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HEPORT NO. 710/20

MANUFACTURE OF BULLET-RESISTING

BALL MOUNT CASTINGS FOR MEDIUM TANKS, T3E2

By

D. J. MARTIN lot Lt., Ord. Dept.

1934.

f

IvlANUFACTURE OF BULLET-RESISTING

BALL MOUNT CASTINGS FOR MEDIUM TANKS, T3ES

Contents

Imã Abstract. I

Introduction...« . . 2

Cast Plate vs. Rolled Plate. 3

I Foundry Practice . ; . . . ., ..*. 5

Records of Castings Made.. 7

iiimmmuBiitiHiiimHiyiurdiniimmm

1

Abstract

This arsenal undertook to manufacture ball mounts

for 5 T3E2 Medium Tanks made at the American La-France

and Foarnite Corporation, Elmira, New York, in 1933 and

1934.

Due to the small number of pieces involved it was

decided to make steel castings of bullet-resisting

composition for these parts.

Difficulty was experienced in obtaining sound '

castings. It is now felt that satisfactory casting |

practice has been established and that the percentage

of rejections would not be above normal for any of

the castings except the outer shield. A truly

successful casting practice for this part has not yet

been established.

!

Introduction

This arsenal vas directed to manufacture the

ball mount parts fur the T3E2 Medium Tanks built by

the American La-France and Foamite Corporation,

These parts were required to have a resistance to

bullet penetration equal to that of 1/2" rolled

armor plate. If a large number of parts were to

be made it would have been economical to forge them

from armor plate steel. This order, however, for

5 tanks, was so small that the cost ol forging dies

would have been prohibitive. It was decided, therefore,

to make steel castings of suitable armor plat»

composition.

.3-

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Cant Plate vs. Rol led Plate

No information was available upon which to

prescribe the thickness of such castings in order

that they might have the requisite bullet-resisting

qualities. In order to determine what thickness

was necessary several flat plates were cast and

machined to 3/3" and 1/2" in thickness. These plateo

were of the following homogeneous armor plate

corr.posi ti on :

C Mn P 3 Si Cr Mo Va .25/.35 .40/.60 .02 ,02 .15/.35 1.10/1.30 .60/.80 .20/.30

They were normalized and annealed, then machined to

thickness, and then quenched in oil and drawn, in

accordance with the following schedule:

Treatment

(a) Normalize (b) Normalize (c) Anneal (d) Machined (e) Oil Quench (f) Draw

T i m r. a t T e rn p.

6 hr- s . 4 hr a. 4 lira.

1 1/2 hrs . / 9 t in

Temp.

1150°C 950°C 850°C

870 °C 540°C

( furnace cooled)

The plates were then subjected to ballistic test

at this arsenal. The 3/8" plate showed a ballistic

limit (Tent. Spec. 31) of 2100-2300 f.s., using pre-

loaded Frankford Arsenal cal. .30 A.P., M1922

ammunition, at 100 yards. The 1/2" plate withstood

impacts of service velocity cal. .30 A.P., M1922

U -

Sit

.fh-V..

ammunition at 100 yards (approx, striking velocity

2490 Photographs of the front and back

surfaces of these plates are shown in Figures 1 to 4.

These plates showed evidences of a large number of

blowholes when subjected to radiographic examination

and some of the impacts were obtained on metal

containing these blowholes. In such casee it was

evident that the blowhole deflected the bullet t#

some extent. Impacts on the 1/2" plate were obtained

in metal that was shown by radiographic test to be

sound. On this basis, the ball mount castings were

designed to finish 5/8" thick.

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Foundry Frac tice

Due to a shortage of trained moldera at this

arsenal a cooperative arrangement was made with, the

Boston Navy Yard whereby this arsenal furnished the

melting stock and melted the steels in the high

frequency induction furnaces at the Navy Yard and

the Navy Yard personnel did the molding. The castings

were then brought to this arsenal for X-ray examination.

As is very evident from the casting records, great

difficulty was experienced in developing a suitable

foundry practice for the particular composition of

steel and type of easting.

Many different types and positions of the gates

and risers were used in an effort to obtain sound

castings* Methods that proved satisfactory are

shown by sketches in Figures 5 to 10. Sand and metal

conditions being satisfactory, these layouts should

produce good castings in all of the pieces except

the outer shield. A satisfactory practice for the

outer shield casting was not definitely established.

The layout shown in Figure 10 is that used for most

of the accepted outer shield castings.

All of the castings ware made in dry-sand molds.

Analysis of the facing sand,, as determined by the

5

Naval Research Laboratories, Anacostia Station,

Washington, D.C., was as follows:

Green 2U.

