surface quality in the grinding of stainless steels (2nd ... · surface quality in the grindind of...

Surface quality in the grinding of stainlesssteels (2nd report) : effects of number ofpass times of grinding in surface grinding onthe surface qualities of the works

著者 "TANAKA Hideho"journal orpublication title

鹿児島大学工学部研究報告

volume 31page range 1-12別言語のタイトルステンレス鋼の研削時における表面性状 : 平面研

削における研削回数が工作物の表面性状におよぼす影響

URL http://hdl.handle.net/10232/11506

Surface quality in the grinding of stainlesssteels (2nd report) : effects of number ofpass times of grinding in surface grinding onthe surface qualities of the works

著者 TANAKA Hidehojournal orpublication title

鹿児島大学工学部研究報告

volume 31page range 1-12別言語のタイトルステンレス鋼の研削時における表面性状 : 平面研

削における研削回数が工作物の表面性状におよぼす影響

URL http://hdl.handle.net/10232/00010598

SURFACE QUALITY IN THE GRINDING OF

STAINLESS STEELS (2nd Report) —Effects of Number

of Pass Times of Grinding in Surface Grinding

on the Surface Qualities of the Works—

Hideho TANAKA

(Received May 31, 1989)

Abstract

The CBN abrasive wheel has recently been used in practice as a beneficial wheel from the stand

point of surface qualities.

In this report, surface grinding experiments were carried out with stainless steels using alumina,

silicon—carbide and CBN wheels.

The effects of (1) the number of pass times of grinding, (2) the types of wheel, and (3) the work

materials on the affected layers, and on the ground surface roughness and, finally, on the grinding

forces were examined. And, then, the degrees of work hardening or the thermal influences on the con

strained and unconstrained works were explored in order to examine the effects of the conditions of

constraint of working stress on surface qualities.

Of all types of wheels employed, the CBN wheel showed excellent results in the affected layer

and in the grinding forces except in the area of surface roughness.

1. Introduction

In previous report surface qualities of stainless steels (SUS 304, SUS 403, SUS 440C)ground

with 19A, GC and CBN abrasive wheels were compared with each other in one pass grinding, and it

was shown that CBN abrasive wheel obtains good results for the affected layer of small size work and

hardened steel especially.

It was expected in that report that the differences in the condition of stress constraint in grind

ing are occured according to the sizes of the works and the condition of work holding.

However, because of that the test was carried out one pass grinding in that report, it seems to be

not usual for practical. So, in this report giving the depth of cut of 10 jum at evety pass and varing

the number of pass times 3, 5, 7 and 10 times, tests were carried out in surface grinding.

And moreover, the effects on the affected layer are also discussed on the cases that made severe

the constraint conditions of working stress due to grinding forces by using the constraint holder for

the work.

2. Test conditions

Tests were carried out as shown in Table 1, at constant table speed f=5m/min and giving the

depth of cut ^ = 10/am at the right and left end of the work respectively in every pass.

ft S k ¥ X ^ SB flF ft IS 31 •§• (1989)

The number of grinding pass time 3, 5, 7 and 10 times were tested on each test piece. Grinding

forces (Ft ; tangential, Fn ; normal) and actual depth of cut were measured at each one pass, and mean

measurement values were adopted at every pass. More, the variations of hardness of work material

and microphotographs are ones after grinding pass 3, 5, 7 and 10 times respectively. The other test

conditions are omitted because same as in 1st report.

Table 1 Test conditions

Grinding machine Surface grinder PSG-3A-D0.75 KW

Grinding wheel

A) 19A180KV75R ' 200X ' 38. IX 19B) GC180KV81RC) CBC170N75BW4

*200X*38.1X20TX 3 XX10L

Work material

1) SUS 304 hejght width length2 SUS 403 45X15X40mm3) SUS440C

Heat treatment; same as 1st report

Grinding condition

Wheel speed V m/min 2300Table speed f * 5

Depth of cut/one pass A/itn 10Pass times of grinding 3, 5, 7, 10

Cut without spark-out

CoolantEmulsion (for CBN wheel) 5 %solution (for 19A, GC wheel) 1. 25% 4 1/min

3. Experimental results and discussions.

3.1 Variations in hardness of work material

3.1.1 Effects of types of abrasive wheel

(A)19A

abrasivewheel

GCabrasivewheel

(C)

CBCabrasivewheel

1.4r

1.3SUS 403

H=404

••"

;**%• •

•

•

._!•-•_.• .

H=448

\

'

H=446

#•• •• *• - .

