The 1973 Extractive Metallurgy Lecture The Metallurgical Society of AIME

The Linde Argon-Oxygen Process for Stainless Steel; A Case Study of Major Innovation in a Basic Industry

W. A. KRIVSKY

The L e c t u r e t r a c e s the development of the Linde Argon-Oxygen P r o c e s s f r o m its conception in 1955 to its full s c a l e and w i d e s p r e a d utilization in the s p e c i a l t y s t e e l industry on a w o r l d wide b a s i s at the p r e s e n t time. The basic invention was d e r i v e d from f i r s t p r i n c i p l e s of p h y s i c a l c h e m i s t r y known to a l l third y e a r college c h e m i s t r y students. Its long saga of development over a f i f t e e n - y e a r p e r i o d r e q u i r e d a g r e a t deal more; namely, a c o r p o r a t i o n with tremendous r e s o u r c e s and, m o r e i m p o r t a n t l y , a l m o s t boundless faith to continue in spite of some d e v a s t ating r e v e r s a l s , a s m a l l company with g r e a t vision and engineering ingenuity to evolve a nontraditional p r o c e s s for the manufacture of s t a i n l e s s s t e e l which many l a r g e r companies had d e s p a i r e d of, and a m a r k e t i n g effort which was able to do the a l m o s t i m p o s s i b l e which was to convince a basic industry such as s t e e l of the m e r i t s of a r e v o l u t i o n a r y new p r o c e s s s i g nificantly different in method of operation and c a p i t a l r e q u i r e m e n t s without being a p a r t of that industry i t s e l f and without means of proving the p r o c e s s in-house. The development of the Linde Argon-Oxygen P r o c e s s is a m a s s i v e tribute to A m e r i c a n industry, the dedication of many of its m e m b e r s , and the tremendous ability of different i n d u s t r i e s to work together in a m a j o r development. The L e c t u r e a t t e m p t s , as any good c a s e h i s t o r y should, to g e n e r a l i z e f r o m this specific c a s e the l e s s o n s to be learned by i n d u s t r y , by individual e n g i n e e r s and s c i e n t i s t s , by government, and the a c a d e m i c community in m a j o r p r o c e s s innovation in a b a s i c i n d u s t r y . Such an i n c r e a s e d understanding leading to improved implementation of new knowledge into m a j o r industry is c r i t i c a l l y i m p o r t a n t if the United States is to improve its standing in i n t e r n a t i o n a l m a r k e t s . Since the Linde Argon-Oxygen P r o c e s s is an a l l - A m e r ican development, its study should lead us to fuller understanding of both the unique a d v a n t ages our s y s t e m p r o v i d e s for such innovation and means by which we may a c c e l e r a t e such b a d l y - n e e d e d developments in the future. DR. WILLIAM A. KRIVSKY is president, Crucible Specialty Metals Div., Colt Industries, Syracuse, N. Y. Dr. Krivsky, who holds his doctorate (1954) in process metallurgy from MIT, joined Union Carbide Corp. that year and as research metallurgist and later manager of metals research invented the Argon-Oxygen Process for stainless steel which forms the subject matter of the EMD Lecture. He holds the basic patent on the process assigned to the Union Carbide Corp. After 1959 he was associated with Brush Beryllium Co. as vice president and general manager; Continental Copper and Steel Industries as administrative vice president; and General Cable Corp. as group vice president. METALLURGICAL TRANSACTIONS

Dr. Krivsky has served on several technical committees of AIME and is a past chairman of the Extractive Metallurgy Division. He has also served as a director of TMS and is currently an AIME director. In 1959 he was recipient of the Extractive Metallurgy Division's Gold Medal,jointly with Dr. R. Schuhmann, for their contribution on the thermodynamics of copper smelting. In 1965 he edited the book High TemperatureRefractory Metals based upon an international symposium which he organized and chaired for the AIME. The 1973 Extractive Metallurgy Division Lecture was delivered on Feb, 28 at the 102nd TMS-AIME Annual Meeting in Chicago.

V O L U M E 4, J U N E 1 9 7 3 - 1 4 3 9

A

2%- g r e a t deal has been written and spoken about the effectiveness of b a s i c i n d u s t r i e s in the United States in applying advanced technology to l a r g e s c a l e m e t a l l u r g i c a l p r o c e s s e s . Arguments have been put forth about the amount and type of fundamental r e s e a r c h that should be done, the methodology of t r a n s l a t i n g b a s i c r e s e a r c h in economical new p r o c e s s e s , the r o l e of the F e d e r a l government in this endeavor, the educational p r o c e s s which r e s u l t s in individuals who can a c c o m plish this objective, and the v a r i o u s f o r m s of o r g a n i zational alignments within c o r p o r a t i o n s that s t i m u l a t e and make effective such effort. In spite of many d i f f e r ing views on these subjects, g e n e r a l a g r e e m e n t e x i s t s on the fundamental p r i n c i p l e which gives such g r e a t importance to the subject; namely, the corporation, the industry, or the nation which makes most effective use of technology will be the m o s t competitive, the m o s t p r o s p e r o u s , and will t h e r e b y be capable of supporting the highest s t a n d a r d of living for its m e m b e r s . In reaching g e n e r a l conclusions on such a complex and vital i s s u e , it has been useful in many fields to e x amine, in detail, many case h i s t o r i e s of specific ins t a n c e s . We have a v a i l a b l e to us in the s t e e l m a k i n g industry the r e c e n t example of the Linde A-O2 D e c a r b u r i z a t i o n P r o c e s s . Let us examine its origin, its d e v e l opment, and its c o m m e r c i a l i z a t i o n and d e t e r m i n e what g e n e r a l l e s s o n s it t e a c h e s which will p e r m i t us to m o r e effectively exploit our knowledge and technology in the future.

