TIG & MIGTIG & MIG

NORMAL ARC WELDING

Arc welding provides you the ability to join two metals by melting them with an arc generated between a coated-metal electrode and the base metal. The temperatures developed by the arc can reach as high as 10000°F. The arc energy is provided by a power source that generates either direct or alternating current. The electrodes that carry the current produce a gas that shields the arc from the atmosphere and supplies filler metal to develop the weld shape.

Principles of   arc   welding

Dr. Dmitri Kopeliovi

Arc welding is a welding process, in which heat is generated by an

electric arc struck between an electrode and the work piece.

Electric arc is luminous electrical discharge between two electrodes

through ionized gas.

Any arc welding method is based on an electric circuit consisting of the

following parts:

  Power supply (AC or DC);

  Welding electrode;

  Work piece;

  Welding leads (electric cables) connecting the electrode and work piece to

the power supply.

  Electric arc between the electrode and work piece closes the electric

circuit. The arc temperature may reach 10000°F (5500°C), which is

sufficient for fusion the work piece edges and joining them. When a long

join is required the arc is moved along the joint line. The front edge of

the weld pool melts the welded surfaces when the rear edge of the weld

pool solidifies forming the joint.  When a filler metal is required for

better bonding, filling rod (wire) is used either as outside material fed to

the arc region or as consumable welding electrode, which melts and fills

the weld pool. Chemical compositions of filler metal is similar to that of

work piece.

 Molten metal in the weld pool is chemically active and it reacts with the

surrounding atmosphere. As a result weld may be contaminated by oxide

and nitride inclusions deteriorating its mechanical properties.

Neutral shielding gases (argon, helium) and/ shielding fluxes are used for

protection of the weld pool from atmospheric contamination. Shields are

supplied to the weld zone in form of a flux coating of the electrode or in

other forms.

Advantages of Shielded Metal Arc Welding (SMAW):

  Simple, portable and inexpensive equipment;

  Wide variety of metals, welding positions and electrodes are applicable;

  Suitable for outdoor applications.

Disadvantages of Shielded Metal Arc Welding (SMAW):

  The process is discontinuous due to limited length of the electrodes;

  Weld may contain slag inclusions;

  Fumes make difficult the process control.

GAS SHIELDING ARC WELDING MIG

GAS SHIELDING ARC WELDING-MIG

Metal Inert Gas Welding (MIG, GMAW)Dr. Dmitri Kopeliovich

Metal Inert Gas Welding (Gas Metal Arc Welding) is a arc welding

process, in which the weld is shielded by an external gas (Argon, helium,

CO2, argon + Oxygen or other gas mixtures).

Consumable electrode wire, having chemical composition similar to that

of the parent material, is continuously fed from a spool to the arc zone.

The arc heats and melts both the work pieces edges and the electrode

wire. The fused electrode material is supplied to the surfaces of the work

pieces, fills the weld pool and forms joint.

Due to automatic feeding of the filling wire (electrode) the process is

referred to as a semi-automatic. The operator controls only the torch

positioning and speed. 

Advantages of Metal Inert Gas Welding (MIG, GMAW): 

  Continuous weld may be produced (no interruptions);

  High level of operators skill is not required;

  Slag removal is not required (no slag);

Disadvantages of Metal Inert Gas Welding (MIG, GMAW): 

  Expensive and non-portable equipment is required;

  Outdoor application are limited because of effect of wind, dispersing the

shielding gas.

TIG

GAS SHIELDING ARC WELDING-TIG

TIG PRINCIPLES

Gas Tungsten Arc Welding (GTAW), also known as Tungsten Inert Gas (TIG) welding is a process that produces an electric arc maintained between a non-consumable tungsten electrode and the part to be welded. The heat-affected xone, the molten metal and the tungsten electrode are all shielded from atmospheric contamination by a blanket of inert gas fed through the GTAW torvh. Inert gas (usually Argon) is inactive or deficient in active chemical properties. The shielding gas serves to blanket the weld and esclude active properties in the sorrounding air. Inert gases such as Argon and Helium do not chemically react or combine with other gases. They pose no odor and are transparent, permitting the welder maximum visibility of the arc. In some instances Hydrogen gas may be added to enhance travel speeds.The GTAW process can produce temperatures of up to 35,000 degrees F (19,426 degrees C). The torch contributes heat only to the workpiece. If filler metal is required to make the weld, it may be added manually in the same manner as it is added in the oxyacetylene welding process.GTAW is used to weld stainless steel, nickel alloys such as Monel and Inconel, titanium, aluminum, magnesium, copper, brass, bronze and even gold. GTAW can also weld dissimilar metals to one another such as copper to brass and stainless to mild steel.

Tungsten Inert Gas Arc Welding (TIG, GTAW)

Dr. Dmitri Kopeliovich 

Tungsten Inert Gas Arc Welding (Gas Tungsten Arc Welding) is a welding

process, in which heat is generated by an electric arcstruck between a

tungsten non-consumable electrode and the work piece.

The weld pool is shielded by an inert gas (Argon, helium, Nitrogen)

protecting the molten metal from atmospheric contamination.

The heat produced by the arc melts the work pieces edges and joins

them. Filler rod may be used, if required.

Tungsten Inert Gas Arc Welding produces a high quality weld of most of

metals. Flux is not used in the process.

Advantages of Tungsten Inert Gas Arc Welding (TIG, GTAW): 

  Weld composition is close to that of the parent metal;

  High quality weld structure

  Slag removal is not required (no slag);

  Thermal distortions of work pieces are minimal due to concentration of

heat in small zone.

Disadvantages of Tungsten Inert Gas Arc Welding (TIG, GTAW): 

  Low welding rate;

  Relatively expensive;

  Requres high level of operators skill.