Evaluating Material Properties of SA387 Chrome Moly

[muld0020]

Our customer requested "Chrome Moly" plates. This is a non-code part, but machinability is important to us and the part is CrMoly for resistance to erosion (steam/water service). Allowable stress for design is not a factor and the part is not welded.

Does anyone have a SA387 Grade recommendation(s) for best selection based on the above criteria?

 

[metengr]

I would use Grade 22 from the given information. This plate material is a work-horse material in the Power Generation industry, and is used in many applications for steam flashing service. Higher chromium grades, like 5Cr and 9Cr can be more difficult to work and have higher cost.

 

[stanweld]

Without knowing your service, 5Cr-1/2 Mo wear plates on steam blow down drums have out performed Grade 22.

 

[blacksmith37]

If the customers problem is droplet impingement, the alloy in the steel won't make any difference (at the same hardness) so , use what is convient for your shop.

 

[Guest102023]

Enquire as to what the customer actually wants/needs.

I've had a career's worth of questions caused by similarly sloppy use of the word 'stainless'.

 

[muld0020]

Thank you for the input. Outside experiance is very valuable.

The customer is concerned about Flow Accelerated Corrosion (FAC)(power generation heat exchangers). My origianl short list was Gr11, 12, and 22. I think that they should all hold up equally well for the FAC. I didn't know if another grade was far superior for this type of issue (ie Grade 5). We are drilling a significant amout of holes, so the machinability is of intrest to us. I'm not sure yield strength directly corrolates to machinability, but the Grade 22 (Cl 1) has the least yield of the three grades so I'm inclined to use that material.

Does anyone know if there is a noticable difference in machining (drilling) bewteen Grade 11, 12, 22 (Class 1 or 2)?

 

[metengr]

Grade 5 is not needed for FAC resistance. Use Grade 22 or Grade 11. If you have 2- phase FAC, use Grade 22.

 

[muld0020]

To wrap up this post.

The mill finally got back to me and they said that there is no difference in the way the Grade 11 or 22 machine. This probably makes sense given the Sulfur content of the materials in question is the same.

We opted for Gr11 since the improvement will be significant compared to the A36 that these parts are replacing. I think the improvement that Gr 22 has over Gr 11 (for FAC) in this application is not worth the extra cost in materials.

Thanks to everyone who contributed to this post.