CA1052668A - Method of making powdered metal parts - Google Patents
Method of making powdered metal partsInfo
- Publication number
- CA1052668A CA1052668A CA259,720A CA259720A CA1052668A CA 1052668 A CA1052668 A CA 1052668A CA 259720 A CA259720 A CA 259720A CA 1052668 A CA1052668 A CA 1052668A
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- Canada
- Prior art keywords
- preform
- forging
- temperature
- case depth
- carbon content
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
A B S T R A C T
Gas carburizing of a briquetted powder metal preform prior to hot forging of the preform to acquire a fully dense, carburized powdered metal part.
Gas carburizing of a briquetted powder metal preform prior to hot forging of the preform to acquire a fully dense, carburized powdered metal part.
Description
105;~68 `
BACKGROUND OF THE INVENTION
This invention relates generally to an improved method of obtaining fully dense, carburized, powdered metal, low alloy steel parts, the most common of which are the powdered metal equivalents of AISI 4000 and 4600 wrought steel series and particularly those having sintered carbon levels in the range of 0.22% to 0.37% by weight. More specifically, this invention is related to the improved method oi carburizing powdered metal briquetted preform during the sintering step, or alternatively successively thereafter, and precedent to the forging step. Prior to our invention such powdered metal low alloy steel parts were first brought from a sintered preform to full density by a forging operation such as shown in U.S. Patent No. 3,772,935, owned by assignee of the present invention; and subsequently, carburized by methods conventional for wrought steels. Such conventional heat treat methods include both liquid and gas carburizing. Where gas carburizing is used, either a batch type or continuous rurnaco may bc used. The parame~crs to be controlled to , . ,.
't -1-:;~
~, ~
, Il 105;~68 achieve carburization of a fully dense part of speciflc hardness, case depth and carbon gradient are generally well kno~vn, as described, for example, ln Metals Handbook, Eighth Edition, Vol. 2, pp. 67-114, published by the American Society ior Metals.
'' SUMMARY OF THE INVENTION
Our invention is to carburize the briquette, either during slntering, or successively thereafter in a two zone operation, and before the further consolidation of the preform to fully dense condition and final . ~ ~
.,,j shape, i.e. by iorglng. The advantage oi 90 doing over the conventional carburizing techniques for any one particular part are substantial and include:
(a) the carburizing is obtained more quickly because the preiorm is at the most at only 70 to 90% of its full density, and there-~'.,,~,'1 . ' l i'ore the carbon being liberated by the carbon rich carburizing gas -i penetrates the preform more rapidly than in conventional wrought carburiz-; ing techniques;
~j~ . I
~ (b) carburizing is further hastened by reason of the fact ,j the preform case depth can be.substantially less than the required case depth of the final forged part provided one orientates the preform in the 1~ 20 forging die so that by compression and flow the case depth at the crltical ~ wall of the part ïs incrcascd.
,;' _~
liOS'~668 Additionnl ndvnnta6es accruing over thc prior art, all of which perhaps should be regarded as ancillary to the above are substantial rt-duction in capital investment for equipment, greater utillzation oi' plant space, longer carburizing equipment life, and less carburizing gas, heat and other utllities as well as less manpower, to achieve the same results as presently obtained wlth conventional methods.
.
A BRIEF DESCRIPTION OF THE DRAWINGS
- Fig. 1 shows a schematic layout of the overall process of the subject invention beginning with the step of blending and concluding wlth post-forging steps of quenching and stress reliei'.
Fig. 2 shows a cross-sectional side view of a transmission stator clutch cam manui'actured in accordance with the sub~ect invention and after i'orging, Fig. 3 shows a cross-sectional side view o~ the transmission ~ 15 stator clutch cam taken along section line A-A of Fig. 2.
`~ Fig. 4 shows an expanded side view of the sintered carburized preform in the forging die prior to forging.
~::`
DETAILED DESCRIPTION OF THE INVENTION
~eferring to Fig. 1, the inventive process includes the steps 20of blcnding 1, prcssing or briquctting 2, sintering nnd cnrburizing 3, 3', _3_ ~ 105'~668 forging 4, quenchlng 5 and stress relicving 6.
