MEMB Perform routine gas metal arc welding

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1、Perform routine gas metal arc weldingMEM05050B(2 POINTS)Student WorkbookName: _Date: _Teacher: _Unit / Module DescriptionPerformance criteriaMEM05050B Perform routine gas metal arc welding1. Identify weld requirements1.1Weld requirements are interpreted from work instructions1.2Location of welds are

2、 identified in accordance with standard operating procedures and job specifications2. Prepare materials for welding2.1Materials are cleaned and prepared ready for welding3. Prepare equipment for welding3.1Welding equipment is set up correctly3.2Settings and consumables are selected to suit applicati

3、on4. Perform routine welding using GMAW4.1Safe welding practices are applied4.2Materials are welded to job requirements4.3Welds are cleaned to standard operating procedures During assessment the individual will: demonstrate safe working practices at all times; communicate information about processes

4、, events or tasks being undertaken to ensure a safe and efficient working environment; take responsibility for the quality of their own work; plan tasks in all situations and review task requirements as appropriate; perform all tasks in accordance with standard operating procedures; perform all task

5、s to specification; use accepted engineering techniques, practices, processes and workplace procedures. Tasks involved will be completed within reasonable timeframes relating to typical workplace activities.Preparation of Material for Welding and Welding PracticeCareful consideration must be given s

6、o that the operator chooses the most suitable and economical process at his/her disposal to prepare the edges of the material that is to be welded.Welding standards exist that require welds to be of full penetration and free of defects. However A.S. 1250 Welding in Building allows for welds that hav

7、e incomplete penetration and some defects as being acceptable.Plate Edge PreparationButt welds The purpose of preparing plate edges for butt welding is to give access to the root of the weld for penetration and on completion to provide a continuity of metal that produces a weld of equal strength to

8、that of the parent metal. Where no backing is to be used on the weld joint a root face is used to minimise the tendency to burn through. A feather-edge preparation is more prone to burn through than a joint with a root face. This especially applies if the root gap is excessive.Fillet welds Full stre

9、ngth fillet welds require that plate fit-up at the root of the joint be tight. Incorrectly prepared or badly fitted joints can cause slag inclusions, porosity in the weld and insufficient or excessive penetration of the weld root. As previously mentioned in certain instances incomplete penetration i

10、n welds are acceptable.Methods of PreparationFor plate edge preparation there are many processes available.These can be broadly classified as: mechanical; flame; arc; plasma; grinding; filing.Each process has claims to its particular advantages for a given application but the final selection of the

11、process will mainly be governed by availability.In some circumstances the selection of process may have to comply with Australian Standards or with an Engineers approval.Safety Before you start any welding, ensure that you are properly prepared.You will need to check: your personal safety gear; the

12、environment of your working area, including ventilation; the machine and equipment.Equipment GMA welding plant; protective helmet; protective clothing including:o gloves;o apron;o overalls;o footwear;o spats;o eye protection (face shield). screens; wire brush.Materials Several strips of LCS 6 mm x 2

13、00 mm x 50 mm.Procedure PreparationPrepare the metal you are going to weld: clean the metal by removing any rust, scale, or paint with a wire brush; degrease if necessary.NOTE:GMA welding machines do not operate efficiently if dust, paint or dirt are present, and may not produce the desired weld if

14、the metal is not clean.Initial Problems, Causes and RemediesMost problems for the beginner are due to: a rate of travel that is too fast and uneven; excessive stickout length.Maintaining a steady and uniform rate of travel and the correct stickout can solve many welding problems.Weld bead too smallI

15、f the weld bead is too small, it may indicate that the settings are too low or rate of travel too fast. Increase the setting on both the voltage and the wire speed and slow down the rate of travel.Lack of fusionIf there is a lack of fusion, the voltage is too low or stickout too long. Increase the v

16、oltage or decrease wire stickout.Excessive spatterA number of faults can cause excessive spatter: The voltage is either too high or too low.o Adjust accordingly. An incorrect shielding gas.o Select the correct shielding gas for the material being welded. A blocked gas nozzle.o Clean the gas nozzle r

