Added Life for Brazing Fixtures

Reprint from

June 27,

Presented by

As Bulletin No. 4

In a series of informative articles on the uses and

propsifies of alloys far high temperature service.

Added Life for Brazing Fixtures Sy CHARLES EMERY and

Simnnds Sow & Sfeel Co. Wfchburg, Mass.

DESIGNERS of furnace trays and futures often hold the key to low- cost brazing operations. Selection of the proper alloy is only part of the xtory. It's equally important to know what will happen t o the as- sembIy when it encounters job con- ditions. By integrating design with the

required properties of t h e alloy, the deeigmr can increase the service Life of fixtures and frequently re- duce his materials costs. As more manufacturers turn to high-volume furnace brazing, the future of the process is tied more importantly to tray and fixture life and their replacement costs.

First Rule - Tbere are many variatione of trays or fixtures, but the designer ahauld keep light weight, articulation and loose joints in mind. Heat rersi~ting al- loys expand and contract about 7/32-in. per ft through a cycle from room tempemture to 2050" F,

PAUL GOETCHEUS Rolled Alloys lnc.

DatraIt

so adequate clearance must be pro- vided In d directions.

One tight joint that will not al- low for this movement can suffi- cientl y overstress the involved member to cause immediate frac- ture m preliminary deformation leading to ultimate fracture.

Another Reason-The tray or fixture should be flexible and uni- formly supported, If it is made rigid, it will be subjected to greater ~titresaeg than if articuIated in some

manner. These stresses could be caused by expansion and cantrac- tion of the alloy and the load car- ried by the fixture, or even from the weight: of thc fixture itself.

For example, a new fixture en- tering a new furnace might be uni- formly supported by level rollers. But rolls seldom stay level, and a rigid tray is then subjected to severe bending moment as i t rides over high sputa in a warped roll.

Barn-Roof D es i g n-A widdy

Satisfactory structure of heat-wsisting alloy is shown at left. Intergranular penetration of copper caused by spillage of braze metal (center) and heavy carbide precipitation (right) ultimately destroy fixture strength

used m y is tbts ,parn-mar typeJ $0

adled bemuse gap~psrhhg cbqf4p;la are roll@ into tbB ~hqpe. AlIw sheet of 0.078 to d B 5 ig. sick- n e s is wed, Lea& ugually do n&i 36 i ~ , If tray& are lhWr h a ib6 in, s joht tb re+ d m Wiling Ire pi.avidd.

Ttlese channels have holes p ~ c h x d a%6ut every iS +a. thrmgh W W i 55Sb&, dun& bars are Io&y fitted, They are capped Uh 68ch end by a welded-on wash- er., Bwm of pipe, Weld& or un- wdded tubit~g we $hen atmg or^ tho bm ta suppert fbe c%annel legs in the vertical @me.

Cqpper Ptablsth--X&m copper bnws metd has a trmeeddous af- finity ta wet o v p a lag& surface. When punching or abttasiw p t ~ for the fixture, miauts fraetn~es in adjacmb metal often reNt when fobIs haus b a d e dull. 6 p p w geepa into -the expas& mew, and a rWwt EvppPer-nic-kel zlJlay that i# weak may b$ hfmed- Thiir weak-

TVpical born tray of "bdrnFraoJ" M g n rods and spacer tubing. this one was

*

Choose #ha Riqh4 Allw

rsPe Evdu&bn 380 Exbehent thermal &ock ~ e s j s t ~ c e , mch

as mencnunfere& in oil qlten-g frtim hfn- (33 Px-lM peratup qhw raoo* F, cuiftbind- wl$h

makest I E l W - ~ r n w sti*eng%% fwwes WmlUPr ragl$tSm:@ to cir:Mrpbn of

dtro&u in working t=ernperatures, 4 ~xidatiw r e k m c e up l o i8tib0 F.

3.M stan& up under msdmate t h e m shock & a ~ p a h l 3 ~ 1!& eorwion f r m meu-

($5 Cr-20 NU t ~ d or Mildly murizfng atrngapkm presenm of ~ulphur, it Is prefwed nmr hig+r allup. E x e e W bha~&w&+ ti- ztnd wii3t-& t@ Si2-g Wtp ZOW" F.

