AGMA Major Metallurgical Factors

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AGMA Major Metallurgical Factors

AGMA Major metallurgical factors affecting the allowable contact stress number, s_ac, and allowable bending stress number, s_at, of flame or induction hardened steel gears^{1, 2, 3}

Metallurgical factor	Grade 1	Grade 2
ASTM E112 grain size	Predominantly 5 or finer	Predominantly 5 or finer
Material composition	Not specified	Medium carbon alloy steel
Prior structure	Not specified	Quenched and tempered
Material form	Not specified	Forgings and wrought steel; castings with magnetic particle inspection of gear tooth area
Cleanliness⁴	Not specified	AMS 2301 or ASTM A866 for wrought steel (certification not required); cast-ings are permissible with primarily round (Type 1) sulfide inclusions.
Sulfur content	Not specified	0.025% maximum for wrought 0.040% maximum for castings
Core hardness, center of tooth at root diameter, s_ac only	Not specified	28 HRC minimum
Core hardness, center of tooth at root diameter, s_at only	Not specified	Type A - 28 HRC minimum Type B - not specified
Non-martensitic transformation products in hardened zone	Limited by effect on specified hardness	10% maximum, no free ferrite
Surface hardness, s_ac only	-	-
Surface hardness at root, s_at only	Type A -50 HRC min Type B - not specified	Type A -54 HRC min Type B - not specified
Hardness pattern, s_at only	As required per table 4 ANSI/AGMA Standard D04	Type A Contour pattern with a ductile core Type B not specified
Magnetic particle (method per ASTM E709 on teeth)⁵	Not specified Not specified	Pitch P_nd	Maximum indication, inch
		≤ 3 >3 to <10 ≥10	1/8 3/32 1/16

NOTES

1) Criteria for grades 1 & 2 apply to both stress numbers unless otherwise specified in the metallurgical factor column.
2) All criteria in any given grade must be met to qualify for the stress number in that grade.
3) Unless otherwise specified, proper process control with periodic verification is an acceptable method to meet these requirements.
4) The grade cleanliness requirements apply only to those portions of the gear material where the teeth will be located to a distance below the finished tip diameter of at least two times the tooth depth. On external gears, this portion of the gear blank normally will be less than 25 percent of the radius.
5) No cracks, bursts, seams or laps are permitted in the tooth area of finished gears, regardless of grade. Limits: maximum of one indication per inch of face width and maximum of five in one tooth flank. No indications allowed below 1/2 working depth of tooth. Indications smaller than 1/64 inch are not considered. Removal of defects which exceed the stated limits is acceptable provided the integrity of the gear is not compromised.

AGMA Allowable Contact Stress for Steel Gears Table
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Source:

ANSI/AGMA American National Standards Institutue. American Gear Manufacturers Association Specification AGMA 201-D04