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Welding & Braze Evaluation
MTA has broad experience with a variety of welding processes, including metal arc welding, metal inert gas, tungsten inert gas, electron beam, laser welding, and polymer welding.​​
Examples of Case Studies:
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316L Stainless Steel welding procedure development with the aid of metallographic sectioning.
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Incorrect weld repair of centrifugally cast piping for reformer furnaces.
Example One
PROCEDURAL WELDS WITH LOW DELTA FERRITE ROOT RUNS IN TYPE 316L STAINLESS STEEL
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These welds were made to qualify the procedures necessary to obtain root runs with a high resistance to delta ferrite corrosion. The root runs are almost pure austenite for good corrosion resistance while the succeeding runs contain delta ferrite for adequate hot cracking resistance of the massive centre section of the weld.
Figure 1: Weld made with J preparation. One run TIG with low ferrite filler wire. Succeeding runs with higher ferrite using manual metal arc. x25
Figure 3: Selective corrosion of delta ferrite containing areas. x200
Figure 2: Weld made with J preparation. Three runs TIG with low ferrite filler wire. Succeeding runs with higher ferrite using manual metal arc. x25
Figure 4: Selective corrosion of delta ferrite containing areas. x200
Example Two
HK 40 CENTRIFUGALLY CAST REFORMER TUBING INCORRECTLY REPAIRED BY WELDING​
Extensive interdendritic bore porosity was repaired by welding. Weld repair is generally very difficult with this type of defect and is not recommended. It is far better to cut back tube until sound metal is found and then make use of the shorter but sound section.
Figure 1: Section of tube showing area which had been ground after weld repair.
Figure 2: Weld repair of interdendritic bore porosity. The porous areas had not been removed completely and cracking had occurred at the interface between base metal and weld.
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