Welding,Filler Metal,Rods and Fluxes

a)Filler metal:
-The material which is added in the weld pool to assist in filling the gap (or grooves).It forms an integrated part of the weld.
-Filler metal is usually available in stick or in a rod form.This rod is called filler metal.
-Filler rod have the same or nearly the same chemical composition as the base metal.
-Welding filler rods are available in a variety of composition(for welding different materials) and sizes.
Some of them are given in table below.

b)Fluxes:-
-During welding if the metal is heated/melted in air,
oxygen from the air combines with the metal to form oxides
which results in poor quality,low strength welds or in some cases may even make welding impossible. In order to avoid this difficulty, a flux is employed during welding.
-A flux is material used to prevent dissolve or facilitate
removed of oxides and other undesirable substance. A flux prevents the oxidation of molten metal.
-A flux is fusible and non-metallic
-During welding flux chemically reacts with the oxides and a slag is formed that floats and covers the top of the molten puddle of metal and thus helps keep out atmospheric oxygen and other gases.
-Fluxes are available as powders, pastes or liquids.
-Flux may be used either by applying  directly on to the surface of the base metal to be welded or by dipping the heated end of the filler rod in it. The flux sticks to the filler rod end.
-After welding the slag from over the welded joint can be
removed by chipping,filing, or grinding.
-No flux is used in the gas welding of Steel
-Fluxes are used in the gas welding of cast iron,stainless steel,and most non-ferrous metals other than lead,zinc and some precious metals.

   

ADVANTAGES OF RIGHTWARD TECHNIQUE

Rightward techniques has certain advantages over the leftward techniques.

-Up-to 8.2mm plate thickness no bevel is necessary. This saves the cost of preparation and reduces the consumption of filler rod.

-To weld thicker metal, where beveling of plate edges becomes necessary, the included angle of V is only 60 degree which require less filler metal against 80 degree V preparation used in leftward welding technique.

-The welders view of the weld pool and the sides and bottom of the V groove is unobstructed. This result in better control and higher welding speed.

-The smaller volume for deposited metal as compared to leftward welding reduces shrinkage and distortion.

-The weld quality is better than that obtained from leftward technique.

-Due to less consumption of filler metal, the rightward technique involves lower cost of welding than leftward
technique.

LIGHTNG THE WELDING TORCH

                                                                 

 1) Crack the cylinder valve on oxygen and cylinder by opening the valve and closing it quickly in order to blow out foreign matter.

2)Attach the oxygen and acetylene pressure regulator to the respective oxygen and acetylene cylinders.

3)Attach the hoses to the pressure regulators.

4)Attach the other ends of the two hoses to the welding torch.

5)Select the proper tip(nozzle) and mixing head and attach it to the welding torch.

6)Back off the regulator screws on both units until the screws turns freely.This is necessary to eliminate a
sudden surge of excessive pressure on the working side of the regulator when the cylinder is turned on.
7)Make sure that both torch needle valves are turned off  (clock-wise).

8)Open the acetylene cylinder valve 1/4 to 1/2 turn. Open the oxygen cylinder valve all the way.

9)Open the acetylene (torch) needle valve one full turn.Turn the adjusting screw on the acetylene pressure regulator clockwise until acetylene gas comes from the torch tip.

10)Light the welding torch using a spark lighter.

11)The acetylene pressure regulator screw should then be adjusted until there is a gap of about 6mm between the torch tip and the flame.This is the proper pressure for the size of the tip being used regardless for the gauge pressure shown on the working pressure gauge on the regulator.

12)Oxygen needle valve on the torch is then opened to adjust the welding flame.

PRACTICAL APPLICATIONS OF WELDING

Welding has been employed in industry as a tool for
(a) Regular fabrication of automobile cars, air-crafts, refrigerators etc.
(b)Repair and maintenance work, e.g. joining broken parts, rebuilding worn out components etc.
A few important applications of welding are listed below.

1. Aircraft Construction:
 (a)  Welded engine mounts
(b) Turbine frame for jet engine
(c)  Rocket motor fuel and oxidizer tanks.
(d0 Ducts, fittings and cowling components etc.

2 Automobile Construction:
 (a) Arc welded car wheels
(b) Steel rear axle housing.
(c) Frame side rails.
(d) Automobile frame, brackets etc.

3. Bridges:
 (a) Pier construction
 (b) Section lengths
 (c )  Shop and field assembly of lengthe etc.

4. Buildings:
 (a) Column base plates
 (b) Trusses
 (c) Erection of structures, etc.

5. Pressure vessels and tanks
 (a) Clad and lined steel plates
 (b) Shell construction
 (c) Joining of nozzle to the shell etc.

6. Storage tanks:
 (a) Oil, Gas and Water storage tanks.

 (7) Rail Road Equipment:
 Locomotive
(a) Under frame
(b) Air Receiver
(c) Engine
(d) Front and rear hoods etc 

8. Piping and Pipelines:
 (a) Rolled plate piping
 (b) Open pipe joints
 (c) Oil, Gas and Gasoline pipelines, etc

9. Ships:
 (a) Shell frames
 (b) Deck beams and Bulkhead stifeners.
 (c) Girders to shells
 (d) Bulkhead webs to plating etc.

10. Trucks and Trailers.
11. Machine tool frames, cutting tools and des
12. Earth moving machinery and cranes.

In addition to arc welding finds following application in repair and maintenance work.
 12. Repair of broken and damaged components and machinery such as tools, punches, dies, gears, shears,
       press and machine tool frames.
 13. hard facing and rebuilding of worn out or undersized parts rejected under inspection.
 14. Fabrication of jigs, fixtures, clamps and other work holding devices. 

Welding-A Fabrication Process

Welding is a method for joining different metals.The large number of materials that are welded are metals and their alloys, although the term welding refers to the joining of other materials such as thermoplastics.
Welding joins different metals alloys with the help of a number of processes in which heat is supplied either electrically or by a gas torch.
In order to join two or more pieces of metals together the most essential requirement is heat.Pressure may also be employed, but this is not essential in many processess.
The use of welding in today's technology is extensive. It had a phenomenal rise since 1930; this growth has been faster than the general industrial growth. Many common everyday use items e.g. automobiles,aircraft,ships,electronics equipments,machinery,household appliances etc, depends upon welding for their commercial construction.