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Welding defects refer to the defects formed in the welding process of the welded joint. Welding defects include stoma, slag inclusion, incomplete penetration, non-fusion, crack, pit, edge bite, welding bump, etc. The porosity and slag inclusion (point) in these defects belong to volume-type defects. Slime, non-penetration, non-fusion and crack are linear defects, which can also be called surface defects. In particular, cracks and non-fusion are surface defects. Pits, edge bites, weld bumps and surface cracks belong to surface defects. Other defects (including internal buried cracks) are buried defects.
[1]
- Chinese name
- Weld defect
- Foreign name
- WELDING DEFECT
- unscramble
- Incomplete welded joint
- categorize
- Welding crack, incomplete welding
- danger
- Weld cracks and non-fusion
The edges of the components must be prepared as specified, clean,
burrfree
,
No gas cutting slag
,
No grease or paint
In addition to workshop protection primer.
Joints must be dry. The spot welding should not be too deep, and the spot welding position should allow it to reintegrate when welding is applied.
Before welding, the inspector must ensure that all solder joints are in good condition, and bad spot welding and burst spot welding must be removed before welding.
No matter what kind of welding method is used, welding in a low temperature climate (below +5℃), the following protective measures must be taken to avoid the adverse effects caused by low temperature welding joints (easy to brittle, hard and crack, easy to produce defects such as small eyes and slag caused by rapid cooling and weld solidification on the welded joint) :
a) Welding in an area that is not disturbed by bad weather (such as wind, moisture, airflow, etc.);
b) Dry welded joints to avoid material shrinkage caused by moisture;
c) Preheat the welded joint to slow down the cooling rate of the weld after welding;
d) Cover the weld after welding to prevent sudden cooling of the weld.
e) The minimum welding temperature shall be -10℃, and the protective measures shall be taken.
f) Slow and uniform preheating of the flame when the preheating temperature is at least 50℃.
1, appearance defect: appearance defect (surface defect) refers to the defect that can be found from the surface of the workpiece without the aid of the instrument. The common appearance defects are edge bites, welding nodules, dents and welding deformation, and sometimes surface pores and surface cracks. The root of single side welding is not welded through.
A. The edge of the bite refers to the dip or groove formed along the toe of the weld in the base metal part, which is caused by the gap left by the arc melting the base metal at the edge of the weld and not being fully supplemented by the deposited metal. The main reason for the biting edge is that the arc heat is too high, that is, the current is too large and the rod speed is too small. The Angle between the electrode and the workpiece is not correct, the swing is unreasonable, the arc is too long, and the welding order is unreasonable. The magnetic deflection of the arc in DC welding is also a cause of edge biting. Certain welding positions (vertical, horizontal, and tilted) can exacerbate edge biting.
The biting edge reduces the effective cross-sectional area of the base material, reduces the bearing capacity of the structure, and causes stress concentration, which develops into a crack source.
Correcting the operating posture, selecting reasonable norms and adopting good transportation methods will help eliminate the biting edge. When welding fillet welds, AC welding instead of DC welding can also effectively prevent edge biting.
B, in the welding seam
Liquid metal
Flow to the underheated and unmelted base material or overflow from the root of the weld, the metal nodules formed after cooling that are not fused with the base material are welding nodules. Welding specifications are too strong, welding electrode melting too fast, poor quality of welding electrode (such as off-core), unstable characteristics of welding power supply and improper operation posture are easy to bring welding burr. Welding nodules are more likely to form in horizontal, upright and upright positions.
Welding nodules are often accompanied by non-fusion and slag inclusion defects, which can easily lead to cracks. At the same time, welding nodules change the actual size of the weld, which will cause stress concentration. The weld nodules inside the pipe reduce its inner diameter and may cause flow blockage.
Measures to prevent welding tumors: make the weld in the flat welding position, the correct selection of specifications, the selection of non-biased core electrode, reasonable operation.
C, pits pits refers to the weld surface or back of the local part below the base material.
The pits are mostly caused by the welding rod (wire) not staying for a short time when the arc is closed (the pits are called arc pits at this time), and the pits are often concave at the root of the back of the weld when the vertical and horizontal welding is done.
The effective cross-sectional area of the weld is reduced by pits, which often have cracks and shrinkage holes.
Measures to prevent pits: choose a welding machine with a current attenuation system, try to choose a flat welding position, choose a suitable welding specification, and let the electrode stay in the weld pool for a short time or swing in a circle when the arc is closed to fill the arc pit.
D, not fully welded not fully welded refers to the continuous or intermittent groove on the surface of the weld. Insufficient filling metal is the root cause of incomplete welding. The specification is too weak, the electrode is too thin, and the improper rod will lead to incomplete welding.
Incomplete welding also weakens the weld, easy to produce stress concentration, at the same time, because the specification is too weak to increase the cooling rate, easy to bring porosity, cracks and so on.
Measures to prevent incomplete welding: increase the welding current, add welding cover weld.
E. Burning through means that during the welding process, the melting depth exceeds the thickness of the workpiece, and the molten metal flows out from the back of the weld, forming perforating defects.
The welding current is too large, the speed is too slow, and the arc stays in the weld for too long, which will result in burn-out defects. The workpiece gap is too large, and the blunt edge is too small.
Burn through
Boiler pressure vessel
A defect that is not allowed on the product completely destroys the weld, causing the joint to lose its connection and bearing capacity.
Using small current and appropriate welding speed to reduce the assembly gap, adding a pad or a cushion on the back of the weld, using pulse welding, can effectively prevent burning through.
F, other surface defects:
(1) Poor forming means that the appearance geometry of the weld does not meet the requirements. The weld is too high, the surface is not smooth, and the weld is too wide, and the transition of the weld to the base material is not smooth.
