NOTES ON SOVIET-EAST GERMAN AVIATION TECHNICIANS' DISCUSSION OF PRECISION CASTING TECHNIQUES

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A048400270001-5
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 10
• Document Creation Date: December 22, 2016
• Document Release Date: August 2, 2010
• Sequence Number: 1
• Publication Date: May 7, 1959
• Content Type: REPORT

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I M,12,00,101
CENTRAL INTELLIGENCE AGENCY
This material contains Information affecting the National Defense of the United States within the meaning of the Espionage Laws, Title
18, U.S.C. Secs. 793 and 794, the transmission or revelation of which in any manner to an unauthorized person Is prohibited by law.
COUNTRY USSR/East Germany
SUBJECT Notes on Soviet-East German Aviation DATE DISTR. 7 May 1959
Technicians' Discussion of Precision
Casting Techniques NO. PAGES 1
DATE OF
INFO.
PLACE &
DATE ACQ.
A theoretical discussion of the following
items was held: pressing dies for patterns, investment-casting
patterns, refractory coatings, investment and melting-out, melting and
casting, testing the casting, and heat treatment.
STATE I X ARMY I X NAVY AIR X FBI AEC
50X1-HUM
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Item 1: Pressing Dies for Patterns
In general, steel dies are used, but also aluminum alloy dies,
which have withstood several thousand pressings. No master blades 50X1-HUM
5atternsJ are produced; rather, the corrected aluminum mold is used
as a copying pattern for the steel die to be used in the final series.
They reject the use of master patterns, because it would double the
errors.
Soft metal dies, the surfaces of which are chromium plated, are
usedl only in the light industry. Shrinkage value generally 1.4% for
all alloys (ii K4, S 3, B J1 7 - 45 Ch).
Final correction done according to the results of the first castings.
The machining allowance amounts to + 0.1 to + 0.2 mm per surface.
Smaller machining allowances are not good, since the blades are machined
on all sides.
Item 2: Invest6ent-Casting Patterns (Ausschmelzmodelle)
As described in Instruction 550, the material used for the pattern
is preferably colophony, polystyrene and ceresin. The latter is a
hard material with a high softening point, thus there are no special
requirements for the temperature in the pattern shop (Modellraum).
Up to 50% recovered investment compound can be added to the pattern
mass for new patterns. Two methods are used to fill the molds:
1. with a poured-off measure of liquid `n;x and subsequent
pressing of the wax for about one minute;
2. with a wax spraying machine operating at a pressure of
5-10 atmospheres gauge and removal of the wax pattern
after 13-20 seconds.
Three pressed molds, stretched on a wire-gauge table, are used.
Each step lasts about 20 seconds. It was suggested
research on hollow plastic patterns since the plastics industry in
East Germany is very highly developed.
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The gating practice is about the same as in ordinary foundry work,
i.e., the ratio of gate: flow-channel: spree a 2 : 3 : 4.
Bottom casting is not recommended.
Item 3. Refractory Coatings
The coating materials ("Marschallit" : marahite : finely ground
quartz) used are those specified in the instruction.
Analysis of marshite: Si02 2 98.0%
CaO - 1.0 #pprm?iaatoy
A1203 and MgO : 1. approximately
100.0
In the prehydrolysis the total amount of water is added along with
the usual amounts of ethyl silicate, alcohol and hydrochloric acid.
After 24 hours, the fillers, SiO 2 and Alt 3, are added. A check is
made on the coating material by dipping a wax blade into the coating
material to be tested, and allowing it to dry (without sprinkling sand).
In the case of the formation of cracks in the coating, the hydrolyzed
ethyl silicate is not released for the operation. The acceptance test
for the ethyl silicates is a 3102 analysis and a boiling analysis.
The latter test is only for uniformity; no specific determinations are
made. If the deviations are rather large, the material is not used after
changing the additives, but is rejected for delivery. The originally
(in the instruction) wide tolerance for the HC1 content has now been
narrowed, allegedly to 0.6%. An air-conditioned room with a temperature
of 20 deg Cent is recommended as a drying room. If the humidity of
the room is too low, the drying process is too rapid.
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Item 4. Investment, Melting-Out, Heating
Investment is done in the wet state, in accordance with the
instruction; no dry mold-facing material (Hinterfuellung) is used.
The melting out and annealing is done in a 4-zone furnace. The
melting-out temperature is 160 deg Cent; the annealing temperature
is 900-950 deg Cent. The molds are cleaned of dust and foreign
particles before the pouring-out.
Item 5. Melting and Casting
A high-frequency furnace with a 75-100 kg capacity is used for
the melting; the generator output is 100-150 kw. Alloy 'S 3 should
be worked only in small 10-kg tilting furnaces. As specified by the
instructions, the crucibp materials consist of magnesite or chromium
magnesite (Chrosieagnesit). The crucibles are rammed up and heated
within the induction coil. The induction coil itself is washed
(eingeschlaemmt) with a mixture of A1203, water glass or ethyl silicate
as a binder. The drying time for the crucible, at 150-180 deg Cent,
is 2-3 hours; this is followed by a slow heating up to the melting
temperature of the invested steel or cast iron for a period of
3-4 hours, followed by a slow cooling.
Lifrenko ten years ago, cast 10 charges
with such a crucible, which corresponds to about 1,000 kg, without
damage to the crucible. The melting temperatures are checked with
optical pyrometers.
