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Naveed Habib Khan Mechanical Department 6th August 2009 WELDINGWELDING.

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Presentation on theme: "Naveed Habib Khan Mechanical Department 6th August 2009 WELDINGWELDING."— Presentation transcript:

1 Naveed Habib Khan Mechanical Department 6th August 2009 WELDINGWELDING

2  Welding Basics  Types of Weld Joints  Welding Positions  Welding Types  Welding Processes  Welding Symbols  Welding Safety Contents Contents

3 Fabrication Fabrication “ Metal Fabrication is the forming of metal, usually steel plate, into various forms either by welding or other forms of metal joining processes Welding Welding “ A fabrication process that joins materials, usually metals by causing coalescence” Coalescence means “Fusion” What is Fabrication / Welding?

4  Weldments  Weld puddle  Slag  Weld Bead  Backing  Tack Weld  Heat Affected Zone (HAZ) Welding Terms

5 5 Parts of a Weld Joint and Weld Heat Affected Zone

6 6 Fillet Weld Fillet welds should: Fillet welds should: Have a flat to slightly convex face Have a flat to slightly convex face Be uniform in appearance Be uniform in appearance Have equal leg size Have equal leg size

7 7 Types of Weld Joints There are 5 types of joints … There are 5 types of joints … 1)B – Butt Joint 2)L – Lap Joint 3)T – Tee Joint 4)E – Edge Joint 5)C – Corner Joint

8 8 Fillet and Groove Welds Groove and fillet welds can be made on many types of joints Groove and fillet welds can be made on many types of joints

9 9 Types of Joints

10 WELDED JOINT CATEGORY ASME Code defines welded joints by category. The term “Category” defines the location of a joint in a vessel. The term “Category” defines the location of a joint in a vessel. The joints included in each category are designated as joints of Categories A, B, C, and D. The joints included in each category are designated as joints of Categories A, B, C, and D. The “Categories” established by UW-3 are for use in specifying special requirements (based on Service, Material, and Thickness) regarding joint type and degree of inspection for certain welded pressure joints. The “Categories” established by UW-3 are for use in specifying special requirements (based on Service, Material, and Thickness) regarding joint type and degree of inspection for certain welded pressure joints. Weld joint efficiency “E” It is a measure of weld quality and accounts for stress concentrations. E is needed in component thickness calculations

11 Figure illustrates typical joint locations included in each category.

12 Category A: Category A: Longitudinal welded joints within the main shell or nozzles; any welded joint within a formed or flat head; circumferential welded joints connecting hemispherical heads to main shells, to transitions in diameters. Category B: Category B: Circumferential welded joints within the main shell, nozzles, or transitions in diameter; circumferential welded joints connecting formed heads other than hemispherical to main shells, to transitions in diameter. Category C: Category C: Welded joints connecting flanges, tubesheets, or flat heads to main shell, to formed heads, to transitions in diameter, to nozzles. Category D: Category D: Welded joints connecting nozzles to main shells, to spheres, to transitions in diameter, to heads.

13 Weld joint efficiency vs. Joint Type, Category & Radiographic Examination

14 14 Welding Positions There are various positions that a weld can be made in: There are various positions that a weld can be made in:

15 Root PassHot Pass Fill PassCover Pass Weld Passes

16 TYPES OF WELDING APPLICATION CONSTRUCTIONIN-SERVICE PROCESS ARCGAS RESISTANCESOLID STATE ENERGY BEAM

17 Arc Welding Arc Welding “Arc welding process use electric power supply to create & maintain an electric arc b/w an electrode and the base material to melt metals at the welding point”. Welding Process

18 How an arc is formed? The arc is like a flame of intense heat that is generated as the electrical current passes through a highly resistant air gap. The arc is like a flame of intense heat that is generated as the electrical current passes through a highly resistant air gap.

19 19 The Arc Welding Circuit The electricity flows from the power source, through the electrode and across the arc, through the base material to the work lead and back to the power source The electricity flows from the power source, through the electrode and across the arc, through the base material to the work lead and back to the power source

20 20 Basic Steps of Arc Welding Choose the right welding process Choose the right welding process Preparation of Welding Preparation of Welding Prepare the base materials: remove scale, rust, oil, grease and any foreign material Prepare the base materials: remove scale, rust, oil, grease and any foreign material Qualified Welders Qualified Welders Welding Procedure Welding Procedure Tack Welds Tack Welds Choose the right filler material Choose the right filler material Pre-heating Pre-heating Connections Connections Welding & Removal of Temporary Attachment Welding & Removal of Temporary Attachment Assess and comply with safety requirements Assess and comply with safety requirements Use proper welding techniques and be sure to protect the molten puddle from contaminants in the air Use proper welding techniques and be sure to protect the molten puddle from contaminants in the air Inspect the weld Inspect the weld

21 Factors Affecting the Welding 1. Welding Procedure 2. Thickness 3. Electrode extension 4. Angle of bevel 5. Travel speed 6. Cleanliness 7. Type of joint 8. Polarity, Current & Voltage 9. Root Opening distance 10. Welding Position

22 Types of Arc Welding Types of Arc Welding  Shielded Metal - Arc Welding(SMAW)  Gas Metal - Arc Welding(GMAW)  Gas Tungsten - Arc Welding(GTAW)  Submerged - Arc Welding(SAW)  Plasma - Arc Welding(PAW)  Flux Cored - Arc Welding(FCAW) GAS WELDING GAS WELDING  Oxyacetylene Welding (OAW)

23 Gas Tungsten Arc Welding (GTAW) Also called T Also called Tungsten inert gas (TIG) This uses a similar inert gas shield to MIG, but the tungsten electrode is not consumed. Filler metal is provided from a separate rod fed automatically into the molten pool

24 Equipment for GTAW Welding Equipment for GTAW Welding

25 Type of Current & polarity Type of Current & polarity  Direct Current Direct current straight polarity (DCSP) Direct current straight polarity (DCSP) Direct current reverse polarity (DCRP) Direct current reverse polarity (DCRP)  Alternating Current Type of Power Source Type of Power Source  Generator  Transformer

26 Tungsten Electrode Tungsten Electrode  Non consumable  Melting point = 6170°F  Tungsten Alloys : Thoria, Zirconia, Ceria, Lanthana or a combination of oxides. Thoria, Zirconia, Ceria, Lanthana or a combination of oxides.  Length = 3 to 24 inches  Diameter =.01 to.25inches  Extension & Shape

27 GTAW Shielding Gases GTAW Shielding Gases  Argon, Helium or mixture of Gases  Inert gases don't form compound with other elements.  These gases protect the tungsten electrode and weld metal from contamination.

28 Properties Of Inert Gases Properties of ArgonProperties of Helium Argon is a heavy gas that is obtained from the atmosphere by the liquification of air Helium is a light gas that is obtained by separation from natural gas May be used as a compressed gas Quieter & smoother arc actionDeeper penetration Lower costExpensive Suitable gas for GTAWGives a smaller heat affected zone Better for thin metalsBetter for thicker metals Good cleaning action Lower flow rates are requiredHigher flow rates are required Better for welding dissimilar metals More availabilityLess available Better for welding at higher speeds Argon - helium mixture are used when better control of argon and the deeper penetration of helium are needed. (75% helium, 25% Argon)

29 E7018R Electrode Type of Covering (usually for GTAW only) Tensile Strength in Ksi Position of Welding (1 6) Current Condition A1 Allow Constituent of Filler  Selection of Filler metal depends upon chemical composition of base metal.  To increase the tensile strength, ductility, and corrosion resistance.  Filler metal is kept in “HOT OVENS” for preheating for smooth operation.  Classification of Filler metals in AWS  Stainless steelA5.9  Carbon steelsA5.18  Low alloy steelA5.28 Deposition Rate Deposition Rate Filler Metals

30 Cost of GTAW Cost of GTAW  Labor (20% to 40%)  Overhead cost (Major Cost)  Filler metal cost  Shielded gas cost  Electric power cost (Minor cost)  Tungsten Electrode cost (4%of Shielding gas cost)  Welding Torch

31 Advantages Advantages  High Quality Weld  No Flux or Slag  Used for both Ferrous & Non-Ferrous metals  No Smokes or Fumes  Welding can be done in all position  Filler metal is not always required  The arc & weld pool is clearly visible to the welder  For many application, it is the best method   Excellent for welding thin metals and pipeline welding

32 Limitations Limitations  Welding speed is slow  Electrode is easily contaminated  Not efficient for welding thick sections  Thickness should not exceed ¾”.  Lower filler metal deposition rate  Not Economical  Hand eye co-ordination skill is required  Highly skilled labor needed for this process

33 Shielded Metal Arc Welding(SMAW) This is the most commonly used technique. There is a wide choice of electrodes, metal and fluxes, allowing application to different welding conditions. The gas shield is evolved from the flux, preventing oxidation of the molten metal pool. Also referred to as “Stick Welding” Also referred to as “Stick Welding” Used for everything from pipeline welding, farm repair and complex fabrication. Used for everything from pipeline welding, farm repair and complex fabrication. Uses a “stick” shaped electrode. Uses a “stick” shaped electrode. Can weld: steel, cast iron, stainless steel, etc. Can weld: steel, cast iron, stainless steel, etc.

34 Shielded Metal Arc Welding (SMAW)

35 Gas Metal Arc Welding (GMAW) Electrode metal is fused directly into the molten pool. The electrode is, therefore, consumed rapidly, being fed from a motorized reel down the centre of the welding torch Electrode metal is fused directly into the molten pool. The electrode is, therefore, consumed rapidly, being fed from a motorized reel down the centre of the welding torch Also referred to as “MIG” welding Also referred to as “MIG” welding Uses a shield gas and a continuous wire electrode Uses a shield gas and a continuous wire electrode Used for all types of fabricatio Used for all types of fabricatio Great for thin metals up to ¼” Great for thin metals up to ¼” Excellent speed of deposition Excellent speed of deposition Used for metals such as: steel, aluminum and stainless steel. Used for metals such as: steel, aluminum and stainless steel.

36 Gas Metal Arc Welding (GMAW)

37  Higher deposition rates than SMAW  All position capability  Less operator skill required  Long welds can be made without starts and stops  Minimal post weld cleaning is required MIG Welding Benefits

38 Instead of using shielding gas, the arc and weld zone are completely submerged under a blanket of granulated flux. A continuous wire electrode is fed into the weld. This is a common process for welding Submerged arc welding (SAW)

39   This is similar to the MIG process, but uses a continuous hollow electrode filled with flux, which produces the shielding gas.   The advantage of the technique is that it can be used for outdoor welding, as the gas shield is less susceptible to draughts. Flux-cored arc welding (FCAW)

40 Plasma welding is similar to the TIG process. A needle-like plasma arc is formed through an orifice and fuses the base metal. Shielding gas is used. Plasma welding is most suited to high-quality and precision welding applications. Plasma - Arc Welding (PAW)

41 Oxygen/ Fuel Welding Utilizes oxygen and a fuel gas to heat metal until it is in a molten state and fuse multiple pieces of metal together. Can be used with or without a filler rod. Utilizes oxygen and a fuel gas to heat metal until it is in a molten state and fuse multiple pieces of metal together. Can be used with or without a filler rod. Great for brazing dissimilar metals together. Great for brazing dissimilar metals together. Older technology that can be replaced by GTAW Older technology that can be replaced by GTAW

42 42 Welding Symbols Welding symbols contain information about the weld to be made

43 43 Welding symbols give the welder specific instructions about the weld including: Welding symbols give the welder specific instructions about the weld including: Placement, Size, Length, Process Placement, Size, Length, Process Any other special notes Any other special notes Welding symbols are Welding symbols are Universally used Universally used Governed by the AWS Governed by the AWS Found on engineering drawings Found on engineering drawings