(2) The wrong side refers to the staggered position of the two workpieces in the thickness direction, which can be regarded as both the weld surface defect and the assembly forming defect.
(3) Collapse single-side welding due to the input heat is too large, too much molten metal, so that the liquid metal to the back of the weld collapses, the back of the weld protrudes after forming, the front collapse.
(4) Surface porosity and arc pit shrinkage.
(5) All kinds of welding deformation, such as Angle deformation, distortion, wave deformation, etc. are welding defects.
2. Stomata and slag inclusion
A. Porosity refers to the holes formed when welding, the gas in the molten pool does not escape before the metal solidifies and remains in the weld. The gas may be absorbed by the molten pool from the outside world, or it may be generated by the reaction in the welding metallurgy process.
(1) Classification of stomata according to its shape, there are globular stomata, slime stomata; The number can be divided into single stomata and group stomata. The group stomata are divided into uniformly distributed stomata, dense stomata and chain stomata. According to the gas composition in the stomata, there are hydrogen stomata, nitrogen stomata, carbon dioxide stomata, carbon monoxide stomata, oxygen holes. The welding pores are mostly hydrogen pores and
Carbon monoxide
Air hole.
(2) The formation mechanism of pores The solubility of gases in solid metals at normal temperature is only high temperature
Liquid metal
In the
Gas solubility
In the solidification process of molten pool metal, a large amount of gas has to escape from the metal. When the solidification rate is greater than the gas escape rate, the porosity is formed.
(3) The main reason for the porosity is rust and oil on the surface of the base metal or filled metal. The welding rod and flux are not dried, which will increase the porosity, because the rust, oil and water in the electrode coating and flux decompose into gas at high temperature, increasing the content of gas in the high temperature metal. The energy of welding line is too small, and the cooling rate of molten pool is too high, which is not conducive to gas escape. Insufficient deoxidation of the weld metal can also increase oxygen holes.
(4) The harm of the porosity porosity reduces the effective cross-sectional area of the weld, makes the weld loose, thereby reducing the strength of the joint, reducing plasticity, and causing leakage. Porosity is also a factor causing stress concentration. Hydrogen pores may also contribute to cold cracks.
(5) Measures to prevent porosity a. Remove oil, rust, moisture and debris on the surface of the welding wire, working groove and its vicinity. b. Adoption
Basic electrode
, flux, and dry thoroughly. c. Use DC reverse welding and short arc welding. d. Preheat before welding to slow down the cooling rate. e. Welding with strong specifications.
B, slag inclusion Slag inclusion refers to the phenomenon of residual slag in the weld after welding.
(1) Classification of slag inclusion a. Metal slag inclusion: refers to tungsten, copper and other metal particles remaining in the weld, customary known as tungsten, copper. b. Non-metallic slag inclusion: refers to the unmelted electrode coating or flux, sulfide, oxide, nitride residues in the weld. Metallurgical reaction is not complete, slag removal is not good.
(2) The distribution and shape of slag inclusion include single point slag inclusion, strip slag inclusion, chain slag inclusion and dense slag inclusion
(3) The causes of slag inclusion a. the groove size is unreasonable; b. There is dirt in the groove; c. When multi-layer welding, the slag cleaning between layers is not thorough; d. Welding line energy is small; e. Weld heat dissipation too fast, liquid metal solidification too fast; f. Electrode cover, the chemical composition of flux is unreasonable, and the melting point is too high; g. During tungsten inert gas welding, the polarity of the power supply is improper, the electrical and current density is large, and the tungsten electrode is melted and falls off in the molten pool. h. When manual welding, the welding rod is not swinging, which is not conducive to the floating of slag. Corresponding measures can be taken according to the above reasons to prevent the occurrence of slag inclusion.
(4) The harm of slag inclusion The harm of point-like slag inclusion is similar to the porosity, and the slag inclusion with sharp corners will produce tip stress concentration, and the tip will develop into a crack source, which is more harmful.
3, the crack weld atom bond is destroyed, the formation of a new interface caused by the gap called the crack.
A. Classification of cracks
According to the size of the crack, it is divided into three categories: 1) macroscopic cracks: cracks visible to the naked eye. (2) Microscopic cracks: can be found under the microscope. (3) Ultra-microscopic cracks: they can be found under a high-power microscope, generally referring to intergranular cracks and intragranular cracks.
From the point of view of generation temperature, cracks are divided into two categories:
(1) Hot crack: the crack produced near the Ac3 line. Generally, it appears after welding, also known as crystallization crack. The two cracks mainly occur at the grain boundary, and the oxidation color is lost on the crack surface
Metallic luster
.
(2) Cold crack: refers to the cold to the end of welding
Martensitic transformation
The cracks generated below the temperature M3 point generally appear after a period of time (a few hours, a few days or even longer), so it is also called delayed cracks.
According to the cause of the crack, the crack can be divided into: (1) reheat crack: the crack generated when the joint is cooled and reheated to 500~700℃. Reheat cracks occur in precipitation-strengthened materials (such as metals containing Cr, Mo, V, Ti, Nb)
Welding heat affected zone
The inner coarse-grained zone generally develops from the fusion line to the coarse-grained zone of the heat affected zone, showing the characteristics of intergranular cracking.
(3) Layer tearing is mainly due to the fact that during the rolling process of steel, impurities such as sulfide (MnS) and silicates are sandwiczed in it, forming anisotropy. Under the use of welding stress or external restraint stress, the metal cracks along the rolling direction of debris.
