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Metallization doesJa^Jicrease the casting strength
and it |
is used |
both without and in combination with welding* |
|
The |
surface |
to’ be |
metallized must be primerily cleaned |
by shot |
blasting, o il |
and grease spots are removed either |
|
with benzine or by the heating of a casting upto a temperatyre 350-370°C*
Cavities are dressed as shown in fig*3 * ll, after that
they should not be located nearer than 2.5mm from the cast
ing ddge. Small cavities are recommended |
to |
dress up to |
|||
8- 12 mm in diameter, |
very deep cavities may be primerily |
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knurled with 4ead or |
fille d with plastic |
fillers» |
|
||
For |
metallization an metal rod made of |
the alloy |
of |
||
a needdd |
ohemical composition is meltld |
by |
an electric |
a;:® |
|
and the molten metal being pulverized by a jet of oompress- p
ed air under the pressure 6 kg/опг is drifted on the defect
surface until it is entirely fille d with metal*
To protect the casting surface beside the defect from
the sticking of the pulverized metal it is covered with thin foiljj or cartoon. Also special templets made in accor dance with the shape of the defect may be used to prevent formation of excrescences on defect edges.
Settinajplugfe |
and |
liners* |
Small blows |
and cavities |
|||||
upto |
20mm in |
diameter |
can be repaired |
with the help of |
|||||
plugs |
(fig .3 |
. 1 2 ). |
Blows |
in casting |
holes |
can be closed |
|||
with |
liners (fig .3.13). |
Elugs |
are |
set |
in |
the hole with |
|||
a thread, liners |
either |
with |
a thread |
or with pressing. |
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Electric—are welding ia amost universally need for repairing steel oas-ings* Shielded arc welding (are weld
ing with coated electrodes) is the most widely used type but Inert—feas metal-arc welding (bare metal consumable electrode with inert gas shield) is gaining favor for rep airing large defects*
Specialized procedures and equipment are often necessary for the higher-alloy steels*
Gray cast iron castings can be repaired by most of the
standard fusion welding processes, but careful preheating and slow' cooling are necessary to prevent (1) welding
crvacking and (2) transformation of |
the structure |
to |
hard, |
||||
b rittle mairfeensite* |
Gas welding is |
usually found |
to |
be |
|||
preferable to minimize these effects* |
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|
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|
Eor applications where corrosion or thermal stresses |
||||||
are not a problem, or where a color |
match is not |
necessary, |
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braze welding with fellow brass is |
a desirable repair meth |
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od* |
The strength o f the |
join tiis |
fully comparable |
tot |
|||
that |
obtained with |
a cast |
iron fille r metal* |
|
|
||
|
Malleable iron |
castings |
are seldom welded in |
the anne |
|||
aled |
or heat-treated condition because of the d ifficu lty |
||||||
of achieving a ductile weld* In the |
as-cast state (white |
||||||
iron#, they can be |
readily |
repaired |
using white cast |
iron |
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/ |
|
|
|
|
|
|
|
wilding rods * Gas welding 1в usually employed* The weld
solid ifies as white |
iron and malleableizes equally as well |
as the base metal* |
After cleaning the repaired castings |
are satisfactory in |
a ll respects* |
References:
1, Laing,J. and Rolfe, R,T#,A Manual of Foundry practice
for
for Cast Iron” # London dhapmen & Hall , I960.
2# Ainbinder, A,B# and Bastrakov ,V,K« Stabilizing o^ cylinder
dimensions# Collection of articles”Increase pf parts lia b ility ” •(Povyshenie nadezhnosty detalei mashin", Perm,Rotaprint PPI, 1969(in Rissian ).
3# Bastrakov, B«K# To the question of calculation of ingatss
number «Collection of articles "Increase of parts liab ility* (Povyahemie nadezhnosty detalei mashin"),Perm
Potaprint PPI' , 1969 (in Russian) •
M
4# Parkes ,W#B* "Clay - bonded foundry sand,London,1971 • $. Adams ,C.M?, Jr. Flemings ,M#C# and Taylor, E.F# ,
Solidification and Risering of Gray Iron Castings", Transactions A.F.S., 6I,XI3I >1955
6# Taylor,H#F., Flemings ,M#C. Wulff* J«" Foundry Engineering" , New York -London,Sydney, 1959 •
19."Technology of the Transport Machinlbullding"$Tekhnologia transportnogo ma shinocbroeria"), 1956,173,P.P.
52-53 ( ih Hussian) .
20.Manakin, A .M., Denisov, 1Г.А. and others .large steel Castings” (“Гги^пуе staln^e оtlivky” ),Moscow Jivlashinostroenie ” , 19-29
21.Sylvie fG.J. “Cast Metals Technology ” , London ,Addiso* L esley | 1972
22.Kondic,V. “Metallurgical Principles of Founding” ,1968,
Pew York .
23. Impregnation of Porosity in Castings, Process fo r,
MI&3TJD-276, General Services Administration, Pew