History Factory storing castings outside to "age"

I worked at the Ford Engine Plant back in the 60s. I heard about the "seasoning" of flathead blocks many times.
And I remember an Indy car with a super high mileage SBC out of a schoolbus.

 

An iron casting poured in a sand moldis going to have some "locked in stresses". The sand moldis madeusing sand mixed with clay and has some watercontent. The sand is then faced with a carbon dust (typically, powdered soft coal) to try to keep the sand from vitrifiying (fusing to glass) at the surfaces of the mold cotnacted by the molten iron. Nevertheless, when the molten iron gets near the sand moldsurfaces, there is alocalized rapid cooling. This produces a stressed and somewhat harder "skin" on iron castings poured in sand molds. When the castings are machined, if portions of the skin ar eleft intact while other portions are machined off, there is bound to be some "settling out" due to the stressed portions of the skin becoming partially untrestrained due to the machining.

The term "Seasoned Iron Castings" was used in advertising for machine tools and auto engines. Years ago, on a job out in Ohio, I rented a house from an oldtimer who had worked for Willys-OverlandMotor Company. The oldtimer had worked for Willys-Overlandin the 1920's and 1930's, mostly delivering new cars. What he did tell me was that Willys-Overlandalways had huge stacks of iron castings outdoors "seasoning". Willys, it seemed, had taken over several other smaller automakers. I think Hupmobile may have been one of them. In taking over the other automakers, Willys got piles of rough castings which they left stacked outdoors until they could figure out what to do with them. Some of the piles of castings went into engine series that Willys based on some other makers' block designs. By that point, the castings had been outdoors for several years. They found the castings machined a lot easier than "green castings" fresh from the foundry. As it was, Willys and the other automakers in that era did not make significant changes to the engines from one model year to the next, using the same basic block and head castings. The castings would be poured, cleaned and snagged ( sprues, gates and risers ground off). The castings would then be stacked outdoors and left there for at least a year. The weather did the rest. The oldtimer told me the belief was that repeated freeze/warming cycles plus the changes of the seasons would make for high mileage engines. In the 1920's or 1930's anyone who got near 100,000 miles on an automobile engine without a rebuild including a rebore of the cylinders thought that was remarkable. It could well be that the automakers' advertising departments figured to get some mileage out of the fact that the engine castings were left outdoors for a year or two by hyping the business of "seasoned iron castings". This was the 1920's and the public was a lot more familiar with seasoning of wood, so could relate to the business of "seasoning" engine blockcastings. People passing the auto plants saw the castings stacked like so much cordwood and began to wonder about buying a car with an engine made from rusted old castings. Advertising the outdoor storage of engine castings as "outdoor seasoning" made for good advertising. Remember, this was an era when the US was a manufacturing nation. The public in general had a bit more knowledge of how things were made and took some interest in it. Look at ads for that time period for cars- things like "Tocco Hardened Cranksahft Journals" or "Superfinished surfaces" or "Seasoned Iron Castings" were the kind of things that were advertised to consumers.

At Brooklyn technical High School in the 1960's, we had machine shop teachers who had come through their time as toolmakers or machinists in industry. These guys had been around some before they settled down to teaching us kids. They told us that time along with the seasoning of iron castings or any other precsion parts was a necessity to get dimensional stability. They kidded about, telling us that to make things like "Jo" blocks and similar, it was necessary to "get the molecules to nearly stop moving around". The way this happened was to let things "season" using time and thermal cycling. Some of the teachers told us when they were apprentices or young toolmakers, they had made their own 1-2-3 blocks, sine bars, and similar. In so doing, they left the parts out on window sills in winter weather for days or weeks, letting the freeze/warming cycling do its work.

Within the last couple of years, I was talking with Mr. Robert Yancey out at Yancey Machine Tool. Mr. Yanceyhas been around heavy machine tools and heavy machine toolbuilding for many years. We were discussing the building of heavy precision machine tools. We shared the view that the best way to insure accuracy and rigidity in a machine tool isto use properly designed massive iron castings. I mentioned that the older machine toolbuilders had specified that they used "seasoned iron castings". Mr. Yanceysaid the effectiveness of "seasoning" iron castings to get dimensional stability was debatable. He held that if iron castings are proplery designed and then properly cooled, the outdoor seasoning may not really be what makes the casting so stable. He felt that automobile makers had started the idea of "seasoning" castings simply by having to store enough castings outdoors for a production run. At that time, as Mr. Yanceypointed out, the methods of cleaning castings were not what they are today. In addition, castings came from the foundry with a kind of harder "skin" where the iron had solidified against the damp molding sand. This skin also held some additional stresses. Letting the castings sit outdoors in the weather for a year or two also let some rusting of this skin occur. This rusting tended to get partially through the skin, letting the stresses in the skin relieve over much more of the surfaces of the castign than would have occurred through machining only slected areas. The other idea was that the rusting got through the harder skin,making for easier machining.

My own sense of the things is that the best dimensionally stable castings are the ones which have been outdoor seasoned for a couple of years. During WWII, machine toolbuilders were cranking out machine tools from what amounted to "green castings"- castings that had been poured only days or weeks earlier. Those machine tools went into use and held close tolerances. That would seem to blow the theory that "outdoor seasoning" of iron castings was a necessity for dimensional stability. Perhaps, with machine toolcastings needed as fast as possible, these castings were put into a "soaking" furnace and brought back up to heat and allowed to normalize by slow/furnace cooling. This would achieve a similar result to the "outdoor seasoning". However, these same machine tools built during the WWII era simply had more massive castings to start with, so dimensional stability was easier to maintain.
from http://www.practicalmachinist.com/vb/general-archive/seasoning-cast-iron-87355/ ...

 

Bill Jenkins liked used / old truck blocks that had around 100,000.0 miles on
em , seasoned blocks did not move around like new GREEN ones.

 

I worked for a Diesel engine manufacturer for my career.

The factory yard had stacks of thousands of crankcase castings in the yard "seasoning" in the late Seventies when I started my career. The seasoning was a primitive, low cost of stress relieving the castings by alternatively heating and cooling the casting with the natural weather change.

Later, there was a lot of engineering structural and stress analysis done to understand and control the residual stresses induced in the casting and cooling process. Understanding the stresses lead to design changes that reduced the residual stresses in the castings such that the blocks didn't benefit from being "seasoned "in the yard prior to machining.

Big cost reduction from not having to carry all than unfinished inventory on the books.

 

In the 80s I beleive it was bracket racer David Rampy that was quoted in an article that he cured all of his bolcks out back. Neat article I will have to dig it up.

 

Yes the stories about Ford blocks, but nothing that can be backed up by actual facts ?

 

....I bet they PAID A LOT FOR THAT 1000 HORSEPOWER ,.....( also bet they wish it was given to them!....at least it's not a belly button sb Chevy!...

 

My Father worked for Hudson Motors in Detroit in the 40's and 50's and he told me of engine block castings being left out in the weather before being machined.

 

I was of the belief that castings were aged out in the foundry yard to subject them to temperature cycling to reduce the stresses from the actual casting process, no actual stress relieving was undertaken but the seasoning took place at normal outside temperatures. I'm not a metallurgist but technology has come a long way since then.

 

Wouldn't that be similar to a Top Fuel engine making 10K horsepower? Of course, F1 engines have to make it more than an eighth of a mile.

 

Until fairly recently, it was common practice to fill a mainframe casting for cone crushers with every pallet and wood scrap that could be found, light it up and let it normalize back to ambient temperatures for a week or so then check tolerances and adjust/remachine before even thinking about assembly. The old timers call that process "seasoning".