Materials needed to construct the Junkers Jumo 004?

Discussion in 'Aviation' started by DerGiLLster, Jul 25, 2015.

  1. DerGiLLster

    DerGiLLster Member

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    Okay so I know the Nickel, Cobalt and Molybdenum were the primary metals to construct the jet engines. What was the percentage of each metal going into the jet engine? Also what other metals am I missing? How much of each metal was needed in order to construct 8,000 units?
     
  2. davebender

    davebender Well-Known Member

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    27.41kg. DB605. Oct 1943.
    19.01kg. DB605. Oct 1944.
    21lbs. Jumo004A.
    7lbs. Jumo004B. Early variants.
    5lbs. Jumo004B. Late variants.
     
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  3. blueskies

    blueskies Member

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  4. kool kitty89

    kool kitty89 Well-Known Member

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    Cobalt and molybdinum were used in the Jumo 004A and possibly some other prototypes, but not in any German production turbojets. (I don't believed war-time british turbojets used such alloys either -I believe Whittle engines relied on Nimonic turbine alloys comprised mostly of nickle and chromium along with small amounts of titanium, though american turbines may have adapted cobalt alloys since I seem to recall GE was already adopting those for some turbocharger developments during the war). Outside of the turbine and turbine stators, I think most of the hot components used more mundane stainless steel alloys in the US and UK, while german's resorted to mild steel for many components (often with ceramic coating -aluminum oxide in Jumo's case) while the air cooled turbines were made from stainless steel alloys (Cromadur -an iron-chrome-nickle alloy with traces of titanium, Tinadur -an iron-chrome-manganese alloy, and BMW used a similar alloy called Sicromal).

    Early jet engines (similar figures have been quoted several times on the forums, I believe Delcyros has supported them with additional information at some point years ago but I haven't dug up that post)

    The production Junkers Jumo 004B-1 and the Jumo 004B-4 turbines and
    stator blades used an austinitic 'stainless steel' like steel alloy
    called tinadur or an concurrently used alternative called cromadur.
    Tinadur was about 6% titanium 18% nickel 12% chromium with the balance
    steel while cromadure substituted super scarce nickel with manganese to
    achieve an alloy of about 18% chromium, 15% manganese with only traces
    of nickel with the balance steel. The BMW engines used a similar
    alloy series called sicromal. This alloy was also used on gasoline
    engined turbo superchargers and its shortage also explains the minimal
    use of turbos on German aircraft.

    The prototype series Jumo 004A used full refractory alloys in uncooled
    blades and achieved service lives of around 140 hours. Transition to
    non strategic series alloys in the Jumo 004B series caused a
    considerable delay as the resonances of the blades changed necisitating
    a redesigne.


    It's important to note that it was predominantly the resonance issues that delayed 004 production and not sheer structural or thermal wear tolerances of the less costly alloys used. (those were limitations as well, but ones with solutions eventually addressed to large extent with the 004D entering production just prior to the end of the war and the 004E which was to shortly follow -some of those advancements would have likely materialized sooner if not for the vibration issues)

    Additionally, it should be noted that nickel only became extremely scarce late in the war after their supply lines to Finnish nickel ore were cut off. Chromium was in short supply during the entire war, but was still available at the war's end unlike Nickel. (which was limited to existing small reserves) Hitler's strategic planning didn't favor heavy stockpiling of resources, so available raw materials were on a continuous supply basis for the most part and the alloys used in production jet engines would have been in much greater supply earlier in the war than when they finally entered service in 1944.

    It's useful to note that Heinkel's jet engines (or at least Ohain's centrifugal designs) only used more common Krupp stainless steel alloys of a similar type to the 004B (I believe Tinadur in particular was used, but in considerably larger proportion than production 004Bs at least relative to the smaller engine -roughly half the weight of the 004) At a rough guess on my part, I suspect the HeS 8 prototypes of 1942 were using significantly less chromium in their components than their piston engine counterparts, probably well under half the amount, perhaps less than one third (likely still more than the later production 004B, though). As such, the He 280 should have been using lesser amounts of strategic materials in its engines in 1942 than the Bf 109F. (though the engine overhaul life of the DB-601E should have been significantly longer, I'm not sure how much that pertains to chrome alloys being 'used up' in a manner they cannot be efficiently re-used or reclaimed/recycled)

    Similar construction methods apply for the earlier (1939 vintage) HeS 3 and HeS 6. I'm not sure of the proof of concept hydrogen burning HeS 1. (it may have made do with mild steel or may have used stainless steel -honestly, either should have been satisfactory given the fairly tame combustion characteristics of hydrogen)


