Multipass weld metals were deposited on q345 base steel using metal powderfluxcored wire with various ni contents to investigate the effects of the ni content on the weld microstructure and. The effect of grain boundary on the dissolution of base metal. To fully understand weld discontinuities, we must first examine some welding terminology. Influence of niobium on mechanical properties and hot crack susceptibility of nickelbase coredwire weld metal type 7020 and 7015 g. Defects and discontinuities tim turner elizabethtown technical college defect a flaw. Influence of niobium on mechanical properties and hot. Discontinuities that exceed established acceptance standards are. It is the failure of filler metal or base metal to completely fill the root of the weld.
Apr 24, 2015 base metal discontinuities lamellar tearing laminations and delaminations laps and seams 45. Similar charpy impact toughness test results were obtained for weld metal and heat affected zone. The matrix structure of the base metal shown in fig. Understand and recognize common false and nonrelevant indications found when nde is being performed. It is often found on one leg of a fillet weld and is caused by incorrect welding angle that allows for an imbalance of heat between both sides of the joint. Hightemperature tensile behaviors of base metal and. What weld discontinuity results when the welder travels too slowly, causing excess weld metal to flow out of the joint and lay on the base metal surface without fusing. Weld and base metal discontinuities weldingteacher. Overlap the protrusion of weld metal beyond the weld toe or weld root. Ultrasonic testing of ferritic or martensitic steel forgings. From a linear intercept method for measuring a mean grain size 30, the austenitic grain size was 6. Defects classed as discontinuities may in this case be the same as defects of casts. Typically, none or up to 5% of metal thickness not to exceed 2 as long as the thickness is made up in the opposite reinforcement.
Welding discontinuities and defects hobart institute of. Fins, scabs, seams and laps are all terms that describe base metal discontinuities located in. May 11, 2018 electron beam welding of ni20cr9mo4nb alloy sheets was carried out, and hightemperature tensile behaviors of base metal and weldments were studied. The effect of grain boundary on the dissolution of base.
Overlap is measured with a square edge such as a 6 rule. The following discontinuities are typical of all types of welding. Common causes of discontinuities related to internal inconsistencies and weld metal irregularities. Sensitivity shall be sufficient to ensure the detection of the smallest discontinuities required by the recordingevaluation levels for the particular quality class specified see tables 5, 6 and 7. Some defects can be tolerated while others can be repaired, otherwise they must be eliminated. Microstructure of the weld consisted of columnar dendritic structure and revealed. Also be careful of fusion discontinuities hidden by grinding. Welding discontinuities can affect product performance and longevity. Since the weld metal and base metal will, in general, work harden differently, the degree of mismatch will vary with plastic strain. This alloy has such high strength, ductility and resistance against high temperature oxidation as equivalent to those of inconel 718, but have a slight higher susceptibility to hot cracking. During tlp bonding, the dissolution of the base metal into insert. Tlp bonding of single crystal, coarse grained and fine grained cmsx2 specimens was carried out at 731548 k for 019.
Structural failures precipitated by weld discontinuities. Base metal discontinuities lamellar tearing laminations and delaminations laps and seams 45. Enjoy full access to the digital edition of stamping journal, which serves the metal stamping market with the latest technology advancements, best practices, and industry news. Sheet metal fabricator develops fullfledged diversification strategy fabricating custom adaptive bicycles that change lives check fixtures do far more than verify a tubular components dimensions. Above 35% iron, the welds have less strength and are more brittle. What weld discontinuity results when the welder travels too slowly, which causes excess weld metal to pour out of the joint and lay on the base metal surface without fusing. Identi cation of postnecking hardening phenomena in ductile sheet metal 3 the identi cation strategies for such material models are usually driven by the amount of experimental e ort to obtain a certain level of accuracy. Introduction discontinuities are imperfection in welds or base metals. Weld discontinuities part 3 cracking cracks in a weldment are probably the most dreaded of all the weld discontinuities. Identi cation of postnecking hardening phenomena in.