(4)
Stress corrosion cracking
: Cracks caused by the combined action of stress and corrosive media. In addition to the residual stress or restraint stress, the stress corrosion crack is mainly related to the structure and shape of the weld.
B. The harm of cracks Cracks, especially cold cracks, the harm is catastrophic. In addition to very few pressure vessel accidents in the world are caused by unreasonable design and improper material selection, most of them are caused by cracks
Brittle failure
.
C. Hot crack (crystallization crack)
(1) The formation mechanism of crystal crack hot crack occurs at the end of the weld metal solidification, the sensitive temperature zone is roughly in the high temperature zone near the solid phase line, the most common hot crack is the crystallization crack, the reason is that in the weld metal solidification process, the crystallization segregation of impurities generated by low melting point eutectic enriched in the grain boundary, forming the so-called \" liquid film \", in the specific sensitive temperature zone ( Also known as the brittle temperature zone), its strength is very small, due to the solidification and contraction of the weld is subjected to tensile stress, and eventually cracks form cracks. The most common case of crystallization crack is cracking along the center length of the weld, which is a longitudinal crack, and sometimes it occurs between two columnar crystals inside the weld, which is a transverse crack. Crater crack is another form of common thermal crack.
Hot cracks are cracking along grain boundaries, usually occurring in carbon steel with more impurities, low alloy steel,
Austenitic stainless steel
Such material gas weld
(2) Factors affecting crystallization cracks
The effect of alloying elements and impurities The increase of carbon, sulfur, phosphorus and other impurity elements will expand the sensitive temperature zone and increase the opportunity for crystallization cracks.
b. The effect of cooling speed the cooling speed increases, one is to increase the crystallization segregation, the other is to increase the crystallization temperature interval, both will increase the chance of crystallization cracks;
c. The influence of crystallization stress and restraint stress in the brittle temperature zone, the strength of the metal is very low, and the welding stress makes the flying part of the metal strained, when the tensile stress reaches a certain degree, there will be crystallization cracks.
(3) Measures to prevent crystallization cracks a. Reduce the content of harmful elements such as sulfur and phosphorus, and weld with materials with lower carbon content. b. Add certain alloying elements to reduce columnar crystals and segregation. Such as aluminum, sharp, iron, mirror can be refined grains. c. The weld with shallow penetration depth is used to improve the heat dissipation conditions so that the low-melting point material floats on the surface of the weld and does not exist in the weld. d. Reasonable selection of welding specifications, and the use of preheating and post-heating, reduce the cooling speed. e. Adopt reasonable assembly order to reduce welding stress.
D. Reheat crack
(1) Characteristics of reheat cracks
a. The reheat crack occurs in
Welding heat affected zone
The superheated coarse crystal region. Produced in the process of reheating such as post-welding heat treatment.
b. The generation temperature of reheat crack: carbon steel and alloy steel 550~650℃
Austenitic stainless steel
About 300℃
c. The reheat crack is grain boundary cracking (intergranular cracking).
d. most easily produced in precipitation-strengthened steel grades.
(2) Generation mechanism of reheat crack
a. There are many explanations for the mechanism of reheat cracking, among which the model cracking theory is as follows: Under the action of high temperature thermal cycling, the reinforced phase carbide (such as iron carbide, carbonization starvation, carbonization mirror, carbonization dislocation, etc.) is deposited on the dislocation zone in the crystal, so that the strength of the in-grain strengthening is much higher than that of the grain boundary strengthening, especially when the reinforced phase is dispersed in the grain. Hindering the local adjustment within the grain will hinder the overall deformation of the grain, so that the plastic deformation caused by stress relaxation is mainly borne by the grain boundary metal, so that the grain boundary stress concentration will produce cracks, the so-called mold cracking.
(3) Prevention of reheat cracks a. Pay attention to the strengthening effect of metallurgical elements and their impact on reheat cracks. b. Reasonable preheating or post-heating to control the cooling speed. c. Reduce residual stress to avoid stress concentration. d. When tempering, try to avoid the sensitive temperature zone of reheat crack or shorten the residence time in this temperature zone.
E. cold crack.
(1) The characteristics of cold crack A. it occurs at a lower temperature and after a period of time after welding, so it is also called delayed crack. b. Mainly produced in the heat affected zone, but also in the weld zone. c. Cold cracking may occur in intergranular cracking, transgranular cracking or a mixture of both. d. The damage caused by cold crack is a typical brittle fracture.
(2) Mechanism of cold crack generation a. Hardening structure (martensite) reduces the plastic reserve of the metal. b. The weld is strained by the residual stress of the joint. c. There is a certain amount of hydrogen in the joint.
Hydrogen content and tensile stress are cold cracks (here refers to
Hydrogen induced cracking
Two important factors arise. In general, the arrangement of atoms inside a metal is not completely ordered, but there are many microscopic defects. Under the action of tensile stress, hydrogen diffuses and accumulates towards the high stress area (defect site). When hydrogen accumulates to a certain concentration, it breaks the bonding bonds of atoms in the metal, and some microscopic cracks appear in the metal. The stress continues to act, the hydrogen continues to accumulate, and the microscopic cracks continue to expand, leading to the development of macroscopic cracks, and finally fracture. To determine whether a cold crack occurs, there is a critical hydrogen content and a critical stress value o when the concentration of hydrogen in the joint is less than the critical hydrogen content, or the stress is less than the critical stress, there will be no cold crack (that is, the delay time is infinite). Of all the cracks, cold cracks are the most harmful.