The blending step comprises blending either the alloyed me~tal powder, or a combination of metal powders which together make up the desired steel alloy powder, with graphite and die lubricant, for example acrawax. The purpose of the graphite addition is to raise the carbon content of the preform, as is well known. And the purpose of acrawax is to act as a die lubricant for the preform, as is well known. Any other equivalent additives could be added for those mentioned, The pressing or briquetting step 2 comprises pressing the blended powder lnto a low-density, semi-final shape. In the example illustrated in Flg. 4 this semi-final shape resembles a ring.
The sintering and carburizing step comprises in our preferred embodiment the simultaneous sintering and carburizing o~ the preform as ~ shown in ~tep 3, which can be re~erred to as a single furnace single zone ~ 15 operation. As an alternative, as shown in dotted lines, the sintering ? and carburizing of the preform can be accomplished in separate successive steps, shown in 3'. This process may be referred to as a single furnace two-zone operation. With either embodiment lt is contemplated one should : use a single conventional sinte ing furnace of the horizontal, continuous ~
~, . ..
-.
5'~668 feed typc equipped with the utilities and controls neccssary to provide a ca uriz1ng ~as atDospùere.
With the single furnace, single zone process 3, standard slntering conditions, namely temperature and time, sre maintained within S the ~urnace and there ls provided a carburizing gas atmosphere throughout, either within or without forced circulation of the gas, l.e. by internal fan With the single furnace, two zone, process 3', the first zone is primarily for purposes of sintering and the second zone for carburizing.
As is well known, conventional sintering $urnaces, as are contemplated for use herewith comprise a plurality of zones including, in order, a preheat zone i'or burning out lubricants and anywhere from one to three separate hot zones ior sintering depending on the choice of the operation. For purposes of describing our invention, the first zone referred to is the ~- 15 hot zone, regardless if a sintering zone, whether it Fomprises a multiple oi' zones. In such case the temperature in the i'irst zone will be in the range of 2000 F to 2080 F and the parts held a period of time sufficient to achieve the desired degree of sinter; while in the second zone the carburizing temperature will range from 1500 F to 1800 F, again depending : on the part specification, gas and other parameters.
It is also within the scope of our invention to accomplish thc sintering and carburizing step 3' ln two separate furnaces, onc for 105'~6~i8 sintering nnd the other for subsequent carburizing.
Not one of the aforementioned embodiment is considered partlcularly desirable over the other since in each case one must consider the particular part specifications to arrive at the most efficient operation. However, where close control of case depth or carbon and hardness gradient is required, it will generally be more sdvantageous to u the two zone ~lnter and carburlzlng procezz step 3'. Speclrlc examples are given hereafter.
After sintering and carburizing, the preform is forged, as shown at 4, to its final shape and then quenched 5. Forging is done at preform temperature ranging generally from 1600-1750F, The temperature oi the forged part ls then allowed to substantially stabilize before the part is quenched as shown at 5, preferably in a quenchant such as oil.
The generally preferred forge/quench process is described more fully in ~-, W,~
co-pending patent application-Ur~. Serial No. ~C~C81 assigned to the assignee of the sub~ect invention. A final step of stress relieving, shown as numeral 6, may also be desirable for particular application.
¦~ The sult i9 e fully denze, full carùurlzed powdered metal part o~ Rc60 minimum hardness on the exterior,- a hardness gradient as required, and a tough inner core for strength characteristics. The known primary application for the invention is in the production of nutomotive trnns-, -6-.' .. _ ~:
1 105;~68 mlssion parts such as the low-reverse position ovcrrunning clutch cam and l the stntor clutch cam. Additionally, gears and antifriction bearing ¦ components commonly must meet these same requirements.
¦ A typical stator clutch cam is shown in Fig. 2, wherein the ¦ race lO into which the clutch rollers ride constitutes the critical wall l surface sub~ect to wear and accordingly requires high hardness.
¦ According to a second feature of the invention, the preform is designed with an upset ratio substantially greater than one to one so , that metal flow as distinguished from metal powder densification of the prei'orm in the forging die takes place. This technique together with proper selection o~ geometry of the pre~orm in the die cavity is used to cause the metal to flow in the area oi' the critical wall thickness ~hich in turn efi'ects an increase in the desired case depth. This happening, although discovered by accldent, is used to advantage by carburizing the preform during the sintering operation to a lesser depth than required in the iinal i'orged product and making up the difference during forging.
