Welding of CrMo steels for power generation and petrochemical ...

Jan Hilkes, Volker GrossWelding CrMo steels for power generationand petrochemical applications - past, present and futureIntroductionCreep and high temperature resistantCrMo steels have been around for a very longtime and have found use with great successfor applications in the petrochemical, andrespectively in the power generation industry.Typical products for these industries areboilers, heaters, heat exchangers, reactors,and hydrocrackers, usually built as heavywall pressure vessels.In a continuous strive for optimizing theeconomics in the various process installationsin these industries, the service pressuresand/or temperatures have increased.This implied that the respective base materialseither had to be made available in heavierthicknesses or they had to be developedto meet higher strength and impact toughnessrequirements. Increased mechanicalproperties will reduce or at least restrict thenecessary wall thickness which generatesan additional economical advantage in production,handling and installation of heavyprocess equipment. An example of a heavyall pressure vessel is a part of a HydroConversion Unit as shown in Figure 1.The basic and classic CrMo steels arealloyed with 0,5%Mo – 1%Cr/0,5%Mo– 2,25%Cr/1%Mo – 5%Cr/1%Mo –9%Cr/1%Mo and 12%Cr/1%Mo. Fromthese steels further development has takenplace by adding elements such as V, W, Ni, Ti,Nb, B and/or N to arrive at the new grades oftoday such as the T/P22V, T/P23, T/P24, T/P91, T/P92 and VM 12-SHC. Many of thesenew grades have been applied successfullyin industry but the development continues.Obviously, development of the weldingconsumables had to and still must follow thedirection of the base materials with the assuranceof meeting the same stringent requirementsfor the process equipment as the basematerials, even more so since the HAZ isusually also considered part of the weld. Extensiveresearch and development has takenplace at Böhler Schweisstechnik in Germanyto arrive at a full consumable range for thenew generation of CrMo(V) steels for whichalso creep data up to 60 000 hours have beencollected. With increasing alloy level the specificwelding procedures have to be adjustedand will call for more precise and strict controlof welding parameters and heat treatment.Fig. 1: Part of Hydro Conversion Unit by ATB, ItalyTechnical Details of a Hydro Conversion UnitBase material: 2,25%Cr-1%MoSizes: thickness: 358 mmlength: 21 mdiameter: 5.3 mtotal weight: 706 tServiceconditions:215.5 bar pressure and max. 454°CWeldingconsumables:SAW: Union S1CrMo2/UV 420TTRSMAW: Phoenix SH Chromo 2 KSJan Hilkes, Volker Gross - Böhler Schweisstechnik Deutschland GmbH, Hamm, GermanyNo. 2/2013 BIULETYN INSTYTUTU SPAWALNICTWA11

Creep resistant CrMo steelsBasic metallurgy for base materialand weldmetal designCreep resistant steels are steels that canresist a certain stress at a specific servicetemperature without exceeding a specifiedamount of elongation. The maximum stressto rupture at a specific temperature after aspecific time, e.g. 600°C and 105 h, is referredto as Creep Rupture Stress. For example,an engineering design criterion for apower plant could require a minimal stressof 100MPa for 105 h at service temperature.The basic idea is that the vessel remains itsoriginal sizes and shape while in service forup to 20 to 30 years. Due to the fact that in theprocesses used within the Power Generationand Petrochemical Industry and the manydifferent service conditions such as pressure,temperature and environment, a widevariety of CrMo creep resistant steels withadditions of V, W, Ti, Nb, B and/or N havebeen developed, while new types are alsostill under development. Due to increasedpressures and temperatures, up to 370 barand 650°C, as for example in componentsfor Ultra-Super-Critical (USC) steam powergeneration plants, CrMo creep resistantbase materials with increased strength arerequired to allow wall thicknesses that arewithin the range of what fabricators canhandle in their facilities. Also for petrochemicalapplications (P22V), sizes nowup to 350mm are no longer an exception.An overview of the international standards,chemical compositions and maximum servicetemperatures of the actual and mostpopular CrMo creep resistant steels is givenin Table 1.Table 1: Overview of the international standards, chemical composition and maximum service temperatureof the actual and most popular CrMo creep resistant steelsCrMo typeINTERNATIONAL STANDARDSASTM & ASME DIN/VdTÜV EN0.5Mo T/P 1 16 Mo 3 8MoB 5-41.25Cr-0.5Mo T/P 11 10 CoMo 5-5 10 CrMo 5-51,00Cr-0.5Mo T/P 12 13 CrMo 4-5 13 CoMo 4-51.25Cr-1MoV - 15 CrMoV 5-10 -T/P 36 15 NiCuMoNb 5 (WB 36) 15 NiCuNb 52.25Cr-1Mo T/P 22 10 CrMo 9-10 10 CrMo 9-102.25Cr-1MoV T/P 22V - -2.25Cr-MoVW T/P 23 HCM 2S 7CrWVMoNb 9-62.25Cr-1MoVTiB T/P 24 7CrMoVTiB 10-10 7CrMoVTiB 10-105Cr-0.5Mo T/P 502 12 CrMo 19-5 -9Cr-1Mo T/P 9 X12 CrMo 9-1 X12 CrMo 9-19Cr-1Mo mod. T/P 91 X10 CrMoVNb 9-1 X10 CrMoVNb 9-19Cr-0.5MoWV T/P 911 X11 CrMoWVNb 9-1-1 X11 CrMoWVNb 9-1-19Cr-0.5MoWV T/P 92 X10 CrWMoNb 9-2 -12Cr-0.25Mo+1.4W1.3Co0.2V-X12 CrCoWVNb 11-2-2(VM 12-SHC) t

Heat treatments for CrMo steels andwelded jointsThe heat treatments for the base materialsare reasonably complex but are requiredto obtain the optimal mechanical properties.Depending on the alloy content a Normalising,Tempering and Annealing treatment atvarious temperatures for several hours witha controlled cooling rate have to be executedaccording strict procedures. The same isvalid for the weldmetal, with increasing alloycontent the Post Weld Heat Treatment(PWHT) for welded joints gets more complicatedas illustrated in Figure 2.When in subsequent PWHT, IntermediateStress Relieving (ISR) or in service, the ultimateheat treatment temperature of the basematerial is exceeded too much and too long,the precipitations can dissolve again whichcauses reduction of the mechanical propertiesof the base material. This implies that,for example, for this reason the maximumtemperature of 760°C for P91 in Figure 2shall not be exceeded. For T/P23 in Figure2, an Intermediate Stress Relieving is indicatedfor constructions with different materialthicknesses. For each application the optimumPWHT shall be determined. Furtherelaboration will follow in the welding chapterof this paper (Table 4).Temper EmbrittlementWhen CrMo base material and the weldmetal is exposed to a temperature range of400-500°C for a very long time there is arisk of Temper Embrittlement. This typeof embrittlement is caused by trace elementsas P, Sb, Sn and As that migrate to thegrain boundaries and can reduce the ductilityin both base material and weldmetal.To which extent this phenomena will occurdepends merely on temperature and time.Fig. 2: Temperature cycle and heat control duringwelding and PWHT of martensitic steel P91, E911 andP92 (above) and ferritic/bainitic steel T/P23 (below).For GTAW joints in