(3) Measures to prevent cold cracks a. Use low hydrogen type
Basic electrode
Strictly dried, stored at 100~150 ° C, ready to use. b. Increase the preheating temperature, adopt post-heating measures, and ensure that the interlayer temperature is not less than the preheating temperature, select a reasonable welding specification, to avoid the appearance of hard tissue c in the weld. Choose a reasonable welding sequence to reduce welding deformation and welding stress d. Timely hydrogen heat treatment after welding.
4, not welded through not welded through refers to the base metal is not melted, the weld metal does not enter the joint root phenomenon.
A, the cause of non-penetration (1) welding current is small, shallow melting. (2) The groove and gap size are unreasonable, and the blunt edge is too large. (3) magnetic bias effect. (4) The electrode deflection is too large (5) The layer and welding root cleaning is poor.
One of the hazards of non-penetration is to reduce the effective cross-sectional area of the weld and reduce the strength of the joint. Secondly, the damage caused by stress concentration caused by welding penetration is much greater than the harm caused by strength reduction. Lack of penetration seriously reduces the fatigue strength of the weld. Incomplete penetration may be the source of crack, which is an important cause of weld failure. The harm caused by stress concentration caused by non-penetration is much greater than the harm caused by strength reduction. Lack of penetration seriously reduces the fatigue strength of the weld. Incomplete penetration may be the source of crack, which is an important cause of weld failure.
C, non-penetration prevention Using a large current to weld is the basic method to prevent non-penetration. In addition, when welding fillet welds,1 use AC instead of DC to prevent magnetic bias, rationally design the groove and strengthen cleaning, and use short arc welding and other measures can also effectively prevent the occurrence of non-penetration.
5. Non-fusion Non-fusion refers to the defect that the weld metal and the base metal, or the weld metal are not fused together. According to its location, the non-fusion can be divided into three types: groove non-fusion, interlayer non-fusion root non-fusion.
A. Causes of non-fusion defects (1) welding current is too small; (2) Welding speed is too fast; (3) The Angle of the electrode is wrong; (4) the phenomenon of arc bias blowing occurs; Wang,(5) the welding is in the downhill welding position, and the base metal has been covered by hot metal when it is not melted; (6) There is dirt or oxide on the surface of the base metal that affects the melting combination between the deposited metal and the base metal.
Failure to fuse is an area type defect, failure to fuse groove and root failure to fuse the bearing cross-sectional area is very obvious reduction, stress concentration is also more serious, its harm is second only to cracks.
C. To prevent the use of large welding current for non-fusion, correctly perform welding operations, and pay attention to the cleanliness of the groove.
6. Other defects
(1) The chemical composition or tissue composition of the weld does not meet the requirements: the welding material and the base material are not matched properly, or the elements are burned during the welding process, which is easy to change the chemical composition of the weld metal, or cause the weld tissue to fail to meet the requirements. This may lead to a decrease in the mechanical properties of the weld, and also affect the corrosion resistance of the joint.
(2) overheating and overburning: if the welding specification is used improperly, the heat affected zone will stay at high temperature for a long time, which will make the grains coarse, that is, the superheated structure. If the temperature is further increased and the residence time is longer, oxidation or local melting of grain boundaries may occur, and overburned tissue may appear. Superheat can be eliminated by heat treatment, while overburning is an irreversible defect.
(3) White spots: The fish-like white spots that appear on the tensile surface of the weld metal, that is, the white spots from the point F are caused by hydrogen accumulation, which is extremely harmful.
Rough appearance quality,
Fish scale wave
Sudden changes in height, width and narrowness; Non-smooth transition between weld and base material.
Main reasons: improper operation, repair caused.
Hazard: Stress concentration, weakened load carrying capacity.
The main reason: improper operation of the construction worker
Hazard: the size is small, the bearing section is small; The larger size weakens some of the dynamic load bearing structures
Fatigue strength
.
The welding parameters are not selected correctly, U and I are too large, and the welding speed is too slow.
⒉ The arc is stretched too long. The molten metal cannot fill the melting gap in time.
Hazard: The working section of the base metal is reduced, and the stress is concentrated at the biting edge.
A low-lying section formed at the end of the bead due to improper arc closing and breaking.
Reason: The residence time of the welding wire or electrode is short, and the filling metal is not enough.
Harm: reduce the cross-sectional area of the weld;
⒉ Inadequate reaction at the arc pit is easy to occur
segregation
Or impurities gather, so there are often pores, ash, cracks and so on in the arc pit.
Reason: A. The welding current is too large;
The groove joint clearance is too large;
The welding speed is slow, and the arc residence time is long.
Hazard: Poor surface quality
The burned through the following often porosity, slag, pits and other deficiencies.
Prevention and control points: the root weld should not be too thin, with a thickness of 3 mm, the root welding process parameters should not be too large; Stop welding immediately after burning through, and grind out the groove Angle and root gap. Then re-root welding, hot welding until the completion of this process
[2]
.
Molten metal
A partial failure to fuse that flows onto an unmelted base material outside the weld.
Reason: improper selection of welding parameters; The groove cleaning is not clean, and the arc heat loss on the oxide skin makes the base material not melt.
Harm: the surface is welded nodules below are often not fused, not welded through; The change of weld geometry, stress concentration and internal welding nodule reduce the cross-sectional area of the pipe medium.
Reason: The arc protection is not good, the arc is too long.
⒉ The welding rod or flux is damp and the gas protective medium is not pure.
The groove is not clean.
Harm: from the surface is to reduce the working section of the weld; What is more dangerous is that it is superimposed with other defects to cause penetrating defects and destroy the density of the weld. The continuous porosity is one of the causes of structural failure.
Prevention and control points: before welding, check the gas path (including pressure reduction table, heater, flow meter, conduit, etc.) to ensure the purity of the gas; In the welding process, it is necessary to choose the appropriate arc voltage and wire feed speed. Maintain a certain length of wire extension. Control the appropriate welding speed for vertical downward welding.