The result is improved efficiency during the sinter-carburizing step with no loss of efficiency elsewhere in the process. It has also been determined that the metal flow itself enhances the overall strength of the forged part.
To illustrate what is meant by "upset ratio" there is shown in full lines ~n Fig. 3 the section A-A of tha forged stator clutch cam of Fig. 2.
_7_ 1~5~68 Superimposcd tllereon and shown schematically in dashed lines ls a preform p' of width b' and thickness a' in accordance with the invention and halving an upset ratio substantially greater than one to one; while shown ~, ln dotted lines ls a preform p" of width b" and thlckness a" which represents a conventional upset ratio slightly greater than one to one, Each preform p' and p" has a plan surface area designated as Ap' and Ap , repsectively, as shown in Fig. 2. The upset ratio for the example given ~ is: I
Af - Ao Ao WHEREIN: A~ is the plan area of the forged part;
,' Ao is the plan area of the part before forg-~, ing; and 1 15 WHEREIN: Ao = Ap, ¦ In pr tlce, an upget ratlo o2 generally 40% has been found to be deslrable.
An acceptabl,e upset ratio range would be 10% to 80%. Of course, in the ' example of Figs. 2 and 3 referred to, the preform height a' must be -,~, increased to such extent that the volume of preform p' is the same as that of the conventional preform p" to insure full densification. The ' conventional upset ratio is usually referred to as a tolerance of ,,;~ 1 / 1 in order to assure full densification of 99.6 - 100% of .~' _o.o , , wrought density.
A suitable conventional forging die ~s shown ln Flg. 4 wherein ''; . ., I
~ -8- ,1 l 1 105;~68 there is shown a die 20 having corc 221 a lower punch 2~ and upper punch 26.
The = er p~=ch 22 a=d die 20 de~l=e the dle cavity 28 I=to whi=h 1s placed the preform p'. The die cavity is notably of greater width than the preform as referred to above. Upon lowering of upper punch 26 with a force in the order of 60-90 tons per square inch, full consolidation is achieved.
Despite the i'act Fig. 4 is not intended to be to scale, it is intended to be shown that width s of the die cavity is greater than width b' of preform p', and that as depicted by dotted reference line r preform p' is sized or orientated with respect to die cavlty 28 such that substantially all lateral metal flow occurs between critical wall lO and the adJoining dle surface o~ core 22, , - Having described the invention generally, specific examples 15 ll nrs 1 e= here1nbslow 1= Tab1s I.
~., .
~`~
.
:~ _9_ ,, .~ ' 105;~8 T A B L E
PHYSICAL DESCRIPTION
O,D, (inches) 4,52 4,52 3,64 I,D, (inches) 3,52 3,52 2,75 HEIGHT (inches) 1,22 1,22 ,590 SPECIALS (Tooth Hrd.) I,D, AND O.D, CASE HARDENED
E.B, WELD AREA LO~V CARBON
PLAN SURFACE AREA (in, ) 6,52 6,52 4,24 SINTER (@ #/hr,) 400 400 400 ~,:
SINTERING AND CARBURIZING
CONDITIONS:
ENDOTHERMIC GAS (ft /hr) 2400 2400 2400 2400 TEMPERATURE (F) 2050+15 2050~15 1600 to 2050+15 . 1700 TIME (minutes) 30 30 10 to 20 30 DEW POINT (F) -8 to -18-5 to tO to -10 to -18 -18 ~10 NO, OF FURNAOE S ONE TWO ONE
NO. OF ZONES ONE TWO ONE
~. _ .
~ FORGE ~
., .
~` 20 PRESSURE (Tons/in, ) 70 to 90 70 to 90 70 to 9O
~- TEMP. AT FORGE ( F) 1600-1750 1600-1750 1600-1750 QUENCH ~4 to 8 sec, ~4 to 8 sec, ~4 to 8 sec, ~- dwell before dwell before dwell before quench quench quench -~ BATH COMPOSITION Park AAA Oil Park AAA Oil Park M A Oil BATH TEMPERATURE ( F) 140-180 140-180 140-180 ~:
; 25 FINAL
CHARACTERISTICS Core Hrd. Core Hrd, Core Hrd, HARDNESS. 31 to 48 Rc 31 to 48 Rc 31 to 48 Rc Surface 62 Rc Surface 62 Rc Surfnce 62 Rc CASE DEPTI{ (inches~ O.Q60 min. .090 min.
