Heat Treatment

COOPERHEAT

25

INTRODUCTION TO HEAT

TREATMENT

OF WELDED STRUCTURES

AND TECHNICAL DATA

1. Welding Process Br its EffectsThe welding process appliedto metals joins twocomponents together byfusion. The surfaces to bejoined are raised locally tomelting point by a source ofheat provided by a variety ofwelding methods based onelectric arc, electricresistance, flame. Theprocess energy creates alocalised molten pool intowhich the consumable is fed,fusing with the componentsurfaces and/or previouslydeposited weld metal.

As the molten pool is movedalong the joint axis, thecomponents are heated, non­uniformly and subsequentlycooled, also non-uniformly.Neighbouring elements ofmaterial try to expand andcontract by differing amountsin accordancee with thesequence of the localisedthermal cycle.

Characteristically the coolingweld metal contracts underconditions of severe restraint,leading to the introduction ofthermally induced stresses.

As contraction tries to takeplace and the stress systemstrives to reach its lowestlevel to achieve stability,distortion will occur asyielding takes place. If thejoint is restrained and cannotdistort, then high levels ofstress will occur and maylead to failure in the form ofcracking.

Unrestrained Contraction CausesDistortion

In making a joint, gaps wouldoccur at the plate ends if theweld metal were allowed toexpand and contract withoutrestraint.

I1IUnfused Weld Metal

A longitudinal force on theweld is required to close thegap giving a tensile stresswhilst correspondingcompressive stresses in theplate material provide theequilibrium.

Fused Weld Metal

Residual stresses will act intwo principle directions;longitudinal stresses parallelto the joint and transversestresses normal to the joint.

I /./Residual Stress Directions

The distribution oflongitudinal residual stressesin the section will be asshown with tensilecomponent confined to theregion of the joint.

Stress Distribution

It should not be forgotten thatthe value of the tensilestresses can be high oftenexceeding yield pointmagnitude.

So far the mechanical effectsof welding in the form ofresidual stresses have beenconsidered. The deposition ofweld metal in a molten pooland the localised melting ofthe joint faces of thecomponents, along withsubsequent cooling, all havemetallurgical implicationsaffecti ng the microstructu reof these regions.

Cooling after welding can berelatively rapid. From themolten pool of weld metal an

'as cast' type of structuredevelops. In the region ofparent metal at the fusionface raised to melting point,metallurgical restructuringtakes place to give the heataffected zone (HAZ).

OJ Weld Metal 0 HAZo Parent Plate

In steel the heat affectedzones are generally harderthan the parent material withcorresponding loss ofductility and resistance toimpact.

Since the basic sources ofweld failure are aconsequence of thermalbehaviour, a series ofpotential solutions arisebased on the application ofheat. The welding processeshave to be controlled so thatthe residual stresses areminimised to protect theintegrity ofthe overallfabrication and themetallurgical structures ofthe weld metal and heataffected zones are controlledto give properties which arenot inferior to those of theparent material which havebeen used in the design ofthe product.

A series of heat treatmentoperations are associatedwith the welding processes,arising from the need tocontrol these changes. Theseform the basis of the subjectof Heat TreatmentEngineering.

2. Preheat Br Postheat

27

High

Thick Section

Heat -- ~

Loss ~

Where preheat is applied,every effort should be madeto ensure that the correctlevels for a particularapplication are attained, bothuniformly over the length ofthe joint and for the durationof the welding process.

For the purposes ofillustration, the preheatrequirements of highpressure pipework codes8S2633, ANSI 831.1, andANSI 831.3 are compared.

Post heat treatments are notreflected in nationalstandards or codes, but areoften specified by the clientwho has incorporated theirequivalent into the weldprocedure qualification test.The temperatures and soaktimes are derived fromnumerous technical paperspublished on this topic.

Guidance for the need topreheat is generally obtainedfrom the national fabricationcodes, which will listrecommended minimumtemperatures for steel typesgrouped by composition andalso relate the minimumsection thickness to whichthey apply.

