S e c o n d a n d co n clu d in g a rtic le on d a ta w o r k e d ou t b y m eta l
lu rg ists o f Rustless Iron & S te e l C o rp . co v e rs stra ig h t chrom ium a n d chrom ium n ick e l n o n h a rd e n a b le g ra d e s . P ro ce d u re s re co m m e n d e d fo r stra ig h t chrom ium h a rd e n a b le g r a d e s w e re d e
s c rib e d in S T E E L A p r il 16
GROUP II, the straight chromium, nonhardenable grades (ferritic) of stain
less steel, is made up of alloys also con
taining chromium as the chief alloying element (from 14.0 to 27.0 per cent) and with generally low carbon contents (from about 0.08 to 0.20 per cent).
Nickel is present in these alloys only as traces. Principally because of their higher chromium contents, as well as lower carbon contents, these alloys do not harden to any appreciable extent when quenched from high temperatures. They are also magnetic. When annealed, their crystalline structure is composed pri
marily of the microconstituent alpha fer
rite. Accordingly, they are referred to as “ferritic” stainless steels. The chemi
cal analysis of this group is given in T a
ble IX.
H eat Treating: The alloys in this group cannot be hardened to any ap
preciable extent by quenching from high temperatures. Types 430 and 430F harden to about 250 to 275 brinell when rapidly cooled from 1800 to 1850 de
grees Fahr. Types 442 and 446 cannot be hardened even to a small degree by such a treatment. The alloys tend to develop a coarse grained structure if held for any prolonged period above 1650 decrees Fahr. and may become embrittled by such treatment. Accord
ingly, they are. normally subjected only to annealing treatm ent consisting of heat
ing to 1450 to 1550 degrees Fahr. for 1 to 2 hours followed by water quench
ing.
If a temperature of 1550 degrees Fahr.
is not exceeded in heat treating Type 430, or 1450 degrees Fahr, in the case of 430F, they may be water quenched after annealing. Types 442 and 446 may be rapidly cooled from any tem
perature without harmful results. In general, cooling these alloys rapidly from annealing tem peratures results in better impact properties. Annealing procedure is given in Table X.
In some special cases where Type 430 is subjected to severe cold form
ing operations as in cold heading, tire following annealing cycle is employed.
Heat to 1500 to 1650 degrees Fahr. for 2 to 3 hours, slow cool to 1000 to 1200 degrees Fahr. at a rate of 25 to 50 de
grees Fahr. per hour, then air cool to room temperature. This special treatment is not generally recommended for most applications for, while it produces slight
ly lower hardness, it also reduces the notch toughness of this grade.
If the grain structure of the allovs is coarsened by overheating, this condition can be corrected to some extent by cold working the material before annealing.
Moderate cold deformation is required, however, and very slight cold working should be avoided. Average results of this annealing are given in Table XI, and Fig. 16 illustrates typical structures obtained.
Group III, the chromium-nickel,
non-hardenable grades (austenitic), is made up of alloys containing nickel (6.0 to 22.0 per cent) as well as chromium (16.0 to 26.0 per cent) as the chief al
loying elements. Other elements such as molybdenum, titanium , and columbium may also be present to confer special corrosion properties. Except for surface
( Please turn to Page 128)
Fig. 16— Structures of typical Group II annealed stairless stech (A ) T ype 430, (J3) Type 446.
