Evaluating Arc Welds

Area and/or Course Introduction to Welding
Lesson Title Evaluating Arc Welds (SMAW)
No. Periods 1 (73-minute period)
Teacher Goal(s):
1. Students will be able to accurately judge whether an
arc weld is consistent with industry standards for
2. Students will clearly communicate how to improve
their peers’ arc welds
The student will be able to (TSWBT). (Oregon Skill Set numbers in parentheses at the
end of the objective statement.)
1. Understand and describe a defect in an arc weld (CS.PS.06)
2. Describe the causes of defects in arc welds (CS.PS.06)
3. Evaluate welds in comparison to industry standards (CS.HS.03)
4. Communicate to peers the corrective action to be taken in order to correct arc defects
5. Justify peers’ weld grades in a well written paragraph (CS.PM.05)
State Standards met by Objectives:
4. English
5. English
6. English
7. Power Science
and Technology
PST 04.04.07.c.
Eligible Content
Assess results and take corrective action.
Maintain appropriate interactions with colleagues.
Give and receive feedback in a positive manner.
Produce writing that shows accurate spelling.
Write legibly.
Understand, learn, and use new vocabulary that is
introduced and taught directly through
informational text, literary text, and instruction
across the subject areas.
Construct and/or repair metal structures and
equipment using welding fabrication procedures,
including those associated with SMAW, GMAW,
GTAW, fuel-oxygen and plasma arc torch methods.
Knowledge: 1=awareness; 2=comprehension; 3=application; 4=analysis; 5=synthesis; 6=evaluation
Application: 1=knowledge in one discipline; 2=apply knowledge in one discipline; 3=apply knowledge across disciplines; 4=apply knowledge to real-world predictable situations; 5=apply
knowledge to real-world unpredictable situations
Materials, Equipment, Audio-Visual Aids:
1. Pen or pencil
2. Paper
3. Arc welder
4. Helmet
5. Gloves
6. Welding helmet
Anticipatory Set/Introduction/Motivation/Interest Approach:
Review Yesterday’s Lesson:
Yesterday we discussed the correct operation of the Oxy-acetylene torch and then you were able
to practice on the scrap metal. We are going to go randomly around the room and each person I
call on is going to tell me the next step in the O/A set up process. Try and visualize the set up as
we are going around.
(Q) What kind of flame are we looking for when we are cutting?
(A) Neutralizing
(Q) What should a proper cut look like?
(A) Nice clean cut, should look like it was done with a sharp saw blade
(Q) How many people received industry standard grades on their welds
1. No. 2 pencils
2. Pliers
3. Note cards
When teaching students the basics behind arc welding, begin the class with this competition
which teaches speed of travel, manipulation, angle of travel, and holding the rod in the electrode
holder. Before anything is passed out, explain to students that this is a welding competition, and
they must wait to start until the teacher says the word. Students are to make a line across the
paper using half moons or circles (demonstrate on board) and the lines must be completely filled
in by holding the electrode holder (pliers) in one hand and placing pencils in pliers. When the
teacher says go, students will begin to make a line about 2 spaces across the note card. Students
will be more successful when they discover if they put the pencils at more of a 45 degree angle
the circles fill in faster. Students will now evaluate their “weld” on a 50 point scale compared to
the teachers weld (should be a perfect 50)
Transition (Use Objective):
1. Understand and describe a defect in an arc weld
2. Describe the causes of defects in arc welds
3. Evaluate welds in comparison to industry standards
4. Communicate to peers the corrective action to be taken in order to correct arc defects
5. Justify peers’ weld grades in a well written paragraph
Strategy – Includes Teacher
Activity, Student Activity,
Questions/Answers and
Subject Matter Outline/Problem and Solution (Application
Points Lace in Throughout Lesson) (Modeling, Guided
Practice, and Content)
Objective #1
What is a defect in an arc weld?
The teacher will put pictures of
arc weld defects on the wall,
and ask students to try and
match the defect to the picture.
