SS304 as brake disk material 7

[Rantty]

Hello guys,
Can ss304 be used to manufacture brake disks for cars? What is the current standard used while manufacturing disk brakes? What are the chemical treatments and hardening processes that can be carried out on ss304 which will improve its characteristics as a brake disk material? What are the advantages and disadvantages for the same?

 

[CoryPad]

Stainless steel type 304 is one of the worst options for a brake disk (also known as a rotor). It has low strength, high density, tendency to gall during wear, and low thermal conductivity.

The standard for high volume automobile applications is gray iron according to custom standards created by each automobile manufacturer.

I suppose nitriding of the stainless steel could be done to improve the wear resistance (nitriding is used for gray iron rotors). It still would be a poor rotor.

 

[EdStainless]

If you need corrosion resistance I would look at an alloyed cast iron.
Remember that today high performance rotors are made from ceramic.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Rantty]

I have actually been given a task to find out how ss304 could be used as a disk brake material. Will any hardening process help the case?

 

[FennLane]

What kind of vehicle?

Motorcycles and bicycles commonly use a stainless steel but they don't need the same heat capacity as those required for automobiles.

I would also think that ferritic stainless steels may be more suitable than Austenitic grades which also work harden significantly.

The CoE is also lower and this needs to be considered in terms of the hub/rotor connection

 

[SnTMan]

Rantty, in general austenitic SS cannot be hardened by heat treat, usually only by cold-work.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[tbuelna]

"Can ss304 be used to manufacture brake disks for cars?" Yes it could be used as an automotive disc brake rotor material, in theory.

"What are the advantages and disadvantages for the same?" I can't think of a single advantage over existing automotive brake rotor materials, and I can think of numerous disadvantages.

Corrosion resistance is not normally a concern with automotive brake rotors. Given the combined requirements of production cost, manufacturability of a vented brake rotor, durability/wear, performance, etc, some type of cast iron is usually best. The added raw material cost alone from using 304 rather than cast iron would likely triple the price of the brake rotor, while providing no benefit.

 

[Rantty]

Could you name some cold working processes that could be used? The vehicle under consideration is a college race car which we build from scratch. Maximum speed it can achieve is around 150 kph. The car uses a ktm duke 390s engine.

 

[tbuelna]

OK. So this is a Formula SAE project, right? The best approach would be to purchase an off-the-shelf brake rotor from someone like Wilwood and machine it to fit your vehicle. You can do your analysis once you figure out what material the Wilwood rotor is made of.

 

[SnTMan]

Rantty, any process that reduces the cross section, such as drawing thru a die. Probably rolling a flat plate to reduce thickness would give some hardening.

I tend to agree with the others, you might find a worse material for a brake rotor than 304, but it would not be easy.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[MintJulep]

Just use the rear rotors from any small car.

Fiat 500, VW Golf, Mini, Scion, etc.

 

[swall]

As the others have noted, an off the shelf cast iron rotor would be the "no brainer" choice. Barring that, I have seen plain carbon steel plate (A-36) brake rotors in off road construction equipment. However, if I were going to use steel plate, I would go for a free machining plate like Freemax 45 or E-Z-Cut 45. These are resulfurized medium carbon steels. In my experience, a resulfurized steel will exhibit better galling resistance than plain carbon steel. Google is your friend--should be able to find the free machining steel plate at various service centers. Some may also have water jet, flame, or plasma cutting services to rough fabricate a disc form for you.

 

[EdStainless]

I have seen disc rotors on equipment (not vehicles) that were in bad environments use 410SS for rotors. You can find 410 that has enough carbon to give it strength, but not enough to really make it hardenable (sort of between ferritic and martensitic). Still not a great choice.

In order to use 304 it would need to be hard, like sheet that had been rolled to 3/4 hard or so. I would still expect galling and thermal fatigue cracking (too high of CTE and too low of thermal conductivity).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Tmoose]

These fairly reputable guys claim to use some flavor of stainless for some kind of motorcycle

http://ebcbrakes.com/product/stainless-steel-rear-brake-rotors/

Similarly Wilwood offers "stainless steel" rotors for Harley Davidsons.

http://www.jegs.com/p/Wilwood/Wilwood-Stainless-Steel-Motorcycle-Brake-Rotors/2385068/10002/-1

 

[Rantty]

Thank you guys for your help

 

[EdStainless]

Tmoose, I'll bet that they are 409/410. Notice that they are heat treated, that rules out an austenitic.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube