ESAB TRAINING & EDUCATION

Welding procedures

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Welding proceduresContent

Welding procedures ............................................... 3The welder’s working instructions ........................ 4Alloys in steel .......................................................... 5Heat affected zone, HAZ ....................................... 7Tempering (C-Mn steel) ......................................... 8High-alloy steel ....................................................... 9Corrosion, cracking, fractures, wear, scaling, creep and welding defects ............ 10Types of corrosion ................................................ 10Cracking ................................................................ 10

The mechanical properties of a weld joint are determined by the composition of the parent metal, the characteristics of the consumable, the welding parameters and the welder’s skill. A welding procedure describes how a correct weld joint should be performed. Less complex welds that are subjected to small loads seldom require compli-cated procedures, but factors that affect the welding result must always be taken into account. Load- and pressure-bearing structures always represent a danger to life and property in the event of accidents and production of this kind is therefore always governed by detailed rules and regula-tions. These rules and regulations are based on standards and norms that govern quality and traceability. Traceability in order to resolve questions relating to responsibil-ity in the event of an accident and thereby find the cause in order to prevent the same mistakes being made in the future.

Welding is always a risk factor and is therefore strictly governed by a specific welding standard where a professional procedure ensures the desired quality. A professional procedure is based on an ap-proved sample taken from a weld joint of the same type as the one that is going to be used in production. This sample shows the mechanical properties of the weld joint and the heat affected zone – or, to put it another way, the tensile strength and ductility. The testing is destructive and can therefore not be performed on the struc-ture. The available information about the welding procedure constitutes the welder’s working instructions and compliance with these instructions is monitored by a third party. This third party is usually a classi-fication society which is independent of both the producer and customer and safe-guards the interests of the general public so that products that are socially harmful do not reach the market.

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Iron = Fe, constitutes the basis of steel production

Carbon = C, the most important alloy in steel, it produces strength and hardness

Silicon = Si, a deoxidant, increases strength, reduces expansion

Manganese = Mn, deoxidant, forms austenite, increases the tensile yield limit of steel

Chromium = Cr, forms carbide, increases the heat resistance of steel, improves corrosion resistance, increases strength

Nickel = Ni, forms austenite, increases the impact strength of steel at low temperatures

Molybdenum = Mo, increases the tensile yield limit, improves corro-sion resistance, raises the conventional creep limit

Tungsten = W, forms carbides

Vanadium = V, forms carbides, increases the tensile yield limit

Lead = Pb, improves the machinability of automatic steel, for example, causes pores

Phosphorus = P, contaminant, should be kept at a low level,

reduces impact strength, increases the risk of cracking

Sulphur = S, contaminant, sometimes used to increase machinability, produces sulphides which cause lamellar tearing

Aluminium = Micro-alloy, reduces sulphide dissipation

The instructions in the WPS are based on data from the material producer, the consumable manufacturer and the result of performed tests. In the square entitled ”Company”, the manu-facturer’s name is given. In addition, information relating to the date, the WPS number, the issuer and the standard that is being used, plus refer-ences to the WPAR, should be specified. The other information provides the pre- requisites for the final result. As welding involves relatively uncontrolled heat treatment of the material, some knowledge of the impact weld-

In Sweden, the welder’s working instructions can be translated as ”Welding data sheets”, whilethe English version is called WPS, Welding Pro-

ing heat has on steel and the risks this entails is needed. The following simplified presentation of the science of engineering and building materials provides some basic information and an explana-tion of some terms and expressions. Steel is the name that is given to alloys of iron. The alloy content differs sharply in different steels, depending on the purpose. The German ”Stahlschlussel” lists more than 10,000 steels. Depending on the alloy content, the steel is af-fected differently by temperature changes. This then results in the concept of “weldability”.

The welder’s working instructions

cedure Specification. The appearance of a WPScan vary, but it always contains the following in-formation.

Alloys in steel

The alloys that are used in steel are all elements. A selection of these elements is given below, to-gether with a short description of the effect they have on the properties of steel. In the remainder of this document, the chemical designation and not the trade names will be used.The properties

of steel vary with the alloy content and the dif-ference is so great that the steel has to be put in classes. This then results in the following groups: unalloyed steel, low-alloy steel and high-alloy steel. The characteristics of the unalloyed and low-alloy steels are similar and they are grouped

under the designation of C-Mn steel, carbon-manganese steel, as a result of their most impor-tant alloys. The consumables are divided up in a similar manner, but they are given additional designations, depending on the slag system and welding charac-teristics.

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There is actually no such thing as unalloyed steel, as these steels are in fact alloyed with C, Mn and Si. The term mild steel, which is perhaps a better description of its characteristics, is also sometimes used. A mild steel with alloy contents like those listed above is generally easy to weld, but it could be difficult if the carbon content in-creases to 0.4% or the phosphorus and sulphur exceed 0.040%. Lead is sometimes added to improve chip breaking, in conjunction with ma-chining, so-called free-cutting or automatic steel. This type of steel is unsuitable for welding be-cause of large-scale pore formation. In addition to C, Mn and Si, low-alloy steel contains other alloys up to a total alloy content of 5%. Steel is generally weldable, but its sensitiv-ity increases as the alloy content increases. The total alloy content of high-alloy steel ex-ceeds 5%. In principle, the alloy content can reach a level at which the dominant alloy content exceeds the iron content. It is normally nickel that reaches these high levels and the material is therefore known as nickel basic. The brand names include Inconel. High-alloy steels can be welded, but they are also sensitive to varying degrees to welding heat, but for different reasons than C-Mn steels. To un-derstand the effect of welding heat on the steel, it is necessary to understand how the alloying ele-ments change the material properties. Iron is the basis of steel. In pure form, this metal is useless, as it has no strength or hardness. A small addition of carbon gives it hardness and strength and these characteristics increase as the

CMn steel, exemples of alloy cotent in i %

C Mn Si P S Cr Mo Ni

Unalloyed steel 0.2 1.0 0.5 0.015 0.015

Low-alloy steel 0.2 1.0 0.5 0.015 0.015 2.5 0.5 1.0

High-alloy steel, stainless austenitic, examples of alloy content in

C Mn Si P S Cr Mo Ni

Stainless 308 (2333) 0.03 1.0 0.5 0.015 0.015 18 10

Acid-proof 316 (2343) 0.03 1.0 0.5 0.015 0.015 17 3 12

carbon content rises. The material is brittle and rigid and closely resembles cast iron. A tensile test will reveal a higher value and the difference between the tensile yield limit and ultimate ten-sile strength at the same value. Alloying with manganese makes the steel ductile and it under-goes plastic deformation when subjected to a load. A tensile test will now reveal a higher value and the difference between the tensile yield limit and ultimate tensile strength is striking. Alloying with Si increases the strength still further. The plastic deformation is measured along a length that is five times the diameter of the sample rod and the extension is given in per cent. Typical values are around 30%. The tensile yield limit and ultimate tensile strength can be increased still further by alloying with chromium. A higher alloy content increases the strength, but it also increases the hardness. The hardenability also increases. Steel is manufactured using a rigorously con-trolled method in which the steel is rolled into sheets or profiles in an advanced cooling proce-dure, which produces the required characteris-tics. These characteristics can be lost completely as a result of the heat treatment a welding pro-cess involves, which is so difficult to control. This finished steel is given its characteristics by the alloy content and by rolling. Understand-ing the material properties of steel is a science in itself and cannot be explained in just a few pages. To understand the effect welding heat has on the steel and the benefit of a WPS, a straightforward model of the sequence of events is sufficient.

Heat affected zone, HAZ

Steel consists of grains of metal (reguli) made of iron. In these iron grains, there are alloying elements which are oriented in a certain way, depending on the heat treatment. When steel is produced, an attempt is made to keep the grains

as small as possible. This increases the strength in the same way as when children discover that it is easier to make sand cakes than gravel cakes. The size of the grains is determined by the heat treatment.

