EXTRUSION TECHNOLOGY
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INVESTIGATION OF AA6082 GRAIN TEXTURE
EVOLUTION AND PREDICTION
A. Segatori (1), A. Foydl (2), L. Donati (1), N. Ben Khalifa (2), L. Tomesani (1), A. E. Tekkaya (2)
(1) University of Bologna, DIEM Department, Italy,
(2) Institute of Forming Technology and Lightweight Construction (IUL), Universität Dortmund, Germany
Abstract
Microstructure of aluminum is of high importance for product mechanical properties. During extrusion the material undergoes a wide range of different strain, strain rates and temperature gradients, how many works reported (1).
Final microstructure and texture is the result of the effects of multiple mechanisms as grain shape change, recrystallization, recovery, and grain growth. To get optimized profiles a well-direct adjustment of the microstructure through process parameter is a typical and critical aim. Therefore the correlation between extrusion process parameters and the change of texture and grain size needs to be investigated (2).
The present paper reports a study on grain evolution during the first stages of material response to deformation in direct extrusion process. The investigation was carried out by means of a circular profile extrusion of AA6082 alloy with the aim of evaluate dependency of texture change over process parameters such as temperatures, velocity and extrusion ratio.
Sequentially experimental measurements on grain size have been coupled with strain evaluation of finite element model in order to define an evolution model, always taking into account existing evolution theories and laws.
NEW MATERIALS AND INTELLIGENT DESIGN
ON EXTRUSION TOOLING
W. Hähnel, K. Gillmeister, Kind & Co Edelstahlwerk KG, Germany 1. Abstract
The principal range of activities of Kind & Co. Edelstahlwerk is the development and manufacture of forged tool steels at both of its facilities in Germany (Wiehl and Lindlar) with more than 100 years of experience in the production and refinement of tool steels.
Today, the machinery and equipment technology available serves to optimise the requie characteristics of classical tool steels and to also design new tool steels to accommodate the market requirements. Particular focus is placed on designing temperature resistant high premium tool steels and top quality products of high toughness.
In close consultation with extrusion press experts, the know how in developing new tool steels, along with experience compiled in a focused Service Centre, forms the basis for designing new tools. This continuous process of improvement leads to increased service life of the tools, a safe and reliable production process at the extrusion press, enhanced product quality and consequently, a cost saving.
The following report includes a number of examples shown on actual tools of an extrusion press and it also illustrates improvement potentials in the future.
FURNACE ENERGY SAVING MYTHS
The approximate cost of these ideas for aluminum melting and holding furnaces will be presented...
David W. White, The Schaefer Group Inc., USA
Abstract
This article will enlighten you as to the true energy saving ideas that work verses the myths that are out there. The approximate cost of these ideas for aluminum melting and holding furnaces will be presented. You will learn about recuperation, regenerative burners, heat exchangers, refractory linings and pre-heat hearths, circulation pumps and their respective ROI.
Introduction
In traveling across the world I have found one thing common among die casters and foundries. They are all very
concerned with the cost of energy used in their operations.
Everything from electricity used per building to the plant air
system is being looked at to reduce energy usage.
One of the most common areas to look at first is the melting of the metal that goes into producing the part that each
particular company makes. It is typically one of the higher
usages of natural gas or electricity in the plant. What
baffles me is the approach a lot of folks are talking about to
reduce the energy consumption in all industrial furnaces.
There are a lot of salesmen selling energy saving ideas. In this article we will weed through the myths and truths of saving energy.
myth # 1. recuperation
There is a buzz in the industry now for recuperation. How can I recoup all of the energy going up the flues of all of these furnaces? There is a great myth spreading across this worldthat recuperation will gain the most bang for your buck (in return on investment) where energy saving is concerned.
While there is little doubt that there is a great deal of savings possible in recouping heat lost out a flue, some care needs to be taken as to how far you go with this. Some examples:
1. Keep your recuperated temperatures below 700 degrees F and you will reduce your cost for the system substantially. Below 700 degrees you can stick with mild steel manifolds that are insulated as opposed to stainless steel which has increased in price by 114% over the last 3 years. Even at 700 degree preheated combustion air you can save 23% in fuel usage.