::

1.4

1.3

1.2

1.1.'

SUS

• •

304

H=219

* "

0.8

0.8

0.7

0.8 '

1.4

1.3

1.2 .«...

1.1H=207

~

0.8

0.8

0.7

1.4

1.3

1.2

1.1#, .'.'•%•

H=183

. * - » •

0.8 V

0.8

0.7

100 200 300 400 500 BOO 100 200 300

SUS 440C

H=644

•• ••

H=656

H=718

0 100 200 300 400 S00 E9

Depth from ground surface L jim

^s- = 10/t/m/passFig. 1 Variation in hardness of work material (on grinding pass time n= 5) £_^ m/min

Surface Quality in The Grindind of Stainless Steels (2nd Report)—Effects of Number

of Pass Times of Grinding in Surface Greining on the Surface Qudlities of the Works 3

Fig. 1 shows the vatiations in hardness of work material measured in vertical cross section to

ground surface on the case of 5 times grinding passes. The distributions of hardness from ground sur

face to bottom of work are shown as the hardness ratio H'/H, where H and H' are Vicker's hardness

of base metal and affected layer respectively.

For all the work materials SUS 304, SUS 403 and SUS 440C, CBN abrasive wheel (C, in same

figure) shows that the degrees of annealing or tempering due to grinding and of the work hardening

due to grinding force in the grinding surface layer are small compared with 19A (A, in same figure)

and GC abrasive wheel (B, in same figure). Accordingly, it is evident that CBN abrasive wheel does

not affect thermal and stress influences on the ground surface layer compared with the otheres: 19A

and GC abrasive wheel develop annealed layer in the surface by grinding heat for SUS 304 had a re

markable work hardenablity, and for SUS 403 and SUS 440C hardened material develop tempered

layer or re—hardened layer, while, CBN abrasive wheel does not shows those tendencies or even if

they were shown those tendencies it's degree is small. This is due to the characteristics of CBNabrasive particle with higher heat conductivity.

3.1.2 Effects of number of grinding pass time

,4

,3

,2

,1

0

9

8

7 •

64

3

2

1

0

9

8

7 •

64

3

2

1

0

9

8

7

8

1.

1.

0.

0.

0.

0.1.

1.

_ 1-

>1.as

1.

0.

0.

0.

0.1.

1.

1.

>1.

1.

0.

0.

0.

0

19A180KV75R

• SUS 304

'•• • •

• • •

n=3

• ••

• • *

••• • .

n=5

•

• •

• •

n=7

0 100 200 300 400 500 600

Depth from ground surface L /im

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

M

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.61.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.8

GC180KV81R

SUS 403

- •*

*•

.*!• n=3

•

*-+%• • * m. *- .«

I•

\ n=5

••••

..It •,.%••» • V

n=7

#

0 100 200 300 400 500 600

Depth from ground surface L urn

Fig. 2 Variations in hardness of work material (on effects of grinding pass time)

ie6*^I^3Bfflf£ m 31 •§• (1989)

It is considered that the effects on the affected layer are to be accumulate when repeat the grind

ing pass giving the depth of cut at every pass without spark—out.Fig.2 is an example examined the effects of the number of grinding pass time n on the affected

layer by the distributions of hardness ratio H'/H, on the case of 19A abrasive wheel for SUS 304 andGC abrasive wheel for SUS 403.

It is obvious from the figure that the degree of work hardening in SUS 304 due to working stressand in SUS 403 the degree of annealing due to grinding heat, both increase with the increase of num

ber of grinding pass time n.

In CBN abrasive wheel these tendencies as in 19A and GC wheel were not clearly seen and not

affected by n in every material adopted, therefore difficult to see the states of affected layer with increasing of n. It is obvious to depend on the characteristics of CBN abrasive particle. It is consideredthat CBN particle characteristics of excellent heat conductivity, higher hardness and toughness are

caused.

Now, to make futher clear these, Fig.3 is shown. —A qualitative tendency shown the degree of

thermal effects and of the work hardening obtained by applying the procedure of Mizutani and Naka-

jima 2) is shown—In same figure Si shows the any scale shown the degree of thermal effect due tore—hardening, S2 the degree of tempering and S3 the degree of work hardening. As obvious from thefigure, SUS 304 (A) had a high work hardenability is shown by only S3 which shows a work hardeninglayer in all abrasive wheels. CBN wheel shows the smallest effects compared with 19A and GCwheels. The degrees of work hardening increase with the increase of n in both 19A and GC wheels,but in CBN wheel, the degree is smaller than other wheels and the relation between n and S3 cannot

clear.

