×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

SS304 as brake disk material
7

SS304 as brake disk material

SS304 as brake disk material

(OP)
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?

RE: SS304 as brake disk material

2
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.

RE: SS304 as brake disk material

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

RE: SS304 as brake disk material

(OP)
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?

RE: SS304 as brake disk material

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

RE: SS304 as brake disk material

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

RE: SS304 as brake disk material

"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.

RE: SS304 as brake disk material

(OP)
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.

RE: SS304 as brake disk material

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.

RE: SS304 as brake disk material

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

RE: SS304 as brake disk material

Just use the rear rotors from any small car.

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

RE: SS304 as brake disk material

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.

RE: SS304 as brake disk material

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

RE: SS304 as brake disk material

(OP)
Thank you guys for your help :)

RE: SS304 as brake disk material

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources