Question about A6M Duraluminum?

[FLYBOYJ]

OK. Im doing a lot of research on this topic. I think a lot of you guys are assuming that the Japanese used standard aircraft aluminum. What they did use was something called Extra-Super Duraluminum (Or ESD) produced by the Japanese company of Sumitomo Metals.

Here is what I found about ESD so far.

"The development of wrought aluminum alloys in Japan about transportations, mainly, airplanes, railway cars, motor cycles and automobiles are summarized. In airplanes, especially fighters before World War II, higher strength aluminum alloys were required to compete with European or American fighters. ESD (Extra Super Duralumin), which strength was higher than duralumin or super duralumin, was invented and applied to Zero Fighter. This alloy was modified as 7075 in USA during WW II."

Anyone have the values of ESD? Im not comming up with anything solid on ESD other then it was used in the A6M.

First off it is difficult to make thin sheet from 7075 -when heat treated it is very "brittle." 7075 is generally used for castings and forgings or machined parts made from billets. It is also used for "wing planks," milled sheets of 7075 with "risers" machined into them. This method is used on modern airliners and larger aircraft to assemble the wings in a "box." I could give you more information on this if it will help your research.

2024 is generally used for most skins and structure on WW2 aircraft. Back in the day it was known as 24T as the alloying designations were different. The "ESD" the Japanese used probably did not vary much from the alloys found in 7075 - remember, the Japanese got almost of their metallurgical technology from us prior to the war (and even till today will still copy some of our production methods when they have the chance - I worked with them on their P-3 program.) The above chart I posted shows the alloying elements of 7075. The alloying of the material is only half the equation of its strength, it depends on how it is heat treated after the item is made.

Here's a full list...

Aluminum Tempers



Aluminum is a lightweight structural material that can be
strengthened through alloying and, depending upon composition,
further strengthened by heat treatment and/or cold working.
Among its advantages for specific applications are:
low density, high strength-to—weight ratio, good corrosion
resistance, ease of fabrication and diversity of form.
Wrought and cast alloys are identified by a four-digit number,
the first digit of which generally identifies the major
alloying element as shown in the table below. For casting
alloys, the fourth digit is separated from the first three
digits by a decimal point and indicates the form, i.e.,
casting or ingot.
Number Element Number Element
lXXX 997. Mm. Aluminum lXX.X 997. Mm. Aluminum
2XXX Copper 2XX..X Copper
3XXX Manganese 3XX.X Silicon with added copper and/or
magnesium
4XXX Silicon 4XX.X Silicon
5XXX Magnesium 5XX.X Magnesium
6XXX Magnesium and Silicon
6XX.X Unused series
7XXX Zinc
7XX.X Zinc
SXXX Other Elements
8XX.X Tin
9XXX Unused series
9XX.X Other Elements

 

[FLYBOYJ]

