Welding Inspection For the benefit of business and people Shanghai July 2007.

Welding Inspection

For the benefit of business and people

Shanghai July 2007

2FOR BUREAU VERITAS INTERNAL USE ONLY – MARINE TRAINING ON MATERIALS

Introduction 0

Introduction about this material;

• Use the “AMERICAN WELDING SOCIETY (AWS)” published book named ’WELDING INSPECTION” as a fundamental training material, and

• Supplemented with the AWS “Standard for AWS Certification of Welding Inspectors” Training course material.

Introduction of Weld and Weld Related Discontinuities

3

1 General

2 Weld and Weld Related Discontinuities

3 Dimensional Discontinuities

4 Weldment and Related Discontinuities

5 Mechanical and Chemical Weld Metal Properties

6 Visual Inspection of Welding

SUMMARY

4

> General

1


General 1

Introduction about this Training material;

• Use the “AMERICAN WELDING SOCIETY (AWS)” published book named ’WELDING INSPECTION” as a fundamental training material, and

• Supplementing with the AWS “Standard for AWS Certification of Welding Inspectors” Training course material.

Introduction of Weld and Weld Related Discontinuities


Weld Discontinuities General1

Introduction about AWS CWI certifications;• Three levels of Welding Inspector, they are;

» Senior Certified Welding Inspector

» Certified Welding Inspector

» Certified Associated Welding Inspector

• Qualification of Welding Inspector;

» Relevant education and work (welding-related) experience.

» Training Record

» To qualify for the Certified Welding Inspector Examination.

• The examination consists of the following;

» Part A - Fundamentals

» Part B - Practical

» Part C – Open Book Code, Following Codes are applicable to this position of the examination;

– AWS D 1.1 – Structural Welding Code

– API 1104 – Welding of Pipelines and Related Facilities

– AWS D 1.5 – Bridge Welding Code

– AWS D 15.1 – Railroad Welding Specification

– ASME Code Section V, VIII, Boiler and Pressure Vessel Code



Essential Requirements of Welding Inspector

• Physical Condition;

» Must be sufficiently good to permit him to fulfill his duties

» Good vision and color vision capabilities

• Attitude;

» All decisions must be considered, impartial, and consistent.

» A definite policy of inspection procedure and standards should be adopted and followed faithfully.

» Can be neither stubborn nor easily swayed.

• Knowledge of Drawings, Rules and Procedures

• Knowledge of Welding;

» Knowledge of Welding Metallurgy

» Knowledge of Welding processes to know what defects are most likely to occur and where to look for them.

» Familiar with all procedure specifications that apply.

» Know the variables of particular welding process and monitor this variables during the operation.

• Knowledge of Testing Methods;

» Including Destructive and Nondestructive tests.



Welding Inspection Operations

• Knowledge of Drawings, Rules, Shipyard Practice;

» Familiar with yard building practice including the Definition of Butt Joint groove code and Fillet Joint Welding symbols.

» Assure consistent compliance with criteria. Deviations beyond the level of inspector’s expertise or jurisdiction should be referred to appropriate technical activity for resolution.

• Welding Procedure and Welder and Welding Operator Qualifications;

» Welding Procedures must be capable of producing welded joints to certain acceptance criteria in accordance with the Rules.

» Prior to the start of production welding, ensures that only approved WPS are used and welders and Welding Operators are qualified.

» Welding Inspector should be alert the changes or deviations in excess of the procedural requirements. Revision of WPS or New WPS should be qualified by test.

» Welders worked out of their qualifications or excess the WPS requirement, Inspector may ask Shipyard to suspend Welders’ qualification.

• Application of Welding and Allied Procedure;

» Verify that those procedures specifically approved are being applied. The Inspector may prepare a checklist for each procedure to guide him in performing his duty.

» Inspection processes should be performed in sequence with the shipyard operations.



Welding Inspection Procedure

• Prior to welding;

» Material identification, Chemical analysis, Mechanical properties.

• Base metal discontinuities;

» Laminations and cracks, surface imperfection and defects, flatness.

• Joint geometry (fit-up);

» Edge preparation (Including root face and beveling), dimensions, cleanliness, root opening, tacking and backing.

• Special set-ups used for assembly and fabrication;

» Jigging and bracing, and pre-stressing or pre-cambering.

