Review Questions on Welding Processes
Rivera Medina Paola Sofia
Universidad Politecnica de Yucatan
Computational Robotics Engineering
Date: July 6, 2025
R EVIEW Q UESTIONS they stabilize the arc, shield the weld area from the atmo-
30.1 Describe fusion as it relates to welding operations. sphere, introduce alloying elements, and form a slag to protect
the molten weld. Electrodes are classified by standards such
Fusion in welding refers to the process where the base as the AWS system, which indicates tensile strength, welding
metals are melted at the joint interface so they can coalesce position, type of coating, and current characteristics (e.g.,
and solidify to form a strong bond. This process may or may E6013).
not involve the addition of filler metal. The heat required is
typically supplied by an electric arc, a gas flame, or other
30.6 What are the similarities and differences between con-
energy sources.
sumable and nonconsumable electrodes?
30.2 Explain the characteristics of neutral, reducing, and Both consumable and nonconsumable electrodes conduct
oxidizing flames. Why is a reducing flame so named? electricity and maintain the arc. Consumable electrodes (e.g.,
A neutral flame has a balanced ratio of oxygen and fuel in SMAW and GMAW) melt and become part of the weld.
gas, producing a clean, short inner cone and a light blue Nonconsumable electrodes (e.g., tungsten in GTAW) do not
outer envelope. It is suitable for most welding applications. A melt, and a separate filler metal may be added. Consumables
reducing flame has an excess of fuel gas, resulting in a longer, require replacement more frequently, while nonconsumables
feathered inner cone and a luminous outer zone. It adds carbon are more durable.
to the weld area, which is why it is called “reducing” — it
reduces oxidation. An oxidizing flame contains excess oxygen 30.7 Explain how cutting is done when using an oxygen-fuel
and has a shorter, sharper inner cone. It can cause oxidation gas torch. How is cutting done under water?
and is used when rapid heating is required, such as in brazing
or cutting. Oxy-fuel cutting involves heating the metal with a flame
until it reaches ignition temperature, then injecting a stream
30.3 Explain the basic principles of arc welding processes. of pure oxygen to oxidize the metal and blow away the molten
Arc welding relies on an electric arc formed between an oxide. Underwater cutting can be done using oxy-arc methods
electrode and the base metal. The arc generates intense heat with specially designed torches and electrodes, where arc heat
(around 6,000 to 10,000°F), which melts the base metal and and oxygen perform the cutting in a submerged environment.
the electrode (if consumable), creating a weld pool. As the
arc moves along the joint, the molten metal solidifies to form 30.8 What is the purpose of flux? Why is it not needed in gas
the weld. Shielding is often used to protect the weld from tungsten arc welding?
atmospheric contamination. Flux cleans the metal surface, prevents oxidation, and
30.4 Why is shielded metal arc welding commonly used? Why promotes the flow of filler metal. It forms a protective slag
is it called stick welding? over the weld. In gas tungsten arc welding (GTAW), flux is
not needed because an inert shielding gas (e.g., argon) protects
Shielded metal arc welding (SMAW) is widely used due to the weld area from atmospheric contamination, making flux
its simplicity, low equipment cost, portability, and ability to redundant.
weld in various positions. It is called stick welding because
it uses a consumable electrode coated in flux, shaped like a
30.9 What does weld quality involve? Discuss the factors that
stick. The flux provides shielding gases and slag to protect the
affect it.
weld.
Weld quality refers to the strength, durability, and ap-
30.5 Describe the functions and characteristics of electrodes. pearance of the weld, and its freedom from defects. It is
What functions do the coatings perform? How are electrodes affected by factors such as proper material selection, joint
classified? design, welding technique, process parameters, cleanliness,
Electrodes conduct electricity to the arc and provide filler and adequate shielding. Inspection methods (visual, ultrasonic,
metal for the weld. Coated electrodes have several functions: radiographic) are used to verify quality.
30.10 Explain why some joints must be preheated before 30.17 Describe the differences between oxy-fuel gas cutting of
welding. ferrous and nonferrous alloys. What properties are important?
