MANUFACTURE OF TURBINE BLADE BLANKS BY THE EXTRUSION METHOD

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82-00039R000100250004-0
• Release Decision: RIPPUB
• Original Classification: R
• Document Page Count: 20
• Document Creation Date: December 22, 2016
• Document Release Date: March 15, 2012
• Sequence Number: 4
• Publication Date: March 26, 1952
• Content Type: REPORT

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STAT
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STAT
M U''lUFACTURE OF TURBINE BIL.DE BLANKS
BY THE EXTRUSION METHOD
Ye P. Unksov, Candidate
in Technical Sciences
N. Batagov, Candidate
in Technical Sciences
(The follow`i.ng persons have participated in this work;
Chief Engineer II. I. Kagan, Engineers S. M. Sergeye
and P. A. Korshok, and Designer G. N. Alekseye)
INTRODUCTION
At turbine plants of the Soviet Union, turbine blades of con
scant-Length cross-section and greater stem cross-section area than
working cross-section area are usually manufactured by the following
methods;
1. By machining out a bar, the length of which is equal to
the length of the blade (and stem), with transverse dimensions car
responcsng to the cross-section dimensions of the working portions
of the blade and stem.
Machining by cutting from drop forged blanks.
3, By the so-called +lintegra? " rolling with subsequent
machining by cutting.
The first method (most universal) is characterized by the
utilization of a considerable quantity of metal-cutting equipment
and comparatively low efficiency, and results in considerable waste
of alloy steels, since wastage in chips for certain blade configura~
tions reaches 200-300 percent of the weight of a finished blade.
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The second method is more economical and efficient. How
ever, allowances for machining in drop hammer forging are usually
aui.te large, with small durability of stampings and their high
a
relative cost. Besides, the surface of stamped products is fre~
quently of low quality due to impressed slag. The use of a sub-
Sequent cold calking process has not yet received widespread ac-
ceptance by turbine plants in view of its unprofitableness in the
small scale nature of turbine production; therefore, drop forging
of turbine blade blanks with subsequent machining by cutting is
united only to blades of large dimensions (more than 2~O-300
millimeters long) ,
Integral rolling is an advanced process. However, the
rolling of short blades on cylindrical rollers entails the labor-
consuming process of making a special tool. Rapidly developing
domestic turbine-building requires the utilization of more ecoM
nomical and efficient technological processes of turbine blade
manufacture. Such a process is the hereinbelow described new
technological process of manufacture of blade blanks having a
constant length working cross-section, which permits the reduction
of natal losses, and speeds up the mechanical machining of blades.
The process involves the direct extrusion of blade blanks with a
minimum allowance for mechanical macbi.ning. The stern of the blade
of rec uired shape can be made out of the remai?ing metal.
Blanks are extruded on standard forge-pressing equipment
(friction, crank, or hydraulic presses, horizontal forging machines).
The die is of simple design and can be made on the usual metal-cutting
machine tools.
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The technological process of extrusion was developed and
tested in application to four types of blades having constant.-
lerigth working portion profiles. The first type are blades with
stems 1thin the working cross-section profile (Figure 1, a, b, c).
Figure 1, Blades with stems within the working cross-
section profile. Type one.
Types two and three are blades with sterns of complex
shape (Figure 2) e
Type 24. are blades with rectangular shaped stems (Figure 3).
Blades of the first type, with profiles of 3 different dimensions
were made of brass, similar in chemical composition and mecnanicai.
characteristics to Grade LS 59-1.
Figure 2. Blades with stems of complex shaper Types 2 and
3. On Figure iT there are shown blade blanks of the first type made
'ail extrusion. (The process o? extrusion permits the production of
very long blanks, The length of the depicted blanks was limited,
during the experiment, by power of the equipment),
In making tile blades of to second, third and fourth types
he fol:! owing grades of carbon, stain.Less and heat-resistant steels
were used; 50, u7, u8, 12Kh14A, 13KhlI~.A, EI-69 and Armco iron, In
Figure 5 there are shown extruded blade blanks of the fourth ty- e~
Figure 3. Blade with the rectangular shaped stem. Type four,
MA.NUFACTUIED PRODUCTS
Figure L. Shapes of blade blanks of the first type,
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Figure 5. Shapes of blade blanks of the fourth type
2. EXTRUSIOI`T DIES
The basic requirements of. extrusion die design are sirnpl
of rnanuf acture, ensuring of min~.rnum tolerances and allowances
city
for the size of the product, elimination of the effect of die
chamfer on the precision of the manufactured product, and the possi~
blla.ty of replacement of the most rapidly wearing parts, such as the
die matrices.
