motorcycle rear axle 2

[dracer]

i have been using 4140 and 4340 materials in 30 mm diameter
and they consistently bend and the bearing is trying to push through the shaft. I have built one now from en30b
but have yet to use it. Will this work in its raw state or would some heat treating improve it for this application?

 

[NickE]

What are you hardening the 4xxx series steels to?
nick

 

[dracer]

after some investigation turns out the material was a core from some 4xxx type We didn't know it would be softer than
the od it came from. apparently a core cut from en30b does not suffer the same losses strength wise. True?
thanks for any help

 

[NickE]

That all depends on how the steel is heat treated. 4340 will through harden in thicker section size than 4140.

What hardness was the 4xxx alloy you tried? What hardness is the En30b?

nick

 

[Metalguy]

NickE is right on target. I can only add that given the probable safety concerns, I'd be inclined to use an axle made by someone/company who is very familiar with steels and their properties. There are a lot of variables to be considered. It's something like amateur gunsmithing-very high risk because something quite basic just wasn't known/applied.

 

[dracer]

you are correct, normally i buy from a known reputable source. this product came as a gift with the assurance of what it was supposed to be.
I am currently having the two pieces hardness tested.
I will post those numbers when I have them

 

[dracer]

well the en30b has rockwell of 34. The supposed core from some 4xxx material does not read any rockwell number, some insignificant brunnell # though. thanks for the assistance and lesson learned for me. I am sure the en30b will be fine
If i bend that Oh well try something else

 

[NickE]

If thats the way you want to do this and put your life in some unknown persons hands then feel free. Personally here are some reccommendations.

1. Contact a reliable supplier of axles, ask what they use.

2. Dont use the en30b. Looking up on my quick reference gives a UTS of aprox. 150ksi. not at all that strong for a steel alloy.

3. brinnel hardness is often times better than rockwell due to the larger indent. What was the brinnel hardness?

4. 4340 is a very strong steel, used for all kinds of high load high fatigue parts. Doing a little research on en30b I think (and YMMV) that the 4340 is a better choice for this application. here's why: Higher nominal carbon and higher nominal Mn will allow the hardenability to be better providing a fully through hardened axel.


nick

ps: to the rest of the mets out there:

What does the additional ~3%Ni do for en30b, seems that I remember that Ni is an austenite stabilizer and aids corrosion resistance, I didn't think that it aided hardening, in fact quite the opposite.

 

[metengr]

Nick;
The added nickel in this alloy will promote low temperature toughness, and as you mentioned, it will be an austenite stabilizer resulting in deeper hardening capacity because of the affect on the martensite start temperature during heat treatment.

I did locate some information on En30b, as well. The source (Wilkinson Steel and Metals, Western Canada)indicated a comparable heat treatment to AISI Type 4340; see below (Q&T data from their spec sheet);

en30b (Nickel, chrom, moly) AISI 4340
UTS 160 ksi UTS 160 ksi
YS 135 ksi YS 135 ksi
Elong 13% Elong 11%
RA 50% RA 30%
Hardness 321-363 HBN Hardness 320-350 HBN

 

[unclesyd]

Aside from the afore mentioned improvements achieved by the addition of Ni it lowers the critical temperature widening the range for a simplified and successful HT. This lowering of the CT in turn less the severity of th quench needed after Austinizing which in turn lessens the distortion.
The properties achieved allows a successful HT by most any shop without the need for special equipment. The addition of Ni makes a steel especially suitable for carburizing.
The addition of Ni also allows the production of high strength levels without the addition additional carbon. This in turn permits high strength levels in welded structures as there is lower carbon. Everyone knows of the 9% Ni steels.

Taken from Modern Steel and Their Properties by Bethlehem Steel.

 

[NickE]

Thanks guys for the info and a star to each....

 

[dracer]

thanks metengr
the specs fall in line with my sources here.
they tell me the 321-363HBN of the en 30b is RC 35-39
the 4340 320-350HBN is RC 34-37
so the en30B core I had tested that comes in at RC 34 I'm sure will do the job