• During Welding;

» Preheat and interpass temperatures; measurement and controls.

» Filler metal (Consumers); identification, control and handling.

» Root pass; contour and soundness.

» Root preparation prior to welding.

» Cleanliness between passes and appearance of passes.

» Conformance to approved welding procedure.


Welding Metallurgy General1

Metallurgical properties influence welding processes and welding quality control;

• Carbon Equivalent (Rules Pt D, Ch2, Sec 1);

» A unit called “Carbon Equivalent” is often employed to predict the combined effect of Carbon and Manganese upon the tendency to form martensite.

» The Carbon Equivalent, (CE) is used to evaluate the Weldability.

» For Normal strength Steels (A, B, D & E Steels), the CE is not to exceed 0.40 %. The calculation formula is;

» For Higher Strength Steels (AH, DH, EH & FH Steels), the CE Max. (%) is different from steel grades, such as for AH, DH, EH FH 32 Steels with thickness less than 50mm, the CE Max is 0.36 %. The Calculation formula is;



Metallurgical process

• Most defects of welding are occurred during the cooling period of welding. Following temperatures are effecting the changing of the weld properties;

» 500 oC: Started from this temperature, the Yield strength of the Steel will be reduced.

» 720 oC: It is called as Lower transformation temp. (A1). When heat above A1, both Body-centred Cubic (BCC) phase (ferrite and cementite) begin to transform into a Face-Centred Cubic (FCC) phase call austenite. ,

» Above 850 oC: It is called as Upper transformation temp (A3), depends upon the specified chemical composition. All are Austenite.

» 1390 oC; Above this temperature, the austenite will be changed to Ferrite and become liquid.

» Temperature kept above 1390 oC longer (Long Holding time), the larger the Austenite grain size.



Metallurgical Considerations for Welding

• Welding can result in significant changes in both the temperature of the metal as well as the rate of cooling from that elevated temperature.

• Depending on the location of a point within or adjacent to the weld, there can be various metallurgical structures produced.

• Within the Weld, the region of highest temp., the metal can cool from the liquid through the various phase regions.

• Adjacent to the weld, in the Heat Affected Zone (HAZ), no melting occurs but extremely high temp. can be reached. Then cooling down from the temp. just below the melting temp..

• Cooling rate of this HAZ are most rapid (quenching), it is a significant effect on the resulting microstructure.



Metallurgical Considerations for Welding during cooling down;

• Two major events, one mechanical and one metallurgical, occur during cooling operation;

» Residual stresses and distortions are caused by shrinkage.

» The metallurgical process change, the HAZ will contain a combination of ferrite, pearlite, and cementite . The slow cooling rate will permit the formation of pearlite. The repid cooling rate associated with welding tends to produce harder and less ductile metallurgical structure or phases called martensite and bainite.



Metallurgical Considerations for Welding during cooling down;

• Where certain amount of Martensite and Bainite is normally unavoidable, there amount and their effect can be minimized by proper base metal and electrode selected, welding technique, and preheating and interpass temperatures.

• As the heat input increases, the cooling rate decreased. The formula for welding heat input is shown below, the unit is joules/Inch:



Laminations and Lamellar Tearing;

• Laminations are inclusions or separations that exist in the material as the result of impurities (such as Sulfates or Silicates) that segregate during ingot solidification and are subsequently flattened during rolling or hot working applications. (Mostly occurred at or near the centre of plates.

• Lamellar tearing occurs during a welding operation and is not a pre-existing condition. For most steel plates; the percent elongation is approximately the same in the direction of rolling (X) and in the transverse direction (Y). (In Rules “Z25/ZH25” quality steel plates is recommended in some locations.)


Welding Metallurgy General1

Preheating;• Prior to welding, the entire weld joint area should be heated through the metal thickness to the

desired minimum temperature. To obtain uniform temp. through the metal thickness, the temp. measurement is desirable to locate on opposite surface. When it is impossible to measure on opposite side. The preheating time prior to welding is to be considered.

Interpass temperature limitation;

• An Interpass temperature limitation may need to be considered for many materials (i.e. low alloy steels with impact requirements). In such case, the weld area must be checked prior to deposit the next bead.

• Depending upon the metallurgical or mechanical properties of weldment, preheating and interpass temp. may be specified as follows;

» Minimum temp. only (i.e. Cast steel, Normal and high strength Steels)

» Maximum temp. only (i.e. aluminum and nickel alloyed)

» Minimum and maximum temp. (i.e. low alloy steels with impact requirements).

