FIELD OF THE INVENTION
The present invention relates to a device for determining the secondary working
embritlement (SWE) property of sheet-metals. The invention further relates to a
method of determining SWE property of sheet metals adapting the innovative
device.
BACKGROUND OF THE INVENTION
Cold rolled annealed sheet steels are used for making various automobile
components. These components are fabricated by various kinds of forming
operations. After forming, these components may be subjected to further
deformation, by following ways:
• The fabrication requirement of the particular component may necessitate
multiple forming treatments.
• The formed component, during actual service, may be subjected to some
kind of loading, e.g. when a car experiences an accidental impact.
In either case, an already formed component may be subjected to a secondary
forming. This is known as 'Secondary Working'. During secondary working, the
material may behave like a brittle material, especially at low temperatures, and
this phenomenon is known as 'Secondary Work Embritlement', or SWE in short.

It is therefore important to determine the duclite-brittle transition temperature
for those materials, which are prone to SWE problem, for example high strength
interstitial free steels. The determination of SWE property requires developing a
suitable device.
Presently, there is no known device, which can determine in a single set-up the
duetile-brittle transition temperature for such materials / components for
example, high strength interstitial steels which are susceptible to secondary work
embrittlement. The property of SWE is basically characterized by the parameter
called as ductile-brittle transition temperature, which provides data to evaluate
whether or not a material is duetile or brittle at a certain temperature.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for determining the
SWE property of sheet metals.
Another object of the invention is to propose a device for determining the SWE
property of sheet metals, which evaluates a duetile-brittle transition temperature.
A still another object of the invention is to propose a method of determining the
SWE property of sheet metals.

SUMMARY OF THE INVENTION
A device for determining secondary working embrittlement (SWE) property of sheet-
metals, comprising a hollow chamber means accommodating a liquid susceptible to
absorb varying temperature, the chamber means having a top opening to allow
ingress and egress of a piston element and a hydraulically-operated pressing means
incorporated with said piston element detachably attached on the chamber means,
the pressing means being energized by an external electrical source and an anvil fixed
to a bottom portion of the chamber means being submerged in said liquid, the anvil
having a conically-shaped head portion and a deep drawn sheet metal specimen and
being correspondingly configured for fixing on the anvil and characterized in that said
device applies an incremental static load via a pressing means on several steel
samples in the form of a drawn cup at different temperatures such that a deformation
takes place without fracture in a non-reactive subzero liquid medium wherein the
minimum temperature at which consequtive three cups are deformed without fracture
is considered as the ductile - brittle transition temperature of sheet metal.
A method of determining secondary working embrittlement (SWE) property of sheet-
metals in a device as claimed in claim 1, the method comprising the steps of
preparing a specimen by drawing a sheet-metal into a cup and placing the cup in a
inverted manner (open bore at the bottom), on a conical head of an anvil and
disposing the anvil with the cup in a chamber means which is filled with a liquid and
slowly applying a static load on the cup at different temperature of the liquid via a

hydraulically-operated pressing means, the pressing means being detachably placed
on the chamber means and collecting repetitive data on crack-development on the
cup and/or on a several number of replaced cups to determine the minimum
temperature at which the cups sustain the load, thereby evaluating the SWE property
of the sheet-metal.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - show a hydraulic power pack in a schematic view, which constitutes a
feature of the device of the invention.
Fig.2 - shows a line diagram of the device of the invention.
Fig.3 - shows an anvil configured according to the invention.

DETAILED DESCRIPTION OF A PREFFERED EMBODIMENT OF THE
INVENTION
Fig. 1. shows a hydraulically-operated pressing means (1) having a vertically-
movable piston element (19). The pressing means (1) is energized by an
external electrical source (2). The pressing means (1) is operable in such a
manner that an incremental pressure-cum-load can slowly be exerted on a deep-
drawn specimen of sheet-metal.
As shown in Fig - 2, the pressing means (1) is releasably disposed on a hollow
chamber means (3) accommodating a liquid which can absorb incremental and
decremental temperature when created therein. An anvil (4) having a conically-
shaped head to detachably attached by a deep-drawn cup-shaped specimen (5)
of sheet-metal.
A static load when slowly applied on the specimen (5) held on the anvil (4) by
the piston element (la), a propagatable crack is formed on the specimen (5) if
the cup (5) constitutes a brittle material. On the other hand, if the material of
the cup (5) is non-brittle, the open bore of the cup (5) gets enlarged / deformed,
without forming any crack. The activity of slow-loading is repeated for number of
times, at different temperatures with different specimen, and the observations
are tabulated. The minimum temperature, at which none of the specimens fail, is
determined as the duetile-brittle tension temperate.