Where weld metal does not form a cohesive bond with the base metal. On the other hand for monelsteel welds, test results showed that the welds had good strength and integrity between 10% and 27% iron in the weld. Electron beam welding of ni20cr9mo4nb alloy sheets was carried out, and hightemperature tensile behaviors of base metal and weldments were studied. The discontinuous weld bead defect in highspeed gas metal arc. Welding discontinuities and defects planning advisory notice. Detecting discontinuities through weld inspection matching. Request pdf characterization of bond line discontinuities in a highmn twip steel pipe welded by hferw in this work, the microstructure and defects in a highfrequency electrical resistance.
Obviously, the primary aim in industry is to reduce the time period to bring a new material or product to market. Undercut a groove melted into the base metal adjacent to the weld toe or weld root and left unfilled by weld metal. Fins, scabs, seams and laps are all terms that describe base metal discontinuities located in the heat affected zone of the weld and result from fabrication operations. Since the line between discontinuities and defects varies from one industry to another, only a generalized explanation can give a good guide to isolating defects from discontinuities. Because of the wide range of applications and the many types of materials welded, cracking is an extremely complex subject. Understand the different classifications of discontinuities. Module 9 weld and base metal discontinuities welding. Inclusions occur when slag, oxides or other nonmetallic materials become trapped between the bases metal and the weld, between the beads of the weld or in the weld metal. The differences between discontinuities and defects. The tensile test results showed that the strength of weld metal and heat affected zone were higher than of base metal. The base material is prone to hardening because of a high c content or other alloying elements. Module 9 weld and base metal discontinuities free download as powerpoint presentation. Effect of iron dilution on strength of nickelsteel and. Low amperage, steep electrode angles, fast travel speed, short arc gap, lack of preheat, electrode too small, unclean base metal, arc off seam.
Failure of weld metal to fuse completely with the base metal or preceding bead. In oh position, too hot or too wide will cause drooping of the open root. Base metal discontinuities lamellar tearing laminations and. The weld metal metallurgy for cmn and low alloy steels differs significantly from the base metal metallurgy in several aspects. Understand the origin and nature of common discontinuities. Hand tool cleaning of metal surfaces 2074 steel castings 2121 saa earthquake code 2214 saa structural steel welding supervisors certification code 2312 guide to the protection of iron. Characterization of bond line discontinuities in a highmn. Weld defects as per different codes dr g ravichandran sr manager, wri bhel, tiruchirappalli. Acceptance criteria of weld defects as per different codes. Ksl operational procedure liquid penetrant examination document no 1630007 release date. During tlp bonding, the dissolution of the base metal into. Weld discontinuities part 1 porosity incomplete fusion. Module 9 weld and base metal discontinuities welding business. The likelihood of discontinuities occurring depends on a number of factors.
Weld and base metal discontinuities comimsa module 9. Cold lap is a condition where the weld filler metal does not properly fuse with the base metal or. Apparently they have a corporate policy that predict and predetermines the haz. Structural failures precipitated by weld discontinuities 77 temperatures and cooling rates during welding that promote the formation of carbides around grain boundaries within the weld haz. Weld and base metal discontinuities flashcards quizlet. Pinnacle alloys ernicr3 provides high strength and good corrosion resistance, resists oxidation, and delivers creeprupture strength at elevated temperatures.
Weld metal hardness was almost similar to the base metal hardness, nevertheless, the heat affected zone indicated higher values. Microstructure of the weld consisted of columnar dendritic structure and. Weld discontinuities part 1 porosity incomplete fusion incomplete penetration. Ramesh singh, in applied welding engineering second edition, 2016. Discontinuities and defect should be carefully distinguished by wi. Dirty base metal inadequate gas coverage possible cures use proper arc length clean base metal check for proper gas coverage possible causes. Hightemperature tensile behaviors of base metal and electron. Incomplete joint penetration lack of fusion welding fusion that fails to penetrate to complete thickness of the materials being joined. Design and construction of steel diagrid structures. The 35% iron content also corresponds to the iron dilution in monel welds that has been shown to produce an increase in corrosion rate. Any weld would be a defect if the welder or the quality control department rejects it and blacklists the product.