During welding, the molten pool reaches a tem-perature of 3,000°C, which is sufficient to heat the parent metal closest to the weld to more than 1,000°C. This area is known as the heat affectedzone. In a low-alloy steel with a low carbon con-tent, which is not subjected to forced cooling,

only the grain size is affected. The grains grow in size and, the longer the steel is kept hot, the lar-ger the grains become. This reduces the strength and, as a result, the heat affected zone is gene-rally the weakest part of the joint.

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The hardenability of steel is determined by the al-loy content, primarily that of carbon. Increasing the carbon content increases hardenability. The reason for this is that the carbon forms hard struc- tures with metals. Iron is the dominant metal in steel, but high strength steel is alloyed with other metals, such as chromium and molybdenum. These metals increase hardenability still further. To make it easy to calculate hardenability, a comparison is made between hardenability depending solely on the carbon content and the corresponding harden-ability depending on other alloying elements. A carbon equivalent is sought:

Ec. Ec = C+Mn + Cr+Mo+V + Ni+Cu

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There are other calculation methods.

A hardened/tempered material is harder, but it loses its ductility at the same time. The tensile strength is not reduced, but the ability of the material to ac-commodate stress and impact is lost. The distance between the tensile yield limit and ultimate tensile strength is reduced. In the hardening model, the material is in position A when it is delivered. The structure is ferritic and the grain size is small. In the B position, the heat affected zone has reached a temperature of 1,000°C. The grains expand as a result of the heat. At this temperature, the structure changes to austenite. From this temperature, the material cools. The hardenability varies, depending on the carbon equivalent. A low carbon equivalent requires fast cooling for hardening to occur. Deliberate hardening is performed in water or oils to accelerate the cooling process. If the carbon equivalent increases, the hardening takes places at a far slower cooling rate. The reason for this is that the structure once again changes, primarily in the 800-270°C temperature range. The new structure is known as martensite – position C. It is hard and brittle. If the material cools slowly, it expands and regains its ferrite structure. Grain enlargement can-not be avoided. The WPS specifies the tensile energy and work-ing temperatures. The tensile energy is an indica-tion of the energy input per mm of weld and is influenced by the current, voltage and advancing

Tempering (C-Mn steel)

speed. These parameters are given in the WPS. The working temperature is the pre-heating temperature and inter-run temperature. In steel with a high car-bon equivalent, longer cooling times are desirable to prevent hardening. The cooling time is extended by pre-heating the material. If the object is large, the joints have time to harden before the next run is performed, in spite of the welding heat that is ap-plied. The temperature should be checked and, if necessary, the joint should be heated before the next run is started. This is the inter-run temperature. The welding heat increases as the current and voltage rise and this extends the cooling time. A slow advancing speed results in more energy per mm of weld and this also extends the cooling time. Unfortunately, slow cooling results in larger grain growth. It is therefore best to strive for a balance between grain growth and the risk of hardening. If hardening takes place in the heat affected zone, it becomes hard and brittle. This alone does not mean that the material will crack, as stress and the additional weakening of the material are required for this to happen. At a later stage, brittleness can lead to fracture. The stress in the material occurs when the weld joint cools. The hot material has a larger volume than the cold material and, when shrinkage begins, this affects the structure of the tensile strength of the weld metal, which is as high as its strength. It is not unusual for it to be far higher than the unaffected parent metal. In unfortunate circumstances, hydrogen can be enclosed in the heat affected zone. These inclusions are microscopic and rounded. In a ferritic material, they press up a space from which the hydrogen eventually diffuses from the sheet metal without causing any real damage. In a martensitic material, this cannot take place and the grain boundaries in-stead crack and the heat. affected zone is weakened by micro-cracks. When shrinkage stress occurs, the material is unable to accommodate the forces and the heat affected zone cracks during welding. This is known as hydrogen cracking. It is easy to recognise, as it always occurs in the heat affected zone and always on only one side of the joint, as the stress is relieved when the crack occurs. Hydrogen is transferred to the heat affected zone via the weld metal. The hydrogen comes from the