• Compensation for heatloss. Thicker section steelswith high thermalconductivity benefit frompreheat during welding withimproved fusion.

Post Heat This is the termgiven to the extension ofpreheat on completion ofwelding at the same orincreased temperature. Itspurpose is to effect diffusionof hydrogen from the jointand reduce susceptibility tothe associated form ofcracking. It is usually appliedto the higher strength carbonmanagenese steels and thelow alloy steels where therisk of hydrogen cracking ishigher.

Low

Thin Section

'///J///.

PorosityHeat Affected

Zone (Haz)

The presence of preheat, andassociated benefits oncooling rate, helps tofacilitate the diffusion of thehydrogen molecules out ofthe metallic structure.

• To reduce thermalstresses. Thermal strainsare set up as the molten weldpool cools. Partially madewelds can crack as the parentmetal restrains thecontraction of the weld metaland the cross sectional areaof the joint is insufficient towith stand the resfJltantstress. Preheat can controlthe level of strain by reducingtemperature differentials andreducing cooling rates.

Moisture is also introducedfrom the weldingconsumables being presentin electrode coatings andfluxes. To obtain themaximum benefits frompreheat in controllinghydrogen, it must beaccompanied by carefulcontrols over removal ofmoisture from the weldingconsumables by followingmanufacturers baking andstorage instructions.

Time ----..

preparartion area is dry andremains dry throughout thewelding operation.

The solid curve shows the temperature in theheat affected zone as the arc passes byThe dotted curve is the temperature whenpreheat is used. Preheating provides slowercooling

i:=l~L:J\ ~ OXYGEN

HYDROGEN

• To control the diffusionrate of hydrogen in awelded joint.The intensity of the electricwelding arc breaks downwater, present as moisture,into its base elements ofhydrogen and oxygen. 80thof these gases are easilydissolved into the weld metalat high temperatures andhydrogen can play animportant role in weld andheat affected zone crackingwith a phenomenon knownas hydrogen or cold cracking.Preheat can also help byensuring that the weld

Mater;al Hardens Material Softens

• To control the rate ofcooling, especially in theheat affected zone, to reducehardness. High carbon andlow alloy steels harden ifthey are quenched from hightemperatures (above cherryred). Exactly the sameprocess can happen in awelded joint at the fusionface with the parent material.8y raising the temperature ofthe base metal to be welded,to reduce the temperaturedifferential between ambientand the resultant heat input,hardening may be contr911edas the weld cools. Reducinghardness reduces the risk ofcracking.

Preheating involves raisingthe temperature of the parentmaterial locally, on bothsides of the joint to a valueabove ambient. The need forpreheat is usually determinedby the pertinent fabricationcode and verified by the weldprocedure qualification test.Preheat may be required asan aid to welding for one offour basic reasons.

~>\~~:~/.(~ ~-,: •••;~;~••••.•• -- tffY..~~~~.\\\,S,~ -~~--~--=====::_--------

RED HOT FILE QUENCHEO IN~'ATER BECOMES HARD

~>\~~:~/.(~- •.·.~f;.;•••".•.•~ -­.-.,~.. ,. "~//.\\\""

RED HOT FILE COOLED SLOWLY BECOMES MALLEABLEAND DUCTILE

:1/ \ Ome ocl~

An estimate of weld metal

hydrogen levels can be madefrom a knowledge of thepotential hydrogen level in theconsumables

