## LIFESAVIN G SYSTEM S CORP
. 22 0 ELSBERRYRD . •APOLL O BEACH , FL3357 2 ' ' PHON E 813/645-274 8 •FA X813/645-276 8 www.lifesavingsystems.co m Februar y11 , 201 0 U S Departmen t o fTransportatio n Docke t Operations , M-3 0 Wes t Buildin g Groun d Floor , Roo m W12-14 0 120 0 Ne wJerse yAvenue , SE
. Washington , D C 2059 0 Ref : Airworthines s Directive , Docke t No . FAA-2009-114 8 Attn : Mar k

R . Schilling , Actin g Manage r- Rotorcraf t Directorate GaryRoach , Aviatio n Safet yEnginee r- Rotorcraf t Directorat e Dea rSirs : Th e purpos e o fthi s lette ri s a forma l reques t byLifesavin g System s Corp
. (LSC) , manufacture ro fth e D-LO KHois t Hook , t o hav e th e FAArescin d th e abov e reference d A D o n th e followin g grounds : 1 . Informatio n cite d i n support o fth e A D i s erroneou s an d withou t basis . Th e A D claim s "Testin g show s tha t th e affecte d hook s coul d fai l a t 20 0 lifts. " Thi s i s false
. Ther e i s n o tes t dat a supportin g thi s claim . Ther e i s rea l worl d physica l testin g performe d bybot h LS C an d Goodric h providin g verifiabl e counte revidenc e t o suc h claim . T o dat e n o defects , othe rtha n mino rsurfac e discontinuitie s (whic h hav e bee n classifie d a s cosmeti ci n natur e only) , hav e bee n reported . 2 . Th e argumen t presente d bybot h FAAan d EAS Aa s basi s fo rth e A D i s a n "unapprove d chang e i n manufacturin g proces s fro m forge d materia l t o cas t materia l tha t hav e differen t physica l properties. " LS C present s th e counte rclai m tha t th e physica l propertie s o fth e cas t part , havin g bee n subjecte d t o Ho t Isostati cPressur e Densificatio n (HIP'D) , ar e endue d wit h physica l propertie s simila ran d nea r identica l t o th e wrough t form
. Th e meta l allo yan d al l subsequen t processin g ar e identical . An ymino r differenc e i n obtainin g th e sam e en d for m byon e o rth e othe rmetho d i s mor e tha n compensate d fo r byth e safet yfactor s inheren t i n th e D-LOK' s robus t desig n an d b yth e 25 % increas e i n cross-sectio n a t th e poin t o fgreates t stres s implemente d i n th e cas t & HIP' D hooks . Al l physica l testin g confirm s th e cas t & HIP' D hoo k

t o b e o fsuperio rstrengt h t o th e origina l forge d part . 3 . A D make s th e clai m tha t th e part s cos t t o replac e th e hoo k i s $300 0 pe rhoist . Thi s informatio n i s no t correct . LS C ha s provide d al l customer s wit h a replacemen t hoo k a t n o charg e o n exchange . Thus , wit h exceptio n o flabor , th e effectiv e part s cos t fo rreplacemen t i s $ 0 reflectin g a tota l cos t t o U.S
. operator s o fonl y$7,280
. Significantl yles s tha n th e amoun t $280,28 0 reporte d i n th e AD . 4 . LSC , a s manufacture ro fth e D-LO KHois t Hook , wa s no t consulte d prio rt o FAA' s releas e o fth e AD , an d a s suc h no t permitte d th e opportunit yt o provid e supportin g engineerin g analysis . LS C ha d brie f telephon e discussio n wit h FAArepresentativ e i n Jul yo f2009 . At whic h tim e th e implie d FAAconcer n wa s o fminima l nature . However , 7 month s late ran d 6 month s afte rreleas e o fth e EAS AAD , th e FAAclaim s ther e i s n o tim e fo rcomment/verificatio n o ffact s du e t o safet ypriority . A s well , th e majorit yo faffecte d hook s hav e alread ybee n replace d prio rt o releas e o fth e FAAAD . T o summarize , th e caus e an d issuanc e o fth e A D i s withou t basis , an d appear s t o b e a direc t resul t o fa knee-jer k

an d unjus t reactio n withi n an d byindustrytha t ha s no t considere d th e ful l engineerin g analysi s o fth e entir e manufacturin g proces s an d intende d application . LS C make s th e clai m tha t th e transitio n t o th e cas t manufacturin g process , subsequentl yfollowe d byth e Ho t Isostati cPressur e Densification , result s i n a finishe d produc t wit h propertie s nea ridentica l t o th e wrough t form
. Further , withi n th e intende d applicatio n o fhois t system s havin g a 60 0 lb s workin g loa d limit , th e inheren t safet yfacto ro fth e robus t D-LO Kdesig n mor e tha n compensate s fo ran ymino rdifferenc e i n materia l propertie s betwee n cas t wit h HI P densificatio n an d forge d processes . Th e severit yo fan ysafet yconcer n i n referenc e t o th e affecte d hook s i s thu s nil .T o substantiat e th e abov e clai m LS C provide s th e followin g information :