air, the consumable, dirt, surface treatment and dew on the parent metal. From the air, it reaches the weld metal because of an insufficient gas shield. From the consumable, it is primarily generated by damp, covered electrodes, but it is also produced by dirt or oxidised solid wire. Dirt on the parent metal always contains hydrogen, so residual cutting oil, corrosion, dust and so on must be removed. Surface treatments, and residual paint in particular, contain hydrocarbons and must be carefully removed. Dew on sheet metal occurs when material is taken direct-ly from cold storage into the workshop where the warmer air has higher relative humidity. The sheet metal should either be skin-dried or it should be al-lowed to lie in the welding shop until it has reached the ambient temperature. The material in a weld joint can be a combination of mild and low-alloyed steel. The consumable is chosen to match the mild steel, as there is no reason to make the joint stronger than the weakest steel. In addition, increased strength results in increased hardness. The procedure, i.e. the working tempera-tures and welding parameters, is determined by the low-alloy steel. It is important that the mild side is pre-heated in the same way as the low-alloy side, as the most important thing is to extend the cool-ing time. This is determined by the cooling effect of the parent metal. When tack welding a crack-sensitive structure, this must be done at a higher working temperature. The tacks may be small, but the material closest to them is hot and is cooled im-mediately by the material around it. If pre-heating is excluded, the tacks and the material closest to them must be ground out before final welding takes place. In these cases, this is specified in the WPS. In exceptional cases, final welding is permitted with-out grinding, if it is performed using SAW.

High-alloy steel

There are an endless number of different high-alloy steels with the most varied characteristics. They are covered in ESAB’s continuation cours-es. A schematic description of the most common austenitic stainless steels now follows. The approximate alloy contents of austenitic stainless steel are given on page 6. Compared with C-Mn steels, the carbon content is extremely low. An austenitic steel has the same structure at all temperatures and hardening through cooling is not possible. The hardness of the material is in-creased by deformation hardening. This is associ-ated with the crystal structure of the material. In simple terms, the resistance of the atomic level increases the more it is displaced. Everyone who has drilled stainless steel will recognise this phe-nomenon. If the tip of the drill is allowed to slip on the surface instead of cutting it immediately, the surface hardens and drilling is impossible. The material recovers its original shape as a result of annealing. Austenite differs markedly from C-Mn steel and this means that another procedure must be chosen. Low tensile energy and low inter-run temperatures are desirable. Austenite is sensitive to hot cracking. To re-duce the risk, the consumable contains a small percentage of ferrite. If the ferrite is kept in the temperature range of 550-950°C, it is transformed to a brittle structure known as sigma phase. So the welding should be performed at a high advanc-ing speed, without weaving, without preheating and with a controlled inter-run temperature of less than 150°C. Austenite on C-Mn steel must be performed in the correct way, otherwise the weld joint will be sensitive to both cracking and cor-rosion. Electrodes intended for C-Mn steel must never be welded to austenite. Stainless electrodes for austenitic steel function more effectively in a mixed joint, but this is not recommended. Some 70% of the weld metal is consumable, while the remaining 30% is parent metal. This means that the weld metal in a mixed joint receives 15% from the C-Mn side. Carbon is a powerful source of austenite formation and it also releases chro-mium. As a result, the desired ferrite content of the weld metal is lost, with hot cracking as a result, and the chromium depletion increases the corro-sion. The consumable should be over-alloyed with chromium.

