Sheet Metal Haynes

8/13/2019 Sheet Metal Haynes

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H YN S CORROSION RESISTANT ALLOYSI n t e r n a t i o n a l

F BRIC TION GUIDELINES FOR THIN SHEET MET LLIC

LINING OF FLUE G S DESULFURIZ TION SYSTEMS

General Guidelines forWeldings Pattern Layoutand Structural Attachments

Contents

Introduction

General FabricationGuidelines

Safety and HealthConsiderations 5

Shop Preforming 5

Duct Preparation 6

Structural AttachmentWelding 6

Seal Welding 7

Inspection 8

Repairs 8

Mechanical and CorrosionProperties of Weldments 9

Summary


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INTRO U TION

The use of thin-sheet metallic lining of high-performance alloys has become a recognizedcorrosion protection technique for many components of flue gas desulfurization FGD) systems. In this technique, thin-gauge sheet is welded to a variety of substrate alloys to form aleak-tight corrosion shield. Thin-sheet metallic lining has become an alternative to heavysection alloy plate fabrication as well as non-metallic coating systems.

Suggested fabrication guidelines are outlined herein that can be used during the installation1/16 inch 1.6 midetailed information on mechanical and corrosion properties of weldments is provided.

To date, more than 1 million square feet 90,000 square meters) of high-performance nickelbase alloy sheet, produced by Haynes International, Inc., has been installed in various stacks,breaches, inlet/outlet ducts and absorber units using this metallic lining technique AppendixA Figure 1 shows installation of C-22 sheet in outlet ducts. In addition to applications in FGDsystems, this corrosion protection technique can also be applied in other chemical processingsystems.

The guidelines contained in this brochure are based upon both laboratory work and fieldinstallation experience. This fabrication method is considered straight forward and requires nospecial tools, equipment or highly trained personnel. The general configuration is shown inFigure 2 One of the important features of this installation technique is the lack of concern oversubstrate dilution of the weld metal during seal welding. This is because all seal welding isperformed in an alloy to alloy configuration. Additionally, this fabrication technique greatlyreduces fabrication time due to the fit-up simplicity of overlapping one sheet onto another.

The key points that should be considered when fabricating with this thin-sheet liningtechnique are:

* Layout the installation pattern in advance.* Develop welding procedures and train welding personnel in advance.* Shear, punch holes, preform sheets in the shop whenever possible* Prepare substrate surface as necessary.* Structurally attach sheets to substrate and perform midsheet attachment.* Seal weld all-around.* Inspect and test all seal welds to insure leak-tight condition.* Repair questionable areas using GTAW. SMAW or GMAW welding processes.


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Over the past five years, 0.035 inch 0.89 millimeters diameter layer wound wire has beenrecommended exclusively for this thin-sheet technique. It continues to be the diameter ofchoice for thin-sheet applications. Recently some fabricators have moved toward 0.045 inch 1.1 millimeters diameter wire and claim improved arc characteristics. Selection of filler wirediameter should be considered carefully as larger diameter wires are capable of highamperages and thus excessive heat input and potential sheet melt-back.

Welding currents and arc voltages, for 0.035 inch diameter wire, are generally in the 70-90ampere and 18-20 volt range. Detailed welding parameters, that were used to develop theincluded mechanical and corrosion property data, are documented in Table 1 for GMAW shortcircuit transfer welding. Examples of welds, made using the short circuit transfer mode, aredocumented in Figure 4 for the flat, vertical and overhead positions.

The parameters for plug welding are the same as those used for fillet welding Table 1 . Aprepunched hole is necessary for plug welding 1/2 inch diameter is considered optimum . Aswith seal welding, it is important that the sheet be in intimate contact with the substrate duringplug welding.

The GMAW arc spot welding method is a process that has been suggested as an alternativemidsheet attachment method. This midsheet attachment method does not require aprepunched hole. In this process, the amperage and voltage are raised to such levels that thesheet is penetrated allowing fusion with the substrate. In this work, A-1025 shielding gas wasused. Pure argon or NiCoBrite gas is considered an appropriate shielding gas as well. Thisprocess could potentially save time during fabrication, but tight control is necessary over theprocess.

