| |
 |
| |
| WELDING NON-FERROUS
ALLOYS |
|
 |
|
| |
| NICKEL AND NICKEL ALLOYS |
| Nickel and nickel based alloys are used in industrial
applications for |
- Corrosion resistance
- Heat resistance and high temperature properties
- Cryogenic properties
|
| Preheating is not normally required unless there is a risk
of porosity from moisture condensation. PWHT is not
usually needed to restore corrosion resistance. |
| |
| Inconel type of deposit is used for obtaining high
temperature, high strength joints designed to perform
at over 200°C such as on creep resistant chromemolybdenum
steels to stainless steels. These types
are suitable when welding sections over 25 mm. For
welding tool steels requiring toughness under repeated
cyclic stress and oxidation resistance upto 1000°C,
Hastelloy C type of deposit is regularly used. The drop
in strength and hardness as the temperature goes up is
very gradual. |
| |
| COPPER AND COPPER ALLOYS |
| The main features of copper and its alloys |
- Corrosion resistance
- Electrical and thermal conductivity
|
 |
| In terms of weldability, the alloys have quite different
welding characteristics. Copper needs substantial
preheat to counteract the high thermal conductivity. But
alloys like cupro-nickel can be fusion welded without
any preheat, as the thermal conductivity is similar to low
carbon steel. |
| |
| Buttering technique should be used to join copper
alloys to carbon / stainless steel. This is to take care of
the copper migration to the HAZ and precipitation at the
grain daries. The buttering, with a pure nickel electrode,
can be applied on either the copper or the steel side.
The groove has to be filled up a stainless or a bronze
type of deposit. |
|
|
| |
| The preheating should be 300-500°C when buttering
copper or bronze whereas the preheating temperature
has to be chosen according to the base material if the
buttering is done on the steel side. |
| |
| ALUMINIUM AND ALUMINIUM ALLOYS |
|
The characteristics of aluminium and its alloys that
make them amenable to fabrication are enlisted below.
These are |
- Light weight
- Good corrosion resistance
|
| The filler metals used for welding aluminium alloys are
selected considering the following aspects |
- Weldability of the parent metal
- Minimum mechanical properties of the weld metal
- Corrosion resistance
|
| Nominally matching filler metals are often employed
for non-heat-treatable alloys. However, for unalloyed
or low alloyed materials and heat-treatable alloys,
non-matching fillers are used to prevent solidification
cracking. |
| |
| COBALT ALLOYS |
| Cobalt alloys are known for excellent wear resistance at
high temperatures and the weld metal is used in cutting
and shearing operations at temperatures exceeding
600°C. These deposits exhibit high shock resistance,
high hardness at elevated temperatures and scaling
resistance and can be used in stamping dies, trimming
cutters, trimming punches, etc. |
| |
| |
| More Info... |
| |
