WELD TESTING

DESTRUCTIVE AND NON-DESTRUCTIVE

DESTRUCTIVE TESTING These can be divided into two parts, Tests capable of being performed in the workshop.Laboratory tests. microscopic-macroscopic , chemical and corrosive.

REASONSDefects occur during welding which affect the quality and hardness of the plateOther defects occur through lack of knowledge of and skill of the welderFor the training of welders

WORKSHOP TESTS

TENSILE BENDING

IMPACT HARDNES

FATIGUE CRACKING

TENSILEMaterial is sectioned and edges rounded of to prevent cracking.Punch marks are made to see elongation.

TENSILE

BEND TESTINGShowsPhysical condition of the weldDetermine welds efficiency Tensile strengthDuctilityFusion and penetration

BEND TESTBend through 180Othe specimen should be a minimum of 30mm wideThe fulcrums diameter is 3x thickness of the plateThe bottom rollers have a distance of the diameter of the former + 2.2 times the thickness of the plateUpper and lower surfaces ground or filed flat and edges rounded off.the tests should be one against the root -another against the face ,and in some cases a side bend.

Root bend

FACE BEND

IMPACTCHARPY AND IZODGives the toughness and shock loading of the material and weld at varying temperatures with a notch such as under cut The measurement is the energy required to to break a specimen with a given notch2mm depth at a 45obevel or a U notch.

TEST MACHINE

CHARPY

IZOD

HARDNESS TESTS.This gives the metals ability to show resistance to indentation which show its resistance to wear and abrasion.The tests areBrinellRockwellVickers diamond pyramidScleroscope

VICKERS HARDNES

FATIGUEthe testing of Material that is subject to fluctuating loadsHAIGH Electro magnetic tester.WOHLER Uses rotating chuck with weight

CRACKINGREEVES Test study the hardening and cracking of welds.The compatibility of electrodes for the metal being joined.

CRACKINGThree Sides Are Welded With Known Compatible Electrodes.The front edge is welded with the test electrode.if incompatible it will crack.

MICROSCOPICUsed to determine the actual structure of the weld and parent metalUp to 50,000 times magnification with an electron beam microscopePolishing must be of a very high standard

MACROSCOPICExamined using a magnifying glass .magnification from 2 to 20 time.it will show up slag entrapment or cracks .polishing not as high as micro.

ETCHING REAGENTSThese are acids used to show up different structures in metalsFor steels the most common is 1-2 % nitric acid in distilled water or alcohol.Aluminum uses a solution of 10-20%caustic soda in water

NON-DESTRUCTIVE TESTING

VISUALWhile welding The rate the electrode meltsThe way the weld metal flowsSound of the arcThe light given of

After weldingUnder cut Lack of root fusionAny pin holes from gas or slagAmount of spatterDimensions of weld

DYE PENETRANTSThese are an aid to visual inspection

Will only find surface defects

Use correct type

DYE PENETRANTS

DYE PENETRANTSTypesRed Flouresant

CAUTIONOil basedWater washable

DETECTION

MAGNETIC PARTICLEMainly for surface defectsSome sub surface defects can be foundOnly ferrous metal

ACOUSTICSStriking with a rounded object

Ringing tone if no defect

Tone changes when object is cracked

APPLICATION OF A LOADUsed to test pressure vesselsPipe lines The item for testing is filled with water or oil it is then pressurised using a pumpA safety valve is set 1.5 to 2 times below the working pressure.

PRESSURE TEST

RADIOGRAPHICX-RAYGAMMA RAYElectro magnetic radiation of short durationBoth of these methods are a danger to health

X- RAY

X-RAY VIEWERPictures taken are viewed as negativeswill only give flat image not in three dimensionaldarkened area must be used for viewing

ULTRASONIC TESTINGThis uses high pitched soundThe sound will not pass through an air gap so bounces back and is picked up on a receiver The reader is a oscilloscope

ULTRA SONIC