Hard spot in cast iron

[AndySomogyi]

Yes, carbon content can be quite variable in cast iron, and it can create localized hard spots. We are spoiled by working with crucible steels today for a lot of our projects, which have better control and distribution of carbon and other elements. This tends to make us surprised when we learn the uneven distribution which can be found with Cast Iron. I run across this in antique Tamahagane steel Japanese swords quite frequently.

Yes, I think carbon and alloy content could be super variable.

I’ve only found one small void on this mill, and it’s on the side, not a bearing surface. Overall, the quality of this casting seems surprisingly decent, definitely WAY less porosity and irregularities than my 1950s Clausing lathe.

 

[rwm]

This is a well known casting issue. It is called "chill." Areas of cast iron that cool too rapidly can become as hard as tool steel and appear white. There is a lot of research into this if you google it.

White cast iron​

White cast iron is formed when, on solidification, carbon in solution is not able to form graphite. White cast irons are hard and brittle; they cannot easily be machined. White cast iron is unique in that it is the only member of the cast iron family in which carbon is present only as carbide. Due to the absence of graphite, it has a light appearance. White cast iron has high compressive strength and retains good hardness and strength at a higher temperature. The presence of different carbides, depending on the alloy content, makes white cast irons extremely hard and abrasion resistant but very brittle. An improved form of white cast iron is the chilled cast iron, discussed further in this chapter.

Robert

 

[Larry$]

My first new car was a Corvette with a 327-240hp engine. It consumed oil at the rate of 1 qt. for every fill of gas from the day it was new. It fouled the plugs in less than a week. Many trips to two different dealers got all sorts of superficial things done, to no avail. Finally after being told I couldn't see inside the engine while they had the heads off, I went around back. Talked to the mechanic and he showed me what the problem was. Shinny hard somethings imbedded in the cast iron cylinders. Each one formed a bump that caused the rings to gap and leak oil. I finally got a face to face meeting with a factory rep. He told me that GM would never replace a block, no matter what. POS!

 

[AndySomogyi]

My first new car was a Corvette with a 327-240hp engine. It consumed oil at the rate of 1 qt. for every fill of gas from the day it was new. It fouled the plugs in less than a week. Many trips to two different dealers got all sorts of superficial things done, to no avail. Finally after being told I couldn't see inside the engine while they had the heads off, I went around back. Talked to the mechanic and he showed me what the problem was. Shinny hard somethings imbedded in the cast iron cylinders. Each one formed a bump that caused the rings to gap and leak oil. I finally got a face to face meeting with a factory rep. He told me that GM would never replace a block, no matter what. POS!

Wow, seriously GM wouldn’t replace the block ?!?!? That’s crazy.

We had a similar issue with our Honda, at 75,000 mi, started burning oil, turns out some had a bad batch of piston rings. At 75,000 mi, out of warranty, Honda replaced the engine no problem.

 

[Larry$]

Andy, My family has been driving Hondas for quite some time. Way better than the GM cars. Wife recently got a Subaru, nice car, will see how it holds up.

 

[AndySomogyi]

Andy, My family has been driving Hondas for quite some time. Way better than the GM cars. Wife recently got a Subaru, nice car, will see how it holds up.

GM does make some good engines like the LS. I’m actually swapping a built Subaru N/A 2.5 into my 76 Porsche 912 (originally came with a VW bus engine.)

Andy, My family has been driving Hondas for quite some time. Way better than the GM cars. Wife recently got a Subaru, nice car, will see how it holds up.

GM does make some good engines like the LS.

I’m actually swapping a built N/A Subaru 2.5 into my 76 Porsche 912 (originally came with a VW bus engine )

That’s why I need to finish rebuilding my stupid mill: so I can get back to making car parts.

 

[ericc]

Is there any way to soften the hard spot using friction?

 

[AndySomogyi]

Is there any way to soften the hard spot using friction?

I’m pretty sure it’s a slag inclusion.

As I was scraping, every time I’d touch this spot, I hit it with a diamond bit in the Dremel, so it’s all good now.

As it’s a slag inclusion, impossible to soften it, only way to deal with it is a diamond bit, or chipping it out. Was smaller than I thought, only about 1/8 so no big deal


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[Richard King 2]

One of my students last week in the class had a Keith Rucker SE and it had a hard spot. I pulled out my small Dremel hand grinder and he ground it down below the surface. I suspect it was due to heat treating as it was on a narrow edge. I have seen first hand where a foundry mixes steel Allen Caps screws in his recipe or a filler. My OLD foundry did that and a customer dam near broke his clapper box on his planner when he hit it.
I called the owner of the foundry and he acted like it was normal and refused to pay or male a anew one.. I went and got my patterns and now have another foundry. I have also seen lousy castings in those cheap machines . Bad design and bad everything. You get what you pay for.

 

[rwm]

I’m pretty sure it’s a slag inclusion.

As I was scraping, every time I’d touch this spot, I hit it with a diamond bit in the Dremel, so it’s all good now.

As it’s a slag inclusion, impossible to soften it, only way to deal with it is a diamond bit, or chipping it out. Was smaller than I thought, only about 1/8 so no big deal


Sent from my iPhone using Tapatalk Pro

It could be a slag inclusion also. But a chilled area in the iron is way more technically interesting...
Robert