Part 2

Basic Aluminum Temper Designations
The temper designation appears as a hyphenated suffix to the
basic alloy number. An example would be 7075-T73 where -T7 is the temper designation. Four basic temper designations are
used for aluminum alloys. They are -F: as fabricated; -0:
annealed; -H: strain hardened and -T: thermally treated. A
fifth designation, -W, is used to describe an as—quenched
condition between solution heat treatment and artificial or
room temperature aging. Following is a list of tempers which
define aluminum alloys.
-H1ll: Applies to products which are strain-hardened less than
the amount required for a controlled Hll temper.
-H112: Applies to products which acquire some temper from
shaping processes not having special control over the amount
of strain-hardening or thermal treatment, but for which there
are mechanical property limits.
The following H temper designations have been assigned for
wrought products in alloys containing over a nominal 4 percent
magnesium.
-H311: Applies to products which are strain-hardened less than
the amount for a controlled H31 temper.
-H321: Applies to products which are strain-hardened less than
the amount for a controlled H32 temper.
-H323: Applies to products which are specially fabricated to
have acceptable resistance to stress corrosion cracking.
Products which are thermally treated with or without
supplementary strain-hardening are designated with a -T
temper. The T is followed by a digit or digits which designate
the specific thermal treatment. Temper designations for
aluminum alloys are as follows:
-Tl: Cooled from an elevated temperature shaping process and
naturally aged to a substantially stable condition.
-T2: Annealed (cast products only).
-T3: Solution heat treated and then cold worked. Applies to
products which are cold worked to improve strength or in which
the effect of cold work in flattening or straightening is
recognized in mechanical property limits.
-T31: Solution heat treated and then cold worked by flattening
or stretching. Applies to 2219 and 2024 sheet and plate per
MIL-A-8920. Also applies to rivets driven cold immediately
after solution heat treatment or cold storage. 2024 rivets are
an example.
-T351: Solution heat treatment and stress relieved by
stretching. This is equivalent to -T4 condition. It applies to
2024 plate and rolled bar and 2219 plate per MIL-A-8920.
-T3511: Solution heat treated and stress relieved by
stretching with minor stretching allowed. This is equivalent
to -T4 condition and applies to 2024 extrusions.
-T36: Solution heat treated and then cold worked by a
reduction of 6 percent. Applies to 2024 sheet and plate.
-T37: Solution heat treated and then cold worked by a
reduction of 8 percent. Applies to 2219 sheet and plate.
-T4: Solution heat treated and naturally aged to a
substantially stable condition. Applies to products which are
not cold worked after solution heat treatment, or in which the
effect of cold work in flattening or straightening may not be
recognized in mechanical property limits.
-T42: Solution heat treated and naturally aged by the user to
a substantially stable condition. Applies to 2014-0 and 2024-0
plate and extrusions which are heat treated by the user from
the annealed condition.
-T451: Solution heat treated and stress relieved by
stretching. Equivalent to -T4 and applies to plate and rolled
bar stock except 2024 and 2219.

 

[FLYBOYJ]

Part 3

—T4511: Solution heat treated and stress relieved by
stretching with minor straightening allowed. Equivalent to -T4
and applies to all extrusions except 2024 and 2219.
-T5: Cooled from an elevated temperature shaping process and
then artificially aged.
-T51: Cooled from an elevated temperature shaping process,
stress-relieved by stretching and then artificially aged.
-T52: Cooled from an elevated temperature shaping process,
stress-relieved by compressing and then artificially aged.
-T54: Cooled from an elevated temperature shaping process,
stress-relived by stretching and compressing and then
artificially aged. Applies to die forgings which are
stress-relieved by restriking cold in the finish die.
-T6: Solution heat treated and then artificially aged.
Mechanical property limits not affected by cold working. Most
alloys in the -w and -T4 conditions artificially aged to -T6.
-T61: Solution heat treated and then artificially aged.
Applies to forgings which receive a boiling water quench to
avoid internal quenching stress. Applies to solution heat
treated and artificially aged castings when more than one
aging cycle is available for that alloy.
-T611: Solution heat treated and artificially aged. Applies
only to 7079 forgings which are quenched in 1750 to 1850F
water.
-T62: Solution heat treated and then artificially aged by the
user. Applies to any temper which has been heat treated and
aged by user which attains mechanical properties different
from those of the -T6 condition.
-T651: Solution heat treated, stress-relieved by stretching
and artificially aged. Equivalent to -T6 and applies to plate
and rolled bar' except 2219.
-T6510: Solution heat treated, stress-relieved by stretching
and artificially aged with no hard straightening after aging.
Applies to extruded rod, bar and shapes except 2024.
-T6511: Solution heat treated, stress-relieved by stretching
and artificially aged with minor straightening. Equivalent to
-T6 and applies to extruded rod, bar and shapes except 2024.
-T652: Solution heat treated, stress-relieved by compressive
deformation and artificially aged. Equivalent to -T6 and
applies to hard forged squares, rectangles and simply shaped
die forgings except 2219.
-T7: Solution heat treated and then stabilized. Applies to
products which are stabilized to carry them beyond the point
of maximum strength to provide control of growth and residual
stress.
-T73: Solution heat treated and then specially artificially
aged. Applies to 7075 alloys which have been specially aged to
make the material resistant to stress-corrosion.
-T7351: Solution heat treated and specially artificially aged.
Applies to 7075 alloy sheet and plate which have been
specially aged to make the material resistant to
stress-corrosion.
-T73511: Solution heat treatment and specially artificially
aged. Applies to 7075 alloy extrusions which have been
specially aged to make the material resistant to
stress-corrosion.
-T7352: Solution heat treated and specially artificially aged.
Applies to 7075 alloy forgings which have both
compression-stress relief and special aging to make the
material resistant to stress-corrosion.
-T8: Solution heat treated, cold worked and then artificially
aged. Applies to products which are cold worked to improve
strength, or in which the effect of cold work in flattening or
straightening is recognized in the mechanical property limits.
-T81: Solution heat treated, cold worked and then artificially
aged. Applies to 2024-T3 artificially aged to T-81.
-T851: Solution heat treated, stress-relieved by stretching
and artificially aged. Applicable to plate, rolled bar and rod.
-T8511: Solution heat treated, stress-relieved by stretching
and artificially aged. Applies to 2024 extrusions and 2219.
-T86: Solution heat treated, cold worked by a thickness
reduction of 6 percent and then artificially aged. Applies to
2024 sheet and plate.
-T87: Solution -heat treated, cold worked by a thickness
reduction of 10 percent and then artificially aged. Applies to
2219 sheet and plate.

