Method of welding a soft-iron guide band to a steel projectile body

A method of welding a soft-iron guide band on a steel projectile body includes the steps of applying a layer of nickel or a nickel alloy to the projectile body and applying a soft-iron wire as the guide band to the layer by electric protective gas welding.

CROSS REFERENCE TO RELATED APPLICATION 
This application claims the priority of German Application No. P 43 30 
416.8 filed Sep. 8, 1993, which is incorporated herein by reference. 
BACKGROUND OF THE INVENTION 
This invention relates to a method of welding a soft-iron guide band to a 
steel projectile body. 
It is known to affix a copper or a copper-zinc alloy guide band to a 
projectile body by arc welding. Since copper or copper-zinc alloys have a 
lower melting point than the steel of the projectile body, the bonding 
operation is equivalent to soldering since the steel surface is only very 
slightly melted if at all and is, in fact, not allowed to do so, otherwise 
the iron would mix with the copper melt. This would lead to an 
impermissible hardening of the guide band and thus would result in an 
increased wear of the weapon barrel. Upon firing from relatively long 
barrels of artillery pieces with large propellant charges, it has been 
found, however, that the guide bands have been worn out to such an extent 
as they pass through the barrel that the webs which form in the rifling 
profile have been entirely or almost entirely consumed. This may lead to 
an insufficient number of revolutions of the projectile and thus to an 
unstable flight, that is, to shortened trajectories with lateral 
deviations and, occasionally to a tumble of the projectile during flight. 
It is known, as disclosed in German Offenlegungsschrift (application 
published without examination) 35 39 310 to mount guide bands made of 
copper-zinc alloys on thin-walled projectile bodies by means of flame or 
arc spraying to affect the thin-walled projectile body as little as 
possible. As an adherence layer for the guide band, for example, nickel 
aluminide or a cermet based on aluminum nickel oxide could be applied by 
spray-coating. Such a process, however, is relatively complex and 
expensive. 
Therefore, instead of copper guide bands soft-iron guide bands have been 
used in order to achieve the desired properties, to thus ensure that the 
full guide band profile is preserved without significant changes even when 
the projectile is fired through a long barrel with a maximum propellant 
charge. If, however, the projectile body has a small wall thickness, 
pressing in the soft-iron guide band, as known from German 
Offenlegungsschrift 33 23 386 is not feasible. A securement of the 
soft-iron guide band by electron beam spot welding, in turn, leads to 
rusting underneath the guide band. 
The electron beam welding, even if it is not a spot welding but is 
performed in the axial direction as it is known, for example, from German 
Offenlegungsschrift 40 39 956 for a guide band made of a copper-nickel 
alloy, leads to a significant hardening of the weld seam. This is so, 
because as the base alloy mixes with the soft iron, the resulting 
extremely rapid cooling in the melt zone leads to a martensite formation, 
possibly with fissures.

DESCRIPTION OF THE INVENTION 
It is an object of the invention to provide an improved method of welding a 
soft-iron guide band to a steel projectile body permitting a welding of a 
soft-iron guide band in a simple manner on a projectile body without 
increasing the strength (hardness) of the guide band. 
This object and others to become apparent as the specification progresses, 
are accomplished by the invention, according to which, briefly stated, 
first a thin layer of nickel or a nickel alloy is applied to the 
projectile body and thereafter by means of electric protective gas welding 
the guide band formed of soft-iron wire is bonded to the nickel or nickel 
alloy layer. 
The nickel or nickel alloy layer may be applied by electron beam welding or 
explosive plating. The protective gas welding of the soft-iron guide band 
is expediently a TIG (tungsten inert gas) welding. 
Upon welding the nickel layer, the latter mixes at the boundary zone with 
the material of the steel body while during the protective gas welding of 
the soft iron, the soft iron mixes with the upper layer of the 
already-applied nickel layer but does not mix with the material of the 
projectile body. In this manner, a large-surface mixing of the steel of 
the projectile body and the soft iron is prevented and the required low 
strength (hardness) of the guide band required for the reduction of barrel 
wear is preserved because the soft iron is not hardened by the steel alloy 
elements of the projectile body. This method is economical to a 
substantial extent and is particularly expedient in case of thin-walled 
projectile bodies. 
It will be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations, and the 
same are intended to be comprehended within the meaning and range of 
equivalents of the appended claims.