    But again, the significance of molybdenum and cobalt (as well as likely much higher proportions of chromium and nickel than in mass produced stainless steel alloys) should be emphasized here in the context of the 004A. The limited production run of 004A engines was using alloys of extremely limited supply not available in mass produced quantities, they were specialized high temperature metals intended for more limited and exclusive uses for specialized industrial, scientific, and engineering equipment. (I wish I knew more exact details about the alloys used, but I've only seen more generalized information on the topic)
     
  5. davebender

    davebender Well-Known Member

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    I suspect this had an impact. Type XXI submarine program was massive, top priority and happened around same time that Germany might have ordered Jumo 004A engine into mass production.
     
  6. Gixxerman

    Gixxerman Member

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    I think an interesting follow-up question might also be, given the dire state of German manufacturing in late 44 1945, how much of what they were producing was unfit for purpose or manifestly sub-standard.
    I have seen stories of aircraft supposedly made to 'standard' specs having to be, where possible, refinished (by hand), Me262's with issues, poor welding on tanks and so on.
    A Jumo 004 with 'book' service life of 10 - 25hrs might often have a lot less (and ditto any improved later versions), no?
     
  7. kool kitty89

    kool kitty89 Well-Known Member

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    #7 kool kitty89, Jul 28, 2015
    Last edited: Jul 28, 2015
    The official man-time-between-overhaul (MTBO) was either 25 hours or somewhat higher. 10 hours is related more to anecdotal evidence from pilots. There's a lot of information on this scattered around the forum. If noone else manages to point them out, I'll try to dig them up eventually.

    I believe the Jumo 004D raised the TBO to 50 hours and should have managed that more consistently given it featured improved throttle control that prevented overthrottling and maintained the proper air/fuel mixture limits. (the 003 featured a similar mechanism, but included it from the start of its mass production, the 003 also had a very well designed mild steel combustion chamber that lasted 100 hours between overhaul -might have been longer, I'd have to check to confirm)

    The biggest problem with the Me 262 was it being fielded at a time when Germany was a mess and logistics, transporation, and command organization were all breaking down. So they might have had the engines, the airframes, and the fuel (lots of kerosene and diesel reserves), but having all those in the same place and in operational condition was the tricky part, as was having properly trained pilots. (the ones that adapted best were former twin-engine heavy fighter or bomber pilots -namely Bf 110 or Me 410, possibly some Ju 88 pilots, the transition from Bf 109s or Fw 190s was far more problematic)


    But keeping with the engine alloy composition theme, I'll leave the Me 262 discussion there for now.


    Did the Type XXI use some of the same alloys as the 004A? I could certainly see it using tons of stainless steel alloys, but those weren't the limiting factor for the 004A. I'm sure there were a good amount of 'common' stainless steel components (I suspect a large portion of the combustion chambers and exhaust) but some of the key components like the turbine and turbine stator used more exotic high temperature alloys that, as I understand, were not available in quantities suitable for mass production.

    Beyond that, the raw molybdenum and cobalt would be very critically needed for producing the high speed steel used for machine tools that were in constant shortage throughout the war.

    I'm not sure if the 004A used any Tungsten alloys, but I believe that was in very short supply as well.

    Edit: there's some information here:
    Why was Nazi Germany short of Tungsten? - Axis History Forum

    It seems what limited supplies of tungsten there were also went predominantly into tungsten carbide components of machine tools.

    Molybdenum may have been less critical for cemented carbide tools (very important for high quality tool steel though) but cobalt tends to be one of the common cementing/bonding agents for tungsten carbide ceramics.



    I'll admit, it might have been possible to divert chrome-moly steel alloys into turbine engine production to some extent, and that might have been what the 004A needed, but it seems likely to have been limited to production in the hundreds per year, not thousands. (it probably would have been useful for expediting initial Me 262 service trials and training and getting limited operational service units activated much sooner)

    Without more specific information on the 004A's composition, it's heavy guesswork, though.
     
  8. davebender

    davebender Well-Known Member

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    Submarine machine tools required the same alloys as aircraft machine tools. Same goes for concrete and labor required for factory construction. That's the issue during fall 1942 / spring 1943 when Germany might have been tooling up for mass production of Jumo 004A engine and Me-262 airframe beginning fall 1943.
     
