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December, 1925
chisel must be hard enough to cut comparatively hard
steel and tough enough to withstand breakage. On
medium grade steel one chisel will sometimes cut
several hours, while on hard steel the same chisel
will cut but a very few minutes before it must be
reground.
Rigid supervision is necessary to insure that all
the injurious defects are removed by the chipper.
The chipper is inclined to reduce the amount of chipping
done to a minimum, especially when working
under a bonus incentive. In order to offset this condition,
every side of every bloom or bar must be personally
inspected and released by an experienced and
responsible man assigned to this work alone.
Certain high priced steels receive three cleaning
operations to insure 100 per cent product. First, the
ingot is inspected and any surface defects or irregularities
which might cause trouble later are chipped
out. Second, after the ingot has been rolled down
into a bloom it is pickled and again any surface irregularities
are chipped out. Third, after the bloom
has been rolled on the finishing mill into the size required
by the customer, it is again pickled and after
carefully inspecting it, any surface irregularities are
removed.
Each one of these operations requires time to
perform and this time should be considered when
quality of product is desired. It must be remembered
in this connection that common low priced steels are
not subjected to these cleaning and inspecting operations
with the result that the interval of time between
making in the furnace and shipping to the customer
is correspondingly shorter on low priced steel.
Grinding.
Blooms, billets, and finished stock which are too
hard, or on which for any reason chipping is undesirable,
are ground. The great majority of blooms
and billets are ground without any preliminary pickling.
On finished stock very frequently it is desirable
to pickle before hand grinding.
Bloom and billet grinding is done on swing frame
grinders. These machines are motor-driven and carry
a grinding wheel which is 24 in. in diar.ieter and :ias
a face which is 2 in. wide. For cleaning finished
stock hand grinders, which are pneumatic driven,
with a grinding wheel 8 in. in diameter, are used.
Next to labor the most important and expensive
item in connection with grinding is the wheel used
for grinding. It is essential that this wheel give a
satisfactory finish to the stock when ground, the wheel
must have long life and the cutting rate must average
high. The type of steel to be ground will determine
the wheel to be used. Where the type of steel
varies widely, it is advisable to carry several kinds
of wheels in stock. In general, grinding wheels are
all made from the same electric furnace product,
but they differ in grain size and combination as well
as in the bond used and method of burning. Some
wheels are treated, others are untreated. By treatment
is meant that the pores of the wheel after burning
are filled with some liquid substance like rosin
which has a lubricating effect.
The supervision and inspection on ground stock
must be very keen and considerable experience with
close application is necessary to insure removal of all
imperfections.
Forging- Stamping - Heat Treating 437
Lining Furnace Bungs
By Meredith F. King*
In the plant of the Canadian Steel Foundries at
Montreal, annealing furnace bungs of large dimension
are used. The bung casting has a span of 11 ft.
3 in. and is 2 ft. 6 in. wide, with a total weight when
lined of approximately 6,635 lbs. For many months
past this concern has adopted monolithic linings in
place of fire brick for these bungs, on account of
1—Lower cost of refractory material,
2—Lower labor cost,
3—Greatly increased service.
The monolithic lining consists of crushed old fire
brick, bonded with high temperature cement mixed
FIG. 1—A wooden form is used when ramming the
monolithic lining in place.
in proportion to make a plastic mixture which is
rammed with an air hammer into the bung casting, to
a depth of 9 in., in place of laying up fire brick in
these castings to the same depth.
A wood form is used as shown in Fig. 1. This
form is made of rough 1 in. stock which is clamped
securely with 2x4 braces against the sides of the
casting and securely fastened by wire ties drawn
tight. These forms can be repeatedly used for relining
a group of bung castings.
It is the practice of this plant to have a reserve
supply of bungs, and as soon as one is out of service,
it is relined in the manner described. The newly
lined bungs are usually placed on top of a core oven
for 3 or 4 days for drying, after which they can be
easily handled. They are then placed to one side and
allowed to air set thoroughly for about 3 or 4 weeks.
A sufficient number of bung castings are kept on hand
so that an ample supply of lined bungs is always
ready for service.
Lining.
The bung is first placed in the position and the
form securely clamped in place. Before ramming in
the mixture of crushed old fire brick and high temperature
cement, the interior face of the bung casting
is painted with a batter of high temperature cement
which bonds the rammed-in mixture to the
casting-.
•Service Engineer, Quigley Furnace Specialties Company,
New York.