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MECHANICAL PROPERTIES AND

MICROSTRUCTURES OF AISI 41B30 FORGINGS IN

AS FORGED AND NORMALIZED CONDITIONS

(DUSAN MILICEVIC M.Sc.)(COMMERCIAL FORGED PRODUCTS) (CFP)

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Content

• Introduction• Test plan• Results• Discussion • Conclusions• Future work

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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

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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.

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•

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1F 2F 3F

•

1F 2F 3F

••

•1HT 2HT 3HT

1HT 2HT 3HT

SAMPLES LOCATION AND DESIGNATION

1F- AS FORGED AT THE END OF STEM2F- AS FORGED, NEAR THE FLANGE3F- AS FORGED, FLANGE1HT- NORMALIZED, END OF STEM2HT –NORMALIZED NEAR THE FLANGE3HT- NORMALIZED, FLANGE

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Results

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

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Chemistry and SegregationC MN P S Si Cu Ni Cr V Mo Al Ti B N0.32 1.25 0.011 0.03 0.19 0.2 0.2 0.4 0.005 0.16 0.031 0.04

30.0017

0.0087

0.32

0.54

0.010

0.01

0.2 0.17

0.1

1.05

0.004

0.23

0.03 0.002

0.0 0.0065

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

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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.

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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

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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)

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Microstructures in as forged and normalized condition

• Top row:1F, 2F , and 3 F

• Bottom row:1HT, 2HT and 3HT

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Microstructural Difference

AISI 41B30 AISI 4130

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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.

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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.

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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.

• .

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Discussion -continuation

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

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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.

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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.

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Metallurgical lab in CFP

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Future Work

• Evaluate as rolled +tempered Widmanstätten microstructure

• Evaluate direct quenching in water from the press and self tempering