FIELD OF INVENTION
[001] The present invention relates generally to a process of manufacturing of 30 mm VOG
cartridge case and grenade body out of micro alloyed steel in coil form by cold forging
process on multi station pans former‘
BACKGROUND
[002] Conventionally both cartridge case and grenade body are either manufactured~ by
machining from a cold draWn steel bars or by cold forging process in which the input blank is
cut from a steel bar material and subsequently it is ‘Annealed’, ‘Phosphates’ and’ cold
forged’ on vertical or horizontal presses. If multiple stages of cold forging are needed, then
the earlier forged part should be intermediately ‘Stress relieved’ and ‘Phosphate’ before
forging again. Here the cold forging process denotes forging the steel parts at ‘room
temperature’ without any pre-heating.
[003] However, rm there are several disadvantages are associated with cold forging process.
For example (i) cold forging process cannot be used for every metal. For example, steel types
with a carbon content of 0.5% or above can't be forged at room temperature. (ii) Limited
Shapes: cold forging can only create cenain sh'apes, usually more basic and mass-produced.
(iii) Cleaning: The metal surface must be clean before forging. Din or contaminants could
adversely affect the workpiece's dimensions. (iv) Less ductile: The metal is much less ductile
compared to 'hot forging. (v) Residual stress: Residual stress can occur during the
deformation process. (vi) Equipment: Heavier and more powerful machinery and tools are
required. (vii) Intermediate anneal's: Because of the loss of ductility that accompanies strain
hardening, intermediate anneals may be required. (viii) Heat treatment: Cold forging
' extrusion requires a heat treatment to eliminate possible cracks, creeks hardening or rafters.
[004] Hence, there exists a need for an efficient method for cartridge case and grenade body
manufacturing.
OBJECT OF THE INVENTION
|005] A primary object ofthe invention is to produce cartridge case and grenade body from
‘micro alloyed steel material in coil form. The steel material in coil form is Annealed and
phosphaled before fed into the multistage cold pan fom1er machine where ‘Net’ or ‘Near
Net’ shape products are produced in multiple forming stages. This multi station parts formers,
does not need any intermediate anneal and phosphate.
SUMMARY OF THE INVENTION
[006] To overcome the above-mentioned technical problems the present invention
provides A method of mariufacturing of 30 mm VOG cartridge case and grenade body. The
method comprises receiving input raw material, wherein input raw material is a micro alloyed
‘
steel is received as a hot rolled rod in coil form;
[007] In some example embodiments, the method funher comprises annealing,
phosphate and lube coating as per process requirement, wherein annealing corresponds to a
process of heating the steel coil material to around 750 deg. C, hold it at that temperature for
two hours and then slowly cooled at the rate of 10/15 degrees per hour, until drop to 600
degrees.
[008] In some example embodiments, the phosphating corresponds to creating a
coating over the surface of the steel, wherein the coating is a form of lubricant that helps in
substantially reducing the friction generated.
[009] In some example embodiments, the lube coating corresponds to a process
where zinc phosphates coil is immersed into bath containing Sodium separate dissolved in
water and kept at 90 deg. C, wherein during the lube coating process, the zinc phosphate
layer on the steel material reacts with sodium stearate and a layer of zinc stearate is formed.
[0010] In some example embodiments, the method further comprises drawing the
steel coil on a wire drawing machine to [he required diameter.
[00“] In some example embodiments, the method further comprises loading the coil
onto the 6-station parts former: wherein the parts former is carrying out automatically six
operations sequentially by moving the part from one station to the other.
[0012] In some example embodiments, the method further comprises stress relieving
the forged cartridge case’s mouth area reducing the hardness to the desired level, wherein the
stress relieving is a process where the front step is precisely heated only to the required length
to 700 deg. C through an inductio'n heating system:
[0013] In some example embodiments, Lhc method further comprises machining a
product from the six-station parts former 6n a CNC Turning centre to the finished part
dimensions;
[0014] In some example embodiments, the method funher comprises zinc plating and
de-embrittling the finished part.