Magnification 500X Fig. 17— Effect of cold-work on the tensile strength of some typical
stainless steels
Fig. 18— Structures of typical Group I I I nonhardenable chro
mium-nickel stainless steels (A ) annealed T ype 304, carbides dis
solved, ( B ) ‘‘sensitized” T ype 302 showing precipitated carbides, (C ) annealed T ype 347 and (D ) cold- worked Tune 301. Magnification
A, B-200X; B, C-500X
T A B L E IX
G H O U P I I S T R A IG H T C H R O M IU M , N O N H A R D E N A B L E S T A IN L E S S S T E E L G R A D E S (F E R R IT IC ) C H E M IC A L ANALYSIS
A IS I
T y p e C M n Si P S C r
4 3 0 ... .. 0 .1 2 m ax. 1.00 max'. 1 .0 0 m ax. 0 .0 4 m ax, 0 .0 4 m ax. 1 4 .0 /1 8 .0 4 3 0 F ... 0 .1 2 m ax. 1.0 0 m ax. 1.0 0 m ax. 0 .0 4 m ax. 0 .0 7 m in .» 1 4 .0 /1 8 .0 4 4 2 ... 0 .3 5 m ax. 1.0 0 m ax. 1 .0 0 m ax. 0 .0 4 m ax. 0 .0 4 m ax. 1 8 .0 /2 3 .0 4 4 6 ... 0 .3 5 m ax. 1.0 0 m ax. 1.00 m ax. 0 .0 4 m ax. 0 .0 4 m ax. 2 3 .0 /2 7 .0
»A nalysis fo r R ustless Iro n A S teel C o rp . G ra d e 17 F M ; U su al ra n g e 0 .1 8 /0 .3 5 . T A B L E X
A N N E A L IN G P R O C E D U R E F O R S T R A IG H T C H R O M IU M N O N H A R D E N A B L E S T A IN L E S S S T E E L G R A D E S
A IS I A n n e alin g H ard n e ss
T y p e T e m p e ra tu re T im e in H o u rs C ooling B rin ell R o ckw ell
4 3 0 1 4 5 0 -1 5 5 0 ° F . 1-2 A ir o r w a te r 1 4 0 -1 6 5 B 7 7 -8 5
4 3 0 F ... 1 2 5 0 -1 4 5 0 'F . 1-2 A iro rx v a te r 1 6 5 -1 9 0 B 8 5 -9 1
4 4 2 1 4 5 0 -1 5 5 0 'F . 1-2 A ir o r w a te r 1 5 0 -1 7 5 B 8 0 -8 8
4 4 6 1 4 5 0 -1 5 5 0 ° F . 1-2 A iro r x v a te r 1 6 0 -1 8 5 B 8 4 -9 0
T A B L E X I
A V E R A G E R E S U L T S O F A N N E A L IN G T H E S T R A IG H T C H R O M IU M , N O N H A R D E N A B L E ST A IN L E S S S T E E L G R A D E S
H a rd n e ss R an g e A verage M ech an ical P ro p ertie s
U lt. 0.2% % R ed . of Ixod Im
-T e n s. Str. YId. Str. E lo n g . A rea p a c t R an g e
T y p e B rin ell R ockw ell P .S .I. P .S .I. in 2 " % F t . L b s.
4 3 0 1 4 0 -1 6 5 B 7 7 -8 5 7 0 ,0 0 0 4 0 ,0 0 0 3 5 70 1 5 -3 5
4 3 0 F ... 1 6 5 -1 9 0 B 8 5 -9 1 8 5 ,0 0 0 5 0 ,0 0 0 2 7 5 7 1 5 -3 5
4 4 2 1 5 0 -1 7 5 B 8 0 -8 8 7 5 ,0 0 0 4 5 ,0 0 0 31 60 5 -1 5
4 4 6 1 6 0 -1 8 5 B -S4-90 8 0 ,0 0 0 5 0 ,0 0 0 2 7 60 1 -10
