New High Strength Baini/c Steel 20MnCrMo7 for Automobile Applica/ons in Powertrains

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1 New High Strength Baini/c Steel 20MnCrMo7 for Automobile Applica/ons in Powertrains Dr.- Ing. Serosh Engineer, Dipl.- Ing. Charlo5e Merkel EZM EdelstahlZieherei Mark GmbH, We5er 1

2 Agenda Steel development 20MnCrMo7 Steel design and microstructure Mechanical Proper'es Examples of Automo've Applica'ons High Strength Baini'c Steel 20MnCrMo7 2

3 Development of a New Steel: Requirements Use for components in common- rail- diesel engines with pressures bar and high alterna'ng loads Possibility of manufacturing components directly on cooling from hot rolling /forging temperatures Steel with N/mm² tensile strength and good duc'lity due to fine grained baini'c microstructure Acceptable weldability (CE<0.8) Microstructure suitable for autofrewage (process to improve alterna'ng stress resistance on tube surfaces) High Strength Baini'c Steel 20MnCrMo7 3

4 Steel Design Carbon content < 0,23% for acceptable weldability Manganese (Mn), Chromium (Cr) and Molybdenum (Mo) addi'ons to obtain baini'c microstructure directly on cooling from hot rolling/forging temperatures Niobium (Nb), Titanium (Ti) and Nitrogen (N) to allow fine grain sizes stable up to temperatures of C High Strength Baini'c Steel 20MnCrMo7 4

5 Microstructure of 20MnCrMo7 Wire Rod Ø 21 mm Longitudinal sample, magnifica'on 100:1 surface core Homogeneous fine grained structure (finer than 8 ASTM) Automo've Steels Dr.- Ing. S. Engineer June 2013 High Strength Baini'c Steel 20MnCrMo7 5

6 TiN / TiCN Inclusions Par'cles of 20 µm are embedded in a duc'le baini'c matrix No nega've influence on the technological proper'es has been determined as yet (up to pressures of bars). Automo've Steels June 2013 Dr.- Ing. S. Engineer High Strength Baini'c Steel 20MnCrMo7 Bildquelle: Dr. Härtel 6

7 Hardenability of 20MnCrMo7 and 18CrNiMo76 Jominy Test High Strength Baini'c Steel 20MnCrMo7 7

8 Mechanical Proper/es 20MnCrMo7 vs 50CrMo4, 34CrNiMo6 Tensile strength Rm [Mpa] Yield strength [MPa] R p0,2% 20MnCrMo7 (1.7911) air cooled from hot rolling Ø 21mm 50CrMo4 (1.7228) Quenched & Tempered Ø mm 34CrNiMo6 (1.6582) Quenched &Tempered Ø mm Elonga/on A 18 % 10 % 10 % Reduc/on in Area Z DVM Notch Impact [J] 62 % 45 % 45 % High Strength Baini'c Steel 20MnCrMo7 8

9 Fine Grain Stability of 20MnCrMo7 (1.7911) Grain Size in accordance with ASTM E 112 / EN ISO 643. Ø 21mm Fine grained structure is essen'ally stable up to C and 20h holding 'me. High Strength Baini'c Steel 20MnCrMo7 source SCT 2011 [1] 9

10 Microstructure aaer AC- Annealing for Cold Forging Spherodized annealed microstructure suitable for cold forging Magnifica'on: 1000:1 Automo've Steels June 2013 Dr.- Ing. S. Engineer High Strength Baini'c Steel 20MnCrMo7 10

11 Strain Hardening Behaviour 20MnCrMo7 (1.7911) Low strain hardening rate aper spherodized annealing High Strength Baini'c Steel 20MnCrMo7 11

12 Case Hardening Behaviour of 20MnCrMo7 (1.7911) Corresponding data of 18CrNi8 at 250 C and 300 C are less favorable High Strength Baini'c Steel 20MnCrMo7 12

13 20MnCrMo7 as Case Hardening and Q&T- Steel 20MnCrMo7 can be used in the quenched and tempered as well as in the case hardened state Proper'es of 20MnCrMo7 are comparable to or bewer than more expensive NiCr- Steels 20MnCrMo7 has lower alloy surcharge due to lower Ni content High Strength Baini'c Steel 20MnCrMo7 13

14 Machinability Results 20MnCrMo7: Turning Fc= cutting force Ff= feed force Fp= passive force f =feed rate, rε= Edge radius, VB=flank wear Cuung depth 1 mm Cuung speed 200m/min source: CIRP 2013 [2] Tool life is improved by adjus'ng tool geometry and tool material composi'on 14

15 Applica/ons in Common Rail Diesel Engines Common Rail Connec'on Bolt Automo've Steels June 2013 Injector Nozzle Nut, connects Injector and Nozzle Body Dr.- Ing. S. Engineer High Strength Baini'c Steel 20MnCrMo7 Source: SCT 2008 [3] 15

16 20MnCrMo7 A Promising Steel Development

17 Summary The new fine grained baini'c steel is very suitable for applica'ons at high pressures. This steel has a higher strength AND duc'lity in comparison to the microalloyed ferri'c pearli'c steels developed for the automo've industry approximately 35 years ago. 20MnCrMo7 can also be used as quenched and tempered or case hardening steel. In comparison to NiCr steels, 20MnCrMo7 has comparable proper'es at lower cost. High Strength Baini'c Steel 20MnCrMo7 17

18 New High Strength Baini/c Steel 20MnCrMo7 for Automobile Applica/ons in Powertrains Thank you for your awen'on! High Strength Baini'c Steel 20MnCrMo7 18

19 References [1] Engineer, S., Janßen, P., Härtel, M., Hampel, C., Randelhoff, F.: Technological Proper'es of the New High Strength Baini'c Steel 20MnCrMo7, Proceedings of the 3rd Interna'onal Conference on Steels in Cars and Trucks, Salzburg 2011, pp [2] Biermann, D., Hartmann, H., Terwey, I., Merkel, C., Kehl, D.: Turning of high - strength baini'c and quenched and tempered steels, 46 th CIRP Conference on Manufacturing Systems, May 26 th - 29 th 2013, Setúbal, Portugal (in Press) [3] Langner, H., Beyer, C., Engineer, S., Franke, A., Hölzl, H., Janßen, P.:,, A new high strength steel 20MnCrMo7, Proceedings of the 2nd Interna'onal Conference on Steels in Cars and Trucks, Wiesbaden 2008, p. 72 [4] Biermann, D., Felderhoff, F., Engineer, S., Jus'nger, H.: Machinability of high- strength baini'c steel 20MnCrMo7, Proceedings of the 3rd Interna'onal Conference on Steels in Cars and Trucks, Salzburg 2011, pp