Circulating material (Kreislauffeaterial) is placid into a 100 kg
crucible and heated to about 1,800 deg Cent, or at least 1,750 deg Cent,
for the purpose of deoxidation. A violent reaction (boiling) begins
in the bath.
When the boiling begins, the current is cut off. Limestone flux
or calcium oxide are used as slag additives.
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The reaction takes place when the chromium oxide reacts with the
carbon of the melt, and CO gas is given off. The other oxides react
the same (compare Bessemer process). Finally, at the completion of
the reaction, the crucible contents are poured into pigs at 1,500 -
1,600 deg Cent. A proinced decrease of carbon takes place in the
alloy. //``
For the castings, 50 percent new material is added to these pigs
in smaller furnaces (25 kg). At 1,680 deg Cent, deoxidation is
carried out with CaSi, CrB, CrAl, or metallic Si.
Limestone flux and calcium oxide are added as slag.
The pouring temperature is 1,580 - 1,600 deg Cent. The molds are
at a temperature of 900 deg Cent, or 950 deg Cent with very small
cross sections.
For S 3 and B cA 7 - 45 Y the same applies, with respect
to the treatment of the circulation material.
Alloy S 3, however, is melted in 8 kg tilting furnaces in
5-8 minutes without slag and poured into the warm mold on the furnace.
The ordinary J K - 4 method does not work in the case A S 3,
because of its high aluminum content. No vacuum has been used up until
now. The use of an argon protective atmosphere produced no better
results.
In the case of B 7 - 45 Y. special ferrotungsten containing
no Pb, Sn and Sb is used. No experience has been had with centrifugal
casting. NiB is added for the purpose of reducing the grain size;
thus 0.01 - 0.02% B is contained in the preliminary alloy. NO contains
7-10% B. If the melt contains aluminum, the burning off of B is
unimportant. In the case of B CA 7 - 45 Y, NO is also added to
the casting material, whereby the boron content is computed according
to the amount of new material added.
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Item 6. Testing the Casting
The profile dimensions are checked on three cross sections by
means of templates. Every wax pattern and every casting is tested.
Measurements of these parts can also be made with light beam scanning
and projection. In practice, only templates are used.
There are no specifications regarding the surface quality of the
raw products, since they are all slated for machining. Of course,
no faults can be present which might possibly effect the quality of
the finished part. The admissibility of faults in the finished parts
depends on teststand experience. No faults are permitted along the
edges; on the other hand, pores of up to 1 mm 0 and 0.5 mm depth
fare allowed) on the faces. Checking is done with calibrated standards.
The final decision in regard to blades rejected on the basis of-: cali-
brated standards is up to the chief metallurgist.
Most rejects result from inadmissible size deviations, and very
seldom because of too low mechanical properties. Impurities, oxide
skins and slag inclusions can also cause rejects. A reject figure
of 20% is considered good for a series operation in the foundry.
Rejects of flK - 4 and D J7 7 - 45 Y are generally more numerous than
for 8 3.
The following materials tests are made:
10% a-ray tests
100% etching tests for oxide skins, etc., which are revealed as
extensive grain boundaries.
The toughness test (Festigkeitsnachweis) is carried out on every
charge, not for every melt. No fatigue tests (Zeitstandversuche) are
made; no grain size specifications are in force.
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Item 7. Heat Treatment
For A K 4 only an annealing for 3-4 hours at 790-800 deg Cent
is proscribed for the purpose of stress relief.
Items 8 and 9. -
Various Additional Questions
1. Method of cutting out specimen rods
Specimen rods are melted as a cross of four pieces, either
alone or together with a cluster of blades (Schaufeltraube). The
mechanical working is done after the heat treatment. The specimen
rods can also be worked out of the gate or sprue (Eiaguss), but this
is not recommended. After being separated, the specimen rods are
machined by means of carbide cutters. The pouring of individual
specimen rods is not recommended because of the danger of inclusions
and oxide skins.
2. Straightening the Blades
The blades are heated to 700-900 deg Cent and straightened in
a die. The form of the die is determined through practical experiments.
At the place to be straightened, there must be a plastic deformation,
thus corresponding shims are used. The alloy 0 K 4 and B 47 - 45 Y
are easy to straighten, but S 3 is difficult to straighten.
In the final discussion, the Soviets promised to submit via the
Moscow office:
1. The standards for K 4, S 3 and B 4 7 - 45 Y
2. The standard for ethyl silicate
3. The standard for P 24
4. Normal chip of 7* S 3 with analysis
5. Sketch of the specimen form for temperature change test.
-7-
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The colleagues at the Soviet ministry asked us for the following
data:
1. technology for the chemical treatment (etching) of steel and
castings;
2. specifications for sulfiding with data on what layer thickness
is produced;
3. technology for the heat treatment of P 18 and a series of
photomicrographs showing admissible and inadmissible polished sections
with respect to overheating and martensite formation;
4. technology for casting teflon around bronze parts for
shielding;
5. sample of our material for patterns for testing by them.
To the wuestion of what grain sizes are admissible in forgings
of EI 617 and EI 435 B, the reporter remarked that a special danger
was the lack of uniformity of grain size. Grain sizes up to 2 mm are
admissible for blades, and up to 3 amt for slides.
At the end of the talks the Sotiets expressed interest in a further
exchange of experiences.
Moscow, 3 June 1958
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