1 . Counte rt o industrystatement s th e hook s wer e manufacture d i n a controlle d process . Hook s wer e cast , solutio n hea t treat , an d homogenizatio n hea t treat i n accordanc e wit h SA E AMS-5355
. Fina l precipitatio n hea t trea t i s i n accordanc e wit h SA E AMS-2759/3C
. Al l vendor s i n relatio n t o suppl yo f th e cas t hook s o fth e affecte d lot s hav e IS O accreditation , NADCA P accreditation , o rothe raviatio n sourc e approval . 2 . Al l hook s underwen t Ho t Isostati cPressur e Densificatio n whic h eliminate s interna l voids , remove s castin g porosit y(increasin g fatigu e strength ) an d bring s part densit yt o nea rforg e characteristics . Th e proces s endue s overal l integrit ysimila rt o wrough t form s (referenc e "Ho t Isostati cProcessin g o f Cas t Steel s - Exhibi t A)
. Th e HIP' D proces s ha s bee n utilize d withi n aerospac e an d powe rindustrie s fo rman yyears . Technolog yadvancemen t an d cost s reduction s enabl e th e HIP' D proces s t o b e applie d t o a greate rrang e o fproduct s an d industrie s tha t wer e previousl yrestricte d acces s du e t o hig h costs . Successfu l implementatio n o fHIP' D processe s ha s produce d bot h cas t an d powdere d meta l part s acros s a broa d spectru m o falloy s wit h nea rwrough t properties , whil e retainin g th e manufacturin g an d comple xdesig n benefit s o fth e cast/p m process . 3 . Al l affecte d hook s receive d multipl e visua l inspection s an d eac h hoo k wa s proo floa d teste d t o 400 0 lb s byLifesavin g System s prio rt o release . 4 . Durin g th e transitio n t o th e cas t & HIP' D manufacturin g process , LS C too k th e opportunit yt o improv e th e geometryo fth e hoo k bod yan d increas e th e materia l cross-sectio n o fth e hoo k a t it s poin t o f greates t stres s o rmaximu m bendin g moment . Th e note d cross-sectio n o fth e hoo k wa s increase d by approximatel y25 % compare d t o th e previou s forge d design . Se e attache d drawin g (Exhibi t B ) fo r comparison . Thi s chang e i n cross-sectio n result s i n a n approximat e increas e o f20 % i n tensil e strengt h ove rtha t o fth e forge d hoo k i n pul l test s performe d byLSC
. 5 . Fo ral l intent s an d purposes , an d wit h th e exceptio n o fth e manufacturin g proces s (cas t & HIP' D vs . forged ) th e affecte d hook s ar e identica l i n materia l (17- 4 P H stainles s steel ) an d functio n t o th e prio r forge d design . O n thi s basi s an d du e t o th e fac t tha t th e part s wer e cas t i n accordanc e wit h aerospac e standard s an d furthe rsubjecte d t o th e Ho t Isostati cPressur e Densificatio n proces s whic h impart s characteristic s an d integrit ysimila rt o wrough t forms , LSC' s analysi s i s primaril yb y similarity/improvemen t ove rth e curren t approve d part . Al l structura l testin g byLS C show s th e cas t & HIP' D desig n t o b e stronge rtha n th e previou s forge d design . Al l othe rconsideration s concerning corrosion , temperature , environment , etc . ar e relate d t o materia l propertie s o fwhic h th e bas e meta l an d genera l desig n ar e unchanged . 6 . T o dat e n o defects , othe rtha n mino rsurfac e discontinuitie s (whic h hav e bee n classifie d a s cosmeti c i n natur e only) , hav e bee n reporte d i n respec t t o th e affecte d hooks . An yreferenc e a s t o testin g and/o rsimulatio n showin g failur e i s fals e o rwithou t rea l worl d correlation . Physica l testin g performe d bybot h LS C an d Goodric h Hois t an d Winc h prove s a s such . Th e followin g test s hav e bee n performe d an d ca n b e verified
. a . LS C Tes t Report date d 3 0 Novembe r200 7 (Exhibi t C)
. Apre-productio n sampl e o fth e cas t hoo k bod ywa s pulle d t o 8,00 0 lb s withou t permanen t deformatio n an d the n t o 10,00 0 lb s (limi t o fLS C tes t fixture ) withou t failure
. b . LS C Tes t Report date d 1 6 January200 8 (Exhibi t D)
. Acas t hoo k bod ywa s cycle d 10 0 time s a t 310 0 lb s an d subsequentl ypulle d t o 9,40 0 lb s withou t failure
. c . Goodric h successfull ycomplete d a fatigu e tes t consistin g o f1.02 millio n cycle s a t limi t loa d (2,10 0 lbs ) o fa n affecte d hoo k (lo t 1108 ) withou t failure
. The n subsequentl ysubjecte d th e sam e hoo k