Post Welding Heat Treatment;

• Heating the weldment above the Upper transformation Temperature and holding it long enough in that range to achieve complete transformation into Austenite. Depends on the cooling rate, following specified name assigned to the heat treatment;

» Annealing: cooled slowly, as in furnace, it produces the softest or “dead soft” steel.

» Normalizing: cooled at a moderate rate, as in air. Increase strength

» Quenching: cooled at an accelerated rate, as in water or oil

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> Weld and Weld Related Discontinuities

2


General 2

Welding Symbols;

Weld and Weld Related Discontinuities


General 2

Weld and Weld Related Discontinuities;

• A discontinuities is an interruption of the typical structure of weldment, such as in homogeneity in mechanical, metallurgical, or physical characteristics of material or weldment. A discontinuities is by nature not necessarily a defect.

• A weld that does not meet any or all of the specific requirements of a particular specification or code is considered a defective.

Weld and Weld Related Discontinuities


Classification Weld and Weld Related Discontinuities2

Weld discontinuities can be classed in four major groups; • Dimensional;

» Incorrect Joint preparation

» Distortion

» Incorrect weld size

» Incorrect weld profile

» Incorrect final dimensions

» Excessive weld reinforcement

• Weldment and related discontinuities in weld

» Porosity

» Slag inclusions

» Tungsten inclusions

» Incomplete fusion

» Inadequate joint penetration

» Undercut

» Cracks

» Surface irregularities

» Other irregularities

• Mechanical and chemical weld metal properties

• Base metal proerities;

21

> Dimensional Discontinuities

3


Distortion Dimensional Discontinuities3

Incorrect Joint Preparation;

• Welding practice required proper joint dimensions, consistent with the thickness of material being welded. Failure to meet these criteria may result tendency to produce discontinuities in the weld and creating distortion.

Distortion;

• Stresses of high magnitude will result from thermal expansion and contraction and weld metal solidification, and will remain in the weldment after the structure has cooled. Such stresses tend to cause distortion.

• Rigid fixture and careful selection of welding sequence (balance the stresses as well), welding processes, and joint design will minimize the distortion.

• Correction of distortion in a completed weldment by following procedures;

» Straightening operation, with or without application of heat.

» The removal of weld or welds causing the distortion and subsequent rewelding

» The addition of weld metal in specific areas.

» A postweld heat treatment


Incorrect Weld Size3

Incorrect Weld Size;

• Weld size may be detected by visually, or by using of welding gauge.

• The Size of a normal equal-leg fillet weld is expressed as the leg length of the largest isosceles right triangle that can be inscribed within the fillet weld cross section.

• The size of groove weld is joint penetration (depth of chamfering plus the root penetration).

Dimensional Discontinuities


Incorrect Weld Profile3

Incorrect Weld Profile;

• The profile of a finished weld may have considerable effect on its performance under load.

• The profile of one pass of a multi-pass weld may have considerable effect on the tendency for discontinuities such as incomplete fusion or slag inclusions to be produced when subsequent layers are deposited

• The defects of Weld Profile, such as, Overlap, Undercut and Excess Convexity tend in produce notches that are dangerous, due to the resultant concentration of stress under load.



Incorrect Final Dimensions3

Incorrect Final Dimensions;

• Weldments are fabricated to meet certain dimensions, which specified on the Working Drawings (such as Block Drawings);

» The Shipyard aware of the amount of shrinkage to be expected at each weld joint. This will affect the final overall dimensions of the products. (The Shrinkage rate depends on how many welds and how much the specified welding heat inputs of each weld.).

» Shipyard normally use the how many mm shrinkage of each frame space or each longitudinal space as the unit of the shrinkage rate, such as 0.2 mm per 910 mm length for the double bottom block, when the frame space is 910 mm, and 0.2 mm per 860 mm, when the bottom longitudinal space is 860 mm.).

» Tolerance in final dimensions might be specified as from plus or minus a few mm of a block length and width. (i.e. The length of SWS normal blocks is 20 meter, the standard tolerance in final dimension is plus and minus of 4 mm. The acceptable tolerance for plan blocks is +- 6 mm, and same for curved blocks is + - 8 mm.


