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عدد المساهمات : 2041 التقييم : 3379 تاريخ التسجيل : 21/01/2012 العمر : 44 الدولة : مصر العمل : مدير الصيانة بشركة تصنيع ورق الجامعة : حلوان
 | موضوع: كتاب Welded Connections— A Primer For Engineers الخميس 15 نوفمبر 2012, 8:03 am | |
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احبتى فى الله الى كل مهتم بعمليات اللحام اليكم هذا الكتاب المميز الا وهو Welded Connections— A Primer For Engineers Table of Contents 1. INTRODUCTION ............................................... 1 1.1 IMPORTANCE OF WELDING ............................ 1 1.2 SCOPE OF WELDING ......................................... 1 1.3 WELDING-RELATED CODES AND SPECIFICATIONS 1.3.1 AISC Specification for Structural Steel Buildings ......................................... 1 1.3.2 AWS D1.1 Structural Welding Code—Steel .............................................. 2 1.3.3 AISC Seismic Provisions for Structural Steel Buildings ........................ 2 1.3.4 AWS D1.8 Structural Welding Code—Seismic Supplement ..................... 3 1.3.5 AWS D1.3 Structural Welding Code—Sheet Steel .................................... 3 1.3.6 Other AWS D1 Codes .............................. 3 2. WELDING AND THERMAL CUTTING PROCESSES ........................................................ 5 2.1 INTRODUCTION ................................................. 5 2.1.1 Requirements for Welding ....................... 5 2.1.2 Arc Welding as Compared to Other Welding Processes ................................... 6 2.1.3 Process Issues and Concerns for the Engineer ................................................... 6 2.2 SMAW ................................................................... 8 2.2.1 Fundamentals ........................................... 8 2.2.2 Equipment ................................................ 8 2.2.3 Consumables ............................................ 9 2.2.4 Electrode Classification System .............. 9 2.2.5 Low-Hydrogen SMAW Electrodes ........ 10 2.2.6 Care and Storage of Low-Hydrogen Electrodes .............................................. 10 2.2.7 Process Advantages/Limitations ............ 12 2.2.8 Applications ........................................... 12 2.3 FCAW .................................................................. 12 2.3.1 Fundamentals ......................................... 12 2.3.2 Equipment .............................................. 13 2.3.3 Consumables .......................................... 13 2.3.4 Electrode Classification ......................... 14 2.3.5 FCAW Advantages and Limitations ...... 15 2.3.6 FCAW-G Advantages and Limitations .. 16 2.3.7 FCAW-G Applications ........................... 16 2.3.8 FCAW-S Advantages and Limitations ... 16 2.3.9 FCAW-S Applications ............................ 16 2.3.10 FCAW-S Intermix Concerns .................. 16 2.4 SAW .................................................................... 17 2.4.1 Fundamentals ......................................... 17 2.4.2 Equipment .............................................. 18 2.4.3 SAW Consumables ................................ 18 2.4.4 Electrode and Flux Classification .......... 19 2.4.5 Flux Recovery ........................................ 20 2.4.6 Crushed Slag .......................................... 20 2.4.7 Process Advantages and Limitations ..... 20 2.4.8 Applications ........................................... 21 2.5 GMAW ................................................................ 21 2.5.1 Fundamentals ......................................... 21 2.5.2 Equipment .............................................. 21 2.5.3 Consumables .......................................... 22 2.5.4 Electrode Classification System ............ 22 2.5.5 Shielding Gas ......................................... 22 2.5.6 Modes of Transfer .................................. 23 2.5.7 Process Advantages and Limitations ..... 24 2.5.8 Applications ........................................... 25 2.6 ESW/EGW .......................................................... 25 2.6.1 Fundamentals ......................................... 25 2.6.2 Equipment .............................................. 26 2.6.3 Consumables .......................................... 26 2.6.4 Electrode Classification ......................... 26 2.6.5 Process Advantages and Limitations ..... 26 2.6.6 Applications ........................................... 27 2.7 GTAW .................................................................. 27 2.8 ARC STUD WELDING ...................................... 27 2.9 THERMAL CUTTING PROCESSES ................ 28 2.9.1 Oxyfuel Gas Cutting and Gouging ........ 29 2.9.2 Plasma Arc Cutting and Gouging .......... 29 2.9.3 Air Carbon Arc Gouging and Cutting .... 30 3. WELDED CONNECTIONS ............................ 31 3.1 JOINTS ................................................................ 