  9. Koopernic

    Koopernic Active Member

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    #9 Koopernic, Jul 28, 2015
    Last edited: Jul 28, 2015
    The quantities are given in Anthony Kay's German Jet Engines and Gas Turbines as about 6kg of Nickel and 6kg of Chromium per jumo 004 engine when Tinidur was used. I don't have the book to hand so working from memory. The alloys were really only on the turbine and its stator. A lot of problems would have been solved if the alloy could be applied to combustion chambers (which needed to be replaced every 25 hours as they were mild steel) the exhaust duct and exhaust nozzle.

    Most of the German quality problems related to unskilled labour, often working with inadequate tooling in some production lines and the reality that it can take a few months to sort out production issues, naturally detractors focus on these. The clue is big variations in say service life: some engines lasting hundreds of hours and others only dozens. That's indication of a variation control problem.
    You will often find quality issues on allied equipment as well. The AZON bomb had around a 40% dud rate. A lot of folks were learning mass production, one reason new types were introduced only slowly.
     
  10. Gixxerman

    Gixxerman Member

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    Fair comment....except that so much German production was, by late 44/1945, reliant on unskilled and often forced labour - as well as outright deliberately calculatedly murderous slavery (which was an additional, separate, part of the equation, to the forced deportations of millions of workers from occupied countries).

    Wow, 'detractors', really?

    In a thread about materials used I would have thought it a reasonable point to consider what was being produced at this time and effectively wasted and/or under-used.
    (and which went hand-in-hand with forced/slave labour)

    Interesting.
    So, which German jets (outside of a manufacturers primary test facility) lasted 'hundreds of hours', in the field?

    My bet is not a single one.

    That's a different (normal) early production issue, whilst it is one that also involves a wastage of raw materials it is one that does not arise from depending on a relatively huge pool of forced/slave labour.
     
  11. davebender

    davebender Well-Known Member

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    No worse then anyone else. However late war Germany had an additional problem which is rarely mentioned.

    Component production was widely dispersed in order to mitigate effects of British and USA bombing. This made quality control much more difficult. Even the top priority Type XXI submarine had problems with prefabricated sections which had to be corrected before the boat became operational.
     
  12. kool kitty89

    kool kitty89 Well-Known Member

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    I had meant that materials normally used for machine tools were being used IN the turbine components themselves. Molybdenum and cobalt alloys in the ENGINES rather than just in the machines making them.


    On the note of machining, though, the 004B of course was optimized around stamped, pressed, drawn, folded, and extruded parts with a minimum of machining necessary. (requirements for machined blades was one of the reasons the more efficient reaction compressor blading was avoided -not just lack of skilled machinists, but more so a limited amount of machine tools and blades/tips for those machines and jigs -though given the context is aluminum alloy machining, I'm not sure if more traditional carbon tool steel could be substituted; it may have been more an overall infrastructure problem with standard mass production machine tools optimized for more exotic cutting steels and ceramics and additional changes to designs and engineering -and entire production lines- for substitute cutting materials to be effectively used -heavier use of cooling oil and reduced duty cycle might have been required to avoid overheating carbon steel blades/bits and ruining their temper/hardness)

    The Jumo 004A really shouldn't have needed machined compressor blades either, being relatively similar to that of the 004B. (it was mostly the hot section that changed)



    The German transportation network and overall logistical resource management/directing was already problematic pre-war, so those added stresses would have further complicated matters there. That was my point regarding 'getting engines, airframes, and fuel all in the right place at the right time' but it applies on the broader 'materials, components, engines in need of overhaul, etc' as well.

    Had they had more efficient and organized transportation and resource management pre-war and a dispersed industrial infrastructure already established as well (on top of the primary centralized industry) they'd have been much better prepared to make further changes/expansion of the dispersed manufacturing base. (had they gone with dispersed manufacturing for the majority of their industrial expansion pre-war, that might have been the toughest for the allies to counter while also being some benefit to large cities as bombing efforts would need to be much more spread out or simply taking the grim route of attacking population centers even if there was only a minority of the military manufacturing facilities housed there ... except with industry dispersed, you could more easily disperse the population and make those cities ineffective targets somewhat more like the Soviets did but without nearly as much raw area to disperse over)


    This is getting into a broader topic, but the 'synthetic methanol/alcohol centered fuel network' (using dispersed small Fischer–Tropsch fuel plants rather than large, centralized hydrogenation plants) that came up a while back would be very relevant to this.
     
  13. Gixxerman

    Gixxerman Member

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    You must be joking Dave.

    I've seen numbers as high as a peak of 12 million forced labourers (with many millions more in slavery).
    How you imagine this would not impact quality any differently to any others defies belief.
    No different to the USA?
    No different to the UK?
    No different to Canada?

    With the USSR/Japan you might make something of a case given the similarities the dictatorships shared but anyone else!?
     
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