3218

flame is particularly veil adapted to welding. Flame temper­

atures as high as 3100°to 3300°C are obtained, and the chem­

ica l characteristics of the

flame and its action on the

weld metal aan be regulated

closely.

acetylene flame may be neutral (the ratio is about

1.04-1.14);

oxidizing ( the ratio is about 1.15-1.51)

, or carburizing

(the ratio is about 0.$5-0.95).

^he neutral flame is edeal for welding

steel;

the

molten pool of weld metal remains clear

and quielr’;

with

no boiling, foaming, or sparking.

The flame protects the metal from oxidation

• The result

is clean, sound, and ductilo weld .metal

i f

all other var­

iables as welding rod and manipulation are

under control.

ods*

This

technique*' is similar to

that

used for

exother­

mic risers*

The area to be repaired

is

cleaned as

for

standard welding, and a dgm of sand or other refractory

built

around it* For repairing steel

castings, a mixture

proper

composition in the

fille r

metal)

is either charged

into a

separate

melting chamber,

or used

to

f i l l

a large

mould

above the

defective

area#

The mixture

is

ignited

satisfactorily.

Lletal is formed by the

exothermic reaction*

Fe2°3

+ 2 A1 * A1203 + 2 Fe

and about 2500°C,

and this metal ^ttlea readily from the

AlgO^ slag*

The porous area is melted by

the

high heat

and

a sound weld

is formed# The weld deposit

can be made

to

the chemsitjy

desired, and is not limited to ferrous

compositions, by using other exothermic

reactants, non—

-ferrous alloys can also be repaired*

Plow welding,(’burning

in")

,_______

localized shrink­

Папу times casting defects such as

age cavities are repaired by remelting and recastingln

situ", using metal from the Idadle.The

casting is embedded

in

sand, or

a dam of sand molded around

the defective area*

squore cm, ia created in the tank*

After this it is dried

in air during 2-3 hours and heat -treated in a furnace.

Regi'-rai of the heat-treatment is the following: an in itia l

temperature in the furnace should be about 25-35°C, the

rising of a temperature up to 80-100°C

during 2 hours

and then up to 130-160°C during 1

hour

additionally, heat-

-treatment at a

temperature 160-1S0°G during 1.5 hours

and cooling the

casting together with the furnace up to

the temperature

about 30-36°C.

Hot natural drying o il As used

for impregnation too.

The impregnation is carried out under the pressure 2-3

kg/omo , iftet1 which the casting is

dried in air during one

day.

When 10%-somtlon of liquid glass is used as an impreg­

nant the casting is also primerily

heated up to a temperature

This Is a pasty mixture of

iron

filin gs

in

a hardening

agent, which ’’sets" in air to very nearly the hardness

and color of the oasting. It is

d ifficu lt

to

notice repairs

of

this

sort

on

tiie

surface

of

iron castings,

particularly

i f

the

part

is

later ground

or

machined

and cleaned by

tumbling or shot-blasting.

Today*

repair

of

casting

defects with

epoxide compounds

is

widespreaded

in

practice

of

foundries*

In this case

acetone, etc,

The composition

of

the

compound whioh is used Is the

following:

epoxide

resin

-100 weight parts

dibutyl

phthalate

- 10-25 w.p*

polyethylene polyamine - 8-9 w,p,

intei

fille r

-

about

60% of the resin weight

Portland cement

,

zini

oxide,

aluminium oxide, maroh-

a lite,

ta ll may be

used

as

a fille r

material. All inert

fille r s

should be

dried

at

a temperature about 110 - 120°C,