2 - Welding, Allied Processes & Development

WELDING ENGINEERING OVERVIEW

WELDING AS UNDERSTOOD BY ASSOC.PROF SUNHAJI KIYAI ABAS

OF

FACULTY OF MECHANICAL ENGINEERING UiTM SHAH ALAM

Welding Fabrication

• Selected – light, simple, cheap

• Application – steel structures, bridge construction, ship industries, pressure vessel, pipeline. Repair e.g. Cast and Worn Products. Hard Facing.

• Employment requires synchronization of welding characteristics with product function and the environment.

WHAT IS WELDING?

• A JOINING PROCESS THAT IS INTENDED TO MAKE THE MATERIAL AT THE JOINT OR JOINT SURFACES AS HOMOGENOUS AS POSSIBLE WITH THE BASE MATERIAL.

• HOMOGENOUS IN TERMS OF MATERIAL, CHEMICAL COMPOSITION, METALLURGICAL, MECHANICAL OR PHYSICAL CHARACTERISTICS

SO, WHAT IS WELDING?

• WELDING IS MORE OF A PROCESS OF CREATING A CONTINUITY OF MATERIAL HOMOGENITY AT THE JOINT WITH THE BASE MATERIAL.

WHEN CAN WELDING HAPPEN?

• WELDING CAN HAPPEN WHEN THE FACES OF THE MATERIAL TO BE JOINED EITHER IN SOLID PHASE OR IN LIQUID PHASE

HOW CAN WELDING HAPPEN IN SOLID PHASE?

• IT CAN HAPPEN WHEN THE MATERIAL AT THE SURFACES TO BE JOINED IS IN PLASTIC CONDITION (STILL IN SOLID PHASE)

HOW IS WELDING BEING CLASSIFIED?

• THE SIMPLEST WAY TO CLASSIFY WELDING IS BY ITS PROCESS PHASES.

WHAT ARE THE PROCESS PHASES IN WELDING?

• THERE ARE 2 KINDS OF PROCESS PHASES IN WELDING:

1. SOLID PHASE WELDING PROCESS

2. LIQUID PHASE WELDING PROCESS

WHAT IS SOLID PHASE WELDING PROCESS?

• SOLID PHASE WELDING PROCESS IS A PROCESS OF JOINING MATERIAL WITHOUT MELTING IT EITHER BY HEATING, OR BY PRESSURE, OR BY USING BOTH.

• THIS IS BY BRINGING THE MATERIAL AT THE JOINT INTO PLASTIC CONDITION SUITABLE FOR WELDING TO OCCUR.(IN THIS CONDITION THE MATERIAL IS STILL IN A SOLID STATE)

WHAT IS LIQUID PHASE WELDING PROCESS?

• LIQUID PHASE WELDING PROCESS IS A PROCESS OF JOINING MATERIAL BY MELTING IT.

• THIS IS BY BRINGING THE MATERIAL AT THE JOINT INTO LIQUID STATE

WHAT ARE THE EXAMPLES OF WELDING THAT UNDER THE CATEGORY OF SOLID

PHASE!!

• EXAMPLES ARE:ULTRASONIC WELDINGFRICTION WELDINGFRICTION STIR WELDINGEXPLOSIVE WELDINGCOLD OR HOT ROLL BONDINGBLACKSMITH & FORGED WELDINGDIFFUSION BONDING

WHAT ARE THE WELDING PROCESSES UNDER LIQUID PHASE?

• EXAMPLES ARE:-GAS WELDINGSMAW (MMAW)GMAW (MIG & MAG)GTAW (TIG)FCAWSAWSPOT WELDINGPLASMA WELDING (involvement of key-holing process)LASER WELDINGELECTRON BEAM WELDING THERMIT WELDINGELECTROSLAG WELDING

SMAW (MMAW)

GTAW (TIG)

GMAW (MIG)

SAW

IS SOLDERING WELDING?

• NO!!!!• BECAUSE THE MATERIAL USED FOR

JOINING IS NOT THE SAME MATERIAL (i.e. NOT HOMOGENOUS) WITH THE BASE MATERIAL.

• IT MELTS AT LOWER TEMPERATURE THAN THE BASE METAL

• ITS STRENGTH IS LOWER THAN THE BASE METAL

• THE MATERIAL USED FOR JOINING IS CALLED SOLDER (alloy of Lead and Tin)

IS BRAZING WELDING?

• NO!!!!• BECAUSE THE MATERIAL USED FOR

JOINING IS NOT THE SAME MATERIAL (i.e. NOT HOMOGENOUS) WITH THE BASE MATERIAL.

• IT MELTS AT LOWER TEMPERATURE THAN THE BASE METAL

• ITS STRENGTH IS LOWER THAN THE BASE METAL

• THE MATERIAL USED FOR JOINING IS BRASS (alloy of Copper and Zinc)

Then, what is the difference between Soldering and Brazing?

• MATERIAL FOR SOLDERING IS SOLDER WHILE MATERIAL FOR BRAZING IS BRASS

• THE MELTING TEMPERATURE OF SOLDER IS MUCH LOWER THAN THAT OF BRASS

• THEREFORE, THE STRENGTH OF JOINT MADE BY SOLDERING IS MUCH LOWER THAN THAT MADE BY BRAZING

WHAT IS THERMAL CUTTING?

