2. Presentation Topic : Welding
Group : 1 Group Members Muhammad Summair Hariss Bin Waheed Mohsin Mumtaz Jahanzeb Qdeeir Khaqan Asad Kashif Amin

3. What is Welding
Join together (metal parts) by heating the surfaces to the point of melting with a blowpipe, electric arc, or other means, and uniting them by pressing, hammering, etc

4. Welding Welding conditions
Parts are joined together by Fusion. Fusion is brought about by a combination of heat and pressure between parts being joined. In normal welding processes very high temperatures and little or no pressure is used.
Welding conditions
Smooth joint surfaces that match each other
Surfaces clean and free from oxides, grease and dirt.
Metals to be joined have same microstructure

5. Welding Preparation Weld Joints Welding Symboles Welding Techniques
The metals should be good quality (no internal impurities)
Welding Preparation
Before starting a weld, the joint edges should be carefully prepared.
Beveling large edges
Cleaning (Chemical/Mechanical)
Weld Joints
Welding Symboles
Welding Techniques

6. Weld Joints - Parts of a Weld Joint
Joint root
Groove face, Root face and Root edge
Root opening and Bevel
Bevel angle, Groove angle and Groove radius
Weld Joints - Types of Weld Joint
Butt Joint
Lap Joint
T Joint
Corner joint
Edge Joint
Splice Member

7. Joint Root
is that portion of a joint to be welded where the members are closest to each other
The joint root may be either a point, line, or an area
The joint roots are shown as shaded areas in (A)-(D) and lines in (E) (F)

8. Groove face, Root face and Root edge
Groove face is “ that surface of a member included in the groove”
Root face (land) is “that portion of the groove face within the joint root”
Root edge is a root face of zero width

9. Root opening and Bevel
Root opening is the separation between the work pieces at the joint root
Bevel (chamfer) is an angular edge preparation

10. Bevel angle, Groove angle and Groove Radius

11. Welding Joints Butt Joint
A joint between two members aligned approximately in the same plane

12. Lap Joint
A joint between two overlapping members

13. T Joint
A joint between two members located approximately at right angles to each other

14. Corner Joint
A joint between two members located at right angles to each other

15. Edge Joint
A joint between the edges of two or more parallel or nearly parallel members

16. Splice member
is “ the work piece that spans the joint in a spliced joint
Single-spliced butt joint
Double-spliced butt joint with joint filler

17. Basic components of a welding symbol
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.

18. OTHER SIDE ARROW SIDE Weld Symbol Terminology Work
Fillet Weld (Arrow Side Only)
Fillet Weld (Both sides)

19. Welding Techniques Types of Welding
There are many different methods of welding. The difference between them is outlined by two important features
The way the metal is heated
The way additional filler metal if any is fed into the weld
Types of Welding
Electric arc welding
Gas Welding
Resistance Welding
Friction Welding
Robotic Welding

20. Electric Arc Welding
The heat for fusion is supplied by an electric arc
Arc is formed between electrode and work this melts and fuses the joint edges

21. Manual Metal Arc (MMA) Applications
Most widely used of all the arc welding processes
Commonly called “stick” welding
Applications
repair work, structural steelwork,

22. Electric Arc welding Electrode
In arc welding an electrode is used to conduct current through a workpiece to fuse two pieces together.,

23. The Electrode and Coating
Coating is a combination of chemicals
Cellulosic electrodes contain cellulose
Rutile electrodes titanium oxide (rutile)
Basic electrodes contain calcium carbonate (limestone) and calcium fluoride (fluorspar)

24. Advantages of Electric arc welding
Used with many electrode types & sizes
Used in all positions
Used on great variety of materials
Flexibility in operator control makes it the most versatile of all welding processes
Low cost of equipment
Dis-advantages
Rod becomes shorter & periodically needs replacing
Slows production rate (% time welder welding)

25. Metal Arc Gas Shielded (MAGS) MIG
MIG is similar to MMA in that heat for welding is produced by forming an arc between a metal electrode and the workpiece.But we use very long electrode wire rolled on pulley.
Applications
Welding Sheets and Heavy plates, production
welding by robots on cars

26. MIG is similar to MMA in that heat for welding is produced by forming an arc between a metal electrode and the workpiece; the electrode melts to form the weld bead. The main difference
is that the metal electrode is a small diameter wire fed from a spool and a sheilding gas is used. As the wire is continuously fed, the process is often referred to as semi-automatic welding.

