MaProF sas. R. Moschini PRODUCTION OF HOLLOW COMPONENTS IN HPDC THROUGH THE USE OF CERAMIC LOST CORES.

Transcription

1 MaProF sas R. Moschini PRODUCTION OF HOLLOW COMPONENTS IN HPDC THROUGH THE USE OF CERAMIC LOST CORES.

2 Overview Introduction Drivers Engine components High Pressure Die Casting: strengths & weaknesses Lost Cores for HPDC Experimental activity Component design Prototype die Casting trials Cores removal Results Conclusion

3 Drivers for vehicles mass reduction Fossil fuel consumption and CO 2 emissions related to the transport sector keep rising, despite improvements to new vehicles. Passenger cars account for 12% of total kg EU Roadmap to FC & CO 2 reduction l/100 km Fuel Consumption reduction ~ 300 l less fuel used in the vehicle life (= 750 kg CO 2 ) For 17 Millions car/year produced in Europe that equates to potential saving of 5,1 Mio m³ of fuel and 12,75 Mio tons of CO 2

4 Application to engine components: Closed-deck cylinder block HPDC kg DS Iron Block 60% GS Iron Block 13% GS Aluminum Block 23% DS Aluminum Block 4% Europe - Engines > 1.6 L kg

5 Closed deck vs Open deck cylinder block Configuration required by diesel or highly loaded engines. Typically made by GDC or LPDC Configuration used for gasoline engines. Can be produced by conventional HPDC

6 HPDC for aluminum components Strengths: Cost competitive for high volume manufacture Thin walls capability Near net shape Weaknesses No undercuts or complex hollow section allowed DESIGN LIMITS Relatively high porosity level Generally parts cannot be T6 heat treated, in particular if thick sections are present MECH. PROPs LIMITS

7 How to overcome these limits? HPDC RESISTANT CORES SEMI SOLID FORMING DESIGN LIMITS MECH. PROPs LIMITS

8 HPDC RESISTANT CORES CERAMIC CORES DEVELOPMENT

9 HPDC: Lost Cores Main Requirements Strength to resist standard HPDC conditions (not only reduced structural stress in Semi-Solid Metalforming): Ingate velocity ( > 40 m/s) Packing pressure ( > 1000 bar); Shape stability; Dimensional accuracy; Surface quality; Complex shapes (mandatory for a variety of casting components); Clean removability

10 From Campbell Problem: Dynamic pressure due to flow Example: Impact Pressure of a free jet of metal against a core: p = ρ V 2 ρ = 2490 kg/m 3, V = 40 m/s Then p ~ 4.0 MPa = 40 bar Campbell:..no sand core could withstand it! (F =ρ Q V)

11 Ceramic Cores Properties High mechanical properties on demand; No binders no outgassing; Good-enough dimensional accuracy; Good internal surface of the casting; Complex shapes.

12 Ceramic Cores Properties Non-conventional de-coring Al alloys: - high-pressure water; - sand blasting; - leaching. Peculiar thermal properties: Low heat diffusivity; Low thermal diffusivity. Low cost raw material and forming process.

13 Ceramic Cores Properties High mechanical properties in terms of: Flexural strength (R f ) Pressure resistance (P) Stiffness (Young modulus, E) - R f : 4 60 MPa (on demand); - P > 1500 bar; - E > 6 GPa Simulation: v ingate = 55 m/s; E = 4 GPa (stiffness of shell sand core)

14 Ceramic Cores Properties No binders No outgassing Organic binders: sometimes gases are forced to escape through the molten metal, with consequential bubble damage to the casting Gas evolution from various binder systems

15 EXPERIMENTAL ACTIVITY Component design; Prototype cores production; HPDC die design and manufacture; Casting trials Conventional HPDC SSR TM De-coring

16 Prototype single cylinder block design Single cylinder demonstrator Closed deck configuration, based on real Diesel engine geometry. Approx weight: 3.6 kg Alloy : Al Si9 Cu3 UNI-EN AC Water jacket core: approx. volume 265 cc, minimum thickness 4.5 mm, mass 0.4 kg

17 Water-Jacket ceramic core Ceramic WJ core Shell molding sand core

18 Prototype HPDC die for single cylinder block Water-Jacket core positioning

19 Casting trials: SSR TM Process How does it work? Rapid cooling Stirring Fine globular structure in s

20 SSR TM Die Casting Cell Layout Easy to integrate in existing cells No special machine required Robust process

21 Parts produced in the try-outs Casting Die installed in the HPDC press Produced parts

22 Prototype of mono-cilinder block (closed deck) before de-coring

23 Behavior of conventional sand cores in HPDC and SSR TM tests Process Binder Inorganic R f = 7 MPa Organic R f = 12 MPa HPDC - o SSR TM Bad: many broken cores o Fair: few broken cores + Good: no broken cores

24 Behavior of ceramic cores in HPDC and SSR TM tests Process R f X min X mean X max HPDC o + + SSR TM Bad: many broken cores o Fair: few broken cores + Good: no broken cores

25 HPDC: infiltration and distortion of sand cores

26 SSR TM : distortion and reduced infiltration of sand cores Filling in HPDC: metal arrives on the core from the top Filling in SSR: metal flows in the cavity from the bottom

27 High pressure water: de-coring prototype station High pressure nozzle Robot Part clamping fixture

28 Prototype of mono-cilinder block (closed deck) after de-coring

29 Sectioned casting after de-coring

30 Blistering effect after heat treatment Effects of solution heat treatment ( C) HPDC casting: blisters appear SSR TM casting: no blisters

31 New applications under evaluation Courtesy of Fonderia Atti

32 New applications under evaluation Courtesy of Fonderie 3m

33 Summary Objective of the present work was to demonstrate the technical and economic feasibility of the production of hollow components in HPDC, through the use of ceramic lost cores. The following results have been achieved: Ceramic cores, developed during the project and tested in a single cylinder block casting, proved to be able to resist injection and overpressure conditions typical of HPDC or Semi Solid forming processes. A system, based on High Pressure Water Jet technology, to remove the cores from castings has been built and successfully tested. Parts cast with the SSR TM process showed excellent soundness and could undergo a solution heat treatment without formation of blisters on the surface. HPDC with ceramic cores may become competitive, from a cost point of view, with conventional casting process for the production of hollow parts, provided that they are properly designed.