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Corrosion types

General corrosion. The right amount of oxide provides protection from corrosion. However, if a corrosive medium breaks down the oxide layer, the corrosion continues. If the oxide layer is completely broken down, general corrosion re-sults, producing more or less uniform erosion. Corrosion is accelerated by heat, moisture and chlorides, such as common salt. Here is an example. Steel in inland areas, which is affected by wind and weather, corrodes less than steel in coastal areas, which is exposed to high salt levels. Pitting. The layer of oxide is only broken down at certain points. This is caused by something damaging the oxide layer, such as welding spat-ter from mild and low-alloy steel in stainless or contact with more precious metal. Crevice corrosion. Overlap joints in a corro-sive medium are quickly exposed to crevice cor-rosion. Stationary water containing salt between two sheets of steel, such as old cars, is a good example of this phenomenon. Erosion corrosion. This type of corrosion is caused by high liquid speeds, especially in cop-per alloys. Erosion corrosion does not occur in stainless material. Intergranular corrosion or intercrystalline cor-

rosion. This type of corrosion can occur at high temperatures in stainless steel. What happens is that the grain boundaries corrode, while the ac-tual grains remain intact. The object retains its shape, but its strength disappears. The material can, in fact, become so brittle that it can disinte-grate between the fingers. Stress corrosion can occur in structures sub-jected to static loads which are exposed to partic-ularly corrosive media. The stress may be caused by external loads or integral welding stress. Tanks that are used for storing ammonia or hot salt solutions are particularly sensitive.

Galvanic corrosion. If two metals come into contact with one another, the most precious of them will be protected at the expense of the least precious. Combining stainless with C-Mn steels requires planning. Galvanic corrosion is some-times used to protect steel. This is known as galvanisation. Another way is to equip shipping vessels with zinc sheets which function as sacri-ficial anodes which corrode instead of the steel. In nickel-plated items, the steel will corrode if the nickel coating is damaged.

Cracking

Cracks in a material can occur for many reasons. When it comes to welding, the most common causes are hydrogen cracks, hot cracks, shrink-age cracks, stress cracks, lamellar tears, re-heat-ing cracks and fatigue cracks. Hydrogen cracks are described on pages 8 and 9 and the causes can be summarised in the com-ponents of brittle structure, stress and hydrogen. Hot cracks occur as a result of incorrect run geometry and/or contamination. Aluminium is most sensitive to this phenomenon. Stainless steel is sensitive in unfortunate circumstances and the same thing applies to C-Mn steel on rare occasions. Incorrect run geometry means that the height of the welding run is greater than the breadth. The ratio should not exceed 0.7x b. The principal contaminants are sulphur and phospho-rus, but other impurities from surface treatments and so on can also contribute to the formation. To obtain the correct run geometry, a joint angle that enables good accessibility and creates the poten-tial to produce the correct breadth: height ratio is necessary. In metal thicknesses under 40 mm, the joint in steel should be prepared with a joint an-gle of 60 degrees, while the corresponding angle in aluminium should be 80-90 degrees.

Corrosion, cracking, fractures, wear, scaling, creep and weld defects

The welding heat is transported away from the joint through the parent metal and solidification therefore begins closest to the joint edges. The strongest structures solidify first and push weaker structures ahead of them. As a result, the weakest structures gather in the centre of the upper part of the run, so-called segregation. Contaminants easily cause segregation. When the shrinkage

forces begin to take effect, the segregation is un-able to withstand the load and a crack appears at the centre of the weld. It usually continues to the surface and is easy to see, but in exceptional cases it may be concealed. Hot cracks always occur along and in the centre of the weld, along the entire length of the weld.

If the joint angle and run geometry are incorrect, the segregation is concentrated in the centre of the joint as a result of a dendritic solidification process vertically from the joint. The segregation is unable to accommodate the shrinkage stress. If the joint angle and run geometry are correct, the solidification does not take place vertically from the edge of the joint and the structures are distributed in the welding run. The weld metal dissolves contaminants, the strength of the joint is uniform and the joint is able to accommodate the shrinkage forces. Crater cracks are a variant of hot cracks. If the weld is completed incorrectly, there is less weld metal in the crater than there is in the rest of the run. During solidification, there will

not be enough weld metal, a pipe will form and a crack will occur next to this pipe. Shrinkage cracks always continue to the sur-face, they are shallow and are positioned across the weld. They occur when the weld metal is unable to accommodate the longitudinal shrinkage. Shrink-age cracks are most common in connection with hardfacing, when the brittle material is unable to accommodate shrinkage stress. Lamellar tearing can be confused with hydrogen cracking in fillet welds. The reason is completely different, however. This phenomenon is less com-mon in modern steel, but it may be seen when weld-ing inexpensive grades from low-price countries. Z-steel is a term that is applied to steel which has

Corrosion is the result of a metal reacting with oxygen and oxidising. Corrosion has many forms and can be accelerated for a number of reasons.

