AISI 8620H Forgings

Q: What is the difference between 8620 and 8620H?

Both are the same alloy family, and the difference lies in what the mill guarantees. Plain 8620 is ordered to a chemical composition. 8620H is ordered to a hardenability band, so each heat is Jominy end quench tested to ASTM A255 and the result must fall inside the band published in SAE J1268 and ASTM A304. In return, 8620H is permitted a slightly wider chemistry range, because hardenability is the controlled property. 8620H is specified where the response to carburising and quenching has to repeat from batch to batch.

Q: Can AISI 8620H be through hardened?

No. At approximately 0.20 per cent carbon, a direct quench and temper produces roughly 30 to 40 HRC in light sections and less in heavy sections, well below the hardness reached by the carburised surface. AISI 8620H is designed to be case hardened. Where high strength is needed through the whole section, a through hardening grade such as AISI 4140 or 42CrMo4 is used, or AISI 4340 or 34CrNiMo6 for heavier sections.

Q: In what heat treatment condition are AISI 8620H forgings supplied?

Jiangyin Jiangnan Metal Co., Ltd. supplies AISI 8620H forgings normalised or annealed as standard, which suits machining prior to carburising, and annealed material runs at approximately 149 HB maximum. Material can also be supplied as forged and descaled, rough machined with an allowance of 6 to 15 mm, or fully finish machined and heat treated to the customer specification. The required condition should be stated on the purchase order.

Q: What certification is supplied with AISI 8620H forgings?

Every order from Jiangyin Jiangnan Metal Co., Ltd. is supplied with an EN 10204 3.1 certificate covering heat and product chemical analysis, mechanical test results, hardness, the heat treatment record and ultrasonic test results. Certification to EN 10204 3.2, witnessed by SGS, BV, TUV, Lloyd's or the customer's own inspector, is available on request. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388.

Q: What is the largest AISI 8620H forging you can produce?

Jiangyin Jiangnan Metal Co., Ltd. forges seamless rolled rings up to 3,000 mm outside diameter, discs and gear blanks up to 2,500 mm, shafts up to 1,200 mm diameter and 8,000 mm long, with unit piece weights from 20 kg to 25,000 kg. Drawings sent to sales@steelforgepieces.com are confirmed against the press and ring mill schedule.

Seamless rolled rings, discs, shafts, flanges, sleeves and gear blanks forged in AISI 8620H (UNS H86200), heat treated, ultrasonically tested and supplied with EN 10204 3.1 or 3.2 certification.

Grade: AISI / SAE 8620H
UNS: H86200
Type: Ni-Cr-Mo carburising
Standards: ASTM A29, A304, SAE J1268
Melt route: EAF + LF + VD
Certificate: EN 10204 3.1 / 3.2

AISI 8620H at a glance

AISI 8620H is the hardenability controlled ("H" band) version of AISI 8620, a low nickel chromium molybdenum case hardening steel of medium hardenability used for carburised gears, shafts, pinions and bearing components. The H suffix means that each heat is Jominy end quench tested and must fall within the hardenability band published in SAE J1268 and ASTM A304, which gives repeatable case and core hardness from batch to batch. The permitted chemistry range is slightly wider than for plain 8620, because hardenability rather than composition is the property being guaranteed.

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The company manufactures AISI 8620H forged rings, discs, shafts, flanges, sleeves and gear blanks to customer drawings, with EN 10204 3.1 or 3.2 material certification and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.

Carbon 0.17 to 0.23 %, Ni 0.35 to 0.75 %, Cr 0.35 to 0.65 %, Mo 0.15 to 0.25 %.
Case hardness after carburising and tempering is 58 to 63 HRC. Core hardness is typically 25 to 40 HRC according to section size.
In the annealed condition, tensile strength is about 530 MPa, yield strength about 385 MPa, hardness about 149 HB and the machinability index is 65 (AISI 1212 = 100).
Closest equivalent grades are 20NiCrMo2-2 / 1.6523 (EN), 805M20 (BS), SNCM220 (JIS), 20NCD2 (AFNOR) and 20CrNiMo (GB).
8620H is not a through hardening grade. Where high core strength is required in heavy sections, 4140, 4340 or 18CrNiMo7-6 are normally used instead.

1. What AISI 8620H is

Definition, and the difference between 8620H and plain 8620

AISI 8620H is a low alloy carburising (case hardening) steel containing nominally 0.20 % carbon with additions of nickel, chromium and molybdenum. It is intended to be carburised, so that carbon is diffused into the surface and the part is then quenched, producing a hard and wear resistant case over a tough core that absorbs shock. It is one of the most widely used gear steels in production worldwide.

