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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Steel specifications for gun barrels, comparing Arsenal and S.A.E. standards.

Identifier  ExFiles\Box 170\4\  img040
Date  24th August 1940
  
C
O
P
Y

August 24, 1940

Mr. Maurice Olley
Rolls-Royce, Inc.
Detroit, Michigan

Dear Maurice:

Gun Barrels

Today I got together with Dr. Lester and Mr. Mann of the Watertown Arsenal and obtained the following information with reference to gun barrel steels.

1. General

The Arsenal specification for 37 m/m guns and smaller calibres is a Cr.{Mr Cra???ster / Mr Chichester} Mo. Va. of the following analysis:

C Mn Cr{Mr Cra???ster / Mr Chichester} Mo Va
.25/.35 .60 .90/1.20 .20/.35 .12/.18

They prefer the carbon kept on the low side as compared with S.A.E. 4340 specified in Rm.{William Robotham - Chief Engineer}2 of July 17/40. This S.A.E. standard is:

C Mn Ni Cr{Mr Cra???ster / Mr Chichester} Mo
.35/.45 .50/.80 1.5/2.0 .5/.8 .30/.40

While the above Cr.{Mr Cra???ster / Mr Chichester} Mo. Va. steel represents the chemistry of the steel held in greatest favor by the Arsenal, they do not purchase on this but on two counts:

a) Macroetch
b) Tensile test (Yield Point and Reduction of Area)

These are further discussed below.

In certain cases the Arsenal buy forgings from other analyses, particularly:

C Ni Cr{Mr Cra???ster / Mr Chichester} Mo
.45 2.5 1.6 .20

provided the mechanical properties are met. They prefer, however, the Cr.{Mr Cra???ster / Mr Chichester} Mo. Va. grade of steel since the higher carbon may lead to temper brittleness even with Mo. present. (See also report of writer of April 30 on Cr.{Mr Cra???ster / Mr Chichester} Mo. Va. steels.)

2. Steel Source

The steel can be made either by O.H. or Electric Furnace
  
  


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