-T9: Solution heat treated, artificially aged and then cold
worked. Applies to products which are cold worked to improve
strength.
-TlO: Cooled from an elevated temperature shaping process,
artificially aged and then cold worked. Applies to products
which are artificially aged after cooling from an elevated
temperature shaping process, such as casting or extrusion and
then cold worked to further improve strength.

 

[drgondog]

OK. Im doing a lot of research on this topic. I think a lot of you guys are assuming that the Japanese used standard aircraft aluminum. What they did use was something called Extra-Super Duraluminum (Or ESD) produced by the Japanese company of Sumitomo Metals.

Here is what I found about ESD so far.

"The development of wrought aluminum alloys in Japan about transportations, mainly, airplanes, railway cars, motor cycles and automobiles are summarized. In airplanes, especially fighters before World War II, higher strength aluminum alloys were required to compete with European or American fighters. ESD (Extra Super Duralumin), which strength was higher than duralumin or super duralumin, was invented and applied to Zero Fighter. This alloy was modified as 7075 in USA during WW II."

Anyone have the values of ESD? Im not comming up with anything solid on ESD other then it was used in the A6M.

I posted the mag content of 7075 for you several posts back - it's range for ALL tempers is 2.0-2.8% up to a full percent above the range for 2024.

Net - the aluminum in the Japanese Zero was no more flammable than any other aluminum clad aircraft in WWII or today.

I would say I am officially bored with the discussion at this point. I spent a lot of time both designing and analyzing structures made of this stuff. We didn't spend any cycles on flammability - because there wasn't an issue.

For the benefit of clarity - I am not assuming that the Japs used only 2024. I am assuming it was a form of aluminum with adequate strength to weight ratios and is a known content alloy today... we have exhausted the possibilities for you.

Further, I suspect that the combined experience in the airframe industry of the three guys you have been sparring with exceeds the number of years you have been on this planet in this life cycle... but neither the explanations nor the references seem you work for you. That's ok with me.



Regards,

Bill

 

[FLYBOYJ]

I posted the mag content of 7075 for you several posts back - it's range for ALL tempers is 2.0-2.8% up to a full percent above the range for 2024.

Net - the aluminum in the Japanese Zero was no more flammable than any other aluminum clad aircraft in WWII or today.

I would say I am officially bored with the discussion at this point. I spent a lot of time both designing and analyzing structures made of this stuff. We didn't spend any cycles on flammability - because there wasn't an issue.

For the benefit of clarity - I am not assuming that the Japs used only 2024. I am assuming it was a form of aluminum with adequate strength to weight ratios and is a known content alloy today... we have exhausted the possibilities for you.

Further, I suspect that the combined experience in the airframe industry of the three guys you have been sparring with exceeds the number of years you have been on this planet in this life cycle... but neither the explanations nor the references seem you work for you. That's ok with me.



