we share about welding inspection tips,welding procedures and techniques for SMAW,MIG,TIG,FCAW,SAW and other welding process for stainlles steel and other alloys,equipments,welders,materials,inspector,NDT,NDE.
Inspection by penetrating liquid By means of the inspection with penetrating or technical liquid of penetrating dye, discontinuities can be detected as cracks that enter the surface. A liquid dye is attracted by hair action towards a thin crack, that of another way would be invisible.
Welding is usually regarded as a joining process in which the work pieces are in atomic contact often with a filler metal with broadly similar properties. Hence soldering and brazing are excluded but both solid state and fusion welding are included.
LAMELLAR TEARING.
A step like crack that occurs in thick section tee joints and closed corner joints.
Occurs in the HAZ due to the precipitation of chromium carbides. In the 5500C - 8500C range, the chromium leaches out of the grain and reacts with the carbon to form chromium carbides, due to the chromium having a greater affinity for carbon.
Most material products contain residual stresses, often up to yield point. Pipe products, for example, are usually very highly stressed.
The tendency to develop residual stresses increases when the heating and cooling are localised.
Many metals must be given heat treatment before and after welding. The inspector’s function is to ensure that the treatment is given, and given correctly, to the details supplied.
A crack is a linear discontinuity produced by fracture. Cracks may be longitudinal, transverse, edge, crater, centreline, fusion zone, underbead, weld metal or parent metal.
Below some welding defects, Roots Defects :
Incomplete root penetration, lack of fusion, Excess penetration bead, Root concavity. (suck-back, underwashing), etc
Porosity.
Is the result of gas being entrapped within the solidifying weld metal. Porosity will be present in a weld if the welding technique, materials used or condition of the weld joint promotes gas formation.
There are some cause and remedies welding defects :
Inclusions
Cause:Failure to remove slag, Remedies: Clean surface and previous weld bead
Cause:Entrapment of refractory oxides, Remedies: Power wire brush the previous bead
One is a full fruit of properties for the health and the beauty. Here we told you because to include the fruit prohibited in your diet.
Non Destructive Testing, Ultrasonic Testing :
Type of operation:Manual or mechanized.
Equipment:Main unit comprising pulse generator, display oscilloscope, probe (chosen to suit work).
The work is magnetized either by passing a current through it, or through a coil surrounding it. Defects on or near the surface disrupt the magnetic field (unless they are parallel to it)
Gamma rays, similar to X-rays but of shorter wavelength, are emitted continuously from the isotope. It cannot be ‘switched off’ so when not in use, it is kept in a heavy storage container that absorbs radiation. They pass through the work to be inspected.
The repair of defects that occur during welding ranges from simple welding operations to improve weld profile to extensive metal removal and subsequent welding to rectify extensive cracking.
The defect may be in a single run fillet weld requiring only a small amount of metal to be removed or it may be a large crack extending deep into parent metal.
A special dye is applied to the surface of the article to be tested. A suitable time interval allows it to soak into any surface defects. The surface is then freed from surplus dye and the dye in the crack revealed by either
Before a welding repair is carried out the need for repair must be carefully considered. If a component or structure contains defects of a known size, whether these are fabrication or service defects,
Welding consumables are:
Electrodes. Wire (lengths or rolls). Fluxes. Gases.
Each consumable is critical in respect to:
Specification / supplier.
Condition.
Treatment (if any).
43 items | 1 visits
share and learn knowledge,welding,inspections,inspectors,code, standards,rules and specification,welding inspector,welder,safety, weld geometry and welding terminology,non destructive test(NDT), destructive testing,welding procedure and welder qualification,form, download,job vacancy
Updated on Mar 15, 10
Created on Sep 08, 09
Category: Science
URL:
