Table of Contents
Abstract..........................................................................................................................................2
Introduction....................................................................................................................................2
Equipment......................................................................................................................................2
Experimental Procedure................................................................................................................3
Results...........................................................................................................................................4
Discussion.....................................................................................................................................4
Conclusion.....................................................................................................................................5
Answer to the questions................................................................................................................5
References....................................................................................................................................7
Abstract
The soldering joint applied in this report for the preparation of a lap joint between two galvanized
iron sheets involves the application of a filler metal, which is normally a lead-tin alloy. The filler
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melts at a somewhat lower temperature and spreads between the workpieces by capillary
action. The report highlights the experimental procedure involved in making the soldering joint,
the equipment used, and the observations. The processes consider the critical parameters of
the joining, which includes the role of flux, the heat source, and surface preparation. In the
study, good alignment, even distribution of solder, and cleanliness were identified as the key
factors to a strong and reliable joint, though temporary and relatively weak as compared to other
metal-joining techniques.
Introduction
Soldering is a simple, yet extensive use of metal-joining processes in many industries due to
their simplicity, versatility, and low application temperature. Soldering is performed with the help
of a filler metal, mainly an alloy of lead and tin, whose melting point should be less than 450°C.
This molten filler metal will flow by capillary action between the workpieces to form, when cooled
down and solidified, a bond. Unlike welding, which deals with the melting of the base metals to
join them, soldering does not involve the base materials in fusion; hence it is known to be a non-
fusion joining technique. This is one great advantage when dealing with sensitive components
that will be compromised by the high temperature involved in welding. (1) The secret of good
soldering is the utmost preparation of the workpieces, followed by temperature and flux
maintenance. Flux involves the use of a chemical substance on an area of the joint to exclude
the process of oxidation and allow molten solder to flow nice. Surfaces have to be cleaned
properly because impurities such as dirt, rust or oxidation can reduce strength substantially. In
addition, aside from surface preparation, proper heat and solder application and distribution
provide consistency and strength to the joint.
Everything in the modern world seemingly depends upon soldering: from electronics and circuit
boards to plumbing and automotive work. Soldering finds its most constructive field of
application in electronics, where conducting joints among different components are joined
together on printed circuit boards. It is also applied in automotive and aerospace industries
when the necessity arises to make low-temperature joints that may protect fragile materials from
destruction. Its versatility extends to joining dissimilar metals, a task not so easy to perform with
other methods, such as welding. (2)
The experiment also involves preparing a lap joint between galvanized iron sheets using a lead-
tin solder alloy. The project is carried out in order to understand in detail the basic principles
involved in such processes as material preparation, the application of flux, heat input, and any
problems associated with the soldering operation. The experiment also points to the relevance
of correct fit-up and even outflow of melted solder for arriving at a strong and sound joint. As a
general rule, soldered joints are weaker than welded joints; however, due to their economy,
ease of manipulation, and applicability for temporary couplings, the process is widely utilized.
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Equipment
1. Work piece: GI Sheet (Galvanized iron sheet)
2. Preheating device: Cutting Torch
3. Filler metal: Soldering iron axe
4. Flux: Ammonium Chloride (NH4Cl)
5. Cleaning agent: Hydrochloric Acid (HCl)
6. Heating source: Gas Flame
7. Gas cylinders: Oxygen and acetylene gas cylinders
Experimental Procedure
• Surface preparation and cleaning:
The surfaces of two galvanized iron sheets were cleaned with a wire brush to eliminate dust,
rust, or impurities on their surface. The surfaces needed hydrochloric acid treatment in order to
remove the zinc layer from the galvanized sheets for good adhesion during the soldering
process.
• Preheating:
The workpieces of metal and the filler metal, or solder, were preheated separately, as was the
flux ammonium chloride, NH₄Cl. Preheated also was the soldering iron itself to the needed
temperature for a sufficiently hot temperature that would melt the filler metal to be able to join
the workpieces.
• Fluxing:
The hot solder tip was dipped in flux [ammonium chloride (NH₄Cl)]. This will further clean the
surfaces, protect them from oxidation to facilitate smooth flow of molten solder between
workpieces.
