LOW CARBON AND SILICON STEEL QUADRUPOLE MAGNETS

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LOW CARBON AND SILICON STEEL QUADRUPOLE MAGNETS

H. Fukuma, N. Kumagai, Y. Takeuchi, K. Endo, M. Komatsubara

To cite this version:

H. Fukuma, N. Kumagai, Y. Takeuchi, K. Endo, M. Komatsubara. LOW CARBON AND SILICON

STEEL QUADRUPOLE MAGNETS. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-301-C1-

304. �10.1051/jphyscol:1984160�. �jpa-00223716�

JOURNAL DE PHYSIQUE

Colloque C1, suppl6ment a u n o I, Tome 45, janvier 1984 page C l - 3 0 1

LOW CARBON AND S I L I C O N S T E E L QUADRUPOLE MAGNETS

H. Fukuma, N. Kumagai, Y. Takeuchi, K. Endo and M. ~ o m a t s u b a r a * National Laboratory for High Energy Physics, Oho-machi, Ts'sukuba-gun, Ibaraki-ken, 305, Japan

* ~ a w a s a k i SteeZ Corporation, Kawasaki-cho, Chiba-shi, 260, Japan

Resum6

-

L ' a c i e r bas carbone d6velopp6 pour l e s c i r c u i t s magnetiques e s t com- p a r 6

a

l ' a c i e r au s i l i c i u m du p o i n t de vue des performances d ' u n a i m a n t qua- d r u p o l e

.

A b s t r a c t

-

The l o w carbon s t e e l developped f o r t h e magnet c o r e m a t e r i a l i s compared w i t h t h e s i l i c o n s t e e l i n r e g a r d t o t h e performance o f t h e quadrupole magnet.

A l a r g e a c c e l e r a t o r needs a l a r g e amount o f i r o n w i t h good magnetic and mechanical p r o p e r t i e s f o r t h e c o n s t r u c t i o n o f t h e magnets. A l l magnets must have t h e u n i f o r m f i e l d p r o p e r t i e s t o c o n f i n e t h e charged p a r t i c l e s , such as p r o t o n and e l e c t r o n , s t a b l e i n t h e a i r gaps o f t h e magnets a1 i g n e d a l o n g an o r b i t . Several hundreds o f magnets a r e made o f s e v e r a l thousand t o n s o f i r o n . As t h e magnet has a l a r g e w e i g h t on t h e a c c e l e r a t o r c o s t , i t i s i m p o r t a n t t o reduce t h e magnet c o s t i n b o t h s i d e s o f f a b r i c a t i o n and m a t e r i a l . U s u a l l y i r o n f o r t h e magnet has been s e l e c t e d m a i n l y f r o m t h e q u a l i t y i t s e l f . The s i l i c o n s t e e l and t h e decarbonized s t e e l a r e t h e c a n d i d a t e s , b u t t h e y a r e r a t h e r expensive. R e c e n t l y t h e cheaper l o w carbon s t e e l i s used f r e q u e n t l y t o economize t h e expenses. However, t h e l o w carbon s t e e l which i s a v a i l a b l e c o m m e r c i a l l y i s made f o r t h e s t r u c t u r a l i r o n which does n o t r e q u i r e t h e magnetic p r o p e r t i e s b u t r e q u i r e s t h e workabi 1 i t y . I t s magnetic p r o p e r t i e s o b t a i n e d by t h e E p s t e i n method on a s m a l l s c a l e correspond t o t h e l o w grade s i l i c o n s t e e l and l a c k i n t h e u n i f o r m i t y .

As f o r t h e s i l i c o n s t e e l , one can choose t h e magnetic p r o p e r t i e s which a r e d i f f e r e n t depending on t h e s i l i c o n c o n t e n t and t h e i r f l u c t u a t i o n can be made s m a l l by s e l e c t i n g t h e s t e e l w i t h t h e s p e c i f i e d q u a l i t y . T h i s s e l e c t i o n i s p o s s i b l e because t h e s i l i c o n s t e e l i s w i d e l y used t o t h e e l e c t r i c a l machines and produced i n l a r g e q u a n t i t i e s . Therefore, t h e aims o f t h i s work a r e summarized as f o l l o w s ,

-

q u a l i t y improvement o f t h e l o w carbon s t e e l by t h e s l i g h t m o d i f i c a t i o n o f t h e p r o d u c t i o n process,

-

p o s s i b i l i t y o f t h e l a r g e s c a l e p r o d u c t i o n o f t h e l o w carbon s t e e l w i t h t h e u n i f o r m qua1 i t y , and

-

s u f f i c i e n t mechanical s t r e n g t h r e q u i r e d t o t h e stamping process.

A f t e r many t r i a l s on t h e chemical c o n t e n t s o f elements and i m p u r i t i e s and on t h e h e a t t r e a t m e n t , t h e low carbon s t e e l h a v i n g t h e s i m i l a r magnetic p r o p e r t i e s t o t h e m i d d l e c l a s s s i l i c o n s t e e l was obtained.

I

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LOW CARBON STEEL

From t h e a c c e l e r a t o r view p o i n t s , we impose t h e s p e c i f i c a t i o n s on t h e magnet c o r e m a t e r i a l such as hardness ( o r mechanical s t r e n g t h ) , p e r m e a b i l i t i e s ( v ) a t t h e s p e c i f i e d f l u x d e n s i t i e s , c o e r c i v e f o r c e ( H c ) , u n i f o r m i t i e s o f t h e p e r m e a b i l i t y and c o e r c i v e f o r c e , e t c . These s p e c i f i c a t i o n s a r e r e q u i r e d f r o m b o t h t h e f a b r i c a t i o n process and t h e t o l e r a n c e o f t h e magnet performance. T h e i r r e l a t i o n s a r e

-

hardness - w o r k a b i l i t y under t h e punching d i e , mechanical s t r e n g t h

-

p e r m e a b i l i t y

-

i r o n s a t u r a t i o n , magnet dimensions

-

c o e r c i v e f o r c e - remanent f i e l d s t r e n g t h

-

u n i f o r m i t y - s h u f f l i n g o f l a m i n a t i o n s .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984160

CI-302 JOURNAL DE PHYSIQUE

Another p r o p e r t y t o be c o n s i d e r e d i s t h e magnetic a f t e r e f f e c t o f t h e s t e e l . I f t h e a f t e r e f f e c t c o n t i n u e s f o r a l o n g t i m e , i t i s r e q u i r e d t o w a i t o r a d j u s t t h e e x c i t a t i o n c u r r e n t t o e s t a b l i s h t h e magnetic f i e l d c o r r e s p o n d i n g t o t h e energy o f t h e p a r t i c l e s c i r c u l a t i n g i n t h e a c c e l e r a t o r . T h i s phenomenon i s m e t a l l u r g i c a l l y e x p l a i n e d as t h e m i g r a t i o n o f t h e n i t r o g e n atoms i n t h e s t e e l and can be suppressed by removing t h e n i t r o g e n i m p u r i t y o r by adding a n o t h e r elements such as aluminum t o suppress t h e m i g r a t i o n .

The t y p i c a l magnetic and mechanical p r o p e r t i e s o f t h e l o w carbon s t e e l compared w i t h t h e s i l i c o n s t e e l a r e g i v e n i n T a b l e 1.

The m a g n e t i c p r o p e r t i e s depend g r e a t l y on t h e l a m i n a t i o n t h i c k n e s s . The b e s t c h o i c e i s around 0.5 mm. I n i t i a l l y t h e t h i c k n e s s was aimed more t h a n 1 mm. However, t h e b e t t e r p r o p e r t i e s were o b t a i n e d f o r t h e t h i n n e r one. The 0.5 mm t h i c k l o w carbon s t e e l was t e s t e d f u r t h e r i n r e g a r d t o t h e r e p r o d u c i b i l i t y a t t h e mass p r o d u c t i o n stage. These t r i a l s gave t h e s a t i s f a c t o r y r e s u l t s as shown i n Table 2.

Table 1 Mgnet?c and mchamcal propertier af steels

- -

Th>cknerr Uc a t 1.5 1 dm) _8". ^{Table 2} Repraduelbility runs at the mrr production stage

Inn1 (Oel .

8 = 1 T 8 = 1.5T

Law carbon rteel LOW carbon HC a t 1.5 T u(eou1

E l 1.2 0.78 steel

H2 1.2 0.89 I *

::

^{(Oe) 8 ; 1 T B = 1 . 8 T Hv}

HZ 1.0 1.0 3756 1297 i l l

HZ 0.5 1 . 0 r 2.0 4060 1695 110

c 4233 .r 1121 R _{B 0.96} 1.03

-

_x ^1.05 _1.00 ⁶³⁹⁷ ₁₆₈₁ ^% _% ⁶⁶⁵⁶ ₄₇₉₃ ¹⁷⁹⁴ ₁₈₆₅ ^* _x ¹⁹²⁹ ₁₉₂₅ ¹⁰² ₁₀₇ ⁺ _* ¹⁰⁵ ₁₁₃

Silicon rteel

high grade 0.5 0.38 7500 1030 x ZOO

middle grade 0.5 0.85 5377 1492 x 145 Average 1.04 4479 1826

low grade 0.5 2.4 2510 1330 108

A t t h e mass p r o d u c t i o n stage, b e t t e r r e s u l t s were o b t a i n e d t h a n a t t h e l a b o r a t o r y stage. The h i g h p e r m e a b i l i t y a t t h e h i g h magnetic f i e l d i s s u i t a b l e f o r t h e c o r e m a t e r i a l o f t h e quadrupole magnets f o r t h e c o l l i d i n g a c c e l e r a t o r , because t h e o p e r a t i o n a t h i g h e r f i e l d g r a d i e n t w i l l be f r e q u e n t l y r e q u i r e d t o a t t a i n h i g h e r l u m i n o s i t y .

I 1

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PERFORMANCE 06 QUADRUPOLE MAGNETS

The quadrupole magnet w i t h t h e dimensions of F i g . 1 was made o f t h e l o w carbon s t e e l w i t h t h e p r o p e r t i e s o f T a b l e 2. Parameters o f t h e magnet a r e g i v e n i n T a b l e 3. The

shape o f t h e magnet was designed t o use t h e m i d d l e grade s i l i c o n s t e e l (S23 grade of t h e Japanese I n d u s t r i a l Standards) f o r t h e TRISTAN a c c u m u l a t i o n r i n g / I / . Two quadrupole magnets made o f t h e d i f f e r e n t s t e e l s were i n v e s t t g a t e d t o compare t h e i r performances.

The B-H c u r v e s o f b o t h s t e e l s a r e shown i n F i g . 2. Almost t h e same c h a r a c t e r i s t i c s w i 11 promise t h e sirni 1 a r performances.

G(x)/G(o)

1 6 - I = 8 0 0 A

I .O I ^{- -} 1 4 -

1 2 -

10-

.-.

^{5 x k m )}

0 6 -

0 tow carbon steel silicon steel

s~l~con steel (S23 grade1 0 9 9

lowcarbonsteel(i0wgrade) F i g . 3 R a d i a l d i s t r i b u t i o n s o f t h e

1 f i e l d g r a d i e n t , t h e s e x t u p o l a r

o

-.". . . . * . . -

* " " " " ' ' ' "

";04

asymmetry was c o r r e c t e d .

10 lo' H h / m ) lo3

F i g . 2 B-H curves.

F i e l d p r o p e r t i e s The two dimensional d i s - t r i b u t i o n s o f t h e f i e l d g r a d i e n t s were measured w i t h t h e f l i p t w i n c o i l s a t t h e magnet c e n t e r

( F i g . 3 ) . B o t h curves h o l d up t o 1200 A w i t h o u t any f i e l d d e t e r i o r a t i o n . As expected from t h e B-H curves, t h e magnet s a t u r a t i o n i s l a r g e r f o r

t h e s i l i c o n s t e e l t h a n t h e l o w carbon s t e e l above

(+I* ¹

^(+)400fi

2000 A/m. F i g . 4 shows t h e d i f f e r e n c e o f t h e e x c i t a t i o n curves o f b o t h magnets. An a b s c i s s a g i v e s t h e e x c i t a t i o n c u r r e n t and an o r d i n a t e t h e f i e l d g r a d i e n t n o r m a l i z e d a t 400 A. A small improvement i s seen above 1100 A (17 T/m).

