low pressure casting of the actual situation …

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23.05.2017 RAUCH MELTING TECHNIQUE 01

LOW PRESSURE CASTING OF MAGNESIUM AND ALUMINIUM

> A flexible system for sand mold casting of high quality parts in magnesium or aluminium

> Peter Rauch – RAUCH - AUSTRIA


THE ACTUAL SITUATION

>  Magnesium sand casting parts are mainly casted by gravity casting >  High melt temperatures for casting – up to 800°C

−  Protective gas problematically to use because of low activity at high temperatures −  SF6 is the only gas which can be used at this temperatures but with very high

concentration = high impact on GWP and future restrictions are expected −  Thus flux is used – but contamination of the parts is unavoidable

>  Different length of runner systems causes pre-solidification and uneven temperature distribution during casting due to lateral filling

>  Low filling speed at the end of filling due to low hydrostatic pressure is problematic for thick walled parts in the upper section of the mold

>  No post pressure possible after freezing of the feeder system


THE ACTUAL SITUATION

>  To overcome the problems of gravity casting producers shift to low pressure casting by creating the filling pressure with gas as there is no other option left

>  High consumption of protective gas −  Protective gas is used as propellant to feed melt into the mold −  High impact on GWP because of high consumption and direct blow out of the gas into

the atmosphere −  Protective gas attacks furnace parts and heating elements

>  Pressure vessel for magnesium melt −  Gas tight furnace and crucible system for magnesium is required

>  Feeding of ingots only possible after disruption of casting process


ADDITIONAL CHALLENGES AND FUTURE ASPECTS OF SAND CASTING

>  3D Printing of molds will revolutionize casting

−  Time to market is reduced (3D model directly to mold)

−  Caster is very flexible in case of revisions of the part

−  Prototyping is easy to realize



>  Reject rates are too high

−  Casting process has to be reproducible with storage of all casting parameters

>  Reduce weight of casted parts

−  Near net shape −  Shorten machining times

8,28 kg 23.05.2017 RAUCH MELTING TECHNIQUE 06


>  Reduced weight of casted part

−  Part casted with low pressure casting −  Machining time is 30% of original part

3,84 kg

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THE SOLUTION

Pump housing

Feeding tube to mold

23.05.2017 RAUCH MELTING TECHNIQUE

>  Low pressure casting with mechanical pump


THE SOLUTION

>  A mechanical pump is used to apply the feeding pressure and is combined with a sophisticated control and measuring system −  No pressure tight furnace and crucible system is needed −  No protective gas for creating the filling pressure −  Exact post pressure after filling of mold and freezing of the feeder system is easy to apply

>  Adaptive filling rates can be programmed in correlation with the results of casting simulation >  As the casting process is controlled by the actual casted weight and not the casting

pressure!!!!, the process becomes independent from the various drags in the mold >  High filling rate for magnesium up to 17 kg/sec


THE SOLUTION

>  Adaptive filling rates

−  The filling curve is divided into 15 stages −  For every stage the filling rate is adjusted in

kg/s −  Every stage is correlated with the casted

weight

Set curve Real casted curve


THE SOLUTION

>  Adaptive filling rates

−  Same casted weight as before with steeper (faster) filling in the first stages

Set curve Real casted curve


Magnesium furnace

Casting machine

Aluminium furnace

11

CASTING MACHINE


>  Low pressure casting machine


THE SOLUTION

>  The system can be used flexible for magnesium and aluminium as well >  Aluminium is realized with conventional low pressure gas equipment >  Both casting processes for magnesium and aluminium are controlled by casted weight >  Filling rate in aluminium up to 40kg/sec >  Aluminium and Magnesium can be combined even in one furnace >  Remaining melt weight in the crucible is measured and allows specific production planning >  Reference point for start of filling curve is realized inside the mold >  Integrated safety concept for magnesium casting >  Automatic aligning of raiser tube and mold by means of laser triangulation >  The casting machine is modularly expandable to increase production rates

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CASE STUDY

>  With courtesy of

Helicopter secondary gear box


CASE STUDY

>  Traditional gravity filling system −  Dimensions: 620 x 570 x 370 mm. −  MIN wall thickness: 8mm −  Material details: AZ91 −  Weight: 33 kg


CASE STUDY

>  Low pressure filling system −  Dimensions: 480 x 360 x 440 mm. −  MIN wall thickness: 8mm −  Material details: AZ91 −  Weight: 25kg


CASE STUDY

>  Gravity casting filling system −  The main defects after crystallization


CASE STUDY

>  Simple runner system for low pressure filling

−  Low recycling rate −  Short runner length


CASE STUDY

>  Low pressure filling system and casted part

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CASE STUDY

>  Simulation of filling


CASE STUDY

>  All gatings are working correct


CASE STUDY

>  Defects only in gating system


LOW PRESSURE CASTING OF MAGNESIUM AND ALUMINIUM

> THANK YOU VERY MUCH FOR YOUR ATTENTION

low pressure casting of the actual situation …

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