The method of the invention can be performed by carrying-out the following
sequential steps :-
1. A steel sheet sample is drawn into a cup having for example, 50 mm
diameter, with a drawing ratio of approximately 2.0.
2. The drawn cup is placed on a conical anvil, and the entire system is
immersed in a cold bath.
3. A piston slowly applies a static load on the cup.

• If it is a brittle material, a crack is formed and it gets propagated
immediately.
• If the material is not brittle, the open bore of the cup gets
enlarged/deformed, but no cracking takes place.
• This test is carried out for a certain number of times (with as many
samples) at a certain temperature.
• A chart is made, based on the observations.
• The minimum temperature at which none of the three cups fail, is
considered as the ductile-brittle transition temperature.

Fig. 3 shows an embodiment of an anvil designed according to the invention. The
two parallel arms (pa) of the trapezodical-shaped anvil (4) can be designed
between 10 to 20mm, the top and bottom bases (tb, bb) respectively should be
40 and 100 mm, the height between the top and bottom bases (tb, bb) shall be
between 60 to 70 mm, the two trapezodical arms (ta) shall be intersecting at an
apex making an angle of 60°.


WE CLAIM
1. A device for determining secondary working embrittlement (SWE) property of
sheet-metals, comprising:
- a hollow chamber means (3) accommodating a liquid susceptible to
absorb varying temperature, the chamber means (3) having a top
opening (3a) to allow ingress and egress of a piston element (la);
- a hydraulically-operated pressing means (1) incorporated with said
piston element (la) detachably attached on the chamber means (3), the
pressing means (1) being energized by an external electrical source (2);
- an anvil (4) fixed to a bottom portion (3b) of the chamber means (3)
being submerged in said liquid, the anvil having a conically-shaped head
portion (3c); and

- a specimen of deep drawn sheet-metal (5) and being correspondingly
configured for fixing on the anvil (4);
characterized in that said device applies an incremental static load via a
pressing means on several steel samples in the form of a drawn cup at
different temperatures such that a deformation takes place without
fracture in a non-reactive subzero liquid medium wherein the minimum
temperature at which consequtive three cups are deformed without
fracture is considered as the ductile - brittle transition temperature of
sheet metal.
2. A method of determining secondary working embrittlement (SWE) property of
sheet-metals in a device as claimed in claim 1, the method comprising the
steps of:
- preparing a specimen by drawing a sheet-metal into a cup (5);
- placing the cup (5) in a inverted manner (open bore at the bottom), on
a conical head of an anvil (4);

- disposing the anvil (4) with the cup (5) in a chamber means (3) which is
filled with a liquid;
- slowly applying a static load on the cup (5) at different temperature of
the liquid via a hydraulically-operated pressing means (1), the pressing
means (1) being detachably placed on the chamber means (3);
- collecting repetitive data on crack-development on the cup (5) and/or on
a several number of replaced cups (5) to determine the minimum
temperature at which the cups (5) sustain the load, thereby evaluating
the SWE property of the sheet-metal.
3. A device and a method for determining secondary working ebrittlement (SWE)
property of sheet-metal as substantially described herein with reference to the
accompanying drawings.

ABSTRACT

A DEVICE FOR DETERMINING THE SECONDARY WORKING
EMBRITTLEMENT PROPERTY OF SHEET-METAL
A device for determining secondary working embrittlement (SWE) property of sheet-
metals, comprising a hollow chamber means (3) accommodating a liquid susceptible
to absorb varying temperature, the chamber means (3) having a top opening (3a) to
allow ingress and egress of a piston element (1a) and a hydraulically-operated
pressing means (1) incorporated with said piston element (1a) detachably attached on
the chamber means (3), the pressing means (1) being energized by an external
electrical source (2) and an anvil (4) fixed to a bottom portion (3b) of the chamber
means (3) being submerged in said liquid, the anvil having a conically-shaped head
portion (3c); and a deep drawn sheet metal specimen (5) and being correspondingly
configured for fixing on the anvil (4) and characterized in that said device applies an
incremental static load via a pressing means on several steel samples in the form of a
drawn cup at diff erent temperatures such that a deformation takes place without
fracture in a non-reactive subzero liquid medium wherein the minimum temperature
at which consequtive three cups are deformed without fracture is considered as the
ductile - brittle transition temperature of sheet metal.