17、egularly and spray it with spatter guard, or use nozzle dip.Weld crackingA number of conditions and faults can cause weld cracking. A dirty workpiece, contaminated by rust, grease, scale or paint.o Clean the workpiece. Weld beads that are too small.o Slow the rate of travel or increase the voltage a

18、nd wire speed. The weld is too deep.o Reduce the current (through wire speed) and voltage, and increase travel speed.NOTE:Once an adjustment has been made, always test the settings by doing another trial weld.Joint Preparation and AssemblyBasically there are two common types of weld joints: Fillet w

19、elds Butt weldsThere are many variations of these weld joints, all of which require some type of material preparation.Material preparation Ensure that the material is clean prior to assembly. Scale, grease, paint or rust will present problems in depositing a good quality weld therefore must be clean

20、ed by wire brushing or mechanical means. Straighten material if necessary. Definition of a fillet weldA fillet weld is a fusion weld which is approximately triangular in transverse cross-section.Assembly of fillet weld couponsFor a Horizontal/Vertical fillet weld the face of the vertical plate requi

21、res to be square and straight for a tight fit-up. Hold or clamp the vertical plate at 90o to the horizontal plate. Keep the fit-up tight and tack across the ends of the plates. Strong tacks across ends and one placed approximately centre of the vertical plate will help to control angular distortion.

22、Definition of a butt weldA fusion weld in which the metal lies substantially within the extension of the planes of the surfaces of the parts to be joined.Assembly of butt weld coupons Prepare plates for flame cutting or mechanical process; check for straightness. Prepare a 3035 bevel on both plates.

23、 Grind and file 2 mm root face on both plates. Preset plates at 5 to counteract distortion and assemble with a 2 mm root gap. Tack weld the plates inside the preparation.o These tacks are to be incorporated in the completed root run.Stopping and Restarting Welds on Practice CouponsStopping and resta

24、rting is an important operation and should be part of all welding processes. Each weld run should be restarted within the central 50 mm weld length. Outside Corner Fillet Weld Natural VAt the completion of this practice exercise you should be able to: Correctly assemble coupons for welding; Complete

25、 an outside corner fillet weld natural vee using 6 mm to 10 mm and 12mm LCS plate; Complete the weld tests required. Material: 2 pieces 50 mm x 10 mm x 225 mm maximum length.Weld qualityThe weld quality required will vary depending on the competencies to be achieved. Refer to the module descriptor o

26、r your trainer for the weld quality required. Such a quality could be:For an outside corner weld, the weld metal is to completely fill the groove and not to exceed 1mm variation throughout the length of the weld. Both toes to be free of edge of plate burn-off for a minimum of 60% of the length of th

27、e weld. Penetration to be complete for a minimum of 60% of the length of the weld. Penetration not to exceed 1.5 mm. Throat thickness to be a minimum of 75% of the material thickness. Maximum allowable surface defects:o No more than two significant surface defects with a cumulative defect area less

28、than the square of the plate thickness.Preparation and assembly Follow the recommended plate preparation and assembly procedure. Plates to be correctly assembled and aligned to within the allowable tolerances.Method Deposit approximately 50 mm of root run. Examine the bead for shape and penetration.

29、 Completely fill the remainder of the joint in a logical weld sequence. Evaluate your weld and complete the weld procedure sheet. Submit your weld to your trainer for assessment.NOTE: All welds to be stopped and restarted in the central 50 mm.TestingVisually inspect the weld to see if the above weld

30、 quality has been achieved.NOTE: After the completion of the weld, prepare the inside of joint by grinding out any excessive penetration and retain for use on inside corner welds using flux cored wire.Safety Observe all workshop safety procedures.Inside Corner Fillet Weld Natural VAt the completion

31、of this practice exercise you should be able to: Complete inside corner fillet welds on 6 mm10 mm and 12 mm LCS plate using flux cored wire. Complete a visual weld inspection to the standard required.Material: From previous outside corner welds.Weld qualityThe weld quality required will vary dependi