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good strength in terms of its thickness. According to the generally accepted world co-ordinates for specifying a position, the roller direction, which has the highest strength, is designated as X. Across the roller direction, which has poorer strength, the designation is Y, while it is Z in the thickness di-rection, which has the lowest strength. In the Z-direction, the strength may decline dramatically as a result of calendered sulphides. If the sheet metal is exposed to a load over a weakness zone of this kind, it will fail. Welding stress may cause these lamellar tears. This can be avoided by grinding away all the damaged material and buttering the joint surfaces with a consumable of relatively low strength which is ductile enough to accommodate the shrinkage stress. Z-steel is micro-alloyed with lantane, for example, so-called sulphide modifica-tion, which means that the sulphides gather to form balls rather than forming extended inclusions. Re-heating cracks occur in the coarse-grain zone in the heat affected zone and on occasion in the weld metal. They are relatively unusual. They do, however, occur more frequently if fully austenitic consumables are used in C-Mn steel and if some old austenite is not ground away when repairing the weld area. Fatigue cracking – sooner or later, structures that are exposed to dynamic stress will crack. If this occurs at an unreasonably early stage, it is

The information in the WPS can be obtained in the following manner:

Company: The company performing the weldingWPS: Specifies the objectDate: Date of printingWPS no: Gives the sequence number of the objectIssued by: Specifies the individualStandard: Specifies the selected standard, such as EN 288-6 (from the customer)Welding method: This is either printed or has a standard designation (from drawings)Shielding gas: This is either printed or has a standard designation (from drawings)Pipe/sheet: This is either printed or has a standard designation (from drawings)Welding position: This is specified with the designation for the standard (from drawings)Weaving: This is specified either in mm or using X number x diameter of core wire(from WPAR)Joint type: This is either printed or has a standard designation (from drawings)Cleaning: This is printed (from WPAR)Root support: This is printed (from WPAR)One-/two-sided: This is printed (from drawings)Chiselling root: This is printed (from WPAR)Tungsten electrode: This is printed (from WPAR) Gas sleeve Ø This is printed (from WPAR)Tack welding: This is printed, length of the tacks and number per metre (from WPAR)Pre-heating: This is printed (from the steel supplier or WPAR) Inter-run temperature: This is printed (from WPAR)Material: When welding different materials in the same joint, they should be num bered 1, 2 and so onDesignation: The brand name or standard of the materialStandard: Standard designation if a brand name is used as a designationGroup: Material grouping according to the SS-EN standard, if it is usedDelivery condition: Sheet steel, pipe or profile. Cold-hot rolling or tempering/hardening may also be specifiedThickness range: Specifies the thickness range approved by the WPS (from standard)Diameter range: Specifies the diameter range approved by the WPS (from standard)Consumable: When several consumables are used in the same joint, they should be called A, B and so onManufacturer: Normally ESABDesignation: The manufacturer’s product nameStandard, class: According to either standard or classification (from drawings or standard)Handling/storage: According to the manufacturer

Welding parameters:

