Laser cutting aircraft brake parts... HAZ? 2

[heloman29]

My company is looking to manufacture aircraft brake parts, the part I'm discussing here is the brake rotor. The rotor has ten segments that attach to each other like jig saw pieces. When the rotor is assembled the pieces simply slide together on a table. Each rotor segment has to be cut to within +- .002". We know other companies are manufacturing aircraft brakes using laser cutting, which seems to be much cheaper than using a water jet that will hold the required tolerance. So I'm looking for ways to both minimize the effect of the HAZ and explain it away for part certification. These parts are made of AMS 6385 (17-22). I talked to one manufacturer that says they heat treat after the part is cut, but we were worried about warping if we heat treat after the part is cut (it will also be ground to the correct thickness by almost a tenth), and will heat treating in this order completly remove the affect of the HAZ? This part will be quenched, tempered and through hardened to 23 HRC. Any thought are greatly appreciated.

 

[NickE]

A full austenitize, quench, and temper should remove the HAZ completely. You definately will see dimensional changes with a full heat treat. How thick are these components in final form?

HRc 23 is not that hard. particularaly for a low alloy composition like the AMS 6385. (that took a bit of searching, spec is linked below.)

There are other types of processes that may be able to produce a good part. there are blended water/laser methods, wire edm if theyre flat (will still have HAZ's just lots smaller).

Even (if they're not too thick) stamping might be an option.

http://www.mykitplane.com/Planes/PeoplesFiles/steel spec.pdf

Nick
I love materials science!

 

[heloman29]

Thanks for the reply, they are flat, they start at about .520 and are ground down to about .460".

 

[TVP]

This grade of steel must be heat-treated after laser cutting in order to have a proper microstructure consisting of tempered martensite. Since the hardness requirement is quite low, a low-intensity quench can be used that will minimize distortion. Marquenching would be best. Using this process, grinding should be able to accommodate whatever distortion remains. Another option would be to press-quench the parts, similar to what is used for high quality clutch springs (plate-type).

 

[swall]

Heloman29--not clear to me if you are interested in making rotor segments or the rotor spiders that hold the segments. Both are typically made from 17-22AS

 

[heloman29]

This post is in regard to the rotor segments, Thanks for your interest.

 

[swall]

Rotor segments typically have slots milled in the ends, which is how they are held in the spiders. A heat affected zone on this edge will shorten milling cutter life. I used to work in the aircraft brake industry and we looked at various alternative for making segments. Ultimately, none of the processes were economically viable compared to blanking or forging. Never had any distortion issues during heat treat of the slotted segments. We were austenitizing in endothermic atmosphere and oil quenching. No salt, no marquench, no quench pressing.