Welding slag remains in the weld. It is easy to produce non-smooth transition between the edge of the groove and each layer of weld passage, the shape of the weld passage changes, and the part with deep groove is also easy to produce slag inclusion.
Reason: The temperature of the molten pool is low (the current is small),
Liquid metal
The viscosity is large, the welding speed is large, and the slag can not emerge before solidification.
Improper handling and unclear moisture of slag and iron;
The groove shape is irregular, and the groove is too narrow, which is not conducive to the floating of slag;
Multilayer welding slag cleaning is not clean.
Harm: more serious than pores, because of its geometric shape irregular sharp corners, edges and corners have a cutting effect on the body, stress concentration is the origin of cracks.
Formed when the penetration depth of the weld is less than the thickness of the plate. In single-side welding, the weld penetration can not reach the bottom of the steel plate; In double-sided welding, the sum of the depth of the two welds is less than the thickness of the steel plate.
Reason: The Angle of the bevel is small, the gap is small, and the blunt edge is too large;
The current is small, the speed is too fast to melt;
The weld rod deviates from the center of the weld bead.
Harm: The working area is reduced, the sharp Angle is easy to produce stress concentration, causing cracks.
Prevention and control points: carefully grinding and matching welds before welding to ensure that the welding wire or electrode can extend smoothly into the root of the groove during root welding; When the root welding can not appear holes, grinding out the root gap and appropriate adjustment of welding parameters. The root non-fusion defect is relatively difficult to repair, especially for some large thick wall welding passes, grinding and welding are very difficult, so it should be avoided as far as possible.
The part that is not fully fused between the bead and the base material or between the bead and the bead in fusion welding.
Reason: small current, fast speed, insufficient heat;
The groove or weld has oxide skin, slag, etc., a part of the heat is lost in melting debris, and the remaining heat is not enough to melt the groove or weld metal.
The swing Angle of the electrode or wire deviates from the normal position, and the molten metal flows to cover the unmelted part of the weak arc, which is easy to produce non-fusion.
Hazard: Because the gap is small, it can be regarded as
Lamellar flaw
Owe, similar to crack. It is easy to cause stress concentration, which is a dangerous defect.
One of the most harmful welding defects
Under the joint action of welding stress and other embrittleness factors, the atomic bond of the material is destroyed, and the gap generated by the formation of a new interface is called a crack. It has the characteristics of sharp notch and large aspect ratio, easy to cause high stress concentration, and has the tendency to extend and expand, so it is the most dangerous defect.
Prevention and treatment points: ① avoid strong group pairs; ② Preheat before welding, moderately increase the thickness of the root welding bead, and immediately after the completion of the root welding, filling and covering; (3) Welding in winter, but also pay attention to the slow cooling of the weld bead after welding, in order to diffuse hydrogen escape.
According to ISO 5817:2003, welds are divided into three grades B, C and D according to weld defects
The following table shows the standards and ranges of defect values for various grades:
|
.
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t
mm
|
Limit values for allowable deficiencies in different rating groups
|
|||||||
|
D
|
C
|
B
|
||||||||||
|
1
Surface defect
|
||||||||||||
|
1.1
|
100
|
crack
|
-
|
Acuity 0, 5
|
Not allow
|
Not allow
|
Not allow
|
|||||
|
1.2
|
104
|
Crater crack
|
-
|
Acuity 0, 5
|
Not allow
|
Not allow
|
Not allow
|
|||||
|
1.3
|
2017
|
Surface porosity
|
Maximum size of individual stomata
- Symmetrical weld
- Fillet weld
|
0,5 to 3
|
d≤
0, 3
s d
0 or less,
a
|
Not allow
|
Not allow
|
|||||
|
Maximum size of individual stomata
- Symmetrical weld
- Fillet weld
|
> 3
|
d≤
0, 3
s
, a Max. 3 mm
d≤
0, 3
a
, Max. 3mm
|
d≤0,2s, maximum.2mm d≤0,2a, maximum.2mm
|
Not allow
|
||||||||
|
1.4
|
2025
|
Open crater
|
0,5 to 3
|
h
≤ 0,2
t
|
Not allow
|
Not allow
|
||||||
|
> 3
|
h
≤ 0,2
t
, Max. 2 mm
|
h
≤ 0,1
t
, Max. 1 mm
|
Not allow
|
|||||||||
|
1.5
|
401
|
Lack of fusion
Not fully fused
|
-
|
≥ 0,5
|
Not allow
|
Not allow
|
Not allow
|
|||||
|
permit
|
permit
|
permit
|
||||||||||
|
Microscopic failure to fuse
|
||||||||||||
|
1.6
|
4021
|
Insufficient root penetration
|
For single-side butt welds only
|
≥ 0,5
|
Shortage owed:
h
≤ 0,2
t
, Max. 2 mm
|
Not allow
|
Not allow
|
|||||
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
1.7
|
5011
5012
|
Cover bite edge
|
The transition should be smooth, not in clusters
|
0,5 to 3
|
Shortage owed:
h
≤ 0,2
t
|
Shortage owed:
h
0, 1 or less
t
|
Not allow
|
|
> 3
|
h
≤ 0,2
t
, Max
1mm
|
h
0, 1 or less
t
, Max
The 0.5 mm
|
h
0 or less, 05
t
, Max. 0,5mm
|
||||
|
1.8
|
5013
|
Root edge
|
Make the transition smooth
|
0,5 to 3
|
h
≤ 0,2 mm + 0,1
t
|
Shortage owed:
h
≤ 0,1
t
|
Not allow
|
|
> 3
|
Shortage owed:
h
≤ 0,2
t
, Max. 2 mm
|
Shortage owed:
h
≤ 0,1
t
, Max. 1 mm
|
Shortage owed:
h
≤ 0,05
t
, Max.0,5 mm
|
||||
|
1.9
|
502
|
Excessive excess height
(Butt weld)
|
Make the transition smooth
|
Acuity 0, 5
|
h ≤1 mm + 0,25 b,
Max. 10mm
|
h
≤ 1 mm + 0,15
b
,
Max. 7mm
|
h
≤1 mm + 0,1
b
,
Max. 5mm
|
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
1.10
|
503
|
The cover is too high
(fillet weld)
|
Acuity 0, 5
|
h
≤ 1 mm + 0,25
b
,
Max. 5mm
|
h
≤ 1 mm + 0,15
b
,
Max. 4mm
|
h
≤1 mm + 0,1
b
,
Max. 3mm
|
|
|
1.11
|
504
|
The root height is too high
|
0,5 to 3
|
h
≤ 1 mm + 0,6
b
,
|
h
≤ 1 mm + 0,3
b
,
|
h
≤ 1 mm + 0,1
b
,
|
|
|
> 3
|
h
≤ 1 mm + 1,0
b
Max. 5mm
|
h
≥ 1 mm + 0,6
b
, Max. 4mm
|
h
≤ 1 mm + 0,2
b
, Max. 3mm
|
||||
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
1.12
|
505
|
The weld transition is too steep
|
- Butt weld
|
≥ 0,5
|
α ≥ 90°
|
α ≥ 110°
|
α ≥ 150°
|
|
- Fillet weld
|
≥ 0,5
|
α ≥ 90°
|
α ≥ 100°
|
α ≥ 110°
|
|||
|
1.13
|
506
|
Weld metal spill
|
≥ 0,5
|
Shortage owed:
h
≤ 0,2
b
|
Not allow
|
Not allow
|
|
|
1.14
|
509
511
|
Cover depression
Underfilling of root
|
Make the transition smooth
|
0,5 to 3
|
Shortage owed:
h
≤ 0,25
t
|
Shortage owed:
h
≤ 0,1
t
|
Not allow
|
|
> 3
|
Shortage owed:
h
≤ 0,25
t
Max
2mm
|
Shortage owed:
h
≤ 0,1
t
Max
1mm
|
Shortage owed:
h
≤ 0,05
t
Max
0
,
5mm
|
||||
|
1.15
|
510
|
burn-through
|
-
|
≥ 0,5
|
Not allow
|
Not allow
|
Not allow
|
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
1.16
|
512
|
Excess fillet weld
dissymmetry
(Welding Angle excessive unequal length)
|
When symmetrical fillet welds are required
|
≥ 0,5
|
h
≤ 2 mm + 0,2α
|
h
≤ 2 mm + 0,15α
|
h
≤ 1,5 mm + 0,15α,
|
|
1.17
|
515
|
Root depression
|
Make the transition smooth
|
0,5 to 3
|
h
≤ 0,2 mm + 0,1
t
|
Shortage owed:
h
≤ 0,1
t
|
Not allow
|
|
> 3
|
Shortage owed:
h
≤ 0,2
t
Max
2mm
|
Shortage owed:
h
≤ 0,1
t
Max
1mm
|
Shortage owed:
h
≤ 0,05
t
Max
0, 5 mm
|
||||
|
1.18
|
516
|
Root diffuse porosity
|
Bubbles in the weld form at the root during crystallization
A spongy distribution of pores (e.g., when the roots lack gas protection)
|
≥ 0,5
|
Local permit
|
Not allow
|
Not allow
|
|
1.19
|
517
|
Joint defect
|
-
|
≥ 0,5
|
defect
The limit value depends on the type of defect that occurs at the reignition location
|
Not allow
|
Not allow
|
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
1.20
|
5213
|
Fillet weld thickness
Too small
|
Not suitable for processes requiring greater penetration
|
0,5 to 3
|
Shortage owed:
h
≤ 0,2 mm + 0,1α
|
Shortage owed:
h
≤ 0,2 mm
|
Not allow
|
|
> 3
|
Shortage owed:
h
≤ 0,3 mm + 0,1α, Max
2mm
|
Shortage owed:
h
≤ 0,3 mm + 0,1α maximum
1mm
|
Not allow
|
||||
|
1.21
|
5214
|
Fillet weld thickness
oversize
|
The actual thickness of fillet weld is too large
|
≥ 0,5
|
permit
|
h
≤ 1 mm + 0,2α Max
4mm
|
h
≤ 1 mm + 0,15α
Max
3mm
|
|
1.22
|
601
|
Striking point
|
-
|
≥ 0,5
|
Allowed, when does not affect the properties of the base material
|
Not allow
|
Not allow
|
|
1.23
|
602
|
Weld splash
|
-
|
≥ 0,5
|
Whether it is allowed depends on the actual application, how the material is used, whether there are corrosion protection requirements, etc.
