Heats School of Welding Technology Inc. (TESDA Accredited)

There 7 Welding Processes, these are;

1. Arc Welding
2. Solid State Welding
3. Resistance Welding
4. Brazing
5. Oxyfuel Gas Welding
6. Soldering
7. Other Welding Processes

The most commonly used processes in the industry are:

1. SMAW
2. GMAW
3. GTAW
4. FCAW
5. SAW

WQT means Welder’s Qualification Test
WPS means Welding Procedure Specification
PQR means Procedure Qualification Record
GTAW means Gas Tungsten Arc Welding
SMAW means Shielded Metal Arc Welding
FCAW means Flux Cored Arc Welding
GMAW means Gas Metal Arc Welding
SAW mean Submerged Arc Welding

The types of weld are:
1. Butt Weld
2. Fillet Weld
3. Edge Weld
4. Spot Weld

The Types of Joints are:
1. Butt Joint
2. Tee Joint
3. Corner Joint
4. Lap Joint

Some Possible Causes of Porosities are:

1. Wet Electrode
2. Heavy Wind
3. Moisture in the base metal
4. Rains
5. Dust
6. Nitrogen & hydrogen absorption in the weld pool due to poor gas shielding
7. Grease and oil on base metals
8. coating on base metal

Thre are three factors that causes hydrogen cracking, these are:

1. Hydrogen generated by the welding process
2. Hard brittle structure (of base metal)
3. Residual stresses acting on the weld joint

To avoid Hydrogen Cracking the following shall be done:

1. Clean the join and remove all contaminants
2. Use low hydrogen electrodes
3. Bake the low hydrogen electrodes/fluxes
4. Ensure correct joint design (avoid large root gaps and high restraints
5. Preheat joints
6. Control Preheat/Interpass temperature
7. Conduct PWHT immediately

The Types of Testing are:

1. Quantitative Testing
2. Qualitative Testing

The NDT Methods are:
1.) Ultrasonic Testing
2.) Magnetic Particle Testing
3.) Pentrant Testing
4.) Radiographic Testing
5.) Eddy Current Testing

Principle of Ultrasonic Testing

High frequency sound waves are sent into a material by use of a transducer. The sound waves travel through the material and are received by the same transducer or a second transducer. The amount of energy transmitted or received and the time the energy is received are analyzed to determine the presence of flaws. Changes in material thickness, and changes in material properties can also be measured.

Principle of Penetrant Testing

Penetrant solution is applied to the surface of a precleaned component. The liquid is pulled into surface-breaking defects by capillary action. Excess penetrant material is carefully cleaned from the surface. A developer is applied to pull the trapped penetrant back to the surface where it is spread out and forms an indication. The indication is much easier to see than the actual defect.

Principle of Eddy Current Testing

Alternating electrical current is passed through a coil producing a magnetic field. When the coil is placed near a conductive material, the changing magnetic field induces current flow in the material. These currents travel in closed loops and are called eddy currents. Eddy currents produce their own magnetic field that can be measured and used to find flaws and characterize conductivity, permeability, and dimensional features.

Magnetic Particle Tesing
ADVANTAGES
Large surface areas of complex parts can be inspected rapidly.

Can detect surface and subsurface flaws.

Surface preparation is less critical than it is in penetrant inspection.

Magnetic particle indications are produced directly on the surface of the part and form an image of the discontinuity.

Equipment costs are relatively low.

DISADVANTAGES
Only ferromagnetic materials can be inspected.

Proper alignment of magnetic field and defect is critical.

Large currents are needed for very large parts.

Requires relatively smooth surface.

Paint or other nonmagnetic coverings adversely affect sensitivity.

Demagnetization and post cleaning is usually necessary.

Eddy Current Testing

ADVANTAGES
Detects surface and near surface defects.

Test probe does not need to contact the part.

Method can be used for more than flaw detection.

Minimum part preparation is required.

DISADVANTAGES
Only conductive materials can be inspected.

Ferromagnetic materials require special treatment to address magnetic permeability.

Depth of penetration is limited.

Flaws that lie parallel to the inspection probe coil winding direction can go undetected.

Skill and training required is more extensive than other techniques.

Surface finish and roughness may interfere.

Reference standards are needed for setup.

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Hi Peter, salamat sa pagbisita mo. Oo nag ka conduct kami ng WQT, witnessed po ng third party inspector at under ng third party inspection company yung WQT. P500 lang po per test ang bayad, pero sa Third Party kayo magbabayad hindi sa amin. thanks.

ang email ng third party inspection company ay corroweld@yahoo.com