Note: Descriptions are shown in the official language in which they were submitted.
~S3L758
The invention relates to the manufacture of circular
workpieces, more precisely to the manufacture of circular work-
pieces from hypereutec-toid steel, forming after hardening or
quenching a martensite of low carbon content with a dislocation
substructure. The process permits for instance the manuEacture
of rings for antifriction bearings,from rings prepared from
hollow ingots, the surface of which has been cleaned from
slack and other impurities.
Centrifugal casting, that is casting of metal into
a quickly rotating ingot mould on a centrifugal casting device
with a vertical or horizontal rotation axis is frequently used
in modern casting practice. The rotation speed is thereby
determined by the kind of metal and by the speed of cooling,
whether a temporary sand mould or a permanent metal mould is
used. This method is applied for manufacture of products of the
shape or solids of rotation from special steels, of tubes,
sleeves, rings and mass manufactured smaller objects. The
utilization of the molten metal is very good as no shrinkage
cavities and few segregates are formed, which are by the
centrifugal force brought to the surface of the molten metal.
This advantage has, particularly for steels, an economic
signiflcance.
This process has been elaborated in detail for
different applications. For manufacture of hollow circular
work~ieces from centrifugally cast tubes, at first parts are cut
off, the width of which corresponds to the width of the final
product and which parts are subsequently formed by forgin~ or
rolling to the required shape. Semiproducts of rings of anti-
friction bearings are formed immediately after removal from the
mould of a centrifugal casting device at temperatures of 1050
to 900 C. Hollow circular workpieces are formed from centrifugally
cast hollow solids of rotation, for instance ingots or bodies of
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different shape, from which tubes are formed which are cut to
smaller parts. These smaller parts are subsequently worked
by rolling, ~orging or upsetting, after machining they are heat
treated and finished after achieving the optimum hardness.
~ 11 these processes proved to be rather efficient
manufacturing methods, enabling due to the direct manufacture
of semiproducts by centrifugal casting and by eliminating
intermediate semiproducts relatively high savings of material.
They have however a common drawback in that the heat supplied
into the steel in the course of melting is not fully utilized
during forming and further heat treatment. Consequently
additional heat has to be supplied to -the processed products
for further working processes accomplished at higher than
normal temperatures.
It proved therefore to~be useful and advantageous
to attempt to provide a manufacturing method of objects of
the shape of solids of rotation by centrifugal casting without
drawbacks of actually known processes and where particularly
the heat supplied originally for melting steel would be utilized
~to the highest degree.
According to the present invention, there is
provided a process for the manufacture of circular workpieces
from hypereutectoid steel forming after quenching or hardening
low carbon martensite with a dislocation substructure, or ins-
tance for manufacture of bearing rings, the process consisting
in the preparation of ring shaped semiproducts by centrifugal
casting, cleaning of these semiproducts from layers of slag and
other impurities, cooling these rings from the casting temperature
to a temperature at the maximum 100 C below the temperature of
eutectoid change of the structure of this steel, again heated
to a temperature at the maximum 100 C above the temperature of
eutectoid changej whereafter after obtaining a structure of
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spheroidized perlite, the temperature is raised to a value at
the maximum 1150 C the semiproduct is formed, thereafter ~uenched
and tempered.
The at-tached drawing shows schematically the
changes of temperature of the workpiece in the course of treatment
from casting up to tempering, drawn against time, if the
process according to this invention is applied.
Fig. 1 shows the course of temperature where the
forming process proceeds above the temperature of the eutectoid
change of steel, Fig. 2 this course, where this forming process
proceeds below the temperature of the eutectoid change of steel
after quick cooling.
According to this lnvention rings obtained by
centrifugal _ _ 7
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ca~ting or by cutt~ng of os:nt~fugally ca~t; hollow lngot~ ar~
cooled from the oa~ting tela~erature to a temperature at the
max:l~um 100~ ~ belo~ the temperature oî eutectoid ~ha~ge ol
~3toel9 srhex~a~ter they are additio~3.ally heated to a temperature
at the maximum 100 C h~gh~r tha~ the temperature of eutecto;Ld
cha~ge o~ ~tael with a ~ub~o~u~nt inerea~ of the temperature
a:Eter a~hie~ing a ~truoture of spheroidi~ed p~rlit~ at the
m~mum to 1150 ~59 ~herea~tel~ the semiproduet i~ ~ormed for
i~sta;nc~ by rol~ a~d th~n q~ oh~d a~d temp~red (~e~ FLgo l~o
Prior to cooling îrom th~ oa~ti~ telup~ture up to
a temperat~ra ma~um 100~ C below the te~perature u~ th~
euteotoid ~ f ~te~l~ the ~urfao~ o~ th~ ri~ iL5 ole~l~a
i~rom ~lag ~d othar impuritie~ on the ~urfaoe for ~tan~a by
machi~ng. Pxior to fo~g,~ p~ti~ularl~ ~rior to roll~g"
the ri:ngs are heated to a tem~erature ~f ma~mum 1~0 C~ ~here~
after thsy ea~ be oooled at a ~peed o~ cooling at lea~t 5~ e
pcr ~e~nd to a temperatur~ a r~ge betaee:ll ~e t2mper~
ture of the eutl3ctotd cha~ge a~ad the ma:rte~ite ~tart temp~ra~
ture (~ee Fi~ 2)~,
~he ~e~tion i~3 ba~ed o~ the ~a~ that in comparl~on
with krlo~m method~ it i~ pos~ible to util~e ~ox~ eeotivel~r
the heat ~pplied during t~he Dle~ g proce~s al~o ~or the
eub~equ~nt ~orm~g a;~d heat treatlaellt of ths ~at~Lal" ~o ~at
~he~ ~u;Eaot~ring ~om~ laxe~ bodle~ o:E ~he ~h~pe oî ~olid~ o.