Permeabi1 ity Compression (lbs.) Shear (lbs.) Tensile (lbs.) Moisture Bond 13.40¾

170 1.85

0 0

6.65¾

146 94

13.2 2.11

Or. 6 t.0

20 28 35 48

M e s h

Scroen Analysis

On 0¾ 0.2 4.2 7.4 6

16.76 21.8

65 Mesh 100 150 200 270

•270

21.10 8.84 1.86 1.40 0.70 0.90

These tests were made for the undersigned

through the courtesy of Mr. C. ’.V. Briggs, Department

of Physical Metallurgy, at the Naval Laboratories

who r”ported that the sand, in his opinion, was

satisfactory. Since it was used for facing sand only,

it was Mr. Brigg's suggestion that the backing, if

not good, might have been the cause of some of the

troubles encountered. The sand tests wore made in

accordance With the recommended practice of The

American Foundrymens' Association.

i 1.' ! • I iUiiitl«] iilUWtlÄWk. i,

Records of Cast,íhrb Made

Sixteen heats of steel were made in the fcC’O//

and 1000// Ajax -Nor4 hr up high frequency furnaces at

the Boston Navy Yard. All heats except the last

one wore made in magnesia crucibles. The last heat

was made in a •'aminc i silica l ining of the type

described in Experimental Report No. 382» Watertown

Arsenal, by Lt. S. L. Conner, Ord. Dept. In addition

tc the usual de ox it a hi on with manganese and silicon

a. i heats except E54, Ebb, E9QD, and Ell3, were

further "killed" by the use of ferro-carbon-titanium

in the ladle. Heats E90D and E113 were further

deoxidized with silicon-zirconium instead of titanium.

Chemical analyses of all heats are shown below:

lie at No. CMnP SSiCr^MoVa

E54 E56 E58 E60 E61 E65 E66 E70 E71 E83 E97 E98 E98D El 12 E113 El 50

,29 .50 ,35 .51 .32 .42 .33 .51 .32 .69 .31 .56 ,32 .56 .32 .57 .31 .59 135 .60 .38 >70 >37 >68 ,38 ,68 .36 .43 .39 .57 .34 .53

.007

.008

.008

.009

.007

.007

.010

.007

.008

.006

.006

.006

.009

.012

.009

.020 .23 3.20

.020 .35 3 „13

.015 .28 1,25

.020 .28 1.27 .22 (Navy

.016 .25 1.27

.016 .25 1.27

.016 .34 1.30

.016 ,32 1,29

.016 .33 1.18

.020 .45 1.30

.020 .30 1.26

.019 .41 1.25

.014 .17 1.08

.018 .30 1.17

.020 .30 1.19

.74 .24

.70 .23

.70 .25

.62 .27 Yard Analysis)

.67 .23

.66 .23 .66 ,23 .65 >23 ,66 .26 >63 .25 .65 .26 Zr .66 .26 .041 .60 .24 .65 .24 .039 .70 .26

(All analyses except E61 by A. Sloan, Chemist, Watertown Arsenal ).

7

A list of the castings made, with pertinent

information concerning each, is presented herewith.

Drawings for these pieces are included at the .-.nd of

this report.

Drwg. Pie c a No.

Brocket C53259

!' .at M o.

F54

E56

E5Q

E59

E88

E97

El 50

E60- to

E71

X-ray Peg. to.

r 4 8

D4 9

B50

851

B55

B63

B62

Remarks Accepted

(16 pcs O.K. )

Porous

Porous

Porous

Porous

Porous

Sound

Sound

Sound

Sound

Sound

No

No

No

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Total -- Made:- 26: Required:- 20: Accepted:- 21

Bracket C53257

(w/flange)

E50

E59

E60- to E71

B65

B66

B64

(3 pcs. O.K.)

Sound

Sound

Sound

Yes

Yes

Yes

Yes

Total -- Made:- 6: Required:- 5: Accepted:- 6

Piece

Bracket

(offset flange )

Total ;

Drwg. Heat X-ray No. No. Neg.No. Remarks Accepted

D26610 E&4 B52 Porous r. ^

Ei:6

i :b

"61

E71

E71

E87

E88

E97

E98

E98D

El 12

El 13

B53

B56

B57

B58

B67

B71A

B7 2

B73

B81

B82

B83

B84

B8 6

B102

3103

B104

B124

B122

B123

B136

B137

B134

B135

Porous

Por ous

Doubtful

Porous

Sound

Porous

Sound

Doubtful

Sound

Sound

Sound

Porous

Bod Pipe

Porous

Doubtful

Sound

Doubtful

Doubtful

Sound

Sound

Doubtful

Sound

Doubtful

No

No

Yes

No

Yes

No

Yes

Yes

Yes

Yes

Yes

No

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

N«

Made:- 24: Required:- 15: Accepted:- 15

9

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Piece Drwg. No.

