This document analyzes the optimization of spheroidized annealing process parameters on AISI 10B21 steel wire using the Taguchi approach. It aims to improve the mechanical properties of steel wires for cold forming of screws. Three annealing parameters - temperature, heating time, and cooling temperature - were tested at different levels using an orthogonal array experiment. Results found that annealing temperature was the most significant factor affecting tensile strength and ductility. The optimum conditions were determined to be 725°C temperature, 7 hours heating time, and 500°C cooling temperature to achieve a tensile strength of 40.94 kgf/mm2 and ductility of 26.03% while minimizing hardness. This provides a reference for wire manufacturers to improve

1. Chih-Cheng Yang1
, Shih-Ting Wang2
and Jung-Tai Tsai2
Kao Yuan University
1
Department of Mechanical and Automation Engineering
2
Graduate School of Fasteners Industry Technology
ICASI 2017 (May 14)
Optimization of Spheroidized Annealing
Process Parameters on AISI 10B21 Steel Wire
Using Taguchi Approach

2. Outline
IntroductionI.
Optimum ExperimentII.
Results and DiscussionIII.
ConclusionIV.

3. I. Introduction
1. The wire has to be annealed → cold formability.
2. Spheroidizing annealed wire → forming quality of
screws.
3. Various parameters affect the quality of spheriodized
annealing
Various Parameters Quality Characteristics
Spheroidized annealing
temperature
Tensile strength
Prolonged heating time Hardness
Furnace cooling temperature Ductility

4. I. Introduction
4. A series of experimental tests-Taguchi method
→ Optimum spheroidized annealing conditions
→ Improve the mechanical properties of steel wires
→ Screws cold forming quality
→ AISI 10B21 steel wire, vacuum drying oven
5. The results show the main factor
→ Spheroidized annealing temperature

5. 6. Spheroidizing treatment on steel → cold formability.
7. Drawn wire is required to soften wire before cold
heading.
8. With increasing motion of dislocation,
increases:
(1) yield strength
(2) tensile strength
(3) hardness
decreases:
ductility→zero
I. Introduction

6. 9. Material will lead to brittle fracture
→ The material is deformed continuously
→ Yield point is passed.
10. The drawn wire must go through annealing process [1]
for
→ Improve the cold formability and mechanical properties.
→ Enhance ductility.
→ Remove the effects of internal stress
→ Reduce the forming impact force.
I. Introduction

7. In bolt Industry
→use a subcritical spheroidized annealing
→heating to below the lower critical and holding
I. Introduction
C (furnace cooling)
A (annealing temperature)
B
(prolonged heating)
Time (hours)
Temperature
(°C)

8. A cold heading quality AISI 10B21 steel wire is usually
used to manufacture welding bolts and flange weld nuts for
automotive fasteners. The wire has to be spheroidize
annealed after drawing wire coil (φ9.0mm) to the size with
section-area reductions of about 23.3%, with mechanical
properties of 70.0 kgf/mm2
tensile strength, 27.6%
ductility and 231HV hardness.
I. Introduction

9. In this study, a series of experimental tests on AISI 10B21
steel wire is carried out in a vacuum drying oven (CVM-
20S) and Taguchi method is used to obtain optimum
spheroidized annealing conditions to improve the
mechanical properties of steel wires for cold forming.
I. Introduction

10. Wire Coil Manufacturing Process
球 化
Wire Rod Surface Treatment
1st Drawing
Patenting
2nd DrawingStranding
Wire RopeClosing

11. In this study, a series of experimental tests on AISI 10B21
low carbon steel wire is carried out in a vacuum drying
oven. The chemical composition is listed in Table 1.
Table 1
Chemical composition of AISI 10B21 low carbon steel wires (wt.%).
II. Optimum Experiment
Composition C Mn P S Si Al B
China Steel 0.19 0.87 0.019 0.006 0.05 0.0380 0.002

12. II. Optimum Experiment
Factor Level 1 Level 2 Level 3
A
Spheroidized annealing
temperature (°C)
705 720 725
B Prolonged heating time (hr) 7 6 5.5
C
Furnace cooling
temperature (°C)
500 450 400
Three process parameters with three levels, as listed in Table 2,
are chosen as the experimental factors in this study.
The parameters of Level 2 are the original spheroidized
annealing process conditions.
Table 2
Experimental factors and their levels for L9 orthogonal array

13. II. Optimum Experiment
The orthogonal array table, L9(34
), is used as experimental
design for these three factors [9], as listed in Table 3.
Table 3
L9(34
) orthogonal array experimental parameter assignment.
A:
Spheroidized annealing
temperature (°C)
B:
Prolonged
heating time (hr)
C:
Furnace cooling
temperature (°C) X
L1 705 7 500
L2 705 6 450
L3 705 5.5 400
L4 720 7 450
L5 720 6 400
L6 720 5.5 500
L7 725 7 400
L8 725 6 500

14. II. Optimum Experiment
Three quality characteristics of shpheroidized annealing wire,
tensile strength, ductility and hardness are investigated.
Each test result, including five specimens, followed by each
fabricate process and transformed to S/N ratio.
The main quality characteristic is tensile strength with a
nominal value of 41 kgf/mm2
. The S/N ratio for the nominal-
the-best response is [9]
µ is mean of each test result
m is nominal value, and S is standard deviation.
( )[ ]22
μlog10/ SmNS +−−= (1)