THE LINDE AOD PROCESS

TODAY

First of all, let us discuss the process itself. A charge containing essentially all of the important alloying elements of the stainless steel composition to be produced in their entirety is melted down in an electric arc furnace. Fig. 1 shows such a heat being poured from a furnace after slag-off. The molten steel is then transferred by ladle to a separate refining vessel which is similar to a Bessemer converter with two or more tuyeres in the bottom, Fig. 2. Oxygen is blown through the molten bath admixed with varying amounts of argon, with the ratio of argon to oxygen increasing with time during the blow and finishing with pure argon in m a n y cases, Fig. 3. Very small final additions of alloying elements and deoxidizing elements are made to the melt, Fig. 4, and the finished steel is tapped directly from the vessel, Fig. 5. This new duplex process replaces conventional stainless steelmaking which used only a single melting and refining vessel; namely, the electric furnace. The significant changes in practice brought about m a y be seen by the comparison of the older conventional practice and the A O D Process shown in Table I. In the conventional practice the charge melted down in the electric furnace in the production of a typical 18 pct Cr-8 pct Ni grade could only contain about 4 pct Cr. If the extra low carbon (ELC) product was sought, even less chrom i u m could be included in the charge. With the new practice all the chromium required in the final product (~ 18 pct) is charged into the furnace. In the conventional p r a c t i c e , the molten furnace c h a r g e was lanced with pure oxygen to the end point of 3300~ and a c a r bon content of 0.02 pct. During this step a p p r o x i m a t e l y one-half of the o r i g i n a l chromium charged (4 pct) was oxidized into the slag, leaving the metal with about a 1440-VOLUME 4, JUNE 1973

Fig. 1--Tapping an electric furnace after melting of charge only. 2 pct Cr content. In the Linde AOD P r o c e s s , blowing the heat with v a r y i n g A-O2 m i x t u r e s in a s e p a r a t e v e s s e l is done to an end point of 3100~ and 0.03 pct C. It should be noted that the t e m p e r a t u r e is about 200~ lower than at the conventional p r a c t i c e end point. During this step the chromium content in the bath is about 16.5 pct Cr. In the conventional p r a c t i c e following blowing, reducing agent in the form of FeSi or FeCrSi was added to the s l a g to reduce about one-half of the c h r o mium in the slag back into the bath (1 pct). This was followed by a v e r y l a r g e addition of low carbon f e r r o chrome (15 to 17 pct) to the bath to r e a c h final composition. In the Linde AOD P r o c e s s , FeSi or FeCrSi is added to the slag to r e c o v e r about one-half of the oxidized chromium (0.75 pct). G e n e r a l l y no additions of low carbon f e r r o c h r o m i u m a r e n e c e s s a r y and it should be evident at this point that a m a j o r economic advantage of the p r o c e s s is in the substitution of low cost high carbon f e r r o c h r o m e in the charge for the r e l a t i v e l y high cost low carbon f e r r o c h r o m e in the heat finishing. Graphically, the p r o g r e s s of the chromium and carbon during the two different p r a c t i c e s is shown in Fig. 6 for the production of 304L s t a i n l e s s s t e e l . It can be seen f r o m this figure that t h e r e is roughly one o r d e r of m a g nitude difference in the C r - C r e l a t i o n s h i p when blown with A-O2 m i x t u r e s r a t h e r than with pure oxygen. This is the r e a l crux of the invention and the s u c c e s s f u l a p plication of high t e m p e r a t u r e p h y s i c a l c h e m i s t r y to s t e e l m a k i n g innovation. METALLURGICAL TRANSACTIONS

Fig. 2--Transferring hot metal to separate refining vessel.

ORIGIN O F T H E P R O C E S S How did it all begin ? What was the o r i g i n of the i n v e n t i o n and how was it d e v e l o p e d into the c o m m e r c i a l p r a c t i c e we h a v e today ? It all s t a r t e d in 1954 at the M e t a l s R e s e a r c h L a b o r a t o r i e s of the Union C a r b i d e C o r p o r a t i o n in N i a g a r a F a l l s , New York, in quite an innocent m a n n e r and w i t h out s p e c i f i c a l l y a t t e m p t i n g to d e v e l o p a new s t e e l m a k trig p r o c e s s . J u s t p r i o r to that t i m e , R i c h a r d s o n in England had p u b l i s h e d a t h e r m o d y n a m i c study of the r e l a t i o n s h i p of c h r o m i u m to c a r b o n in s t a i n l e s s s t e e l r e f i n i n g in which he had c l a s s i c a l l y e q u i l i b r a t e d c a r b o n m o n o x i d e - c a r b o n dioxide gas m i x t u r e s with F e - C r - C m e l t s . His r e s u l t s w e r e s o m e w h a t d i f f e r e n t than t h o s e of Hllty and C r a f t s p u b l i s h e d e a r l i e r . The e x p e r i m e n t a l m e t h o d of Hilty and C r a f t s was s u b s t a n t i a l l y d i f f e r e n t f r o m that of R i c h a r d s o n in that t h e y had blown s m a l l induction f u r n a c e h e a t s of F e - C r - C with oxygen, a t t e m p t i n g to e s t a b l i s h e q u i l i b r i u m v a l u e s for c h r o m i u m and c a r b o n by a p p r o a c h i n g s u c h v a l u e s f r o m both high and low c a r b o n c o n t e n t s . The p r e s e n t a u t h o r s e t out to r e s o l v e the d i f f e r e n c e in the two s t u d i e s by extending the r a n g e of C r - C r e l a t i o n s h i p studied following the g e n e r a l e x p e r i m e n t a l m e t h o d of Hilty and C r a f t s . The i n i t i a l w o r k w a s done in a 100-pound induction f u r n a c e ; and it b e c a m e r a p i d l y e v i d e n t that, in a t t e m p t i n g to e s t a b l i s h e q u i l i b r i u m Cr-42 r e l a t i o n s h i p s , i t was e s s e n t i a l l y i m p o s s i b l e to a c h i e v e the i s o t h e r m a l conditions n e c e s s a r y b e c a u s e of the highly e x o t h e r m i c n a t u r e of the C r - O METALLURGICAL TRANSACTIONS

Fig. 3--Argon-oxygen decarburization in refining vessel. r e a c t i o n . Some t e n t a t i v e a t t e m p t s w e r e m a d e to c o n t r o l the e x o t h e r m i c i t y of the r e a c t i o n by diluting the oxygen with a r g o n in the s m a l l f u r n a c e , and It was i m m e d i a t e l y noted that f o r any g i v e n c h r o m i u m l e v e l and t e m p e r a t u r e , the c a r b o n l e v e l was a p p r o x i m a t e l y an o r d e r of m a g n i t u d e l o w e r than those p r e d i c t e d by the e a r l i e r w o r k of e i t h e r R i c h a r d s o n or Hilty and C r a f t s ! At this point a r e v i e w of the b a s i c p h y s i c a l c h e m i s t r y of the s y s t e m r e v e a l e d what was taking p l a c e and began t o l e a d us in the p r o p e r d i r e c t i o n f o r the i n v e n Table I. Stainless Staelmaking Conventional vs Argon-Oxygen

Conventional

A-O2

1.) Meltcharge in electricfurnace a) 4 pet Cr chargenormal;less Cr chargedfor ELC grades

Meltcharge in electricfurnace a) 18 pct Cr chargedevenfor ELC grades b) deslagmeltedchargetransfer charge;to AODvessel Blowwith oxygen-argonmixture;end point 3100~ 17 pet Cr 0.03 pet C Recover0.75 pct Cr fromslag.Pure argon injection Nolowcarbon FeCraddition necessary

2.) Lancewith oxygen;end point 3300~ 2 pet Cr 0.02 pet C 3.) Recover ~ of Cr (1 pct) in slag with FeCrSior FeSiadd'n. 4.) Add 15 to 17 pct Cr as low carbon FeCrto final specification Final Composition: Cr-18.5 pet C-0.02 pet

Final Compositon: Cr-18.5 pct C-0.OI pet VOLUME 4, JUNE 1973-1441

Fig. 4--Adding final additions to r e f i n i n g v e s s e l a f t e r blowing.

tion of the Linde AOD P r o c e s s . Table II s u m m a r i z e s the b a s i c p h y s i c a l c h e m i s t r y of the Linde AOD P r o c e s s and b r i n g s us to a full u n d e r s t a n d i n g of the d i f f e r e n c e s b e t w e e n c o n v e n t i o n a l p r a c t i c e and the new p r o c e s s . It i s c l e a r f r o m t h i s Table that in c o n v e n t i o n a l s t e e l m a k ing the p r e s s u r e of c a r b o n monoxide i s 1 a t m , s i n c e a l l the oxygen blown into the bath is c o n v e r t e d to e s s e n t i a l l y c a r b o n monoxide a s it e x i t s the s y s t e m and t h e r e f o r e , f o r a g i v e n t e m p e r a t u r e , the e q u i l i b r i u m c a r b o n content will be p r o p o r t i o n a l to the t h r e e - f o u r t h s p o w e r of the c h r o m i u m content. In the Linde AOD P r o c e s s the c a r b o n content will be a function of both the t h r e e - f o u r t h s p o w e r of the c h r o m i u m l e v e l a n d the r e s u l t i n g p a r t i a l p r e s s u r e of c a r b o n m o n o x i d e after d i l u tion with a r g o n which p a s s e s through the b a t h unchanged. Table III i l l u s t r a t e s the e f f e c t of the r a t i o of a r g o n to oxygen in the input g a s s t r e a m on the c a r b o n content r e d u c t i o n r e l a t i v e to c o n v e n t i o n a l p r a c t i c e . The r e s u l t i n g c a r b o n m o n o x i d e p r e s s u r e , which c o n t r o l s the c a r b o n content, i s d e r i v e d f r o m the c o n s i d e r a t i o n that while a m o l of a r g o n g o e s t h r o u g h the b a t h unchanged, a c o r r e s p o n d i n g m o l of oxygen r e s u l t s in the f o r m a t i o n of 2 m o l e s of c a r b o n m o n o x i d e . T h e s e t h e o r e t i c a l c o n s i d e r a t i o n s a r e now b o r n e out in p r a c t i c e l i t e r a l l y h u n d r e d s of t i m e s d a i l y a r o u n d the w o r l d . It should not b e o v e r l o o k e d at t h i s point that the P r o c e s s h a s an a l t e r n a t i v e m e t h o d of u t i l i z a t i o n ; n a m e l y , that the s a m e C r - C r e l a t i o n s h i p can b e a c h i e v e d at s i g n i f i c a n t l y l o w e r t e m p e r a t u r e s than in c o n v e n t i o n a l p r a c tice. F u r t h e r w o r k in the l a b o r a t o r y was then continued to f u l l y v e r i f y what had b e e n found i n i t i a l l y and, f o r the f i r s t t i m e , c o n s c i o u s l y d i r e c t e d to the p o s s i b l e d e v e l o p m e n t of a new s t e e l m a k i n g p r a c t i c e . T h e r e w e r e s e v e r a l e c o n o m i c f a c t o r s that gave i m p e t u s to the c o m m e r c i a l e x p l o i t a t i o n of t h e s e l a b o r a t o r y f i n d ings at the t i m e . It had b e e n known f o r s o m e t i m e that the d e c a r b u r i z a t i o n of e x p e n s i v e , n i c k e l - b a s e a l l o y s could be e n h a n c e d b y the use of a v a c u u m . Extending such a p r a c t i c e to s t a i n l e s s s t e e l was c o n s i d e r e d t o t a l l y i m p r a c t i c a l b e c a u s e of the low c o s t of the p r o d uct and i t s s c a l e of m a n u f a c t u r e . The effect of the p r e s e n t p r o c e s s w a s to d e v e l o p a c r u d e v a c u u m w i t h out the u s u a l e q u i p m e n t ; i t was a f f e c t i o n a t e l y l a b e l e d "a p o o r m a n ' s v a c u u m . " S i m u l t a n e o u s l y t h e r e was a g r o w i n g m a r k e t d e m a n d f o r the e x t r a low c a r b o n (ELC) g r a d e s of s t a i n l e s s s t e e l s , but the p r o d u c t i o n c o s t s 1442-VOLUME 4, JUNE 1973

Fig. 5--Tapping finished steel from refining vessel.

0.5-

Conventional Practice

Argon-Oxygen Practice

x

0.2 --

[ Oxygen Blow [)

0.1

~rgon-Oxygen / Blow

O

@ 0.05

i+>. . . . . . . . . . I

0.02 0.01

-

--

0.005

0

y

\-"

/

,--

/\

Finish-Using Major Additions of Fe Cr Si, LC-Fe Cr, etc

I

4

I

8

X

/

X

Finish-Using Minor Additions of Fe Cr Si, Fe Si, etc.