31 3.2 WELD TYPES—GENERAL .............................. 31 3.3 COMPLETE JOINT PENETRATION (CJP) GROOVE WELDS .............................................. 31 3.3.1 CJP Groove Weld Backing .................... 32 3.3.2 Single-Sided vs. Double-Sided Welds ... 34 3.3.3 Groove Weld Preparations ..................... 34 3.3.4 Spacer Bars ............................................ 34 3.4 PARTIAL JOINT PENETRATION (PJP) GROOVE WELDS .............................................. 34 3.4.1 Effective Throats for PJP Groove Welds ......................................... 35 3.4.2 Minimum PJP Groove Weld Sizes ......... 35 3.4.3 Restrictions on the Use of PJP Groove Welds ......................................... 35 3.4.4 Required Filler Metal Strength for PJP-Groove Welds ............................ 36 3.4.5 Flare-V and Flare-Bevel Groove Welds ..................................................... 36 3.4.6 Single-Sided vs. Double-Sided Welds ... 36 3.4.7 PJP-Groove Weld Details ....................... 36 3.5 FILLET WELDS ................................................. 36 3.5.1 Minimum Size of Fillet Welds ............... 37 3.5.2 Maximum Size of Fillet Welds .............. 38 3.5.3 Minimum Fillet Weld Lengths ............... 38 3.5.4 Maximum Fillet Weld Lengths .............. 38 3.5.5 Intermittent Fillet Welds ........................ 38 3.5.6 Penetration in Fillet Welds ..................... 39 3.5.7 Longitudinal vs. Transverse Fillet Welds ............................................ 39 3.5.8 Combined Longitudinal vs. Transverse Welds ................................... 40 3.5.9 End Returns (Boxing) ............................ 40 3.5.10 Weld Termination (Fillet Welds) ............ 41 3.5.11 Fillet Welds and Fitup ............................ 42 3.6 PLUG/SLOT WELDS ......................................... 42 3.7 INTERACTION OF JOINT TYPES AND WELD TYPES ........................................... 43 3.8 SELECTION OF WELD TYPES ....................... 43 3.9 WELD DETAILS ................................................ 45 3.9.1 Weld Tabs ............................................... 45 3.9.2 Weld Access Holes ................................. 45 3.9.3 Fillers ..................................................... 46 3.9.4 Welds and Mechanical Fasteners ........... 46 3.9.5 Strength of Welds in Combinations ....... 47 3.9.6 k-Area Detailing ..................................... 47 3.10 LAMELLAR TEARING AND JOINT DETAILS ................................................. 48 3.11 REQUIRED FILLER METAL STRENGTH ...... 48 3.11.1 Matching Filler Metal ............................ 48 3.11.2 Undermatching Filler Metal .................. 48 3.11.3 Overmatching ........................................ 49 3.12 DETERMINING WELD STRENGTH ............... 50 3.12.1 CJP Groove Welds ................................. 50 3.12.2 PJP Groove Welds .................................. 50 3.12.3 Fillet Welds ............................................ 50 3.12.4 Plug/Slot Welds ...................................... 51 3.13 SPECIAL WELDS .............................................. 51 3.13.1 Arc Spot Welds (Puddle Welds, Deck Welds) ........................................... 51 3.13.2 Repair Welds .......................................... 51 3.13.3 Seal Welds .............................................. 52 3.13.4 Tack Welds ............................................. 53 3.13.5 Temporary Welds ................................... 54 3.13.6 Compatibility of Weld Metals ................ 54 3.14 SPECIFIC REQUIREMENTS FOR VARIOUS JOINTS ............................................. 54 3.14.1 Butt Joints .............................................. 54 3.14.2 Corner Joints .......................................... 54 3.14.3 T-Joints ................................................... 55 3.14.4 Lap Joints ............................................... 55 3.15 WELDING SYMBOLS ...................................... 55 3.16 SAMPLE CALCULATIONS .............................. 57 4. METALLURGICAL ISSUES .......................... 59 4.1 INTRODUCTION ............................................... 59 4.2 STEEL—PROPERTIES OF INTEREST ............ 59 4.3 DESCRIPTIONS OF STEEL GROUPS ............. 60 4.3.1 AWS D1.1 Prequalified Steels ............... 60 4.3.2 AWS D1.1 Approved Steels ................... 60 4.3.3 AWS D1.1 Unlisted Steels ..................... 60 4.3.4 AISC Specification Treatment of Unidentified Steels ................................. 604.4 WELDING REQUIREMENTS FOR SPECIFIC STEELS ............................................. 60 4.4.1 Weathering Steels .................................. 60 4.4.2 Quenched and Tempered Steels ............. 61 4.4.3 Historical (Obsolete) Steels ................... 62 4.5 WELDING NONSTRUCTURAL STEELS ....... 63 4.5.1 Anchor Rods .......................................... 