Page 108 - MY STORY
P. 108

The  alloy  we  chose  to  evaluate  was  18%  nickel,  7%

            cobalt,  5%  molybdenum,  .5%  Titanium,  balance  iron
            (called 18-7-5 Maraging Steel).  The thermal treatments
            required  to  reach  high  strength  levels  was  inexpensive

            and simple. However, little was known about its fracture
            toughness and weldability, critical for this application.


            The issue of doing this at Douglas Aircraft was manifold.
            At  the  expected  strength  levels,  internal  tank  pressure,
            and diameter the tank wall thickness would be about ¾”.

            There were few steel companies that could manufacture
            plate  of  this  thickness  in  the  sizes  required  to  build

            something this large,  and  the  weights  of  the  fabricated
            hardware  were  well  beyond  the  crane  and  handling
            capacity of Douglas’ shops.


            For the first problem solution, we made contact with U.S.
            Steel research people in Pittsburgh to inquire if they’d be

            willing to engage in cooperative development of this alloy.
            Our  plan  was  to  obtain  enough  plate  material  (about
            1,000 pounds) to develop mechanical design properties

            and begin work on developing welding techniques (and
            properties) that met the requirements for the large booster
            rockets.
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