I

12

I

16

I

20

Chromium % Fig. 6--Conventional vs Argon-oxygen p r a c t i c e for 302L.

w e r e n e a r l y p r o h i b i t i v e b e c a u s e of the e f f e c t of the high f i n i s h i n g t e m p e r a t u r e s on r e f r a c t o r y life a s well a s the p o o r r e p r o d u c i b i l i t y of the c o n v e n t i o n a l p r o c e s s . The a r g o n dilution p r i n c i p l e a p p e a r e d to a f f o r d METALLURGICAL TRANSACTIONS

F A I L U R E O F THE FIRST PRODUCTION ATTEMPTS

Table II. Chemistry of Argon-Oxygen Stainless Steelmaking

Cr304(s) + 4C # 3Cr + 4 C 0 (g) - a 3 . 4 a 4. Kt - Cr Poa / _c acrsO,

K~ = (~ C_0~P'r I(~ CD~ Conventional steelmaking %C = I/Ka(% Cr) 314 A-Oa steelmaking % C_= 1/Ka(% C_r)3/4p

Table III. Carbon Content as a Function of Argon-Oxygen Ratio v$ Conventional Practice

Constant Chromium Level;Constant Temperature A/O2 Input

Pco Atm

Reduction in Carbon Level, pct 33-~

1

2

2

1

50

4

-~

66 2

-~

8o

~

90

8 18

an i d e a l m e t h o d for the m a n u f a c t u r e of such g r a d e s . Another s i m u l t a n e o u s d e v e l o p m e n t of the t i m e w a s the r i s i n g u s e o f the B O F p r o c e s s in the United S t a t e s which w a s l e a d i n g to s i g n i f i c a n t i n c r e a s e s in oxygen p r o d u c i n g c a p a c i t y which, f o r r e l a t i v e l y m i n o r a d d i t i o n a l c a p i t a l i n v e s t m e n t , could p r o d u c e v a s t q u a n t i t i e s of a r g o n a t l o w e r c o s t than p r e v i o u s l y . A l l t h e s e c o n s i d e r a t i o n s l e d us to p u r s u e the d e v e l o p m e n t of the Linde AOD P r o c e s s . The o r i g i n a l w o r k to r e s o l v e the m i n o r d i f f e r e n c e s b e t w e e n the r e s u l t s of R i c h a r d son and those of H i l t y and C r a f t s w a s n e v e r c o m p l e t e d . T h o s e d i f f e r e n c e s had a d m i r a b l y s e r v e d t h e i r p u r p o s e ! Scale up of the p r o c e s s was s u c c e s s f u l l y a c c o m p l i s h e d f r o m the 100-pound f u r n a c e to a o n e - t o n a r c f u r n a c e . V e r i f i c a t i o n of the s m a l l e r s c a l e h e a t s was e x c e l l e n t and f u r t h e r w o r k on s c a l e - u p p r o c e e d e d with g r e a t c o n f i d e n c e . It should b e c l e a r l y u n d e r s t o o d that t h i s i n i t i a l w o r k was b e i n g done following the c o n v e n t i o n a l p r a c t i c e r i g h t in the e l e c t r i c a r c f u r n a c e but m e r e l y s u b s t i t u t i n g A - 0 2 m i x t u r e s f o r the p u r e o x y gen n o r m a l l y i n j e c t e d . V a r i o u s t r o u b l e s w e r e e x p e r i e n c e d with s p l a s h i n g of the bath and r e f r a c t o r y e r o s i o n even in the o n e - t o n t e s t s but, g e n e r a l l y s p e a k i n g , it was e x p e c t e d that such p r o b l e m s would be o v e r c o m e with i m p r o v e d and m u l t i p l e l a n c e s a s h e a t s i z e i n c r e a s e d . The n e x t s t e p in d e v e l o p m e n t u t i l i z e d the 3 ton and 5 ton f u r n a c e s of the Haynes Stellite Company, then y e t a d i v i s i o n of Union C a r b i d e . S u c c e s s was a g a i n d e m o n s t r a t e d b u t a g r e a t d e a l of d i f f i c u l t y was e x p e r i e n c e d in m a k i n g the l a n c i n g p r a c t i c e e f f e c t i v e . L a n c e s w e r e e x p e r i m e n t a l l y c o a t e d with j u s t about e v e r y known r e f r a c t o r y , and s i n g l e and m u l t i h e a d e d l a n c e s w e r e a t t e m p t e d p o s i t i o n e d a b o v e the b a t h . It w a s found t h a t the a r g o n , at l e a s t , had to be i n j e c t e d into the b a t h and was not e f f e c t i v e when blown on the s u r f a c e . F u r t h e r , the r e s u l t s showed the i m p o r t a n c e of getting gas d i s p e r s a l t h r o u g h o u t the bath f o r if the b e n e f i c i a l dilution p r i n c i p l e f u n c t i o n e d o n l y l o c a l l y , the e f f e c t on the t o t a l bath was minimal. METALLURGICAL TRANSACTIONS