|
||
|
2
Internal deficiency
|
|||||||
|
2.1
|
100
|
crack
|
Other than microscopic cracks and crater cracks
All kinds of cracks
|
≥ 0,5
|
Not allow
|
Not allow
|
Not allow
|
|
2.2
|
1001
|
microcrack
|
It is usually found in microscopic crack metallography
Crack (50 χ2)
|
≥ 0,5
|
permit
|
Whether it is allowed or not depends on the type of base material, and mainly on the aggregation of cracks
|
|
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
2.3
|
2011
2022
|
Air hole
Diffuse porosity
(uniform distribution)
|
The following conditions and deficiency limits must be met:
See Appendix B a1) Maximum area of deficiency as a percentage of the projector area (including cluster deficiency) Note: The dispersion porosity in the projector surface depends
Number of layers (weld volume)
|
≥ 0,5
|
Single layer: ≤ 2, 5%
Multilayer: ≤ 5%
|
Single layer: ≤ 1, 5%
Multilayer: ≤ 3%
|
Single layer: ≤ 1%
Multilayer: ≤ 2%
|
|
a2) The maximum area of the section missing
(including clustered defects) as a percentage of the fracture surface area (only used in the production field involving welder examination and process evaluation)
b) Maximum size of individual stomata
- Butt weld
- Fillet weld
|
≥ 0,5
|
≤ 2,5
|
≤ 1,5 %
|
≤ 1%
|
|||
|
≥ 0,5
|
d
≤ 0,4
s
, Max. 5 mm
d
≤ 0,4
a
, Max. 5 mm
|
d
≤ 0,3
s
, Max. 4 mm
d
≤ 0,3
a
, Max. 4 mm
|
d
≤ 0,2
s
, Max. 3 mm
d
≤ 0,2
a
, Max. 3
mm
|
||||
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
unscramble
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
2.4
|
2013
|
Dense porosity
|
condition
1
(
D
>
d
A2)
condition
2
(
D
<
d
A2=
The sum of the areas of each stomata group
(
A
1 +
A
2 +...) with
Rating area
l
p ×
w
p Compare (case 1) base length
l
p is 100mm when D is less than
d
A1 OR
d
A2, the smallest one between the two, draws a pack of lines will
A
1 +
A
2 Envelope goes in as a deficiency area (case 2)
|
||||
|
a)
The maximum total area of pores in the projection plane is missing
Percentage of size (including clusters of defects)
b)
The maximum size of a single stoma
- Butt weld
- Fillet weld
|
≥ 0,5
≥ 0,5
|
≤ 16%
d
≤ 0,4
s
, Max. 4 mm
d
≤ 0,4
a
, Max. 4 mm
|
≤ 8%
d
≤ 0,3
s
, Max. 3 mm
d
≤ 0,3
a
, Max. 3mm
|
≤ 4%
d
≤ 0,2
s
, Max. 2 mm
d
≤ 0,2
a
, Max. 2 mm
|
|||
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
2.5
|
2014
|
Chain porosity
|
Case 1 (D>
d
2)
Case 2 (D <
d
2)
The sum of the areas of each hole accounts for the area of the evaluation zone
l
p ×
w
Percentage of p (Case 1) Two pores when D is less than the minimum diameter of adjacent pores
The area of the envelope as the missing area (case 2)
|
Single layer: ≤ 4%
Multilayer: ≤ 8%
|
|||
|
The limit values for deficiencies shown below must be met; See Appendix B
a1) The maximum size of the surface defect (including the cluster defect) as a percentage of the projector surface
Note: The diffusion pores in the projection surface depend on the number of welding layers
(weld volume)
a2) Maximum area of pores (including clusters of defects) on the undercross section as a percentage of the fracture surface area (only applied when the production area involves welder exams and process evaluation
|
≥ 0,5
|
Single layer: ≤ 8%
Multilayer: ≤ 16%
|
Single layer: ≤ 4%
Multilayer: ≤ 8%
|
Single layer: ≤ 2%
Multilayer: ≤ 4%
|
|||
|
≥ 0,5
|
≤ 8%
|
≤ 4%
|
≤ 2%
|
||||
|
b) Maximum size of individual stomata
- Butt weld
- Fillet weld
|
≥ 0,5
|
d
≤ 0,4
s
, Max. 4 mm
d
≤ 0,4
a
, Max. 4 mm
|
d
≤ 0,3
s
, Max. 3 mm
d
≤ 0,3
a
, Max. 3mm
|
d
≤ 0,2
s
, Max. 2 mm
d
≤ 0,2
a
, Max. 2 mm
|
|||
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
2.6
|
2015
2016
|
Strip porosity
Electric stomata
|
- Butt weld
|
≥ 0,5
|
h
≤ 0,4
s
, Max. 4 mm
l
Or less
s
, maximum 75mm
|
h
≤ 0,3
s
, Max. 3 mm
l
Or less
s
Max. 50mm
|
h
≤ 0,2
s
, Max. 2 mm
l
Or less
s
, Max. 25mm
|
|
- Fillet weld
|
≥ 0,5
|
h
≤ 0,4
a
, Max. 4 mm
l
Or less
a
, maximum 75mm
|
h
≤ 0,3
a
, Max. 3mm
l
Or less
a
But the maximum is 50mm
|
h
≤ 0,2
a
, Max. 2 mm
l
Or less
a
, Max. 25mm
|
|||
|
2.7
|
202
|
Shrinkage cavity
|
-
|
≥ 0,5
|
Allow shortages and debts,
