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Alloy Cast Steel Designation and Chemistry

Moly-Telastic is a medium carbon, chromium-molybdenum type cast steel which is

similar to an AISI 4135 specification, except with reduced chromium content. It can

be heat treated by annealing or normalizing and tempering to an approximate

hardness of 180 HB for all section sizes.

No. 1 Gearalloy is a medium carbon, chromium-nickel-molybdenum type cast steel

used for applications requiring higher harden ability than Falk Moly-Telastic. It is

similar to an AISI 8630 steel, but higher in alloy content.

No. 2 Gearalloy is a low carbon (0.20% nominal), chromium-nickel-molybdenum

type cast steel containing 0.04-0.06% vanadium for grain refinement in gear

castings. Chemistry is similar to an AISI 8620 steel, but higher in alloy content.

This is our standard cast steel for carburized and hardened gears and has

comparable harden ability to an AISI 4320 H steel.

It is also used in the through-hardened, quenched, and tempered heat treat

condition to a maximum hardness range of 245-285 HB for impact applications (this

condition is not intended for gearing or wear applications).

No. 3 Gearalloy has higher carbon and molybdenum content than No. I Gearalloy

This results in higher harden ability for increased section size or higher hardness

ranges for quench and temper heat treatment. It is similar to an "8633" steel (not a

standard AISI designation) but higher in alloy content.



No. 4 Gearalloy has higher carbon content than No. 3 Gearalloy. This results in the

highest harden ability alloy cast steel (maximum section size or maximum

hardness) intended for hardening by quench and temper The harden ability is

equivalent to an AISI 4340. Chemistry is similar to an AISI 8640 steel but higher in

alloy content.

No. 6 Gearalloy has the same carbon content as No. 4 Gearalloy but has increased

alloy content. This enables hardening by normalize and temper heat treatment to

higher hardness ranges (325-365 HB maximum) than can be achieved with No. 4

Gearalloy normalized and tempered. No. 6 Gearalloy is not intended to be quench

hardened because of quench cracking susceptibility.

Moly-Telastic and No. I through No. 4 and No. 6 Gearalloy grades of alloy cast steel do not, by intent, conform to

specific standard SAE or AISI steel designations regarding carbon and alloy content, but contain modified carbon and

generally higher alloy content for improved depth of hardening (harden ability).

The chemical analyses for our Moly-Telastic and Gearalloy grades of alloy cast steels are shown in Table 1.

TABLE 1 - Chemical Analyses of Our Alloy Steels*

Type % Carbon % Manganese % Chromium % Nickel%

Molybdenum

Moly Telastic 0.30-0.40 0.70-1.00 0.40-0.65 . . . 0.15-0.25

AISI 4135 0.33-0.38 0.70-0.90 0.80-1.10 . . . 0.15-0.25

No. 1 Gearalloy 0.27-0.37 0.70-1.00 0.60-0.90 0.60-0.90 0.30-0.40

AISI 8630 0.28-0.33 0.70-0.90 0.40-0.60 0.40-0.70 0.15-0.25

No. 2 Gearalloy** 0.17-0.23 0.70-1 00 0.60-0.90 0.60-0.90 0.30-0.40

AISI 8120 0.18-0.23 0.70-0.90 0.40-0.60 0.40-0.70 0.15-0.25

No. 3 Gearalloy 0.30-0.37 0.70-1.00 0.60-0.90 0.60-0.90 0.40-0.50

AISI 8633*** 0.30-0.37 0.70-0.90 0.40-0.60 0.40-0.70 0.15-0.25

No. 4 Gearalloy 0.38-0.45 0.70-1.00 0.60-0.90 0.60-0.90 0.40-0.50

AISI 8140 0.38-0.43 0.75-1.00 0.40-0.60 0.40-0.70 0.15-0.25

No. 6 Gearalloy 0.38-0.45 1.05-1.35 0.90-1.20 0.60-0.90 0.55-0.60



No. 6 Gearalloy 0.38-0.45 1.05-1.35 0.90-1.20 0.60-0.90 0.55-0.60

No Similar AISI Grade

No. 5 Gearalloy - Discontinued

* Percent phasphorus and sulfur (both 0.030% max.) are less than ASTM A148 permitted maximums of 0.05% and

0.06%, respectively. Silicon content is typically 0.45%

** No. 2 Gearalloy also contains 0.04-0.06% vanadium for grain refinement. Vanadium additions are also available for

other grades when required.

*** "8633" is not a standard AISI designation.

Our alloy cast steels can be heat treated to meet the strength requirements of ASTM A148 (High Strength Steel

Castings for Structural Purposes) up to grade 165-150. Minimum tensile ductility values (elongation and reduction of

area) for corresponding strength levels are shown in Table 2.

Other alloy cast steels which meet your specifications can be furnished for special pressure, low temperature and high

temperature applications.

The selection of the appropriate alloy cast steel depends upon specified chemistry, hardness, strength and design

considerations.

We will assist you in the proper selection of the appropriate grade to meet your design requirements.

Machinability and ProcessingAlloy grades of cast steels (Moly-Telastic and Gearalloy grades) are readily machinable and ductile, due to our ladle

deoxidation practice which uses primarily calcium and not aluminum. This, in itself, can easily result in lowering

machining costs by as much as 15%.

A well equipped sand laboratory monitors sand molding and core making practices. A sodium silicate sand binder is

exclusively used in our core making process. This high grade material requires no oven curing, is environmentally safe,

and drastically reduces potential metal solidification defects.

Pattern molding can accommodate items up to 150" in diameter or diagonal. Beyond 150'*. We utilize sweep or pit

molding. The largest pits measure 24' x 50' x 7.5' and 36' x 36'x 10'.

The use of aluminum is limited to castings less than 8T finish weight, as it develops aluminum oxides and decreases

machinability. Aluminum content used is less than 0.020%. The index of machinability, shown in Table 10, is based on

hardness and is related to machinability of B1112 steel (100%).

TABLE 10 - Machinability Index

Hardness, HB Per Cent Index

210-250 66

225-265 57

245-285 50

265-305 43



285-325 38

300-340 33

335-375 28

350-390 25

Although microstructure considerations, as well as hardness, determine machinability, our machinability rating system

is based on tool life as a function of cutting speed (surface feet per minute).

Mechanical PropertiesMechanical properties of steel castings are generally determined from test bars machined from standard ASTM A781

test coupons. These test coupons may be attached to the casting or cast separately.

Minimum tensile properties, obtained from standard cast test coupons, for our alloy cast steels are shown in Table 2.

Table 2 - Minimum Tensile Properties of Our Alloy Cast Steel

TYPEHeat

TreatmentHardness HB Minimum Tensile Properties

Tensile

Strength PSI

Yield

Strength PSI

% Elongation in

2 Inches

% Reduction

in Area

Moly-Telastic

Annealed or

Normalized &

Tempered

160

(Minimum)80,000 45,000 23 35

Moly-TelasticQenched &

Tempered

210-250 90,000 60,000 15 35

225-265 100,000 70,000 14 33

245-285 110,000 80,000 13 31

245-295@ 115,000 85,000 12 29

265-305@ 118,000 90,000 11 28

270-310@ 120,000 95,000 11 28

285-325@ 130,000 100,000 10 26

300-340@ 135,000 110,000 9 23

No.1 Normalized &

210-250 90,000 60,000 15 35

225-265 100,000 70,000 15 33



Gearalloy Tempered 245-285 110,000 80,000 13 31

255-295 115,000 85,000 12 29

265-305 118,000 90,000 11 28

No.1

Gearalloy

Quenched &

Tempered

245-285** 110,000 80,000 13 31

255-295** 115,000 85,000 12 29

265-305** 118,000 90,000 11 28

270-310 120,000 95,000 11 28

285-325 130,000 100,000 10 26

300-340 135,000 110,000 9 24

310-350 140,000 115,000 9 23

335-375 150,000 125,000 8 20

No. 2 #

Gearalloy

Water

Quenched &

Tempered

210-250 90,000 60,000 20 45

225-265 100,000 70,000 20 45

245-285 110,000 80,000 18 42

No. 3

Gearalloy

Normalized &

Tempered

245-285 110,000 80,000 13 31

255-295 115,000 85,000 12 29

265-305 118,000 90,000 11 28

285-325 130,000 100,000 10 26

No. 3

Gearalloy

Quenched &

Tempered

265-305** 118,000 90,000 11 28

270-310** 120,000 95,000 11 27

285-325** 130,000 100,000 10 26

300-340 135,000 110,000 9 23

310-350 140,000 115,000 9 22

335-375 150,000 125,000 8 20

350-390 157,000 130,000 7 16



360-400 160,000 135,000 6 12

375-415 170,000 140,000 5 10

390-430 175,000 145,000 5 10

400-445 180,000 150,000 5 10

No. 4

Gearalloy

Normalized &

Tempered

265-305 118,000 90,000 9 22

285-325 130,000 100,000 8 18

300-340 135,000 110,000 6 15

No. 4

Gearalloy

Oil Quenched

& Tempered

310-350 140,000 115,000 9 22

335-375 150,000 125,000 8 20

350-390 157,000 130,000 6 12

360-400 160,000 135,000 6 12

375-415 170,000 140,000 5 10

390-430 175,000 145,000 5 10

No. 6

Gearalloy

Normalized &

Tempered

300-340 135,000 110,000 6 15

310-350 140,000 115,000 5 13

325-365 145,000 120,000 4 9

@ Rough machine before heat treating.

** This hardness can also be obtained by normalizing and tempering.

# Unless carburized hardened, No. 2 Gearalloy is for through hardened impact applications and not for gearing or

wear applications.

Test bar results for tensile ductility (per cent elongation and reduction of area) and impact strength may not be

representative of actual castings due to harden ability and section size considerations. Strength properties such as

tensile, yield, and to a lesser degree, endurance or fatigue strength, show better correlation between test bars and

actual castings, provided hardnesses are equivalent. For further information regarding the limitations of test bar data,

please contact our Materials Technology Department through your local Rexnord account executive.

