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CA6NM vs. 9Cr-1Mo
4

CA6NM vs. 9Cr-1Mo

CA6NM vs. 9Cr-1Mo

(OP)
which is better for high temperature application and has good corrosion resistant "Cast CA6NM" or "Cast 9CR-1MO (V,Nb)" STEEL?

RE: CA6NM vs. 9Cr-1Mo

What is the part,that you plan to manufacture nd why select CA6NM for a high temperature(what temperature) application? Traditionally,CA6NM was developed over 410 grade of castings for better impact and wear properties.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

RE: CA6NM vs. 9Cr-1Mo

Not enough information to make a valid comparison between these alloys. It is known cast Grade 91 will have much better high temperature strength properties in comparison to cast CA6NM because Grade 91 is a creep strength enhanced ferritic steel, and was developed primarily for use in the Power Generation industry.
Regarding corrosion applications in certain environments, the higher chromium containing alloy CA6NM (12%) will have better corrosion resistance in comparison Grade 91 (9%).
 

RE: CA6NM vs. 9Cr-1Mo

There are hundreds(+) of alloys in the range between 9Cr and modified 13Cr, why limit yourself to 2 ?

RE: CA6NM vs. 9Cr-1Mo

(OP)
we use before CA6NM in casting exhaust parts that in contact with hot gasses but now purchaser want to replace it with Cast "9CR-1MO (V,Nb)" STEEL. I want to know that, this changing in material is because of price or performance?  

RE: CA6NM vs. 9Cr-1Mo

The change is definitely towards performance as Metengr suggested,in an earlier post. However,please look at the castability of the alloy.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

RE: CA6NM vs. 9Cr-1Mo

(OP)
it is hard to control Nitrogen and Al content of 9CR-1MO steel,
I think castability of CA6NM is better!

RE: CA6NM vs. 9Cr-1Mo

(OP)
The Max. temprature of exhausting gasses is 550 C. but this parts are static.

RE: CA6NM vs. 9Cr-1Mo

(OP)
The Max. temprature of exhausting gasses is 550 C. but these parts are static.

RE: CA6NM vs. 9Cr-1Mo

I would certainly not recommend 9Cr-1 Mo ,grade to be used in traditional casting techniques. There are other grade of heat resistant stainless steels as per ASTM A297,you can consider those for your application.

As suggested earlier,it is advised you engage the services of a knowledgeable and experienced metallurgist. It helps!

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

RE: CA6NM vs. 9Cr-1Mo

I have seen CA6NM used in traditional gas and large steam turbine casings where metal temperatures do not exceed 1000 deg F. The elevated temperature strength of the CA6NM shows a significant decrease above 1000 deg F.

If you want an alternative alloy that can be used  go with a 1%Cr-1%Mo- 0.5%V casting. This alloy has been used by turbine OEM's for many years, is reliable for elevated temperature service  and castable. I would  not use Grade 91 cast material.
 

RE: CA6NM vs. 9Cr-1Mo

(OP)
about Hot corrosion, which is better at 550 C ?

RE: CA6NM vs. 9Cr-1Mo

If you mean high temperature oxidation in air, the CA6NM will be better because of the higher chromium content.

RE: CA6NM vs. 9Cr-1Mo

This is not cost driven, Cr is $1.5/lb and Mo is $18.
While the oxidation resistance of 9-1 is better than a straight 9%Cr I am not sure that it would match 13%Cr.
I am more concerned about castability and resulting properties.
CA6NM has proven toughness, which could be a problem with 9-1.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: CA6NM vs. 9Cr-1Mo

I believe cast 9 cr 1 Mo is officially known as C12A.

RE: CA6NM vs. 9Cr-1Mo

(OP)
that is true its C12A. It is creep resistance steel but the part that we made is in contact with hot gasses such as SO2 ... and working temperature is 550 C.  

RE: CA6NM vs. 9Cr-1Mo

(OP)
Thank to all
Can anybody introduce some books or papers about corrosion resistance of 9cr-1Mo-V steel?

RE: CA6NM vs. 9Cr-1Mo

For castability and weldability, CA-6NM is superior.  Having about the minimum Cr required to qualify as stainless, it will have superior corrosion resistance (although if you leave it out in the rain it will develop rust).  In my experience it is mainly a hydro turbine and pump grade.  

Strange pair of alloys to compare.   

RE: CA6NM vs. 9Cr-1Mo

lidbasky,
Please note that while 9Cr-1Mo-V casting is grade C12A under A-217, 9Cr-1Mo castings have grade designation C12.

Regarding high temperature strength at 550 C, agree with Metengr that C12A is superior to CA6NM but not C12.

Regarding oxidation resistance at 550 C, castability of the alloy and weldability of the alloy, I agree with metengr and brimstoner CA6NM will prove superior to C12A and C12.  

RE: CA6NM vs. 9Cr-1Mo

Having said the above, I can not recommend CA6NM at the 550 C operating temperature due to its proclivity for embrittlement.

RE: CA6NM vs. 9Cr-1Mo

(OP)
Brimstoner
you right, that is srange pair of alloys to compare, but the design department replace CA6NM with C12A in some hot sections and as you know castability and weldability of CA6NM is better. we dont have any experience about casting of C12A and how to control Nitrogen content of steel, I didnt find any document about casting C12A and its problems.  

RE: CA6NM vs. 9Cr-1Mo

(OP)
Could any one introduce some refrences for cating C12A?

RE: CA6NM vs. 9Cr-1Mo

(OP)
Dear Metengr
Thank you for your post. I had already valve magazine article about C12A but it is about properties of this steel.
How we can control Nitrogen content in steel making? How can measure Nitrogen content of steel?

RE: CA6NM vs. 9Cr-1Mo

lidbasky,

    There are several ways of controlling the amount of Nitrogen in the steel.  First off your specification, you just need to specify how much you need.  For your reference, BOF steels can typically have much lower Nitrogen content than EAF material.  This has to do with how steel is made.  That being said, 150 ppm Nitrogen is easily attainable using an EAF.
    However, this is a very unique situation due to alloy content.  Unless the supplying mill is primarily a "stainless" mill, you may encounter problems with a EBT type EAF, since all of the alloys will be added to the ladle, due to the hot heel practice.  
   What is driving the nitrogen up is the use of alloying elements.  Since the amount of Chrome and Moly in a 9Cr-1Mo added is fairly extensive, there is alwaoys a little bit of nitrogen in the alloys so you will have to watch it.  
   Specifying a vacuum degas product will signficantly aid in the nitrogen reduction of the steel. So clean steel practices need to be employed.  A VOD product will have even tighter nitrogen content, but at a significant cost premium.
    In summary to a slightly rambling post, the only way you guarantee a particular nitrogen content is to specify it at time of order andh ave the mill agree to the limit.  There are so many factors that determine the Nitrogen content as a function of production so there is no one answer to your question.
    As far as analyzing the nitrogen content of a steel, there are two widely accepted industry methods.  The first is combustion analysis, (Leco O/N2). Yes I know Leco is a brand name but everyone calls it that.  And the second is through new OES.  I am rather old school and prefer combustion, but there are many people that swear by OES.  I hope this helps

 

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