Arc spot welding parameters, that were used to develop the included mechanical and corrosion property data, are documented in Table 2. In this process, 0.062 inch 1.6 millimetersdiameter wire is normally recommended. A standard constant potential welding power supplyis used in the spray transfer mode. However, a more sophisticated wire feeder, that containscircuitry for controlling arc times, is required.

Typical photographs and cross-section photomicrographs are included in Figure 5 for bothplug welds and arc spot welds. It is important to note that while the surface dimensions of thetwo types of welds are quite similar, the area of actual fusion at the substrate is quite different.

It should be recognized that the filler wire conduit liner assembly part of the GMAW weldingtorch is a high wear item and should be expected to be replaced periodically. Wear of theliner occurs as a result of galling between the carbon steel liner and the nickel-base weldingfiller wire. A worn liner can cause erratic wire feeding and this can lead to arc instability.

Some welding torches can be fitted with a nylon conduit liner. Such a liner would be expectedto reduce wear and thus increase liner life. is recommended that sharp bends in the GMAWtorch cable be minimized. If possible, the wire feeder should be moved so that the torch cableis nearly straight during welding.


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S FETY N H LTH ONSIDER TIONS

Those involved with the welding industry are obligated to provide safe working conditions andbe aware of the hazards associated with welding fumes, gases, radiation, electrical shock,heat, eye injuries, burns, etc. Various local, municipal, state and federal regulations OSHA,for example) relative to the welding and cutting processes must be considered.

The operation and maintenance of welding and cutting equipment should conform to theprovisions of American National Standard NSI Z49.1-88, Safety in Welding and Cutting .Attention is especially called to Section 4 Protection of Personnel), Section 5 Ventilation) andSection 7 Confined Spaces) of that document. Adequate ventilation is required during allwelding and cutting operations. Specific requirements are included in Section 5 for naturalventilation versus mechanical ventilation methods. When welding in confined spaces, ventilation shall also be sufficient to assure adequate oxygen for life support.

The following precautionary warning, which is supplied with all welding products, should beprovided to and fully understood by all employees involved with welding.

CAUTION: Welding may produce fumes and g ases h aza rdo u s to health. Avoidbreathing these fumes and gases. Us e adequate ventilation. Se e ANSI/ AWS Z49.1-88 Safety in Welding and Cutting published by the American Welding Society.EXPOSURES: Maintain al l exposures below the limits shown in the Material SafetyData Sheet and the product label. Us e industriat hygiene air monitoring to ensurecompliance with the recommended exposure limits. W YS USE EXHAUST VENTILATIONRESPIRATORY PROTECTION: Be sure to use a fume respirator or ai r suppl ied respr a to r w h en welding in confined spaces o r w he re local exhaust or ventilation does nkeep exposure below the PEL and TLV limits.WARNING: Protect yourself and others. Be sure the label is read and understoodth e we ld er. F UME S and GASES can be dangerous to your health. Overexposure tofumes and gases can result in LUNG DAMAGE ARC R YS can injure eyes and buskin. ELECTRIC SHOCK can kill

SHOP PREFORMING .

There are several areas where shop formed parts can save time and effort. Because thesheets are overlapped, close fit-up into corners is not necessary. Edge molding pieces, suchas those shown in Figure 6A, and corner molding pieces, such as those shown in 68, can bplaced over the intersecting wall sheets and form a sealed joint without the need of accuratelysheared alloy sheets.

Preformed sheets with one or two edges bent 90 degree can be fitted into a ceiling or floorsee Figure 6C), thus eliminating edge molding installation. Intermittent fillet welds and mid

sheet attachments will hold the sheet to the ceiling and seal welds on side walls form thefinished edge. Another example of shop preforming is shown in Figure 60. In this case, asheet can be bent 90 degree with holes punched for an expansion joint seal.

Each of these examples presents ideas on how preformed parts might decrease fabricationtime. If the job is laid out in advance, many other time saving situations should becomet h if ll e


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As general statement, the ductility of C-22 sheet is very high 50 percent tensile elongationand thus allows cold forming of parts with virtually no problems. Bend radii can be one timesthe thickness, with no cracking or tearing noted. Generally, cold formed pieces are installed in the cold worked condition. Any hot working that is performed on the alloy sheet orplate must be followed by solution annealing to restore corrosion resistance to the material.

DUCT SUBSTRATE PREPARATION

In retrofitting FGD systems, it is necessary to thoroughly clean the substrate material beforethe alloy sheet is attached. Sand blasting of the corroded substrate surface, followed by freshwater rinse, is typical. Sand blasting and rinsing will open up corrosion pits, remove theremaining lining system from the substrate and wash away corrosion products and dirt.

In some cases in the past, sand blasting was followed by a basic chemical rinse that wasintended to neutralize the acidic condition of the corrosion product found in the corrosion pits.A clean, fresh water rinse followed such a neutralizing process. This added neutralization stephas, for most retrofit installations, been eliminated without any consequent problems.

In a new construction system, sand blasting or light grinding of the substrate is advised toremove heavy rust or mill scale. This need only be done in the areas where alloy to substratewelding will be performed.

The use of rust preventive paint is often suggested to control rust bloom that occurs on freshlysand blasted carbon steel surfaces. Such a practice is neither recommended nor discouraged. It is, however, recommended that welding procedure qualification work take into account the use of such products and that the use be considered an essential variable of welding procedure qualification.

STRUCTURALATTACHMENTWELDING

Two distinct welding phases are noted during the installation process. First the sheet is structurally attached to the substrate. Then the alloy sheet is seal welded all-around to provide aleak-tight structure.

The structural attachment of the sheet to the substrate is made with intermittent fillet weldsbetween the alloy sheet and the substrate material. These welds are generally about 1 inch 25 millimeters long on about 6 inches 150 millimeters centers.

It should be recognized that all the structural strength of the lining system comes from thesealloy to substrate intermittent fillet welds. High quality welding is, therefore, mandatory. Weld

ing techniques that provide a flush attachment substrate weld are desirable. If not possible, itis recommended that fillet welds be ground flush with the alloy sheet before overlapping asubsequent sheet. This will be helpful in maintaining intimate contact between the sheetsduring seal welding.

As additional sheets are installed, a nominal 1inch 25 millimeters overlap of the sheets ismade. To hold and position the sheet during structural fillet welding, some alloy to alloy tackwelding is necessary. Additional instructions concerning alloy to alloy tack welding are givenin the next section of this brochure.


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General cleaning of both the substrate and the alloy sheet should be done before welding toremove greases, oils, corrosion product, scale/deposit, water and other contaminates. Practices similar to those used during the welding of stainless steels should be considered minimum requirements. The use of stainless steel tools and tooling is not necessary whenfabricating with HASTELLOY alloy sheets. The use of stainless steel wire brushes is recommended during welding and subsequent cleaning operations.

Surface iron contamination rust staining) resulting from contact of the nickel-base alloy sheetwith carbon steel is not considered a serious problem. Therefore, it is not necessary to remosuch rust stains prior to service. In addition, melting of these very small amounts of surfaceiron contamination into the weld puddle is not expected to affect weld metal corrosion resistance.

While such contamination is not considered a serious problem, it is assumed that reasonablecare will be exercised to avoid the problem. If such care is exercised, no particular correctivemeasures should be necessary prior to service.

Midsheet attachment can be used to provide additional structural strength and rigidity to thelining system by attaching the sheet to the substrate at intervals between the structural filletwelds. A row of plug welds down the middle of a 48 inches 120 centimeters) wide sheet24 inches 60 centimeters) centers has been used at many installations. Because FGDsystems normally operate under positive pressure conditions, the incorporation of these additional structural welds is not considered mandatory and is left to the discretion of the individudesigner.

The use of the carbon arc cutting method is not recommended for shaping or cutting holesthe alloy sheets. This is because high levels of carbon may be present after cutting and thiswill reduce the corrosion resistance of the alloy. Plasma cutting, prepunching or drilling ofholes is recommended. It is recommended that the dross formed during plasma cutting beremoved by grinding to bright metal.

Because the midsheet attachment welds connect directly to the substrate material, the meltedsubstrate will mix with the weld metal. This fusion zone dilution will lower the corrosion resistance of those welds. Two alternatives are suggested to minimize the effect of midsheet weldmetal dilution. First, after the attachment weld is made, a second pass weld overlay isadded. A second alternative is to place a small patch of alloy sheet over the weld zone andthen seal weld all-around the patch.

SE L WEL ING

After the alloy lining has been structurally attached to the substrate, the seal welds are madeat the overlapped sheets. The seal welds provide both structural strength to the overlappedsheets and provide a leak-tight system.

s discussed in the previous section, the overlapped sheet will need to be securely tackwelded so structural welding can be accomplished. Before seal welding, additional tackwelding should be performed to insure that the two overlapped sheets are in intimate contaThese tack welds are usually very small, 1/4 inch 6 millimeters) long tacks on 3 inches 75millimeters) centers. Large gaps or bridges between the two overlapped sheets will increasethe possibility of seal weld defects and can ultimately cause the lining system to leak.


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is strongly recommended that these tack welds be ground and feathered before the continuous seal welding operation. The tack welds need only be strong enough to hold the twosheets in intimate contact during seal welding. The larger these welds are, the more difficultseal welding becomes. It is further recommended that the seal weld starts and stops beground and feathered. It should be emphasized that seal welding defects are usually associated with starts, stops or tack welds. Care at this stage of the welding process will greatlyreduce repair costs.

INSPECTION

Nondestructive Examination NOE must be considered a very important part of this fabricationprocess. It should be remembered that the seal welds are single pass welds and thereforeany lack-of-fusion or other welding defects will probably cause the lining system to leak. It issuggested that Weep holes be installed in the substrate so that any possible leakage of thelining system can be quickly detected and repaired.

Visual examination will probably pick up 80 to 90 percent of possible welding defects. isrecommended that a detailed visual inspection be conducted before other NOE testing isperformed. Then repair of suspect welds can be made quickly without concern over contamination by NOE detection fluids dye penetrant or vacuum box soap).

Currently, the vacuum leak test method seems to be the most accurate and cost effective therefore the most popular) test. This is due to the sensitivity of the test ability to determinethat a leak exists) and speed. Liquid dye penetrant inspection is considered an alternativemethod and might be used for small areas or regions where access of the vacuum box is notpossible.

R P IR

The GTAW, GMAW or SMAW welding processes can be used for repair of seal welding defects. The GTAW welding process is considered the most appropriate and is recommended.Repairs using the GTAW process can be made with or without the addition of filler material,depending on the extent of the defect. Smalilack-of-fusion defects can be washed out withno problems. Larger areas that require grinding will probably require addition of filler material.


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MECHANICAL AND CORROSION PROPERTIES OF WELDMENTS

MECHANICAL PROPERTIES OF STRUCTURAL ATTACHMENT WELDS

As stated above, the structural fillet welds and the seal fillet welds are made using the samewelding process and parameters Table 1 . The size of the structural fillet welds has historically been left to the discretion of the architect/engineering firm that designed the FGD systemand components. Generally, structural fillet welds have been about 1 inch 25 millimeterslong on about 6 inches 150 millimeters centers. This weld spacing has proved to be sufficient based upon fully acceptable results observed at many FGD sites.

Actual strength of structural fillet welds has been evaluated to assist the system designer imaking weld recommendations. By necessity, this testing was conducted using a shear testconfiguration. HASTELLOY C-22 alloy sheet materials were welded to plain carbon steelsubstrate material using the welding parameters documented in Table 1 Fillet welds 3/4 in 19 millimeters , 1 inch 25 millimeters and 1-1/4 inches 32 millimeters in length were madas shown in Figure 7 In each case, HASTELLOY C-22 alloy was used as the welding fillermaterial. Duplicate samples were tested in each configuration.

The tensile force average of duplicate tests necessary to separate the sheet from the substratereported in Table 3 Clearly the force necessary to separate the sheet from the substrate increasesas the weld length increases. In all cases documented in Table 3 the failure location was in thesheet base material near the weld zone None of the welds were pulled free of the substrate. Aswould be expected, the calculated ultimate tensile strength of the tested welds based upon theshear load, the fillet weld width and the sheet thickness is close to the ultimate tensile strength ofwrought base material. Figure 8 shows a set of fillet weld shear tests.

MECHANICAL PROPERTIES OF PLUG WELDS AND R SPOT WELDS

As stated earlier, most FGD systems operate under positive pressure, and therefore midsheetattachment has not been considered mandatory. In most cases, however, designers have feltit necessary to include midsheet attachment to insure the sheet is held flush to the substrateand to lessen concern about damage due to vibration.

