Aluminium killed 1

[VinceFabspec]

Hi,
I'm looking for 1-1/2" thick steel plate per ASME SA-516 gr. 70 Aluminium killed. What should be the weight % of Aluminium so the steel to be considered as Aluminium killed? Can I get some references (web site, journal, article or book) to learn about the steel's Aluminium killing process?
Regards

 

[metengr]

Not sure, but are you looking to purchase steel as a substitute for ASME SA 515 Grade 70 or are you purchasing SA 515 Grade 70?

 

[metengr]

Correction; that should be SA 516 not SA 515.

 

[metengr]

VinceFabspec;
I am going to provide some additional information here because I am assuming you are purchasing SA 516 Grade 70 steel plate. Since this is a pressure vessel plate specification, ASME SA 20 specification is invoked and should be reviewed.

To summarize, SA 20 provides General Requirements for Steel Plates for Pressure Vessels, and as such covers items like steel melting practice , heat treatment, testing and marking in addition to specific requirements listed in any of the referenced plate grades, like SA 516.

With that, in reference in SA 20 and SA 516, silicon is used to de-oxidize, and not aluminum, by both specifications. For fine grain practice as is required for SA 516, in ASME SA 20 specification, Section 8, 8.2.2.1, there is a section on Aluminum for fine grain practice, and I quote;

If aluminum is used as the grain refining element, the fine austenitic grain size requirement shall be deemed to be fulfilled, if on heat analysis, the aluminium content is not less than 0.020% total aluminum, or alternatively 0.015% acid soluble aluminum.

The aluminum specified for use in SA 516 and invoked by SA 20 for pressure vessel steel plates is used for grain refinement purposes, and not for de-oxidation (to kill the steel).

 

[dbooker630]

For wrought steel .015 wt% is a recommended minimum. Nominal value around .030 wt%.

 

[VinceFabspec]

metengr;
I looked to the ASME SA-20 and I also looked to another reference I got, the latest edition of the Gooderham Centre section 8, which says that Si and Al are used as de-oxidizing elements.
Do the Al become a de-oxidizing element when added to steel with Si? Finally, the silicon do de-oxidizes the steel, so what is the % needed to do so with reference again please.
Best regards

 

[vesselfab]

If your looking to buy some sa-516-70 1.5" plate, it will automatically come fully killed (either by de-oxidation element or vacumn treatment) and fine grain practice (usually by addition of aluminum to refine grain).

If you wish to add some requirements such as particular ways a mill is to produce the plate that is not normal production, be prepared to be put waaaaaaaaaay back at the end of the line.

Perhaps someone mis-understood what was going on in the steel making process. I would go back and look to who ever is wanting it "aluminum killed" to find out what they REALLY want.

 

[metengr]

VinceFabspec;
The aluminum will also help to de-oxidize the steel, but this is primarily the function of silicon to produce killed steel under SA 516. For fine grain practice that is specified, aluminum is typically added for grain refinement purposes (again, it will also de-oxidize as a side benefit).

For other steel plate specifications, where fine grain practice is not specified, aluminum in conjunction with silicon and manganese and other oxidizing elements can be used to de-oxidize the melt.

Finally, the silicon do de-oxidizes the steel, so what is the % needed to do so with reference again please.

The last part of your question is answered by reviewing the chemical composition requirements in ASME SA 516. For silicon, content the product analysis range is 0.13 to 0.45 mass percent.


If you want further information on this subject, I would suggest you Google search a key phrase like "killed steel" and you will obtain plenty of information on steel making practices for your reading pleasure.

 

[SJones]

Could it be that strain ageing is an issue and somebody has pointed Vince in the direction of aluminium to tie up nitrogen?

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[metengr]

SJones;
Perhaps, however I would see this more applicable to SA 515 Grades of steel plate where prolonged exposure to elevated service temperature (above 500 deg F) would require the use of Aluminum to reduce susceptibility to stain ageing affects from higher nitrogen levels, not SA 516 Grades.