63 4.5.2 Bolts and Nuts ........................................ 64 4.5.3 Stainless Steel to Steel ........................... 64 4.5.4 Cast Iron ................................................ 64 4.5.5 Wrought Iron ......................................... 65 4.5.6 Steel Castings ......................................... 65 5. WELD CRACKING .......................................... 67 5.1 INTRODUCTION ............................................... 67 5.2 SHRINKAGE AND RESTRAINT ...................... 67 5.2.1 Shrinkage ............................................... 67 5.2.2 Constraint ............................................... 67 5.3 TYPES OF WELD CRACKS ............................. 68 5.3.1 Centerline Cracking ............................... 68 5.3.2 Heat-Affected Zone Cracking ................ 72 5.3.3 Transverse Cracking .............................. 74 5.4 LAMELLAR TEARING ..................................... 75 5.5 REDUCING SHRINKAGE STRESSES ............ 77 5.6 REDUCING RESTRAINT ................................. 78 5.7 POST-WELDING STRESS REDUCTION MEASURES ........................................................ 78 6. DISTORTION .................................................... 79 6.1 INTRODUCTION ............................................... 79 6.2 CAUSES OF DISTORTION ............................... 79 6.3 DISTORTION CONTROL ................................. 80 6.3.1 General ................................................... 80 6.3.2 Angular Distortion ................................. 81 6.3.3 Transverse Shrinkage ............................. 82 6.3.4 Longitudinal Shortening ........................ 82 6.3.5 Twisting ................................................. 83 6.3.6 Longitudinal Sweep or Camber ............. 83 6.3.7 Buckling and Warping ........................... 84 6.3.8 Rotational Distortion ............................. 84 6.4 SPECIALIZED DISTORTION CONTROL MEASURES ........................................................ 85 6.4.1 Adding Restraint .................................... 85 6.4.2 Weld Placement ..................................... 86 6.4.3 Welding Sequence .................................. 86 7. WELDING PROCEDURE SPECIFICATIONS ........................................... 89 7.1 INTRODUCTION ............................................... 89 7.2 WRITING WELDING PROCEDURE SPECIFICATIONS .............................................. 89 7.3 USING WELDING PROCEDURE SPECIFICATIONS .............................................. 89 7.4 PREQUALIFIED WELDING PROCEDURE SPECIFICATIONS .............................................. 90 7.5 QUALIFIED WELDING PROCEDURE SPECIFICATIONS .............................................. 91 7.6 EFFECTS OF WPS VARIABLES ...................... 92 7.6.1 Amperage ............................................... 92 7.6.2 Arc Voltage ............................................ 92 7.6.3 Travel Speed .......................................... 92 7.6.4 Wire Feed Speed .................................... 93 7.6.5 Electrode Extension ............................... 93 7.6.6 Contact Tip to Work Distance ................ 93 7.6.7 Electrode Diameter ................................ 93 7.6.8 Polarity ................................................... 93 7.6.9 Heat Input .............................................. 93 7.6.10 Preheat and Interpass Temperature ........ 94 7.6.11 Post-Heat ................................................ 94 7.6.12 Stress Relief ........................................... 94 8. WELD QUALITY ............................................. 95 8.1 INTRODUCTION ............................................... 95 8.2 TYPES OF WELD DISCONTINUITIES ........... 95 8.2.1 Planar Discontinuities—Weld and Base Metal ............................................. 95 8.2.2 Volumetric Discontinuities—Specific to the Weld ............................................. 97 8.2.3 Volumetric Discontinuities External to the Weld ............................................... 100 8.2.4 Metallurgical Deficiencies ................... 1009. WELD INSPECTION ..................................... 101 9.1 INTRODUCTION ............................................. 101 9.2 VISUAL INSPECTION (VT) ........................... 101 9.2.1 Visual Inspection Before Welding ....... 101 9.2.2 Visual Inspection During Welding ....... 102 9.2.3 Visual Inspection After Welding .......... 102 9.3 NONDESTRUCTIVE TESTING — GENERAL ........................................................ 102 9.4 PENETRANT TESTING (PT) .......................... 102 9.5 MAGNETIC PARTICLE INSPECTION (MT) 103 9.6 RADIOGRAPHIC INSPECTION (RT) ............ 104 9.7 ULTRASONIC INSPECTION (UT) ................. 104 10. SEISMIC WELDING ISSUES ....................... 107 10.1 INTRODUCTION ............................................. 107 10.2 SPECIFICATIONS AND CODES .................... 108 10.3 SEISMIC WELDING TERMINOLOGY ......... 