WELDING&

NON DESTRUCTIVE TESTING

• Welding – A joining process of two materials, metals/non-metals, that are coalesced by the application of pressure and/or temperature.

• Welding – Local coalescence of two similar or dissimilar metallic parts at their faying surfaces.

• Weldment – The assemblage of two or more elements• Sometime a filler material is needed to facilitate

coalescence in Arc/Fusion welding process.• Autogenous welding – without filler materials

Welding - definition

Advantage - disadvantage

• Advantage: Welding is portable, permanent, stronger than the parent materials with a filler metal, the most economical method to join.

Disadvantage: Manual Labor, high energy and dangerous, does not allow disassemble and defects

Classification of welding processesWelding

Solid state welding

Soldering and brazing

Fusion welding

Electrical energy Chemical energy

Other processes Non

consumable electrode

Consumable electrode

Resistance welding Cold weldingFriction welding Diffusion weldingFlash weldingUltrasonic weldingExplosion welding

Gas metal arc welding Shielded metal arc weldingSubmerged arc weldingFlux cored arc welding Electrogas weldingElectroslag welding

Gas tungsten arc weldingAtomic hydrogen welding Plasma arc welding

Oxyacetylene welding Oxyfuel gas welding

Laser beam weldingThermit weldingElectron beam welding

SolderingBrazing

Types of joints

– Butt joint

– Corner joint

– Lap joint

– Tee joint

– Edge joint

Weld Joint

• Types of Welds

– Fillet weld

– Groove weld

– Plug and slot welds

– Spot and Seam welds

– Flange and Surfacing welds

Weld Orientation Plate groove positions 1G, 2G, 3G, 4GPipe groove positions 1G, 2G, 5G, 6GPlate fillet positions 1F, 2F, 3F, 4FPipe fillet positions 1F, 2F, 2FR, 4F, 5F

GROOVE WELDS IN PLATE — TEST POSITIONS

GROOVE WELDS IN PIPE — TEST POSITIONS

FILLET WELDS IN PLATE — TEST POSITIONS

FILLET WELDS IN PIPE — TEST POSITIONS

Features of a Fusion Welded Joint

• Fusion zone: a mixture of filler metal and base metal melted together homogeneously due to convection as in casting. Epitaxial grain growth (casting)

• Weld interface – a narrow boundary immediately solidified after melting.

• Heat Affected Zone (HAZ) – below melting but substantial micro structural change in the base material (heat treating)

• Unaffected base metal zone (UBMZ) – high residual stress

Reinforcement

BMHAZ

Fusion zone

Weld Interface

Weldability• Similar to Machinability, it defines the capacity of a metal

to be welded into a suitable design and the resulting weld joint to perform satisfactorily in the intended service.

• The factors affecting weldability, welding process, base metal, filler metal and surface condition.

• Base metal – melting point, thermal conductivity and CTE• Moisture and oxide film affects porosity and fusion

respectively.• Carbon Equivalent(CE)= %C + %Mn/6 + (%Cr+Mo+V)/5 +

(%Cu+Ni)/15

MetalsFerrous Nonferrous

Carbon steels Aluminium,copper,

Nickel

Low carbon steels [Carbon 0.01 to 0.3%]

Medium carbon steels [Carbon 0.3-0.6%]

High carbon steels [carbon 0.6 to 1.4%]

Low alloy steels [ Mn, Cr,Ni,Mo < 7% total]

High alloy steels [Mn, Cr,Ni,Mo > 7% total]

Purpose of WPS & PQR

To determine that the weldment proposed for construction is capable of having the required properties for its intended application

WPS

A WPS is a written qualified welding procedure prepared to provide direction for making production welds to Code requirements.

The WPS or other documents may be used to provide direction to the welder or welding

operator to assure compliance with the Code requirements.

PQRA PQR is a record of the welding data used to weld

a test coupon.The PQR is a record of variables recorded during the welding of the test coupons. It also contains

the test results of the tested specimens. Recorded variables normally fall within a small range of the

actual variables that will be used in production welding.

