Faqs
One needs to understand the basic fundamentals of Brazing alloys & the
related procedures. In order to make the cumbersome & complex topic easy
& comprehensible for readers & users, some vital questions have been
dealt with in details throwing enough light on the confusing topic. Here, we
are going to highlight on some of the fundamental elements which will help
in answering frequently asked questions.
Q.1. What differentiates brazing, soldering &
welding?
Ans. Brazing has been defined as a group of joining processes
specially arranged in a manner to produce coalescence of materials. The
process involves heating of these materials at a brazing temperature by
using a filler metal (solder) which has a liquidus above 840°F (450°C),
and below the solidus of the base metals.
In the case of Soldering, the only fact which distinguishes it from brazing
is the filler metal used, since, here the liquidus is below 840°F (450°C)
while it is above the solidus of the base metals.
Welding involves the process of fusion which takes place along with
the melting of base metal and a filler metal.
Q.2. What is a brazing procedure?
Ans. A kind of metallurgical bond is created between the filler
metal and the surfaces which are joined using the brazing procedure. The
process involves application of heat directly on the base metals, thereby,
the filler metal is brought into contact with the heated parts. Once the
melting of filler metal takes place, capillary action is applied to draw the
melted part through the joint.
Q.3. What is provided through a brazed
joint?
Ans. Brazing joint process provides many properties which are namely
:
- Sturdy joints
- Cheap temp/lower cost
- Base metals integrity is maintained
- Dissimilar joints are efficiently joined
- well defined joint appearance
- Easy acquirement of skills
Q.4. Define oxidization.
Ans: Oxidization is generally defined as a process where after the
metal exposed to oxygen, the oxides form from oxygen atoms attach to the
metal. Once formed, these oxides prevent the molten alloy from
metallurgically joining to the metal.
Q.5. What are the filler metal form
types?
Ans: Availability of filler metals in certain forms depends upon the
alloy that are chosen. These firms are widely categorized as :
Mostly, the preforms are made from strip and wire.
Q.6. What does Flux mean?
Ans: When the joint surface is shielded from air, thus, preventing
oxide formation after applying chemical compound, it is s is known as Flux.
The metals in the process of joining are cleaned before the start of a
brazing procedure, though, the flux material will dissolve and absorb
oxides.
Q.7. What are the different flux forms
available?
Ans: Depending upon the type of flux, flux is made available in the
form of paste, slurry, liquid and powder form. Though, dispensable fluxes
are found with petroleum base, the paste, slurry, and liquid fluxes are all
water based. Even a torch in use is used to deliver the flux to the joint.
Q.8. How to clean a flux off of joint after
brazing?
Ans: By quenching & soaking the assembly in hot water that the
flux can be cleaned smoothly off the brazed joint. In order to clean a
stubborn flux residue, HCl (up to 25%) can be added to the water &
exclusive made cleaners can also be used for the cleaning purpose.
Q.9. What is the right process of
reconstituting & thinning of flux?
Ans: In order to thin water-based flux, water is applied which is
generally in the form of distilled or de-ionized meant specifically for
this.
Q.10. What is a flux's shelf life?
Ans. Generally, the warranty period of a flux metal is of one year
from the date of manufacture if properly stored in the original unopened
container. The quality might not deteriorate even after the expiry of this
period.
Q.11. What do we understand by a brazing
paste?
Ans. When we talk of a brazing paste, we mean a material consisting
of metal alloy in a powder form well mixed with a binder. Flux is added to
this paste whenever required to provide protection from oxidization.
Q.12. What is the most feasible
applications for applying a brazing paste?
Ans. The application of a brazing paste is required in functions
such as :
To make a paste formulation, flux is generally added which has an
exception as well, i.e. say it has no role to play in the paste formulation
when it is to be used in a vacuum or atmosphere furnace.
Q.13. What is a brazing paste's shelf
life?
Ans. A warranty of 90 days is given in case of brazing paste stored
in its original unopened container. The quality may not deteriorate even
after the expiry of this period. The functional aspect of this paste form
can be determined only by melting the paste to check if it flows or not
which ultimately determines the functionality of the paste.
Q.14. In brazing, what types of joint
configurations can be used?
Ans. Joints of distinct types are used in brazing where the most
common of them are :
- Butt joints
- Lap joints
- Butt lap joints
Q.15. What is the proper clearance in
case of brazing?
Ans. In flux brazing, a joint clearance with a range varying from
0.002"-0.005" is there to produce a sound high strength joints.
Whereas, this joint clearance should be 0.000"-0.002" in case of
atmosphere and vacuum brazing. Lot of care is taken while using brazing
metals with different coefficients of thermal expansion. When determining a
joint clearance, the amount the materials expand has to be kept in
consideration.
Q.16. What is a brazing joint's strength?
Ans. There are certain factors which determine a brazing joint's
strength which are mainly :
- Joining of the base metals
- Joint clearance
- Usage of filler metal
- Use of varied base & filler metals
- The gap between the two metals when being joined
- Whenever there is an increment in the gap, it leads to an automatic
decrement in the joint strength. But at times, the braze joint strength
will equal or surpass the the strength of the base metals when used in
proper conditions.
Q.17. What should be the right
temperature for furnace in furnace brazing?
Ans. The temperature for furnace in furnace brazing is generally
heated at 50°F-100°F above the liquidus of the filler metal being
used.
Q.18. What do we mean by Handy One?
Ans. For simplification of a brazing process, a flux cored product
or a Handy one is made use of. Available in the form of a brazing alloy in
strip form, it is rolled around a measured amount of powdered flux. The flux
gets released whenever the part is heated, thus, providing enough protection
from oxidization. Handy one is found in multiple filler metals and flux
combinations which joins virtually all common metals.
Air
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