H y s t e r e s i s One o f t h e i m p o r t a n t problems t o t h e c o l l i d i n g t y p e o f a c c e l e r a t o r i s t h e hys- t e r e s i s o f t h e s t e e l . I n t h e a c c e l e r a t o r oper- a t i o n , t h e f i n e a d j u s t m e n t i s f r e q u e n t l y r e - q u i r e d and t h e h y s t e r e t i c o p e r a t i o n t r a c i n g a m i n o r l o o p i s u s u a l l y encountered. By t h i s

o p e r a t i o n t h e i n i t i a l c o n d i t i o n i s n o t r e p r o - ⁰ low carbon steel d u c i b l e a f t e r r e t u r n i n g t o t h e i n i t i a l c u r r e n t .

0,90t

^{silicon steel}

F i q . 5 c 8 show t h e r e s u l t s o f t h e d e v i a t i o n s o f - t h e f i e l d g r a d i e n t s when t h e magnet e x p e r i - enced t h r e e s u c c e s s i v e m i n o r l o o p s . The ex- t e n t o f t h e m i n o r l o o p s i s g i v e n b y t h e change o f t h e e x c i t a t i o n c u r r e n t i n p e r c e n t a t t h e a b s c i s s a . The i n i t i a l c u r r e n t was 938 A (14.6

T/m) f o r a l l cases. Both upward and downward 0.85- changes o f t h e c u r r e n t were a p p l i e d . Three

s u c c e s s i v e measurements under t h e same m i n o r l o o p s were made a f t e r t h e i n i t i a l i z i n g opera- t i o n o f t h e magnet, which means t h r e e l a r g e l o o p e x c i t a t i o n s f r o m 0 t o 1330 A (20 T/m) t o

e l i m i n a t e t h e memory o f t h e s t e e l of t h e p r - 0 8 0 0 ^{a 1 8 1}

-

^{rn I}

eceding run. The change o f t h e f i e l d g r a d i e n t 1000 2 0 0 0

a f t e r t r a c i n g a m i n o r l o o p i s g i v e n i n t h e Excitation current ( A ) o r d i n a t e i n p e r c e n t . Each d e v i a t i o n a f t e r t h e

s u c c e s s i v e m i n o r l o o p o p e r a t i o n s d i f f e r s , b u t

approaches t o t h e f i n a l value. The h y s t e r e t i c F i g . 4 E x c i t a t i o n curves.

C1-304 JOURNAL DE PHYSIQUE

- 8 -4 \ 0

I -

I.

I ^{O (W}

F i g . 5 H y s t e r e t i c e f f e c t t r a c i n g 3 s u c c e s s i v e m i n o r l o o p s .

I. = 9 3 8 A

0 low carbon steel

1.01 A silicon steel

I - I 0 I 0 (%I

F i g . 6 H y s t e r e t i c e f f e c t .

I. = 9 3 8 A

0.5 0 low carbon steel

I

^A silicon steel

I - I 0 I 0 (%I F i g . 7 H y s t e r e t i c e f f e c t .

I,

-

^{9 3 8 A}

2.0 0 low carbon steel

A silicon steel

F i g . 8 H y s t e r e t i c e f f e c t .

e f f e c t o f t h e l o w carbon s t e e l i s about 1.5 t i m e s l a r g e r t h a n t h a t o f t h e s i l i c o n s t e e l . T h i s i s a l s o expected f r o m t h e c l o s e c o r r e l a t i o n between t h e c o e r c i v e f o r c e and t h e h y s t e r e t i c l o s s .

Authors acknowledge t h e d i s c u s s i o n s o f P r o f e s s o r s T. Nishikawa and Y. Kimura on t h e s t e e l p r o p e r t i e s . They a r e a l s o g r a t e f u l t o Messrs. Y . I t o and T. S e k i t a o f Kawasaki S t e e l Corp. f o r t h e i r a c t i v e i n t e r e s t t o t h e new s t e e l .

Reference

1) K. Endo, H. kukuma, A. Kabe, Ta. Kubo, To. Kubo, N. Kumagai and Y. Takeuchi, KEK I n t e r n a l 82-10 (1982).