Guidelines For Shielded Metal Arc Welding (SMAW)_2

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Nội dung Text: Guidelines For Shielded Metal Arc Welding (SMAW)_2

Simpo Positioningand Split Unregistered Version - http://www.simpopdf.com 3-5. PDF Merge Electrode Holder After learning to start and hold an arc, practice running beads of weld Groove Welds metal on flat plates using a full elec- trode. Hold the electrode nearly perpen- dicular to the work, although tilting it ahead (in the direction of travel) 10°- 30° will be helpful. . To produce the best results, hold a short arc, travel at a uni- form speed, and feed the elec- 90° 90° trode downward at a constant rate as it melts. Direction Of Welding End View Of Work Angle Side View Of Electrode Angle Fillet Welds 10°- 30° 45° 45° Direction Of Welding End View Of Work Angle Side View Of Electrode Angle S-0660 155 095 Page 9
Simpo Electrode MovementUnregistered Version - http://www.simpopdf.com 3-6. PDF Merge and Split During Welding .A single stringer bead is satisfac- 1 tory for most narrow groove weld joints; however, for wide groove weld joints or bridging across gaps, a weave bead or multiple stringer beads work better. 1 Stringer Bead − Steady Move- ment Along Seam 2 Weave Bead − Side To Side Movement Along Seam 3 Weave Patterns Use weave patterns to cover a wide area in one pass of the electrode. Limit weave width to a maximum of 2-1/2 2 times diameter of electrode. 3 S-0054-A Notes Work like a Pro! Pros weld and cut safely. Read the safety rules at the beginning of this manual. 155 095 Page 10
Simpo Conditions and Split Unregistered Version - http://www.simpopdf.com 3-7. PDF Merge That Affect Weld Bead Shape IMPORTANT: Weld bead shape is affected by electrode angle, arc length, travel speed, and thickness of base metal. Electrode Angle Correct Angle 10° - 30° Drag Angle Too Small Angle Too Large Arc Length Spatter Normal Too Long Too Short Travel Speed Too Slow Normal Too Fast S-0661 155 095 Page 11
Simpo Poor Merge Bead Characteristics Version - http://www.simpopdf.com 3-8. PDF Weld and Split Unregistered 1 Large Spatter Deposits 2 Rough, Uneven Bead 3 Slight Crater During Welding 4 Bad Overlap 5 Poor Penetration 1 2 4 3 5 S-0053-A 3-9. Good Weld Bead Characteristics 1 Fine Spatter 2 Uniform Bead 3 Moderate Crater During Welding Weld a new bead or layer for each 1/8 in (3.2 mm) thickness in metals being welded. 4 No Overlap 5 Good Penetration Into Base Metal 1 2 3 4 5 S-0052-B 155 095 Page 12
Simpo Typical Weld Joints Unregistered Version - http://www.simpopdf.com 3-10. PDF Merge and Split Butt Joint Butt Joint Lap Joint Tee Joint Lap Joint Tee Joint Flat Position Welds Horizontal Position Welds Butt Joint Butt Joint Lap Joint Tee Joint Lap Joint Tee Joint Vertical Position Welds Overhead Position Welds 804 248 155 095 Page 13
Simpo Welding Butt Joints Unregistered Version - http://www.simpopdf.com 3-11. PDF Merge and Split Types Of Butt Joint Welds 1 Tack Welds Prevent butt joint distortion by tack weld- 1 ing the materials in position before final weld. Workpiece distortion occurs when heat is applied locally to a joint. One side of a metal plate will “curl” up toward the weld. Distortion will also cause the edges of a butt joint to pull together ahead of the electrode as the weld cools. 2 Square Groove Weld 3 Single V-Groove Weld 4 Double V-Groove Weld Materials up to 3/16 in (5 mm) thick can often be welded without special prepara- tion using the square groove weld. How- ever, when welding thicker materials it may be necessary to prepare the edges (V-groove) of butt joints to ensure good welds. 2 The single or double V-groove weld is good for materials 3/16 − 3/4 in (5-19 mm) thick. Generally, the single V- groove is used on materials up to 3/4 in (19 mm) thick and when, regardless of thickness, you can weld from one side only. Cut the bevel with oxyacetylene or plasma cutting equipment. Remove scale from material after cutting. A grind- er can also be used to prepare bevels. Create a 30 degree angle of bevel on ma- terials in V-groove welding. Butt Joint Training Procedure Practice welding butt joints on 1/8 in (4 mm) or thicker material. (Avoid thinner 30° materials since they require greater 1/16 in. skill.) Separate the squared edges of the (1.6 mm) material about 1/16 in (1.6 mm) and make a butt weld all the way through with a 1/8 in electrode. (You