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Патент USA US3092502

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1
atent
3,092,492.
-
Patented June 4, 1963
2
and corrosion resistance of the alloy. Preferably the
3,092,492
alloy contains at least 95 percent of magnesium.
MAGNESIUM-BASE ALLOY
George S. Foerster, Midland, Mich, assignor to The Dow
Chemical Company, Midland, Mich, a corporation of
The present alloy exhibits superior creep resistance,
at temperatures above about 400° F., compared to mag
nesium-zinc alloys which do not contain thorium and
which are outside the scope of the invention.
In general, the zirconium referred to herein, when in
Delaware
No Drawing. Filed Dec. 27, 1960, Ser. No. 78,317
4 Claims. (Cl. 75—168)
This invention relates to a magnesium-base alloy con
corporated in the alloy of the present invention, should
taining at least 85 weight percent of magnesium and is
be in a condition in which it (together with the mag
nesium which contains it) is readily soluble in an aqueous
solution of hydrochloric acid consisting of 30 ml. of HCl
more particularly‘concerned with a thorium-free mag
nesium alloy having primarily the following composition.
Weight percent,
Alloying constituent:
balance Mg
Rare earth metal ________________ ..|
Zinc
_
0.1 to 3
0.1 to 1.4
(speci?c gravity 1.16) added to 85 ml. of water, sufficient
acid being added during dissolution to maintain the in
it-ial concentration.
15
The alloy may be made in the desired proportions ac
cording to the invention by melting together the alloying
Zirconium ______________________ __ 0.01 to 1.0
ingredients in proper proportions or by using “ ardeners”
The alloy of the invention exhibits excellent high tem
of magnesium alloys containing the alloy constituents.
Protection from oxidation during alloying is effected by
perature properties comparable to the thorium-containing
alloys but avoids the use of expensive thorium metal. 20 the use of a magnesium chloride-free saline ?ux as in
The alloy also exhibits good resistance to creep both
conventional alloying. The molten alloy may be ?ux re
at ambient room temperatures and at elevated temper
fined by stirring the alloy with additional ?ux. The so
atures such as 400° F.
re?ned alloy is allowed to settle ‘and then is separated
The rare earth metals suitable for use in preparing
from the ?ux as by decanting into a suitable casting mold,
the present alloy include: cerium, lanthanum, praseo 25 e.g., a slab mold for rolling stock.
dymium, neodymium, didymium (a mixture of rare earth
metals having praseodymium and neodymium as major
EXAMPLES
constituents) or misch metal (a mixture of rare earth
To illustrate the advantageous results which can be
metals). Any of the foregoing rare earth metals may
achieved ‘by the present invention a series of compositions
be used alone or in ‘any combination in compounding 30 according to the invention were prepared and cast into
the alloy. A commercially available misch metal, some
respective rolling slabs (e.g., 2 inches x 4 inches x 8
times known .as cerium misch metal, containing from 35
inches). Each slab was treated as follows: the faces of
to 80 percent of cerium, the balance being rare earth
the slab werev scalped to remove surface impurities or
metal and up to 5 percent of none-rare earth metal, is
the preferred rare earth metal ingredient of the alloy.
35
The binary magnesium-base alloys containing rare
earth metal are improved by the addition of zirconium
thereto, i.e., they exhibit better strength properties. Now
it has been found that the ternary magnesium-base alloys
inclusions.
The slab was heated to about 900° F. and
reduced in thickness to about 0.1 inch sheet by rolling.
The so-obtained sheet was further reduced by rolling ac
cording to conditions indicated in Tables I and II, to
bring the sheet to one of several standard ASTM temper
designations. Test coupons were cut from the so-pre
containing certain proportions of rare earth metal and 40 pared sheet and subjected to physical testing including
zirconium are further improved by the addition of small
tests of resistance to creep extension. Compression yield
amounts of zinc in the range of 0.1 to 1.4 percent by
strength and tensile yield strength tests were carried out
weight. Both the zinc content of the alloy and the zinc
in the longitudinal direction of rolling. The alloy com
zirconium relationship are critical. The alloy of the in—
positions, test conditions and the static strength properties
vention containing zirconium in low concentration should 45 are listed in Tables I and II.
contain a correspondingly low zinc concentration. The
Table I
use of more than ‘a low concentration of zinc results in
an alloy having slightly higher room temperature proper
Physical properties of sheet,
ties but lower strength properties at temperatures above 50
strengths in 1,000’s of p.s.i.
300-400“ F. However, more zinc may be used to ad
a
vantage 'at higher zirconium levels within the scope of
Composition,l
Test and temperature
the invention.
weight percent
Test No.
Thus it is found that the percent by weight of zinc
CYS, 75°F.
TYS, 500°F.
employed in the alloy may vary from 0.1 to 1.4 percent 55
but must not exceed a numerical value equal to about
0.5 plus 1.5 times the percent of zirconium in the alloy,
i.e., percent Zn§O.5 +1.5 ><percent Zr. The percent rare
earth metal in the present alloy should equal or exceed,
i.e., not be less than, the numerical difference between 60
the percent of zinc and 1.5 times the percent of zir
conium. Desirably the percent rare earth metal equals
about 1.5 times the percent of zinc.
