A36 Steel Plate Porosity 2

[shnoel]

I am manufacturing a part from a 19" OD x 4.25" thick piece of A36 plate and while machining it, porosity was opened up. I am used to seeing this in castings but not in A36 plate. We performed a liquid penetant test on the machined surface and the porosity was visually worse. Can anyone speak to A36 plate and porosity? I always thought a plate material could have laminations but not porosity. Is this correct?

 

[redpicker]

It's difficult to tell without a metallurgical analysis. Many things get called "porosity", so the term itself does not define the condition. A metallurgical analysis will reveal the cause and what needs to be done to prevent it.

rp

 

[shnoel]

I'm using the word "porosity" for this plate becuase there are actually voids or holes in the material which I would expect to see in a cast part, not rolled plate.

 

[weldstan]

I could not open your attachment; however, continuous cast slab may be the culprit based on the thickness of the plate and potential for insufficient hot work.

 

[redpicker]

I can't open your attachment, either. It appears to be a link to your computer's root directory.

I didn't intend to doubt your use of the word, only that there are many causes. Porosity is the presence of voids in the material. It does not address how they got there.

Yes, porosity is more common in castings. You can also see it in weldments. As weldstan pointed out, it can exist in wrought materials due to insufficient hot work. It can also result from poor steelmaking practice. The list goes on.

rp

 

[arunmrao]

"Porosity" is a grossly used term even for castings. Quite often we read " Castings shall be free from porosity", without any further qualification.

The porosity in the plate can be as a result of failure to close the defect from a continuously cast slab during rolling . It is not surprising that the plates are tested (ultrasonic testing) before sourcing from the dealers or mills.

 

[tbuelna]

I am manufacturing a part from a 19" OD x 4.25" thick piece of A36 plate and while machining it, porosity was opened up...

19" OD plate? Is this plate or a tube form?

As others noted, A36 steel plate is often produced starting from a continuous cast slab that is repeatedly hot rolled to your 4.25" thickness. I don't have a copy of ASTM A36 handy, but I believe it references other ASTM specs that cover specific metallurgy and quality requirements for rolled A36 plate. These ASTM documents will help you determine whether your material is non-conforming.

If your material delivery included certs or a CofC from the vendor stating the material conformed to ASTM A36 standards, and you make a determination it does not, then you should take up the issue with the vendor. On the other hand, if you simply purchased a piece of steel plate with no guarantee of pedigree or quality and you find it to be defective, then caveat emptor and chalk it up to experience.

Look at the bright side, at least you discovered the problem during manufacturing rather than after the component was put into service.

Good luck to you.
Terry

 

[mrfailure]

As Redpicker noted, you will understand better what is going on with metallurgical analysis. Specifically, examination of a cross-section through the "pores" in the etched and unetched conditions in the direction of rolling as well as microhardness will tell you quite a bit about what is going on.

 

[Ron]

Are you sure you were seeing porosity or was it lamination?

 

[shnoel]

Attached should be a picture of what I am calling "porosity" in the A36 plate.

 

[mrfailure]

Bleedout of developer found on dye penetrant can have the appearance of porosity but may only be cracks or laminations. You should circle the indications, remove the penetrant, then examine these locations using a handheld microscope to determine if pores really exist.

 

[weldstan]

Looks like inclusions.

 

[TVP]

Or rolled in scale...

 

[arunmrao]

Agree with TVP, rolled scale. I was imagining one large cavity,but we see numerous small cavities. It is clearly a poor quality steel. I can't help comparing, a steel casting is far cleaner than the plate material.

 

[gtaw]

It looks like a casting with inclusions to me.

Are you sure the raw shape was cut from a plate?

Do you have a certified material test report that can be verified to be for the material you received?

Did your company cut the raw shape from plate or was it supplied by a vendor?

Best regards - Al

 

[IFRs]

4.5 inch is pretty thick for A-36 plate, rolling imperfections may not be rare in such a beast

 

[shnoel]

This part is a cut shape from plate. The CMTR confirmed it and it also came from a mill in China so the thought on poor quality is not out of the question. The pores due exist prior to applying the developer because they were seen while maching the part. The part isn't completed yet and when the machinist was in the middle of machining, that is when he saw the pores and then we did the penetrant test. If this is rolled scale, would this be detected with a UT exam prior to purchase? I'm not familiar with any defects in plate meterial and almost never have we had an issue in the past with any plate material. I hate to have to impose purchasing NDE on parts but I'm not sure hat other options we have.

 

[gtaw]

If you are purchasing the material, you get what you get. Its like shopping at Walmart.

Even if you specify NDT by the supplier, I wouldn't hold my breath.

I would agree that it is worthwhile performing UT upon receipt. If it doesn't pass, send it back. Once you start machining it, you own it.

Best regards - Al

 

[arunmrao]

It is a good practice to do UT and perform independent analysis before using them . One can reduce further cost ,and time.