4-25 ppm. Surface hydride, cathodi- 
cally applied prior to corrosion testing 
in 750° F steam, does nol appear to 
have any effect. 
Corrosion behavior in 750° F steam 
at 1,500 lb/in?, with or without pre- 
oxidation in dry oxygen at 750°, is 
analogous to behavior in dry oxygen at 
750° F. Pure erystal-bar Zr is cor- 
rosion resistant to dry O»; however, all 
resistance is lost in steam. 
No corrosion dependence on pressure 
was found in 680° F water (2,705 
lb/in?) or in 680° F steam at 2,500 
lb/in?. However, tests in 680° F 
steam at 1,500 lb/in? show decreased 
post-breakdown corrosion rate. 
The microstructure of Zirealoy-2 
shows inclusions, which are presumably 
iReduchon. 
All low-hafnium zirconium supplied 
for AEC and commercial reactor use is 
now produced by the Kroll process. 
W. W. Stephens (Carborundum Metals 
Co.) explained how ZrCl, is reduced by 
this method at Carborundum. 
Quality-control costs amount to 
about two-thirds as much as all of the 
direct labor involved in manufacturing 
the product. Table 2 shows that the 
maximum allowable limits are for the 
most part 0.01% or lower. The excep- 
tions are iron, carbon, oxygen, mag- 
nesium, and chlorine. The last two 
are removed almost completely when 
the metal is melted into ingots. These 
specifications are met through ex- 
tremely rigid quality-control standards. 
TABLE 2—Max. Sponge Impurities 
Weight Weight 
Element % Element % 
Hf 0.01 Cc 0.02 
Al 0.0075 N 0.01 
B 0.0001 oO 0.10 
Cl 0.06 Li 0.0001 
Cr 0.010 Rare 
earths 0.0015 
Fe 0.10 1P 0.001 
Pb 0.005 W 0.005 
Mg 0.060 Zn 0.01 
Mn 0.005 Co 0.004 
Ni 0.007 Ca 0.003 
Ti 0.005 Cd 0.00005 
V 0.005 
Brinell hardness = 150 for sponge arc- 
melted in inert atmosphere 
intermetallics of Niand Cr. Stringers 
also occur parallel to the rolling direc- 
tion. While these do not affect me- 
chanical properties, as measured in con- 
ventional tests, ductility is affected in 
operations such as shearing. Stringers 
may be inert gas trapped during melting. 
Zircaloy-3. Zircaloy-3 was devel- 
oped to provide corrosion resistance at 
higher temperatures than are possible 
for Zircaloy-2. 
Zircaloy-2 studies show that Sn-con- 
tent variation of 0-1.5 wt % has negligi- 
ble effect on corrosion resistance. In- 
creasing Ni, Fe, and Cr in the range 
0.20-0.35 wt% improves resistance. 
Fe and Ni can be substituted for one 
another and are more effective in im-: 
parting resistance than is Cr. 
R. C. Dalzell (AEC Reactor Devel- 
opment Div.) commented that too 
much stress is placed on the mysteri- 
ousness of Zr behavior, e.g., 0.2% oxy- 
gen being damaging to mechanical 
properties. The standard for com- 
mercial copper is 0.03-0.05% for most 
products. What should be empha- 
sized is the difficulty of keeping oxygen 
out of the metal, not that it is harmful. 
Describing how reactor-grade zir- 
conium specifications (Table 2) were 
Fabrication 
Currently, zirconium powder metal- 
lurgy is secondary in importance to are- 
melting techniques. While tubular, 
sheet, and bar products are generally 
made with the arc-melted product, 
powder metallurgy is used for certain 
special products. 
Arc-Melted Products 
The fabrication of zirconium from 
ingot to finished mill products, such 
as forgings, billets, bars, slabs, plate, 
sheet, and strip, present no problems 
not easily mastered by mills experi- 
enced in handling stainless, high-alloy 
steels, and titanium for high-temper- 
ature applications. 
General considerations. In his dis- 
cussion of fabrication methods, W. C. 
Greenleaf (Allegheny Ludlum Steel 
The following three alloys (in wt%) 
were evaluated, leading to Zircaloy-3: 
A—0.25 Sn, 0.25 Fe; B—0.50 Sn, 0.40 
Fe; C—0.50 Sn, 0.20 Fe, 0.20 Ni. 
These Zircaloy-3 compositions exhibit 
lower post-breakdown corrosion rates 
than does Zircaloy-2; composition A is 
the lowest. Variations within 0.10% 
of nominal compositions have no effect. 
The maximum permissible impurity 
content (mainly Nz and Al) appear the 
same as for Zircaloy-2. 
That the amenability to cold-work- 
ing of compositions A, B, and C is much 
better than that of Zircalloy-2 was 
brought out by R. L. Hoff (Superior 
Tube Co.). Thus the cost of fabricated 
products—tubing particularly—should 
be less than for Zircaloy-2. 
established, Dalzell said that zirconium 
within these limits was found to meet 
requirements and that it could be pro- 
duced. Thus, it was necessary to 
specify a great many impurities. 
The main goal in alloy development is 
to minimize zirconium’s neutron cross 
section and then to pinpoint those im- 
purities affecting corrosion resistance 
and mechanical properties. More 
complete data should permit less strin- 
gent specifications. 
Methods 
Corp.) remarked on the workability 
characteristics of.zirconiun.. 
The methods of fabricating Zr are 
about the same as for Ti. The crystal 
structure of these metals is similar to 
magnesium. They are less easily 
worked than iron or copper. 
Zirconium has a wide hot-workabil- 
ity temperature range; above 400° F 
the tensile strength, yield strength, and 
hardness drop off rapidly (modulus 
drops only slightly); elongation rises 
steadily, then sharply above 750° F. 
Zr hot-rolls and forges satisfactorily. 
Crystal structure changes from hex- 
agonal close-packed (alpha phase) to 
body-centered cubic (beta phase) at 
1,580° F. Quenching from above this 
temperature results in slight hardening. 
Zr can be stress-relief annealed by heat- 
57 