Union C a r b i d e , not b e i n g a s t a i n l e s s s t e e l p r o d u c e r , had gone about a s f a r a s it could go a l o n e in the s c a l e up e f f o r t s . It o b v i o u s l y n e e d e d a p a r t n e r with l a r g e r f u r n a c e s in o r d e r to b r i n g the p r o c e s s to full c o m m e r c i a l s c a l e . A long s e a r c h of a l l the s t a i n l e s s s t e e l p r o d u c e r s followed, with v e r y d i s c o u r a g i n g r e s u l t s in g e n eral. For various reasons, nearly every company dec l i n e d to p a r t i c i p a t e in the f u r t h e r d e v e l o p m e n t until the J o s l y n S t a i n l e s s Steel C o m p a n y was a p p r o a c h e d . H e r e , in s p i t e of the f a c t that t h e y w e r e one of the s m a l l e r p r o d u c e r s without the t e c h n i c a l and f i n a n c i a l r e s e r v e s of s o m e of t h e i r l a r g e r c o m p e t i t o r s , t h e y n e v e r t h e l e s s had the c o u r a g e and f o r e s i g h t to p r o c e e d . In 1960 Union C a r b i d e and J o s l y n s i g n e d a j o i n t d e v e l opment agreement. The f i r s t t e s t s c o n d u c t e d at J o s l y n on a 15 ton s c a l e t u r n e d out to b e n e a r l y a b s o l u t e , d i s m a l f a i l u r e s . A l though a g r e a t d e a l of a t t e n t i o n had b e e n p a i d to the l a n c e p r o b l e m and v a r i o u s m e t h o d s , including the u s e of t h r e e f i r e c l a y - s l e e v e d l a n c e s p o s i t i o n e d above the b a t h , w e r e t r i e d , no s u c c e s s f u l h e a t s w e r e p r o d u c e d . V e r y c a r e f u l and d e t a i l e d a n a l y s i s of the r e s u l t s i n d i c a t e d that while l o c a l a c t i o n of the a r g o n dilution p r i n c i p l e n e a r the point of i n j e c t i o n was e f f e c t i v e , the net e f f e c t on the e n t i r e b a t h , a f t e r it had h o m o g e n i z e d f o l lowing the blow , w a s i n c o n s e q u e n t i a l . L a r g e s c a l e t e s t i n g was r e g r e t f u l l y a b a n d o n e d but w o r k w a s c o n t i n u e d on a l a b o r a t o r y s c a l e . This w o r k a g a i n c l e a r l y i n d i c a t e d the f e a s i b i l i t y of the p r o c e s s if the a r g o n could be d i s t r i b u t e d t h r o u g h o u t the e n t i r e bath. The p r o c e s s n e v e r f a i l e d to p e r f o r m under such c i r c u m s t a n c e s . C o n v e r s e l y , w h e n e v e r the b a t h d i a m e t e r was l a r g e r e l a t i v e to s u r f a c e i n j e c t i o n d e v i c e s , no d i s c e r n ible b e n e f i t was a c h i e v e d in the b a t h a s a whole. R E C O V E R Y FROM F A I L U R E A r m e d with t h i s m o r e c l e a r u n d e r s t a n d i n g , Union C a r b i d e and J o s l y n m a d e the h i s t o r i c d e c i s i o n to b u i l d a r e f i n i n g v e s s e l a p a r t f r o m the e l e c t r i c a r c f u r n a c e . T h i s f i r s t such v e s s e l w a s only -~ ton in c a p a c i t y and p r o v i d e d f o r the top blowing of oxygen and the b o t t o m i n j e c t i o n of a r g o n t h r o u g h a t u y e r e . The r e s u l t s w e r e d r a m a t i c a l l y f a v o r a b l e and s u p p o r t e d a l l the l a b o r a t o r y s c a l e w o r k p r e v i o u s l y done. H o w e v e r , the i d e a of a p p l y i n g the a r g o n d i l u t i o n p r i n c i p l e d i r e c t l y in the e l e c t r i c f u r n a c e d i e d v e r y s l o w l y . T h e r e was obvious r e l u c t a n c e to d e v e l o p a p r o c e s s that would c r e a t e a n o t h e r s t e p in the m a n u f a c t u r i n g p r o c e s s and t h a t would r e q u i r e an a d d i t i o n a l c a p i t a l i n v e s t m e n t . What was not r e a l i z e d at t h i s p o i n t in t i m e , w a s that the s e p a r a t e r e f i n i n g v e s s e l would double the s t e e l output of a given f u r n a c e . Since its c o s t w a s o n l y a s m a l l f r a c t i o n of the c o s t of an a d d i t i o n a l e l e c t r i c f u r n a c e , it r e p r e s e n t e d a v e r y i n e x p e n s i v e m e a n s of i n c r e a s i n g s t e e l m a k i n g c a p a c i t y . N e v e r t h e l e s s , f o r t y - f i v e a d d i t i o n a l 15-ton h e a t s w e r e t r i e d in the a r c f u r n a c e , which, in s p i t e of v a r i o u s c o n f i g u r a t i o n s of l a n c e s , t o t a l l y f a i l e d to give a n y b e n e f i c i a l r e s u l t s c o m p a r e d to the -~ ton s e p a r a t e v e s s e l . As a r e s u l t of t h e s e e f f o r t s , the two c o m p a n i e s p r o c e e d e d with the d e s i g n of a 1 5 - t o n s e p a r a t e r e f i n i n g v e s s e l . A f t e r much e x p e r i m e n t a t i o n with top and b o t V O L U M E 4, J U N E 1 9 7 3 - 1 4 4 3

t o m i n j e c t i o n of one o r both g a s e s , use of p o r o u s b o t t o m s , and with v a r i o u s t u y e r e d e s i g n s , t h e r e f i n a l l y e m e r g e d in 1967 a s i m p l e m u l t i p l e t u y e r e which c o m b i n e d both g a s e s in the i n j e c t i o n . Fig. 7 is a photograph of this e a r l y unit which on October 24, 1967 p r o duced the f i r s t full heat of s t a i n l e s s s t e e l e v e r c o m p l e t e l y r e f i n e d , finished, and p o u r e d d i r e c t l y into m o l d s u t i l i z i n g the Linde AOD P r o c e s s . This was a heat of type 304 ELC and its log of m a n u f a c t u r e is shown in Table IV. Two a d d i t i o n a l h e a t s were p r o duced in this unit with equal s u c c e s s . The tide in the f o r t u n e s of d e v e l o p m e n t w e r e s i m u l t a n e o u s l y t u r n i n g for an o v e r s e a s company, also w o r k i n g with Linde, which r e p o r t e d s i m i l a r s u c c e s s w o r k i n g in a n 8 - t o n s e p a r a t e r e f i n i n g v e s s e l . Noting the a d d i t i o n a l b e n e f i c i a l effect of the Ltnde AOD P r o c e s s a s a m e a n s to l o w - c o s t c a p i t a l i n v e s t m e n t for a d d i t i o n a l s t e e l m a k i n g capacity as well as a lower o p e r a t i n g c o s t p r a c t i c e , J o s l y n made the d e c i s i o n to b u i l d a full c o m m e r c i a l i n s t a l l a t i o n b a s e d on the a r g o n dilution p r i n c i p l e and s e p a r a t e m e l t i n g and r e f i n i n g v e s s e l s . This unit was b u i l t e a r l y in 1968 and is shown in Fig. 8. It f e a t u r e d two t u y e r e s i n s t a l l e d on the bottom back side of the v e s s e l which e m e r g e d above the bath when the v e s s e l was r o t a t e d for c h a r g i n g , s a m p l i n g , holding o r tapping. The v e s s e l was 9 ft in d i a m e t e r and 1389 ft high. D u r i n g 1968 s o m e one h u n d r e d h e a t s were made in this unit f r o m which the following g e n e r a l c o n c l u s i o n s w e r e reached: 1) P r o c e s s e c o n o m i e s were e s t a b l i s h e d beyond a n y question. 2) The c h a r g e to the e l e c t r i c f u r n a c e could be made up of the lowest cost c h r o m i u m and n i c k e l units without any r e s t r i c t i o n on s t a r t i n g c a r b o n o r s i l i c o n l e v e l s . 3) R e c o v e r y of c h r o m i u m was v e r y h i g h - - a p p r o x i m a t e l y 97 pct a s was total m e t a l l i c s . 4) Silicon usage to r e c o v e r oxidized m e t a l s was r e duced by 40 pct. Following this c a m p a i g n , J o s l y n modified this f i r s t p r o d u c t i o n v e s s e l , Fig. 9, and c o n v e r t e d its e n t i r e m e l t shop to 100 pct AOD P r a c t i c e in July 1969. By D e c e m b e r of that y e a r they w e r e able to r e p o r t the r e s u l t s of 1300 heats to the E l e c t r i c F u r n a c e C o n f e r ence. The d e s i g n p r i n c i p l e s used in this J o s l y n p r o duction unit a r e the b a s i s of e v e r y AOD i n s t a l l a t i o n c u r r e n t l y in use throughout the world, r a n g i n g in size f r o m 5 to 100 ton. Table V s u m m a r i z e s the m a j o r e c o n o m i c a d v a n t a g e s of the fully c o m m e r c i a l i z e d p r o c e s s . In addition to the a l r e a d y - d i s c u s s e d a b i l i t y to u t i l i z e v e r y l a r g e q u a n t i t i e s of the lowest cost r a w m a t e r i a l s in the charge a l m o s t without l i m i t a t i o n and with v e r y high yields, t h e r e b y m i n i m i z i n g the use of e x p e n s i v e f i n i s h i n g a d d i t i o n s , the p r o c e s s g r e a t l y i n c r e a s e s the p r o d u c t i v i t y of an e l e c t r i c f u r n a c e . One a r c f u r n a c e p l u s an AOD v e s s e l has the p r o d u c t i v i t y of two a r c f u r n a c e s o p e r a t e d c o n v e n t i o n a l l y . Since an AOD v e s s e l is s i g n i f i c a n t l y l e s s e x p e n s i v e c a p i t a l - w i s e than a s e c ond a r c f u r n a c e , the c o m b i n a t i o n is the m o s t e c o n o m i cal method to i n c r e a s e capacity. O p e r a t i n g cost c o m p a r i s o n s with c o n v e n t i o n a l p r a c t i c e v a r y in detail f r o m 9 i n s t a l l a t i o n to i n s t a l l a t i o n but g e n e r a l l y s p e a k i n g it m a y be said that the cost of o p e r a t i n g the r e f i n i n g v e s s e l is m o r e than offset by the s a v i n g s in raw m a t e r i a l s a n d the e l i m i n a t i o n of the r e f i n i n g and f i n i s h i n g s t e p s f r o m the e l e c t r i c a r c f u r n a c e . D e s u l f u r i z a t i o n is a c c o m p l i s h e d r a p i d l y and effectively with a d e s u l f u r i z i n g 1444-VOLUME 4, JUNE 1973

Fig. 7 --First 15 -ton refining vessel.

Table IV. Log of First Complete Stainless AOD Heat October 24, 1967

304L

Time, min

Pet C

Pct Cr

ppm 02

~

B/4tap B/402 ~ep 1 ~ep 2 argon addns. product

-4 6 28 46 51 58 -

0.290 0.259 0.084 0.033 0.027 0.021 0.008

18.08 18.02 16.99 16.46 16.46 17.60 18.62

600 230 560 800 660 390 170

3140 2990 3160 3130 3100 2980 -

Fig. 8--Original Joslyn production unit.

Fig. 9--Final Joslyn production unit. METALLURGICALTRANSACTIONS

EXPLOITATION OF THE JOSLYN SUCCESS

TaMs V. C~mme~clal Advantages M the AOD Process

1.) Lower Cost Materials -No practical limitations on starting carbon contents -Almost completely eliminates expensive low carbon chromium units -Readily adaptable to new materials 2.) Sigoificanfly increased yield of metallic elements 3.) Greater Productivity -One arc furnace plus AOD vessel equals two times arc furnace output -AOD vessel significantly less expensive than a second arc furnace 4.) Operating Costs -Savings of eliminating the tel'ruing and finishing stages from the arc furnace more than offset the operating cost of the AOD 5.) Desnlfurization -7 to 10 rain to slag off, add desulfurizing slag and stir 6.) Lead Residuals -Routine removal of lead to below 0.007 pct 7.) Quality -Cleaner, more reproducible, more easily machined steel

TaMe VI. AOD Installations in the U. S.

Company

Startup Date

Vessel Capacity Tons

Armco Steel Corp./Advanced Materials Div. Baltimore, Maryland

1/71

35

Baldwin-l.Jma-Hamihon Corp. Standard Steel Division Burnham, Pennsylvania

8171

18

Mid. 1973

25

Cabot Corporation/Stellite Division Kokomo, Indiana

1170

5

Carpenter Technology Corp. Reading, Pennsylvania

1172

15

Colt Industries, Inc./Crucible Stainless Steel Div. Midland, Pennsylvania

3/72

100

Eastern Stainless Steel Co. A Division of EASCO Corp. Baltimore, Maryland

11/70

50

Eleetralloy Corporation Off City, Pennsylvania

9/70

17

International Nickel Co., Inc. Huntington Alloy Products Div. Huntington, West Virginia

10/71

38

Jessop Steel Co. Washington, Pennsylvania

10/71

20

Jones and Laughlin Steel Corp. Stainless and Strip Division Detroit, Michigan

12/71

70

4/68

17

12171

100

Babcock and Wilcox Beaver Falls, Pennsylvania

Joslyn Mfg. and Supply Co. Joflyn Stainless Steels Div. Fort Wayne, Indiana United States Steel Corp./South Works South Chicago, Illinois

TaMe VII. Oversees AOD Instellatiom

Company

slag and argon agitation. Lead is routinely removed to below the 0.007 pct level. Quality of the steel produced is far more reproducible than in conventional practice, especially in the ELC grades and is substantially cleaner and more freely machining. METALLURGICAL TRANSACTIONS

It must be r e m e m b e r e d that Union Carbide Corporation is not a stainless steel producer and the outstanding success at Joslyn needed to be repeated m a n y m o r e times before the project would be a commercial s u c c e s s for Union Carbide. P r a c t i c a l l y e v e r y major s t a i n l e s s s t e e l p r o d u c e r in the world was contacted. With the cooperation of Joslyn, d e m o n s t r a t i o n s were a r r a n g e d for v a r i o u s companies at F o r t Wayne. Savings calculations were made for e v e r y potential l i c e n see under l i t e r a l l y thousands of local conditions and p r o c e s s a l t e r n a t i v e s . Questions of f u r t h e r s c a l e - u p and product quality had to be answered. P r o s p e c t s were enabled to take J o s l y n - p r o d u c e d AOD ingots, finish them in their own m i l l s , evaluate, and test m a r k e t them. In c e r t a i n c a s e s Union Carbide even a r r a n g e d to have the 15-ton t e s t v e s s e l at Joslyn shipped to v a r i o u s p r o s p e c t s so that they might a c tually c a r r y out t h e i r own t e s t s . In spite of local diff i c u l t i e s in accommodating the v e s s e l , this p r o g r a m was highly developed and e x t r e m e l y s u c c e s s f u l in convincing p r o s p e c t s to obtain l i c e n s e s to the p r o c e s s . The second l i c e n s e e to the p r o c e s s in the United States was E l e c t r a l l o y in September of 1970; the f i r s t foreign l i c e n s e e was Illsa Viola in Italy in July of 1970. The final t r i b u t e s to Llnde and Union Carbide m a r k e t i n g efforts may be seen in Table VI and Table VII which r e s p e c t i v e l y l i s t s U. S. and foreign l i c e n s e e s . During 1973 Union Carbide expects 50 pct of the s t a i n l e s s

Avesta Jemwerks AB/Axel Johnson and Co. Avesta, Sweden

Startup Date

Vessel Capacity Tous

6/73

60

10173

18

11/71

60

7/72

15

1175

70

7/70

22

3/71

8

7/72

75

Nippon Metal Industry Co. Sagamihara, Japan Olarra S.A. Bilbao, Spain

11/71

55

10172 7173

14 10

Rotherham Stainless and Nickel Alloys, Ltd. Rotherham, U. K. Southern Cross Steel Middelburg, South Africa Spartan Steel and Alloys Ltd. Birmingham, U. K.

11171

8

9172

25

10/71

8

8172

60

Boschgotthardshutte Siegen, W. Germany British Steel Corp./Panteg Works Pontypool, Wales, U. K. British Steel Corp./Stuckshridge Works Stucksbridge, U. K. FIAT, Sp. A. Torino, Italy llssa Viola Pont St. Martin, Italy IMI Alloy Steels Ltd. Somercotes, U. K. Nippon Metal Industry Co. Kinuura, Japan

Temi/Fmisider Group Temi, Italy

VOLUME 4, JUNE 1 9 7 3 - 1 4 4 5

s t e e l produced in the U. S. will be by means of AOD and that a d d i t i o n a l l y 625,000 ton will be produced overseas. THE PURSUIT OF PATENT PROTECTION Obviously, the m a r k e t i n g effort had to be b a s e d on a v e r y strong patent s t r u c t u r e and p r o c e s s know-how. The struggle for patent coverage was n e a r l y as e p i c a l as was the p r o c e s s development h i s t o r y . The author o r i g i n a l l y filed patent applications on behalf of Union Carbide on June 27, 1956. There followed a t e n - y e a r campaign with the U.S. Patent Office which finally culminated on May 24, 1966 in the issuance of the b a s i c patent a f t e r s e v e r a l i n t e r f e r e n c e and appeal p r o c e d u r e s were s u c c e s s f u l l y o v e r c o m e . The tenacity of the Union C a r b i d e ' s patent counsel was e x t r e m e but t u r n e d out to be highly r e w a r d i n g since the b a s i c patent has now ten m o r e y e a r s to run, w h e r e a s had it been uncontested and i s s u e d quickly it could well be expiring in the next y e a r or two, j u s t about the t i m e the p r o c e s s i t self had been c o m m e r c i a l l y fully substantiated. F u r t h e r , an i m p r o v e m e n t patent was granted in 1962 which b a s i c a l l y r e l a t e d to the sequencing of v a r i o u s gas m i x t u r e s for optimum r e s u l t s during the refining p r o c e s s .

LESSONS F R O M THIS D E V E L O P M E N T It is a g r e a t p l e a s u r e to able to recount the long and arduous saga of an u l t i m a t e l y overwhelming s u c c e s s s t o r y , e s p e c i a l l y when one has had a p a r t in it. This, however, is not the main p u r p o s e ; f a r m o r e important at this point is what we can l e a r n f r o m this e x p e r i e n c e for our future mutual benefit. It is b e l i e v e d that there a r e many l e s s o n s to be l e a r n e d h e r e concerning t e c h nical innovation which affect many c l a s s e s of individuals. F o r the Individual R e s e a r c h e r 1) The l e s s o n taught h e r e is that of the e x t r e m e i m p o r t a n c e of looking for the unexpected or the unusual in any r e s e a r c h work and the total acceptance of the r e s e a r c h data. This may sound e l e m e n t a r y but it is not always e a s y to do as a young, unknown r e s e a r c h e r when faced with apparent contradictions with the published word of f a r m o r e well-known and r e s p e c t e d inv e s t i g a t o r s . In this case, the m a r k e d l y different r e sults obtained in the v e r y f i r s t argon t e s t s f r o m those of the e a r l y Hilty and Crafts and Richardson studies could have been a s c r i b e d to some m y s t e r i o u s and unknown e x p e r i m e n t a l e r r o r and the total development could have been lost right at that point. 2) All unexpected r e s u l t s can be understood ultim a t e l y in t e r m s of b a s i c t h e o r y if a sufficient effort is made. This e x t r e m e l y important step is highly p r o ductive of inventions and must be thoroughly pursued. In this p a r t i c u l a r case, going back to fundamental p h y s i c a l c h e m i s t r y led to a highly i m p o r t a n t new p r o c e s s which would have not been r e a c h e d had not this step been c o m p l e t e l y executed. 3) R e g a r d l e s s of the scientific nature of r e s e a r c h work, the r e s e a r c h e r must s t r i v e to understand the p r a c t i c a l and c o m m e r c i a l environment of the s y s t e m he is studying. In the p r e s e n t case it was not the o r t g 1446-VOLUME 4, JUNE 1973

inal intent of the work to invent a b e t t e r p r o c e s s to produce s t a i n l e s s s t e e l - - a s has a l r e a d y been s a i d the work was p r i m a r i l y intended to r a t i o n a l i z e d i s a g r e e ing data between two s e p a r a t e investigations. F o r t u nately sufficient information had been l e a r n e d about s t a i n l e s s s t e e l melting p r o b l e m s and the impact of l a r g e s c a l e oxygen plants to p e r m i t recognition of the potential i m p o r t a n c e of the p r o c e s s . Without this knowledge, the development of a c o m m e r c i a l p r o c e s s could have been totally m i s s e d at a v e r y e a r l y stage. 4) Abiding p e r s i s t e n c e and t e n a c i t y is absolutely r e q u i r e d if one is going to evolve a b s t r a c t r e s e a r c h r e s u l t s into c o m m e r c i a l development. There is a t i m e during this p e r i o d when the individual r e s e a r c h e r , and only the individual r e s e a r c h e r , has any idea at a l l of the c o m m e r c i a l significance of that which has been d i s c o v e r e d . He must be able to convince o t h e r s for the n e c e s s a r y support and r e j e c t any d i s c o u r a g e m e n t until the work is complete.

F o r the Educators in the M e t a l l u r g i c a l Profession 1) Traditionally, p a r t i c u l a r l y in r e c e n t y e a r s , it is believed that an excellent job has been done in our m e t a l l u r g i c a l c u r r i c u l a of teaching fundamental p r i n c i p l e s of p h y s i c s , c h e m i s t r y , and m a t h e m a t i c s and t h e i r applications to m e t a l l u r g y . It is definitely b e lieved that this type of t r a i n i n g is the b e s t suited to p r e p a r e a student for making a contribution to his profession. 2) It is b e l i e v e d that m e t a l l u r g i c a l education would benefit f r o m g r e a t e r depth in teaching of the e n g i n e e r ing p r i n c i p l e s involved in m e t a l l u r g i c a l p r o c e s s i n g . This development n e a r l y floundered on the design of the r e f i n i n g v e s s e l ; and had individuals had s t r o n g e r backgrounds in heat and fluid flow a s s o c i a t e d with high t e m p e r a t u r e p r o c e s s e s , it is believed that design solutions would have been r e a c h e d m o r e d i r e c t l y . This is in no way meant to mitigate the significant ingenuity that was d e m o n s t r a t e d in the final design solution. It is only to say that teaching engineering technology a p plied to high t e m p e r a t u r e p r o c e s s e s would be highly productive and has not been done in m e t a l l u r g i c a l education to the s a m e extent as has been done in the case of p h y s i c a l c h e m i s t r y . 3) In teaching p r i n c i p l e s and t h e i r application, the simultaneous teaching of s o - c a l l e d d e s c r i p t i v e c o u r s e s concerning the h i s t o r i c a l production of the v a r i o u s m e t a l s has n e c e s s a r i l y been significantly reduced. Yet to make a contribution in the r e a l world one must know and understand the c u r r e n t s t a t u s ; some means m u s t b e provided to f a m i l i a r i z e the student with the c u r r e n t state of the a r t . It must be r e m e m b e r e d that there is a t i m e in the development sequence when only the individual r e s e a r c h e r can know what he r e a l l y has. Unless he can r e l a t e it r e a d i l y to the r e a l world, he will have an a l m o s t i m p o s s i b l e t a s k of convincing o t h e r s as well as h i m s e l f that he should p e r s i s t . He cannot e x i s t in a vacuum of knowledge concerning present practice. 4) A v e r y s i m i l a r comment may be made r e l a t i v e to p r o c e s s economics. The most difficult t a s k for a young r e s e a r c h e r is to convince h i m s e l f of the u l t i mate economies of his new p r o c e s s vs existing p r a c METALLURGICAL TRANSACTIONS

tice. He must be taught to make p r o c e s s economic studies at least to be able to highlight major differences in cost. This important aspect of an engineering education requires considerable strengthening in most metallurgical curricula as they exist today. Courses taken in other departments simply do not sufficiently relate; they must be made specific to the metallurgical industry to be of maximum benefit.

For the Metallurgical Industry 1) Those of us in the metallurgical industry--be it ferrous or nonferrous--who are more or less responsible for technical innovation in o r d e r to stay competitive in world markets can learn much from Union Carbide's example. In this case, 15 y e a r s persistence on all fronts including technological, marketing, and legal a r e a s was maintained. The faith and absolute conviction to invest millions of dollars without return for many years is absolutely n e c e s s a r y for significant innovation in a basic industry. 2) It is absolutely n e c e s s a r y to have top technical talent in several disciplines in order to develop the full conviction to p e r s i s t or to change direction. 3) Discouragements enroute to a major development will be legion, but they must be viewed for what they really are, and effort cannot be discontinued just because a specific timetable, written in ignorance of later-developed facts, is violated. We, in business, tend to live by schedules and timetables. Too rigorous application of this discipline in the area of technical innovation can p r e m a t u r e l y terminate potentially profitable inventions. 4) Industry needs to understand that there is far more scientific knowledge available today than has been brought to bear on the profit problem. To fully bring it to bear requires a complex harnessing of many different scientific and engineering disciplines together with knowledgeable and, to a degree, imaginative economic analysis. The pay bachs on technical innovation in basic indushries are longer in maturing than generally expected but, compensatingly, are larg e r in magnitude than anticipated. In the present case, while the lower raw material cost and the lower r e f r a c t o r y costs were envisioned from the beginning, the decreased cost of installed capacity and the significant improvements in quality were late developments and were really not added to the benefits until the p r o c e s s was well along into its advanced engineering form.

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For the Government 1) We hear a great deal currently about the d e s i r a bility of breaking industry into smaller competing units. It should be clear from the present case that only a corporation with similar r e s o u r c e s to Union Carbide could have proceeded for 15 y e a r s without compensation for its efforts. It should be also clear that without significant staffs in research, engineering, marketing, and patent development, a successful conclusion would not have been attained. Bigness, per se, is not bad. 2) It should be noted that the successful c o - p a r t n e r in this development was Joslyn Stainless Steel, one of the smallest producers in the United States. While superficially this might seem to enhance some of the arguments of the advocates for a larger number of smaller competitors, size, p e r se, had very little to do with it. What was significant was the courage and vision of the individuals involved and this type individual, however r a r e , can be found in any size organization. 3) What was uniquely American about this development, and what needs to be p r e s e r v e d and enhanced, is that one of the largest corporations in the world sought out and found in one of the smaller c o r p o r a tions the right partner for this particular development. This is free choice and true natural selection. No amount of outside legislated cooperation would have produced the same result because the natural selection p r o c e s s would have been violated. Cooperation on the scale demonstrated here can only be obtained from two partners freely convinced of a common goal that individually benefits each partner to a degree that justifies the expense and the risk. That freedom to search and select the most appropriate partner is one of the precious heritages of the American free enterprise system. C ONC LUSION It has been both an honor and a pleasure to recount the development of the Linde AOD P r o c e s s and to attempt to generalize from the teachings of this particular development, concepts which may accelerate other basic developments in the future. It is particularly interesting that this Extractive Metallurgy Division Lecture of 1973 b e a r s on a subject of interest to the Iron and Steel Division. Possibly that fact, more than all others, testifies to the relevantness of the AIME where special interests stem from common basic knowledge and the resulting cross-fertilization of concepts is one of the great strengths of the Institute.

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