Number of pass times n

Fig. 3 Evaluation of the degrees of heat and stress effects in the affected layer shown by any scalesSi, S2, S3

SUS403

Ll31 1: 19A180KV75R• S2 2: GC1B0KV81RP7J33 3: CBC170K75BWi

I 1

ll.H.ll.1IS) 171

Number of pass times

susuoc 2 (C)•si

m •S2OT,5 E2s3

• 2

W i 1-10 :l •

W

111 2

•

5 11 ,3

Hil 3 .

1 •i 1(SI 171

Number of pass times

In same figure (B) of hardened steel SUS 403, the most of affected layer show S2 that is a tem

pered layer due to grinding heat, on the other hand, CBN wheel shows little effects of grinding heat,

the degree is small and subjected rather the work hardening in part. So, it can be considered that the

temperature of ground surface with CBN wheel was considerably low.

In same figure (C) of SUS 440C, the degrees of tempering are greater than the case (B) SUS

403. This seems to be sensitive for tempering because of high hardeness of this material compared

with SUS 403. In this case also the thermal effects of CBN wheel on ground surface are very small.

In any case, the degrees of thermal and working stress effects of CBN wheel on ground surface

are smaller than the other wheels examined.



3.2 Microstructure of affected layer

Fig.4 is an example showing the effects of number of grinding pass time n on affected layer using

S.E.M.

With the increase of n as seen from (A) to (C) in same figure, in SUS 304 with 19A abrasive

wheel, the variation in the degree of work hardening is observed on the microstrucuture, TWIN" isobserved on the case 7 times (C). So, it is considered to be subjected fairly highly working stress.

Fig. 4

HMK1P. •->• ''iuitjM.' ' 10/um

SUS 304

19A abrasive wheel

lOym

SUS 403

CBN abrasive wheel

Microstructure of damaged layer ground with 19A and CBN abrasive wheel (on effects ofgrinding pass times n)

SI^:?If»i^ % 31 -t (1989)

On the other hand, in SUS 403 with CBN abrasive wheel as same as mentioned above 3.1, there

is little obvious variation in the microstructure with the increase of n.

3.3 Grinding force

3.3.1 Tangential and normal grinding forces Ft, Fn.

The relations between grinding forces and number of grinding pass times n are shown in Fig.5.

Each force is shown by mean values per one pass on each pass and per unit width of work.

18

=16

flif

12

10r

:b

6

4

•

SUS 304

— 19A180KV75R

—— GC180KV81R

CBC170N75BW4

"" *

•

it2

0

18

g16

55

12

10

£8

6

4

2

0

2 4 6 8 10

Number of grinding pass times n

SUS 403

18

18

55

12

10

£8

6

4

2

0

2 i 6 8

Number of grinding pass times

SUS 440C

2 4 6 8Number of grinding pass times

10

18

i16

12

10

£8

6

4

2

0

•

SUS 304

ii:E16rE

12

10

L^8

6

4

2

0

18

E1B

12

10

£8

6

4

2

0

2 A 6 8 10

Number of grinding pass times r

SUS 403

2 4 6 8 10


2 4 6 8 10Number of grinding pass times n

Fig. 5 Relation between grinding forces and number of grinding pass times



The grinding forces become small in order GC, 19A, CBN abrasive wheels, especially the forces

by CBN wheel are very small among of them.

Among of 3 types stainless steels, in SUS 304 and SUS 403 relatively softer material, grinding

forces increase with the increase of n together with 3 types abrasive wheel, but in hardest SUS

440C, with 19A and GC wheels, the forces begin to decrease on about n = 5 times, while in CBN

wheel the forces rather increase with the increase of n especially in Fn. It is evident from the differ

ences among of each abrasive, that is, each abrasive particle has a characteristics to suit for each

material respectively.

3.3.2 Grinding force ratio Ft/Fn

Fig.6 shows the ratio Ft/Fn of tangential (Ft) and normal (Fn) grinding forces of 3 types of abra

sive wheel for the work materials, as the mean values over the all cases for every work material.

GC abrasive wheel shows largest ratio and CBN wheel shows smallest ratio of 3 types wheel for

every work material, that is, the ratios are in the order of the brittlness of abrasive particles of 3

types of wheel.

Now, if consider the ratio Ft/Fn apparent coefficient of friction ju between wheel and ground sur-

facem, it may be explained as follow that the irregularties of abrasive grain protrusion from wheel

surface are decreased and flattened with repeating the pass grinding giving the depth of cut at evety

pass. So, the number of abrasive particles subjected to cut at same time increases, then frictional re

sistance increases. This is also obvious from tangential forces in Fig. 5.

