Energibesparende smiprosesser

In the StøpSmi project we have used an advanced simulation program to define the pre-form as close to the final form as possible, yet so that the last forging step will be able to completely deform the component. It is just such a combination of deformation and heat treatment which increases the mechanical properties of forgings. It is possible either to deform the entire preformed object or localize deformation and heat treatment where high mechanical properties are desirable. This will reduce the number of process steps and the amount of beard. This reduces the required energy demand, since only a portion of the component is heat treated. A deformed microstructure provides better mechanical properties, especially in the surface of the component. The first task of the project was to design a simple generic component and establish a process flow for this. Simulations were carried out to look at the flow conditions in the forging tools before the final geometry of the tool was determined. This was also the basis for the casting geometry. In this regard solidification simulations also were carried out. Physical tools both for casting and forging was then manufactured. In 2012 and 2013 several StøpSmi-experiments were carried out at SINTEF with the appropriate tools, both with the foundry alloy AlSi7Mg and wrought alloy AA6082.50. The finished material was examined closer with respect to microstructure and mechanical properties. Very good mechanical properties were obtained. The planned forging experiments on parts of a casting component were changed to just forge tensile test specimens because of practical problems of handling the actual component in a forging process. The actual component was a flywheel housing to a Scania truck. Preliminary experiments were performed on high-pressure die-cast tensile test specimens of the same material as in in the flywheel housing in the autumn 2013. It proved to be difficult to perform the forging experiments because the high-pressure die-casting test specimens cracked during forging. However, the work continued in 2014 with sand castings and low-pressure die-castings. Test specimens were forged during autumn 2015, and sent to Scania for fatigue testing in their test equipment. This test is still not finished, but will be finalized in January 2016. In 2014 Benteler Automotive Farsund made castings with the cast alloy AlSi7Mg with low-pressure die-casting that were meant for forging experiments. These were sent to Raufoss Technology for forging. The process went smoothly and the forgings were thereafter heat treated. They were then sent to Benteler Automotive Farsund Farsund who performed the mechanical testing. The results of the tensile tests showed very good mechanical properties of this alloy. The good results led to a strong desire that BAF also would make similar castings with the alloy AA6082.50. However, it proved to be very difficult for BAF to carry out this task because of logistical issues in melt handling system which is linked to their casting machines. It was therefore decided to use a material that was cast with the Flexstreem process. Flexstreem is a horizontal continuous casting process making rods with constant cross sections. In 2015 mechanical testing and metallography were performed on forged control arms (FLCA - Front Lower Control Arm) where forgings were made from cast rods of the alloy AA6082.50. The rods had been cut in right lengths from a material that had been continuously cast by the Flexstreem process. The mechanical properties were very high. They were compared with corresponding control arms that had been manufactured from extruded rods. This showed that the materials were equal with respect to strength, but the microstructures of the two materials were different. Extruded bolt results in a fibrous structure, while a bolt from the Flexstreem process results in a microstructure that will provide approximately the same mechanical properties in all directions. During the startup of the project Raufoss Technology obtained information on energy consumption by manufacturing control arms to be about 4 kWh/component. They based their calculations on real measurements in their own production line. However, in the way this project was run, it was difficult to measure the energy consumption. It was therefore decided to make a theoretic calculation of the energy consumption. An energy model for making a forged control arm of 3 kg with a standard forging process shows an energy consumption of 3.07 kWh/component. This includes casting of billet, homogenizing the ingot, extrusion to the right dimension, forging and heat treatment of the forging. Making a similar control arm by the StøpSmi process shows an energy consumption of 2.42 kWh/component. This includes casting of a pre-shape, forging and heat treatment of the forging. This means that the StøpSmi process need 21.2% less energy than a conventional forging process.

Smiprosess med nær-form støpt smiemne: En aktuell komponent må velges. En vil foreta nødvendige beregninger for å finne fram til den geometrien smiemnet må ha for at det skal bli utsatt for ønsket deformasjon i det siste smitrinnet for å få optimale mekan iske egenskaper. Et støpeverktøy for utstøping av smiemne og et smiverktøy må tilvirkes. Effektforbruket i de forskjellige prosesstrinnene skal måles. De første StøpSmi forsøk skal gjennomføres i september 2012 hos SINTEF. Deretter skal det gjennomføres m ekanisk prøving og studier av mikrostrukturen. I 2013 skal fokus settes på implementering av resultatene ved støping av smiemner hos FAC og smiing hos RT. Effektforbruket skal registreres også i disse bedriftsforsøkene. Det ferdige smigodset skal gjennom gå mekanisk prøving og mikrostrukturen skal vurderes. Avansert lokal varmsmiing: I midten av 2013 vil en velge ut en ny komponent der en i prosessen skal sørge for at kun spesielle områder blir deformert under smiingen. Det vil si at en må ha litt overs kuddsmateriale her. Støpeverktøyet og smiverktøyet må designes etter dette formålet. I forbindelse med arbeidet vil en benytte simuleringsverktøy både for støpeprosessen og smiprosessen. Støpeverktøyet og smiverktøyet vil bli satt i bestilling i januar 2 014 med levering i andre kvartal 2014. Verktøyene kan så settes inn i aktuelt utstyr for støping hos FAC og smiing hos RT. Effektforbruket skal registreres. Dette kan skje i andre halvår 2014 og i første halvår 2015. Måling av de mekaniske egenskapene v il bli gjennomført fortløpende i forbindelse med prøveproduksjonen og sammenlignet med resultatene fra den første prosessen. Effektforbruket skal vurderes og sammenlignes med den første prosessen. I andre halvår i 2015 vil en sammenfatte resultatene og a rbeide med sluttrapporteringen for å dokumentere energiforbruket i prosessene en har benyttet. Energiforbruket i disse prosessene skal sammenlignes med energiforbruket i dagens produksjon av smigods.