US2469146A - Steel helmet - Google Patents

Description

May 3, 1949- R. H. BARNES Erm.' 2,459,146

S TEEL HELME T `lorigixml Filed nec. `18, 1943 Patented May 3, 1949 STEEL HELMET Raleigh H. Barnes, deceased, late of Cleveland Heights, Ohio,

by Miriam M. Barnes, executrix,

Cleveland Heights, Ohio, and Harold J Elmendorf, Worcester, can Steel and Mass., assignors to The Ameri- Wire Company of New Jersey, a

corporation of New Jersey Original application December 18, 1943, Serial Divided and this cember 19, 1946, Serial No.

application De- 717,134

7 Claims. (Cl. 2 3) This invention is concerned with shaped armor and, particularly, with steel helmets.

At the present time, steel helmets are made from high-alloy, manganese steel, containing from 12% to 15% manganese, because it satisfactorily meets the present requirements in regard to resistance to fracturing and bulging in ballistic tests. Such steel is costly and might become unavailable because of its high manganese content.

considerable diiculty is encountered in shaping the helmet, which, sometimes, involves excessive breakage of the steel.

The present invention provides shaped armor and, particularly, steel helmets, that can meet present ballistic tests, by using any effectively quench hardening steel of the low alloy class containing an effective amount of an austenite transformation retarding alloy, which would be a great advantage if manganese becomes unavailable, a further and immediately useful feature of the invention being that it permits relatively easy shaping of the armor by cold drawing and the steel used is much less expensive than the presently used high-alloy, manganese steel.

In the accompanying drawing:

Figure 1 is a view in perspective of a helmet made in accordance with the invention, and Figure 2 is a view, partially in vertical section of heat treating apparatus employed in making the helmet.

An example of a steel that is made suitable for use as light armor, by the present invention, is steel approximately containing ,70% carbon, .70% manganese, .30% maximum silicon, .04% maximum phosphorus and sulphur and from .20 to .30% molybdenum. While this particular steel is preferred, at present, any other low alloy composition steel may also be used providing it has sufficient carbon to be effectively quench hardened. Other examples of steels contemplated by this invention are to be found in chapter 5 ci the fifth edition of The Making, Shaping and Treating of Steel, published by Carnegie-Illinois Steel Corporation. In this text the steels contemplated are termed medium alloy steels but the present inventors prefer to consider them as low alloy steels, and where the latter term is used, herein, it is to be understood as meaning steels of the type described in chapter 5 of the named text, providing they contain suiiicient carbon to be eiectively quench hardening.

In making the helmet of the invention, of which that shown at 6 in Figure l is illustrative, the described steel is hot rolled to a iiat having a thickness requiring further reductions of from 30 to to giveit the thickness of the finished armor, this iiat then being spheroidized, which in the case of the exemplary steel may be by annealing it for about eight hours at about 1300 F. and then slow cooling it at a rate effecting spheroidizing Other spheroidizing treatments may also be used. Such spheroidizing is unnecessary if the hot rolling is carefully carried out to nish above the critical temperature of the steel, but it is always preferable.

The spheroidized flat is next cold rolled to about the thickness required by the contemplated armor, this producing a cold-rolled flat. The next step is to spheroidize this cold-rolled hat, the previously described annealing practice again being applicable, in the case of the particularly speciiied steel, although other spheroidizing treat- .ments might be resorted to. The necessity is to anneal to soften the cold-rolled steel. It is to be understood that the described cold rolling is carried out without any intermediate anneal so that the flat receives from 30 to '70% cold rolling prior to its second spheroidizing treatment, the amount being sumcient to give it the thickness required by the armor. After this second spheroidizing treatment it is considered preferable to give the spheroidized cold-rolled flat about a 1% cold rolling for the purpose of even further improving its now improved drawing properties.

Next, the spheroidized, cold-rolled flat is c'old drawn to the desired shape, is then austenitized by a proper heating cycle, and is then quench hardened by being quenched to within the temperature range producing the austenite-to-bainite transformation, and held within this range until substantial amounts of bainite are produced. In the case of the specific steel disclosed, the quenching temperature is so selected as to produce a Rockwell C hardness of approximately 48 to 50, and a toughness suiiicient to withstand present ballistic tests of the type given the highalloy, manganese steel.