108 10.4 SPECIAL CONNECTION DETAILS .............. 109 10.5 FILLER METAL REQUIREMENTS ............... 110 10.6 WELDER QUALIFICATION TESTS .............. 111 10.7 NONDESTRUCTIVE TESTING ..................... 111 11. FATIGUE CONSIDERATIONS .................... 113 11.1 INTRODUCTION ............................................. 113 11.2 STRESS RANGE .............................................. 113 11.3 CONNECTION GEOMETRY .......................... 116 11.4 COMPUTATIONS ............................................ 118 11.5 INSPECTION ISSUES ..................................... 119 11.6 SPECIAL FABRICATION/ERECTION REQUIREMENTS ............................................ 119 12. SPECIAL WELDING APPLICATIONS ...... 121 12.1 WELDING ON ANCHOR RODS .................... 121 12.1.1 General ................................................. 121 12.1.2 Extending Anchor Rods ....................... 121 12.1.3 Welding Anchor Rod to Base Plates .... 121 12.2 WELDING ON COATED STEELS .................. 122 12.2.1 General ................................................. 122 12.2.2 Galvanized Materials ........................... 122 12.2.3 Testing .................................................. 122 12.2.4 Ventilation ............................................ 123 12.3 WELDING ON HEAVY SECTIONS ............... 123 12.4 WELDING ON HEAVILY RESTRAINED MEMBERS ....................................................... 124 12.5 WELDING HSS ............................................... 125 12.5.1 Introduction .......................................... 125 12.5.2 Connections and HSS Member Size ... 126 12.5.3 Overall Configurations of HSS Assemblies ........................................... 126 12.5.4 Cutting and Preparing Joints in HSS .. 126 12.5.5 Welding HSS ....................................... 127 12.6 WELDING AESS ............................................. 127 12.7 SHOP VS. FIELD WELDING .......................... 128 12.8 WELDING ON EXISTING STRUCTURES .... 128 12.8.1 General ................................................. 128 12.8.2 General Welding Precautions ............... 128 12.8.3 Welding on Members under Load ....... 129 12.8.4 Repair of Plastically Deformed Steel .. 129 12.9 HEAT SHRINKING .......................................... 130 13. THE ENGINEER’S ROLE IN WELDED CONSTRUCTION ........................ 131 13.1 INTRODUCTION ............................................. 131 13.2 CONTRACT DOCUMENTS ............................ 131 13.2.1 Design Drawings ................................. 132 13.2.2 Static vs. Cyclic Loading ..................... 132 13.2.3 Inspection Requirements ..................... 132 13.2.4 Alternate Acceptance Criteria .............. 133 13.2.5 Notch Toughness Requirements .......... 133 13.2.6 Welding on Existing Structures ........... 133 13.2.7 Structural Details ................................. 134 13.2.8 Certification of Welding Materials ....... 134 13.3 APPROVALS .................................................... 134 13.3.1 Background .......................................... 134 13.3.2 New Materials and Processes .............. 135 13.3.3 Routine Items ....................................... 135 13.3.4 Practices Requiring Review ................. 135 13.3.5 Practices That May or May Not Be Acceptable ....................... 136 13.4 UNEXPECTED CIRCUMSTANCES .............. 136 13.4.1 Background .......................................... 136 13.4.2 Base Metal Discontinuities .................. 13613.4.3 Fit-up and Alignment Problems ........... 137 13.4.4 Welding Problems ................................ 137 13.4.5 Post-Welding Corrections .................... 137 14. ECONOMY IN WELDING ........................... 139 14.1 INTRODUCTION ............................................. 139 14.2 SELECTION OF PROPER WELD TYPE ........ 139 14.2.1 CJP Groove Welds vs. Alternatives ..... 139 14.2.2 Fillet Welds vs. PJP Groove Welds ...... 140 14.2.3 Combination PJP/Fillet Weld Option ... 140 14.3 PROPER DETAILING OF WELDS ................. 141 14.3.1 Fillet Welds: Leg Size vs. Length ........ 141 14.3.2 Fillet Welds: Intermittent vs. Continuous ........................................... 141 14.3.3 CJP Groove Welds: Single vs. Double Sided ....................................... 142 14.3.4 CJP Groove Weld Details: Included Angle vs. Root Opening ........ 142 14.3.5 CJP Groove Welds: V and Bevel vs. U and J ................................. 145 14.3.6 PJP-Groove Welds: Single vs. Double Sided ....................................... 145 14.3.7 Flare Groove Welds ............................. 146 14.3.8 Shop vs. Field Welding ........................ 146 14.3.9 Welded vs. Bolted Connections ........... 146 15. WELDING SAFETY ...................................... 147 REFERENCES .............................................................. 149
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