Upper temperature limits for WCB and LCC Steel

[Pegasus2]

I need to know the following regarding WCB and LCC Steel (Valve Body).

1. Is WCB acceptable for NACE?

2. When Stress relieving WCB material, does the final product have the same properties as LCC material, and does it conform to NACE stds?
2a. What is the upper most temperature limit for the material if it does conform to nace specs without compromising the structural integrity?

3. At prolonged use above 600°F, Do the characteristics of HT TRT WCB material start to degrade? And does it start to form graphite at 700-775°F?

4. When using WCB that has been heat treated, and when using at the upper temperature limits (650°F) for long periods of time what effect does this have on the structural integrity of the valve body (valve body is heat treated WCB)?

 

[metengr]

I can try to answer questions 3 and 4;

3). No, because the tempering temperature to achieve the desired mechanical properties for heat treated WCB material is well above 600 deg F. To affect the original heat treatment, the service temperature would have to reach the original tempering temperature (usually, 1150 deg F). At 700 deg F and higher service temperatures, creep deformation becomes the major contributor to service life. Graphitization typically does not occur until service temperatures of 800 deg F or higher are sustained. Even then, other factors come into play like stress level and specific chemical composition.

4). At 650 deg F, no adverse effects on structural integrity.

 

[GRoberts]

For question #1 - WCB and LCC can comply with NACE MRO107 and RP0472 if manufactured processed correctly. They both fall under the carbon steel category.

For question #2 - No. In general, most LCC is Quenched and tempered, and WCB is normalized or normalized and tempered. Foundries may have different internal chemistry aims to meet the different properties of the different materials. The obvious differences is that LCC has higher yield strenth requriements, and CVN requirements.