27. Advantages Large gaps filled or bridged easily
Welding can be done in all positions
No slag removal required
High welding speeds
High weld quality
Less distortion of work piece

28. Equipmnt used in MAGS Three major elements are :
Welding torch and accessories
Welding control & Wire feed motor
Power Source is Transformer
Shielding Gas

29. Welding torch and accessories
GAS DIFFUSER
NOZZLE
CONTACT TIP
The welding torch guides the wire and shielding gas to the weld zone.
Brings welding power to the wire also
Major components/parts of the torch are the contact tip, shielding gas nozzle, gas diffuser, and the wire conduit

30. Welding control and wire feed motor
Main function is to pull the wire from the spool and feed it to the arc
Controls wire feed speed and regulates the starting and stopping of wire feed

31. Sheilding Gas
Purpose of shielding gas is to protect the weld area from the contaminants in the atmosphere
Gas can be Inert, Reactive, or Mixtures of both
Argon, Helium, and Carbon Dioxide are the main three gases used in MAGS

32. Tungsten Arc Gas Shielded (TAGS) TIG
TIG is similar to MMA in that heat for welding is produced by forming an arc between a metal electrode and the workpiece
Applications
Used in joining magnesium and
Aluminium, stainless steels
for high quality welding
Thin sheet material

33. In the TIG process the arc is formed between a pointed tungsten electrode and the work piece in an inert atmosphere of argon or helium. The small intense arc provided by the pointed electrode is ideal for high quality and precision welding.
The electrode is not consumed during welding. When filler metal is required, it must be added separately to the weldpool. There are two currents one for starting the arc the other switched on using a trigger or foot pedal, this is a high frequency current
to maintain the arc, this is generated by a separte unit.

34. Advantages Superior quality welding Can be used in mechanised systems
Used to weld aluminium and stainless steels
Low distortion

35. Equipment used in TAGS Power source Electrodes
TIG must be operated with a constant current power source - either DC or AC
Electrodes
Electrodes for DC welding are normally pure tungsten. In AC welding, as the electrode will be operating at a much higher temperature, It should be noted that because of the large amount of heat generated at the electrode, it is difficult to maintain a pointed tip and the end of the electrode assumes a spherical or 'ball' profile.

36. Sheilding Gas
Shielding gas is selected according to the material being welded.
 Argon
 Argon + Hydrogen
 Argon/Helium
Helium is generally added to increase heat input (increase welding speed or weld penetration).  Hydrogen will result in cleaner looking welds and also increase heat input, however, Hydrogen may promote porosity or hydrogen cracking.

37. Gas Welding (Oxy-acetylene)
A number of welding processes use a flame produced by burning a mixture of fuel gas and oxygen. The gas usually used is Acetylene but other gases are also used.
Separate cylinders and a hose pipe from each cylinder transports the gases to a torch.
Gas and fuel mix in the torch
3100°C.

38. During the welding heat from the flame is concentrated on the joint edges until the metal melts and starts to flow. When the molten metal from both sides melts it starts to fuse, when the metal cools down the two parts become Permanently joined
Additional Filler Metal is fed in by hand into the weld pool, at regular intervals where it becomes molten and joins with the parent metal.

39. The Oxy-acetylene welding Flame
Carburising
This kind of flame is used for welding High carbon steel & cast iron.
Amount of acetylene gas is high in carburising.
Neutral
A flame resulting from the burning of gases supplied in the proper proportions for perfect combustion as approximately equal volumes of acetylene and oxygen
Oxidising
Widely used for cutting and not suitable for welding. When the amount of oxygen increases, the flame shortens but temperature goes too high.

