Machining of Austempered Ductile Iron Challanges and Solutions

Transcription

1 Machining of Austempered Ductile Iron Challanges and Solutions - Austempering a technology for substitution - Prof. Dr.-Ing. Dr.-Ing. E. h. Dr. h. c. Dr. h. c. Fritz Klocke Dr.-Ing. Dipl.-Wirt.-Ing. Benjamin Döbbeler Dipl.-Ing. Sven Lung Bevilacqua, 6. and 7. October

2 Agenda 1 Fundamentals in Metal Cutting 2 Machining properties of ADI 3 Improvement of the ADI machining process 4 Investigation of Contact Fatigue for ADI1200, ADI900 and AST 5 Summary 2

3 Shear zones during chip formation Work piece Primary shear zone Secondary shear zone (rake face) Primary shear zone: Transition from workpiece structure to chip structure The material is getting deformed to a chip due to simple shear in the primary shearzone. Chip Rake face A γ Secondary shear zone: Tensile load in combination with perpendicularly pressure and high temperature leads to strong deformation at the rake and flank face Secondary shear zone (flank face) Cutting speed v c r b β o Tool The shear in combination with high pressure leads to a strong deformation in the border areas of the rake face and the flank face (secondary shearzone). The boundary conditions during chip formation: High temperatures in the contact zone (approx C) High deformation rate (approximately /s) Feed rate f Flank face A α 3

4 Resolution of the Effective cutting speed and the resultant force v c : Cutting speed v f : Feed velocity v e : Effective cutting speed v e v c Rotational speed (Work piece) The vector of the effective cutting speed can be partitoned into two vectors Cutting Speed: In rotation direction Feed velocity: In feed direction F z : Resultant force F c : Cutting force F f : Feed force F p : Passive force F p v f F c F f The machining force F z can be partitioned in different components. Cutting force F c : Force in cutting speed direction Feed force F f : In Feed direction Passive force F p F z Feed motion (Tool) 4

5 Agenda 1 Fundamentals in Metal Cutting 2 Machining properties of ADI 3 Improvement of the ADI machining process 4 Investigation of Contact Fatigue for ADI1200, ADI900 and AST 5 Summary 5

6 Wear Formation when Turning Ductile Iron GJS Ferritic Matrix Flank wear Crater wear Criterion : Flank wear Cutting time GJS (GGG40) v c = 360 m/min t = 12,6 min f = 0,2 mm a p = 1 mm GJS Perlitic Matrix Criterion : Flank wear GJS (GGG70) v c = 260 m/min t = 6,8 min f = 0,2 mm a p = 1 mm Cutting time GJS Austenitic- Ferritic Matrix Criterion : Flank & Crater wear GJS (ADI 900) v c = 140 m/min t = 18,8 min f = 0,2 mm a p = 1 mm 6

7 ADI DAYS th 7th October Minerbe 42CrMo4+QT Wear mechanisms of Quenched and Temperd Steel and ADI 500 µm etched 500 µm Cutting parameters HM-K10 vc = 70 m/min GJS f = 0,25 mm ap = 1,5 mm Dry Machining tc = 8,00 min 500 µm etched 500 µm 7 Source: C. Klöpper, Phd-Thesis RWTH Aachen Austempering, A Technology for Substitution

8 Comparison of the Cutting Forces Cutting Force F c / N Cutting Force Oscillation v c = 100 m/min, f = 0.2 mm 42CrMo4V EN-GJS Related Cutting force F c / N/mm Related Cutting Force F c / (N/mm) v c = 100 m/min (150 m/min for conventional GJS) EN-GJS EN-GJS EN-GJS CrMo4V F c ' = h F c ' = h F c ' = h F c ' = h Cross section of undeformed chip Direction of rotation k r v! f b A a p f h v! f Related cutting force k r Work piece Tool Cutting Time t c / ms Undeformed Chip Thickness / mm 8

9 Stages of the chip formation of ADI materials First contact Start of deformation Crack initiation Sliding End of sliding 6 Segmentation 7 Start of deformation 8 Crack initiation 62, , ,5 Material speed / m/min 0 Source: C. Klöpper, Phd-Thesis RWTH Aachen 9

10 Influence of Material Hardness on Wear and Tool life in dry Turning GJS 700-2; T = 26,8 min ADI 900; T = 13,5 min ADI 1200; T = 3 min 600 µm 600 µm 600 µm 600 µm GJS % GJS % ADI 1200; T = 3 min (etched) ADI % Tool life T / min External longitudinal turning (Criterion: KT = 75 µm; VB max = 300 µm): v c = 160 m/min; f = 0.2 mm; a p = 2 mm; dry; κ r = 95 ; α o = 6 ; λ s = -6 ; γ eff = -6 HC-K20,Coating: Ti(C, N)/ Al2O3, CNMA ; µm 10

11 Agenda 1 Fundamentals in Metal Cutting 2 Machining properties of ADI 3 Improvement of the ADI machining process 4 Investigation of Contact Fatigue for ADI1200, ADI900 and AST 5 Summary 11

12 Optimisation of Tool life in External longitudinal turning using Emulsion 30 ADI Dry ADI 900 GJS Tool life T / min ADI 900 GJS ADI Cutting speed v c / (m/min) Emulsion ADI 1200 ADI 900 GJS External longitudinal turning (KT = 75 µm; Vb max = 300 µm): v c f a p κ r HC- K20 = var. = 0,2 mm = 2 mm = 95 CNMA Ti(C, N)/ Al 2 O 3 α o γ eff λ s = 6 = - 6 =

13 Increase of Material removal rate and Tool life by adapted Feed, Cutting speed and Tool geometries Material removal rate Q / cm 3 / min Q = 128 cm 3 /min Q = + 50 % T = 9.4 min T = 7 min v c = 320 m / min f = 0.2 mm T + 36 % Q = 192 cm 3 /min T = 10 min T = 11 min v c = 240 m / min f = 0.4 mm Tool life T / min Process: External turning (Emulsion) Material: ADI 900 Tool holder: MCLNL2525 Tool geometry: CNMA/ CNMG Material removal rate: Q = v c a p f Depth of cut: a p = 2 mm Cutting speed: v c = 240 / 320 m/min Feed: f = 0,2 / 0,4 mm γ eff = -6 r β = 60 µm α o = 6 CNMA γ eff = µm γ eff = -1 r β = 60 µm α o = 6 12 CNMG γ eff = -1 13

14 Increase of Tool life in Turning ADI 900 by Material-sided optimisation Tool life T / min Wall thickness: 20 mm Wall thickness: 30 mm Wall thickness: 60 mm Wall thickness: 90 mm 4,0 3,0 2,0 1,0 0 Content of alloying elements / % Nickel-Content Molybdenium-Content External longitudinal turning (Tool life criterion: KT = 75 µm, VB max = 300 µm): v c = 160 m/min; f = 0.2 mm; a p = 2 mm; dry; κ r = 95 ; α o = 6 ; γ eff = -6 ; λ s = -6 ; MCLNR 2525M12; HC-K20, Coating: Ti(C, N)/ Al 2 O 3, CNMA ; Scatter from average value to maximum and minimum 14

15 Influence of Heat Treatment on Tool life when turning ADI Austempering time: 30 min Austempering time: 60 min Austempering time: 90 min Austempering time: 120 min Austempering Haltezeit Salzbad: time: min min Tool life T / min External longitudinal turning (ADI 900; dry; Criterion: KT = 75 µm, VB max = 300 µm): Cutting speed: v c = 160 m/min Cutting material: HC-K20 Feed: f = 0.2 mm Cutting insert: CNMA Depth of cut: a p = 2 mm Coating: Ti(C, N)/ Al 2 O 3 Setting Angle: κ r = 95 Clearance Angle: α ο = 6 Inclination Angle: λ s = -6 15

16 ADI DAYS th 7th October Minerbe Cutting forces Fc / N Casting skin T = 10 min 1 mm Amplitude 700 N Influence of the casting skin on cutting forces in roughing operations of ADI t = 0,5 s T = 10 min 1 mm 1500 Amplitude 70 N Cutting forces Fc / N Core material t = 0,5 s External longitudinal turning (ADI 900): vc = 240 m/min; f = 0.2 mm; ap = 2 mm; Emulsion; κr = 95 ; αo = 6 ; λs = -6 ; HC-K20, Coating: Ti(C,N)/ Al2O3, CNMG (γeff = -1 ); Austempering, A Technology for Substitution 16

17 ADI DAYS th 7th October Minerbe Optimization of the roughing process of ADI 900 by using adapted tools HC- K20, γeff = - 6 Core material HC- K15, γeff = - 6 Core material HC- K15, γeff = - 6 Cast skin HC- K15, γeff = - 1 Cast skin HC- K20, γeff = - 1 Cast skin HC- K20, γeff = - 6 Cast skin 0 2 Comb cracks Tool life T / min Tcast skin = 10 min HC-K20, γeff = -1 1 mm 500 µm 14 External logitudial turning (ADI 900, Emulsion, Criterion: VB = 200 µm): vc = 240 m/min; f = 0,2 mm; ap = 2 mm; κr = 95 ; αo = 6 ; λs = -6 ; MCLNR 2525M12; Coating: Al2O3 / Ti(C, N), CNMx Austempering, A Technology for Substitution 17

18 Agenda 1 Fundamentals in Metal Cutting 2 Machining properties of ADI 3 Improvement of the ADI machining process 4 Investigation of Contact Fatigue for ADI1200, ADI900 and AST 5 Summary 18

19 Project Overview Aim The aim of the project is to determine the contact fatigue of different ADI types (JS/900-8, JS/1200-3) and casted steels (AST) by disk-on-disk and back-to-back testing Quality of Specimen Investigation of Contact Fatigue Evaluation of Test Results Geometry & Roughness Disk-on-Disk Back-To-Back Analysis of Wear Calculation ISO6336 ISO 6336 Teil 3 ISO 6336 Teil 2 ISO 6336 Teil 1 19

20 SN-Curves: Comparison of Variants ADI900 and ADI1200 Disk-on-Disk Test a = 42,05 mm s 1 = -28 % n = 3000 min -1 Q Oil = 1,5 l/min T Oil,in = 90 C Oil: FVA3 A 4% Anglamol Specimen material: ADI1200 material: ADI900 d 1/2 = 42,05 mm R bal1/2 = /166 mm Rz 3 µm Hertzian Contact Pressure / MPa Load Cycles / x106 Damage ADI900 Damage ADI1200 SN-Curve ADI900 Run Out ADI900 Run Out ADI1200 SN-Curve ADI

21 Agenda 1 Fundamentals in Metal Cutting 2 Machining properties of ADI 3 Improvement of the ADI machining process 4 Investigation of Contact Fatigue for ADI1200, ADI900 and AST 5 Summary 21

22 Summary Tool life criterion by machining of ADI is the flank and crater wear. In comparison to a quenched and tempered ADI has a more abrasive tool wear. The dynamic tool load due to the chip formation leads to material fatigue of the tool. The thermal tool load can be reduced by using emulsion. The cutting speed should be decreased and the feed rate increased to achieve a high tool life A high molybdenum content leads to a higher tool life scatter Machining the casting skin leads to a higher dynamic tool load due to the different material allowance 22