Preheating is necessary for materials that are thick, have Ferrous metals, particularly carbon steels, can be cut easily
high carbon content, or are prone to cracking. It reduces ther- because they oxidize exothermically. Nonferrous metals like
mal gradients, minimizes residual stresses, and helps prevent aluminum and stainless steel do not oxidize in the same way
hydrogen-induced cracking. Preheating allows for better fusion or form refractory oxides, making oxy-fuel cutting ineffective.
and reduces the cooling rate after welding. Important properties include oxidation behavior and melting
point.
30.11 How is weldability defined?
30.18 Could oxy-fuel gas cutting be used on a stack of metal
Weldability is the capacity of a material to be welded sheets? Explain your answer.
under fabrication conditions into a specific design, and to
perform satisfactorily in the intended service. It depends on Oxy-fuel gas cutting is not ideal for cutting stacks because
the material’s chemical composition, thermal properties, and the molten metal and slag can flow between layers, causing
the welding process used. poor quality cuts and fusing sheets together. Specialized tech-
niques or mechanical methods are preferred for stacks.
30.12 Describe the common types of discontinuities in welded
joints. 30.19 What are the advantages of electron beam and laser
beam welding compared to arc welding?
Common discontinuities include porosity (gas pockets), slag
inclusions, lack of fusion, incomplete penetration, cracks, and Both processes offer deep penetration, high precision, min-
undercut. These imperfections can weaken the weld and may imal distortion, and narrow heat-affected zones. They are
result in failure if not properly controlled. especially useful in aerospace, electronics, and high-precision
manufacturing, though they require vacuum or safety enclo-
30.13 What does joint design mean? sures and high capital cost.
Joint design refers to the configuration and preparation of 30.20 Discuss the need for and the role of fixtures in welding
the parts to be welded. It includes the type of joint (butt, lap, T, operations described in this chapter.
corner, edge), groove preparation, and fit-up. Good joint design
ensures adequate strength, accessibility, and cost-effectiveness. Fixtures hold components in place during welding to main-
tain alignment, prevent distortion, and ensure dimensional ac-
30.14 What types of destructive tests are conducted on welded curacy. They are essential in automated and precision welding
joints? tasks.
Destructive tests include tensile tests (to measure strength), 30.21 Describe the common types of discontinuities in welds
bend tests (to evaluate ductility and fusion), impact tests (e.g., and explain the methods by which they can be avoided.
Charpy for toughness), and macro-etch tests (to reveal weld
structure). These tests assess weld quality and performance Common discontinuities include porosity, cracks, slag inclu-
characteristics. sions, incomplete fusion, and undercut. They can be avoided
by using proper welding parameters, clean base materials,
correct technique, and suitable filler materials and shielding
C ONCEPTUAL P ROBLEMS
gases.
30.15 Explain the reasons why so many different welding
processes have been developed. 30.22 Explain the importance of the rigidity of welded com-
ponents in weld quality and workpiece shape.
Different welding processes have been developed to address
variations in materials, thicknesses, positions, production vol- Rigidity prevents deformation during welding by resisting
umes, quality requirements, environmental conditions, and cost thermal stresses. Lack of rigidity can lead to misalignment,
constraints. No single process is suitable for all applications. warping, and distortion, compromising both the geometry and
mechanical properties of the weld.
30.16 What is the effect of the thermal conductivity of the
workpiece on the kerf width in oxy-fuel gas cutting? 30.23 How would you detect cracks under the weld bead?
High thermal conductivity in the workpiece causes heat to Subsurface cracks can be detected using non-destructive
dissipate quickly, requiring more energy to maintain cutting testing methods such as ultrasonic testing, radiographic (X-
temperature. This typically results in a wider kerf due to ray) inspection, magnetic particle inspection, or dye penetrant
increased heating area and slower cutting speeds. testing, depending on material and crack location.
30.24 Could plasma arc cutting be used on non-metallic 30.31 Explain the importance of residual stresses in welded
materials? If so, would you select a transferred or non- structures.
transferred arc type? Explain your answer.