t o a n ultimat e loa d o f11,10 0 lb s withou t fracture
. d . Goodric h successfull ycomplete d a secon d fatigu e tes t wit h a gros s fla wpurposel yintroduce d consistin g o fa .170 " diamete rhol e drille d throug h th e cross-sectio n o fa n affecte d hoo k a t it s poin t o fgreates t stres s (se e attache d drawing , Exhibi t E)
. Th e hoo k wit h induce d fla wwa s subjecte d t o 100,000 + cycle s a t limi t loa d (2,10 0 lbs ) prio rt o failure
. I t shoul d b e note d tha tFEA/Simulatio n softwar e predicte d failur e a t 2 cycles . Thi s tes t highlight s tw o points . First , eve n wit h th e grossl yinduce d fla wth e hois t hoo k i s o fsuc h a robus t desig n wit h over engineere d safet yfactors , tha t th e potentia l fo rfailur e wit h eve n sever e defec t i s minima l t o ni l i n rea l worl d use . Secon d i t prove s t o illustrat e th e poo rcorrelatio n o fsimulatio n analysi s t o physica l actualit ytha t leave s al l simulatio n analysi s suspect . 7 . A n overal l analysi s o fth e end-us e applicatio n an d safet yfactor s inheren t i n th e desig n o fth e affecte d hook s i s als o warranted . Th e cas t & HIP' D hook s ar e installe d o n hois t system s rate d a t 60 0 lbs . Pe r FAA' s mos t stringen t requirement s (Huma n Externa l Cargo ) th e limi t loa d fo rth e intende d applicatio n i s establishe d a s (3.5)*(600 ) = 2,10 0 lbs , wit h a n ultimat e loa d o f(1.5)*(limi t load ) = 3,15 0 lbs . Al l testin g t o dat e clearl yshow s tha t th e affecte d hois t hook s excee d th e limi t loa d requirement s prio rt o deformatio n bya n additiona l safet yfacto ro f3. 8 (800 0 lbs/210 0 lbs) , an d ultimat e loa d i s exceede d b y a n additiona l safet yfacto ro f3.5 + (11,10 0 lbs/315 0 lbs)
. I t shoul d als o b e note d tha t CF R Part 29.62 1 require s castin g factor s no t les s tha n 1.2 5 fo rcritica l parts . Th e affecte d hook s excee d thi s requiremen t by280% . I n conclusion , ther e ha s bee n misinformatio n release d withi n industryconcerning LS C an d th e D-LO Khois t hook . Thi s misinformatio n i s withou t meri t an d shoul d no t b e include d i n th e basi s o fa n FAA AD/Ruling
. Inclusio n o funfounde d statement s regardin g non-existen t tes t dat a lead s th e compan yt o questio n th e purpos e o fmakin g suc h comments . Thes e statements , whethe ro rno t o fpurposefu l intent , hav e th e effec t o fdefamin g th e subjec t manufacture ran d undermin e th e legitimac yo fth e FAAservin g a s a Governmen t Authority. Further , LS C wa s no t presente d wit h th e opportunit yt o provid e supportin g evidenc e prio rt o issuanc e o fth e AD . Th e abov e claim s an d supportin g evidenc e issue d byLS C serv e t o illustrat e tha t th e affecte d hook s hav e bee n manufacture d i n a controlle d proces s an d th e desig n an d manufactur e mor e tha n satisf yth e safet yrequirement s o fth e intende d application . Althoug h LS C recognize s FAA' s legitimat e concer n t o ensur e th e safet yo fal l aviatio n operator s an d public , th e safet y concer n an d severit yi n referenc e t o th e affecte d hook s a s liste d i n th e A D ha s bee n extende d wel l beyon d reason . I t i s therefor e requeste d tha t th e FAArescin d th e curren t AD . An yan d al l unsupporte d an d fals e statement s shoul d b e remove d an d i t i s agai n questione d wh yFAAwoul d releas e fals e statements . I t i s LSC' s recommendatio n tha t th e FAAthoroughl yevaluat e LSC' s clai m a s t o th e cas t & HIP' D part s havin g nea rwrough t physica l properties . Thu s permittin g analysi s bysimilarit yt o th e previou s forge d part an d renderin g th e clai m a s t o "proces s change " t o b e a non-factor
. Afte rrescissio n o fth e curren t AD , an d i n orde rt o compl ywit h CF R Part 29.62 1 i t i s recommende d tha t a ne wA D b e issue d requirin g operator s t o retur n affecte d hook s t o th e manufacture rfo rreprocessing . Reprocessin g t o includ e 100 % magneti c particl e an d 100 % radiographi cinspection s o fth e hoo k bod yi n accordanc e wit h SA E AM S 217 5 Clas s 1 / Grad e Athu s satisfyin g th e requirement s o fCF R part 29.621 . Upo n reprocessin g th e hook s wil l b e issue d a ne wpart numbe ro rlo t numbe rfo ridentificatio n purpose s an d the n mayb e returne d t o service . LS C wil l b e pleas e t o provid e an yanalysi s o rsuppor t t o enabl e FAAt o perfor m th e require d evaluation . Respectfully ,
Sa m Manes s CE O Enclosures ; Exhibi t A- E