44 Reference Line (Required element) Reference Line Always Horizontal

45 Reference Line (Required element) Arrow Arrow Line

46 Reference Line (Required element) Arrow Tail Tail

47 Reference Line (Required element) Arrow Tail Reference Line must always be horizontal, Arrow points to the line or lines on drawing which clearly identify the proposed joint or weld area. The tail of the welding symbol is used to indicate the welding or cutting processes, as well as the welding specification, procedures, or the supplementary information to be used in making the weld.

48 Reference Line (Required element) Arrow Tail Reference Line must always be horizontal, Arrow points to the line or lines on drawing which clearly identify the proposed joint or weld area. The tail of the welding symbol is used to indicate the welding or cutting processes, as well as the welding specification, procedures, or the supplementary information to be used in making the weld. Basic components of a WELDING SYMBOL Tail omitted when reference not used Arrow connects reference line to arrow side member of joint or arrow side of joint

49 A circle at the tangent of the arrow and the reference line means welding to be all around. All the way Around

50 A flag at the tangent of the reference line and arrow means Field Weld. Field Weld Symbol

51 ARROW SIDE OTHER SIDE Weld Symbol Terminology

52 Break in arrow means arrow side must be side that beveling or other preparation required.

53 Fillet Weld (Arrow Side Only)

54 Fillet Weld (Other Side)

55 1/4 1/4 Size of Fillet Weld

56 1/4 (5/16) Depth of preparation or groove Depth of penetration Example of Double Bevel Groove weld

57 Plug or Slot Weld Symbol Arrow Side

58 5/16 Single-Bevel-Groove and Double Fillet Weld Symbol

59 Single-Bevel-Groove and Double Fillet weld Symbols

60 Chain Intermittent Fillet Weld Weld both sides each end and 10 inches center to center in between 1/ in

61 Staggered Intermittent Fillet Weld Weld ends than 10 inch centers staggered each side 10 in /4

62 Standard Weld Symbols As per AWS

63 Some common symbol List published by AWS

64 Back Purging  Back Purging Procedure  Used to protect the electrode and the molten weld metal from atmospheric contamination  Protect the underside of the weld & its adjacent base metal surfaces from oxidation during Welding  Application : All e.g.: Pipe Fabrication  Gas Backing : for minimum of the first two passes  Minimum purge time before welding, flow rate and venting, etc  Shielding Gas type (Argon, He or mixture of 2-Inert Gases for shielding).

65 Occupational Opportunities in Welding Welders Welders Tack Welders Tack Welders Welding Helper Welding Helper Welding Operators Welding Operators Welder Assemblers/ Welder fitters Welder Assemblers/ Welder fitters Welding Inspection Welding Inspection Welding Shop Supervisor Welding Shop Supervisor Welding Engineers Welding Engineers

66 66 Arc Welding Safety Protect yourself and others from potential hazards including: Protect yourself and others from potential hazards including: Fumes and Gases Fumes and Gases Electric Shock Electric Shock Arc Rays Arc Rays Fire and Explosion Hazards Fire and Explosion Hazards Noise Noise Hot objects Hot objects

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69 REFERENCES Technical Guide for GTAW by Hobart Institute Technical Guide for GTAW by Hobart Institute American Welding Society (AWS) American Welding Society (AWS) ASME Section II- Part C : Specifications for Welding Rods, Electrodes, and Filler Metals ASME Section II- Part C : Specifications for Welding Rods, Electrodes, and Filler Metals ASME Section VIII – Div.1: Rules for Construction of Pressure Vessels ASME Section VIII – Div.1: Rules for Construction of Pressure Vessels ASME Section IX - Welding and Brazing Qualifications for personnel and procedures ASME Section IX - Welding and Brazing Qualifications for personnel and procedures

70 Questions?

71 Thank You


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