3.4 Metal removal rate and surface roughness

Fig.7 shows the ratios actual metal removal rate qact to theoretical one qth with mean values the

all of number of grinding pass time on each material. As a matter of course the differences shall becaused in the metal removal rates according to the toughness, hardness of abrasive particles them

selves and the grades of the abrasive wheels etc, owing to repeating the grinding pass without spark-

out.

In this test however, the obvious differences are not caused probably because of that the depth of

cut was relatively small at 10 jum and maximum number of grinding pass time n was also small at 10

times, and moreover, because of that the varieties of actual depth of cut by elastic deformation due to

grinding forces or of thermal expansion of work materials due to the differences of each abrasive sthermal conductivity. Only, it is seen that CBN wheel shows slightly good performance in SUS 440C

hardened material.

I I 19A180KV75R•I GC180KV81R

"CBC170N75BW41.0

0.8

0.6,

0.4 •

0.2

0SUS304 SUS403 SUS440C

Fig. 6 Comparison of Ft/Fn

1.0

0.8

0.6

0.4

0.2

0

ES3

19 A 180KV75R

GC180KV81R

CBC170N75BWA

1SUS304 SUS403 SUSiiOC

Fig. 7 Comparision of qact/Qth

m ft jik ± ¥ x ¥ mm ft m 31 -§• (1989)

15

u

13

12

1 1

10

' 9

SUS440C

o 19A180KV75R

/-\• GC180KV81R

^ \

\

\

• CBC170N75BWi

Rl

\\

Rn

\\\^3

A^/ \

// X

J \

2^.L__

1 2 3 I 5 6 7 8 9 10


Fig. 8 Variations of surface roughness

It is considered for grinding surface that the toughness or hardness of abrasive particle and the

grade of bond of wheel etc affect complexly on, and repeating the grinding pass n improves surface

roughness.

Though it cannot been obtained the obvious qualitative relations between n and surface rough

ness, the results as shwn in Fig. 8 were obtained in SUS 440C hardest material. Rl and Rn are sur

face roughness along to and across to the grinding direction respectively.

The surface roughness of across direction Rn is larger than that of grinding direction Rl in ev

ery wheel.

The surface roughness Rl and Rn decrease with n increases.

In CBN wheel Rn decreases rapidly as exceeds n —5, in 19A wheel though the degree is small

shows also similar tendency, and in GC wheel that tendency is smallest.

The Rn values become small in the order of the brittleness of abrasive particles, that is, the

values of Rn are largest in CBN, then in 19A and in GC wheel the values of Rn are smallest. The

values of Rn are improved in the order of the brittleness of abrasive particles. On the other hand the

values of Rl the roughness along to grinding direction are not like so, rather improved with the CBN

wheel that the toughness of abrasive is highest of 3 types of the wheel employed.

In surface grinding without cross feeding of table, the irregularities of wheel surface become to

be copied, as they are, on the ground surface as a roughness across to grinding direction. Therefore

the condition of wheel surface is important.

However, in the surface roughness along to grinding direction it's generation mechanisms are

complex, the slippings of abrasive particles, the remainings not beeing cut and number of cutting

edges acting at same time, or thermal expansion of works etc linking together complexly give a com

plicated generated surface on ground surface. Accordingly, the roughness along to grinding direction

is not alway in the order of the brittleness of abrasive particles as in the case of roughness across to

grinding direction.

Fig. 9 is the comparison of Rl and Rn, where the values of Rl and Rn, are the mean values in the

15

~14

513

«12

3 7

* 600 u

5

4

3

2

1

0


of Pass Times of Grinding in Surface Greining on the Surface Qudlities of the Works

| I 19A180KV75R

•i GC180KV81R

Y77A CBC170N75BW4

(A) Rl

direction of

longitude

SUS304 SUS403 SUS440C

15

-14

513

-12

"11w

Sio

S 9

2 8

s 7

5

4

3

2

0

(B) Rn

direction of width

VA

SUS304 SUS403 SUS440C

Fig. 9 Comparison of surface roughness

all of grinding pass on each work marerial.

It is seen that in same figure (A) roughness Rl are smallest with CBN wheel for every material,

on the contrary in (B), roughness Rn is on the whole greater than in Rl. Especially in SUS 403 and

SUS 440C comparative hard material the values of Rn with CBN are lager, as mentioned above this

is dependent on the toughness of each abrasive particles.

