VISUAL INSPECTION OF WELDING

VISUAL INSPECTION OF WELDING

INTRODUCTION
Inspection starts with examination of the material prior to fabrication, scabs, seams, scale or other harmful surface conditions may be detected in visual inspection.

The inspector should check the following :

Weld preparation, dimensions and finish.
Clearance dimensions of backing strips.
Alignment and fit up to the pieces being welded.
Verification of cleanliness.

Visual Inspection During Welding
Visual inspection checks details of the work while welding is in progress. Among the details to be checked are :

Welding process.
Cleaning.
Preheat and inter pass temperature.
Joint preparation.
Filler metal.
Flux or shielding gas.
Chipping, grinding, or gouging.
Post heating temperature and time.

Visual Inspection After Welding
Visual inspection is useful for finished-product verification of such items as :

Profile irregularities of the weldment.
Conformity to drawing requirements.
Acceptability of welds with regard to appearance (eg: surface roughness).
The presence of unfilled undercut, overlaps and cracks.
Evidence of mishandling from center punch or other inspection markings or excessive grinding.

Part -4 Most commonly asked Mechanical Interview Questions

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TRANSVERSE TENSILE TEST

TRANSVERSE TENSILE TEST Object: Used to measure the transverse tensile strength under static loading of a butt joint employing butt welds. The reduced section tensile test normally fails in the parent metal and so it is not designed to give the tensile strength of the weld. The radius reduced tensile test is a test of the as deposited diluted weld metal. The all weld tensile test, using a longitudinal section from the weld only, is used to check the as deposited undiluted weld metal. (Usually used by consumable manufacturers.) Method: The test piece is clamped at each end and a load is applied by an hydraulic or screw mechanism. The load is increased until fracture occurs. Reporting Results: Type of specimen (e.g. reduced section). Whether excess eld metal is removed or not. Tensile strength, in Newtons per mm squared, is calculated from maximum load and original cross sectional area. When excess weld metal is not removed, the cross sectional area shall ...

MAGNETIC PARTICLE EXAMINATION (M.P.I.)

MAGNETIC PARTICLE EXAMINATION (M.P.I.) INTRODUCTION This method is used for detecting cracks and other discontinuities open to surface or sub surface in ferromagnetic materials. Fine magnetic particles are applied to the surface of a part which has been suitably magnetized. The particles are attracted to regions of magnetic non-uniformity associated with defects and discontinuities, thus producing indication which are observed visually. PRINCIPLE When a piece of metal is placed in a magnetic field and the lines of magnetic flux get intersected by a discontinuity such as a crack or slag inclusion in a casting, magnetic poles are induced on either side of the discontinuity. The discontinuity causes an abrupt change in the path of magnetic flux flowing through the casting normal to the discontinuity, resulting a local flux leakage field and interfering with the magnetic lines of force. This local flux disturbance can be detected by its affect upon magnetic particles that collect o...

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