The meaning of the H suffix

The H suffix identifies a hardenability requirement rather than a change of alloy family. An H grade is ordered against a hardenability band instead of against a single hardness value. Each heat is tested by the Jominy end quench method to ASTM A255, and the resulting hardness against distance curve must lie inside the band published in SAE J1268 and ASTM A304.

The practical result is that depth of hardening is repeatable from heat to heat, so a component that was quenched successfully on one batch will respond in the same way on the next. Manufacturers of transmissions, axles and pinions therefore specify 8620H rather than 8620 for production quantities. The slightly wider chemistry range permitted for 8620H exists so that the mill can adjust composition within the band in order to meet the hardenability target.

Selection guide. 8620 is ordered where only the chemical composition has to be met. 8620H is ordered where the response to carburising and quenching has to be controlled and repeatable.

2. Chemical composition of AISI 8620H

Heat analysis limits to ASTM A29/A29M and SAE J1268

Table 1. AISI 8620H (UNS H86200) chemical composition, weight per cent
Element	Symbol	Content (%)	Function
Carbon	C	0.17 to 0.23	Held low for core toughness. Case carbon is added during carburising
Manganese	Mn	0.60 to 0.95	Hardenability and deoxidation
Silicon	Si	0.15 to 0.35	Deoxidation, with slight strengthening
Nickel	Ni	0.35 to 0.75	Core toughness, including at low temperature
Chromium	Cr	0.35 to 0.65	Hardenability and case wear resistance
Molybdenum	Mo	0.15 to 0.25	Hardenability and resistance to temper embrittlement
Phosphorus	P	0.035 max	Residual element, controlled for toughness
Sulfur	S	0.040 max	Residual element, reduced by LF and VD refining
Iron	Fe	Balance

Restricted residuals. For gear and bearing duty the material can be supplied with tighter residual limits, typically S 0.015 % max and P 0.020 % max, together with oxygen content and a non-metallic inclusion rating to ASTM E45 or DIN 50602. Please state these requirements at the enquiry stage so that they can be written into the heat specification.

Carbon equivalent

At mid band chemistry the carbon equivalent CE_IIW of 8620H is approximately 0.50, calculated as C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Welding is practicable with preheat, as described in the frequently asked questions below.

3. Mechanical and physical properties

Annealed bar reference values. Forged and heat treated parts are tested individually

Table 2. AISI 8620H typical properties in the annealed condition
Property	Metric	Imperial
Tensile strength, R_m	530 MPa	76,900 psi
Yield strength, R_p0.2	385 MPa	55,800 psi
Elongation (50 mm)	31 %	31 %
Reduction of area	31 %	31 %
Izod impact	115 J	84.8 ft lb
Hardness, Brinell	149 HB approx.	149 HB approx.
Hardness, Rockwell B	80 HRB approx.	80 HRB approx.
Modulus of elasticity	190 to 210 GPa	27,600 to 30,500 ksi
Shear modulus	80 GPa	11,600 ksi
Poisson's ratio	0.27 to 0.30	0.27 to 0.30
Density	7.85 g/cm³	0.284 lb/in³
Thermal conductivity	46.6 W/m K	323 BTU in/hr ft² °F
Machinability index	65 (AISI 1212 free machining steel = 100)

Note on design values. The figures above are annealed bar reference data intended for grade comparison. A carburised 8620H component has a hardness gradient rather than a single hardness value, so design should be based on the specified case depth, case hardness and core hardness. These can be verified on a test coupon forged from the same heat, which is supplied with the parts on request.

After carburising, quenching and low tempering

Table 3. Typical properties of carburised and tempered AISI 8620H
Zone	Typical hardness	Typical microstructure
Surface (case)	58 to 63 HRC	Tempered high carbon martensite with retained austenite
Effective case depth (550 HV)	0.5 to 2.0 mm typical	Falling carbon gradient
Core	25 to 40 HRC (approx. 250 to 400 HV)	Low carbon martensite or bainite, tough

Figure 1. Hardness gradient through a carburised AISI 8620H section.