0.080 max. 0.120 max, .`~ `.
. `
- ¦ ~05~ 8 Part No. 1 wns ~ low-reverse position overrunning clutch cam and o~ the came general shape as Part No. 2, the stator clutch cam shown in Fig. 2.
As will be noted from Table 1, Part 1 was sub~ected to both a slngle furnace, single zone sintering and carburizing step and a two furnace two zone sinter-carb~rize step. While the single zone step is advantageous for acquiring conventional case depth, the two zone sinter-carburize step yields a deeper case depth without prolonging the time or elevating the temperature requlred to achieve desired degree of sinter, and more importantly allows for better control of case depth and carbon gradlent bécause the carburizlng is iinished at lower temperature.
Using conventional batch carburizing techniques, namely carburizing a$ter forging, this same part would have required 6-12 hours -~ carburizing time at a furnace temperature o~ 1650-1750F, plus an additional two hours diffusion at lower temperature.
During forging of Part No. 2, the required case depth for C> . C~ ~ O
wear surface 10 was e~ffrinches. The preform a', b' was carburized to a .;~ o c~ o, o 6~
~; case depth of 0.10 inches minimum and the increase to O.C0 inches minimum ~` was achieved by forging using an upset ratio of 40%.
While the invention has been described in connection with a pre~erred embodiment and specific examples thereof, it is not intended to '' '" -11-' , "
I 105'~668 llmit thc inventlon to any pnrticulnr form set forth, but, on the contrary, it ls intended to cover such alternatives, modifications and equivalents as may be lncluded ~vithin the spirit and scope oi' the lnvention as defined by the appended claims.
BACKGROUND OF THE INVENTION
This invention relates generally to an improved method of obtaining fully dense, carburized, powdered metal, low alloy steel parts, the most common of which are the powdered metal equivalents of AISI 4000 and 4600 wrought steel series and particularly those having sintered carbon levels in the range of 0.22% to 0.37% by weight. More specifically, this invention is related to the improved method oi carburizing powdered metal briquetted preform during the sintering step, or alternatively successively thereafter, and precedent to the forging step. Prior to our invention such powdered metal low alloy steel parts were first brought from a sintered preform to full density by a forging operation such as shown in U.S. Patent No. 3,772,935, owned by assignee of the present invention; and subsequently, carburized by methods conventional for wrought steels. Such conventional heat treat methods include both liquid and gas carburizing. Where gas carburizing is used, either a batch type or continuous rurnaco may bc used. The parame~crs to be controlled to , . ,.
't -1-:;~
~, ~
, Il 105;~68 achieve carburization of a fully dense part of speciflc hardness, case depth and carbon gradient are generally well kno~vn, as described, for example, ln Metals Handbook, Eighth Edition, Vol. 2, pp. 67-114, published by the American Society ior Metals.
'' SUMMARY OF THE INVENTION
Our invention is to carburize the briquette, either during slntering, or successively thereafter in a two zone operation, and before the further consolidation of the preform to fully dense condition and final . ~ ~
.,,j shape, i.e. by iorglng. The advantage oi 90 doing over the conventional carburizing techniques for any one particular part are substantial and include:
(a) the carburizing is obtained more quickly because the preiorm is at the most at only 70 to 90% of its full density, and there-~'.,,~,'1 . ' l i'ore the carbon being liberated by the carbon rich carburizing gas -i penetrates the preform more rapidly than in conventional wrought carburiz-; ing techniques;
~j~ . I
~ (b) carburizing is further hastened by reason of the fact ,j the preform case depth can be.substantially less than the required case depth of the final forged part provided one orientates the preform in the 1~ 20 forging die so that by compression and flow the case depth at the crltical ~ wall of the part ïs incrcascd.
,;' _~
liOS'~668 Additionnl ndvnnta6es accruing over thc prior art, all of which perhaps should be regarded as ancillary to the above are substantial rt-duction in capital investment for equipment, greater utillzation oi' plant space, longer carburizing equipment life, and less carburizing gas, heat and other utllities as well as less manpower, to achieve the same results as presently obtained wlth conventional methods.
.
