mechanical properties including core hardness may not be the same after nitride hardening as they were before nitride hardening.
9) Specialty nitriding steels are typically alloyed with 1% aluminum to provide higher surface hardness after nitriding than normally
attained with nitrided through hardening steels.
10) For a discussion of test coupons see clauses 3 and 4.
11) Removal of defects that exceed the stated limits is acceptable, provided the integrity of the gear is not compromised.
12) Cracks in non--functional areas require engineering disposition.
13) Limits: maximum of one indication per inch (25 mm) of face width with a maximum of five such indications on any one tooth flank.
Indications less than 1/32 inch (0.8 mm) are not considered.
29
AGMA 923--B05
30
AGMA 923--B05
Bibliography
The following documents are either referenced in the text of AGMA 923--B05, Metallurgical Specifications for
Steel Gearing, or indicated for additional information.
31
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