Maximizing the Value and Performance of Chromium, Manganese, and Silicon Containing PM Steels

Transcription

1 Maximizing the Value and Performance of Chromium, Manganese, and Silicon Containing PM Steels Michael L. Marucci & Bruce Lindsley - Hoeganaes Corporation USA 31. Hagern Symposium

2 Outline Introduction & Background Part 1: Chromium Containing PM Steels Part 2: Manganese Containing PM Steels Conclusions

3 Nickel Dust Exposure Limits Currently REACH and AGW are upgrading their exposure limits for nickel dust exposure AGW proposed a move of 0.5 mg Ni/m 3 <0.05 mg Ni/m 3 Methods to reduce nickel dust exposure include Removing or reducing nickel in mixes Using bonded powder mixes such as ANCORBOND

4 Alloy Price Volatility (Kassakurs) (Datum)

5 Test Alloy Compositions Alloy Fe Mo* Ni Cr Si Mn Gr Ancorsteel 4300 Bal ANCORBOND FLM-4000 Bal ANCORBOND FLM-4400 Bal * Prealloyed The powders used in this study use proprietary master alloys for Cr, Si, and Mn All powders are ANCORBONDED to limit segregation and reduce dusting

6 Compressibility Comparison (Gründichte) (Pressdruck)

7 Part 1: Effect of Sintering Conditions on Chromium Containing PM Steels Alloy Fe Mo Ni Cr Si Gr Ancorsteel 4300 Bal Sintering atmosphere control is essential to avoid oxidation of the chromium dew point < -40 C required N2-H2 with a minimum of 5-10 vol%h2 Endothermic gas is not recommended Sintering temperature, time, and cooling rate need to be closely controlled to optimize performance and manufacturability of chromium containing PM steels

8 Dimensional Change (Maßänderung zur Matrize) (Sintertemperatur)

9 Apparent Hardness (Härte) (Sintertemperatur)

10 Ultimate Tensile Strength (Zugfestigkeit) (Sintertemperatur)

11 Total Elongation (Bruchdehnug) (Sintertemperatur)

12 Microstructure 1120 C 8 min 1150 C 15 min 1180 C 30 min Etch 2% Picral 4% Nital

13 Effect of cooling rate Cooling Rate* C/s Fe - 1Cr + 1Ni + 0.6Si + 0.8Mo C Sintered 1120 C 30 min, Tempered at 205 C Dimensional Change % Härte Apparent Hardness HRC Ultimate Tensile Strength MPa Yield Strength MPa Total Elongation % Abkühlgeschw. Maßänderung Zugfestigkeit Strenkgrenze Bruchdehnung Kerbschlagarbeit Impact Energy *Average cooling rate from C J

14 Part 1 Summary: Chromium Containing PM Steels Dimensional change is minimally impacted by changes in sintering temperature but part size change can be modified by adjusting the sintering time at temperature A minimum sintering temperature of 1150 C is recommended to allow the chromium containing master alloy to diffuse Accelerated cooling can be used to increase apparent hardness and strength Tempering is recommended when using accelerated cooling

15 Part 2: Effect of Sintering Conditions on Manganese Containing PM Steels Alloy Fe Mo Mn Gr ANCORBOND FLM-4000 Bal ANCORBOND FLM-4400 Bal Sintering atmosphere control is essential to avoid oxidation of the manganaese dew point < -40 C required N2-H2 with a minimum of 5-10 vol%h2 Endothermic gas is not recommended

16 Effect of Sintering Time and Temperature Fe - 1.3Mn + 0.5Mo C 7.0 g/cm 3, Cooled 0.7 C/s, Tempered at 205 C Sintertemperatur Sintering Temperature C Maßänderung Beigefestigkeit Härte Dimensional Change % Transverse Rupture Strength MPa Apparent Hardness HRB 5 min 15 min 5 min 15 min 5 min 15 min The manganese containing master alloy begins to diffuse at a low sintering time and temperature

17 Dimensional Change (Maßänderung zur Matrize) (Abkühlgeschwindigkeit)

18 Apparent Hardness (Härte) (Abkühlgeschwindigkeit)

19 Ultimate Tensile Strength (Zugfestigkeit) (Abkühlgeschwindigkeit)

20 Total Elongation (Bruchdehnug) (Abkühlgeschwindigkeit)

21 Impact Energy (Kerbschlagarbeit) (Abkühlgeschwindigkeit)

22 Microstructure 1120 C C/s 1120 C C/s 1260 C C/s Etch 2% Picral 4% Nital

23 Part 2 Summary: Manganese Containing PM Steels These manganese containing alloys can be easily sintered at 1120 C because the master alloy readily diffuses These alloys exhibit dimensional growth after sintering. Part size adjustments can be made by adjusting the sintering temperature and the belt speed The use of accelerated cooling increases strength and performance of these alloys via sinter-hardening Tempering is recommended when sinter-hardening Use of sintering temperatures >1200 C result in properties similar to Fe-Ni-Cu-C PM alloys

24 Final Conclusions Chromium, manganese, and silicon can be used in place of copper and nickel in PM steels as long as the alloys, mix composition, compaction, sintering, and post-sintering heat-treatments are designed as a complete system Special care needs to be taken to avoid oxidizing these alloys during processing Production control of dimensional change is different for chromium and manganese PM alloys. This needs to be factored into the production design