Bulk Metal Forming I

Transcription

1 Buk Meta Forming I Simuation Techniques in Manufacturing Technoogy Lecture 1 Laboratory for Machine Toos and Production Engineering Chair of Manufacturing Technoogy Prof. Dr.-Ing. Dr.-Ing. E.h. Dr. h.c. Dr. h.c. F. Kocke

2 Lecture objectives Basic knowedge in metaurgy for a better understanding of the mechanisms during meta forming Eastic and pastic materia behaviour and its infuence on the process resuts in forming technoogy Mathematica modes for a description of the eastic and pastic materia behaviour Introduction of processes in cod and warm buk forming as we as in forging Seite 1

3 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 2

4 Metaurgica Basics 4 Basic Chemica Bonds meta bond ionic bond covaent bond Van-der-Waas bond positive charged meta ions eectron gas (e - ) meta bond ionic bond Seite 3

5 Metaurgica Basics The Meta Bond meta atoms basicay emit eectrons positive charged ions in pure metas no eectron-absorbing atoms do exist un-combined eectrons (outer eectrons) form an eectron gas outer eectrons in metas can freey move good eectrica and therma conductivity in absoute pure metas a atoms are totay equa pastic deformation positive charged meta ions eectron gas (e - ) meta bond Seite 4

6 Metaurgica Basics Lattice Types of an Unit Ce face-centred cubic (fcc) body-centred cubic (bcc) hexagona (hex) exampes: γ-fe, A, Cu α-fe, Cr, Mo Mg, Zn, Be siding panes: siding directions: siding systems: formabiity: very good good poor Seite 5

7 Metaurgica Basics Atomic and Macroscopic View of Meta Structures unit ce idea crysta structure crysta attice a rea crysta structure microstructure 2D Cut of the microstructure schematicay photograph specia aggomeration of crystas section pane Seite 6

8 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 7

9 Eastic Deformation Tensie Test Load-Dispacement Diagram specimen 1 oad F 1 specimen 2 F 2 foows: A 1 = 2 A 2 F 1 = 2 F 2 tensie specimen 1 = 1 2 dispacement reate force to cross section surface Seite 8

10 Eastic Deformation Stress-Strain Curve of Eastic Behaviour F stress R e specimen no. 1 no. 2 engineering stress: σ = F A 0 engineering strain: 0 A A 0 σ e 1 d 1 0 ε = = = d dε = 0 α e e strain For eastic behaviour: F tan α = σ ε e e E = σ ε e e σ R e E = Young s Moduus Seite 9

11 Eastic Deformation Stress Determination Depending on Load tensie test compression test shear test A 1 F F A 0 a F 1 A 1 q A 0 F F F A 0 σ = F A 0 σ = F A 0 τ = F A 0 tensie stress compression stress shear stress Seite 10

12 Eastic Deformation Atomic Representation of Pure Eastic-Tensie Deformation unoaded tensie-oaded s 0 1 s E = σ ε e e eastic strain based on tensie oad 1 0 ε e = = 0 0 σ - nomina stress ε - strain E - Young s Moduus Seite 11

13 Eastic Deformation Atomic Representation of Pure Eastic-Shear Deformation unoaded shear-oaded τ γ τ τ E G = = γ e 2(1+ µ ) eastic shearing based on shear oad γ - shear ange τ - shear stress G - shear moduus ν - Poisson s ratio E - Young s moduus Seite 12

14 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 13

15 Pastic Deformation Stress-Strain Curve up to the Uniform Eongation F true tensie stress: (reated to rea section) stress R m σ σ σ = F A 0 A A 0 R e, s e oad reieving reoad engineering stress: (reated to starting section) σ = F A0 e p e e strain F Seite 14

16 Seite 15 Pastic Deformation Strain Determination of an Ideaized Upsetting Process d d d x x = = = = ε ε n ; n ; n h h b b z y x = = = ϕ ϕ ϕ 0 1 n 1 0 d d d = ϕ = = ϕ engineering strain (eastic) true strain (pastic) incuding of voume constancy 1) n( n n u n n x = + = + = + = = x ϕ x ε const = = b h b h 0 = + + z y x ϕ ϕ ϕ connection between true strain - engineering strain

17 Pastic Deformation Types of Pastic Deformation siding before disocation movement after high energy required ow energy required Seite 16

18 Pastic Deformation Siding and Disocation Movement siding disocation movement Seite 17

19 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 18

20 Fow Stress Fow Curve fow stress required stress to break the strain hardening required stress for pastic deformation effective strain Seite 19

21 Fow Stress Strain Hardening Depends on Disocations schematic diagram disocation movement disocation origin grain boundary siding panes moving direction disocation structure of itte-formed copper pied up disocations at boundary grains grain boundary Seite 20

22 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 21

23 Recrystaisation Static Recrystaisation Schematic course of recrystaisation of cod formed structure requirements: - ϕ v > 0 - T > T Recrystaisation - impact time ductie yied A 10, tensie strength R m crysta regeneration sma decrease of R m temperature, C arge increase of A 10 Seite 22

