Secat, Inc.

Providing Aluminum Answers

ET ’16 (Innovations for Tomorrow) Conference

The Eleventh Annual International Aluminum Technology Seminar & Exposition (ET ’16) was held May 2-6 in Chicago, Illinois. The conference was attended by more than 1,200 people within the aluminum extrusion industry. The conference featured 120 technical and management presentations from industry and academic participants as well as an exposition hall showcasing products and services from 120 suppliers. Secat participated in the three-day exposition, presenting its analytical capabilities to aluminum extruders, billet casting companies, and industry suppliers. The photo below shows Shridas Ningileri (VP Engineering) and Dr. Quancang Ma (Materials Engineer) in front of the Secat display booth.

Presentations were divided into six tracks consisting of Billet Process and Equipment, Theoretical Extrusions Process, Extrusions Equipment, Management Issues, Extrusions Process, and Value-Added Processes. The tracks were sub-divided into several categories such as Anodizing, Die Design, Billet Casting, Operations, Melting & Homogenization, etc. The technical sessions were led by industry experts. A few interesting topics presented during the conference are discussed below.

Inverse segregation zone (ISZ) is common in the cast billet that usually results in alloying elements (e.g. Si, Mg, Fe, etc.) segregation at the billet surface. The ISZ distance normally varies with casting process parameters and alloy chemistry. An increase in ISZ can effect extrusion profile surface quality. Increasing homogenization temperature can permit a reduction in holding time and increase the phase transformation of beta to alpha. However, higher homogenization temperature could cause re-melt of the ISZ. Thus, control of the ISZ thickness is critical in controlling billet quality. One presentation discussed a Low Pressure Cast (LPC) technique to reduce the billet ISZ where the liquid level is kept low in the cast mold, and may be as low as the launder liquid level. Examples were discussed where normal ~80 µm ISZ in the 200 mm diameter AA6XXX billet decreased to ~20µm after application of this method. Hard alloy AA7075 with a normal ISZ of ~400 µm for 16″ diameter billet can be reduced to near zero using LPC with an improved cast billet surface. The melting point of ISZ is lower than matrix without ISZ and therefore minimizing ISZ would increase the melting point of the billet at the surface. Therefore there is a possibility to increase homogenization temperatures.

Another paper discussed the use of Al-Ti-C Al grain refiner as an alternate to classic Al-Ti-B. The paper discussed the use of Al-Ti-C during the production of AA6063 7″ diameter industrial billets. THe feed rate, grain size, die wear and extrusion surface quality data was presented and compared with the product made using Al-Ti-B. The data showed that the grain size (~127 µm) of the billet with a feed rate of 1.8 kg/ton rate of Al-Ti-C was similar to billet produced using 3 kg/ton of Al-Ti-B. In addition, the extrusion surface quality was reported to be better than Al-Ti-B, with the die lifespan increased by ~40-70% using Al-Ti-C for the given extrusion profile.

The occurrence of blisters in the extrusion profile was discussed in another paper. Blisters are common and can occur in extrusions due to several causes. Potential causes could include entrapped hydrogen, shrinkage, surface contamination, moisture in the table or in refractory materials, high environmental humidity, inadequate degassing and/or press processes. The presentation discussed sixteen causes that could result in blisters. Besides the common causes of blisters, one idea was that there existed an ideal extrusion upset pressure and if it was not maintained, the potential for blisters to form was possible. In this case, the blister was the air that was entrapped in the profile during extrusion. Normally, there is a ~10% void between container and billet during the extrusion process. If the upset pressure is too low, void/air would be squeezed into the extrusion and blisters could form. The presentation noted that different profile shapes had different potential for blister occurrence with ideal upset pressures.

Due to the increasing demand for aluminum extrusions in the automotive industry, the properties of heat-treatable AA6XXX and non-heat-treatable AA5XXX alloys has attracted a great deal of attention due to their great potential usage in vehicles. One presentation discussed the comparative properties of AA6063 T6 and T7 temper. It was indicated that AA6063 T7 may be more attractive than T6 as T7 has shown better crashworthiness. T7 which is slightly overaged temper, has slightly lower strength by ~16-19% YS and ~13-15% UTS than T6 with similar elongation (El=12%). However, T7 has 2-3 times the crash fracture strain of T6 material. The reason for this difference was ascribed to the possible particle free zone (PFZ) along grain boundaries due to over-aging.


May 30, 2016 - Posted by | Blog Posts

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