I r~XI Low I Medium I High

Weld hydrogen level

PREHEAT REQUIREMENTS FOR BS 2633: 1987· HIGH PRESSURE PIPEWORK

Minimum preheat temperature

Hydrogen controlledNon hydgrogen controlledfor tig welding of root run

weld metal18S 1719)weld metal

Material

Carbon steel Matching rootMaterialMinimumMaterialMinimum

root run

run. All diameterthicknesspreheatthicknesspreheat

Upto 127mm

Above 127mmand thicknesses(greatesttemp(greatesttempdiameter and

diameter or thicknessthickness

12.5mm thick

12.5mm thick of joint mm Iof joint mm I

Carbon Steel

5'CUp to 30mmUp to 30mm 5'CUp to 305'CUp to 205'C

to 0.25%C

5'C

Above30mm

Above 30mm 100'CAbove 30100'CAbove 20100'C

100'C

Carbon steel

50'C100'C100'C All150'CAll200'C

above 0.25%C Up to 0.40%C

Carbon-moly

5'C100'CUp to 12.5 - 20'CUp to 12.520'CUp to 38150'C

Above 12.5 - 100'CAbove 12.5100'C

lCr 'I) Mo

5'C100'C100'C Up to 12.5100'CUp to 12.5150'C

Above 12.5

150'CAbove 12.5200'C

Up to 20

'11Cr'/1Mo '/4V

50'C100'C100'C Up to 12.5150'CNot permissableAbove 12.5

200'CLow H1rods required

2'14 Cr 1Mo

50'C100'C100'C Up to 12.5150'CUp to 12.5 200'CAbove 12.5

200'CLow H1rods required

5Cr'/1Mo

Carbon SteelCarbon steel

7Cr'I)Mo

root run notroot run not150'C All200'CLow H1rods required9Cr lMo

allowedallowed

Special Note re 8S.2633

The table is for guidance only. It illustrates the contents of the preheat section of BS. 2633

(Table 5) which should be consulted in its entirety.

A number of other important standards give guidance on preheat, these include:Hydrogen-induced cracks

in HAZ of a butt weldASME Code

BS 1113

BS 4570

BS 5135

BS 5500

Section III : Nuclear power plant components

Section VIII: ASME Boiler and pressure vessel code

Water tube steam generating plant

Fusion welding of steel castings

Part 1 - Production, rectification and repair

Part 2 - Fabrication welding

Metal arc welding of carbon and carbon-manganese steels

Unfired fusion welded pressure vessels

100 0 100 200 300 400·C

Weld hydrogen level

Effect of preheating on residual stresses

120%Weldmg at sub-zero temperaturescauses increased residual stress

11 1~::sne~~;:;~~;~~~'

Special Note re ANS1/B31-1 Br ANS1/B31-3

The table below is for guidance only. Reference should be made to the appropriate specification

PREHEAT REQUIREMENTS FOR PETROLEUM REFINERY PIPING (ANSI B.31-1.19901 & POWER PIPING (ANSI B31.1-1992)

8ase

MaterialMinimum Recommended Preheat Temperature 'F

MetalNumber

Group AN SI 8.31.3ANS1831.1

1

Carbon Steel 71 KSI & below 1" - 50Carbon above 0.30% or 1" -175

1" & above -175

Others - 50

Above 71 KSI - 1753

Chromium '/1% max71 KSI & below '/{ - 50Above 60 KSI OR '/{ - 175

'I{ & above - 175

Others - 50

4

Chromium '1)%-2% 300 Above 60 KSI or '/{ - 250

Others - 505

Chromium 2'/4% - 10%350 Above 60 KSI or both above '/1" & chromium above 6% - 400

Others - 3006

High Alloy Martensitic300 400

7

High Alloy Ferritic 50 50

8

High Alloy Austenitic 50 50

9A98

Nickel Alloys 200 P-9A 250. P98 - 300

lOA

Manganese Vanadium175

10E

27 Chromium 300 300

11A

8%,9% Nickel 50

group 1 P21-P52

50

3. Post Weld Heat Treatment

29

PostheatedWeld

Weld notPostheated

Complete relief ofresidual stresses-

700 200 300 400 500 600Stress relieving temperature ("C)

Effect of stress relievingat various temperatures

iReduced Residual Stresses

engineered system is capableof providing appropriatelevels of performance.

0%

Improved Metallurgical Structure

'"'"'"c:-0

"­

co

J::

Benefits of Post WeldHeat Treatment

~ 100%

"c:

"il;

~~ 80%"-~",0>

~~ 60%"'-~~~ Q3 40%"-~-0 co'"

~ 20%o-J

The heating and cooling ratesare at least compliant withthe necessary coderequirements. These rateswill indicate absolutemaximum values, and arecalculated from simpleformulae related tocomponent thickness to offerprotection against thermallyinduced stresses. With thickerand more complex structuresan experienced heattreatment engineer may wishto consider lower rates thanrequired by the code toensure acceptabletemperature profiles andgradients with a view tokeeping these thermallyinduced stresses to anabsolute minimum.

With localised heattreatment, the temperaturegradients away from the hotzone must not be undulysevere, again the objectivebeing the minimisation ofthermally induced stresses.British Standards BS 5500,BS 2633 offer guidence in thisissue, quoting the2.5 -V Rt rule.

required temperature andprovide a temperature profiletherein which is uniformwithout creating additionalundue thermally inducedstresses. This aspect hasgreater significance in thecase of localised heattreatments, but neverthelessmust also be considered withfurnace heat treatments.

The stress distributions at thehigher temperatures becomemore uniform and theirmagnitude reduces to a lowlevel. On cooling, provided itis carried out in a controlledmanner, the improved stressdistribution is retained.

In addition to a reduction andre-distribution of residualstresses, postweldtreatments at highertemperatures permits sometempering or aging effects totake place. Thesemetallurgical changes arevery beneficial in that theyreduce the high hardness ofthe as-welded structures,improving ductility andreducing the risks of brittlefracture.

Post Weld HeatTreatment. This is a processcommonly referred to asstress relief, so calledbecause it is carried out attemperatures at which yieldstrength has fallen to a lowvalue. If the structure isheated uniformly, the yieldstrength of the materialaround the weld is unable tosupport the initialdeformation. Creep occurs atthe elevated temperaturesand strain will occur by adiffusion mechanism,relaxing the residual stresseseven further. The extent towhich residual stresses arerelaxed will depend ontemperature for any givenmaterial and on material forany given temperature.

Post weld heat treatment hasmandatory significancegoverned by the nationalstandards and codes, as wellas being required to offeracceptable component life inonerous environments. Aswith preheat, the alloyingcontent of the steel is relatedto the significance of heattreatment temperature.

Features of Post WeldHeat Treatment. There arefive aspects to a post weldheat treatment that must beaddressed.

The hot zone is adequate toraise the weldment to the

The soak tempertures areheld within the upper andlower limits of the soak rangefor the appropriate period oftime.

The heat treatment system(including insulation), zonaldivision and number ofthermocouples is such thatthe energy input and level ofcontrol is capable of enablingthese objectives to be metensuring that the integrity ofthe overall structure is notjeopardised.

For local heat treatments,controls have to beimplemented to provideassurance that the

Improved Corrosion Resistance

Remove

~qr~w~~~¥'U PWHT

Improved Machinability

o

POSTWELD HEAT TREATMENT REQUIREMENTS FOR SS 2633: 1987 - HIGH PRESSURE PIPEWORK

Time at temperature: Minutes/mm thicknessMaterial

Soaking Temperature in furnace (pipework and welds)Local heattreatment

temperature

. (welds only)

Carbon up to 0.25%OC

580-620 2.5 (minimum 301 2.5 (minimum 30)

Carbon 0.25 up to 0.4%(

630-670 2.5 (minimum 301 2.5 (minimum 30)

Carbon-Moly

630-670 2.5 (minimum 601 2.5 (minimum 60)

lCr '/2 Mo

630-670 5 (minimum 120) 2.5 (minimum 1801

'h Cr '/2Mo '/,V

680-720 180 irrespective of thickness but thin wall up to 127mm2.5 (minimum 180)

diameter & 12.5mm thick may be 30 minutes minimum

2'/,Cr lMo

680-720 (optimum creepl180 irrespective of thickness but thin wall up to 127mm2.5 {minimum 601

diameter & 12.5mm thick may be 30 minutes minimum710-750 (softening where

5 (minimum 1201 2.5 (minimum 601

optimum creep properties not required)

5Cr '/2Mo

710-760 5 (minimum 1201 2.5 (minimum 120)

7Cr'/2Mo 9Cr lMo12CrMoV(WI

720-760 180 irrespective of wall thickness 2.5 (minimum 60)

3'/2Ni

590-620 2.5 (minimum 60) 2.5 (minimum 60)

9Ni

None Not required Not required

Special Note re BS.2633

The table is for guidance only. It illustrates the contents of the post weld heat section of SS. 2633

(Table 6) which should be consulted in its entirety.

