This document summarizes testing done to compare the microstructures and mechanical properties of AISI 41B30 steel forgings in the as-forged and normalized conditions. Chemistry tests, hardness tests, tensile tests, impact tests, and microstructural analysis were performed on samples from different locations in the forgings. The normalized forgings showed more uniform hardness but reduced impact properties compared to the as-forged condition, likely due to boron segregation during normalization. Fully austenitizing the forgings and faster cooling rates after heat treatment could help reduce boron segregation and improve impact properties. Future work may include evaluating tempered microstructures from direct quenching after forging.

1. MECHANICAL
PROPERTIES AND
MICROSTRUCTURES OF
AISI 41B30 FORGINGS IN
AS FORGED AND
NORMALIZED CONDITIONS
(DUSAN MILICEVIC M.Sc.)
(COMMERCIAL FORGED PRODUCTS)
(CFP)

3. Content
• Introduction
• Test plan
• Results
• Discussion
• Conclusions
• Future work

4. Introduction
• Upset forged and normalized axles
• Upset forgings are forged only on
one end at 4000T press at CFP.
Forging temperature was 2300⁰F.
CFP has induction heating coils.
• Batch furnace;1650⁰F /3-5 hours, air
cool

5. Test Plan
• Goal:
• To compare as forged and normalized
microstructures and properties of AISI 41B30
forgings in effort to improve the quality of the
axles.
• Test Plan:
• Two forgings; one as forged , one normalized
• Specimens for mechanical and impact testing
were taken from ends of the stems and near the
flanges. Only specimens for microstructures
were taken from flanges.

6. •
1F 2F 3F
•
1F 2F 3F
•
•
•1HT 2HT 3HT
1HT 2HT 3HT
SAMPLES LOCATION AND DESIGNATION
1F- AS FORGED AT THE END OF
STEM
2F- AS FORGED, NEAR THE
FLANGE
3F- AS FORGED, FLANGE
1HT- NORMALIZED, END OF STEM
2HT –NORMALIZED NEAR THE
FLANGE
3HT- NORMALIZED, FLANGE

7. Results
• Results of chemistry , hardness,
mechanical properties, impact
properties and microstructure are
presented.

8. Chemistry and Segregation
C MN P S Si Cu Ni Cr V Mo Al Ti B N
0.32 1.25 0.011 0.03 0.19 0.2 0.2 0.4 0.005 0.16 0.031 0.04
3
0.001
7
0.008
7
0.3
2
0.5
4
0.01
0
0.0
1
0.2 0.1
7
0.
1
1.
05
0.00
4
0.2
3
0.03 0.0
02
0.0 0.00
65
Top row is AISI 41B30 ; bottom row is AISI 4130; red fonts represents a major
difference in chemistry between two grades.
C Mn P S Si Ni Cr Mo Al Ti B
0.283 1.25 0.011 0.027 0.199 0.196 0.477 0.166 0.049 0.045 0.0032 surface 1F
0.286 1.29 0.012 0.039 0.198 0.205 0.482 0.169 0.037 0.052 0.0023 midradius 1F
0.27 1.22 0.011 0.028 0.197 0.204 0.469 0.158 0.045 0.040 0.0016 core 1F
0.278 1.26 0.011 0.029 0.197 0.198 0.479 0.167 0.045 0.046 0.0030 surface 2F
0.302 1.30 0.012 0.038 0.199 0.204 0.486 0.172 0.038 0.052 0.0031 midradius 2F
0.285 1.26 0.011 0.029 0.195 0.198 0.476 0.164 0.041 0.045 0.0031 core 2F
0.302 1.24 0.011 0.030 0.203 0.196 0.496 0.168 0.067 0.044 0.0033 surface 1H
0.354 1.29 0.013 0.041 0.203 0.201 0.50 0.175 0.051 0.049 0.0035 midradius 1H
0.306 1.25 0.011 0.033 0.199 0.193 0.491 0.168 0.039 0.044 0.0028 core 1H
0.288 1.25 0.011 0.029 0.201 0.196 0.497 0.168 0.037 0.044 0.0026 surface 2H
0.279 1.27 0.011 0.033 0.198 0.196 0.496 0.169 0.034 0.045 0.0029 midradius 2H
0.281 1.23 0.010 0.029 0.197 0.194 0.488 0.164 0.038 0.040 0.0029 core 2H