For the purposes of maximum universaJ.ity and simplicity of
production of blade blanks of the first and fourth types, layer
extrusion dies were designed and manufactured which permit the
performance of extrusion on the usual forging presses, friction,
hydraulic or r?tecianical.
Figure a is shown the general view of the layer-type ex-
on dies for a blade of type L. Into the housing (1) there
truss.
are pressed in dies 2 and 3 to effect the intimate contact of the
die surfaces, constant restriction of working recesses and precise
guiding of vile punch. Die 3 has only one projection which :Forms the
groove of the worldng portion of the blade. Die 2 has a groove
corresponding in size and shape (considering minimum ailoances) to
the dimensions of the stern and back portion of the blade.
Figure b. General view of the layer extrusion die for
blades of type 1;.: i 4Iousing. 2,3-Dies. lvpunch.
Figure 7. General view of extrusion die for blades of
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types 3 and, L. l-Punch; 2-Upper die, 3-Lower die; L>-inter
~
mediate insert; Housing; 6--Blade blank
For bl d.es of types 2 and 3 there has been manu-
factured and tested a highly efficient extrusion die
r,
('EP -j
1 The extrU.sion die is efficient in the case of
~tre t, . ~
exact fit of the sliding surfaces) The u~ricn (1) is fi'cd
- _
in the P, u d id~_nM slide and has a ro jectiort. for piesb.inthe
.,, ~tra ,,
b1 de blank the e, trusion die on the return stroke of
L out of the ProductiVity of the extr Sion die is deteITrlined
~IPS~.s,
by c %)er of press strokes corrected by the coefficienthe Ztur>,
of atil.~ltian, which depends on the shop-sp~Lce arrail;erie1 b.
.~z ~
Great attention in the design of the e;ruSiOfl die
hrni7.a be de1roted. to the choice of the die PJte material
and its shape. Correctly chosen die pte steel and proper
reati tent ensure the successf 7.l extrusion of a la rge
ti1eLlcal t
nurnoer of blades. ~l'he sane consi deratio~zs are eually ap~
? o the punch materia7_, although decrease in its size,
olicaolc t ~
due to the weari..il out of its pressare portion, does not affect
d.imensiona of the ~rorking proi:i.le of the
the cross-sccti0a1al
1)l.dc, and ~d olil fesulLS in the increase of tiie size of the
chamfer and increased extru.sian stress. The die p~! to
a should be war-res1st3.u1 t 1i(1 ca )able of Sri thstandin
ma ter: L l
' ~ a riable tcmpera,tures and ~)ress~.~res during the extrusion
11.'t1 V 1.
process. l'ocess. Quality of the Working, surfaCes of tie die plates
hardness shauld not change appreciably th time.
and their
he die ).plate and its interior should not exhibit
The S1Lrf~Ce of t
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-ams of Cracks due to thermal treatment, l+oi n1ate ials
any s1 ,~t
o~, die plates used. in hot extras o11 of compliCS.ted pro~'i1es, ac-
m technical sources, the failoWing steels
cording 4~
to certain
listed in rpa-)le 1 are recommended.
TABLE 1
GompoSitiOIB of Tools for Hot Extrusion of Coiilple x profiles
Steel
Chemical Compositioll
Country
~St
U
G! R. ir111Y
C. x
0,30
aIn Cr Ni W V Cu
0,20 2,2
rl.L~. 1O ~ 11.3i r.1!.
J ~o
V
C-7
0
0.03 0.03
0.22
0?30 0?30 0o21. 2.05 11.1 0.2 0.3 0.03 0.03
I
_ -_ .... .......... .. .... ... 0 03 0 0~
3 0 00 9.7 , 3 . , 5 . lJ .
Us
0J~2 o. L0 0.30 3 . ~0 10.7 0.60
---
.,.._..-.....-- -- w-- ------
---------------------------
0.~2 0.20 0.20 3.2 13.50 0.60 0.02; 0.02
0.2 0.3 0.1.0 3.7 1.00 0.7
_~...~...w~.~~.. - .----.--
Experience in hot extrusion of brass blade blanks ( first
Experience
typo) has confirmed the possibility of utilizing extrusion dies
with matrices made of steel, Grade
of Rc= I_i,1-l-119.