• A PROCESS OF REMOVING MATERIAL FROM THE BASE METAL BY THE HELP OF HEAT either by melting it or without melting it.

EXAMPLES OF THERMAL CUTTING

• Oxy Acetylene Gas Cutting

• Powder Cutting

• Air Arc Cutting / gouging

• Air Plasma Arc Cutting

• Laser Cutting

• Electron Beam Cutting

AIR ARC CUTTING/GOUGING

WHY ARE WELDING TECHNOLOGIES DEVELOPED?

• SMAW > GTAW > GMAW > SAW > FCAW

• GTAW > PLASMA

SMAW HAS SHORTCOMING!!

• NEED TO CHANGE THE ELECTRODE

• ELECTRODE WASTAGE IS HIGH• WELD BEAD NEEDS THOROUGH

CLEANING – CHIPPING, BRUSHING, GRINDING, GOUGING

• HIGH POSSIBILITY OF SLAG INCLUSION

• LOW PRODUCTIVITY

WHY GTAW BEING DEVELOPED?

• THEORETICALLY TO SOLVE PROBLEM IN ALUMINIUM WELDING CREATED BY SMAW AND GAS WELDING

• THE ALUMINIUM OXIDE FORMED ACTS AS INSULATOR WHICH MAKE WELDING (AND CUTTING) BECOMES DIFFICULT

• SHIELDING BY INERT GAS OF ARGON AND HELIUM - GIVES BETTER PROTECTION AND PENETRATION

• AC CURRENT IS MORE SUITABLE FOR WELDING ALUMINIUM BECAUSE WHEN THE ARC REVERSES IT WILL CLEAN THE OXIDE THAT IS BEING FORMED

HOW ABOUT GMAW?

• CONTINUOUS FEEDING OF FILLER WIRE – PRODUCTIVITY BECOMES HIGH

• VIRTUALLY NO CLEANING REQUIRED

• BETTER PROTECTION OF WELD, WELD POOL AND WELD ARC - BY INERT/INACTIVE GAS (e.g. Argon) OR SEMI-INERT/SEMI-ACTIVE GAS (e.g. Carbon Dioxide)

WHY SAW DEVELOPED?

• FASTER WELDING FOR THICKER METAL• CAN USE BIGGER DIAMETER OF WIRE,

HENCE, USING HIGHER CURRENT• USING BOTH FLUX AND CONTINUOUS

FILLER WIRE SEPARATELY – TAKING ADVANTAGE OF BOTH OF SMAW AND GMAW

• FAST SPEED WELDING• PRODUCTIVITY HIGHER THAN GMAW

WHY FCAW DEVELOPED?

• USING CONTINUOUS TUBE TYPE OF SMALL DIAMETER OF FILLER WIRE WITH FLUX FILLED INSIDE THE TUBE > LESS BULKY

• USING BOTH FLUX AND CONTINUOUS FILLER WIRE – TAKING ADVANTAGE OF BOTH OF SMAW AND GMAW

• FAST SPEED WELDING• PRODUCTIVITY HIGHER THAN GMAW• 2 METHODS OF WELDING CAN BE DONE -

EITHER SHIELDED OR UNSHIELDED BY GAS

WHY PLASMA WELDING?

• PLASMA ARC VIRTUALLY HOTTER THAN NORMAL ARC EVEN FROM TIG

• WELD IS CLEANER• CAN WELD THICKER METAL• CAN DO KEYHOLE WELDING/FINE QUALITY

OF WELDING• NOWADAYS THE PLASMA ARC CAN BE

CONTROLLED TO PRODUCE MICROPLASMA (0.1 to 15A) FOR WELDING VERY THIN METAL, OR MEDIUM PLASMA (15 to 200A) OR KEYHOLE PLASMA (over 100A)

WHY NEW EVOLUTION OF WELDING POWER SOURCES?

• TO SOLVE PROBLEMS IN WELDING• TO IMPROVE WELDING QUALITY• TO MINIMISE WELDING SKILL• TO EASE WELDING• TO MINIMISE ‘HUMAN TENSION/STRESSES’ IN WELDING• TO MINIMISE PROBLEMS DUE TO HUMAN FACTORS• WELDING BECOMES MORE COMFORTABLE AND USER

FRIENDLY• PRODUCTIVITY INCREASED• WELD QUALITY INCREASED• WELDING POWER SOURCES BECOME SMALLER, LIGTHER

AND MORE PORTABLE AND COMFORTABLE TO CARRY• ENERGY CONSUMPTION BECOMES LOWER

Rectification

STUDENT HOME ASSIGNMENT1. Is Ultrasonic Welding Liquid Phase

Welding? Justify your statement

2. What reactions take place during oxy-cutting of Carbon Steel? What Thermal Cutting Process suitable for cutting aluminium and why?

3. Why FCAW welding technology developed?

4. Draw schematic diagram of Inverter Welding Power Source. What are the philosophies behind this development?

THANK YOU

HOPE YOU ENJOY

THE DAY !!!!!