Advanced Arc Welding Mr. ConradoAgm 210

Multi-Pass WeldingUsed for 100% penetration on metal inch thick or greater.Joint preparation is required Single bevel V notch U notch J bevel Joint preparation Improves joint strength Improves penetration Require multiple welds per joint

Multi-Pass WeldsRoot PassFuses the parts together Seals off possible atmospheric contamination Must be thoroughly cleaned before cover welds are applied Filler or Cover weldsOften made with high strength electrodes Used to fill and cap the weld groove

Root Pass The first weld bead in a multi-pass weld

Fuses the two parts together

Establishes deep penetration

Can be open or closed

Root PassA closed weld is created using a backing strip and may become part of the weld.

Root PassGouge CleaningOn plates with both sides prepared the root pass can be gouge cleaned.

After the root pass is applied a grinder is used to clean the underside of the weld.

Root PassOpen root weldsThe back of the open root is highly important and can not be manipulated after welding.

In contrast the top of the root pass can be gouged, ground, or burned before a cover pass is applied.

Hot Pass Used to fix imperfections in a root pass.Irregular shape Undercut Overlap Slag inclusion The hot pass uses higher than normal amperage and a fast travel speed.Very little filler metal is deposited Easily cleaned by chipping, brushing, or grinding

Filler Pass After the root pass is completed and cleaned the remaining groove is filled with weld metal. Filler passes are made with stringer beads or weave beads.

Each filler pass must overlap the previous pass enough for the finished bead to be smooth.

Filler WeldsEach weld bead must be cleaned before the next bead is applied.

Chipping, brushing, or grinding work best.

Cover PassThe last bead on a multi-pass weld.

Keeping uniform and neat are important.

Must be free of Undercut Overlap Porosity Inclusions

Plate Preparation Often to achieve 100% penetration a weld groove is necessary.Single grooveDouble groove

The type, depth, angle, and location is usually determined by code.

Pre and Post Heating Preheating Application of heat to base metal before it is welded Reduces cracking Reduces distortion Reduces stress Used mostly on Thick plate Cold conditionsComplex shapes High carbon steels

Pre and Post Heating Post Heating The application of heat to the base metal after welding. Used to slow cooling rate and reduce hardening.