Beaasssöissaa
T A B L E X II
G R O U P I I I C H R O M IU M -N IC K E L . N O N H A R D E N A B L E S T A IN L E S S S T E E L G R A D E S (A U S T E N IT IC )
C hem ical A nalysis A IS I
T y p e C M n Si P S C r Mi
o v er 2 .0 0 1.00 0 .0 4 0 04
301 0 .0 8 /0 .2 0 m ax. m ax. m ax. m ax. 1 6 .0 /1 8 .0 6 .0 / 8.0
o v e r 2 .0 0 1.00 0 .0 4 0 .0 4
3 0 2 . . 0 .0 8 /0 .2 0 m ax. m ax. m ax. m ax. 1 7 .0 /1 9 .0 8 .0 /1 0 .0
0 .0 8 2 .0 0 1.00 0 .0 4 0 .0 4
30 4 m ax. m ax. m ax. m ax. m ax. 1 8 .0 /2 0 .0 8 .0 /1 0 .0
0 .2 0 2 .0 0 1.00 ° o
30 3 max. m ax. m ax. 1 7 .0 /1 9 .0 8 .0 /1 0 .0
0 .0 8 2 .0 0 1.00 0.0 4 0.0 4
30 8 m ax. m ax. m ax. max. m ax. 1 9 .0 /2 1 .0 1 0 .0 /1 2 .0
0 .2 0 2 .0 0 1.00 0.0 4 0 .0 4
3 0 9 m ax. m ax. m ax. m ax. max. 2 2 .0 /2 4 .0 1 2 .0 /1 5 .0
0 .2 5 2 .0 0 1 .50 0 .04 0 .04
3 1 0 m ax. m ax. m ax. m ax. max. 2 4 .0 /2 6 .0 1 9 .0 /2 2 .0
0 .1 0 2 .0 0 1.00 0 .0 4 0 .0 4
8 1 6 m ax. m ax. max. max. m ax. 1 6 .0 /1 8 .0 1 0 .0 /1 4 .0
0 .1 0 2 .0 0 1.00 0.0 4 0 .0 4
321 m ax. m ax. m ax. max. m ax. 1 7 .0 /1 9 .0 8 .0 /1 1 .0
0 .1 0 2 .0 0 1.00 0 .0 4 0 .0 4
3 4 7 m ax. max. max. max. max. 1 7 .0 /1 9 .0 9 .0 /1 2 .0
O th e r E lem en ts
A nalysis fo r R ustless Iro n & S te e l C o rp o ratio n .
° P , S o r Se— -U sual ra n g e e ith e r 0 .1 8 /0 .3 5 S an d 0 .0 4 P o r 0 .1 8 /0 .3 5 Se T A B L E X III
A N N E A L IN G P R O C E D U R E , C IIR O M IU M -N IC K E L G R O U P H I G R A D E S O F S I A IS I
T ype
A n n ealin g
T e m p e Te tu re T im e in M in. Q uench B rinell
301 ... . . . 1 7 5 0 “-2 0 5 0 ° F . 1 0 -3 0 W a te r 1 5 5 -1 7 5 30 2 ... . . . 1 7 5 0 ° -2 0 5 0 ° F . 1 0 -3 0 W a te r 1 4 0 -1 6 0 30 4 ... 1 7 5 0 ^ -2 0 5 0 ° F. 1 0 -3 0 W a te r 1 4 0 -1 6 0 3 0 3 ... . . . 1 8 0 0 ° -2 0 5 0 ° F . 1 0 -3 0 W a te r 1 5 5 -1 7 5 3 0 8 ... . . . 1 7 5 0 ° -2 0 5 0 ° F . 1 0 -3 0 W a te r 1 4 5 -1 6 5 3 0 9 ... . . . 18 5 0 ° -2 0 5 0 °F. 1 5 -3 0 W a te r 1 6 5 -1 8 5 3 1 0 ... . . . 1 9 0 0 ° - 1 9 5 0 ° F . 1 0 -3 0 W a te r 1 6 5 -1 8 5 3 1 6 ... . . , 1 8 5 0 ° -2 0 5 0 ° F . 1 5 -3 0 W a te r 1 4 0 -1 6 0 321 ... . . 1 7 0 0 ° -1 9 5 0 ° F . 1 0 -3 0 W a te r 1 4 5 -1 6 0 3 4 7 ... 1 7 0 0 ° -2 0 0 0 ° F . 1 0-30 W a te r 1 4 5 -1 6 5
M o. 1 .7 5 /2 .5 0 T i 4 X C m in.
C b 8 X C m in.