• Applications of Solder:
When the tip of the soldering iron had reached a high enough temperature and was dipped in
flux, molten solder was applied between the two preheated workpieces. The solder was allowed
to flow into the joint area by capillary action, forming a lap joint.
• Final Cleaning:
The joint by soldering had to be water quenched in order to cool it. Then, it had to be cleaned
manually with a cloth as the flux leaves residues in the soldered area. Lap joint had to be
inspected for proper bonding and alignment.
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Results
The galvanized iron sheets are lap joined with solder (filler metal) at temperatures below 450°C
using the soldering technique.
Figure: Lap joint by soldering process. (Sample of 2011022)
Discussion
The soldering process involved the joining of two GI sheets using the lead-tin alloy as the filler
metal. During the process, several observations and challenges were recorded which show how
complex it can be to have a quality joint.
Lead-tin alloy use in soldering is appropriate because its melting point is quite low hence the
base metals are not damaged. In the process, the solder effectively melted and wadded
between the GI sheets through a capillary action-necessary to be able to form an effective lap
joint. However, it was challenging to distribute the solder equally. Since the operator was not
experienced enough, the soldering was uneven; thus, it came to be a lopsided joint. This
irregular flow sent the solder to collect in some spots, forming a swollen and imperfect bond that
can easily distort.
Amongst the major challenges that were experienced in the experiment was the correct
alignment of the workpieces. Soldering, especially manual, requires a proper positioning of
metals to be joined. A slight misalignment results in an irregular joint. GI sheets in this
experiment could not be kept quite stable and perfectly aligned; hence, the joint line was
irregular. Understandably, even slight positional shifts during soldering may result in poor
bonding as experienced in this case. That means, workpieces to be joined must be well-
clamped or stabilized both before and during heat and solder application.
The other major influencing factor was the input heat. The excess of heat in some instances
during the experiment had caused distortion of GI sheets. The high heat input had caused the
base metals to expand unevenly, and the visible joining zone also became wider. This probably
occurred because of the extremely low power density; hence, the heat was not concentrated
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enough to be precisely controlled. Another might be that the solder got overheated, which would
lose its efficacy and wouldn't flow easily and smoothly. Temperature control of soldering iron and
work pieces are of great significance in this regard to avoid such distortions.
The flux used in the process was helpful in order not to allow any oxidation, thus creating a
cleaner joint. Flux is such substance that creates around the joint some sort of protective
environment to minimize oxidation, hence poor bonds. It also reduces electrical conductivity.
Even with flux, the result is highly dependent on the operator's skills. In this case, though flux
was used, the joint was not perfect since solder was not applied accordingly and fitting was not
aligned correctly.
Through the experiment, the fact that soldering gave a relatively weak joint when compared with
other means of joining like welding came into view. A joint that was satisfactory in applications
where it is temporary did not have strength for more permanent applications, much less heavy
loads. This represents one of the major limitations of soldering: it becomes applicable in only
low-strength applications in which ease of assembly and disassembly becomes important over
structural integrity.
Conclusion
Among the wide list of metal joining techniques, soldering enjoys one of the widest uses
whenever the temperature requirements are low and the joints temporary. The experiment
demonstrated that for a bond to be reliable, it needs good alignment, preparation of surfaces,
and even distribution of solder. Even though soldering produces a joint much weaker compared
to welding, the process is still useful due to its simplicity, low cost, and the fact that dissimilar
metals can be joined using this process. Uneven flow, misalignment, and other defects do call
for precision and experience in the soldering process. If done properly, in a closely watched
manner, soldering can make efficient and durable joints in many areas of application.
Answer to the questions
a) Mention the operating steps that you performed in soldering.
Answer: The steps involved in operating during soldering are explained as follows:
1.There were two GI sheets taken and placed in such a way that an overlap is formed like a lap
joint
2.Mechanical cleaning was performed on the surface of GI sheets, and HCl was applied so that
the coating of zinc breaks and thereby increasing the life of the joint.
3. The oxy-acetylene cutting torch was lit first opening the acetylene and then the oxygen valve
up to obtaining a neutral flame.
4. The soldering iron was then heated with the cutting torch to the temperature that would allow
it to melt the filler metal.