[0015] In some example embodiments, the six operations of the part former which is
performed sequentially as follows: (i) a small piece equal (blank) to the weight of the forged
pan is cropped out of the coil material in the first station, (ii) both ends of this blank are made
squarer in‘the second station, (iii) the blank is upset to form larger diameter as needed, (iv)
an indent of the internal circular shape is made in the third station, (v) the internal diameter is
formed by backward extrusion in the fourth and fifth station respectively, and (vi) choosing
suitable coolant oils which enhances formability of part while sewing its main application of
cooling the forging tools to maintain the expected forging tool life and dimensional stability
of product.
[0016] In some example embodiments, a criterion for stress relieving is a pull-out
load, wherein the pull-out load is the load required to pull the grenade out, after it is crimped
with 1t cartridge case. In order to achieve the pull-out load within limits, the cartridge cas:
from step’s tensile stress is kept between SOKg/mm2 to 70 Kg/mmZ. The cartridge case front
step’s tensiie stress is kept between 50Kg/mm2 \o 70 Kg/mmZ by suitably adjusting the
clearance between the induction coil= the cartridge case, and the heating time. _
|0017] These together with other objects of the invention, along with the various features of
novelty which characterize the invention, are pointed out with particularity in the disclosure.
For a better understanding of the invention, its operating advantages and the specific objects
attained by its uses, reference should be had to the accompanying drawings and descriptive
matter in which there are illustrated preferred embodiments of the invention.
BRIEF DESCRIPTION OF DRAWINGS
[0018] This invention is illustrated in the accompanying drawings, throughout which, like
reference letters indicate corresponding parts in the various figures.
[0019] FIG. 1 illustrates a flowchart depicting manufacturing of 30 mm VOG cartridge case
and grenade body out of micro alloyed steel in coil form, in accordance with an example
embodiment.
[0020] FIG. 2 illustrates a block diagram depicting the advantages of manufacturing of 30
mm VOG cartridge case and grenade body out of micro alloyed steel in coil form, in
accordance with an example embodiment.
[0021] FIG. 3 illustrates a comparison between the present invention (SAF Cold Forge
method of production in multistage part Former machine) and Prior Art (Bar stock machining
route).
[0022] FIG. 4 illustrates a graph showing comparison plot showing the improvement in
productivity and material saving between conventional and the manufacturing method
described in the preset invention.
DETAILED DESCRIPTION OF INVENTION
|0023| The embodiments herein and the various features and advantageous details thereof are
explained elaborately with reference to the non-limiting embodiments that are illustrated in
the accompanying drawings and / or detailed in the following description. Descriptions of
well-known components and processing techniques are omitted so as to not unnecessarily
obscure the embodiments herein. The examples used herein are intended merely to facilitate
an understanding of ways in which the embodiments herein may be practised and to further
enable those of skill in the art to practice the embodiments herein. Accordingly, the examples
should not be construed as limiting the scope of the embodiments herein.
[0024] Reference will now be made in detail to the description of the present subject matter,
one or more examples of which are shown in figures. Each example is provided to explain the
subject matter and not a limitation. Various changes and modifications obvious to fine skilled
in the art to which the invention pertains are deemed to be within the spirit, scope and
contemplation of the invention.
[0025] In order to describe and point out the subject matter of the claimed invention, the
following definitions axe provided for specific terms, which are used in the following written
description more clearly and concisely.
[0026]’ Reference in this specification to “one embodiment” or “an embodiment” means that
a paflicular feature, structure, or characteristic described in connection with the embodiment
is included in at least one embodiment of the present disclosure. The appearance of the phrase
“in an embodiment” in various places in the specification are not necessarily all referring to
the same embodiment, nor are separate or alternative embodiments mutually exclusive of
other embodiments. Moreover, various features are described which may be exhibited by
some embodiments and not by others. Similarly, various requirements are described which
{nay be requirements for some embodiments but not for other embodiments.
|0027l The present invention overcomes the drawbacks of the existing state of the an
technologies by providing a manufacturing process of 30 mm VOG canridge case and
grenade body lhat will produce parts from ‘micro alloyed steel material in coil form. The
steel material in coil form is Armealed, and phosphated before fed into the multistage cold
part former machine where ‘Net’ or ‘Near Net’ shape products are produced in multiple
forming stages. This multi station Parts Formers, does not need any intermediate anneal and
phosphate.
[0028] Considering Raw Material as a scarce resource, price fluctuation in raw material
markets, wastage, higher pfoductivity, high dimensional expectations and functional
requirements of this family of pans, Cold Forging to the near net shape is found to be the
ideal method of manufacturing.
[0029] FIG. 1 illustrates a flowchart depicting manufacturing of 30 mm VOG cartridge case
and grenade body out of micro alloyed steel in coil form, in accordance with an exampie
embodiment.
[0030] Referring to Fig. l, at step 101, the input raw material i.e., a micro alloyed steel is
received as a hot rolled rod in coil form. Each coil weighing 3 tons, approximately. In some
example embodiments, the raw material is inspected and approved for dimensional, chemical,
and metallurgical properties. In the conventional prior art, a medium carbon steel’,
corresponding to SAE 1040, machine the part is used and then heat treat to achieve the;
required metallurgical properties.
[0031] The present invention process will use lower carbon micro alloyed steel containing
very marginal amount of BORON (0.005% maximum), which not only aids cold forging but
also aidé in elevating the mechanical properties of the part to the required levels only due to
the work hardening taking place during the cold forging process itself. There is no need for a
separate heat treatment to achieve the required mechanical properties.
|0032] Referring back 10 Fig. I: at step 103, the steel coil (which is received at step 101) is
then “Annealed’: ‘Phosphale’ and ‘Lube coaled’ as per process requiremenL
[0033] Annealing: “Annealing; is a process of heating the steel goil material to around 750
deg. C, hold it at that temperature for two hours and then slowly cooled at the rate of 10/15
degrees per hour, until drop to 600 degrees. The purpose of ‘Annealing’ is to soften the steel
coil to a level where it will be highly amenable for cold forging.
[0034] Phosphating: During the cold forging process, enormous amount of friction will be
generated between the part and the ‘Tooling’. ‘Phosphating’ aids in reducing the friction, as
this process includes creating a coating over the surface of the steel which is coming out from
the annealing. The coating is a form of lubricant that helps in substantially reducing the
friction generated.
[0035] Lube Coating: Lube coating is a process wherein the ‘Zinc phosphated’ coil (from
the process of phosphating) is immersed into bath containing Sodium stearate dissolved in
water and kept at 90 deg.C. During this process the Zinc phosphate layer on the steel material
reacts vw'th Sodium Stearate and a layer of Zinc stearate is formed. This layer exponentially
increases the ability of the steel surface to slip under frictional forces.
[0036] In some example embodiments, at step 105, drawing the steel coil on a wire drawing
machine to the required diameter. Coil wire drawing is a process in which the material
diameter is reduced to the required level by pulling the wire material thru’ a ‘carbide die’ of
the required size. This process is done on a “wire drawing” machine.
[0037] Referring back to Fig. I, at step 107, loading the coil onto the 6-station parts former.
The parts Former will carry out automatically six operations sequentially by moving the pan
from one station to the other. The following are the six individual operations performed by
the Parts Former.
|0038| In some example embodiment; the part former is basically a forging machine. It is a
combination of six individual presses built on a same frame adjacent to each oxher. There are
quite a few reputed manufacturers of such ‘parts formers’ across the globe. This machine
incorporates following features: (i) Pull in the material loaded on this machine in the form of
3 Ton wire rod coil‘ (ii) Cut off the required blank in the first station. (iii) Automatically take
the blank thru’ the five forging stations as soon as the forging is done on each station, (iv)
Flow of a lubricant cum coolant solution over the parts and tools during the process to reduce
friction as well as reducing the heat generated.