H a rd n e ss R ockw ell
B 8 0 -9 0 B 7 5 -8 4 B 7 5 -8 4 B 8 0 -9 0 B 7 5 -8 5 B 8 5 -9 5 B 8 5 -9 5 B 7 5 -8 5 B 7 5 -8 5 B 7 5 -8 5 T A B L E X IV
A V E R A G E M E C H A N IC A L P R O P E R T IE S O F A N N E A L E D , C IIR O M IU M -N IC K E L G R O U P I I I G R A D E S O F ST A IN L E S S S T E E L
H a rd n e ss R ange A v erag e M ec h a n ic al P ro p ertie s
U lt. 0.2% % R ed. of Iz o d Im
A IS I T en s. Str. Y ld. Str. E lo n g . A rea p a c t R an g e
T y p e B rin ell R ockw ell P.S .I. P.S .I. in 2 " % F t. L b s.
30 1 ___ ___ 1 5 5 -1 7 5 B 8 0 -9 0 1 0 5 ,0 0 0 4 5 ,0 0 0 60 70 1 0 0 -1 1 5
3 0 2 . . . ___ 1 4 0 -1 6 0 B 7 5 -8 5 8 5 .0 0 0 3 0 0 0 0 60 7 0 1 0 0 -1 1 5
3 0 4 . . . ___ 1 4 0 -1 6 0 B 7 5 -8 5 8 5 ,0 0 0 3 0 ,0 0 0 60 7 0 1 0 0 -1 1 5
3 0 3 ___ ___ 1 3 5 -1 7 5 B 8 0 -9 0 8 8 .0 0 0 3 3 ,0 0 0 54 60 6 5 - 80
3 0 8 . . . ___ 1 4 5 -1 6 5 B 7 5 -8 5 8 7 ,0 0 0 3 2 .0 0 0 55 65 1 0 0 -1 1 5
3 0 9 . . . ___ 1 6 5 -1 8 5 B 8 5 -9 5 9 3 .0 0 0 4 5 00 0 4 8 67 1 0 0 -1 1 5
3 1 0 ___ ___ 1 6 5 -1 8 5 B 8 5 -9 5 9 5 .0 0 0 4 5 .0 0 0 45 65 1 0 0 -1 1 5
3 1 6 ___ ___ 1 4 0 -1 6 0 B 7 5 -8 5 8 5 ,0 0 0 3 0 .0 0 0 60 70 9 5 -1 1 0
321 ___ ___ 1 4 0 -1 6 0 B 7 5 -8 5 8 5 .0 0 0 3 0 .0 0 0 55 70 9 5 -1 1 0
3 4 7 1 4 5 -1 6 5 B 7 5 -8 5 8 7 ,0 0 0 3 2 ,0 0 0 50 70 9 5 -1 1 0
T A B L E XV
E F F E C T O F S T R E S S -R E L IE V IN G C O L D -W O R K E D TY PES 302 A N D 3 0 4 S T A IN L E S S S T E E L BARS A N D W IR E
U lt. 0.2% P ro p . % R ed. of
T en s. S tr. Yld. Str. L im it E lo n g . A rea
Size P .S .I. P.S .I. P .S .I. in 2 " %
1% " d ia ... 1 0 8 ,0 0 0 0 .1 8 8 " d i a ... 2 1 5 .0 0 0 0 .0 8 0 " d i a ... 2 7 9 ,0 0 0
1 H " d i a ... 1 0 8 .0 0 0 0 .1 8 8 " d ia ... 2 2 0 .0 0 0 0 .0 8 0 " d i a ... 3 0 0 ,0 0 0
C o n d itio n as C o ld D ra w n
6 9 .0 0 0 3 3 ,0 0 0 39 .5
1 7 2 .0 0 0 6 4 ,0 0 0 6.0
2 6 5 .0 0 0 1 5 7 ,0 0 0 2.0
C o n d itio n as C o ld D raw n P lu s Stress R elief 7 5 0 -8 0 0 °F . fo r 1 H o u r
7 5 .0 0 0 4 2 ,5 0 0 37 .0
1 9 4 .0 0 0 9 6 ,5 0 0 6.0
2 9 2 .0 0 0 1 8 7 ,0 0 0 2.0
64 .5 5 3.5
65.0 5 7.5
r i t c t « I s F t i t ) t t i i C T i m
April 23, 1945 89
. . . . in W e'trfon S te e l C o .'s tin p la te d e p a rtm e n t h a s re su lte d in 2 5 p e r cen t re d u ctio n in p u rch a se s o f n e w oil, sa v in g s in fin a n d im p ro v e d q u a lity
o f p la te th ro u g h elim in a tion o f "fish e y e s " a n d o th e r fla w s
Fig. 1— Layout of system for cleaning palm oil in tin house of Weirton Steel Co., Weirton,
