Weld Evaluation And Welder Approval

Deep Metallurgical Services provides specialized service in welding and welder’s approval services. DMS can weld testing to evaluate soundness, toughness, brittleness, hardness, macroscopic and microscopic weld profile, other properties of weld before production design. DMS also provides service on root cause analysis of failure or degradation of weld in services. The techniques of weld evaluation are as follows:
  1. Macroscopic examination of weld
  2. Optical Microscopic examination at magnification up to 1000
  3. ESEM examination at magnification up to 10,000
  4. Macro and micro hardness
  5. All weld or transverse weld tensile test
  6. Side, face or root bend test
  7. Impact test of weld, heat affected zone (HAZ) and base
  8. IGC practice for stainless steel weld
  9. Diffusible hydrogen
  10. Non Destructive test
A significant amount of engineering applications involves welding to join two materials together. Welding is a highly specialized discipline that requires expertise, knowledge and training. An improperly executed welding procedure can cause severe damage to material or joint resulting structural failure or loss of strength. Welding and weld process evaluation are important parameter in preventing the failure of weld. Welder procedure specification (WPS), welder performance qualification (WPQ) and welder procedure qualification records (WPQR) can ensure that welding are performed an account as possible.
DMS can perform welder qualification record and weld inspection to evaluate soundness of weld, brittleness and other relevant inspection . Weld imperfection consists of four level of examinations .

Macroscopic examination up to 50magnfication is employed with stereo microscope. Macroscopic examination is commonly carried out on cross section through welded joint. The macroscopic specimens are prepared by sectioning, coarse or fine grinding up to 400 or 600Grit paper and finally by rough polishing or lapping. Normally 600Grit polishing is considered to be adequate for macroscopic examination. The etching procedure is followed either by IS 13015 or by or ASTM E 340 . The weld parameter that are evaluated by macro examinations are as follows:
  1. Weld geometry
  2. Multi passes or number pass,
  3. Depth or extent of penetration
  4. Extent or HAZ
  5. Imperfection such as crack, porosity, under cut, lack of fusion , lack of penetration or slag
Microscopic examination is performed at magnification above 50 and below 1000 using optical microscope and even up to 10000 by electron microscope. The specimen is required to be prepared as similar macroscopic examination. The polishing must be adequate to reveal structure features such as phase structure, micro crack, porosity, shrinkage cavity, grain size, dendrite, segregation, weld structure and even phase like sigma phase in molybdenum bearing stainless steel.

Micro hardness traverse is also an important technique of weld inspection. Micro hardness identification the strength of weld, and HAZ, and also identifies the presence of selective phase, DMS utilizes the digital camera to photograph the weld area, Additional test such as transverse tensile test, side bend, root and face bend can be conducted on weld to coupon plate to assess the quality of weld as part of weld quality evaluation.
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