4. Heat treatment and carburising

Reference cycle, to be confirmed against part geometry and the applicable specification

Forging

Heat to 1,150 to 1,200 °C and finish forging above 900 °C. Cool slowly in still air or in the furnace. Heavy sections are covered during cooling to avoid cracking at corners.
Normalising

900 to 925 °C, held until through heated, then cooled in still air. This refines the as forged grain structure and gives more uniform machinability before carburising.
Annealing

Where a soft and stable machining condition is required, anneal at 840 to 870 °C, furnace cool at 25 °C per hour or slower to about 600 °C, then air cool. The result is approximately 149 HB maximum.
Carburising

900 to 925 °C in a gas, vacuum or pack carburising atmosphere. Time at temperature determines the case depth. Approximately four hours at 925 °C gives about 1 mm of effective case. Surfaces that are to remain soft should be masked.
Quenching

Oil quench directly from the carburising temperature, or reheat to 815 to 845 °C and oil quench for a finer and tougher case. Reheat quenching is normally preferred where distortion and grain size are controlled.
Tempering

150 to 200 °C for a minimum of two hours. Tempering relieves quenching stress with little loss of case hardness. Temperatures above approximately 200 °C reduce case hardness below 58 HRC.
Sub-zero treatment, where required

Where retained austenite has to be minimised, for example on precision gears and dimensionally critical bearing races, treat at minus 70 to minus 80 °C between quenching and tempering, then temper without delay.

Hardenability verification. Because 8620H is an H grade, the mill certificate carries Jominy end quench results to ASTM A255, and those results have to fall inside the SAE J1268 and ASTM A304 band. The J values can be supplied with the certificate where the heat treater needs them to set the quench.

5. International equivalent grades

Nearest equivalents by standard. Confirm suitability before substituting

Table 4. AISI 8620H cross reference to international standards
Region and standard	Designation	Notes
USA, AISI / SAE	8620H	Base designation. 8620 is the non H version
USA, UNS	H86200	G86200 applies to plain 8620
USA, ASTM	A29/A29M, A304, A322	A304 governs the hardenability requirement
USA, SAE	J1268, J404	J1268 publishes the H band
Europe, EN 10084	20NiCrMo2-2 (1.6523)	Closest EN grade. 1.6526 where restricted hardenability +HH or +HL applies
Germany, DIN (former)	21NiCrMo2	Superseded designation, still in common use
United Kingdom, BS 970	805M20 / 805H20 (En362)	805H20 is the hardenability controlled version
France, AFNOR	20NCD2 / 22NCD2
Italy, UNI	20NiCrMo2
Japan, JIS G4053	SNCM220 / SNCM220H	Formerly SNCM21 and SNCM21H
China, GB/T 3077	20CrNiMo	Closest domestic grade, widely stocked in China
Australia, AS 1444	8620H	Same designation
ISO	20NiCrMo2	ISO 683-11 case hardening steels

Substitution. The grades listed are nearest equivalents and are not direct replacements. Chemistry bands, hardenability bands, permitted residuals and inclusion ratings all differ between standards. Before substituting, check the hardenability band and the required case depth against the intended heat treatment cycle, since differences in hardenability cause more problems in practice than differences in chemistry.

6. AISI 8620H forged forms supplied

All parts are forged to the customer drawing

Figure 2. Open-die forged and ring rolled shapes produced in AISI 8620H by Jiangyin Jiangnan Metal Co., Ltd.

Seamless rolled rings. Ring rolled so that grain flow follows the circumference, for gear rims, bearing races and slewing rings.
Forged discs, blanks and gear blanks. Upset forged for radial grain flow, used as the starting stock for carburised gears.
Forged shafts, stepped shafts and pinion blanks. Drawn out under the press and then stress relieved.
Forged flanges, hubs and tube sheets.
Forged sleeves, bushings and cylinders, trepanned or bored.
Forged blocks, rectangles and stepped bars.
Forged round bars, supplied where mill bar cannot meet the required reduction ratio or ultrasonic test class.

7. Sizes forged in AISI 8620H

Capability range. Drawings are checked against press and ring mill capacity before quotation

Table 5. AISI 8620H forging size capability
Form	Outside diameter or width	Thickness or wall	Length or height
Seamless rolled rings	200 to 3,000 mm	40 to 500 mm	up to 1,000 mm
Discs and gear blanks	up to 2,500 mm	30 to 600 mm
Shafts and round bars	80 to 1,200 mm dia.		up to 8,000 mm
Sleeves and bushings	up to 1,800 mm	30 to 400 mm	up to 2,000 mm
Blocks and rectangles	to drawing	to drawing	to drawing
Unit piece weight	20 kg to 25,000 kg

Delivery condition and machining allowance

As forged, black and descaled, with all machining carried out by the customer.
Normalised or annealed, which is the usual condition for parts that will be carburised after machining.
Rough machined, with a typical allowance of 6 to 15 mm per surface according to size and expected heat treatment distortion.
Finish machined to drawing, with or without heat treatment, on request.

The minimum order quantity is one piece for trial and prototype work. Repeat production is scheduled against the customer release plan.