A BRIEF DESCRIPTION OF THE DRAWINGS
- Fig. 1 shows a schematic layout of the overall process of the subject invention beginning with the step of blending and concluding wlth post-forging steps of quenching and stress reliei'.
Fig. 2 shows a cross-sectional side view of a transmission stator clutch cam manui'actured in accordance with the sub~ect invention and after i'orging, Fig. 3 shows a cross-sectional side view o~ the transmission ~ 15 stator clutch cam taken along section line A-A of Fig. 2.
`~ Fig. 4 shows an expanded side view of the sintered carburized preform in the forging die prior to forging.
~::`
DETAILED DESCRIPTION OF THE INVENTION
~eferring to Fig. 1, the inventive process includes the steps 20of blcnding 1, prcssing or briquctting 2, sintering nnd cnrburizing 3, 3', _3_ ~ 105'~668 forging 4, quenchlng 5 and stress relicving 6.
The blending step comprises blending either the alloyed me~tal powder, or a combination of metal powders which together make up the desired steel alloy powder, with graphite and die lubricant, for example acrawax. The purpose of the graphite addition is to raise the carbon content of the preform, as is well known. And the purpose of acrawax is to act as a die lubricant for the preform, as is well known. Any other equivalent additives could be added for those mentioned, The pressing or briquetting step 2 comprises pressing the blended powder lnto a low-density, semi-final shape. In the example illustrated in Flg. 4 this semi-final shape resembles a ring.
The sintering and carburizing step comprises in our preferred embodiment the simultaneous sintering and carburizing o~ the preform as ~ shown in ~tep 3, which can be re~erred to as a single furnace single zone ~ 15 operation. As an alternative, as shown in dotted lines, the sintering ? and carburizing of the preform can be accomplished in separate successive steps, shown in 3'. This process may be referred to as a single furnace two-zone operation. With either embodiment lt is contemplated one should : use a single conventional sinte ing furnace of the horizontal, continuous ~
~, . ..
-.
5'~668 feed typc equipped with the utilities and controls neccssary to provide a ca uriz1ng ~as atDospùere.
With the single furnace, single zone process 3, standard slntering conditions, namely temperature and time, sre maintained within S the ~urnace and there ls provided a carburizing gas atmosphere throughout, either within or without forced circulation of the gas, l.e. by internal fan With the single furnace, two zone, process 3', the first zone is primarily for purposes of sintering and the second zone for carburizing.
As is well known, conventional sintering $urnaces, as are contemplated for use herewith comprise a plurality of zones including, in order, a preheat zone i'or burning out lubricants and anywhere from one to three separate hot zones ior sintering depending on the choice of the operation. For purposes of describing our invention, the first zone referred to is the ~- 15 hot zone, regardless if a sintering zone, whether it Fomprises a multiple oi' zones. In such case the temperature in the i'irst zone will be in the range of 2000 F to 2080 F and the parts held a period of time sufficient to achieve the desired degree of sinter; while in the second zone the carburizing temperature will range from 1500 F to 1800 F, again depending : on the part specification, gas and other parameters.
It is also within the scope of our invention to accomplish thc sintering and carburizing step 3' ln two separate furnaces, onc for 105'~6~i8 sintering nnd the other for subsequent carburizing.
Not one of the aforementioned embodiment is considered partlcularly desirable over the other since in each case one must consider the particular part specifications to arrive at the most efficient operation. However, where close control of case depth or carbon and hardness gradient is required, it will generally be more sdvantageous to u the two zone ~lnter and carburlzlng procezz step 3'. Speclrlc examples are given hereafter.
After sintering and carburizing, the preform is forged, as shown at 4, to its final shape and then quenched 5. Forging is done at preform temperature ranging generally from 1600-1750F, The temperature oi the forged part ls then allowed to substantially stabilize before the part is quenched as shown at 5, preferably in a quenchant such as oil.
The generally preferred forge/quench process is described more fully in ~-, W,~
co-pending patent application-Ur~. Serial No. ~C~C81 assigned to the assignee of the sub~ect invention. A final step of stress relieving, shown as numeral 6, may also be desirable for particular application.
¦~ The sult i9 e fully denze, full carùurlzed powdered metal part o~ Rc60 minimum hardness on the exterior,- a hardness gradient as required, and a tough inner core for strength characteristics. The known primary application for the invention is in the production of nutomotive trnns-, -6-.' .. _ ~:
1 105;~68 mlssion parts such as the low-reverse position ovcrrunning clutch cam and l the stntor clutch cam. Additionally, gears and antifriction bearing ¦ components commonly must meet these same requirements.