W. Va.
Fig. 2— Operator feeding p i c k l e d black plate into tinning machine Fig. 3— Tin plate being stacked au
tomatically follow
ing bran polishing Fig. 4 — General view of installa
tion for centrifug
ing used palm oil.
A t rear, left, is sludge tank for dirty oil. Pump in foreground l i f t s clarified oil to stor
age tanks above
COATING of light-gage steel sheets to make tin plate is accomplished by passing them through a molten bath of tin. The sheets pass into the tin bath through a layer of molten flux and emerge from it through a layer of palm oil which assists in the uniform distri
bution of the coating and protects it during die "freezing” period. A concise statem ent about the equipm ent and its operation in this process is quoted as follows from Bulletin 4 of the Interna
tional Tin Research and Development Council:
"The tinning apparatus consists of a cast-iron subdivided pot suitably en
closed, and usually gas heated, into which a tinning machine fits. The pot is divided vertically to make two com
partments, interconnected at the bottom.
A molten tin bath of 2% to 5 tons oc
cupies the lower portion of the pot; a thin layer of molten zinc chloride flux floats on top in the front compartment and a much deeper bath of palm oil oc
cupies the rear division (Fig. 1). Many of the newer installations use immersion
Legend
f- Flnx 5. Receiving tank 8. Centrifuges
2. Tin bath 6. Pumps 9. Clean palm oil
3. Palm oil 7. Sludge & cooling storage
4. Gutter tank 10. Manifold
(All tanks are provided with steam coils. In addition, sludge tank, 7, has cooling coil. Insulated oil lines also can be heated)
PATH OF SHEET IHROUGH TIW POT
/ T E E L
gas heaters inserted in the tin bath in the first or entering division of the pot.
These automatically control the tem pera
ture closely and are efficient in fuel consumption.
The tinning machine is essentially a system of rolls for conducting the sheets singly down through the flux and tin bath and up through the palm oil.
An important feature, however, is the manner in which the final rolls in the palm oil can be used to press off ex
cess tin, thus regulating the thickness of coating.” (Fig, 2)
Use of Palm Oil: Although the tem perature at the feed end of the pot may vary from 575 to 650 degrees Fahr., it is im portant to maintain the palm oil at about 460 to 465 degrees Fahr., or only 10 to 15 degrees above the melting point of tin. Tem peratures above 470 degrees in the palm oil are apt to result in a yellow discoloration of the plate. Furtherm ore, such high tem pera
tures cause polymerization and resultant poor efficiency and high loss of the oil.
Therefore, tem perature control is neces
sary. It is the practice to hold palm oil in storage tanks of the system at tem peratures between 250 to 350
de-ly at the time of dressing the pots, or when the accumulation of finely divided solids increased the viscosity of the oil too greatly and the oil bath was com
pletely discarded and a new bath placed in service. The discarded oil brought a slightly increased price over that of new oil when sold to soap m anufacturers and chemical refineries.
A considerable proportion of the scruff or dross in the bath was not only wasted, b u t was also one of the causes for production of the flaw called fish eyes on tire tin plate. Recovery of the tin from the scruff would make available a larger supply of the scarce m aterial (tin) now at a premium be
cause of increased need and decreased supply due to w ar conditions.
Centrifuge Trial Run: The National Acme centrifuge was chosen as a heavy- duty commercial machine whose bowl capacity is large enough for the col
lection of considerable quantities of solids betw een cleanings, and through its simple and rugged design mechani
cal maintenance is easy. These are im portant items in labor expenditure and operating cost.
Research leading to the now com
plete installation in the mill for all tin baths was supervised by the late Fred H. Prahl with the co-operation of the author. A portable centrifuge with circulating pumps was put in the line to continuously clarify the oil in one tin pot. The tem perature of the oil as it passed through the centrifuge was 325 degrees Fahr. The plate produced by this experimental pot was carefully examined and compared with the prod
ucts of the other 16 operating units.
Subsequently the oil circulation of other ( Please turn to Page 112)
By H. P. WILKINSON
N a tio n a l A cm e C o.
C le v e la n d
grees Fahr. This oil is brought into the bath continuously to maintain the tem perature required. New oil is added to the system to replace old oil which has been unavoidably lost on the plate or to replace old oil whose viscosity is too great for proper operation. The amount of new oil added in such cases is a comparatively insignificant am ount of tire total quantity in circulation in the tin bath.
Solids collect in the oil due to oxida
tion products of tin which have been removed as the sheet passes through the bath. This “scruff,” w hich is largely iron-tin alloy, tends to settle to the bot
tom of the bath and tin can be re
covered from it when the pot is
"dressed.”
Cleaning: Bran middlings, oil absorb
ent, are rubbed over the surface of the sheets to remove most of the oil. Then the plates are carefully polished and mechanically stacked for shipm ent as they come from these processes. (Fig.
3).
W eirton Steel Co., W eirton, W . Va., through its quality control service, recog
nized tire possibility of improving the quality of hot tin plate by keeping the palm oil free from suspended solids. If this could be done, there could be not only a saving of tin, because of a de
crease in tin plate rejects, b u t tire life of the oil in the bath might be pro
longed.
U nder conventional methods it was customary to dispose of solid m atter on
April 23, 1945
91
D e ta ils o f in trica te d ie d e sig n a n d p ro d u c tio n m eth o d s in Y a le
& T o w n e's S ta m fo rd p la n t a re d e s c r ib e d in firs t o f tw o a rtic le s.
M a c h in in g , fin ish in g a n d testin g p ro c e d u r e s w ill b e c o v e r e d in the A p r il 3 0 issue o f S T E E L
YALE locks and padlocks normally require more than 50,000,000 die casting parts a year. Experience with die cast
ing for more than 15 years suggests that the war-accelerated improvements and applications in die casting methods will benefit the manufacture of many other civilian products in the postwar period.
Yale engineers are constantly on the alert to discover better methods of metal fabrication, because of the diver
sity of the products made by the seven divisions of the Yale & Towne Mfg. Co.
For example, in the Stamford, Conn.
division are made locks, builders’ hard
ware, door closers, and rotary pumps.
The Philadelphia division makes hand lift and electric industrial trucks, hand- chain and electric hoists, and industrial,
springless, dial scales. The Automatic Transportation Division, Chicago, makes electric industrial trucks; and other divi
sions in Chicago, North Chicago, Canada and England make products requiring similar processing methods.
This article refers specifically to Yale’s Stamford division. Here are facilities for sand casting in all the usual metals, departments devoted to stamping and screw machine operations, machine shops, forge shops, polishing and plat
ing departments and a large die casting department.
On the basis of comparative perform ance, therefore, we believe th at die casting is the best method to attain high speed production of parts for some lines of automotive locks, padlocks, rim latches, cabinet and trunk locks.
Prac-By H. E. NAGLE
S u p e r in te n d e n t o f M eth o d s Yolo & Tow ne M fg. C o.
S ta m fo rd , C o n n .
tice has taught us to adopt for die cast
ing the zinc base alloys, more specifi
cally the Zamak alloys developed by the New Jersey Zinc Co., New York. In
cidentally, its research departm ent has been one of the principal leaders in the perfection of zinc alloys, and this has helped much to increase their in
dustrial application.
The quality hardware dealers at first were won over only slowly to handle locks composed of zinc base die cast
ings, such as those shown in Fig. 4.
This trade acceptance of locks employ
ing die castings has, however, not only been retained b u t greatly widened, due to the constant improvement of the zinc alloys and in die-making.