Dalí

(2 dif¬ ferent fini she8 r e q1 d. - Both made fr cm same carting)

Heat No.

E56

EBB

B61

E70

E70

E83

E37

EQ8

E98

X-ray Neg.No.

E98D

B59

B60

DÏ1

BV8

B86

BC7

B88

B91

B92

B9 3

B94

D9 5

B99

B109

B] 10

Bill

B112

B113

B125

B126

B128

B127

-10-

Remarks Accept

Doubtful Yes

Porous

Sound

Sound

Doubtful

Doubtful

Po-ous

Porous

Porous

Doubtful

Doubtful

Porous

Cracked

Sound

Sound

Sound

Sound

Sound

Doubtful

Doubtful

Sound

Sound

Mo

j:!ty.

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Plüce

Pall

Total -

InriC” Sliie id

Total -

Outer Shield

Drvvg.i No.

Made ' -

Heat X-ray No. Hek.No.

B129

1,112 D140

B141

B14 4

B145

1113 B142

LU 3 B14 3

29: Required:- 20:

Remark g / j. ;..

Doubtful ios

Doubtful Yes

Doubtful Yes

Porous No

Porous No

Sound Yes

Sound Yes

Accepted:- 20

C 53261 E54 B54

E58 B69

E61 B75

E60 B74

E83 1396

B97

EÖ7 B105

- Made:- 7: Required:- 5:

Porous No

Sound Yes

Doubtful No

Doubtful Yes

Sound Yes

Doubtful Yes

Sound Yes

Accepted:- 5

C53260 E56

E56

E61

E60

E83

E87

E88

B61 Porous No

B70 Doubtful No

B77 Doubtful No

B76 Doubtful No

B98 Porous No

B108 Doubtful Yes

B106 Porous No

B107 Doubtful No

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X-ray Neg^o« Hcmarka Ac;/ .¿ Ill

B130 Doubtful Yes

B131 Doubtful Yes

B133 Porous No

B132 Cracked Yes Doubtful

Bl38 Porous No

B139 Cracked Yes Doubtful

Total -- ..lade : ~ 14 : Required:- 5: Accepted:- 5

Castings marked as "doubtful" were those that

showed a small amount of porosity under radiographic

examination in such position that it was felt that

tre defects might be removed in machining operations.

In some cases porous areas were chipped out and welded

up with material of the same composition. The two

outer shields marked "cracked" were cracked on the

inside at the head of the dome. These cracks were

also chipped out and welded. In every case where

welding was performed the casting was annealed

carefully at 950°C and then X-rayed again to make

sure there were no cracks or other defects in or

adjacent to the weld, These castings were again

X-rayed after complete heat treatment as a further

-12-

Drwg. Heat Piece No. No.

Outer Shield C53260 F97

E98D

PI 12

1' 1.13

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'

precaution. The weide were found to be sound and

no further defects developed as a result cf Iv-vt

treatment.

A porous ball was machined, heat treated as

described above, and subjected to ballistic test.

The results obtaincl were very satisfactory.

Records of this test are isnown in Report No.

710/9, Watertown Arsenal, September 29, 1933.

All of the rough castings that were accepted,

or tentatively accepted, were subjected to the

following heat treatment:

Time at Temp.

28 hrs.

9 hrs,

9 hrs.

3 hrs.

3 hrs.

Temp.

1160°C

Treatment

(a) Normalize

^,1) Normalize

(c) Anneal

(d) Machined as required.

(e) Oil Quench

(f) Draw

(g) Ground to finish as required

All of the castings finished for assembly were subjected

to Brine11 hardness test and showed a hardness of

400-430.

950°C

850°C

870°C

540°C

This order afforded the arsenal much valuable

information in connection with the manufac v

castings of this nature. In the first place, xt is

interesting to note that cast plate, if properly

heat treated, is equal to rolled plate of similar

composition in its efficiency as armor. Further,

it was found that .,teel of this composition is

difficult to use for steel castings. It has a ten

dency to "die" quickly from high temperatures and does

not shrink well. In addition to these points it

is felt that satisfactory practices have been developed

for all of the castings except the outer shield and

that future work of this nature could, therefore,

be done at a much smaller expense.

Respectfully submitted:

D. J. Martin, 1st Lt., Ord.Dept.

ï

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