Chemical and physical characterisation of metal grinding dusts

J. Aerosol Sci., Vol. 18. No. 6, pp. 671-675, 1987.

0021-8502/87 $3.00+0.00 Pergamon Journals Ltd.

Printed in Great Britain

CHEMICAL AND PHYSICAL CHARACTERISATION

H. P. K~nig,

OF METAL GRINDING

DUSTS

W. Koch,

L. N e d e r * and U. G r a v e s I n s t i t u t of T o x i c o l o g y and Aerosol Research N i k o l a i F u c h s Sir. 1, 3000 H a n n o v e r 61, F B G * F r a u n h o f e r Institut for P r o d u c t i o n T e c h n o l o g y S o m m e r f e l d s t r a G e , 5 1 0 0 A a c h e n , FRG Fraunhofer

Introduction

In the a p p l i e d g r i n d i n g p r o c e s s e s we o b t a i n e d c o a r s e and f i n e d u s t f r a c t i o n s by v a r y i n g p h y s i c a l p a r a m e t e r s like c u t t i n g speed, w o r k i n g part speed, m e t a l r e m o v a l rate and a v e r a g e grit d i a m e t e r (I). T h e m e t a l s i n v e s t i g a t e d are: CK 45 N w i t h 0~ Ni, X5 CrNi 18/9 w i t h 9~ Ni and N i C r 20 T i A l w i t h 60~ Ni. F u r t h e r = m o r e w e c h a r a c t e r i z e d the r e s u l t i n g d u s t s b y e l e c t r o n m i c r o s c o p i c and a t o m i c a b s o r p t i o n s p e c t r o m e t r y m e t h o d s .

Experimental

C o a r s e d u s t s w e r e taken d i r e c t l y f r o m the f i l t e r s out of the s a m p l i n g unit, as a l r e a d y d i s c r i b e d (1), a n d fixed on s p e c i m e n m o u n t i n g p i n s for i n v e s t i g a t i o n s w i t h s c a n n i n g e l e c t r o n m i c r o s : copy (Hitachi S-405A). Fine dust fractions from Berner Impactor L P - 3 0 w e r e s q u e e z e d to c a r b o n c o a t e d n y l o n - g r i d s , t r e a t e d w i t h t r i c h l o r o m e t h a n e , c o a t e d a g a i n and e x a m i n e d w i t h t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y (Philips T E N 420). T h e s e f r a c t i o n s a l t h o u g h were a n a l y s e d with atomic a b s o r p t i o n spectrometry (Perkin-Elmer 4000 a n d H G A 500) w i t h r e s p e c t to t h e i r n i c k e l and c h r o m i u m - c o n = centrations.

Results

D e p e n d i n g on the p h y s i c a l p a r a m e t e r s o f the g r i n d i n g p r o c e s s and on the c h e m i c a l p r o p e r t i e s of the w o r k p i e c e we found a c e r t a i n a m o u n t of s p h e r e s w i t h h i g h e n e r g y input (e.g. h i g h c u t t i n g speed) a m o n g all k i n d s of cuttings. T h e i r m o r p h o l o g y is a l s o d e p e n d i n g on the p h y s i c a l p a r a m e t e r s . T h i s is p r o b a b l y explainable by m e l t i n g and o x i d a t i o n p r o c e s s e s ( s p a r k l e r e f f e c t ) . T h e effect leads to a large a m o u n t of s p h e r e s in g r i n d i n g d u s t s f r o m CK 45 N ( p i c t u r e I) w i t h a r e m a r k a b l e share of h o l l o w s p h e r e s . T h e s e m i g h t be d u e to s e c o n d a r y and t e r t i a r y m e l t i n g and o x i d i s i n g p r o c e s s e s (2), e a c h step g e n e r a t i n g a lot of s m a l l e r p a r t i c l e s ( p i c t u r e 2 and 3). G r i n d i n g d u s t s f r o m X5 CrNi 18/9 s h o w s p h e r e s with d i f f e r e n t k i n d of d e n d r i t i c p a t t e r n s ( p i c t u r e 3-5). U n d e r the c h o o s e n c o n d i t i o n s we f o u n d in N i C r 20 TiAl c u t t i n g s only.

671

672

H . P . KONIO et al.

Picture

Picture

1. S p h e r e

in h o l l o w

2. C r a c k e d

hollow

sphere

sphere

in c o a r s e

in c o a r s e

dust

dust

from

from

CK

CK

45 N

45 N

(SEM)

(SEM)

Characterisation of metal grinding dusts

Picture

3.

Small

spheres

15700X,

Picture

4.

in f i n e

dust

(0.5-1.0~m)

673

from

CK

45 N

(TEM,

lOOkV)

Dendritic pattern 1819 (SEM)

of a s p h e r e

in

coarse

dust

from

X5

CrNi

674

H . P . KONIG et al.

Picture

5.

Small sphere dust from X5

on a CrNi

recrystallized 18/9 (SEM)

Picture

6.

Dendritic forms, cubic and o f a s p h e r e in c o a r s e d u s t

large

particle

in

coarse

octahedral crystals in a h o l e from X5 CrNi 18/9 (SEM)

Characterisation of metal grinding dusts

Picture

7. C u t t i n g s

in c o a r s e d u s t

from N i C r

675

20 T i A I

(SEM)

References

(1) K o c h , W., Konig, H.P., L o d d i n g , H., H o l l a n d e r , M., N e d e r , L. (1986) " S a m p l i n g und C h a r a c t e r i s a t i o n of metal g r i n d i n g d u s t s " , A I ~ O S O L S : F o r m a t i o n and R e a c t i v i t y , 2nd Int. A e r o s o l Conf. B e r l i n , P. 1208, P e r g a m o n J o u r n a l s Ltd., O x f o r d (2) P f e n d e r , E., Young, R.M. (1986) " G e n e r a t i o n of U l t r a f i n e P a r t i c l e s in thermal P l a s m a s " , A E R O S O L S : F o r m a t i o n and R e a c t i v i t y , 2nd Int. A e r o s o l Conf. B e r l i n , P. 918, P e r g a m o n J o u r n a l s Ltd., Oxford