<img alt="" src="https://secure.hims1nice.com/150891.png" style="display:none;">

Die Casting News

Solving Hot Spot Die Casting Cracks, "If it's hot, cool it. If it's cold, warm it."

Posted by Hill and Griffith Company on Nov 7, 2018 3:36:38 PM

Some highlights from NADCA’s online webinar – Defects in Die Casting: Surface Defects and Other Problems.


This second course covers defects caused by such things as venting problems, surface defects such as “white surface” and die spray marking. It then goes into the two main types of cracking, leakers, flash and flaking/spalling during machining.

For information on purchasing a downloadable copy of this webinar in its entirety, please visit: http://www.diecasting.org/store/detail.aspx?id=WEB228

Transcript from the video highlight,

"Cracks. We know the cause, often relatively easy to stop. I was in a plant two weeks ago where intermittent cracks kept occurring and disappearing. When we checked, the casting was always cracked but it was not on the surface, it was inside the casting, it was a hot crack. We'll go through those.


Cracks are one of the easiest things to fix and one of the most annoying. So you've got hot cracks, sitting here usually in the middle of a place where the heat is coming from both directions called converging heat flow and these are usually hot cracks and I'll show you those in a minute.


Cracks or tears or hot cracks have many causes but usually are at least partially caused by shrinkage cracks on the surface. If you imagine that area in the previous slide here, this is all frozen but this part is not. It starts to shrink in both directions, it opens up a crack. Most often the casting is stretched in the die as it cools because the die doesn't change dimensions, still is strong. While the casting is cooling and contracting, the stretching causes cracks at the weakest points. The last place to solidify where the aluminum hasn't totally frozen or where it is still very, very weak. So as these hot cracks are a localized thermal effect.

Solidification cracks on the surface occur during solidification, have a dark surface so when you break it open, you often see dark marks on the surface.


Or it can look like this on the right where you have a number of little shrinkage cracks on the surface and the castings that crack while cooling in the die, the crack will also be a hotspot. But it will not have a light surface increase radii.


We look at a typical hot crack, it looks like that. They're usually not long but they're wide, the distance between the two faces. And if you cut it and polish it, you see that. So again, the crack is not deep but it is wide on the surface. That means it cracks while it was hot. So that means this area is most probably a hot area and if it's hot, cool it. If it's cold, warm it.

Mechanical stresses can cause cracks while the die opens or the casting ejects. These are usually sharp cracks. Cracks at the base of long cores or fins dragging or sticking of projections into one die half may indicate die shift when the dies separate. The factors in die alignment should be checked, such as die droop, saw that four weeks ago. As the die opened, it dropped slightly. Worn guide pins, worn linkage, worn tie bar bushings, worn shoes, uneven tie bar stresses. But the most common is that the casting is in the die too long.

To purchase access to this course, visit the NADCA Market Place at www.diecasting.org/store. Purchasing a course through the online education system grants you one year of access to the recording, presentation, support material and test when applicable."

Die Casting News from the North American Die Casting Association:

Attention Industry Professionals - Register Today for NADCA's Die Casting Executive Conference

NADCA National Courses are Underway – Register Today

NAFTA Negotiations

Hill and Griffith Customer Service

We're known for our hands-on approach. Let us visit your plant, offer die casting technical support and recommend release agents, lubricants, plunger lubricants and permanent mold lubricants that suit your needs. Products that represent the latest in technology and ongoing research that enhance competitiveness and increase productivity. 

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy." Die Casting and Squeeze Lubricants- Diluco®, Permanent Mold Coatings- Concote™, Plunger Lube™- Graphite and non-graphite oils and pastes with excellent anti-wear properties, Casting Operations Products: Start-up lubes, Ladle coatings, Anti-soldering pastes, Water glycol, Trim press lubricants, Surface protection for casting storage, Corrosion protection for die storage, Cleaners for machines and dies, Corrosion protection for machines, Heat treatment quenchants, and Heat-transfer fluids. Also, Industrial Lubricants Griflube®, Hydraulic fluids with fire-resistant and anti-wear properties, Bio-Syn natural ester-based hydraulic fluid, Way oil knuckle lubes and Metalworking Fluids- Grifcut™

Contact us for Product Samples

Hill and Griffith Customer Service

Technical Services & Support

On-site process surveys, Casting defect investigations, Product testing, Tooling start-ups and Statistical process controls and much more. Also, lab facilities are available to provide testing upon request. 

Contact us to Arrange a Visit

Bulletins and Technical Papers for Die Casting Products

Tags: Die Casting, Die Casting Process Improvement, Die Casting Process Evaluation, Die Casting Process, NADCA Video Highlight