# Exhibi t ATH

EHO TISOSTATIi i PtmeSSi mOFCASTSTBa S

I . Stroa» , Polytechni c o f U»Xm$ , Pont^priaa . U K D . Evtnt , HX

PLiMtma , c/t«i%rfi«l<* . U K
ABSTRAC T Th « reUtlonshl p betwewsth e iwcrostriiictur e snc t th e fflechanlcsl propirtle s of « thic k sectlont dhig hst>lsngt

hcas t stw V ha s been Investigated . The' intdwnlcs l proptirtie s wer e foun dt o vary frbir

i thi i ed ^ tf

l tfe | centff t of th e casting . Thi s jlia s btt n relate dt o th e Inddent e o f trifcropproilt y Mthie hii^fect* ^ th e ductflity l relate d j«%>pertie* » * *Jons(»t1on | < treductiiei B I n are s andChii'py V*iiotiCf

c value s t o tgreiitB r exten t 1*8 nt* e proiof

jtris s i>

r ijansH e strength . th e presiihc e o f si»rfa? e mlcroporosll ^ reveal ^ afte r wacli^l^ng als o drastfwll y Induce dth e ffitlgu t istrength . Simila r specimen s lier e suWectf) ^ t o Jw t Isfltatl c presslnjgi a t 'differen t te«p*ratureJ8 ' an

dth t resttttln j ntecharttca

V pfOl»iNs1e $ deterilfled*i . < Th

e efftctlv e closuf * .of

h\nUm^y-«ifi^pQpQiv$^^ ^ a ViSlgnimcsnt'i^n»W-«iii8t--ffc-::-th « .;)ij^8ii*,pa 1 , ::;pwipertte s 1s.::*epoi»^Bed»
- /W.tiJBCliSiBSt

Hff M ' tO i 70 XIntU

f l^tipi e *t«tojBl * t»i * obtained . Th

e SJJ Pt*iperetti ^ wit . vafletf fn» ! 930* c t o i2ao»C , "'4i t i s sjrtwn^itha

t » HI Ptonperatur e o f

SW'^tfvwa

s suffldim t

t o e.ff«i«*1ve1 y clos e th e Bifcfo^rcfslt y an a secur e th e sasi e leve l ;»f tucreas e I nth e weehanlcal proi;irt1e* , a s th» t obtalhe di t highe r HI Ptemi^retuires . Th

e liichentca t propertie s achieve dafte r HI Par e cosfarabt e Mlth,th& « ^|«ine di nsimila r wrought . steiBls . l 

# tmmai m Th e Intlderw e of

interna l mlcrpporoslt y In cas t stee l ha s a

nadvirs e eff«ic t

o nth e mechanica

l propertlt l particularl y th e S elongatio nan

dIreductio ni narea . In additio nan

y surfac e porosit y resalt s 1 na marke dreductio nInth e fatigu e strength . I t ha s als o beenshe w by^Eveh s et;.at..(l ) tha t th e mechanical propertie s o f "sound " cas t steel s ir e inferio r t o thos e of comparable wrough

t steels . I nth e past , effort s hav e beef t mad e t o mlnffrilse th e Incidenc e o f porOslt y b

y improve dfoundr y methods bu t

a nalternativ e approacht o th e problemi s no w available . Th e cloisur e o f

Interna l porosit y i ncas t metal s b y nean s o f

ho t Isostati c pressin g I s nt w aflntil y establishe dproces s an dth e consetjuent

Improvemen

t I nfltechantcal propertie s ha s bee

nrepqtrte d(2) . HI

PHt i beenextensivel y applie dt o cas t stainles s stepl s an

dsuperalliiy'composition s (3 ) bu t sighlflean t

advantase s ma

y als o b e -gaine dby i t s applitatlo nt o lo* f allo y e)»st

steet s (4) . Itesult s ha« « bee

npreviously ; repbirte d o nth e Ippllcatlp B o f

HIP
- t o thic k tectlbht d cas t carbo nsteel s fS ) an

dIs s chros^si

m<i H stee l (6) . I nthes e steel s afixe dHi p timpeiritur e t»as used . Ittt^ e presen t vrtir k a hig hstrengt halloy . eas t silie l wa