Based on numbers produced by a major burner manufacturer at $10.00 per MMBTU’s on a 4,000#/hr radiant roof melter, you can expect to pay about $85,000.00-$100,000.00 more for a burner system using a recuperator installed and save about $54,750.00 per year or have a 17.4 -24 month payback on this investment differential. Actual costs may vary due to age of furnace and components or type of furnace and number of burners.
2. The newest heat exchanger on the market allows you to turn the system off during cleaning and fluxing. If you do not buy this one make sure you damper the flue gases to be able to bypass the exchanger when you flux the furnaces. Otherwise you will see excessive wear and maintenance on the heat exchanger.
3. Change the nozzles in the burner to stainless steel to handle the additional temperature of the pre-heated combustion air.
4. You might want to consider (on an older furnace) changing to a ultra low NOx burner.
As you increase combustion air temperature your NOx emissions go up.
myth #2 regenerative burners are too expensive!
In most cases from a strictly up front cost basis recuperation will give you a faster payback than does regeneration on smaller 6,000#/hr and less furnaces. When you get into the big units, that is where the regenerative burners really begin to pay off. In the same 4,000#/hr furnace with a regenerative system on board you will have a differential of about $250,000 vs conventional burner system and your payback will be about 5.73 years. Depending upon the type and age of the furnace you are installing the equipment on this will vary. For these examples, we are using new furnaces. Certainly if your furnace is melting metal at a high end 1800-2000BTU’s/# of metal melted then the ROI becomes more lucrative. The myth has been that regenerative burner systems are too costly. When gas reaches $10.00/Dekatherm you can afford to look at regenerative. If you are looking at buying a 7,000#/hr melter with regenerative burners to replace a high headroom gas guzzler that melts at 2,000BTU’s/# of metal melted, you will see a savings of over $500,000.00 a year in fuel cost. That ROI is less than two years.Based on $10.00/Dekatherm. Raise the gas cost to $13.00/therm and your savings becomes $649,987.00/year or a 15-18 month payback depending upon the options you choose on your furnace. This folks is a no brainer. Gas is not likely to come down further anytime soon. {These figures are based on 7,000#/hr for 20 hrs of melting a day, 340 days a year and $10.00/ $13.00 respectively per 1000 cubic feet of gas}
RESPONDING TO TECHNICAL REQUIREMENTS FOR EXTRUSION CONTAINERS AND STEMS
G. Strehl, S+C Extrusion Tooling Solutions, GermanyAbstract
The design of new presses for ever higher specific pressures and larger billets has put higher demands on the specifications for extrusion containers and stems in the last years. The incre-ased mechanical loads have to be incorporated into the design
and the material choice.
For containers a tool to judge the stress distribution in the con-tainer has been developed. Thermal expansion and shrink rates are taken into account to calculate the maximum loads during extrusion and billet loa-ding. These values are needed to select appropriate materials and heat treatments of the con-tainer components for each indi-vidual application.
As stresses are also connected to temperatures and the thermal situation in the container, the purpose and efficiency of the cooling and heating systems ha-ve to be discussed.
The highest requirements are found for stems in indirect pres-ses. Their lifetime is linked to the material and the design. Criteria to judge on the applicability of the stem have to be defined. The maximum load and the risk of buckling can be calculated
from the length of the shaft, the inner and outer diameter and the material properties of the stem.
LARGE DIAMETER BILLET CASTING WITH WAGSTAFF® ARC™ CASTING TECHNOLOGY AND ABB EM STIRRING
Tim Scott, Research Metallurgist, Wagstaff, Inc. Christer Carlsson, Area Sales Manager, ABB
Introduction
Wagstaff, Inc. has been involved with billet casting technology design for many years with sizes typically below 530 mm diameter. Interest in increased billet diameters recently induced a fresh look at the need to cast a wide range of alloys in extended sizes. The intent of the Wagstaff® ARC™ (Advanced Refractory Channel) Large Diameter Billet Technology development is to push the boundaries of current market capabilities.
To date development has been primarily focused on casting the challenging 2XXX and 7XXX alloys with the ARC mold. First production tooling has been manufactured and shipped to be commissioned this year.
To broaden the benefits to the casthouse, a parallel research project was established to investigate the effect of Electro Magnetic (EM) stirring as an additional method to increase value to end users of large diameter billets produced with ARC Technology.
Wagstaff, Inc. provided the casting tooling and casting expertise, while ABB provided the modeling, electromagnet and power supply control for the stirring.