[0039] The six operations of the part former which is performed sequentially as follows: (i) A
small piece equal (blank) to the weight of the forged part is cropped out pf the coil material in
the first station. (ii) Both ends of this blank are made 'squarer in the second station; (iii) the
blank is upset to form larger diameter as needed. (iv) An indent of the internal circular shape
is made in the third station. (v) The internal diameter is formed by backward extrusion in the
fourth and fifih station respectively. All key internal dimensions including the radius on the
bottom face are achieved in this process-(vi) choosing suitable coolant oils which enhances
formability of part while serving its main application of cooling the forging tools to maintain
the expected forging tool life and dimensional stability of product.
[0040] The main challenge faced during the process development includes the need to go for
tungs‘ten c'arbide dies, pvd coated special pm grade steel punches for backward extrusion.
Considering the amount of deformation carried out on the sheared billet continuously which
induces work hardening through the progression, the speed of deformation and the
temperature of the tools during production run, the conventional HSS tools cannot be used for
mass production of parts.
[0041] In some example embodiments, at step 109, stress relieving the forged cartridge
case’s mouth area reducing 'the hardness to the desired level. The cold forging process
enhances the mechanical properties due to work hardening to a level where, it is not
necessary to ‘heat treat’ the part as being done when machined from bar material as done in
Prior Art.
[0042] However, the front step of thé Cartridge case: where it is to be crimped with the
grenade required to be softer to enable proper crimping to the desired ‘pu'll out load’.
[0043] Stress relieving is a process wherein the front step is precisely heated only to the
required length to 700 deg. C thru’ the Induction heating system. The required heating is
achieved in 5 seconds and then the part is allowed to be cooled in natural air.
[0044] In some example embodiments, the pull-out load which is the criteria for stress
relieving, is the load required to pull the grenade out, after it has been crimped with the
cartridge case. In order to achieve the ‘Pull out load’ within limits, it is essential to bring
down the Cartridge case front step’s Tensile stress between 50Kg/mm2 to 70 Kg/mm2. By
suitably adjusting the clearance between the Induction coil and the Cartridge case as well as
the time of heating, this level of Tensile Stress can be easily achieved,
[0045] Referring to Fig. 1, at step 111, the process further includes machining the product
formed as above in the six-station parts former on a CNC Turning cefitre to the finished pan
dimensions.
‘
[0046] In some example embodiments, the process further includes at step 113, zinc plating
and de-embittering the finished part.
[0047] FIG. 2 illustrates a block diagram depicting the advantages of manufacturing of 30
mm VOG cartridge case and grenade body out of micro alloyed steel in coil form, in
accordance with an example embodiment. In the present invention, the adoption of cold
forging process to near net shape saves around 40% raw material compared to machining
process; thus, saving in material cost.
|00;18| FIG. 3 illustrates a comparison between the present invention (SAF Cold Forge
methdd of production in multistage part Former machine) and Prior Art (Bar stock machining
route)
4
[0049| Considering Raw Material as a scarce resource, price fluctuation in raw material
markets, wastage, higher productivity, high dimensional expectations and functional
requirements of this family of parts, Cold Forging to the near net shape is found to be the
ideal method of manufacturing.