During the holding of the steel within the temperature range producing the bainite from the austenite, it being understood that the steel is quenched to this temperature range at a rate at least no slower than its critical cooling rate, there may be some tendency for the shaped armor to deform. However, in the case of the present invention this is prevented by mechanically restraining the steel against deformation during the austenite-to-bainite transformation.

Applying the foregoing specifically to steel helmets, the steel is preferably hot rolled to a flat strip 18 inches wide and from .078 to .093 of an inch thick, this strip being then spheroidized as described, processed to clean it from any scale it might have acquired and then cold rolled to about a .044 of an inch thickness with no inter mediate annealing. Thereafter the steel strip is straightened and cut, given its final spheroidizing Each helmet is then austenitized by heating to approximately 1550 F. for a suitable period ofI time, and is then immediately quenched in a quenching medium maintained at the temperavture of approximately 650` F., the helmets being mechanically restrained against any deformation during this period and being held for approximately one hour, whereupon they will have the hardness previously noted and will be able to meet present ballistic tests.

Since the brim will have the same hardness of the crown, there may be some danger of the brim being cracked when struck by a bullet. To avoid this the edges of the helmet brim areA subjected to an annealing treatment ranging from 700 to 1200 F., for a very short time, so as to soften the edges by giving the steel around the periphery of the brim a soft steel structure. This treatment is best accomplished by subjecting the edge or rim of the helmet brim to the controlled iiame of a torch, or, more preferably, by dipping the edges of the helmet in a molten metal bath having the temperatures noted. It is to be understood that this softening of the brim is carried out so as not to materially affect the hardness of the crown.

In Figure 2 of the accompanying drawing there is schematically illustrated equipment suitable for mechanically retaining the helmet 6 during its austenite-to-bainite transformation.

In this figure the quenching bath l is held by a container 2 also containing a support 3 mounting a heavy castingll, tting the inside of the helmet, having perorations 5. The austenitized helmet 6 is thrust into the bath andA fitted over this casting d. Immediately thereafter, a second movable casting 1, fitting the outside-'of the helmet, having perforations 8, is lowered by any convenient means, such asthe generally indicated mechanism 9, onto the outside of the helmet, the latter being then held between the two heavy castings 4 and 7, the perforations 5 and 8 serving to give the quenching bath access to the helmet. The quenching bath may be agitated if desired. In this fashion the helmet may bel mechanically restrained against deformation or distortion during its quenching and holding required for the production ofthe bainitic structure.

The result ofthe foregoing is a steel helmet having a crown and brim integrally made of quench hardening steel of the low alloy class containing an eiective amount of an austenite transformation retarding alloy, the crown having a bainitic structure and the brim having a structure that is softer than the bainitic structure. Preferably the helmet is made of the described low-alloy, molybdenum steel. It is to be understood that the austenite transformation retarding alloy is present in an effective amount when it slows down the austenite-to-bainite transformation rate, within the temperature ranges causing austenite to transform, to a suiiicient degree to provide time for proper quenching of the helmet, so as to produce a properly bainitic structure having the necessary hardness and toughness.

This application is a division of application Serial No. 514,844, led December 18, 1943, now abandoned.

We claim:

1. An improved manufacture comprising a steel helmet having a crown and brim integrally made of quench hardening steel of the low alloy class containing an effective amount of an austenite transformation retarding alloy, said crown having a, bainitic structure and' said brim having a structure that is softer than the bainitic structure.

2. An improved manufacture comprising a steel helmet having a crown and a brim and made of steel containing approximately .70% carbon, .70% manganese, .30% maximum silicon, .04% maximum phosphorus and sulphur, and from .20 to .39% molybdenum, and the remainder' iron, with the crown having a substantially bainitic structure and the brim a relatively softer structure.

3. In a steel helmet, a crown and a brim, said crown being' of greater hardness than said brim.

4. In a steel helmet, an integral crown and brim, said crown being of' greater hardness than said brim,

5. In a helmet, a crown of bainitic steel and a brim of steel softerthan bainitic steel.

6. In a helmet, a crown of bainitic steel and an integral brim of steel softer than bainitic steel.

-7. In a helmet, a crown of low alloy7 bainitic steel and an integralsteel brim softer than said crown.

MIRIAM M. BARNES, Exccutrz of the Estate of Raleigh H. Barnes,

Deceased.

HAROLDJ ELMENDORF.

REFERENCES CITED The following references are of record in the nie of this. patent:

UNITEB STATES PATENTS'

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