Impact PropertiesTypical Charpy V-Notch impact strengths for Moly-Telastic and No. I through No. 4 Gearalloys are shown in Tables 3



through 6. These values were obtained from separate cast keel blocks and 5.0 & 10.0 inch test sections. Impact

strength is also a function of heat treatment, hardness and test temperature. Impact properties were evaluated at T/3

depth for test sections.

Table 3 is the typical Charpy V-Notch impact strength for Moly-Telastic cast steel in a 5.0 test section in the normalized

and tempered (N&T) condition at 160-200 HB.

TABLE 3 - Moly-Telastic Cast Steel

(5.0" section) Normalized & Tempered 160-200HB

Temperature -20oF 0oF 70oF 150oF 212oF

Ft-lbs. 7 11 22 44 52

Impact strength in the quenched and tempered condition is higher than for the normalized and tempered condition.

Specific data may be obtained upon request.

For applications requiring higher impact strength, due to shock loading and/or low ambient temperatures, No. I or No. 2

Gearalloy is recommended depending on the specified hardness.

Table 4 shows the typical Charpy V-Notch impact strength (ft-lbs.) for keel blocks of No. I Gearalloy cast steel, as a

function of heat treatment and specified hardness.

TABLE 4 - No. 1 Gearalloy Cast Steel

Keel Blocks (2.0" section)

Heat TreatHardness,

HB-50oF -20oF 0oF 70oF 150oF 212oF

Quenched and

Tempered

225-265 37 49 58 67 69 77

265-305 21 26 35 51 55 57

300-340 16 21 24 39 46 48

Table 5 shows the typical Charpy V-Notch impact strength for No. 2 Gearalloy cast steel at 70*F in the water quenched

and tempered condition at 207-223HB.


(5.0" Section)

Heat Treat Hardness, HBImpact Strength

(ft. lbs.)

Water Quenched & Tempered207 65

217-223 55



Table 6 shows the typical Charpy V-Notch impact strength for No. 4 Gearalloy cast steel (5" and 10" section thickness)

according to hardness in the oil quenched and tempered condition.


(5" and 10" section thickness)

Heat TreatHardness,

HB

Test

TemperatureSize

Impact

Strength

(ft. lbs.)

Quenched and

Tempered

311 70oF 5" 16

277 212oF 5" 38

302 70oF 10" 18

326 212oF 10" 16

Metallurgical ConsiderationsHarden Ability

Control of melting is accomplished through computer-aided harden ability (Di) calculations, coupled with statistical

process control in order to ensure uniform response to heat treatment.

The ideal critical diameter (Di) is defined as the diameter of a round that can be quenched under ideal conditions (ice

brine) in order to obtain a 50% martensitic microstructure at the center of the section. The multiplication factors for

calculating (Di) harden ability, which vary according to ASTM grain size, carbon, and individual alloy content, are

available in literature and from the Materials Technology Department.

Cast (Di) harden ability ranges, established in our Melt Shop as acceptance criteria for our heats, are shown in Table 7.

TABLE 7 - Cast Hardenability Range

Inches

Grade (DI) Range, Inches

Moly-Telastic 3.1-4.9

No. 1 Gearalloy 5.3-7.8





The harden ability ranges are presented for reference purposes only and should not be considered as part of a material

specification. They are intended to illustrate the degree of control used during manufacturing to assist in the production



and heat treatment of castings, and may be subject to slight modification.

Jominy End Quench

Jominy end quench harden ability ranges from testing alloy cast steels per ASTM A255 are shown in Figures I through

4. For the same reason cited above for (Di), these Jominy end quench curves should not be part of a material

specification. harden ability ranges in Figures I through 4 are narrower than those for wrought AISI designations, as

illustrated in Figure 4 for No. 4 Gearalloy. Jominy end quench curves were not developed for No. 6 Gearalloy as the

curves were expected to be nearly horizontal and No. 6 Gearalloy is not quench hardened.

WeldabilityMoly-Telastic and Gearalloy grades can be welded satisfactorily, providing that necessary preheating and post-heating

precautions are followed. Minimum preheating temperatures are shown in Table 9.

TABLE 9 - Minimum Preheat Temp.

GRADE Minimum Preheat Temp. oF

Moly-Telastic 300oF*

No. 1 Gearalloy 350oF





* In most instances, a 300oF minimum preheat is sufficient.

Higher preheat temperature is not necessary unless extensive welding is required.

The maximum preheat temperature should not be greater than 200 F above the minimum required. Minimum preheat

temperature should be maintained during welding by torch heating and monitored by temperature indicating pencils or a

surface pyrometer.

The stress relieving temperature should be 1000-1250F for annealed castings and 50-1 00F below the final tempering

temperature for normalized and tempered or quenched and tempered castings of all grades.

Whenever possible, furnace preheating and post-heating are preferred to local heating with large torches. The choice of

electrodes and welding techniques is normally governed by the nature and position of the weld and the mechanical

properties required. Low hydrogen type manual arc weld rods, or CO2 shielded flux core process wire, selected on the

basis of the required strength, are recommended. When the deposited weld metal is designed to meet the tensile

properties of the casting, welding before heat treating, using heat treatable electrodes, e.g., 4340, is recommended.

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