Regards,

Bill

 

[JoeB]

First I'd reiterate, ESD=7075, per more than one source, so the question was answered when %Mg of 7075 was given, way too small to affect flammability.

One other familiar theme I'd add is Zeroes were more likely to down if hit than most of their Allied fighter opponents, at least Zero models in the plane's heyday lacking pilot armor and fuel tank protection, because they lacked such protection. But the quantitative degree to which that was true is not certain. We can't derive it directly from contemporary Allied reports because those are based on the number of Zeroes the Allied pilots believed they were downing, which was a couple to several times as many as they were really downing. Whereas their impression of their own planes' ruggedness was based on their own known losses; that bias always existed in evaluating own v. opposing plane's toughness.

The USN found that in period Sept 1944-end of war, 80% of USN a/c hit in the fuel system, typically well protected on USN a/c, were lost. The rate for early Zeroes couldn't have been, obviously, that much higher than 80%. Only 11% of '44-45 USN a/c hit just in structure were lost; here the Zero rate was probably higher but there's no solid evidence to say it was far higher. We know from Japanese accounts Zeroes frequently came back with holes in them too.

In case of both fuel and pilot protection, the impact on *pilot* survivability may have been much greater than the effect on *plane* survivability. That's obvious wrt to armor (especially with any wide reading of first hand accounts) but probably also self sealing tanks. They probably prevented catastrophic fire/exposion more than preventing eventual plane loss; anyway that's the strong implication of the 80% figure combined with the widespread opinion of the necessity of fuel tank protection in all WWII air arms, including Japanese too eventually.

Here's a link with Zero construction details, including thicknesses, for A6M3.
Design Analysis of the Zeke 32 (Hamp - Mitsubishi A6M3)

Joe

 

[FLYBOYJ]

Great site Joe, thanks!

 

[drgondog]

First I'd reiterate, ESD=7075, per more than one source, so the question was answered when %Mg of 7075 was given, way too small to affect flammability.

One other familiar theme I'd add is Zeroes were more likely to down if hit than most of their Allied fighter opponents, at least Zero models in the plane's heyday lacking pilot armor and fuel tank protection, because they lacked such protection. But the quantitative degree to which that was true is not certain. We can't derive it directly from contemporary Allied reports because those are based on the number of Zeroes the Allied pilots believed they were downing, which was a couple to several times as many as they were really downing. Whereas their impression of their own planes' ruggedness was based on their own known losses; that bias always existed in evaluating own v. opposing plane's toughness.

The USN found that in period Sept 1944-end of war, 80% of USN a/c hit in the fuel system, typically well protected on USN a/c, were lost. The rate for early Zeroes couldn't have been, obviously, that much higher than 80%. Only 11% of '44-45 USN a/c hit just in structure were lost; here the Zero rate was probably higher but there's no solid evidence to say it was far higher. We know from Japanese accounts Zeroes frequently came back with holes in them too.

In case of both fuel and pilot protection, the impact on *pilot* survivability may have been much greater than the effect on *plane* survivability. That's obvious wrt to armor (especially with any wide reading of first hand accounts) but probably also self sealing tanks. They probably prevented catastrophic fire/exposion more than preventing eventual plane loss; anyway that's the strong implication of the 80% figure combined with the widespread opinion of the necessity of fuel tank protection in all WWII air arms, including Japanese too eventually.

Here's a link with Zero construction details, including thicknesses, for A6M3.
Design Analysis of the Zeke 32 (Hamp - Mitsubishi A6M3)

Joe

Good stuff Joe but can't help but ask "how does the USN know what the loss attributes were??".

For example, in a USAAF Macr there is no category beyond "flak" or "fighters' to describe losses and few of the Macr's I have studied (percentage wise) go to point of describing 'in flames' or fireball' or 'took hits in fuselage fuel cell' ... every once in awhile one can find a match between the 'claimant' and the victim in which the shooter is more descriptive..

I have looked at perhaps 1500 8th AF fighter Macrs to provide some relative measure of review - which certainly is not exhaustive on this subject

The second question that pos up is what were the statistics in which a/c were lost with no witnesses and how does that factor into the 80%?

Regards,

Bill

Candidly I have not read USN equivalent loss reports, so enlighten me?