W Excellent bengkh addation m i s h w to 20.00' FT Patihlarly surf& fwr-X)rF&

(26 & a 2 Nij Whtch operate at relatisay c'amtmt mh- ,@~%tm or rewive mad- ep@ic b~qt:

eyl4 qaolhg, 0 H - h n~ Esfstmce b caryxan 4T 'niW&b. ahwrptim.

,430 R&t ~ ' x ~ ~ U O R fur intwraltWnt u8?: up t6 160DR F. Should not be uaed cmtinmusly

I17 ov6r 14W" F bw~me Pf >W&W@JW wNW. Has lbwer c a e f f l c h t of expambn than rrPckel-beeu?ng types, work faardeni less, and Eim tightly Mhering m& whsm wed In right temperature range.

448 m e , d thp ao;Fit axWtbn-m&~taf alloys t%T CrF tiW can Be pmduaec?. l3igh-c.hram eah-

tent mema lass Wetility &cl fm&flit.p+ Resists distortion horn heating and mef- irg* Life vf auippmt o p t i n g in * btertm&ab? t e i ! w e q n be in- oreasep % perioFme8libg.

r

- 'I made ofi 3311 alley steel

havk nat been pickled. They d l 1 offar a pmkectlas: @kitid& ciogtihg. BY the Q ~ Y , '.It's desbble to run

new3 Wpty *aye tbMugh the fur- mct3 for &q hour or so at lB50Q F.

&kcking the Alloy-Primary £&&am t& m d r , am in the selew

O f dl hi& EeMljRP&EtI% ~ I Q Y S , arb: t e ~ a i e strength, kmep stem&, mm8ion r&taace# tbemal 'ex- ~ , & m i o ~ , '6trmd and, meclanfed #bwk $tabfbtLity arid cost, The n m - W of allws aemptaQb, for brazing appLimkbm is imm&a%dy lhited to only a few (see table>. They wg tha ohme-nickel types whi& am mpedwx ta the. hitraight-cham ate& im load-aamying: iapcgb.

Heat resistace of the dlays is derived £row the fornation of pro- tective ad& coating whi& re- tards bf g m t s $&her attack mi a e mdf~Im mbi. mimi is tba plftwiw alloying d ~ - Wf Wt W a d e su& 'proE&- tion, w&h n i b 1 md siUcm a@ wgpm@~g element&

About Atmaspheres - Operating >CMU~VQUSIJF -in a straight MWng awaBphgke at ZOOUP F, thd o#er of ~ W t i a n mMame, of the three allom WUUM 314, 309 ma 33& U n h prot&jve at,rnoqphqe, how^ ewr, dl three resist miling well.

In irFswtjpas whep mntml of atmosphere isi d&iault, sulphn~aus gases are s~znethes persent. @ thle &BB the higher chromium d- lhyk ~utp&om higher s ick4 al- Eojrs. C~dvemIy, in &ghBy cap buikdng afmosp41!res kigher nE&e% fm& h the 330, b&& re- ai&aPlcJe to. ca?Pu&at son.

BULLETIN

NO. 4

BECAUSE

Practical informafion on the properties and selection of hecit resisting alloys. Facts proved by experience on the design, con- struction and operation of high temperature equipment essential fo cuccessful perfom- ance of the alloy.

The largest distributor of rolled heat resist- ing alloys i n the country. The only or- ganization working exclusively with such specialfy metals, with technically qualified personnel to serve you,

The knowledge and experience of special- ists in applying heat resisting alloys, rom- bined with the knowledge and experience of leading specialty mills in producing them, give you the best performance, at the lowest cost, with the quickest service.

An inventory of more than a million pounds and over 400 mill forms, all rigidly con- trolled for quality to have the optimum high temperature properties.

/fA-Leatd- P-Ay s p d A81 5 BELLEVUE AVENUE. DETROIT 7. MICHIGAN - TEL WALNUT 1.4682