Welding and joining

Arc welding (MIG/MAG, TIG, MMA, FCAW): what goes wrong and where to inspect

Most fabricated products in Turkey are welded with MIG/MAG, TIG, MMA or flux cored processes, manually or by robot. Weld quality is controlled before, during and after welding.

ISO3834 ISO9606 ISO15614 ISO5817 ISO17637

01How the process works

An electric arc melts the base metal and a filler wire or electrode, shielded by gas or flux. Welding procedure specifications (WPS) define processes, consumables, parameters, preheat and sequence; procedures and welders are qualified by test.

Weld quality cannot be fully verified after the event, which is why standards such as ISO 3834 require control of the whole chain: qualified procedures and welders, consumable handling, fit-up, preheat, interpass temperature and NDT.

WPS and qualification. Procedures qualified, welders certified.
Fit-up. Joint preparation, gap and alignment checked.
Welding. Root, fill and cap with controlled parameters.
Post weld. Cleaning, PWHT if required.
Inspection. VT, NDT, dimensional checks.

02What typically goes wrong

Defect	Typical cause	How it is found
Porosity	Gas coverage, contamination, moisture	VT, RT
Lack of fusion	Low heat input, technique	UT, RT
Cracks	Hydrogen, restraint, preheat	MT, PT, UT
Undercut	Current, travel speed	VT with gauges
Incomplete penetration	Joint prep, root gap	RT, UT
Distortion	Heat input, sequence	Dimensional check

03Where an inspector should look

Before production

WPS, WPQR and welder certificates
Consumable certificates and storage
Weld map and NDT plan

During production

Fit-up and tack welds
Preheat and interpass temperature
Parameters against WPS

After production

Visual inspection to ISO 5817 level
NDT per plan
Dimensions and distortion

04Standards and references

ISO3834 ISO9606 ISO15614 ISO5817 ISO17637 EN1090 ASMESection IX AWSD1.1

ISO 14175 (shielding gases), ISO 14341 and ISO 17632 (consumables), ISO 6520 (imperfection classification).

Standards are named for orientation. The applicable edition and acceptance criteria are those in your contract and specification.

05How we support buyers of arc welding parts

Welding InspectionBefore, during and after welding inspection: consumables, fit-up, preheat, parameters, visual inspection and repair control. WPS, PQR and Welder Qualification ReviewReview of welding procedures and qualification records against ISO 15614, ISO 9606, ASME IX or AWS, and test witnessing. NDT Coordination and WitnessingPlanning, witnessing and report review of VT, PT, MT, UT and RT, including personnel and procedure verification.