Incomplete Fusion-Incomplete Joint Penetration PDF

WSS Study Guide WD2.1 cwbgroup Intermediate Weld Discontinuities 2.12 Incomplete Fusion Incomplete fusion is used to describe the failure to fuse between weld metal and fusion faces or adjoining weld beads. It may occur at any point in the welding groove or fillet weld as illustrated in Figures...

WSS Study Guide WD2.1 cwbgroup Intermediate Weld Discontinuities 2.12 Incomplete Fusion Incomplete fusion is used to describe the failure to fuse between weld metal and fusion faces or adjoining weld beads. It may occur at any point in the welding groove or fillet weld as illustrated in Figures 29. Incomplete root fusion Incomplete root fusion Incomplete sidewall fusion Incomplete root fusion mm Incomplete fusion WSS Study Guide WD2.1 cwbgroup Intermediate Weld Discontinuities Incomplete fusion may be caused by a number of factors, either singly or in combination. Some of these factors are listed below: $ Improper electrode selection: selection of an electrode that is too large for the joint preparation inhibits electrode manipulation Improper welding parameters: welding parameters that are too low in in current and/or voltage Improper manipulation of the electrode: improper work or travel angles and travel speed that is too fast Improper cleaning of material: rust, oxides and mill scale that are not removed from the joint prior to welding Improper joint design: an example of this would be a narrow V-groove weld ïn a thick plate, inhibiting electrode manipulation. Figure 30 illustrates how a narrow V-groove weld would inhibit electrode manipulation. Poor joint preparation and fit-up: examples of this would be uneven root faces, uneven bevel angles and general inconsistencies in the preparation and fit-up. Narrow V- groove Inhibits electrode manipulation Wider V- groove Allows for electrode manipulation riG.20| Effect oƒ bevel øngle on the qbility to manipulate the electrode WSS Study Guide WD2.1 Intermediate Weld Discontinuities 2.13 Incomplete Joint Penetration \ The term incomplete joint penetration is a condition at the root of a groove weld where the weld metal does not extend through the joint thickness (see Figure 31). z= S _ lỀ — —<— —. Incomplete joint penetration a) Incomplete penetration - Square Butt Pu —< NI mu Incomplete joint ma b) Incomplete penetration - Single”V” penetration - „—. — mi x*. iieompielejoii - penetration — =g im c) Incomplete penetration - Double”V” I HH d) Incomplete penetration -Double Fillet —=. II Incomplete Jjoint penetration FiG.21i Incomplete joint penetrotion ® WSS Study Guide WD2.1 CWBI H Em see HN Intermediate Weld Discontinuities lt must be noted that incomplete joint penetration is not necessarily a weld defect. Some welded connections are designed with partial joint penetration welds. Incomplete joint penetration becomes a weld defect only when the codes, specifications and designs require complete joint penetration or when the required depth of penetration and resulting weld size is not achieved. The causes of incomplete joint penetration are very similar to those causing incomplete fusion and are: 1. Improper electrode seleciion. The selection of an electrode that is too large for the joint preparation limits access to the root of the joint. 2. Improper welding parameters. Current values that are too low may cause incomplete joint penetration. A voltage that is too high may also lead to incomplete joint penetration due to increased arc length and width resulting in a welding arc that is less focused at the root of the joint. 3. Improper manipulation of the electrode. Travel angle, work angle, travel speed, arc length and contact tip-to-work distance all affect penetration. An increase in travel angle beyond 15° wiïll decrease penetration and may result in incomplete Jjoint penetration. Welding the root pass of a groove weld with an angle other than 90° to the work plane will decrease root penetration and may result in incomplete joint penetration. Travel speed is optimum for achieving penetration when the electrode is at the leading edge of the weld pool. A faster or slower travel speed will reduce penetration and may result in incomplete Joint penetration. Arc length for processes using constant current power supplies (SMAW and GTAW) varies as the operator moves the electrode closer or farther from the joint. An unsteady welder may hold the electrode too far from the joint resulting in an increased (less focused) arc, which will decrease root penetration and may result in incomplete Joint penetration. For processes that use constant voltage power sources (GMAW, FCAW and MCAW), the welding current decreases as the contact tip-to-work distance increases. An unsteady welder may hold the welding gun too far away, resulting in a contact-tip-to-work distance that is too long and decreased root penetration that may result in incomplete joint penetration. Page 38 Copyright © 2015 CWB Group Industry 5ervices ï s¡ cwbgroup Intermediate Weld Discontinuities 4. Improper cleaning of the material. Rust, oxides, and mill scale that is not removed from the joint prior to welding, may result in incomplete Joint penetration. 5. Improper joint design. An example of this would be an included angle on a V-groove weld for a thick plate preventing access of the welding gun below the top surface of the plate. This would result in a contact tip-to-work distance that is too great, reducing welding current and resulting in decreased penetration, which may result in incomplete Joint penetration. 6. Poor joint preparation and fit-up. An example of this would be insufficient root gap resulting in reduced root penetration, which may cause incomplete joint penetration. Incomplete joint penetration in a joint designed as a complete joint penetration groove weld is always determined to be a defect requiring repair. Repair is performed by grinding or gouging from one side to sound weld metal, and depositing a new weld pass or weld passes. Incomplete Joint penetration of a fillet weld requires the complete removal of the fillet weld and a new weld must be deposited. Incomplete joint penetration of a partial joint penetration groove weld will most likely require the weld to be removed and a new weld deposited, or a second weld pass performed from the other side of the joint. 9 2015 CWJ Group Industr