Preferably the present —alloy composition contains, by
weight, from about 0.5 to 1.5 percent of rare earth metal,
from 0.1 to 0.5 percent of zirconium, and from 0.3 to
0.7 percent of zinc, the balance being substantially com
mercial magnesium.
‘If desired, small ‘amounts of manganese (0.1 to 0.5%)
Sheet preparation
R.E
1 _____________ __
Comparison
2_____ __
Zn
Zr
—H24 —T8 —0 —H24 —T8 —0
0.4
0. 4
0.4
0. 2 0
0. 2 ____ __
0.4 0. 2
0.4
0. 4
24
0. 4
0.4
0.4 ____ __
0.6 ____ __
24
24
0. 4
0.4
0.4
1. 2
1. 2
0. 6
0.6
0.6
0. 2
0. 5
28
27
28
23
25
22
22
23
18
21
0.07
0. 2
0.3
0. 5
0. 04
0. 1
26
24
27
21
21
24
16
12
17
9
10
12
17
14
16
11
8
11
22
16
20
21
14
14
10
14
10
9
8
13
11
18
18
19
14
16
9
8
9
9
11
14
14
16
16
17
16
16
12
11
12
1O
12
1 Balance magnesium.
NorE.—R.E.=rare earth metal; CYS=compression yield strength;
may advantageously be added to the alloy of the inve - 70 TYS=tensile yield strength; —H24=sheet reduced 30% in one pass,
750° F. entry and 450° F. exit; then heat treated 1 hour at 500° F.; —T8=
tion containing less than about 0.2 percent of zirconium
thereby to improve room temperature strength properties
sheet reduced 20% in one pass, 950° F. entry and 550° F. exit; then heat
treated 1 hour at 500° F.; —0=sheet reduced 40% in one pass, 750° F.
entry and 450° F. exit; then heat treated 1 hour at 700° F.
3,092,492
3
sistance to creep. These test results are also listed in
Table III as comparison tests.
From the data’ listed in Table III it may be seen that
By way of comparison, magnesium-rare earth metal
alloys containing zinc but no added zirconium were pre
pared and rolled into sheet form ‘and simi larly tested.
The results of these comparison tests are also listed in
Tables I and II.
the present alloy exhibits creep resistance comparable to
5 the thorium-containing alloys.
-
Table II
Percent creep extension
Load and temperature
Composition,1 weight
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1 Balance magnesium.
1! Alloy sheet in ~H24 tempen, rolling slab reduced 92% by hot rolling at 850° F., then reduced 40% in one
pass at 750° F. (450° F. exit), and heat treated 1 hr. at 500° F.
NoTE.—MM=misch metal, a mixture of rare earth metals; Di =didymium, commercial rare earth metal
product, a mixture of neodymium and praseodymium; 0.10 =0.1% elastic extension under load values listed;
0.21‘ =0.2% permanent extension on der load values listed; 0. 5T=0.5% permanent extension under load ve lues
listed.
1 claim
the manner described above. Test coupons cut from
I. A magnesium-base ‘alloy consisting of by Weight
the so-prepared sheet were tested for resistance to creep
70 from 0.1 to 3 percent of rare earth metal, from 0.01 to 1
at 400° F. In Table III are listed the compositions and
percent of zirco nium, from 0.1 to 1.4 percent of zinc and
the amount of stress necessary to produce the indicated
the balance magnesium, the percent of zinc being not
percent extension in 100 hours.
greater than 0.5 plus 1.5 times the percent of zirconium
and the percent of rare earth metal being not less than
taining alloys were similarly prepared and tested for re- 75 the percent of zinc less 1.5 times the percent of zircon iurn.
' For purposes of comparison, coupons of thorium-con
5
3,092,492
6
2. The magnesium-base alloy as in claim 1 in which
of rare earth metal being not less than 1.5 times the per
cent of zinc.
the rare earth metal is misch metal.
3. A magnesium-base alloy consisting of, by weight,
from 0.5 to 1.5 percent of rare earth metal, from 0.1 to
References Cited in the ?le of this patent
UNITED STATES PATENTS
0.5 percent of zirconium, from 0.3 to 0.7 percent of zinc 5
and the balance magnesium, the percent of zinc being not
greater than 0.5 plus 1.5 times the percent of zirconium
‘and the percent of rare earth metal being not less than
1.5 times the percent of zinc.
2,420,293
2,604,396
2,788,272
Beck et al _____________ __ May 13, 1947
Jessup _______________ __ July 22, 1952
Whiteheand et a1 _______ __ Apr. 9, 1957
4. A magnesium-base alloy consisting of, by weight,
2,979,398
Foerster _____________ __ Apr. 11, 1961
513,627
Great Britain _________ .. Oct. 18, 1939
532,143806,104
Great Britain __________ __ Jan. 17, 1941
Great Britain _________ __ Dec. 17, 1958
10.
from 0.1 to 3 percent of rare earth metal, from 0.01 to
0.2 percent of zirconium, from 0.1 to 0.8 percent of zinc,
from 0.1 to 0.5 percent of manganese ‘and the balance
magnesium, the percent of zinc being not greater than 0.5
plus 1.5 times the percent of zirconium and the percent 15
FOREIGN PATENTS
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