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> Weldment and Related Discontinuities

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Porosity Weldment and Related Discontinuities4

Porosity;

• The porosity differ from slag inclusion in that they contain gases rather than solids and are generally spherical shape.

• The primary causes for porosity are dirt, rust and moisture on the surface of base metal and in the welding consumables.

• High consumption of the deoxidizing elements of covering of shielded metal arc electrodes may take place during deposition if excessive current and arc length are used, leaving insufficient quantities available to combine with gases in molten metal during cooling. Excessive current and excessive arc lengths should be avoided. Low hydrogen electrodes should be chose.

• Distribution of porosity within a weld is some of importance. It occuraence may be generally classified as follows;

» Uniformly scattered porosity; The voids or pores are scattered more or less uniformly throughout the weld metal.

» Cluster porosity; Pores occur in clusters separated by considerable lengths of porosity-free weld metal. (Clusters are often associated with changes in arc condition when welding is stopped or started.).

» Linear porosity; Linear porosity occurs generally in the root pass and is often regarded as a special case of inadequate joint penetration. (Linear porosity is defined by the number and size of pores and their linear distribution with respect to the axis of the weld.



Porosity;

• Typical examples of various forms of porosities in below;

• Fig. 9.6, in additional to illustrating porosities, also shows a welding fit-up (hi-low mismatch) problem.

• Fig. 9.7, also illustrates porosity together with a slag inclusion.



Porosity;

• When porosity is shown on a weld radiographic, it will appear as a well-defined dark region, because it represents a significant loss of material density.

• It will normally appear as a round indication except in the case of piping porosity. The type of porosity will have a tail associated with the rounded indication.

• Typical examples of various forms of porosities illustrated from AWS shown in below;

» Fig. 29 – Linear pr aligned Porosity near the root of the weld

» Fig. 27 – Scattered porosities

» Fig. 28 – Cluster porosity


Slag Inclusions Weldment and Related Discontinuities4

Slag Inclusions;

• The oxides and other non-metallic solids that are entrapped in weld metal or between weld metal and base metal.

• During deposition of filler metal many chemical reactions occur between the weld metal and the electrode covering materials, soluble only to a slight degree in molten metal. Due to their lower specific gravity, slags rise to the surface of molten metal unless they are restrained.

• For shielded metal arc process (SMAC), slag may be formed and forced below the surface of molten metal by stirring action of the arc.

• When slag is present in the molten metal from any cause, factors are high viscosity of weld metal, rapid solidification, or too low a temperature may prevent its release. (High heat input and quick cooling down.).

• With some type electrodes lag in crevices of previously deposited weld metal will not re-melt and will be trapped in the same location.

• Most slag inclusions can be prevented by proper preparation of the groove before each bead is deposited.



Slag Inclusions; • Since the density of slag is usually much less than that of metals, slag inclusions will

generally appear on a Radiographic as relatively dark indications.

• Fig. 9.7, 9.8 and 9.9 illustrate typical examples of slag inclusions.

• Fig. 9.9, in additional to illustrating a slag inclusions, also shows another welding defect known as a shrinkage crack..



Slag Inclusions;

• Fig. 9.19, illustrate typical examples of surface slag inclusions.

• Fig. 9.21, illustrating an elongated slag inclusions.


Tungsten Inclusions Weldment and Related Discontinuities4

Tungsten Inclusions;

• The gas tungsten arc welding process used a non-consumable tungsten electrode to create an arc between the tungsten electrode and the workpiece. Filler metal may of may not be added.

• The occasional touching of the electrode to the work piece or to the molten weld metal may transfer particles of tungsten into the weld deposit.

• Inmost cases, a limited number of tungsten inclusions are accepted; often they are evaluated on the same basis as porosity or slag inclusion.

• Since tungsten has a much greater density than steel or aluminum, it will show up as a definite light area on the radiographic film.


Incomplete Fusion Weldment and Related Discontinuities4

Incomplete Fusion;

• Fusion did not occur between weld metal and fusion faces or adjoining weld beads. (Especially, when using Gas Metal Arc Welding). This failure to obtain fusion may occur at any point in the welding groove. Rules does not accept such kind linear defects.

• Incomplete fusion may be caused by:

» Failure to raise the temperature of base metal (or previously deposited weld metal) to the melting point.

» Insufficient groove angle.

