Casting Clinic! ~ Ask Kanae ~

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Episode 1 Challenges for Nagisa and Minato

Nagisa: "Another shrinkage cavity... The client pointed out hard spots, so we added more flux and worked hard on the treatment, but why aren't they decreasing...?"

Minato: "Still glued to that little book of yours, Nagisa? In the real world, experience is king. I understand the urge to innovate, but if the defect rate goes up, it's on your head. You get that, right?"

Nagisa: "Chief! The melt temperature and casting conditions are unchanged. Even with that massive increase in flux, the problem persists. It’s strange... We must be overlooking something."

Minato: "Chasing that ‘overlooked something' is a never-ending game. That's just how aluminum works. Always has been."

Minato: "Anyway, I'll fine-tune the next batch with my 'gut-puter.' You sit this one out, Nagisa."

Episode 2 Presidens Yamasaki and XX Industrial’s Sales Rep

Yamasaki: "I ordered a fix for the casting defects, but the rate is up again. It’s eating into our profits, plus we have to cover machining costs and broken tooling. With this many returns, we can't re-melt it all, and scrap value is peanuts. I've told Minato until I'm blue in the face that lot variation is fatal. It stops the client's line and destroys trust. They haven't exploded at us yet, but it's a ticking time bomb..."

Yamasaki: "We need to break through the limits of experience-based quality control."
Alright, decided. We're going to try the technical advisory service that Ohtani from XX Industrial Supply & Solutions introduced. His confident pitch really stuck with me: 'The fees might seem high at first, but with fewer defects, it pays for itself in no time. Plus, it builds your staff's wisdom, so it pays dividends in the long run.'

Ohtani: "Hello, XX Industrial, Ohtani speaking. Good afternoon, President! What can I do for you today? Oh, by the way, did you try that flux sample I left? Worked like a charm, didn't it?"

Yamasaki: "Ah, hello, Shohei. Actually... Minato insists on playing it safe with the usual stuff, so we haven't tried it yet. More importantly, remember that technical support service you introduced? I’d like to request that. We tried increasing the flux, but it’s just not working."

Episode 3 KANAE

"Mr. Ohtani informed me that you're looking to incorporate new insights and technologies into your aluminum casting. Today, I’ll start by explaining melt quality control using Thermal Analyzer, followed by an on-site trial. I understand you also want to test flux and feeder, depending on the results. This is a paid service, so I will conduct a thorough investigation. However, real mastery takes time—so to truly internalize the know-how, I highly recommend considering our annual technical support contract."

Kanae: "Oh, I haven't introduced myself properly! I'm Kanae from KANAE Hi-Tec. It's a pleasure to meet you all!"

Minato: "Right, Ms. Kanae. Yeah, yeah, nice to meet you." (Just another run-of-the-mill consultant. What kind of nonsense did she fill the President's head with? I bet I'm in for a lecture on useless academic theory. I don't buy this for a second! I told the boss I would handle this...!)

Nagisa: "Wait, Kanae... from KANAE Hi-Tec!?" (Yay! I just love learning new things! This is so exciting!)
Kanae: "Yup, that's me! Let's do this!"

Kanae: "Alright, let's go over melt quality control using Thermal Analyzer. You're familiar with the Aluminum-Silicon phase diagram, right?”

Kanae: "See this white line on the left? That's the standard Al-Si phase diagram you know. This is theoretical data based on pure materials, tested in a clean lab with controlled temperature and humidity.　However, real production ingots contain impurities—even within JIS or ASTM specs—which shifts the curve to the red line.

In other words, it’s not solidifying at the temperature you assume. And you know exactly what kind of defects arise from delayed solidification. After all, we don't cast in a lab; we cast in the real world. Don't you think so, Mr. Minato?"

"The red phase diagram on the left connects to the cooling curve on the right via these blue dotted lines. Basically, the cooling curve shows the real temperature changes from the phase diagram, plotted over time on the X-axis. The Y-axis is temperature, just like in the diagram. You can clearly see the primary crystals and eutectic of AC4CH appearing on the curve.

T-h-i-s is the 'unfolded view' that reveals exactly what the aluminum and silicon are doing—something you won't find in any textbook. By the way, we aren't just doodling curves for fun. We're performing precise measurements and calculations. Take a look at the next figure."

Kanae: "This screen shows an actual analysis. I've blurred out the specific metrics and calculations here for confidentiality, but for example, we are analyzing oxides and nucleation potential. The levels of these elements have a huge impact on casting defects."

Kanae: "This is a free Python script we've released. Simply input the coordinates (x=SLS, y=SSPC) for each analysis, and it generates a Dot Diagram like this. I’ll cover how to evaluate the results in a future Episode, but basically, by tracking the movement of these dots, you can see whether the melt quality is improving or degrading. This allows for scientific selection of ingots and flux, as well as optimization of flux quantities and processing methods. Even if you're sourcing lower-cost materials, this tool helps you identify which options are least likely to cause defects."

"SLS and SSPC are proprietary metrics. SLS relates to 'Local Solidification Time,' while SSPC relates to 'Supercooling.' If the theory sounds complex, don't worry. Just use the free Python program to input the numbers, and it will plot this graph for you. It runs on smartphones and tablets, so feel free to customize and use it however you like!"

"Every melt can be mapped into these zones. The ideal target zone depends on your alloy composition, gating design, equipment, and casting parameters.

So... where does your melt fall?"

Kanae: "Shall we head to the shop floor?"
Yamasaki: "Ms. Kanae, thank you for the fascinating insights. Please proceed with the plan. I'll leave the rest in the Chief and Nagisa's hands."

Episode 4 On-site demonstration

Minato: "So, what exactly are you gonna do?"
Nagisa: "Chief, never mind that. Just move the skimming tool, please."

Nagisa: "So, this is the 'Leibniz' Thermal Analyzer!!"
Minato: "I moved the tools."
Nagisa: "Good job, Chief! You're very handy today."
Kanae: "Anyway... I'll just plug into this 220-240V outlet. I'm connecting the thermocouple cable to the built-in temp controller... and placing the sampling cup on the stand."

Kanae: "This melt was treated with your standard amount of flux, correct? Alright, pouring the melt into the cup now..."

Kanae: "The trick to high accuracy is to pour in one smooth motion—don't hesitate—and let it overflow. Then, cover it with a pail to shield it from the wind and ambient temperature. This ensures consistent results, whether it's summer or winter."

5 minutes later

Nagisa: "So, what's the verdict?"
Kanae: "Just as I suspected, the melt is dirty. I could tell just by how the melt reacted when I moved the ladle through the crucible, but the oxide levels are high. There are actually two types of oxides, but I'll explain that another time. The cause is either insufficient flux, or the flux itself isn't working. Shall we try adding more flux, treating it, and measuring again? If the results get worse after that, it means this flux is ineffective."

Re-analysis after re-treatment

5 minutes later

Kanae: "I hope you don't take this the wrong way, but your flux might be ineffective—or simply the wrong type. It relates to those 'two oxide types' I mentioned. If the flux were working, it would remove the harmful oxides, so this number would be lower. Meanwhile, it would enhance the nucleation sites, making that one higher. If you had zero defects, it wouldn't matter. But since you do, they won't go away unless we fix this. Looking at these numbers... aren't you seeing gas defects and misruns? It also suggests internal residual stress, so... deformation after machining?"

Minato: "You can figure that out from just this?"
Kanae: "Yes. Plotting the values on the SLS-SSPC matrix reveals it all."

カナエ：「先ほど会議室で見ていただいた、これです．それから．．．」

Kanae: "It's common knowledge that sodium-based fluxes shorten the lifespan of crucibles and furnaces. I'll spare you the technical details for now, but they actually leave traces in the melt, too. We’re seeing a characteristic curve here that indicates exactly that. This means the Silicon is being affected... which implies your tensile strength is likely being compromised."

Episode 5 Solutions

Kanae: "I actually brought our own flux and flux feeder today. Ours is highly effective, with none of those harmful side effects. So, let's treat the melt with this and analyze it again in the same way."

To be continued…

Coming Up Next
Flux Selection and Optimal Addition Rates
The Difference Between "Settling" and "Holding"
Ingot Selection Strategy
Understanding the K-Mold Fracture Test
Effective Use of Ti-B Grain Refiners
Rotary Degassing Equipment
Degassing Units with Integrated Flux Feeders
Reduced Pressure Test (RPT) Equipment
Fluidity Testing Equipment
SEM Analysis and Mechanical Property Testing
Producing High-Quality Castings Using 100% Returns via Thermal Analysis

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