32、ng on the competencies to be achieved. Refer to the module descriptor or your trainer for the weld quality required. Such a quality could be: Leg lengths to be 0 + 2 of the required size and not to exceed 1 mm variation throughout the length of the weld. Both toes to be free of undercut for a minimu

33、m of 60% of the length of the weld. Smooth regular weld contour. Smooth transition of weld join in central 50 mm. Maximum allowable surface defects:o No more than two significant surface defects with a cumulative defect area less than the square of the plate thickness.Preparation and assembly Follow

34、 the recommended plate preparation and assembly procedure. Plates to be correctly assembled and aligned to within the allowable tolerances.Method Deposit approximately half of the weld. The width of the weld is to be as follows:o 6 m for 6 mm plate;o 8 mm for 10 mm plate;o 10 mm for 12 mm plate.NOTE

35、:To increase the weld size a weave technique may be required. Examine the bead shape and size before continuing the weld. Complete the remainder of the weld. Evaluate your weld and complete the weld procedure sheet. Submit your work to your trainer for assessment.SafetyObserve all workshop safety pr

36、ocedures.Three-Run 10 mm Horizontal Fillet WeldAt the completion of this practice exercise you should be able to: Correctly assemble coupons for welding; Complete a 3-run 10 mm horizontal fillet weld on 12 mm LCS plate; Complete the weld tests required.Material: 2/100 x 12 x 225 maximum length.Weld

37、qualityThe weld quality required will vary depending on the competencies to be achieved. Refer to the module descriptor or your trainer for the weld quality required. Such a quality could be: Leg lengths to be 0 +2 of the required size and not to exceed 1 mm variation throughout the length of the we

38、ld. Both toes to be free of undercut for a minimum of 60% of the length of the weld. Penetration to be complete for a minimum of 60% of the length of the weld. Smooth regular weld contour. Angular distortion to be 0 +5. Maximum allowable surface defects:o No more than two significant surface defects

39、 with a cumulative defect area less than the square of the plate thickness.Preparation and assembly Follow the recommended plate preparation and assembly procedure. Plates to be correctly assembled and aligned to within the allowable tolerances.Method Deposit approximately half of the first pass. St

40、op in the central 50 mm.o Leg lengths should be a minimum of 6mm. Examine the bead shape and size. Complete the first pass. Repeat the above procedure with the second and third passeso On a multipass weld, the second pass should always be on the bottom. Evaluate your weld and complete the weld proce

41、dure sheet. Submit your work to your trainer for assessment.TestingWhen the above weld quality is achieved the following tests are to be carried out: One macro etch test. One fracture test for visual internal inspection.SafetyObserve all workshop safety procedures.Outside Corner Fillet Weld Horizont

42、alAt the completion of this practice exercise you should be able to: Correctly assemble coupons for welding; Deposit multiple run corner welds;o the coupon being placed in the horizontal position. Complete the visual weld inspection to the standard required. Material: 2/50 x 10 x 225 maximum length.

43、Weld quality The weld quality required will vary depending on the competencies to be achieved. Refer to the module descriptor or your trainer for the weld quality required. Such a quality could be: For an outside corner weld, the weld metal is to completely fill the groove and not to exceed 1 mm var

44、iation throughout the length of the weld. Both toes to be free of undercut for a minimum of 60% of the length of the weld. Penetration to be complete for a minimum 60% of the length of the weld. Penetration not to exceed 1.5 mm. Throat thickness to be a minimum of 75% of the material thickness. Maxi

45、mum allowable surface defects:o To be no more than two significant surface defects with a cumulative defect area less than the square of the plate thickness.Preparation and assembly Follow the recommended plate preparation and assembly procedure. Plates to be correctly assembled and aligned to withi

46、n the allowable tolerances.Method Deposit approximately half of the first pass. Stop in the central 50 mm.o Leg lengths should be a minium of 6mm. Examine the bead shape and size. Complete the weld pass. Repeat the above procedure with the second and third runs.o On a multipass weld, the second pass

47、 should always be on the bottom. Evaluate your weld and complete the weld procedure sheet. Submit your work to your trainer for assessment.NOTE: After the completion of the weld prepare the inside of joint by grinding out any excessive penetration and retain for use on inside for overhead fillet wel