The pictures are listed below
This type of defect is found in any of three ways: 1) When the
weld bead does not penetrate the entire thickness of the base
plate. 2) When two opposing weld beads do not
interpenetrate. 3) When the weld bead does not penetrate the
toe of a fillet weld but only bridges across it.
Non-metallic solid material entrapped in weld metal or between
weld metal and base metal.
lack of
Undercutting is a defect that appears as a groove in the parent
metal directly along the edges of the weld. It is most common
in lap fillet welds, but can also be encountered in fillet and butt
Porosity is gas pores found in the solidified weld bead. As seen
Inclusion in Figure 10-4, these pores may vary in size and are generally
distributed in a random manner. However, it is possible that
porosity can only be found at the weld center. Pores can occur
either under or on the weld surface.
Other Weld Discontinuities
Excessive melt-through
Incomplete joint penetration
Slag inclusions
Objective #2
What causes defects in arc welds?
The teacher will discuss with
the students what the potential
causes are for many defects in
arc welding.
usually caused by the use of too low a welding current and can
be eliminated by simply increasing the amperage. Other causes
can be the use of too slow a travel speed and an incorrect torch
The teacher will also mention
other defects which are
appropriate to use when
evaluating welds such as
Inconsistent speed
Inconsistent arc travel
Inconsistent electrode
(Q) If there is not enough
penetration in the metal; what
can be done to solve the
The most common cause of lack of fusion is a poor welding
technique. Either the weld puddle is too large (travel speed too
slow) and/or the weld metal has been permitted to roll in front
of the arc. Again, the arc must be kept on the leading edge of
the puddle. When this is done, the weld puddle will not get too
large and cannot cushion the arc.
Caused by low amperage, improper techniques, or trying to
weld in too tight of an area
The most common causes of porosity are atmosphere
(A) Increase amperage or bring contamination, excessively oxidized work piece surfaces,
the electrode closer to the
inadequate deoxidizing alloys in the wire and the presence of
foreign matter. Atmospheric contamination can be caused by:
1) Inadequate shielding gas flow. 2) Excessive shielding gas
(Q) What would cause slag
flow. This can cause aspiration of air into the gas stream.
3) Severely clogged gas nozzle or damaged gas supply system
(leaking hoses, fittings, etc.) 4) An excessive wind in the
(A) The electrode being too
welding area. This can blow away the gas shield.
close to the weld
Objective #3
Evaluating an Arc Weld with Industry Standards
Students will self-evaluate
their welds in comparison to
industry standards
The teacher will provide
industry standard SMAW or
arc welds which will enable
the students to make
comparisons to the welds
which they have created
Spatter. Although it does not affect weld strength, spatter does
create poor appearance and increases cleaning costs. There are
several ways to control excessive spatter. First, try lowering the
current. Make sure it is within the range for the electrode type
and size you are welding with and that the polarity is correct.
Another way to control spatter is to try a shorter arc length. If
the molten metal is running in front of the arc, change the
electrode angle. Finally, look for arc blow conditions
(commonly referred to as a wandering arc), and be sure the
electrode is not wet.
Students have an
understanding of what certain
defects look like, and the
teacher will ask that each
students writes down the
similarities and
inconsistencies of their welds
in a well written paragraph
Undercutting. While frequently just an appearance problem,
undercutting can impair weld strength when the weld is loaded
in tension or subjected to fatigue. To eliminate undercut,
reduce the current and travel speed, or simply reduce the
puddle size until you have a size you can handle. Then change
the electrode angle so the arc force holds the metal in the
corners. Use a uniform travel speed and avoid excessive
The paragraph will be graded
on the following:
1. Correct grammar
2. Correct spelling
3. Usage of vocabulary
introduced in class
4. Comparison and
contrasts of student
welds to industry
5. Ways to improve welds
Wet Electrodes. If polarity and current are within the electrode
manufacturer's recommendations but the arc action is rough
and erratic, the electrodes may contain excessive moisture. Try
dry electrodes from a fresh container. If the problem recurs
frequently, store open containers of electrodes in a heated
Wandering Arc. With DC welding, stray magnetic fields cause
the arc to wander off course. This is a greater problem at high
currents and in complex joints. To control a wandering arc, the
best option is to change to AC welding. If that doesn't work, try
using lower currents and smaller electrodes or reduce the arc
length. In addition, you can change the electrical path by
shifting the work connection to the other end of the workpiece
or by making connections in several locations. You also may
do this by welding toward heavy tacks or finished welds, using
run-out tabs, adding steel blocks to change the work current
path, or tacking small plates across the seam at the weld ends.