The Bruscato formula, also referred to asthe X-factor, is valid for both weld metal andbase material. For weldmetal the specificationsare becoming more and more stringentwith increasing wall thickness and desirefor additional assurance of the mechanicalproperties. Initially, the required value of theX-factor was X < 15, but present specificationsalready ask for X < 10. An additionalrequirement for the Mn and Si content can beset accordingly: Mn + Si < 1.1%.Specifically for SAW where the trace elementscan be picked up from both wire andflux, the combination should be tested tocomply with the requirements. This meansone source for both wire and flux would berecommended /5/.Corrosion: Resistance to Oxidation,Sulphidation and Hydrogen attackIn addition to the creep resistance andresistance to embrittlement, CrMo steelsalso show increased high temperature oxidationresistance with increasing alloy content.Comparing the scaling loss for plaincarbon steel and 1%Cr0.5%Mo with thatof 5%Cr0.5%Mo steel at 675°C, the scalingloss is reduced from >2.5 mm/y for thefirst two to about 0.1 mm/y for the latter.This makes these steels also very suitablefor gas-fired furnaces in the petrochemicalindustry /6/.Also sulphidation corrosion resistance increaseswith increasing alloy content. Comparingthe corrosion rate of carbon steel withthat of 9%Cr1%Mo steel at 700°C, the corrosionrate is reduced from 1.0 to 0.2 mm/y.Sulphur combines with Chromium to formChromium-Sulphides, and hence reduces theamount of Cr-carbides required for creep resistance.Since most crude oils and other gaseousfuels contain either certain amounts ofSulphur or H2S, sufficient sulphidation corrosionresistance is required for petrochemicalinstallations.Another important phenomena is HighTemperature Hydrogen Attack (HTHA), aformation of Methane from Cementite (Fe 3 C+ 2H 2 → CH 4 + 3Fe) in the base material underhigh Hydrogen pressures at high temperatures,as for example in heavy wall pressurevessels for high-temperature, high hydrogenservices in oil refineries. The 2.25%Cr1Moand 3%Cr1Mo steels are typical base materialswith good resistance to HTHA in thisapplication.Welding and welding consumablesfor CrMo steelsIn general, creep resistant CrMo-steels arewelded with matching consumables in orderto have a homogeneous welded joint withabout equal mechanical properties. Matchingcompositions also have the same coefficientof thermal expansion, which preventsor at least reduces the risk of thermal fatiguein service. In this respect, the heat affectedzone (HAZ) is a vulnerable area.In principle, all arc welding processes canbe applied as SMAW. GTAW, GMAW, SAWand FCAW. For manual processes it is importantto take sufficient measures to protectthe welders from heat, and then it is of utmostimportance that the preheat as well asthe interpass temperatures are respected andnot reduced to accommodate the welders, aswell as while tacking. With the gas-shieldedprocesses it is vital to assure proper shieldingof the weld. Due to the high preheat, thegas-shield can be distorted and provide lessprotection as required. Special nozzles andgas cups are available to reduce the problem.Over the last decades, Böhler SchweisstechnikGermany has developed a wide rangeof welding consumables for welding CrMosteels for the processes: SMAW, GTAW,SAW, GMAW and FCAW. A selection tablefor the respective welding consumables andwelding processes for creep resistant CrMosteels can be found in listed in Table 3.No. 2/2013 BIULETYN INSTYTUTU SPAWALNICTWA15

Table 3: Selection table for the respective welding consumables and welding processes for creep resistant CrMo steelsCrMo typeBASE MATERIAL WELDING CONSUMABLES FOR CrMo STEELSASTMSAW& EN SMAW GTAW GMAWASMEwire flux0.5Mo T/P 1 8MoB 5-41.25Cr--0.5Mo1.00Cr--0.5Mo1.25Cr--1MoVT/P 11T/P 12-- T/P 36- -2.25Cr--1Mo2.25Cr--1MoVT/P 22T/P22V10 CrMo5-513 CoMo4-515 CrMoV5-1015 NiCuNb5 (WB 36)20 MnMo-Ni 5-510 CrMo9-107CrMo-2.25Cr--MoVW T/P 23 WVMoNb9-62.25Cr--1MoV5Cr-0.5MoT/P 24T/P5029Cr-1Mo T/P 99Cr-1Momod.9Cr--0.5Mo-WV9Cr--0.5Mo-WV12Cr--0.25Mo+1.4W1.3Co0.2V12Cr-1Mo-NiVT/P 91T/P911T/P 92---7CrMo-VTiB10-1012CrMo19-5X12 CrMo9-1X10 CrMo-VNb 9-1X11 Cr-MoWVNb9-1-1X10CrWMoNb9-2X12 Cr-CoWVNb11-2-2(VM12--SHC)t