8. Manufacturing and inspection of AISI 8620H forgings

Melt route, forging, heat treatment and the tests recorded on the certificate

Melting and raw material

AISI 8620H billet is melted by EAF + LF + VD, that is electric arc furnace melting, ladle furnace refining and vacuum degassing. Vacuum degassing reduces hydrogen to a level at which flake cracking in heavy sections is avoided, and lowers sulfur and oxygen content, which gives a cleaner and more consistent case. ESR material can be supplied where the specification calls for it.

Forging

Forging is carried out on hydraulic open-die presses, with ring rolling used for seamless rings. A minimum reduction ratio of 3:1 from billet is applied, and higher ratios are available on request, so that the as cast structure is broken down and grain flow follows the contour of the part rather than being cut through during machining.

Tests and certification

Table 6. Standard test package for AISI 8620H forgings
Test	Standard	Applied
Chemical analysis	Spectrometric, heat and product analysis	Every heat
Jominy end quench hardenability	ASTM A255, against the SAE J1268 and ASTM A304 band	Every heat
Ultrasonic testing	EN 10228-3, SEP 1921, ASTM A388	Standard on rings, discs and heavy sections
Tensile test	ASTM A370, ISO 6892-1	Per heat treatment batch
Charpy V-notch impact	ASTM E23, ISO 148-1	On request, including at low temperature
Hardness	ASTM E10 (HB), ASTM E18 (HRC)	Every part
Grain size	ASTM E112	On request, normally specified for gear applications
Non-metallic inclusions	ASTM E45, DIN 50602	On request
Magnetic particle inspection	ASTM E709, ASTM A275	On request
Dimensional report	To customer drawing	Every part

Material certificates are issued to EN 10204 3.1 as standard. Certification to EN 10204 3.2, witnessed by a third party such as SGS, BV, TUV or Lloyd's, or by the customer's own inspector, is available on request. Please advise at the enquiry stage so that inspection can be scheduled into production.

9. Applications for AISI 8620H forgings

Typical components by industry

Table 7. Typical AISI 8620H forged components by industry
Industry	Components forged in 8620H
Power transmission and gearboxes	Gear blanks, ring gears, pinions, planet carriers, shafts, spline shafts, couplings
Wind energy	Planetary gear blanks, slewing ring blanks, pinion shafts
Off-highway and agriculture	Axle shafts, differential housings, crown wheels, final drive gears
Oil and gas	Drilling motor shafts, sleeves, bushings, bearing housings, wellhead components
Heavy machinery and mining	Mill pinions, rolls, crusher shafts, cement and sugar mill gearing
Marine and shipbuilding	Reduction gear blanks, thrust sleeves, rudder bushings
Pumps and compressors	Pump shafts, compressor gear blanks, wear sleeves
Bearings	Roller bearing rings and races for carburised bearing duty

Most of these components are subject to contact fatigue. Surfaces that mesh, roll or slide under load, such as gear tooth flanks, bearing races and splines, require a hard case, while sections subject to bending and impact, such as gear roots and the shafts carrying them, require a tough core. AISI 8620H provides both conditions within a single component, which accounts for its wide use in medium duty gearing.

10. AISI 8620H compared with other forging grades

Case hardening and through hardening routes

Table 8. AISI 8620H compared with commonly considered alternatives
Grade	Hardening route	Surface hardness	Core strength	Typical basis for selection
AISI 8620H	Carburise and quench	58 to 63 HRC case	Moderate	Medium duty gears and shafts where case depth must be repeatable
AISI 8620	Carburise and quench	58 to 63 HRC case	Moderate	Same alloy without a guaranteed hardenability band, suitable for single parts
18CrNiMo7-6, AISI 4320	Carburise and quench	58 to 62 HRC case	Higher	Heavier sections or higher tooth loading than 8620H will support
AISI 4140, 42CrMo4	Through harden, quench and temper	28 to 32 HRC approx.	High throughout	Strength through the whole section matters more than surface wear
AISI 4340, 34CrNiMo6	Through harden, quench and temper	30 to 36 HRC approx.	Very high	Large sections requiring high strength together with toughness
20MnCr5, 1.7147	Carburise and quench	58 to 62 HRC case	Moderate	European supply, contains no nickel and is often lower in cost

Where the grade has not yet been fixed, please send the part drawing together with the service conditions, including tooth load, section size, required case depth and service temperature. A grade recommendation is given with the quotation.

11. Frequently asked questions about AISI 8620H

Answers written to stand on their own

What is AISI 8620H steel?

