Standardization of DI Calculation for Ordering Steel 3

[MetalGuy10]

DI calculations for harden ability are useful for determining the max material thickness which will have sufficient through wall hardening. Is there a standardized DI calculation that can be place into the specifications that are used for ordering material, or does the purchaser have to specify the DI calculation method to be used in the ordering specification? (41XX), (86XX)

Using DI values would have advantages for raw material procurement and production availability. However, I have seen several methods including Grossman’s method for A255-look up tables and equations, ASM Ste-Cal software, and references to Caterpillar’s specification. The various methods do seem to have some variability. If you have ordered product using DI or have calculated DI for your customers, you comments would be appreciated.

 

[swall]

SAE J406 has a recommended method for calculating hardenabilty. My previous employer used it and all of our suppliers were on board as well. I recommend it.

 

[MetalGuy10]

Thanks for the inf0 SWALL, I gave you a star. I looked up the spec on IHS standards and the cost is about $63 for a down load.

The IHS website comments on the spec are noted below.

"Attendantly, the ability to predict hardenability from chemical composition has become increasingly important when comparing various steel grades or developing new steels for specific applications. One such procedure is described in Appendix A. Other hardenability prediction methods are available from the selected references in Section 2. However, it should be emphasized that the use of any hardenability prediction procedure does not preclude the importance of conducting Jominy end-quench tests to determine the actual hardenability of any specific grade of steel."

Did you use Appendix A, for estimation based on chemical comosition?

 

[swall]

Yes, Appendix A. It was part of our incoming QC inspection on steel coming into the plant.

 

[steelmtllrgst]

As a supplier, we have to work to DI calculations per the customer's specification. Not very fun as different calculations are preferred by different customers.

Agree it would be nice if the "standards were more standardized", if that makes any sense at all...

 

[MetalGuy10]

Thanks, steelmtllrgst

I agree with you comments, "Agree it would be nice if the "standards were more standardized", if that makes any sense at all... ". So I gave you a Star!

I understand your frustration; in a former life, I worked in the specifications department at a steel mill that made flat roll and erw pipe. Many customers had their own specs which often was a regurgitation of API or ASTM that frequently referenced out dated specs.

With your and swall's comments, it appears that calculated DI should be imposed on purchase orders; however, a inquiry regarding DI will likely have to be reviewed by both mills and distributers.

 

[salmon2]

We as steel customer always specify specific chemistry to buy and don't give steel mill the freedom. I see people are buying mechanical properties, not chemistry or hardenability. Our case is slightly different from most steel users because our application is at very high strain rate. So tighting up mechanical properties with standard tests is not enough.

 

[LiquidSteel]

We deal in a large part with Caterpillar specifications and they reference A255 on their drawings. We also use Ste-Cal extensively but not by choice.

To clarify, I believe the discrepancies that is seen in the DI, at least between Caterpillar and A255 are probably just the programs that are used to calculate it. Some programs round to the nearest .05 carbon when determining factors for each of the different elements which will cause some rounding errors.

As for Ste-Cal, It is off by a larger margin and the difference between this and A255 becomes increasingly larger as the DI increases. I still don't understand why this difference exists.