Rigor/Relevance Framework LESSON PLAN Knowledge Area and/or Course Introduction to Welding Lesson Title Evaluating Arc Welds (SMAW) No. Periods 1 (73-minute period) 6 5 4 3 2 1 C D Assimilation _______ Adaptation ___X____ A B Acquisition _______ Application _______ 1 Teacher Goal(s): 1. Students will be able to accurately judge whether an arc weld is consistent with industry standards for acceptable 2. Students will clearly communicate how to improve their peers’ arc welds 2 3 4 Application Objectives: 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 (EL.HS.RE.08) 5. Justify peers’ weld grades in a well written paragraph (CS.PM.05) State Standards met by Objectives: Subject Strand 1. CRLS 2. CRLS 3. CRLS 4. English 5. English 6. English CS.PS.06 CS.PM.05 CS.HS.03 EL.HS.WR.14 EL.HS.WR.20 EL.HS.RE.08 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 5 Materials, Equipment, Audio-Visual Aids: References: 1. Pen or pencil http://www.esabna.com/EUWeb/ _handbook/592mig10_9.htm 2. Paper 3. Arc welder 4. Helmet 5. Gloves 6. Welding helmet http://www.weldingengineer.com/1flux.htm http://www.peaceandhealing.com/criticism/ constructive.asp 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 Set: Supplies: 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 Objectives 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 INCOMPLETE PENETRATION 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. SLAG INCLUSION Non-metallic solid material entrapped in weld metal or between weld metal and base metal. lack of fusion UNDERCUTTING 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 joints. POROSITY Slag 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. Porosity Other Weld Discontinuities Excessive melt-through Incomplete joint penetration Cracks 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. INCOMPLETE PENETRATION 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 angle. The teacher will also mention other defects which are appropriate to use when evaluating welds such as - Inconsistent speed Inconsistent arc travel Inconsistent electrode angle (Q) If there is not enough penetration in the metal; what can be done to solve the problem? LACK OF FUSION 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. SLAG INCLUSION Caused by low amperage, improper techniques, or trying to weld in too tight of an area POROSITY 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 metal 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. inclusion? 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 weaving. 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 standards 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 cabinet. 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 on: 1. Correct grammar 2. Correct spelling 3. Usage of vocabulary introduced in class 4. Comparison and contrasts of student welds to industry standards 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 others. Crossing your arms can send the message that you don't care or you can't be bothered with the message being communicated to you. 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 weld 3. Providing constructive criticism about the weld 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.