Passenger cars, light trucks, and even larger trucks use gray cast iron for the clutch pressure plates. A typical alloy is a lamellar pearlitic gray iron like G11H20b according to SAE J431a. Here is an excerpt from SAE J431:
G11H20b (formerly G3500b)
Brake drums and clutch plates for heavy-duty service where high carbon and high hardness are both required to minimize heat checking and provide higher strength.
Sorry about that, I was just trying to be precise with the specific grade of gray cast iron typically used. I realize you are extremely knowledgeable on automotive materials, etc. It is my understanding that essentially all high volume automotive applications use cast iron pressure plates, but I am not completely familiar with what our competitors do.
Glad, that this thread has been resurrected. I wanted to add CG irons and also that in some military vehicles, I have seen alloy steel plates being used. Though gray iron was always considered as candidate material for this application.
Yes, Arunmrao, steel plate is where I seem to be heading, as my client (gratis) does not have the wherewithal for even a small production run of castings. Based on availability, 4140 and 1144 seem to be the main candidates. Another possibility might be some sort of flame spray coating on a 50ksi HSLA steel ring or even a T-1 ring.
Is the clutch assy for an automatic or manual transmission? AT clutch plates are usually wrought steel, not cast iron.
Since clutches are usually sized based on heat loads, your particular pressure plate material selection will need to take into account the surface temperatures that the pressure plate will experience during operation. The material and heat treatment should have adequate margins for safe operation at those temps combined with any mechanical loads.
Before you select a material, I'd suggest a quick thermal analysis. Estimating the input heat loads at the friction interface is fairly straightforward. The more difficult part is the heat transfer rate away from that surface, through the pressure plate structure, and into whatever local atmosphere it's operating in.
Thanks, Terry. Application is manual transmission and this is basically a reverse engineering job. Original piece (which the OEM has discontinued)is a steel forging, and I plan to mimic it as much as possible using a part fab'ed from steel plate. As the production quantities will be small, my client does not have the deep pockets to procure forgings or castings.