Objective #4
Communicating to Peers
Students will be asked to grade
one other student weld besides
their own. Students will use
another student’s weld to write
a well-written paragraph
about the weld, and
communicate back to the other
student about the weld.
Maintaining a good relationship is part of living healthy. Your
communication skills are important to maintaining those
relationships that help you be healthy. How do you
communicate? How often do you communicate? Do you
initiate conversation?
The paragraph will be graded
1. Correct grammar
2. Correct spelling
3. Usage of vocabulary
introduced in class
4. Comparison and
contrasts of student
welds to industry
5. Ways to improve welds
No one likes to be offended and no one likes to be insulted.
These are common sense statements, but it is amazing how
often this is ignored. The usage of profanities in any
conversation can be taken as insults at anytime. One of the best
ways to avoid this mistake is to make a conscious choice to not
use profanity.
Think about how you communicate. Sometimes the way you
say something can mean the exact opposite of what you
intended. Think about the message your body communicates to
Crossing your arms can send the message that you don't care or
you can't be bothered with the message being communicated to
Objective #5
Justify their grade
Once the student have written
the paragraph about the other
student’s grade, the students
will communicate to each
other about the weld.
Usually the goal in constructive criticism is to critique an
individual so they will benefit or improve. We frequently see,
this especially when adults are teaching children in sports, to
increase their knowledge and performance. We also see this in
the workplace, when a supervisor is critiquing an employee
with the goal in mind to improve their performance or work
habits. Unfortunately in this day and age, especially in
athletics, we find it more and more difficult to give any type of
criticism to children at the grade school, high school and even
college level. Bobby Knight all too well has found this out,
when he was coaching for the University of Indiana. His
techniques needless to say reached the ultimate extreme in
criticism, and were by far not that constructive.
Students are graded on:
1. Speaking clearly to the
other student
2. Providing positive
feedback about the
3. Providing constructive
criticism about the
Closure/Summary/Conclusion (Tie in Objectives)
Student will be asked to reflect back on how the feedback from their peers. Was the feedback
good to hear? Did you receive compliments and constructive criticism? What have you learned
today about evaluating welds?
1. Understand and describe a defect in an arc weld
2. Describe the causes of defects in arc welds
3. Evaluate welds in comparison to industry standards
4. Communicate to peers the corrective action to be taken in order to correct arc defects
5. Justify peers’ weld grades in a well written paragraph
Evaluation: (Authentic forms of Evaluation, Quizzes, or Written Exam)
Self-evaluation and peer evaluation has been used so students are more self-sufficient in the shop
and are able to use their own reasoning and processing to solve problems and over come
difficulties during arc welding.
Assignments: (Student Activities Involved in Lesson/Designed to Meet Objectives)
Self-evaluation paragraph
Peer-evaluation paragraph
Daily calendar
Lesson Reflection
This lesson stretched out into two class periods because students struggled writing a full
paragraph about the welds. I found that I spent more time with students on their writing rather
than time improving their welding, but overall I think the critical thinking involved with the
lesson helped the students to better understand what they need to improve. They received
feedback from their peers, which was a different form than just me telling them what to improve.
Next time I prepare this lesson I might only include one writing assignment.