¦ A typical stator clutch cam is shown in Fig. 2, wherein the ¦ race lO into which the clutch rollers ride constitutes the critical wall l surface sub~ect to wear and accordingly requires high hardness.
¦ According to a second feature of the invention, the preform is designed with an upset ratio substantially greater than one to one so , that metal flow as distinguished from metal powder densification of the prei'orm in the forging die takes place. This technique together with proper selection o~ geometry of the pre~orm in the die cavity is used to cause the metal to flow in the area oi' the critical wall thickness ~hich in turn efi'ects an increase in the desired case depth. This happening, although discovered by accldent, is used to advantage by carburizing the preform during the sintering operation to a lesser depth than required in the iinal i'orged product and making up the difference during forging.
The result is improved efficiency during the sinter-carburizing step with no loss of efficiency elsewhere in the process. It has also been determined that the metal flow itself enhances the overall strength of the forged part.
To illustrate what is meant by "upset ratio" there is shown in full lines ~n Fig. 3 the section A-A of tha forged stator clutch cam of Fig. 2.
_7_ 1~5~68 Superimposcd tllereon and shown schematically in dashed lines ls a preform p' of width b' and thickness a' in accordance with the invention and halving an upset ratio substantially greater than one to one; while shown ~, ln dotted lines ls a preform p" of width b" and thlckness a" which represents a conventional upset ratio slightly greater than one to one, Each preform p' and p" has a plan surface area designated as Ap' and Ap , repsectively, as shown in Fig. 2. The upset ratio for the example given ~ is: I
Af - Ao Ao WHEREIN: A~ is the plan area of the forged part;
,' Ao is the plan area of the part before forg-~, ing; and 1 15 WHEREIN: Ao = Ap, ¦ In pr tlce, an upget ratlo o2 generally 40% has been found to be deslrable.
An acceptabl,e upset ratio range would be 10% to 80%. Of course, in the ' example of Figs. 2 and 3 referred to, the preform height a' must be -,~, increased to such extent that the volume of preform p' is the same as that of the conventional preform p" to insure full densification. The ' conventional upset ratio is usually referred to as a tolerance of ,,;~ 1 / 1 in order to assure full densification of 99.6 - 100% of .~' _o.o , , wrought density.
A suitable conventional forging die ~s shown ln Flg. 4 wherein ''; . ., I
~ -8- ,1 l 1 105;~68 there is shown a die 20 having corc 221 a lower punch 2~ and upper punch 26.
The = er p~=ch 22 a=d die 20 de~l=e the dle cavity 28 I=to whi=h 1s placed the preform p'. The die cavity is notably of greater width than the preform as referred to above. Upon lowering of upper punch 26 with a force in the order of 60-90 tons per square inch, full consolidation is achieved.
Despite the i'act Fig. 4 is not intended to be to scale, it is intended to be shown that width s of the die cavity is greater than width b' of preform p', and that as depicted by dotted reference line r preform p' is sized or orientated with respect to die cavlty 28 such that substantially all lateral metal flow occurs between critical wall lO and the adJoining dle surface o~ core 22, , - Having described the invention generally, specific examples 15 ll nrs 1 e= here1nbslow 1= Tab1s I.
~., .
~`~
.
:~ _9_ ,, .~ ' 105;~8 T A B L E
PHYSICAL DESCRIPTION
O,D, (inches) 4,52 4,52 3,64 I,D, (inches) 3,52 3,52 2,75 HEIGHT (inches) 1,22 1,22 ,590 SPECIALS (Tooth Hrd.) I,D, AND O.D, CASE HARDENED
E.B, WELD AREA LO~V CARBON
PLAN SURFACE AREA (in, ) 6,52 6,52 4,24 SINTER (@ #/hr,) 400 400 400 ~,:
SINTERING AND CARBURIZING
CONDITIONS:
ENDOTHERMIC GAS (ft /hr) 2400 2400 2400 2400 TEMPERATURE (F) 2050+15 2050~15 1600 to 2050+15 . 1700 TIME (minutes) 30 30 10 to 20 30 DEW POINT (F) -8 to -18-5 to tO to -10 to -18 -18 ~10 NO, OF FURNAOE S ONE TWO ONE
NO. OF ZONES ONE TWO ONE
~. _ .