15. II. Optimum Experiment
Spheroidizing provides the needed ductility for cold heading.
Through spheroidize annealing, the ductility of steel wire may
be improved, and the hardness may be reduced as well.
Therefore, the ductility is larger-the-better characteristic and
the S/N ratio is [9]
yi is ductility (εf) of each specimen
n is test number
(2)
n
y
NS
n
i
i∑=
−= 1
2
/1
log10/

16. II. Optimum Experiment
Hardness is smaller-the-better characteristic
S/N ratio is [9]
µ is mean of each test result
S is standard deviation.
(3)[ ]22
μlog10/ SNS +−=

17. III. Result and Discussion
The tensile strength varies from 40.17 to 40.93 kgf/mm2
, the
ductility varies from 26.8% to 32.6% and the hardness varies
from 121.4 to 133.5 HV.
Table 4
The test result and S/N ratios for tensile strength, ductility and hardness
Exp. Tensile strength Ductility (εf
) Hardness
No
µ
(kgf/mm2
)
S
S/N
ratio
µ
(%)
S S/N ratio
µ
(HV)
S
S/N
ratio
L1 40.41 0.14 4.35 32.6 0.46 30.27 126.6 3.15 -42.05
L2 40.48 0.14 5.37 32.0 1.95 30.06 131.3 5.72 -42.37
L3 40.17 0.43 0.54 32.5 2.00 30.19 131.9 4.82 -42.41
L4 40.34 0.39 2.31 27.7 0.43 28.85 132.8 4.63 -42.47
L5 40.46 0.21 4.69 28.2 0.37 29.01 131.8 5.49 -42.41
L6 40.64 0.61 3.05 27.9 0.83 28.89 131.7 6.29 -42.40
L7 40.79 0.25 9.67 26.8 0.71 28.56 121.4 4.48 -41.69
L8 40.84 0.19 12.10 27.7 0.68 28.85 133.5 8.19 -42.52
L9 40.93 0.29 10.51 26.8 0.34 28.57 131.9 5.01 -42.41

18. III. Result and Discussion
A. Tensile Strength
The original levels (Level 2) are not the optimum fabricating
parameters to obtain the target tensile strength.
The spheroidized annealing temperature (A) is a significant
factors
Optimum conditions
A3 725°C
B2 (prolonged heating time, 6.0 hr)
C1 (furnace cooling temperature, 500°C)
Fig. 1
The factor response diagram for tensile strength.

19. III. Result and Discussion
B. Ductility
The original levels (Level 2) are not the optimum fabricating
parameters to obtain the target ductility.
The spheroidized annealing temperature (A) is a significant
factors
Optimum conditions
A1 705°C
B2 (prolonged heating time, 6.0 hr)
C1 (furnace cooling temperature, 500°C)
Fig. 2
The factor response diagram for ductility.

20. III. Result and Discussion
C. Hardness
The factor of prolonged heating time (B) responds the highest
effect.
Optimum conditions
B1 7.0 hr
A3 725°C (spheroidized annealing temperature )
C3 (furnace cooling temperature, 400°C)
Fig. 3
The factor response diagram for hardness.

21. III. Result and Discussion
The significant factors of spheroidized annealing temperature
(A): tensile strength and ductility. The optimum conditions
A3 (spheroidized annealing temperature, 725°C
B1 (prolonged heating time, 7 hr)
C1 (furnace cooling temperature, 500°C) >>not significant
Table 5
Optimum condition table for spheroidized annealing
Factor Tensile strength Ductility Hardness Optimum
A A3* A1* A3 A3
B B2 B2 B1* B1
C C1 C1 C3 C1

22. III. Result and Discussion
D. Confirmation Experiments
Figs. 4~6 show the original and optimum probability
distributions for tensile strength, ductility and hardness of
wire.
Fig. 4
Fig. 5
Fig. 6

23. IV. Conclusion
1. The quality of spheroidize annealed steel wire affects the
forming quality of screws.
2. Three factors affect the quality of spheroidized annealing.
3. The effects of spheroidized annealing conditions affect the
quality characteristics of wire.
4. Spheroidized annealing temperature (A) is the significant
factor.
Various Parameters Quality Characteristics
Spheroidized annealing temperature Tensile strength
Prolonged heating time Hardness
Furnace cooling temperature Ductility

24. IV. Conclusion
4. Tensile strength with a nominal value of 41 kgf/mm2
.
5. The optimum conditions:
A3 (spheroidized annealing temperature, 725°C)
B1 (prolonged heating time, 7 hr)
C1 (furnace cooling temperature, 500°C) >>not significant
7. The optimum mean:
tensile strength: 40.94 kgf/mm2
ductility: 26.03%
hardness: 131.1 HV
8. The results: as a reference for wire-manufacturers.

25. Acknowledgements
The authors would like to acknowledge the support of
Jinn Her Enterprise Co., Ltd., Koahsiung, Taiwan for
providing the materials to carry out the spheroidized
annealing experimental work.

26. Thank you for your attention!