s lelecte d en dth e optiitwr

nHlf: temperiij/r e dftirwlne i consisten t

wltf^ i atchlevihfj g tlMK

= niax^ * obtatnabi e ffieehsniisal pro^rtlis . Specia l «Bph*$l s wa

s give nt o th e fatigu e strerigt h whic hI s of particula r

Importanc e i nIslgh strengt hsteels , ixPERWEStA

t DffiiitL S • '', ' The stee l wa

s pro^tocf dcbnJBierclalf.l

y b y ^ electri c n-

H process: . Th

f eiiposiwo n{«tJf

) 1 $ ,i s foll^ : C QM , S i <J.40 , $ 0.^18 , PQ.QZ7 , i n0.94 , m1.32 , fer l.l| , M o Oi*! , € u 0,11 , $f

t O.Oll . t«s t

specJiliBen

s were c^-^alnedffrrt

B rtBttangulae castlifg s SSSOR W lon g an dIBOn o sqirare cas t

vertlsatl y Ili a iir y san dmoul

dhavin g grevlS y ffede' r heads(5) . T^

e tastin g wa

s sUbse<juei>tl

y sectione dInt o sllcii s an dcu t t o obtai n specimen s fro

mth e edge , mid-sectio nan d centr e Fig.l . Th e hea t trfeattnent

consiste dof

oi l quenchin g frtw

n880*C . Whe

nsufficientl y cool , th e specimen s Wer e ijperse dt nliqui d nitroge nt o obtai nthe : fnsximim t transformatio no

f retaine daustenlt e t o martenslte . These wer e subsequentl y tempere da t

COO' C prio r t o wichlnln g t o th e fina l : dlniensions . Th e microstfUctur e i s show ni nFig.2 . Som e o f th e specimen s wer

e subjecte dt o HI

P usin g gaseou s argonan

dth e parameter s show

n i nTabl e 1 . Thes e wer e subsequentl y give n th e sam e hea t treatmen t

a s th e origina l specimens .

### 4. 8 TA8L C I RESULT S

.:: 5

• - . i



### i t 110 0 116 0 10 3 2

10 3 4 

## _Ji 2 L- .

Dimsinsion s I nm m f1g. i JNwtiisnln

g of Casting

Fig . Microstructyr e Tensil e test s wer e conducte d i n accordanc e wit h8S1 8 an d Charp ytest s a s specifie d I n BS131 . Roun d fatigu e specimen s 4. 1 mm . diamete r wer e carefull yprepare d t o giv e a fina l surfac e finis ho f >0,01 0 Raum , an d teste d usin g a rotatin g bendin g machin e wit ha zer o mea nstres s a t a spee d o f 50Hz . Th e result s ar e presente d a s stres s vlo g N curves . Bot hth e fatigu e limi t (FL ) an d th e fatigu e rati o (FR«Fatigu e limit/tensil e strength ) ar e reported . Th e fracture d end s o f th e fatigu e specimen s wer e examine d by bot hoptica l microscop yan d a scannin g electro nmicroscope . Th e macrostructur e Fig. 3 showe d columna r crystal s extendin g t o a dept ho f approximatel ylOmnfro mth e edg e o f th e casting . N o microporosit ywa s observe d i n thi s region , bu t th e are a containin g equlaxe d crystal s containe d microporosit y whic hincrease d I n severit ytowar d th e centr e o f th e castin g Fig.4 .

Fig. 3 Macrostructur e 

### ia?r«*jj'T^feir'-''^si7:vlSiSi ' '•••.••'• •

Fig, 4 Microporosit y Afte r HI P n o porosit ywa s observed . SE M photograph s o f fracture d fatigu e specimen s fro m th e m1d-sect1o nan d centr e o f th e castin g showe d fatigu e crack s originatin g a t area s o f porosit yFig.5 . Th e closur e o f microporosit ybyHI P resulte d I n Increase d fatigu e strengt han d broke nspecimen s showe d a norma l fatigu e fractur e Fig.6 .

### I A . 1 0 TABL E3 "HTA TTREATHW : O O ^O' C t^MPE R eoo-c . TEMp° C MN/m ' WM/m ' % S V(J 1 N O HI P HI D gao' c MI D llOO' C CENTR E 1100* C 85 7

99 5 99 2 89 0 89 0 91 0 86 4 

# -w r 97 6 108 5 107 8 102 8 102 5 102 6 100 7 

## "X T 5. 0 13. 4 12, 2 15. 8 14. 3 9. 5 14. 5 3. 4 49. 7 52. 2 28. 0 26. 0 23. 0 •27. 2 3 0 4 0 4 0 TABL E 4 H^A f Yfe^AMwT