9. Test Number Hardness HRB
(HRC) -1F
Hardness HRB (HRC)
-2F
Hardness HRB
(HRC) -1HT
Hardness HRB (HRC)
-2HT
Hardness AISI4130
1 99.1 100.0 (22 HRC) 99.3 95.1 100 (22HRC)
2 93.8 100.0 (22HRC) 97.6 97.9 100 (22 HRC)
3 98.4 102.0 (25HRC) 96.7 97.8 102 (25HRC)
4 100.7 (23HRC) 102.2 (25HRC) 100.0 (22HRC) 99.6 102 (25HRC)
5 100.8 (23HRC) 102.5 (25HRC) 99.8 99.6 102 (25HRC)
6 100.9 (23HRC) 101.3 (24HRC) 99.8 100.4 (22HRC) 102 (25HRC)
7 100.4 (23HRC) 102.7 (25HRC) 98.9 100.5 (22HRC) 102 (25HRC)
8 101.2 (24HRC) 102.3 (25HRC) 100.1 (22HRC) 101.0 (24HRC) 100 (22HRC)
9 99.7 104.6 (29HRC) 100.2 (22HRC) 101.4 (24HRC) 100 (22HRC)
10 99.7 101.6 (24HRC) 99.5 100.4 (22HRC) 100 (22HRC)
11 100.5 (23HRC) 103.9 (28HRC) 98.7 100.6 (22HRC) 100 (22HRC)
12 99.2 99.2 99.2 100.9 (22HRC) 100 (22HRC)
13 97.7 103.0 (25HRC) 98.4 100.6 (22HRC) 100 (22HRC)
14 98 101.0 (25HRC) 98.7 101.5 (24HRC) 100 (22HRC)
15 98.2 100.3 (22HRC) 98.2 99.6 100 (22HRC)
16 100.3 (23HRC) 100.2 (22HRC) 95.9 99.7 100 (22HRC)
17 98.1 99.5 99.6 99.6 100 (22HRC)
18 100.5 (23HRC) 102.0 (25HRC) 98.7 98.3 100 (22HRC)
19 97.6 99.9 99.5 100.1 (22HRC) 100 (22HRC)
20 96.5 105.0 (29HRC) 99.5 98.8 100 (22HRC)
Hardness
results
Testing done
every 1/8 " of
diameter.

10. Mechanical Properties
Tensile strength psi
(MPa)
Yield strength psi (MPa) Elongation (%) Reduction in area
(%)
Sample
118,577 (817) 90,268 (622.3) 18.3 51.31 1F longitudinal
115,125 (793.7) 80,681 (556.2) 16.36 48.6 2F longitudinal
118,774 (818.9) 89,804 (619.17) 17.61 53.21 1HT longitudinal
118,353 (817.5) 84,542 (582.9) 11.24 30.90 1HT transverse
117,061 (807.1) 84,700 (583.9) 8.11 54.33 2HT longitudinal
117,126 (807.5) 84,536 (582,8) 6.77 31.06 2HT transverse
123,000 (848,05) 76,100 (524.69) 9.05 21.4 AISI4130 as rolled longitudinal

11. Impact Properties
ft- lb (J) ft-lb (J) ft-lb (J) Average ft-lb (J)
4 (5.43) 4 (5.43) 5 (6.77) 4 (5.43) 1F (room temperature) longitudinal
5 (6.77) 4 (5.43) 4 (5.43) 4 (5.43) 2F (room temperature) longitudinal
10 (13.55) 13 (17.6) 11 (14.9) 11 (14.9) 1HT (room temperature) longitudinal
10 (13.5) 10 (13.5) 11 (14.9) 10 (13.5) 2HT (room temperature) longitudinal
9 (12.2) 8 (10.84) 8 (10.84) 8 (10.84) AISI4130(room temperature)
longitudinal
6 (8.13) 8 (10.84) 7 (9.49) 7 (9.49) AISI 4130 (room temperature)
(transverse)

12. Microstructures in as forged and
normalized condition
• Top
row:1F, 2F ,
and 3 F
• Bottom
row:1HT,
2HT and
3HT

13. Microstructural Difference
AISI 41B30 AISI 4130

14. Discussion
• Small amount ( up to 0.025%) of Boron
increases hardenability of steel. As
rolled and normalized AISI 41B30 have
uniform hardness from surface to the
core similar to standard grade.
• Segregation of Boron negatively
affected impact properties of
normalized AISI 41B30.

15. Discussion -continuation
• Excess amount of Titanium may
increase hardenability but reduce
impact properties.
• Boron suppresses ferrite nucleation
at grain boundaries. Presence of
ferrite in normalized structure is
results of slow cooling rate.

16. Discussion -continuation
• High cooling rate suppresses Boron
segregation and ferrite formation on
γ grain boundaries.
• Based on 2F and 2HT
microstructures, cooling rate after
normalizing was slower than after
rolling.
• .

17. Discussion -continuation
• Axles might be induction hardened.
Strong case and brittle core might
not be the best engineering solution.

18. Conclusions
• As rolled 5.5“ in diameter billet
microstructure is very similar to
normalized microstructure of AISI
41B30 forgings.
• Normalized AISI41B30 microstructure,
for axles, is in essence brittle.

19. Conclusions-continuation
• Normalized structure may stay in the
core of axles after induction
hardening.
• Strong case and brittle core may not
be the best solution for dynamically
loaded axles.

20. Metallurgical lab in CFP

21. Future Work
• Evaluate as rolled +tempered
Widmanstätten microstructure
• Evaluate direct quenching in water
from the press and self tempering