» Improper manipulation of the welding electrode by the Welder. Not enough concentrated heat to adequately melt and fuse the metals.

• If Incomplete fusion is Radiographically visible, it will appear on the film as darker density lines which are generally straighter than the images of either cracks or elongate slag.


Incomplete Fusion Weldment and Related Discontinuities4

Incomplete Fusion;

• Figure (A) shows the occurrence of incomplete fusion at the original groove face as well as between individual weld beads. Quite often, incomplete fusion also has slag inclusions associated with it.

• Figure (B); Most often of Incomplete fusion as being some internal weld flaw, but it can occur at the surface of the weld as well.

• Figure (C); Incomplete fusion shows in the fillet welding when the full penetration is not required.


Inadequate Joint Penetration

Weldment and Related Discontinuities4

Inadequate Joint Penetration;

• Failure of the weld metal does not extend entirely through the joint thickness when complete penetration is required. Its location is always adjacent to weld root.

• Rules does not accept any such kind defects, due to stress concentrations in the unfused area.

• In arc welding, the arc will establish itself between the electrode and the closest part of the base metal. All other areas of the base metal will receive heat principally by conduction. If the potion of the base metal closest to the electrode is a considerable distance from the root, conduction of heat may be insufficient to attain fusion temperature at the root.

• Inadequate Joint penetration may be caused by:

» Use of a groove design not suitable for the welding process. (Groove opening too small, root face dimension is too great, or the included angle of a V-groove is too small.

» Electrode type have a tendency to bridge, an abnormally high rate of travel, or insufficient welding current.





• Figure 9.11 – illustrate typical inadequate penetration

• Figure 9.12 – In addition to illustrating inadequate penetration, also shows a mismatch (Hi-low) condition.





• Typical examples shown in the Fig. 9.16. It is not acceptable for “Full Penetration” welds.

• However, for the design of “Partial Penetration” Welds on the Fillet Welding, which shown in the Fig. 9.16 would be acceptable.

• “Inadequate Penetration (IP)” or “Lack of Penetration (LP) is called by several non-standard terms..





• The Radiographic image caused by Incomplete Penetration will typically be a dark, straight line. It will usually be much straighter than incomplete fusion because it is associated with the original weld preparation at the root. It will be centered in the width of weld for those groove welds..


Undercut Weldment and Related Discontinuities4

Undercut;

• Undercut is a surface discontinuity which occurs in the base metal directly adjacent to the weld. It is a condition in which the base metal has been melted away during the welding operation and there was insufficient filler metal deposited to adequately fill the resulting depression.

• The result is a linear groove in the base metal which may have a relatively sharp configuration. Excessive undercut at the surface should not be permitted since it may materially reduce the strength of joint, particularly with regard to fatigue stress.

• Undercut may be caused by:

» Improper welding technique employed by the Welder, such as excessive traval speed, excessive current (welding heat is too high) or too long an arc and when electrode manipulation is incorrect.

» Different type of electrode shos widely varyoing ch

» Electrode type have a tendency to bridge, an abnormally high rate of travel, or insufficient welding current.


Undercut Weldment and Related Discontinuities4

Undercut;

• On a radiographic, undercut will appear as a dark, fuzzy indication at the toe or root of welding reinforcement.

• Radiographic detection of surface undercut is definite waste of time, money and resources. Surface undercut is to be found by careful visual inspection.


Cracks Weldment and Related Discontinuities4

Cracks – most critical discontinuities;

• Cracks are characterized as liner, as well as exhibiting very sharp end conditions. Since that, there is a tendency for the crack to flow, or propagate, if a stress is applied.

• When welding two plates together, the root of the weld is subjected to tensile stress as successive layers are deposited, and a partially fused root will frequently permit a crack to start and progress through practically the entire thickness of the weld.

• Can categorize cracks in several different ways:

» Hot and Cold cracks

» Longitudinal and Transverse cracks

» Throat cracks, Root cracks, Toe cracks, Crater cracks and Underbead cracks.

» Weld Metal cracking and Base metal cracking




• Hot Cracks – occur as the metal solidified, at some elevated temperature. The propagation of these cracks is considered to be intergranular, that is the cracks occur between individual grains,

• Cold cracks – occur after the metal has cooled to ambient temperature. Delayed, or Underbead, cracks resulting from entrapped hydrogen. The propagation of cold cracks can be either intergranular or transgranular; that is, either between or through the individual grains, respectively.




