API 6A: QTC (ER Method)

[PCS30]

In accordance with API 6A, the size of a TC or a QTC for a part shall be determined using the ER method give in 5.7.2. What is exactly the method ER? Could you give me an example?

 

[metengr]

It is explained in API 6A, Section 5.6.2 Equivalent Round (ER). There are equations to calculate ER.

If you review API 6A they even provide a definition under Terms and Conditions

3.1.41
equivalent round ER
standard for comparing various shaped sections to round bars, in determining the response to hardening characteristics when heat-treating low alloy and martensitic corrosion-resistant steel

The reason for the above is that hardenability curves during quenching, like Jominy Curves were performed using round bars as a standard.

 

[JHWC]

As far as I understand, ER is mainly used to determine the size of the test coupon during heat treatment process.

Different shapes will have different ER and this will come handy during QTC.

ER calculation ---> See the diagram in Chapter 5.6.2 (a), (b) and (c)

Thanks,
Jeffrey