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Die Casting News

Blistering in Semi-Solid Die Casting of Aluminum Alloys and Its Avoidance

Posted by Hill and Griffith Company on May 28, 2020 11:07:38 AM

Excerpt from the article in the June 2005 issue of Acta Materialia by X.G. Hu, Q. Zhu, S.P. Madison, H.V. Atkinson, et. al.

Semi-solid die casting of relatively high solid-fraction aluminum alloys (0.5–0.7 fraction solid) can be used for the production of high quality industrial components. However, surface blistering during solution heat treatment can still be a problem and is associated with the entrapment of gas whether from air or from burned lubricant. Here the mechanism for formation of blisters is presented. The Reynolds number in the surface layer of the semi-solid flow is then analyzed to obtain the relationships with hydraulic diameter and flow velocity for different slurry temperatures. The hypothesis is that it is some flow instability at the flow front, even where the overall nature of the flow is essentially laminar, which is leading to the entrapment. The crucial finding is that if the Reynolds number is plotted against temperature there is a decrease followed by an increase. The position of this minimum is dependent on the ratio of fill velocity to the hydraulic diameter, v/D. Thus there is a ‘sweet spot’ in terms of temperature (i.e. fraction liquid), flow velocity and hydraulic diameter (i.e. die design) where the flow front has the maximum stability, giving maximum resistance to blister formation. This is in contrast with conventional wisdom which would suggest that low fractions liquid would give the most stable flow front. A rationale for this is presented in terms of the particle crowding at the relatively low fraction of liquid.

Experimental results with aluminum alloy 319s as an exemplar, and a die which has varying cross sectional dimensions, are presented and validate the hypothesis.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Release Agents for Die Casting, Aluminum Die Casting Process, Die Casting Defects, Die Casting Lubricant, Aluminum Die Casting, die casting lubricant management, acta materialia

NADCA Webinars: Inclusions, Leakers, and Cracks

Posted by Hill and Griffith Company on May 20, 2020 2:16:57 PM

The material presented in this video are some highlights from NADCA’s online webinar - Die Casting Defects - Inclusions, Leakers and Cracks. This course discusses various types of inclusions and corrective measures to minimize inclusions. In addition, causes of leakers and corrective measures are presented. Lastly, the various causes of cracks in die castings are discussed.

For information on purchasing a downloadable copy of this webinar in its entirety, please visit: http://www.diecasting.org/store/detail.aspx?id=WEB297

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, NADCA Education

Die Lubrication: The Big Picture

Posted by Hill and Griffith Company on May 13, 2020 11:57:39 AM

Excerpt from the article in the June 2005 issue of The Fabricator by Steven Rainwater

The activities, costs, and results of die lubrication do not neatly occupy related columns on a spreadsheet. When maintenance employees are deciding the best way to replenish fluid reservoirs, they usually do not review the previous quarter's shipping costs. When die designers select a tool steel, they usually do not focus on whether the fluid actuation is integrated with the press controls. When engineers determine a fluid viscosity, they seldom consider how many bundles of rags the press operators use each quarter. These seemingly unrelated categories and many others are related by die lubrication decisions.

Perhaps no other process in a stamping, forming, or fabricating facility reaches as broadly into the operation as die lubrication does. Yet, because it must be adapted to each manufactured part, lubrication sometimes is the last thing planned, and frequently it is approached haphazardly.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, The Fabricator

NADCA Webinars: Shrink Porosity

Posted by Hill and Griffith Company on May 6, 2020 6:17:34 PM

The material presented in this video are some highlights from NADCA’s online webinar - Die Casting Defects - Shrinkage Porosity. This course describes how to identify shrinkage porosity, discusses the causes, and provides corrective measures to minimize shrinkage porosity.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, NADCA Education

Factors That Contribute to Extending Die Life - NADCA Webinar Series

Posted by Hill and Griffith Company on Apr 29, 2020 3:57:18 PM

Failure of dies is typically caused by thermal fatigue cracking or gross cracking. Other modes of failure include soldering to the die surface, erosion and corrosion of the die surface. It is clear that many factors can impact die life, including steel composition, heat treatment conditions, fabrication techniques and die casting processing parameters. The approach used in this 6-part webinar series is to summarize recent research published by NADCA on extending die life.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, NADCA Education

Methods and Measures to Reduce the Solder Defect of Die Casting Surfaces

Posted by Hill and Griffith Company on Apr 22, 2020 9:15:15 PM

Excerpt from the January 2020 Issue of Global Casting Magazine

The solder defect in die casting affects surface quality and strength, especially in castings with a high seal requirement. The defect could lead to leakage that would mean more wasted cost (Fig 1.). Four aspects of soldering were analyzed, including:

  • chemical principle
  • mold structure
  • release agent
  • die casting process

For example, JAC die casting company in Suzhou, China, supplies parts to customers that don’t allow solder to be visible to the naked eye. For a German company in Shandong, China, which produces automobile parts, the solder defect area can be no more than 20 x 20 mm. Another company which produces parts with thin walls and high temperature pouring, have found it is at higher risk for solder defects.

What factors cause the solder defect? What’s the physical or chemical change between the liquid aluminum and hot iron mold? This article will share the results of a study on this defect based on the chemical principle, mold structure, release agent and die casting process.

Interfacial reaction is a series of chemical interactions that occur between the interface of two phases, according to chemical type, content, status and properties.

Solder defect is started by the chemical and physic reaction due to the strong affinity in Fe-Al. A new compound is created when the mold and liquid Al connect closely. The higher the temperature, the more intense the thermal vibration of the atoms, causing the solder ratio to rise and the corrosion of the mold to increase, until finally, it causes the solder area. When polished, the surface containing a thin nitride layer will be destroyed, causing worse cycle. Some data in the study showed that the affinity of Fe-Al will become more serious as the Fe element is decreased, creating more solder.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, Global Casting Magazine

Releasing, Cooling and Protecting

Posted by Hill and Griffith Company on Apr 15, 2020 8:00:00 AM

Release agents are of central significance in die casting technology.

Excerpt from the January 2020 Issue of Metalworking World by Fabio Boiocchi

Release agents affect the quality of the cast parts, the lifetime of molds and length of casting cycles. Release agents must be matched with the respective casting material and should meet high requirements in terms of economic efficiency and environmental compatibility.

Release agents are indispensable for the trouble-free production process in a die casting foundry. The most widely used release agents for die casting are water-based chemicals [1]. They form a separating film between the casting mold and the casting material during the casting process and cool the casting mold, which has a strongly elevated surface temperature after a casting process. In the long run, such a temperature load – in the case of aluminum, for example, up to 500°C [2] – would cause severe wear of the mold. Therefore, release agents also protect the casting molds.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, Metalworking World Magazine

Lubrication and Wear in Die Casting

Posted by Hill and Griffith Company on Mar 25, 2020 11:07:03 AM

Although die casting lubricant is continuously exposed to changing pressures and velocities and differing degrees of wear, a dynamic equilibrium – and, therefore, realistic data – may be attained through careful control.

Excerpt from the May 2018 Issue of Gear Solutions by K.D. Clarke and C.J. Van Tyne

Both hot- and cold-chamber die casting are batch-type processes in which steady-state conditions are never fully achieved and the initial lubricant supply must perform adequately for the duration of the operation. The lubricant is continuously exposed to changing pressures and velocities, and wear or pickup products in the lubricant also continuously vary, although a dynamic equilibrium may be attained through careful control. The absence of steady-state conditions creates challenges for the systematic analysis of lubrication and wear in forging processes.

In many ways, various forging processes are competitive with one another, and the competitive position of each is greatly influenced by the lubrication system employed. Thus, hot forging followed by finish machining may be replaced by cold forging, with all the associated advantages, provided that a suitable lubricant can be found. Indeed, economy of production has often been the major impetus for the development of new forging processes and associated lubrication techniques.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, Gear Solutions

Challenges in the Market for Structural Castings Posed by Globalization

Posted by Hill and Griffith Company on Mar 18, 2020 11:54:04 AM

Excerpt from the December 2018 post of Metalworking World by Fabio Boiocchi

Die casting is an economical method for the manufacturing of structural components. The foundries that operate in this area have to cope with a number of challenges. The use of modern manufacturing technology and the cooperation with other companies in the value chain strengthen their competitiveness. Structural components made by light metal die casting, above all aluminum and magnesium, are an integral part of modern automotive bodies and chassis. These components can be reliably manufactured with die casting methods, meet important requirements in terms of lightweight construction, strength and crash behavior and can be completely recycled at the end of their useful life [1].

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, Metalworking World Magazine

Nanocomposite Costings for Die Casting

Posted by Hill and Griffith Company on Mar 4, 2020 1:58:06 PM

Excerpt from the March 2014 issue of Metalworking World by Fabio Boiocchi

The working instruments and the dies for forming metal parts, especially in the HPDC (High-Pressure Die casting) technology, are very complex components subjected to strong stresses. In those applications, different failure mechanisms can, therefore, occur: thermal fatigue, cracking, abrasive wear, plastic deformation, transfer of die-cast metal on the die surface. Those problems can cause frequent downtimes of productive lines. It is assessed on average a productivity decrease equal to at least 15%, which causes 15% of the volume of production rejects. This has naturally relevant economic and environmental implications related to the process, efficiency, and energy and raw materials consumption.

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Tags: Die Casting, Die Casting Release Agents, Die Casting Lubricants, Die Casting Release Agent, Die Casting Lubricant, Die Casting Process, die casting lubricant management, Metalworking World Magazine

 


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