; 6 6 ^b K tmt Rm ^ 

# mrmTT i MI D CENTR E CENTR E 3 6 0 32 0 22 0 

## •05 r

0.36 5 0.33 0 0.23 0 REDUCTION

7 . 7 18. 0 38. 0 TABL E5 HgA t tRgAMNT-.QO §SO*

C tfeWp S TiT P TEMP.' C 

# -m — NO HI P MI D 930« C MI O llOO' C MI O 1160* C MI D 1210" C CENTR E llOO' C MN/n » 

# w

r INCREAS E 36 0 53 0 54 0 56 0 S5 0 55 0 0.36 5 0.50 0 0-53 0 0.54 5 0.53 5 0.54 0 -

47. 0 50. 0 53. 0 56, 5 71. 9


# f 3 » o V , IS) . turmii i aatitii*Mo* c • (ge t nitirii M > M D • • ciwra e» I

CTCLE S T

O fWLUHeil. ) \ SSO^ 

# I
a 3

»00— • CM ) »M 1 ) f« amitw i •M<I M r . HIPISO t OO--TtN Pm T

» « (Tci-t s T

OMiLun ei w FIG. 8 Effec t

o f HI Pa t 930» C onFatigu e Strengt h 

# I

!!« ' > " ••M.iUlW t I«««posm w » ••«HIHW t

CTCLI S T O MHUd l« l FIG. 9 Effec t O f HI P a t llOO' C o n Fatigu e

Strengt h

- ^ •\^* ' •'^^^ . f.4i<t"tiii>''i!'^iyii;'ftMPia'c '
• dit>TiM*5'-6a.,TO«>*«' C « aa.-rty>oo' c 

# m

5 500 . » £ 5 i» 1 

## 3 a

- w» - MS - \

• ' \

•

C'tlS S T O FAILUSEIN ; FIG. 7 Effec t o f Microporosit yon Fatigu e

Strengt h FIG.1 0 Effec t o f HI P a t XISC C and 1210° C o n Fatigu e Strengt hI •Cas t Steel s afte rH.I. P 110

0 " C 700 H "Wrough t Sfeel s 600
- SOO H 40 0 300 - 200 - 100 - •Cast steet s Unnofched-Wrough t Enduranc e Rafi o 0 5
Notched-Cas t Wrough t
"~ i 1 1 1 r Uti O 60 0 80 0 — f 12 0 FIG.1 1 Compariso no f Fatigu e Propertie s wit htha t o f Evan s et-al,,(l ) DISCUSSIO N Th e mechanica l propertie s o f cas t stee l ar e relate d t o th e solidificatio nprocess . Athic k sectione d castin g wil l coo l rapidl y a t th e edg e formin g columna r crystal s whic h hav e superio r mechanica l propertie s t o tha t foun d I n th e centra l areas . Th e rat e o f coolin g progressivel ydecrease s wit h increasin g distanc e froni th e edge , formln f equlaxie l crystal s en d associate d micro
porosity . Th e mechinica l propertie s ar e shownt o deteriorat e towar d th e centr e o f th e castin g du e BJalnlyt o th e increase d incidenc e o f microporosity . Th e proo f stres s an d tensil e strengt har e onl y marginall yaffecte d bu t th e S elongatio n an d t reductio ni n are a ar e drasticall y reduced , Tabl e 2 . Thi s I s a characteristi c featur e o f thic k sectione d stee l casting s (7) . Th e minimummechanica l propertie s require d b ystandar d specification s ar e thos e generall yobtaine d fro mthi n sectione d tes t piece s suc ha s "kee l blocks" . Th e macrostructur e consist s entirel yo f columna r crystal s an d wil l provid e th e highes t attainabl e mechanica l properties . I t i s therefor e eviden t tha t thes e wil l no t b e representativ e o f th e mechanica l propertie s obtaine d i n thicke r sections . I t ha s previousl ybee nshown(5)(6 ) tha t ho t isostati c pressin g a t a ten^)eratur e o f llOC C t o UIO' C i s a n effectiv e mean s o f closin g interna l porosit yan d improvin g th e mechanica l propertie s o f cas t steels . However , i n th e presen t wor k simila r result s wer e obtaine d i n a cas t stee l wit h a tensil e strengt ho f 100 0 HN/m * a t a HI P temperatur e o f 930°C . Th e mechanics ! propertie s o f specimen s fro mth e mid-sectio n and centr e o f th e castin g wer e restore d t o th e sam e value s a s tha t o f th e nonne l edg e specimen s Table s 2 en d 3 . Th e improvemen t i nth e Xelongatio nand S reductio ni n e m wa s greate r tha ntha t o f th e proo f stres s and tensil e strength . I t i s therefor e clea r tha t HI P produce s unifor mmechancia l propertie s fro mth e edg e t o th e centr e o f th e casting . Afte r machinin g th e mid-sectio nan d centr e specimens , surfac e microporosit ywa s reveale d whic hcause d a reductio nt n th e fatigu e limi t o f up t o 38X , Tabl e 4 , Fig.7 . Notche d fatigu e value s determine d o n edg e specimen s showe d tha t thi s i s equivalen t t o a stres s concentratio n(Kt ) o f 2. 2 whic hi s considerabl ygreate r tha nth e K t o f <1. 4 generall yrecommende d i n th e desig no f stee l casting s (8) . Th e sever e stres s concen tratio ncause d b

yth e microporosit yi s du e t o th e acuit yo f th e roo t radiu s o f th e cavity , Fig.4 . SE M photograph s o f broke n fatigu e specimen s clearl ysho wtha t micro
porosit yformnucleatin g site s fo r th e initiatio no f fatigu e cracks , Fig.5 . Afte r HI P an d th e closur e o f microporosit ya norma l fatigu e fractur e occur s F1g-6 , Afte r HI P a t temperature s frcM » gSC C t o 1210" C th e mid-sectio nan d centr e specimen s showe d a n Increas e i n th e fatigu e limi t o f fro m 47-70S , Tabl e 5 , F1g.8 . A s i n th e cas e o f th e tensil e ductilit ys o wit hth e fatigu e strengt hther e i s n o advantag e t o b e gaine d b yusin g HI P temperature s i n exces s o f 930*C , Figs. 9 & 10 . Tidbur yan d Ricklnso n (9 ) hav e als o showntha t effectiv e closur e o f microporosit ywa s achieve d i n e n allo y cas t stee l a t a KI P temperatur e o f 900''C . I t wil l b e observe d tha t a fatigu e limi t o f 530-55 0 MN/m » achieve d afte r HI P i s greatl y I nexces s o f th e 39 0 MN/m * obtaine d i n th e norma l edg e specimens . Sinc e th e tensil e strengt hi s onl ymarginall yimprove d du e t o th e closur e o f microporosit yb yHIP , th e increas e i n th e fatigu e rati o i s considerable , fro m0.3 9 i n th e edg e specimen s withou t HI P t o 0.5 4 i n th e mid/centr e specimen s afte r HIP , Asimila r fatigu e rati o wa s obtaine d i n th e edg e specimen s afte r HIP . I t i s therefor e clea r tha t durin g th e HI P cycl e bot hth e closur e o f microporosit yan d th e consolidatio no f th e dendriti c structur e occurs . Whe nth e mechanica l propertie s achieve d afte r HI P ar e compare d wit hth e wor k o f Evan s et.al.,(l ) Fig.1 1 i t i s see ntha t th e fatigu e limi t afte r HI P i s considerabl yhighe r tha ntha t o f norma l cas t steel s a t th e sam e strengt h leve l an

d approache s tha t o f comparabl e wrough t steels . I t i s therefor e eviden t tha t th e HI P proces s i s capabl e o f transformin g a severel y"notched " cas t stee l wit hinferio r nwchancia l propertie s int o a materia l wit hth e highes t integrit ywithou t th e anisotrop yi nmechanica l propertie s 4.1 1.-a-ai v .fiSfti : 

# m SU'i
.

4.1 2 whic

hI s characteristi c of wrough t steels . I nvie w o f th e advantage s of

castin g e s a productio nrout e thi s aspec t wil l be of considerabl e interes t

t o desig nengineers . Afte r HI Pa t 930' C th e grai nsiz e wa s muc h small'e r tha ntha t

obtaine dafte r

HI Pa t highe r temperatures . Wit

hth e advent

of faste r coolin g rate * Inmode mHI P equipment (10) , acombine

dHI Pplu s hea t tnsatraen t cycl e I s feasible . Th e us e of a n ai r hardenin g cas t

stee l wit

haHI P t«i^)eratur e of

930» C followe db

y rapi d coolin g an

dtemperin g a t

600*C shoul d produc e acceptabl e mechanical properties . Th e econcHfll c advantag e I s sel f

evident . CONCLUSION S 1 ) Microporosit yi n cas t stee l ha s a n advers e effec t o n th e mechanica l propertie s particularl yth e i elongatio n% reductio n I nan aan dfatigu e strength . 2 ) Interna l microporosit yma yb e effectivel yclose d a t a HI P twoperatur e o f SSO' C resultin g I n unifor mtensil e propertie s throHjghoti t a 400B» I thic k casting . 3 ) Afte r HIP , specimen s machine d fro mth e centra l area s o f th e castin g showe d a n increas e f n fatigu e limi t o f 50-70S . Th e fatigu e rati o wa s substantiall yhighe r tha n tha t normall yobtaine d I ncas t steels . 4 ) Bymean s o f HIP , cas t steel s wit ha conqjarabl e Integrit yt o wrough t steel s ma y b e produced . ACKNOWLEDGEMENT S Th e author s wis ht o acknowledg e th e assistanc e o f roenbers o f th e technicia n staff . Polytechni c o f Wale s wit hth e machinin g o f specimen s an d Mrs . C . Tyndall , Scienc e Departmen t fo r th e operatio no f th e scannin g electro nmicroscope . REFERENCE S 5 ) t . Strode , M.B . Bassett , C . Oavles : Effec t o f Ho t Isostati c Pressin g o n Fatigu e Strengt ho f Cas t Steel , Metal s Technology , 9 , Sept.1982 , 349-354 . 6 ) I . Strode , Ho t Isostati c Pressin g o f H1 2 Cas t Di e Steel . Proc . Thir d Int.Conf . o n Isostati c Pressing . London , Vol.1 , 1986 , 37.1-37. U 7 ) P.J . Ahearn , G.W . Form , J.F . Wallace : Hig hStrengt hStee l Casting s Mas s Effec t o nTensil e Properties , Irans . Amer , Foundrywen s Soc. , 1962 , 70 , 1154-1160 . 8 ) C . Vishnevsk yan d J.F . Wallace : AStudy o f th e Notc hEffec t an d o f Specime n Desig nand Loadin g o nFatigu e Propertie s o f Cas t Steel , Amer . Foundrymen s Soc , Cas t Metal s Researc hJnl. , 4,2,1968 , 95-102 . 9 ) I.E . Tidbur yan d B.A . (Dickinson , Opportunitie s fo r combine d HIP/HEA T Treatment . Proc . Thir d Int.Conf , o n Isostati c Pressing , London , 1986 , Vol.2 . 34,2-34. 9 10 ) Mammot hIsostati c Pres s Gommlssloned , Metal s an d Materials , 3,1 , Ja n1987 , 20 .


# i

1 ) E.B . Evans , L.J . Eber t and C.W . Briggs : Fatigu e Propertie s o f Cwnparabl e Cas t and Wrough t Steels , Proc . ASTM , 56 , 1956 , 979-1010 , 2 } H.D . Hanes , D.A . Seifer t an d C.R . Watts : Ho t Isostati c Pressing , Pub,No . MCIC-77.34 , 1979 , Columbus . Ohio , Battell e Memoria l Institute , 3 ) Superalloy s "80" , ASM , Proc.Conf . Champion , Pa. , U.S.A. , 21-2 5 Sept.1980 . 4 ) B.A . Rickinson , HIPpin g Bring s He w Horizon s fo r Castin g Manufacture , Metal s and Materials , 1,2 , Feb.1985 . 104-107 . 

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# Exhibi t C

# Lifesavin g System s Corp . Tes t Dat aShee t Tes t Name : Reference : Lo t Number : Seria l Number : Tes t Device : Date : Loa dTes t D-LO K Cas t Hois t Hoo k Body LSCp/nMW-l C Preproductio nSampl e n/ a LS C Loa dCel l an dPull-Tes t Fixtur e 3 0 Novembe r

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cas t hoo k bod y finishedinaccordanc e withth e processe s define dfo r

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ahydrauli c cylinde r i nLSC' s pul l tes t

fixture. Arin g wa s place do nth e throa t o f th e hoo k body a s woul dh e use dinactua l service . Th e opposit e sid e o f th e rin g wa s secure dt o afixedloa dcel l fo r forc e measurements . The hoo k bod y wa s the nsubjecte dt o stati c loa dtes t i nwhic hth e followin g observation s wer e made : 800 0 lb s loa d N o observabl e deformatio n 10,00 0 lb s loa d Sligh t deformatio namountin g t o 0.020 " defectio ni nth e nos e o f

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# Exhibi t D

# Lifesavin g System s Corp . Tes t Dat aShee t Tes t Name ; Reference : Lo t Number : Seria l Number : Tes t Device : Date : Cycl e Tes t o f D-LO K Cas t Hois t Hoo k Body LSCp/nU4'lO-l C Preproductio nSampl e n/ a LS C Loa dCel l an dPull-Tes t fixtur e 1 6 Januar y 200 8 Tes t Resluts : U410-1 C D-LO K

cas t hoo k bod y finishedi naccordanc e wit hth e processe s define dfo r

par t (~1 . hoo k

body ) o f

drawin g M l 0-0 1 rev . C wa s threade d (1/2-20 ) an dsuspen db y threade dshan k t o th e fre e en do f

ahydrauli c cylinde r i nLSC' s pul l tes t

fixture. Arin g wa s place do nth e throa t o f th e hoo k body a s woul db e use di nactua l service . The opposit e sid e o f th e rin g wa s secure dt o afixedloa dcel l fo r forc e measurements . The hoo k bod y wa s the nsubjecte dt o 10 0 cycle s a t SI0 0 lbs . Fo r

eac hcycl e th e loa dwa s applie dmomentaril y (2- 3 seconds) , an dthe nth e loa drelease d momentaril y (2- 3 seconds ) prio r t o repeatin g cycle . Upo ncompletio no f th e cycl e test , th e hoo k

wa s visuall y inspecte dan ddimenstonall y compare dt o it s pretes t

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