~ FORGE ~
., .
~` 20 PRESSURE (Tons/in, ) 70 to 90 70 to 90 70 to 9O
~- TEMP. AT FORGE ( F) 1600-1750 1600-1750 1600-1750 QUENCH ~4 to 8 sec, ~4 to 8 sec, ~4 to 8 sec, ~- dwell before dwell before dwell before quench quench quench -~ BATH COMPOSITION Park AAA Oil Park AAA Oil Park M A Oil BATH TEMPERATURE ( F) 140-180 140-180 140-180 ~:
; 25 FINAL
CHARACTERISTICS Core Hrd. Core Hrd, Core Hrd, HARDNESS. 31 to 48 Rc 31 to 48 Rc 31 to 48 Rc Surface 62 Rc Surface 62 Rc Surfnce 62 Rc CASE DEPTI{ (inches~ O.Q60 min. .090 min.
0.080 max. 0.120 max, .`~ `.
. `
- ¦ ~05~ 8 Part No. 1 wns ~ low-reverse position overrunning clutch cam and o~ the came general shape as Part No. 2, the stator clutch cam shown in Fig. 2.
As will be noted from Table 1, Part 1 was sub~ected to both a slngle furnace, single zone sintering and carburizing step and a two furnace two zone sinter-carb~rize step. While the single zone step is advantageous for acquiring conventional case depth, the two zone sinter-carburize step yields a deeper case depth without prolonging the time or elevating the temperature requlred to achieve desired degree of sinter, and more importantly allows for better control of case depth and carbon gradlent bécause the carburizlng is iinished at lower temperature.
Using conventional batch carburizing techniques, namely carburizing a$ter forging, this same part would have required 6-12 hours -~ carburizing time at a furnace temperature o~ 1650-1750F, plus an additional two hours diffusion at lower temperature.
During forging of Part No. 2, the required case depth for C> . C~ ~ O
wear surface 10 was e~ffrinches. The preform a', b' was carburized to a .;~ o c~ o, o 6~
~; case depth of 0.10 inches minimum and the increase to O.C0 inches minimum ~` was achieved by forging using an upset ratio of 40%.
While the invention has been described in connection with a pre~erred embodiment and specific examples thereof, it is not intended to '' '" -11-' , "
I 105'~668 llmit thc inventlon to any pnrticulnr form set forth, but, on the contrary, it ls intended to cover such alternatives, modifications and equivalents as may be lncluded ~vithin the spirit and scope oi' the lnvention as defined by the appended claims.
Claims (6)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for obtaining a substantially fully dense, carburized, low alloy ferrous, powdered metal part comprising the sequential steps of:
a) briquetting a low alloy ferrous metal powder preform having a fixed uniform initial carbon content throughout both the case and inner core thereof, the briquetted preform having at least one surface thereof which in the final forged form is required to be of a certain case depth, b) sintering said preform at a temperature from 2000-2100°F, c) carburizing said preform to substantially increase the initial carbon content thereof in said case by providing a controlled carbon atmosphere of rich endothermic gas and maintaining said preform in said controlled atmosphere for a predetermined period of time sufficient to obtain a desired case depth of final carbon content substantially greater than said initial carbon content of the case as well as the final carbon content of said inner core, d) forging said preform at a temperature range from about 1600°F to about 1750°F to a density of 99.6% to 100% that of wrought density to obtain a forged part, e) cooling said forged part by quenching to thereby obtain a desired case depth.
a) briquetting a low alloy ferrous metal powder preform having a fixed uniform initial carbon content throughout both the case and inner core thereof, the briquetted preform having at least one surface thereof which in the final forged form is required to be of a certain case depth, b) sintering said preform at a temperature from 2000-2100°F, c) carburizing said preform to substantially increase the initial carbon content thereof in said case by providing a controlled carbon atmosphere of rich endothermic gas and maintaining said preform in said controlled atmosphere for a predetermined period of time sufficient to obtain a desired case depth of final carbon content substantially greater than said initial carbon content of the case as well as the final carbon content of said inner core, d) forging said preform at a temperature range from about 1600°F to about 1750°F to a density of 99.6% to 100% that of wrought density to obtain a forged part, e) cooling said forged part by quenching to thereby obtain a desired case depth.