• Longitudinal cracks – Those lying in a direction parallel to the longitudinal axis of weld. Can result from transverse shrinkage stresses of welding

• Transverse Cracks - Those lying in perpendicular to weld’s longitudinal axis of weld. Generally caused by the longitudinal shrinkage stresses of welding.



Cracks – most critical discontinuities; • Throat cracks; They are longitudinal cracks and are generally considered to be hot

cracks. It is a “Centerline” crack. Joints exhibiting high restraint transverse to the weld axis are susceptible to this weld and where the weld cross section is small. Such as thin root passes and concave fillet welds.

• Root cracks; Usually, longitudinal, however, their propagation may be in either the weld or base metal. Initiate at the weld root or root surface of the weld. Generally considered to be hot cracks. Large root openings may result in a stress concentration which produces root cracks.

• Toe cracks; Are base metal cracks which propagate from the toes of welds. Generally considered to be a Cold crack. Combined with weld reinforcement or convexity and less ductile microstructure in the heat-affected Zone increase the susceptibility of the weldment to Toe cracks.

• Crater cracks; Occur at the termination point of individual weld passes, due to not providing the complete filling of molten weld puddle and combined with the shrinkage stresses from welding, or filler metals performed concave profile. Considered to be hot cracks. Normally, radiating from the center of crater cracks. (Commonly called as star cracks.)

• Underbead cracks; Mostly it is located in the HAZ, some of base metal. When cross sectioned, underbead cracks will often appear to run directly parralled to the fusion line of a weld bead. May propagate to the surface, which allows for their discovery during visual inspection. Underbead cracks result from the presence of Hydrogen in the weld zone. Since the HAZ is typically less ductile than the weld and base metal, cracking may also there without the presence of hydrogen.



Cracks – most critical discontinuities; • Throat cracks

• Toe cracks.

• Crater cracks

• Underbead cracks




• Weld Metal Cracking;

» Mult-layer welds, cracking is most likely to occur in the first layer of weld and, unless repaired, will often continue through other layers as they are deposited.

» Different types of Weld metal cracking are;

– Transverse weld cracks

– Longitudinal weld cracks

– Crater Cracks

» Improvement may be obtained by one or more of the following modifications;

– Change the electrode manipulation or electrical condition

– Decrease the travel speed

– Use pre-heating to reduce thermal stresses

– Use low hydrogen electrodes

– Sequence welds to balance shrinkage stresses

– Avoid quenching and cooling conditions




• Three radiographic illustrations;




• Base Metal Cracking;

» This type of cracking, usually longitudinal in nature, occurs within the Heat-Affected Zone (HAZ) of metal being welded (Hardness and low ductility) and is always associated with hardenable material.

» For low and medium carbon steels, hardness and deformation depend upon the cooling rate. The rate of cooling depends upon following factors;

– Temperatures produced by the welding

– Temperatures of base metal

– Thickness and thermal conductivity of base metal

– Heat input per unit time at a given section of the weld

– The ambient temperature

» Two types of base metal cracking, they are;

– Transverse weld cracks

– Longitudinal weld cracks (For fillet welds may be divided to Toe cracks and Root cracks)

» Improvement may be obtained by one or more of the following modifications;

– Use of preheat to control cooling rate

– Controlled heat input

– Use of correct electrodes

– Proper control of welding materials




• Base Metal Cracking;


Weld Discontinuities Insufficient throat

thickness of a fillet weld4

For steel ships, the required throat thickness is given by the Rule

(BV Rule Part B Chapter 12 Section 1 Req. 2.3)

Note that leg length is required to be not less than 1.4 times the required throat

thickness.

1) Nominal throat thickness

2) Actual throat thickness


Weld Discontinuities Insufficient leg length of a

fillet weld (and excessive assymetry)4

1) Nominal shape

2) Actual shape


Weld Discontinuities

Excessive Reinforcement of a Butt weld4


Weld Discontinuities Undercut4

An irregular groove at the toe of a run in the parent metal, or in previously deposited weld metal due to welding.