Table 4: Overview of typical guidelines for Preheat & Interpass temperatures and PWHT as SR, ISR and STCfor CrMo steels. Also see Figure 2.CrMo typeASTM &ASMESTANDARDS0.5Mo T/P 1 8MoB 5-4 RT RT1.25Cr--0.5Mo1,00Cr--0.5Mo1.25Cr--1MoVT/P 11 10 CrMo 5-5T/P 12 13 CrMo 4-5T/P 36PREHEAT & INTERPASS TEMPERATURE, PWHT as SR, ISRand STC GUIDELINES for CrMo STEELSEN Tp °C Ti °C SR h, °C ISR h, °C PWHT/STC h, °C15 CrMoV 5-1015 NiCuNb 5(WB 36)21 MnMoNi 5-52.25Cr-1Mo T/P 22 10 CrMo 9-102.25Cr--1MoV2.25Cr-Mo-VW2.25Cr--1MoVT/P 22VT/P 23 7CrWVMoNb 9-6T/P 247CrMoVTiB 10-105Cr-0.5Mo T/P 502 12 CrMo 19-59Cr-1Mo T/P 9 X12 CrMo 9-19Cr-1Momod.9Cr-0.5Mo-WV9Cr-0.5Mo-WV12Cr-0.25Mo+1.4W1.3Co0.2V12Cr-1Mo-NiVT/P 91T/P 911T/P 92X10 CrMoVNb9-1X11 CrMoWVNb9-1-1X10 CrWMoNb9-2X12 CrCoWVNb11-2-2(VM 12-SHC)t 200°C 2-4h @660-700°C200-250°C > 200°C 2-4h @660-700°C200-250°C > 200°C 2-4h @660-700°C200-250°C > 200°C 2-4h @580-620°C200-250°C > 200°C 2-4h @580-620°C200-300°C200-300°C200-300°C200-280°C200-300°C200-250°C200-300°C200-280°C2-4h @670-720°C225-300°C > 225°C 2-4h @730-760°C200-300°C200-300°C200-300°C200-300°C200-280°C200-280°C200-300°C200-300°C200-300°C200-300°C200-280°C200-280°C* with great differences in wall thickness** no PWHT required for GTAW up to wall thickness of 10mmslow coolafter weldingslow coolafter weldingslow coolafter weldingslow coolafter weldingslow coolafter weldingslow coolafter welding1h @680°C1h @ 540-560°C*STC depending onapplication60h @ 550°C +40h @ 620°C8h @ 705°C + STC+32h @ 705°C0.5-4h @ 740°C**0.5-4h @ 740°C**xh@ 750°Cxh @ 730-780°Cxh @ 730-780°Cxh @ 770°Cxh @ 760°Cx dependson thicknessdepends also on the thickness of the constructionand has to be determined by thefabricator as part of the welding proceduredevelopment. The main factor is to have acontrolled, slow and even heating up andcooling down to prevent additional stressesin the welded joint. For heavy thicknessesthis means heating up from as many sidesas possible to get the required heat distributionin the material. These precautions haveNo. 2/2013 BIULETYN INSTYTUTU SPAWALNICTWA17

to be taken to safeguard the base material,the weldmetal and the heat affected zone(HAZ).Recent developments in P22V, P23,P24, P92 and VM 12-SHC havegoverned more detailed and precisewelding and production proceduresto retain control over theoutcome of the final product. Althoughthese materials are not asforgiving as the basic CrMo steel,the weldability is excellent whenthe correct procedures are followed.Depending on the application,there can be requirementsfor STC and Bruscato´s X- factor.For very heavy wall-thickness inP22V it could be necessary to applyintermediate stress relieving treatmentsas to reduce the overall stress level beforethe final heat treatments applied. With theexperience that Böhler SchweisstechnikGermany has built up over the last decades,the support that can be provided to the customershas become a vital link in the supplychain in today’s business.As already mentioned, the thicknessesfor a welded part in the power generationand petrochemical industry keeps increasingand higher tensile strength materials,with more stringent mechanical propertiesand chemical composition, are used to keepfabrication feasible. This means that thewelding consumables have to be adapted tofollow this trend.Figure 3 shows a very heavy wall exampleof a pipe connection of a live-steam pipeof P91 base material in a Power Station.Fig. 3: Weld preparation and final weld in a pipe connectionof a live-steam pipe of P91, welded with SMAWusing Thermanit Chromo 9 VAs indicated the heat treatments includingpreheat and interpass temperature haveto be under strict control to successfullycomplete these types of welded joints. Thetemperature ranges for the preheat and interpasstemperatures given in Table 4 areto be respected throughout completion ofthe joint. For this application, SMAW isvery suitable due to its flexibility and lowinvestments regarding equipment. In orderto increase efficiency, higher weldmetaldeposition per unit of time, developmentis ongoing for FCAW consumablesfor CrMo steels. As listed in Table 3, anumber is already available but the rangewill be extended upon the demand of theindustry.Technical Details of the Reactor:Base2,25%Cr-1%Momaterial:Fig. 4: Heavy wall Reactor in 2.25%Cr-1%Moby GODREJ, INDIAthickness:total weight:Serviceconditions:Weldingconsumables:124, 132 and 153 mmabout 500 t120 bar pressure and 437°CSAW: Union S1CrMo2/UV 420TTRSMAW: Phoenix SH Chromo 2 KS18 BIULETYN INSTYTUTU SPAWALNICTWANo. 2/2013