How Yale Adopted Die Casting: In 1928, it was decided to use die casting in addition to traditional methods of fabricating certain, lock parts, following
Fig. 1— The die maker is pointing out five pin tum bler holes die cast 0.14-inch center to center and within 0.002-inch tolerance, in the ctjlinder lock shell for rim latch. N ote die inserts used in casting gate of 8 cylinder lock shells. Should a die insert become defective, it is filled tern*
porarily and the other 7 continued in use until replacement or repair of the damaged insert can be effected
P i g . 2— Three multiple-cored dies are shown here. Note unassembled die at bottom of photo.
In each die insert, there are m ultiple cores for casting the hole for the key and also the five holes for five lock pins
Fig. 3— This die was designed to cast plugs for plate tumbler locks in multiples of 8 . In each plug are cast 5 slots for sliding plates operated by the key and th e key hole section. Note com
plexity of core assembly. Under body of die at top right, are shown 4 and 8 sliding side cores which m ake slots for the plate tumblers and other slots or holes in the side as called for in design of the plug. Slots have walls only 0.02-inch thick and are held to plus or minus 0.002-inch
4 Three grades of die cast padlocks are made by Yale & Tow ne (1 ) upper right, pin left and lower right, disk-tumbler (3 ) lower left, warded padlocks
Anril 23 1945 93
successful tests conducted by engineers at the Stamford Division. Improve
ments in zinc alloys lead to increased applications and wider acceptance of die casting in the lock field and Yale &
Towne therefore enlarged its own die casting department.
Today, the Stamford Division uses 180 different dies made at costs ranging from several hundred dollars for a single
cavity die to several thousand dollars for a complex die with multiple cavities, forming 1 to 22 parts in a single “shot” . And the 15 die casting machines under normal conditions produce more than 50,000,000 parts a year. Because the castings can be made in such large quantities and require little, if any, ad
ditional finishing, costs are lower than by other fabricating methods despite the initial high cost of the original dies.
Designing Die Casting Dies: W hen a product is accepted for manufacture, tire general superintendent assigns it for production analysis to the superintend
ent of methods. If die casting is one m ethod selected, the parts to be pro
duced are given to the tool designing departm ent, where engineers design the die casting dies under the supervision of mechanical equipment. Die designers have learned much about how to increase the life of the dies by employing certain design principles and by using specially heat-treated die steels.
Since die casting involves forcing molt
en metal into a steel die under high pressure followed by rapid cooling, pre
in designing the die so range and rapid tempera- under which it operates
advantage of the wide scope in design now perm itted with die casting, at the same time collaborating closely with company die makers and die casters to simplify die dies, improve the quality and surface finish of die castings, and reduce assembly time by combining as many parts as possible into one cast.
The aim is to produce a die capable of faster and longer production runs of die castings accurate within a tolerance of plus or minus 0.002-inch, and which, therefore, require a minimum of machin
ing and finishing. See Figs. 2, 3 and 8.
Some dies are designed to make cast
ings w ith threads diat are both accurate within a plus or minus 0 .002-inch and also require no additional “chasing” or turning of the core to remove the die casting from die die.
D ie Making: From the die design engineers die designs go for execution to the die making room. Here the steel die casting dies are made, inspected, re
paired and, if. necessary, replaced under die supervision of the general foreman of die die and die casting departm ent. And here, too, are made and maintained the necessary additional dies and fixtures that are used in trimming, broaching, wall not shorten its life and
dius increase unit costs.
Dies with “inserts” of speci
ally hardened steel are used for the coring and casting sec
tions. These inserts may be individually repaired, or re
placed, if worn out or other
wise damaged, w idiout holding up producdon from the un
dam aged “inserts.” Duplicate
“inserts” are kept in reserve for just this purpose. W hen die casting impressions are cut into a solid die block, the whole die may become worn out far sooner
“inserts” are kept in reserve for just this purpose. W hen die casting impressions are cut into a solid die block, the whole die may become worn out far sooner