Residual stresses can affect fatigue life, dimensional stabil-
Yes, plasma arc cutting can be used on some non-metallic ity, and crack propagation in welded structures. Understanding
materials, especially those that are electrically conductive. A and controlling them (e.g., by stress-relief heat treatment) is
non-transferred arc system is preferred for non-conductive essential in critical applications.
materials since it does not require current to pass through the
workpiece. 30.32 Comment on your observations regarding the weld bead
shapes shown in Figure 30.5. Which would you recommend for
30.25 What factors influence the size of the two weld beads thin metal sheets?
shown in Figure 30.14? Bead shapes with narrow width and shallow penetration are
Bead size is influenced by welding current, travel speed, better for thin sheets to avoid burn-through. Techniques like
electrode size, welding position, heat input, and base metal GTAW or GMAW with low current are suitable.
properties. Higher current and slower travel increase bead size.
30.33 Why is oxy-fuel gas welding generally limited to thin
30.26 Which processes described in this chapter are not sections?
portable? Can they be made portable? Explain your answer. It provides lower energy density and slower heat input, mak-
Processes like electron beam welding and laser beam weld- ing it unsuitable for thick sections due to limited penetration.
ing are typically not portable due to equipment size and Thin sections are easier to melt and fuse using this method.
operating conditions (e.g., vacuum chambers). Miniaturized or
fiber-delivered laser systems can offer some portability. 30.34 Classify the processes described in this chapter in terms
of (a) cost, and (b) weld quality.
30.27 Describe your observations regarding the content of (a) Low cost: SMAW, GMAW. High cost: EBW, LBW. (b)
Table 30.1. High quality: GTAW, EBW, LBW. Moderate: GMAW. Quality
Table 30.1 compares welding processes in terms of porta- depends on control and application.
bility, quality, speed, and cost. It highlights that high-precision
methods like EBW and LBW offer excellent quality but are 30.35 What are the sources of welding spatter? How can
expensive and non-portable, while arc processes are more spatter be controlled?
accessible. Spatter comes from unstable arcs, incorrect polarity, ex-
cessive current, or poor shielding. It can be minimized by
30.28 What determines whether a welding process can be used optimizing parameters, using proper shielding gas, and using
in horizontal, vertical, or overhead positions? Explain and anti-spatter spray.
give application examples.
Welding position suitability depends on the fluidity of the 30.36 Should filler metal be made of the same composition as
molten pool, process control, and electrode type. Processes the base metal? Explain your answer.
like SMAW and GTAW are suitable for all positions; GMAW Not necessarily. Filler metals may differ to improve
requires adjustments. Overhead welding is common in pipeline strength, corrosion resistance, or compatibility. However, they
or structural fabrication. must be metallurgically compatible to avoid defects.
30.29 Explain the factors involved in electrode selection in arc 30.37 Describe your observations regarding Figure 30.18.
welding processes.
[Note: Without the figure, general comments can be made
Electrode selection is based on base metal type, joint design, on joint configurations or weld shapes depending on its
welding position, desired mechanical properties, and current content. Add observations based on the image.]
type. Coating type and AWS classification also guide selection.
30.38 In Figure 30.24b, suppose most of the top part of the
30.30 In Table 30.1 there is a column on distortion, ranked upper workpiece is cut horizontally with a sharp saw. Now
from lowest to highest. Explain why distortion varies among that the residual stresses are disturbed, the part will change
different welding processes. shape. In this case, do you think it will bend downward or
upward? Explain your answer.
Distortion is influenced by heat input and thermal gradients.
High-energy, concentrated processes (EBW, LBW) produce Cutting releases tensile stresses on the surface. The part is
less distortion due to localized heating, while arc processes likely to bend upward due to compressive residual stress in
with wider heat input cause more expansion and contraction. the lower region, similar to behavior in Figure 2.29d.