Points to be considered for establishing WPS

• Code of construction

• Detailed drawing of weldment

• Material• Thickness• Configuration• Process

• Contract/Customer/ Code/TPI

• Preheat/Postheat/ PWHT requirements

• Skilled welder• Good welding m/c

with accessories• Application

Essential Variables

A change in welding condition which will affect the mechanical properties of the weldment.(Change in P Number, Welding process, Filler metal, Electrode, Pre-heat, PWHT, etc.)

Non Essential Variables

A change in welding condition which will NOT affect the mechanical properties of the weldment.(Change in Joint Design, Methods of Back gauging, Cleaning, etc.)

Supplementary Essential Variables

A change in welding condition which will affect the Notch-Toughness (Impact) properties of the weldment.(Change in Heat input, Uphill or Down Vertical welding, Diameter of Electrode, Position, etc.)

Base Metal Classification Why P numbers?To reduce the number of welding procedure qualifications, base metals have been assignedP-nos and for ferrous base metals which have specified impact test requirements, group numbers within P-nos are again givenP no's depend on composition, weldability & mechanical properties. •Group no's classify metals within P nos for procedure qualification where notch toughness requirements are specified. •The above assignments do not imply that base metals can be substituted without consideration of metallurgical properties,etc.,

Base Metals

• P. Number• Group Number• Specification• Chemical Analysis & Mechanical

Properties• Thickness Range• Pipe Diameter Range

Filler Metals

• AWS Number• SFA Number• F. Number• A. Number

• Size of Filler metal

• Flux trade name

• Consumable insert

• Electrode flux class

CLASSIFICATION OF ELECTRODES (AWS 5.1)

EXXXXElectrode

60 Psi

70

80

90

100

110

120

Welding position Coating and current

conditions

Type of defects

• PLANAR CRACKS, LAMELLAR TEARS LACK OF FUSION

LACK OF PENETRATION• VOLUMINAR

POROSITYSLAGTUNGSTEN INCLUSION

The use of noninvasive techniques to determine the integrity of a material, component or structure

or quantitatively measuresome characteristic ofan object.

i.e. Inspect or measure without doing harm.

Definition of NDT

What are Some Uses of NDE Methods?

• Flaw Detection and Evaluation• Leak Detection • Location Determination• Dimensional Measurements • Structure and Microstructure Characterization • Estimation of Mechanical and Physical Properties • Stress (Strain) and Dynamic Response

Measurements • Material Sorting and Chemical Composition

Determination

Fluorescent penetrant indication

When are NDE Methods Used?

– To assist in product development – To screen or sort incoming materials– To monitor, improve or control manufacturing

processes– To verify proper processing such as heat treating– To verify proper assembly– To inspect for in-service damage

Six Most Common NDT Methods• Visual• Liquid Penetrant • Magnetic • Ultrasonic• Eddy Current• Radiography

• A liquid with high surface wetting characteristics is applied to the surface of the part and allowed time to seep into surface breaking defects.

• The excess liquid is removed from the surface of the part.

• A developer (powder) is applied to pull the trapped penetrant out the defect and spread it on the surface where it can be seen.

• Visual inspection is the final step in the process. The penetrant used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity.

Liquid Penetrant Inspection

Magnetic Particle InspectionThe part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. These particles are attracted to magnetic flux leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be visually detected under proper lighting conditions.

Magnetic Particle Crack Indications

RadiographyThe radiation used in radiography testing is a higher energy (shorter wavelength) version of the electromagnetic waves that we see as visible light. The radiation can come from an X-ray generator or a radioactive source.

High Electrical Potential

Electrons-+

X-ray Generator or Radioactive Source Creates Radiation

Exposure Recording Device

Radiation Penetrate the Sample

Film Radiography

Top view of developed film

X-ray film

The part is placed between the radiation source and a piece of film. The part will stop some of the radiation. Thicker and more dense area will stop more of the radiation.

= more exposure

= less exposure

The film darkness (density) will vary with the amount of radiation reaching the film through the test object.

High frequency sound waves are introduced into a material and they are reflected back from surfaces or flaws.

Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen showing the depth of features that reflect sound. f

plate

crack

0 2 4 6 8 10

initial pulse

crack echo

back surface echo

Oscilloscope, or flaw detector screen

Ultrasonic Inspection

Thank you