Run no: This specifies the run/s to which the parameters apply (from WPAR)Consumable: The product name is specified here (from WPAR)Diameter: The diameter of the consumable (from WPAR)Method: Printed or according to standardWire feed: Wire-feed speed (from WPAR)Current: The current is specified within a range (from WPAR)Voltage: The arc voltage is specified within a range (from WPAR)Polarity: The polarity is specified as AC or DC+ and DC- respectivelyWelding speed: The weld length per minute or secondGas: The type and gas flow in litres per minuteHeat input: Tensile energy. The result of current x voltage/v x K x 10-3 (kJ/mm) Q = (U x I ) / v x K x 10-3 U = voltage in volt s I = current in amperes V = advancing speed in mm/sec K = thermal efficiency All methods apart from the following have K=0.8: SAW 1.0, TIG, FCW 0.85 and plasma 0.6

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due to some kind of indication of fracture. This can include root defects, slag inclusions, incom-plete penetration or an unfavourable run profile. It is assumed that welders are sufficiently skilled to avoid root defects, slag inclusions and incom-plete penetration. An unfavourable run profile can be attributed to some degree to the choice of con-sumable. A welding procedure can also include the after-treatment of the weld in the form of TIG treatment or steel-ball blasting. TIG treatment pro-duces more uniform transitions and a thin layer of martensite on the surface. Martensite has a larger volume than ferrite and produces compression stress which balances the shrinkage stress to some degree. Steel-ball blasting produces more uniform transitions and produces compression stress which balances the shrinkage stress. TIG treatment or steelball blasting produce a ten-fold increase in joint durability. Scaling. At high temperatures, the steel oxidises and an oxide scale forms. It falls off and a new one forms. Eventually, the material disappears. With al-loys, the scaling temperature can be raised. Certain high-alloy steels are able to withstand 1,100°C. The choice of consumable has a decisive effect on the service life of the structure. Creep. This phenomenon occurs in all materi-als at all temperatures, but it is incredibly slow at room temperature. When the steel is exposed to

temperatures of around 500°C, creep rapidly oc-curs. A steel which is loaded above its tensile yield limit at room temperature will undergo plastic de-formation at that moment and retain its new shape when the force ceases. If this takes place at high temperature, the deformation will continue after the force ceases. This phenomenon is known as creep. The creep temperature can be raised using

alloys. Wear. The causes are corrosion, abrasion and impact, plus every conceivable combination of these factors. The requirements that are set for the welder’s skills and know-how cannot be found directly in the WPS, but the selected standard and welding method provide some indication of the level and scope. The information in the WPS can be obtained in the following manner.

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When a WPS is produced, a tested procedure should be used as the starting point. The sophis-tication of the test depends on the application for which the structure is designed. In the case of less complicated structures, an ocular inspection may be sufficient. If there is a risk of injury in connection with accidents, the scope of the tests should be increased accordingly – everything from non-destructive testing comprising ocular inspections, penetration tests, ultrasonic tests, magnetic powder tests and X-rays to destructive testing of impact and tensile strength or macro-images of the weld cross-section. When samples are welded, no final WPS is available. The person responsible for welding produces should draw up a preliminary WPS (pWPS), which is based on information from the designers, material producers, consumable sup-

pliers, welder and his/her own experience. During welding, unsuitable methods and pa-rameters will be adjusted and documented on a new WPS (WPAR). If the tests comply with the set requirements, this WPAR will form the basis of the WPS that will be used in future produc-tion. You are responsible for welding at AB Elsvets. Draw up a pWPS for a 40 mm V-joint, 60 de-grees, 4 mm gap and 2 mm root face. Position 1F. The material is 15Mo3. One-sided GMAW welding. Fill in the relevant details and put a line in the other boxes. The necessary information is in the electrode handbook. In the test procedure, it is not necessary to refer to any standard, but, if the MNC Handbook 530 is available, it is a good idea to use it.

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ESAB AB

Box 8004, SE-402 77 Göteborg, Sweden

Phone: +46 31 50 90 00. Fax: +46 31 31 50 93 90

info@esab.se www.esab.com

Content

• Welding procedures

• The welder’s working instructions

• Alloys in steel

• Heat affected zone, HAZ

• Tempering (C-Mn steel)

• High-alloy steel

• Corrosion, cracking, fractures, wear, scaling,

creep and welding defects

• Types of corrosion

• Cracking

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