But not allowed to the surface
- Butt weld
h
Delta 0,4
s
, Max. 4 mm
- Fillet weld
h
Delta 0,4
a
, Max. 4 mm
|
Not allow
|
Not allow
|
|
2.8
|
2024
|
Arc pit shrinkage hole
|
Measure the larger of the h or l dimensions
|
0,5 to 3
> 3
|
h/l
Delta 0,2
t
h/l
Delta 0,2
t
, Max
2
mm
|
Not allow
|
Not allow
|
|
2.9
|
300
301
302
303
|
Solid inclusion,
Slag inclusion, flow medium inclusion, oxide inclusion
|
- Butt weld
|
≥ 0,5
|
h
≤ 0,4
s
, Max. 4 mm
l
Or less
s
, maximum 75mm
|
h
≤ 0,3
s
, Max.3 mm
l
Or less
s
Max. 50mm
|
h
≤ 0,2
s
, Max. 2 mm
l
Or less
s
, Max. 25mm
|
|
- Fillet weld
|
≥ 0,5
|
h
≤ 0,4
s
, Max. 4 mm
l
Or less
a
, maximum 75mm
|
h
≤ 0,3
s
, Max. 3mm
l
Or less
a
Max. 50mm
|
h
≤ 0,2
a
, Max. 2 mm
l
Or less
a
, Max. 25mm
|
|||
|
2.10
|
304
|
Other than copper
Metal inclusion
|
- Butt weld
|
≥ 0,5
|
h
≤ 0,4
a
, Max. 4 mm
|
h
≤ 0,3
a
, Max. 3mm
|
h
≤ 0,2
a
, Max. 2 mm
|
|
2.11
|
3042
|
Copper insert
|
- Fillet weld
|
≥ 0,5
|
Not allow
|
Not allow
|
Not allow
|
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
2.12
|
401
4011
4012
4013
|
Lack of fusion
(not fully fused) Groove not fused between layers not fused at the root
|
≥ 0,5
|
Shortage is allowed, but not to the surface
- Butt weld
h
≤ 0,4
s
, Max. 4 mm
- Fillet weld
h
≤ 0,4
a
, Max. 4 mm
|
Not allow
|
Not allow
|
|
|
2.13
|
402
|
Lack of penetration
|
T-joint (fillet weld)
|
> 0, 5
|
Shortage owed:
h
≤ 0,2
a
, Max. 2 mm
|
Not allow
|
Not allow
|
|
T-joint (not fully welded)
Butt joint (not fully welded)
|
≥ 0,5
|
Shortage owed:
- Butt weld
h
≤ 0,2
s
, Max. 2 mm
- T-type connector
h
≤ 0,2
a
, Max. 2mm
|
Shortage owed:
- Butt weld
h
≤ 0,1
s
, Max. 1,5 mm
- Fillet weld
h
≤ 0,1
a
, Max. 1,5 mm
|
Not allow
|
|||
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
2.13
|
402
|
Lack of penetration
|
Butt joint (fully welded)
|
≥ 0,5
|
Shortage owed:
h
≤ 0,2
t
, Max. 2 mm
|
Not allow
|
Not allow
|
|
3.
The geometry of the weld is deficient
|
|||||||
|
3.1
|
507
|
misalignment
|
The limit value of the deviation is based on the position where there is no defect. If not
Specify other values where the center lines match and only reflect the position without a deficiency (see section 1). T is for smaller thickness. Wrong edges in the given limit values are not treated as clusters (see Figures A and B)
Figure A: Longitudinal seam of the plate
|
0,5 to 3
|
h
Delta 0,2 mm+ 0,25
t
|
h
Delta 0,2 mm + 0,15
t
|
h
Delta 0,2 mm + 0,1
t
|
|
> 3
|
h
≤ 0,25
t
, Max. 5 mm
|
h
≤ 0,15
t
, Max. 4 mm
|
h
≤ 0,1
t
, Max. 3 mm
|
||||
|
Figure B: Ring gap
|
≥ 0,5
|
h
≤ 0,5
t
, Max. 4 mm
|
h
≤ 0,5
t
, Max. 3 mm
|
h
≤ 0,5
t
, Max. 2 mm
|
|||
|
ID
|
On the basis of
ISO 6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
3.2
|
508
|
Angular deformation
|
≥ 0,5
|
β ≤ 4°
|
β ≤ 2°
|
β ≤ 1°
|
|
|
3.3
|
617
|
Fillet weld
|
The limitations in section 5 relate to the cluster deficiency discomfort
us
|
0,5 to 3
|
h
≤ 0,5 mm + 0,1
a
|
h
≤ 0,3 mm + 0,1
a
|
h
≤ 0,2 mm + 0,1
a
|
|
> 3
|
h
≤ 1 mm + 0,3
a
Max
4mm
|
h
≤ 0,5 mm + 0,2
a
Max. 3mm
|
h
≤ 0,5 mm + 0,1
a
Max. 2mm
|
||||
|
4
Multiple deficiency
|
|||||||
|
4.1
|
There is no
|
In any cross-section
A cross section with multiple deficiencies at the most unfavorable weld
(Macroscopic metallography)
|
0,5 to 3
> 3
|
Not allow
The maximum value Σ of the total height is missing
h
≤ 0,4
t
Or ≤ 0,25
a
|
Not allow
The maximum value Σ of the total height is missing
h
≤ 0,3
t
Or ≤0,2
a
|
Not allow
The maximum value Σ of the total height is missing
h
0 or less,
t
Or ≤0,15
a
|
|
|
Refer to appendix
A
|
|||||||
|
ID
|
On the basis of
ISO
6520-1
ID
|
Missing name
|
explain
|
t mm
|
Limit values for allowable deficiencies in different rating groups
|
||
|
D
|
C
|
B
|
|||||
|
4.2
|
There is no
|
Projecting plane
Or a longitudinal cross-section
|
Case 1 (
D
>
l
3)
Case 2 (
D
<
l
3)
Sum of surface areas
h l
Occupies the area of the evaluation area
l
p×
w
Percentage of p (Case 1)
When D is the minimum length of the adjacent defect, join the two defects into one defect (case 2)
Note: See Appendix B
|
≥ 0,5
|
Σ
h
x
l
≤ 16%
|
Σ
h
x
l
≤ 8%
|
Σ
h
x
l
≤ 4%
|
