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Selected aluminium alloy semi-products produced using indigenous materials           producing Alclad sheets and plates
                                                                                     at BALCO, the extrusion parameters
M/s Siddhi Engineers, Ahmedabad          be added (i.e., in pure elemental form      for alloy BAPL5xxx at CEL and
has been established as an alternate     or in the form of master alloys) into       at BAE, the extrusion parameters
source for the manufacture of tubes for  the furnace for effective melting and       and introduction of intermediate
the alloy BAPL5xxx. The profiles were    obtaining desired cast microstructure       annealing between the pilgering passes
produced at Bhoruka Aluminium            for all the alloys,                         post extrusion for producing seamless
Extrusions (BAE), Mysore for alloys      (iii)	Formulated ingot quality              tubes and pipes of alloy BAPL5xxx at
AA2124 and BAPL5xxx.                     check criteria for attributes such as       NFC, the use of ring rolling together
                                         composition, content of alkali metals       with saddle forging for the production
   These materials were produced         like sodium, potassium, calcium,            of annular cylinders of alloy AA2219
by ingot metallurgical route for the     lithium, hydrogen content, grain size       with high L/D ratios at CHW forge,
first time in the country, thereby       (core) and ultrasonic quality, each of      the thermo-mechanical process
requiring technologies in the areas of   which is to be strictly controlled for all  parameters for producing rolled rings
production of sound cast billets and     the alloys                                  of alloy BAPL5xxx at CHW Forge
slabs; production of semi-products       (iv)	Provided        optimum                and the thermo-mechanical process
in desired shapes and sizes; and         homogenisation schedules for all            parameters for producing BAPL5xxx
formulation of commercially viable       the alloys based on independent             tubes by multiple drawing operations
heat treatment schedules.                experiments involving thermal               at Siddhi Engineers, Ahmedabad
                                         analysis of as-cast alloys, and             (vii)	 Provided details of thermo-
   DMRL made the following               microstructural characterisation of         mechanical processing steps for
contributions:                           as-cast and homogenised materials           producing alloy BAPL5xxx through
(i)	 Providedoptimumcomposition          (v)	 Implemented the use of ring            open die forging route at SIFL, and
range for the alloying elements          rolling (because of the unavailability      (viii)	Provided rolling schedules,
and restricted upper limits for the      of the extrusion press of large capacity)   and alternate pre-artificial aging cold
impurities for all the alloys based      for the manufacture of large annular        working (involving a combination of
on the phase diagrams, mechanical        cylinders                                   cold rolling and stretching) schedule
property and microstructural data        (vi)	 Provided optimum processing           for producing Alclad 1201 plates in
(ii)	 Provided data, such as liquidus    conditions, for manufacturing all           T87 temper at BALCO.
and solidus temperatures and thermal     the eight varieties of semi-products,
conductivity values for all the alloys   such as the hot rolling parameters for         All the heat treated semi-products
to estimate casting parameters, and                                                  met the targeted properties, as
guidance on the sequence and the                                                     inspected by Missile Systems Quality
manners, the alloying elements should                                                Assurance Agency (MSQAA), and in
                                                                                     some cases by Directorate General
                                                                                     of Aeronautical Quality Assurance
                                                                                     (DGAQA) at individual production
                                                                                     centres. The production processes
                                                                                     and the quality control procedures
                                                                                     of the indigenised materials were
                                                                                     approved by NPOM, Russia, the
                                                                                     joint venture partner, in 2016.
                                                                                     The materials were subjected to a
                                                                                     combination of machining, forming,
                                                                                     aging and welding at Godrej &
                                                                                     Boyce, Mumbai. During fabrication
                                                                                     of the components, the indigenised
                                                                                     materials performed at par with
                                                                                     the imported ones. The F3 section
                                                                                     assembly, i.e., the major load bearing

Aluminium Alloy Technologies for Advanced Defence Systems                   	 January-February 2018 5
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