In hot crack, cracks happen because of the preexisting contaminant like. Nonmetallic solid materials entrapped in weld metals or between weld metal and base metal main causes. Those contaminants form a carbide that has a lower melting temperature than the base metal itself. Weld discontinuities weld discontinuities are interruptions ofthe typical structure ofa weldment such as a lack ofcontinuity in its physical, metallurgical or mechanical characteristics discontinuities may be found in the weld metal, the heat affected zone and the base metal. However, a surface irregularity or weld discontinuity is not a rejectable. Nibase superalloy inconel 706 which was developed from inconel 718 has an economical advantage to save the major element ni content less than inconel 718. The dissolution of base metal into insert metal during tlp bonding of ni base cmsx2 superalloys, was studied. Gas tungstenarc, gas metalarc and shielded metalarc welds were prepared using welding conditions. Laminations are flat, elongated discontinuities found in the center of wrought products such as plate.
Evaluating weld metal strength mismatch in x100 girth. This condi tion is the result of the base metal reaching critical c. Henry june 14, 2005 discontinuities, or flaws, can often occur in the welds used to manufacture welded tubular products. Discontinuities may be found in the weld metal, the heat affected zone and the base metal. The subscript x in m defines the plastic strain at which mismatch is defined.
Thoroughly understanding the various defects, their causes, severity, and remedies can help ensure highquality and superior performance. Oct 10, 2014 piping symbols,welding symbols,nde symbols. A discontinuity becomes a defect when it exceeds acceptable limits imposed by acceptance standards. A casting defect is an undesired irregularity in a metal casting process. Incomplete fusion a weld discontinuity in which fusion did not occur between weld metal and fusion faces or adjoining weld beads. Defects classed as discontinuities may in this case be the same as defects of casts from traditional materials, or completely different due to. I could not understand how xray would be the correct method to determine haz. Undercut is defined as a groove melted into the base metal adjacent the weld toe, or weld root, and left unfilled by weld metal. While increasing welding speed and heat input will. This procedure provides for the detection and evaluation of discontinuities open to the surface, such as cracks, linear, round and other types of surface discontinuities utilizing the liquid. Dirty base metal inadequate gas coverage possible cures use proper arc length clean base metal check for proper gas coverage possible causes travel speed too slow cold welding procedures possible cures increase travel speed increase current possible causes improper electrode angle possible cures use correct welding technique possible causes.
Base metal properties such as chemical composition, cleanliness, laminations, stringers, surface conditions, and mechanical properties can affect weld quality. The objective is to be able to identify and define various types of discontinuities and defects in addition to identifying and determining the common causes of those. Effect of welding parameters on the mechanical properties. Incomplete fusion may be caused by the inability, during the welding process, to elevate the base material or previously deposited weld metal to its melting temperature. Neglecting to remove impurities like dirt from the base metal. When the heat from welding highly increases the temperature, those carbides will melt and decrease the materials strength. Common causes of discontinuities related to shape, size and contour. Appears as elongated darkened lines of varying length and width which may occur in any part of the welding groove. Laminations base metal discontinuity may require repair prior to welding formed during the milling process 46. Remedies if possible, choose a material with a better weldability. Learn vocabulary, terms, and more with flashcards, games, and other study tools.
The rt tech told me that their company policy was to limit base metal interpretations b31. Open root reinforcement too little filler metal will cause thinning of the filler metal. The effect of grain size on the dissolution phenomenon was also investigated. Detecting discontinuities through weld inspection matching the inspection method to the welding process by sharon m. Yb are the stresses corresponding to the same amount of plastic strain of the weld metal and base metal, respectively.
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