ASTM A 290 X ASTM A 291

[ibf]

Hello :

ASTM A 291 establishes either a diameter or thickness range for the mechanical properties on table 3 for the different classes of steel.
However , ASTM A 290 doesn`t.

Question : For what thickness and/or diameter range can I use the mechanical properties of ASTM A290 - table 3 ?

Thank you.

 

[metengr]

ibf;
I reviewed both ASTM Specifications (earlier editions, because I have immediate access to them). ASTM A290 applies to rings (a product form) that are either forged or rolled. In this case, thickness or diameter limitations are not applicable for tensile and impact property test requirements in Table 3.

Further review of Table 3 in ASTM A290 provides Brinell Hardness ranges for each class of steel. Brinell Hardness testing is required (7.2), and further into this subparagraph indicates the number and location of Brinell Hardness tests based on forging or rolled ring OD.

 

[ibf]

Thanks metengr.

Does it mean that regardless the thickness of my forging , I can only estimate mechanical properties through the HB figures ?

 

[metengr]

ibf;
Mechanical tests of the forged or ring material are required in addition to hardness testing, in accordance with Table 3. There is no estimating of mechanical properties. The hardness testing is a validation of heat treatment.

 

[ibf]

Understood.

Thanks.

 

[ibf]

MORE QUESTIONS ON THAT THREAD :

A. Am I correct if I say that the only difference between the 2 Stds. is that 290 applies for ring forgings only ?

B. And if the above-mentioned question is true , what would be the difference in designing a forging based on the technical attributes of either one or the other ?

Is there any violation in designing a ring forge as per 291 ?

 

[metengr]

ibf;
I have one basic question for you, what exactly are you designing for using A290 or A 291?

ASTM A290-02 Standard Specification for Carbon and Alloy Steel Forgings for Rings for Reduction Gears

A291/A291M-05 Standard Specification for Steel Forgings, Carbon and Alloy, for Pinions, Gears and Shafts for Reduction Gears

The above titles are very specific and to me should answer your question(s).

 

[ibf]

Answer : GEARS !

 

[metengr]

ibf;
Ok. If you are replacing ring gears in reduction gear cases, stick with ASTM A290, period. You really can do what you want, but if it was up to me I would use the specifications as intended. For pinion gears and bevel gear shafts, I would stick with ASTM A291. These specifications were developed for optimum gear performance.

 

[ibf]

O.K - THANKS again metengr.

 

[kenvlach]

ASTM A291 Table 3 gives an indication of the hardenabilities & toughnesses of the different alloy chemistries when given standard Q&T (except cheapo A & B grades are only normalized & T).

Now note the correlation between chemistries in Table 1 of each spec. So, first design the small diameter Pinions, Gears and Shafts per A291, then choose a matching alloy in Table 1 of A290 for the large diameter ring gear. This is merely a shortcut or guide; you still need to do the calculations to confirm. But can maybe save money on raw using the same material & avoid error by using the same temperature heat treatment.

 

[ibf]

THANK YOU VERY MUCH kenvlach

 

[metengr]

This is merely a shortcut or guide; you still need to do the calculations to confirm.

I would partially agree with kenvlach, but have a ME in gear design double check. The last thing you want is to have a ring gear fail in service because you decided to cut cost.

 

[kenvlach]

I suspect that ASTM intentionally used letter grades A-T in A290 and number grades 1-9 in A291 in order to force some thought processes. Possibly, A290 Classes M & P match well with A291 Class 8; likewise, Class T with Class 9. But, the ASTM committee forces some thinking in order to handle the exceptional cases. Also, one has the option to make the more easily replaced part of an assembly somewhat softer to save on eventual maintainance.