To date, both plug welding and arc spot welding have been suggested as midsheet attachment methods. In the USA, plug welding has been the most common attachment technique.Mechanical testing was conducted on both plug welds and arc spot welds to determine theshear strength of such welds.

Plug weld testing was conducted, using various sizes of predrilled holes, to determine bothoptimum hole size and weldment performance. The welding conditions are documented inTable 1 and the test configuration is shown in Figure 7 Welds were made in the flat, verticaand overhead position. Testing was conducted using A-1025 shielding gas. In each case,two tests were made and results were averaged. The tensile shear strength results reportedin pounds are documented in Table 4


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The tensile test sample failures were of two types as shown in Figure 9 The first type consistsof tearing of the substrate carbon steel. This is demonstrated with the sample on the right sideof Figure 9 All the 3/8 inch 10 millimeters plug welds and the vast majority of the 1/2 inch 13millimeters plug welds failed in this way. The second type of failure consisted of tearing ofsheet material leaving the plug weld nugget attached to the substrate. This is demonstratedwith the sample on the left side of Figure 9 About one-half of the 5/8 inch 16 millimeters plugwelds failed by sheet tearing.

Clearly the larger plug welds require greater tensile shear force for failure. From this one mightconclude that the larger the diameter of the plug weld the better the design. However, whenone considers the ease of welding, the large diameter holes have a marked disadvantage dueto the larger amount of weld metal that the welder must deal with. Results of the welding workconducted in this study, and other weld trials over the past several years, indicate a holediameter of about 1/2 inch 13 millimeters is optimum for plug welding.

Similar mechanical tests were conducted on arc spot welds in the flat, vertical and overheadpositions, even though arc spot welding is not normally considered an all-position weldingprocess see ANSI/AWS C5.6-89, page 5 for an explanation . The shielding gas used in thiswork was A-1025. The welding parameters are documented in Table 2 The shear test configuration was similar to that used in the plug weld test trials. Arc spot welding mechanical testdata are reported in Table 5

One important point, which should be recognized, is the range of values derived from thesetensile shear tests of arc spot welds. The welding conditions used in this work produced in allcases visually acceptable arc spot welds, from the welding operator point of view. Despitethat fact, the shear strengths varied from 978 to 2832 pounds. In other tests, increases in alloysheet thickness of just inch 0 13 millimeter produced marked decrease in weldstrength, all other welding conditions being constant.

Typical arc spot welding tensile test fracture examples are shown in Figure 10 As can beseen, failure occurs by the removal of a small nugget from the substrate material. The sampleon the left failed at 1734 pounds while the sample on the right failed at 2694 pounds. Thenugget on the right is larger than on the left and this accounts for the difference in load atfailure.

Additional work has shown that somewhat higher tensile property results are possible whenargon-base shielding gas is used. This is believed to be a result of the deeper penetrationpattern associated with argon-base shielding gases.

Clearly significant differences in shear strength exist between arc spot welds and plug welds. The

average plug weld strength is about 4 5 times greater than the arc spot weld strength. Experimentswere run in an attempt to increase arc spot weld strength. In nearly all cases, attempts at increasedstrength resulted in increased welding defects holes and/or excessive droop .


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CORROSION PROPERTIES OF P LU G W ELD ND R SPOT WELDS

One of the key features of thin-sheet lining is the lack of concern over substrate dilution duringseal welding. This however does not address the concern of substrate dilution during midsheet attachment.

Three conditions have been used with plug welds over the past several years. Those condi

tions are: one, leave plug weld as-welded; two, overlay a second layer of weld metal on theplug weld and three, seal weld a patch over the plug weld. The selection among the variousplug welding techniques is left to the design engineer. It should be stated that some thinsheet lining systems have been installed using the first method with apparent success. Generally, however, methods two or three are commonly used.

The corrosion resistance of the seal fillet welds is considered equivalent to any other alloy toalloy weld. As a general statement, the corrosion resistance of the cast undiluted weld metallower than the corrosion resistance of wrought base metal. This difference in corrosion resistance is most clearly demonstrated when tests are conducted in environments that causepitting-type corrosion.

Corrosion testing was conducted on both plug welds and arc spot welds to gauge the corrosion resistance degradation of these welds as compared to an alloy to alloy weld. Smallwelded samples were fabricated as shown in Figure 11. Such a configuration makes it possible to perform immersion pitting corrosion testing of attachment welds. An example of acompleted assembly is shown in Figure 12.

Plug welding was performed using the parameters documented in Table 1. The diameter ofthe drilled hole was 1/2 inch 13 millimeters). Testing was conducted using the first two options, discussed above.

Arc spot welding was performed using the parameters documented in Table 2. All testing oarc spot welds was performed on samples left in the as-welded condition.

Corrosion testing was conducted using an oxidizing, acid-chloride solution 11.5 percentH2 4 + 1.2 percent HCI + 1 percent FeCI3 + 1 percent CuCI,). The immersion time was 24hours. Samples were tested at various temperatures in 5 deg. C increments) to determine tcritical pitting temperature at and above which pitting occurred.

The corrosion test results of the midsheet attachment weld assemblies are documented inTable 6. The pitting resistance of the plug weld assemblies in the as-welded condition)appears to have some degree of variability. As noted in Table 6 pitting occurred at 8 deg

and the samples tested at8

deg. C did not pit. However, one of the samples tested at7

deg. C showed attack on one surface. Duplicate samples were run at 7 and 8 deg. C todetermine more accurately a critical pitting temperature. No pitting was detected on theseduplicate samples. This variability in pitting resistance is probably due to differences in theamount of substrate dilution noted from sample to sample.

The results of the plug welds with a second pass applied are also presented in Table 6. Incase, pitting occurred at 8 deg. C and above, while the samples tested at 8 and 7 deg.did not pit. These results show the critical pitting temperature for the second pass plug weldsamples to be 8 deg. C.


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The results of arc spot weld corrosion testing indicate that the critical pitting temperature ofsuch spotw l s is about 8 deg. C This is very similar to the corrosion resistance of an aswelded one layer plug weld.

Table 7 is included to bring together all the critical pitting data for the various midsheet attachment options. The critical pitting temperature of unwelded wrought HASTELLOY C-22 alloybase material is included as a reference point. Clearly the plug welds and arc spot welds leftin the as-welded condition have lower pitting resistance when compared to the alloy to alloyseal welds. Applying a second pass to a plug weld improves the situation but does not bringthe pitting resistance up to the alloy to alloy seal welds.

SU RY

1 The thin-sheet metallic lining technique has been successfully applied in FGD systems byusing these simple fabrication and inspection steps.

2 Thin-sheet metallic lining of HASTELLOY C-22 alloy has been proven to be a reliable andcost effective corrosion protection method.

3 Corrosion and mechanical properties of the C-22 sheet metal and weld filler metal addversatility and reliability to the thin-sheet metallic lining technique.

8552b 1895r

HASTELLOY, NiCoBrite and C-22 are trademarks of Haynes International, Inc.HELISTAR SS is a registered trademark of Union Carbide Industrial GasesTechnology Corporation.


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TABLE 3

Shear Strength of tructur l Fillet Welds HASTELLOYC 22 alloy Filler Wire/Sheet and Carbon Steel Substrate)

Shear force pounds)

Weld position

Flat

Fillet weld size: 3/4

6000

6900

1-1/4

7200

Average of duplicate tests

TABLE 4

Shear Strength of Various Diameter Plug Welds HASTELLOY C 22Filler Wire/Sheet and Carbon Steel Substrate)

Weld position

FlatVerticalOverhead

Plug weld size:

Shear force pounds)

3/8 1/2 5/8

6600 9600 14,7007100 9600 13,500

6700 9600 13,300

Average of duplicate tests

TABLE 5

Shear Strength of Arc Spot Welds HASTELLOY C 22Filler Wire/Sheet and Carbon Steel Substrate)

Weldingposition Shielding gas Avg. Min. Max.

Flat A-1025 2070 1734 2694Vertical 2424 1452 2832Overhead 2013 978 2754

Average 2169


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TABLE 6

Corrosion Test Results of Midsheet Attachment WeldsOxidizing, Acid-Chloride Solution

11.5 H 4 + 1.2 HCI + 1 FeCI + 1 CuCI

Welding Number of Temperature Corrosion VisualProcess Layers OC) Rate mpy) Inspection

Plug weld 1 90 120 Pits 2 /2 sides)

85 36 Pits 2 /2 sides)

80 9 No pits 2 /2 sides)6 No pits 2 /2 sides)

75 9 Pits 1 /2 sides)4 No pits 2 /2 sides)

Plug weld 2 95 429 Pits 2 / 2 sides)

90 211 Pits 2 /2 sides)

85 24 Pits 2 /2 sides)9 No pits 2 /2 sides)

80 7 No pits 2 /2 sides)

75 7 No pits 2 /2 sides)

Arc spot 1 90 150 Pits 1 /2 sides)165 Pits 1 /2 sides)

85 7 Pits 1 /2 sides)

49 Pits 2 /2 sides)

80 33 Pits 2 /2 sides)68 Pits 2 /2 sides)

75 4 No pits 2 /2 sides)2 No pits 2 /2 sides)


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TABLE 7

Critical Corrosion Pitting TemperaturesOxidizing Acid-Chloride Solution

11.5 H 2 4 + 1.2 HCI + 1 FeCI 3 + 1 CuCI 2 )

Midsheet attachment method

Wrought HASTELLOY C-22 alloy

Plug weld with seal welded patch

Plug weld with second layer

Plug weld as-welded one layer)

Arc Spot Weld

Critical PittingTemperature 0C

120

100

8

- 8

80


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Neg no 28366 515

Figure Absorber Outlet Ducts Lined with HASTELLOY C 22 alloy

Neg no 65910


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SealFillet Weld

Arc p ot orPlug Weld midsheetattachment

to 062 in. Nominal

Carbon Steel orLower Alloy Substrate

irst heet econd heet

Approximately 1 in. Overlap oSecond Sheet Over First Sheet

Sheet 1

?Sheet 2Intermittent Fillet Welds

6 in. Center to Center Distance

Third heet eal Weld

Sheet 1Sheet 1

Sheet 2

Sheet 3 Sheet 3

Seal WeldAIIAround


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Neg no 598 8 2X


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SECTION A A Neg no 49548

Flat Position 1 5X Neg no 51391

Vertical Position 1 5X Neg no 5 392

Overhead Position 1 5X Neg no 5 393


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Arc spot weldNeg no 59905

Plug weld X

Arc spot weld cross sectionNeg no 59938 4X

-;7

Plug Weld cross sectionNeg no 59937 4X


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lloy Sheet

IntermittentFillet Welds lloy Sheet

Seal Weld

PreformedEdgeMolding

REQUIRE I I L

~V


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lloySheet

Seal WeldSeam

SealWeld

Substrate

lloySheet

IntermittentFillet Welds

PreformedCornerMolding

BREAK 9 FORCORNERBOX

4 1i f - - . L - - - - - , LLf jI I 4

l 8 l

FIT PREFORMED EDGE MOLDINGTO CORNER M O L N ~THENSEAL VELD ALL AROUND


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Midsheet Attachment i Specified

Intermittent Fillet Welds

Seal Weld

Substrate

9 Break

Alloy Sheet

Seal Weld


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28/31

8 000

1 000

Gener lI s t on f igu ra t ionUsed Fo r Fillet lIela Plug lIeldo r Spot lIeld Te s t

2 000

s t As Shown

8 000

1 1 4 . 0 0 0

~ o yShee t CQrbon Stee l

_ f_O._06_3_ L - - - - . . . , c : : f ~ . : : : = = = / = = = = * f : : : J 0

nsil


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Sheet material tearingNeg no 57760

Plug weld failure at substrate1 2X

Figure 10: Plug Weld Shear Test Results

I

II

1

1734 pounds to failNeg no. 59898 1/2X

2694 pounds to fail


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1 2 3 7 5 ~

t ep ne

Plug Weld or Ar c Spot \ Ipla \ I

r ~ ~ ~ l >F I U t V ld Around C FillerL :;: M t l GT

I - C - 2 7 6Plug Weld Pipe

Section

t e p Two

CarbonStee lenter

Co rbon Steel DIsk n C DIsk

P lu g \J el d or

Ar c Sp o t Weld I C 22Pe r Stando rd I ~ I Disk RequireMents I - - - - - - ~ \

. . . L . . . ~ ~ ~ ~ F o ' . o ; ; : T

0.250

Figure 2: Fabrication Steps for Plug Weld and rc SpotWeld orrosion Test Specimen

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