Materials specified according to ASME standard and we want to use EN material

[charlie2000]

Hello everyone,

We are manufacturing steel components. Recently, we had to provide big nuts (4 inch tread) and wanted to produce them in our work shop.
We did not know for what temperature they should be used, but the customer specified A 194 Gr 4 und we did know that it was for a suspension of a part in a boiler (hanger bolts with these nuts).

As we prefer EN standard materials, that we normally have on stock we tried to find the corresponding EN material.
There are a lot of conversion tables available and ALL of them said 24CrMo5.

So we used this material for production. After that, the inspector had to check our products and stated that the 24CrMo5 was NOT the right choice.

So I ask: What are the criteria for these published tables? Strength values, temperature ranges, chemical composition, hardness?
I really do not know!

Fact is, that the 25CrMO5 was rejected, the reason was the C content, A 194 GR 4 asks for 0.4 to 0.5% and this 24CrMo5 has only about 0.2.

I guess that the A 194Gr4 is used in the same temperature range as the 24CrMo5 and is the right aquivalent, but it was rejected because of the C content.

So again, what are the criteria, are they clearly stated or are they randomly chosen by the inspectors?

Any help will be appreciated.

 

[metengr]

What are the criteria for these published tables? Strength values, temperature ranges, chemical composition, hardness?
I really do not know!

All of the above.

There are two issues here;
First and most important, for pressure retaining material; You cannot indiscriminately select a material specification from another Code or standard to substitute material listed in ASME B&PV Code unless the material specification from the Code or Standard has been approved by ASME B&PV Code book section or Section II.

For nonpressure retaining material; ASME B&PV Code only requires that the material is from either a recognized standard or specification and is weldable. For hardware parts such as nuts or gaskets or casing where no welding is required, the use of material for hardware is based on engineering judgement. Here for example, the Authorized Inspecter rejected based only on chemical composition differences and not suitability for service. They may have been correct or possibly over-conservative because of known service conditions.

For you as the supplier you should have worked more closely with the Purchaser and their Inspector to ensure substitute materials for hardware are equivalent for use. Short answer - verify service conditions, check chemical composition and mechanical properties at the expected service temperature.