3.5 Effects of the conditions of the mounting of work to work holder on affected layer.

In the 1st report it was pointed out that small size work makes the constraint conditions of work

ing stress less strong because of easy elastic deformation due to grinding forces, and so, in SUS 304

had a higher degree of work hardenability the degree of work hardening becomes small, then the

effects on affected layer also vary, and that the size effects of the works exist for the affected layer

as a matter of course not only in SUS 304 but in the other materials.

The differences of the effects on affected layer between constrained and unconstrained works are

examined with the work holder as shown in Fig. 10. Using this holder the elastic defomation of work

difficult to occur.

Fig. 11 shows an example of grinding forces on the cases of constrained and unconstrained of

work. Obviously the grinding forces (Ft : tangential, Fn ; normal) of constrained work are larger than

unconstrained ones.

Fig. 12 shows the microstructure with S. E. M. of the works of constrained and unconstrained in

SUS 304. Plastic flow are seen at surface layer in constrained (A) and not seen in unconstrained (B).

It is seen obviously that the work constrained subjects larger working stress than unconstrained one.

Fig. 13 shows the variations of hardness in work material in SUS 304 ground at 40 /um of depth

of cut and at one pass, on the unconstrained and constrained work. It is obviously seen that the de

grees of the work hardening of constrained work are larger than that of unconstrained work, althogh

10 IP ± m X ¥

c

12 r

10

$ 31 # (1989)

(SUS 4

Fn

Ft

— Constrained

•- Unconstrained

Fig. 10 Specimen holder for constraint

T3c

o

(A) Constrained

(B) Unconstrained

-»-40 60

Radial infeed A (im

80

Fig. 11 Comparison of grinding force at the condition ofconstrained and unconstrained.

10/im

10,um

One pass

A=10ym

f=5.0 m/min

Fig. 12 Microstructure of SUS 304 groundwith CBN abrasive wheel

1.4

1.3

= 1.2

"1.1

1.0

0.9

0.8

0.7

0

f,

1.

.6

0 100 200 300 100 500 600Depth from ground surface L urn

*f

3

2

1= 1.

1.

0.

0.

0.

0.

CBC175N75BW4 abrasive wheel

(A) Unconstrained

.-..-,.•

(B) Constrained

100 200 300 tOO 500

Depth from ground surface L urn

600

ig. 13 Comparison of the hardness of work materialbetween constrained and unconstrained speci

men (SUS 304, A = 40^m)


of Pass Times of Grinding in Surface Greining on the Surface Qudlities of the Works

Unconstrained Constrained

if"

n=5

'10,um

n=7 n=7

11

10/im

J10|im

Fig. 14 Microstructure of SUS 403 ground with CBN abrasive wheel ^ = 10/um, f= 5.0m/min

the depth of affected layer not so varies.

Fig. 14 shows the microstruture with S.E.M. on about n = 5 and 7 times, ground by CBN wheelfor SUS 403. There are not so much differences as in SUS 304 shown in Fig. 12, this will may be

due to the differences whether the material is sensible to working stress or to temperature.

4. Conclusions

The effects of the types of abrasive wheel and of the number of pass time of grinding on surface-

qualities in surface grinding of stainless steels SUS 304, SUS 403 and SUS 440C, were examined,

and then on the case of unconstrained and constrained works, the degrees of effects on affected layer

and grinding forces are also examined.

The results obtained are as follow.

1. The effects on affected layer are small in CBN abrasive wheel compared with 19A and GC wheels,

especially thermal effects are very small, even if repeat the grinding without spark—out giving the

depth of cut.

2. The ground surface roughness across to grinding direction by CBN abrasive wheel is larger than

the other 19A and GC wheels. However, the one along to grinding direction by CBN abrasive wheel

12 ffiiEa;fc^X^«flf%«£ % 31 ^ (1989)

is smaller than the other 19A and GC wheel.

3. When small size works are ground constraining the elastic deformation, the affected layer of mate

rial had easy work hardenability is affected by working stress largely.

4. Therefore, it is expected that the work's size effects for the affected layer by work hardening areexisted.

REFERENCES

1) H. TANAKA, K.KOREEDA and L. YING : THE RESERCH REPORTS OF THE FACULTY

OF ENGINEERING KAGOSHIMA UNIV. 30 (1988) 45 (in Japanese)

2) Y. MIZUTANI and K.NAKAJIMA: MACHINE and TOOL. 12 (1978) 25 (in Japanese)

surface quality in the grinding of stainless steels (2nd ... · surface quality in the grindind of...

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