may need to ad- just the weld current and travel speed to obtain the desired weld.) Perform a simi- lar exercise on 1/4 in (6 mm) material, de- 4 3 positing a bead on each side of the joint and fusing one to the another (no bevel needed). Practice making a single V-groove weld on 1/4 in (6 mm) plate beveled 30°. Start with a 1/8 in electrode for the first bead and finish with a 5/32 in (4 mm) elec- trode. Be sure to penetrate about 1/32 in (1 mm) beyond the bottom of the “V” or root. Perform a similar exercise on thick- er materials. Generally, deposit a bead for each 1/8 in (3mm) of material thick- ness, cleaning the joint between layers. On heavier plates, it may be necessary to weave the top layers to fill the groove. After completing the practice welds, test them as described in Section 3-18. S-0662 155 095 Page 14
Simpo Welding Tee Joints Unregistered Version - http://www.simpopdf.com 3-12. PDF Merge and Split 1 Electrode 2 Fillet Weld Keep arc short and move at definite 1 rate of speed. Hold electrode as shown to provide fusion into the corner. Square edge of the weld surface. 45° For maximum strength weld both Or Less sides of upright section. 2 3 Multi-Layer Deposits Weld a second layer when a heavi- er fillet is needed. Use any of the weaving patterns shown in Section 3-6. Remove slag before making another weld pass. 2 1 3 S-0060 / S-0058-A / S-0061 3-13. Welding Lap Joints 1 Electrode 2 Single-Layer Fillet Weld 30° Or Less Move electrode in circular motion. 3 Multi-Layer Fillet Weld 1 Weld a second layer when a heavi- er fillet is needed. Remove slag be- fore making another weld pass. Weld both sides of joint for maxi- mum strength. 2 Single-Layer Fillet Weld 30° Or Less 1 3 Multi-Layer Fillet Weld S-0063 / S-0064 155 095 Page 15
Simpo Welding Horizontal Beads And Butt Joints 3-14. PDF Merge and Split Unregistered Version - http://www.simpopdf.com . When welding horizontally, Single Pass Bead Weld gravity may distort the mol- ten metal. . This technique is not Tilt Electrode 15° Toward Direction suitable for all electrodes. Of Welding. Direction Of Welding 90° 1 Electrode 1 2 Backing Strip Bevel edges if warranted by ma- terial thickness (see Section 90° 3-11). Tack weld a backing strip to the plates to make the first weld pass (root pass) easier. 15° Single Pass Horizontal Butt Joint Weld Or First Pass Of Multi-Layer Deposit 2 30° 30° Bevel Material If Necessary (See Section 3-11). Direction Of Direction Of 90° Welding Welding 30° Tilt Electrode 15° In Direction Of Travel Make First Weld Pass (Root Pass). Make Second Weld Pass. 45° Direction Of Welding Make Third Weld Pass. Completed Weld. 804 260 155 095 Page 16
Simpo Welding Vertical Beads And Butt Version - http://www.simpopdf.com 3-15. PDF Merge and Split Unregistered Joints . When Single Pass Bead Weld welding vertically, gravity may distort the mol- ten metal. . This technique is not 1/2 in 1 (12 mm) 90° suitable for all electrodes. Direction Of Welding 1 Electrode Whipping Up Motion Direction Of 2 Backing Strip Welding Weld vertically by carrying the weld upward or starting at the top Weave Bead and welding down. Welding up- 1/2 in (12 mm) ward is easier and is shown in Wide these illustrations. Bevel edges if warranted by ma- terial thickness (see Section 3-11). Tack weld a backing strip to the plates to make the first weld pass (root pass) easier. Single Pass Vertical Butt Joint Weld Or First Pass Of Multi-Layer Deposit 2 90° Direction Of Arrows Show Lifting Up Welding Of Electrode And Return To Crater. 90° 1st Pass 2nd Pass Hesitate With Slight Up And Direction Of Direction Of Down Motion. OR Welding Welding Shorten Arc At Arrowheads When At Center Of Weld. 4th Pass 3rd Pass Vertical Butt Joint Weld Subsequent Layers 804 260 155 095 Page 17
Simpo Welding Vertical TeeUnregistered Lap Joints 3-16. PDF Merge and Split Joints And Version - http://www.simpopdf.com . When welding vertically, Tee Joint Weld gravity may distort the mol- 90° ten metal. . This technique is not suitable for all electrodes. For maximum strength, weld both sides of joint. Direction Of Welding Arrows Show Lifting Up Of Electrode And Return To Crater. 90° First Weld Pass Shows Shows Weaving Weaving Motion. Motion. Direction Of Direction Of Welding Welding OR 90° 90° Subsequent Weld Passes Lap Joint Weld Shows Weaving Motion. Direction Of Welding 90° 804 260 155 095 Page 18