approximate expected hardness profile 12" diameter normalized 1045 2

[Tmoose]

A supplier's rep has raised objections to a minimum hardness requirement (150 BHN) on a 12 inch diameter bar of 1045 turned down to about 4 inch diameter. Their wording is awkward as right off the bat it seems to claim we require EQUAL hardness, not minimum.

At any rate, does anyone know of sources for information about hardness profiles generally achieved or realistically acheivable on large normalized bars?

thanks

Dan T

 

[mfgenggear]

Tmoose

I use practical data for metallurgist
it can be down loaded for free from Timken

look at page 45,Harden ability chart for 1045

Mfgenggear

 

[redpicker]

You need to find out why your supplier has an objection. My guess is that they feel that they cannot control the hardness and cannot agree to a requirement that they cannot control. That is, while a hardness of 1045 is most certainly going to be greater than 150 HBW, if, for whatever reason, the hardness was not up to specification, what could they do?

You are either going to have to accept the risk yourself, or pay to have the material tested and agree with the supplier that the results of those tests will qualify the material hardness.

In reality, there is not much risk. If the chemistry is correct, and you have normalized material (not annealed), then you should be well above 150 HBW. That is, if you had to meet a 150 HBW maximum hardness, I doubt you could get them to agree to that, either. But, from your supplier's position, why should they accept the risk for something they cannot control?

If I needed to mitigate any risk, I think I would ask for surface hardness (they should be able to provide that at a minimal cost) and if it at least 187, have a mid-radius hardness and accept the material if it was 163 HBW or higher. The hardness should not change much from a 6" diameter to a 4" diameter, and it is pretty hard to mess up those instructions.

rp

 

[mfgenggear]

Redpicker

According to the Timken harden ability charts the hardness changes rapidly.

please see link below.

http://www.timken.com/en-us/Knowledge/engineers/handbook/Pages/default.aspx

I would turn the bar near net size then would heat treat to the required hardness.
6" to 4" the hardness will change. then finish machine.
or am I viewing the charts wrong.

your comments appreciated

Mfgenggear

 

[mfgenggear]

correction it is on page 68 on the on line version, it has been up dated.

Mfgenggear

 

[redpicker]

I believe you are looking at Jominy end quench data, where the end of the bar received an ideal quench. The data on the right hand side (top?, the page is sideways in the pdf) gives air cooling data, which shows little variation in hardness when air cooled. From about a 2" round to a 15 inch round, the hardness changes from 90 HRB to about 88 HRB (according to the chart). Roughly speaking, that's 180 to 170 HBW. While my initial guestimate of 187 on the surface may seem a bit high, it it meets that requirement, I don't think there would be much problem meeting a 150 minimum anywhere on the bar. You could probably drop that to 175 and still be OK, based on Timken's data, but like I said above, that would be risk that the purchaser is going to have to assume.

My concern would be on internal soundness of such a large bar. How is it produced? What is the reduction ratio from ingot? Carving a 12" bar down to 4 inches is pretty drastic and the center is likely to have shrinkage voids, discontinuities, and other imperfections that could cause problems; 4 inch diameter is only two inches from the center, and that's pretty close. If it's a forged bar from a 36 inch ingot, you're probably OK, but a rolled bar from a 20 inch ingot is likely to have issues. Whether or not these soundness issues would affect the performance, I have no idea (no info on the application).

rp

 

[Tmoose]

I believe (suspected) the requirement for good material properties in the 3.5 inch diameter drive section may have been what prompted the choice of "normalized" material. The Timken info ( they actually have provided some of the bars) seems to confirm the choice.

thanks for all your inputs

Dan T