7.5 C.20
0.3 9.0 O.;O -
7Kh3, heat treated for a hardness
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Determination of the optimum steel composltion is not
the subject of this work, and requires lengthy mass experi.-
merits
However, on the basis of a considerable number of ox-
periments, it has been established the most durable are ox-
trt sion dies mac?.e of 3 ichv8 steel with nitrified grooves,
FROIILE OF ' F[E DIE PLATE Gl'lOuV.n'
The shape, precision and quality of manufacture o. the
die plate grooves have a decisive effect on the course of the
extrusion process, as well as upon the dimension and quality
of the finished producto Cross-section dimensions of extruded
blades correspond with a high degree of accuracy to the cross-
section profile dimensions. The magnitude of possible deviations
usually does not exceed 0,0~-O,1 mill:Lrneters (ln the direction
perpendicular to the axis of the blade) and depends on shrinkage
during cool i.nr; and elastic extrusion die deformations ( in the
transverse erection)
Figure 8, Profile of the working portion of the blade,
Figure 9, Profile of the working portion of the blade 1jiank,
since these two factors act in opposite directions (elastic ox-
trusion die deformation leads to the increase in the transverse
cross-section, while cooling, shrinkage results in the cross-
sectional decrease), their total effect ensures the high precision
7
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of the process, The length of the die plate grooves has a
material effect upon the amount of tiTork done by the extrusion
press durin21 the extruding, and. also upon the shape of the
finished product. The amount of work increases rith the in-
crease in the length of the die plate. However, for a short
groove the profile of the blade, upon emergence from the
groove, suffers considerable twisting, and the extruded blade
roust undergo the additional operation of straighteziin g.
To avoid this, it is necessary that the length of the
die plate be no less than the length of the working portion
of the finished blade. The nature of the groove profile should
also satisfy certain special conditions. The majority of the
blade profile has sharp edges and a comparatively thick middle
portion -- the back (Figure 8). This determines the uneciaal
speed of flow of rna aerial into the profile of the die pla te,
and consequently results in the presence o?' considerable in-
the I. terna.l stresses in metal,
Faster cooling of the thin edges, and, conseq lently,
the decrease in the plasticity of the metal, may cause rupture
of the edges. To forestall these pclenomena it is necessary to
provide for pockets ~rtthin those die grooves which form the
thin edges, which result in some bulging of the profile. The
presence of such bulgin;s (Figure 9) results in the necessity
of supplemental mechanical machining -- reniioval of the bulge
by a cutter (not a shaper) ?-- but fully prevents rejects through
rupture of blade edges.
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Lr `` 1, ~{ 'i 1iZi'1TUR1a 1EGI1iE FO ~~ THE ~'~y 1 RU S IO1`1 PRoc 3 s
.
ExperimerLts conducted in extrusion of blades from
.
different grades rades oi' steel point to the necessity of heating
r. atures close to the upper limit of the
the blanks up to tempe
forging range.
,,,rtx nusiOn at temperatures close to the lower limit of
U
.., ^~r; rr ange results in a large percentage of rejects clue
t he ~. o- ~ ... nr ,,
to ruptures of the thin blade edges, and, besides, leads to
the die plates, in vier of the increased
faster wearing out 01
d.e.,.ornlat:l.on resistance of the metal. In conilec tion tidth this,
g
in order to decrease slag formation during. the heat :Li
anrl. also
flTie furnaces, heatin should be of forced nature, main-
tainin M the furnace temperature 50-100 degrees higher than i the usual in heat:ii'i -; for stamping purposes.
From this stan(J oint the most pro ressive is the util:i. -
r
zat,iofl of electric inductionn heabin;, since exp erirr1ental data
Confirms th possib; _lit~ of heatin of highly alloyed steels
. and overheating to temperatures of 50-BO de-
without oarni>~,,
;tees Oent~. ' s,r,de in excess of the upper level of the forging
,
ran e for these steels.
rjhe tei~rperature of heatin, of the extrusion die has a
decisive effect on the proclucti.on of usable products. The
ternpera,bUre of heatirr of the e:~trusion die is in the
optimum
250-300 degree Oentigra.de range.
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G `TD ITS ROLE, II.'d r1' f EXTR,JSiON PROCES
SLAG,
~, Slag, which elacr.,r.es on the blank duririfurnace 'c]eati n
and which enters to,o... Cher with the metal of the blank i nta the
~-!o]''.iC:LI]T'C;Cessea Of the extrusion die, com;pJ-ictea, d7zr:iflc1~-
increa5e5 the def'oi?fl1at:i.on
tr,~.si on, the shapa,r' of the b7.ade,
r. ,rejects and fast tirearin} of
force and constitutes a reason .for
r,la into
the k' ns, arts of the extrutsion die. Eri tra,fCO o:I'
,..;i.sion die C