AISI 8620H is a low nickel chromium molybdenum case hardening (carburising) alloy steel of medium hardenability, designated UNS H86200 and covered by ASTM A29/A29M, ASTM A304 and SAE J1268. It contains 0.17 to 0.23 % carbon, 0.35 to 0.75 % nickel, 0.35 to 0.65 % chromium and 0.15 to 0.25 % molybdenum. After carburising and quenching it gives a wear resistant case of 58 to 63 HRC over a tough core of 25 to 40 HRC, and it is one of the most widely used gear and shaft steels in production worldwide.

What is the difference between 8620 and 8620H?

Both are the same alloy family. The difference lies in what the mill guarantees. Plain 8620 is ordered to a chemical composition. 8620H is ordered to a hardenability band, so each heat is Jominy end quench tested to ASTM A255 and the result must fall inside the band published in SAE J1268 and ASTM A304. In return, 8620H is permitted a slightly wider chemistry range, because hardenability is the controlled property. 8620H is specified where the response to carburising and quenching has to repeat from batch to batch.

What is the European equivalent of AISI 8620H?

The closest European equivalent is 20NiCrMo2-2, material number 1.6523, under EN 10084, with 1.6526 used where restricted hardenability +HH or +HL is specified. The former German designation is 21NiCrMo2. Other close equivalents are 805M20 and 805H20 (BS 970, formerly En362), SNCM220 and SNCM220H (JIS G4053), 20NCD2 (AFNOR) and 20CrNiMo (GB/T 3077). These are nearest equivalents rather than direct substitutes, so the hardenability band should be checked against the intended heat treatment cycle before any substitution is made.

Can AISI 8620H be through hardened?

No. At approximately 0.20 % carbon, a direct quench and temper produces roughly 30 to 40 HRC in light sections and less in heavy sections, well below the hardness reached by the carburised surface. AISI 8620H is designed to be case hardened. Where high strength is needed through the whole section, a through hardening grade such as AISI 4140 or 42CrMo4 is used, or AISI 4340 or 34CrNiMo6 for heavier sections.

What case depth and case hardness can AISI 8620H reach?

Typical effective case depth, measured at 550 HV, is 0.5 to 2.0 mm, and is set by the time at carburising temperature. Approximately four hours at 925 °C gives about 1 mm. Surface hardness after quenching and tempering at 150 to 200 °C is 58 to 63 HRC. Case depth increases with the square root of time, so cases much beyond 2 mm take disproportionately longer, and a higher hardenability grade such as 18CrNiMo7-6 is usually more economic for deep cases.

Is AISI 8620H weldable?

Yes, in the un-carburised condition. The carbon equivalent CE(IIW) is approximately 0.50 at mid band chemistry, so welding is practicable using preheat of about 150 to 250 °C on heavier sections, low hydrogen consumables and a post weld stress relief. Carburised surfaces should not be welded, because the high carbon case will crack. Where welding is planned it should be completed before carburising, and stated at the enquiry stage so that residual elements can be controlled.

In what heat treatment condition are your 8620H forgings supplied?

The standard delivery condition is normalised or annealed, which suits machining prior to carburising. Annealed material runs at approximately 149 HB maximum. Material can also be supplied as forged and descaled, rough machined with an allowance of 6 to 15 mm, or fully finish machined and heat treated to the customer specification. The required condition should be stated on the purchase order.

What certification is supplied with your AISI 8620H forgings?

Every order is supplied with an EN 10204 3.1 certificate covering heat and product chemical analysis, mechanical test results, hardness, the heat treatment record and ultrasonic test results. Certification to EN 10204 3.2, witnessed by SGS, BV, TUV, Lloyd's or the customer's own inspector, is available on request. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388, and the required class should be stated at enquiry.

What is the largest AISI 8620H forging you can produce?

Seamless rolled rings up to 3,000 mm outside diameter, discs and gear blanks up to 2,500 mm, shafts up to 1,200 mm diameter and 8,000 mm long, with unit piece weights from 20 kg to 25,000 kg. Send the drawing to sales@steelforgepieces.com and the size will be confirmed against the press and ring mill schedule, including whether the required reduction ratio is achievable at that size.

How machinable is AISI 8620H?

Machinability is good. In the annealed and cold drawn condition the machinability index is approximately 65, taking free machining AISI 1212 as 100, so it cuts in a comparable way to other low carbon alloy steels. Normalising before rough machining gives a more uniform structure and a better surface finish than machining directly from the as forged condition.

How do I request a quotation for AISI 8620H forgings?

Email sales@steelforgepieces.com or call +86 189 2135 9659 with the drawing or the finished size, the quantity, the delivery condition (as forged, normalised, annealed or rough machined), the required certificate level and any ultrasonic test class. Where no drawing is available, the raw dimensions and the service conditions are sufficient for a budget price.