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Green Sand Metalcasting Foundry News

Elimination of Pinhole Porosity in Alloy Steels

Posted by Hill and Griffith Company on Feb 23, 2021 4:50:06 PM

Adding small amounts of ferroselenium and keeping charged nitrogen volumes low is effective in preventing subsurface porosity.

Excerpt from Foundry Management & Technology's February 2020 issue by Dr. R. L. (Rod) Naro and D. C. Williams

Nothing is more frustrating in foundry operations than finding an outbreak of subsurface porosity after costly machining operations. Outbreaks of subsurface porosity always seem to occur during high humidity seasons, especially during the rainy spring. The prime culprit universally blamed is hydrogen absorption into molten steels.

The hydrogen atom is the smallest and simplest of all the elements. Hydrogen can be absorbed only in its mono-atomic state. Nitrogen also can play a significant role in the development of porosity, especially in the production of high-alloy steel castings.

Hydrogen and nitrogen absorption in steel casting may result from alloy additions and reactions at the mold-metal interface. The ability of molten steel to absorb large amounts of hydrogen and nitrogen is shown in Figure 1.

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Coatings, Green Sand Release Agents, Green Sand Metal Casting, Green Sand Metalcasting, Core Binders, Green Sand Additive Products, Foundry Management & Technology magazine, Shakeout

Manufacturing Processes for Light Alloys

Posted by Hill and Griffith Company on Feb 16, 2021 8:53:03 PM

7.6.2 Selected expendable mold processes

Excerpt from the publication, Materials, Design and Manufacturing for Lightweight Vehicles by G.T. Kridli, et. al.

Sand casting is the most commonly used expendable mold process. In this process, sand is bound together (as detailed in  Table 7.8 ) and shaped to conform to the negative impression of the desired component. Molten metal is then poured into the sand mold; upon solidification, the metal has the geometry of the desired component.
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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Coatings, Green Sand Release Agents, Green Sand Metal Casting, Green Sand Metalcasting, Core Binders, Green Sand Additive Products, Shakeout

High-Speed, High-Efficiency Core Box and Mold Cleaning

Posted by Hill and Griffith Company on Feb 9, 2021 5:36:28 PM

Progress Casting's dry-ice blasting operation cuts cleaning time by 86% and saves operating costs.

Excerpt from the October 2019 Foundry Management & Technology article

Metalcasters' product quality and performance results are under constant review, and new technologies and techniques are always being tested, or considered. But how often are maintenance methods reconsidered? Progress Casting Group in Plymouth, MN, produces precision die castings and sand castings it supplies to automotive, aerospace, and defense industry customers. It had a fairly standard problem — cleaning core boxes and low-pressure die casting molds — and a fairly standard approach to addressing it.

Core boxes and casting molds are meant to be used over and over again. So, they must be cleaned frequently and effectively in order to maintain dimensional accuracy and process reliability. The refractory coatings (i.e., release agent) and resin spray buildup on the mold faces, as well as sand and binder residue on the core boxes, had been removed by sand blasting and manual brushes. Both processes are slow and not fully effective. Sand blasting degrades the urethane on the molds and both methods routinely destroy the vents on the core boxes. More than this, the cleaning can damage machinery and workers' safety may be at risk in the process.

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Coatings, Green Sand Release Agents, Green Sand Metal Casting, Green Sand Metalcasting, Core Binders, Green Sand Additive Products, Foundry Management & Technology magazine, Shakeout

Reexamining Shakeout to Control Time, Temperature

Posted by Hill and Griffith Company on Feb 2, 2021 3:44:11 PM

What happens to castings during shakeout may be instructive to foundries seeking to optimize production costs and process quality.

Excerpt from the March 2016 Foundry Management & Technology article by G.D. Henderieckx.

Shaking out castings is done in different ways, according to a foundry’s specific molding operation, and mold cooling may require hours or even days for batch production and larger castings. There is much to be learned about the process: In general, shakeout timing is not calculated, and it is determined mainly by older, experienced employees using very safe operating practices (i.e., a long time).

What happens during the shakeout? First, the cast iron in the mold will transform its structure from austenite to ferrite (or pearlite, bainite or martensite). This initiates a transformation stress. The amount of stress depends on the final structure: transforming to martensite leads to the highest stress; transforming to ferrite to the lowest stress level. Austenitic materials have no transformation and will not suffer from transformation stress.

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Coatings, Green Sand Release Agents, Green Sand Metal Casting, Green Sand Metalcasting, Core Binders, Green Sand Additive Products, Foundry Management & Technology magazine, Shakeout

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