30.39 Describe the reasons why fatigue failures often occur 30.44 In oxy-fuel gas cutting, arc cutting, and laser beam
in the heat-affected zones (HAZ) of welds rather than in the cutting...
weld metal itself. ... the process essentially involves melting the workpiece. If
The HAZ undergoes microstructural changes, hardness vari- an 80 mm diameter hole is to be cut into a 250 mm diameter,
ation, and stress concentrations. It becomes more brittle or less 12 mm thick plate, plot the average temperature rise in the
ductile than the weld or base metal, making it prone to fatigue. workpiece as a function of kerf width. Assume that half of
30.40 If the materials to be welded are preheated, does the the energy is absorbed by the workpiece.
likelihood of porosity increase or decrease? Explain your To construct this graph:
answer. • Estimate the mass of the plate.
Preheating reduces moisture and thermal gradients, mini- • Use different kerf widths to calculate heat affected vol-
mizing porosity. It allows gases to escape before solidification, ume.
Q
thus decreasing porosity risk. • Apply ∆T = for each case.
m·c
30.41 List the welding processes suitable for producing (a) This results in a curve showing temperature increase with
butt joints (weld as a line or segment), (b) spot welds, and (c) increasing kerf.
both butt and spot welds.
30.45 Plot the hardness from Figure 30.18d and discuss.
(a) Butt joints: SMAW, GMAW, GTAW, EBW, LBW. (b)
Spot welds: Resistance spot welding (RSW). (c) Both: Laser Using the data in Figure 30.18d, plot hardness versus
welding and electron beam welding can produce both types distance from the top surface. Typically, the hardness:
with proper setup. • Peaks near the fusion zone due to rapid solidification.
• Decreases gradually through the heat-affected zone.
Q UANTITATIVE P ROBLEMS
• Levels out in the base material.
30.42 A welding operation is performed on an aluminum alloy
Discuss implications for mechanical properties and fatigue
plate.
performance.
A tube with a diameter of 50 mm, wall thickness of 4 mm,
and length of 60 mm is butt-welded to a 15 x 15 x 5 mm angle S YNTHESIS , D ESIGN , AND P ROJECTS
section. The angle has an L-shape and a length of 0.3 m. If
30.46 Discuss limitations of the size and shape of the work-
the weld zone in a gas tungsten arc welding (GTAW) process
piece (if any) for each of the processes described in this
is about 8 mm wide, what would be the temperature increase
chapter.
of the whole structure due to heat input only from welding?
What if the process were an electron beam welding (EBW) Different welding processes have limitations based on ac-
operation with a 6 mm weld width? Assume the electrode cess, heat input, joint geometry, and equipment size. For
requires 1500 J and the aluminum alloy needs 1200 J to melt example, electron beam welding requires a vacuum chamber
one gram. and is limited to small-medium parts, while SMAW and
To estimate the temperature increase: GMAW are more versatile.
• Calculate the total volume and mass of the welded
components. 30.47 Review the types of welded joints shown in Figure 30.27
• Estimate the heat input (based on weld width and energy
and provide an application for each.
requirement). Examples include:
Q
• Use the relation: ∆T = , where Q is energy input, • Butt joint – used in pipelines
m·c • Lap joint – automotive body panels
m is total mass, and c is specific heat.
• Corner joint – box-like structures
Assume 100% heat absorption for simplicity. More precise
• Tee joint – structural frames
results require the density and specific heat of the alloy.
• Edge joint – sheet metal enclosures
30.43 A welding operation is to be performed on carbon steel.
The desired welding speed is approximately 0.7 in/s. If an 30.48 Comment on the design guidelines provided in this
arc welding power source with a voltage of 10 V is used, what chapter.
current is needed if the weld width is to be 0.2 in? Design guidelines emphasize minimizing distortion, ensur-
Assuming the required power is proportional to weld area ing proper access for welding, using appropriate joint types,
and travel speed: and considering heat flow and stress distribution. Good design
P simplifies welding and improves quality.
P =V ·I ⇒ I =
V
More information such as penetration depth and heat input 30.49 Prepare a summary table describing the principles of the
per inch would be needed to determine P and thus solve for processes in this chapter with examples of their applications.
I precisely. Table 1 below.
30.55 For shipbuilding, large steel sections must be welded
to form the hull. Consider each welding operation discussed
in this chapter and list the advantages and disadvantages for
this application. Which welding process would you choose and
why?
