52100 Steel Billet Diesel Pistons ????
52100 Steel Billet Diesel Pistons ????
(OP)
Hello, I am currently working on a project with a direct injected common rail diesel engine. I build many diesel racing engines, (drag, truck-tractor pull, etc...). With that being said I want to build a very high output street able engine. My problem is the pistons, cast pistons can't hold the extreme pressures and heat, and forged pistons wear the ring lands out in 15 to 20 thousand miles. Budget is also a major concern. I was wanting to machine a piston from an existing steel forging but none are readily available without a major order. Which leads me to a billet piece that I can machine then heat treat. I was thinking of 52100 steel for my billets, mainly due to its hardness (after treat) and its ability to hold (treat) under high short burst temperatures. I currently use this material for rocker arm and other high stress parts in my engines. My questions are about the thermal expansion of 52100 with various thicknesses (I.E. bore clearance)? Also its ability to run against a compacted graphite (iron) cylinder wall? I feel very good about the design, the pin bore, and ring lands holding tolerance for many cycles with no issues. I have attached a picture of what I'm wanting to build. The pic is a forged piston from a major diesel manufacturer. I am not worried about the weight difference between the cast aluminum and the steel piston. Thanks for any help and I'm open to all suggestions (good and bad).





RE: 52100 Steel Billet Diesel Pistons ????
RE: 52100 Steel Billet Diesel Pistons ????
I am thinking of H13, 19, 21 and so on.
They are not as hard, but they retain very good hot strength, resist thermal fatigue and are tough.
The Mo, W, and Co (depending on the grade) will all improve hot properties.
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Plymouth Tube
RE: 52100 Steel Billet Diesel Pistons ????
(EdStainless) The wrist pins are possibly going to be made from H-21. Very good material (I hope) and finding 10 pcs at 4.25" dia and 4.5" length is another issue in my area. With that said I will check on the availibilty and the expansion rate.
Thank You guys for the Info,
additional comments welcome
RE: 52100 Steel Billet Diesel Pistons ????
RE: 52100 Steel Billet Diesel Pistons ????
To make a better choice of materials, you will need to define the required properties, then a manufacturing process that satisfies the economics of your situation. Off-hand, I'd say the properties you'd want to consider
1) hardness
2) fatigue strength
3) density
4) coefficient of thermal expansion (CTE)
5) toughness
6) temperature resistance
You don't need exact values for these properties, but at least some idea of what is needed. For example, the fatigue strength needs to be at least as good (probably better) than the cast materials you are trying to replace.
With this information, you can make an informed decision on material and, if the new material does not give you the performance you need, you at least have a good definition of what doesn't work.
rp
RE: 52100 Steel Billet Diesel Pistons ????
RE: 52100 Steel Billet Diesel Pistons ????
RE: 52100 Steel Billet Diesel Pistons ????
Thanks Again
RE: 52100 Steel Billet Diesel Pistons ????
HRC 50 is a good choice for keeping brittleness from being an issue but I suggest specifying it as a minimum with allowable hardness as high as HRC 54 for optimizing wear and retention of ring land strength.
My copy of Steel Selection by Manfred Suess is not here at home. He provides formulae for calculating case depth dependeng on stress levels. If you are interested, let me know and I will dig out some info on this when I get the book from my workplace.
Another thing to consider is ring land root geometry. Are these typically designed with a radius between the land and the root of the groove? I would expect this to be the weak point because of high stress intensity at this junction. Is it possible to increase the land thickess and design the root groove with a full radius? Just some thoughts.
Design for RELIABILITY, manufacturability, and maintainability
RE: 52100 Steel Billet Diesel Pistons ????
I think that your local engineering group has provided some very reasonable alloys to use as a starting point. I agree that the part should be ground after case hardening. I also concur with metman that HRC 50 should be a minimum for the case hardness.
RE: 52100 Steel Billet Diesel Pistons ????