40. Gases used
Oxygen extracted from air and compressed into cylinders at high pressure. Cylinder is black.These cylinder have no welding joint these are complete tube like cylinders. Pressure contains 1800 psi
Acetylene (C2H2) is a fuel gas. Cannot be compressed directly as explodes at high pressures. Cylinder colour coded maroon. We made these cylinders by welding three parts. Pressur contains 250 psi

41. Gas Pressure Regulators
One gauge indicates the pressure of the cylinder and the other indicates the pressure in the supply pipe to the torch.

42. Welding torch
Oxygen and acetylene are delivered to the torch by separate hoses. Each gas is controlled by a valve on the torch. The two gases mix in the torch and after they are ignited burn at the nozzle.

43. Flashback Arrestors
These are positioned on both the fuel gas and oxygen supply between the hose and the regulator. Their purpose is to prevent the return of a flame through the hose into the regulator.
Back Fire
Back fire is a process in which a
Tiny fire particle goes into the cylinder
Through torch and pipe. As a result
It cause big blast.

44. Filler Rods and fluxes
Filler rods are used for welding the parts to each other. they come in different diameters.
Fluxes protect the weld pool from contamination by oxygen and nitrogen, they are normally in paste form placed on a heated filler rod before welding begins.11

45. Advantages of gas welding Disadvantages of gas welding
The equipment is inexpensi ve, simple and is easily
  portable.
Useful for welding light 
metals such as automobile 
bodies and repair works.
Alarge variety of material can be welded.
Welds can be produced at reasonable cost.
Equipment must always be handled carefully as in certain circumstances acetylene is explosive.
A high temperature flame  from a hand held torch is dangerous when handled carelessly.
It causes more distortion.
The process is not satisfactory for heavy sections.

46. Resistance welding
Resistance welding uses the application of electric current and mechanical pressure to create a weld between two pieces of metal.  Weld electrodes conduct the electric current to the two pieces of metal as they are forged together. The welding cycle must first develop sufficient heat to raise a small volume of metal to the molten state.  This metal then cools while under pressure until it has adequate strength to hold the parts together.   

47. Spot welding
Seam Welding

48. Spot welding
Ideal for joining light sheet metal. The electrodes are made from copper. Pressure is applied to the electrodes and an electric current is passed through the circuit. The high resistance between the joint faces causes rapid heating and fusing of a small globule of metal from both faces.

49. Seam welding
The rollers allow the workpiece to move through the welder continously. A stream of electrical pulses pass through the rollers and welds the joint

50. Resistance Welding Benefits
  High speed welding
  Easily automated
  Suitable for high rate production
  Economical
Resistance Welding Limitations
  Initial equipment costs
  Lower tensile and fatigue strengths
  Lap joints add weight and material

51. What is Friction Welding
Friction welding is a solid state joining process that produces coalescence by the heat developed between two surfaces by mechanically induced surface motion.

52. Friction welding
One part is held stationary while the other part is rotated
When the parts are hot enough the rotation is stopped and the parts forged together
Workpieces
Non-rotating vise
Motor
Chuck
Spindle
Hydraulic cylinder
Brake

53. Advantage of frictional welding Disadvantages of frictional welding
Easily joins dissimilar metals.
Friction welds are higher strength.
Friction welds often cost less.
Friction welds minimize the Heat Affected Zone.
No need of furnace .
A machine of sufficient power is needed.
T oo high power needed.
Tight concentricity requirements.

54. Robotic welding
Robots are driven using actuators which control the robotic arm from an input signal. They can use hydraulic (large robots), pneumatic(small actuators with simple control movements) or electrical principles of operation.
A computer sends instructions in electrical signals or pulses. An interface converts these digital pulses into analogue electricity for the motors. The robot is fitted with sensors which can send feedback on the position of the robot.

55. Advantages of Robotic welding
Faster production rates
Efficent continous operation
Safe working practice
Reliable and consistent welds
Full automation
Cost effective
Examples
Automated welding of motor vehicles skeletel frames and bodies.