[0050] FIG. 4 illustrates a graph showing comparison plot showing the improvement in
productivity and material saving between conventional and the manufacturing method
described in the present invention. Referring to Fig. 3 and Fig. 4, the use ofa six station Parts
Former eliminates the time consuming intermediate ‘Anneal’ and ‘Phosphate’ processes,
since all five stages will be done in one go on the parts former at 60 parts per minute without
the need for an intermediate ‘Anneal’ and ‘Phosphate’. This results in much higher
productivity (As shown‘in Graph), reduced operational co'st and manpower. Use of ‘micro
alloyed steel’ eliminates the need for the Post ‘Heat treatment” process after Forging
otherwise needed, saving cost and time. Producing out of ‘coil form material’ than from a
‘straight bar form’ eliminates wastage of mat‘erial thru’ large number of end pieces of each
bar. High production ra-te of 50 to 60 part; per minute out of the parts former helps in
producing the parts far quicker than the slower conventional machining process. Forging
results in good compaction and superior grain flow parallel .to the part profile, thus adding
strength to the part.
[0051] Moreover, aléhough the following' description contains man): specifics for the
pu1poses ‘of illustration, anydne skilled in the art will appreciate that many variations and/or
alterations to said details are within the scope of the present disclosure. Similarly, although
many of the features of the present disclosure are described in terms of each other, or in
conjunction with each other: one skilled in the art will appreciate [hall many ofthese features
can be provided independently of other fealures. Accordingly, this description oflhe present
disclosure is set forth without any loss of generality to, and without imposing limitations
upon, the present disclosure.
WE CLAIM,
l. A method of manufacturing of30 mm VOG cartridge case and grenade body, comprising:
receiving input raw material: wherein input raw material is a micro alloyed steel is
received as a hot rolled rod in coil form;
annealing, phosphate and lube coating as per process requiremem, wherein annealing
corresponds to a process of heating the steel coil material to around 750 deg. C, hold it at that
temperature for two hours and then slowly cooled at the rate of 10/15 degrees per hour, until
drop to 600 degrees,
wherein phosphating corresponds to creating a coating over the surface of
the steel, wherein the coating is a form of lubricant that helps in substantially
reducing the friction generated, and
the lube coating corresponds to a process where zinc phosphated coil is
immersed into bath containing Sodium stearate dissolved in water and kept at 90
deg. C= wherein during the lube coating process, the zinc phosphate layer on the
steel material reacts with sodium stearate and a layer of Zinc stearate is formed;
drawing the steel coil on a wire drawing machine to the required diameter;
loading the coil onto the 6-station parts former, wherein the parts former is carrying
out automatically six operations sequentially by moving the part from one station to the other;
stress relieving the forged cartridge case’s mouth area reducing the hardness to the
desired level, wherein the stress relieving is a process where the front step is precisely heated
only to the required length to 700 deg. C through a induction heating system;
machining a product from the six-station parts former on a CNC Turning centre to the
finished part dimensions; and
zinc plating and de-embittering the finished part.
2. The method as claimed in claim 1: wherein the six operafions of the part former which is
performed sequentially as follows:
(i) a small piece equal (blank) to the weight of the forged pan is cropped out of the coil
material iri the first station,
(ii) both ends ofthis blank are made squarer in the second station,
(iii) the blank is upset to fotm larger diameter as needed,
(iv) an indent of the internal circular shape is made in the third station,
(v) the internal diameter is fom1ed by backward extrusion in the fourth and fifth station
respectively,
(vi) choosing suitable coolant oils which efihanges fénnability of part while serving its main
application of cooling the forging tools to maintain the expected forging tool life and
dimensional stability of product.
3. The method as claimed in claim 1, wherein each coil weighing 3 tons.
4. The method as claimed in claim I, wherein a criterion for stress relieving is a pull-out load,
wherein the pull-out load is the load required to pull the grenade out, after it is crimped with
the cartridge case.
5. The method 'as claimed in claim 4, wherein in order to achieve the pull-out load within
limits, the cartridge case front step’s tensile stress is kept between 50Kg/mm2 to 70 Kg/mm2.
6. The method as claimed in claim 5: wherein the cartridge case front slep’s tensile stress is
kept between SOKg/mmZ lo 70 Kg/mmz by suitan adjusting the clearance between the
induction coil: the cartridge case= and the heming time.