5. The red-hot soldering iron was then plunged into the mixture of the filler metal and flux, taking
care that the flux allowed proper adhesion.
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6. The soldering iron was then put on top of the joint to embed the solder beads down the line of
the joint.
7. Once the joint was covered with solder beads and these had set, the joined workpiece was
carefully taken out using the tongs.
8. Afterwards, the joined assembly was cooled in water to complete the soldering process. (3)
b) How does a metallurgical bond form in soldering?
Answer: Soldering involves the formation of a metallurgical bond between metals due to wetting
and capillary action. On application to the joint, the solder filler material dissolves the oxide
layers on the base metals because of the action of flux. The molten solder flowing into the
crevices created in the joint metallurgically reacts with the base metals to an intermetallic
reaction layer. In effect, the process creates a continuous metallurgical bond at the atomic level
between the two materials involved by the time it has solidified. Effectiveness in this area
depends on high wetting properties and low surface tension of the solder, enhancing its ability to
spread uniformly across the joint surfaces. (4)
c) What is the purpose of surface cleaning in soldering?
Answer: Soldering involves surface cleaning, which is all the more essential in light of the fact
that contaminants like oxide films, dust, grease, and oil interfere with the soldering process. A
dirty surface reduces the solder's wettability, preventing the molten filler from flowing into the
joint correctly or, for that matter, at all. Lack of such flow can easily result in weak or brittle
bonds where the solder has not adhered well with the base metals. Therefore, cleaning of the
surfaces before soldering is important, so that the solder can penetrate fully into the joint and
give a strong metallurgical bond when it is solidified. (3)
d) What is the function of flux in soldering?
Answer: Flux provides several critical actions in the soldering process. Firstly, it dissolves oxide
layers on base metal surfaces, improving wettability. That is, the filler metal can spread and
adhere to the joint surfaces much better than it would otherwise if the oxides were present. That
would be, second, because flux prevents the molten solder from oxidizing in the atmosphere
and contamination while the process is taking place, hence preserving the quality of the joint up
to the time of solidification. Flux also minimizes the risk of corrosion at the cooling stage with its
temporary coating over the molten filler, hence providing much stronger final bonding. (5)
e) What are possible ecological and health risks of solder filler and flux (especially vapor)
you used? How would you mitigate or avoid them in the lab and in industry?
Answer: Soldering involves serious health and ecological risks due to the usage of solder fillers
and flux containing lead. Lead is an extremely harmful metal; thus, inhalation of vapors
containing lead eventually leads to grave chronic health hazards, which comprises lung
problems, neurologic damages along with other severe disabilities. Thus, toxic fumes produced
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by soldering lead to severe eye and respiratory problems and various versions, such as asthma.
But burns by soldering will be prone to occur if safety precautions are not carried out. (6)
Certain precautions are necessary to evade these kinds of hazards in both a lab and an
industrial setting. The risk of inhaling soldering fumes is reduced when operation occurs within a
well-ventilated area. Personal protective wear, including gloves, masks, and goggles, will
prevent direct contact with toxic materials and their inhalation. Food and drinks must not be
consumed within soldering environments to avoid contamination. Further, solder waste
management should be kept under control where lead solder and flux residues are to be
disposed of in lead-labeled containers; consideration of alternatives with lead-free materials is
called for. Though the lead-free solder has their own problems, they are more environment-
friendly and eliminate health risks when handled accordingly. (7)
References
1. [Online] https://blog.masterappliance.com/how-to-use-a-soldering-iron-
a-step-by-step-guide/.
2. [Online] https://blog.masterappliance.com/how-to-use-a-soldering-iron-
a-step-by-step-guide/.
3. [Online] Making a Soldered Joint: 7 Steps | Metallurgy
(yourarticlelibrary.com).
4. [Online] https://www.globalspec.com/reference/77773/203279/chapter-
1-solder-bond-formaƟon.
5. Study of Soldering Process. S., Bhowmick.
6. blink.ucsd.edu. [Online]
https://blink.ucsd.edu/safety/occupational/hazard-control/lead.
7. Y., Jason. [Online] https://www.linkedin.com/pulse/soldering-iron-toxic-
lead-free-irons-solders-jason-yang/.
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