24 Recrystaisation Stress Curve of Cod Forming as a Resut of Static Recrystaisation anneaing for recrystaisation anneaing for recrystaisation fow stress ϕ vbr - effective strain at time of fracture ϕ vbr ϕ vbr effective strain anneaing for recrystaisation increases effective strain and decreases fow stress Seite 23

25 Recrystaisation Effective Strain and Temperature Infuence the Grain Size grain size range of recrystaisation effective strain Seite 24

26 Recrystaisation Forming Temperature and Veocity Infuence the Fow Stress fow stress forming temperature beow recrystaisation temperature high forming veocity forming temperature above recrystaisation temperature ow forming veocity effective strain Seite 25

27 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 26

28 Cod forming What is Buk Forming? Buk forming massive semi-finished materia component Seite 27

29 Introduction Advantages of Buk Forming Forming Cutting 1,3 kg 0,4 kg basic workpiece component semi-finished part component Seite 28

30 Cod forming Iron-Carbon Phase Diagram δ-fe δ- + γ-fe Liquid + δ-fe Liquid Fe 3 C (Cementite) fcc Temperature in C γ-fe (Austenite) Liquid + γ-fe γ-fe + Fe 3 C Liquid + Fe 3 C γ- + α-fe α-fe (Ferrite) Recrystaization α-fe + Fe 3 C bcc Carbon content in weight percent Cermentite content in weight percent Seite 29

31 Cod forming Materia Properties Layer of scae / µm Strain ϕ Fow stress k f / MPa Workpiece temperature / C high fow stresses and ow achievabe strains by cassic stee materias Seite 30

32 Cod forming Advantages and Disadvantages of Cod Forming Advantages: Cod Forming ow too materia costs ow infuence of forming veocity no energy costs for heating no dimension fauts caused by dwinding high surface quaity increasing strength of the component Disadvantages: high forces imited pastic strain Seite 31

33 Cod forming Efficiency Forming process IT-Grade according to DIN ISO Centerine average Ra / µm 0, Cod extrusion Warm extrusion Hot extrusion achievabe with specia proceedings achievabe without specia proceedings sma shape, dimension and position toerances as we as good surface quaities are possibe Seite 32

34 Cod forming Efficiency forming cod warm hot workpiece weight 0, kg 0, kg 0, pasticity φ < 1,6 (for cassic r<4 forming stees) r<6 finishing effort ess ow high semi-finished part cod forming by the aid of cod forming processes a good workpiece quaity can be reached Seite 33

35 Cod forming Forming Processes extrusion fu extrusion hoow extrusion cup extrusion forward extrusion before after backward extrusion radia extrusion a: punch, b: die, c: workpiece, d: ejector, e: counter punch, f: spike Seite 34

36 Cod forming Fu Forward Extrusion: pin production workpiece insertion compression extrusion ejection punch workpiece cavity ejector die Seite 35

37 Cod forming Cup Backward Extrusion: cup production workpiece insertion compression extrusion ejection punch workpiece die ejector Seite 36

38 Cod forming Radia Extrusion of a Cardan Joint workpiece insertion cosing of the die extrusion ejection upper punch upper die workpiece ower die ower punch Seite 37

39 Cod forming Mechanica Loads in Fu Forward Extrusion Processes ange of shouder : radia stresses σ r / MPa axia stresses σ z / MPa materia: QST 32-3 effective strain: φ = 1,4 mechanica surface oads in a range of severa 1000 MPa Seite 38

40 Cod forming Reinforcement of extrusion dies tensie compression without interna pressure with interna pressure reinforcement creates compression stresses in the die, in order to reduce process-reated tensie stresses Seite 39

41 Cod forming Typica Cod Formed Components gear shafts Hirschvoge tubes denticuations Hirschvoge screws Fuchs Schraubenwerk Seite 40

42 Fow Stress Fracture as a resut of Radia Extrusion fractures depending on passing a critica deformation vaue Seite 41

43 Cod forming Crack Reduction by Superposition of Compressive Stresses punch gasket die workpiece pressure medium reief pressure vave (conventiona cod forming) Crack (superposition of compressive stresses) Crack tearing coud effectivey be shift to higher strains by superposition of compressive stresses Seite 42

44 Cod forming Chevron Cracks by Fu Forward Extrusion Seite 43

45 Cod forming Chevron Cracks by Fu Forward Extrusion Chevrons DEFORM FEM-Simuation 3. forming step rea workpiece an unfavourabe distribution of the interior materia generates cracks Seite 44

46 Cod forming Phases of Production of a Beve Gear bucking upsetting indirect cup extrusion cutting radia extrusion burr cutting caibration recrystaization recrystaization recrystaization achievabe deformation can be increased by recrystaization Seite 45

47 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 46

48 Warm forming Iron-Carbon Phase Diagram δ-fe δ- + γ-fe Liquid + δ-fe Liquid Fe 3 C (Cementite) fcc Temperature in C γ-fe (Austenite) Liquid + γ-fe γ-fe + Fe 3 C Liquid + Fe 3 C γ- + α-fe α-fe (Ferrite) Recrystaization α-fe + Fe 3 C bcc Carbon content in weight percent Cermentite content in weight percent Seite 47

