2. SUBMITTED BY-FAIZ MOHD.ANSARI(ME-1) 1214340061(B-2) IMS ENGINEERING COLLEGE GHAZIABAD

3.  TO KNOW ABOUT GAS WELDING  TO KNOW ABOUT ARC WELDING  TYPES OF ARC WELDING(SMAW,TIG,MIG,SAW)  PRINCIPLES OF THESE TYPES OF WELDING

4. Oxyacetylene Welding (OAW) The oxyacetylene welding process uses a combination of oxygen and acetylene gas to provide a high temperature flame.

5. OAW is a manual process in which the welder must personally control the the torch movement and filler rod application The term oxyfuel gas welding outfit refers to all the equipment needed to weld. Cylinders contain oxygen and acetylene gas at extremely high pressure.

9. Oxygen Cylinders Oxygen is stored within cylinders of various sizes and pressures ranging from 2000- 2640 PSI. (Pounds Per square inch) Oxygen cylinders are forged from solid armor plate steel. No part of the cylinder may be less than 1/4” thick. Cylinders are then tested to over 3,300 PSI using a (NDE) hydrostatic pressure test.

10. Oxygen Cylinders Cylinders are regularly re-tested using hydrostatic (NDE) while in service Cylinders are regularly chemically cleaned and annealed to relieve “jobsite” stresses created by handling.

11. Cylinder Transportation Never transport cylinders without the safety caps in place Never transport with the regulators in place Never allow bottles to stand freely. Always chain them to a secure cart or some other object that cannot be toppled easily.

12. Pressure Regulators for Cylinders Reduce high storage cylinder pressure to lower working pressure. Most regulators have a gauge for cylinder pressure and working pressure.

13. Pressure Regulators for Cylinders Regulators are shut off when the adjusting screw is turn out completely. Regulators maintain a constant torch pressure although cylinder pressure may vary Regulator diaphragms are made of stainless steel

14. Regulator Hoses Hoses are are fabricated from rubber Oxygen hoses are green in color and have right hand thread. Acetylene hoses are red in color with left hand thread.

15. Check Valves & Flashback Arrestors Check valves allow gas flow in one direction only Flashback arrestors are designed to eliminate the possibility of an explosion at the cylinder. Combination Check/ Flashback Valves can be placed at the torch or regulator.

16. Acetylene Gas Virtually all the acetylene distributed for welding and cutting use is created by allowing calcium carbide (a man made product) to react with water. The nice thing about the calcium carbide method of producing acetylene is that it can be done on almost any scale desired. Placed in tightly-sealed cans, calcium carbide keeps indefinitely. For years, miners’ lamps produced acetylene by adding water, a drop at a time, to lumps of carbide. Before acetylene in cylinders became available in almost every community of appreciable size produced their own gas from calcium carbide.

17. Acetylene Cylinders Acetylene is stored in cylinders specially designed for this purpose only. Acetylene is extremely unstable in its pure form at pressure above 15 PSI (Pounds per Square Inch) Acetone is also present within the cylinder to stabilize the acetylene. Acetylene cylinders should always be stored in the upright position to prevent the acetone form escaping thus causing the acetylene to become unstable.

18. Acetylene Cylinders Cylinders are filled with a very porous substance “monolithic filler” to help prevent large pockets of pure acetylene form forming Cylinders have safety (Fuse) plugs in the top and bottom designed to melt at 212° F (100 °C)

19. Acetylene Valves Acetylene cylinder shut off valves should only be opened 1/4 to 1/2 turn This will allow the cylinder to be closed quickly in case of fire. Cylinder valve wrenches should be left in place on cylinders that do not have a hand wheel.

20. Regulator Pressure Settings The maximum safe working pressure for acetylene is 15 PSI !

21. Typical startup procedures Always use a flint and steel spark lighter to light the oxygen acetylene flame. Never use a butane lighter to light the flame

22. Flame Settings There are three distinct types of oxy-acetylene flames, usually termed: –Neutral –Carburizing (or “excess acetylene”) –Oxidizing (or “excess oxygen” ) The type of flame produced depends upon the ratio of oxygen to acetylene in the gas mixture which leaves the torch tip.

23. Pure Acetylene and Carburizing Flame profiles

24. Neutral and Oxidizing Flame Profiles

26. Flame definition The neutral flame (Fig. 4-1) is produced when the ratio of oxygen to acetylene, in the mixture leaving the torch, is almost exactly one-to- one. It’s termed ”neutral” because it will usually have no chemical effect on the metal being welded. It will not oxidize the weld metal; it will not cause an increase in the carbon content of the weld metal. The excess acetylene flame (Fig. 4-2), as its name implies, is created when the proportion of acetylene in the mixture is higher than that required to produce the neutral flame. Used on steel, it will cause an increase in the carbon content of the weld metal. The oxidizing flame (Fig. 4-3) results from burning a mixture which contains more oxygen than required for a neutral flame. It will oxidize or ”burn” some of the metal being welded.

28. 11 - 27 Shielded Metal Arc Welding (SMAW) Manual arc welding –Heat for welding generated by electric arc established between flux-covered consumable metal rod (electrode) and work Called stick electrode welding Combustion and decomposition of electrode creases gaseous shield –Protects electrode tip, weld puddle, arc, and highly heated work from atmospheric contamination Additional shielding provided by covering of molten slag (flux) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

29. 11 - 28 American Welding Society Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

30. 11 - 29 SMAW Operating Principles Sets up electric circuit –Includes welding machine, work, electric cables, electrode holder and electrodes, and a work clamp Heat of electric arc brings work to be welded and consumable electrode to molten state –Heat intense: as high at 9,000ºF at center Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

31. 11 - 30 Welding Process Electric arc started by striking work with electrode Heat of arc melts electrode and surface of base metal Tiny globules of molten metal form on tip of electrode and transferred by arc into molten pool on work surface After weld started, arc moved along work

32. 11 - 31 SMAW Operating Principle American Welding Society Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

33. Introduction to practical application of wire feed welding

34. MIG – Metal Inert Gas Welding May be called GMAW (Gas Metal Arc Welding) Avoid cutting in drafty or windy conditions Molten pool is shielded by the inert gas envelope Joints are stronger, more ductile, and more corrosion resistant Flux center wire has slag; Solid wire has no slag, thus eliminating slag inclusion Welded metal does not readily distort

35. REQUIREMWNTS FOR MIG Power Supply Gas Supply Wire feeder Gun and Whip Process

37. MIG Machine Operation Wire is fed at a pre-set rate Gas flows at about 35 cubic feet per hour and is directed around the welding wire for shielding

41. Advantages Disadvantages Welding can be done in all positions High rates of metal deposition Excellent filling ability for poor-fit joints High weld Quality No electrode stub loss Less distortion due to narrow, deep weld profile Easier process to learn and use  Welding power source expensive  Shielding gas expensive  Higher electrode wire cost  Most machines require three- phase input power  Not as versatile as SMAW for maintenance 4Welding cast iron 4Cutting 4Carbon arc torch applications

42. TIG Welding Introduction

43. 42 Background ► What is TIG?  Tungsten Inert Gas ► Also referred to as GTAW  Gas Shielded Tungsten Welding ► In TIG welding, a tungsten electrode heats the metal you are welding and gas (most typically Argon) protects the weld from airborne contaminants

44. 43 Background ► TIG welding uses a non-consumable tungsten ► Filler metal, when required, is added by hand ► Shielding gas protects the weld and tungsten

45. Inert Gases for Shielding Argon –Cheap – comes from air –Heavier than air – blankets weld well –Provides clean welding of Aluminum and Magnesium –Best with AC Helium –Arc voltage is greater –Hotter arc –Deeper Penetration –Fast Speed –Less Distortion –May spatter more than Argon Carbon Dioxide –Cooling effect –Low cost –Produces Spatter –Deep penetration –Not same inert characteristics as Argon and Helium

47. 46 Advantages Welds more metals and metal alloys than any other process High quality and precision Pin point control Aesthetic weld beads No sparks or spatter No flux or slag No smoke or fumes

48. 47 Disadvantages ►Lower filler metal deposition rates ►Good hand-eye coordination a required skill ►Brighter UV rays than other processes ►Slower travel speeds than other processes ►Equipment costs tend to be higher than other processes

49. 48 Safety ► Electric shock can kill.  Always wear dry insulating gloves  Insulate yourself from work and ground  Do not touch live electrical parts  Keep all panels and covers securely in place ► Fumes and gases can be hazardous to your health.  Keep your head out of the fumes  Ventilate area, or use breathing device

50. 49 Safety ► Welding can cause fire or explosion.  Do not weld near flammable material  Watch for fire; keep extinguisher nearby  Do not locate unit over combustible surfaces  Do not weld on closed containers ► Arc rays can burn eyes and skin; Noise can damage hearing.  Wear welding helmet with correct shade of filter  Wear correct eye, ear, and body protection

52. SUBMERGED ARCH WELDING WELD ARC IS SHIELDED BY GRANULAR FLUX FLUX CONSIST OF SILICA,MgO,CaF2 FLUX IS FED IN WELD ZONE BY GRAVITY FLOW THROUGH A NOZZLE IN THIS CONSUMABLE ELECTRODE IS USED

53. PURPOSE OF USING FLUX THICK LAYER OF FLUX COMPLETEL COVERS THE METAL THUS, PREVENTS SPATTERS AND SPARKS SUPPRESSES UV RADIATIONS IT ALSO ACTS AS A THERMAL INSULATOR THUS, PROMOTING DEEP PENETRATION OF HEAT INTO THE WORKPIECE

54. SPECIFICATIONS FOR SAW RANGE OF CURRENT – 300 TO 2000A VOLTAGE SUPPLY REQUIRED – 440V CONSUMABLE ELECTRODE IS A BARE ROUND COIL OF 1.5mm-10mm IN DIAMETRE FED THROUGH WELDED GUN

55. ADVANTAGES OF SAW UNUSED FLUX CAN BE RECOVERSD IT CAN BE USED TO WELD VARIETY OF CARBON & ALLOY STEELS THE QUALITY OF WELD PRODUCE IS HIGH THE WELD HAS GOOD TOUGHNESS,DUCTILITY AND UNIFORMITY OF PROPERTIES

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