2. A process as defined in claim 1 wherein the said forged part is cooled by quenching in an oil bath substantially immediately after forging but not until the temperature thereof has been allowed to substantially stabilize.
3. A process as defined in claim 1 wherein the upset ratio of said preform at said one surface is in the range of 10% to 80%
including selecting the geometry of said preform relative to the foregoing die cavity and orientating the preform within said die cavity so that during forging the metal flows in the area of critical wear surface to thereby increase the case depth of the preform.
including selecting the geometry of said preform relative to the foregoing die cavity and orientating the preform within said die cavity so that during forging the metal flows in the area of critical wear surface to thereby increase the case depth of the preform.
4. A process for obtaining a substantially fully dense, carburized, low alloy ferrous, powdered metal part comprising the steps of:
a) forming a briquetted preform, the briquetted preform having at least one surface thereof which in the final forged form is required to be of a certain case depth and wherein the upset ratio of said preform at said critical wear surface is greater than 10% and in the order of 40%.
b) sintering said preform at a temperature from 2000-2100°F, c) simultaneously, during sintering, carburizing said preform by providing a controlled carbon atmosphere of endothermic gas and maintaining said preform in said controlled atmosphere for a predetermined period of time in the range of 20 to 40 minutes to obtain a desired case depth, d) thereafter maintaining said preform in substantially the same atmosphere at a reduced temperature of from 1500-1750°F for a further period of time in the range of 7 to 25 minutes to acquire a deeper, more controlled case depth, e) forging said preform at a temperature ranging from 1600-1750°F, including selecting the geometry of the said preform relative to the forging die cavity and orientating the preform within said die cavity so that the metal flows in the area of said one surface to thereby increase the case depth of the preform, f) cooling said preform by quenching in an oil bath substantially immediately after forging but not until the temperature thereof has been allowed to substantially stabilize.
a) forming a briquetted preform, the briquetted preform having at least one surface thereof which in the final forged form is required to be of a certain case depth and wherein the upset ratio of said preform at said critical wear surface is greater than 10% and in the order of 40%.
b) sintering said preform at a temperature from 2000-2100°F, c) simultaneously, during sintering, carburizing said preform by providing a controlled carbon atmosphere of endothermic gas and maintaining said preform in said controlled atmosphere for a predetermined period of time in the range of 20 to 40 minutes to obtain a desired case depth, d) thereafter maintaining said preform in substantially the same atmosphere at a reduced temperature of from 1500-1750°F for a further period of time in the range of 7 to 25 minutes to acquire a deeper, more controlled case depth, e) forging said preform at a temperature ranging from 1600-1750°F, including selecting the geometry of the said preform relative to the forging die cavity and orientating the preform within said die cavity so that the metal flows in the area of said one surface to thereby increase the case depth of the preform, f) cooling said preform by quenching in an oil bath substantially immediately after forging but not until the temperature thereof has been allowed to substantially stabilize.
5. A process as defined in claim 1 wherein, the fixed uniform initial carbon content of said preform is less than 0.22% by weight and wherein the final carbon content is in the range of 0.22% to 0.37% by weight and to a desired case depth ranging from 0.060 inches to 0.120 inches.
6. A process as defined in claim 5 wherein, said forged part is quenched in an oil bath immediately after forging and substantial temperature stablilization of the forged part.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA259,720A CA1052668A (en) | 1976-08-24 | 1976-08-24 | Method of making powdered metal parts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA259,720A CA1052668A (en) | 1976-08-24 | 1976-08-24 | Method of making powdered metal parts |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052668A true CA1052668A (en) | 1979-04-17 |
Family
ID=4106715
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA259,720A Expired CA1052668A (en) | 1976-08-24 | 1976-08-24 | Method of making powdered metal parts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1052668A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020210045A1 (en) * | 2019-04-12 | 2020-10-15 | Gkn Sinter Metals, Llc | Variable diffusion carburizing method |
-
1976
- 1976-08-24 CA CA259,720A patent/CA1052668A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020210045A1 (en) * | 2019-04-12 | 2020-10-15 | Gkn Sinter Metals, Llc | Variable diffusion carburizing method |
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