Also see SS. 1113 for post weld heat treatment requirements for water tube steam generating plant.

For certain service conditions and for pipes of O.15%OCmaximum, post weld heat treatment of welds in pipes up to and including 12.5mm thick

and fillet welded attachments where the throat thickness does not exceed 12mm is not required subject to satisfactory welding procedure tests.

Special Note re ANSI/B31·1 & ANSI/B31·3

The table below is for guidance only. Reference should be made to the appropriate specification

POST WELD HEAT TREATMENT REOUIREMENTS FOR PETROLEUM PIPING (ANSI B.31.1. 1990) & POWER PIPING (AN SI B31.1-1992)

Base

MaterialPostweld Heat Treatment Requirement of Soak

MetalGroup

ANSI B.31.3AN SI B3.1 Boiler External Piping

1

Carbon Steel Above 3/t -1100/1200 1 hour minAbove 3/t 1100/1200 1 hour {Inch.

3

Chromium '/2% maxAbove 31{ or above 71 KSI - 1100/1325Above 5/s" & Carbon above 0.25% 1100/1200

1 hour min. 225 Brinell max

1 hour{lnch

4

Chromium '12% -2% Above '/2" or above 71 KSI-1300/1375Above '12".4" 00,0.15% carbon 130011375

2 hours min. 225 Brinell max

1 hour{lnch

5

Chromium 2'/4% - 10%Above 'I{ -0.15% carbon, 3% chromiumAbove 'h", 4" 00,0.15% carbon 3% chromium

1300/14001 hour min. 241 Brinell max

1300/1400 1 hourlinch

6

High alloy martensitic1350/14502 hours min. 241 Brinell max1400/14751 hour{lnch

A240 Grad 429. Temp range 1150/1225

7

High alloy ferritic None 1350/14251 hour/inch

8

High alloy austenitic None None

9A 9B

Nickel alloy steels Above 3/"-1100 -11751 hour min9A above '/{, 4 OD, 0.15% carbon 1100/1200

1 hour min. 9B - above 112",1100 - 1175

lOA

Manganese vanadiumAbove 3/4'or 71 KSll100/1300

1 hour min. 225 Brinell max

10E

High Chromium 1225/13001 hour min1250/1300 1 hour {Inch

stainless steel

llA

9% nickel steel Above 2" 1025/10851 hour min (note:

group 1cooling rate to be above 300/Hr down to 600)

Heat Treatment of Pipewelds with48kV A Heat Treatment Unit and Pad Elements

31

®

®

®

®

®

CIRCUIT 2

CIRCUIT 1

Cl:

~Cl:

f--­

<aCl:lJ..

415V 3 PHASE60 AMP SUPPLY

Note:'Circuits 3, 4, 5 and 6 have notbeen shown for clarity.

TYPICAL 48kVA 6 CHANNEL HEAT TREATMENT UNIT PACKAGE

Item No.

Oty.Stock No.Page Description

1

110334448kV A 6 Channel Heat Treatment Unit

2

6350249Triple Cable Sets

3

63200192 way Splitter Cables

4

63200293 way Splitter Cables

5

15See Range12-18Heating Elements

6

642011222m Thermocouple with Plug

7

As Req.4300722High Temperature Cement

8

3See Range19Ceramic Fibre Insulating Mats

9

1417561711Thermocouple Attachment Unit

Items 5,6, 7 and 8 are consumables and quantities required will depend on extent of work and production rate.

Circumferential Stress Relief of Pressure Vessel

Welded Seams using Twin Bulkhead Methodand Channel Elements .

•CABLE ENTRY THROUGHVESSEL 'MAN-WAYS'

@

ROLLER SUPPORTSFOR EXPANSION

6 CHANNEL 415V DISTRIBUTION UNITAND TEMPERATURE RECORDER

FIXED SUPPORTS

STEEL BULKHEADS

4-12mm RODS

n

n

4-BANKCHANNELELEMENTS

THERMOCOUPLESATTACHED TOWELDED SEAM AND ATGRADIENT POSITIONS

J•

IRON MESH WIREDTO BULKHEADS

TYPICALRECOMMENDEDHEIGHT FORMILD STEELCHANNELS

MILD STEELCHANNELS TOSUPPORTELEMENTS

MINERAL WOOL MATS 60mmTHICK WITH SINGLE LAYEROVER GRADIENT ZONESAND DOUBLE LAYER OVERTHE HEATED ZONE

TYPICAL PACKAGE FOR PWHT OF 3M DIAMETER SEAM

Item No.

Qty.Stock No.Page Description

1

11400296 Channel 415V Distribution Unit

2

123000119Feed Cable (4/3 Heating Elements)

3

332002193 way Splitter Cable (11 Phase)

4

927750184-Bank Channel Elements (31 Phase)

5

140006106 Point Temperature Recorder

6

6340002130m Compensating Cable (2 Ptsl Heater)

7

6'42011222m Thermocouple with Plug

8

As Req.4300722High Temperature Cement

9

10 Bales506-01419Mineral Wool Insulation

10

141756(711Thermocouple Attachment Unit

98.9 210410.0204400752 5109501742 81615002732

99.4

211411.8210410770 5169601760 82115102750

100.0

212413.6216420788 5219701778 82715202768

100.6

213415.4221430806 5279801795 83215302786

101.1

214417.2227440824 5329901814 83815402804

101.7

215419.0232450842 53810001832 84315502822

102.2

216420.8238460860 54310101850 84915602840

102.8

217422.6243470878 54910201868 85415702858

103.3

218424.4249480896 55410301886 86015802876

103.9

219426.2254490914 56010401904 86615902894

104.4

220428.0260500932 56610501922 87116002912

105.0

221429.8266510950 57110601940 87716102930

105.6

222431.6271520968 57710701958 88216202948

106.1

223433.4277530986 58210801976 88816302966

106.7

224435.22825401004 58810901994 89316402984

107.2

225437.12885501022 59311002012 89916503002

107.8

226438.82935601040 59911102030 90416603020

108.3

227440.62995701058 60411202048 91016703038

108.9

228442.43045801076 61011302066 91616803056

109.4

229444.23105901094 61611402084 92116903074

110.0

230446.03166001112 62111502102 92717003092

110.6

231447.83216101130 62711602120 93217103110

111.1

232449.63276201148 63211702138 93817203128

111.7

233451.43326301166 63811802156 94317303146

112.2

234453.23386401184 64311902174 94917403164

112.8

235455.03436501202 64912002192 95417503182

113.3

236456.83496601220 65412102210 96017603200

113.9

237458.63546701238 66012202228 96617703218

114.4

238460.43606801256 66612302246 97117803236

115.0

239462.23666901274 67112402264 97717903254

115.6

240464.03717001292 67712502282 98218003272

116.1

241465.83777101310 68212602300 98818103290

116.7

242467.73827201328 68812702318 99318203308

117.2

243496.43887301346 69312802336 99918303326

117.8

244471.23937401364 69912902354 100418403344

118.3

245473.03997501382 70413002372 101018503362

118.9

246474.8404760140071013102390 101618603380

119.4

247476.64107701418 71613202408 102118703398

120.0

248478.44167801436 71213302426 102718803416

120.6

249480.2421790145472713402444 103218903434

121

2504824278001472 73213502462 103819003452

127

2605004328101490 73813602480 104319103470

132

270518438820150874313702498 104919203488

138

2805364438301526 74913802516 105419303506

143

2905544498401544 75413902534 106019403524

149

3005724548501562 76014002552 106619503542

154

310590460860158076614102570 107119603560

160

320608466870159877114202588 107719703578

166

330626471880161677714302606 108219803596

171

340644477890163478214402624 108819901614

177

350662482900165278814502642 109320003632

182

3606804889101670 79314602660 109920103650

188

370698493920168879914702678 110420203668

193

380716499930170680414802696 111020303686

199

3907345049401724 81014902714 111620403704

Temperature Conversion Tables

Find the known temperature to be converted in the Red column. Thenread the Centigrade conversion to the left and Farenheit to the right

Example204 400

therefore400'C400'F

752

752'F204'C

33

Conversion FactorsLength DensityPower, heatflow rate

lcm=0.394 in1 kg m-3=0.0624Ib fr3lW= 0.86 kcalh-1

lm= 3.281 ft1 kg m-3= 0.1 Ib (Imp gal)- 11 kW=3412 Btu h-1

1 km= 0.621 mile1 kg m-3=0.835Ib (US gal)-l1 kW= 56.87 Btu min-1

1 in

= 25.4 mm1 Ib fr 3= 16.02kg m-31 Btu h-1=0.293 W1 ft

= 30.48 cm1 Ib (Imp gal)-l =99.8 kg m-31 kcal h-1=1.163W

1 yd

= 0.9144 mlib (US gal)-l = 119.8 kg m-31 mile

= 1.609 km

J I

Specific heat capacity

1 kJkg-1°C-1= 0.239 Btu Ib-1 °F-1

1 kJm-3OC-1=0.0149 Btu ft-3OF-1

MassArea

1 kg

= 35.27 ounce1 cm2=0.155in2

I1 Btu Ib-10F-l =4.187 kJkg-1°C-l

1 kg=2.205Ib 1 m2= 10.76 ft2 1 Btu fr3OF-l= 67.07 kJmc 30C- 1

1 tonne=22051b 1 km2=0.386 mile2

1 tonne= 0.984 Imp ton1 ha= 2.471 acre

1 tonne= 1.102 US ton

1 in 2=6.452cm2

I

Thermal conductivity1 ounce

= 28.35 g1 ft2=0.093 m2 1 Wm-1OC-1=0.578 Btu ft-1 h-1OF-1

1 Ib= 0.4536 kg1 mile2=2.590 km +1 Wm-1OC-1=6.93 Btu in fr2h-1OF-1

1 Imp ton= 1016 kg1 acre0.405 ha

1 Imp ton

= 1.12 US ton

I1 Btufr' h-1OF-l=

1 US ton= 907 kg 1.73Wm-1 0C- 1

Btu in ft-2 h-10F-1 = 0.144Wm-1°C-lIEnergyVolume1 J=0.239 cal

1 m3= 35.31 ft31 J=0.738 ft Ibf

I

Heat transfer coefficient1 m3

=220 Imp gal1 J= 107 ergs 1 W m-2OC-1=0.176 Btu ft-2h-1 °F-l1 m3

= 264 US gal1 kJ= 0.948 Btu 1 Wm-2OC-1=0.86 kcal m-2h-1OC-l1 m3

= 6.29 barrel1 MJ= 0.0095 therm1 litre

= 0.22 Imp gal1 MJ= 0.3725 hp hourI

1 Btu ft-20F-1 =5.678 Wm-2OC-11 litre

= 0.264 US gal1 kWh=3.60 MJ 1 kcal m-2h-10C-1 =1.163 Wm- 20C-11 ft3

= 0.0283 m31 cal=4.187J1 ft3

= 28.32 litre1 Btu= 1.055 kJ1 ft'

= 6.23 Imp gal1 Btu=0.293 Wh1 ft3

= 7.48 US gal1 therm= 105.5 MJ

I

Temperature intervals1 barrel

=42 US gal1 therm=29.31 kWh1 deg C= 1.8 deg F= K1 barrel

= 159 litre1 ft Ibf= 1.356J 1 deg F=0.556 deg C

Nominal Wall Thickness forStandardImperial(Non-Metric)

Pipe(inches)Double

Nominal

OutsideSch.Sch.Sch.Sch.Std.Sch.Sch.ExtraSch.Sch.Sch.Sch.Sch.Double

Pipe Size Dia.

5S10S2030Wt.4060Strong80100120140160Strong

%

0.8400.0650.083 0.1090.109 0.1470.147 0.1870.294

'%

1.0500.0650.083 0.1130.113 0.1540.154 0.2180.308

1

1.3150.0650.109 0.1330.133 0.1790.179 0.2500.358

lY.

1.6600.0650.109 0.1400.140 0.1910.191 0.2500.382

1%

1.9000.0650.109 0.1450.145 0.2000.200 0.2810.400

2

2.3750.0650.109 0.1540.154 0.2180.218 0.3430.436

2%

2.8750.0830.120 0.2030.203 0.2760.276 0.3750.552

3

3.5000.0830.120 0.2160.216 0.3000.300 0.4380.600

3%

4.0000.0830.120 0.2260.226 0.3180.318 0.636

4

4.5000.0830.120 0.2370.237 0.3370.337 0.4380.5310.674

5

5.5630.1090.134 0.2580.258 0.3750.375 0.5000.6250.750

6

6.6250.1090.134 0.2800.280 0.4320.432 0.5630.7180.864

8

8.6250.1090.1480.2500.2770.3220.3220.4060.5000.5000.5930.7180.8120.9060.875

10

10.7500.1340.1650.2500.3070.3650.3650.5000.5000.5930.7180.8431.0001.125

1212.7500.1560.1800.2500.3300.3750.4060.5620.5000.6870.8431.0001.1251.312

14

14.000 0.2500.3120.3750.3750.4380.5930.5000.7500.9371.0931.2591.406

16

16.000 0.2500.3120.3750.3750.5000.6560.5000.8431.0311.2181.4381.593

18

18.000 0.2500.3120.4380.3750.5620.7500.5000.9371.1561.3751.5621.781

20

20.000 0.2500.3750.5000.3750.5930.8120.5001.0311.2811.5000.7501.968

24

24.000 0.2500.3750.5620.3750.6870.9680.5001.2181.5311.8122.0621.343

TemperatureDensityCoefficientSpecificThermal

of Thermal

HeatConductivity

Expansion

20°C to Temp

20°C to Temp°C

Kg .m-3K-1.10-6J.Kg-1.K-1Wm-1.K-1

Carbon Steel

207850 54

200

785012.751149

400

785013.856143

600

785014.661136

Ferriticalloys

207850 45

200

785012.750342

400

785013.854538

600

785014.660233

Austeniticsteels

207970 14

200

797016.752017

400

797018.054120

600

797018.755523

700

797019.256225

Engineering DataPhysical Properties Of Typical Pressure Part Steels

Tensile Properties Of Typical Pressure Part Steels

....•....

35

TensileYield0.2% Proof Stress (1% for Austenitic Steels)

Strength

Strengthat various temperatures °C N.mm-z

N .mm-z

N .mm-z200250300350400450500550600

Plates Carbon Steel

430230190180160155150

1Cr 1/ZMo

420285210185160150145140135130

21hCr 1Mo

480280205200195190185175160145

18Cr 12Ni 2Mo

510215140130127122120115110105100

Pipes & Sections

Carbon Steel

490340260240220200185170

1Cr11zMo

440290245235190180175170165160

21/4Cr 1Mo

490275245235230225220205190165

18Cr 12Ni 2Mo

510245170165160150145140135130125

Tubes

Carbon Steel

440245195170160150140

1Cr 1/zMo

460180 190180175170165

21/4Cr 1Mo

490275 225220205190165

18Cr 12Ni 2Mo

510245150145140135130128125122

Esshete

540270190187184182179178175170