Incomplete Root Fusion or Penetration4

Incomplete Root Fusion

Incomplete Penetration

Nominal penetration

Actual penetration


Weld Discontinuities Linear Misalignment4


Weld Discontinuities Incompletely Filled Groove4


Weld Discontinuities Root Concavity4


Weld Discontinuities Cavities and Porosity4

Gas pore

- Gas cavity of essentially spheroidal form. Named surface pore when it breaks the

surface of the weld

- Can be uniformly distributed throughout the weld metal

Clustered (localized) porosity

- Group of gas pores having a random geometric distribution

Linear porosity

- Row of gas pores situated parallel to the axis of the weld

Elongated cavity

- Large non-spherical cavity with its major diemension approximately paralle to the

axis of the weld


Weld Discontinuities Cavities and Porosity4

Wormhole

- Tubular cavity in the weld metal caused by release of gas. Generally grouped in

clusters and distributed in herringbone formation

Crater pipe

- A shrinkage cavity at the end of a weld run and not eliminated before or during

subsequent weld runs.

Gas pores

uniformly distributed

Surface pores

In a fillet weld

Clustered porosity



Lack of Sidewall and Inter-run Fusion4


Weld Discontinuities Slag Inclusions4


Weld Discontinuities Cracks4

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> Mechanical and Chemical Weld Metal Properties

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Filler metal properties Mechanical and Chemical Weld Metal Properties5

Mechanical and Chemical Weld Metal Properties;

• Filler Metal Properties;

» Specific mechanical and chemical properties of Filler metals are required in Rules Part D, Ch 5, Section 2 – ‘Approval of Welding Consumables”.

» These properties are determined with specially prepared “Weld test assembles’.

» Surveyor must check and verify the using of approved consumables, using of incorrect welding consumables will be produced defective welds.

• Base Metal Properties;

» Not all discontinuities are due to improper welding conditions, but also due to incorrect using of base metals.

» Specific mechanical and chemical properties of Steel Products are required in Rules Part D, Ch 2 – “Steel and Iron Products”.

» Beside Surveyor should check and verify the BV approved Steel Products being used, he must check;

– Surface conditions (mil-scales, paint, oil, cleanliness, corrosion and lamination)

– Arc strikers, (arc strikers of the area of permanent welds should be avoided on any vase metal, any cracks or blemishes caused by arc strike should be grund to a smooth condition.



Additional radiographs showing welding discontinuities;

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> Visual Inspection of Welding

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Four Phases6

Welding Inspection Programs;

• Phase A – Initial Review of Inspection Program;

» Review purchase order, all codes and drawings

» Develop all necessary inspection plans

» Check welding procedure; welder status

» Establish inspection documentation system

» Publish non-confirming product ID system

» Create a corrective action program

• Phase B – Pre-welding Checks

» Check suitability, condition of welding equipment

» Check conformance of base and filler materials

» Check the positioning of members and joints

» Check joint preparation, fit-up, cleanliness

» Check adequacy of alignment maintenance

» Check Preheat (or initial) temperature

Visual Inspection of WeldingVisual Inspection of Welding


Four Phases6

Welding Inspection Programs;

• Phase C – In-process Inspection;

» Check compliance with WPS provisions

» Check quality, placement of key weld passes

» Check weld bead sequencing and placement

» Check interpass temperature and cleaning

» Check adequacy of backgouging

» Monitor any specified in-process NDE

• Phase D – Postwelding Activities

» Check finished weld appearance, soundness

» Check weld size and dimensions

» Check dimensional accuracy of weldment

» Carry out or monitor/evaluate specified NDE

» Monitor any PWHT or other postweld work

» Finalize and collate inspection documentation



Finished weld6

Check finished weld appearance and soundness

• Weld faces should display uniform ripples with no significant variations in shape of form. Bumps and depressions indicating starts or stops should be minimal. Groove weld reinforcement should be evident, without underfill or excess.

• This similarly applies to filet welds, where minimum ratio of width to depth (W/D) should be 1.25 to 1. Excessive convexity or concavity are equally undesirable.

• Without following surface discontinuities;

» Undercut, Cracks, Incomplete Fusion, Incomplete Penetration, Slag Inclusion, Porosity and other gaseous inclusions, Arc Strike

• Check Weld sizes and dimensions – fillet welding size should be verified as meeting the Rules, drawing requirement. Weld length of fillet welding must be verified.


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END

Welding Inspection For the benefit of business and people Shanghai July 2007.

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Transcript of Welding Inspection For the benefit of business and people Shanghai July 2007.