48、d.Safety Observe all workshop safety procedures.Three-Run Overhead Fillet WeldAt the completion of this practice exercise you should be able to: Correctly assemble coupons for welding; Complete a 3-run overhead fillet weld on 10 mm LCS plate; Complete the weld tests required.Material: Use weld coupo

49、n retained from previous exercise.Weld qualityThe weld quality required will vary depending on the competencies to be achieved. Refer to the module descriptor or your trainer for the weld quality required. Such a quality could be: Leg lengths to be 0 +2 mm of the required size and not to exceed 1 mm

50、 variation throughout the length of the weld. Both toes to be free of undercut for a minimum of 60% of the length of the weld. Penetration to be complete for a minimum of 60% of the length of the weld. Smooth regular weld contour. Angular distortion to be 0 + 5. Maximum allowable surface defects.o N

51、o more than two significant surface defects with a cumulative defect area less than the square of the plate thickness.Preparation and assembly Follow the recommended plate preparation and assembly procedure. Plates to be correctly assembled and aligned to within the allowable tolerances.Method Depos

52、it approximately half of the first pass. Stop in the central 50 mm.o Leg lengths should be a minium of 5mm. Examine the bead shape and size. Complete the first pass. Repeat the above procedure with the second and third passes.o On a multipass weld, the second pass should always be on the bottom. Eva

53、luate your weld and complete the weld procedure sheet. Submit your work to your trainer for assessment.TestingVisually inspect weld to see if the above weld quality has been achieved.SafetyObserve all workshop safety procedures.Butt Weld HorizontalAt the completion of this practice exercise you shou

54、ld be able to: Correctly assemble coupons for welding; Complete a horizontal butt weld in 6mm LCS plate; Complete the weld tests required.Material: 2/100 x 6 x 300 maximum length.Weld qualityThe weld quality required will vary depending on the competencies to be achieved. Refer to the module descrip

55、tor or your trainer for the weld quality required. Such a quality could be: Penetration to be complete for a minimum of 60% of the length of the weld. Penetration not to exceed 1.5 mm. Both toes to be free of undercut for a minimum of 60% of the length of the weld. Weld reinforcement to be within 0

56、+3mm. Surface variations not to exceed 1.5mm. Maximum allowable surface defects:o A maximum of two significant surface defects with a cumulative defect area of less than the square of the plate thickness.Preparation and assembly Follow the recommended plate preparation and assembly procedure. Plates

57、 to be correctly assembled and aligned to within the allowable tolerances.Method Deposit approximately 50 mm of the root run. Examine the bead shape and penetration. Complete the root pass. Completely fill the remainder of the joint in a logical weld sequence.o On a multipass weld, the second pass s

58、hould always be on the bottom. Evaluate your weld and complete the weld procedure sheet. Submit your work to your trainer for assessment.NOTE:All welds to be stopped and restarted in the central 50 mm.TestingVisually inspect the weld to see if the above weld quality has been achieved.Safety Observe

59、all workshop procedures.Review Questions1.Briefly explain the purpose for plate edge preparation for Butt welds and Fillet welds.2.Describe methods of preparation.3.What is the definition of a Butt weld?4.What is the definition of a Fillet weld?5.Explain the preparation and assembly of Butt plates.6

60、.Sketch Single V Butt Weld Plate with root face. Include angles, root gap, maternal thickness.7.Three-Run 10mm Horizontal Fillet Weld. Weld quality will depend on competencys to be achieved. Explain what such a weld quality would be.Welding machine settings, accessories and consumables identifiedThe

61、 GMAW Modes of TransferThe GMAW process differs from other welding processes because it gives a selection in the way metal may be transferred across the arc. Short arc or dip transfer. Free flight transfer.o In free flight transfer the metal may be transferred across the arc in three ways: Spray transfer Globular transfer Pulse transferThe type of metal transfer depends upon: Arc voltage; Current/wire feed setting; Diameter of wire electrode; Type of shielding gas used.Short Arc TransferShort arc is also known as dip