49 Warm forming Materia properties Layer of scae / µm Strain ϕ Fow stress k f / MPa Workpiece temperature / C reduction of fow stress and increase of the achievabe strain Seite 48

50 Warm forming Advantages and Disadvantages of Warm Forming Advantages: Warm forming strengthening of the workpiece sma range of toerance caused by dwinding good surface quaity Disadvantages: energy input for heating high fow stresses Hirschvoge Seite 49

51 Warm forming Efficiency forming cod warm hot workpiece weight 0, kg 0, kg 0, kg pasticity φ < 1,6 φ < 4 j < 6 finishing effort ess ow high semi-finished part cod forming warm forming Seite 50

52 Warm forming Efficiency Forming process IT-Grade according to DIN ISO Centerine average Ra / µm 0, Cod extrusion Warm extrusion Hot extrusion achievabe with specia proceedings achievabe without specia proceedings medium shape, dimension and position toerances as we as medium surface quaity are possibe Seite 51

53 Warm forming Typica Warm Formed Components Audi Hirschvoge Hirschvoge side hinge fange cyinder injector Seite 52

54 Outine 1 Metaurgica Basics 2 Eastic Deformation 3 Pastic Deformation 4 Fow Stress 5 Recrystaisation 6 Cod Forming 7 Warm Forming 8 Forging Seite 53

55 Forging Iron-Carbon Diagram δ-fe δ- + γ-fe Liquid + δ-fe Liquid Fe 3 C (Cementite) fcc Temperature in C γ-fe (Austenite) Liquid + γ-fe γ-fe + Fe 3 C Liquid + Fe 3 C γ- + α-fe α-fe (Ferrite) Recrystaization α-fe + Fe 3 C bcc Carbon content in weight percent Cermentite content in weight percent Seite 54

56 Forging Materia Properties Layer of scae / µm Strain j Fow stress k f / MPa Workpiece temperature / C ow fow stress and high achievabe strain Seite 55

57 Forging Advantages and Disadvantages of Forging Forging Advantages: ess effort high pasticity Disadvantages: high energy input for heating high materia costs for toos dimension fauts by shrinkage materia oss and finishing caused by tinder Seite 56

58 Forging Efficiency forming cod warm hot workpiece weight 0, kg 0, kg 0, kg pasticity φ < 1,6 φ < 4 φ < 6 finishing effort ess ow high initia state cod forming warm forming forging Seite 57

59 Forging Efficiency Forming process IT-Grade according to DIN ISO Centerine average Ra / µm 0, Cod extrusion Warm extrusion Hot extrusion achievabe with specia proceedings achievabe without specia proceedings ow shape, dimension and position toerances as we as ow surface quaity possibe Seite 58

60 Forging Heating Methods Furnace Heating in furnaces: furnaces are heated by gas, oi or eectricity heat transmission to the workpiece by radiation and convection Heating by induction: heat in the workpiece rim is generated by eectromagnetic induction by eddy current formation Inductive heating faciity Conductive heating: heating by high-frequency current with direct workpiece contact inductive and conductive heating reduces the production of primary tinder as a resut of the heating rate Seite 59

61 Forging Tinder If iron-based materias are heated above 500 C under the infuence of oxygen, iron oxide (Fe 3 O 2 ) wi be generated on the surface, which is caed tinder. Tinder pees away off the workpiece during the forming process. This resuts in oss of materia, surface marking and too wear. Saarstah Seite 60

62 Forging Processes Open Die Forging workpiece manipuator upsetting Saarstah upper die stretching workpiece Saarstah ower die fat back gage acuminate back gage round back gage simpe too geometries are used for open die forging processes Seite 61

63 Forging Process cyce Freiformschmieden round forging bank upsetting wastage forging and shearing streching forging a step upsetting forging streching forging a step simpe too geometries can produce compex workpiece geometries Seite 62

64 Forging Open Die Forging Saarstah Seite 63

65 Forging Cosed Die Forging Upper die Forging without burr: ow forming forces compete materia utiization max. permitted voume fuctuation 0,5% exact workpiece positioning required Lower die Upper die Lower die Forging part Burr cavity Forging part Forging with burr: ess standards on workpiece voume fuctuation no exact workpiece positioning required the remova of the burr needs an extra process step Seite 64

66 Forging Die Wear wear / abrasion 1/3/4 2 - therma fatigue / crack formation 1/4 3 - mechanica fatigue / crack formation 4 - pastic deformation /4 the main reason for too change is the abrasion on edges and cracks in cavitations Seite 65

67 Forging Stages of Cosed Die forging crankshaft connection rod hinge bearing an effective preform production is the key for short production chains Seite 66

68 Summary Spannung σ ε e R es ε e σ α 0,2 % ε e ε p R p0,2 σ tan α = ε e E = σ ε e Nenndehnung ε Infuence of the metaurgica composion on the formabiity of metas Basic understanding of the eastic and pastic materia behaviour and it s characterization Introduction of processes in cod and warm buk forming as we as in forging Seite 67