rotatio~ suGh a~ beari2~ of large dimeII~io~ fox rolli~
b~a~ng~ e heat o~ce ~upplied i~ ioi~nt almo~t ~or the
~hole ma~u~aot~1~g p:roce~" The ~u~a~tw~e o~ beari2lg r~g~
o~ ~ller diameter~ require~ ~olely ~ome D~ or additlo~al
heat~e Of the ~a~9rial ~ he le~el o~ lsorld~g t~;peà~ture~0
3o When ma:nu~a~t~ing produot~ acoording to thi~
b~o~ the pXOCe~B CO~l~iBt~ ge~erallg ln tha~ Irom a pxior
olea~cd sbeel!i, cl~an~d ~or insba~e by m~lti~g ~ lr~cuum or
~ 3 ~
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~L~5~75i8
eleotro slag remelting ~lag or i~ 30 ~ome other fllay9 ~ngot~ o~
rotatio~al~ ~or i~ta~c~ cylind:~oal
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shape are centri~ugally cast. Ixl ~he course oî their pa~tial
cooling to a temperature oî eutect~ild change of the used steel,
or possibly to a temperature which i.s maximum 100 C below thi~
temperature o~OEute¢toid change9 the ingots are di~ided to rings,
from which all slag layers or other impuritie~ are remoYed. After
cooling the rings to the ~emperature~ o~eute¢to~dchange~ or to a
temperature at the maximum 100 C lower, the rings ar~ heated to
a temperature at the maximum 100~ C higher tha~ the temperature
o~eutectoidchange ~ whereby they are spheroidiz~d and a~ter a
new heating to a temperature at the maximum ~150 C they are for~
med by a sultable proceæs, ~or instance b~ rolling.
According to ~nother working proceæs the rin~ heated to
maximally 1150 C are cooled to a temperature betweerl the tempexa-
ture of sutectoidch~e OI steel ~d the martensite start tem~
perature (MS ), is *ormed, que~ched alld temperedO
The process of manu:~acturi~ oï products of ~iroular
rotatio~ shape ~rom centri~ cast ssmiprodu~ts c~ be ad-
vantageously applied ~ot o~y ~or manufacture of bearing rings,
but equally of rings ~or bandagi~g oî rotor~ o~ steam engines9 o~
20 tyres îs~ rail ~F~hicles for in~3tance îor railways, o:E t~othed gear
r~ and ~;imilarO
Ad~ tages OI this solution ~re obvious ~rom the fol--
lowing e~cample~ which should ser~re to explain more clearly the
mai~ ~eature~ o~ the in~re~tio~ without howeYer limiti~g it to
a~y degree .
Example.,
Steel o~ a chemical oomposition o:~ 0~7 to 0~,8 percent
by welght o~ ca:rbon, 2 parce~t by weight o~ ga~e~e~ 2 percent
by weight o~ ~ilicon, 1 percent by wsight o~ chromium ~d up to
30 0.03 perce~t by weight of phoæphor ~d sulphur~ the ramaining
sub~tanti~ i ron~ i~ prepared according to some ~teel manufao-
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7S8turing pDocess in an electrio arc :eur~ace~ The steel is cast in-
to a rotatixlg ingot mould, rotating with a spe~d of 8~0 t~ns per
mi~ute around a ho~i~ontal rotation axi~ and left to crystallize~.
~he thus obta~ned hollow ingot of a weight about 3 metric tonæ9
of an external diameter about 380 mm ~d a length oî 4, 400 mm ia
still hot removed from.the mould ancl divided by a rotating saw
to 24 rings. ~h~ rings are allowed to cool belo1lv the temperature
o~ theeute~toidchage9 again heated to 760 C whereby a spheroi-
dizatlon o~ the perlitic cementite proceed~0 The spheroidi~ed
parts are agai~ heated to 820 C9 rolled on a malldrel between the
m~drel and a rolling disc to îorm products whih roughly corres-
pond by their shape to a~ intsrnal and exterllal ring o~ a bearirlg
o~ type 23080. Immsdiately a~ter rolling9 which is :e nished at
the tempexatu~e of 800 ~ C " the material is quenched in an oil bath.
After quenohi~g ~he material is tempered îor 3 hours at a t~pera-
ture of 170 C, the produot Pinished by machining~ th~ ~indiDg
ineluded.
By thi~ process mentior~ed as example~ the time of` wor-
king is substantially reduced against curren;tly used proce~ses,
as the coarse rolling o~ the irgot is eliminated, the same as its
dividing~ upsetting~ pi:ercing, ~orging of the rin~g with a time
~aving about 12 hours~, The tqorki~ t~me~ for machi~ing a~e ~qual;
ly reducad by 205 minutes. ~he ov~rall time ~a~ g is ther~by
about 15 hours ~or one bearillg. ~ addition about 50 peroent by
w~ight o~ liquid i~lgOt steel i~ sav~dO ~he propertie~ o~ th~
prepa;red i~got ~re improved îor about 15 peresnt, cal~ulatad ao~
cording to the actual ætate o~ technology.
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