Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~7'7~2~
This invention relates to the protection of metallic
surfaces susceptible to abrasion by rock-like or sand-like
abrasive material. There are various industrial operations
in which a metallic surface is susceptible to significant
abrasion by abrasive material, for example the upper surface
of a chute down which abrasive material passes and upon
which the abrasive material impinges with considerable
force as a result of its falling down the chute. Another
example is a surface at the leading end of a ground engag-
ing tool of an earth working machine, such as a loadingshovel or drag-like bucket over which abrasive material
passes as it is removed from the ground and forced over
the surface concerned.
Although such surfaces are usually made of
hard wearing metallic material, such surfaces nevertheless
become abraded after a period of time to such an extent
that they have to be renewed. However, such renewal is
difficult because the surface is usually an integral part
of at least a ma~or component of the equipment concerned,
such as a chute or ground engaging tool. Since such
equipment is generally of relatively large size, it is
impractical to transport the equipment,to a repair shop.
Renewal of such hard wearing metallic surfaces is
conventionally carried out in situ by manually arc welding
a consumable electrode of the desired material onto the
surface to form a new surface layer. However, this practice
is time-consuming and expensive because manually arc weld-
ing a new surface layer requires the presence of an operator
with a relatively high level of welding skill, and further
is not entirely satisfactory because the range of wear-
resistant materials which can be welded by such conventional
771;~4
manual arc welding is somewhat limited. Often, a preferred
wear-resistant material is not satisfactorily weldable by
such arc welding and a less desirable material has to be
used because it can be welded to form a new surface layer.
Also, the material is usually diluted with iron during arc
welding, and such chemical dilution alters the wear
characteristics of the material. Even when a preferred
wear-resistant material can be satisfactorily welded by
such arc welding, the cost of the operation is undesirably
high because of the requirement for a relatively highly
skilled operator and the time involved.
According to Canadian patent application No.
347,204, filed March 7, 1980, the above mentioned dis-
advantages can be overcome by stud welding studs of
abrasion resistant metallic material to the surface in
closely spaced relationship to cause the majority of the
abrasive material to contact the abrasion resistant studs
instead of the surface.
Such welding can be carried out by equipment
of the kind used for electric arc welding stud fasteners
in place. Hence, the operator can be a lesser skilled
person, and less time is needed to carry out the welding
operation. Further a wider range of materials can be
applied in this manner than with conventional manual arc
welding.
Thus, for example, ground engaging tools or
chutes of the kind previously mentioned can be provided
with abrasion resistant surfaces in situ by an operator
by use of equipment which is not only less skill demanding
but is also less fatiguin~ to use than equipment of the
kind required for conventional manual arc welding. The
.77~L2~
advantages of the invention disclosed in Canadian applica-
tion No. 347,204 when used in connection with ground engag-
ing tools or chutes for example are therefore readily
apparent.
According to the pxesent invention, a stud suit-
able for use in connection with the process which is the
subject of Canadian application No. 347,204 comprises a
first generally cylindrical portion of abrasion resistant
metallic material weldable to a metal surface by stud weld-
ing, said first portion having a diameter of about 0.125to about 1.25 inches and a cylindrical wall with a height
of about 0.05 to about 0.55 inch, a second generally cylin-
drical metallic portion attachable to said ~elding equip-
ment, said second portion having a diameter of about 0.125
to about 1.25 inches and a cylindrical wall with a height
of about 0.05 to about 1.5 inches, and frangible metallic
connecting means connecting the first portion to the second
portion. The second portion of the stud is removed after
stud welding by breaking the frangible connecting means so
as to leave the first portion welded to the metallic surface.
The first and second portions and the frangible
connecting means are preferably formed by an integral cast-
ing of abrasion resistant metallic material. The abrasion
resistant metallic material may for example be an alloy con-
taining by weight about 20 to about 30% chromium, about 3.5
to about 4.5% carbon, about l.S to about 2.5% manganese,
and about 0.5 to about 1.0% silicon, the balance being iron.
Other suitable alloys will be readily apparent to a person
skilled in the art.
Advantageously, the second portion is of larger
mass than the first portion, so that any porosity occurring
12~
as a result of the casting process is located primarily
in the second portion which is removed after stud welding.
Preferably, the mass of -the second portion is at least
twice that of the first portion.
The height of the cylindrical wall of the first
portion may be from about 0.1 to about twice the diameter
of the first portion. Advantageously, the height of the
cylindrical wall of the first portion is from about one-
third to about one-half the diameter of the first portion.
The first portion preferably has a diameter of
about 0.5 to about 1.0 inch and a cylindrical wall with a
height of about 0.25 to about 0.5 inch.
The second portion preferably has a diameter of
about 0.25 to about 0.75 inch and a cylindrical wall with
a height of about 0.5 to about 1.0 inch.
The first portion may have a diameter greater than
that of the second portion.
Embodiments of the invention will now be des-
cribed, by way of example, with reference to the accompany-
ing drawings, in which:
Figure 1 is a side view of a stud in accordancewith one embodiment of the invention, and
Figure 2 is a similar view of a stud according
to a second embodiment.
Referring first to Figure 1 of the accompanning
drawing, a cast stud is formed from abrasion resistant
metallic material containing 27~ chromium, 4.3% carbon,
2~ manganese, 0.7~ silicon, with the balance being iron.
The stud is made by casting the molten ma-terial in-to the
top of an appropriately shaped mold~
~1771 2~
The stud 10 has a first generally cylindrical
portion 12 and a second generally cylindrical portion 14,
the first and second portions 12 and 14 being connected
by frangible connecting means 16 in the form of an inter-
mediate portion of reduced diameter. The first po~tion 12
has a diameter of 0.6 inch and a cylindrical wall with a
height of 0.3 inch. The second portion 14 has the same
diameter as the first portion 12 and a cylindrical wall
with a height of 0.8 inch namely over twice the height of
the first portion 12. Thus, the mass of the second por-
tion 14 is more than twice the mass of the first portion
12, thus ensuring that any porosity formed as a result of
the casting process is predominantly in the second portion
14. It will be noted that the height of the cylindrical
wall of the first portion 12 is just less than one-half
the diameter thereof.
The lower end of the first portion 12 has a
small central projection 13 to which an aluminum washer
is secured before use to facilitate the subsequent ~elding
operation.
In use, the second portion 14 is fitted into
electric arc stud welding equipment and the first por-
tion 12 is welded to the metallic surface to be protected.
After welding, the second portion 14 is struck by hammer
or other implement to break off the second portion 14
from the first portion 12 by fracture of the reduced
diameter portion 16, thereby leaving the first portion
12 welded to the surface concerned. As described in
Canadian patent application No. 347,204, a number of studs
10 are stud welded to the surface in closely spaced rela-
tionship in order to protect the surface from wear by
abrasive material.
-- 5 --
7~2~
Figure 2 shows a stud 20 in which the first
portion 22 is larger in diameter than the second portion
24, the first and second portions 22 and 24 being connected
by frangible connecting means in the form of a neck 26 of
reduced diameter. The stud 20 is a cast stud of the same
material as the stud 10. The lower end of the first por-
tion 22 has a small central projection 23 to which an alu-
minum washer is fitted before use.
The first portion 22 has a diameter of 0.9 inch
and a cylindrical wall with a height of 0.5 inch. The
second portion 24 has a diameter of 0.6 inch and a cylin-
drical wall with a height of 0.8 inch.
The stud 20 is used in a similar manner to the
stud 10. An advantage of the stud shown in Figure 2 is
that the first portion 22 which is stud welded to the sur-
face to be protected and remains attached thereto after
the second portion has been removed, may be of a relatively
large diameter.
Other embodiments of the invention will be
readily apparent to a person skilled in the art, the scope
of the invention being defined in the appended claims.
