EIGHT PRACTICAL TIPS FOR WELDING STAINLESS STEELS

For the weld to be completely flat, the electrode must maintain a 15° angle with the upper part inclined in the direction of travel. The arc must be kept as short as possible. For vertical welding, the electrode must be held perpendicular to the plate and a slight weaving motion should be used on the root pass. For overhead welding, the deposit must be made in straight, short beads. The arc must be kept short and weaving must be avoided.
For better corrosion resistance, the deposit must be made with minimum current intensity and with stringer beads. Stringer beads minimize heat input and reduce the tendency to cracking. If weaving must be used, it should be limited to 2.5 times the electrode diameter. Craters must always be filled before breaking the arc.
Too low a current will produce an unstable arc, accompanied by electrode sticking, slag interference in the arc, excessive spattering and an incorrect bead shape. Excessively high amperage and/or too long an arc will produce excessive spatter with material loss, weld bead cracking, undercut, poor control of the weld pool, difficult slag removal and a loss of corrosion resistance due to chromium loss.
Difficult slag removal can be caused by contaminants in the base material, irregular welds, moisture absorption by the coating and joints too narrow to allow effective peening. All welds must be allowed to cool before beginning to remove slag.
Cracking in stainless steels can be caused by several factors, including: unfilled craters, an arc that is too long when starting and finishing a weld, overheating of the workpiece, excessive travel speed, incorrect joint design or incorrect electrode selection. Most of the time the problem is high workpiece temperature or unfilled craters before breaking the arc.
Deep penetration is not required, since in the case of stainless steels these are clean and smooth and a high arc force is not needed to produce good penetration. Only sufficient penetration is needed to seal the root and the gap between the last pass and the bevel. More penetration than this can cause problems without offering any advantages.
Cracks detected by X-ray must be evaluated individually. Following the proper welding procedure produces smooth, dense beads where slag can be completely removed with ease, leaving a clean surface to receive the next pass. To ensure radiographic quality, all slag must be removed and depressions eliminated (by grinding if necessary) before the weld is considered complete.
To obtain a clear radiograph, the weld surface must be free of irregularities. All traces of dirt, grease or foreign matter must be removed by means of pickling, degreasing, machining or grinding. Stainless steel wire brushes must be used exclusively to avoid contamination. Oxyfuel cutting and arc-air gouging used to create the bevel leave an oxide layer which must be removed by grinding before welding.

EIGHT PRACTICAL TIPS FOR WELDING STAINLESS STEELS

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