Suitable replacement for AISI 8650 1

[billthebutcher]

Hey guys/girls,

I'm having trouble procuring 8650 steel for an item that my company makes, which is a very high-stress part. Not being terribly knowledgeable about materials, is there a suitable replacement for this material? I would prefer to err on the side of caution and substitute a stronger material, if possible.

The item was designed in the 1950s. Was 8650 in more common use at that time? Is there a better material now?

Thanks,
Bill

 

[swall]

What is the configuration/section size of your part? What hardness level are you working to? What is the production volume of your parts? These things all make a difference in both steel procurement and selection.

 

[billthebutcher]

swall:

The part is about 7" long and 1/2" tall. For most of its length it is .200" thick, with the front 1" being .600" thick. So, it is a long, skinny part.

The front 1-1/2" gets through-hardened to around 55 Rockwell C. The remaining 5-1/2" gets through-hardened to around 45 Rockwell C.

The production volume is variable, but let's assume it is around 1,000 parts a year.

 

[swall]

SAE 5160 would work, as would SAE 4150. Would you be purchasing rectangular bars? And also, how are you hardening to two different hardness levels?

 

[billthebutcher]

swall:

Rectangular bars or round bars would both be options. I'm not sure how the the 2 different hardnesses would be attained.

Out of curiosity, how did you determine that 5160 or 4150 would work?

Thanks,
Bill

 

[swall]

You start with the desired hardness and the section size you are working with. Then, you look at what alloys will work, based on carbon content (gets you the hardness) and jominy hardenability (this insures that your section size will fully harden). Take a look at the FAQ I wrote for SAE 4140 steel to see how this works. Then you consider availability. With your low volumes, you are looking at grades readily available from a warehouse and both 5160 and 4150 are relatively common grades.

 

[billthebutcher]

Thank you for the insight swall. Much appreciated.

 

[billthebutcher]

And good FAQ by the way.