The SAW consumables range covers allthe CrMo steels available today. GTAW ismainly used for root welding or automatedwelding in demanding industries. TheGMAW range is available but not popular inthe Power Generation industry.Another practical example is that of a Reactorbuild in 2.25%Cr-1%Mo steel. Figure 4shows one of a number of these types of heavywall pressure vessels produced by Godrej inIndia. They have built up excellent and practicalexperience to be able to build such units.When dealing with heavy wall thicknesses,modern CrMo creep resistant steels and verystringent specifications, it is absolutely necessaryto build up sufficient experience tobe able to satisfy the demanding engineeringcompanies as well as the Oil and Power companies,who are the ultimate client.Parameter control and suggestions for“Best Practice”CrMo(V) weld metal typically shows abainitic/martensitic micro structure that respondvery sensitively to any kind of heatput in by means of welding and heat treatment.Furthermore, the high strength in theas welded condition requires accurate handlingin terms of Hydrogen and ISR in orderto avoid cracking due to Hydrogen and/or therestrained condition of welds in heavy wallnozzles for example.To elaborate on some of the influences,typical observations in welds made in Cr-Mo(V) creep resistant steels are illustrated inthe next paragraph.Figure 5 shows ferrite precipitations inP11 due to excessive PWHT temperature.The micrograph in figure 6 shows Hydrogendamage due to a improperly applied soakingtreatment, leaving too much residual Hydrogenin the weldmetal. Figure 7 shows the effectof bead-thickness in SMA welds, a shiftof the impact properties to higher temperatures,due to a much courser grain-structure.Applicable manufacturing parameters,which include the welding parameters as wellas the quality of the welding equipment andthe skill-level of the welders, become moreimportant with an increasing initial strength.The “operating window” will become smaller.Therefore suitable control mechanismsand procedures have to be set up to ensurethe proper application of the required parameters.In particular the control of the followingitems shall not be neglected for achievingsuccessful welds:• Selection of the suitable SAW wire & fluxcombination• Proper rebaking of fluxes and electrodes• Verification of preheating & interpasstemperatures• Setting of the electrical welding parameters• Weld build-up and beadsequence• Verification of the heat treatment temperature.Almost all issues encountered in CrMowelds could be related to the non-observanceFig. 5. Ferrite precipitations in P11 SA weldsFig. 6. Crack surface due to Hydrogen in P22V SA weldsNo. 2/2013 BIULETYN INSTYTUTU SPAWALNICTWA19

Table 5: Overview of typical applications of CrMo steels in the Power Generation & Petrochemical IndustryBASE MATERIAL INDUSTRIAL APPLICATIONS ServiceCrMo type ASTM &max. TEN POWER GENERATION PETROCHEMICALASMEin °CPressure vessels; Rp0.2 >0.5Mo T/P1 8MoB5-4Pressure vessels < 460290 MPa, Rm > 500 MPa1.25Cr--0.5Mo1.00Cr--0.5Mo1.25Cr--1MoVT/P11 10CrMo5-5 Steam headersT/P1213CoMo4-5- 15CrMoV5-10Water walls;parts of evaporaterMain steam pipe; reheatersteam pipe; Rp0.2 > 440MPa, Rm 590-780 MPaHeavy Wall PressureVessels, Coke Drums,Hydrofiner Reactors, CatalyticReformer Reactors< 535< 545Heat exchangers < 545- T/P3615NiCuNb5(WB 36)Feed water pipe High pressure steam drums < 545- - 20MnMoNi5-5 Reactor vessels (nuclear) -2.25Cr-1Mo T/P22 10CrMo9-102.25Cr--1MoV2.25Cr-Mo-VW2.25Cr--1MoVT/P22V -T/P23T/P247CrMo-WVMoNb9-67CrMo-VTiB10-10Parts of superheaters;Rp0.2 > 310 MPa,Rm 515-690 MPaRp0.2 > 415 MPa,Rm 585-760 MPa -->Parts of superheater;membrane wallsParts of superheater;membrane walls5Cr-0.5Mo T/P502 12CrMo19-5 -9Cr-1Mo T/P9 X12CrMo9-1 -9Cr-1Momod.9Cr-0.5Mo-WV9Cr-0.5Mo-WV12Cr--0.25Mo+1.4W1.3Co0.2V12Cr-1Mo-NiVT/P91T/P911T/P92--X10CrMo-VNb9-1X11CrMo-WVNb9-1-1X10CrWMoNb9-2X12CrCo-WVNb11-2-2(VM12-SHC)t 450 MPa,Rm 630-790 MPaSteam headers,superheatersSteam headers,superheaters for UltraSuper Critical boilersSuperheater tubes withthickness < 10mmSteam headers,superheaters;Rp0.2 > 500 MPa,Rm 700-850 MPaHigh Pressure &High TemperatureReactors, coke drums,furnaces, pipingHydrocrackers, Heavy WallPressure Vesselsfor Hydrogen Service< 535< 482- < 550- < 550Pressure vessels in high temperaturesulfur corrosion, resistancereactor furnaces and reactorsReactors, High TemperatureSulphur corrosion resistance,furnaces and pipingHigh pressure steam headers& piping< 550< 585< 585- < 625- < 625- < 650Tubing in H2S environments < 585High Pressure, HighTemperature & Corrosion20 BIULETYN INSTYTUTU SPAWALNICTWANo. 2/2013

Fig. 7. Influence of weld build-up on impact toughnessof the above mentioned items. Consequentlysuitable control mechanisms have to bedeveloped to ensure proper welds. Qualityassurance becomes a major factor and mustbe included in the CrMo welding fabrication.QA has to be considered as an essential variable,as illustrated with Figure 8.In conclusion we can state that CrMocreep resistant steels are widely and successfullyapplied in the Power Generation andPetrochemical Industries. The developmenttowards higher service temperatures ask fornew materials, both for base material as forwelding consumables.To illustrate typical examples of wherethe various CrMo materials are applied,an overview of typical applications of CrMosteels in the Power Generation and the PetrochemicalIndustry is given in Table 5.With this paper we intended to providean overview of the available materials, thestandards, the consequences and the implicationswith regard to welding, heat treatmentsand fabrication. When the correct proceduresare developed up front and adheredto throughout the production, projects can beand have been successfully completed.References1. Cole D., Bhadeshia H.K.D.H.: Designof Creep-Resistant Steel Welds. Researchwork. University of Cambridge,Department of Materials Science andMetallurgy, 1998Fig. 8: QA to be included to verify required parameters2. Bhadeshia H.K.D.H: Design of Creep-ResistantSteels. Proceedings of Ultra-Steel2000. National Research Institute forMetals, Tsukuba, Japan 2000, pp. 89-1083. Bruscato R.: Temper Embrittlement andCreep Embrittlement of 2.25%Cr - 1%Moshielded metal arc weld deposits. WeldingJournal 49 (4), 1973, pp. 148-1564. Watanabe J. et. al.: Temper Embrittlementof 2.25%Cr - 1%Mo Pressure VesselSteel. ASME 29 th Petroleum MechanicalEngineering Conference, Dallas,USA, 19745. Gross V., Heuser H., Jochum C.:Schweisstechnische Herausforderung beider Verarbeitung von CrMo(V)-Stählenfür Hydrocracker. Publication of BöhlerThyssen Schweisstechnik, Germany,20076. Handel Geert van den: Chroom-Molybdeenstaalsoorten. Lastechniek, NederlandsInstituut voor Lastechniek (NIL), No. 5,May 2008, pp.10-147. Gross V.: Improved toughness in2.25%Cr - 1%Mo(V) weldmetals for joiningheavy walled reactors. Publicationof Böhler Thyssen Schweisstechnik,Germany, 2006.8. Fuchs R., Gross V., Heuser H., JochumC.: Properties of matching filler metalsfor the advanced martensitic steels P911,P92 and VM12. Proceedings of 5 th InternationalEPRI RRAC Conference, Alabama,USA, June 26-28, 2002No. 2/2013 BIULETYN INSTYTUTU SPAWALNICTWA21

9. Heuser,H, Jochum C.: Neue Schweisszusatzwerkstoffefür neue Kraftwerksstähle.Publication of Böhler ThyssenSchweisstechnik, Germany, 200410. Gross V, Heuser H., Jochum C.: NeuartigeSchweisszusätze für bainitische und martensitische.Publication of Böhler ThyssenSchweisstechnik, Germany, 200511. Valaurec, Mannesmann: Seamless boilertubes and pipes. Publication of Valaurec& Mannesmann Tubes, V&M 507-7e12. Hilkes J., Gross V.: Soldadura de los acerosCrMo para aplicaciones en la Generaciónde Energía y Petroquímica“-- Pasado, Presente & Futuro. CESOLConf. Proc. 1 er Congreso Internacional deSoldadura y Technologías de Unión (17 asJournadas Téchnicas), Madrid, Spain,7-9 October 2008., pp119-124.13. Hilkes J., Gross V.: Het lassen van CrMostalen voor de Energieopwekking en dePetrochemische Industrie - Verleden,Heden en Toekomst. Dutsch & BelgiumWelding Institute, NIL/BIL Lassymposium,Eindhoven, The Netherlands, 26/26November 200822 BIULETYN INSTYTUTU SPAWALNICTWANo. 2/2013