 

[Micdrow]

OK. Im doing a lot of research on this topic. I think a lot of you guys are assuming that the Japanese used standard aircraft aluminum. What they did use was something called Extra-Super Duraluminum (Or ESD) produced by the Japanese company of Sumitomo Metals.

The information you have above is correct. The ESD was used on the Zero but not for the skin, It was used for what is usually the most single heaviest member of the structure, The main wing spar.

This metal is also the main reason why there are so few zeros left that can fly. When it was cast and made it was super strong. But never tested to hold the age of time. Now 60 plus years later the stuff had turned to power. From what Ive read you can take a hammer and screw driver to the wing spar and the stuff comes out like flour laid-en with moisture or packed together like dried mud.

Since this is the main wing spar it is just two expensive to rebuild for a restoration or time consuming because basically you have to start from scratch.

From what I hears its also one of the reasons why one of the CAF's orginal zeros is now a permanent resident in the pearl harbor museum because the main wing spar was starting to disintegrate.

 

[JoeB]

Good stuff Joe but can't help but ask "how does the USN know what the loss attributes were??".

The second question that pos up is what were the statistics in which a/c were lost with no witnesses and how does that factor into the 80%?

I've only seen this in tabular form. One example is "WWII Fighter Conflict" by Price, p.59, so don't know exactly how it relates to standard USN loss reports. Your point about disappeared a/c is well taken; it's mentioned that it doesn't include them, but in case of the 80% it would only increase it. I also agree even for planes whose loss was observed by surviving pilot or sdn mates, the degree of possible precision as to cause would vary a lot.

But another way to slice it is that of 308 a/c in the sample hit but returned safely, where damage assessment was likely more accurate, only 6 were hit in the fuel system. So aside from statistical precision, it seems that even in an air arm well equipped with self sealing tanks, planes actually returning with holes in fuel tanks or lines weren't very common. But again the tank protection might help the pilot more than the plane.

Joe

 

[drgondog]

I've only seen this in tabular form. One example is "WWII Fighter Conflict" by Price, p.59, so don't know exactly how it relates to standard USN loss reports. Your point about disappeared a/c is well taken; it's mentioned that it doesn't include them, but in case of the 80% it would only increase it. I also agree even for planes whose loss was observed by surviving pilot or sdn mates, the degree of possible precision as to cause would vary a lot.

But another way to slice it is that of 308 a/c in the sample hit but returned safely, where damage assessment was likely more accurate, only 6 were hit in the fuel system. So aside from statistical precision, it seems that even in an air arm well equipped with self sealing tanks, planes actually returning with holes in fuel tanks or lines weren't very common. But again the tank protection might help the pilot more than the plane.

Joe

I agree your points Joe - just relating my own research difficulties in pinning a cause. In the case of the 355th FG there were quite a few 'Mechanical' failures resulting in a guy ditching or going over the side - and the 8th tried to distinguish between a mechanical failure (like losing manifold pressure, prop control, etc) from coolant leak to running out of fuel.. but a lot of guess work in the anaysis.

A nick in a fuel line would be insidious if you had been in combat for 15 minutes over Berlin and noticed you were running dry near the coast..

Bill

 

[FLYBOYJ]

The information you have above is correct. The ESD was used on the Zero but not for the skin, It was used for what is usually the most single heaviest member of the structure, The main wing spar.

This metal is also the main reason why there are so few zeros left that can fly. When it was cast and made it was super strong. But never tested to hold the age of time. Now 60 plus years later the stuff had turned to power. From what Ive read you can take a hammer and screw driver to the wing spar and the stuff comes out like flour laid-en with moisture or packed together like dried mud.

Since this is the main wing spar it is just two expensive to rebuild for a restoration or time consuming because basically you have to start from scratch.

From what I hears its also one of the reasons why one of the CAF's orginal zeros is now a permanent resident in the pearl harbor museum because the main wing spar was starting to disintegrate.

Great info Paul - and the Zero that was flying out of Camarillo (now at the Missouri memorial) actually had the spar welded - yikes! Eric posted a bunch of info on this about a year or two ago...