master13g

very technical question here... If anyone has gone to the Darton - International website you might have read up on their Ductile Iron Sleeves. I was pretty sure that iron was worse than steel but that is just based on generic iron vs generic steel. My thoughts are this... Sure the Ductile Iron sounds great but they also clearly stated :

QUOTE :

"dissolving carbon and silicon in liquid iron decreases the freezing temperature of iron. Cast iron freezes at approximately 2,100 ° F (1,150 ° C) compared to the approximate 2,730 ° F (1,500 ° C) freezing temperature of steel. All founding characteristics are improved through this lowered freezing temperature."

Basically my thinking is this, when they say freezing temp they are saying that the state of the material is in a solid state. For instance, Mercury freezes at -38F which means that any temp above this would change it into a liquid state. Most people recognize mercury as a liquid because of this very low freezing temp.

SO, theoretically, wouldn't you want a "HIGHER" freezing temp to make sure that the surface of the material that is going to be surrounding a detonation from internal combustion would be able to withstand HIGH temps??? So therefore wouldn't you want the type of sleeve material made out of steel or something more steel based so that it doesn't melt on you or anything???? Does anyone follow my thinking here? If so, does anyone know who makes a good steel sleeve out there?

I'm not trying to Bash Darton or anything. I was actually planning to use them but I just wanted to see if anyone agrees with me or knows specifically the science behind the sleeves.

Kal

Very interesting point you have brought here. I think it's more cost efficient to manufacture iron sleeves compared to steel. Steel is a mixture of different metals and since the mixture forms a stronger metal crystal structure than just a regular Iron molecule structure that explains the higher melting point/freezing point. I would judge the reasoning behind the use of ductile iron sleeves more because it is easier to handle.

NONFLYT

I fully understand what you are asking but you have to ask "who makes steel sleeves anyway?" Besides the temp in the combustion chamber will never reach those temps. You have cool intake air coming in constantly keeping the temp in the engine manageble.

Besides the melting temperature of the metal you have to consider other aspects like wear, friction, lubrication, etc. and eventually cost. Maybe a steel sleeve could cause the Aluminum piston to gall. Just some more food for thought.

Peace

brokeHonda

[QUOTE=K20EF]have to consider other aspects like wear, friction, lubrication, etc. and eventually cost. Maybe a steel sleeve could cause the Aluminum piston to gall. Just some more food for thought.[QUOTE]

This guys on the right track. If anything, contact darton and see what they have to say about there formulation.

Propulsion

My guess is that it is always a compromise in the strength of the metals, the question is, do you want your cylinders(large surface area) to wear out a bit, or do you want your piston rings (much smaller SA) to wear out a lot?

So the metal of the cylinder walls have to be soft enough to not wear out the rings too fast and keep them sealing for millions of revolutions of the engine.

Of course this is all conjecture

master13g

Yeah, I was thinking about a lot of those different things especially like flex and vibration resistance. I found a site that has some pretty cool info :

basically Ductile Iron is twice as strong as Grey Cast iron but Steel is twice as strong as Ductile Iron.

Quoted from the site :

Material Hardness Tensile Strength Fatigue strength :

Grey cast iron 22-23 HRC 45,000 psi 30,500 psi
Ductile iron 38-40 HRC 180,000 psi 87,300 psi
Steel (SAE9254) 44-53 HRC 240,000 psi 138,600 psi

Like ductile iron, steel is not compatible with cast iron cylinder walls, so it must be coated with either chrome or moly -- or gas nitrided.

The amount of machining that’s required to finish a steel ring is far less than that which is required to finish grey cast iron or ductile iron rings, so steel rings are actually less expensive to manufacture.


Just some more tech info. This was from a site that was talking about rings though but I thought it would be related, considering my initial conjecture.