Heat treatment for diecast parts supplies stronger castings

High pressure diecasting (HPDC) is one of the most cost-effective process for making large quantities of complex aluminum components in netshape. But while other cast aluminum parts can be heat treated to improve their mechanical properties, this had not been possible for many die castings.

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Australia's Commonwealth Scientific and Industrial Research Organization's (CSIRO) Light Metals Flagship has developed a new heat treatment process for strengthening aluminum HPDC parts.

Standard die castings contain trapped gas pores that expand, blister and distort the casting when conventional heat treatment is applied, making the parts unusable. Previous attempts to make them heat-treatable have focused on removing porosity from the cast parts. But Flagship researchers developed a process that did not depend on reducing porosity, and they successfully tested the technology on large batches of parts purchased from the industry.

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"Components treated with the new process do not show surface blistering or dimensional changes," said Roger Lumley, metallurgist for Light Metals Flagship. "They retain an as-cast appearance." The process doubles the strength of parts made from the common diecast aluminum alloys. The heat treated components exhibit fatigue resistance as high as some wrought aluminum products and thermal conductivity about 20% above the as-cast status, meaning that for engine or transmission applications, heat can be transferred or removed more efficiently and quickly. This could mean that HPDC parts would operate with lower amounts of fluid in cooling and lubrications systems.

The new heat treating process also may substantially raise energy absorption during fracture when heat treated for this purpose, which has significant implications for crash-sensitive structural components. For example, one common secondary alloy almost doubled in energy absorption when heat treated for that purpose. "We envisage that this will make it possible to use HPDC components more widely in load carrying structural and safety applications," Lumley said. The heat treating process is designed to be implemented in existing manufacturing facilities using conventional heat treatment equipment, such as continuous belt furnaces, fluidized beds or furnace systems designed specifically for rapid heat treatment.

After the success of the trials for HPDC parts up to 66 lbs. (30 kg), the Light Metals Flagships is looking for companies to collaborate on developing lightweight products through component design and implement the new procedures in the diecasting industry.

Visit http://www.csiro.au/ for more information.

"Heat treatment for diecast parts supplies stronger castings" The Free Library 01 March 2008. 20 May 2008 <http://www.thefreelibrary.com/Heat treatment for diecast parts supplies stronger castings.-a0177175205>.

ALCAN COMPACT DEGASSER

IMPROVED METALLURGICAL UNDERSTANDING OF THE ALCAN COMPACT DEGASSER AFTER TWO YEARS OF INDUSTRIAL IMPLEMENTATIONIN ALUMINUM CASTING PLANTS

Peter D. WaiteAlcan International LimitedArvida Research and Development Centre1955 Mellon Blvd., P.O. Box 1250Jonquike, Quebec, Canada G7S 4K8

Abstract Over the past two years, industrial implementation of the Alcan compact degasser has continued, and it is presently being used inmore than half a dozen casting facilities. During this period, further quantification of the process metal treatment efficiency has been undertaken for a wide range of alloys and casting conditions. The extensive plant data that has been collected was analyzedusing the underlying metallurgical principles as guidelines. This has led to an improved understanding of the ACD specifically, and of multi-stage in-lint treatment processes in general. The relationship between the metallurgical principles used for data analysis and the dcgasser metal treatment performance arediscussed, and factors affecting hydrogen removal performance were identified. Examples illustrating these findings are presented using plant data for the Alcan compact degasser and for conventional in-line degassers.

Aluminum in Cars

Today's European cars contain an average of 132 kg of aluminium components. In the short term, many additional aluminium applications could be realised without significant re-engineering and extensive cost impact (e.g. by the use of more aluminium hang-on parts). This could easily reduce the average weight of the cars produced in Europe by 40 kg.

Aluminium is the ideal light-weighting material as it allows a weight saving of up to 50% over competing materials in most applications without compromising safety.
Because the average mass of passenger cars has dramatically increased since the 1970's and because vehicle weight directly impacts fuel consumption, light-weighting is necessary more than ever to reduce CO2 emissions per km at the exhaust pipe.

The EAA brochure "Aluminium in cars" highlights numerous advantages of aluminium applications in passengar cars.

Grain Refinement of Aluminum Casting Alloys

Grain Refinement of Aluminum Casting Alloys, G. Sigworth and T. Kuhn

The mechanisms and benefits of grain refinement are described.

Abstract

An overview is given of grain refinement in aluminum casting alloys. The mechanisms involved and the benefits of refinement are described. The review shows that current practices were developed long before modern Al-Ti-B refiners became available, and are employed now largely for historical reasons. The results of tests in Al-Si, Al-Si-Cu, Al-Cu, Al-Mg and Al-Zn-Mg alloys are presented. The grain refining response is different for each alloy system. It is important to
understand that titanium can be present in two forms. One dissolves in aluminum; the other is nearly insoluble. Each must be controlled separately. With today's powerful Al-Ti-B refiners, there is no reason for large additions of soluble titanium in most alloys. In fact, it is better to say we grain refine with boron, not titanium. The recommended addition is 10-20 ppm of boron, preferably in the form of Al-5Ti-1B or Al-3Ti-1B rod. Lower dissolved titanium levels provide better grain refinement and an improved resistance to hot cracking in some alloys. Al-Si casting alloys which contain copper are an exception. In alloys such as 319 or 355, it is best to have a minimum of about 0.1 % Ti.

AFS Transactions 2007 © American Foundry Society, Schaumburg, IL USA

Earthquake's impact on aluminum smelters still to be calculated

Shanghai. May 13. INTERFAX-CHINA

Damaged facilities and disrupted power supplies are expected to affect aluminum smelters in earthquake-hit areas of Sichuan Province, though broken communication lines has made it difficult to calculate the degree of impact, analysts told Interfax today.

According to State Grid, six transformer substations were shut down, reducing power supply to the Sichuan power grid by 4 million kilovolts after a 500-KV and five 220-KV transformer substations in Sichuan were affected by the earthquake. In addition, five power plants in western Sichuan were disconnected from the power grid.

"Any possible structural damage to facilities or power cuts will heavily impact aluminum production. Sichuan Meishan Aostar Aluminum Co. Ltd. (Meishan Aostar) and Sichuan Guangyuan Aostar Aluminum Co. Ltd., in Sichuan's Meishan City and Guangyuan City close to Wenchuan County, are likely to be affected," Huang Fulong, an analyst at Kaichao Investment Bank, said.
"Communication in those areas struck by the earthquake was cut though, making it impossible to receive up-to-date information," Huang said.

"Although the possible impact of the earthquake has not yet been confirmed, an aluminum smelter in Sichuan said the affect on production is minimal. However, the current lack of direct communication to the earthquake affected areas prevents us from confirming the information, and all we can do is wait and see if smelters have cut production or shut down altogether," Li Yang, an analyst with Beijing Antaike Information, said today.
"Domestic aluminum prices, which may temporarily go up due to the disruption, are not expected to be affected in the long term as long as there are no major production cuts or halts," Li said.

When contacted by Interfax, a Bosai Minerals Group official based in Nanchuan county, Chongqing Municipality, who asked to remain anonymous, said "Nanchuan experienced slight tremors yesterday afternoon, but it did not impact operation However, we have been trying to get in touch with our smelter in Aba Prefecture, Wenchuan county, and this morning sent out search parties to make contact with the smelter."

Bosai's Aba Aluminum Smelter is set to attain an annual production capacity of 200,000 tons of aluminum this year, and expects to produce 150,000 tons of aluminum. Chongqing-based Bosai, a bauxite miner and alumina smelter, acquired Aba Aluminum in 2006.
China's strongest earthquake in more than three decades hit Wenchuan County at 14:28 Beijing time yesterday, killing more than 11,900 in towns and cities in Sichuan Province and its surrounds. Casualties are expected to rise rapidly. Wenchuan County is about 100 kilometers northwest of Chengdu, the capital city of Sichuan.

Meishan Aostar had just resumed normal production on April 25 at its aluminum smelting lines in Sichuan. It had shut down 84 electrolytic anodes earlier this year after local power transmission infrastructure was damaged and partly shut down during the heavy snowstorms at the beginning of the year. The company's primary aluminum capacity stands at about 280,000 tons per annum.

The most-traded July aluminum contracts on Shanghai Futures Exchange closed at RMB 18,915 ($2,709.89) today, up 0.53 percent from the previous trading day, while the spot aluminum prices today on the Shanghai market were between RMB 18,450 ($2,639.98) and RMB 18,470 ($2,642.84) per ton, up RMB 20 ($2.86) from yesterday.

Molten Aluminum Spills At Detroit Lakes Foundry

DETROIT LAKES, Minn. - Crews were chipping away aluminum that spilled from a valve and coated a floor 2 1/2 inches deep at a Detroit Lakes foundry. Almost three tons of the molten metal spilled at Team Industries on Monday morning. Plant manager Jeff Sullivan says one of four furnaces was being cleaned when the cleaning apparatus struck a value, dumping the aluminum on the floor. No one was hurt. The spill was expected to be cleaned up in time for the second shift. A damage estimate was not available. The aluminum covered an area ranging from 1,200 to 1,500 square feet.

Associated Press

Why does a ball go farther when hit with an aluminum bat?

Babe Ruth's Baseball Bat

Asif Shakur, Chair of Physics and Engineering at Salisbury State University, gives the following explanation:

Aluminum is a hard material. It doesn't have a lot of "give." In other words, aluminum is highly elastic. Therefore, very little of the ball's initial kinetic energy (the energy associated with motion) is used up in permanently deforming the aluminum. Indeed, the aluminum springs back quickly and the ball retains much of its initial energy. In contrast, wood is less elastic: it is deformed permanently and to a greater extent than aluminum. As a result, a ball colliding with a wooden bat, such as the replica of Babe Ruth's Louisville Slugger (below), loses more of its initial kinetic energy. At the extreme, a ball colliding with silly putty--a plastic that is completely inelastic--could lose almost all its kinetic energy.

During an elastic collision, a ball experiences an incredibly large force for an incredibly short time, causing it to reverse direction at a speed that can be greater than its initial speed. For example, a bullet gains speed when it ricochets off an approaching artillery shell, but looses almost all of its kinetic energy when shot into a wooden block. One must be very careful to distinguish between the expressions "losing kinetic energy" and "losing energy." The total energy is not lost; the kinetic energy is transformed into other forms of energy such as heat. Although heat is a wonderful thing on a cold morning, it does not make our ball move any faster.
The law of conservation of momentum--a profound physical law--governs the motion of colliding objects. An object's momentum equals the product of its mass and its velocity, or mv. And conservation means that the total momentum of objects entering into a collision equals their total momentum after the collision. This law holds whether the collision is elastic or inelastic. On the other hand, the objects' kinetic energy--equal to 1/2mv2--before the collision is not necessarily equal to the kinetic energy after the collision. Indeed, elastic collisions are characterized by the conservation of kinetic energy, whereas inelastic collisions are characterized by the "loss" of kinetic energy into heat, sound and so forth.

Unfortunately, the only way to make this discussion more cogent is to resort to equations. Consider a bullet of mass m and speed v colliding with a stationary block of wood of mass M. After the collision, the bullet is lodged in the wood and the "system" of both the bullet and the block move with a common speed V. Conservation of momentum then says that mv + 0 = (m+M)V. It would be incorrect to write a "conservation of kinetic energy" equation for this case, along the lines of 1/2mv2 +0 = 1/2(M+m)V2. That equation is patently incorrect. In fact, the first equation implies that the second cannot be true! Try yourself by plugging in some numbers. To further elucidate this point, let us calculate the ratio of the kinetic energy of the bullet and block system and the initial kinetic energy of the bullet: what is 1/2(M+m)V2 divided by 1/2mv2?

From the first equation, we know that V = m/(M+m). Substituting this value into our ratio, we find that the kinetic energy of the bullet and block divided by the kinetic energy of bullet alone equals m/(M+m). If m is 10 grams and M is 990 grams, the bullet loses more than 99 percent of its initial kinetic energy.

The moral of the story is that if you want the ball to have a high speed (lots of kinetic energy), make sure that the collision is as close to being elastic as possible. Of course, this begs the question: Why not use a big, bad steel bat? But that's another story for another day!

From www.sciam.com