• SMAW – versatile, but slow.
• GMAW – faster and suitable for automation.
• FCAW – good for thick sections.
• SAW – high deposition rate.
• EBW – not feasible due to vacuum.
Choice: Submerged Arc Welding (SAW) for its speed, pene-
tration, and consistency.
30.56 Research and describe the advantages and limitations
of CO2 and Nd:YAG lasers.
CO2 : higher power, good for cutting, limited to line-of-
sight. Nd:YAG: better for fine detail, more expensive, fiber-
optic delivery.
30.57 Inspect various parts and components of a car and
explain if any of the processes in this chapter are used to
join them.
30.50 Create a table listing the welding processes described
in this chapter and the range of welding speeds depending on Spot welding is common for body panels. MIG and laser
materials and thickness. welding used for frames and engine components.
Table 2 up. 30.58 Same as 30.57, but for kitchen utensils and cookware.
Are there major differences? Explain.
30.51 Suppose you are asked to inspect a welded structure Stainless cookware uses TIG or resistance welding. Differ-
for a critical application. Describe the procedure you would ences: thinner metals, hygiene requirements, polished finishes.
follow.
30.59 Describe general safety guidelines for welding opera-
Perform visual inspection, non-destructive tests (e.g., ultra- tions. For each process, prepare a concise safety sign with
sonic, X-ray), check specifications, measure dimensions, and welding or cutting safety instructions. Refer to the National
evaluate weld profile and discontinuities. Document results and Safety Council and similar organizations.
decide on acceptance or rework.
Use PPE, ventilate area, ground equipment, fire protection.
Example sign for GMAW: “Wear gloves, shield eyes, ensure
30.52 Explain the factors that contribute to any difference in gas flow, no flammables nearby.”
properties across a welded joint.
30.60 Are there common factors affecting weldability, casta-
Factors include: heat-affected zone microstructure, cooling bility, formability, and machinability of metals? Explain with
rate, residual stresses, and filler material. These cause varia- examples.
tions in hardness, strength, and ductility across the weld.
Yes. Chemical composition, grain size, and thermal conduc-
tivity affect all. For example, high carbon steel is less weldable
30.53 Explain why preheating components to be welded is and less formable.
effective in reducing the likelihood of crack development.
30.61 If a defect is found in a weld during inspection, how
Preheating reduces temperature gradients and cooling rates,
would you determine whether it is significant?
preventing thermal shock and hydrogen-induced cracking. It
promotes ductile microstructures. Evaluate type, size, location, and orientation. Compare to
acceptance criteria. Use stress analysis to assess impact on
30.54 Review the poor and good joint designs shown in Figure service.
30.29 and explain why they were identified as such. 30.62 Lattice booms for cranes use welded extrusions. Warp-
Poor designs concentrate stress or are hard to access. ing reduces load capacity. Research methods to minimize and
Good designs distribute stress, simplify welding, and provide correct welding distortion in boom construction.
better fusion. Geometry, access, and weld quality define their Methods include: symmetrical welding, fixturing, sequenc-
classification. ing, preheating, and post-weld straightening techniques.
30.63 A common practice for repairing worn or broken
expensive parts is to rebuild with weld passes and re-machine.
List precautions for this method.
Clean surface, control heat input, avoid contamination, use
compatible filler, apply stress relief.
30.64 A welded structure must be disassembled and re-welded.
What procedures would you recommend for disassembly in
preparation for re-welding?
Identify and cut joints, grind clean, avoid overheating, mark
orientation, plan re-welding sequence.
30.65 Suppose you are asked to prepare a quiz for students
about this chapter. Write three qualitative questions and pro-
vide the answers.
• Q1: What is the purpose of shielding gas in arc welding?
A1: To protect the weld pool from atmospheric
contamination.
• Q2: Why is preheating important in welding some steels?
A2: To reduce residual stresses and prevent cracking.
• Q3: What is the heat-affected zone (HAZ)? A3: The area
of base metal whose microstructure is altered by the
heat of welding.
